Materials Handbook: A Concise Desktop Reference [2 ed.] 9780127462752

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Materials Handbook

By the same author Encyclopaedia of Scientific Units, Weight and Measures. Their SI Equivalences and Origin Springer, New York, London (2005), xxiv, 848 pages ISBN 978-1-85233-682-0 Materials Handbook: A Concise Desktop Reference Springer, London, New York (2000), xi, 595 pages ISBN 978-1-85233-168-9 (Out of print) Scientific Unit Conversion. A Practical Guide to Metrication, 2nd Edition Springer, London, New York (1999), xvi, 488 pages ISBN 978-1-85233-043-9 (Out of print) Scientific Unit Conversion: A Practical Guide to Metrication Springer, London, Heidelberg (1997), xvi, 456 pages ISBN 978-3-540-76022-1 (Out of print)

François Cardarelli

Materials Handbook A Concise Desktop Reference 2nd Edition

123

Dr. François Cardarelli, Principal Electrochemist, Materials Materials and Electrochemical Research (MER) Corp. 7960 South Kolb Road Tucson, Arizona 85706 USA phone: +1-520-574-1980 ext. 185 fax: +1-520-574-1983 e-mail: [email protected] URL: www.mercorp.com URL: www.francoiscardarelli.ca Member of ACS, AIChE, ASM, ECS, MAC, MSA, OCQ, SFC and TMS

ISBN 978-1-84628-668-1

e-ISBN 978-1-84628-669-8

DOI 10.1007/978-1-84628-669-8 British Library Cataloguing in Publication Data Cardarelli, Francois, 1966Materials handbook : a concise desktop reference. - 2nd ed. 1. Materials - Handbooks, manuals, etc. I. Title 620.1'1 ISBN-13: 9781846286681 Library of Congress Control Number: 2008921525 © 2000, 2008 Springer-Verlag London Limited Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Cover design: eStudio Calamar S.L., Girona, Spain Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com

Dedication for the First Edition The Materials Handbook: A Concise Desktop Reference is dedicated to my father, Antonio, and my mother, Claudine, to my sister, Elsa, and to my spouse Louise Saint-Amour for their love and support. I want also to express my thanks to my two parents and my uncle Consalvo Cardarelli, which in close collaboration have provided valuable financial support when I was a teenager to contribute to my first fully equipped geological and chemical laboratory and to my personal comprehensive scientific library. This was the starting point of my strong and extensive interest in both science and technology, and excessive consumption of scientific and technical literature. François Cardarelli

Dedication for the Second Edition The Materials Handbook: A Concise Desktop Reference is dedicated to my father, Antonio, and my mother, Claudine, to my sister, Elsa, and to my wife Elizabeth I.R. Cardarelli for their love and support. I want also to express my thanks to my two parents and my uncle Consalvo Cardarelli, which in close collaboration have provided valuable financial support when I was a teenager to contribute to my first fully equipped geological and chemical laboratory and to my personal comprehensive scientific library. This was the starting point of my strong and extensive interest in both science and technology, and excessive consumption of scientific and technical literature. François Cardarelli

Acknowledgements for the First Edition Mr. Nicholas Pinfield (engineering editor, London), Mr. Jean-Étienne Mittelmann (editor, Paris), Mrs. Alison Jackson (editorial assistant, London), and Mr. Nicolas Wilson (senior production controller, London) are gratefully acknowledged for their valued assistance, patience, and advice.

Acknowledgements for the Second Edition Mr. Anthony Doyle (senior engineering editor), Mr. Oliver Jackson (associate engineering editor), and Mr. Nicolas Wilson (editorial coordinator) are gratefully acknowledged for their valued assistance, patience, and advice.

Units Policy In this book the only units of measure used for describing physical quantities and properties of materials are those recommended by the Système International d’Unités (SI). For accurate conversion factors between these units and the other non-SI units (e.g., cgs, fps, Imperial, and US customary), please refer to the reference book by the same author: Cardarelli, F. (2005) Encyclopaedia of Scientific Units, Weights, and Measures. Their SI Equivalences and Origins. Springer, London New York. ISBN 978-1-85233-682-1.

Author Biography Dr. François Cardarelli (Ph.D.) Born in Paris (France) February 17, 1966 Canadian citizen

Academic Background • Ph.D., chemical engineering (Université Paul Sabatier, Toulouse,

France, 1996) • Postgraduate degree (DEA) in electrochemistry (Université

Pierre et Marie Curie, Paris, 1992) • M.Sc. (Maîtrise), physical chemistry (Université Pierre et Marie

Curie, Paris, 1991) • B.Sc. (Licence), physical chemistry (Université Pierre et Marie

Curie, Paris, 1990) • DEST credits in nuclear sciences and technologies (Conserva-

toire National des Arts et Métiers, Paris, 1988)

• Associate degree (DEUG B) in geophysics and geology (Université Pierre et Marie Curie,

Paris, 1987) • Baccalaureate C (mathematics, physics, and chemistry) (CNED, Versailles, France, 1985)

Fields of Professional Activity The author has worked in the following areas (in chronological order) since 1990. (1)

Research scientist at the Laboratory of Electrochemistry (Université Pierre & Marie Curie, Paris, France) for the development of a nuclear detector device for electrochemical experiments involving radiolabeled compounds; (2) research scientist at the Institute of Marine Biogeochemistry (CNRS & École Normale Supérieure, Paris, France) for the environmental monitoring of heavy-metal pollution by electroanalytical techniques; (3) research scientist for the preparation by electrochemistry in molten salts of tantalum protective thin coatings for the chemical-process industries (sponsored by Electricité de France); (4) research scientist for the preparation and characterization of iridium-based industrial electrodes for oxygen evolution in acidic media at the Laboratory of Electrochemical Engineering (Université Paul Sabatier, Toulouse, France); (5) registered consultant in chemical and electrochemical engineering (Toulouse, France); (6) battery product leader in the technology department of ARGOTECH Productions, Boucherville (Québec), Canada, in charge of electric-vehicle, stationary, and oildrilling applications of lithium polymer batteries; (7) materials expert and industrial electrochemist in the lithium department of ARGOTECH Productions, involved in both the metallurgy and processing of lithium metal anodes and the recycling of spent lithium polymer batteries; (8) materials expert and industrial electrochemist in the technology department of AVESTOR, Boucherville (Quebec), Canada, in charge of all strategic raw materials entering into the fabrication of lithium polymer batteries, as well as being in charge of the recycling process of spent lithium batteries; (9) principal chemist, materials, in the technology department of RIO TINTO Iron and Titanium, Sorel–Tracy (Québec), Canada working on the electrowinning of titanium metal from titania-rich slags and on other novel electrochemical processes; (10) principal electrochemist at Materials and Electrochemical Research (MER) Corp., Tuscon (Arizona, USA) working on the electrowinning of titanium metal powder from composite anodes and other materials related projects.

Contents

Introduction .................................................................................................................................xxxvii 1

Properties of Materials................................................................................................................. 1 1.1 Physical Properties ..........................................................................................................1 1.1.1 Mass Density ....................................................................................................1 1.1.2 Theoretical Density or X-ray Density of Solids ............................................2 1.1.3 Apparent, Bulk, and Tap Densities ................................................................2 1.1.4 Specific Weight ................................................................................................3 1.1.5 Specific Gravity ................................................................................................3 1.1.6 Buoyancy and Archimedes’ Principle............................................................3 1.1.7 Pycnometers for Solids ...................................................................................4 1.1.8 Density of Mixtures .........................................................................................5 1.2 Mechanical Properties.....................................................................................................6 1.2.1 Stress and Pressure..........................................................................................7 1.2.2 Strain.................................................................................................................7 1.2.3 Elastic Moduli and Hooke’s Law....................................................................7 1.2.4 The Stress–Strain Curve..................................................................................8 1.2.5 Strain Hardening Exponent..........................................................................11 1.2.6 Hardness.........................................................................................................11 1.2.7 Resilience and Modulus of Resilience .........................................................15 1.2.8 Toughness ......................................................................................................15 1.2.9 Maximum Allowable Stress ..........................................................................15 1.2.10 Fracture Toughness .......................................................................................16 1.2.11 Brittleness Indices .........................................................................................17 1.2.12 Creep...............................................................................................................17 1.2.13 Ductile-Brittle Transition .............................................................................18 1.2.14 Fatigue ............................................................................................................18 1.2.15 Tribological and Lubricating Properties of Solids .....................................19 1.2.15.1 Static Friction Coefficient ........................................................19 1.2.15.2 Sliding Friction Coefficient......................................................20

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1.3

1.4

1.5

1.2.16 Ashby’s Mechanical Performance Indices.................................................. 21 1.2.17 Order of Magnitude of Mechanical Properties of Solid Materials ........... 21 Acoustical Properties.................................................................................................... 23 1.3.1 Velocity of Sound in Materials .................................................................... 23 1.3.2 Sound Intensity ............................................................................................. 23 1.3.3 Attenuation of Sound at a Given Distance from a Source ........................ 24 1.3.4 Damping Capacity of Solids and Loss Factor............................................. 24 Thermal Properties ....................................................................................................... 25 1.4.1 Molar and Specific Heat Capacities............................................................. 25 1.4.2 Coefficients of Thermal Expansion............................................................. 26 1.4.3 Volume Expansion on Melting.................................................................... 27 1.4.4 Thermal Shock Resistance ........................................................................... 27 1.4.5 Heat Transfer Processes ............................................................................... 28 1.4.6 Thermal Conductivity .................................................................................. 28 1.4.7 Thermal Diffusivity....................................................................................... 29 1.4.8 Spectral Emissivity........................................................................................ 30 1.4.9 Temperature and Latent Enthalpies of Fusion, Vaporization, and Sublimation............................................................................................ 30 1.4.10 Order of Magnitude of Thermal Properties of Materials .......................... 32 Optical Properties ......................................................................................................... 32 1.5.1 Index of Refraction ....................................................................................... 32 1.5.2 Total Reflection and Critical Angle............................................................. 34 1.5.3 Specific and Molar Refraction ..................................................................... 35 1.5.4 Refractivity .................................................................................................... 35 1.5.5 Dispersion...................................................................................................... 35 1.5.6 Coefficient of Dispersion.............................................................................. 36 1.5.7 Abbe Number ................................................................................................ 36 1.5.8 Temperature Dependence of the Refractive Index.................................... 36 1.5.9 Anisotropic Materials................................................................................... 36 1.5.10 Birefringence ................................................................................................. 37 1.5.11 Albedo and Reflective Index ........................................................................ 37 1.5.12 Electromagnetic Radiation Spectrum ......................................................... 38 1.5.13 Order of Magnitude of Optical Properties of Transparent Materials ...... 38 1.5.14 Macroscopic Absorption of Light................................................................ 39 1.5.14.1 Damping Constant................................................................... 39 1.5.14.2 First Law of Absorption (Bouger’s Law)................................ 39 1.5.14.3 Second Law of Absorption (Beer–Lambert Law).................. 40 1.5.14.4 Absorbance or Optical Density .............................................. 40 1.5.15 Microscopic Absorption and Emission Processes ..................................... 41 1.5.16 Einstein Coefficients ..................................................................................... 42 1.5.16.1 Einstein Coefficient of Absorption......................................... 42 1.5.16.2 Einstein Coefficient of Spontaneous Emission ..................... 43 1.5.16.3 Einstein Coefficient of Stimulated Emission......................... 44 1.5.16.4 Relation Between Einstein Coefficients ................................. 44 1.5.16.5 Relations Between Einstein and Extinction Coefficients ..... 45 1.5.17 Luminescence................................................................................................ 45 1.5.17.1 Excitation.................................................................................. 46 1.5.17.2 Internal Conversion................................................................. 46 1.5.17.3 Fluorescence............................................................................. 46 1.5.17.4 Intercombination..................................................................... 46 1.5.17.5 Delayed Fluorescence .............................................................. 47 1.5.17.6 Phosphorescence ..................................................................... 47

Contents

1.6

1.7 1.8 1.9

2

Other Properties.............................................................................................................47 1.6.1 Biocompatibility ............................................................................................47 1.6.2 Electronegativity............................................................................................48 1.6.3 Chemical Abstract Registry Number ...........................................................50 Fundamental Constants ................................................................................................50 Conversion Factors........................................................................................................52 Further Reading .............................................................................................................54 1.9.1 Mathematics and Statistics ...........................................................................54 1.9.2 Units and Conversion Tables .......................................................................55 1.9.3 Physics ............................................................................................................55 1.9.4 Physical Chemistry ........................................................................................55 1.9.5 Engineering Fundamentals...........................................................................56 1.9.6 General Handbooks.......................................................................................56 1.9.7 Mechanical Properties...................................................................................56 1.9.8 Electrical Properties ......................................................................................56 1.9.9 Thermal Properties........................................................................................56 1.9.10 Metallurgy ......................................................................................................57 1.9.11 Materials Science ...........................................................................................57

Ferrous Metals and Their Alloys............................................................................................... 59 2.1 Iron and Steels................................................................................................................59 2.1.1 Description and General Properties ............................................................59 2.1.2 Phase Transitions and Allotropism of Iron ................................................64 2.1.3 Metallographic Etchants for Iron and Steels...............................................66 2.1.4 History ............................................................................................................66 2.1.5 Natural Occurrence, Minerals, and Ores.....................................................66 2.1.6 Mining and Mineral Dressing.......................................................................70 2.1.7 Iron- and Steelmaking...................................................................................71 2.1.8 Pure Iron Grades............................................................................................73 2.1.9 The Iron-Carbon (Fe-C) and Iron-Cementite (Fe-Fe3C) Systems.............73 2.1.10 Cast Irons .......................................................................................................78 2.1.10.1 Gray Cast Iron or Graphitic Iron ............................................79 2.1.10.2 White Cast Iron.........................................................................79 2.1.10.3 Malleable Cast Irons.................................................................79 2.1.10.4 Ductile (Nodular) Cast Irons...................................................79 2.1.10.5 High-Silicon Cast Irons............................................................80 2.1.11 Carbon Steels (C-Mn Steels) .........................................................................84 2.1.11.1 Plain Carbon Steels...................................................................85 2.1.11.2 Low-Alloy Steels .......................................................................89 2.1.11.3 Cast Steels..................................................................................95 2.1.12 Stainless Steels ...............................................................................................95 2.1.12.1 Description and General Properties .......................................95 2.1.12.2 Classification of Stainless Steels..............................................96 2.1.12.3 Martensitic Stainless Steels......................................................97 2.1.12.4 Ferritic Stainless Steels.............................................................97 2.1.12.5 Austenitic Stainless Steels......................................................101 2.1.12.6 Duplex Stainless Steels ...........................................................102 2.1.12.7 Precipitation-Hardening Stainless Steels .............................103 2.1.12.8 Cast Heat-Resistant Stainless Steels......................................103 2.1.12.9 Processing and Melting Process............................................103

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2.3

2.4

2.1.12.10 Simplified Selection of Stainless Steels ................................ 108 2.1.12.11 Stainless Steel Application Guidelines................................. 109 2.1.13 High-Strength Low-Alloy Steels (HSLA) .................................................. 112 2.1.14 Ultrahigh-Strength Steels........................................................................... 115 2.1.15 Tool and Machining Steels......................................................................... 115 2.1.16 Maraging Steels ........................................................................................... 120 2.1.17 Iron-Based Superalloys .............................................................................. 121 2.1.18 Iron Powders ............................................................................................... 122 2.1.18.1 Water-Atomized Iron Powders ............................................ 122 2.1.18.2 Gas-Atomized Iron Powders ................................................ 123 2.1.18.3 Sponge-Reduced Iron............................................................ 123 2.1.19 Further Reading .......................................................................................... 123 Nickel and Nickel Alloys ............................................................................................ 124 2.2.1 Description and General Properties.......................................................... 124 2.2.2 History ......................................................................................................... 124 2.2.3 Natural Occurrence, Minerals and Ores ................................................... 125 2.2.4 Processing and Industrial Preparation ..................................................... 126 2.2.5 Nickel Alloys................................................................................................ 127 2.2.6 Nickel Alloys and Superalloys ................................................................... 128 2.2.7 Nickel-Titanium Shape Memory Alloys ................................................... 139 2.2.7.1 History .................................................................................... 139 2.2.7.2 Fundamental .......................................................................... 139 2.2.7.3 Shape Memory Effect............................................................. 140 2.2.7.4 Superelasticity ........................................................................ 140 2.2.7.5 Fabrication ............................................................................. 140 2.2.8 Major Nickel Producers ............................................................................. 141 Cobalt and Cobalt Alloys............................................................................................ 141 2.3.1 Description and General Properties.......................................................... 141 2.3.2 History ......................................................................................................... 142 2.3.3 Natural Occurrence, Minerals and Ores ................................................... 143 2.3.4 Processing and Industrial Preparation ..................................................... 144 2.3.4.1 Cobalt as a Byproduct of Nickel Processing........................ 144 2.3.4.2 Electrowinning of Cobalt ...................................................... 144 2.3.5 Properties of Cobalt Alloys and Superalloys ............................................ 145 2.3.6 Corrosion Resistance of Stellites ............................................................... 148 2.3.7 Industrial Applications and Uses .............................................................. 148 2.3.8 Major Cobalt Producers ............................................................................. 149 Manganese and Manganese-Based Alloys ................................................................ 149 2.4.1 Description and General Properties.......................................................... 149 2.4.2 History ......................................................................................................... 151 2.4.3 Natural Occurrence, Minerals, and Ores .................................................. 152 2.4.4 Processing and Industrial Preparation ..................................................... 153 2.4.4.1 Mining and Beneficiation of Manganese Ores .................... 153 2.4.4.2 Preparation of Pure Manganese Metal ................................ 153 2.4.4.3 Ferromanganese and Silicomanganese................................ 155 2.4.5 Industrial Applications and Uses .............................................................. 156 2.4.5.1 Metallurgical Uses ................................................................. 156 2.4.5.2 Nonmetallurgical Uses .......................................................... 156 2.4.6 Major Manganese Producers ..................................................................... 157

Contents

3

Common Nonferrous Metals................................................................................................... 159 3.1 Introduction .................................................................................................................159 3.2 Aluminum and Aluminum Alloys..............................................................................159 3.2.1 Description and General Properties ..........................................................159 3.2.2 History ..........................................................................................................164 3.2.3 Natural Occurrence, Minerals, and Ores...................................................165 3.2.4 Processing and Industrial Preparation......................................................166 3.2.4.1 The Bayer Process...................................................................166 3.2.4.2 The Hall–Heroult Process for Electrowinning Aluminum ...............................................................................168 3.2.4.3 Secondary Aluminum Production and Recycling of Aluminum Drosses ............................................................169 3.2.5 Properties of Aluminum Alloys .................................................................170 3.2.5.1 Aluminum Alloy Standard Designations .............................171 3.2.5.2 Wrought Aluminum Alloys ...................................................172 3.2.5.3 Cast Aluminum Alloys ...........................................................172 3.2.6 Industrial Applications and Uses...............................................................176 3.2.7 Major Aluminum Producers and Dross Recyclers ...................................177 3.2.8 Further Reading...........................................................................................178 3.3 Copper and Copper Alloys..........................................................................................179 3.3.1 Description and General Properties ..........................................................179 3.3.2 Natural Occurrence, Minerals, and Ores...................................................179 3.3.3 Processing and Industrial Preparation......................................................180 3.3.4 Properties of Copper Alloys........................................................................181 3.3.4.1 UNS Copper-Alloy Designation ............................................181 3.3.4.2 Wrought Copper Alloys .........................................................183 3.3.4.3 Cast Copper Alloys .................................................................183 3.3.5 Major Copper Producers.............................................................................187 3.3.6 Further Reading...........................................................................................187 3.4 Zinc and Zinc Alloys....................................................................................................187 3.4.1 Description and General Properties ..........................................................187 3.4.2 History ..........................................................................................................188 3.4.3 Natural Occurrence, Minerals, and Ores...................................................188 3.4.4 Processing and Industrial Preparation......................................................189 3.4.4.1 Beneficiation of Zinc Ore.......................................................189 3.4.4.2 The Roasting Process .............................................................190 3.4.4.3 Mercury Removal ...................................................................191 3.4.4.4 Hydrometallurgical Process ..................................................191 3.4.4.5 Pyrometallurgical Process .....................................................192 3.4.4.6 Treatment of Ferrite Residue ................................................193 3.4.5 Industrial Applications and Uses...............................................................195 3.4.6 Properties of Zinc Alloys.............................................................................196 3.5 Lead and Lead Alloys...................................................................................................196 3.5.1 Description and General Properties ..........................................................196 3.5.2 History ..........................................................................................................199 3.5.3 Natural Occurrence, Minerals, and Ores...................................................199 3.5.4 Beneficiation and Mineral Dressing ..........................................................199 3.5.5 Processing and Industrial Preparation......................................................199 3.5.6 Industrial Applications and Uses...............................................................201 3.5.7 Properties of Lead Alloys ............................................................................201 3.5.8 Further Reading...........................................................................................201

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3.7

4

Tin and Tin Alloys ...................................................................................................... 204 3.6.1 Description and General Properties.......................................................... 204 3.6.2 History ......................................................................................................... 205 3.6.3 Natural Occurrence, Minerals, and Ores .................................................. 205 3.6.4 Processing and Industrial Preparation ..................................................... 206 3.6.4.1 Mining and Beneficiation...................................................... 206 3.6.4.2 Processing and Smelting ....................................................... 207 3.6.5 Industrial Applications and Uses .............................................................. 208 3.6.6 Properties of Tin Alloys.............................................................................. 208 Low-Melting-Point or Fusible Alloys ........................................................................ 209 3.7.1 Further Reading .......................................................................................... 211

Less Common Nonferrous Metals .......................................................................................... 213 4.1 Alkali Metals................................................................................................................ 213 4.1.1 Lithium ........................................................................................................ 217 4.1.1.1 Description and General Properties..................................... 217 4.1.1.2 History .................................................................................... 219 4.1.1.3 Natural Occurrence, Minerals, and Ores............................. 220 4.1.1.4 Processing and Industrial Preparation ................................ 223 4.1.1.5 Industrial Applications and Uses......................................... 228 4.1.1.6 Lithium Mineral and Chemical Prices ................................. 230 4.1.1.7 Lithium Mineral, Carbonate, and Metal Producers............ 230 4.1.1.8 Further Reading ..................................................................... 231 4.1.2 Sodium ......................................................................................................... 232 4.1.2.1 Description and General Properties..................................... 232 4.1.2.2 History .................................................................................... 233 4.1.2.3 Natural Occurrence, Minerals, and Ores............................. 233 4.1.2.4 Processing and Industrial Preparation ................................ 234 4.1.2.5 Industrial Applications and Uses......................................... 235 4.1.2.6 Transport, Storage, and Safety ............................................. 236 4.1.2.7 Major Producers of Sodium Metal ....................................... 236 4.1.2.8 Further Reading ..................................................................... 236 4.1.3 Potassium .................................................................................................... 237 4.1.3.1 Description and General Properties..................................... 237 4.1.3.2 History .................................................................................... 238 4.1.3.3 Natural Occurrence, Minerals, and Ores............................. 238 4.1.3.4 Processing and Industrial Preparation ................................ 238 4.1.3.5 Industrial Applications and Uses......................................... 239 4.1.3.6 Further Reading ..................................................................... 239 4.1.4 Rubidium ..................................................................................................... 239 4.1.4.1 Description and General Properties..................................... 239 4.1.4.2 History .................................................................................... 240 4.1.4.3 Natural Occurrence, Minerals, and Ores............................. 240 4.1.4.4 Processing and Industrial Preparation ................................ 240 4.1.4.5 Industrial Applications and Uses......................................... 240 4.1.4.6 Major Rubidium Producers .................................................. 241 4.1.4.7 Further Reading ..................................................................... 241 4.1.5 Cesium ......................................................................................................... 241 4.1.5.1 Description and General Properties..................................... 241 4.1.5.2 History .................................................................................... 241 4.1.5.3 Natural Occurrence, Minerals, and Ores............................. 242

Contents

4.2

4.1.5.4 Processing and Industrial Preparation.................................242 4.1.5.5 Industrial Applications and Uses..........................................242 4.1.5.6 Cesium Metal Producers........................................................243 4.1.5.7 Further Reading......................................................................243 4.1.6 Francium ......................................................................................................243 Alkaline-Earth Metals..................................................................................................243 4.2.1 Beryllium ......................................................................................................244 4.2.1.1 Description and General Properties .....................................244 4.2.1.2 History .....................................................................................244 4.2.1.3 Natural Occurrence, Minerals, and Ores..............................248 4.2.1.4 Mining and Mineral Dressing ...............................................248 4.2.1.5 Processing and Industrial Preparation.................................248 4.2.1.6 Industrial Applications and Uses..........................................249 4.2.1.7 Major Beryllium Metal Producers.........................................250 4.2.1.8 Further Reading......................................................................250 4.2.2 Magnesium and Magnesium Alloys...........................................................250 4.2.2.1 Description and General Properties .....................................250 4.2.2.2 History .....................................................................................251 4.2.2.3 Natural Occurrence, Minerals, and Ores..............................251 4.2.2.4 Processing and Industrial Preparation.................................252 4.2.2.5 Properties of Magnesium Alloys ...........................................255 4.2.2.6 Industrial Applications and Uses..........................................255 4.2.2.7 Recycling of Magnesium Scrap and Drosses .......................255 4.2.2.8 Major Magnesium Metal Producers .....................................259 4.2.2.9 Further Reading......................................................................260 4.2.3 Calcium.........................................................................................................260 4.2.3.1 Description and General Properties .....................................260 4.2.3.2 History .....................................................................................260 4.2.3.3 Natural Occurrence, Minerals, and Ores..............................260 4.2.3.4 Processing and Industrial Preparation.................................261 4.2.3.5 Industrial Applications and Uses..........................................261 4.2.3.6 Calcium Metal Producers ......................................................262 4.2.3.7 Further Reading......................................................................262 4.2.4 Strontium .....................................................................................................262 4.2.4.1 Description and General Properties .....................................262 4.2.4.2 History .....................................................................................263 4.2.4.2 Natural Occurrence, Minerals, and Ores..............................263 4.2.4.3 Processing and Industrial Preparation.................................263 4.2.4.4 Industrial Applications and Uses..........................................263 4.2.5 Barium ..........................................................................................................263 4.2.5.1 Description and General Properties .....................................263 4.2.5.2 History .....................................................................................264 4.2.5.2 Natural Occurrence, Minerals, and Ores..............................264 4.2.5.3 Processing and Industrial Preparation.................................264 4.2.5.4 Industrial Applications and Uses..........................................264 4.2.6 Radium .........................................................................................................264 4.2.6.1 Description and General Properties .....................................264 4.2.6.2 History .....................................................................................265 4.2.6.3 Natural Occurrence ................................................................265 4.2.6.4 Processing and Industrial Preparation.................................265 4.2.6.5 Industrial Applications and Uses..........................................265

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Contents

4.3

Refractory Metals ........................................................................................................ 266 4.3.1 General Overview........................................................................................ 266 4.3.1.1 Common Properties .............................................................. 266 4.3.1.2 Corrosion Resistance............................................................. 271 4.3.1.3 Cleaning, Descaling, Pickling, and Etching......................... 271 4.3.1.4 Machining of Pure Reactive and Refractory Metals ........... 273 4.3.1.5 Pyrophoricity of Refractory Metals...................................... 273 4.3.2 Titanium and Titanium Alloys .................................................................. 274 4.3.2.1 Description and General Properties..................................... 274 4.3.2.2 History .................................................................................... 276 4.3.2.3 Natural Occurrence, Minerals, and Ores............................. 276 4.3.2.4 Mining and Mineral Dressing............................................... 280 4.3.2.5 Titanium Slag and Slagging .................................................. 281 4.3.2.6 Synthetic Rutiles .................................................................... 283 4.3.2.7 Titanium Dioxide (Titania) .................................................. 286 4.3.2.8 Titanium Sponge.................................................................... 288 4.3.2.9 Ferrotitanium......................................................................... 296 4.3.2.10 Titanium Metal Ingot ............................................................ 297 4.3.2.11 Titanium Metal Powder ........................................................ 298 4.3.2.12 Commercially Pure Titanium ............................................... 301 4.3.2.13 Titanium Alloys ..................................................................... 302 4.3.2.14 Corrosion Resistance............................................................. 313 4.3.2.15 Titanium Metalworking ........................................................ 319 4.3.2.16 Titanium Machining.............................................................. 320 4.3.2.17 Titanium Joining.................................................................... 320 4.3.2.18 Titanium Etching, Descaling, and Pickling ......................... 320 4.3.2.19 Titanium Anodizing .............................................................. 321 4.3.2.20 Industrial Applications and Uses......................................... 322 4.3.2.21 Major Producers of Titanium Metal Sponge and Ingot ..... 324 4.3.2.22 World and International Titanium Conferences................ 325 4.3.2.23 Further Reading ..................................................................... 325 4.3.3 Zirconium and Zirconium Alloys.............................................................. 326 4.3.3.1 Description and General Properties..................................... 326 4.3.3.2 History .................................................................................... 327 4.3.3.3 Natural Occurrence, Minerals, and Ores............................. 328 4.3.3.4 Mining and Mineral Dressing............................................... 328 4.3.3.5 Processing and Industrial Preparation ................................ 329 4.3.3.6 Zirconium Alloys ................................................................... 331 4.3.3.7 Corrosion Resistance............................................................. 333 4.3.3.8 Zirconium Machining ........................................................... 333 4.3.3.9 Industrial Uses and Applications ......................................... 334 4.3.3.10 Zirconium Metal Producers.................................................. 334 4.3.3.11 Further Reading ..................................................................... 334 4.3.4 Hafnium and Hafnium Alloys ................................................................... 336 4.3.4.1 Description and General Properties..................................... 336 4.3.4.2 History .................................................................................... 336 4.3.4.3 Natural Occurrence, Minerals, and Ores............................. 337 4.3.4.4 Processing and Industrial Preparation ................................ 337 4.3.4.5 Industrial Applications and Uses......................................... 337 4.3.4.6 Major Hafnium Metal Producers ......................................... 337 4.3.4.7 Further Reading ..................................................................... 338

Contents

4.3.5

4.3.6

4.3.7

4.3.8

4.3.9

Vanadium and Vanadium Alloys...............................................................338 4.3.5.1 Description and General Properties .....................................338 4.3.5.2 History .....................................................................................339 4.3.5.3 Natural Occurrence, Minerals, and Ores..............................339 4.3.5.4 Processing and Industrial Preparation.................................340 4.3.5.5 Industrial Applications and Uses..........................................342 4.3.5.6 Major Vanadium Producers ..................................................342 4.3.5.7 Further Reading......................................................................342 Niobium and Niobium Alloys ....................................................................343 4.3.6.1 Description and General Properties .....................................343 4.3.6.2 History .....................................................................................344 4.3.6.3 Natural Occurrence, Minerals, and Ores..............................345 4.3.6.4 Processing and Industrial Preparation.................................346 4.3.6.5 Properties of Niobium Alloys................................................347 4.3.6.6 Niobium Metalworking..........................................................347 4.3.6.7 Niobium Machining ...............................................................347 4.3.6.8 Niobium Joining and Welding ..............................................349 4.3.6.9 Niobium Cleaning, Pickling, and Etching............................349 4.3.6.10 Industrial Applications and Uses..........................................350 4.3.6.11 Major Producers of Niobium Metal......................................350 4.3.6.12 Further Reading......................................................................350 Tantalum and Tantalum Alloys .................................................................353 4.3.7.1 Description and General Properties .....................................353 4.3.7.2 History .....................................................................................354 4.3.7.3 Natural Occurrence, Minerals, and Ores..............................355 4.3.7.4 Processing and Industrial Preparation.................................356 4.3.7.5 Properties of Tantalum Alloys ..............................................357 4.3.7.6 Tantalum Metalworking ........................................................357 4.3.7.7 Tantalum Machining..............................................................359 4.3.7.8 Tantalum Joining....................................................................359 4.3.7.9 Tantalum Cleaning and Degreasing .....................................360 4.3.7.10 Tantalum Cladding and Coating Techniques ......................361 4.3.7.11 Industrial Applications and Uses..........................................365 4.3.7.12 Major Tantalum Metal Producers.........................................366 4.3.7.13 Further Reading......................................................................367 Chromium and Chromium Alloys .............................................................367 4.3.8.1 Description and General Properties .....................................367 4.3.8.2 History .....................................................................................368 4.3.8.3 Natural Occurrence, Minerals, and Ores..............................368 4.3.8.4 Processing and Industrial Preparation.................................369 4.3.8.5 Industrial Applications and Uses..........................................372 4.3.8.6 Major Chromite and Ferrochrome Producers.....................372 4.3.8.7 Further Reading......................................................................372 Molybdenum and Molybdenum Alloys.....................................................373 4.3.9.1 Description and General Properties .....................................373 4.3.9.2 History .....................................................................................373 4.3.9.3 Natural Occurrence, Minerals, and Ores..............................374 4.3.9.4 Processing and Industrial Preparation.................................374 4.3.9.5 Properties of Molybdenum Alloys ........................................375 4.3.9.6 Molybdenum Metalworking..................................................377 4.3.9.7 Molybdenum Joining .............................................................377 4.3.9.8 Molybdenum Machining .......................................................378

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4.4

4.5

4.3.9.9 Molybdenum Cleaning, Etching, and Pickling ................... 380 4.3.9.10 Industrial Applications and Uses......................................... 380 4.3.9.11 World Molybdenum Metal Producers................................. 384 4.3.9.12 Further Reading ..................................................................... 384 4.3.10 Tungsten and Tungsten Alloys.................................................................. 385 4.3.10.1 Description and General Properties..................................... 385 4.3.10.2 History .................................................................................... 386 4.3.10.3 Natural Occurrence, Minerals, and Ores............................. 386 4.3.10.4 Processing and Industrial Preparation ................................ 387 4.3.10.5 Properties of Tungsten Alloys .............................................. 387 4.3.10.6 Industrial Applications and Uses......................................... 387 4.3.10.7 Major Tungsten Metal and Hardmetal Producers.............. 389 4.3.10.8 Further Reading ..................................................................... 391 4.3.11 Rhenium and Rhenium Alloys .................................................................. 391 4.3.11.1 Description and General Properties..................................... 391 4.3.11.2 History .................................................................................... 392 4.3.11.3 Natural Occurrence, Minerals, and Ores............................. 392 4.3.11.4 Processing and Industrial Preparation ................................ 393 4.3.11.5 Industrial Applications and Uses......................................... 393 Noble and Precious Metals......................................................................................... 393 4.4.1 Silver and Silver Alloys............................................................................... 396 4.4.1.1 Description and General Properties..................................... 396 4.4.1.2 History .................................................................................... 397 4.4.1.3 Natural Occurrence, Minerals, and Ores............................. 397 4.4.1.4 Processing and Industrial Preparation ................................ 397 4.4.1.5 Silver Alloys............................................................................ 398 4.4.1.6 Industrial Applications and Uses......................................... 398 4.4.1.7 Further Reading ..................................................................... 400 4.4.2 Gold and Gold Alloys.................................................................................. 400 4.4.2.1 Description and General Properties..................................... 400 4.4.2.2 History .................................................................................... 401 4.4.2.3 Natural Occurrence, Minerals, and Ores............................. 402 4.4.2.4 Mineral Dressing, and Mining.............................................. 402 4.4.2.5 Processing and Industrial Preparation ................................ 403 4.4.2.6 Gold Alloys ............................................................................. 404 4.4.2.7 Industrial Applications and Uses......................................... 406 4.4.2.8 Major Gold Producers and Suppliers................................... 406 Platinum-Group Metals.............................................................................................. 407 4.5.1 General Overview........................................................................................ 407 4.5.2 Natural Occurrence, Chief Minerals, and Ores ........................................ 408 4.5.3 Common Physical and Chemical Properties............................................ 409 4.5.4 The Six Platinum Group Metals ................................................................ 409 4.5.4.1 Ruthenium.............................................................................. 409 4.5.4.2 Rhodium ................................................................................. 413 4.5.4.3 Palladium................................................................................ 413 4.5.4.4 Osmium .................................................................................. 414 4.5.4.5 Iridium.................................................................................... 414 4.5.4.6 Platinum ................................................................................. 415 4.5.5 PGM Alloys .................................................................................................. 416

Contents

4.5.6

4.6

4.7

5

PGMs Corrosion Resistance .......................................................................417 4.5.6.1 Industrial Applications and Uses..........................................420 4.5.6.2 Major Producers and Suppliers of PGMs .............................421 4.5.7 Further Reading...........................................................................................422 Rare-Earth Metals ........................................................................................................422 4.6.1 Description and General Properties ..........................................................422 4.6.2 History ..........................................................................................................423 4.6.3 Natural Occurrence, Minerals, and Ores...................................................425 4.6.4 Processing and Industrial Preparation......................................................427 4.6.5 Industrial Applications and Uses...............................................................429 4.6.6 Major Producers and Suppliers of Rare Earths ........................................431 4.6.7 Further Reading...........................................................................................432 4.6.8 Scandium (Sc) ..............................................................................................433 4.6.8.1 Description and General Properties .....................................433 4.6.8.2 History .....................................................................................433 4.6.8.3 Natural Occurrence, Minerals, and Ores..............................433 4.6.8.4 Processing and Industrial Preparation.................................434 4.6.8.5 Industrial Applications and Uses..........................................434 4.6.8.6 Scandium Metal, Alloys, and Chemicals ..............................435 Uranides........................................................................................................................436 4.7.1 Uranium .......................................................................................................438 4.7.1.1 Description and General Properties .....................................438 4.7.1.2 History .....................................................................................439 4.7.1.3 Natural Occurrence, Minerals, and Ores..............................440 4.7.1.4 Mineral Dressing and Mining ...............................................441 4.7.1.5 Processing and Industrial Preparation.................................442 4.7.1.6 Industrial Applications and Uses..........................................446 4.7.1.7 Further Reading......................................................................447 4.7.2 Thorium........................................................................................................447 4.7.2.1 Description and General Properties .....................................447 4.7.2.2 History .....................................................................................447 4.7.2.3 Natural Occurrence, Minerals, and Ores..............................448 4.7.2.4 Processing and Industrial Preparation.................................449 4.7.2.5 Industrial Applications and Uses..........................................451 4.7.2.6 Further Reading......................................................................452 4.7.3 Plutonium.....................................................................................................452 4.7.3.1 Description and General Properties .....................................452 4.7.3.2 History .....................................................................................453 4.7.3.3 Natural Occurrence, Minerals, and Ores..............................454 4.7.3.4 Processing and Industrial Preparation.................................454

Semiconductors......................................................................................................................... 455 5.1 Band Theory of Bonding in Crystalline Solids..........................................................455 5.2 Electrical Classification of Solids ...............................................................................456 5.3 Semiconductor Classes................................................................................................457 5.3.1 Intrinsic or Elemental Semiconductors.....................................................457 5.3.2 Doped Extrinsic Semiconductors...............................................................458 5.3.3 Compound Semiconductors.......................................................................459 5.3.4 Grimm–Sommerfeld Rule...........................................................................459 5.4 Concentrations of Charge Carriers ............................................................................460

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5.5

5.6 5.7 5.8

5.9 5.10 5.11

Transport Properties .................................................................................................. 461 5.5.1 Electromigration ......................................................................................... 461 5.5.2 Diffusion ...................................................................................................... 462 5.5.3 Hall Effect .................................................................................................... 462 Physical Properties of Semiconductors .................................................................... 463 Industrial Applications and Uses .............................................................................. 463 Common Semiconductors.......................................................................................... 463 5.8.1 Silicon........................................................................................................... 463 5.8.2 Germanium.................................................................................................. 469 5.8.3 Boron............................................................................................................ 470 5.8.4 Other Semiconductors................................................................................ 471 Semiconductor Wafer Processing ............................................................................. 471 5.9.1 Monocrystal Growth................................................................................... 472 5.9.2 Wafer Production ....................................................................................... 473 The P-N Junction ........................................................................................................ 475 Further Reading .......................................................................................................... 475

6

Superconductors ....................................................................................................................... 477 6.1 Description and General Properties.......................................................................... 477 6.2 Superconductor Types................................................................................................ 478 6.2.1 Type I Superconductors ............................................................................. 478 6.2.2 Type II Superconductors............................................................................ 480 6.2.3 High-critical-temperature Superconductors ........................................... 481 6.2.4 Organic Superconductors .......................................................................... 482 6.3 Basic Theory ................................................................................................................ 482 6.4 Meissner–Ochsenfeld Effect....................................................................................... 483 6.5 History.......................................................................................................................... 483 6.6 Industrial Applications and Uses .............................................................................. 485 6.7 Further Reading .......................................................................................................... 485

7

Magnetic Materials.................................................................................................................... 487 7.1 Magnetic Physical Quantities..................................................................................... 487 7.1.1 Magnetic Field Strength and Magnetomotive Force ............................... 487 7.1.2 Magnetic Flux Density and Magnetic Induction...................................... 488 7.1.3 Magnetic Flux.............................................................................................. 489 7.1.4 Magnetic Dipole Moment .......................................................................... 490 7.1.5 Magnetizability, Magnetization, and Magnetic Susceptibility ............... 491 7.1.6 Magnetic Force Exerted on a Material ...................................................... 492 7.1.7 Magnetic Force Exerted by Magnets ......................................................... 493 7.1.8 Magnetic Energy Density Stored ............................................................... 493 7.1.9 Magnetoresistance ...................................................................................... 494 7.1.10 Magnetostriction......................................................................................... 494 7.1.11 Magnetocaloric Effect................................................................................. 495 7.1.12 SI and CGS Units Used in Electromagnetism........................................... 498 7.2 Classification of Magnetic Materials ......................................................................... 498 7.2.1 Diamagnetic Materials ............................................................................... 499 7.2.2 Paramagnetic Materials.............................................................................. 500 7.2.3 Ferromagnetic Materials ............................................................................ 501 7.2.4 Antiferromagnetic Materials ..................................................................... 503 7.2.5 Ferrimagnetic Materials ............................................................................. 504

Contents

7.3

7.4 7.5 8

Ferromagnetic Materials .............................................................................................504 7.3.1 B-H Magnetization Curve and Hysteresis Loop .......................................504 7.3.2 Eddy-Current Losses ...................................................................................506 7.3.3 Induction Heating .......................................................................................507 7.3.4 Soft Ferromagnetic Materials .....................................................................507 7.3.5 Hard Magnetic Materials ............................................................................510 7.3.6 Magnetic Shielding and Materials Selection .............................................512 Industrial Applications of Magnetic Materials .........................................................516 Further Reading ...........................................................................................................516

Insulators and Dielectrics........................................................................................................ 519 8.1 Physical Quantities of Dielectrics...............................................................................519 8.1.1 Permittivity of Vacuum...............................................................................519 8.1.2 Permittivity of a Medium............................................................................519 8.1.3 Relative Permittivity and Dielectric Constant ..........................................520 8.1.4 Capacitance ..................................................................................................520 8.1.5 Temperature Coefficient of Capacitance...................................................520 8.1.6 Charging and Discharging a Capacitor .....................................................521 8.1.7 Capacitance of a Parallel-Electrode Capacitor..........................................521 8.1.8 Capacitance of Other Capacitor Geometries.............................................521 8.1.9 Electrostatic Energy Stored in a Capacitor................................................522 8.1.10 Electric Field Strength .................................................................................522 8.1.11 Electric Flux Density ...................................................................................522 8.1.12 Microscopic Electric Dipole Moment ........................................................522 8.1.13 Polarizability ................................................................................................523 8.1.14 Macroscopic Electric Dipole Moment .......................................................523 8.1.15 Polarization ..................................................................................................523 8.1.16 Electric Susceptibility ..................................................................................524 8.1.17 Dielectric Breakdown Voltage....................................................................524 8.1.18 Dielectric Absorption ..................................................................................524 8.1.19 Dielectric Losses ..........................................................................................525 8.1.20 Loss Tangent or Dissipation Factor ...........................................................525 8.1.21 Dielectric Heating........................................................................................526 8.2 Physical Properties of Insulators................................................................................526 8.2.1 Insulation Resistance ..................................................................................526 8.2.2 Volume Electrical Resistivity......................................................................526 8.2.3 Temperature Coefficient of Electrical Resistivity.....................................527 8.2.4 Surface Electrical Resistivity.......................................................................528 8.2.5 Leakage Current...........................................................................................528 8.2.6 SI and CGS Units Used in Electricity .........................................................529 8.3 Dielectric Behavior ......................................................................................................530 8.3.1 Electronic Polarization................................................................................530 8.3.2 Ionic Polarization ........................................................................................531 8.3.3 Dipole Orientation.......................................................................................531 8.3.4 Space Charge Polarization ..........................................................................531 8.3.5 Effect of Frequency on Polarization ..........................................................531 8.3.6 Frequency Dependence of the Dielectric Losses.......................................532 8.4 Dielectric Breakdown Mechanisms............................................................................532 8.4.1 Electronic Breakdown or Corona Mechanism..........................................533 8.4.2 Thermal Discharge or Thermal Mechanism .............................................533 8.4.3 Internal Discharge or Intrinsic Mechanism..............................................533

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8.5 8.6 8.7 8.8 8.9 8.10 8.11 9

Electrostriction............................................................................................................ 533 Piezoelectricity ............................................................................................................ 534 Ferroelectrics ............................................................................................................... 534 Aging of Ferroelectrics ............................................................................................... 538 Classification of Industrial Dielectrics...................................................................... 538 8.9.1 Class I Dielectrics or Linear Dielectrics .................................................... 538 8.9.2 Class II Dielectrics or Ferroelectrics ......................................................... 539 Selected Properties of Insulators and Dielectric Materials ..................................... 539 Further Reading .......................................................................................................... 542

Miscellaneous Electrical Materials ......................................................................................... 543 9.1 Thermocouple Materials ............................................................................................ 543 9.1.1 The Seebeck Effect ...................................................................................... 543 9.1.2 Thermocouple ............................................................................................. 544 9.1.3 Properties of Common Thermocouple Materials.................................... 545 9.2 Resistors and Thermistors ......................................................................................... 548 9.2.1 Electrical Resistivity.................................................................................... 548 9.2.2 Temperature Coefficient of Electrical Resistivity .................................... 548 9.3 Electron-emitting Materials ....................................................................................... 552 9.4 Photocathode Materials.............................................................................................. 553 9.5 Secondary Emission.................................................................................................... 554 9.6 Electrolytes .................................................................................................................. 555 9.7 Electrode Materials ..................................................................................................... 556 9.7.1 Electrode Materials for Batteries and Fuel Cells ...................................... 556 9.7.2 Intercalation Compounds .......................................................................... 559 9.7.3 Electrode Materials for Electrolytic Cells ................................................. 561 9.7.3.1 Industrial Cathode Materials................................................ 563 9.7.3.1.1 Low-Carbon Steel Cathodes.............................. 563 9.7.3.1.2 Aluminum Cathodes.......................................... 563 9.7.3.1.3 Titanium Cathodes ............................................ 564 9.7.3.1.4 Zirconium Cathodes .......................................... 565 9.7.3.1.5 Nickel Cathodes ................................................. 565 9.7.3.1.6 Mercury Cathode ............................................... 565 9.7.3.2 Industrial Anode Materials................................................... 565 9.7.3.2.1 Precious- and Noble-Metal Anodes ................. 568 9.7.3.2.2 Lead and Lead-Alloy Anodes............................ 569 9.7.3.2.3 Carbon Anodes................................................... 572 9.7.3.2.4 Lead Dioxide (PbO2) .......................................... 573 9.7.3.2.5 Manganese Dioxide (MnO2).............................. 575 9.7.3.2.6 Spinel (AB2O4)- and Perovskite (ABO3)-Type Oxides .......................................... 575 9.7.3.2.7 Ebonex®(Ti4O7 and Ti5O9) ................................. 576 9.7.3.2.8 Noble-Metal-Coated Titanium Anodes (NMCT)............................................................... 578 9.7.3.2.9 Platinized Titanium and Niobium Anodes (70/30 Pt/Ir) ........................................................ 579 9.7.3.2.10 Dimensionally Stable Anodes (DSA®) for Chlorine Evolution ...................................... 580 9.7.3.2.11 Dimensionally Stable Anodes (DSA®) for Oxygen .......................................................... 581 9.7.3.2.12 Synthetic Diamond Electrodes ......................... 585

Contents

9.7.4

9.8

Electrodes for Corrosion Protection and Control ....................................586 9.7.4.1 Cathodes for Anodic Protection ...........................................586 9.7.4.2 Anodes for Cathodic Protection............................................587 9.7.5 Electrode Suppliers and Manufacturers ....................................................589 Electrochemical Galvanic Series.................................................................................590

10 Ceramics, Refractories, and Glasses....................................................................................... 593 10.1 Introduction and Definitions .....................................................................................593 10.2 Raw Materials for Ceramics, Refractories and Glasses ............................................594 10.2.1 Silica..............................................................................................................594 10.2.1.1 Quartz, Quartzite, and Silica Sand ........................................595 10.2.1.2 Diatomite.................................................................................595 10.2.1.3 Fumed Silica............................................................................595 10.2.1.4 Silica Gels and Sol–Gel Silica.................................................595 10.2.1.5 Precipitated Silica ...................................................................595 10.2.1.6 Microsilica...............................................................................596 10.2.1.7 Vitreous or Amorphous Silica...............................................596 10.2.2 Aluminosilicates ..........................................................................................596 10.2.2.1 Fireclay ....................................................................................597 10.2.2.2 China Clay ...............................................................................598 10.2.2.3 Ball Clay...................................................................................598 10.2.2.4 Other Refractory Clays...........................................................599 10.2.2.5 Andalusite, Kyanite, and Sillimanite ....................................599 10.2.2.6 Mullite......................................................................................600 10.2.3 Bauxite and Aluminas .................................................................................600 10.2.3.1 Bauxite .....................................................................................600 10.2.3.2 Alumina Hydrates ..................................................................603 10.2.3.3 Transition Aluminas (TrA) ...................................................606 10.2.3.4 Calcined Alumina ...................................................................606 10.2.3.5 Tabular Alumina ....................................................................607 10.2.3.6 White Fused Alumina ............................................................608 10.2.3.7 Brown Fused Alumina ...........................................................608 10.2.3.8 Electrofused Alumina-Zirconia.............................................609 10.2.3.9 High-Purity Alumina .............................................................609 10.2.4 Limestone and Lime ....................................................................................610 10.2.5 Dolomite and Doloma.................................................................................610 10.2.5.1 Dolomite..................................................................................610 10.2.5.2 Calcined and Dead Burned Dolomite (Doloma) .................611 10.2.6 Magnesite and Magnesia.............................................................................612 10.2.6.1 Magnesite ................................................................................612 10.2.6.2 Caustic Seawater and Calcined Magnesia ............................612 10.2.6.3 Dead Burned Magnesia ..........................................................613 10.2.6.4 Electrofused Magnesia ...........................................................614 10.2.6.5 Seawater Magnesia Clinker....................................................614 10.2.7 Titania...........................................................................................................614 10.2.7.1 Rutile........................................................................................614 10.2.7.2 Anatase ....................................................................................616 10.2.7.3 Brookite ...................................................................................616 10.2.7.4 Anosovite.................................................................................616 10.2.7.5 Titanium Sesquioxide ............................................................617 10.2.7.6 Titanium Monoxide or Hongquiite ......................................617

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10.3 10.4

10.5

10.6 10.7 10.8

10.2.7.7 Titanium Hemioxide ............................................................. 618 10.2.7.8 Andersson–Magnéli Phases .................................................. 618 10.2.8 Zircon and Zirconia.................................................................................... 618 10.2.8.1 Zircon...................................................................................... 618 10.2.8.2 Zirconia................................................................................... 618 10.2.9 Carbon and Graphite .................................................................................. 623 10.2.9.1 Description and General Properties..................................... 623 10.2.9.2 Natural Occurrence and Mining .......................................... 623 10.2.9.3 Industrial Preparation and Processing ................................ 625 10.2.9.4 Industrial Applications and Uses......................................... 625 10.2.10 Silicon Carbide ............................................................................................ 625 10.2.10.1 Description and General Properties..................................... 625 10.2.10.2 Industrial Preparation........................................................... 626 10.2.10.3 Grades of Silicon Carbide...................................................... 628 10.2.11 Properties of Raw Materials Used in Ceramics, Refractories, and Glasses .................................................................................................. 628 Traditional Ceramics .................................................................................................. 629 Refractories.................................................................................................................. 630 10.4.1 Classification of Refractories ..................................................................... 630 10.4.2 Properties of Refractories .......................................................................... 631 10.4.3 Major Refractory Manufacturers............................................................... 634 Advanced Ceramics .................................................................................................... 635 10.5.1 Silicon Nitride ............................................................................................. 635 10.5.1.1 Description and General Properties..................................... 635 10.5.1.2 Industrial Preparation and Grades ...................................... 635 10.5.2 Silicon Aluminum Oxynitride (SiAlON) .................................................. 636 10.5.3 Boron Carbide ............................................................................................. 637 10.5.3.1 Description and General Properties..................................... 637 10.5.3.2 Industrial Preparation........................................................... 637 10.5.3.3 Industrial Applications and Uses......................................... 637 10.5.4 Boron Nitride .............................................................................................. 637 10.5.4.1 Description and General Properties..................................... 637 10.5.4.2 Industrial Preparation........................................................... 638 10.5.4.3 Industrial Applications and Uses......................................... 638 10.5.5 Titanium Diboride ...................................................................................... 638 10.5.5.1 Description and General Properties..................................... 638 10.5.5.2 Industrial Preparation and Processing ................................ 639 10.5.5.3 Industrial Applications and Uses......................................... 639 10.5.6 Tungsten Carbides and Hardmetal ........................................................... 639 10.5.6.1 Description and General Properties..................................... 639 10.5.6.2 Industrial Preparation........................................................... 640 10.5.6.3 Industrial Applications and Uses......................................... 640 10.5.7 Practical Data for Ceramists and Refractory Engineers.......................... 641 10.5.7.1 Temperature of Color............................................................ 641 10.5.7.2 Pyrometric Cone Equivalents ............................................... 641 Standards for Testing Refractories............................................................................ 643 Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides).................................................................................................................. 647 Further Reading .......................................................................................................... 670 10.8.1 Traditional and Advanced Ceramics ........................................................ 670 10.8.2 Refractories.................................................................................................. 670

Contents

10.9

Glasses...........................................................................................................................671 10.9.1 Definitions....................................................................................................671 10.9.2 Physical Properties of Glasses ....................................................................671 10.9.3 Glassmaking Processes................................................................................671 10.9.4 Further Reading...........................................................................................676 10.10 Proppants .....................................................................................................................677 10.10.1 Fracturing Techniques in Oil-Well Production........................................677 10.10.1.1 Hydraulic Fracturing..............................................................677 10.10.1.2 Pressure Acidizing..................................................................678 10.10.2 Proppant and Frac Fluid Selection Criteria ..............................................678 10.10.2.1 Proppant Materials.................................................................678 10.10.2.2 Frac Fluids...............................................................................679 10.10.2.3 Properties and Characterization of Proppants ....................679 10.10.2.4 Classification of Proppant Materials ....................................679 10.10.2.5 Production of Synthetic Proppants ......................................682 10.10.2.6 Properties of Commercial Proppants ...................................683 10.10.2.7 Proppant Market ....................................................................687 10.10.2.8 Proppant Producers ...............................................................687 10.10.3 Further Reading...........................................................................................689

11 Polymers and Elastomers ........................................................................................................ 691 11.1 Fundamentals and Definitions ...................................................................................691 11.1.1 Definitions....................................................................................................691 11.1.2 Additives and Fillers....................................................................................692 11.1.3 Polymerization and Polycondensation......................................................693 11.2 Properties and Characteristics of Polymers ..............................................................694 11.2.1 Molar Mass and Relative Molar Mass........................................................694 11.2.2 Average Degree of Polymerization ............................................................695 11.2.3 Number-, Mass- and Z-Average Molar Masses ........................................695 11.2.4 Glass Transition Temperature....................................................................697 11.2.5 Structure of Polymers..................................................................................697 11.3 Classification of Plastics and Elastomers ..................................................................697 11.4 Thermoplastics.............................................................................................................697 11.4.1 Naturally Occurring Resins ........................................................................697 11.4.1.1 Rosin ........................................................................................697 11.4.1.2 Shellac......................................................................................699 11.4.2 Cellulosics.....................................................................................................699 11.4.2.1 Cellulose Nitrate .....................................................................699 11.4.2.2 Cellulose Acetate (CA) ...........................................................700 11.4.2.3 Cellulose Propionate (CP) .....................................................700 11.4.2.4 Cellulose Xanthate..................................................................700 11.4.2.5 Alkylcelluloses ........................................................................701 11.4.3 Casein Plastics..............................................................................................701 11.4.4 Coumarone-Indene Plastics .......................................................................702 11.4.5 Polyolefins or Ethenic Polymers ................................................................702 11.4.5.1 Polyethylene (PE) ...................................................................702 11.4.5.2 Polypropylene (PP) ................................................................703 11.4.5.3 Polybutylene (PB)...................................................................704 11.4.6 Polymethylpentene (PMP)..........................................................................704

xxv

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11.4.7

11.5

11.6

11.7 11.8

Polyvinyl Plastics ........................................................................................ 704 11.4.7.1 Polyvinyl Chlorides (PVCs) .................................................. 704 11.4.7.2 Chlorinated Polyvinylchloride (CPVC) ............................... 705 11.4.7.3 Polyvinyl Fluoride (PVF) ...................................................... 705 11.4.7.4 Polyvinyl Acetate (PVA) ....................................................... 705 11.4.8 Polyvinylidene Plastics ............................................................................... 705 11.4.8.1 Polyvinylidene Chloride (PVDC) ......................................... 705 11.4.8.2 Polyvinylidene Fluoride (PVDF).......................................... 706 11.4.9 Styrenics....................................................................................................... 706 11.4.9.1 Polystyrene (PS)..................................................................... 706 11.4.9.2 Acrylonitrile Butadiene Styrene (ABS) ................................ 706 11.4.10 Fluorinated Polyolefins (Fluorocarbons) ................................................. 707 11.4.10.1 Polytetrafluoroethylene (PTFE) ........................................... 707 11.4.10.2 Fluorinated Ethylene Propylene (FEP) ................................ 708 11.4.10.3 Perfluorinated Alkoxy (PFA)................................................ 708 11.4.10.4 Polychlorotrifluoroethylene (PCTFE) ................................. 708 11.4.10.5 Ethylene-Chlorotrifluoroethylene Copolymer (ECTFE).... 709 11.4.10.6 Ethylene-Tetrafluoroethylene Copolymer (ETFE) ............. 709 11.4.11 Acrylics and Polymethyl Methacrylate (PMMA) ..................................... 709 11.4.12 Polyamides (PA) ......................................................................................... 710 11.4.13 Polyaramides (PAR) ................................................................................... 710 11.4.14 Polyimides (PI)............................................................................................ 710 11.4.15 Polyacetals (PAc) ........................................................................................ 711 11.4.16 Polycarbonates (PC) ................................................................................... 711 11.4.17 Polysulfone (PSU)....................................................................................... 711 11.4.18 Polyphenylene Oxide (PPO) ...................................................................... 712 11.4.19 Polyphenylene Sulfide (PPS)...................................................................... 712 11.4.20 Polybutylene Terephthalate (PBT)............................................................ 712 11.4.21 Polyethylene Terephthalate (PET) ............................................................ 712 11.4.22 Polydiallyl Phthalate (PDP) ....................................................................... 713 Thermosets .................................................................................................................. 713 11.5.1 Aminoplastics.............................................................................................. 713 11.5.2 Phenolics...................................................................................................... 714 11.5.3 Acrylonitrile-Butadiene-Styrene (ABS) .................................................... 714 11.5.4 Polyurethanes (PUR).................................................................................. 715 11.5.5 Furan Plastics .............................................................................................. 715 11.5.6 Epoxy Resins (EP)....................................................................................... 715 Rubbers and Elastomers............................................................................................. 715 11.6.1 Natural Rubber (NR) .................................................................................. 716 11.6.2 Trans-Polyisoprene Rubber (PIR) ............................................................ 716 11.6.3 Polybutadiene Rubber (BR) ....................................................................... 716 11.6.4 Styrene Butadiene Rubber (SBR) .............................................................. 717 11.6.5 Nitrile Rubber (NR) .................................................................................... 717 11.6.6 Butyl Rubber (IIR) ...................................................................................... 717 11.6.7 Chloroprene Rubber (CPR) ....................................................................... 717 11.6.8 Chlorosulfonated Polyethylene (CSM) ..................................................... 718 11.6.9 Polysulfide Rubber (PSR)........................................................................... 718 11.6.10 Ethylene Propylene Rubbers...................................................................... 718 11.6.11 Silicone Rubber ........................................................................................... 719 11.6.12 Fluoroelastomers ........................................................................................ 719 Physical Properties of Polymers ................................................................................ 720 Gas Permeability of Polymers.................................................................................... 734

Contents

11.9 Chemical Resistance of Polymers...............................................................................734 11.10 IUPAC Acronyms of Polymers and Elastomers........................................................745 11.11 Economic Data on Polymers and Related Chemical Intermediates .......................746 11.11.1 Average Prices of Polymers ........................................................................746 11.11.2 Production Capacities, Prices and Major Producers of Polymers and Chemical Intermediates.......................................................................747 11.12 Further Reading ...........................................................................................................750 12 Minerals, Ores and Gemstones ............................................................................................... 751 12.1 Definitions ....................................................................................................................751 12.2 Mineralogical, Physical and Chemical Properties ....................................................756 12.2.1 Mineral Names.............................................................................................756 12.2.2 Chemical Formula and Theoretical Chemical Composition ...................757 12.2.3 Crystallographic Properties ........................................................................757 12.2.4 Habit or Crystal Form .................................................................................758 12.2.5 Color .............................................................................................................759 12.2.6 Diaphaneity or Transmission of Light.......................................................760 12.2.7 Luster ............................................................................................................760 12.2.8 Cleavage and Parting...................................................................................760 12.2.9 Fracture ........................................................................................................761 12.2.10 Streak ............................................................................................................761 12.2.11 Tenacity ........................................................................................................761 12.2.12 Density and Specific Gravity ......................................................................762 12.2.13 Mohs Hardness ............................................................................................762 12.2.14 Optical Properties........................................................................................765 12.2.15 Static Electricity and Magnetism................................................................766 12.2.16 Luminescence...............................................................................................766 12.2.17 Piezoelectricity and Pyroelectricity ...........................................................766 12.2.18 Play of Colors and Chatoyancy ..................................................................767 12.2.19 Radioactivity ................................................................................................767 12.2.20 Miscellaneous Properties ............................................................................767 12.2.21 Chemical Reactivity.....................................................................................767 12.2.22 Pyrognostic Tests or Fire Assays................................................................768 12.2.22.1 The Flame Test........................................................................768 12.2.22.2 The Fusibility Test ..................................................................770 12.2.22.3 The Reduction on Charcoal...................................................771 12.2.22.4 Tests with Cobalt Nitrate and Sulfur Iodide ........................771 12.2.22.5 The Closed Tube Test.............................................................772 12.2.22.6 The Open Tube Test ...............................................................774 12.2.22.7 The Bead Tests ........................................................................775 12.2.23 Heavy-Media or Sink-float Separations in Mineralogy ...........................776 12.2.23.1 Selection of Dense Media.......................................................777 12.2.23.2 Common Heavy Liquids Used in Mineralogy .....................777 12.3 Strunz Classification of Minerals ...............................................................................777 12.4 Dana’s Classification of Minerals...............................................................................779 12.5 Gemstones ....................................................................................................................781 12.5.1 Diamond.......................................................................................................783 12.5.1.1 Introduction............................................................................783 12.5.1.2 Diamond Types.......................................................................784 12.5.1.3 Diamond Physical and Chemical Properties .......................784 12.5.1.4 Diamond: Origins and Occurrence.......................................786

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12.6 12.7 12.8 12.9

12.5.1.5 Industrial Applications ......................................................... 787 12.5.1.6 Diamond Prices...................................................................... 788 12.5.1.7 Treatments ............................................................................. 788 12.5.1.8 Diamond Shaping and Valuation......................................... 788 12.5.2 Beryl Gem Varieties .................................................................................... 789 12.5.2.1 Emerald................................................................................... 790 12.5.2.2 Aquamarine............................................................................ 791 12.5.2.3 Morganite ............................................................................... 792 12.5.2.4 Heliodor.................................................................................. 792 12.5.2.5 Goshenite................................................................................ 792 12.5.3 Corundum Gem Varieties .......................................................................... 792 12.5.3.1 Ruby ........................................................................................ 794 12.5.3.2 Sapphire.................................................................................. 794 12.5.4 Synthetic Gemstones .................................................................................. 795 12.5.4.1 Synthesis from Melts ............................................................. 795 12.5.4.2 Synthesis from Solutions ...................................................... 796 12.5.4.3 Diamond Synthesis................................................................ 797 IMA Acronyms of Rock-forming Minerals .............................................................. 798 Mineral and Gemstone Properties Table .................................................................. 800 Mineral Synonyms ...................................................................................................... 868 Further Reading .......................................................................................................... 878 12.9.1 Crystallography........................................................................................... 878 12.9.2 Optical Mineralogy ..................................................................................... 879 12.9.3 Mineralogy................................................................................................... 880 12.9.4 Industrial Minerals ..................................................................................... 881 12.9.5 Ores .............................................................................................................. 881 12.9.6 Gemstones ................................................................................................... 882 12.9.7 Heavy Liquids and Mineral Dressing........................................................ 883

13 Rocks and Meteorites ............................................................................................................... 885 13.1 Introduction ................................................................................................................ 885 13.2 Structure of the Earth’s Interior ................................................................................ 886 13.3 Different Type of Rocks.............................................................................................. 889 13.4 Igneous Rocks ............................................................................................................. 890 13.4.1 Classification of Igneous Rocks................................................................. 891 13.4.1.1 Crystals Morphology and Dimensions ................................ 892 13.4.1.2 Mineralogy.............................................................................. 892 13.4.1.3 Coloration............................................................................... 894 13.4.2 Texture of Igneous Rocks........................................................................... 895 13.4.3 Chemistry of Igneous Rocks ...................................................................... 896 13.4.4 General Classification of Igneous Rocks .................................................. 899 13.4.5 Vesicular and Pyroclastic Igneous Rocks ................................................. 904 13.5 Sedimentary Rocks ..................................................................................................... 904 13.5.1 Sediments .................................................................................................... 906 13.5.2 Residual Sedimentary Rocks...................................................................... 906 13.5.3 Detritic or Clastic Sedimentary Rocks ...................................................... 907 13.5.4 Chemical Sedimentary Rocks .................................................................... 908 13.5.5 Biogenic Sedimentary Rocks ..................................................................... 909 13.5.6 Chemical Composition............................................................................... 910

Contents

13.6

Metamorphic Rocks ....................................................................................................910 13.6.1 Classification of Metamorphic Rocks........................................................911 13.6.2 Metamorphic Grade ....................................................................................911 13.6.3 Metamorphic Facies ....................................................................................912 13.7 Ice ..................................................................................................................................912 13.8 Meteorites .....................................................................................................................914 13.8.1 Definitions....................................................................................................914 13.8.2 Modern Classification of Meteorites..........................................................914 13.8.3 Tektites, Impactites, and Fulgurites ..........................................................920 13.9 Properties of Common Rocks.....................................................................................921 13.10 Further Reading ...........................................................................................................925 14 Soils and Fertilizers .................................................................................................................. 927 14.1 Introduction .................................................................................................................927 14.2 History ..........................................................................................................................928 14.3 Pedogenesis ..................................................................................................................929 14.3.1 Weathering and Alteration of Minerals and Clays Formation................929 14.3.2 Incorporation of Organic Matter ...............................................................929 14.3.3 Mass Transfer between Horizons...............................................................930 14.3.3.1 Descending Processes ............................................................930 14.3.3.2 Ascending Processes ..............................................................931 14.4 Soil Morphology...........................................................................................................931 14.4.1 Major Horizons............................................................................................931 14.4.2 Transitional Horizons .................................................................................931 14.4.3 Subdivisions of Master Horizons ...............................................................932 14.5 Soil Properties ..............................................................................................................936 14.5.1 Horizon Boundaries ....................................................................................936 14.5.2 Coloration of Soils .......................................................................................936 14.5.2 Soil Texture ..................................................................................................938 14.5.4 Soil Structure................................................................................................941 14.5.5 Consistency ..................................................................................................944 14.5.6 Roots .............................................................................................................945 14.5.7 Acidity (pH) and Effervescence..................................................................945 14.6 Soil Taxonomy .............................................................................................................945 14.6.1 USDA Classification of Soils.......................................................................945 14.6.2 FAO Classification of Soils..........................................................................948 14.6.3 French Classification of Soils......................................................................954 14.6.4 ASTM Civil Engineering Classification of Soils........................................956 14.7 Soil Identification ........................................................................................................957 14.8 ISO and ASTM Standards ...........................................................................................958 14.9 Physical Properties of Common Soils........................................................................961 14.10 Fertilizers ......................................................................................................................961 14.10.1 Nitrogen Fertilizers .....................................................................................962 14.10.2 Phosphorus Fertilizers ................................................................................963 14.10.3 Potassium Fertilizers ...................................................................................964 14.10.4 Role of Micronutrients in Soils ..................................................................965 14.11 Further Reading ...........................................................................................................966 15 Cements, Concrete, Building Stones and Construction Materials .................................... 967 15.1 Introduction .................................................................................................................967 15.1.1 Nonhydraulic Cements ...............................................................................968

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15.2

15.3 15.4 15.5 15.6 15.7

15.8

Portland Cement ......................................................................................................... 968 15.2.1 History ......................................................................................................... 969 15.2.2 Raw Materials for Portland Cement.......................................................... 969 15.2.3 Processing of Portland Cement ................................................................. 970 15.2.4 Portland Cement Chemistry ...................................................................... 971 15.2.5 Portland Cement Nomenclature ............................................................... 973 Aggregates.................................................................................................................... 974 15.3.1 Coarse Aggregates....................................................................................... 975 15.3.2 Fine Aggregates ........................................................................................... 976 Mineral Admixtures.................................................................................................... 976 Mortars and Concrete................................................................................................. 976 15.5.1 Definitions ................................................................................................... 976 15.5.2 Degradation Processes ............................................................................... 977 Ceramics for Construction......................................................................................... 978 Building Stones............................................................................................................ 979 15.7.1 Limestones and Dolomites......................................................................... 979 15.7.2 Sandstones................................................................................................... 979 15.7.3 Basalt ............................................................................................................ 979 15.7.4 Granite ......................................................................................................... 979 Further Reading .......................................................................................................... 981

16 Timbers and Woods.................................................................................................................. 983 16.1 General Description .................................................................................................... 983 16.2 Properties of Woods ................................................................................................... 985 16.2.1 Moisture Content ........................................................................................ 985 16.2.2 Specific Gravity and Density...................................................................... 986 16.2.3 Drying and Shrinkage................................................................................. 987 16.2.4 Mechanical Properties ................................................................................ 987 16.2.5 Thermal Properties ..................................................................................... 988 16.2.6 Electrical Properties.................................................................................... 989 16.2.7 Heating Values and Flammability............................................................. 989 16.2.8 Durability and Decay Resistance............................................................... 990 16.3 Properties of Hardwoods and Softwoods ................................................................. 990 16.4 Applications................................................................................................................. 997 16.5 Wood Performance in Various Corrosives............................................................... 997 16.6 Further Reading .......................................................................................................... 998 17 Fuels, Propellants and Explosives........................................................................................... 999 17.1 Introduction and Classification................................................................................. 999 17.2 Combustion Characteristics....................................................................................... 999 17.2.1 Enthalpy of Combustion ............................................................................ 999 17.2.1.1 Stoichiometric Combustion Ratios .................................... 1001 17.2.1.2 Low (Net) and High (Gross) Heating Values .................... 1001 17.2.1.3 Air Excess ............................................................................. 1002 17.2.1.4 Dulong’s Equations and Other Practical Equations ......... 1002 17.2.1.5 Adiabatic Flame Temperature............................................ 1003 17.2.1.6 Wobbe Index for Gaseous Fuels......................................... 1003 17.3 Solid Fuels: Coals and Cokes.................................................................................... 1004 17.4 Liquid Fuels ............................................................................................................... 1008 17.5 Gaseous Fuels ............................................................................................................ 1009

Contents

17.6 17.7

17.8 17.9

Prices of Common Fuels ...........................................................................................1011 Propellants..................................................................................................................1011 17.7.1 Liquid Propellants .....................................................................................1011 17.7.1.1 Petroleum-based Propellants ..............................................1012 17.7.1.2 Cryogenic Propellants..........................................................1012 17.7.1.3 Hypergolic Propellants ........................................................1012 17.7.2 Solid Propellants........................................................................................1014 Explosives ...................................................................................................................1015 Further Reading .........................................................................................................1018 17.9.1 Fuels and Combustion ..............................................................................1018 17.9.2 Propellants and Explosives .......................................................................1018

18 Composite Materials............................................................................................................... 1019 18.1 Definitions ..................................................................................................................1019 18.2 Properties of Composites..........................................................................................1021 18.2.1 Density........................................................................................................1021 18.2.2 Tensile Strength and Elastic Moduli ........................................................1022 18.2.3 Specific Heat Capacity...............................................................................1023 18.2.4 Thermal Conductivity ...............................................................................1023 18.2.5 Thermal Expansion Coefficient................................................................1024 18.3 Fabrication Processes for Monofilaments...............................................................1024 18.4 Reinforcement Materials...........................................................................................1025 18.4.1 Glass Fibers ................................................................................................1025 18.4.2 Boron Fibers...............................................................................................1025 18.4.3 Carbon Fibers.............................................................................................1026 18.4.4 Polyethylene Fibers ...................................................................................1027 18.4.5 Polyaramide Fibers....................................................................................1027 18.4.6 Ceramic Oxide Fibers ................................................................................1028 18.4.7 Silicon Carbide Fibers ...............................................................................1028 18.5 Polymer Matrix Composites (PMCs) .......................................................................1029 18.6 Metal Matrix Composites (MMCs) ..........................................................................1031 18.7 Ceramic Matrix Composites (CMCs).......................................................................1033 18.8 Carbon–Carbon Composites (CCs) .........................................................................1034 18.9 Further Reading .........................................................................................................1035 19 Gases ......................................................................................................................................... 1037 19.1 Properties of Gases ....................................................................................................1037 19.1.1 Pressure ......................................................................................................1037 19.1.2 The Boyle–Mariotte Law ...........................................................................1039 19.1.3 Charles and Gay-Lussac’s Law .................................................................1040 19.1.4 The Avogadro–Ampere Law.....................................................................1040 19.1.5 Normal and Standard Conditions............................................................1040 19.1.6 Equation of State of Ideal Gases ...............................................................1041 19.1.7 Dalton’s Law of Partial Pressure ..............................................................1041 19.1.8 Equations of State of Real Gases ..............................................................1042 19.1.8.1 Van der Waals Equation of State ........................................1042 19.1.8.2 Virial Equation of State........................................................1043 19.1.9 Density and Specific Gravity of Gases .....................................................1044 19.1.10 Barometric Equation .................................................................................1045 19.1.11 Isobaric Coefficient of Cubic Expansion .................................................1046

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19.1.12 19.1.13 19.1.14 19.1.15 19.1.16 19.1.17 19.1.18 19.1.19 19.1.20 19.1.21 19.1.22 19.1.23

19.2 19.3

19.4

Compressibility Factor ............................................................................. 1046 Isotherms of Real Gases and Critical Constants .................................... 1046 Critical Parameters ................................................................................... 1047 The Principle of Corresponding States ................................................... 1048 Microscopic Properties of Gas Molecules............................................... 1048 Molar and Specific Heat Capacities......................................................... 1049 Dynamic and Kinematic Viscosities ....................................................... 1049 Solubility of Gases in Liquids .................................................................. 1050 Gas Permeability of Polymers.................................................................. 1051 Dielectric Properties of Gases, Permittivity and Breakdown Voltage . 1052 Psychrometry and Hygrometry ............................................................... 1054 Vapor Pressure.......................................................................................... 1054 19.1.23.1 Absolute Humidity or Humidity Ratio.............................. 1054 19.1.23.2 Mass Fraction of Water Vapor or Specific Humidity....... 1056 19.1.23.3 Relative Humidity................................................................ 1056 19.1.23.4 Humid Heat.......................................................................... 1056 19.1.23.5 Humid or Specific Volume ................................................. 1056 19.1.23.6 Dry-Bulb Temperature........................................................ 1057 19.1.23.7 Wet-Bulb Temperature ....................................................... 1057 19.1.23.8 Wet-Bulb Depression .......................................................... 1057 19.1.23.9 Dew Point Temperature ...................................................... 1057 19.1.23.10 Specific Enthalpy ................................................................. 1057 19.1.23.11 Latent Heat of Fusion .......................................................... 1057 19.1.23.12 Latent Heat of Vaporization ............................................... 1058 19.1.23.13 Refractivity of Moist Air...................................................... 1058 19.1.23.14 Psychrometric Charts .......................................................... 1058 19.1.23.15 Psychrometric Equations .................................................... 1058 19.1.24 Flammability of Gases and Vapors ......................................................... 1062 19.1.24.1 Flammability Limits ............................................................ 1062 19.1.24.2 Explosive Limits................................................................... 1062 19.1.24.3 Autoignition Temperature.................................................. 1063 19.1.24.4 Ignition Energy .................................................................... 1063 19.1.24.5 Maximum Explosion Pressure............................................ 1063 19.1.24.6 Maximum Rate of Pressure Rise ........................................ 1063 19.1.24.7 High and Low Heating Values............................................ 1063 19.1.25 Toxicity of Gases and Threshold Limit Averages .................................. 1064 Physico–Chemical Properties of Major Gases........................................................ 1064 Monographies on Major Industrial Gases .............................................................. 1074 19.3.1 Air............................................................................................................... 1074 19.3.2 Nitrogen ..................................................................................................... 1075 19.3.3 Oxygen ....................................................................................................... 1076 19.3.4 Hydrogen ................................................................................................... 1078 19.3.5 Methane ..................................................................................................... 1086 19.3.6 Carbon Monoxide ..................................................................................... 1087 19.3.7 Carbon Dioxide ......................................................................................... 1089 19.3.8 Helium and Noble Gases .......................................................................... 1090 19.3.8.1 Neon...................................................................................... 1091 19.3.8.2 Argon .................................................................................... 1092 19.3.8.3 Krypton................................................................................. 1092 19.3.8.4 Xenon.................................................................................... 1092 19.3.8.5 Radon.................................................................................... 1092 Halocarbons............................................................................................................... 1093

Contents

19.5 19.6

19.7 19.8

Hydrates of Gases and Clathrates.............................................................................1094 Materials for Drying and Purifying Gases ...............................................................1095 19.6.1 Drying Agents and Dessicants..................................................................1095 19.6.2 Molecular Sieves ........................................................................................1095 19.6.3 Getters and Scavengers .............................................................................1099 Producers and Manufacturers of Major Industrial Gases......................................1100 Further Reading .........................................................................................................1101

20 Liquids ...................................................................................................................................... 1103 20.1 Properties of Liquids .................................................................................................1103 20.1.1 Density and Specific Gravity ....................................................................1103 20.1.2 Hydrometer Scales.....................................................................................1104 20.1.3 Dynamic and Kinematic Viscosities ........................................................1104 20.1.3.1 Shear Stress ...........................................................................1105 20.1.3.2 Shear Rate..............................................................................1105 20.1.3.3 Absolute or Dynamic Viscosity...........................................1105 20.1.3.4 Kinematic Viscosity..............................................................1105 20.1.3.5 Temperature Dependence of the Dynamic Viscosity .......1106 20.1.4 Classification of Fluids ..............................................................................1106 20.1.5 The Hagen–Poiseuille Equation and Pressure Losses............................1106 20.1.5.1 Pressure Drop .......................................................................1106 20.1.5.2 Friction Losses ......................................................................1106 20.1.6 Sedimentation and Free settling...............................................................1109 20.1.7 Vapor Pressure...........................................................................................1110 20.1.8 Surface Tension, Wetting and Capillarity ...............................................1110 20.1.8.1 Surface Tension ....................................................................1110 20.1.8.2 Temperature Dependence and Order of Magnitude of Surface Tension ................................................................1112 20.1.8.3 Parachor and Walden’s Rule ...............................................1113 20.1.8.4 Wetting ..................................................................................1113 20.1.8.5 Contact Angle .......................................................................1113 20.1.8.6 Young’s Equation .................................................................1113 20.1.8.7 Work of Cohesion, Work of Adhesion and Spreading Coefficient .............................................................................1114 20.1.8.8 Two Liquids and a Solid.......................................................1115 20.1.8.9 Antonoff’s Rule.....................................................................1116 20.1.8.10 Capillarity and the Young–Laplace Equation....................1116 20.1.8.11 Jurin’s Law.............................................................................1116 20.1.8.12 Measurements of Surface Tension......................................1117 20.1.9 Colligative Properties of Nonvolatile Solutes .........................................1118 20.1.9.1 Raoult’s Law for Boiling Point Elevation ...........................1118 20.1.9.2 Raoult’s Law and Freezing Point Depression ....................1119 20.1.9.3 Van’t Hoff Law for Osmotic Pressure.................................1120 20.1.10 Flammability of Liquids............................................................................1121 20.2 Properties of Most Common Liquids ......................................................................1121 20.3 Monographies on Liquids .........................................................................................1121 20.3.1 Properties of Water and Heavy Water.....................................................1121 20.3.2 Properties of Liquid Acids and Bases ......................................................1168 20.3.3 Properties of Heavy Liquids (Heavy Media)...........................................1171 20.3.3.1 Dense Halogenated Organic Solvents.................................1171 20.3.3.2 Dense Aqueous Solutions of Inorganic Salts .....................1172

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20.4 20.5 20.6 20.7 20.8

20.3.3.3 Low Temperature of Molten Inorganic Salts .................... 1174 20.3.3.4 Dense Emulsions and Suspensions .................................... 1174 20.3.3.5 Paramagnetic Liquid Oxygen ............................................. 1175 Properties of Liquid Metals...................................................................................... 1175 Properties of Molten Salts ........................................................................................ 1177 Properties of Heat Transfer Fluids .......................................................................... 1178 Colloidal and Dispersed Systems............................................................................. 1180 Further Reading ........................................................................................................ 1180

A Background Data for the Chemical Elements..................................................................... 1181 A.1 Periodic Chart of the Elements ................................................................................ 1181 A.2 Historical Names of the Chemical Elements .......................................................... 1181 A.3 UNS Standard Alphabetical Designation................................................................ 1181 A.4 Names of Transfermium Elements 101–110........................................................... 1184 A.5 Selected Physical Properties of the Elements ......................................................... 1185 A.6 Geochemical Classification of the Elements........................................................... 1185 B NIST Thermochemical Data for Pure Substances .............................................................. 1195 C Natural Radioactivity and Radionuclides ........................................................................... 1201 C.1 Introduction .............................................................................................................. 1201 C.2 Mononuclidic Elements............................................................................................ 1202 C.3 Nuclear Decay Series................................................................................................. 1202 C.4 Non-Series Primordial Radionuclides .................................................................... 1205 C.5 Cosmogenic Radionuclides...................................................................................... 1206 C.6 NORM and TENORM ............................................................................................... 1206 C.7 Activity Calculations................................................................................................. 1207 C.7.1 Activity of a Material Containing One Natural Radionuclide .............. 1207 C.7.2 Activity of a Material Containing Natural U and Th............................. 1207 D Crystallography and Crystallochemistry............................................................................. 1209 D.1 Direct Space Lattice Parameters .............................................................................. 1209 D.2 Symmetry Elements .................................................................................................. 1210 D.3 The Seven Crystal Systems ....................................................................................... 1211 D.4 Conversion of a Rhombohedral to a Hexagonal Lattice ....................................... 1211 D.5 The 14 Bravais Space Lattices .................................................................................. 1211 D.6 Characteristics of Close-Packed Arrangements..................................................... 1211 D.7 The 32 Classes of Symmetry..................................................................................... 1212 D.8 Strukturbericht Structures ....................................................................................... 1215 D.9 The 230 Space Groups............................................................................................... 1221 D.10 Crystallographic Calculations.................................................................................. 1228 D.10.1 Theoretical Crystal Density...................................................................... 1228 D.10.2 Lattice Point and Vector Position ........................................................... 1228 D.10.3 Scalar Product ........................................................................................... 1228 D.10.4 Vector or Cross Product........................................................................... 1228 D.10.5 Mixed Product and Cell Multiplicity....................................................... 1229 D.10.6 Unit Cell Volume ...................................................................................... 1230 D.10.7 Plane Angle between Lattice Planes ........................................................ 1230 D.11 Interplanar Spacing .................................................................................................. 1231 D.12 Reciprocal Lattice Unit Cell ..................................................................................... 1232

Contents

E Transparent Materials for Optical Windows...................................................................... 1233 F Corrosion Resistance of Materials Towards Various Corrosive Media.......................... 1237 G Economic Data for Metals, Industrial Minerals and Electricity ...................................... 1245 G.1 Prices of Pure Elements.............................................................................................1245 G.2 World Annual Production of Commodities............................................................1248 G.3 Economic Data for Industrial Minerals ...................................................................1249 G.4 Prices of Electricity in Various Countries ...............................................................1254 H Geological Time Scale............................................................................................................. 1255 I

Materials Societies .................................................................................................................. 1257

Bibliography................................................................................................................................... 1269 1 General Desk References...........................................................................................1269 1.1 Scientific and Technical Writing..............................................................1269 1.2 Chemicals ...................................................................................................1270 1.3 Plant Cost Estimation and Process Economics ......................................1270 1.4 Thermodynamic Tables ............................................................................1271 1.5 Phase Diagrams..........................................................................................1271 2 Dictionaries and Encyclopedias ...............................................................................1272 3 Comprehensive Series in Material Sciences ............................................................1272 Index................................................................................................................................................ 1277

xxxv

Introduction

Despite the wide availability of several comprehensive series in materials sciences and metallurgy, it is difficult to find grouped properties either on metals and alloys, traditional and advanced ceramics, refractories, polymers and elastomers, composites, minerals and rocks, soils, woods, cement, and building materials in a single-volume source book. Actually, the purpose of this practical and concise reference book is to provide key scientific and technical materials properties and data to materials scientists, metallurgists, engineers, chemists, and physicists as well as to professors, technicians, and students working in a broad range of scientific and technical fields. The classes of materials described in this handbook are as follows: (i) (ii) (iii) (iv) (v) (vi)

metals and their alloys; semiconductors; superconductors; magnetic materials; dielectrics and insulators; miscellaneous electrical materials (e.g., resistors, thermocouples, and industrial electrode materials); (vii) ceramics, refractories, and glasses; (viii) polymers and elastomers; (ix) minerals, ores, and gemstones; (x) rocks and meteorites; (xi) soils and fertilizers; (xii) timbers and woods; (xiii) cement and concrete; (xiv) building materials; (xv) fuels, propellants, and explosives;

xxxviii

Introduction

(xvi) composites; (xvii) gases; (xviii) liquids. Particular emphasis is placed on the properties of the most common industrial materials in each class. The physical and chemical properties usually listed for each material are as follows: (i) (ii)

physical (e.g., density, viscosity, surface tension); mechanical (e.g., elastic moduli, Poisson’s ratio, yield and tensile strength, hardness, fracture toughness); (iii) thermal (e.g., melting and boiling point, thermal conductivity, specific heat capacity, coefficients of thermal expansion, spectral emissivities); (iv) electrical (e.g., resistivity, relative permittivity, loss tangent factor); (v) magnetic (e.g., magnetization, permeability, retentivity, coercivity, Hall constant); (vi) optical (e.g., refractive indices, reflective index, dispersion, transmittance); (vii) electrochemical (e.g., Nernst standard electrode potential, Tafel slopes, specific capacity, overpotential); (viii) miscellaneous (e.g., relative abundances, electron work function, thermal neutron cross section, Richardson constant, activity, corrosion rate, flammability limits). Finally, detailed appendices provide additional information (e.g., properties of the pure chemical elements, thermochemical data, crystallographic calculations, radioactivity calculations, prices of metals, industrial minerals and commodities), and an extensive bibliography completes this comprehensive guide. The comprehensive index and handy format of the book enable the reader to locate and extract the relevant information quickly and easily. Charts and tables are all referenced, and tabs are used to denote the different sections of the book. It must be emphasized that the information presented here is taken from several scientific and technical sources and has been meticulously checked and every care has been taken to select the most reliable data.

Properties of Materials

This section presents the most important mechanical, thermal, and optical quantities used to describe and characterize the properties of various classes of solid materials discussed in various sections of this book, while electrical and magnetic properties are described in the sections dealing with semiconductors, dielectrics, and magnetic materials. Finally, the properties of gases and liquids are described in their respective sections. For each physical quantity, the definition, physical equation, and SI unit are provided along with some orders of magnitude and range. The most common conversion factors encountered in metallurgy and materials science are listed in Table 1.14 at the end of this chapter.

1.1 Physical Properties 1.1.1 Mass Density 1

The mass density, or simply density, of a material is an intensive physical quantity denoted by the Greek letter ρ (or d), which corresponds to the mass of the material, m, expressed in kg, divided by 3 the total volume of the material, V, expressed in m . Hence, it has 3 −3 the dimension [ML ] and is then expressed in the SI in kg.m− : ρ = m/V.

1

An intensive quantity does not vary with dimensions of the system (e.g., mass, volume).

2

Properties of Materials

The temperature dependence of the density is given in a first approximation by the following linear relationships: ρ(T) = ρ0/[1 + β(T − T0)] = ρ0 · [1 − β(T − T0)] = (ρ0 + ρ0βT0) − ρ0βT = A − BT , where T is the absolute thermodynamic temperature in K and β the cubic thermal expansion 1 coefficient in K− .

1.1.2 Theoretical Density or X-ray Density of Solids The mass density ρ of crystallized solids expressed in kg.m− can be calculated quite accurately from both the number of atoms or molecules per formula unit and the crystal lattice parameters obtained by x-ray diffraction. For that reason, it is sometimes called the x-ray density , or simply the theoretical density, of the crystal. It can be calculated using the following equation: 3

ρxray = ZM/NAVcell, with Z M NA Vcell

the dimensionless number of atoms or molecules per formula unit (apfu), 1 the molar atomic or molecular mass in kg.mol− , 23 −1 Avogadro’s constant, 6.02204531 × 10 mol , and 3 the volume of the unit cell based on crystal lattice parameters in m .

1.1.3 Apparent, Bulk, and Tap Densities The apparent density, also called the true density, real density, or absolute density, ρapp, 3 expressed in kg.m− , is obtained when the volume measured excludes the pores as well as the void spaces between particles within the bulk sample. Absolute density is determined by pycnometry using water or another liquid that is expected to fill the pores in the sample, thus removing their volume from the measurement. Sometimes the material is subjected to boiling in the same liquid to ensure pore penetration, and sometimes the sample is evacuated prior to immersion to assist pore filling. However, surface-tension effects and entrapped gases resist the filling of very small pores. Therefore the best method consists in determining the apparent density by helium pycnometry: ρbulk = mparticles / Vparticles. The bulk density, ρbulk, expressed in kg.m− , is used for characterizing solids in powder form and particulates and corresponds to the mass of a solid in powder form divided by the overall volume of the solids including voids containing air trapped between particles: 3

ρbulk = mparticles /(Vparticles + Vvoids). The tap density, ρtap, expressed in kg.m− , corresponds to the apparent density of a powder obtained from filling a container with the sample material and vibrating or tapping it under specified conditions (e.g., ASTM standard test methods B527, D1464, and D4781) to obtain near-optimum packing. 3

Physical Properties

1.1.4 Specific Weight The specific weight of a material, denoted by the Greek letter γ, corresponds to the weight of 2 3 2 material per unit volume. Its dimensions are [ML− T− ], and it is expressed in N.m− : γ = mgn /V = ρgn.

1.1.5 Specific Gravity The specific gravity, denoted d, S.G., or simply G, is a dimensionless physical quantity equal to the ratio of the mass density of the material at a given temperature (t1) to the mass density of a reference fluid selected as a standard at a given temperature (t2). Since the mass density of materials varies with temperature, for a precise definition the temperature of both materials must be stated: d = ρmaterial(t1)/ρref(t2) = S.G. Usually, the specific gravity of liquids and solids refers to the maximum mass density of pure 3 3 water (i.e., 999.973 kg.m− measured at 3.98°C or sometimes 999.972 kg.m− measured at 4°C), but other solvents could also be used as standards. For instance, common specific gravities 20° 20° 60°F commonly used in the industry are d 4°, d 15°, and G 60°F. While the specific gravity of gases refers to the mass density of dry air measured for normal conditions of temperature and pressure (NTP; i.e., 273.15K and 101.325 kPa), for ideal gases, the specific gravity relative to air at the same temperature and pressure can be written as the ratio of their relative molar masses: dgas = ρgas(P, T)/ρair(P, T) = Mgas /Mair. Therefore, under normal temperature and pressure, the specific gravity of a gas is given approximately by the following practical relation: dgas ~ Mgas / 28.964.

1.1.6 Buoyancy and Archimedes’ Principle The Archimedes theorem explains that all bodies immersed in an ideal fluid encounter a vertical thrust force oriented toward the top, called the buoyancy force, and equal as absolute value to the weight of the volume of the fluid displaced. This force is called the buoyancy force, denoted b and expressed in newtons (N). Actually, for a solid material, S, having a vol3 3 ume VS in m immersed in a fluid (i.e., gas or liquid), F, with a mass density, ρF in kg.m− , the buoyancy force acting on the solid body can be written as follows: b = −ρFVS gn. It is then possible to express the apparent weight of a solid material immersed in a fluid: Papparent = Pactual + b, Papparent = mS gn − ρFVS gn,

3

1 Properties of Materials

4

Properties of Materials

where mS is the actual mass of the solid material in kg, i.e., the mass of the solid measured in a vacuum. Introducing the mass density of the solid body, ρS, we obtain the equation for the apparent weight: Papparent = mS [1 − (ρF /ρS)] gn. It is therefore possible to express the apparent mass of the solid body in a given fluid, denoted m*S: m*S gn = mS [1 − (ρF /ρS)] gn, m*S = mS [1 − (ρF /ρS)]. From the above equation it can be seen clearly why weighing heavier materials in air with precision balances introduces less error than with lighter materials. This equation can also be used to calculate the mass density of a solid material by weighing it in air and in water using a hydrostatic balance (e.g., Westphal balance). The apparent masses in air and in water are given respectively by the following two equations: mS(air) = mS(vacuum) [1 − (ρair /ρS)], mS(water) = mS(vacuum) [1 − (ρwater /ρS)]. Therefore, arranging the two above equations and equating the mass in a vacuum we obtain the mass density of the solid: ρS = [mS(air)ρwater − mS(water)ρair]/[mS(air) − mS(water)]. Because the density of air (1.293 kg.m− ) is much smaller than that of water (1000 kg.m− ), the second term in the equation’s numerator can be omitted and the equation simplified as follows: 3

3

ρS ~ [mS(air)ρwater]/[mS(air) − mS(water)] = ρwater [mS(air) /ΔmS].

1.1.7 Pycnometers for Solids Three-mass method. The determination of the mass density of a solid material, ρS, by pycnometry consists simply in the accurate determination of the volume of a small sample of the solid by a displacement method using a small glass standard flask called a pycnometer having a large neck closed by a ground join tap with a capillary. First, a small sample of the solid as a powder or crystal is weighed and its mass mS recorded. Secondly, the pycnometer is filled with a reference liquid of accurately known density, ρL. The pycnometer is allowed to rest 15 min until thermal equilibrium is reached. The volume of liquid is adjusted until meniscus reaches the gauge mark on the capillary. Afterward, the system is weighed and its mass M1 recorded. Third, the sample of the solid is carefully introduced displacing some liquid, which is wiped with a filter paper. Then the pycnometer is introduced into a vacuum enclosure for 30 min for gently degassing the dissolved gases until no microbubbles remain visible. The volume of liquid is finally adjusted until meniscus reaches the gauge mark on the capillary and its mass M2 is recorded. The final mass corresponds to the mass of the pycnometer with the solvent plus the mass of the solid minus the mass of the liquid displaced by the volume of the immersed solid as follows: M2 = M1 + mS − ρLVS.

Physical Properties

The mass density of the solid is given by ρS = mS /VS:

1

M2 = M1 + mS − mS(ρL /ρS).

Properties of Materials

Therefore the density of the solid can be expressed as follows: ρS = ρL [mS /(M1 + mS − M2)]. Four-mass method. In this method, which is identical to the previous one, the mass of the empty pycnometer, M0, is also taken into account. The final mass corresponds to the mass of the pycnometer with the solvent plus the mass of the solid minus the mass of the liquid displaced by the volume of the immersed solid as follows: M2 = M0 + M1 + mS − ρLVS. The density of the solid is given by ρS = mS /VS: (M2 − M0) = (M1 − M0) + mS − mS(ρL /ρS). Hence we obtain: ρS = ρL{mS /[(M1 − M0) + mS − (M2 − M0)]}. Selection of the proper liquid must satisfy all of the following requirements: (i) (ii) (iii) (iv) (v) (vi)

the density ρL of the liquid must be accurately known at a given temperature; it must exhibit a low temperature variation of its density with temperature; it must have a low vapor pressure owing to degassing under a vacuum; it must demonstrate chemical inertness toward a solid; it must have low dynamic viscosity to allow for a quick release of bubbles; it must have a good wetting angle. Suitable solvents include, but are not restricted to, water, xylene, and ethyl orthophthalate.

1.1.8 Density of Mixtures If we consider an intimate mixture of two solid materials A and B, the total mass of the mixture can be written as follows: M = mA + mA , while the total volume of the material, taking into account the volume occupied by voids, denoted Vvoids, is given by the following equation: V = VA + VB + Vvoids. Hence the density of the materials, denoted ρ and expressed in kg.m− , is given by 3

ρ = M /V = (mA + mB)/(VA + VB + Vvoids). Introducing the dimensionless mass fractions (wA, wB) and the mass densities (ρA, ρB) of the two materials: wA = mA /(mA + mB) wB = mB /(mA + mB)

5

6

Properties of Materials

with wA + wB = 1 ρA = mA /VA ρB = mB /VB we obtain: ρ = [wA /ρA + wB /ρB+ Vvoids /(mA + mA)]− . 1

If the term Vvoids/(mA + mA) is negligible, then the mass density of the mixture can be roughly assessed using the following equation: ρ = 1/[wA /ρA + wB /ρB].

1.2 Mechanical Properties The most important terms for describing the mechanical behavior of solid materials are listed in Table 1.1. The detailed definition of each property related to these behaviors, with equations, SI units, and orders of magnitude, will be discussed in the following paragraphs. Table 1.1. Mechanical behavior of solid materials Mechanical behavior

Typical property or figure of merit involved

Description

Brittleness

Brittleness indices

Tendency of a material to fail without appreciable deformation

Creep

Creep rate

Slow continuing deformation of materials when subjected to a constant stress

Damping

Damping factor

Ability of a material to absorb elastic sound waves by internal frictions

Ductility

Elongation (Z)

Ability of a material to withstand deformation without failure

Fatigue

S–N plots

Failure under the action of repeated or cyclic stresses

Fracture toughness

KIC

Ability of a material containing a flaw to withstand an applied load

Hardness

Hardness (HV)

Ability of a material to resist indentation, scratching, or abrasion

Hardening

Strain hardening exponent Ability of a material to harden during cold working

Impact strength

Charpy index

Ability of a material to resist a mechanical shock without failure

Malleability

Elongation (Z)

Ability of a material to be rolled or hammered into sheets without failure

Resilience

Modulus of resilience (UR)

Ability of a material to absorb elastic energy and to return it, i.e., rebound, springback)

Stiffness

Young’s modulus (E)

Ability of a material to withstand elastic deformation

Toughness

Modulus of toughness (UT) Ability of a material to absorb energy in the plastic range before failure

Mechanical Properties

1.2.1 Stress and Pressure When a material is subjected to an external force, it will either totally comply with that force and be pushed away, like a liquid or powder, or it will set up internal forces to oppose those applied from outside. Solid materials generally act rather like a spring when stretched or compressed. A material subjected to external forces that tend to stretch that material is said to be in tension, whereas forces that squeeze the material put it in compression. The stress consists in the force applied per unit of cross-section area: σ = F/A0. Compressive stress is usually denoted by the Greek letter sigma (σ), while shear stress is 3 2 denoted by the Greek letter tau (τ). In the SI, stress with the dimension [ML T− ] is expressed in the SI with the derived unit having the special name pascal (Pa), which corresponds to a force of one newton per square meter. Because the SI unit of stress and pressure is usually small compared to the properties of most solids, it is normally necessary to use large SI multiples such as the megapascal (MPa) and gigapascal (GPa).

1.2.2 Strain A solid material put under uniaxial tension or compression changes in length, and the change in length ΔL = L − L0 compared to the original length L0 is referred to as the engineering linear strain or simply linear strain and denoted by the Greek letter epsilon with subscript L, εL, and defined as follows: εL = (ΔL/L0). The concept of linear strain can be applied to the other axis as follows: εx = (Δx/x), εy =(Δy/y), and εz =(Δz/z). Since strain is a dimensionless ratio, it is frequently expressed as a percentage (%). For instance, a strain of 0.005 corresponds to a 0.5% change in the original length. The true strain, also called the natural strain, denoted by e, takes into account that the initial section A0 of the material changes with the applied load. It is defined as the Napierian logarithm of the ratio of the actual cross-section area of the sample, A, at a given applied load F to the initial cross-section area A0: e = ln (A/A0) = ln (L/L0). It is important to note that the cross-section area change becomes important only after the specimen begins to neck. The relationship between the engineering strain and the true strain can be drawn from the properties of the logarithm.

1.2.3 Elastic Moduli and Hooke’s Law When a solid material is subjected to a small stress (i.e., tension, compression, or torsion), the resulting strain is proportional to the applied stress and the proportional factor is called an elastic modulus, and this simple linear relationship between stress and strain is called Hooke’s law.

7

1 Properties of Materials

8

Properties of Materials

In a uniaxial tensile test, the slope of the stress–strain curve in the linear region is called Young’s modulus or the modulus of elasticity and is denoted by uppercase E (sometimes Y). It is expressed in Pa and defined as follows: σ = E ε. Engineering materials frequently have a Young’s modulus of the order of GPa. For instance, plain carbon steel exhibits a Young’s modulus of ca. 200 GPa. When a solid is subjected to a shear stress (i.e., torsion), the resulting plane angle change expressed in radians associated with two orthogonal lines is called the shear strain. The slope of the shear-stress versus shear-strain curve in the linear region is called the shear modulus, Coulomb’s modulus, or the modulus of rigidity, all denoted by uppercase G and expressed in GPa and defined as follows: τ = G γ. When a solid is subjected to a compressive stress, this results in a volume decrease, and the relative volume change (ΔV/V) adopts therefore a negative value. The slope of the hydrostatic stress versus relative volume change curve in the linear region is called the compression modulus, the bulk modulus, or the volumetric modulus of elasticity, denoted by uppercase K and expressed in GPa: ΔP = −K(ΔV/V). Because the relation between the bulk modulus and the applied pressure involves a relative change in volume (ΔV/V) of the material, it is possible to introduce the isothermal compressibility of the material defined as: βT = −1/V(∂V/∂P)T . Hence: K = 1/βT . It can be seen from the above equation that the bulk modulus is the reciprocal of the compressibility of a material; this holds for liquids as well. The three elastic moduli are a direct measure of the elasticity of a solid material and of its stiffness. Some elastic moduli of selected materials are listed for instance in Table 1.7. For an isotropic solid, the three elastic moduli and Poisson’s ratio are related by the following relationship: E = 3G/(3K + G), G = E/[2(1 + v)], and K=E/[3(1 − v)]. In practice, the following approximated relations can be used: • For metals, ceramics, and glasses: v ≈ 1/3, G ≈ 3/8 E, and K ≈ E; • For polymers and elastomers: v ≈ 1/2, G ≈ E/3, and K ≈ 10 E.

The order of magnitude of elastic properties of selected materials is given in the section Table 1.7.

1.2.4 The Stress–Strain Curve The mechanical testing of a material involves the application of a load to a given specimen and the recording of the strain as a function of applied stress. The corresponding stress– strain and true stress-true strain curves are presented in Figures 1.1 and 1.2.

Mechanical Properties

9

1 Properties of Materials

Figure 1.1. Engineering stress–strain curve

Figure 1.2. True stress–strain curve

In the particular case of uniaxial tensile tests (Figure 1.3), initially the strain recorded is linearly proportional to the applied stress (Hooke’s law), and in this region the material is said to be elastic because the strain due to an applied load is fully recovered when the load is removed. The yield strength (YS) of a material, denoted σYS or Rp, is the stress corresponding to the end of the linear portion of the stress–strain curve for the uniaxial tensile test. The 0.002 (or 0.001) proof strength (i.e., 0.2% offset yield strength) is used when the material shows no pronounced yield point. Afterward any additional stress leads to a residual permanent deformation of the material (i.e., plastic deformation) indicated by a hysteresis. The ultimate tensile strength (UTS) of a material, denoted σUTS or Rm, is the stress corresponding to the maximum load during the uniaxial tensile test. Deformation is uniform up to the tensile strength but becomes localized, and necking (i.e striction) occurs afterward. For most engineering purposes, metals are regarded as having failed once they have yielded, and when a metal or alloy imposed by the design is selected, they are normally loaded at well below the yield point. With some materials, including mild steel, the stress–strain graph shows a noticeable dip beyond the elastic limit, where the strain increases without any need

10

Properties of Materials

Figure 1.3. Deformation parameters

to increase the load. The material is said to have yielded, and the point at which this occurs is the yield point. Materials such as aluminum alloys, on the other hand, do not show a noticeable yield point, and it is usual to specify a proof test. As shown in Figure 1.1, the 0.2% proof strength is obtained by drawing a line parallel to the straight line part of the graph, but starting at a strain of 0.2%. The elongation denoted by Z is a dimensionless quantity that corresponds to the average strain measured at failure in the tensile test. The gauge length must be stated because materials ultimately fail as a result of excessive strain in localized regions. The necked region must be contained within the gauge length: Z(%) = 100 × [(L − L0)/LF)]. In a uniaxial tensile or compression test (Figure 1.3), the ratio of lateral compressive strain to axial tensile strain is constant for a given material loaded within the elastic limits. The dimensionless ratio is known as Poisson’s ratio and denoted by the Greek v or μ: v = − εx /εz = − εy /εz. Theoretically, for all isotropic and homogeneous materials Poisson’s ratio should be equal to 0.5 (i.e., isochoric transformation), but for most metals and alloys Poisson’s ratio is usually close to 0.33, while for strongly anisotropic materials such as beryllium it can be below 0.01. The compressive strength or crushing strength is the maximum compressive stress that a material can withstand without being crushed. Some typical stress–strain curves for the three categories of materials are presented in Figure 1.4.

Mechanical Properties

11

1 Properties of Materials

Figure 1.4. Schematic stress–strain curves for metals, ceramics and polymers

1.2.5 Strain Hardening Exponent The strengthening mechanisms in solids are of four types: (i) (ii) (iii) (iv)

by formation of solid solutions; by precipitation of secondary phases that block the propagation of dislocations; by dispersion of solids that also block the propagation of dislocations; and finally by cold working or strain hardening that consists in producing an intricate network of dislocations in the material, which impedes the development of other dislocations.

With these modes, the strain hardening results from mechanical deformation of the material. When a material undergoes a mechanical deformation that brings the material into its plastic domain by means of hammering, rolling, etc., the material hardens. This mechanism is called cold working or strain hardening and can be quantified introducing the following nonlinear relationship established between stress σ and strain ε: σ=Kε, n

with the two constants K and n called the strength hardening coefficient and the strain hardening exponent, respectively. The logarithmic transform of the equation gives the following equation: ln σ = ln K + n ln ε. The above equation is then represented by a straight line in a log–log plot, and the linear slope yields the strain hardening exponent while its ordinate gives the strength coefficient. The strain hardening exponent may exhibit values from n = 0 for perfectly plastic solids (e.g., waxes) to n = 1 for elastic solids (e.g., diamond). For most metals the strain hardening exponent usually ranges between 0.10 and 0.50.

1.2.6 Hardness Hardness is another measure of the ability of a material to be deformed. There are many different tests for measuring hardness, but all of them measure the resistance of a material to indentation or scratching, applying a known load or force to a tool of defined radius or diagonal that

Properties of Materials

is much harder than the material being tested. Empirical hardness numbers are calculated from measurements of the indentation dimensions. For common hardness scales used in mineralogy (e.g., Mohs, Rosival, and Ridgeway), see Chapter 12, Minerals, Ores, and Gemstones. Table 1.2. Hardness scales for metals and advanced ceramics Hardness scale (ASTM standard)

Indenter type

Test loads

Formula for hardness number (HN)

Vickers hardness (ASTM E 19)

136° diamond pyramid indenter

Macro Vickers: 1 to 120 kg Micro Vickers: 15 to 500 g

VHN = [2P sin(θ/2)]/d d diagonal length in mm θ diamond pyramid plane angle in degrees P load in kg

Knoop hardness (ASTM E 19)

Knoop diamond indenter

1 g to 1 kg

KHN = P/Kd 2 K = 7.028 × 10− d long diagonal length in mm P force or load in kg

Brinell hardness (ASTM E 10)

10-mm ball indenter (5-mm ball on lighter loads used on thin materials)

Load is 3000 kg for ferrous metals, 1500 kg for aluminum alloys, and 500 kg for soft alloys

BHN = F/[(πD/2)[D − (D − d ) ] P load in kg D ball diameter in mm d indentation diameter in mm

2

2

2

2 1/2

Incremental depth of penetration is measured between that caused by a minor load given as 10 kg and a major load using either a 120° diamond cone indenter or 1/16-in, 1/8-in, 1/4-in, or 1/2-in steel ball penetrators. Hardness is read directly on the dial indicator.

Rockwell hardness scales (ASTM E 18)

12

A scale (HRA)

120° diamond cone

60-kg major load

Extremely hard materials (e.g., cemented tungsten carbides)

B scale (HRB)

1/16-in. steel ball

100-kg major load

Medium-hard materials (e.g., low and medium carbon steels, brass, bronze)

C scale (HRC)

120° diamond cone

150-kg major load

Hardened steels and tempered alloys

D scale (HRD)

120° diamond cone

100-kg major load

Case-hardened steels

E scale (HRE)

1/8-in. steel ball

100-kg major load

Cast irons, aluminum, and magnesium alloys

F scale (HRF)

1/16-in. steel ball

60-kg major load

Annealed brass and copper

G scale (HRG)

1/16-in. steel ball

150-kg major load

Beryllium copper, phosphor bronze

H scale (HRH)

1/8-in. steel ball

60-kg major load

Aluminum sheet

K scale (HRK)

1/8-in. steel ball

150-kg major load

Cast irons, aluminum alloys

L scale (HRL)

1/4-in. steel ball

60-kg major load

M scale (HRM)

1/4-in. steel ball

100-kg major load

Plastics and soft metals such as lead alloys and tin alloys

P scale (HRP)

1/4-in. steel ball

150-kg major load

R scale (HRR)

1/2-in. steel ball

60-kg major load

S scale (HRS)

1/2-in. steel ball

100-kg major load

V scale (HRV)

1/2-in. steel ball

150-kg major load

Superficial

Minor load of 3 kg and major loads of 15 kg, 30 kg, and 45 kg

Sclero- Hard steel pin meter

Varies from 1 g to 1 kg

Scratch depth and length

Mechanical Properties

(continued) Table 1.3. Approximative conversion between several hardness scales

13

1

Vickers hardness Brinell hardness (/HV) (3000 kg mass, WC 10-mm ball) (/HB)

Rockwell hardness

Scleroscope hardness number

A scale (60 kg mass, diamond cone indenter) (/HRA)

B scale (100 kg mass, diamond cone indenter) (/HRB)

C scale (150 kg mass, diamond cone indenter) (/HRC)

940

—

85.6

—

68.0

97

920

—

85.3

—

67.5

96

900

—

85.0

—

67.0

95

880

767

84.7

—

66.4

93

860

757

84.4

—

65.9

92

840

745

84.1

—

65.3

91

820

733

83.8

—

64.7

90

800

722

83.4

—

64.0

88

780

712

—

—

—

87

780

710

83.0

—

63.3

85

772

698

82.6

—

62.5

83

746

684

82.2

—

61.8

81

730

682

82.2

—

61.7

80

720

670

81.8

—

61.0

79

700

656

81.3

—

60.1

78

697

653

81.2

—

60.0

77

674

647

81.1

—

59.7

76

653

638

80.8

—

59.2

75

648

630

80.6

—

58.8

644

627

80.5

—

58.7

633

601

79.8

—

57.3

612

578

79.1

—

56.0

595

555

78.4

—

54.7

565

534

77.8

—

53.5

544

514

76.9

—

52.1

528

495

76.3

—

51.0

513

477

75.6

—

49.6

484

461

74.9

—

48.5

471

444

74.2

—

47.1

458

429

73.4

—

45.7

446

415

72.8

—

44.5

423

401

72.0

—

43.1

412

388

71.4

—

41.8

395

375

70.6

—

40.4

382

363

70.0

—

39.1

372

352

69.3

—

37.9

363

341

68.7

—

36.6

350

331

68.1

—

35.5

336

321

67.5

—

34.3

Properties of Materials

14

Properties of Materials

Table 1.3. (continued) Vickers hardness Brinell hardness (/HV) (3000 kg mass, WC 10-mm ball) (/HB)

Rockwell hardness A scale (60 kg mass, diamond cone indenter) (/HRA)

B scale (100 kg mass, diamond cone indenter) (/HRB)

C scale (150 kg mass, diamond cone indenter) (/HRC)

327

311

66.9

—

33.1

318

302

66.3

—

32.1

310

293

65.7

—

30.9

302

285

65.3

—

29.9

294

277

64.6

—

28.8

286

269

64.1

—

27.6

279

262

63.6

—

26.6

272

255

63.0

—

25.4

260

248

62.5

—

24.2

254

241

61.8

100.0

22.8

248

235

61.4

99.0

21.7

243

229

60.8

98.2

20.5

235

223

—

97.3

20.0

230

217

—

96.4

18.0

220

212

—

95.5

17.0

214

207

—

94.6

16.0

210

201

—

93.8

15.0

205

197

—

92.8

—

200

192

—

91.9

—

196

187

—

90.7

—

194

183

—

90.0

—

190

179

—

89.0

—

185

174

—

87.8

—

180

170

—

86.8

—

176

167

—

86.0

—

170

163

—

85.0

—

163

156

—

82.9

—

159

149

—

80.8

—

150

143

—

78.7

—

145

137

—

76.4

—

139

131

—

74.0

—

130

126

—

72.0

—

126

121

—

69.8

—

120

116

—

67.6

—

110

111

—

65.7

—

Scleroscope hardness number

Mechanical Properties

1.2.7 Resilience and Modulus of Resilience The resilience, denoted WE and expressed in Joules (J), is the ability of a solid material to absorb elastic energy and release it when unloaded (e.g., rebound, springback). In practice, the absorbed elastic energy can be calculated from the true stress–strain plot (S - e) by integrating the surface area under the curve between the true yield strength SYS and the origin. This area represents the amount of elastic work per unit volume that can be done on the material without causing it to rupture:

WE = V ∫ Sde SYS

0

The modulus of resilience, denoted UR and expressed in Pa, corresponds to the strain energy stored per unit volume required to stress the material from zero to the true yield strength. Several mathematical approximations for the area under the true stress–strain curve can be used:

UR = 1/2 WE ~ 1/2 SYSe0. For solids in tension or compression, it can be written as: 2

UR ~ SYS /2E, while for solids under torsion, it can be written as: 2

UR ~ SYS /2G. These last two equations indicate that an ideal material for resisting energy loads in applications where the material must not undergo permanent energy distorsion, such as mechanical spring, is one having a high yield strength and a low modulus of elasticity.

1.2.8 Toughness A material’s toughness is its ability to absorb energy in the plastic range. It is commonly measured by the modulus of toughness, UT, that is, the amount of work stored per unit volume without causing rupture. As for the modulus of resilience, several mathematical approximations for the area under the true stress–strain curve can be used: For ductile materials (e.g., metals and alloys):

UT ~ SUTSeF or eF(S0 + Su)/2. For brittle materials (e.g., ceramics and glasses):

UT ~ 2/3 SUTSeF.

1.2.9 Maximum Allowable Stress In most engineering calculations, especially when designing structures and pressure vessels, the engineer must determine the maximum stress that a structure can withstand safely without any risk of rupture. As a rule of thumb, it is useful to introduce the maximum allowable stress denoted σA and defined by

σA = inf (σUTS/4; 2σYS/3).

15

1 Properties of Materials

16

Properties of Materials

Table 1.4. Maximum allowable thickness and pressure for high-pressure cylindrical and spherical shells Shell geometry

Allowable thickness

Maximum allowable internal pressure

Cylindrical shell with circumferential stress long joints

x = [P . Ri] / [σa . j − 0.6P]

Pmax = [σa . j . x] / [Ri + 0.6 x]

Cylindrical shell with longitudinal stress circumferential joints

x = [P . Ri] / [2σa . j + 0.4P]

Pmax = [2σa . j . x] / [Ri − 0.4 x]

Spherical shell

x = [P . Ri] / [2σa . j − 0.2P]

Pmax = [2σa . j . x] / [Ri + 0.2 x]

Symbols and units of physical quantities: x = required thickness in m p = design or working pressure in Pa Ri = inner-shell radius in m σa = maximum allowable stress in Pa j = dimensionless joint efficiency factor

Joint efficiency factors: j = 1.0 for x-rays NDT j = 0.85 for spot x-rays j = 0.70 for other NDT

The above mathematical equation indicates that the maximum allowable stress is taken as the lowest value of either 25% of ultimate tensile strength or 66% of the yield strength of the material. For more rigorous calculations, especially when designing high-pressure vessels, the engineer must refer to specialized calculation methods such as those recommended in the ASME Boiler and Pressure Vessels Code [Section III, Division 1 and 2]. Some detailed calculations for high-pressure reactors having a cylindrical shell are given as examples in Table 1.4.

1.2.10 Fracture Toughness The fracture toughness of a material, in simplest terms, can be described as the stress required to initiate a crack when a stress is applied. In that sense ceramics are not as tough as metals and alloys. A measure of the fracture toughness of a material is the critical stressintensity factor, denoted K1c, most commonly called the fracture toughness, which is ex1/2 pressed in MPa.m . Fracture toughness describes the resistance of a material to failure from fracture starting from a preexisting crack (e.g., flaws). This definition can be mathematically expressed by the following expression:

K1c = σ Y πa , where σ is the normal stress in Pa, a is half of the crack dimension in meters, and Y is a dimensionless factor that depends on the following features: (i) geometry of the crack; (ii) anisotropy of the material; (iii) loading configuration, that is, if the sample is subject to compression, tension, or bending; and finally (iv) ratio of crack length to specimen width, b. Several mechanical tests, including indentation methods, are used to measure the fracture toughness of materials. Example: A plate made of carbon steel grade AISI 4340 having a fracture toughness of 1/2 46 MPa.m− with a flaw of 2 mm in length has a critical stress of 820 MPa. Above that threshold value a disastrous fracture of the plate could occur.

Mechanical Properties

1.2.11 Brittleness Indices During the breakage of a material, from an energy balance point of view, the external mechanical work applied to the material is entirely absorbed in both the deformation and the 2 fracture processes. Rationalized indices such as those introduced by Michael F. Ashby are excellent properties to assess a material’s breakage ability, and hence they must combine at least a deformation property (e.g., hardness, Young’s modulus) and a fracture property (e.g., fracture toughness) to cover the entire breakage process correctly. To achieve this task, in the early 1960s materials scientists had already introduced the concept of brittleness indices. The goal was to predict the performance of materials with regard to comminution and allow one to identify clearly and quickly the best suited material. The first practical brittleness rationalized 3 1/2 3 index, denoted B and expressed in 10 m− , was first introduced by Lawn and Marshall in the late 1970s. This brittleness was defined as the ratio of micro-Vickers hardness (HV) expressed 1/2 in GPa and the fracture toughness, K1c, expressed in MPa.m , as in the following equation:

B = Hv/K1c. However, more recently a new brittleness rationalized index, denoted B* and expressed in 1 4 μm− , has been introduced by Quinn and Quinn from the National Institute of Standards and Technology (NIST) as the ratio of the deformation energy per unit volume to the fracture energy per unit surface area. This brittleness index is more accurate than the previous one because it includes three intrinsic properties of the material rather than only two. Therefore, brittleness can be described in terms of the micro Vickers hardness (HV), Young’s modulus (E), and the fracture toughness of the ceramic materials (K1c), as described in the following rationalized Quinn’s equation: 2

B* = Hv E/K1c . Thus the brittleness rationalized index compares the deformation to the fracture process. For instance, a material exhibiting a low brittleness index is more apt to deform than to fracture, and conversely, a material exhibiting a high brittleness has a tendency to fracture rather than to deform. Quinn’s brittleness index increases with both hardness and stiffness and decreases rapidly with increasing fracture toughness. This parameter is then extremely important to compare the capability of brittle materials to withstand compressive strength and therefore to assess the crushing resistance of materials. Moreover, because Quinn’s brittleness index incorporates the largest set of mechanical properties compared to other indices, it is preferred.

1.2.12 Creep When a material is loaded under a fixed stress, after a certain time the strain continues to increase at a rate depending on the type of material. This slow continuing deformation of a material when subjected to a constant stress is called the creep mechanism, which is a typical anelastic behavior. The rate at which the strain change occurs is called the strain rate and 1 is denoted ∂ε/∂t and expressed in s− . For each material loaded under a constant stress it is 2

3

4

Ashby, M.F. (1999) Materials Selection and Process in Mechanical Design. Butterworth-Heinemann, Oxford. Lawn, B.R.; Marshall, D.B. (1979) Hardness, toughness, and brittleness: an indentation analysis. J. Am. Ceram. Soc. 62(7–8):347–350. Quinn, J.B.; Quinn, G.D. (1997) Indentation brittleness of ceramics: a fresh approach. J. Mater. Sci. 32:4331–4346.

17

1 Properties of Materials

18

Properties of Materials

Figure 1.5. Creep behavior

possible to record the strain as a function of time (Figure 1.5). The creep curve can be repre5 sented by Andrade’s equation :

ε(t) = ε0(1 + At ) · exp(Bt). 1/3

Usually creep occurs in materials when the temperature reaches a certain fraction of the melting point. For metals and alloys the creep occurs when the temperature is

Tcreep > 0.5 Tm (metals and alloys), while for ceramics it occurs at higher temperatures:

Tcreep > 0.8 Tm (ceramics).

1.2.13 Ductile-Brittle Transition Most materials become brittle at cryogenic temperatures, except metals having a facecentered cubic (fcc) lattice at cryogenic temperatures (e.g., Ta), because the yield stress decreases with increasing temperature while the tensile strength is quite insensitive to temperature. When the solid is brought to a particular temperature, called the ductile-to-brittle transition temperature (DBTT), where the yield strength is above the fracture strength, brittle fracture occurs. The transition temperature is influenced by several factors such as the microstructure of the materials. In practice, a Charpy test conducted on a wide temperature range allows one to determine the DBTT.

1.2.14 Fatigue Fatigue is a phenomenon that leads to fracture under repeated or cyclic stresses having a maximum value less than the tensile strength of the material. Commonly, stresses alternate between tension and compression. Because the number of stress cycles, N, prior to fracture is a function of the applied stress, S, the graphic representation of stress versus the number of stress cycles or simply S–N plots are frequently used to report and describe the fatigue 5

Andrade, E.N.C. (1914) Creep and recovery. Proc. R. Soc. Lond. 90A:329–342.

Mechanical Properties

19

1 Properties of Materials

Figure 1.6. Schematic of a S–N plot

capability of a given material. Fatigue is a progressive phenomenon that begins with minute cracks that usually start at the surface of the material because bending or torsion leads to the highest stresses at the outer surface of a solid and because the inescapable surface irregularities induce a concentration of stresses. Therefore, both the surface finish and the corrosive environment of a material impact its endurance limit under cyclic stresses. However, it is important to note that when a material undergoes a high level of stress, cracks can be initiated inside the material. In practice, the endurance limit of a material is determined graphically from the S–N plot (Figure 1.6).

1.2.15 Tribological and Lubricating Properties of Solids The resistance to motion that a solid experiences while moving across a surface is called friction. Frictional forces between solids affect the sliding between two solid materials and are strongly related to the type and nature of the interfaces and thin films existing at the surface of these solids. Deformation phenomena like elasticity, flow and creep, adhesion, friction, and lubrication arise during sliding of two solids over each other.

1.2.15.1 Static Friction Coefficient Consider a block of a solid material put in contact with a solid surface under its own weight and lying at rest. To start moving the block across the surface, a minimum force, Fmin, must be exerted to overcome the existing static-frictional force, FR, that always acts in an opposite direction to that of motion (Figure 1.7). This frictional force is independent of the contact area and the sliding velocity except on very soft materials (e.g., rubber). Moreover, the

Figure 1.7. Displacement of a solid onto a surface

20

Properties of Materials

static-frictional force is proportional to the normal force, FN, applied to the solid, and the dimensionless proportional coefficient is called the static friction coefficient of the material and is usually denoted µS: Fmin ≥ FR = µSFN and

µS = FR/FN. The static friction coefficient of a solid material depends not only on the material but also on the nature of the substrate, its surface finish (e.g., roughness), its surface conditions (e.g., oxidized, etched), and the type of atmosphere (e.g., air, gas, vacuum). For most materials the static coefficient of friction is drastically increased when contact surfaces are put under vacuum because the lubricating action of molecules disappears. This explains why moving parts and bearing in a vacuum or under reduced pressure are technological challenges. On the other hand, the lubricating action of liquids is obvious except if they react chemically:

µS(vacuum) >> µS(air) >> µS(water).

1.2.15.2 Sliding Friction Coefficient After the sliding motion of the solid is initiated, the force Fk that must be exerted to maintain its motion at a fixed velocity is also proportional to the normal force, but the proportional coefficient is lower than the static friction coefficient, and it is called the sliding friction coefficient or dynamic friction coefficient µD:

µS >> µD. Orders of magnitude of both static and sliding friction coefficients of selected solids are presented in Table 1.5. Table 1.5. Static friction coefficients of selected solids on themselves in air and in a vacuum Solid material

Air

Vacuum

Diamond on diamond

0.05

0.1

PTFE on PTFE

0.04

0.1

Iron

1.0

1.5

Silver

1.4

>10

Aluminum

1.3

>10

Cobalt

0.3

0.6

Chromium

0.4

1.5

Magnesium

0.5

0.8

Platinum

1.3

4

Lead

1.5

>10

Tungsten carbide

0.15

0.6

Mechanical Properties

1.2.16 Ashby’s Mechanical Performance Indices

1

To compare the performance of various materials and to select the most appropriate candidates for a given application or a specific design, a novel approach was introduced by Michael F. Ashby that consists in combining several relevant properties (e.g., mechanical, thermal, or electrical) to yield a performance index. Then plotting one property against another onto a log–log plot, together with the relevant performance indices, allows one to do the following: (i) group a large amount of information in a compact manner; (ii) reveal correlations existing between materials; and finally (iii) rapidly select a material or a class of material. It is not the purpose of this book to explain how to obtain such performance indices, and 6 the reader is encouraged to read Ashby’s manual . However, selected performance indices used to assess mechanical behavior are presented in Table 1.6. Table 1.6. Selected Ashby’s mechanical performance indices Properties

Guidelines for optimal selection

Modulus density

Minimum mass design: E/ρ 1/2 Minimum mass design of beam: E /ρ 1/3 Minimum mass design of stiff plate: E /ρ

Strength density

Minimum mass design: σYS/ρ 1/2 Minimum mass design of beam: σYS /ρ 1/3 Minimum mass design of stiff plate: σYS /ρ

Fracture toughness density

Minimum weight design: K1c/ρ 2/3 Minimum weight design of brittle beam: K1c /ρ 1/2 Minimum weight design of brittle plate: K1c /ρ

Modulus strength

Elastic energy stored per unit volume: σYS /E 3/2 Elastic energy stored per unit volume (blade): σYS /E Elastic energy stored per unit volume (hinge): σYS/E

Fracture toughness modulus

Constant toughness: K1c/E 2 Limited brittle fracture: K1c /E

Fracture toughness strength

Yield before break: σYS/E 2 Leak before break: σYS /E

2

1.2.17 Order of Magnitude of Mechanical Properties of Solid Materials See Table 1.7, page 22

6

21

Ashby, M.F. (1996) Materials Selection in Mechanical Design. Butterworth-Heinemann, Oxford.

Properties of Materials

3

2

3160

19,293

3987

7800

8902

7800

8941

4450

7133

2699

2532

7298

2300

1738

2300

11,350

760

534

920

1140

120

Silicon carbide

Tungsten

Alumina

Steel 4340

Nickel

Iron

Copper

Titanium

Zinc

Aluminum

Glass (sodalime)

Tin

Concrete

Magnesium

Bone

Lead

Oak wood

Lithium

Natural rubber

Nylon

Balsa wood

Polyvinylchloride 1160

3.3

3.6

4.9

12

16

30

45

50

50

72

70

104

120

130

196

200

206

390

411

470

1050

3520

Diamond

Young’s modulus (E/GPa)

Density 3 (ρ/kg.m− )

Material

n.a.

n.a.

1.2

4.2

n.a.

6

n.a.

34

18

26

42

46

48

82

76

81

170

161

n.a.

300

Coulomb’s modulus (G/GPa)

n.a.

n.a.

2.2

11.4

n.a.

46

n.a.

36

58

75

70

108

143

170

177

170

350

415

n.a.

500

Bulk modulus (K/GPa)

0.40

n.a.

0.36

n.a.

0.44

n.a.

0.29

0.36

0.23

0.35

0.25

0.35

0.34

0.29

0.31

0.28

0.25

0.28

0.22

0.10

27

59

0.5

n.a.

70

25

3600

55

140

69

131

148

475

255

550

10,000

5000

55

82

17

1.16

17

176

15

3600

110

104

235

221

689

462

745

255

620

10,000

5000

Poisson Yield strength Ultimate ratio proof tensile strength (ν) (σYS /MPa) (σYS /MPa)

Table 1.7. Order of magnitude of mechanical properties of selected materials

5

300

650

n.a.

35

n.a.

nil

54

55

47

22

nil

2

nil

nil

Elongation ratio (Z/%)

5

35

460

400

640

3000

360

2500

8000

Vickers hardness (HV)

0.5–0.7

2.6

1.4

2–8

117

0.2–1.4

0.7–0.8

22–50

120

35–110

50

40–120

100–150

50

3–5.3

16

3.3–4.5

0.9

Fracture toughness 1/2 (K1c /MPa.m− )

2.068

0.117

0.037

0.232

Modulus of resilience (UR /MPa)

22 Properties of Materials

Acoustical Properties

1.3 Acoustical Properties

1 Properties of Materials

1.3.1 Velocity of Sound in Materials Sound is an alteration in pressure, stress, particle displacement, and particle velocity, propagated in an elastic medium. Wave propagation is only longitudinal (i.e., compression) in gases and liquids but may also be transverse (i.e., shear) surface or other type in elastic media that can support such energy. The human bandwidth for sound ranges from 20 Hz to 20 kHz. Below 20 Hz is the domain of infrasounds while above 20 kHz is the region of ultrasounds. 1 The velocity of sound longitudinal waves in a medium, denoted VL and expressed in m.s− , is given by the following equations: For solids: VL = [(λ + μ)E/ρ] = [E/3ρ(1 − 2ν)] 1/2

1/2

For liquids: VL = [K/ρ] = 1/[βρ] 1/2

For gases: with VL λ, μ, and ν E and K ρ β γ

1/2

VL = [∂P/∂ρ] = [γP/ρ] = [γRT/M] 1/2

1/2

1/2

longitudinal velocity of sound in m.s− , dimensionless Lamé coefficients and Poisson’s ratio, Young’s and bulk moduli in Pa, 3 mass density in kg.m− , 1 isochore compressibility in Pa− , dimensionless isentropic exponents, γ = Cp /Cv. 1

As a general rule, the stiffer a material is, the higher the velocity of sound is; for instance 1 1 in carbon steel the sound velocity reaches 5200 m.s− , while it is only 1450 m.s− in water and −1 331 m.s in air. On the other hand, we can see that the velocity of sound in gases is independent of pressure due to the compensation by density changes. The temperature dependence of the velocity of sound in a given medium is influenced mainly by the temperature variation of the density of the medium (see Density), and in a first approximation it can be written as follows:

VL(T) = VL(T0) · [1 + β(T − T0)] , 1/2

where T is the absolute thermodynamic temperature in K and β the cubic thermal expansion 1 coefficient in K− .

1.3.2 Sound Intensity The sound intensity in a medium, denoted S, is a dimensionless quantity that expresses the ratio of two sound powers, W, or sound pressures, P, or intensity levels, X and X0, as a Napierian or Briggs logarithm difference:

S (dB) = 10 log10(I/I0), S (Np) = ln(I/I0), where I0 is the threshold sound intensity level (SIL) of hearing stated as 10− W.m− , while if sound pressure levels (SPL) are used we have: 12

S (dB) = 20 log10(P/P0), S (Np) = 2 ln(P/P0).

23

2

24

Properties of Materials

where P0 is the threshold sound pressure level detected by the human ear stated as 2 × 10− 5 barye (2 × 10− Pa) measured at 100 Hz. Finally, for sound power level (SPL) it is:

4

S (dB) = 20 log10(W/W0), S (Np) = 2 ln(W/W0). where W0 is the threshold sound power level detected by the human ear defined as 10− W measured at 1000 Hz. The unit of sound intensity expressed as the decadic logarithm difference is expressed in bel units, named after A.G. Bell (1847–1922), or in its submultiple, the decibel dB, while if expressed as a Napierian logarithm difference is expressed in neper, named after John Napier (1550–1617). The relationship existing between the two units is as follows: 12

S(Np) = (20/ln10) S(dB).

1.3.3 Attenuation of Sound at a Given Distance from a Source In a gas, the attenuation of the intensity of sound S in dB emitted by a point source (S) at a distance x is given by the exponential equation below:

S(x) = S0 · exp(−μx). The sound attenuation coefficient, denoted μ and expressed in m− , is dependent on the physical properties of the medium as follows: 1

μ(T) = (4π f /ρVL) · [(2η/3VL ) + (kTβ /2c )], 2 2

with μ f ρ η β VL

2

2

2

sound attenuation coefficient of the gas in m− , frequency in Hz, 3 density of the gas in kg.m− , dynamic viscosity of the gas in Pa.s, 1 cubic thermal expansion coefficient in K− , −1 velocity of sound in m.s . 1

1.3.4 Damping Capacity of Solids and Loss Factor In solids, the attenuation or damping of sound and elastic waves is usually characterized macroscopically by the loss coefficient or the specific damping capacity. Actually, it was shown in the previous paragraphs that the modulus of resilience measured the elastic or vibrational energy stored per unit volume of material during loading. However, if the material is repeatedly loaded and unloaded, with constant amplitude, it dissipates a certain energy per unit volume, denoted ΔU, due to hysteresis caused by dislocation movements. Hence, to characterize this anelastic behavior, a dimensionless acoustical quantity called the loss coefficient, denoted η, was introduced by acoustical engineers. The loss coefficient measures the ability of a material to dissipate vibrational energy and consists of the ratio of dissipated energy to the modulus of resilience of the material:

η = ΔU/2πUR. Sometimes, the specific damping capacity, denoted D, is used instead of the loss coefficient:

D = 2π · η = ΔU/UR.

Thermal Properties

From a microscopic point of view, damping is directly related to internal frictions that absorb the vibrations of the atoms in the crystal lattice (i.e., phonons). In practice, internal frictions are usually measured by a system that is set in motion with a certain initial amplitude A0 and then allowed to decay freely at an indiscernible amplitude. Then the amplitude follows the exponential equation listed below:

A(t) = A0 · exp(−Bt), where B is the time attenuation coefficient expressed in Hz. Therefore, the internal friction is usually measured using the logarithm decrement, or simply the log decrement, denoted Δ, that is, the Napierian logarithm of the ratio of two successive amplitudes of natural vibrations:

Δ = ln[A(t)/A(t+1)]. If the internal frictions are not dependent on the amplitude, then the plot of the Napierian logarithm of the amplitudes versus the number of cycles is linear with a slope equal to the logarithmic decrement. Moreover, during damping of a sound wave, the anelastic behavior leads to a lag between the stress and strain, and the phase angle, δ, between the two waves is then related to the Napierian logarithmic decrement by the simple equation:

Δ = π · tanδ ~ π · δ (for small δ). Usually, for a given energy, the maximum amplitude of vibration occurs at the resonant frequency, vres, and the logarithmic decrement for a resonance curve is given by the equation:

Δ = π (Δv/vres). In practice and by analogy of resonating electrical circuits, the resonance factor, or simply the Q-factor, is given by

Q− = Δ/π = (Δv/vres). 1

For small damping only, all these quantities are related by the following equation:

η = D/2π = Q− = Δ/π = tanδ = (Δv/vres). 1

1.4 Thermal Properties 1.4.1 Molar and Specific Heat Capacities The heat capacity is defined as the thermal energy or heat required to raise the temperature of the material by 1 K one kelvin:

ΔQ = CΔT. The molar heat capacity, denoted by uppercase C and expressed in J.mol− , is the heat required to raise the temperature of a given amount of substance in moles by one kelvin. It can be defined at constant volume (isochoric) or at constant pressure (isobaric) as a function of molar internal energy or molar enthalpy, respectively: 1

ΔQv = ΔU = nCvΔT, ΔQp = ΔH = nCpΔT.

25

1 Properties of Materials

26

Properties of Materials

Both physical quantities Cv and Cp are state functions, and it is easier to use the intensive 1 1 quantities expressed in J.K− .mol− defined by:

ΔU = nCvΔT, ΔH = nCpΔT. In practice, engineers use the specific heat capacities denoted by lowercase letters cv and cp, 1 1 expressed in J.K− .kg− , and defined by the following two equations:

Δu = mcvΔT, Δh = mcpΔT. The molar and specific heat capacities are related by the equation:

Cp,v = Mcp,v. Usually, the molar and specific heat capacities or pure substances and compounds vary with temperature, and the molar heat capacity is usually provided by the polynomial equation: 2

Cp(T) = Ak + BkT + Ck/T , 2

cp(T) = ak + bkT + ck/T , with the empirical molar coefficients Ak, Bk, and Ck (ak, bk, and ck) determined experimentally and found in tables. The molar and specific heat capacities of mixtures can be approached quite accurately by the weighted average of the molar or specific heat capacities of each component:

Cp = ΣkxkCpk,

cp = ∑kwkcpk.

At room temperature, the molar heat capacity of most solids, especially metals, can be approximated using the empirical rule of Dulong and Petit, which is based on many experimental studies and states that the molar heat capacity is three times the constant for ideal gases:

Cp ~ 3R

(Dulong–Petit rule).

1.4.2 Coefficients of Thermal Expansion When a solid or a liquid is heated, it undergoes a reversible thermal expansion linearly proportional to the temperature difference. In practice, the thermal expansion of each material is fully characterized by three coefficients of thermal expansion. First, when a solid having an initial length L0, measured at a reference temperature T0, is heated to a final temperature T, it exhibits a final length L > L0. The relative increase of length ΔL/L0 is directly proportional to the temperature difference ΔT. The proportionality coefficient is called the coefficient of linear thermal expansion and is denoted by the Greek letter αL 1 or by the acronym CLTE and expressed in K− . It is defined by the following equation:

αL = 1/L0(∂L/∂T)p. Second, when a solid having an initial cross-sectional surface area A0, measured at a reference temperature T0, is heated to a final temperature T, it exhibits a final cross-sectional surface area A > A0. The relative increase of cross-section ΔA/A0 is directly proportional to

Thermal Properties

the temperature difference ΔT. The proportionality coefficient is called the coefficient of surface thermal expansion and is denoted by the Greek letter ΣL or by the acronym CSTE and 1 expressed in K− . It is defined by the following equation:

ΣS = 1/A0(∂A/∂T)p. Finally, when a solid having an initial overall volume V0, measured at a reference temperature T0, is heated to a final temperature T, it exhibits a final volume V > V0. The relative increase of cross-section ΔV/V0 is directly proportional to the temperature difference ΔT. The proportionality coefficient is called the coefficient of cubic thermal expansion and is denoted 1 by the Greek letter βL or by the acronym CVTE and expressed in K− . It is defined by the following equation:

βV = 1/V0(∂V/∂T)p. Because the volume and the cross-sectional area of a material are both simply related to the 3 2 length by the two equations V = L and A = L , their first derivatives versus length are also simply related as follows: ∂V = 3 ∂L and ∂A = 2 ∂L. Therefore the relationships between the three coefficients of thermal expansion are straightforward and are listed below:

βV = 3 αL and ΣS = 2 αL and βS = (3/2) ΣL.

1.4.3 Volume Expansion on Melting The volume expansion on melting for a given material (e.g., metal, alloy, ceramic, polymer), expressed in vol.% and denoted ΔV/V, corresponds to the relative difference of the volume occupied by a unit mass of the material before and after the melting temperature is reached. It can be described by the following simple equation:

ΔV/V(vol.%) = 100 × (VL − VS)/VS. Introducing the mass density of the material in the liquid and solid state, respectively, we obtain the general equation:

ΔV/V(vol.%) = 100 × (ρS − ρL)/ρL. For most materials that expand on melting, the volume expansion is positive, except for covalent or Van der Waals solids for which the solid is less dense than the liquid (i.e., with a negative Clausius–Clapeyron slope) such as ice and some elements of group IVA(14) (e.g., C, Si, Ge, and Sn).

1.4.4 Thermal Shock Resistance When a solid material is heated rapidly from room temperature to a high temperature or cooled (i.e., quenched) rapidly from a glowing temperature down to cryogenic temperature, this abrupt change in the temperature of the material is always accompanied by strong internal mechanical stresses due to the expansion or contraction of the material. If these stresses are greater than the mechanical resistance of the material, then a breakage or failure can occur. As a rule of thumb and in a first approximation, the thermal shock resistance of a material can be assessed using a straightforward approach. Actually, knowledge of the

27

1 Properties of Materials

28

Properties of Materials

linear thermal expansion coefficient αL allows us to express the linear strain that a given material can withstand when it is subjected to a temperature difference ΔT as follows: (ΔL/L) = αLΔT. Introducing the strain in Hooke’s law

σ = E(ΔL/L) we obtain the relationship between the mechanical stress and the temperature difference:

σ = αLEΔT. Therefore stiffer materials having a large coefficient of thermal expansion are more prone to thermal shock than those with a lower coefficient.

1.4.5 Heat Transfer Processes Thermal properties describe the heat transfer processes occurring in materials subjected to a temperature difference. The heat transfer in materials is always ensured by three distinct modes briefly described below. (i)

The conduction or thermal diffusion is a heat transfer process that occurs across a medium (e.g., plasma, gas, liquid, or solid) with no bulk motion. The transfer of heat from high-temperature regions to low-temperature regions is only ensured by microscopic exchange of thermal energy between free electrons (i.e., Fermi’s gas) and/or vibration of the atoms in the crystal lattice (i.e., phonons) in the case of crystallized solids. The most important intrinsic physical quantities describing conduction in materials are the thermal conductivity (k) and diffusivity (α). (ii) The convection that occurs only in fluids involves two mechanisms of heat transfer: (1) the random molecular motion (i.e., diffusion) of atoms and molecules and (2) the bulk or macroscopic motion of the fluid. Free convection or natural convection is induced by buoyancy forces due to the formation of density gradients, while in forced convection the fluid motion is induced by external forces. The most important physical quantity used for describing convection is the heat transfer coefficient (U), but this physical quantity is not an intrinsic property of the material as it strongly depends on the forces acting on the fluid motion. (iii) The radiation represents the thermal energy emitted by matter at a definite temperature. Radiation may occur either from a solid surface or from liquids and gases. The thermal energy of the radiation is transported by the electromagnetic waves (i.e., photons), and hence the radiation mode, in contrast to conduction and convection, does not require the presence of a material medium for propagating and occurs most efficiently in a vacuum. The important physical quantity describing the radiation properties of a material is its spectral emissivity.

1.4.6 Thermal Conductivity When a homogeneous material is subjected to a temperature difference, a heat transfer rate or heat flux, i.e., energy per unit surface area and time, occurs and flows from highertemperature regions to low-temperature regions, as imposed by the second law of thermodynamics. The heat flux is a vector quantity and is proportional to the temperature gradient

Thermal Properties

across the material. The linear vector relationship existing between the heat flux and the temperature gradient is called Fourier’s first law, the proportional quantity being the thermal conductivity of the material, and it is described as follows: JQ = − k grad T

(Fourier’s first law),

with 2 heat flux in W.m− , JQ T absolute thermodynamic temperature in K, 1 1 k thermal conductivity of the material in W.m− .K− . As a general rule, the thermal conductivity of crystalline solids corresponds to the sum of the conduction of heat by free electrons (i.e., Fermi’s gas) in the conduction band and to the vibration of the atoms in the crystal lattice (i.e., phonons):

ksolid = kelectrons + kphonons. Therefore the thermal conductivity of highly ordered solid materials with stiff chemical bonds (i.e., with a high Young’s modulus) will be higher (e.g., diamond) than that of soft solids (e.g., polymers). Moreover, in the case of metals, there exists a close relationship between the thermal and electrical conductivities. While for anisotropic or inhomogeneous solids (e.g., uniaxial and biaxial crystals, composites, fibers, and polymers) the thermal conductivity is a second-rank tensor. Finally, in amorphous materials (e.g., glass), liquids, gases, and plasmas, because the lattice contribution is negligible or zero, the conduction mechanism is ensured by other entities (e.g., ions, atoms, molecules). The order of magnitude of thermal conductivities varies widely. Crystallized solids ex1 1 hibit the highest thermal conductivities, which range from 10 to 1000 W.m− .K− . Of these, diamond and graphite, which are advanced ceramics and face-centered cubic metals (e.g., Ag, Cu, Au, and Al), are typical examples. Good thermal insulators are usually ceramics, 1 1 glasses, and liquids with thermal conductivities ranging from 10 to 0.5 W.m− .K− . Gases with −1 −1 thermal conductivities ranging from 0.6 to 0.02 W.m .K can be considered excellent thermal insulators, but in practice, due to the free convection that always occurs, convection must be prevented by immobilizing the gas into tiny cavities that impedes the convection mechanism to occur. Materials with a cellular structure, such as foam, or with fibers, like mineral wool, are typical examples of insulating materials. A vacuum is the best thermal insulator from a conduction and convection point of view if radiation is not a concern.

1.4.7 Thermal Diffusivity When a material is submitted to a transient temperature change, the temperature profile inside the material can be obtained using Fourier’s second law:

∂T/∂t = α ΔT + ∑iSi

(Fourier’s second law),

where ∑iSi is the sum of contribution rate of heat generation (i.e., Si < 0) or absorption (i.e., Si > 0) by physical processes other than mechanical or thermal energy (e.g., chemical, electromagnetic, nuclear) and α is the thermal diffusivity of the material defined as follows:

α = k/ρcp, with 2 1 α thermal diffusivity in m .s− , 3 ρ density of the material in kg.m− , 1 1 cp specific heat capacity of the material in J.K− .kg− .

29

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30

Properties of Materials

1.4.8 Spectral Emissivity Every body emits electromagnetic radiation, but only hot bodies emit thermal radiation with a wavelength in the infrared region. In all cases the irradiance is given by the Stefan– Boltzmann equation:

J = εσT , where 2 J irradiance in W.m− , ε spectral emissivity, 8 2 4 σ Stefan–Boltzmann constant 5.673 × 10− W.m− K− , T absolute thermodynamic temperature of the source in K. 4

1.4.9 Temperature and Latent Enthalpies of Fusion, Vaporization, and Sublimation Usually any material undergoes a reversible transformation of state with an increase of its temperature in the order depicted in Figure 1.8. Each reversible transformation requires a certain amount of energy to occur. At constant pressure, this energy per unit amount of matter of the material is called the standard latent molar enthalpy of the transformation (for1 merly the latent heat), denoted ΔHtr and expressed in J.mol− . For practical reasons, engineers prefer to use the latent enthalpy per unit mass of the substance called the specific latent en1 thalpy of the transformation, denoted Δhtr and expressed in J.kg− . The simple relationship between the two quantities is as follows:

ΔHtr = M · Δhtr.

Figure 1.8. Solid–liquid–gas reversible transformations

Thermal Properties

The slope of the transformation curves in the P-T diagram is given by the Clausius–Clapeyron equation:

∂P/∂T = ΔStr /Δvm = ΔHtr /Ttr Δvm, where ΔStr is the standard molar entropy in J.mol− of the transformation and vm the molar volume: 1

∂P/∂T = ΔSfusion /Δvm = ΔHfusion /Tm Δvm, ∂P/∂T = ΔSvap /Δvm = ΔHvap /Tb Δvm, ∂P/∂T = ΔSsub /Δvm = ΔHsub /Tsb Δvm. In practice, in the technical literature many tables list the latent enthalpies of fusion and vaporization of usual compounds, but few data are given regarding the latent enthalpy of sublimation. When such a value is missing, a rule of thumb for assessing the latent enthalpy consists in using the Trouton’s first empirical rule, i.e., the latent molar enthalpy of sublimation of a solid corresponds to the sum of its latent molar enthalpies of fusion and of vaporization as follows:

ΔHsublimation ~ ΔHfusion + ΔHvaporization

(Trouton’s first empirical rule).

When the latent molar entropies of the transformation must be found, it is possible to use the Trouton’s second empirical rule. Based on the experimental fact that the values of Svap are very close for many compounds, Trouton’s second rule states that in a first approximation:

ΔSvap = 88 J.K− .mol− at the boiling point 1

1

(Trouton’s second empirical rule).

This simple rule indicates that the latent entropy of vaporization of one mole of liquid leads to the same disorder. However, there are several exceptions, especially for liquids with a hydrogen bond (e.g., H2O, NH3, alcohols), that exhibit greater latent entropies ranging 1 1 from 96 to 109 J.K− .mol− . Trouton’s third rule states that the latent molar entropies are obtained from the ratio of the latent molar enthalpies by the absolute thermodynamic temperature of the transformation:

ΔSfus ~ ΔHfus /Tfus,

ΔSvap ~ ΔHvap /Tvap,

ΔSsub ~ ΔHsub /Tsub.

On the other hand, the latent enthalpy of melting for a pure metal can be approximated by Richard’s rule:

ΔHfus ~ RTfus. The empirical Dulong–Petit rule states that at room temperature all solid elements exhibit the same molar heat capacity, which is roughly equal to three times the ideal gas constant. This is, however, not true for all solids (e.g., diamond, silicon, boron, and beryllium), but it gives a good order of magnitude for engineers and scientists in the absence of data, especially in the field or at the plant. This behavior was later confirmed theoretically by the work of Einstein and Debye, who demonstrated that at temperatures above the Debye temperature of the element (TD), the molar heat capacity of solids tends to 3R:

CP(solids, T > TD) = 3 · R = 24.9429 J.K− mol− . 1

1

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32

Properties of Materials

1.4.10 Order of Magnitude of Thermal Properties of Materials Table 1.8. Order of magnitude of thermal properties of selected materials Material

Melting point Thermal conductivity Specific heat capacity Linear thermal expansion 1 1 1 1 1 6 (mp/°C) (k/W.m− .K− ) (cp /J.kg− .K− ) (αL /10− K− )

Diamond

3500

900

506

2.2

Tungsten

3414

174

132

4.6

Molybdenum

2620

138

251

5.3

Silicon carbide

2400

42.5

690

4.5

Alumina

2054

36

796

8

Titanium

1668

22

538

8.4

Iron

1535

80

447

12

Nickel

1452

91

471

13

Stainless 304

1400

15

477

17

Concrete

1100

1.4

880

10

Steel 1010

1200

64

434

19

Copper

1084

401

494

17

Glass (sodalime)

780

1.4

835

89

Aluminum

660

237

903

23

Magnesium

649

156

1025

26

Zinc

420

121

389

29

Lead

327

35

129

30

Nylon

255

0.25

1670

40

Tin

232

67

229

21

Polyvinylchloride 198

0.13

1339

190

Lithium

181

85

3548

56

Wood (oak)

decomp

0.19

2385

n.a.

1.5 Optical Properties 1.5.1 Index of Refraction When an incident beam of electromagnetic radiation (e.g., light) having a wavelength, λ, travelling through a vacuum, impinges obliquely on the surface of a transparent medium, a fraction of the light is reflected while the remainder penetrates the medium and is refracted (Figure 1.9). The plane angle measured between the incident beam and the normal to the surface plane is called the angle of incidence, denoted i, while the angle between the refracted beam and the normal to the surface is called the angle of refraction, denoted r, both expressed in radians. The incident and refracted light beams lie in the same plane, and according to the Snellius–Descartes law, the ratio between the celerity of light in a vacuum, c, and in a medium, V, and the ratio between the sines of the plane angles of incidence and of refraction are

Optical Properties

33

1 Properties of Materials

Figure 1.9. Principle of refraction of a light beam

equal and constants for the medium concerned at given pressure and temperature and for a given wavelength: sin i /sin r = c /V = constant. The constant is a direct measure of the refractive power of a medium for a given wavelength λ and is called the index of refraction or refractive index (RI) or absolute refractive index of the medium and denoted nλ. Hence, the RI index of refraction is a dimensionless physical quantity defined as the ratio of the celerity of light in a vacuum, c, to the celerity of the elec1 tromagnetic radiation in a medium, V, in m.s− . By definition the index of refraction of a vacuum is taken arbitrarily to equal unity:

nλ = c /V. Sometimes the relative index of refraction or relative refractive index, denoted ñ, is used and corresponds to the dimensionless ratio of the absolute index of refraction of a substance to that of a reference substance, usually air. Because the index of refraction of air is close to unity, the two quantities are often confused:

ñ = nλ /nair,

hence at 273 K,

ñ = nλ /1.00027.

NB: The absolute index of refraction of all materials is always a positive integer and is always greater than unity, except for electromagnetic radiation with shorter wavelengths in the x-ray region, where it can be less than unity due to more complex radiation-matter interactions. Some orders of magnitude for the indices of refraction of various transparent substances are listed in Table 1.10. In the general situation, where the incident beam of light obliquely impinges on the interface plane separating two transparent media of different indices of refraction, n1 and n2, as in the previous case, a fraction of the light is reflected while the other fraction penetrates the medium and is refracted (Figure 1.10). The relationship between the two indices of refraction and angle of incidence and angle of refraction follows the Snellius–Descartes law:

n1sin i = n2sin r. Therefore, the celerity of light in a medium is proportional to the inverse of the refractive index. Consequently, the angle of refraction is smaller (resp. larger) than the angle of incidence for a second medium having a higher (resp. lower) RI than the first medium, that is, the refracted beam is more (resp. less) bent.

34

Properties of Materials

Figure 1.10. Refraction in two media

In most tables and materials databases, the index of refraction of transparent substances (i.e., gases, liquids, and solids) is measured for a monochromatic radiation; unless otherwise specified, it is measured at a temperature of 20°C and for a standardized wavelength taken equal to that of the D-line of the resonance atomic transition in the vapor of sodium metal 20 (λ = 589.3 nm). Therefore, the standardized symbol is then n D, or simply nD.

1.5.2 Total Reflection and Critical Angle When a beam of incident light passes from a transparent medium with a high index of refraction to a second medium with a lower refractive index, it was mentioned that the angle of refraction is always smaller than the angle of incidence. Therefore the angle of refraction reaches its maximum value of π/2 radians for a particular value of the angle of incidence called the critical angle, denoted αc. If the angle of incidence is further increased, the refracted beam cannot emerge and is reflected back into the medium having a higher RI and with an angle of total reflection equal to that of incidence (Figure 1.11):

n1sin αc = n2

Figure 1.11. Total refraction and critical angle

sin αc = n2 /n1.

Optical Properties

When the phenomenon occurs between a denser transparent medium and air having an index of refraction close to unity (1.00027), the sine of the critical angle can be assumed to be equal to the reciprocal of the index of refraction as follows: sin αc ~ 1/n.

1.5.3 Specific and Molar Refraction The specific refraction rD (λ = 589 nm) is independent of pressure and temperature and is given by the Lorentz equation as follows:

rD = (nD − 1)/(nD + 2)·(1/ρ). 2

2

The molar refraction RD (λ = 589 nm) is given by

RD = (nD − 1)/(nD + 2)·(M/ρ). 2

2

1.5.4 Refractivity Sometimes, other physical quantities are used in tables and in calculations, such as the refractivity, which corresponds to the index of refraction minus the unity, the specific refractivity, that is, the refractivity divided by the mass density of the substance, and the molar refractivity: Refractivity λ; Rλ = (nλ − 1) Specific refractivity λ; Rmλ = (nλ − 1)/ρ Molar refractivity λ; RMλ = M(nλ − 1)/ρ

1.5.5 Dispersion Dispersion is the variation of the index of refraction with the wavelength of the incident light. Its variation as a function of wavelength is a reciprocal function also called Abbe’s equation:

nλ = a + b/λ + c/λ + ··· etc., 2

4

where a, b, and c are empirical constants that characterize the material and are determined by experiment. For most substances, the following simple equation is sufficient:

nλ = a + b/λ . 2

Another practical dispersion formula, used for high-precision measurement, is the Sell–Meier formula:

nλ −1 = [A1λ /(λ −B1)] + [A2λ /(λ −B2)] + [A3λ /(λ −B3)]. 2

2

2

2

2

2

2

The empirical constants A1, A2, A3, B1, B2, and B3 are computed by the method of least squares on the basis of refractive indices at standard wavelengths.

35

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36

Properties of Materials

1.5.6 Coefficient of Dispersion Finally, the index of refraction of a substance is strongly dependent on the wavelength of the incident beam; this variation is called dispersion. Actually, for a given material the celerity of light across a medium is faster for large wavelengths (i.e., lower energies) and lower for smaller wavelengths (i.e., higher energies). In practice, the dispersion is measured by the coefficient of dispersion, that is, the difference between the index of refraction of the substance measured at two different wavelengths, usually red light (763 nm) and violet light (397 nm), and multiplied by 10,000:

Δnλ (in ‰) = (nλ2 − nλ1) × 10 . 4

1.5.7 Abbe Number Another measure of dispersion is the Abbe number or nu-number, denoted vD, which is the ratio of the refractivity divided by the dispersion as follows:

vD = (nD − 1)/(nF' − nC'), Formerly the refractive indices were measured for the sodium-D-line (λD = 589.3 nm, yellow), the cadmium F' line (λF' = 480.0 nm), and the C' line (λC' = 643.8 nm). This has been more recently updated as follows:

vD = (nD − 1)/(nF − nC), where the refractive indices are measured for the sodium-D-line (λD = 589.3 nm, yellow), and the hydrogen Fraunhofer lines (λF = 486.1 nm, blue) and (λC = 656.3 nm, red).

1.5.8 Temperature Dependence of the Refractive Index The index of refraction is affected by temperature variations. This can be ascertained through the temperature coefficient of refractive index, denoted ∂nλ /∂T. Hence, the Abbe number also changes with temperature. There are two ways of showing the temperature coefficient of the refractive index. One is the absolute temperature coefficient of refractive index (∂nλ /∂T)abs, measured in a vacuum, and the other is the relative temperature coefficient of refractive index (∂nλ /∂T)rel, measured in ambient air (101.3 kPa in dry air). They are related by the following formula: (∂nλ /∂T)abs = (∂nλ /∂T)rel+ nλ · (∂nλ /∂T)air.

1.5.9 Anisotropic Materials The three-dimensional surface describing the variation in the refractive index in relation to the vibration direction of incident light is called the indicatrix. Isotropic materials have the same refractive index regardless of vibrational directions, and the indicatrix is a sphere. Isotropic materials are: (i) crystals with a cubic crystal lattice; (ii) amorphous materials (i.e., vitreous or glassy); or (iii) fluids (e.g., liquids and gases).

Optical Properties

By contrast, a solid material with more than one principal index of refraction is called anisotropic Anisotropic materials are divided into two subgroups: (i) solid materials having a tetragonal, hexagonal, and rhombohedral crystal space lattice structure are called uniaxial, while (ii) solid materials having an orthorhombic, monoclinic, and triclinic crystal space lattice structure are called biaxial. Uniaxial crystals belong to the rhombohedral, hexagonal, or tetragonal crystal systems and possess two mutually perpendicular refractive indices, ε and ω, which are called the principal refractive indices. Intermediate values occur and are called ε', a nonprincipal refractive index. The uniaxial indicatrix is an ellipsoid, either prolate (ε > ω), termed positive (+), or oblate (ε < ω), termed negative (−). In either case, ε coincides with the single optic axis of the crystal, yielding the name uniaxial. The optic axis also coincides with the axis of highest symmetry of the crystal, either the fourfold for tetragonal minerals or the three- or sixfold of the hexagonal class. Because of the symmetry imposed by the three-, four-, or sixfold axis, the indicatrix contains a circle of radius ω perpendicular to ε (i.e., perpendicular to the optic axis). Light vibrating parallel to any of the vectors would exhibit the refractive ω. Light vibrating parallel to the optic axis would exhibit ε. Light that does not vibrate parallel to one of these special directions within the uniaxial indicatrix would exhibit an index of refraction intermediate to ε and ω and is termed ε'. Biaxial crystals belong to the orthorhombic, monoclinic, or triclinic crystal systems and possess three mutually perpendicular refractive indices (α, β, and γ), which are the principal refractive indices. Intermediate values also occur and are labeled α' and γ '. The relationship between these values is α < α' < β < γ ' < γ. The three principal refractive indices coincide with three mutually perpendicular lattice vector directions, a, b, and c, which form the framework for the biaxial indicatrix. The point group symmetry of the biaxial indicatrix is 2/m 2/m 2/m. In orthorhombic minerals the a, b, and c vectors coincide with either the twofold axes or normals to mirror planes. In monoclinic minerals, the a, b, and c vectors coincide with the single symmetry element. In triclinic minerals, no symmetry elements necessarily coincide with the axes of the indicatrix. The birefringence (i.e., double refraction), δ, is the physical quantity equal to the mathematical difference between the largest and smallest refractive index for an anisotropic mineral. Pleochroism is the property of exhibiting different colors as a function of the vibration direction. Dichroism refers to uniaxial minerals, while trichroism refers to biaxial minerals.

1.5.10 Birefringence Birefringence, or double refraction, is the decomposition of a beam of light into two rays, the ordinary ray and the extraordinary ray, when it passes through anisotropic materials. Birefringence is measured as the difference between the greatest and the lowest index of refraction of an anisotropic and transparent material:

δ = Δn = ng − np.

1.5.11 Albedo and Reflective Index When a ray of light falls upon a plane surface of a material, it is reflected in such way that the angle of reflection, θr, in radians is equal to the angle of incidence, θi, and the rays of reflected and incident light lie in the same plane. The main parameter to characterize materials under reflected light is the reflective index, also called albedo and denoted Rλ, for a given wavelength, λ, usually set at 650 nm, which corresponds to the dimensionless ratio expressed as a percentage of the intensity of reflected light to the intensity of incident light:

Rλ (%) = 100 × IR /I0.

37

1 Properties of Materials

Properties of Materials

1.5.12 Electromagnetic Radiation Spectrum Table 1.9. Electromagnetic radiation spectrum

Ionizing radiation

7

Electromagnetic radiation

Wavelength range

Wavenumber range

100,000 to 0.1 fm

1000 to 10 nm

X-rays (X-rays)

Hard (HXR)

0.1 to 1.0 nm

10,000 to 1000 μm−

Soft (SXR)

1.0 to 10 nm

1000 to 100 μm−

12.4 MeV to 12.4 keV 1

12.40 to 1.24 keV

1

1240 to 124 eV

−1

124 to 12.4 eV

10 to 100 nm

100 to 5.556 μm

100 to 180 nm

100 to 55.56 μm−

1

12.4 to 6.89 eV −1

Far-UV (FUV)

180 to 200 nm

55,556 to 50,000 cm

Near-UV (NUV)

200 to 380 nm

50,000 to 26,316 cm−

1

6.20 to 3.26 eV

380 to 780 nm

26,316 to 12,821 cm−

1

3.26 to 1.59 eV

Visible light (Vis) Infrared (IR)

Energy range

−1

Gamma rays (γ-rays)

Ultraviolet Extreme (EUV) (UV) Vacuum (VUV)

Nonionizing

38

−1

6.89 to 6.20 eV

Near (NIR)

0.78 to 2.5 μm

12,821 to 4000 cm

1.59 to 0.496 eV

Medium (MIR)

2.5 to 50 μm

4000 to 200 cm−

0.496 to 0.025 eV

−1

50 to 1000 μm

200 to 10 cm

Microwaves (MWs)

0.1 to 100 cm

10 to 0.01 cm−

Radiowaves (RW)

1 to 1000 m

1 to 0.001 m−

Far (FIR)

1

25 to 1.24 meV 1

1

1240 to 1.24 μeV 1240 to 1.24 neV

1.5.13 Order of Magnitude of Optical Properties of Transparent Materials Table 1.10. Index of refraction and related quantities of selected transparent substances Substance

Density Refractive Critical Coefficient Abbe Refrac- Specific Molar 3 (ρ/kg.m− ) index angle dispersion number tivity refractivity refractivity 8 9 10 11 12 (nD ) (αc ) (Δnλ ) (νD) (nλ − 1) (nλ − 1)/ρ M(nλ − 1)/ρ

Air (0°C)

1.293

1.00027

w/o

Ice (0°C)

917

1.310

49.78°

Water

997

1.33299

48.65°

Fused silica

0.0000076

60.557

0.310

338.06

6.085

56.4

0.33299 333.98

6.012

67.7

0.459

208.64

12.52

31.0

0.590

491.67

2200

1.459

43.28°

Polycarbonate 1200

1.590

38.97

Crown glass

2800

1.517

41.25°

0.020

58.2

0.517

184.64

Flint glass

5900

1.575

39.43°

0.048

55.0

0.575

97.46

Sapphire

3990

1.769

34.43°

72.2

0.769

193.22

19.71

Diamond

3520

2.4195

24.45°

1.517

430.97

5.17

Rutile

4245

2.605

22.58°

1.605

378.09

30.25

7

8 9 10 11 12

0.017

0.00027 208.82

0.063

In radioprotection, an electromagnetic radiation is defined as ionizing if its energy is above 12 eV, i.e., if it is capable of ionizing both atoms and molecules constituting living matter. Measured at 293.15 K for the D-line of the vapor of sodium metal (λ = 589.3 nm). Air at 273.15 K and 101.325 kPa as surrounding medium of lower refractive index. Measured between red light (λ = 763 nm) and violet light (λ = 397 nm). 1 6 3 Measured at 293.15 K and 101.325 kPa and expressed in 10− m .kg− . 1 6 3 Measured at 293.15 K and 101.325 kPa and expressed in 10− m .mol− .

Optical Properties

1.5.14 Macroscopic Absorption of Light

1 Properties of Materials

1.5.14.1 Damping Constant In fact, the index of refraction can be fully described as a complex number denoted by N and defined as follows: N = n − i k, where n is the real part that corresponds exactly to the actual index of refraction discussed previously while the imaginary part k is the damping constant, also called the attenuation index, or extinction. The imaginary index of refraction is also related to the imaginary relative permittivity of the medium by N = (n − i k) = εr = εr' + iεr". 2

39

2

1.5.14.2 First Law of Absorption (Bouger’s Law) When a beam of monochromatic electromagnetic radiation of wavelength λ and intensity I0(λ) strikes under a normal (i.e., orthogonal) incidence, any isotrope, homogeneous, and nonluminescent medium (i.e., pure solid, liquid, or gas) that exhibits plane and parallel faces with a thickness x, expressed in m, the variation of light intensity follows a linear differential relation given by: dI(λ) = −α(λ)I(λ)dx. After integration, we obtain the following exponential Bouger’s absorption equation:

I(λ) = I0(λ)exp[−α(λ)x] = I0(λ)e−α λ , ( )x

with α(λ) the Napierian linear coefficient of absorption for a given wavelength λ, expressed 1 in reciprocal meter, m− . This physical quantity is an intrinsic property of the medium at a given monochromatic radiation. However, both for historical reasons and to simplify calculations, Bouger’s law is usually written as a power of ten rather than the previous exponential form:

I(λ) = I0(λ)10−Κ λ , ( )x

with Κ(λ) the decadic linear coefficient of absorption or Bunsen–Roscoe absorption coeffi1 cient for a given monochromatic radiation, expressed in reciprocal meter, m− . As for the Napierian coefficient, this physical quantity is an intrinsic property of the medium at a given wavelength. The relationship between the Napierian α(λ) and the decadic K(λ) coefficients is as follows:

α(λ) = K(λ) ln10 ≈ 2.302585093 K(λ). The physical meaning of the quantities α(λ) and K(λ) can be stated thus: the reciprocal of the Napierian coefficient of absorption α(λ) corresponds to the thickness of the medium for which the incident intensity is divided by the base of the Napierian logarithm (i.e., e = 2.718281828…), while the reciprocal of the Bunsen–Roscoe coefficient of absorption K(λ) corresponds to the thickness of the medium for which the incident intensity is divided by ten. In most practical applications the decadic absorption coefficient is used, but the Napierian absorption coefficient is introduced more naturally in theoretical equations. NB: Neither the coefficient of absorption α(λ) nor K(λ) takes into account concentration, and hence Bouger’s law must be restricted only to pure substances (i.e., solids, liquids, and gases).

40

Properties of Materials

1.5.14.3 Second Law of Absorption (Beer–Lambert Law) In the particular case of a beam of monochromatic radiation of wavelength λ and intensity I0(λ) striking under a normal incidence, any isotropic, homogeneous, and nonluminescent solution containing a solute dissolved in a transparent solvent with a given molarity, de3 noted C and expressed in mol.m− , exhibiting plane and parallel faces with a thickness denoted x and expressed in meters, the variation of light intensity follows a linear differential relation given by: dI(λ) = −Σ(λ)CI(λ)dx. After integration, we obtain the following exponential equation:

I(λ) = I0(λ)exp[−Σ(λ)Cx] = I0(λ)e−Σ λ , ( )x

with Σ(λ) the Napierian molar extinction coefficient for a monochromatic radiation λ, 1 2 expressed in mol− m . This physical quantity is an intrinsic property of the solute of species i at a given wavelength. However, both for historical reasons and to simplify the calculations, Beer–Lambert’s law is usually written as a power of ten rather than in exponential form:

I(λ) = I0(λ)10−ε λ , ( )Cx

with ε(λ) the decadic molar extinction coefficient for a monochromatic radiation λ, ex1 2 pressed in mol− m . As for the Napierian molar extinction coefficient, this physical quantity is an intrinsic property of the medium at a given wavelength. The relationship between the Napierian Σ(λ) and the decadic ε(λ) coefficients is given below:

Σ(λ) = ε(λ) ln10 ≈ 2.302585093 K(λ). The physical meaning of the quantities Σ(λ) and ε(λ) for a given molarity of solute is as follows: the reciprocal of the Napierian coefficient of absorption α(λ) corresponds to the thickness of the medium for which the incident intensity is divided by the base of the Napierian logarithm (i.e., e = 2.718281828…), while the reciprocal of the decadic coefficient of absorption ε(λ) corresponds to the thickness of the solution for which the incident intensity is divided by ten. In addition, note that in analytical chemistry, the solution is in a rectangular cell with optical path denoted l, expressed in centimeters, while the molarity of the 3 solute is expressed in mol.dm− ; hence in this particular case the molar extinction coefficient is 3 −1 −1 expressed in mol .dm .cm . Moreover, in some textbooks (e.g., pharmacy), a derived quan1% tity called the specific molar extinction coefficient, denoted E 1cm, is defined for a mass concentration of solute of 1 wt.% and a cell having an optical path 1 cm in length.

1.5.14.4 Absorbance or Optical Density The absorbance, sometimes called the optical density or extinction, denoted A, DO, or Δ, is a dimensionless physical quantity that corresponds to a monochromatic radiation to the logarithm of the ratio of incident radiation intensity over a transmitted radiation intensity. Depending on the selected logarithm function type, both the Napierian (B and Ae) and the decadic absorbance (A, A10, and DO) can be defined and related to transmittance:

A(λ) = A10(λ) = DO(λ) = log10[I0(λ)/I(λ)] = ε(λ)Cl = colog10T(λ), B(λ) = Ae(λ) = ln[I0(λ)/I(λ)] = Σ(λ)Cl = −lnT(λ). The combination of Beer–Lambert’s law and the absorbance definition tells us that mathematically for monochromatic radiation both the Napierian and decadic absorbance of a solution consisting of a transparent solvent containing a solute are a linear function of the following factors:

Optical Properties

(i) the molarity of the solute, C; (ii) the molar extinction coefficient, ε; and (iii) the cell optical path, l. Hence, by plotting absorbances of several standard solutions with increasing concentration of solute for a given wavelength and cell optical path, we are able to determine the concentration of an unknown sample. This method is the basis of spectrochemical quantitative analysis. Absorbance additivity. When a beam of monochromatic radiation λ and intensity I0(λ) strikes under a normal incidence any isotrope, homogeneous, and nonluminescent solution containing n solutes i dissolved in a transparent solvent with a given molarity, denoted Ci for 3 each species, expressed in mol.m− , and contained in a cell exhibiting plane and parallel faces with an optical path length denoted l, the total absorbance A is the sum of the contributions of individual absorbances of each species:

A(λ) = ∑iAi(λ) = l ∑iεi(λ)Ci.

Beer–Lambert’s law deviation. For monochromatic radiation, Beer–Lambert’s law is always verified and linear in a wide range of solute concentrations. However, experimental deviations occur due to intermolecular interactions (i.e., associations), chemical reaction (e.g., ionization, etc.), or equilibrium displacement due to pH, colloids, or high coloration. Nevertheless, another parameter is the temperature, and for accurate measurements temperaturecontrolled cells must be used. Finally, the bandwidth of monochromatic radiation is critical in certain region of spectra where slight variations in wavelength lead to large variations in the molar extinction coefficient.

1.5.15 Microscopic Absorption and Emission Processes Interaction between electromagnetic radiation and matter follows vertical Franck–Condon transitions for both absorption and emission. This means that during electronic transitions, both the positions and the spin angular momentum of an atom’s nucleus remain virtually unchanged due to the high velocity of electrons compared to the displacement of a heavy nucleus. Three type of interactions occur: (i) absorption; (ii) emission; (iii) stimulated emission. • Absorption process. During the absorption process of a quantum of electromagnetic radiation, denoted hν, by microscopic entities (i.e., elementary particles, ions, atoms, or molecules) the irradiated system passes from a low-energy quantum level (i.e., initial or ground/fundamental state), denoted Ei, to a higher energy level (i.e., excited or final state), denoted Ek. The energy required to achieved this transition should be at least equal to or greater than the energy variation ΔEik = Ek − Ei. As a general rule, the required energy is positive from a thermodynamic point of view, i.e., energy is absorbed by the system, and is related to the energy of incident radiation by the Planck–Einstein equation listed below:

ΔE = Ek − Ei = hνik = hc/λik = hcσik = h /Tik = hωik /2π.

41

1 Properties of Materials

42

Properties of Materials • Emission process. During the emission process the opposite process occurs, i.e.,

microscopic entities (i.e., elementary particles, ions, atoms, or molecules) decay from a high-energy excited state (i.e., initial state), denoted Ek, to a final lower energy level (i.e., ground or fundamental state), denoted Ei. This quantum state change is accompanied by the emission of a quantum of electromagnetic radiation, denoted hν. This quantum corresponds exactly to the negative energy variation, denoted ΔEki = Ek − Ei, between the two states, i.e., energy is released by the system, and is related to the energy of emitted radiation by the Planck–Einstein equation. In molecular spectroscopy, absorption/emission processes can be grouped into three classes: (i)

Rotation is associated with transitions between molecular rotational states without changes in either the vibrational or electronic states. The radiation involved ranges between far-infrared and microwaves. (ii) Rotation-vibration is associated with transitions between molecular vibrational states with modifications to rotational states. The radiation involved is in the mid-infrared region. (iii) Finally, electronic processes are associated with transitions between electronic states, with radiation ranging between vacuum ultraviolet and visible regions. • Stimulated emission. During this process the emission of monochromatic electromagnetic radiation occurs. This particular emitted radiation exhibits the same wavelength, the same phase (i.e., coherent), and the same direction as those of incident radiation but exhibits a higher intensity (e.g., MASER and LASER). The procedure to produce stimulated emission consists in the following:

(i)

(ii)

The natural population of entities in the ground state with low energy, Ei, is inverted to a fully occupied excited state population of higher energy, Ek, by irradiation by photon of minimal energy hνij = Ek − Ei. This operation is called optical pumping. Second, an incident beam of electromagnetic radiation irradiates the excited entities and produces a relaxation of excited states to ground state with emission of light with an intensity several times the intensity occurring during normal emission. Despite being feasible in theory with only two energy levels, stimulated emission usually requires two or more energy levels to allow proper inversion of the populations.

1.5.16 Einstein Coefficients The relationship between the absorption and emission of electromagnetic radiation can be easily established using a phenomenological approach that provides important quantities called Einstein coefficients.

1.5.16.1 Einstein Coefficient of Absorption In the process of absorption of an electromagnetic radiation by microscopic entities (i.e., elementary particles, ions, atoms, or molecules) from a ground (i.e., fundamental) state of energy, denoted Ei, to an excited state of higher energy, denoted Ej, the transition requires the absorption of a photon (i.e., quantum) having at least the minimum energy per entity:

ΔEij = Ej − Ei = hνij = hcσij.

Optical Properties

From a chemical kinetic point of view, the electromagnetic radiation absorption process of a photon having an energy hνij can be seen as the following pseudoreaction scheme:

hνij + Ai —> Aj*, where Ai and Aj* represent the microscopic entities in the ground (i) and excited (j) state, respectively. Therefore, the disappearing rate of entities Ai can be written as a second-order kinetic equation:

vd = −dNi /dt= kij[ni][hνij], where ni is the density of entities in the ground state Ai expressed in m− , kij the second-order 3 kinetic rate constant of the absorption process, and [hνij] the photon density expressed in m− . Introducing a new physical quantity, the photon energy density, denoted ρij and expressed in 3 J.m− , the photon density corresponds to the photon energy density divided by the photon individual energy hνij; hence the absorption rate can be rewritten as follows: 3

vd = −dNi /dt= (kij /hνij)[ni]ρij = Bij[ni]ρij. The quotient of the second-order kinetic rate constant over the energy of transition is called 6 1 1 the Einstein coefficient of absorption, denoted Bij and expressed in m J− s− . Precise, quantum-mechanical calculations give the following equation for the absorption coefficient (wavenumber basis):

Bij = 8π /[(4πε0)3h c]∑ij. 3

2

1.5.16.2 Einstein Coefficient of Spontaneous Emission Considering the emission process of electromagnetic radiation by microscopic entities (i.e., elementary particles, ions, atoms, or molecules) from an excited state of higher energy, denoted Ej, to a ground (i.e., fundamental) state of energy, denoted Ei, the transition emits a photon (i.e., quantum) having an energy equal to the energy variation per entity:

ΔEji = Ej − Ei= hνji. From a chemical kinetic point of view, the electromagnetic radiation emission process of a photon having an energy hνji can be seen as the following pseudoreaction scheme: Aj* —> Ai + hνji, where Ai and Aj* represent the microscopic entity in the ground (i) and excited (j) states, respectively. Therefore, the disappearing rate of excited states of entity Ai* can be written as a second-order kinetic equation:

v*d = −dN*j /dt= kji[ni*], where ni is the density of excited states Ai* expressed in m− , kji the second-order kinetic rate 3 constant of emission process, and [hνji] the photon density expressed in m− ; hence the emission rate can be rewritten as follows: 3

v*d = −dN*j /dt= (kji /hνji)[n*j] = Aji[n*j]. The quotient of the second-order kinetic rate constant over the energy of transition is called 3 1 the Einstein coefficient of emission, denoted Aji and expressed in m s− . Precise, quantummechanical calculations give the following equation for the absorption coefficient (wavenumber basis):

Aji = 64π /[(4πε0)3hcσ ]∑ij . 4

3

2

43

1 Properties of Materials

44

Properties of Materials

1.5.16.3 Einstein Coefficient of Stimulated Emission During this process, emission of monochromatic electromagnetic radiation occurs exhibiting the same wavelength, in phase (i.e., coherent), with the same direction as that of incident radiation but with higher intensity. From a chemical kinetic point of view, the stimulated emission process can be seen as the following pseudoreaction scheme:

hνij + A*j —> Ai + 2hνij, where Ai and Aj* represent the microscopic entities in the ground (i) and excited (j) state, respectively. Therefore, the disappearing rate of excited states A*j can be written as a secondorder kinetic equation:

vd = −dN*i /dt = kji[nj*], where nj is the density of excited state A*i expressed in m− , kji the second-order kinetic rate 3 constant of the stimulated emission process, and [hνij] the photon density expressed in m− . −3 Introducing the photon energy density, denoted ρij and expressed in J.m , the photon density corresponds to the photon energy density divided by the photon individual energy hνij; hence the emission rate can be rewritten as follows: 3

vd = −dN*i /dt= (kji/hνji)[n*j]ρij = Bji[n*j]ρij. The quotient of the second-order kinetic rate constant over the energy of transition is called 6 1 1 the Einstein coefficient of stimulated emission, denoted Bji and expressed in m J− s− . Precise, quantum-mechanical calculations give the following equation for the absorption coefficient (wavenumber basis):

Bji = 8π /[(4πε0)3h c]∑. 3

2

1.5.16.4 Relation Between Einstein Coefficients Consider a system containing microscopic entities A in an evacuated space in thermal equilibrium at an absolute temperature, denoted T, expressed in K. The distribution of population quantum states i and j follows the classical distribution of Maxwell–Boltzmann:

ni = g (i) exp (−Ei /kT) and n*j = g*(j) exp (−Ej/kT), where g(i) and g(j) represent the degenerating degrees of each state. Using the energetic condition of Bohr, we obtain the equation: (n*j /ni) = [g*(j)/g (i)] · exp[−(hνij /kT)]. In addition, at thermodynamic equilibrium we have dni /dt = dnj /dt; therefore the conservation of energy can be written as follows: radiation absorbed is equal to radiation emitted spontaneously and by stimulated emission:

Bij[ni]ρij = Bji[n*j]ρij + Aji[n*j]. We can now express the energy density as follows:

ρij = ρij + Aji[n*j]/{Bij[ni] + Bji[n*j]} = [Aji /Bji] · {1/{[Bij·g (i)/Bji·g*(j)]·[exp(hνij /kT) − 1]}}. This equation can be identified with the spectral radiant energy density, denoted dρ/dσ and 2 2 expressed in J.m− , given by the first Planck radiation formula given below, where c1 = 2πhc is the first radiation constant and c2 = hc/k the second radiation constant:

dρ c1 ⋅σ3 8πhcσ3 . = = dσ ⎡ ⎛ c 2 ⋅σ ⎞ ⎤ ⎡ ⎛ hcσ ⎞ ⎤ − − exp 1 exp 1 ⎜ ⎟ ⎥ ⎢ ⎜ ⎟⎥ ⎢ ⎝ T ⎠ ⎦ ⎣ ⎝ kT ⎠⎦ ⎣

Optical Properties

By identification between the two equations we find the three relations between the three Einstein coefficients:

Bij =

g ( j) ⋅ Bji , g (i )

Aji = 8πhcσ3 Bij ,

Aji ⎛ hcσ ⎞ = exp ⎜ ⎟ −1 . ρ ( σ ) Bji ⎝ kT ⎠

1.5.16.5 Relations Between Einstein and Extinction Coefficients The relation existing between the Einstein coefficient of absorption Bij and the molar extinction coefficient is given by the equation: Bij = [C/(NA·hνij)]·∫ Σ(ν)dν = [(ln10·C)/(NA·hνij)]·∫ ε(ν)dν.

1.5.17 Luminescence Luminescence describes the process during which reemission of previously absorbed radiation occurs. Luminescence includes both fluorescence and phosphorescence processes. Actually, when a microscopic entity (e.g., ion, atom, or molecule) absorbs sufficient energy, its electrons may be promoted to higher energy levels. Subsequent return of the electrons from an excited state to ground electronic state is often accompanied by emission of electromagnetic radiation. When the source of irradiation used to produce luminescence is light radiation, the process is termed photoluminescence. The difference between fluorescence and phosphorescence requires one to focus on the fundamental nature of radiation emission. Actually, electronic states for both atoms and molecules are entirely described by their electron spin angular momentum, denoted S or by their spin multiplicity (2S + 1). Because electrons follow the

Figure 1.12. Jablonski photophysical diagram

45

1 Properties of Materials

46

Properties of Materials

quantic Fermi–Dirac distribution, the electronic states can be split into two distinct groups: singlet states (i.e., S = 0, or 2S + 1 = 1) and triplet states (i.e., S = 1, or 2S + 1 = 3). In addition, each of these electronic states is subdivided into vibrational and rotational states. Therefore, an understanding of electronic transitions between excited to unexcited states can be described by photophysical processes usually reported in a Jablonski diagram (Figure 1.12).

1.5.17.1 Excitation Consider a molecule M in the ground state irradiated by an incident beam of photons having energy hν0: 1

*

hν0 + M —> M (v = 2). When absorbing radiation the molecule first interacts with the incident electromagnetic radia15 tion in a time interval (i.e., excitation timelife, τex ) of ca. one femtosecond (i.e., 1 fs = 10− s), i.e., the period of oscillation of the electromagnetic wave. The π-electrons of the molecule are raised by a Franck–Condon vertical transition from singlet ground or unexcited state (S0) to a singlet excited electronic state, usually from the lowest vibrational level of the ground electronic state and proceeding to the v = 2 vibrational level of the excited electronic state. Other transitions occur, but with lower probabilities.

1.5.17.2 Internal Conversion In returning to the ground electronic state, the favored route involves first dropping to the lowest vibrational level of the lowest excited singlet state within (i.e., excitation timelife, τic ) 12 one picosecond (i.e., 10− s) by means of a radiationless process called internal conversion during which energy is converted only into heat according to the dexcitation scheme: M (v >0) —> M (v = 0) + ΔQ.

1

*

1

*

1.5.17.3 Fluorescence 1

*

When an electron reaches the lowest vibrational level of the lowest excited singlet state M , fluorescence can occur when the electron returns to any fundamental state S0. The mean 9 duration of fluorescence is in the order of a nanosecond (i.e., 1 ns = 10− s): 1

*

M (v = 0) —> M(v = 0) + hνF.

1.5.17.4 Intercombination This nonradiative process violates the Laporte rule, which states that only Franck–Condon transitions occurring between states having the same spin multiplicity are allowed, the others being forbidden. It is important to note that in quantum physics forbidden transitions are not impossible, but this means that their probability is extremely low, i.e., with a longer duration or timelife of the transition. Therefore, the radiative transition occurring between a singlet with no vibrational excitation to a triplet state has a mean timelife (τic ) of several 6 3 microseconds (i.e., 1 μs = 10− s) to milliseconds (i.e., 1 ms = 10− s): 1

*

3

*

M (v = 0) —> M (v > 0).

This intercombination is usually followed by the internal conversion between triplet states as follows: M (v > 0) —> M (v = 0) + ΔQ.

3

*

3

*

Other Properties

1.5.17.5 Delayed Fluorescence Sometimes, thermal agitation (i.e., Brownian motion) induces a nonradiative transfer (i.e., reverse of the internal conversion) from a nonexcited triplet state to an excited triplet state. Afterward, intercombination between the excited triplet and excited singulet state occurs. Finally, by internal conversion down to the nonexcited singulet state, light is emitted by fluorescence, according to the following successive reaction schemes: M (v = 0) + ΔQ —> M (v > 0),

3

*

3

3

*

1

*

1

*

1

*

*

M (v > 0) —> M (v > 0),

M (v > 0) —> M (v = 0),

M (v = 0) —> Μ (v = 0) + hνFR.

1

*

1

1.5.17.6 Phosphorescence Phosphorescence is a radiative process occurring between a nonexcited triplet state down to the ground state (singulet). Because it is a forbidden transition, its timelife (τP) is larger than any other radiative transition, usually greater than one millisecond: M (v = 0) —> Μ(v = 0) + hνp.

3

*

1

1.6 Other Properties 1.6.1 Biocompatibility Table 1.11. Major requirements for biomaterials used for implants, prosthetic devices, and dental repair Requirements

Description

Biocompatible

A material is biocompatible if it does not induce any reactions inside the body.

Corrosion resistance

The material must exhibit outstanding corrosion resistance toward bodily fluids, i.e., dimensional stability, and must not release deleterious metal cations or breakdown products into the body environment either in vitro or in vivo.

Cycle life

The material exhibits a long-lasting resistance to cyclic loading.

High strength-todensity ratio

The material has a high mechanical strength to withstand important stresses and a low density to reduce the mass of the implant.

Low cytotoxicity

The material does not induce harmful or noxious unwanted effects on a cell-culture system.

Low fretting fatigue

The material must exhibit excellent tribological properties that prevent the wear and corrosion process in which the material is removed from contacting surfaces when motion is restricted to very high frequency and small-amplitude oscillations.

Nonmagnetic

The material must be nonferromagnetic to avoid dislodging of the device when subjected to a strong magnetic field such as those encountered during magnetic resonance imaging (MRI).

Passivation

The material must exhibit an active passive behavior that produces a thin, impervious, and protective oxide film in corrosive environments.

Surface treatment The material must allow a surface treatment that ensures a good adhesion of biocompatible ceramic coatings or living tissues.

47

1 Properties of Materials

48

Properties of Materials

1.6.2 Electronegativity The dimensionless quantity called electronegativity is an important concept that is extremely useful both in inorganic and solid-state chemistry because it allows one to understand and explain qualitatively the molecular and crystal structure of various compounds. Basically, the electronegativity of a chemical element can be defined as the ability of an atom to gain electrons; by contrast, electropositivity is the ability to capture electrons. Five approaches have been devised to calculate the electronegativity of an element, and hence five types of electronegativity scales can be encountered in the literature: (i) (ii) (iii) (iv)

Pauling’s electronegativity; Mulliken electronegativity; Allred’s electronegativity; and finally absolute electronegativity introduced by Pearson.

Pauling’s electronegativity. The Pauling electronegativity scale was originally introduced 13 by Karl Linus Pauling in 1932. To establish the practical scale, Pauling compared the bond enthalpies of known homopolar and heteropolar diatomic molecules, and hence this scale is thermochemical in nature. First, he defined the ionic contribution, denoted DAB, to the A-B bond by the following simple equation:

DAB = [ΔHAB − (1/2)(ΔHAA − ΔHBB)], where ΔHAB, ΔHAA, and ΔHBB are the bond enthalpies of the homopolar diatomic molecules A-B and the heteropolar diatomic molecules A-A and B-B, respectively, all expressed in 1 eV.molecule− . From this value, the relative electronegativity of A with respect to B is then calculated using the equation: ΔχAB = χA − χB = (DAB) = [ΔHAB − (1/2)(ΔHAA − ΔHBB)] , 1/2

1/2

with the difference in electronegativity expressed in (eV.molecule− ) . The difference in electronegativities between two species is used as a guide to the ionicity of the interaction between two such atoms, a high value indicating high ionicity. As a direct consequence, any homopolar bond, i.e., A-A, has thus an electronegativity difference of zero and is then purely covalent with an equal sharing of electrons (e.g., F2, Cl2, N2, O2, H2). As the difference in electronegativity of the two atoms in a heteropolar bond increases, the bonding electrons are found to lie closer to the more electronegative atom. In CsF, with an electronegativity difference of 2.3, one would expect the bond to be ionic and hence the net negative charge to lie closer to the fluorine atom. Therefore, it is possible to introduce the degree of ionicity expressed as a percentage: 1 1/2

I(%) = 100 · [1 − exp(−a·ΔχAB)], where a is a constant. Despite the fact that other scales have been calculated from ionization potentials and electron affinities, the Pauling scale has remained the most widely used. 14,15 Mulliken–Jaffe’s electronegativity. Mulliken and Jaffe proposed in the 1930s an electronegativity scale in which the electronegativity of a given species, M, is defined as the arithmetic mean of its electron affinity, denoted EA, i.e., a measure of the tendency of an atom to form a negative species, and its ionization potential denoted IE, a measure of the tendency of an atom to form a positive species, both expressed in eV: χM = (EA + IE)/2. 13 14 15

Pauling, K.L. (1932) J. Am. Chem. Soc., 54, 3570. Mulliken, R.S. (1934) J. Chem. Phys., 2, 782. Mulliken, R.S. (1935) J. Chem. Phys., 3, 573.

Other Properties Table 1.12. Pauling’s electronegativity values of the elements in (eV.molecule− )

49

1 1/2

1

Chemical element

Electronegativity

Chemical element

Electronegativity

Chemical element

Electronegativity

Actinium Aluminum

1.1 1.5

Gold Hafnium

2.5 1.3

Promethium Protactinium

n.a. 1.5

Americium Antimony Argon Arsenic Astatine Barium

1.3 1.9 w/o 2.0 2.2 0.9

Holmium Hydrogen Indium Iodine Iridium Iron

n.a. 2.1 1.7 2.5 2.2 1.8

Radium Radon Rhenium Rhodium Rubidium Ruthenium

0.9 w/o 1.9 2.3 0.8 2.2

Berkelium Beryllium Bismuth Boron Bromine Cadmium

1.3 1.5 1.9 2.0 2.8 1.7

Krypton Lanthanum Lawrencium Lead Lithium Lutetium

3.0 1.1 n.a. 1.8 1.0 1.3

Samarium Scandium Selenium Silicon Silver Sodium

1.2 1.4 2.4 1.8 1.9 0.9

Calcium Californium Carbon Cerium Cesium Chlorine

1.0 1.3 2.5 1.1 0.7 3.0

Magnesium Manganese Mendelevium Mercury Molybdenum Neon

1.2 1.6 1.3 2.0 2.3 w/o

Strontium Sulfur Tantalum Technecium Tellurium Terbium

1.0 2.5 1.5 1.9 2.1 n.a.

Chromium Cobalt Copper Curium Dysprosium Einsteinium

1.7 1.9 2.0 1.3 1.2 1.3

Neptunium Nickel Niobium Nitrogen Nobelium Osmium

1.3 1.9 1.6 3.0 1.3 2.2

Thallium Thorium Thulium Tin Titanium Tungsten

1.8 1.3 1.3 1.8 1.5 2.4

Erbium Europium Fermium Fluorine Francium Gadolinium

1.2 n.a. 1.3 4.0 0.7 1.2

Oxygen Palladium Phosphorus Platinum Plutonium Polonium

3.5 2.2 2.1 2.3 1.3 2.0

Uranium Vanadium Xenon Ytterbium Yttrium Zinc

1.7 1.6 2.6 n.a. 1.2 1.7

Gallium Germanium

1.6 1.8

Potassium Praseodymium

0.8 1.1

Zirconium

1.3

Ionic character (%)

1 2 4 6 9 12 15 19 22 26 30 34 39 43 47 51 55 59 63 67 70 74 76 79 82 84 86 88 89 91 92

Difference electronegativity

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2

Table 1.13. Percentage of ionic character of a single chemical bond

Properties of Materials

50

Properties of Materials

The equation is valid for a given valence state. For instance, for trigonal boron compounds, 2 a value of electronegativity can be defined for sp hybrid orbitals. Moreover, if the values of 1 the ionization energy and electron affinity are expressed in MJ.mol− , then the Mulliken electronegativity scale can be related to the Pauling scale by the relationship: χPauling = 3.48[χMulliken − 0.602]. 16

Allred–Rochow’s electronegativity. Allred and Rochow introduced in 1958 a new definition for electronegativity. It was defined as the electrostatic force exerted between the nucleus and valence electrons. Accounting for the observation that the position of bond points relates to the polarity of a bond, a scale of atomic and group electronegativities, which are comparable in magnitude to the Pauling values, was derived on the basis of topological properties of the electron density distributions in model hydrides (like in Metal hydrides).

1.6.3 Chemical Abstract Registry Number The identification of chemical compounds according to a systematic numbering method established by the Chemical Abstract Service (CAS), Columbus, OH, and now called the CAS Registry Number denoted by [CARN], includes up to nine digits separated by hyphens into three groups [NN…NN - NN - N]. The first part of the number, starting from the left, has up to six digits, and the second part has two digits (NN). The final part consists of a single check digit (N). The CAS Registry Number may be written in a general form as: [N(n) … N(k) … N(4) N(3) − N(2) N(1) − R] with nmax = 6 The check digit R is developed by following a standard calculation method in which R represents the check digit and N represents a fundamental sequential number. The check digit is derived from the following formula: [nN + … + 4N + 3N + 2N + 1N]/10 = Q + R/10, where Q represents an integer that is discarded. For instance, consider the CARN [107-07-3]; the number validity is checked as follows: [(5 × 1) + (4 × 0) + (3 × 7) + (2 × 0) + (1 × 7)]/10 = 33/10 = 3 + 3/10. Q = 3 is discarded and R (the check digit) is then equal to 3.

1.7 Fundamental Constants Table 1.14. Universal constants (CODATA 1998) Constant

Symbol

SI value

Celerity of light in vacuum

c, c0

c0 = 2.99792458 × 10 m.s− (defined)

Permeability of vacuum

µ0 = 1/(ε0c )

µ0 = 4π × 10− H.m− (defined)

Permittivity of vacuum

ε0 = 1/(µ0c )

ε0 = 8.85418781758 × 10−12 F.m−1

8

2

2

7

1

1

Characteristic impedance of vacuum Z0 = (µ0 /ε0)

Z0 = 376.730313461 Ω

Newtonian constant of gravitation

G = 6.673(10) × 10− N.kg− .m

1/2

16

G

Allred, A.L.; Rochow, E.C. (1958) J. Inorg. Nucl. Chem., 5, 264.

11

2

2

Fundamental Constants

Table 1.14. (continued)

1

Constant

Symbol

SI value

Planck’s constant

h

h = 6.62606876(52) × 10− J.s 15 h = 4.13566727(16) × 10− eV.s

Planck’s constant (rationalized)

h = h/2π

h = 1.054571596(82) × 10− J.s 16 h = 6.58211889(26) × 10− eV.s

Elementary electric charge

e

e = 1.602176462(63) × 10− C

Standard acceleration of gravity

gn

Properties of Materials

34

34

19

gn = 9.80665 m.s− (defined) 2

1/2

Planck’s mass

mP = (hc/G)

Planck’s length

lP = (hG/c )

3 1/2

mP = 2.17671(12) × 10− kg 8

lP = 1.6160(12) × 10− m 35

−44

Planck’s time

tP = (hG/c )

tP = 5.3906(40) × 10

Quantum of magnetic flux

Φ0 = h/2e

Φ0 = 2.067833636(81) × 10−15 Wb

Avogadro’s constant

N A, L

NA = 6.02214199(47) × 10 mol−

5 1/2

s 23

1

−27

Atomic mass unit

u, uma, mu

u = 1.66053873(13) × 10 kg 2 u = 931.494013(37) MeV/c

Faraday’s constant

F = NAe

F = 96485.3415(39) C.mol−

Boltzmann’s constant

k = R/NA

k = 1.3806503(24) × 10 J.K− 1 5 k = 8.617342(15) × 10− eV.K−

Ideal gas molar constant

R

R = 8.314472(15) J.mol− .K−

Molar Planck’s constant

N Ah

NAh = 3.990312689(30) × 10− J.s.mol−

Standard atmosphere

p0

p0 = 101325 Pa (defined)

Standard molar volume (STP) (ideal gas)

V0 = RT0 /p0

V0 = 22.413996(39) × 10− m .mol− [273.15K, 101325 Pa] 1 3 3 V0 = 22. 710981(40) × 10− m .mol− [273.15 K, 100 kPa]

Loschmidt constant

n0=NA /Vm

n0 = 2.6867775(47) × 10 m−

Sackur–Tetrode’s constant 17 (absolute entropy constant)

S0 /R

S0 /R = −1.1517048(44) [T = 1 K, P = 100 kPa] S0 /R = −1.1648678(44) [T = 1 K, P = 101325 Pa]

Stefan–Boltzmann’s constant

σ = (π2/60)(k4/h3c2)

1

−23

1

1

1 10

3

1

3

25

3

σ = 5.670400(40) × 10−8 W.m−2.K−4

First radiation constant

c1 = 2πhc

c1 = 3.74177107(29) × 10− W.m

Second radiation constant

c2 = hc/k

c2 = 0.014387752(25) m.K

Wien displacement law constant

B = c2/4.965114231…

b = 2.8977686(51) × 10− m.K

Electron rest mass

me

me = 9.10938188(72) × 10− kg 4 me = 5.485799110(12) × 10− u 2 me = 0.510998902(21) MeV/c

Bohr magneton (B.M., µB)

µB = eh/4πme

µB = 9.27400899(37) × 10− J.T− 1 5 µB = 5.788381749(43) × 10− eV.T−

Fine structure constant

α = e2/4πε0hc

α = 7.297352533(27) × 10−3 α −1 = 137.03599976(50)

Rydberg constant

R∞ = α mec/2h

R∞ = 1.0973731568548(83) × 10 m−

17

51

2

2 3/2

2

3

31

2

S0 /R= 5/2+ln[(2πm0kT/h ) kT/p0]

16

24

1

7

1

1

52

Properties of Materials

Table 1.14. (continued) Constant

Symbol

SI value

Rydberg

Ry = R∞hc

Ry = 2.17987190(17) × 10− J Ry = 13.60569172(53) J

First Bohr atomic radius

a0 = 4πε0h /mee

Quantized Hall resistance (Von Klitzing constant)

RK = h/e

= 25812.807572(95) Ω

Proton rest mass

mp

mp = 1.67262158(13) × 10− kg

Nuclear magneton (N.M., βN, μN)

μN = eh/4πmp

μN = 5.05078317(20) × 10 J.T−1 μN = 3.152451238(24) × 10−8 eV.T−1

Hartree energy

Eh = e /4πε0a0

Eh = 4.35974381(34) × 10− J Eh = 27.2113834(11) eV

Josephson constant

KJ = 2e/h

KJ = 4.83597898(19) × 10 Hz.V−

2

18

2

2

a0 = 0.5291772083(19) × 10− m 10

27

−27

18

2

14

1

1.8 Conversion Factors (continued) Table 1.15. Most common conversion factors used in materials science and metallurgy Quantity, dimension SI unit Unit (symbol) and exact (E) or rounded conversion factor(s) Mass [M]

kg

1 atomic mass unit (u) = (1/12) m12C = 1.66053873 × 10− kg 9 1microgram (μg) = 10− kg (E) 9 1 gamma (γ) = 10− kg (E) 6 1 milligram (mg) = 10− kg (E) 6 1 point (jewellers) = 1/100 ct (E) = 2 mg (E) = 2 × 10− kg (E) −6 1 grain (jewellers) = 50 mg (E) = 50 × 10 kg (E) 6 1 grain (gr) = 1/7000 lb (E) = 64.79891 mg = 64.79891 × 10− kg −4 1 carat metric (ct) = 200 mg (E) = 2 × 10 kg (E) 3 1 gram (g) = 10− kg (E) 3 1 pennyweight (dwt) = 1/20 oz tr (E) = 1.55517384 × 10− kg 3 1 ounce troy (oz tr) = 1/12 lb (troy) (E) = 31.1034768 × 10− kg 1 pound troy (lb tr) = 5760 grains (E) = 0.3732417216 kg 1 pound (lb) = 7000 grains (E) = 0.45359237 kg (E) 1 kilopond (kip) = 9.80665 kg (E) 1 metric ton unit (mtu) = 1/10 ton (E) = 10 kg 1 short ton unit (shtu) = 1/10 short ton (E) = 20 lb (E) = 9.0718474 kg 1 long ton unit (lgtu) = 1/10 long ton (E) = 22.4 lb (E) = 10.16046909 kg 1 slug (geepound) = 14.5939029372 kg 1 flask (UK, mercury) = 76 lb (E) = 34.4730201 kg 1 bag (UK, cement) = 94 lb (E) = 42.63768278 kg (E) 1 hundredweight (gross) = 100 lb (E) = 45.359237 kg (E) 1 bag (US, cement) = 100 lb (E) = 45.359237 kg (E) 1 hundredweight (gross) = 112 lb (E) = 50.8023454 kg 1 quintal (metric) = 100 kg (E) 1 short ton (sht) = 2000 lb (E) = 907.1847 kg 1 ton (t) = 1 metric ton = 1000 kg (E) 1 long ton (lgt) = 2240 lb (E) = 1016.046909 kg

Length [L]

m

1 Angstrom (A) = 10− m (E) 9 1 nanometer (nm) = 10− m (E) −6 1 micrometer (μm) = 10 m (E)

27

10

Conversion Factors

Table 1.15. (continued)

53

1

Quantity, dimension SI unit Unit (symbol) and exact (E) or rounded conversion factor(s) 1 millinch (mil) = 10− inch (E) = 25.4 μm (E) 3 1 millimeter (mm) = 10− m −2 1 centimeter (cm )= 10 m (E) 2 1 inch (in) = 2.54 × 10− m (E) 1 foot (ft) = 12 inches (E) = 0.3048 m (E) 1 mile (stat.) = 5280 feet (E) = 1609.344 m (E) 1 mile (naut. int.) = 1852 m (E) 3

Length [L]

Volume, capacity 3 [L ]

m

1 cubic millimeter (mm ) = 10− m (E) 9 3 1 microliter (μL) = 10− m (E) 3 −9 1 lambda (λ) = 10 m (E) 9 3 1 drop (drp) = 1/480 fl oz (E) = 61.61152 × 10− m 3 3 −6 1 cubic centimeter (cm ) = 10 m (E) 6 3 1 milliliter (mL) = 10− m (E) 6 3 3 1 cubic inch (in ) = 16.387064 × 10− m 6 3 1 fluid ounce (fl oz) = 1/128 gal (US liq) (E) = 29.57352956 × 10− m 3 3 −3 1 liter (L) = 1 dm (E) = 10 m (E) 3 3 3 1 board foot measure (bfm) = 1/12 ft (E) = 2.359737216 × 10− m 3 3 −3 1 gallon (US, liq) = 231 in (E) = 3.785411784 × 10 m 3 3 3 1 gallon (US, dry) = 268.8025 in (E) = 4.40488377086 × 10− m 3 −3 1 gallon (UK) = 4.546092 × 10 m 3 3 3 1 cubic foot (ft ) = 28.316846592 × 10− m 3 3 1 barrel (US, oil) = 42 gal (US, liq) = 158.987294928 × 10− m 3 1 stère (st) = 1 m (E) 3 3 1 ocean-ton (UK) = 40 ft (E) = 1.13267386368 m 3 3 1 register-ton (UK) = 100 ft (E) = 2.8316846592 m 3 3 1 cord (US) = 128 ft (E) = 3.62455636378 m 3 3 1 standard (std) = 165 ft (E) = 4.67227968768 m

Time [T]

s

1 minute (min) = 60 s (E) 1 hour (h) = 60 min (E) = 3600 s (E) 1 day (d) = 24 h (E) = 86400 s (E) 7 1 year (a) = 365 days (E) = 3.1536 × 10 s (E) 6 13 1 million years (Ma) = 10 years (E) = 3.1536 × 10 s (E) 9 16 1 billion years (Ga) = 10 years (E) = 3.1536 × 10 s (E)

Density 3 [ML− ]

kg.m−

Pressure, stress 2 1 [ML− T− ]

Pa

3

9

3

3

3

1 pound per cubic foot ( lb.ft− ) = 16.0184634 kg.m− 3 1 1 pound per gallon ( lb.gal− ) = 119.826427 kg.m− 3 −3 1 geepound per per cubic foot (slug.ft ) = 515.3788184 kg.m− (E) 3 3 1 gram per cubic centimeter (g.cm− ) = 1000 kg.m− (E) 3 3 1 kilogram per cubic centimeter (kg.dm− ) = 1000 kg.m− (E) 3 3 1 ton per cubic meter (ton.m− ) = 1000 kg.m− (E) 3 3 1 pound per cubic inch (lb.in− ) = 27679.9047102 kg.m− (E) 3

3

1 barye = 1 dyn.cm− (E) = 0.1 Pa (E) 1 micrometer of mercury (μmHg) = 0.133322368421 Pa 2 1 newton per square meter (N.m− ) = 1 Pa (E) 1 Torr = 1 mm Hg (0°C) = 133.322368421 Pa 6 1 kilopascal (kPa) = 10 Pa (E) 1 centimeter of mercury (cmHg) = 1.33322368421 kPa 1 inch mercury (inHg) = 3.38638815789 kPa 2 1 pound-force per square inch (psi) = 1 lbf .in− (E) = 6.89475729317 kPa 2 1 kilogram-force per square centimeter (kgf .cm− ) = 98.0665 kPa (E) 1 bar = 100 kPa (E) 1 technical atmosphere (at) = 100 kPa (E) 2

Properties of Materials

54

Properties of Materials

Table 1.15. (continued) Quantity, dimension SI unit Unit (symbol) and exact (E) or rounded conversion factor(s) Pressure, stress 2 1 [ML− T− ]

1 atmosphere (atm) = 101.325 kPa (E) 6 1 megapascal (MPa) = 10 Pa (E) 2 1 kilopound per square inch (ksi) = 1 kip.in− (E) = 1000 psi (E) = 6.8947529317 MPa 2 1 ton per square inch (tsi) = 1 ton.in− (E) = 2000 psi (E) = 13.7895145863 MPa 9 1 gigapascal (GPa) = 10 Pa (E)

Energy, work 2 2 [ML T− ]

J

1 electron-volt (eV) = 1.602176462 × 10− J 7 1 erg = 1 dyn.cm (E) = 10− J (E) 1 calorie (therm) = 4.1840 J (E) 1 calorie (15°C) = 4.1855 J 1 calorie (IT) = 4.18674 J 1 calorie (mean) = 4.19002 J 1 kilojoule (kJ) = 1000 J (E) 1 British thermal unit (39°F) = 1059.67 J 1 British thermal unit (60°F) = 1054.678 J 1 British thermal unit (ISO) = 1055.06 J (E) 1 British thermal unit (IT) = 1055.05585262 J (E) 1 British thermal unit (mean) = 1055.87 J 1 British thermal unit (therm) = 1054. 35026449 J 1 pound centigrade unit (pcu) = 1.8 Btu (IT) (E) = 1.8991008 kJ 1 watt-hour (Wh) = 3600 J (E) 1 kilowatt-hour (kWh) = 3.6 MJ (E) 5 1 therm (EEG) = 10 Btu (IT) (E) = 105.505585262 M J 6 1 million Btu (MMBtu) = 10 Btu (IT) (E) = 1.055056 GJ (E) 1 ton of TNT = 4.184 GJ 1 barrel oil equivalent (bboe) = 6.12 GJ 1 ton coal equivalent (tce) = 7 Gigacalories (therm) (E) = 29.288 GJ (E) 1 ton oil equivalent = 10 Gigacalories (therm) (E) = 41.840 GJ (E) 15 1 quadrillion Btu (quad) = 10 Btu (IT)(E) = 1.05505585262 E J 18 1 Q-unit = 10 Btu(IT) (E) = 1.05505585262 ZJ

Power

W

1 cheval-vapeur (CV) = 75 kgf .m/s (E) = 735.49875 W (E) 1 horsepower (hp) = 550 lbf .ft/s (E) = 745.699871581 W 1 kilowatt = 1000 W (E)

19

from Cardarelli, F. (2005) Encyclopaedia of Scientific Units, Weights and Measures. Their SI equivalences and Origins. Springer, Berlin Heidelberg New York

1.9 Further Reading 1.9.1 Mathematics and Statistics ABRAMOWITZ, M.; STEGUN, I.A. (1972) Handbook of Mathematical Functions, with Formulas, Graphs, and Mathematics Tables. Dover, New York. BEYER, W.H. (1991) CRC Standard Mathematical Tables and Formulae, 29th ed. CRC Press, Boca Raton, FL. BRONSHTEIN, I.N.; SEMENDYAYEV, K.A.; MUSIOL, G.; MUEHLIG, H. (2004) Handbook of Mathematics, 4th ed. Springer, Berlin Heidelberg New York, XLII. ISBN: 3-540-43491-7. DAVIS, J.R. (1983) ASM Handbook of Engineering Mathematics. ASM International, Materials Park, OH.

Further Reading

TALLARIDA, R.J. (1992) Pocket Book of Integrals and Mathematical Formulas, 2nd ed. CRC Press, Boca Raton, FL. RADE, L.; WESTERGREN, B. (2003) Mathematics Handbook for Science and Engineering, 4th ed. Springer, Berlin Heidelberg New York. SACHS, L. (1984) Applied Statistics: a Handbook of Techniques, 2nd ed. Springer, Berlin Heidelberg New York. TUMA, J.J. (1979) Engineering Mathematics Handbook. McGraw-Hill, New York.

1.9.2 Units and Conversion Tables CARDARELLI, F. (2005) Encyclopaedia of Scientific Units, Weights and Measures. Their SI equivalences and origin. Springer, Berlin Heidelberg New York. CARDARELLI, F. (1999) Scientific Unit Conversion: Practical Guide to Metrication, 2nd ed. Springer, Berlin Heidelberg New York. Collective (1998) The Economist Desk Companion: How to Measure, Convert, Calculate and Define Practically Anything. Wiley, New York. JERRARD, G.; MCNEILL, D.B. (1992) Dictionary of Scientific Units, 6th ed. Chapman & Hall, London. JOHNSTONE, W.D. (1998) For Good Measures. The Most Complete Guide to Weights and Measures and their Metric Equivalents. NTC, Lincolnwood, IL. MILLS, I.; CVITAS, T.; HOMANN, K.; KALLAY, N.; KUCHITSU, K. (1993) Quantities, Units and Symbols in Physical Chemistry, 2nd ed. IUPAC/Blackwell, Oxford. WILDI, Th. (1995) Metric Units and Conversion Charts: a Metrication Handbook for Engineers, Technologists, and Scientists, 2nd ed. IEEE, New York.

1.9.3 Physics ANDERSON, H.L. (ed.) (1989) A Physicist’s Desk Reference, Physics Vade Mecum, 2nd ed. American Institute of Physics (AIP) Press, New York. BENNENSON, W.; HARRIS, J.W.; STOCKER, H.; LUTZ, H. (2001) Handbook of Physics. Springer, Berlin Heidelberg New York. BESANÇON, R.M. (ed.) (1985) Encyclopedia of Physics, 3rd ed. Van Nostrand Reinhold, New York. COHEN, R.E.; LIDE, D.R.; TRIGG, G.L. (eds.) (2003) AIP Physics Desk Reference, 3rd ed. Springer, Berlin Heidelberg New York. CONDON, E.U.; ODISHAW, H. (1958) Handbook of Physics. McGraw-Hill, New York. DRISCOLL, W.G. (1978) Handbook of Optics. Optical Society of America (OSA), McGraw-Hill, New York. FLUGGE, S. (ed.) (1955–1988) Handbuch der Physik (55 volumes) 2nd ed. Springer, Berlin Heidelberg New York. GRAY, D.E. (ed.) (1972) American Institute of Physics AIP-Handbook, 3rd ed. McGraw-Hill, New York. GRIGORIEV, I.S.; MEILIKHOV, E.Z. (eds.) (1996) Handbook of Physical Quantities. CRC Press, Boca Raton, FL. LAPEDAS, D.N. (1978) McGraw-Hill Dictionary of Physics and Mathematics. McGraw-Hill, New York. LERNER, R.; TRIGG, G.L. (1991) Encyclopedia of Physics, 2nd ed. VCH, New York.

1.9.4 Physical Chemistry ADAMSON, A.W. (1986) A Textbook of Physical Chemistry, 3rd ed. Academic, Orlando, FL. ATKINS, P.W. (2002) Physical Chemistry, 7th ed. Freeman, San Francisco. GLASSTONE, S. (1946) Textbook of Physical Chemistry, 2nd ed. Van Nostrand Reinhold, Princeton, NJ.

55

1 Properties of Materials

56

Properties of Materials

MCQUARRIE, D.A.; SIMON, J.D.; CHOI, J. (1997) Physical Chemistry: A Molecular Approach. University Science Books, University of California, Davis. METZ, C.R. (1976) Theory and Problems of Physical Chemistry. Schaum’s Outline Series in Science, McGraw-Hill, New York.

1.9.5 Engineering Fundamentals ESHBACH, O.W.; SOUDERS, M. (1974) Handbook of Engineering Fundamentals, 3rd ed. Wiley, New York. GANIC, E.; HICKS, T. (1990) The McGraw-Hill Handbook of Essential Engineering Information and Data. McGraw-Hill, New York. PERRY, R.H.; GREEN, D.W. (eds.) (1998) Perry’s Chemical Engineer’s Handbook, 7th ed. McGrawHill, New York.

1.9.6 General Handbooks BUDAVARI, S. (ed.) (1996) The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 12th ed. Merck Research Laboratory, Whitehouse Station, NJ. DEAN, J.A. (ed.) (1999) Lange’s Handbook of Chemistry, 15th ed. McGraw-Hill, New York. KAYE, G.W.C.; LABY, T.H. (1995) Tables of Physical and Chemical Constants, 16th ed. Longman, New York. LIDE, D.R. (ed.) (2003) CRC Handbook of Chemistry and Physics, 84th ed. CRC Press, Boca Raton, FL. Smithsonian Institution (1954) Smithsonian Physical Tables. 9th rev. ed. Smithsonian Institution Press, Washington, DC.

1.9.7 Mechanical Properties AVALLONE, E.; BAUMEISTER, T. (1997) Mark’s Standard Handbook for Mechanical Engineers, 10th ed. McGraw-Hill, New York. BEITZ, W.; KUTTNER, K.-H. (1995) Dubbel’s Handbook of Mechanical Engineering. Springer, Berlin Heidelberg New York. OBERG, E.; GREEN, R.E. (1992) Machinery’s Handbook, 24th ed. Industrial, Press New York.

1.9.8 Electrical Properties FINK, D.G.; BEATY, H. (1994) Standard Handbook for Electrical Engineers, 13th ed. McGraw-Hill, New York. FINK, D.G.; CHRISTIANSEN, D. (eds.) (1994) Electronics Engineers’ Handbook, 3rd ed. McGraw-Hill, New York.

1.9.9 Thermal Properties HOTTEL, H.C.; SAROFIM, A.F. (1967) Radiative Transfer. McGraw-Hill, New York. INCROPERA, F.P.; WITT, D.P. (1996) Fundamental of Heat and Mass Transfer, 3rd ed. Wiley, New York.

Further Reading

ORFEUIL, M.; ROBIN, A. (1987) Electric Process Heating: Technologies, Equipment and Applications. Batelle Press, Columbus, OH. TAINE, J.; PETIT, J.-P. (1989) Transfert thermiques. mécanique des fluides anisothermes. Collection Dunod Université, Éditions Bordas, Paris.

1.9.10 Metallurgy BARETT, C.S. (1952) Structure of Metals, 2nd ed. McGraw-Hill, New York. BOUSFIELD, B. (1992) Surface Preparation and Microscopy of Materials. Wiley, Chichester. BRANDES, E.A.; BROOK, G.B. (1992) Smithell’s Metal Reference Handbook, 7th ed. ButterworthHeinemann, London. BRINGAS, J.E. (1995) The Metals Black Book, Vol. 1 Ferrous Metals, 2nd ed. CASTI, Edmonton, Canada. BRINGAS, J.E. (1995) The Metals Red Book, Vol. 2 Nonferrous Metals. CASTI, Edmonton, Canada. CAHN, R.W.; HAASEN, P. (1995) Physical Metallurgy, 4th ed. North-Holland, New York. DIETER, G.E. (1984) Mechanical Metallurgy, 3rd ed. McGraw-Hill, New York. HABASHI, F. (1997) Handbook of Extractive Metallurgy (Vols. I, II, III, and IV). VCH, Weinheim. HUME-ROTHERY, W.; RAYNOR, G.V. (1954) The Structure of Metals and Alloys, 3rd ed. Institute of Metals, London. PEARSON, W.B. (ed.) (1959) Handbook of Lattice Spacing and Structures of Metals, Vol. I. Pergamon, New York. PEARSON, W.B. (ed.) (1972) Crystal Chemistry and Physics of Metals and Alloys. Wiley, New York. SMITH, W.F. (1981) Structure and Properties of Engineering Alloys. McGraw-Hill, New York. VANDERVOORT, G.F. (1984) Metallography: Principles and Practice. McGraw-Hill, New York. WOLDMAN, N.E.; GIBBONS, R.C. (eds.) (1979) Woldman’s Engineering Alloys, 6th ed. ASM, Metals Park, OH.

1.9.11 Materials Science ASHBY, M.F. (1992) Materials Selection in Mechanical Design. Pergamon, Oxford. BRADY, G.S.; CLAUSER, H.R.; VACCARI, J. (1997) Materials Handbook. An Encyclopaedia for Managers, Technical Professionals, Purchasing and Production Managers, Technicians, and Supervisors, 14th ed. McGraw-Hill, New York. BUDINSKI, K.G. (1996) Engineering Materials. Properties and Selection, 5th ed. Prentice Hall, Englewood Cliffs, NJ. CAHN, R.W.; HAASEN, P. (1995) Physical Metallurgy, 4th ed. North-Holland, New York. CARDARELLI, F. (2001) Materials Handbook. A Concise Desktop Reference. Springer, Berlin Heidelberg New York. DIETER, G.E. (1984) Mechanical Metallurgy, 3rd ed. McGraw-Hill, New York. FLINN, R.A.; TROJAN, P.K. (1981) Engineering Materials and Their Applications, 2nd ed. Houghton Mifflin, Boston. GOTTSTEIN, G. (2004) Physical Foundations of Materials Science. Springer, Berlin Heidelberg New York. HUMMEL, R.E. (1998) Understanding Materials Science. History, Properties and Applications. Springer, Berlin Heidelberg New York. MINER, D.F.; SEASTONE, J.B. (eds.) (1955) Handbook of Engineering Materials. Wiley, New York. SHACKELFORD, J.F.; ALEXANDER, W. (ed.) (1991) The CRC Materials Science and Engineering Handbook. CRC Press, Boca Raton, FL. VAN VLACK, L.H. (1970) Materials Science for Engineers. Addison-Wesley, Reading, MA.

57

1 Properties of Materials

Ferrous Metals and Their Alloys

The ferrous metals are defined as the three upper transition metals of group VIIIB (8, 9, and 10) of Mendeleev’s periodic chart, that is, iron (Fe), cobalt (Co), and nickel (Ni), along with chromium (Cr) and manganese (Mn), despite the fact that these two metals belong to groups VIB(6) and VIIB(7), respectively. Manganese is included in this chapter because it has an important role in iron- and steelmaking, while chromium, owing to its refractory behavior, will be described in the chapter on refractory metals (see Section 4.3.8). The selected physical and chemical properties of these five elements are listed in Table 2.1.

2.1 Iron and Steels 2.1.1 Description and General Properties Iron [7439-89-6], chemical symbol Fe, atomic number 26, and relative atomic mass 55.845(2), is the first element of the upper transition metals of group VIIIB(8) of Mendeleev’s periodic chart. The word iron comes from the Anglo-Saxon iren, while the symbol Fe and words such as ferrous and ferric derive from the Latin name of 3 iron, ferrum. Pure iron is a soft, dense (7874 kg.m− ), silvery-lustrous, magnetic metal with a high melting point (1535°C). In addition, when highly pure iron has both a good thermal conductivity 1 1 (80.2 W.m− .K− ) and a low coefficient of linear thermal expansion (11.8 μm/m.K), it is a satisfactory electric conductor (9.71 μΩ.cm).

Designations [F00001]

Unified numbering system [UNS]

Natural occurrence and economics

Atomic properties 0.151 7.9024 16.1878 30.652 1.83 1.64 4.06 308 2.56 49–63 16

Covalent radius (/pm)

Electron affinity (EA /eV)

First ionization energy (EI /eV)

Second ionization energy (eV)

Third ionization energy (eV)

Electronegativity χa (Pauling)

Electronegativity χa (Allred and Rochow)

Electron work function (WS /eV)

X-ray absorption coefficient CuKα1,2 ((μ /ρ) /cm .g− )

Thermal neutron cross section (σn /10− m )

Isotopic mass range

Isotopes (including natural and isomers)

2

116

Atomic or Goldschmidt radius (/pm)

28

126

Fundamental ground state

1

5

D4

[Ar]3d 4s

6

55.845(2)

Electronic configuration (ground state)

Relative atomic mass Ar ( C = 12.000)

2

26 1

Atomic number (Z)

12

0.350 (98)

Price of pure metal in 2004 1 (C/$US.kg− ) (purity in wt.%)

4

F9/2

17

35–64

37.2

313

4.30

1.75

1.88

33.50

17.083

7.8810

0.662

116

125

4

7

2

[Ar]3d 4s

58.933200(9)

27

55–57 (99.8)

35,000

940 × 10

World annual production of metal in 2004 (P/tonnes)

n.a.

6

110 × 10

World estimated reserves (R/tonnes)

9

25 0.2 × 10−

20 × 10−

[R30001]

[7440-48-4]

Co

Cobalt

4

56300

Seawater abundance (/mg.kg− )

1

Earth’s crust abundance (/mg.kg )

2

[7439-89-6]

−1

Fe

Chemical abstract registry umber [CARN]

Iron (Ferrum)

Chemical symbol (IUPAC)

Properties at 298.15 K (unless otherwise specified)

Table 2.1. Selected properties of iron, cobalt, nickel, chromium, and manganese

4

6

F4

14

53–67

37.2

45.7

4.40

1.75

1.91

35.19

18.16884

7.6398

1.160

115

125

3

8

2

[Ar]3d 4s

58.6934(2)

28

12.85–13.35 (99.8)

1.033 × 10

70 × 10 6

5.6 × 10−

84

[N02200]

[7440-02-0]

Ni

Nickel

4

4

S3

13

45–57

3.1

260

3.72

1.56

1.66

30.96

16.4857

6.76664

0.666

118

129

7

5

1

[Ar]3d 4s

51.9961(6)

24

6

100,000

700 × 10

2 × 10−

950

[M20001]

[7439-96-5]

Mn

Manganese

S5/2

5

15

49–62

13.3

285

3.72

1.60

1.55

33.668

15.63999

7.43402

n.a.

118

137

6

2

[Ar]3d 4s

54.938049(9)

25

10.25–10.65 1.3–1.4 (99.4) (99.7)

30,000

1 × 10

9

3 × 10−

102

[R20001]

[7440-47-3]

Cr

Chromium

60 Ferrous Metals and Their Alloys

Nuclear properties

Crystallographic properties a = 286.65 5.11 914 7874 208.2 81.6 169.8 4.0 50–90 (460–520) 160 (608) 131 689

Crystal lattice parameters (/pm) [293.15 K]

Latent molar enthalpy transition (Lt /kJ.mol− )

Phase transition temperature α−β (T/ K)

Density (ρ/kg.m ) [293.15 K]

Young’s or elastic modulus (E/GPa) (polycrystalline)

Coulomb’s or shear modulus (G/GPa) (polycrystalline)

Bulk or compression modulus (K/GPa) (polycrystalline)

Mohs hardness (/HM)

Brinell hardness (/HB)

Vickers hardness (/HV) (hardened)

Yield strength proof 0.2% (σYS /MPa)

Ultimate tensile strength (σUTS /MPa)

Mechanical properties (annealed) 3220 1.0 0.290

Transversal velocity of sound (VT /m.s )

Static friction coefficient (vs. air)

Poisson ratio ν (dimensionless)

−1

Longitudinal velocity of sound (VL /m.s− )

Creep strength (/MPa) (hardened)

Charpy impact value

Elongation (Z/%)

5920

cI2

Pearson’s notation

1

Im3m

Space group (Hermann–Mauguin)

−3

A2(W)

Strukturbericht designation

1

bcc

Crystal structure (phase α)

0.320

0.30

3000

5730

15–30

800–875

758

310 (1043)

81–250

5.5

181.5

82

211

8900

690 (ε−α)

0.25

a = 250.71 c = 406.94

hP2

P63 /mmc

A3(Mg)

hcp

0.312

0.70

3080

5810

230

48

462

148

172–184 (640)

85–109

4.5

177.3

76

199.5

8902

631.15

2.98

a = 352.38

cF4

Fm3m

A1(Cu)

fcc

392–411

5.0

139.67

79.5

191

7440

983.15

2.22

a = 891.39

cI58

I43m

A12(α-Mn)

Complex bcc

0.210

0.46

3980

6850

160

44

415

362

0.240

0.69

3280

5560

40

496

241

1060 981 (1875–2000)

125

8.5

160.2

115.3

279

7190

311.5

0.0008

a = 288.46

cI2

Im3m

A2(W)

bcc

Iron and Steels 61

Ferrous Metals and Their Alloys

2

Thermal and thermodynamic properties [293.15K]

2

–272.0 (FeO) 9.71 6.51 –23.4 × 10− +0.080

Molar enthalpy of formation 1 0 (Δf H /kJ.mol− ) (oxide)

Electrical resistivity (ρ/μΩ.cm)

Temperature coefficient of electrical resistivity 1 3 (0–100°C) (/10− K− )

Pressure coefficient of electrical resistivity (/MPa− )

Hall coefficient at 293.15 K (RH /nΩ.m.T− ) [0.5 T < B < 2.0 T]

260 +1.89

Thermoelectric power vs. platinum (QAB /mV vs. Pt) (0–100°C)

−2

Thermoelectronic emission constant (A/kA.m K )

−2

Seebeck absolute coefficient (eS /μV.K ) (thermoelectric power)

–51.34

398.6 (7138)

Latent molar enthalpy of sublimation 1 (ΔHsub /kJ.mol− )

1

340.4 (6095)

Latent molar enthalpy of vaporization 1 1 (ΔHvap /kJ.mol− ) (Δhvap /kJ.kg− )

−1

15.2 (272)

Latent molar enthalpy of fusion 1 1 (ΔHfus /kJ.mol− ) (Δhfus /kJ.kg− )

1

27.280

1

Standard molar entropy (S 298 /J.mol− K− ) 1

0.35 (1200°C)

0

447

Spectral normal emissivity (650 nm)

−1

Specific heat capacity (cp /J.kg .K )

−1

11.8

Coefficient of linear thermal expansion (α /10− K− ) 1

+3.5

Volume expansion on melting (/vol.%) 6

80.2

Thermal conductivity (k /W.m− .K− ) 1

2749.9 (2476.75)

Temperature of vaporization (TV /K) Boiling point (b.p./°C)

1

1808.05 (1534.90)

Iron (Ferrum)

Temperature of fusion (TF /K) Melting point (m.p./°C)

Properties at 298.15 K (unless otherwise specified)

Table 2.1. (continued)

5

–1.33

410

+17.5

+0.360

–9.04 × 10−

6.60

6.24

–237.7 (CoO)

425 (7211)

382.4 (6489)

15.5 (263)

30.067

0.37 (1200°C)

421

13.4

+3.5

99.2

3143.05 (2869.90)

1728.05 (1454.90)

Cobalt

5

–1.48

300

–18.0

–0.060

+1.82 × 10−

6.92

6.844

–240.6 (NiO)

429.6 (7320)

377.5 (6431)

17.16 (292)

29.796

0.34 (1000°C)

471

13.3

+4.5

90.7

3005.05 (2731.90)

1726.05 (1452.90)

Nickel

5

+2.20

n.a.

n.a.

+0.363

–17.3 × 10−

2.14

12.7

–1140 (Cr2O3)

397 (7635)

348.78 (6708)

20.90 (402)

23.618

0.34 (1000°C)

459.8

6.2

+10.15

93.7

2945.05 (2671.90)

2130.05 (1856.90)

5

Chromium

+0.70

n.a.

n.a.

+0.084

–35.4 × 10−

0.4

144

–385.2 (MnO)

291 (4267)

231.1 (4207)

12.058 (219)

32.010

0.59 (1200°C)

479

21.7

+1.7

7.82

2335.05 (2061.90)

1517.05 (1243.90)

5

Manganese

62 Ferrous Metals and Their Alloys

Electrical and electrochemical properties

2

0.659

633 0.644

TNéel = 311

0

0

0.606

TNéel = 100

+121

n.a.

2+

Mn /Mn –1.170

Standard atomic masses from: Loss, R.D. (2003) Atomic weights of the elements 2001. Pure Appl. Chem., 75(8), 1107–1122. Thermodynamic properties from: Chase, Jr., M.W. (1998) NIST-JANAF Thermochemical Tables, 4th ed., Part I & II. J. Phys. Chem. Reference Data, Monograph No. 9 published by Springer, Berlin Heidelberg New York.

Magnetic and optical properties

1

0.675

1394.15

0.563

n.a.

3+

Cr /Cr –0.740

Reflective index under normal incidence (650 nm)

384

0

1043

n.a.

2+

Ni /Ni –0.257

Curie temperature (TCurie /K)

3

0

Ferromagnetic Ferromagnetic Ferromagnetic +44.50

−1

425

+

2+

Co /Co –0.277

Mass magnetic susceptibility (χm /10 kg m ) (at 295 K)

−9

2

0

Hydrogen overvoltage (η/mV) with [H ] = 1M, and jc = –200 A.m− )

2+

Fe /Fe –0.440

Nernst standard electrode potential (E/V vs. SHE)

Iron and Steels 63

Ferrous Metals and Their Alloys

2

64

Ferrous Metals and Their Alloys

Table 2.2. Reactions of pure iron metal with acids Acid

Soln.

Chemical reaction scheme 0

Notes

−

2+

Hydrochloric acid (HCl)

Conc.

Fe + 2HCl —> Fe + 2Cl + H2(g)

Dissolves with effervescence

Sulfuric acid (H2SO4)

Dil.

Fe + H2SO4 —> Fe + SO4 − + H2(g)

Dissolves with effervescence

0

2+

2

Conc. cold No reaction Nitric acid (HNO3)

Does not dissolve

0

2−

3+

Conc. hot

2Fe + 6H2SO4 —> 2Fe + 3SO4 + 3SO2(g) + 6H2O

Dissolves

Dil. cold

4Fe + 10HNO3 —> 4Fe + NH4 + 9NO3− + 3H2O

Dissolves

Dil. hot

0

0

2+

+

−

3+

Fe + 4HNO3 —> Fe + 3NO3 + NO(g) + 2H2O 0

+

Conc. cold 3Fe + 16HNO3 + 16H —> Fe3O4(surface) + 8NO2(g) + 8H2O

Dissolves readily Does not dissolve due to passivation by Fe3O4

At room temperature, highly pure iron crystallizes into a body-centered cubic (bcc) space lattice. From a mechanical point of view, pure iron exhibits a high elastic Young’s modulus of 208.2 GPa, with a Poisson ratio of 0.291, but it is malleable and can be easily shaped by hammering. Other mechanical properties such as yield and tensile strength strongly depend on interstitial impurity levels and type of crystal space lattice structure. Pure iron is a soft 6 1 ferromagnetic material with a saturation magnetization MS of 1.71 × 10 A.m− and a rema−1 nent magnetic induction of 0.8 T and a low coercivity of 80 A.m . These properties explain why iron cores are extensively used in electromagnets. However, the high hysteresis core 1 losses of 500 W.kg− act to decreases its electric resistivity by alloying it with silicon in order to be suitable in transformers. However, iron loses its ferromagnetism above its Curie temperature of 769°C (1043 K) and becomes paramagnetic. Natural iron is composed of four 54 56 57 58 stable nuclides— Fe (5.845 at.%), Fe (91.754 at.%), Fe (2.1191 at.%), and Fe (0.2819 at.%)— and the element has a thermal neutron cross section of 2.56 barns. From a chemical point of view, pure iron is an active metal, and hence it rusts (i.e., oxidizes) when put in contact with moist air, forming a porous nonprotective hydrated ferric-oxide layer. In addition, pure iron readily dissolves in several diluted strong mineral acids such as hydrochloric and sulfuric acids, but it is not attacked by concentrated sulfuric or nitric acids due to the passivation by a scale of insoluble magnetite (Fe3O4). The major reactions of iron metal with the most common acids are summarized in Table 2.2. Various types of relatively pure or high-purity iron can be found on the market, although only a few of them are used as structural material. Most commercial irons, except ingot iron and electrolytic iron, contain perceptible quantities of carbon, which affects their properties. Other common high-purity iron types include reduced irons and carbonyl iron (powders). Prices (2006). Pure iron metal (i.e., 99.99 wt.% Fe) is priced US$2.205/kg (i.e., US$1.00/lb.), while common iron (99 wt.% Fe) is priced US$0.350/kg (US$0.159 US$/lb.).

2.1.2 Phase Transitions and Allotropism of Iron The wide variations in the properties of iron and iron alloys must be related to the existence of pure solid iron in more than one phase, i.e., several crystallographic structures. This characteristic of many chemical elements including iron is called allotropism. Allotropism must not be confused with the term applied to a pure compound (e.g., a molecule or an alloy) that exhibits several crystal lattices and is called polymorphism. The temperature at which a change in

Iron and Steels

the crystal structure occurs under constant pressure is called the phase transition temperature or critical point. These phase changes occurring in the phase diagram of iron can be accurately pointed out by means of X-ray diffraction, thermal analysis, and dilatometry techniques. Under atmospheric pressure, pure iron metal exhibits the four allotropes as follows and a highpressure form. Alpha-iron (α-Fe). Between room temperature and a transition temperature of 769°C, pure iron exhibits a body-centered cubic (bcc) crystal lattice (a = 286.645 pm at 25°C). Alpha3 iron is a soft, ductile metal with a density of 7875 kg.m− . Alpha-iron is also ferromagnetic, 2 1 with a saturation magnetization at room temperature of 220 A·m ·kg− , and the cubic anisot4 4 −3 −3 ropy constants are K1 = 4.7 × 10 J·m and K2 = 1.5 − 3.0 × 10 J·m . Carbon exhibits a poor solubility in alpha-iron with a maximum content of 0.025 wt.% C at 723°C. It is important to note that the word ferrite describes a solid solution of carbon into alpha-iron, though it is sometimes improperly used to describe alpha-iron (Section 2.1.9): α-Fe (bcc, ferromagnetic) —> β-Fe (bcc, nonmagnetic) [Tt = 769°C; ΔHαβ = 0 kJ.mol− ]. 1

Beta-iron (β-Fe). When heated above its Curie temperature of 769°C, alpha-iron loses its ferromagnetic properties but retains its body-centered cubic structure (i.e., second-order transition). This particular form of iron is called beta-iron, which is considered a different allotropic form owing to its paramagnetic properties. However, because no changes in the crystal lattice structure occurs, it is customary to consider it nonmagnetic alpha-iron: β-Fe (bcc, nonmagnetic) —> γ-Fe (fcc, nonmagnetic) [Tt = 910°C; ΔHβγ = +0.9 kJ.mol− ]. 1

Gamma-iron (γ-Fe). At 910°C, the crystallographic structure of iron changes into a facecentered cubic (fcc) structure (a = 364.680 pm at 916°C). At this transition temperature, a considerable absorption of latent heat occurs due to the endothermic reaction, and the volume of the iron unit cell expands to 25 vol.%. Gamma-iron is nonmagnetic and has

Table 2.3. Physical properties of four iron allotropes and high-temperature forms Properties (SI units)

α-Fe

β-Fe

γ-Fe

δ-Fe

ε-Fe

Crystal structure

bcc

bcc

fcc

bcc

hcp

Lattice parameters (/pm)

a = 286.645

a = 286.645

a = 364.680

a = 291.35

a = 248.5 c = 399.0

Space group (Hermann–Mauguin)

Im3m

Im3m

Fm3m

Im3m

P63 /mmc

Pearson symbol

cI2

cI2

cI4

cI2

hP2

Strukturbericht

A2

A2

A1

A2

A3

Transition temperature (T/K)

1042

1183

1665

1812

P > 13 GPa

Latent enthalpy of transition 1 1 (ΔHt /kJ.mol− )(kJ.kg− )

0.00 ()

+0.900 ()

+0.837 ()

+13.807 ()

(?)

Density (ρ/kg.m− )

7875

7875

7648

7357

(?)

3

Coefficient of linear thermal 1 6 expansion (α/10− K− ) Thermal conductivity 1 1 (k/W.m− .K− ) Specific heat capacity 1 1 (cp /J.kg− K− ) Electrical resistivity (ρ/μΩ.cm)

65

2 Ferrous Metals and Their Alloys

66

Ferrous Metals and Their Alloys

a lower density (7648 kg.m− ) than low-temperature phases, which have a body-centered cubic structure. Gamma-iron dissolves a nonnegligible amount of carbon, e.g., 1.7 wt.% C, at 1150°C. It is important to note that the word austenite describes a solid solution of carbon in gamma-iron, though it is also used improperly for denoting gamma-iron (Section 2.1.9): 3

γ-Fe (fcc, nonmagnetic) —> δ-Fe (bcc, magnetic) [Tt = 1392°C; ΔHγδ = +0.837 kJ.mol− ]. 1

Delta-iron (δ-Fe). At 1392°C, a third transformation occurs and the face-centered cubic lat3 tice reverts to a body-centered cubic form (a = 293.22 pm) with a density of 7357 kg.m− , which again becomes ferromagnetic. Finally, at a melting point of 1535°C, iron absorbs the latent heat required for fusion and becomes liquid (i.e., molten iron): δ-Fe (bcc, ferromagnetic) —> Fe (liquid) [Tm = 1535°C; ΔHm = +13.807 kJ.mol− ]. 1

Epsilon-iron (ε-Fe). Scientists subjecting iron to high pressure using diamond anvil experiments have discovered that there also exists a high-pressure form of metallic iron called epsilon-iron (ε-Fe) that forms only above a pressure of 13 GPa. Epsilon-iron exhibits the hexagonal close-packed (hcp) structure. Despite the fact that this phase has no effect on the metallurgy of iron, the phase is of particular interest for geophysicists because it seems to be one of the major constituents of the dense and solid inner core of the Earth.

2.1.3 Metallographic Etchants for Iron and Steels The recipes for preparing the most common etchants used to reveal the microstructure of iron and steel are listed in Table 2.4.

2.1.4 History Iron has been known since prehistoric times, and no other element has played a more important role in human material progress. Iron beads dating from around 4000 B.C. were no doubt of meteoritic origin, and later samples produced by reducing iron ore with charcoal were not cast because adequate temperatures were not attainable without use of some form of bellows. Instead, the spongy material produced by low-temperature reduction would have had to be shaped by prolonged hammering. It seems that iron was first smelted by Hittites sometimes in the third millenium B.C., but the value of the process was so great that its secret was carefully guarded, and it was only with the fall of the Hittite empire around 1200 B.C. that the knowledge was dispersed and the “Iron Age” began. In more recent times the introduction of coke as the reductant had far-reaching effects and was one of the major factors in the initiation of the Industrial Revolution.

2.1.5 Natural Occurrence, Minerals, and Ores Because nuclides of iron are especially stable with the highest binding energy per nucleon 56 (e.g., −8.79 MeV/nucleon for Fe), its cosmic abundance is particularly high, and it is thought to be the main constituent of the Earth’s inner core as an iron-nickel alloy (see Section 13.2), named for its chemical composition NiFe by the Austrian geophysicist Suess. The relative Earth’s crust abundance is about 5.63 wt.% Fe; hence it is the fourth most abundant element after oxygen, silicon, and aluminum and the second most abundant metal after aluminum.

Iron and Steels

67

Table 2.4. Common metallographic etchants for iron and steels Etchant Nital

Composition 3

99-90 cm EtOH 3 1-10 cm HNO3

Description Nital is the most common etchant for steels. Do not store nital with more than 3 wt.% nitric acid in ethanol due to decomposition. Use by immersion or swabbing applying a low pressure.

3

Picral is better than nital for revealing annealed microstructures. Does not reveal ferrite grain boundaries. Etch by immersion or swabbing.

3

Picral

100 cm EtOH 4 g picric acid

Villela’s reagent

100 cm EtOH 3 5 cm HCl 1 g picric acid

Vilella's reagent is good for higher alloyed steels, tool steels, and martensitic stainless steels. Etch by immersion or swabbing.

Carpenter’s reagent

85 mL EtOH 15 mL HCl

Etch for duplex stainless steels. Immerse specimens 15−45 min to reveal the grain and phase boundaries in duplex stainless steels.

Klemm’s I reagent

50 cm saturated Klemm's I tint etch colors ferrite strongly; also colors martensite and Na2S2O3 bainite, but not carbides or retained austenite. Use by immersion only 1 g K2S2O5 until the surface is colored.

Alkaline picrate

100 cm H2O 25 g NaOH 2 g picric acid

Electrolytic etching

100 cm H2O 20 g NaOH

Murakami’s reagent

3

3

Alkaline sodium picrate must be used at 80−100°C by immersion only. Colors cementite (Fe3C) and M6C carbides.

3

Electrolytic etching for stainless steels. Specimen polarized as anode (+) under a cell voltage of 3 V during 10 s to color ferrite (tan or light blue) and sigma (orange) but does not affect austenite.

100 cm H2O 10 g NaOH (KOH) 10 g K3Fe(CN)6

3

Used to color ferrite and sigma (80−100°C for up to 3 min) in stainless steels. At room temperature will not color ferrite but will color certain carbides. At high temperatures, colors ferrite, sigma, and carbides, but not austenite.

Beraha’s sulfamic acid reagent

100 cm3 H2O 3 g K2S2O5 2 g sulfamic acid 0.5-1 g NH4HF2

Color phases in highly alloyed tool steels and martensitic stainless steels. Use by immersion only, 30−180 s in a freshly prepared solution. Due to ammonium hydrogen fluoride PTFE or PP beaker and tongs must be used.

Beraha’s reagent

85 cm H2O 3 15 cm HCl 19 g K2S2O5

3

Beraha-type etch for duplex stainless steels in a freshly prepared solution. Use by immersion until surface is colored. Colors ferrite but not austenite.

Native metallic iron, owing to its chemical reactivity to oxygen, occurs rarely free in nature. Native iron occurs either as telluric iron or meteoric iron. Terrestrial iron, also called telluric iron to distinguish it from native iron of meteoric origin, is found in masses occasionally of great dimensions weighing up to 80 tonnes, as well as small embedded particles of a few grams in basalts such as at Blaafjeld, Ovifak on Disco Island (Western Greenland). Terrestrial iron usually exhibits a low carbon content (i.e., between 0.2 and 0.7 wt.% C) and also contains 0.5 to 4 wt.% Ni with 1000 to 4000 ppm wt. Co. Moreover, nickeliferrous metallic iron, called awaruite (FeNi2, cubic), occurs in the drift of the George River, which empties into Awarua Bay on the west coast of the South Island of New Zealand, while josephinite (FeNi3) occurs in alluvial deposits such as stream gravels in Oregon, USA. Meteoric iron – native meteoric iron is of extraterrestrial origin coming from falling meteorites. In most cases, it forms the entire mass of the meteorite, i.e., iron meteorites or siderites, it forms a spongy cellular matrix with embedded grains of silicates such as olivine, i.e., lithosiderites or siderolites, and finally it is disseminated through a silicate matrix, i.e., stony meteorites or litholites. Meteorites are described in more detail in Section 13.8.

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Ferrous Metals and Their Alloys

Iron in nature is essentially combined with other chemical elements in a wide variety of mineral species found in igneous, metamorphic, or sedimentary rocks or as weathering products of various primary iron-bearing materials (laterites) and also in other geologic materials (e.g., soils). However, sedimentary deposits account for 80% of the world reserves of iron. Among them, the most widely distributed iron-bearing minerals of economic importance are oxides such as hematite [Fe2O3, rhombohedral with 70 wt.% Fe], magnetite [Fe3O4, cubic with 72.4 wt.% Fe], and limonite [Fe2O3.H2O, orthorhombic with 63 wt.% Fe], the carbonate siderite [FeCO3, rhombohedral with 48.2 wt.% Fe], and the two sulfides pyrite [FeS2, cubic] and marcasite [FeS2, orthorhombic], both with 47 wt.% Fe. Of these minerals only oxides are commonly used as iron ores for ironmaking. Iron ore deposits have a wide range of formation in geologic time as well as a wide geographic distribution. They are found in the oldest known rocks of the lithosphere, with an age in excess of 2.5 Ga, as well as in rock units formed in various subsequent ages; in fact, iron ores are still forming today in areas where iron hydroxides are being precipitated in marshy areas and where magnetite placers are being formed on certain beaches. Many thousands of iron occurrences are known throughout the world. They range in size from a few tonnes to many hundreds of millions of tonnes. Many of the world’s largest deposits of iron ore are located in Precambrian formations. These deposits account for 90% of world reserves. These iron ores exhibit an elevated Fe/Si ratio of 0.7 and are rich in aluminum and phosphorus and sometimes manganese. Commercially profitable extraction requires iron ore deposits that have a raw ore with more than 30 wt.% Fe. Although certain exceptional iron ores contain as much as 66 wt.% Fe, the major commercial iron ores usually contain 50 to 60 wt.% Fe. In addition, the quality of the iron ore is influenced by the type of inert gangue materials. In addition to iron content, the amount of silica, phosphorus, and sulfur-bearing compounds is also important because they strongly affect the steelmaking process. Although iron ore production is widely distributed, i.e., occurring in ca. 50 countries, the bulk of the world production comes from just a few countries. For instance, in 2004, the 10 most important iron-ore-producing countries were, in decreasing order of mining production, Brazil, Australia, India, China, Russia, Ukraine, South Africa, Canada, Venezuela, and Sweden (Table 2.5 for more details). Together, these countries produce 70% of the world total. Note that China was the largest producer of crude ore in 2002, but, owing to the low iron content of its ore of about 32 wt.% Fe, it must be concentrated to 60 wt.% Fe or more. Hence its usable ore production is ranked well below that of both Brazil and Australia for that year. Table 2.5. Major iron-ore-producing countries (2002)

3

Rank Producing country

Major iron ore districts and ore type

Production 6 (/10 tonnes)

1

Brazil

Quadrilatero Ferrifero (Minas Gerais): Precambrian marine sedimentary 239.4 deposits (35−60 wt.% Fe). Carajas ore district: Precambrian metamorphic ore beds enriched by weathering (60−65 wt.% Fe)

2

Australia

Hamersley Range in the Pilbara district (WA): Precambrian banded sedimentary deposits heavily metamorphized (itabarite)

187.2

3

China

Provinces of Liaoning and Hebei; ores of itabirite type

108.8

4

India

Bihar (State of Orissa) and Mahya (India Pradesh) Precambrian sedimentary rocks

86.4

5

Russia

Kursk (Western Siberia); magnetite ore bodies with iron and zinc sulfides 84.2

Adjustment of the original value of 231 million tonnes to account the lower average mined grade.

3

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Table 2.5. (continued) Rank Producing country

Major iron ore districts and ore type

Production 6 (/10 tonnes)

6

Ukraine

Krivoi Rog; Precambrian sedimentary ores

58.9

7

United States

Lake Superior Taconites (Michigan, Wisconsin, Minnesota)

51.5

8

South Africa

Sishen hematite

36.5

9

Canada

Labrador geosyncline (Wabush): Precambrian sedimentary deposits enriched by weathering (>60 wt.% Fe)

30.8

10

Venezuela

Imataca belt (Cerro Bolivar, El Pao, San Isidro); taconite type

20.9

11

Sweden

Northern Lapland (Kiruna, Malmberget); magnetite intrusion with apatite

20.3

12

Kazakhstan

15.4

13

Iran

12

14

Mexico

11

15

Mauritania

Zouerat

9.6

World total

1008

Sources: (i) Record trade in iron ore. Min. J. (London) no. 8744 July 11 (2003), pp. 21−23; (ii) The Iron Ore Market 2002–2004, UNCTAD Iron Ore Trust Fund, UNCTAD, Geneva, Switzerland (2003)

The world’s eight largest iron ore producers (2002 annual production expressed in millions of tonnes) are listed in Table 2.6. Table 2.6. Major iron ore producers (2002) Company (Country)

Production 6 (/10 tonnes)

Companhia Vale do Rio Doce (CVRD) (Brazil)

163.6

Rio Tinto (UK/Australia)

93.8

BHP Billiton (UK/Australia)

80.8

State of India (India) (incl. SAIL, NMDC, Kudremukh)

38.6

Mitsui (Japan)

31.8

Kumba Resources (RSA)

18.6

Metalloinvest (Russia)

27.7

State of Ukraine (Ukraine) (incl. Ukrrudprom)

20.5

State of Sweden (Sweden) (incl. LKAB)

20.3

Lebedinsky GOK (Russia)

18.4

State of Venezuela (Venezuela) (incl. CVG Ferrominera Orinoco) 16.5 USX (USA)

16.4

State of China (PRC) (incl. Anshan Iron & Steel)

14.9

Cleveland-Cliffs (USA)

14.4

Sokolovsky-Sarbaisky GPO (Kazakhstan)

13.1

Sources: (i) Record trade in iron ore. Min. J. (London) No. 8744 July 11 (2003), pp. 21−23; (ii) The Iron Ore Market 2002–2004, UNCTAD Iron Ore Trust Fund, UNCTAD, Geneva, Switzerland (2003)

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Table 2.7. Top ten crude-steel-producing countries (2003) Rank

Producing country

Production 6 (/10 tonnes)

1

China

220.1

2

Japan

110.5

3

United States

91.4

4

Russia

61.3

5

South Korea

46.3

6

Germany

44.8

7

Ukraine

36.7

8

India

31.8

9

Brazil

31.1

10

Italy

26.7

Other

261.80

World total

962.5

In terms of crude steel production, according to the International Iron and Steel Institute (ISII), in 2003 the total world crude steel production reached 962.5 million tonnes, with 40% produced in Asia. The top ten crude-steel-producing countries are listed in Table 2.7.

2.1.6 Mining and Mineral Dressing Most iron ores are mined by common open-pit techniques. Some underground mines exist, but, wherever possible, surface mining is preferred because it is less expensive. After mining, depending on the quality of the raw iron ore, two methods can be used to prepare the concentrated ore. Common ore is crushed and ground in order to release the ore minerals from the inert gangue materials (e.g., silica and silicates). Gangue minerals are separated from iron ore particles by common ore beneficiation processes in order to decrease silica content to less than 9 wt.%. Most concentration processes use froth flotation and gravity separation based on density differences to separate light gangue minerals from heavier iron ores. Electromagnetic separation techniques are also used, but hematite is not ferromagnetic enough to be easily recovered. After beneficiation, the iron ore concentrate is in the powdered form and, hence, unsuitable for use directly in the blast furnace. It has a much smaller particle size than ore fines and cannot be agglomerated by sintering. Instead, concentrates must be agglomerated by the process of pelletizing (which originated in Sweden and Germany in 1911 and was optimized in the 1940s). In this process, humidified concentrates are first fired into a rotary kiln in which the tumbling action produces soft, spherical agglomerates. These agglomerates are then dried and hardened by firing in air at a temperature ranging between 1250°C and 1340°C, yielding spherical pellets with about a 1-cm diameter. For certain rich iron ore deposits the raw ore (above 66 wt.% Fe) is crushed to reduce the maximum particle size and sorted into various fractions by passing it over sieves through which lump or rubble ore (i.e., 5 to 25 mm) is separated from the fines (i.e., less than 5 mm). Due to the high iron content, the lumps can be charged directly ino the blast furnace without any further processing. Fines, however, must first be agglomerated, which means reforming them into lumps of suitable size by a process called sintering, an agglomeration process in which fines are

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heated in order to achieve partial melting, during which ore particles fuse together. For this purpose, the elevated heat required is generated by burning the fine coke known as coke breeze. After cooling, the sinter is broken up and screened to yield blast-furnace feed and an undersize fraction that is recycled. 2

2.1.7 Iron- and Steelmaking Highly pure iron is prepared on a small scale by the reduction of pure oxide or hydroxide with hydrogen, or by the carbonyl process in which iron is heated with carbon monoxide under pressure and the Fe(CO)5 so formed decomposed at 250°C to give off the powdered metal. By contrast, the industrial production of steel by the conversion of iron ore into steel in a blast furnace accounts for the largest tonnage of any metal produced by humans. Actually in 2005, 9 1.107 × 10 tonnes of crude steel were produced worldwide, with 62% produced by the oxygen steelmaking method, 34% by electric steelmaking, and the remaining 4% by smelting reduc9 tion. This amount of crude steel requires upstream ca. 1.292 × 10 tonnes of iron feedstocks, which breaks down as follows: 749 million tonnes (58%) of hot metal, 491 million tonnes (38 %) of reclaimed steel scrap, and finally 52 million tonnes (4%) of direct reduced iron. The blast furnace. Ironmaking consists in winning iron metal from iron chemically combined with oxygen. The blast-furnace process, which consists in the carbothermic reduction of iron oxides, is industrially the most efficient process. From a chemical engineering point of view, the blast furnace can be described as a countercurrent heat and oxygen exchanger in which rising combustion gas loses most of its heat on the way up, leaving the furnace at a temperature of about 200°C, while descending iron oxides are reduced to metallic iron. The blast furnace is a tall, vertical steel reactor lined internally with refractory ceramics such as high-alumina firebrick (45 to 63 wt.% Al2O3) and graphite. Five sections can be clearly identified: (i)

At the bottom is a parallel-sided hearth where liquid metal and slag collect. This is surmounted by (ii) an inverted truncated cone known as the bosh. Air is blown into the furnace through (iii) tuyeres, i.e., water-cooled copper nozzles, mounted at the top of the hearth close to its junction with the bosh. (iv) A short vertical section called the bosh parallel, or the barrel, connects the bosh to the truncated upright cone that is the stack. (v) Finally, the fifth and top section, through which the charge is fed into the furnace, is the throat. The lining in the bosh and hearth, where the highest temperatures occur, is usually made of carbon bricks, which are manufactured by pressing and baking a mixture of coke, anthracite, and pitch. Actually, carbon exhibits excellent corrosion resistance to molten iron and slag in comparison with the aluminosilicate firebricks used for the remainder of the lining. During the blast-furnace process, the solid charge (i.e., mixture of iron ore, limestone, and coke) is loaded either by operated skips or by conveyor belts at the top of the furnace at temperatures ranging from 150 to 200°C, while preheated air (i.e., 900 to 1350°C) in hot-blast stoves, sometimes enriched up to 25 vol.% O, is blown into the furnace through the tuyeres. During the process, the coke serves both as fuel and reducing agent, and a fraction combines with iron. The limestone acts as a fluxing agent, i.e., it reacts with both silica gangue materials and traces of sulfur to form a slag. Sometimes fluorspar is also used as fluxing agent. During the carbothermic reduction, the ascending carbon monoxide (CO) resulting from the exothermic combustion of coke at the tuyere entrance begins to react with the descending

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charge, partially reducing the ore to ferrous oxide (FeO). At the same time the CO is cooled by the descending charge and reacts, forming carbon dioxide (CO2) and carbon black (soot). This soot is dissolved in the iron, forming a eutectic, and hence decreases the melting temperature. At this stage, the temperature is sufficiently high to decompose the limestone into lime (CaO) and CO2. Carbon dioxide reacts with the coke to give off CO, and the free lime combines with silica gangue to form a molten silicate slag floating upon molten iron. Slag is removed from the furnace by the same taphole as the iron, and it exhibits the following chemical composition: 30 to 40 wt.% SiO2, 5 to 15 wt.% Al2O3, 35 to 45 wt.% CaO, and 5 to 15 wt.% MgO. As the partially reduced ore descends, it encounters both increasingly high temperature and high concentration of CO, which accelerates the reactions. At this stage the reduction of ferrous oxide into iron is completed and the main product, called molten pig iron (i.e., hot metal or blast-furnace iron), is tapped from the bottom of the furnace at regular intervals. The gas exiting at the top of the furnace is composed mainly of 23 vol.% CO, 22 vol.% CO2, 3 vol.% H2O, and 49 vol.% N2, and after the dust particles have been removed using dust collectors, it is mixed with coke oven gas and burned in hot-blast stoves to heat the air blown in through the tuyeres. It is important to note that during the process, traces of aluminum, manganese, and silicon from the gangue are oxidized and recovered into the slag, while phosphorus and sulfur dissolve into the molten iron. Direct reduction iron. The blast-furnace process is strongly dependent on the commercial availability of coke. For that reason, numerous substitute processes have been investigated since the 1950s to produce a prereduced product for crude steelmaking based on iron ore reduction without using coke as a reductant and to avoid operation of a capital-intensive coke oven plant. These technologies have been especially attractive in countries suffering a coke supply deficit, and hence they are used in Central and South America, India, and Africa. These processes are grouped under the term direct reduction and smelting reduction. Direct reduction processes produce solid direct reduced iron (DRI) or hot briquetted iron (HBI), while smelting reduction processes produce liquid hot metal. However, despite their great promise, these technologies have never superseded the blast furnace, especially in industrialized countries, for the following reasons: (i) (ii)

Direct reduction is attractive at locations where cheap energy and particularly cheap natural gas is available. The development of a market for steel scrap as a raw material acts against direct reduction. Direct reduction can be divided according to the type of reductant used (i.e., natural gas, coal) or the screen size of iron ore (i.e., coarse, fines).

Table 2.8. Processes for direct reduction Gas reduction Shaft furnace

Coal-based reduction Midrex

Rotary kiln

SL/RN

HyL III

Fluidized bed

Circofer

Arex

Rotary hearth

Inmetco

Retort

HyL I and II

Fastmet

Fluidized bed

Fior

Sidcomet

Finmet Iron Carbide

DRyrlon Multiple hearth furnace

Primus

Circored Source: Steffen, R.; Lüngen, H.-B. State of the art technology of direct and smelting reduction of iron ores. La Revue de Métallurgie, No.3, March 2004, pp. 171−182

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2.1.8 Pure Iron Grades Table 2.9. Pure iron grades Pure iron grade

Purity Description (/ wt.% Fe)

Ingot iron

99.8−99.9

Ingot iron is a nearly chemically pure iron type (i.e., 99.8 to 99.9wt.%Fe) that is used for construction work where a ductile, rust-resistant metal is required. It is mainly applied for boilers, tanks, enamel ware, and galvanized culvert sheets, as well as for electromagnetic cores and as a raw material for producing specialty steels. A well-known commercial type is Armco ingot iron (99.94 wt.% Fe). Typical ingot irons have as little as 0.02 wt.% C or less. The Armco ingot iron, for example, typically has carbon concentrations of 0.013 wt.% C and a manganese content around 0.017 wt.% Mn. Ingot iron may also be obtained in grades containing 0.25 to 0.30 wt.% copper, which increases the corrosion resistance. Ingot iron is made by the basic open-hearth process and highly refined, remaining in the furnace 1 to 4 h longer than the normal time, and maintained at a temperature of 1600 to 1700°C.

Electrolytic iron

99.9

Electrolytic iron is a chemically pure iron (i.e., 99.9 wt.% Fe) produced by the cathodic deposition of iron in an electrochemical refining process. Bars of cast iron are used as consumable and soluble anodes and dissolved in an electrolyte bath containing iron (II) chloride (FeCl2) with a current density ranging from 2 200 to 1000 A.m− at a pH close to 1.1 to prevent both hydrogen evolution that decreases faradaic efficiency and the precipitation of iron hydroxides. Due to the ease of stripping, the cathodic reduction of ferrous cations yields pure iron deposited onto titanium metal cathodes, which are often hollow cylinders. The deposited iron tube is removed by hydraulic pressure or by splitting and then annealed and rolled into plates. The product is used for magnetic cores and in general in applications where both elevated ductility and purity are required.

Pig iron

94.6

Pig iron is obtained from the smelting of hemo-ilmenite with anthracite coal in ac- or dc-electric arc furnaces. Pig iron with typically 4.25 wt.% C is commercialized under the tradename Soremetal and has been produced since 1950 by slagging at the metallurgical complex of QIT-Fer & Titane in SorelTracy, Qc, Canada and later in the 1970s at Richards Bay Minerals, South Africa.

Reduced iron

99.9

Reduced iron is a fine gray amorphous powder made by reducing crushed iron ore by heating in hydrogen atmosphere. It is used for special chemical purposes.

Carbonyl iron

99.99

Carbonyl iron or carbonyl iron powder is metallic iron of extreme purity, produced as microscopic spherical particles by the reaction of carbon monoxide on iron ore. This reaction gives a liquid, called iron carbonyl Fe(CO)5, that is vaporized and deposited as a powder. Carbonyl iron is mainly used for magnetic cores for high-frequency equipment and for pharmaceutical application of iron.

Wrought iron

99

Whrought iron, which is no longer commercially produced, is a relatively pure iron containing nonmetallic slag inclusions produced by a blast furnace. Modern wrought iron products are actually made of low-carbon steel.

2.1.9 The Iron-Carbon (Fe-C) and Iron-Cementite (Fe-Fe3C) Systems Because carbon is a ubiquitous element in both iron- and steelmaking processes due to its essential use as a reductant during the extractive process of iron from its ores, carbon has a predominant role in siderurgy (i.e., the metallurgy of iron and its alloys). Although other

2 Ferrous Metals and Their Alloys

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Ferrous Metals and Their Alloys

alloying elements may be added to produce steels for special purposes, usually the structure of iron and steels is determined first by the content of carbon, secondly by the type of other alloying elements, and finally by the rate of cooling from the molten state. For all the above reasons, a solid grasp of the iron-carbon system is a mandatory step for understanding iron and iron alloys (i.e., steels and cast irons). As for the phase diagram of pure iron, the major phases occuring in the Fe-C phase diagram (Figure 2.1) can be accurately characterized by means of X-ray diffraction, thermal analysis, and dilatometry techniques. In practice, the iron-carbon phase diagram is a graphical plot of phases existing in thermodynamic equilibrium as a function of temperature versus the mass fraction of total carbon in the iron. The diagram depicted in this book is only a detail of the entire diagram. Actually, the phase diagram extends on the abscissa axis at left from pure iron free of carbon to a content of total carbon reaching 6.70 wt.% C that corresponds to the theoretical composition of iron carbide or cementite (Fe3C), while temperatures range from 200°C to 1600°C, the temperature at

Figure 2.1. Simplified iron-carbon phase diagram. Source: Simplified iron-carbon phase diagram. Metal Prog., vol. 52. Copyright © 1947 ASM International (reprinted with permission)

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which the system is fully liquid. The binary phase diagram exhibits, in addition to the four critical points of the allotropes of pure iron, three other important characteristics: (i) a eutectic point at 4.30 wt.% C and 1148°C; (ii) a eutectoid point at 0.77 wt.% C and 727°C; (iii) a peritectic transformation occurring at 1495°C. Moreover, experimentally the following solid phases were identified. Alpha-ferrite (α-ferrite, bcc). Sensu stricto and historically, ferrite consists of a solid solution of carbon inside a body-centered cubic crystal lattice in alpha-iron. As mentioned in Section 2.1.2, the solubility of carbon in alpha-iron is extremely low, ca. 0.01 wt.% C at ambient temperature, and reaches only 0.025 wt.% C at 723°C. Therefore, at room temperature under conditions of equilibrium, any carbon present in excess of that small amount will exsolute in the form of cementite. Due to this low carbon content, some textbooks treat the ferrite phase substantially as pure iron, but this view must be discontinued to avoid confusion. Usually, the ferrite of an alloyed steel may contain in solid solution appreciable amounts of other elements; ab extenso, any solid solution of which alpha-iron is the solvent is called ferrite (i.e., a solid solution of any element in alpha-iron). Alloying elements that stabilize ferrite are listed in Table 2.11. Beta-ferrite (β-ferrite, bcc). Like alpha-ferrite, beta-ferrite consists of a solid solution of any element in body-centered cubic beta iron. Delta-ferrite (δ-ferrite, bcc). Like alpha-ferrite, delta-ferrite consists of a solid solution of any element in body-centered cubic delta iron. In the case of carbon, its maximum solubility in delta-iron is only 0.1 wt.% at 1487°C. Gamma-austenite (γ-austenite, fcc). Austenite is a solid insertion solution of carbon into the crystal lattice of face-centered cubic gamma-iron. It has been definitively established that the carbon atoms in austenite occupy interstitial positions in the face-centered cubic space lattice causing the lattice parameter to increase progressively with the carbon content. Cementite. Cementite is an iron carbide with the chemical formula Fe3C. At room temperature, cementite is a hard, brittle, and ferromagnetic material with a Curie temperature of 210°C. It is formed by chemical reaction between iron and excess carbon. Three distinct origins must, however, be distinguished: (i)

primary cementite resulting from the separation during solidification of liquid iron with carbon content ranging between 4.3 wt.% and 6.69 wt.% C; (ii) secondary cementite formed after demixion of carbon as a result of a decrease in miscibility during the cooling of ferrite; (iii) tertiary cementite resulting from demixion during the cooling of austenite. Actually, at room temperature under conditions of equilibrium, any carbon present in excess of that small amount must exist in a form other than that of a solute in a solid solution. Perlite. A biphasic eutectoidic constituent that consists of an interlamellar growth of ferrite and cementite. Perlite is formed during the transformation of austenite with a eutectoid composition (i.e., 0.77 wt.% C). Ledeburite. A biphasic eutectic constituent resulting from the solidification of a molten metal having a eutectic composition. Hence it consists of an austenite containing 1.7 wt.% C in solid solution and cementite. In the phase diagrams in Figures 2.1 and 2.2, the transition temperatures or critical points previously identified for the four iron allotropes must now be replaced by two temperature limits or points. Actually, due to hysteresis phenomena occurring upon heating and cooling, the equilibrium curves are greatly influenced by the rate of cooling and heating, and they form distinct plots. The various temperatures at which pauses occur in the rise or fall of temperatures when iron or steel is heated from room temperature or cooled from the molten

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Ferrous Metals and Their Alloys

Figure 2.2. Detailed iron-cementite phase diagram. Source: Ullmann’s Encyclopedia of Industrial Chemistry, 5th enhanced ed., vol. A14, p. 484, figure 11 in encyclopedia. Iron-cementite phase diagram. Copyright © 1989 Wiley-VCH (reproduced and redrawn with permission)

state are called arrest points, denoted by uppercase letter A. Due to the previously mentioned hysteresis behavior during heating and cooling, the arrest points obtained on heating are denoted Ac and those obtained on cooling are denoted Ar, while arrest points at equilibrium are denoted Ae. Historically, the subscripts c , r, and e were derived from the first letters of the French words chauffage (heating), refroidissement (cooling), and équilibre (equilibrium), respectively. These arrest points are described in detail in Table 2.10. From the iron-carbon phase diagram several important characteristics regarding the classification of iron and iron alloys can be seen. Iron alloys are classified according to their total content of carbon. Steel are particular iron alloys having a carbon content below 2.1 wt.% C. Above this limit, we have cast irons up to a practical limit of 3.75 wt.% C. A steel containing 0.77 wt.% C is called a eutectoid steel. Eutectoid steel consists of an intimate mixture of alpha-ferrite and cementite forming an intergrowth of thin plates or lamellae known as perlite. Therefore, a steel having a carbon content below 0.77 wt.% C is called a hypotectoid steel. Its structure consists of a small amount of pearlite with an excess of alpha-ferrite, which collectsat the grain boundaries. Hypotectoid steels are hence softer and more ductile than eutectoid steels. On the other hand, a steel with more than 0.77 wt.% C is called a hypertectoid steel. Its structure consists of pearlite with an excess of cementite. Hypertectoid steels are harder, more brittle, and les ductile than eutectoid steels. Above 2.11 wt.% C, molten iron solidifies

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Table 2.10. Critical arrest points in iron-carbon phase diagram Point Description A0

A1

A2

A3

A4

Acm

The first critical point; occurs at 210°C, the temperature at which cementite loses its ferromagnetism (Curie point). This arrest point exhibits the same temperature either on heating or on cooling, and it has little importance in both iron- and steelmaking. Temperature at which the transformation between austenite and perlite occurs (738°C). Austenite forms upon heating or decomposes upon cooling into a lamellar eutectoid made of alpha-ferrite plus cementite according to γ−(Fe,C) —> α−(Fe,C) + Fe3C. Ae1

Temperature of equilibrium.

Ac1

Temperature at which austenite with eutectoid composition forms upon heating (formerly called decalescence point).

Ar1

Temperature at which the transformation austenite with eutectoid composition transforms into ferrite and cementite upon cooling (formerly called recalescence point). The latent heat released during transformation is so high that the steel can be seen to redden with a distinct sound.

Temperature at which the transformation from austenite into perlite occurs (768°C). Austenite forms upon heating or decomposes upon cooling into a lamellar eutectoid made of beta-ferrite plus cementite according to γ−(Fe,C) —> β−(Fe,C) + Fe3C. Ae2

Temperature of equilibrium of transformation.

Ac2

Temperature at which austenite with eutectoid composition forms upon heating.

Ar2

Temperature at which the transformation austenite with eutectoid composition transforms into paramagnetic beta-ferrite and cementite upon cooling.

Temperature at which austenite and alpha-ferrite coexist temporarily and above which only austenite exists. Ae3

Temperature of equilibrium of transformation.

Ac3

Temperature at which the transformation alpha-ferrite-austenite is completed upon heating.

Ar3

Temperature at which the transformation of austenite into alpha-ferrite initiates upon cooling.

Temperature at which austenite and beta-ferrite coexist temporarily and above which only austenite exists. Ae4

Temperature of equilibrium of transformation.

Ac4

Temperature at which the transformation beta-ferrite-austenite is completed upon heating.

Ar4

Temperature at which the transformation of austenite into beta-ferrite initiates upon cooling.

Temperature at which austenite and cementite coexist for steel with hypereutectoid composition and above which only austenite exists and below which only cementite exists. Ae cm

Temperature of equilibrium of transformation.

Ac cm

Temperature at which the dissolution of cementite in austenite is completed upon heating.

Ar cm

Temperature at which the segregation of cementite from austenite initiates upon cooling.

always below 1350°C and the resulting low liquidus temperature iron alloys are called cast irons due to their ease of melting. The eutectic point in the Fe-C diagram is located at 4.3 wt.% C. At this composition, when the alloy solidifies, it forms a mixture of austenite with 1.7 wt.% C in solid solution and cementite; this eutectic structure is called ledeburite. In practice, cast irons exhibit a carbon content ranging between 2.11 and 3.75 wt.%. Upon cooling, cast irons exhibit a mixture of pearlite and cementite. The iron-carbon phase diagram only applies to alloys that contain only iron and carbon. But because other desired or undesired alloying elements are usually originally present from

2 Ferrous Metals and Their Alloys

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Ferrous Metals and Their Alloys

Table 2.11. Ferrite- and austenite-stabilizing elements Effect

Alloying elements or impurities

Effect

Ferrite stabilizers (alphagenous)

Cr, Si, Al, Mo, W, Ti, V

Favor the existence of alpha-ferrite.

B, S, Zr, Nb, Ce, Ta

Restrict domain of austenite.

Austenite stabilizers (gammagenous)

C, N, Cu

Enlarge domain of existence of austenite.

Ni, Mn,Co

Allow the existence of the austenite structure even at room temperature.

the ironmaking process (e.g., O, C, Si, P, Mn, V) or are added intentionally (e.g., Ni, Cr, Mo), during steelmaking the iron-carbon phase diagram cannot show accurately the conditions that apply to actual steels. Hence it has to be modified appropriately to take into account the effect of the elements. These additional elements impact both the arrest points and equilibrium lines, and they also determine the existence or not of certain phases. Alloying elements with their related impact on iron-carbon phases are listed in Table 2.11.

2.1.10 Cast Irons Cast irons contain much higher carbon and silicon levels than steels, theoretically higher than 1.8 wt.% but typically 3 to 5 wt.% Fe and 1 to 3 wt.% Si. These comprise another category of ferrous materials that are intended to be cast from the liquid state to the final desired shape. Various types of cast irons are widely used in industry, especially for valves, pumps, pipes, filters, and certain mechanical parts. Cast iron can be considered a ternary Fe-Si-C alloy. The carbon concentration is between 1.7 and 4.5%, most of which is present in insoluble form (e.g., graphite flakes or nodules). Such material is, however, normally called unalloyed cast iron and exists in four main types: (i) (ii)

white iron, which is brittle and glass hard; unalloyed gray iron, which is soft but still brittle and which is the most common form of unalloyed cast iron; (iii) the more ductile malleable iron; (iv) nodular or ductile cast iron, the best modern form of cast iron, which has superior mechanical properties and equivalent corrosion resistance. In addition, there are a number of alloy cast irons, many of which have improved corrosion resistance and substantially modified mechanical and physical properties. Generally, cast iron is not a particularly strong or tough structural material. Nevertheless, it is one of the most economical and is widely used in industry. Its annual production is surpassed only by steel. Iron castings are used in many items of equipment in the chemical-process industry, but its main use is in mechanical engineering applications: automobile and machine tools. Some of the best known classes, listed below, include the high-silicon and nickel cast irons. • gray cast iron • white cast iron • chilled iron (duplex) • malleable cast irons • ductile or nodular cast irons

Iron and Steels

79

• alloy cast irons • high-silicon cast irons • nickel cast irons

2.1.10.1 Gray Cast Iron or Graphitic Iron Gray cast irons contain 1.7 to 4.5 wt.% of C and other alloying elements such as Si, Mn, and Fe. Due to the slow cooling rate during casting, the carbon is precipitated as thin flakes of graphite dispersed throughout the metal. Therefore, gray cast irons are relatively brittle. Gray cast iron is the least expensive material, is quite soft, has excellent machinability, and is easy to cast into intricate shapes. Various strengths are produced by varying the size, amount, and distribution of the graphite. For instance, ultimate tensile strength typically ranges from 155 to 400 MPa and the Vickers hardness from 130 to 300 HV. Gray iron has excellent wear resistance and damping properties. However, it is both thermal and mechanical shock sensitive. Gray iron castings can be welded with proper techniques and adequate preheating of the components.

2.1.10.2 White Cast Iron White cast iron is made by controlling the chemical composition (i.e., low Si, high Mn) and rate of solidification of the iron melt. Rapid cooling leads to an alloy that has practically all its carbon retained as dissolved cementite that is hard and devoid of ductility. The resulting cast is hard, brittle, and virtually unmachinable, and finishing must be achieved by grinding. Typically, the Vickers hardness ranges from 400 to 600 HV. Its main use is for wear- or abrasion-resistant applications. In this respect white irons are superior to manganese steel, unless deformation or shock resistance is required. The major applications of cast irons include pump impellers, slurry pumps, and crushing and grinding equipment.

2.1.10.3 Malleable Cast Irons Malleable iron exhibits a typical carbon content of 2.5 wt.% C. It is made from white cast iron by prolonged heating of the casting. This causes the carbides to decompose, and graphite aggregates are produced in the form of dispersed compact rosettes (i.e., no flakes). This gives a tough, relatively ductile material. There are two main types of malleable iron, standard and pearlitic. The latter contains both combined carbon and graphite nodules. Standard malleable irons are easily machined. This is less so for pearlitic iron. All malleable cast irons withstand cold working and bending without cracking.

2.1.10.4 Ductile (Nodular) Cast Irons This is the best modern form of cast iron as it has superior mechanical properties and equivalent corrosion resistance. Ductility is much improved and may approach that of steel. Ductile iron is sometimes also called nodular cast iron or spheroidal graphite cast iron, as the graphite particles are approximately spherical in shape, in contrast to the graphite flakes in gray cast iron. Ductile cast iron exhibits a typical microstructure. This is achieved by the addition of a small amount of nickel-magnesium alloy or by inoculating the molten metal with magnesium or cerium. Furthermore, composition is about the same as gray iron, with some nickel, and with more carbon (3.7 wt.% C) than malleable iron. There are a number of grades of ductile iron. Some have maximum machinability and toughness, others have maximum oxidation resistance. Ductile iron castings can also be produced to have improved low-temperature impact properties. This is achieved by adequate thermal treatment, by control of the phosphorus and silicon content, and by various alloying processes.

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Ferrous Metals and Their Alloys

2.1.10.5 High-Silicon Cast Irons Cast irons with a high silicon level (i.e., 13 to 16 wt.% Si), which are called Duriron, exhibit, for all concentrations of H2SO4, even up to the boiling point, a constant corrosion rate of 130 μm/year (i.e., 5 mpy). For these reasons, it is widely used in sulfuric acid service. Duriron is a cheap material that does not contain any amount of strategic metal. Nevertheless, it is very hard and brittle and thermal shock sensitive, so it is not readily machined or welded. Table 2.12. Classification of cast irons Cast iron class

4

Average chemical composition range

Carbon-rich phase

Matrix

Fracture

Gray cast iron (FG) (flake 2.5−4.0 wt.% C graphite cast iron) 1.0−3.0 wt.% Si 0.2−1.0 wt.% Mn 0.002−1.0 wt.% P 0.02−0.25 wt.% S

Lamellar graphite

Pearlite

Gray

Compacted graphite cast iron (CG)

2.5−4.0 wt.% C 1.0−3.0 wt.% Si 0.2−1.0 wt.% Mn 0.01−0.1 wt.% P 0.01−0.03 wt.% S

Compacted vermicular graphite

Ferrite, pearlite

Gray

Ductile cast iron (SG) (nodular or spheroidal graphite cast iron)

3.0−4.0 wt.% C 1.8−2.8 wt.% Si 0.1−1.0 wt.% Mn 0.01−0.1 wt.% P 0.01−0.03 wt.% S

Spheroidal graphite

Ferrite, pearlite, austenite

Silver gray

White cast iron

1.8−3.6 wt.% C 0.5−1.9 wt.% Si 0.25−0.8 wt.% Mn 0.06−0.2 wt.% P 0.06−0.2 wt.% S

Cementite Fe3C

Pearlite, martensite

White

Malleable cast iron (TG)

2.2−2.9 wt.% C 0.9−1.9 wt.% Si 0.15−1.2 wt.% Mn 0.02−0.2 wt.% P 0.02−0.2 wt.% S

Temper graphite

Ferrite, pearlite

Silver-gray

Mottled cast iron

Lamellar Graphite and cementite Fe3C

Pearlite

Mottled

Austempered ductile iron

Spheroidal graphite

Bainite

Silver-gray

Note: Type of graphite flakes in gray cast iron: (A) uniform distribution, random orientation; (B) rosette grouping, random orientation; (C) superimposed flake size, random orientation; (D) interdendritic segregation, random orientation; (E) interdendritic segregation, preferred orientation.

4

from Stefanescu, D.M. (1992) Classification and Basic Metallurgy of Cast Irons. In: ASM Metals Handbook, vol. 1: Ferrous Metals. ASM, Metal Park, OH p. 3.

7200–7600 7200–7600 7200–7600 7200–7600 7200–7600 7200–7600 7200–7600

Grade

20

25

30

35 (coarse pearlite)

40 (fine pearlite)

50 (acicular iron)

60

Gray cast iron (FG) (flake graphite cast iron)

Density 3 (ρ/kg.m− )

Type of Iron

Table 2.13. Physical properties of gray cast irons Young’s modulus (E/GPa) 141–162

130–157

110–138

100–119

Shear modulus (G/GPa)

90–113

54–59

50–55

44–54

40–48

36–45

32–41

Tensile strength (/MPa)

79–102

431

362

293

252

214

179

Shear strength (/MPa) 610

503

393

334

276

220

1293

1130

965

855

752

669

572

Compressive strength (/MPa)

179

302

262

235

212

210

174

156

Brinell hardness (/HB)

152

13

13

13

13

13

13

13

Coefficient linear thermal –6 –1 expansion (/10 K )

27–39

46–49

46–49

46–49

46–49

46–49

46–49

46–49

Thermal conductivity –1 –1 (k/W.m .K )

66–97

Iron and Steels 81

Ferrous Metals and Their Alloys

2

Table 2.14. Physical properties of nodular and other cast irons

7200–7600 7200–7600 7200–7600 7200–7600 7200–7600

80-55-06

100-70-03

120-90-02

D4018

D4512

D5506

Malleable cast iron (TG)

7200–7600 7200–7600 7200–7600

A602

A603

A604

7200–7600

7200–7600

65-45-12

Young’s modulus (E/GPa)

Pearlitic

7200–7600

60-40-18

168

168

168

165

162

169–172

169–172

169–172

169–172

169–172

169–172

169–172

169–172

169–172

Shear modulus (G/GPa)

7200–7600

7200–7600

80-60-03

67.5

67.5

67.5

68

68

66–69

66–69

66–69

66–69

66–69

66–69

66–69

66–69

66–69

Yield strength 0.2% proof (/MPa) 230–280

190

180

330

290

600

480

420

370–864

320

320–362

270–332

200–250

190–220

400–480

320

300

440

365

900

800

700

600–974

500

450–559

420–464

300–410

300–350

300–350

Ultimate tensile strength (/MPa)

190–220

12

10

6

1.5

4.5

3

1–3

7

11

12

18

18

22

Elongation (Z/%)

66–69

150

150

150

225–245

140–155

359

352

302

269

241

221

212

180

160

150

Brinell hardness (/HB)

169–172

n.a.

n.a.

n.a.

n.a.

n.a.

12

12

12

12

12

12

12

12

12

12

Coefficient linear thermal expansion –6 –1 (/10 K )

Ferritic

7200–7600

60-40-18

Ductile cast iron (SG) (nodular or spheroidal graphite cast iron)

n.a.

n.a.

n.a.

41

41

35

35

35

35

35

35

35

35

35

35

Thermal conductivity –1 –1 (k/W.m .K )

Compacted graphite cast iron (CG)

7200–7600

Grade

Density –3 (ρ/kg.m )

Type of iron

82 Ferrous Metals and Their Alloys

Alloyed cast iron type

Density –3 (ρ/kg.m ) 7600–7800 n.a.

7400–7600 170–310 690–1100 7400

High-nickel gray iron

High-nickel ductile

7100 7400 7400 7500 7700

High-Ni ductile (20 wt.% Ni)

High-Ni ductile (23 wt.% Ni)

High-Ni ductile (30 wt.% Ni)

High-Ni ductile (36 wt.% Ni)

5500–6400 180–350 n.a.

High-aluminum iron

Medium-silicon ductile iron

7330–7450 140–310 480–690

Nickel-chromium-Si iron

Heat-resistant ductile iron

7300–7500 170–310 690–1100

High-nickel iron

120–250 8.1–19.3

250–740 9.4–9.9

30

n.a.

n.a.

n.a.

n.a.

n.a.

400–450 n.a.

n.a.

n.a.

20

n.a.

n.a.

13

7.2

n.a.

12.6–14.4 n.a.

130–170 18.4

210

78

n.a.

n.a.

100

77

58–87

120

n.a.

150–170

37–40 140–170

37

140–400 10.8–13.5 n.a.

250–500 9.3–9.9

180–350 15.3

n.a.

50

80

53

38–40 100

n.a.

110–210 12.6–16.2 30

130–250 8.1–19.3

170–250 10.8

380–415 1240–1380 140–200 18.7

n.a.

7300–7500 210–620 690

6800–7100 170–310 620–1040

Medium-silicon iron

High-chromium iron

8–9

22

480–520 12.4–13.1 n.a

n.a.

12

380–480 1240–1380 130–240 12.6–18.7 13.4

7300–7500 205–380 690

690

n.a.

High-chromium iron

High-silicon iron (Duriron®) 7000–7050 90–180

Heat-resistant white iron

Heat-resistant gray iron

Ultimate tensile strength (σUTS/MPa)

Martensitic nickel Cr iron

Compressive strength (σ/MPa)

Corrosion-resistant irons

Brinell hardness (/HB) n.a.

Coefficient linear thermal –6 –1 expansion (α/10 K )

n.a.

Thermal conductivity –1 –1 (k/W.m .K )

7600–7800 n.a.

Electrical resistivity (ρ/μΩ.cm)

Abrasion-resistant white iron Low-carbon white iron

Alloyed cast iron class

Table 2.15. Properties of alloyed cast irons

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Ferrous Metals and Their Alloys

2.1.11 Carbon Steels (C-Mn Steels) Iron containing more than 0.15 wt.% C chemically combined is normally termed steel. This 0.15 wt.% C is a somewhat arbitrarily chosen borderline, and sometimes the nearly chemically pure “ingot iron” is referred to as mild steel. To make it even more confusing, the term

Table 2.16. Carbon- and low-alloy steel designation (AISI-SAE) Series Main group

Subgroups

1XXX (Plain) carbon steel

10XX: Plain carbon (1.00 wt.% Mn, max) 11XX: Resulfurized 12XX: Resulfurized and rephosphorized 13XX: Manganese steels (1.75 wt.% Mn) 15XX: Nonresulfurized (1.00–1.65 wt.% Mn max)

2XXX Nickel steels

23XX: 3.5 wt.% Ni 25XX: 5.0 wt.% Ni

3XXX Nickel-chromium steels

31XX: 1.25 wt.% Ni and 0.65 to 0.80 wt.% Cr 32XX: 1.75 wt.% Ni and 1.07 wt.% Cr 33XX: 3.50 wt.% Ni and 1.50 to 1.57 wt.% Cr 34XX: 3.00 wt.% Ni and 0.77 wt.% Cr

4XXX Molybdenum steels

40XX: 0.20 to 0.25 wt.% Mo 44XX: 0.40 to 0.52 wt.% Mo

Chromiummolybdenum steels

41XX: 0.50 to 0.95 wt.% Cr, 0.12 to 0.30 wt.% Mo

4XXX Nickel-molybdenum steels

46XX: 0.85–1.82 wt.% Ni, and 0.20–0.25 wt.% Mo 48XX: 3.50 wt.% Ni, 0.25 wt.% Mo

4XXX, Nickel-chromium8XXX, molybdenum 9XXX steels

43XX: 1.82 wt.% Ni, 0.50 to 0.80 wt.% Cr, and 0.25 wt.% Mo 43BVXX: 1.82 wt.% Ni, 0.50 wt.% Cr, and 0.12–0.25 wt.% Mo 47XX: 1.05 wt.% Ni, 0.45 wt.% Cr, and 0.20 to 0.35 wt.% Mo, 0.03 wt.% V 81XX: 0.30 wt.% Ni, 0.40 wt.% Cr, and 0.12 wt.% Mo 86XX: 0.55 wt.% Ni, 0.50 wt.% Cr, and 0.20 wt.% Mo 87XX: 0.55 wt.% Ni, 0.50 wt.% Cr, and 0.25 wt.% Mo 88XX: 0.55 wt.% Ni, 0.50 wt.% Cr, and 0.35 wt.% Mo 93XX: 3.25 wt.% Ni, 1.20 wt.% Cr, and 0.12 wt.% Mo 94XX: 0.45 wt.% Ni, 0.40 wt.% Cr, and 0.12 wt.% Mo 97XX: 0.55 wt.% Ni, 0.20 wt.% Cr, and 0.20 wt.% Mo 98XX: 1.00 wt.% Ni, 0.80 wt.% Cr, and 0.25 wt.% Mo

5XXX Chromium steels

50XX: 0.25 to 0.65 wt.% Cr 51XX: 0.80 to 1.05 wt.% Cr 50XXX: 0.50 wt.% Cr, min. 1 wt.% C 51XXX: 1.02 wt.% Cr, min. 1 wt.% C 52XXX: 1.45 wt.% Cr, min. 1 wt.% C

6XXX Chromium-vanadium steels 61XX: 0.6 to 0.95 wt.% Cr, 0.10 to 0.15 wt.% V 7XXX Tungsten-chromium steels

72XX: 1.75W, and 0.75Cr

9XXX Silicon-manganese steels

92XX: 1.40 to 2.00 wt.% Si, 0.65 to 0.85 wt.% Mn, and 0.65 wt.% Cr

NB: The letter L, inserted between the second and third digits of the AISI or SAE number (e.g., 12L15 and 10L45), indicates a leaded steel, while standard killed carbon steels, which are generally fine-grained, may be produced with a boron treatment addition to improve hardenability. Such boron steels are produced within a range of 0.0005 to 0.0030 wt.% B and are identified by inserting the letter B between the second and third digits of the AISI or SAE number (e.g., 10B46).

Iron and Steels

mild steel is often also used as a synonym for low-carbon steels (see below), which are materials with 0.15 to 0.30 wt.% C. Steels that have been worked or wrought while hot are covered with a black scale, also called a mill scale made of magnetite (Fe3O4), and are sometimes called black iron. Cold-rolled steels have a bright surface, accurate cross section, and higher tensile and yield strengths. They are preferred for bar stock to be used for machining rods and for shafts. Carbon steels may be specified by chemical composition, mechanical properties, method of deoxidation, or thermal treatment and the resulting microstructure. However, wrought steels are most often specified by their chemical composition. No single element determines the characteristics of a steel; rather, the combined effects of several elements influence hardness, machinability, corrosion resistance, tensile strength, deoxidation of the solidifying metal, and the microstructure of the solidified metal. Standard wroughtsteel compositions for both carbon and alloy steels are designated by the SAE-AISI four-digit code, the last two digits of which indicate the nominal carbon content (Table 2.16).

2.1.11.1 Plain Carbon Steels Carbon steels, also called plain carbon steels, are primarily Fe and C, with small amounts of Mn. Specific heat treatments and slight variations in composition will lead to steels with varying mechanical properties. Carbon is the principal hardening and strengthening element in steel. Actually, carbon increases hardness and strength and decreases weldability and ductility. For plain carbon steels, about 0.20 to 0.25 wt.% C provides the best machinability. Above and below this level, machinability is generally lower for hot-rolled steels. Plain carbon steels are usually divided into three groups: (i)

Low-carbon steels (e.g., AISI-SAE grades 1005 to 1030), or mild steels, contain up to 0.30 wt.% carbon. They are characterized by a low tensile strength and a high ductility. They are nonhardenable by heat treatment, except by surface hardening processes. (ii) Medium-carbon steels (e.g., AISI-SAE grades 1030 to 1055) have between 0.31 wt.% and 0.55 wt.% C. They provide a good balance between strength and ductility. They are hardenable by heat treatment, but hardenability is limited to thin sections or to the thin outer layer on thick parts. (iii) High-carbon steels (e.g., AISI-SAE grades 1060 to 1095) have between 0.56 wt.% and about 1.0 wt.% C. They are, of course, hardenable and are very suitable for wear-resistant and/or high-strength parts. Low-carbon or mild steels. The lowest carbon group consists of the four AISI-SAE grades 1006, 1008, 1010, and 1015. All these grades consist of very pure iron with less than 0.30 wt.% C having a ferritic structure, and they exhibit the lowest carbon content of the plain carbon group. These steels exhibit a relatively low ultimate tensile strength and are not suitable for mechanically demanding applications. Both tensile strength and hardness rise with increases in carbon content and/or cold work, but such increases in strength are at the expense of ductility or the ability to withstand cold deformation. Hence mild steels are selected when cold formability is required. They are produced both as rimmed and killed steels. Rimmed steels are used for sheet, strip, rod, and wire where excellent surface finish or good drawing qualities are required, such as oil pans and other deep-drawn and formed products. Rimmed steels are also used for cold-heading wire for tacks, and rivets and low-carbon wire products. Aluminum-killed steels (i.e., AK steels) are used for difficult stampings or where nonaging properties are needed. Silicon-killed steels (i.e., SK steels) are preferred to rimmed steels for forging or heat-treating applications. With less than 0.15 wt.% C, the steels are susceptible to serious grain growth, causing brittleness, which may occur as the result of a combination of critical strain from cold work followed by heating to elevated temperatures. Steels in this group due to their ferritic structure do not machine freely and should be avoided for

85

2 Ferrous Metals and Their Alloys

86

Ferrous Metals and Their Alloys

cut screws and operations requiring broaching or smooth finish on turning. The machinability of bar, rod, and wire products is improved by cold drawing. Mild steels are readily welded. Carburizing steels. This second group consists of the 13 AISI-SAE grades 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023, 1024, 1025, 1026, 1027, and 1030. Because of their higher carbon content they exhibit enhanced tensile strength and hardness but at the expense of cold formability. For heat-treating purposes, they are known as carburizing or case-hardening steels. Killed steels are recommended for forgings, while for other uses semikilled or rimmed steel may be suitable. Rimmed steels can ordinarily be supplied with up to 0.25 wt.% C. Higher carbon content provides a greater core hardness with a given quench or permits the use of thicker sections. An increase in manganese improves the hardenability of both the core and the case along with machinability; in carbon steels this is the only change in composition that will increase case hardenability. For carburizing applications, grades AISI 1016, 1018, and 1019 are widely used for thin sections or water-quenched parts. AISI 1022 and 1024 are used for heavier sections or where oil quenching is desired, and AISI 1024 is sometimes used for such parts as transmission and rear axle gears. AISI 1027 is used for parts given a light case to obtain satisfactory core properties without drastic quenching. AISI 1025 and 1030, although not usually regarded as carburizing types, are sometimes used in this manner for larger sections or where greater core hardness is needed. For cold-formed or cold-headed parts, the lowest manganese grades (i.e., AISI 1017, 1020, and 1025) offer the best formability at their carbon level. AISI 1020 is used for fan blades and some frame members, and 1020 and 1025 are widely used for low-strength bolts. The next highest manganese types, i.e., AISI 1018, 1021, and 1026, provide increased strength. All carburizing steels can be readily welded or brazed. Medium-carbon steels. This group consists of the 16 AISI-SAE grades 1030, 1033, 1034, 1035, 1036, 1038, 1039, 1040, 1041, 1042, 1043, 1045, 1046, 1049, 1050, and 1052 with a carbon content of between 0.31 and 0.55 wt.% C. They are usually selected for their higher mechanical properties and are frequently further hardened and strengthened by heat treatment or by cold work. They are usually produced as killed steels and are suitable for a wide variety of automotive-type applications. Increases in the mechanical properties required in section thickness or in depth of hardening ordinarily indicate either higher carbon or manganese content or both. The heat-treating practice preferred, particularly the quenching medium, has a great effect on the steel selected. In general, any of the grades over 0.30 wt.% C may be selectively hardened by induction heating or flame methods. The lower-carbon and manganese steels in this group find usage for certain types of cold-formed parts. AISI 1030 is used for shift and brake levers. AISI 1034 and 1035 are used in the form of wire and rod for cold upsetting such as bolts, and AISI 1038 for bolts and studs. The parts cold-formed from these steels are usually heat treated prior to use. Stampings are generally limited to flat parts or simple bends. The higher-carbon AISI 1038, 1040, and 1042 are frequently cold drawn to specified physical properties for use without heat treatment for some applications such as cylinder head studs. Any of this group of steels may be used for forgings, the selection being governed by the section size and the physical properties desired after heat treatment. Thus, AISI 1030 and 1035 are used for shifter forks and many small forgings where moderate properties are desired, but the deeper-hardening AISI 1036 is used for more critical parts where a higher strength level and more uniformity are essential, such as some front-suspension parts. Forgings such as connecting rods, steering arms, truck front axles, axle shafts, and tractor wheels are commonly made from the AISI 1038 to 1045 group. Larger forgings at similar strength levels need more carbon and perhaps more manganese; for instance, crankshafts are made from AISI 1046 and 1052. These steels are also used for small forgings where high hardness after oil quenching is desired. Suitable heat treatment is necessary on forgings from this group to provide machinability. It is also possible to weld these steels by most commercial methods, but precautions should be taken to avoid cracking from too rapid cooling.

Iron and Steels

High-carbon steels. These are the 14 AISI-SAE grades 1055, 1060, 1062, 1064, 1065, 1066, 1070, 1074, 1078, 1080, 1085, 1086, 1090, and 1095. These steels contain more carbon than is required to achieve maximum “as quenched” hardness. They are used for applications requiring improved wear resistance for cutting edges and to make springs. In general, cold forming cannot be used with these steels, and forming is only limited to flat stampings and springs coiled from small-diameter wire. Practically all parts from these steels are heat treated before use. Uses in the spring industry include AISI 1065 for pretempered wire and 1066 for cushion springs of hard-drawn wire; 1064 may be used for small washers and thin stamped parts, 1074 for light flat springs formed from annealed stock, and 1080 and 1085 for thicker flat springs. 1085 is also used for heavier coil springs. Finally, valve spring wire and music wire are special products. Easily machinable carbon steels. The three AISI-SAE grades 1111, 1112, and 1113 are intended for applications where easy machining is the primary requirement. They are characterized by a higher sulfur content than comparable carbon steels, machinability improving within the group as sulfur increases but at the expense of cold-forming, weldability, and forging properties. In general, the uses are similar to those for carbon steels of similar carbon and manganese content. These steels are commonly known as Bessemer screw stock and are considered the best machining steels available. Although of excellent strength in the cold-drawn condition, they have an unfavorable property of cold shortness and are not commonly used for vital parts. These steels may be cyanided or carburized, but when uniform response to heat treating is necessary, open-hearth steels are recommended. The nine AISI-SAE grades 1109, 1114, 1115, 1116, 1117, 1118, 1119, 1120, and 1126 are used where a combination of good machinability and more uniform response to heat treatment is required. The lower-carbon varieties are used for small parts that are to be cyanided or carbonitrided. AISI 1116, 1117, 1118, and 1119 contain more manganese for better hardenability, permitting oil quenching after case-hardening heat treatments. The higher-carbon 1120 and 1126 provide more core hardness when this is needed. Finally, grades AISI-SAE 1132, 1137, 1138, 1140, 1141, 1144, 1145, 1146, and 1151 exhibit a composition similar to that of carbon steels of the same carbon level, except they have a higher sulfur content. They are widely used for parts where large amounts of machining are necessary or where threads, splines, or other contours present special problems with tooling. AISI 1137 is widely used for nuts and bolts. The higher-manganese grades 1132, 1137, 1141, and 1144 offer greater hardenability, the higher-carbon types being suitable for oil quenching for many parts. All these steels may be selectively hardened by induction or flame heating. Table 2.17. Typical chemical composition of plain carbon steels (wt.%) AISI-SAE

UNS

C

Mn

Pmax

Smax

1005

G10050

0.06 max

0.35

0.040

0.050

1006

G10060

0.08 max

0.25–0.40

0.040

0.050

1008

G10080

0.10 max

0.30–0.50

0.040

0.050

1010

G10100

0.08–0.13

0.30–0.60

0.040

0.050

1012

G10120

0.10–0.15

0.30–0.60

0.040

0.050

1015

G10150

0.13–0.18

0.30–0.60

0.040

0.050

1016

G10160

0.13–0.18

0.60–0.90

0.040

0.050

1017

G10170

0.15–0.20

0.30–0.60

0.040

0.050

1018

G10180

0.15–0.20

0.60–0.90

0.040

0.050

1019

G10190

0.15–0.20

0.70–1.00

0.040

0.050

87

2 Ferrous Metals and Their Alloys

88

Ferrous Metals and Their Alloys

Table 2.17. (continued) AISI-SAE

UNS

C

Mn

Pmax

Smax

1020

G10200

0.18–0.23

0.30–0.60

0.040

0.050

1021

G10210

0.18–0.23

0.60–0.90

0.040

0.050

1022

G10220

0.18–0.23

0.70–1.00

0.040

0.050

1023

G10230

0.20–0.25

0.30–0.60

0.040

0.050

1025

G10250

0.22–0.28

0.30–0.60

0.040

0.050

1026

G10260

0.22–0.28

0.60–0.90

0.040

0.050

1029

G10290

0.25–0.31

0.60–0.90

0.040

0.050

1030

G10300

0.28–0.34

0.60–0.90

0.040

0.050

1035

G10350

0.32–0.38

0.60–0.90

0.040

0.050

1037

G10370

0.32–0.38

0.70–1.00

0.040

0.050

1038

G10380

0.35–0.42

0.60–0.90

0.040

0.050

1039

G10390

0.37–0.44

0.70–1.00

0.040

0.050

1040

G10400

0.37–0.44

0.60–0.90

0.040

0.050

1042

G10420

0.40–0.47

0.60–0.90

0.040

0.050

1043

G10430

0.40–0.47

0.70–1.00

0.040

0.050

1044

G10440

0.43–0.50

0.30–0.60

0.040

0.050

1045

G10450

0.43–0.50

0.60–0.90

0.040

0.050

1046

G10460

0.43–0.50

0.70–1.00

0.040

0.050

1049

G10490

0.46–0.53

0.60–0.90

0.040

0.050

1050

G10500

0.48–0.55

0.60–0.90

0.040

0.050

1053

G10530

0.48–0.55

0.70–1.00

0.040

0.050

1055

G10550

0.50–0.60

0.60–0.90

0.040

0.050

1059

G10590

0.55–0.65

0.50–0.80

0.040

0.050

1060

G10600

0.55–0.65

0.60–0.90

0.040

0.050

1064

G10640

0.60–0.70

0.50–0.80

0.040

0.050

1065

G10650

0.60–0.70

0.60–0.90

0.040

0.050

1069

G10690

0.65–0.75

0.40–0.70

0.040

0.050

1070

G10700

0.65–0.75

0.60–0.90

0.040

0.050

1078

G10780

0.72–0.85

0.30–0.60

0.040

0.050

1080

G10800

0.75–0.88

0.60–0.90

0.040

0.050

1084

G10840

0.80–0.93

0.60–0.90

0.040

0.050

1086

G10860

0.80–0.93

0.30–0.50

0.040

0.050

1090

G10900

0.85–0.98

0.60–0.90

0.040

0.050

1095

G10950

0.90–1.03

0.30–0.50

0.040

0.050

1110

G11100

0.08–0.13

0.30–0.60

0.040

0.08–0.13

1117

G11170

0.14–0.20

1.00–1.30

0.040

0.08–0.13

1118

G11180

0.14–0.20

1.30–1.60

0.040

0.08–0.13

1137

G11370

0.32–0.39

1.35–1.65

0.040

0.08–0.13

1139

G11390

0.35–0.43

1.35–1.65

0.040

0.13–0.20

Iron and Steels

89

Table 2.17. (continued) AISI-SAE

UNS

C

Mn

Pmax

Smax

1140

G11400

0.37–0.44

0.70–1.00

0.040

0.08–0.13

1141

G11410

0.37–0.45

1.35–1.65

0.040

0.08–0.13

1144

G11440

0.40–0.48

1.35–1.65

0.040

0.24–0.33

1146

G11460

0.42–0.49

0.70–1.00

0.040

0.08–0.13

1151

G11510

0.48–0.55

0.70–1.00

0.040

0.08–0.13

1211

G12110

0.13max

0.60–0.90

0.07–0.12 0.10–0.15

1212

G12120

0.13max

0.70–1.00

0.07–0.12 0.16–0.23

1213

G12130

0.13max

0.70–1.00

0.07–0.12 0.24–0.33

1215

G12150

0.09max

0.75–1.05

0.04–0.09 0.26–0.35

1513

G15130

0.10–0.16

1.10–1.40

0.040

0.050

1522

G15220

0.18–0.24

1.10–1.40

0.040

0.050

1524

G15240

0.19–0.25

1.35–1.65

0.040

0.050

1526

G15260

0.22–0.29

1.10–1.40

0.040

0.050

1527

G15270

0.22–0.29

1.20–1.50

0.040

0.050

1541

G15410

0.36–0.44

1.35–1.65

0.040

0.050

1548

G15480

0.44–0.52

1.10–1.40

0.040

0.050

1551

G15510

0.45–0.56

0.85–1.15

0.040

0.050

1552

G15520

0.47–0.55

1.20–1.50

0.040

0.050

1561

G15610

0.55–0.65

0.75–1.05

0.040

0.050

1566

G15660

0.60–0.71

0.85–1.15

0.040

0.050

12L14(*)

G12144

0.15max

0.85–1.15

0.04–0.09 0.26–0.35

(*) 0.15–0.35 wt.% Pb.

2.1.11.2 Low-Alloy Steels Steels that contain specified amounts of alloying elements other than carbon and the commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus are known as alloy steels. Alloying elements are added to change mechanical or physical properties. A steel is considered to be an alloy when the maximum of the range given for the content of alloying elements exceeds one or more of these limits: 1.65 wt.% Mn, 0.60 wt.% Si, or 0.60 wt.% Cu, or when a definite range or minimum amount of any of the following elements is specified or required within the limits recognized for constructional alloy steels: aluminum, chromium (up to 3.99%), cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or other element added to obtain an alloying effect. According to the previous definition, strictly speaking, tool and stainless steels are also considered alloy steels. However, the term alloy steel is reserved for those steels that contain a minute amount of alloying elements and that usually depend on thermal treatment to develop specific properties. Subdivisions for most steels in this family include through-hardening grades, which are heat treated by quenching and tempering and are used when maximum hardness and strength must extend deep within a part, while carburizing grades are used where a tough core and relatively shallow, hard surface is needed. After a surface-hardening treatment such as carburizing or nitriding for nitriding alloys, these steels are suitable for parts that must withstand wear as well as high stresses. Cast steels are generally through-hardened, not surface treated. Carbon content and alloying elements influence the overall characteristics of

2 Ferrous Metals and Their Alloys

90

Ferrous Metals and Their Alloys

both types of alloy steels. Maximum attainable surface hardness depends primarily on the carbon content. Maximum hardness and strength in small sections increase as carbon content increases, up to about 0.7 wt. % C. However, carbon content greater than 0.3% can increase the possibility of cracking during quenching or welding. Alloying elements primarily influence hardenability. They also influence other mechanical and fabrication properties including toughness and machinability. Lead additions (i.e., 0.15 to 0.35 wt.% Pb) greatly improve the machinability of alloy steels by high-speed-tool steels. For machining with carbide tools, calcium-treated steels are reported to double or triple tool life in addition to improving surface finish. Alloy steels are often specified when high strength is needed in moderate to large sections. Whether tensile or yield strength is the basis of design, thermally treated alloy steels generally offer high strength-to-weight ratios. In general, the wear resistance can be improved by increasing the hardness of an alloy, by specifying an alloy with greater carbon content, or by using nitrided parts, which have better wear resistance than would be expected from the carbon content alone. Fully hardened and tempered, low-carbon (i.e., 0.10 to 0.30 wt.% C) alloy steels have a good combination of strength and toughness, at both room and low temperatures. Carburizing alloyed steels. The properties of carburized and hardened cases depend on the carbon and alloy content, the structure of the case, and the degree and distribution of residual stresses. The carbon content of the case depends on the carburizing process and on the reactivity of iron and of the alloying elements to carburization. The original carbon content of the steel has little or no effect on the carbon content produced in the case; hence the last two digits in the AISI-SAE specification numbers are not meaningful as far as the case is concerned. The hardenability of the case, therefore, depends on the alloy content of the steel and the final carbon content produced by carburizing. With complete carbide solution, the effect of alloying elements on the hardenability of the case is about the same as the effect of these elements on the hardenability of the core. As an exception to this statement, any element that inhibits carburizing may reduce the hardenability of the case. Some elements that raise the hardenability of the core may tend to produce more retained austenite and consequently somewhat lower hardness in the case. Alloy steels are frequently used for case hardening because the required surface hardness can be obtained by moderate quenching speeds. Slower quenching may mean less distortion than would be encountered with water quenching. It is usually desirable to select a steel that will attain a minimum surface hardness of 58 or 60 HRC after carburizing and oil quenching. Where section sizes are large, a high-hardenability alloy steel may be necessary, whereas for medium and light sections, low-hardenability steels will suffice. The case-hardening alloy steels may be divided into two classes: high- and mediumhardenability case steels. High-hardenability case steels. The five AISI-SAE grades 2500, 3300, 4300, 4800, and 9300 are high-alloy steels; hence both the case and the core possess a high hardenability. They are used particularly for carburized parts with thick sections, such as pinions and heavy gears. Good case properties can be obtained by oil quenching. These steels are likely to have retained austenite in the case after carburizing and quenching, and hence refrigeration may be required. Medium-hardenability case steels. The AISI-SAE grades 1300, 2300, 4000, 4100, 4600, 5100, 8600, and 8700 have medium hardenability, which means that their hardenability is intermediate between that of plain carbon steels and the higher-alloy carburizing steels discussed previously. In general, these steels can be used for average-size case-hardened automotive parts such as gears, pinions, and crankshafts. Satisfactory case hardness is usually produced by oil quenching. The core properties of case-hardened steels depend on both the carbon and alloy content of the steel. Each of the general types of alloy case-hardening steel is usually made with two or more carbon contents to permit different hardenability in the core. The most desirable hardness for the core depends on the design and the type of

Iron and Steels

application. Usually, where high compressive loads are encountered, relatively high core hardness is beneficial in supporting the case. Low core hardnesses may be required if great toughness is important. The case-hardening steels may be divided into three general classes, depending on the hardenability of the core: (i)

low-hardenability core such as AISI-SAE 4017, 4023, 4024, 4027, 4028, 4608, 4615, 4617, 8615, and 8617; (ii) medium-hardenability core such as AISI-SAE 1320, 2317, 2512, 2515, 3115, 3120, 4032, 4119, 4317, 4620, 4621, 4812, 4815, 5115, 5120, 8620, 8622, 8720, and 9420; (iii) high-hardenability core such as AISI-SAE 2517, 3310, 3316, 4320, 4817, 4820, 9310, 9315, and 9317. (continued) Table 2.18. Typical chemical composition of low-alloy steels AISI-SAE UNS

C

Mn

Pmax Smax

Si

Ni

Cr

Mo

1330

G13300 0.28–0.33 1.60–1.90 0.035 0.040

0.15–0.35 …

…

…

1335

G13350 0.33–0.38 1.60–1.90 0.035 0.040

0.15–0.35 …

…

…

1340

G13400 0.38–0.43 1.60–1.90 0.035 0.040

0.15–0.35 …

…

…

1345

G13450 0.43–0.48 1.60–1.90 0.035 0.040

0.15–0.35 …

…

…

4023

G40230 0.20–0.25 0.70–0.90 0.035 0.040

0.15–0.35 …

…

0.20–0.30

4024

G40240 0.20–0.25 0.70–0.90 0.035 0.035–0.050 0.15–0.35 …

…

0.20–0.30

4027

G40270 0.25–0.30 0.70–0.90 0.035 0.040

0.15–0.35 …

…

0.20–0.30

4028

G40280 0.25–0.30 0.70–0.90 0.035 0.035–0.050 0.15–0.35 …

…

0.20–0.30

4037

G40370 0.35–0.40 0.70–0.90 0.035 0.040

0.15–0.35 …

…

0.20–0.30

4047

G40470 0.45–0.50 0.70–0.90 0.035 0.040

0.15–0.35 …

…

0.20–0.30

4118

G41180 0.18–0.23 0.70–0.90 0.035 0.040

0.15–0.35 …

0.40–0.60 0.08–0.15

4130

G41300 0.28–0.33 0.40–0.60 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4137

G41370 0.35–0.40 0.70–0.90 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4140

G41400 0.38–0.43 0.75–1.00 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4142

G41420 0.40–0.45 0.75–1.00 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4145

G41450 0.43–0.48 0.75–1.00 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4147

G41470 0.45–0.50 0.75–1.00 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4150

G41500 0.48–0.53 0.75–1.00 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15–0.25

4161

G41610 0.56–0.64 0.75–1.00 0.035 0.040

0.15–0.35 …

0.70–0.90 0.25–0.35

4320

G43200 0.17–0.22 0.45–0.65 0.035 0.040

0.15–0.35 1.65–2.00 0.40–0.60 0.20–0.30

4340

G43400 0.38–0.43 0.60–0.80 0.035 0.040

0.15–0.35 1.65–2.00 0.70–0.90 0.20–0.30

4615

G46150 0.13–0.18 0.45–0.65 0.035 0.040

0.15–0.35 1.65–2.00 …

0.20–0.30

4620

G46200 0.17–0.22 0.45–0.65 0.035 0.040

0.15–0.35 1.65–2.00 …

0.20–0.30

4626

G46260 0.24–0.29 0.45–0.65 0.035 0.040

0.15–0.35 0.70–1.00 …

0.15–0.25

4720

G47200 0.17–0.22 0.50–0.70 0.035 0.040

0.15–0.35 0.90–1.20 0.35–0.55 0.15–0.25

4815

G48150 0.13–0.18 0.40–0.60 0.035 0.040

0.15–0.35 3.25–3.75 …

0.20–0.30

4817

G48170 0.15–0.20 0.40–0.60 0.035 0.040

0.15–0.35 3.25–3.75 …

0.20–0.30

4820

G48200 0.18–0.23 0.50–0.70 0.035 0.040

0.15–0.35 3.25–3.75 …

0.20–0.30

91

2 Ferrous Metals and Their Alloys

92

Ferrous Metals and Their Alloys

Table 2.18. (continued) AISI-SAE UNS

C

Mn

Pmax Smax

Si

Ni

Cr

Mo …

5117

G51170 0.15–0.20 0.70–0.90 0.035 0.040

0.15–0.35 …

070–0.90

5120

G51200 0.17–0.22 0.70–0.90 0.035 0.040

0.15–0.35 …

0.70–0.90 …

5130

G51300 0.28–0.33 0.70–0.90 0.035 0.040

0.15–0.35 …

0.80–1.10 …

5132

G51320 0.30–0.35 0.60–0.80 0.035 0.040

0.15–0.35 …

0.75–1.00 …

5135

G51350 0.33–0.38 0.60–0.80 0.035 0.040

0.15–0.35 …

0.80–1.05 …

5140

G51400 0.38–0.43 0.70–0.90 0.035 0.040

0.15–0.35 …

0.70–0.90 …

5150

G51500 0.48–0.53 0.70–0.90 0.035 0.040

0.15–0.35 …

0.70–0.90 …

5155

G51550 0.51–0.59 0.70–0.90 0.035 0.040

0.15–0.35 …

0.70–0.90 …

5160

G51600 0.56–0.64 0.75–1.00 0.035 0.040

0.15–0.35 …

0.70–0.90 …

6118

G61180 0.16–0.21 0.50–0.70 0.035 0.040

0.15–0.35 …

0.50–0.70 0.10–0.15 V min

6150

G61500 0.48–0.53 0.70–0.90 0.035 0.040

0.15–0.35 …

0.80–1.10 0.15 V min

8615

G86150 0.13–0.18 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8617

G86170 0.15–0.20 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8620

G86200 0.18–0.23 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8622

G86220 0.20–0.25 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8625

G86250 0.23–0.28 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8627

G86270 0.25–0.30 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8630

G86300 0.28–0.33 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8637

G86370 0.35–0.40 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8640

G86400 0.38–0.43 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8642

G86420 0.40–0.45 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8645

G86450 0.43–0.48 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8655

G86550 0.51–0.59 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.15–0.25

8720

G87200 0.18–0.23 0.70–0.90 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.20–0.30

8740

G87400 0.38–0.43 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.20–0.30

8822

G88220 0.20–0.25 0.75–1.00 0.035 0.040

0.15–0.35 0.40–0.70 0.40–0.60 0.30–0.40

9260

G92600 0.56–0.64 0.75–1.00 0.035 0.040

1.80–2.20 …

…

50B44

G50441 0.43–0.48 0.75–1.00 0.035 0.040

0.15–0.35 …

0.40–0.60 …

50B46

G50461 0.44–0.49 0.75–1.00 0.035 0.040

0.15–0.35 …

0.20–0.35 …

50B50

G50501 0.48–0.53 0.75–1.00 0.035 0.040

0.15–0.35 …

0.40–0.60 …

50B60

G50601 0.56–0.64 0.75–1.00 0.035 0.040

0.15–0.35 …

0.40–0.60 …

51B60

G51601 0.56–0.64 0.75–1.00 0.035 0.040

0.15–0.35 …

0.70–0.90 …

81B45

G81451 0.43–0.48 0.75–1.00 0.035 0.040

0.15–0.35 0.20–0.40 0.35–0.55 0.08–0.15

94B17

G94171 0.15–0.20 0.75–1.00 0.035 0.040

0.15–0.35 0.30–0.60 0.30–0.50 0.08–0.15

94B30

G94301 0.28–0.33 0.75–1.00 0.035 0.040

0.15–0.35 0.30–0.60 0.30–0.50 0.08–0.15

E4340c

G43406 0.38–0.43 0.65–0.85 0.025 0.025

0.15–0.35 1.65–2.00 0.70–0.90 0.20–0.30

E51100c

G51986 0.98–1.10 0.25–0.45 0.025 0.025

0.15–0.35 …

0.90–1.15 …

E52100c

G52986 0.98–1.10 0.25–0.45 0.025 0.025

0.15–0.35 …

1.30–1.60 …

…

Iron and Steels

93

Thermal conductivity –1 –1 (k/W.m .K )

Specific heat capacity –1 –1 (cP/J.kg .K ) (50–100°C)

Electrical resistivity (ρ/μΩ.cm) 14.3

386–425

37–39 111–126 111–115 12.2

51.9

486

15.9

395–690

12–21 126–179 87–123

11.7

51.9

486

15.9

315–360

450–505

34–35 137–149 81–121

215–415

430–770

11–20 n.a.

12.0

51.9

486

15.9

1030 G10300 7750

230–415

460–775

10–20 126–207 69–94

11.7

51.9

486

16.6

1035 G10350 7750

280–480

490–775

9–18

179–229 n.a.

11.1

50.8

486

16.3

1040 G10400 7750

245–530

510–770

7–17

149–255 45–65

11.3

50.7

486

16.0

1045 G10450 7750

280–525

540–770

7–16

n.a.

11.6

50.8

486

16.2

1050 G10500 7750

280–585

570–1000

8–14

187–229 18–31

11.1

51.2

486

16.3

1060 G10600 7750

370–485

625–815

17–23 179–241 11–18

1090 G10800 7750

380–585

615–1015

12–25 174–293 7

1095 G10950 7750

380–570

655–1015

9–13

192–293 3–5

1117 G11170 7750

285–305

430–490

33

121–143 81–94

1118 G11180 7750

285–315

450–525

32–35 131–149 103–109

1137 G11370 7750

345–400

585–670

23–27 174–197 50–83

12.8

50.5

n.a.

17.0

1141 G11410 7750

340–495

540–850

7–20

12.6

50.5

461

17.0

1144 G11440 7750

345–420

585–705

21–25 167–212 43–65

1151 G11510 7750

12.6

50.5

502

17.0

1330 G13300 7750

12.0

n.a.

n.a.

n.a.

1335 G13350 7750

12.2

n.a.

n.a.

n.a.

1345 G13450 7750

12.0

n.a.

n.a.

n.a.

1522 G15220 7750

12.0

51.9

486

n.a.

25

121

n.a.

1015 G10150 7750

285–325

1020 G10200 7750

200–355

1022 G10220 7750 1025 G10250 7750

6

310

Density –3 (ρ/kg.m )

n.a.

UNS

1010 G10100 7750

AISI type

Izod impact strength (J)

14.2

450

Brinell hardness (/HB)

481

n.a.

Elongation (Z/%)

59.5

12.2

Ultimate tensile strength (σUTS/MPa)

12.6

Yield strength 0.2% 5 proof (σYS/MPa)

Coeff. linear thermal –6 –1 exp. (α/10 K )

7

(continued) Table 2.19. Physical properties of plain carbon steels and low-alloy steels

1008 G10080 7750

1340 G13400 7750

435–560

705–835

n.a.

n.a.

152–255 11–53

22–26 207–248 71–92

2330 G23300 7750

689

841

19

248

10.9

n.a.

n.a.

n.a.

2515 G25150 7750

648

779

25

233

10.9

34.3

n.a.

n.a.

11.3

n.a.

n.a.

n.a.

3120 G31200 7750

5 6 7

3140 G31400 7750

420–600

690–890

20–25 197–262 34-40

11.3

n.a.

n.a.

n.a.

3150 G31500 7750

n.a.

n.a.

n.a.

11.3

n.a.

n.a.

n.a.

n.a.

Maximum values: as-rolled or normalized conditions; minimum values: annealed conditions. Minimum values: as-rolled or normalized conditions; maximum values: annealed conditions. Minimum values: as-rolled or normalized conditions; maximum values: annealed conditions.

2 Ferrous Metals and Their Alloys

Ferrous Metals and Their Alloys

Brinell hardness (/HB)

Coeff. linear thermal –6 –1 exp. (α/10 K )

Thermal conductivity –1 –1 (k/W.m .K )

Specific heat capacity –1 –1 (cP/J.kg .K ) (50–100°C)

Electrical resistivity (ρ/μΩ.cm)

20

255

11.7

n.a.

n.a.

n.a.

1620

10

461

11.9

n.a.

n.a.

n.a.

4053 G40530 7750

1538

1724

12

495

n.a.

n.a.

n.a.

n.a.

4063 G40630 7750

1593

1855

8

534

n.a.

n.a.

n.a.

n.a.

4130 G41300 7750

360–1172

560–1379

16–28 156–375 62–87

12.2

42.7

477

22.3

4140 G41400 7750

1172

1379

15

385

12.3

42.7

475

22.0

4150 G41500 7750

1482

1586

10

444

11.7

41.8

n.a.

n.a.

4320 G43200 7750

1062

1241

15

360

11.3

n.a.

n.a.

n.a.

4337 G43370 7750

965

1448

14

435

11.3

n.a.

n.a.

n.a.

4340 G43400 7750

475–1379

745–1512

12–22 217–445 16–52

12.3

n.a.

n.a.

n.a.

4615 G46150 7750

517

689

18

n.a.

11.5

n.a.

n.a.

n.a.

4620 G46200 7750

655

896

21

n.a.

12.5

44.1

335

n.a.

4640 G46400 7750

1103

1276

14

390

n.a.

n.a.

n.a.

n.a.

4815 G48150 7750

862

1034

18

325

11.5

n.a.

481

26.0

4817 G48170 7750

n.a.

n.a.

15

355

n.a.

n.a.

n.a.

n.a.

4820 G48200 7750

n.a.

n.a.

13

380

11.3

n.a.

n.a.

n.a.

5120 G51200 7750

786

986

13

302

12.0

n.a.

n.a.

n.a.

5130 G51300 7750

1207

1303

13

380

12.2

48.6

494

21.0

5140 G51400 7750

1172

1310

13

375

12.3

45.8

452

22.8

5150 G51500 7750

1434

1544

10

444

12.8

n.a.

n.a.

n.a.

6120 G61200 7750

648

862

21

n.a.

n.a.

n.a.

n.a.

n.a.

6145 G61450 7750

1165

1213

16

429

n.a.

n.a.

n.a.

n.a.

6150 G61500 7750

1234

1289

13

444

12.2

n.a.

n.a.

n.a.

8617 G86170 7750

676

841

n.a.

n.a.

11.9

45.0

481

30.0

8630 G86300 7750

979

1117

14

325

11.3

39.0

449

n.a.

8640 G86400 7750

1262

1434

13

420

13.0

37.6

460

n.a.

8650 G86500 7750

1338

1475

12

423

11.7

37.6

453

n.a.

8720 G87200 7750

676

841

21

245

14.8

37.6

450

n.a.

8740 G87400 7750

1262

1434

13

420

11.3

37.6

448

n.a.

8750 G87500 7750

1338

1476

12

423

14.8

37.6

448

n.a.

9255 G92550 7750

1482

1600

9

477

14.6

46.8

420

n.a.

9261 G92610 7750

1558

1779

10

514

14.6

46.8

502

n.a.

Izod impact strength (J)

Elongation (Z/%)

827

1448

6

Ultimate tensile strength (σUTS/MPa)

586

4042 G40420 7750

Density –3 (ρ/kg.m )

4023 G40230 7750

UNS

Yield strength 0.2% 5 proof (σYS/MPa)

7

Table 2.19. (continued)

AISI type

94

Other properties common to all carbon- and low-alloy steels types. Young’s modulus: 201–209 GPa, Coulomb’s or shear modulus: 81–82 GPa, bulk or compression modulus: 160–170 GPa; Poisson ratio: 0.27–0.30.

Iron and Steels

95

2.1.11.3 Cast Steels Cast steels are steels that have been cast into sand molds to form finished or semifinished machine parts or other components. Mostly, the general characteristics of steel castings are very comparable to those of wrought steels. Cast and wrought steels of equivalent composition respond similarly to heat treatment and have fairly similar properties. A major difference is that cast steel has a more isotropic structure. Therefore, properties tend to be more uniform in all directions and do not vary according to the direction of hot or cold working as in many wrought-steel products. Categories. Cast steels are often divided into the following four categories: cast plain carbon steels, (low-)alloy steel castings, heat-resistant cast steels, and corrosion-resistant cast steels, depending on the alloy content and intended service. Like wrought steels, cast plain carbon steels can be divided into three groups: low-, medium-, and high-carbon steels. However, cast carbon steel is usually specified by mechanical properties (primarily tensile strength) rather than composition. Low-alloy steel castings are considered steels with a total alloy content of less than about 8%. The most common alloying elements are manganese, chromium, nickel, molybdenum, vanadium, and small quantities of titanium or aluminum (grain refinement) and silicon (improved corrosion and high-temperature resistance).

2.1.12 Stainless Steels 2.1.12.1 Description and General Properties In 1821, the French engineer Pierre Berthier observed that a certain amount of chromium added to iron alloys, in addition to enhancing their stiffness, also improved remarkably their corrosion resistance to acids. Almost a century later, in 1909, Léon Guillet and Albert Portevin in France studied independently the microstructure of Fe-Cr and Fe-Cr-Ni alloys. In 1911, the German metallurgist P. Monnartz, following the pioneering activity of his predecessors, explained the passivation mechanism and determined the lowest percentage of chromium required to impart a rustless ability to steels. The new alloy did not corrode or rust when exposed to weather, and the new iron alloy was then simply referred to as rostfrei Stahl in Germany, rustless or rustproof iron in Great Britain, and acier inoxydable in France. However, in the United States and United Kingdom, it was later denoted by the more modern designation still used today, stainless steel. In 1913, the first casting of a stainless steel was performed at Sheffield in the United Kingdom. Stainless steels are a large family of iron-chromium-based alloys (Fe-Cr) that are essentially low-carbon steels containing a high percentage of chromium, at least above 12 wt.% Cr, to impart the same corrosion resistance conferred by pure chromium in chrome plate. This addition of chromium gives the steel its unique corrosion-resistance properties denoted as stainless or rustproof. The chromium content of the steel allows the formation on the steel surface of a passivating layer of chromium oxide. This protective oxide film is impervious, adherent, transparent, and corrosion resistant in many chemical environments. If damaged mechanically or chemically, this film is self-healing when small traces of oxygen are present in the corrosive medium. It is important to note that in order to be corrosion resistant, the Fe-Cr alloy must contain at least 12 wt.% Cr and that when this percentage is decreased, for instance by precipitation of chromium carbide during heating, the protection is lost and the rusting process occurs. Moreover, the corrosion resistance and other useful properties of stainless steels are largely enhanced by increasing the chromium content usually well above 12 wt.% Cr. Hence the chromium content is usually 15 wt.%, 18 wt.%, 20 wt.%, and even up to 27 wt.% Cr in certain grades. In addition, further alloy additions (e.g., Mo, Ti, S, Cu) can be made to tailor the chemical composition in order to meet the needs of

2 Ferrous Metals and Their Alloys

Ferrous Metals and Their Alloys

different corrosion conditions, operating temperature ranges, and strength requirements or to improve weldability, machinability, and work hardening. Generally, the corrosion resistance of stainless steels is, as a rule, improved by increasing the alloy content. The terminology heat resistant and corrosion resistant is highly subjective and somewhat arbitrary. The term heat-resistant alloy commonly refers to oxidation-resistant metals and alloys (see Ni-Cr-Fe alloys in the nickel and nickel alloys section), while corrosion resistant is commonly applied only to metals and alloys that are capable of sustained operation when exposed to attack by corrosive media at service temperatures below 315°C. They are normally Fe-Cr or Fe-Cr-Ni ferrous alloys and can normally be classified as stainless steels. There are roughly more than 60 commercial grades of stainless steel available, and the global annual production was roughly 25 million tonnes in 2004.

2.1.12.2 Classification of Stainless Steels Following a classification introduced by Zapffe and later modernized to accommodate new grades, stainless steels can be divided into five distinct classes (see Table 2.20). Each class is identified by the alloying elements that affect their microstructure and for which each is named. These classes are as follows: (i) (ii) (iii) (iv) (v)

austenitic stainless steels; ferritic stainless steels; martensitic stainless steels; duplex or austenoferritic stainless steels; and precipitation-hardened (P-H) stainless steels.

In practice, empirical parameters called nickel and chromium equivalents can be utilized to assess the relative stability of austenite and ferrite, respectively. These equivalents are defined as follows: Eq(Ni) = wNi + 30 × wC + 0.5 wMn, Eq(Cr) = wCr + wMo + 1.5 wSi + 0.5 wNb, where wi denotes the mass fraction of the chemical element indicated by the subscript. The Ni and Cr equivalents are usually used to assess the phase formation in weldments. Hence modifying the chemistry of the weld metal can ensure a better result by avoiding hot cracking. Table 2.20. Classification of stainless steels by microstructure Type

STAINLESS STEELS

96

Typical composition Martensitic stainless steels

12–18 wt.% Cr carbon < 1.2 wt.% C

Ferritic stainless steels

17–30 wt.% Cr carbon < 0.2 wt.% C

Austenitic stainless steels

18–25 wt.% Cr 8–20 wt.% Ni

Duplex stainless steels

18–26 wt.% Cr 4–7 wt.% Ni 2–3 wt.% Mo

Precipitation-hardening (P-H) stainless steels

12–30 wt.% Cr (Al, Ti, Mo)

after Zapffe, C.-A. (1949) Stainless Steels. American Society for Metals (ASM), Materials Park, OH, p. 368.

Iron and Steels

97

2.1.12.3 Martensitic Stainless Steels Martensitic stainless steels (i.e., AISI 400 series) are typically iron-chromium-carbon (Fe-Cr-C) alloys that contain at least 12 and up to 18 wt.% Cr and may have small quantities of additional alloying elements. The carbon content usually ranges between 0.07 and 0.4 wt.% C and in all cases must be lower than 1.2 wt.% C. The high carbon content expands the gamma loop in Fe-Cr phase diagram and hence the crystal structure transforms into austenite upon heating, allowing hardening of the steel by quenching. These steels are called martensitic owing to the distorted body-centered cubic crystal lattice structure in the hardened condition. Martensitic stainless steels exhibit the following common characteristics: (i) (ii) (iii) (iv) (v)

they have a martensitic crystal structure; they are ferromagnetic; they can be hardened by heat treatment (quenching); they have high strength and moderate toughness in the hardened-and-tempered condition; they have poor welding characteristics.

Forming should be done in the annealed condition. Martensitic stainless steels are less resistant to corrosion than the austenitic or ferritic grades. Two types of martensitic steels, AISI 416 and AISI 420F, have been developed specifically for good machinability. Martensitic stainless steels are used where strength and/or hardness are of primary concern and where the environment is not too corrosive. These alloys are typically used for bearings, molds, cutlery, medical instruments, aircraft structural parts, and turbine components. The most commonly used grade is AISI 410; grade AISI 420 is used extensively in cutlery for making knife blades, and grade AISI 440C is used when very high hardness is required. Grade AISI 420 is used increasingly for molds for plastics and for industrial components requiring hardness and corrosion resistance. The physical properties of selected martensitic stainless steels are listed in Table 2.21.

2.1.12.4 Ferritic Stainless Steels Ferritic stainless steel alloys (i.e., AISI 400 series) exhibit a chromium content ranging from 17 to 30 wt.% Cr but have a lower carbon level, usually less than 0.2 wt.% C, than martensitic stainless steels. Ferritic stainless steels exhibit the following common characteristics: (i)

they exhibit a body-centered cubic ferrite crystal lattice due to the high chromium content; (ii) they are ferromagnetic and retain their basic microstructure up to the melting point if sufficient Cr and Mo are present; (iii) they cannot be hardened by heat treatment, and they can be only moderately hardened by cold working; hence they are always used in the annealed condition; (iv) in the annealed condition, their strength is ca. 50% higher than that of carbon steels; (v) like martensitic steels, they have poor weldability. Ferritic stainless steels are typically used where moderate corrosion resistance is required and where toughness is not a major need. They are also used where chloride stress-corrosion cracking (SCC) may be a problem because they have high resistance to this type of corrosion failure. In heavy sections, achieving sufficient toughness is difficult with the higher alloyed ferritic grades. Typical applications include automotive trim and exhaust systems and heattransfer equipment for the chemical and petrochemical industries. The two common grades are grade AISI 409, used for high-temperature applications, and grade AISI 430, the most widely used grade.

2 Ferrous Metals and Their Alloys

UNS

S40300

S41000

S41040

S41008

S41400

S41600

S41610

S41623

S42000

S42023

S42200

AISI type

403

410

410 Cb

410 S

414

416

416 Plus X

416 Se

420

420 FSe

422

Fe-12.5Cr-1Mo-1Mn-1W-0.75Ni-0.75Si-0.22C

Fe-13Cr-1Mn-1.25Si-0.15C-0.15Se

Fe-13Cr-1Mn-1Si-0.15C-0.04P-0.03S

Fe-13Cr-1.25Mn-1Si-0.6Mo-0.15C-0.15Se

Fe-13Cr-2Mn-1Si-0.6Mo-0.15C

Fe-13Cr-1.25Mn-1Si-0.6Mo-0.15C

Fe-12.5Cr-1.88Ni-1Mn-1Si-0.15C

–3

Fe-12.5Cr-1Mn-1Si-0.6Ni-0.08C

Density (ρ/kg.m ) 7800

7800

7740

7800

7800

7800

7800

7800

7730

7800

Yield strength 0.2% proof (σYS/MPa)

Fe-11.9Cr-0.24Si-0.19Mn-0.15Nb-0.12C-0.027Mo -0.021P-0.04S

585–760

1480

276–1344

275

n.a.

275

620

205–240

503–1034

275–620

Ultimate tensile strength (σUTS/MPa)

Fe-12.5Cr-1Mn-1Si-0.15C-0.75Ni-0.04P-0.03S

825–965

1720

483–1586

845

585–1210

485–1210

795–1030

415–450

655–1248

450–825

Elongation (Z/%) 13–17

8–15

8–25

20

n.a.

20

15

22

15–26

12–20

12–20

n.a.

96

HRB 88–HRC 55

n.a.

n.a.

n.a.

n.a.

95

HRB 89–HRC32

95

88

Rockwell hardness (/HRB)

485–825

11.2

n.a.

10.2

n.a.

n.a.

9.9

10.4

n.a.

5.5

9.9

n.a.

Coef. lin. thermal –6 –1 exp. (a/10 K )

205–620

23.9

n.a.

24.9

n.a.

n.a.

24.9

24.9

n.a.

24.8

24.9

n.a.

Thermal cond. –1 –1 (k/W.m .K )

7800

59

n.a.

55

n.a.

n.a.

57

70

n.a.

57

57

n.a.

Electrical resist. (ρ/μΩ.cm)

Fe-12.25Cr-1Mn-0.5Si-0.15C-0.6Ni

Average chemical composition (/ wt.% )

Table 2.21. Physical properties of martensitic stainless steels

98 Ferrous Metals and Their Alloys

S44002

S44003

S44004

S44023

S45000

S45500

S41500

S41050

S41800

S42300

S42010

440 A

440 B

440 C

440 FSe

450

Custom 455

CA6NM

E4

Greek Ascoloy

Lapelloy

TrimRite

Fe-14Cr-1Mn-0.7Mo-0.625Ni-1Si-0.2C

Fe-11.5Cr-3Mo-1.15Mn-0.6Si-0.5Ni-0.3C

Fe-13Cr-3W-2Ni-0.5Mn-0.5Si-0.15C

Fe-11.5Cr-0.85Ni-1Mn-1Si-0.1N-0.04C

Fe-12.75Cr-4Ni-0.75Mn-1Mo-0.6Si-0.05C

Fe-12Cr-7.5Ni-2Cu-1.1Ti-0.5Mn-0.5Mo-0.5Si-0.3 (Nb+Ta)-0.05C-0.04P-0.03S

Fe-13Cr-6Ni-1.5Cu-1.1Ti-1Mn-0.75Mo-1Si -0.4Nb-0.05C-0.03P-0.03S

Fe-17Cr-1.25Mn-1Si-0.75Ni-0.95C

Fe-17Cr-1Mn-1Si-0.75Mo-1.1C

Fe-17Cr-1Mn-1Si-0.75Mo-0.85C

Fe-17Cr-1Mn-1Si-0.75Mo-0.68C

Fe-16Cr-1.88Ni-1Mn-1Si-0.2C

7800

7800

7800

7800

7800

7800

7800

7800

7800

7800

7800

7800

n.a.

760

760

205

620

794–1518

807–1270

n.a.

450–1900

425–1860

415–1650

620–930

690–725

965

965

415

795

1000–1587

994–1352

n.a.

760–1970

740–1930

725–1790

795–1210

n.a.

8

15

22

15

10–14

14

n.a.

2–14

3–18

5–20

13–15

n.a.

n.a.

n.a.

88

n.a.

31–48 HRC

28–42 HRC

n.a.

97

96

95

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

10.2

10.2

10.2

10.2

72 60 60 60 n.a.

n.a. n.a. n.a. n.a. n.a.

20.1 24.2 24.2 24.2 n.a.

n.a. n.a. n.a. n.a. n.a.

Other properties common to all martensitic stainless steel types: Young’s modulus: 204–215 GPa; Coulomb’s or shear modulus: 83.9 GPa; bulk or compression modulus: –1 –1 166 GPa; Poisson ratio: 0.283; specific heat capacity: ca. 460 J.kg .K .

S43100

431

Iron and Steels 99

Ferrous Metals and Their Alloys

2

S40500

S40900

S42900

S43000

S43020

S43023

S43036

S43400

S43600

S43900

S44200

S44400

S44600

S44627

S44635

S44660

S44735

S44800

405

409

429

430

430F

430FSe

430 Ti

434

436

439

442

444

446

E-Brite 26-1

Monit 25-4-4

Sea-cure (SC-1)

AL 29-4C

AL 29-4-2

Fe-29Cr-4Mo-2Ni-0.3Mn-0.2Si-0.15Cu-0.025C

Fe-29Cr-4Mo-1Mn-0.75Si-0.5Ni-0.025C

Fe-26Cr-2.5Ni-1Mn-1Si-3Mo-0.025C

Fe-25Cr-4Ni-4Mo-1Mn-0.75Si-0.025C

Fe-26Cr-1Mo-0.5Ni-0.4Mn-0.4Si-0.2Cu-0.2Nb-0.01C

Fe-25Cr-1.5Mn-1Si-0.25N-0.2C

Fe-18.5Cr-1Ni-1Mn-1Si-2Mo-0.025C

Fe-20.5Cr-1Mn-1Si-0.6Ni-0.2C

Fe-18Cr-1.1Ti-1Mn-1Si-0.5Ni-0.15Al-0.07C

Fe-17Cr-1Mn-1Si-1Mo-0.12C-0.7(Ta+Nb)

Fe-17Cr-1Mn-1Si-1Mo-0.12C

Fe-18Cr-1Mn-1Si-0.75Ni-0.75Ti-0.1C

Fe-17Cr-1.25Mn-1Si-0.15Se-0.12C

Fe-17Cr-1.25Mn-1Si-0.6Mo-0.12C

Fe-17Cr-1Mn-1Si-0.75Ni-0.12C-0.04P-0.03S

Density –3 (ρ/kg.m )

Fe-15Cr-1Mn-1Si-0.75Ni-0.12C

7800

7800

7800

7800

7800

7500

7800

7800

7700

7800

7800

7800

7800

7800

7800

7800

7612

Yield strength 0.2% proof (σYS/MPa)

Fe-11.125Cr-1Mn-1Si-0.5Ni-0.48Ti-0.08C-0.045P-0.03S

380–415

415

380–450

515–550

275

275

275

275–310

205–275

365

365–315

310

275

275

205–275

205–275

207

Ultimate tensile strength (σUTS/MPa) 480–550

550

550–585

620–650

450

480–515

415

515–550

450–485

530

530–545

515

485–860

485–860

415–480

450–480

380–415

15–20

20

18–20

20

16–22

16–20

20

20

20–22

23

23–33

30

20

20

30

20–22

20–25

20

Elongation (Z/%)

415–480

98

98

100

100

90

95

95

90–95

88

83

83–90

n.a.

n.a.

n.a.

88

88

76

88

Rockwell hardness (/HRB)

170–280

n.a.

n.a.

n.a.

n.a.

n.a.

10.8

10.0

n.a.

10.4

9.3

10.4

10.4

10.4

10.4

10.4

10.3

11.7

10.8

Coef. linear thermal –6 –1 exp. (a/10 K )

7800

n.a.

n.a.

n.a.

n.a.

n.a.

20.9

26.8

n.a.

24.2

23.9

26.3

26.1

26.1

26.1

26.1

25.6

n.a.

27.0

Thermal cond. –1 –1 (k/W.m .K )

Fe-13Cr-1Mn-1Si-0.2Al-0.6Ni-0.2Al-0.08C-0.04P-0.03S

Average chemical composition (/ wt.% )

n.a.

n.a.

n.a.

n.a.

n.a.

67

62

n.a.

63

60

60

60

60

60

60

59

60

60

Electrical resistivity (ρ/μΩ.cm)

Other properties common to all ferritic stainless steel types: Young’s modulus: 200–215 GPa; Coulomb’s or shear modulus: 80–83 GPa; Poisson ratio; 0.27–0.29; specific –1 –1 heat capacity: ca. 460 J.kg .K .

UNS

AISI type

Table 2.22. Physical properties of ferritic stainless steels

100 Ferrous Metals and Their Alloys

Iron and Steels

101

2.1.12.5 Austenitic Stainless Steels Austenitic stainless steels, which exhibit the unique austenite crystal structure even at room temperature, are the largest and most popular family of stainless steels. They were discovered around 1910 when nickel was added to chromium-bearing iron alloys. Actually, austenitic stainless steels are iron-chromium-based alloys containing at least 18 wt.% or more Cr; in addition, they also contain sufficient nickel and/or manganese to stabilize and insure a fully austenitic metallurgical crystal structure at all temperatures ranging from the cryogenic region to the melting point of the alloy. Carbon content is usually less than 0.15 wt.% C. As a general rule, they exhibit the common following characteristics: (i) (ii) (iii) (iv) (v) (vi) (vii) (viii)

they possess an austenitic crystal lattice structure; by contrast with other classes, they are not ferromagnetic even after severe cold working; they cannot be hardened by heat treatment; they can be hardened by cold working; they have better corrosion resistance than other classes; they can be easily welded; they possess an excellent cleanability and allow excellent surface finishing; they exhibit excellent corrosion resistance to several corrosive environments at both room and high temperatures.

However, the austenitic stainless steels have some limitations: (i)

the maximum service temperature under oxidizing conditions is 450°C; above this temperature heat-resistant steels are required; (ii) they are suitable only for low concentrations of reducing acid such HCl; super austenitics are required for higher acid concentration; (iii) in service and shielded areas, there might not be enough oxygen to maintain the passive oxide film and crevice corrosion might occur, in which case they must be replaced by super austenitics or duplex and super ferritic steels; (iv) very high levels of halide ions, especially the chloride ion, can lead to the breakdown of the passivating film. It is important to note that upon heating carbon combines with chromium to form chromium carbide. If the chromium content falls below the critical percentage of 10.5 wt.% Cr, the corrosion resistance of the alloy is lost. Austenitic wrought stainless steels are classified according to the American Iron & Steel Institute (AISI) into three groups: (i) AISI 200 series, i.e., alloys of iron-chromium-nickel-manganese; (ii) AISI 300 series, i.e., alloys of iron-chromium-nickel; and (iii) nitrogen-strengthened alloys (with the suffix N added to the AISI grade). Manganese-bearing austenitic stainless steels originated in the early 1930s when shortages of nickel in Germany made it necessary to quickly find a substitute for austenite stabilizers. German metallurgists found that manganese and nitrogen, though less effective than nickel, performed well. Additional work was also conducted in the United States during the Korean War for the same reason. The lower cost and higher strength of manganese stainless steels compared to the 300 series allowed the commercialization of the 200 series despite higher processing costs due to their higher work-hardening rate. Nitrogen-strengthened austenitic stainless steels are alloys of chromium-manganese-nitrogen; some grades also contain nickel. The yield strengths of these alloys in the annealed condition are typically 50% higher

2 Ferrous Metals and Their Alloys

102

Ferrous Metals and Their Alloys

than those of the non-nitrogen-bearing grades. Like carbon, nitrogen increases the strength of a steel, but unlike carbon, nitrogen does not combine significantly with chromium in a stainless steel. This combination, which forms chromium carbide, reduces the strength and the corrosion resistance of an alloy. Because of their valuable structural and corrosionresistance properties, this group is the most widely used alloy group in the process industry. Actually, because nickel-bearing austenitic types have the highest general corrosion resistance, they are more corrosion resistant than lower-nickel compositions. Hence, austenitic stainless steels are generally used where corrosion resistance and toughness are primary requirements. Typical applications include shafts, pumps, fasteners, and piping for servicing in seawater and equipment for processing chemicals, food, and dairy products. However, galling and wear are the most common failure modes that require special attention with austenitic stainless steels because these materials serve in many harsh environments. They often operate, for example, at high temperatures, in food-contact applications, and where access is limited. Such restrictions prevent the use of lubricants, leading to metal-to-metal contact, a condition that promotes galling and accelerated wear. The most widely used grades of austenitic steels are AISI 304 (Fe-18Cr-10Ni), which are the most versatile grade, refractory grade AISI 310 (Fe-25Cr-20Ni) for high-temperature applications, grade AISI 316L (Fe-17Cr-12Ni-2.5Mo) with improved corrosion resistance, and finally AISI 317 (Fe-17Cr-13Ni-3.5Mo) for the best corrosion resistance in chloridecontaining media. The largest single alloy in terms of total industrial usage is AISI 304. The effects of some minor alloying elements on the properties of stainless steels are explained schematically in Table 2.23. The major physical properties of austenitic stainless steels are listed in Table 2.24 (see page 104). Table 2.23. Schematic impact of minor alloying additions on general-purpose stainless steel 300 series Property required

Minor element addition

Typical grade

General -purpose Machinability stainless steel AISI Weldability 304 (Fe-18Cr-8Ni) Corrosion resistance

Sulfur (S) addition

AISI 303

Low-carbon grades

AISI 304L

Molybdenum (Mo) addition

AISI 316

Copper (Cu) addition

AISI 302

Formability

after Magee, J. (2002) Development of type 204 Cu stainless steel, a low-cost alternate to type 304. Wire J. Int., pp. 84–90.

2.1.12.6 Duplex Stainless Steels When the chromium content is high (i.e., 18 to 26 wt.% Cr) and the nickel content is low (i.e., 4 to 7 wt.% Ni), the resulting structure is called duplex. In addition, most grades contain 2 to 3 wt.% Mo. This results in a structure that is a combination of both ferritic and austenitic, hence the name duplex. The most common grade is the AISI 2205. They have the following characteristics: (i) high resistance to stress-corrosion cracking; (ii) increased resistance to chloride ion attack; (iii) high weldability; (iv) higher tensile and yield strengths than austenitic or ferritic stainless steels. See Table 2.25, page 106.

Iron and Steels

103

2.1.12.7 Precipitation-Hardening Stainless Steels Precipitation-hardening stainless steels, widely known under the common acronyms PH or P-H, develop very high strength through a low-temperature heat treatment that does not significantly distort precision parts. Compositions of most P-H stainless steels are balanced to produce hardening by an aging treatment that precipitates hard, intermetallic compounds and simultaneously tempers the martensite. The beginning microstructure of P-H alloys is austenite or martensite. The austenitic alloys must be thermally treated to transform austenite into martensite before precipitation hardening can be accomplished. These alloys are used where high strength, moderate corrosion resistance, and good fabricability are required. Typical applications include shafting, high-pressure pumps, aircraft components, high-temper springs, and fasteners. See Table 2.26, page 107.

2.1.12.8 Cast Heat-Resistant Stainless Steels Cast stainless steels usually have corresponding wrought grades that have similar compositions and properties. However, there are small but important differences in composition between cast and wrought grades. Stainless steel castings should be specified by the designations established by the Alloy Casting Institute (ACI) and not by the designation of similar wrought alloys. The service temperature provides the basis for a distinction between heatresistant and corrosion-resistant cast grades. The C series of ACI grades designates the corrosion-resistant steels, while the H series designates the heat-resistant steels, which can be used for structural applications at service temperatures between 650 and 1200°C. The carbon and nickel contents of the H-series alloys are considerably higher than those of the C series. H-series steels are not immune to corrosion, but they corrode slowly, even when exposed to fuel-combustion products or atmospheres prepared for carburizing and nitriding. C-series grades are used in valves, pumps, and fittings. H-series grades are used for furnace parts and turbine components.

2.1.12.9 Processing and Melting Process The feedstock used in the melting process is essentially made from stainless steel scrap, i.e., scrap arising from sheet-metal fabrication and discarded plant and equipment. This approach enables the economical recycling of valuable alloys by the steel industry. After the chemical identification and analysis of the incoming steel scrap, scrap is sorted by grade, and a charge is prepared adding various alloys of chromium, nickel, and molybdenum depending on the stainless type to produce with an alloy content that is as close as possible to the final grade required for the steel. The scrap charge is then fed into an electric arc furnace, where carbon electrodes are in contact with recycled stainless scrap. Under a high-voltage difference, a current is passed through the electrodes providing sufficient energy to melt the charge. The furnace is connected to a pot lined with refractory ceramic material that resists the high temperatures encountered in the melting process. The molten material from the electric furnace is then transferred into an argon-oxygen decarbonization vessel, where the carbon levels are reduced and the final alloy additions, i.e., nickel, ferrochromium, and ferromolybdenum, are made to achieve the exact desired chemical composition of the final steel. Then the furnace is emptied into a tapping ladle by tilting the furnace forward. The ladle is an open-topped container lined with refractories. The melt is then transferred to a converter, where the steel is refined or purified of impurities of mainly carbon, silicon, and sulfur. This process involves blowing a mixture of oxygen and argon through the melt from the bottom of the converter.

2 Ferrous Metals and Their Alloys

S20430

S20500

S30100

S30200

S30215

S30300

S30323

S30400

204Cu

205

301

302

302B

303

303Se

304

Fe-19Cr-9.25Ni-2Mn-1Si-0.1N-0.08C-0.045P-0.03S

Fe-18Cr-9Ni-2Mn-1Si-0.15C-0.15Se

Fe-18Cr-9Ni-2Mn-1Si-0.6M0-0.15C

Fe-18Cr-9Ni-2Mn-2.5Si-0.15C

Fe-18Cr-9Ni-2Mn-1Si-0.15C

Fe-17Cr-7Ni-2Mn-1Si-0.15C

Fe-17.25Cr-1.5Ni-0.35N-14.75Mn-1Si-0.15C

Fe-16.5Cr-7.8Mn-2.5Ni-0.6Si-0.2Mo-0.2Cu-0.2N-0.09C

–3

Fe-18Cr-8.75Mn-5Ni-0.25N-1Si-0.15C

Density (ρ/kg.m )

S20200

Yield strength 0.2% proof (σYS/MPa)

202

Ultimate tensile strength (σUTS/MPa) 718 40

88–92

88–95

8000 205–760 515–1035 7–40

8000 205–240 515–1000 40

92

n.a.

n.a.

30–40 95 8000 205–240 515–1000 40

8000 205–310 515–620

8000 205–965 515–1275 4–40

100

12–40 100

8000 205–965 620–1280 9–40

7800 450–475 790–830

7800 366

7800 260–515 515–860

100

38–45 86–90

7800 275–965 515–1280 9–40

8080 317–331 627–641

Elongation (Z/%)

Fe-17Cr-4.5Ni-0.25N-6.5Mn-1Si-0.15C

Rockwell hardness (/HRB)

Fe-34Ni-20Cr-2.5Mo-2Mn-1Si-0.06C-0.035P-0.035S-1(Nb+Ta)

17.8

17.2

17.2

16.2

17.2

17.9

17.9

17.5

15.7

14.69

Coef. linear thermal –6 –1 exp. (a/10 K )

S20100

Average chemical composition (/ wt.%)

16.2

16.2

16.2

15.9

16.2

16.2

16.2

16.2

16.2

12.2

Thermal conductivity –1 –1 (k/W.m .K )

201

UNS

72

72

72

72

72

72

69

69

69

108.2

Electrical resistivity (ρ/μΩ.cm)

20Cb-3

AISI type

Table 2.24. Physical properties of austenitic stainless steels (annealed)

104 Ferrous Metals and Their Alloys

S30403

S30453

S30451

S30500

S30800

S30900

S31000

S31400

S31600

S31603

S31651

S31700

S31703

S32100

S32109

S34700

S38400

304 L

304 LN

304 N

305

308

309

310

314

316

316 L

316 N

317

317 L

321

321 H

347

384

Fe-16Cr-18Ni-2Mn-1Si-0.08C

Fe-18Cr-11Ni-2Mn-1Si-0.8Nb-0.08C

Fe-18Cr-10.5Ni-2Mn-1Si-0.35Ti-0.1N-0.07C

Fe-18Cr-10.5Ni-2Mn-1Si-0.4Ti-0.1N-0.08C

Fe-19Cr-13Ni-3.5Mo-2Mn-0.75Si-0.1N-0.045P-0.03C-0.03S

Fe-19Cr-13Ni-3.5Mo-2Mn-1Si-0.1N-0.08C

Fe-17Cr-12Ni-2.5Mo-2Mn-1Si-0.08C-0.13N

Fe-17Cr-12Ni-2.5Mo-2Mn-1Si-0.1N-0.03C

Fe-17Cr-12Ni-2.5Mo-2Mn-1Si-0.1N-0.08C-0.045P-0.03S

Fe-24.5Cr-20.5Ni-2Mn-2Si-0.25C

Fe-25Cr-20.5Ni-2Mn-1.5Si-0.25C

Fe-23Cr-13.5Ni-2Mn-1Si-0.20C

Fe-20Cr-11Ni-2Mn-1Si-0.08C

Fe-18Cr-11.75Ni-2Mn-1Si-0.12C

Fe-19Cr-9.25Ni-2Mn-1Si-0.08C-0.13N

Fe-19Cr-10Ni-2Mn-1Si-0.03C

Fe-19Cr-10Ni-2Mn-1Si-0.03C

Fe-19Cr-9.25Ni-2Mn-1Si-0.08C-0.12N

550

515

100

30

40 92

92

30–40 88

30

30–40 95

30–40 88

550

8000 n.a.

550-585

8000 205–310 515–620

8000 205–310 515–620

8000 205–310 515–620

7889 207–276 517–586

8000 205–310 515–620

8000 240

8000 170–310 450–620

8000 205–310 515–620

7800 205–310 515–620

n.a.

n.a.

30–45 92

30–40 95

30–40 95

40–50 95

30–40 95

30–35 95

30–40 95

30–40 n.a.

30–40 n.a.

8000 340–855 600–1280 46–58 n.a.

8000 205–310 515–620

8000 205–310 515–620

8000 170–310 515–1690 30–40 88

8000 240

8000 205

8000 170–310 450–620

8000 275–345 585–620

17.8

16.6

n.a.

17.8

16.6

16.5

15.9

15.9

15.9

15.1

15.9

17.2

17.8

17.8

n.a.

n.a.

17.2

n.a.

n.a. n.a. n.a. 74 72 72 78 78 77 74 74 72 79 79 72 n.a. 73 79

n.a. 16.0 n.a. n.a. 16.2 15.2 15.6 14.2 17.5 16.2 15.6 15.6 14.1 13.7 16.1 n.a. 16.2 16.2

Other properties common to all austenitic stainless steel types: Young’s modulus: 192–200 GPa; Coulomb’s or shear modulus: 74–86 GPa; Poisson ratio: 0.25–0.29; specific –1 –1 heat capacity: ca. 500 J.kg .K .

S30409

304 HN

Iron and Steels 105

Ferrous Metals and Their Alloys

2

S31260 Fe-25Cr-6.5Ni-3Mo-1Mn-0.75Si-0.03C

S31500 Fe-18.5Cr-4.75Ni-2.75Mo-1.6Mn-1.8Si-0.03C

S31803 Fe-22Cr-5.7Ni-3.1Mo-2Mn-1Si-0.17N-0.02C S32205

S32304 Fe-23Cr-4.5Ni-2.5Mn-1Si-0.3Mo-0.10N-0.02C

S32750 Fe-25Cr-7Ni-4Mo-2Mn-1Si-0.27N-0.02C

S32550 Fe-25.5Cr-5.5Ni-3Mo-1.5Mn-1Si-0.04C

S32950 Fe-27.5Cr-4.35Ni-2Mo-2Mn-0.6Si-0.03C

DP-3

3RE60

SAF 2205

SAF 2304

SAF 2507

Ferralium 255

7-Mo Plus

Ultimate tensile strength (σUTS/MPa)

Yield strength 0.2% proof (σYS/MPa)

Density (ρ/kg.m ) –3

690 630

30

31

7800 480

7800 550

690

760

32 15–20 31

15

7800 530–665 730–895 15–35 29

–1

–1

100

100

13.0

13.0

13.0

Coef. linear thermal –6 –1 exp. (a/10 K )

7800 400–545 600–735 20–35 31

Charpy V-Notch impact (J) 100

17

15

15

Thermal conductivity –1 –1 (k/W.m .K )

7800 460–605 640–835 20–35 32

7800 440

32

20–25 31

25

Elongation (Z/%)

7800 450–485 690

Rockwell hardness (/HRC)

7800 450

80

80

80

Electrical resistivity (ρ/μΩ.cm)

Other properties common to all duplex stainless steels: Young’s modulus: 200 GPa: specific heat capacity: ca. 500 J.kg .K .

S31200 Fe-25Cr-6Ni-2Mn-1.6Mo-1Si-0.03C

44LN

Average chemical composition (/ wt.% )

UNS

Trade name

Table 2.25. Physical properties of duplex stainless steels

106 Ferrous Metals and Their Alloys

S17400 Fe-16.5Cr-4Ni-4Cu-1Mn-1Si-0.2Nb-0.07C

S17700 Fe-17Cr-7.13Ni-1Mn-1Al-1Si-0.09C

S35000 Fe-16.5Cr-4.5Ni-1Mn-2.7Mo-0.5Si-0.07C

S35500 Fe-16.5Cr-4.5Ni-0.75Mn-2.7Mo-0.5Si-0.07C

S45000 Fe-15Cr-6Ni-1Mn-1Si-0.7Mo-1.5Cu-0.05C

S45500 Fe-11.75Cr-8.5Ni-0.5Mn-0.5Si-0.7Ti-1.5Cu-0.05C

17-4PH

17-7PH

AM350 (Type 633)

AM355 (Type 634)

Custom450

Custom455

Yield strength 0.2% proof (σYS/MPa)

Young’s modulus (E/GPa)

Density (ρ/kg.m ) –3

1170–1650 1–7

860–1240

6–18

7800 203 585–1410

860–1520

44–47

26–39 10–16 26–45

7800 n.a. 1280–1520 1410–1620 4–10

7800 n.a. 515–1100

7800 n.a. 1030–1070 1170–1310 10–12 37

36–42

41–44

10–18 40–48

7800 n.a. 1000–1030 1140–1380 2–12

7800 204 965–1590

Ultimate tensile strength (σUTS/MPa) 10–18 40–48

Elongation (Z/%)

795–1310

Rockwell hardness (/HRC)

795–1310

10.6

n.a.

n.a.

n.a.

n.a.

11.0

10.8

10.8

Coefficient linear thermal –6 –1 expansion (a/10 K )

7800 196 515–1170

14.0

n.a.

n.a.

n.a.

n.a.

16.4

18.3

17.8

Thermal conductivity –1 –1 (k/W.m .K )

7800 196 515–1170

102

n.a.

n.a.

n.a.

n.a.

83

80

77

Electrical resistivity (ρ/μΩ.cm)

P-H 13-8Mo S13800 Fe-12.75Cr-8Ni-2Mo-1Al-0.2Mn-0.2Si-0.05C

S15500 Fe-14.75Cr-4.5Ni-3.5Cu-1Mn-1Si-0.2Nb-0.07C

15-5PH

Average chemical composition (/ wt.% )

UNS

AISI type

Table 2.26. Physical properties of P-H stainless steels

Iron and Steels 107

Ferrous Metals and Their Alloys

2

108

Ferrous Metals and Their Alloys

Samples are taken from the melt and analyzed, and the chemical composition of the steel can, if necessary, be modified by the addition of alloying metals in the converter or in the ladle afterwards. Later, the desired molten metal is either cast into ingots or continually cast into a slab or billet form. Then the material is hot-rolled or forged into its final form. Some material receives cold rolling to further reduce the thickness as in sheets or drawn into smaller diameters as in rods and wire. Most stainless steels receive a final annealing and acid pickling in order to remove furnace scale from annealing, and they help to promote the passive surface film that naturally occurs.

2.1.12.10 Simplified Selection of Stainless Steels Three parameters are important to consider when selecting a particular grade of stainless steel for a given application. These parameters are in order of decreasing importance: Corrosion resistance. This is the most important property to consider when selecting a stainless steel. Actually, the corrosion resistance is always the primary reason when considering Fe-Cr-Ni alloys. For best results, the maximum allowable corrosion rate, usually 50 μm/year (2 mils per year), along with an exact knowledge of the corrosive environment, must be known. Mechanical strength. The mechanical strength is the second most important parameter, especially for designing structural applications. Fabrication. The capabilities of the stainless steel to be machined, welded, cold worked, and heat treated are, in combination with the two previous parameters, an important parameter to take into account from a technical and a cost-assesment point of view. 8 Based on an approach developed by the company Carpenter Specialty Alloys , it is possible to summarize the selection process graphically (Figure 2.3), plotting the grade of the stainless steel as a function of both corrosion resistance and mechanical strength.

Figure 2.3. Stainless steel selection chart

8

Collective (1969) Simplifying stainless steel selection with Carpenter’s Selectally® method. Carpenter Technology, Reading, PA.

Iron and Steels

109

2.1.12.11 Stainless Steel Application Guidelines (continued) Table 2.27. Guide for selected stainless steels (corrosion, oxidation, fabrication, application) Grade

Corrosion

201

High work-hardening rate; low-nickel equivalent of type 301. Flatware, automobile wheel covers, trim.

202

General-purpose low-nickel equivalent of type 302. Kitchen equipment, hub caps, milk handling.

205

Lower work-hardening rate than type 202; used for spinning and special drawing operations. Nonmagnetic and cryogenic parts.

301

High work-hardening rate; used for structural applications where high strength plus high ductility are required. Railroad cars, trailer bodies, aircraft structurals, fasteners, automobile wheel covers and trim, pole line hardware.

302

General-purpose austenitic stainless steel. Trim, food-handling equipment, aircraft cowlings, antennas, springs, cookware, building exteriors, tanks, hospital and household appliances, jewelry, oil-refining equipment, signs.

302B

More resistant to scale than type 302. Furnace parts, still liners, heating elements, annealing covers, burner sections.

303

Free-machining modification of type 302, for heavier cuts. Screw machine products, shafts, valves, bolts, bushings, nuts.

303Se

Free-machining modification of type 302, for lighter cuts; used where hot working or cold heading may be involved. Aircraft fittings, bolts, nuts, rivets, screws, studs.

304

Low-carbon modification of type 302 for restriction of carbide precipitation during welding. Chemical and food processing equipment, brewing equipment, cryogenic vessels, gutters, downspouts, flashings.

304Cu

Lower work-hardening rate than type 304. Severe cold-heading applications.

304L

Extra-low-carbon modification of type 304 for further restriction of carbide precipitation during welding. Coal hopper linings, tanks for liquid fertilizer and tomato paste.

304N

Higher nitrogen than type 304 to increase strength with minimum effect on ductility and corrosion resistance, more resistant to increased magnetic permeability. Type 304 applications requiring higher strength.

305

Low work-hardening rate; used for spin forming, severe drawing, cold heading, and forming. Coffee urn tops, mixing bowls, reflectors.

308

Higher-alloy steel having high corrosion and heat resistance. Welding filler metals to compensate for alloy loss in welding, industrial furnaces.

309

High-temperature strength and scale resistance. Aircraft heaters, heattreating equipment, annealing covers, furnace parts, heat exchangers, heat-treating trays, oven linings, pump parts.

309S

Low-carbon modification of type 309. Welded constructions, assemblies subject to moist corrosion conditions.

310

Type 310 provides excellent corrosion resistance and heat resistance plus good strength at room and elevated temperatures. It is essentially nonmagnetic as annealed and becomes slightly magnetic when cold worked. It has a high corrosion resistance to sulfite liquors and is useful for handling nitric acid, nitric-sulfuric acid mixtures, and acetic, citric, and lactic acids. Oxidation resistance is good up to the scaling temperature of 1093°C, and below that temperature it can be used in both continuous and intermittent service. Typical uses include furnace parts, heating elements, aircraft and jet-engine parts, heat exchangers, carburizing-annealing boxes, sulfite liquor-handling equipment, kiln liners, boiler baffles, refinery and chemical-processing equipment, auto-exhaust parts.

314

More resistant to scale than type 310. Severe cold-heading or cold-forming applications. Annealing and carburizing boxes, heat-treating fixtures, radiant tubes.

2 Ferrous Metals and Their Alloys

110

Ferrous Metals and Their Alloys

Table 2.27. (continued) Grade

Corrosion

316

Higher corrosion resistance than types 302 and 304; high creep strength. Chemical and pulp handling equipment, photographic equipment, brandy vats, fertilizer parts, ketchup cooking kettles, yeast tubs.

316L

Extra-low-carbon modification of type 316. Type 316L is a molybdenum-containing austenitic stainless steel intended to provide improved corrosion resistance relative to type 304L in moderately corrosive process environments, particularly those containing chlorides or other halides. Welded construction where intergranular carbide precipitation must be avoided. Type 316 applications require extensive welding. Type 316L has been used in handling many chemicals used by the process industries, including pulp and paper, textile, food, pharmaceutical, medical, and other chemical-processing equipment.

316F

Higher phosphorus and sulfur than type 316 to improve machining and nonseizing characteristics. Automatic screw machine parts.

316N

Higher nitrogen than type 316 to increase strength with minimum effect on ductility and corrosion resistance. Type 316 applications require extra strength.

317L

Extra-low-carbon modification of type 317 for restriction of carbide precipitation during welding with improved corrosion and creep resistance in strongly corrosive process environments, particularly those containing chlorides or other halides such as those encountered in pulp and paper mills. The low carbon permits 317L to be welded without sensitization to intergranular corrosion resulting from chromium carbide precipitation in the grain boundaries. Type 317L is nonmagnetic in the annealed condition but may become slightly magnetic as a result of welding. Dyeing and ink manufacturing equipment.

321

Type 321 is similar to 304 but with titanium addition five times the carbon content that reduces carbide precipitation during welding and in 425–815°C service. It has excellent corrosion resistance toward most chemicals and oxidation resistance up to 815°C. Aircraft exhaust manifolds, boiler shells, process equipment, expansion joints, cabin heaters, fire walls, flexible couplings, pressure vessels.

329

Austenitic-ferritic type with general corrosion resistance similar to type 316 but with better resistance to stress-corrosion cracking; capable of age hardening. Valves, valve fittings, piping, pump parts.

330

Good resistance to carburization and oxidation and to thermal shock. Heat-treating fixtures.

347

Similar to type 321 with higher creep strength. Airplane exhaust stacks, welded tank cars for chemicals, jet-engine parts.

348

Similar to type 321; low retentivity. Tubes and pipes for radioactive systems, nuclear-energy uses.

384

Suitable for severe cold heading or cold forming; lower cold-work-hardening rate than type 305. Bolts, rivets, screws, instrument parts.

403

Turbine-quality grade. Steam turbine blading and other highly stressed parts including jetengine rings.

405

Nonhardenable grade for assemblies where air-hardening types such as 410 or 403 are objectionable. Annealing boxes, quenching racks, oxidation-resistant partitions.

409

General-purpose construction stainless. Greater protection than carbon steels and coated steels but lower than 304. Rusting occurs at inclusion sites resulting from titanium stabilization leading to problems of cosmetic appearance only. Corrosion resistance of HAZ is comparable to that of the base metal and is superior to 410. The destructive scaling in air starts at 789°C, this is the general maximum service temperature for continuous exposure in air. Good fabricating characteristics. Can be cut, blanked, and formed without difficulty. Automotive and truck exhaust systems, tubular manifolds, transformer and capacitor cases, agricultural spreaders, gas turbine exhaust silencers, heat exchangers.

Iron and Steels

111

Table 2.27. (continued) Grade

Corrosion

410

General-purpose heat-treatable type. Machine parts, pump shafts, bolts, bushings, coal chutes, cutlery, hardware, jet engine parts, mining machinery, rifle barrels, screws, valves.

410 Cb

The corrosion resistance of type 410 Cb stainless steel is the same as type 410 as demonstrated in laboratory tests and actual service. The tempering characteristics of 410 Cb offer an advantage over type 410 in resistance to stress corrosion cracking. To develop similar tensile strengths, a higher tempering temperature is used with 410 Cb. The higher temperature results in more effective relief of residual internal stresses that, in some environments, promote stress-corrosion cracking.

414

High-hardenability steel. Springs, tempered rules, machine parts, bolts, mining machinery, scissors, ships’ bells, spindles, valve seats.

416

Free-machining modification of type 410, for heavier cuts. Aircraft fittings, bolts, nuts, fire extinguisher inserts, rivets, screws.

416Se

Free-machining modification of type 410, for lighter cuts. Machined parts require hot working or cold heading.

420

Type 420 provides corrosion resistance similar to 410 plus increased strength and hardness. It is magnetic in both the annealed and hardened conditions. Provides full corrosion resistance only in the hardened or hardened and stress-relieved conditions. In these conditions, its corrosion resistance is similar to that of 410. The alloy is not normally used at temperatures exceeding 427°C due to rapid softening and loss of corrosion resistance. It resists corrosion by the atmosphere, fresh water, mine water, steam, carbonic acid, crude oil, gasoline, perspiration, alcohol, ammonia, mercury, sterilizing solutions, soaps, and other similar corrosive media. Heat treatments. Annealing: for maximum softness, heat uniformly to 816-899°C and cool slowly. Process annealing: heat to 732–788°C, air cool. Hardening: preheat, then heat to 982–1066°C, soak at temperature, and air cool or quench in warm oil. Stress relieving: heat at 149–427°C for 1 to 3 h, cool in air or quench in oil or water. Typical uses include cutlery, surgical and dental instruments, scissors, tapes, and straight edges.

420F

Free-machining modification of type 420. Applications similar to those for type 420 requiring better machinability.

422

High strength and toughness at service temperatures up to 1200°F. Steam turbine blades, fasteners.

429

Improved weldability as compared to type 430. Nitric acid and nitrogen-fixation equipment.

430

General-purpose nonhardenable chromium type. Has excellent corrosion resistance, including high resistance to nitric acid as well as to sulfur gases and many organic and food acids. This alloy does not provide the resistance to pitting by dilute reducing acids that is provided by the chromium-nickel stainless steels. Heat and oxidation resistance with a maximum scaling temperature of 815°C. Decorative trim, nitric acid tanks, annealing baskets, combustion chambers, dishwashers, heaters, mufflers, range hoods, recuperators, restaurant equipment.

430F

Free-machining modification of type 430, for heavier cuts. Screw machine parts.

430FSe

Free-machining modification of type 430, for lighter cuts. Machined parts requiring light cold heading or forming.

431

Special-purpose hardenable steel used where particularly high mechanical properties are required. Aircraft fittings, beater bars, paper machinery, bolts.

434

Modification of type 430 designed to resist atmospheric corrosion in the presence of winter road conditioning and dust-laying compounds. Automotive trim and fasteners.

436

Similar to types 430 and 434. Used where low “roping” or “ridging” required. General corrosion and heat-resistant applications such as automobile trim.

2 Ferrous Metals and Their Alloys

112

Ferrous Metals and Their Alloys

Table 2.27. (continued) Grade

Corrosion

440A

Hardenable to higher hardeness than type 420 with good corrosion resistance. Cutlery, bearings, surgical tools.

440B

Cutlery grade. Cutlery, valve parts, instrument bearings.

440C

Yields highest hardnesses of hardenable stainless steels. Balls, bearings, races, nozzles, balls and seats for oil-well pumps, valve parts.

442

High-chromium steel, principally for parts that must resist high service temperatures without scaling. Furnace parts, nozzles, combustion chambers.

446

High resistance to corrosion and scaling at high temperatures, especially for intermittent service; often used in sulfur-bearing atmosphere. Annealing boxes, combustion chambers, glass molds, heaters, pyrometer tubes, recuperators, stirring rods, valves.

501

Heat resistance; good mechanical properties at moderately elevated temperatures. Heat exchangers, petroleum-refining equipment.

502

More ductility and less strength than type 501. Heat exchangers, petroleum-refining equipment, gaskets.

SAF 2205

SAF 2205 with equal amounts of ferrite and austenite is a duplex stainless steel that exhibits a high strength, low thermal expansion, and higher thermal conductivity than austenitic steels. SAF 2205 has a high resistance to stress corrosion cracking, corrosion fatigue, and erosion. The addition of nitrogen provides a further increase in pitting and crevice corrosion resistance. SAF 2205 offers very good resistance even in acids that have a fairly high halide content. It has good weldability and can be welded using most of the welding techniques for stainless steels. Heat exchangers, tubes and pipes for production and handling of gas and oil, in desalination plants. Pressure vessels, pipes, tanks and heat exchangers for processing and transport of various chemicals or handling solutions containing chlorides.

SAF 2304

SAF 2304 has a high strength, high resistance to stress corrosion cracking, a low thermal expansion, and a high thermal conductivity. The high chromium content provides good and uniform corrosion resistance, even to pitting and crevice corrosion. In very strongly oxidizing acids such as nitric acid, SAF 2304 is often more resistant than molybdenum-alloyed steels. Additional properties are a good weldability and workability and a high impact strength. Hotwater tanks, water heaters, cargo containers, fire and blast walls on offshore platforms, heatexchanger tubing, hydraulic piping, digesters, evaporators.

SAF 2507

SAF 2507 is a ferritic-austenitic stainless steel combining the most desirable properties of both ferritic and austenitic steels. The high chromium and molybdenum contents provides very high resistance to pitting, crevice, and uniform corrosion. The duplex microstructure results in good resistance to stress corrosion cracking. The mechanical strength is also very high. SAF 2507 can be used in dilute hydrochloric acid. Pitting is normally not a problem in the area below the boundary line, but crevices should be avoided.

2.1.13 High-Strength Low-Alloy Steels (HSLA) High-strength low-alloy steels, usually denoted by the common acronym HSLA, represent a specific group of steels in which enhanced mechanical properties and, sometimes, resistance to atmospheric corrosion are obtained by the addition of moderate amounts of one or more alloying elements other than carbon. They were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higher-strength construction-grade materials, particularly in the asrolled condition. Different types are available, some of which are carbon-manganese steels, and others contain further alloy additions governed by special requirements for weldability,

Iron and Steels

formability, toughness, strength, and cost. In practice, HSLA steels are especially characterized by their mechanical properties, obtained in the as-rolled condition, and must exhibit a minimum yield strength of 275 MPa or higher. Such high strength is usually attained through the addition of small amounts of alloying elements, and hence several of these steels exhibit enhanced atmospheric corrosion resistance. Typically, HSLA steels are low-carbon steels containing up to 1.5 wt.% Mn, strengthened by small additions of columbium, copper, vanadium, or titanium and sometimes by special rolling and cooling techniques. Improvedformability HSLA steels contain additions such as zirconium, calcium, or rare-earth elements for sulfide-inclusion shape control. While additions of elements such as copper, silicon, nickel, chromium, and phosphorus improve atmospheric corrosion resistance, they also increase their cost. They are not intended for quenching and tempering. For certain applications, however, they are sometimes annealed, normalized, or stress relieved with some influence on mechanical properties. In addition, most HSLA alloys exhibit directionally sensitive properties. For instance, formability and impact strength vary significantly for some grades depending on whether the material is tested longitudinally or transversely to the rolled direction. Where these steels are used for fabrication by welding, care must be exercised in the selection of grade and in the details of the welding process. Certain grades may be welded without preheat or postheat. Forming, drilling, sawing, and other machining operations on Table 2.28. Description of selected grades of HSLA steels HSLA grade

Description

Grade 942X

A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 945X and 945C except for somewhat improved welding and forming properties.

Grade 945A

An HSLA steel with excellent welding characteristics, both arc and resistance, and the best formability, weldability, and low-temperature notch toughness of the high-strength steels. It is generally used in sheets, strip, and light plate thicknesses.

Grade 945C

A carbon-manganese high-strength steel with satisfactory arc welding properties if adequate precautions are observed. It is similar to grade 950C, except that lower carbon and manganese improve arc welding characteristics, formability, and low-temperature notch toughness at some sacrifice in strength.

Grade 945X

A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 945C, except for somewhat improved welding and forming properties.

Grade 950A

An HSLA steel with good weldability, both arc and resistance, with good low-temperature notch toughness, and good formability. It is generally used in sheet, strip, and light plate thicknesses.

Grade 950B

An HSLA steel with satisfactory arc welding properties and fairly good low-temperature notch toughness and formability.

Grade 950C

A carbon-manganese high-strength steel that can be arc-welded with special precautions, but is unsuitable for resistance welding. The formability and toughness are fair.

Grade 950D

An HSLA steel with good weldability, both arc and resistance, and fairly good formability. Where low-temperature properties are important, the effect of phosphorus in conjunction with other elements present should be considered.

Grade 950X

A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 950C, except for somewhat improved welding and forming properties.

Grades 955X, 960X, 965X, 970X, 980X

These are steels similar to 945X and 950X with higher strength obtained by increased amounts of strengthening elements, such as carbon or manganese, or by the addition of nitrogen up to about 0.015%. This increased strength entails reduced formability and usually decreased weldability. Toughness will vary considerably with composition and mill practice.

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2 Ferrous Metals and Their Alloys

114

Ferrous Metals and Their Alloys

HSLA steels usually require 25 to 30% more energy than do structural carbon steels. Commercially HSLA steels are available in all standard wrought forms (i.e., sheet, strip, plate, structural shapes, bar-size shapes, and special shapes). HSLA alloys can be grouped into four classes: (i) (ii) (iii) (iv)

as-rolled carbon-manganese steels; high-strength low-alloy steels; heat-treated carbon steels; heat-treated low-alloy steels.

Over 20 types of these commercial high-strength alloy steels are produced. Some have been developed to combine improved welding characteristics along with high strength. Most have good impact properties in addition to high strength. An example of the high-yieldstrength grades are HY-80 and HY-100, which is used for naval vessels. This material combines high strength and toughness with weldability. HSLA alloys are particularly attractive for transportation-equipment components where weight reduction is important. Because of their high strength-to-weight ratio, abrasion resistance, and, for certain compositions, improved atmospheric corrosion resistance, these steels are adapted particularly for use in mobile equipment and other structures where substantial weight savings are generally desirable. Common applications are, for instance, in a typical

Table 2.29. Mechanical properties of high-strength low-alloy (HSLA) steels Usual and Density Min. Yield strength Min. ultimate tensile Elongation –3 trade name (ρ/kg.m ) 0.2% proof (σYS/MPa) strength (σUTS/MPa) (Z/%) ASTM A242 7750

290–345

435–480

18

ASTM A517 7750

620–690

760–895

18

ASTM A572 7750

290–450

415–550

15–20

ASTM A588 7750

290–345

435–485

18

ASTM A606 7750

310–345

450–480

21–22

ASTM A607 7750

310–485

410–590

14–22

ASTM A618 7750

290–380

430–655

18–23

ASTM A633 7750

290–415

430–690

18-23

ASTM A656 7750

345-550

415-620

12-20

ASTM A715 7750

345-550

415–620

16–24

ASTM A808 7750

290–345

415–450

18–22

ASTM A871 7750

415–450

520–550

15-18

SAE 942X

7750

290

415

20

SAE 945C

7750

275-310

415–450

18–19

SAE 950 A

7750

290–345

430–483

18

SAE 955 X

7750

380

483

17

SAE 960 X

7750

415

520

16

SAE 970 X

7750

485

590

15

SAE 980 X

7750

550

655

10

HY-80

7750

550–690

n.a.

17–20

HY-130

7750

895–1030

n.a.

14–15

Iron and Steels

passenger car such as door-intrusion beams, chassis members, reinforcing and mounting brackets, steering and suspension parts, bumpers, and wheelstruck bodies, while other applications include frames, structural members, scrapers, truck wheels, cranes, shovels, booms, chutes, conveyors, trucks, construction equipment, and off-road vehicles. Mining equipment and other heavy-duty vehicles use HSLA sheets or plates for chassis components, buckets, grader blades, and structural members outside the body. Structural forms are specified in applications such as offshore oil and gas rigs, single-pole power-transmission towers, railroad cars, and ship construction.

2.1.14 Ultrahigh-Strength Steels Ultrahigh-strength structural steels must exhibit a minimum yield strength above 1380 MPa. Ultrahigh-strength steels start with grade 4340, and the other grades are modifications of this alloy. When these steels are used for aerospace components, they are usually produced by the vacuum-arc-remelt (VAR) process. They are classified into several broad categories based on chemical composition or metallurgical-hardening mechanisms. Medium-carbon alloy steels are generally modifications of grade 4330 or 4340, usually with increased molybdenum, silicon, and/or vanadium. These grades provide excellent hardenability in thick sections. Type H13, which includes modified tool steels of the H11 hot-work tool-steel varieties, provides the next step in increased hardenability and greater strength. Most steels in this group are air hardened in moderate to large sections and therefore are not likely to distort or quench crack. Structural uses of these steels are not as widespread as they once were, mainly because of the development of other steels costing about the same but offering greater fracture toughness.

2.1.15 Tool and Machining Steels Tool steels, owing to their relatively high hardness, were developed in certain carbon-, medium-, and low-alloy steels through compositional adjustments or quenching and tempering at relatively low temperatures. These steels are used for applications that require: (i) (ii) (iii) (iv) (v)

resistance to wear/abrasion; thermal shock resistance; stability during heat treatment; strength at high temperatures; and toughness.

Tool steels are increasingly being used for machining tools and dies. Tool steels are melted in relatively small batches in electric furnaces and produced with careful attention to homogeneity. They can be further refined by techniques such as argon/oxygen decarburization (AOD), vacuum arc melting (VAM), or electroslag refining (ESR). Because of the high alloy content of certain groups, tool steels must be rolled or forged with care to produce satisfactory bar products. To develop their best properties, tool steels are always heat treated. Because the parts may distort during heat treatment, precision parts should be semifinished, heat treated, then finished. Severe distortion is most likely to occur during liquid quenching, so an alloy should be selected that provides the needed mechanical properties with the least severe quench. Tool steels are classified according to the American Institute of Steel and Iron (AISI) designation into several broad groups, some of which are further divided into subgroups according to alloy composition, hardenability, or mechanical similarities.

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Ferrous Metals and Their Alloys

Table 2.30. AISI designation of tool steels Class

AISI type

Description

Air-hardening medium-alloy tool steels (cold worked)

A

Air-hardening medium-alloy tool steels are best suited for applications such as machine ways, brick mold liners, and fuel-injector nozzles. The airhardening types are specified for thin parts or parts with severe changes in cross section, i.e., parts that are prone to crack or distort during hardening. Hardened parts from these steels have a high surface hardness; however, these steels should not be specified for service at elevated temperatures.

Air-hardening high carbon and chromium (cold worked)

D

Air-hardening high-chromium and carbon tool steels possess high wear resistance and high hardenability and exhibit little distortion. They are best suited for applications such as machine ways, brick mold liners, and fuelinjector nozzles. The air-hardening types are specified for thin parts or parts with severe changes in cross section, i.e., parts that are prone to crack or distort during hardening. Hardened parts from these steels have a high surface hardness; however, these steels should not be specified for service at elevated temperatures.

Hot-work steels

H

Hot-work tools steels, due to the addition of tungsten and molybdenum, exhibit good heat and abrasion resistance from 315 to 540°C. Hence, they serve well at elevated temperatures. However, although these alloys do not soften at these high temperatures, they should be preheated before and cooled slowly after service to avoid cracking. Note the chromium-containing grades are less expensive than the tungsten and molybdenum grades. For instance, the chromium grades H11 and H13 are used extensively for aircraft parts such as primary airframe structures, cargo support lugs, catapult hooks, and elevon hinges. Subgroups are divided according to H10 to H19: chromium grades, H21 to H26: tungsten grades, H41 to H43: molybdenum grades.

Low-alloy tool steels

L

Low-alloy tool steels are often specified for machine parts when wear resistance combined with toughness is required.

High-speed-tool steels M (molybdenum alloy)

Molybdenum alloy high-speed-tool steels are the best known tool steels because they exhibit both abrasion and heat resistance, though not toughness. Hence they make good cutting tools because they resist softening and maintain a sharp cutting edge due to high hardness until high service temperatures. This characteristic is sometimes called “red heat hardness.” These deep-hardening alloys, in which cobalt additions improve cutting, are used for steady, high-load conditions rather than shock loads. Note that tempering at about 595°C increases toughness. Typical applications are pump vanes and parts for heavy-duty strapping machinery.

Oil-hardening coldwork tool steels

O

Oil-hardening cold-work tool steels are expensive but can be quenched less drastically than water-hardening types.

Mold tool steels

P

These are special-purpose tool steels containing chromium and nickel as major alloying elements. They exhibit low hardness and low resistance to work hardening when annealed.

Shock-resisting tool steels

S

Shock-resistant tool steels, with Cr-W, Si-Mo, and Si-Mn as major alloys, are strong and tough, but they are not as wear resistant as many other tool steels. These steels resist sudden and repeated loadings. Applications include pneumatic tooling parts, chisels, punches, shear blades, bolts, and springs subjected to moderate heat in service.

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117

Table 2.30. (continued) Class

AISI type

Description

High-speed-tool steels T (tungsten alloys)

Tungsten-alloy high-speed-tool steels are the best known tool steels because they exhibit both abrasion and heat resistance, though not toughness. Hence they make good cutting tools because they resist softening and maintain a sharp cutting edge due to high hardness until high service temperatures. This characteristic is sometimes called “red heat hardness.” These deephardening alloys, in which cobalt additions improve cutting, are used for steady, high-load conditions rather than shock loads. Note that tempering at about 595°C increases toughness. Typical applications are pump vanes and parts for heavy-duty strapping machinery.

Water-hardening, or carbon, tool steels

Water-hardening tool steels containing 0.6 wt.% to 1.4 wt.% C are widely used because they combine low cost, a good toughness, and excellent machinability. They are available as shallow, medium, or deep hardening, so the specific alloy selected depends on part cross section and required surface and core hardnesses. Common applications include drills, shear knives, chisels, hammers, and forging dies.

W

The effects of the most common alloying elements on the properties of tool steel are briefly summarized below. Carbon (C). For unalloyed tool steels, the concentration of carbon is usually above 0.60 wt.% C. Carbon is an essential and ubiquitous alloying element that imparts hardenability of steels. Raising the carbon content up to 1.3 wt.% C also increases the wear resistance considerably, although to the detriment of fracture toughness. Manganese (Mn). Small additions of manganese up to 0.60 wt.% Mn are added to reduce brittleness and to improve forgeability of steels. Larger amounts of manganese improve hardenability, allowing oil quenching for unalloyed carbon steels, thereby reducing deformation. Silicon (Si). Because silicon comes from ferrosilicon used in the deoxidizing treatment of steels, silicon is not considered an alloying element of tool steels. However, silicon improves its hot-forming properties. In combination with other alloying elements, the silicon content is sometimes raised up to 2 wt.% Si to increase the strength and fracture toughness of steels that must withstand heavy shock loads. Tungsten (W). Tungsten is one of the most important alloying elements of tool steels, particularly because it imparts a “hot hardness,” that is, the resistance of the steel to the softening effect of elevated temperature, and it forms hard and abrasion-resistant tungsten carbides (e.g., WC and W2C), thus improving the wear properties of tool steels. Vanadium (V). Vanadium contributes to the refinement of the carbide structure and thus improves the forgeability of tool steels. Moreover, vanadium exhibits a strong tendency to form hard carbides (e.g., VC and V2C), which improves both the hardness and the wear properties of tool steels. However, an excessive amount of vanadium carbides makes the grinding of the tool steel extremely difficult, imparting a low grindability. Molybdenum (Mo). A minute amount of molybdenum improves certain metallurgical properties of alloy steels such as deep hardening and fracture toughness. Molybdenum is used often in larger amounts in certain high-speed-tool steels to replace tungsten, primarily for economic reasons, often with nearly equivalent results. Cobalt (Co). Cobalt increases the hot hardness of tool steels. Substantial addition of cobalt, however, raises the critical quenching temperature of the steel with a tendency to increase the decarburization of the surface and reduces toughness.

2 Ferrous Metals and Their Alloys

Table 2.31. Physical properties of tool steels

Average chemical composition (/ wt.% )

UNS

AISI type

T30109 Fe-1.25Cr-0.5Mn-1.8Ni-1.5Mo-1Si

T30110 Fe-1.25C-1.35Mn-1.8Ni-1.5Mo-1.25Si

A9

A10

T30403 Fe-12Cr-1.5C-1.1V-0.6Mn

T30405 Fe-12Cr-1.5C-1.1V-0.6Mn-0.9M0-0.6Si

T30407 Fe-12Cr-1.5C-4.1V-0.6Mn

D3

D5

D7

T6106

L6

Fe-1.6Ni-0.9Cr-0.5Si-0.7C-0.5Mn-0.5Mo

T61202 Fe-1Cr-0.5Si-0.73C-0.5Mn-0.25Mo

L2

Low-alloy tool steels 7860 380–1790

7860 510–1790

655–2000

710–2000

n.a.

4–25

5–25

n.a.

n.a.

32–54

30–54

50–60

40–55

8150 n.a.

H42 T20842 Fe-6.13W-4Cr-5Mo-2V-0.6C

n.a.

8280 n.a.

H21 T20821 Fe-9.25W-0.3Mn-3.4Cr-0.45V

38–55

58–64

58–64

58–64

58–64

52–62

40–56

48–57

58–66

54–60

7760 1290–1570 1495–1960 13–15 40–53

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

7750 n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

H13 T20813 Fe-5.1Cr-1V-1.4Mo-0.3C

7700 n.a.

7700 n.a.

7700 n.a.

7700 n.a.

7680 n.a.

7780 n.a.

7870 n.a.

7660 n.a.

H11 T20811 Fe-5.1Cr-1Si-1.4Mo-0.45V

Hot-work tool steels

T30402 Fe-12Cr-1.5C-1.1V-0.6Mn

D2

Air-hardening cold-work steels

T30108 Fe-5.1Cr-1.4Mo-1.25W-1Si-0.55C-0.5Mn

–3

A8

Density (ρ/kg.m ) 7840 n.a.

11.3

11.3

11.0

12.4

10.4

11.9

12.2

11.0

12.0

10.4

12.8

12.0

n.a.

12.0

11.5

10.7

Coefficient of linear thermal expansion –6 –1 (a/10 K )

T30107 Fe-5.4Cr-4.5V-2.4C-0.8Mn-1.1Mo-0.5Si-1W

Rockwell hardness scale C (/HRC) 57–62

n.a.

n.a.

n.a.

27

29

42

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Thermal conductivity –1 –1 (k/W.m .K )

T30106 Fe-2.2Mn-1.2Mo-1Cr-0.7C-0.5Si

Elongation (Z/%) n.a.

205–540

205–540

205–540

175–425

510–620

175–595

150–540

150–425

175–540

540–650

540–650 870–900 1095–1205 595–675

845–900 995–1040

845–900 995–1025

870–900 1010–1065 150–540

870–900 970–1010

870–900 925–980

870–900 980–1025

765–795 790–815

845–870 980–1025

845–870 980–1010

870–900 955–980

730–745 830–870

845–870 925–980

O

O, W

760–790 790–845

760–790 845–925

175–540

175–315

O, A, S 845–900 1120–1220 565–650

A, O

A

A

A

A

O

A

A

A

A

A

A

A

Quench medium

A7

Ultimate tensile strength (σUTS/MPa) n.a.

Annealing (/°C)

A6

Yield strength 0.2% proof (σYS/MPa)

7860 n.a.

Hardening (/°C)

T30102 Fe-5Cr-1C-1Mn-1Mo-0.35V-0.5Si

Tempering (/°C)

A2

Air-hardening tool steels

118 Ferrous Metals and Their Alloys

7960 n.a.

M48 T11348 Fe-10W-4Mo-3.75Cr-3V-9Co-1.5C-0.3Si

T31502 Fe-0.9C-0.5Cr-1.2Mn-0.5Si

T31506 Fe-1.4C-0.7Mn-1Si-0.25Mo

T31507 Fe-1.2C-1Mn-1.5W-0.6Cr

O2

O6

O7

T51606 Fe-3.5Ni-1.5Cr-0.5Mn

P6

T12005 Fe-18.5W-4.38Cr-2V-1Mo-0.8C

T12015 Fe-12.4W-5Co-4.8V-4.88Cr-1.55C

T5

T15

T41902 Fer-1.1Si-0.5V-0.48C-0.45Mo-0.40Mn

T41905 Fe-2Si-0.8Mn-0.58C-0.5Cr

T41907 Fe-1.5Mo-0.5C-3.3Cr-0.55Mn-0.6Si

S2

S5

S7

T72302 Fe-1.2C-0.25Si-0.25Mn

T72305 Fe-1.1C-0.5Cr-0.25Si-0.25Mn

W2

W5

Quenching medium: A air, W water, B brine, S salt bath, O oil.

T72301 Fe-1.1C-0.25Si-0.25Mn

W1

Water-hardening, or carbon, tool steels

T41901 Fe-2.3W-1.4Cr-0.75Si-0.48C-0.25Mn

S1

Shock-resisting tool steels

T12001 Fe-18W-1.1V-4.13Cr-0.75C

T1

Tungsten-alloy high-speed-tool steels

T51602 Fe-1Cr-0.3Ni-0.3M0

P2

Mold steels

T31501 Fe-0.9C-1.2Mn-0.5W

O1

Oil-hardening tool steels

8150 n.a.

T11303 Fe-5.5Mo-3.75Cr-5.8W-2.5V-1C

M3

7850 n.a.

7850 n.a.

7840 n.a.

7760 380–1585

7760 440–1930

7790 n.a.

7880 415–1895

8190 n.a.

8750 n.a.

8670 n.a.

7850 n.a.

7860 n.a.

7800 n.a.

7700 n.a.

7660 n.a.

7850 n.a.

8160 n.a.

T11302 Fe-5Mo-3.75Cr-6W-2V-0.8C

M2

7890 n.a.

T11301 Fe-8.7Mo-3.75Cr-1.25W-1.15V-0.8C

M1

Molybdenum-alloy high-speed-tool steels

n.a.

n.a.

n.a.

640–2170

725–2345

n.a.

690–2070

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

7–25

5–25

n.a.

4–24

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

58–65

58–65

58–65

45–57

37–60

n.a.

48–58

64–68

n.a.

63–65

58–64

58–64

58–64

58–63

57–62

57–62

65–70

62–66

63-65

60–65

10.4

10.4

10.4

10.5

11.0

10.9

12.4

9.9

11.2

9.7

12

13

11.2

11.2

11.2

11.2

10.6

10.1

10.1

10.1

48

48

48

n.a.

n.a.

n.a.

n.a.

21.0

n.a.

20.0

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

22

n.a.

175–260 175–260 175–315 175–290 175–260 175–260

760–790 790–815 745–775 760–800 765–790 790–815 790–815 790–885 730–815 830–845 845–870 800–830

W, B

W, B

W, B

A, O

O

W, B

O

205–650 175–425 175–425 205–620 175–345 175–345 175–345

790–815 900–955 760–790 845–900 775–800 870–925 815–845 925–955 740–790 760–845 740–790 760–845 760–790 760–845

O, A, S 870–900 1205–1260 540–650

O, A, S 870–900 1275–1300 540–595

O, A, S 870–900 1260–1300 540–595

A, O

A, O

O, W

O

O

O

O, A, S 870–900 1175–1200 540–595

O, A, S 870–900 1205–1230 540–595

O, A, S 870–900 1190–1230 540–595

O, A, S 815–870 1175–1220 540–595

Iron and Steels 119

Ferrous Metals and Their Alloys

2

Ferrous Metals and Their Alloys

Chromium (Cr). Chromium is added from a few percent to high-alloy tool steels and up to 12 wt.% Cr to types in which chromium is the major alloying element. Chromium improves hardenability and, together with high carbon content, provides both wear resistance and fracture toughness. However, high chromium content raises the hardening temperature of the tool steel and thus can make it prone to hardening deformations. A high percentage of chromium also affects the grindability of tool steels. Nickel (Ni). Nickel is usually used in combination with other alloying elements, such as chromium, to improve the fracture toughness and, to some extent, the wear resistance of tool steels.

2.1.16 Maraging Steels Maraging steels are a particular class of extra-low-carbon (i.e., < 0.03 wt.% C) and nickelrich (i.e., 18 wt.% < Ni < 22 wt.%) iron alloys having an ultrahigh strength. Nickel is the major alloying element followed by cobalt, which is added up to 12 wt.% to accelerate precipitation reactions, molybdenum, and, to a lesser extent, titanium, aluminum, and copper. A typical example of a maraging steel is an iron alloy with the following composition: 17 to 19 wt.% Ni, 7 to 9 wt.% Co, 4.5 to 5.0 wt.% Mo, and 0.6 to 0.9 wt.% Ti. Alloys of this type are

9

1340 1390 11

8000

Grade Fe-18Ni-8Co-5Mo9 250 0.4Ti-0.1Al-0.03C

8000 1430– 186 1620 1700 8–9 1450

520 10.1

Grade Fe-18Ni-12Co-5Mo300 0.6Ti-0.1Al-0.03C

8000

1810 1930 7

570

Grade Fe-18.8Ni-10.8Co350 4.22Mo-1Ti

8000

2318 2339 8.0

Specific heat capacity –1 –1 (cP/J.kg .K ) (50-100°C)

Electrical resistivity (ρ/μΩ.cm)

–1 –1

Coefficient linear thermal –6 –1 expansion (a/10 K )

Vickers hardness (/HV)

Grade Fe-18Ni-8Co-3.2Mo200 0.2Ti-0.1Al-0.03C

450

76.6

Grade Fe-18.5Ni-3Mo-1.26Ti 8000 1800

1647 1696 13.1 46.2

Grade Fe-18.9-4.1Mo-1.93Ti 2000

8000

1957 2017 8.0

74.0

Grade Fe-17.9Ni-14.8Co2800 6.69Mo-1.1Ti

8000

2617 2693 6.0

31.6

G = 71 GPa, v = 0.30, melting range: 1430–1450°C

Thermal conductivity (k/W.m .K )

–1/2

Fracture toughness (KIC/MPa.m )

Elongation (Z/%)

Ultimate tensile strength (σUTS/MPa)

Yield strength 0.2% proof (σYS/MPa)

Young’s elastic modulus (E/GPa)

Melting range (°C)

–3

Density (ρ/kg.m )

Chemical composition (/wt.%)

Table 2.32. Composition and selected physical properties of maraging steels (ASTM A538)

Maraging steel grade

120

19.7

65

Iron and Steels

hardened to martensite and then tempered at 480 to 500°C. The tempering results in strong precipitation hardening owing to the precipitation of intermetallics from the martensite, which is supersaturated with the alloying elements. By analogy with the precipitation hardening in aluminum, copper, and other nonferrous alloys, this process has been termed aging, and since the initial structure is martensite, the steels have been called maraging. Because of the negligible carbon content, the peculiar strengthening behavior of these steels does not rely at all on the usual precipitation of iron carbide common to all carbon steels. Indeed, the strength relies only on the precipitation of the metastable nickel-rich intermetallic phases: Ni3Mo and Ni3Ti. Moreover, the high dispersion of these precipitates ensures a superior strength without loss of malleability. Major suitable characteristics of maraging steels are listed below: (i) (ii) (iii) (iv) (v) (vi)

ultrahigh strength at room temperature; simple heat treatment with minimum shrinkage; superior fracture toughness compared to quenched and tempered steels; low carbon content, which precludes decarburization issues; ease of machining, high surface finish, and good weldability; good corrosion resistance and crack propagation.

Therefore, maraging steels are required in applications requiring ultrahigh strength along with a good dimensional stability during heat treatment. Typical applications are gears, fasteners, rocket and missile cases, aircraft parts, plastic mold dies or shafts, as a substitute for long, thin, carburized, or nitrided parts, and for components subject to impact fatigue, such as print hammers or clutches. Compositions and selected properties of three common grades of maraging steels are listed in Table 2.32.

2.1.17 Iron-Based Superalloys Iron-, nickel-, and cobalt-based alloys used primarily for high-temperature applications are known as superalloys. The iron-based grades, which are less expensive than cobalt- or nickel-based grades, are of three types: (i) (ii)

alloys that can be strengthened by a martensitic type of transformation; alloys that are austenitic and are strengthened by a sequence of hot and cold working, usually forging at 1100 to 1150°C followed by finishing at 650 to 880°C; (iii) austenitic alloys strengthened by precipitation hardening. Some metallurgists consider only the last group to be superalloys, the others being categorized as high-temperature, high-strength alloys. In general, the martensitic types are used at temperatures below 540°C, while the austenitic types are used above 540°C. The American Institute of Steel and Iron (AISI) designation defined the AISI 600 series and divided superalloys into six subclasses of iron-based alloys: (i) (ii) (iii) (iv) (v) (vi)

AISI 601 to 604: martensitic low-alloy steels; AISI 610 to 613: martensitic secondary hardening steels; AISI 614 to 619: martensitic chromium steels; AISI 630 to 635: semiaustenitic and martensitic P-H stainless steels; AISI 650 to 653: austenitic steels strengthened by hot/cold work; AISI 660 to 665: austenitic superalloys; all grades except alloy 661 are strengthened by second-phase precipitation.

121

2 Ferrous Metals and Their Alloys

122

Ferrous Metals and Their Alloys

Iron-based superalloys are characterized by both high-temperature and room-temperature strength and resistance to creep, oxidation, corrosion, and wear. Wear resistance increases with carbon content. Maximum wear resistance is obtained in alloys 611, 612, and 613, which are used in high-temperature aircraft bearings and machinery parts subjected to sliding contact. Oxidation resistance increases with chromium content. The martensitic chromium steels, particularly alloy 616, are used for steam-turbine blades. The superalloys are available in all conventional mill forms (i.e., billet, bar, sheet, and forgings), and special shapes are available for most alloys. In general, austenitic alloys are more difficult to machine than martensitic types, which machine best in the annealed condition. Crack sensitivity makes most of the martensitic steels difficult to weld by conventional methods. These alloys should be annealed or tempered prior to welding; even then, preheating and postheating are recommended. Welding drastically lowers the mechanical properties of alloys that depend on hot/cold work for strength. All of the martensitic low-alloy steels machine satisfactorily and are readily fabricated by hot working and cold working. The martensitic secondaryhardening and chromium alloys are all hot worked by preheating and hot forging. Austenitic alloys are more difficult to forge than the martensitic grades.

2.1.18 Iron Powders Powder metallurgy (P/M) parts are made to net shape by compacting iron metal powders in special dies and sintering them to achieve the final properties desired. These properties depend on the alloy, the shape of the powder particles, the compressive strength, and the sintering temperature. Three basic steps are usually encountered in a P/M process: (i) filling the loose powder into a die; (ii) compaction under pressure and ejection of the green compressed part; (iii) sintering of the workpiece in a furnace under reducing atmosphere. Three major quantities are used in P/M: the bulk density of the loose iron powder (e.g., –3 3000 kg.m for water-atomized powder) which is lower than the apparent density due to air –3 space. After compression, the compressed density doubles to about 6000 kg.m . Finally, after sintering, the fusion that occurs between particles increases the steel's density to a density approaching the theoretical density or pore-free density. Three types of iron powders are available commercially.

2.1.18.1 Water-Atomized Iron Powders Water-atomized iron powder was first introduced industrially in the 1960s by the A.O. Smith Company in the USA. Iron metal or iron alloy is first melted between 1100°C and 1650°C, depending on the carbon content, and then poured into a ceramic vessel with a small plugged hole in the bottom. When the ceramic plug is removed, the molten metal falls, forming a narrow stream about 1 in. (2.54 cm) in diameter. Jets of high-pressure water (14 MPa) strike the liquid metal stream at an angle and disintegrate it into fine droplets. Due to the high specific heat capacity of water, the iron droplets freeze into intricate shapes well before surface tension has time to minimize their surfaces into little spheres, as in gas atomization, while their core is dense. Hence the iron particles become highly irregular in shape. As a result, when these powders are compressed under 414 MPa, parts have only 12 vol.% porosity. Moreover, water-atomized iron powders are very pure, which means they are ductile and do not exhibit a foraminous structure like sponge iron. Their coarse pores are easier to collapse, and thus water-atomized powders are easier to compress and and are known for their good flow rates into dies and their ability to pack well.

Iron and Steels

123

2.1.18.2 Gas-Atomized Iron Powders Gas-atomized iron powders are produced by melting iron metal between 1100°C and 1540°C, depending on the carbon content, and then pouring it into a tundish with a small plugged hole in the bottom. When the ceramic plug is removed, the molten metal falls, forming a narrow stream about 2 cm in diameter. Jets of high-pressure inert gas such as argon or nitrogen strike the liquid metal stream at a given angle and disintegrate it into fine droplets. Surface tension causes the liquid droplets to adopt a spherical form. The chamber surrounding the stream is large enough that the metal droplets solidify before reaching the wall of the chamber. Spherical powders have their uses, due to their virtually perfect spherical shape, and gas-atomized powders pour well into dies, but the compaction is straightforward. Actually, even high compressive strength in the range 275 to 690 MPa are not enough to cause them to stick together. They pack so uniformly that in most cases they make a face-centered cubic dense arrangement of balls, even if the high pressures causes the particle to form a weak metallic bond. When the pressure is released, the green form remains too fragile.

2.1.18.3 Sponge-Reduced Iron Sponge iron powder is obtained by the reduction of mill scale coming from the scale as a byproduct from steel mills processing large steel billets. Actually, during heating and working of the hot mill products, the air oxidation of steel produces a poorly adherent black scale of magnetite (Fe3O4) called mill scale. The scale thickens and eventually flakes off to land on the floor. The mill scale flakes are then collected and sent to companies specializing in the conversion of mill scale into sponge iron powder. The reduction process consists in putting a layer of mill scale 10 to 15 cm thick onto a belt conveyor made of stainless steel sheet that passes through a reduction furnace at about 930°C. Hydrogen gas is used as reducing atmosphere. Usually hydrogen is produced by steam reforming, water electrolysis, or the cracking of ammonia depending on the facility’s proximity to an inexpensive source of hydrogen. The hydrogen gas reduces the magnetite of the mill scale into metallic iron and water vapor. After a few hours the reduction process is complete. Because oxygen is removed from the solid, the final reduced metal exhibits tiny vacancies or pores, giving it a typical porous structure, and for that reason it was called sponge iron. This characteristic of sponge iron ensures an excellent green strength of the pressed material between 276 and 690 MPa. However, today the use of sponge iron powder is declining. Actually, because sponge iron powder particles exhibit a highly angular shape, on pouring it into a die, the particles rub their rough surfaces against each other and flow more slowly. Once they settle in the die, protuberances keep them from packing very closely. To make a part of a given weight, the die has to be much deeper to hold enough powder. Moreover, during pressing, even at a compressive strength of 415 MPa, the final green material has about 19% porosity in the sponge irons, but parts still have high green strength.

2.1.19 Further Reading Collective (2003) The Iron Ore Market 2002–2004. UNCTAD Iron Ore Trust Fund, UNCTAD, Geneva, Switzerland. COLOMBIER, L. (1957) Métallurgie du Fer. Éditions Dunod, Paris. HARVEY, Ph. (1982) Engineering Properties of Steels. ASM Books, Materials Park, OH. PARR, J.G.; HANSON, A.; LULA, R.A. (1985) Stainless Steels. ASM Books, Materials Park, OH. ROBERTS, G.A.; CARY, R.A. (1980) Tool Steels, 4th. ed. ASM Books, Materials Park, OH. WEGST, C.W. (2004) Stahlschlussel (Key to Steel), 20th ed. ASM Books, Materials Park, OH. BRINGAS, J.E. (1995) The Metals Black Book, Vol. 1 Ferrous Metals, 2nd ed. CASTI, Edmonton, Canada.

2 Ferrous Metals and Their Alloys

124

Ferrous Metals and Their Alloys

2.2 Nickel and Nickel Alloys 2.2.1 Description and General Properties Nickel [7440-02-0], chemical symbol Ni, atomic number 28, and relative atomic mass 58.6934(2), is the third element of the upper transition metals of group VIIIB (10) of Mendeleev’s periodic chart. It was named after the English Old Nick. Pure nickel is a dense –3 (8902 kg.m ), tough, silvery-white lustrous metal that exhibits both a high electrical –1 –1 (6.9 μΩ.cm) and thermal conductivity (90.7 W.m .K ) and has a high melting point (1455°C). The face-centred cubic (fcc) crystal structure imparts to the metal a good ductility, and nickel can be fabricated readily by the use of standard hot and cold working methods. Like iron and cobalt, pure nickel is a soft ferromagnetic material but with a lower saturation 6 –1 magnetization MS of 0.480 × 10 A.m . However, like iron and cobalt, nickel loses its ferromagnetism above its Curie temperature of 627 K and becomes paramagnetic. From a chemical point of view, pure nickel is corrosion resistant to attack by moist air or water at room temperature and highly resistant to concentrated alkaline solutions or molten alkalis (e.g., NaOH, KOH). However, nickel dissolves in diluted mineral acids such as hydrochloric acid (HCl) and readily in nitric acid (HNO3). The major reactions of nickel metal with most common acids are summarized in Table 2.33. Nickel metal reacts only slowly with fluorine gas due to the self-formation of a thin protective passivating layer of nickel fluoride (NiF2). Therefore nickel and cupronickel alloys such as Monel®400 and K-500 are used extensively for handling fluorine gas, anhydrous hydrogen fluoride, and hydrofluoric acid. Nickel is extensively used in coinage but is more important either as pure metal or in the form of alloys for its many domestic and industrial applications. Prices (2006). Pure nickel (99.99 wt.% Ni) is priced 18 US$/kg (8.16 US$/lb).

2.2.2 History Nickel was used industrially as an alloying metal almost 2000 years before it was isolated and recognized as a new element. As early as 200 B.C., the Chinese made substantial amounts of a white alloy from zinc and a copper-nickel ore found in Yunnan province. The alloy, known as pai-t'ung, was exported to the Middle East and even to Europe. Later, miners in Saxony (Germany) encountered what appeared to be a copper ore but found that processing it yielded only a useless slaglike material. Earlier, an ore of this same type was called Kupfernickel because the miners considered it bewitched and ascribed this to the devil, Old Nick, and his mischievous gnomes because, though it resembled copper ore, it yielded

Table 2.33. Reactions of nickel metal with acids Acid

Soln.

Hydrochloric acid (HCl) All

Chemical reaction sheme 0

2+

Notes –

Ni + 2HCl —> Ni + 2Cl + H2(g) 0

2+

2–

Dissolves slowly

Sulfuric acid (H2SO4)

Dil.

Ni + 2H2SO4 —> Ni + SO4 + 2H2O

Nitric acid (HNO3)

Dil.

3Ni + 8HNO3 —> 3Ni + 6NO3 + 2NO(g) + 4H2O Dissolves readily

0

Conc. No reaction

2+

Dissolves slowly

–

Does not dissolve due to passivation

Nickel and Nickel Alloys

a brittle, unfamiliar metal. It was from niccolite, studied by the Swedish chemist and mineralogist Baron Axel Fredrik Cronstedt, that nickel was first isolated and recognized as a new element in 1751. In 1776 it was established that pai-t'ung, now called nickel-silver, was composed of copper, nickel, and zinc. Demand for nickel-silver was stimulated in England in about 1844 by the development of silver electroplating, for which it was found to be the most desirable base. The use of pure nickel as a corrosion-resistant electroplated coating developed a little later. Small amounts of nickel were produced in Germany in the mid-19th century. More substantial amounts came from Norway, and a little from a mine at Gap, Pennsylvania in the USA. In 1863, a new large nickel-bearing laterite ore deposit was discovered in New Caledonia. The first production began at the Société Le Nickel in 1877, and it dominated the market until the development in 1885 of the huge copper-nickel orebody of the Copper Cliff in Sudbury, Ontario (Canada). After 1905 the Canadian deposit became the world’s largest source of nickel in the 20th century, until the discovery in the late 1970s of the Norilsk complex in the Soviet Union.

2.2.3 Natural Occurrence, Minerals and Ores Nickel, with a relative abundance in the Earth’s crust of 70 mg/kg, is twice as abundant as copper, and the Earth’s inner core is supposedly made of a Ni-Fe alloy (see Section 13.2). Nickel never occurs free in nature but only as an alloy with iron in certain meteorites. However, due to its chalcophile geochemical character, like copper, most nickel occurs primarily as minerals in combination with arsenic, antimony, and sulfur. Nickel is mined from two types of ore deposits: primary nickel-bearing sulfide orebodies and secondary nickel-bearing laterite deposits. (i)

(ii)

Primary nickel-bearing sulfide orebodies. This type of deposit originates from intrusive or volcanic magmatic activity. As a general rule, in sulfidic ores, the nickel content ranges between 0.4 and 2.0 wt.% Ni and the nickel occurs mainly as pentlandite [(Ni,Fe)9S8, cubic] and, to a lesser extent, in nickeloan pyrrhotite [(Fe,Ni)S1-x, hexagonal], which represent the major nickel lost during the smelting process. In addition to pentlandite and pyrrhotite, nickel also occurs in amounts of less significance in less common sulfides and sulfosalts such as millerite [NiS, hexagonal], niccolite [NiAs, hexagonal], rammelsbergite [NiAs2, orthorhombic], gersdorffite [NiAsS, cubic], and ullmanite [NiSbS, cubic]. Traces of nickel are also found in chalcopyrite [CuFeS2, tetragonal] and cubanite [CuFe2S3, orthorhombic]. It is important to note that in sulfidic ores, traces of precious metals (e.g., Au, Ag) and of the six platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, and Pt), along with Co, Se, and Te, are always present, and they represent important commercial byproducts. Sulfidic ores are relatively easy to concentrate, and the major orebodies of economic importance are extensively found in Canada (Sudbury), Africa, and Russia (Norilsk). The operating costs for extracting nickel from sulfidic ores are higher than for laterites due to underground mining, but recovereable byproducts ensure the economic feasibility of such deposits. Secondary nickel-bearing laterite deposits. Laterites are residual sedimentary rocks such as bauxite resulting from the in situ weathering of ultramafic igneous rocks (e.g., peridotite such as dunite). This near-surface alteration, common in tropical climates, exerts an intense leaching action of the host rock, and the soluble nickel cations percolate down and may reach a concentration sufficiently high to make mining economically worthwhile. Owing to this method of formation, nickel-bearing laterite deposits are found near the surface as a soft, frequently claylike material, with nickel concentrated in strata as a result of weathering. The principal nickel-bearing mineral is nickeloan limonite [(Fe,Ni)O(OH).nH2O, orthorhomic] and also a phyllosilicate called

125

2 Ferrous Metals and Their Alloys

126

Ferrous Metals and Their Alloys

garnierite (formerly noumeite) [(Ni,Mg)6Si4O10(OH)8, amorphous]. The two major laterite deposits of economic importance are found in New Caledonia and Cuba, while smaller deposits occur in Australia, Indonesia, the Philippines, the Dominican Republic, Colombia, and Brazil. Nickel-bearing laterite deposits account for the major part of nickel reserves but only half of world production. Other sources of nickel, especially in deep-ocean polymetallic nodules (see Manganese) lying on the Pacific Ocean floor, will probably have an important economic role in the future. As a general rule, to be mineable, a nickel ore deposit must be able to produce annually at least 40,000 tonnes of nickel, that is, 800,000 tonnes for a period of 20 years. Annual world nickel production is 925,000 tonnes (2003), of which 70% is consumed for stainless steels. The world’s largest nickel-producing countries are Russia, Canada, New Caledonia, and Australia. In 2005, the major nickel projects were the laterite deposit of Goro (New Caledonia, France) and the sulfide ore deposit of Voisey’s Bay (Newfoundland, Canada). Table 2.34. Annual production capacity of major nickel producers Company

Annual production (tonnes)

Inco CVRD

220,900

Xstrata (formerly Falconbridge)

113,852

BHP Billiton Ltd.

133,800

Norilsk Nickel

250,000

Sherritt Gordon Mines Ltd.

15,939

2.2.4 Processing and Industrial Preparation The metallurgy of nickel depends on the type of ore processed, and both pyrometallurgical (smelting) and hydrometallurgical processes are used alone or in combination. As a general rule, the sulfide ore is transformed into nickel(III) sulfide, Ni2S3, which is roasted in air to give nickel(II) oxide, NiO, while the laterite ore is fired to give off nickel oxide. In both processes, the metal is winned by carbothermic reduction of the oxide. Some high-purity nickel is made by refining. Nickel from sulfide ores. Sulfidic nickel-bearing ore deposits are usually mined by underground techniques in a manner similar to that of copper ores. Sulfide ores are crushed and ground in order to liberate nickel-bearing minerals from the inert gangue materials. Afterward, the raw ore is concentrated selectively by common beneficiation processes (e.g., both froth flotation and magnetic separation). After separation from gangue minerals, the ore concentrate contains between 6 and 12 wt.% Ni. For high-copper-containing ores the concentrate is then subjected to a second selective flotation process that produces a lownickel copper concentrate and a nickel-rich concentrate, each processed in a separate smelting process. Nickel concentrates may be leached either with sulfuric acid or ammonia, or they may be dried, roasted to reduce sulfur and impurities, and smelted in bath processes using electric arc furnaces, as is done with copper. Nickel requires higher smelting temperatures of 1350°C in order to produce an artificial nickel-iron sulfide known as nickel matte, which contains 25 to 50 wt.% Ni. The nickel matte can be processed either hydrometallurgically or pyrometallurgically. When processed hydrometallurgically, the matte is cast into anode slabs, and pure nickel cathodes are obtained by electrorefining, or the nickel matte is leached by hydrochloric acid to yield a nickel chloride solution from which the nickel can

Nickel and Nickel Alloys

be recovered by electrowinning. When processed pyrometallurgically, the iron in the matte is converted in a rotating converter into iron oxide, which combines with a silica to form the slag. The slag is removed, leaving a matte of 70 to 75 wt.% Ni. The conversion of nickel sulfide directly into metal is achieved at a high temperature above 1600°C. The matte is then roasted in air to give the nickel oxide. The nickel metal is obtained by carbothermal reduction of the nickel oxide with coal in an electric arc furnace (EAF) operating between 1360°C and 1610°C. Nickel from lateritic ores. Laterites are usually mined in earth-moving operations, with large shovels, draglines, or front-end loaders extracting the nickel-rich strata and discarding large boulders and waste material. Recovery of nickel from laterite ores is an energyintensive process requiring high energy input. The ore is then reduced in an electric arc furnace to yield a ferronickel alloy. In addition, laterites are difficult to concentrate by common ore beneficiation processes, and hence a large amount of ore must be smelted to win the metal. Because these ores contain large amounts of water (i.e., 35 to 40 wt.% H2O), the major operation consists in drying in rotary-kiln furnaces, giving the nickel oxide. Sherritt ammonia pressure leaching. This hydrometallurgical process was first implemented in 1954 by Sherritt Gordon Mines in Fort Saskatchewan, Alberta, Canada. In this process, the finely ground nickel sulfide concentrates obtained after flotation or the metal matte are reacted at 80 to 95°C in a high-pressure autoclave under 850 kPa with an oxygenated ammonia or ammonia-ammonium sulfate liquor. Ammonia dissolves nickel and, to a lesser extent, cobalt, zinc, and copper by forming soluble ammonia complex cations as follows: MS + nNH3 + 2O2 —> M(NH3)nSO4 (for nickel sulfide concentrates), 0

M + (n–2)NH3 + (NH4)2SO4 + 0.5O2 —> M(NH3)nSO4 + H2O (for nickel-containing matte), with M = Ni, Co, Zn, Cu and n = 2–6. After removing iron as iron hydroxide and precipitating copper as copper sulfide, nickel is recovered from the leach liquor by reduction with pure hydrogen at 200°C under a high pressure of 3 MPa: 0

Ni(H2O)4(NH3)2SO4 + H2(g) —> Ni + (NH4)2SO4 + 4H2O. The remaining liquor contains all the cobalt that is recovered by precipitating it as cobalt sulfide with hydrogen sulfide. Finally, the remaining spent solution consists of ammonium sulfate, which is sold as fertilizer. Refining. The two common refining processes are electrolytic refining and the carbonyl process. Electrorefining uses a sulfate or chloride electrolyte and is performed in electrolyzers with two compartments separated by a diaphragm to prevent the passage of impurities from anode to cathode. During electrolysis, the impure nickel anode(+) is dissolved and nickel electrodeposits onto pure nickel cathodes, while more noble metals (e.g., Au, Ag, and PGMs) are recovered in slurries at the bottom of the reactor and soluble metals (e.g., Fe, Cu) remain in the electrolyte. In the carbonyl refining process, carbon monoxide is passed through the matte, yielding nickel and iron carbonyls [i.e., Ni(CO)4 and Fe(CO)5]. After separation, nickel carbonyl is decomposed onto pure nickel pellets to produce nickel shot.

2.2.5 Nickel Alloys Nickel and the nickel alloys constitute a family of alloys with increasing importance in many industrial applications because they exhibit both a good corrosion resistance in a wide variety of corrosive environments and an excellent heat resistance from low to elevated temperatures. Some types have an almost unsurpassed corrosion resistance in certain media, but

127

2 Ferrous Metals and Their Alloys

128

Ferrous Metals and Their Alloys

nickel alloys are usually more expensive than, for example, iron-based or copper-based alloys or than plastic construction materials. Nickel alloys are alloys in which nickel is present in greater proportion than any other alloying element. Actually, nickel content throughout the alloy families ranges from 32.5 to 99.5 wt.% Ni. The most important alloying elements are Fe, Cr, Cu, and Mo, and a variety of alloy classes are commercially available. Two groups of nickel-alloy classes can be distinguished: alloys that depend primarily on the inherent corrosion characteristics of nickel itself and alloys that greatly depend on chromium as the passivating alloying element such as for stainless steels. Common nickel-alloy families include commercially pure nickel, binary systems (e.g., Ni-Cu, Ni-Si, and Ni-Mo), ternary systems (e.g., Ni-Cr-Fe, and Ni-Cr-Mo), more complex systems (e.g., Ni-Cr-Fe-MoCu), and superalloys, and they are usually grouped into the following classes: (i) (ii) (iii) (iv) (v) (vi) (vii) (viii)

commercially pure and high-nickel alloys; nickel-molybdenum alloys; nickel-copper alloys; nickel-chromium alloys; nickel-chromium-iron alloys; nickel-chromium-molybdenum alloys; nickel-chromium-iron-molybdenum-copper alloys; nickel superalloys.

Structural applications that require specific corrosion resistance or elevated temperature strength receive the necessary properties from nickel and its alloys. Some nickel alloys are among the toughest structural materials known. Compared to steel, other nickel alloys exhibit both an ultrahigh tensile strength, a high proportional limit, and high Young’s moduli. At cryogenic temperatures, nickel alloys are strong and ductile. Several nickel-based superalloys are specified for high-strength applications at temperatures up to 1090°C. High-carbon nickel-based casting alloys are commonly used at moderate stresses above 1200°C. Commercial nickel and nickel alloys are available in a wide range of wrought and cast grades; however, considerably fewer casting grades are available. Wrought alloys tend to be better known by tradenames such as Monel, Hastelloy, Inconel, Incoloy. The casting alloys contain additional elements, such as silicon and manganese, to improve castability and pressure tightness. See Tables 2.35 and 2.36, pages 129–131.

2.2.6 Nickel Alloys and Superalloys Nickel-based alloys, which form the bulk of alloys produced, are basically nickel-chrome alloys with a face-centered cubic solid-solution matrix containing carbides and the coherent intermetallic precipitate γ-Ni3(Al,Ti). This latter precipitate provides most of the alloy strengthening and results in useful operating temperatures up to 90% of the start of melting. Further additions of aluminum, titanium, niobium, and tantalum are made to combine with nickel in the γ' phase, and additions of molybdenum, tungsten, and chromium strengthen the solid solution matrix. See Table 2.37, pages 132–138.

Description

Major wrought alloys in this group are commercially pure nickel 200 and 201 grades. The cast grade is recommended for use at temperatures above 315°C owing to its lower carbon content, which prevents graphitization and attendant ductility loss. These two grades are particularly suitable when corrosion resistance to caustic alkaline hydroxides (i.e., NaOH, KOH), high-temperature halogens and hydrogen halides (e.g., HF), and molten fluorides in nonoxidizing conditions are required. These alloys are particularly well suited for food-contact applications. Duranickel® 301, a precipitation-hardened nickel alloy, has excellent spring properties up to 315°C, and corrosion resistance is similar to that of commercially pure wrought nickel. Commercially pure nickel has good electrical, magnetic, and magnetostrictive properties.

In this category the most common cupronickel alloys are the Monel®400 and Monel®K-500. The Ni-Cu alloys differ from nickel 200 and 201 because their strength and hardness can be increased by age hardening. Ni-Cu alloys exhibit higher corrosion resistance than commercially pure nickel, especially to sulfuric and hydrofluoric acids, and chloride brines. Handling of waters, including seawater and brackish water, is the major application of these two alloys in the CPI (e.g., desalination plants). In addition, Monel®400 and K-500 are immune to chloride-ion stress-corrosion cracking, which is often considered in their selection.

The Ni-Mo binary type, Hastelloy®B-2, offers superior resistance to hydrochloric acid, aluminum-chloride catalysts, and other strongly reducing chemicals. It also has excellent high-temperature strength in inert atmospheres and in a vacuum. The Ni-Mo alloys are commonly used for handling hydrochloric acid in all concentrations at temperatures up to the boiling point. These alloys are produced commercially under the tradenames Hastelloy®B and Chlorimet 2.

Ni-Cr-Fe alloys are known commercially under the common tradenames Haynes®214 and 556, Inconel®600, and Incoloy®800. Haynes®214 has excellent resistance to oxidation up to 1200°C and resists carburizing and chlorine-contaminated atmospheres. Haynes®556 combines effective resistance to sulfidizing, carburizing, and chlorine-bearing environments with good oxidation resistance, fabricability, and high-temperature strength. Inconel®600 exhibits good resistance to both oxidizing and reducing environments. Incoloy®800 has good resistance to oxidation and carburization at elevated temperatures, resists sulfur attack, internal oxidation, scaling, and corrosion in many harsh atmospheres and is suited for severely corrosive conditions at elevated temperatures.

Ni-Cr-Mo are commercially known under the common tradenames Hastelloy®C-276 and C-22 and Inconel® 625. Hastelloy®C-22 has better overall corrosion resistance and versatility than any other Ni-Cr-Mo alloy. In addition, it exhibits outstanding resistance to pitting, crevice corrosion, and stresscorrosion cracking. Hastelloy®C-276 has excellent corrosion resistance to strong oxidizing and reducing corrosives, acids, and chlorine-contaminated hydrocarbons. It is also one of the few materials with titanium that withstands the corrosive effects of wet chlorine gas, hypochlorite, and chlorine dioxide. Present applications include the pulp and paper industry, various pickling acid processes, and production of pesticides and various agrichemicals.

Nickel alloys class

Commercially pure nickels and extra-highnickel alloys

Cupronickels (Ni-Cu)

Ni-Mo

Ni-Cr-Fe

Ni-Cr-Mo

(continued) of main nickel-alloy classes Table 2.35. Description

Nickel and Nickel Alloys 129

Ferrous Metals and Their Alloys

2

Description

Nickel -based superalloys

Nickel-based superalloys can be classified in three groups. (i) First are those strengthened by intermetallic compound precipitation in a face-centered cubic matrix. These alloys are well known under the common tradenames Astroloy, Udimet®700, and Rene®95. (ii) Another type of nickel-based superalloy is represented by Hastelloy®X. This alloy is essentially solid-solution strengthened. (iii) A third class consists of oxide-dispersionstrengthened (ODS) alloys such as MA-754, which is strengthened by dispersions of yttria coupled with gamma prime precipitation (e.g., MA-6000). Nickel-based superalloys are used in cast and wrought forms, although special processing (e.g., powder metallurgy, isothermal forging) often is used to produce wrought versions of the more highly alloyed compositions such as Udimet®700 or Astroloy®.

Ni-Cr-Fe-Mo-Cu Ni-Cr-Fe-Mo-Cu alloys are known commercially under the tradenames Hastelloy®G-30 and H, Haynes®230, Inconel® 617, 625, and 718, and Incoloy®825. Haynes®230 has excellent high-temperature strength and heat and oxidation resistance, making it suitable for various applications in the aerospace, airframe, nuclear, and chemical-process industries. Hastelloy®G-30 has many advantages over other metallic and nonmetallic materials in handling phosphoric acid, sulfuric acid, and oxidizing acid mixtures. Hastelloy®H exhibits a localized corrosion resistance equivalent or better to Inconel®625. In addition, it has good resistance to hot acids and excellent resistance to stress-corrosion cracking. It is often used in flue gas desulfurization equipment. Inconel® 617 resists cyclic oxidation at 1100°C and has good stress-rupture properties above 990°C. Inconel®625 has high strength and toughness from cryogenic temperatures up to 1100°C, good oxidation resistance, exceptional fatigue strength, and good resistance to many corrosives. It is extensively used in furnace mufflers, electronic parts, chemical- and food-processing equipment, and heat-treating equipment. Inconel®718 has excellent strength from –250 to 700°C. The alloy is age hardenable, can be welded in the fully aged condition, and has excellent oxidation resistance up to 1800°C. Incoloy®825 resists pitting and intergranular corrosion, reducing acids, and oxidizing chemicals. Applications include pickling-tank thermowell and bayonet heater, spent-nuclear-fuel-element recovery and radioactive-waste handling, chemical-tank trailers, evaporators, sour-well tubing, hydrofluoricacid production, and pollution-control equipment.

Nickel alloys class

Table 2.35. (continued)

130 Ferrous Metals and Their Alloys

UNS

N02200

N02201

N02205

N02211

N02233

N02270

N02290

Usual and trade name

Nickel 200

Nickel 201

Nickel 205

Nickel 211

Nickel 233

Nickel 270

Nickel 290

Table 2.36. Physical properties of commercially pure and high nickel alloys (annealed)

Average chemical composition (/ wt.% )

99.95

99.95

99.00

Density –3 (ρ/kg.m )

93.7Ni-4.75Mn

8890

8890

8890

8890

8890

Yield strength 0.2% proof (σYS/MPa)

99.6

n.a.

60–110

150

240

90

Ultimate tensile strength (σUTS/MPa) n.a.

310–345

400

530

345

403

462

n.a.

50

40

40

45

50

47

Elongation (Z/%)

103

n.a.

85

100

n.a.

80

129

109

Brinell hardness (/HB)

148

13.3

13.3

13.3

13.3

13.3

13.1

13.3

Coeff. linear thermal expansion –6 –1 (a/10 K )

8890

n.a.

86

n.a.

44.7

75.0

79.3

74.9

Thermal conductivity –1 –1 (k/W.m .K )

8890

n.a.

460

n.a.

532

456

456

456

Specific heat capacity –1 –1 (cP/J.kg .K )

99.6

n.a.

7.5

n.a.

16.9

9.5

8.5

9.5

Electrical resistivity (ρ/μΩ.cm)

99.5

Nickel and Nickel Alloys 131

Ferrous Metals and Their Alloys

2

N08031 32Fe-31Ni-27Cr-6.5Mo

N08904 25Ni-21Cr-4.5Mo-2Mn-1Si

N08366 24Ni-21Cr-6.5Mo-2Mn-1Si

N08367 24Ni-21Cr-3.5Mo-2Mn-1Si

N08024 38Ni-32Fe-24Cr-4Mo-1Cu

N13017 54.8Ni-15Cr-17Co-5.3Mo-4Al3.5Ti

N08020 35Ni-38Fe-20Cr-3Cu-2Mo-1Nb W88021

N08026 46Fe-35Ni-24Cr-6Mo-3Cu

N08925 20Ni-25Cr-6.5Mo-2Mn-1Si-1Cu

N03301 94Ni-4.5Al-0.5Ti

N10001 64Ni-28Mo-1Cr-5Fe-1Si W80001

Common and trade name

Alloy 904L

AL-6X

AL-6XN

Alloy® 20Mo-4

Astroloy® M

Carpenter® 20Cb-3

Carpenter® 20Mo-6

Cronifer® 1025

Duranickel® 301

Hastelloy® B

Class

Average chemical composition (/ wt.% )

Hastelloy® B3 N10675 65Ni-28.5Mo-3Co-3W-3Mn-1.5Fe- Ni-Mo alloys 1.5Cr-05Al-0.2Ti-0.1Si

Ni-Mo alloys

Ni-Mo alloys

Low alloy

Fe-Ni-Cr alloys

Fe-Ni-Cr alloys

Fe-Ni-Cr alloys

Ni-Cr alloys

Fe-Ni-Cr alloys

–3

Fe-Ni-Cr alloys

Density (ρ/kg.m ) n.a.

186

n.a.

n.a.

186

n.a.

217

n.a.

9220 1370– 216 1418

9220

9240 n.a.

8250 1400– 207 1440

n.a.

8133

8080

7910

8106

n.a.

600– 980

655– 1170

600

607

550– 655

1410

615

715

400

885

3 914– 96–526 955

n.a.

207– 862

300

275

240– 414

1050

262

315

515

180

n.a.

n.a.

184

n.a.

155

n.a.

100–230

57.8

n.a.

53–55 235

Co + 2Cl + H2(g)

Sulfuric acid (H2SO4)

Dil. hot

Co + 2H2SO4 —> Co + SO4 + 2H2O

Nitric acid (HNO3)

Dil.

3Co + 8HNO3 —> 3Co + 6NO3 + 2NO(g) + 4H2O

Conc.

0

2+

0 0

2–

2+

+

–

3Co + 16HNO3 + 16H —> Co3O4(surface) + 8NO2(g) + 8H2O

Dissolves slowly Dissolves slowly Dissolves readily Dissolve extremely slowly due to passivation by Co3O4

it retains its strength to a high temperature, which explains its uses in cutting tools, superalloys, surface coating, high-speed steels, cemented carbides, and diamond tooling. Molten cobalt vaporizes at 3100°C. The electronic structure of the ground state of the atom 7 2 2+ [Ar]3d 4s leads to cobalt’s commonest valency, i.e., Co , by removal of the two 4s electrons. Other valencies exist, however, in some complex salts, and mixed valencies occur in Co3O4, 2+ 3+ for example (Co and Co ). The major reactions of cobalt metal with most common acids are summarized in Table 2.40. Cobalt imparts to silicate melts intense blue colors used in glassmaking, glazes, and enamels. From a biological point of view, cobalt is one of the world's essential elements. Actually, as one of the 27 elements that are essential to humans, cobalt occupies an important role as the central component of cyanocobalamine (vitamin B12). Industrially, two grades of commercially pure cobalt are available on the market: (i) cobalt (99.3 wt.% Co), used for noncritical metallurgical applications, in the chemical industry, and for permanent magnets and catalysts, while (ii) cobalt (99.8 wt.% Co) is used in rechargeable lithium ion batteries and fine chemicals. Prices (2006). Pure cobalt (99.8 wt.%) is priced US$32.19/kg (US$14.60/lb.).

2.3.2 History The use of cobalt goes back to 2000 to 3000 years before the common era (B.C.E.). Although it had not been identified, the addition of cobalt minerals to glass to impart the traditional cobalt blue color was already known. In the 16th century, the term kobold denoted malicious spirits (gnomes) who frequented mines. This term was then extensively used as a nickname in the Erzgebirge region of Saxony (i.e., Schneeberg and Hartz Mountains) for certain sulfide ores that were difficult to smelt. Actually, these regions were important silver mining areas, and when smelting failed to yield copper or silver and emitted noxious arsenic trioxide fumes during roasting, causing some respiratory problems with the miners, these issues were all attributed to kobolt. The calcined obtained and mixed with silica sand was called zaffre. The fusion of zaffre with potash (K2CO3), or ground soda glass, produced a potash or soda silica glass with blue color called smalt. The blue color obtained was first attributed erroneously by alchemists to arsenic and bismuth. Cobalt metal was first isolated by the Swedish chemist Georg Brandt in 1735. However, the main use of cobalt remained as a coloring agent until the 20th century, and in fact, before World War I, cobalt was really only available or used as an oxide. Its modern uses arose with the work of Elwood Haynes on cobaltchromium-tungsten wear-resistant alloys first commercialized under the tradename Stellite®, and later with the development of Alnico® magnets in Japan and the use of cobalt metal as a binder for tungsten-carbide particles in hardmetal (WC-Co) in Germany.

Cobalt and Cobalt Alloys

143

2.3.3 Natural Occurrence, Minerals and Ores Cobalt is not a particularly rare chemical element, with an abundance in the Earth’s crust of 25 mg/kg, which places it together with lithium and niobium. It is, however, widely scattered in rocks but is found in potentially exploitable quantities in several countries (Table 2.41). Significant sources of cobalt also exist in the deep-sea polymetallic nodules and crusts that occur in the midocean ridges in the Pacific and are estimated to contain anywhere from 2.5 to 10 million tonnes of cobalt. According to the U.S. Geological Survey, in 2004 world ressources were ca. 15 million tonnes. The main cobalt minerals are sulfides and sulfosalts and, to a lesser extent, oxidized compounds such as oxides, carbonates, and sulfates. As a sulfide, cobalt occurs combined with copper in carrolite [CuCo2S4, cubic], which is found in the Democratic Republic of Congo and Tanzania, and with nickel in siegenite [(Ni,Co)3S4, cubic], which is found in cobaltiferrous ore deposits near Frederictown in the Southern Missouri lead district. Cobalt occurs alone as sulfide in linnaeite [Co3S4, cubic], which is found in the Democratic Republic of Congo, or in the Mississipi Valley Pb-Zn deposits. The cobalt arsenides such as safflorite [CoAs2, orthorhombic] are found in North America, in Morocco, and in other parts of the world, while skutterudite [CoAs3, cubic] is found in Morocco. Sulfoarsenides such as cobaltite [CoAsS, orthorhombic] are found in Canada in the Cobalt district of Ontario, in the Blackbird region of Idaho, in Australia, in Myanmar, and in other localities worldwide. Oxidized cobalt minerals include asbolane [(Ni,Co)xMn(O,OH)4.nH2O, hexagonal], which is found in lateritic nickel ore Table 2.41. Cobalt-producing countries (2004) Country

Production (tonnes)

Australia

4000

Botswana

Unknown

Brazil

1000

Belgium

1200

Canada

4000

China

5500

Cuba

Unknown

France

180

Finland

8000

India

260

Japan

350

Morocco

1200

New Caledonia Norway

4500

Russia

4500

South Africa

250

Uganda DRC

1200

Zambia

6500

Total =

43,000

Source: The Cobalt Development Institute (CDI)

2 Ferrous Metals and Their Alloys

144

Ferrous Metals and Their Alloys

deposits such as those of New Caledonia, the heterogeneite [CoO(OH), hexagonal], which is the principal mineral of the Democratic Republic of Congo, and finally as sulfates in bieberite [CoSO4.7H2O, monoclinic]. Primary cobalt is only extracted alone from arsenide ores found in Morocco, Canada, and Idaho, but usually primary cobalt is extracted as a byproduct during the processing of nickel and copper ores and, to a lesser extent, from the 12 processing of zinc ores (e.g., India) and precious metals . In 2003, about 44% of world production came from nickel ores (i.e., laterites and sulfides). Secondary sources of cobalt metal are from metallic products reentering the cobalt cycle such as turnings from the machining of cobalt-based superalloys, spent catalysts, spent samarium-cobalt magnets, and finally used hardmetal cutting tools (i.e., cemented carbides). In 2004, according to the Cobalt Development Institute, ca. 50,000 tonnes of cobalt metal were produced worldwide. In 2005, the major companies producing cobalt worldwide were, in order of decreasing annual production capacity, the 100 Chinese producers (12,700 tonnes), the American producer OMG (8164 tonnes) and the Canadian producer Vale Inco (6350 tonnes), Norilsk Nickel (4990 tonnes) in Russia, and finally Chambashi Metals (3630 tonnes) in Zambia.

2.3.4 Processing and Industrial Preparation 2.3.4.1 Cobalt as a Byproduct of Nickel Processing Cobalt can be recovered from nickel-sulfide concentrates or nickel matte by the SherrittGordon ammonia leaching process in Fort Saskatchewan, Alberta, Canada, and it is also recovered from sulfuric-acid pressure leaching of laterites. In both cases, cobalt is obtained in nickel-free liquor by reduction with hydrogen under elevated pressure and temperature (Section 2.2).

2.3.4.2 Electrowinning of Cobalt Table 2.42. Electrowinning of cobalt metal Parameters

Value

Anode material

Pb-Ca-Sn

Cathode materials

Stainless steel 316L

Diaphragm

Undivided cell

Electrolyte composition

Co 45 g/L pH = 3.7

Operating temperature

55–58°C

Total current

13 kA

Current density

0.5 kA.m

2+

–2

Cell voltage Faradic efficiency

85

Specific energy consumption 6.5 kWh/kg

12

Hawkins, M.L. (1998) Recovering cobalt from primary and secondary sources. J. Mater., 50(10), 46–50.

Cobalt and Cobalt Alloys

145

2.3.5 Properties of Cobalt Alloys and Superalloys Superalloys are usually defined as heat- and oxidation-resistant alloys specially developed for servicing at elevated temperatures under both oxidizing atmosphere and severe mechanical stresses. Three main classes of superalloys are distinguished: (i) iron-based superalloys (Section 2.1.17); (ii) nickel-based superalloys (Section 2.2.6); (iii) cobalt-based superalloys, discussed here. Historically, the development of cobalt-based superalloys has been driven by the jet engine. However, their use has extended into many other fields such as all types of turbines, space vehicles, rocket engines, nuclear-power reactors, thermal power plants, and, recently, the chemical-process industry (CPI), where these alloys are used especially for their hot corrosion resistance. The role of cobalt is not completely understood, but it certainly increases the useful temperature range of nickel-based alloys. Phase γ ' also occurs as γ '', which has a body-centered tetragonal structure (i.e., two stacked cubes). Cobalt is thought to raise the melting point of this phase, thereby enhancing high-temperature strength. In addition to structure, processing has been responsible for enhancing these alloys. Cobalt alloys are called austenitic because the high-temperature face-centered cubic crystal lattice is stabilized at room temperature. They are hardened by carbide precipitation; thus carbon content is a critical parameter. Chromium provides oxidation resistance, while other refractory metals are added to give solid-solution strengthening (e.g., tungsten and molybdenum) and to promote the formation of carbide (e.g., tantalum, niobium, zirconium, and hafnium). Because oxygen content is deleterious, the processing of cobalt alloys requires melting in a vacuum. Moreover, tight specifications make it necessary to prevent an excess of solidsolution metals such as W, Mo, and Cr that tend to form unwanted and deleterious phases similar to the nickel alloys and Laves phases (Co3Ti). Cobalt alloys obtained by powder metallurgy exhibit a finer carbide dispersion and a smaller grain size and hence have superior properties to cast alloys. Further process development by hot isostatic pressing (HIP) has even further improved the properties by removal of possible failure sites. Compared to nickel alloys, the stress rupture curve for cobalt alloys is flatter and shows lower strength up to about 930°C, which is explained by the greater stability of the carbides. This factor is the primary reason for using cobalt alloys in the lower-stress, higher-temperature stationary regime for gas turbines. Casting is important for cobalt-based superalloys, and directionally solidified alloys have led to increased rupture strength and thermal fatigue resistance. Even further improvements in strength and temperature resistance have been achieved by the development of single-crystal alloys. Both these trends have allowed the development of higher-thrust jet engines, which operate at even higher temperatures. The cast and wrought cobalt superalloys, despite the better properties of the γ '-hardened nickel-based alloys, continue to be used for the following reasons: (i)

Cobalt alloys are more heat resistant than nickel- or iron-based superalloys owing to their higher liquidus temperature. (ii) They have a higher chromium content, which leads to a superior oxidation resistance to the harsh atmosphere found in gas turbine operations. (iii) Cobalt superalloys show superior thermal fatigue resistance and weldability over nickel alloys. The physical, mechanical, thermal, and electrical properties of selected commercial cobalt alloys (mainly stellites) are listed in Table 2.43.

2 Ferrous Metals and Their Alloys

Average chemical composition (/wt.% )

R30035

MP35N

Co-35Ni-20Cr-10Mo-1Ti-1Fe

Co-22.5Cr-10Ni-7W-3.5Ta-1.5Fe-1Mo-0.6C-0.4Si0.1Mn

n.a.

MAR-M509

–3

58Co-30Cr-4W-3Fe-2.5Ni-1.5Mn-1Mo-1.1C-0.7Si

Density (ρ/kg.m ) 8430

8860

8390

9130

8980

Yield strength 0.2% proof (σYS/MPa)

n.a.

380–414

585

619–635

445

465

558

Ultimate tensile strength (σUTS/MPa)

39Co-22Ni-22Cr-14W-3Fe-1.25Mn-0.35Si-0.1C0.03La

62

53

33

895–931

780

6.5–7

3.5

998–1005 11

970

945

1020

Elongation (Z/%)

51Co-20Cr-15W-10Ni-3Fe-1.5Mn-1Si-0.1C

R30188

Haynes® 188

Rockwell hardness C (/HRC) (as cast)

n.a.

n.a.

Common and trade name

Haynes® 1233

1265–1354

1329–1410

1302–1330

1333–1335

90

1315–1440

23–34 1290–1400

37

22

98

28

Melting point or liquidus range (/°C) 1495

11.2

8.8

14.8

9.8

10.4

n.a.

96

–1

65

Thermal conductivity (k/W.m .K )

10–25

–1

n.a.

n.a.

n.a.

n.a.

403

n.a.

427

–1

944

Specific heat capacity (cP/J.kg .K )

758

–1

12.8

n.a.

14.1

12.3

11.9

n.a.

12.5

–1

8900

–6

99.9Co

Coef. linear thermal expansion (a/10 K )

Haynes® 6B

n.a.

103

100

91

88.6

101

n.a.

6.34

Electrical resistivity (ρ//μΩ.cm)

Haynes® 25 (L605) R30605

UNS

Cobalt

Table 2.43. Properties of selected cobalt-based alloys

146 Ferrous Metals and Their Alloys

R0003

R30004

R30006

R30007

R30008

R30012

R30012

R30020

R30021

R30100

R30306

R30040

n.a.

n.a.

n.a.

n.a.

n.a.

Stellite® 3

Stellite® 4

Stellite® 6

Stellite® 7

Stellite® 8

Stellite® 12

Stellite® 12P

Stellite® 20

Stellite® 21

Stellite® 100

Stellite® 306

Stellite® X-40

Stellite® SF1

Stellite® SF6

Stellite® SF12

Stellite® SF20

Tantung G

Co-30Cr-16.5W-7Ni-5Fe-4.5(Nb+Ta)-3Mn-3C

Co-19Cr-15W-13Ni-3Si-3B-1.5C

Co-19Cr-13Ni-9W-2.5Si-1.5B-1C

Co-19Cr-13Ni-8W-2.5Si-1.5B-1C

Co-19Cr-13Ni-13W-3Si-2.5B-1C

Co-25Cr-10Ni-7W-0.3C

Co-25Cr-6Nb-5Ni-2W-0.4C

Co-34Cr-19W-2C

Co-28Cr-5.5Mo-2.5Ni-2Fe-2Si-1Mn-0.25C

Co-33Cr-18W-2.5C

Co-31Cr-9W-3Ni-3Fe-2Si-1.4C-1Mo-1Mn

Co-29Cr-8.3W-3Ni-3Fe-2Si-1.8C-1Mo-1Mn

Co-30Cr-6Mo-0.2C

Co-26Cr-6W-0.4C

Co-28Cr-4.5W-3Ni-3Fe-2Si-1.2C-1Mo-1Mn

Co-30Cr-14W-3Ni-3Fe-2Si-1Mo-1Mn-0.57C

Co-30Cr-13W-3Ni-3Fe-2.4C-2Si-1Mo-1Mn

Co-31Cr-12.5W-3Ni-3Fe-2.4C-2Si-1Mo-1Mn

8300

8350

8350

8320

8230

8610

n.a.

8690

8340

9000

8560

8630

8100

8130

8460

8600

8640

8690

n.a.

n.a.

n.a.

373

n.a.

431

n.a.

432

494

618

618

647

490

461

541

618

n.a.

585–620

n.a.

n.a.

627

n.a.

735

n.a.

n.a.

694

n.a.

883

834

932

932

896

1010

618

618

n.a.

n.a.

n.a.

n.a.

n.a.

10

n.a.

Mn

0

(main cathodic reaction),

–

–

2H2O + 2e —> H2 + 2OH

(side reaction),

while at the anode the evolution of oxygen occurs: +

2H2O —> O2 + 4H + 4e 2+

–

Mn + O2 —> MnO2 + 2e

(main anodic reaction), –

(parasitic reaction).

The performances of the electrolyzer are listed in Table 2.49. Once electrodeposited, the 2-mm-thick manganese plates are stripped from the base metal substrate by mechanical shock due to the brittlness of the alpha-manganese deposit. The removed metal flakes are washed and dried. The absorbed hydrogen is removed by heating under inert atmosphere to produce pure manganese metal with a low interstitial oxygen content. Approximately 150,000 tonnes of electrolytic manganese metal were produced in 2004.

Manganese and Manganese-Based Alloys

155

Table 2.49. Electrowinning of manganese metal Parameters

Value

Anode material

Pb-Ag or Pb-Ca, DSA-IrO2

Cathode materials

Stainless steel or titanium

Diaphragm

Polymer fabric

Electrolyte composition

MnSO4 4wt.% (NH4)2SO4 13 wt.% SO2 or SeO2 pH = 7.0 Smoothing additives

Operating temperature

35–45°C

Anodic current density

1 kA.m

Cathodic current density

0.5 kA.m

Cell voltage

5 V to 7 V

Faradic efficiency

42–62 %

2 Ferrous Metals and Their Alloys

–2 –2

Specific energy consumption 9–12 kWh/kg

Table 2.50. Electrolytic manganese grades (ASTM B 601) ASTM grades UNS

wt.% Mn wt.% S

H

N

Grade A

M29450 99.5

0.030 max 0.015

–

Grade B

M29952 99.5

0.030 max 0.005

–

Grade C

M29953 99.5

0.030 max 0.0001 –

Grade D

M29450 94–95

0.035 max –

4.0–5.4

Grade E

M29350 93–94

0.035 max –

5.5–6.5

Grade F

M29954 99.5

0.035 max 0.0030 –

The major producers of electrolytic manganese worlwide are Erachem Comilog and KerrMcGee Chemical in the United States, the Manganese Metal Company (MMC) in the Republic of South Africa, and finally Mitsui Mining & Smelting and Tosoh in Japan. Electrothermal-silicothermic reduction process. In 1966, electrothermic manganese, with a purity ranging between 93 and 98 wt. % Mn, was first produced on a commercial scale in France by Péchiney. The process uses high-silicon silicomanganese to yield extremely low carbon levels. Manganese ore is smelted in an electric arc furnace (EAF with silicomanganese as reductant. This slagging process produces a low-grade ferromanganese with a high phosphorus content.

2.4.4.3 Ferromanganese and Silicomanganese Ferromanganese (Fe-Mn-C). The extractive metallurgy of manganese is very similar to ironmaking except that a higher temperature, over 1200°C, is required for the carbothermic reduction of manganese dioxide. Standard or high-carbon ferromanganese, which is to manganese what pig iron is to iron, is a very commonly used alloy. It contains more than 76 wt.% Mn and various levels of carbon content (i.e., high carbon ca. 7.5 wt.% C, medium carbon 1 to 1.5 wt.% C, and low carbon Ca + 2e

Cd

Cd —> Cd + 2e

0

2+

0

2+

–

–

Fe

Fe —> Fe + 2e

H2(g)

H2(g) —> 2H + 2e

+

0

+

–

Li

Li —> Li + e

Mg

Mg —> Mg + 2e

Na

Na —> Na + e

0

–

2+

–

–

3,4,5

Density –3 (kg.m )

Eq Eq –1 –3 (Ahkg ) (Ahdm )

–1.676

26.981538

2699

2980

8043

–2.840

40.078

1550

1337

2073

–0.403

112.411

8650

477

4125

–0.440

55.845

7874

960

7558

0.000

2.01594

0.084

26,590

2234

–3.040

6.941

534

3861

2062

–2.356

24.3050

1738

2205

3833

–2.713

22.989770

971

1166

1132

0

+

0

2+

–

–0.126

207.2

11,350

259

2936

0

2+

–

–0.760

65.409

7133

820

5846

+0.7991

231.7358

7200

231

1665

+1.772

123.8676

7500

433

3246

+1.360

70.906

2948

756

2229

+0.926

216.5894

11,140

248

2757

+0.5356

253.80894

4933

212

1045

+0.950

86.936849

5080

308

1566

+0.490

91.70017

7400

292

2160

+1.229

31.9988

1330

3350

4456

+1.460

239.1988

9640

224

2160

n.a.

64.0638

1370

419

n.a.

n.a.

118.9704

1631

901

1470

1.000

181.880

3350

147

494

Pb

Pb —> Pb + 2e

Zn

Zn —> Zn + 2e

Ag2O

Ag + e —> Ag

+

–

+

0

–

0

AgO

AgO + 2H + e —> Ag + H2O

Cl2(g)

Cl2+ 2e —> 2Cl

–

+

–

–

0

HgO

HgO+ 2H + 2e —> Hg + H2O

I2(s)

I2(s) + 2e —> 2I

MnO2

MnO2 + 4H + e –> Mn + 2H2O

–

–

+

–

3+

+

–

NiOOH

2NiOOH + 2H + 2e –> 2Ni(OH)2

O2(g)

O2+ 4H + 4e —> 2H2O

+

–

+

–

2+

PbO2

PbO2 + 4H + 2e –> Pb + H2O

SO2(l)

2SO2 + 2e —> S2O4

–

2–

–

SOCl2(l) 2SOCl2 + 4e —> S + SO2 + 4Cl V2O5

2

E 298 Mr 12 (V/SHE) ( C = 12)

+

+

–

2+

–

VO2 + 2H + e —> VO + H2O

where n is the number of electrons required to oxidize or reduce the electrode material, F the –1 Faraday constant 96,485.309 C.mol , ν the dimensionless stoichiometric coefficient of the electrochemical reduction or oxidation, and M the atomic or molecular mass of the electrode –1 –1 material in kg.mol (g.mol ). Sometimes the electrochemical equivalence per unit volume is –3 used, and it is expressed as the electric charge stored per unit volume of material (Ah.m ); in this particular case, it can be calculated multiplying the specific electrochemical equivalence by the density of the electrode material. In addition, in primary and rechargeable batteries, apart from the two previous scientific parameters, several technological requirements must be considered when selecting the most appropriate electrode. These requirements are high electrical conductivity, chemical inertness, 2

3

4

5

Standard relative atomic masses from: Loss, R.D. (2003) Atomic Weights of the Elements 2001. Pure Appl. Chem., 75(8), 1107–1111. Densities of pure elements from: Cardarelli, F. (2001) Materials Handbook. A Concise Desktop Reference. Springer, Berlin Heidelberg New York. Densities of inorganic compounds from: Lide, D.R. (ed.) (1997–1998) CRC Handbook of Chemistry and Physics, 78th ed. CRC Press, Boca Raton, FL, pp. 4–35 to 4–9. Densities for ideal gases calculated with equatiοn ρ = PM/RT at 293.15 K and 101.325 kP.

Electrode Materials

559

ease of fabrication, involvement of nonstrategic materials, low cost, and finally commercial availability. As a general rule, metals and alloys represent the major anode materials in batteries, except for the particular case of hydrogen in fuel cells, while metallic oxides, hydroxides, chlorides, and sulfides represent the major anodic materials, except oxygen, in fuel cells.

9.7.2 Intercalation Compounds Insertion, also called intercalation, is a topotactic reaction that consists of the insertion of a species, atom, or molecule inside the interstitial crystal lattice of a solid host material, with or without charge transfer. Historically, the first intercalation compounds were the graphites (1841) for which the intercalation of cations of alkali metals occurred between the graphene lamellar planes and the hydrogen/palladium system (1866). Later, in 1959, the phenomenon was recorded in lamellar dichalcogenides and since the 1970s hundreds of new compounds have been reported, several of them now being used in rechargeable batteries such as Ni-MH or lithium batteries. In the particular case of lithiation or delithiation of cathode materials used in lithium secondary batteries, the calculation of the electrochemical equivalent involves an additional parameter related to the reaction of intercalation of lithium cations into the crystal lattice of the host cathode materials. Consider the theoretical reversible reaction of intercalation of lithium into a crystal lattice of a solid host material (e.g., oxide, sulfide): +

–

xLi + yM + xe LixMy + with Li lithium cations, M solid host cathode material, x,y dimensionless stoichiometric coefficients, x dimensionless number of electrons exchanged. Hence during the lithiation reaction (i.e., charge), x moles of lithium cations are reduced and intercalated into y moles of the solid host material, and a quantity of electricity, xF, must be supplied to the cell. Conversely, during delithiation (i.e., discharge), x moles of lithium cations are produced and a quantity of electricity, xF, is supplied to the external circuit of the cell. Therefore, the quantity of electricity, Q, expressed in coulombs (Ah), delivered following the deintercalation of lithium from a mass, mM, of the solid host material or a mass, mLixMy, of the final intercalated compound is given by the two following relations: Q = mM . (xF/yMM) = mLixMy . (xF/MLixMy), with mM mass of the solid host material, in kg, mLixMy mass of the intercalated compound, in kg, x, y dimensionless stoichiometric coefficients, –1 molar mass of the solid host materials, in kg.mol , MM –1 MLixMy molar mass of the intercalated compounds, in kg.mol , x dimensionless number of electrons exchanged, –1 F Faraday constant F = 96,485.309 C.mol . From the above equation it is possible to define two types of electrochemical equivalents. The first electrochemical equivalent, denoted Eq(M), is the quantity of electricity consumed per unit mass of the solid host material, M, during the lithiation reaction (i.e., charging) and is defined by the following equation: Eq(M) = xF/yMM.

9 Miscellaneous Electrical Materials

560

Miscellaneous Electrical Materials

Table 9.13. Electrochemical equivalents of solid host materials and intercalated compounds for rechargeable lithium batteries Host Insertion reaction cathode (lithiation/delithiation) material +

–

C

Li + 6C + e LiC6

FeS2

Li + FeS2 + e LiFeS2

FePO4

Li + FePO4 + e LiFePO4

Li1.2V3O8

2.8Li + Li1.2V3O8 + 2.8e Li4V3O8

+

+

+

–

–

Li0.5NiO2

0.5Li + Li0.5NiO2 + 0.5e LiNiO2

Li4Ti5O12

3Li + Li4Ti5O12 + 3e Li7Ti5O12

MnO2

0.7Li + MnO2 + 0.7e Li0.7MnO2

MoS2

0.8Li + MoS2 + 0.8e Li0.8MoS2

TiS2

Li + TiS2 + e LiTiS2

V2O5

1.2Li + V2O5 + 1.2e Li1.2V2O5

VOx

2.5Li + VOx + 2.5e Li2.5VOx

WO2

339

372

126.9180 5020 119.9770

211

223

157.7574 150.8164

167

178

308.5837 289.1489

243

260

3.7

97.8730 94.4025

137

142

3.5

97.6332 94.1627

137

142

1.5

484.9148 464.0918

167

173

3.0

91.7956 86.9369

5080

204

216

1.7

165.6248 5060 160.0720

130

134

2.1

118.940 112.999

3370

225

237

2.8

190.2092 3350 181.8800

170

177

222.7798 10,800 215.8388

120

124

–

Li0.5CoO2 0.5Li + Li0.5CoO2 + 0.5e LiCoO2

+

–

+

+

+

–

–

–

+

+

–

–

–

Li + WO2 + e LiWO2

7

Density Eq (LixMy) Eq(M) Em –3 –1 –1 –3 (kg.m ) (Ahkg ) (Ahkg ) (Wh.kg ) (M) 2200

–

+

6

79.0070 12.011

–

+

+

0

E 298 Mr + (V/Li ) (LixMy) (M)

2.3

The second electrochemical equivalent, denoted Eq(LixMy), is the quantity of electricity released per unit mass of the intercalated compound, LixMy, during the delithiation reaction (i.e., discharging) and is defined by the following equation: Eq(LixMy) = xF/MLixMy. The two electrochemical equivalents of some selected solid host cathode materials and corresponding intercalated compounds used in rechargeable lithium batteries are presented in Table 9.13.

6

7

Standard relative atomic masses from: Loss, R.D. (2003) Atomic Weights of the Elements 2001. Pure Appl. Chem., 75(8), 1107–1111. Densities taken from: Lide, D.R. (ed.) (1998–1999) CRC Handbook of Chemistry and Physics, 78th ed. CRC Press, Boca Raton, FL, pp. 4–35 to 4–9.

Electrode Materials

561

9.7.3 Electrode Materials for Electrolytic Cells Today, in modern the chemical process industry, electrochemistry occupies an important 8 place. Electrochemical processes are actually widely used in the inorganic syntheses. Actually, it is the only method for preparing and recovering several pure elements (e.g., alumi9 num, magnesium, alkali and alkali-earth metals, chlorine, and fluorine). Furthermore, it occupies an important place in hydrometallurgy for electrowinning and electrorefining 10,11 metals of groups IB (e.g., Cu, Ag, Au), IIB (e.g., Zn, Cd), and IVA (e.g., Sn, Pb). In addition, its development also concerns organic synthesis, where some processes reach industrial 12 scale (e.g., Monsanto, Nalco, and Philips processes). Apart from electrochemical processes for preparing inorganic and organic compounds, other electrolytic processes are also used in 13 various fields: in extractive hydrometallurgy (e.g., the electrolytic recovery of zinc ), in zinc 14 electroplating (e.g., high-speed electrogalvanizing of steel plates ), in electrodialysis (e.g., the salt-splitting regeneration of sulfuric acid and sodium hydroxide from sodium sulfate 15,16 waste brines, the regeneration of the leaching solutions of uranium ores, the electrolytic 17 regeneration of spent pickling solutions ), and finally in processes for a cleaner environment, where electrochemistry is used to achieve the electrooxidation of organic pollutants (i.e., electrolytic mineralization or electroincineration), and in the removal of hazardous 18 metal cations from liquid wastes effluents. 19 Electrochemical processes are performed in an electrolytic cell (i.e., electrolyser). The electrolyzer is a reactor vessel, filled with an electrolytic bath or electrolyte, in which the electrodes are immersed and electrically connected via busbars to a power supply. When the electrolyzer is split into two compartments by a separator (e.g., diaphragm, membrane), the electrolyte has two different compositions (i.e., anolyte and catholyte). The electrodes are the main parts of an electrolyzer and consist of the anode (i.e., positive, +) where the oxidation reaction occurs, while at the cathode (i.e., negative, –) a reduction takes place. Among the several issues encountered by engineers for designing an industrial electrochemical reactor, one of them consists in reducing the specific electric energy consumption (i.e., electric energy per unit mass of product). The specific energy consumption can be minimized in two ways: increasing the current efficiency and lowering the operating cell voltage. Other issues for 20,21,22 designing electrochemical cells are discussed in more detail elsewhere in the literature. 8

9 10 11

12

13

14 15

16

17

18

19 20 21

Srinivasan, V.; Lipp, L. (2003) Report on the electrolytic industries for the year 2002. J. Electrochem. Soc., 150(12), K15–38. Pletcher, D.; Walsh, F.C. (1990) Industrial Electrochemistry, 2nd ed. Chapman & Hall, London. Kuhn, A.T. (1977) Electrochemistry of Lead. Academic, London. Gonzalez-Dominguez, J.A.; Peters, E.; Dreisinger, D.B. (1991) The refining of lead by the Betts process. J. Appl. Electrochem., 21(3), 189–202. Baizer, M.M.; Lund, H. (1983) Organic Electrochemistry: An Introduction and a Guide, 2nd ed. Marcel Dekker, New York. Karavasteva, M.; Karaivanov, St. (1993) Electrowinning of zinc at high current density in the presence of some surfactants. J. Appl. Electrochem., 23(7), 763–765. Hardee, K.L.; Mitchell, L.K.; Rudd, E.D. (1989) Plat. Surf. Finish., 76(4), 68. Thompson, J.; Genders, D. (1992) Process for producing sodium hydroxide and ammonium sulfate from sodium sulfate. US Patent 5,098,532; March 24, 1992. Pletcher, D.; Genders, J.D.; Weinberg, N.L.; Spiegel, E.F. (1993) Electrochemical methods for production of alkali metal hydroxides without the co-production of chlorine. US Patent 5,246,551; September 21, 1993. Schneider, L. (1995) Process and apparatus for regenerating an aqueous solution containing metal ions and sulfuric acid. US Patent 5,478,448; December 26, 1995. Genders, D.; Weinberg, N.L. (eds.) (1992) Electrochemistry for a Cleaner Environment. Electrosynthesis Co., Lancaster, NY. Wendt, S.; Kreysa, G. (1999) Electrochemical Engineering. Springer, Berlin Heidelberg New York. Pickett, D.J. (1979) Electrochemical Reactor Design. Elsevier, Amsterdam. Rousar, I.; Micka, K.; Kimla, A. (1985) Electrochemical Engineering, Vols. 1 and 2. Elsevier, Amsterdam.

9 Miscellaneous Electrical Materials

562

Miscellaneous Electrical Materials

The overall cell voltage at a given current density, Ucell, can be classically described as the following algebraic sum: ΔUcell = ∑k(Ea,th – Ec,th) + ∑k(ηa,k – ηc,k) + i∑kRk + ΔUt = ΔUth + Δη + iRtot+ ΔUt,

where the first term corresponds to the Nernstian theoretical or thermodynamic cell voltage and consists of the algebraic difference between the thermodynamic potentials of the anode and cathode respectively (i.e., Nernst electrode potentials), the second term is the summation of all the electrode overpotentials (e.g., activation, concentration, passivation, etc.), the third term is the summation of all the ohmic drops (e.g., electrolytes, both anolyte and catholyte, separators, connectors, and busbars), and finally cell potential drift is due to the aging of electrodes (e.g., corrosion, deactivation, and passivation) and/or separator materials (e.g., fooling, degradation, and swelling). 23 Hence, the operating cell voltage could be reduced In several ways. First, an appropriate counter electrode reaction minimizes the reversible cell voltage. Second, a narrow interelectrode gap and electrode-membrane gap in association with a highly conductive electrolyte and separator and highly conductive metals for busbars, feeders, and connectors diminish the overall ohmic drop. Third, turbulent promoters should be used to enhance convection and hence the mass transfer coefficient in order to reduce the concentration overpotential. Finally, the activation overpotential could be reduced by using an efficient and appropriate electrocatalyst. The selection of a catalyst is an important problem to solve, particularly in the case of oxygen or chlorine anodes. For theoretical aspects of electrocatalysis, they are 24 reviewed extensively in more detail by Trasatti. Indeed, because of the complex behavior of electrodes, the selection of an electrocatalyst for a given process cannot be made simply on the basis of electrochemical kinetic considerations (i.e., exchange current density, Tafel slopes). An experimental approach is compulsory. Actually, the prediction of an electrode’s service life requires real standardized tests (i.e., accelerated service-life tests). For the practicing engineer, several scientific and technical criteria must be considered when selecting an appropriate electrode material. Therefore, electrode materials must exhibit the following requirements: (i) (ii) (iii)

(iv) (v) (vi) (vii)

high exchange current density (jo) and a good electron transfer coefficient (α or β ) for the selected electrochemical reaction to decrease activation overpotential; good electronic conductivity to decrease the ohmic drop and the Joule’s heating; good corrosion resistance to both chemical and electrochemical reactions, combined with no passivating and blistering behavior, leading to abnormal electrode degradation and consumption; a good set of mechanical properties suited for industrial use (i.e., low density, high tensile strength, stiffness); ease of fabrication (i.e., machining, joining, and cleaning) allowing one to obtain clean and intricate shapes; low cost combined with commercial availability and a wide variety of products (e.g., rod, sheet, expanded metal); nonhazardous, nontoxic, and environmentally friendly material.

It is important to note that the combination of criteria (3) and (4) is essential for the dimensional stability of an electrode and its service life. 22 23

24

Hine, F. (1985) Electrode Processes and Electrochemical Engineering. Plenum, New York. Couper, A.M.; Pletcher, D.; Walsh, F.C. (1990) Electrode materials for electrosynthesis. Chem. Rev., 90(5), 837−865. Trasatti, S. In: Lipkowski, J.; Ross, P.N. (eds.) (1994) The Electrochemistry of Novel Materials. VCH, New York, Chap. 5, pp. 207–295.

Electrode Materials

563

9.7.3.1 Industrial Cathode Materials Generally speaking, the selection of a cathode material is easier for the electrochemist or the electrochemical engineer than selecting an anode material. Actually, given that the most important factor in selecting a cathode material is the overpotential for the evolution of hydrogen, there exists a wide range of electronically conductive materials with the desired overpotential for both acid and alkaline electrolytes. For instance, some metals exhibit a high overpotential (e.g., Cd, Pb, Hg), while other materials are characterized by a low overpotential (e.g, Pt, Cu, Ag, platinized C, and Ni). The second most important factor is the stability of the cathode material toward nascent hydrogen gas evolved during the cathodic polarization of the material. Several refractory metals used as cathodes (e.g., Ti, Nb, Ta, Fe, and steels) are prone to hydrogen pickup and hence are extremely sensitive to hydrogen embrittlement, which leads to the blistering or even spalling of the metal affecting its dimensional stability. Therefore, these metals are not suited for the type of manufacturing cathodes that must be used in aqueous electrolytes.

9.7.3.1.1

Low-Carbon Steel Cathodes

Low-carbon steel exhibits a low hydrogen overpotential and a low cost and can be obtained in a wide variety of mill products. In addition, with its ease of fabrication, joining, and cleaning, it is the standard cathode material in the chlor-alkali industry in either the membrane or diaphragm processes. If cathodically polarized during shutdowns and carefully handled, it offers an unlimited service life. When the hydrogen overpotential must be decreased, Niand Co-based coatings can be applied onto it by electrochemical or thermal decomposition techniques. Sometimes a Ni-Zn or Ni-Al coating is deposited and the Zn or Al is later removed by an alkaline hot leach with 50 wt.% NaOH, leaving a Raney nickel catalyst, greatly enhancing the active surface area. Recently, noble-metal coatings, combined with the introduction of a catalyst into the electrolyte, have also been reported in the literature.

9.7.3.1.2 Aluminum Cathodes Aluminum metal and, to a lesser extent, aluminum alloys are suitable materials for manufac–3 turing industrial cathodes. Actually, pure aluminum metal exhibits a low density (2690 kg.m ) –1 –1 and high thermal conductivity (237 Wm K ), is a good electrical conductor (2.6548 μΩ.cm), does not form hydride with nascent hydrogen, and passivates when polarized anodically. All these characteristics, along with a reasonable average cost of 2.734 US$/kg (for 99.7 wt.% Al), are major assets for its wide utilization especially in zinc electrowinning. Industrial applications. In zinc electrowinning, zinc is directly plated onto aluminum cathodes while oxygen is evolved at the Pb-Ag anode. Once the zinc electrodeposit reaches a desired thickness, the aluminum cathodes are removed from the cells, followed by either manually or automatically stripping the zinc deposit. On the other hand, molten aluminum is used as liquid cathode during the electrowinning of aluminum in the Hall–Heroult process. Failure modes. In zinc electrowinning, when the cathodes are lifted from the electrolyte, removed from the cells, and stripped, some corrosive sulfate electrolyte remains on the surface of the cathodes despite the water rinsing treatment. As a result, the cathodes, especially in the area close to the edges of the cathode, is corroded to a varying degree, depending on the amount and concentration of the acid in contact with the cathode. Evaporation of the electrolyte is also observed at the surface of the cathode, resulting in precipitation of insoluble zinc-sulfate salts and other impurities, causing an increase in the corrosion rate of the aluminum cathode. The overall effect of this corrosion attack can be seen on the smoothness of the aluminum cathode, i.e., patches of rough areas appear at times on the surface of the aluminum. Because of the unevenness in the surface of the cathode and of the presence of impurities, the zinc deposition process is affected resulting in the formation of rough zinc

9 Miscellaneous Electrical Materials

564

Miscellaneous Electrical Materials

deposits. Usually, these areas are seen as “puffed” sections of the deposits that, because of their closer proximity to the anode, tend to affect the current distribution in the electrolysis cell. As the zinc electrowinning process is sensitive to variations in current density, the uneven current distribution observed with puffed zinc deposits causes a decrease in the current efficiency of zinc deposition. Under these conditions, higher corrosion rates of the Pb-Ag anode are observed that result in an increase in the Pb content of the zinc deposits. Another effect of the impurities on the surface of the aluminum cathode is the formation of pinholes on the zinc deposit. This also results in lower current efficiency of zinc deposition. A known method of preventing the occurrence of puffed zinc deposits consists of mechanically or manually buffing the aluminum cathodes using metal or plastic brushes. Mechanical buffing is carried out using automated machines that apply a scrubbing action at the surface of the cathode. As a result the surface of the cathode is maintained free of deposited impurities. However, due to the presence of edge strips located at the sides and bottom of the aluminum cathode to prevent electrodeposition of zinc on the sides of the cathode and facilitate the stripping of the deposits, the mechanical buffing machines are not efficient in treating the entire surface of the cathode. Furthermore, mechanical or manual buffing of the affected cathodes does not completely remove the deposited impurities, and insoluble zinc-sulfate salts from the surface of the electrode as the treated areas become affected after about three weeks, necessitating rebuffing of the electrode. To facilitate removal of impurities and insoluble zinc-sulfate salts from an aluminum cathode used in zinc electrowinning, a chemical treatment has been developed consisting of a mild HCl cleaning and water rinsing.

9.7.3.1.3

Titanium Cathodes –3

Titanium metal is a light metal with near half the density of copper (4540 kg.m ), exhibits an excellent strength-to-density ratio allowing one to use thinner and lightweight anode plates without sacrificing the mechanical stiffness of the cathode, and has an excellent corrosion resistance to various corrosive environments. The only drawbacks of titanium are its high electrical resistivity (42 μΩ.cm) and the high cost of the mill products (e.g., sheet, plate, rods), which can reach 46 US$/kg in some cases. Titanium grades. The common titanium grades used in electroplating as cathodes are the chemically pure titanium such as ASTM grades 1 or 2, while for more demanding applications, especially when corrosion resistance to reducing acid is a requirement, titanium when alloyed with palladium (Ti-0.15Pd), like ASTM grades 7 and 11, or recently with ruthenium (Ti-0.10Ru) like ASTM grades 26 and 27, is recommended despite being more expensive than C.P. titanium. Industrial applications. Electrorefining of copper is based on the unsupported process using permanent titanium cathode plates and an associated stripping machine. Electrolytic iron is also electrodeposited from ferrous-chloride or ferrous-sulfate baths onto titanium cathodes owing to the great ease of removal of the iron plate by mechanical stripping. Usually titanium must be etched with hot 20 wt.% HCl or a cold mixture of a fluoronitric mixture (HF-HNO3) prior to performing the cathodic electrodeposition in order to remove the passivating rutile layer. 25 Failure modes. C.P. titanium metal and its alloys are susceptible to hydrogen pickup and 26 hence extremely sensitive to embrittlement by nascent hydrogen gas ; moreover in corrosive electrolytes the cathode must be polarized cathodically during shutdowns.

25 26

La Conti, A.B.; Fragala, A.R.; Boyack, J.R. (1977) ECS Meeting, Philadelphia, May 1977. Bishop, C.R.; Stern, M. (1961) Hydrogen embrittlement of tantalum in aqueous media. Corrosion, 17, 379t–385t.

Electrode Materials

565

9.7.3.1.4 Zirconium Cathodes –3

Zirconium metal (6510 kg.m ) is denser but exhibits a better corrosion resistance and is less prone to hydrogen embrittlement than titanium metal. Moreover, zirconium is highly corrosion resistant in strong alkaline solutions and has a good inertness toward organic and inorganic acids. Zirconium grades: The most common zirconium grade used in electroplating is Zircadyne® 702.

9.7.3.1.5 Nickel Cathodes Nickel, due to its immune behavior, is a strongly alkaline and especially concentrated solution of NaOH and KOH and, because it does not form hydride with hydrogen, is used extensively as a cathode in alkaline electrolytes.

9.7.3.1.6

Mercury Cathode

Mercury is the only liquid metal cathode used industrially in aqueous solutions due to its high overpotential for the evolution of hydrogen, which even allows it to electrodeposit alkali and alkali-earth metals from aqueous electrolytes, forming amalgams. For that reason, it was used extensively in the chlor-alkali industry despite being progressively phased out for both obvious health, safety, and environmental reasons. Moreover, with an average price of 580 US$ per UK flask (i.e., 76 lb.) in 2006, which corresponds to 16.8 US$/kg, it is an expensive material to use in large quantities such as those required in chlor-alkali plants. See Tables 9.14–9.16, pages 566–568.

9.7.3.2 Industrial Anode Materials Although the selection of the right material for an anode follows the same pattern as for cathode materials, this step still represents a critical issue in the final design of an industrial electrolyzer due to the particular operating conditions that anodes must withstand. Actually, historically, the failure of the anode has often led to the abandonment of some industrial processes. For instance, in aqueous solutions, a major problem arises because the anode is the electrode where the electrochemical oxidation occurs; hence the anode material must withstand harsh conditions due to both the elevated positive potential and the high acidity of the electrolyte. Moreover, traces of impurities in the electrolyte might be an additional source of corrosion and deactivation in some cases. Therefore, the material selection process must always be based on: strong knowledge of previous methods and clear understanding of the properties of the materials involved, experimental results acquired from accelerated service-life tests performed in the laboratory, and finally field tests conducted over long periods of time. The following paragraphs present the most common anode materials available industrially with a brief historical background, key properties, their techniques of preparation, their failure modes, and major industrial applications.

9 Miscellaneous Electrical Materials

Miscellaneous Electrical Materials Table 9.14. (continued) Cathode materials for hydrogen (H2) evolution in acidic media

Molarity –3 (C/mol.dm )

Temperature (T/°C)

Cathodic Tafel slope –1 (bc/mV.log10j0 )

Exchange current density decimal logarithm (log10 –2 j0/A.cm )

Absolute value of Overvoltage at 200 –2 A.m (η/mV)

Cathode material

Electrolyte composition Low hydrogen overvoltage

Extralow hydrogen overvoltage

Overvoltage range

Iridium (Ir)

H2SO4

0.5

25

30

–.2.699

30

Palladium (Pd)

HCl

1

25

30

–2.500

24

H2SO4

1

25

29

–3.200

44

HCl

1

25

29

–3.161

43

H2SO4

2

25

25

–3.200

38

Rhodium (Rh)

H2SO4

4

25

28

–3.200

42

Ruthenium

HCl

1

25

30

–4.200

75

Molybdenum (Mo)

HCl

0.1

25

104

–6.400

343

Tungsten (W)

HCl

5.0

25

110

–5.000

363

Nickel (Ni)

HCl

1.0

25

109

–5.222

384

H2SO4

1.0

25

124

–5.200

434

HCl

5.0

25

120

–5.301

432

H2SO4

1.0

25

120

–5.400

444

HCl

0.5

25

133

–5.180

425

H2SO4

0.5

25

118

–5.650

466

HCl

0.1

25

123

–5.500

468

H2SO4

1.0

25

116

–5.400

430

4.0

25

130

–6.500

624

HCl

0.1

25

120

–6.823

615

H2SO4

0.5

25

120

–7.700

720

HCl

1

25

110

–9.000

803

H2SO4

2

25

120

–8.400

804

HCl

1

25

130

–7.500

754

H2SO4

0.5

25

135

–8.200

877

Platinum (Pt)

Silver (Ag) Iron (Fe) Gold (Au)

Copper (Cu) Niobium (Nb) Titanium (Ti) High hydrogen overvoltage

566

1

25

119

–8.150

767

Tin (Sn)

H2SO4

4

25

120

–9.00

877

Zinc (Zn)

HCl

1

25

120

–10.800

1092

H2SO4

2

25

120

–10.800

1092

Cadmium (Cd)

H2SO4

0.25

25

135

–10.769

1225

Lead (Pb)

HCl

1

25

117

–12.900

1311

H2SO4

0.5

25

120

–12.700

1320

HCl

1

25

118

–12.500

1475

H2SO4

2

25

119

–12.107

1239

Mercury (Hg)

ηc = (Ec,j – Eth) = bc(log10 jeq - log10 j) = (ln10RT/βnF)log10 jeq – (ln10RT/βnF)log10 j

Electrode Materials

567

Table 9.15. Anode materials for oxygen (O2) evolution in acidic media

High oxygen overvoltage

Medium oxygen overvoltage

Low oxygen overvoltage

Over- Anode voltage material range

Electrolyte Molarity –3 compo(C/mol.dm ) sition

Temperature (T/°C)

Anodic Tafel Exchange Overvoltage –2 slope current density at 200 A.m –1 (ba/mV.log10j0 ) decimal (mV) logarithm –2 (log10 j0/A.cm )

Ta/Ta2O5-IrO2 H2SO4 30%wt.

3.73

80

52 133

–3.630 –10.21

101

Ti-Pd (Gr.7)/ H2SO4 Ta2O5-IrO2 30%wt.

3.73

80

54 164

–4.53 –8.21

153

Ti/TiO2-IrO2

H2SO4 30%wt.

3.73

80

60

–4.886

191

Ti (Gr.2)/ Ta2O5-IrO2

H2SO4 30%wt.

3.73

80

51 158

–5.82 –7.69

210

Ti/TiO2-RuO2 H2SO4 (DSA®-Cl2) CF3SO3H

1

80

66

–7.900

409

1

80

65

–8.000

410

Rutheniumiridium

H2SO4

1

80

74

–7.020

400

CF3SO3H

1

80

86

–6.630

419

Iridium (Ir)

H2SO4

1

80

85

–6.800

433

CF3SO3H

1

80

84

–6.800

428

alpha-PbO2

H2SO4

4

30

45

–15.700

630

Platinumruthenium

H2SO4

1

80

120

–7.700

710

CF3SO3H

1

80

120

–7.500

670

Platinumrhodium

H2SO4

1

25

115

–7.600

679

Rhodium (Rh)

HClO4

1

25

125

–7.520

727

Platinum (Pt)

H2SO4

1

80

90

–10.900

828

CF3SO3H

1

80

94

–9.800

762

HClO4

1

25

110

–9.000

803

Pt/MnO2

H2SO4

0.5

25

110

n.a.

n.a.

beta-PbO2

H2SO4

4

30

120

–9.200

900

PbO2

H2SO4

4

30

120

–10.000

996

Ti4O7 (Ebonex®, bare)

H2SO4

1

25

n.a.

n.a.

1800

ηa = (Ea,j – Eth) = ba(log10 j – log10 jeq) = (ln10RT/αnF)log10 j – (ln10RT/αnF)log10 jeq

9 Miscellaneous Electrical Materials

Miscellaneous Electrical Materials Table 9.16. Anode materials for chlorine (Cl2) evolution

Low chlorine overpotential

Over- Anode voltage material range (wt.%)

High chlorine overpotential

568

Electrolyte Molarity Tempera- Anodic Exchange Anodic –3 composition (C/mol.dm ) ture Tafel slope current overvoltage –1 –2 (T/°C) (ba/mV.log10j0 ) density at 5 kA.m decadic (/V) logarithm (log10 –2 j0/A.cm )

Pt30-Ir70

NaCl

Satd.

65

0.000

Ti/TiO2-RuO2SnO2 (61-31-8)

NaCl

Satd.

65

+0.020 to +0.060

Ti/TiO2-RuO2 (83-17)

NaCl

Satd.

65

+0.025 to +0.076

Ti/TiO2-RuO2 (65-35)

HCl

1

25

30

–1.409

+0.043

NaCl

5

20

108

–1.409

+0.152

Ti/Ta2O5RuO2-IrO2 (89-6-5)

NaCl

Satd

65

Ti/MnO2

NaCl

6

25

20–110

–4.000 to –2.273

+0.080 to +0.250

37

–2.8861

+0.107

+0.090

HCl

1

20

Ti/Ta2O5RuO2-IrO2 (79-11-10)

NaCl

Satd

65

Graphite

HCl

18

80

70

–4.286

+0.440

Ti/MnO2-SnO2 (56-44)

NaCl

Satd.

65

n.a.

n.a.

+0.620

Fe3O4

NaCl

5.3

25

73

–7.796

+0.569

NaCl

2

25

90

–7.796

+0.702

PbO2

NaCl

6

25

150–200

–4.174 to –4.097

+0.626 to +0.819

Platinum (Pt)

NaCl

2

85

250

–4.200

+1.050

NaCl

2

25

290

–3.700

+1.073

NaCl

5

25

305

–3.700

+1.129

+0.140

ηa = (Ea,j – Eth) = ba(log10 j – log10 jeq) = (ln10RT/αnF)log10 j – (ln10RT/αnF)log10 jeq

9.7.3.2.1 Precious- and Noble-Metal Anodes Electrochemists early on observed that noble and precious metals were stiff materials, with good tensile properties and machinability, high electronic conductivity, and exceptional 27 chemical and electrochemical inertness in most corrosive media, all combined with intrin28 sic electrocatalytic properties. Consequently, the first industrial anodes used in electrochemical processes requiring an excellent dimensional stability were made of the noble and precious metals (e.g., Au and Ag), the six platinum-group metals (PGMs) (e.g., Ru, Rh, Pd, 90 10 90 10 29 Os, Ir, and Pt), or their alloys (e.g., Pt- Ir and Pt- Rh) . Of these, the PGMs, especially platinum and iridium, occupied a particular place owing to their electrochemical inertness 27

28 29

Dreyman, E.W. (1972) Selection of anode materials. Eng. Exp. Stn. Bull. (West Virginia University), 106, 76–83. Cailleret, L.; Collardeau, E. (1894) C.R. Acad. Sci., 830. Howe, J.L. (ed.) (1949) Bibliography of the Platinum Metals 1931–1940. Baker, Newark, NJ.

Electrode Materials

569

and intrinsic electrocatalytic activity. Actually, platinum is the most appropriate anode material for the preparation of persulfates, perchlorates, and periodates and for the regeneration of cerium (IV). However, the extremely high price of the bulk metal, which reached –3 1100 US$/oz. in early 2006, combined with its density (21,450 kg.m ), has drastically restricted its industrial uses. However, early in the century there was an attempt to develop an inert anode for oxygen evolution in sulfuric-acid-based electrolytes. The anode was obtained by coating a cheaper base metal with a thin layer of platinum or iridium. These first compos30,31 ite electrodes were patented in 1913 by Stevens. The thin platinum or iridium layers were electroplated onto a refractory metal such as tungsten or tantalum. The role of the platinum coating was to insure the electrical conduction of the base metal, even under anodic polarization. Despite its novelty, this bright idea was not industrially developed at that time because it was impossible commercially to obtain these refractory metals, especially their mill products (e.g., plates, rods, sheet, and strips) needed for manufacturing large size industrial anodes. It was not until the 1960s that the first commercial platinized anodes appeared. Besides the precious-metal anodes, early electrochemists used anodes made of two inexpensive materials such as lead and carbon-based materials such as graphite. The lead and the graphite were actually the only cheap anode materials that were industrially used up to the 1960s.

9.7.3.2.2

Lead and Lead-Alloy Anodes

Historically, the use of lead anodes resulted first from the widespread use of lead vessels in 32 industrial manufacturing involving corrosive media such as the synthesis of sulfuric acid and later from the original studies in the lead-acid battery invented by Gaston Planté in 33 1859. Properties. Lead is a common and cheap metal, and the average price for lead of 99.99 wt.% 34 purity is 0.980 US$/kg. Pure lead exhibits several attractive features, such as good electronic conductivity (20.64 μΩ.cm) and a good chemical and electrochemical corrosion resistance in numerous corrosive and oxidizing environments (e.g., chromates, sulfates, carbonates, and 35 phosphates). This chemical and electrochemical inertness is due to the self-formation of a protective passivating layer. For instance, the corrosion rate of the pure metal in 50 wt.% sulfuric acid is 130 μm per year at 25°C. When the metal undergoes an anodic current density –2 36,37 of 1 kA.m in 60 wt.% sulfuric acid, the corrosion rate reaches only 9 mm per year. In fact, 38 Pavlov has shown in acidic sulfate electrolytes that, with an increasing anodic polarization, first an insulating layer of anglesite (PbSO4) forms between 1.52 and 1.72 V/SHE, then a brown colored layer of semiconductive lead dioxide (PbO2) appears. If anodic polarization is increased further, an insulating film of PbO forms, preventing the current from flowing. The lead anode is characterized by a high anodic overpotential for the evolution of oxygen. It is important to note that among the dimorphic forms of PbO2 only the plattnerite with a rutile structure is electrocatalytic to oxygen evolution (cf. section on lead-dioxide anodes). Because 30 31 32

33 34 35 36 37

38

Stevens, R.H. (1913) Platinum-plated tungsten electrode. US Patent 1,077,894; November 4, 1913. Stevens, R.H. (1913) Iridium-plated tungsten electrode. US Patent 1,077,920; November 4, 1913. Lunge, G.; Naville, J. (1878) Traité de la grande industrie chimique. Tome I: acide sulfurique et oléum. Masson & Cie, Paris. Planté, G. (1859) Compt. Rend. Acad. Sci., 49, 221. Metal Bulletin Weekly, May 8, 2006. Greenwood, N.N.; Earnshaw, N. (1984) Chemistry of the Elements. Pergamon, Oxford, p. 435. Beck, F. (1971) Lead dioxide-coated titanium anodes. German Patent 2,023,292; May 13, 1971. Beck, F.; Csizi, G. (1971) Lead dioxide-titanium compound electrodes. German Patent 2,119,570; April 22, 1971. Pavlov, D.; Rogachev, T. (1986) Mechanism of the action of silver and arsenic on the anodic corrosion of lead and oxygen evolution at the lead/lead oxide (PbO2–x)/water/oxygen/sulfuric acid electrode system. Electrochim. Acta., 31(2), 241–249.

9 Miscellaneous Electrical Materials

570

Miscellaneous Electrical Materials

Table 9.17. Lead and lead-alloy-anode composition and electrochemical uses Lead alloy [UNS numbers]

Typical composition range

Alloying effect

Electrochemical use

Pure lead (Pb) ‘corroding lead’ [L50000 – L50099]

>99.94 wt.% Pb

w/o

Nickel electrowinning –2 (200 A.m )

Lead-silver (Pb-Ag) [L50100 – L50199]

0.25–0.80 wt.% Ag (usually 0.5 wt.%)

Increases corrosion resistance and oxygen overvoltage

Zinc electrowinning Cobalt electrowinning

Lead-tin (Pb-Sn) [L54000 – L55099]

Usual 5–10 wt.% Sn Tin increases mechanical strength, Historically 4 wt.% Sn forms corrosion-resistant intermetallics, and improves melt fluidity during anode casting

Cobalt electrowinning –2 (500 A.m )

Antimonial lead 40 (Pb-Sb) (hard lead) [L52500 – L53799]

2–6 wt.% Sb

Cobalt electrowinning Copper electrowinning –2 (200 A.m )

Lead-calcium-tin 0.03–0.15 wt.% Ca (Pb-Ca-Sn) (‘nonantimonial’ lead) [L50700 – L50899]

39

Antimony lowers oxygen overvoltage, increases stiffness, strength, and creep resistance, extends freezing range, and lowers the casting temperature

Calcium imparts corrosion Copper electrowinning –2 resistance and minimizes O2 and (500 A.m ) H2 overpotentials, while Sn imparts stiffness

–3

lead is malleable and ductile with a high density (11,350 kg.m ) and has a low melting point –6 –1 (327.5°C) and a high coefficient of linear thermal expansion (30 × 10 K ), it exhibits a severe creep phenomenon when electrolysis is conducted well above the ambient temperature. To improve the mechanical properties of pure lead and its corrosion properties, industrial lead anodes are typically made of lead alloys instead of pure lead metal. Moreover, the use of alloying elements usually decreases the melting temperature required to cast new anode slabs. Actually, castability determines the anode integrity, and the temperature interval between liquidus and solidus temperatures is still an important consideration for anode manufacturers. Grades of pure lead and lead alloys used in industrial anodes. Pure lead grades are called corroding lead and common lead, both containing 99.94 wt.% min Pb, and chemical lead and acid-copper lead, both containing 99.90 wt.% min Pb. Lead of higher specified purity (99.99 wt.% Pb) is also available in commercial quantities but rarely used as anodes. International specifications include ASTM B 29 in the USA for grades of pig lead including federal specification QQ-L-171, German standard DIN 1719, British specification BS 334, Canadian Standard CSA-HP2, and Australian Standard 1812. Corroding lead exhibits the outstanding corrosion resistance typical of lead and its alloys. Chemical lead is a refined lead with a residual copper content of 0.04 to 0.08 wt.% Cu, and a residual silver content of 0.002 to 0.02 wt.% Ag is particularly desirable in the chemical industries and thus is called chemical lead. Copper-bearing lead provides corrosion protection comparable to that of chemical lead in most applications that require high corrosion resistance. Common lead contains higher amounts of silver and bismuth than does corroding lead. In antimonial lead, antimony content ranges 39

40

Hoffmann, W. (1962) Blei und Bleilegierungen. Springer, Berlin Heidelberg New York; English translation in 1962: Lead and Lead Alloys. Springer, Berlin Heidelberg New York. Mao, G.W.; Larson, J.G.; Rao, G.P. (1969) Effect on small additions of tin on some properties of lead 4.5 wt.% antimony alloys. J. Inst. Metal, 97, 343–350.

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571

from 0.5 to 25 wt.% Sb, but it is usually between 2 to 5 wt.% Sb. Antimony imparts greater hardness and strength. Lead-calcium alloys have replaced lead-antimony alloys in a number of applications. These alloys contain 0.03 to 0.15 wt.% Ca. More recently, aluminum has been added to calcium-lead and calcium-tin-lead alloys as a stabilizer for calcium. Adding tin to lead or lead alloys increases hardness and strength, but lead-tin alloys are more commonly used for their good melting, casting, and wetting properties. Tin gives an alloy the ability to wet and bond with metals such as steel and copper; unalloyed lead has poor wetting characteristics. The most common lead alloys used to manufacture industrial anodes together with their electrochemical applications are briefly summarized in Table 9.17. Industrial applications. For those reasons, and despite its poor electrocatalytic properties and problems related to its toxicity arising with anodic dissolution, today lead anodes are the most common industrial anodes used worldwide for electrowinning metals from acidic 41 42 sulfate electrolytes (e.g., Zn, Co, Ni) and in hexavalent chromium electroplating. The low price of lead anodes compared to titanium-coated electrodes and a service life in the range of 1 to 3 years are their major advantages. Moreover, the low melting temperature of lead and its alloys makes it possible to recycle in-house spent industrial lead anodes by simply remelting the discarded anodes and cast the recycled molten metal into new anode slabs. Zinc electrowinning uses lead-silver. Pb-Ag is the standard because cobalt addition cannot be used. The silver alloy imparts some corrosion resistance to the base lead. Lead-based anodes are used because of their low cost and robustness. But the major drawbacks are sludge generation leading to product quality issues and high oxygen overpotential, i.e., higher power costs. Copper electrowinning uses lead-calcium-tin. Lead-calcium-tin is favored to avoid the cost of silver addition. Stabilization of Pb-Ca-Sn anodes is ensured by the careful addition of cobalt (II) as depolarizer in the electrowinning electrolyte. In the electrolytic production of manganese metal, silver-lead anodes (1 wt.% Ag) are used in producing electrolytic metallic manganese, which results in anode sliming of 0.38 to 0.45 tonnes per tonne of Mn. Slime of manganese and lead compounds is a process waste that engenders a number of problems: (i) (ii)

environment pollution by waste products; unproductive raw-material consumption, resulting in an increase in the overall volume of facilities and capital investments; (iii) high specific energy consumption during preparation of additional quantities of manganese-containing solutions for electrolysis baths; (iv) unpredictable anode destruction caused by active corrosion along waterlines; (v) frequent cleanup of anodes and baths (once every 20 to 24 days), replacement of diaphragms, and remelting of anodes. Recent developments. Some work is still being carried out to overcome some of the drawbacks of industrial lead anodes. For instance, the Japanese subsidiary of De Nora, Permelec Co., has developed a reinforced lead anode for the electrowinning of zinc from sulfate baths. This anode is made of a skin portion formed by a conventional silver-lead alloy and a stiffening reinforcing component made of titanium or zirconium mesh. The reduction in the thickness of the anodes, which is made possible by the provision of the reinforcing member, results in substantial savings in the amount of silver-bearing lead that is immobilized and a substantial reduction in the mass of the bulk anode. Later, Eltech Systems Corp. 43 TM introduced its new patented technology, known by the brand name Mesh-on-Lead (MOL) 41 42

43

De Nora, O. (1962) Anodes for use in the evolution of chlorine. British Patent 902,023; July 25, 1962. Nidola, A. (1995) Technologie di cromatura galvanica a spessore. Rivista AIFM: Galvanotecnica e nuove finiture, 5, 203–218. Brown, C.W.; Bishara, J.I.; Ernes, L.M.; Getsy, A.W.; Hardee, K.L.; Martin, B.L.; Pohto, G.R. (2002) Lead electrode structure having mesh surface. US Patent 6,352,622; March 5, 2002.

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anode. The MOL anode is in fact a composite structure obtained by attaching disposable electrocatalytically active titanium mesh to existing lead anodes. Hence, it combines the benefits of a standard lead anode with power savings of a precious-metal-oxide-coated titanium found typically in dimensionally stable anodes (see DSA). The MOL product is still being developed to overcome its major drawback, cost. This new anode is specifically designated for replacing Pb-Ca-Sn anodes for primary copper electrowinning operations (e.g., SXEW process). The MOL concept was demonstrated with full-scale anodes at several premier commercial tankhouses. During these demonstrations MOL anodes exhibited numerous performance advantages relative to standard Pb-Ca-Sn anodes: they reduced specific energy consumption due to lower oxygen evolution overpotential, improved cathode quality, minimized lead-sludge generation, eliminated cobalt addition as a result of stabilized lead sub44 strate, and improved current efficiency due to reduced short circuiting. Failure modes. In acidic sulfate baths, the most common failure mode of lead anodes consists of the formation of a thick solid and intermediate passivating layer of PbSO4 and PbO2 that can grow up to 5 mm thick and that eventually flakes off, leaving patches of freshly exposed surface. This deactivation of the lead anode is accompanied by two major drawbacks of industrial electrolysis: loss of faradic efficiency, usually below 90% for zinc and below 95% for cobalt, and an uneven and dendritic aspect of the electrodeposited metal usually contaminated by traces of lead. Another important failure mode occurs due to the deleterious effect of manganese (II) cations. Actually, the presence of manganous cations as impurities in many electrolyte streams may cause important secondary anodic reactions to 2+ occur. During the anodic process manganous cations Mn may either react at the anode – surface to form soluble permanganate species (MnO4 ) or insoluble manganese dioxide (MnO2) that passivates the anode surface and then impedes the proper evolution of oxygen. Eventually, flakes on the anode can detach as slime that contains oxides and/or sulfates, which are the major source of lead contamination in electrowinned cathodes. In copper electrowinning, Co (II) is often used as depolarizer for the oxygen evolution reaction. However, cobalt can not be used during zinc electrowinning because it affects the overall current efficiency.

9.7.3.2.3 Carbon Anodes History. Carbon-based electrode materials (e.g., carbon, semigraphite, and graphite) have been used in various electrochemical technologies since the beginning of electrochemistry, including electroanalysis, energy storage devices, and electrosynthesis. For instance, due to its chemical inertness toward hydrochloric acid and hydrogen chloride, graphite was the 45 early anode material selected for HCl electrolysis for producing chlorine gas. This process, 46 initially developed in Germany during World War II by Holemann and Messner at IG Far47,48 49,50 51,52 ben Industrie, was continued in the 1950s by De Nora-Monsanto and Hoechst-Uhde. 44

45

46

47 48 49

50

51 52

Moats, M.; Hardee, K.; Brown, Jr., C. (2003) Mesh-on-Lead anodes for copper electrowinning. JOM, 55(7), 46–48 Isfort, H. (1985) State of the art after 20 years experience with industrial hydrochloric acid electrolysis. DECHEMA Monographien, 98, 141–155. Gardiner, W.C. (1946) Hydrochloric Acid Electrolysis at Wolfen. Field Information Agency, Technical (FIAT) Report No. 832, US Office of Military Government for Germany. Gardiner, W.C. (1947) Hydrochloric acid electrolysis. Chem. Eng., 54(1), 100–101. Holemann, H. (1962) The hydrochloric acid electrolysis. Chem. Ing. Techn., 34, 371–376. Gallone, P.; Messner, G. (1965) Direct electrolysis of hydrochloric acid. Electrochem. Technol., 3(11–12), 321–326. Messner, G. (1966) Cells for the production of chlorine from hydrochloric acid. US Patent 3,236,760; February 22, 1966. Grosselfinger, F.B. (1964) New chlorine source: by-product hydrochloric acid. Chem. Eng., 71(19), 172–174. Donges, E.; Janson, H.G. (1966) Chem. Ing. Techn., 38, 443.

Electrode Materials

Structure. As a general rule, carbon-based materials have similar microstructures consist2 ing of a planar network of a six-membered aromatic-forming layered structure with sp hybridized carbon atoms trigonally bonded to one another. The crystallite size and extent of microstructural order can vary from material to material (i.e., edge-to-basal-plane ratio), which has important implications for electron-transfer kinetics. Properties. Carbon-based electrodes are attractive because carbon is a cheap material with an excellent chemical inertness, and it is easy to machine and has a low bulk density –3 (2260 kg.m ). Furthermore, there is a great diversity of commercially available products (e.g., graphite, pyrolytic, impervious, or glassy) and in several forms (e.g., fibers, cloths, blacks, powders, or reticulated). The graphite variety, despite its anisotropy, high electrical resistivity (1375 μΩ.cm), and extreme brittleness, was once widely used for the electrolysis of brines. Graphite is highly corrosion resistant to concentrated hydrochloric acid even at the high anodic potential required for producing chlorine. Corrosion is not detectable if the concentration of hydrochloric acid is always maintained above 20 wt.% HCl during electrolysis. Carbon anodes are also the only appropriate anode material in certain processes where no other materials exhibit both a low cost and a satisfactory corrosion resistance. Actually, several industrial electrolytic processes performed in molten-salt electrolytes continue to use carbon anodes; these processes are: the electrowinning of aluminum by the Hall–Heroult process, the electrolytic production of alkali metals (e.g., Na, Li) and alkaliearth metals (e.g., Be, Mg), and finally the electrolytic production of elemental fluorine. However, the use of carbon anodes in the chlor-alkali process for the production of chlorine gas has now been discontinued due to the replacement by modern and more efficient anodes. In fact, in the 1960s, the improvement of the chlor-alkali processes (e.g., mercury cathode cell and diaphragm cell) required great efforts in research and development. The research was essentially focused on improving graphite anodes, which had some serious drawbacks: first, the nondimensional stability of the carbon anodes during electrolysis led to continuous increases in the interelectrode gap, which caused an ohmic drop; second, it had a high chlorine evolution overpotential; and third, it had a very short service life (i.e., 6 to 24 months) due to the corrosion by the chlorine and the inescapable traces of oxygen, which formed chlorinated hydrocarbons and carbon dioxide. These efforts led to the birth of the third generation of industrial dimensionally stable anodes (vide infra). Failure modes. Due to its lamellar structure, graphite severely corrodes due to the intercalation of anions between graphene planes such as sulfate or perchlorate during anodic discharge, while alkali-metal cations and ammonium intercalate when cathodically polarized leads to severe exfoliation of the electrode materials. The degradation of carbon-based materials depends on the electrolyte, the nature of the carbon materials, and the concentration of intercalating species. Once the graphite particles float on the electrolyte surface, they can lead to serious electrical continuity issues (i.e., short circuit), especially in molten-salt electrolytes that are denser than graphite.

9.7.3.2.4

Lead Dioxide (PbO2)

Structure. Lead dioxide exhibits two polymorphic forms: (i) scrutinyite (α-PbO2) with orthorhombic crystals (a = 497.1 pm, b = 595.6 pm, and c = 543.8 pm) with a density of –3 9867 kg.m , and (ii) plattnerite (β-PbO2) with tetragonal crystals (a = 495.25 pm and –3 c = 338.63 pm) having a rutile-type structure and a density of 9564 kg.m . Properties. Only plattnerite has attractive features for electrochemical applications such as a low electrical resistivity (40 to 50 μΩ.cm), a good chemical and electrochemical corrosion resistance in sulfates media even at low pH, and a high overvoltage for the evolution of oxygen in sulfuric- and nitric-acid-containing electrolytes while it withstands chlorine evolution in hydrochloric acid. In fact, the more electrochemically active phase consists

573

9 Miscellaneous Electrical Materials

574

Miscellaneous Electrical Materials

of a nonstoichiometric lead dioxide with the empirical chemical formula PbOn (with 1.4 < n < 2). 53 A review of its preparation is presented by Thangappan et al. Preparation. Lead dioxide forms on pure lead, in dilute sulfuric acid, when polarized anodically at electrode potentials ranging from +1.5 to +1.8 V/SHE. Hence, industrially, leaddioxide anodes are prepared by in situ anodization of a pure lead anode carried out at 20°C. The lead anode and a copper cathode are immersed in an undivided cell containing a dilute –3 3 –1 sulfuric acid (98 g.dm H2SO4) flowing with a rate ranging from 5 to 10 dm .min , and the electrodeposition is conducted galvanostatically by applying an anodic current density of –2 100 A.m for 30 min. The inherent brittleness of the PbO2 ceramic coating on soft lead can be overcome by electrodepositing anodically lead dioxide onto inert and stiff substrates such as titanium, niobium, tantalum, graphite, and Ebonex®. These supported anodes, that is, 54 55,56 Ti/PbO2 and Ta/PbO2, are now commercially available. The anodic electrodeposition of a layer of PbO2 is usually conducted in an undivided cell with a copper cathode and a station–3 ary or flowing electrolyte consisting of dilute sulfuric acid (98 g.dm H2SO4) containing –3 1 mol.dm lead (II) nitrate with minute amounts of copper (II) or nickel (II) nitrate. Copper and nickel cations are used as cathodic depolarizers to impede the deleterious electrodeposition of lead on the cathode. Prior to coating, the metal substrate is first sandblasted to increase roughness and enhance the coating adhesion; this is followed by chemical etching. Etching is conducted, for instance, in boiling concentrated hydrochloric acid for titanium and its alloys or in cold concentrated hydrofluoric acid for niobium and tantalum. Etching removes the passivation layer that is always present on refractory metals. Then lead dioxide is –2 electrodeposited galvanostatically at 200 A.m for several hours to reach anode loadings of several grams per square meter. The PbO2 coating obtained is smooth, dense, hard, uniform, and free of pinholes and adheres to the surface of the substrate material. Sometimes a thin intermediate platinum layer is inserted between the base metal and the PbO2 coating to enhance the service life by preventing the undermining process. Finally, for particular applications requiring bulk ceramic anodes, the electrodeposited lead dioxide can also be crushed, melted, and cast into intricate shapes. Applications. PbO2-based anodes are used for their inertness and low cost and when the oxidation should be carried out without the competitive evolution of oxygen. PbO2 anodes were once used as a substitute for the conventional graphite and platinum electrodes for 57 regenerating potassium dichromate and in the production of chlorates and perchlorates. These anodes were also extensively used in hydrometallurgy as oxygen anodes for electro58,59,60 plating copper and zinc in sulfate baths and in organic electrosynthesis for the produc61 tion of glyoxilic acid from oxalic acid using sulfuric acid as supporting electrolyte. Failure modes. For lead dioxide supported on lead, the mismatch of strength and thermal expansion between the lead metal substrate and its lead-dioxide ceramic coating leads to flaking and spalling with loss of coating. As mentioned previously, a thin platinum underlayer can 53

54

55 56

57

58 59 60 61

Thangappan, R.; Nachippan, S.; Sampath, S. (1970) Lead dioxide-graphite electrode. Ind. Eng. Chem. Prod. Res. Dev., 9(4), 563–567. Pohl, J.P.; Richert, H. (1980) In: Trasatti, S. (ed.) Electrodes of Conductive Metallic Oxides, Part A. Elsevier, Amsterdam, Chap. 4, pp. 183–220. De Nora, O. (1962) Anodes for use in the evolution of chlorine. British Patent 902,023; July 25, 1962. Kuhn, A.T. (1976) The electrochemical evolution of oxygen on lead dioxide anodes. – Chemistry & Industry, 20, 867–871. Grigger, J.C.; Miller, H.C.; Loomis, F.D. (1958) Lead dioxide anode for commercial use. J. Electrochem. Soc., 105, 100–102. Engelhardt, V.; Huth, M. (1909) Electrolytic recovery of zinc. US Patent 935,250; September 28, 1909. Gaunce, F.S. (1964) Treatment of lead or lead alloy electrodes. French Patent 1,419,356; November 26, 1964. Higley, L.W.; Dressel, W.M.; Cole, E.R. (1976) U.S. Bureau of Mines, Report No. R8111. Goodridge, F.; Lister, K.; Plimley, R.; Scott, K. (1980) Scale-up studies of the electrolytic reduction of oxalic to glyoxylic acid. J. Appl. Electrochem., 10(1), 55–60.

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delay the catastrophic undermining process induced by the loss of coating, but usually the use of lead-dioxide-coated titanium anodes solves this issue but increases capital costs. Another failure mode occurs when manganese (II) cations are present that form insoluble manganese dioxide (MnO2). Eventually, flakes on the anode can detach, entraining the coating and forming slimes at the bottom of the electrolyzer.

9.7.3.2.5

Manganese Dioxide (MnO2) 62

Manganese dioxide was used for a long time following the work of Huth, where hard and dense anodes of MnO2 were obtained by forming a main body of the MnO2 anode and then repeatedly treating this body with Mn(NO3)2 and heating it to decompose the nitrate and form additional MnO2. These anodes were once used extensively in hydrometallurgy for the elec63 trowinning or electroplating of zinc, copper, and finally nickel in sulfate baths. They are 64 prepared by solution impregnation-calcination or by anodization in a sulfuric solution containing manganous cations. However, they never have the same full expansion of lead dioxide owing to their high corrosion rate under extreme conditions, that is, at high temperature, high pH, and elevated anodic current density. Nevertheless, some improvements have been made to increase their stability. Feige prepared a supported Ti/MnO2 anode made by sintering tita65 nium and lead particles with MnO2. De Nora et al. obtained a Ti/MnO2-type anode by the application of the classical painting-thermal decomposition procedure employed for the 66 preparation of DSA®.

9.7.3.2.6 Spinel (AB2O4)- and Perovskite (ABO3)-Type Oxides Structure. It is well known that some ceramic oxides of the inner transition metals (e.g., Mn, II III Fe, Co, and Ni) with a spinel-type structure (A B 2O4) or, to a lesser extent, a perovskite-type II IV structure (A B O3) are electrical conductors with electrocatalytic activities when doped with Li, Ni, and Co. Moreover, being sufficiently stable in corrosive electrolytes, they were developed as good candidates for the development of oxygen-evolving electrodes. Spinels are IV VI oxides with the general formula (A1–xBx) (AxB2–x)O4, where the divalent cations are denoted 2+ 2+ 2+ 2+ 2+ 3+ 3+ 3+ 3+ A = Mg , Fe , Ni , Co , and Zn and trivalent cations B = Al , Fe , Cr , and V . Hence two types of spinel structure must be distinguished: normal spinels with x = 0, meaning that all the divalent cations occupy tetrahedral sites, and inverse spinels with x = 1. Of these, rods 67 of pure magnetite (Fe3O4) or its doped form obtained by casting molten iron oxides have been used as industrial anodes since 1870. Apart from magnetite and ferrites, today other classes of spinels have been investigated such as cobaltites and chromites. Due to their better electrocatalytic properties and fewer health and safety issues, cobaltites (e.g., MCo2O4 with M= Mg, Cu, and Zn) are now preferred and are the only ones being developed. Properties. These anodes, despite their good chemical inertness and electrochemical 68,69 stability under high positive potential, have nevertheless two main drawbacks: they are 62 63 64

65 66

67

68

69

Huth, M. (1919) Anodes of solid manganese peroxide. US Patent 1,296,188; March 4, 1919. Bennett, J.E.; O’Leary, K.J. (1973) Oxygen anodes. US Patent 3,775,284; November 27, 1973. Ohzawa, K.; Shimizu, K.; Takasue, T. (1967) Insoluble electrode for electrolysis. US Patent 3,616,302; February 27, 1967. Feige, N.G. (1974) Method for producing a coated anode. US Patent 3,855,084; December 17, 1974. De Nora, O.; Nidola, O.; Spaziante, P.M. (1978) Manganese dioxide electrodes. US Patent 4,072,586; February 7, 1978. Kuhn, A.T.; Wright, P.M. In: Kuhn, A.T. (ed.) (1971) Industrial Electrochemical Processes, Chap. 14. Elsevier, New York. Matsumura, Takashi; Itai, R.; Shibuya, M.; Ishi, G. (1968) Electrolytic manufacture of sodium chlorate with magnetite anodes. Electrochem. Technol., 6(11–12), 402–404. Itai, R.; Shibuya, M.; Matsumura, T.; Ishi, G. (1971) Electrical resistivity of magnetite anodes. J. Electrochem. Soc., 118(10), 1709–1711.

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brittle, which means a ceramic must be supported on a stiff metal substrate, and they exhibit very high electrical resistivities (27,000 μΩ.cm) with respect to other electrode materials. Preparation. These oxides are usually produced by firing metallic precursors (e.g., nitrates, oxalates) in a moderately oxidizing atmosphere (e.g., steam, or argon-carbon dioxide mixture) at moderate temperatures (700 to 900°C). For reinforcing a brittle ceramic, these 70 oxides can be used supported on a stiff base metal such as titanium. Sometimes, such as for PbO2 anodes, an thin intermediate layer of platinum is deposited between the base metal and the magnetite to enhance the service life and delay the undermining process.

9.7.3.2.7 Ebonex®(Ti4O7 and Ti5O9) 71

Since 1983, the date of the original patent of Hayfield from IMI (Marston) describing a novel semiconductive electrode material that was prepared from substoichiometric oxides of titanium. These ceramics have attracted particular attention in the electrochemical com72,73 munity. Soon after, the intellectual property related to the suboxides of titanium was purchased by the company Ebonex Technologies Incorporated (ETI), which was itself 74 a subsidiary of ICI (Americas) and commercialized under the trade name Ebonex®. Later, in 1992, the company was renamed Atraverda Limited. Bulk ceramic electrodes are manufactured in various forms (e.g., plates, tubes, rods, honeycombs, fibers, powders, and pellets) and grades (e.g., vitreous and porous). From a crystallochemical point of view, these ceramics consist of substoichiometric oxides of titanium with the Andersson–Magnéli crystal lat75 tice structure and the general chemical formula TinO2n–1, where n is an integer equal to or greater than 4 (e.g.,Ti4O7, Ti5O9, Ti6O11, Ti7O13, Ti8O15, Ti9O17, and Ti10O19). They are usually prepared by thermal reduction at 1300°C of pure TiO2 by hydrogen, methane, or carbon monoxide, or a blend of titanium dioxide and titanium metal powder. These oxides have all comparably elevated electronic conductivity similar, and in some cases superior, to that of graphite (e.g., 630 μΩ.cm for Ti4O7 compared with 1375 μΩ.cm for graphite). From a corrosion point of view, Ebonex® exhibits an unusual chemical inertness in several corrosive media such as strong, oxidizing, or reducing mineral acids (e.g., HCl, H2SO4, HNO3, and even HF). The anomalous high resistance to HF, and fluoride anions that usually readily attack titania even in dilute solutions, seems due to the difference in the lattice structure and the absence of hydrates. Ebonex® has also served as substrate for electrodepositing with a plati76 77 num coating and been used as a platinized anode. These anodes show no major differences with bulk platinum anodes. Moreover, Pletcher and coworkers succeeded in electroplating coatings of metals such as Cu, Au, Ni, Pd, and Pt without any pretreatment of the substrate. In addition, by contrast 70

71

72

73

74

75 76

77

Hayes, M.; Kuhn, A.T. (1978) The preparation and behavior of magnetite anodes. J. Appl. Electrochem., 8(4), 327−332. Hayfield, P.C.S. (1983) Electrode material, electrode and electrochemical cell. US Patent 4,422,917; December 27, 1983. Baez, V.B.; Graves, J.E.; Pletcher, D. (1992) The reduction of oxygen on titanium oxide electrodes. J. Electroanal. Chem., 340(1–2), 273–86. Graves, J.E.; Pletcher, D.; Clarke, R.L.; Walsch, F.C. (1991) The electrochemistry of Magneli phase titanium oxide ceramic electrodes. I. The deposition and properties of metal coatings. J. Appl. Electrochem., 21(10), 848–857. Clarke, R.; Pardoe, R. (1992) Applications of ebonex conductive ceramics in effluent treatment. In: Genders, D.; Weinberg, N. (eds.) Electrochemistry for a Cleaner Environment. Electrosynthesis Company, Amherst, NY, pp. 349–363. Andersson, S.; Collen, B.; Kuylienstierna, U.; Magneli, A. Acta Chem. Scand., 11, 1641. Farndon, E.E.; Pletcher, D.; Saraby-Reintjes, A. (1997) The electrodeposition of platinum onto a conducting ceramic, Ebonex. Electrochimica Acta, 42(8), 1269–1279. Farndon, E.E.; Pletcher, D. (1997) Studies of platinized Ebonex electrodes. Electrochimica Acta, 42(8), 1281–1285.

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®

Table 9.18. Miscellaneous properties of Ebonex (Source: Atraverda) Properties (at room temperature unless otherwise specified)

Bulk ceramic

Composite with polymer

Density (ρ/kg.m )

3600–4300

2300–2700

750

n.a.

–3

–1

–1

Specific heat capacity (cP/J.kg K ) –1

–1

Thermal conductivity (k/W.m K )

10–20

n.a.

Coefficient of linear thermal expansion (α/10 K )

6

n.a.

Flexural strength (/MPa)

60–180

n.a.

Vickers microhardness (Hv)

230

n.a.

Electrical conductivity (κ/S.m )

3000–30,000

100–1000

Temperature range (T/°C)

Up to 250°C in air or 800°C Up to 250°C (reducing)

–6

–1

–1

Oxygen overpotential (V/SHE) –3 in H2SO4 (1 mol.dm ) –3 in NaOH (1 mol.dm )

+1.75 +1.65

Hydrogen overpotential (V/SHE) –3 in H2SO4 (1 mol.dm ) –3 in NaOH(1 mol.dm )

–0.75 –0.60

with titanium, which is highly sensitive to hydrogen embrittlement, Ebonex® has no tendency to form brittle titanium hydride in contact with nascent hydrogen evolved during cathodic polarization. From an electrochemical point of view, Ebonex® exhibits poor intrin78 sic electrocatalytic properties and hence has high overpotentials for both hydrogen and 79 80 oxygen evolution reactions (e.g., oxygen starts to evolve at +2.2 V/SHE in 0.1M HClO4). This dual behavior allows Ebonex® to be used without restriction either as cathode or anode. Nevertheless, the use of the bare materials is limited under severe conditions such as high anodic current density due to the irreversible oxidation of Ti4O7 to insulating TiO2. However, the overpotential of the Ebonex® material can be modified by the application of electrocatalysts (e.g., RuO2, IrO2) by the painting-thermal decomposition procedure employed for the preparation of DSA®. By contrast coated Ebonex® is capable of operating with traces of –2 fluoride anions up to anodic current densities of 4 kA.m in baths where DSA® failed rapidly by the undermining mechanism (e.g., conc. HCl, HF-HNO3 mixtures, elevated fluoride content). Industrially, Ebonex® is recommended for several applications including, but not restricted to, the replacement of lead anodes in zinc electrowinning, for cathodic protection of steel reinforcing bars (i.e., rebars) in concrete, in situ electrochemical remediation of contaminated soils, in the purification of drinking water, in the treatment of waste effluents, and as bipolar electrodes in rechargeable batteries and even coated with PbO2 for ozone 81 generation. The high cost of Ebonex®, combined with its brittleness, still limits its widespread uses. 78

79

80

81

Miller-Folk, R.R.; Noftle, R.E.; Pletcher, D. (1989) Electron transfer reactions at Ebonex ceramic electrodes. J. Electroanal. Chem., 274(1–2), 257–261. Pollock, R.J.; Houlihan, J.F.; Bain, A.N.; Coryea, B.S. (1984) Electrochemical properties of a new electrode material, titanium oxide (Ti4O7). Mater. Res. Bull., 19(1), 17–24. Park, S.-Y.; Mho, S.-I.; Chi, E.-O.; Kwon, Y.-U.; Yeo, I.-H. (1995) Characteristics of Ru and RuO2 thin films on the conductive ceramics TiO and Ebonex (Ti4O7). Bull. Kor. Chem. Soc., 16(2), 82–84. Graves, J.E.; Pletcher, D.; Clarke, R.L.; Walsh, F.C. (1992) The electrochemistry of Magneli phase titanium oxide ceramic electrodes. II. Ozone generation at Ebonex and Ebonex/lead dioxide anodes. J. Appl. Electrochem., 22(3), 200–203.

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578

Miscellaneous Electrical Materials

9.7.3.2.8 Noble-Metal-Coated Titanium Anodes (NMCT) During the 1950s and 1960s, at the peak of expansion of the American and Russian aircraft and space programs and with the development of nuclear power plants, industrial processes for the production of refractory metals (e.g., Ti, Zr, Hf, Nb, and Ta) reached commercial scale. 82 These processes, like the Kroll process, made reactive metals with a wide range of alloy compositions available for the first time. This development brought several advantages: a reduction in production costs, the standardization of alloy grades, and a great effort in R&D for using these metals beyond their original aircraft and nuclear applications. At this stage, all the difficulties associated with preparing anodes of refractory metals coated with precious metals vanished, and the idea invented 40 years ago by Stevens reappeared. Hence, niobium83 and tantalum-platinized anodes were prepared following the works of Rhoda and Rosen84 blatt in 1955. In the latter patent, a layer of platinum was obtained on tantalum by the thermal decomposition of H2PtCl6 in an inert atmosphere. This thermal treatment, which was conducted between 800 and 1000°C, gave a thin interdiffusion layer of a few micrometers, consisting of an alloy between Ta and Pt. Furthermore, titanium, now commercially available due to the strong demand for turbine blades in aircraft engines, was studied both from 85,86 a corrosion and electrochemical point of view at ICI by Cotton. The study showed that the exceptional resistance of titanium to corrosion in seawater was due to the valve action property of its oxide, which allowed the metal to be protected under anodic polarization by 87 an insulating layer of rutile (TiO2). It is only in 1957 that Beer at Magneto Chemie (The 88,89 Netherlands) and Cotton with the help of Angell at ICI (UK) showed independently but concurrently that attaching rhodium or platinum at the surface of titanium, either by electroplating or by spot welding, provided sufficient electrical conductivity to the base metal that it could be polarized anodically despite its passivation. It was assumed that anodic current passed through platinum or rhodium metal. These rhodized or platinized titanium bielectrodes were named noble metal coated titanium (NMCT). During the following decade, NMCTs were actively developed through a partnership between ICI and Magneto Chemie 90,91 92 with the close contribution of other companies such as Inco, Engelhard, and IMI-Kynock. 93 94 95 Other firms such as W.C. Heraeus, Metallgeselschaft, and Texas Instruments have also worked independently on the subject. The best preparation procedure involves electroplating with platinum or rhodium because the electrodeposition allows for smooth and nonporous 96 deposits with a good throwing power without requiring an expensive amount of platinum. 82 83 84

85 86 87 88

89

90 91

92

93 94 95

96

Kroll, W.J. (1940) The production of ductile titanium. Trans. Electrochem. Soc., 112, 35–47. Rhoda, R.N. (1952) Electroless palladium plating. Trans. Inst. Met. Finish., 36(3), 82–85. Rosenblatt, E.F.; Cohn, J.G. (1955) Platinum-metal-coated tantalum anodes. US Patent 2,719,797; October 4, 1955. Cotton, J.B. (1958) Anodic polarization of titanium. Chem. & Ind., 3, 492–493. Cotton, J.B. (1958) The corrosion resistance of titanium. Chem. Ind., 3, 640–646. Beer, H.B. (1960) Precious-metal anode with a titanium core. British Patent 855,107; November 11, 1960. Cotton, J.B.; Williams, E.C.; Barber, A.H. (1957) Titanium electrodes plated with platinum-group metals for electrolytic processes and cathodic protection. Electrodes. British Patent 877,901; July 17, 1957. Cotton, J.B. (1958) Platinum-faced titanium for electrochemical anodes. A new electrode material for impressed current cathodic protection. Platinum Metals Rev., 2, 45–47. Haley, A.J.; Keith, C.D.; May, J.E. (1969) Two-layer metallic electrodes. US Patent 3,461,058. May, J.E.; Haley, A.J. (1970) Electroplating with auxiliary platinum-coated tungsten anodes. US Patent 3,505,178; April 7, 1970. Cotton, J.B.; Hayfield, P.C.S. (1965) Electrodes and methods of making same. British Patent 1,113,421; May 15, 1965. Muller, P.; Speidel, H. (1960) New forms of platinum-tantalum electrodes. Metall. 14, 695–696. Schleicher, H.W. (1963) Electrodes for electrolytic processes. British Patent 941,177; November 6, 1963. Whiting, K.A. (1964) Cladding copper articles with niobium or tantalum and platinum outside. US Patent 3,156,976; November 17, 1964. Balko, E.N. (1991) Electrochemical Applications of the Platinum Group: Metal Coated Anodes. In: Hartley, F.R. (ed.) Chemistry of the Platinum Group Metals: Recent Developments. Elsevier, New York.

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The electroplating baths contain a platinum salt such as the so-called P-salt, the hexachloro97 platinic acid, or the sodium hexachloroplatinate (IV). The electrocatalytic coating consists of platinum and rhodium present in their metallic forms. However, both rhodium and plati–2 num have high chlorine overvoltage (e.g. 300 mV for Rh and 486 mV for Pt at 10 kA.m ) and exhibit a slight corrosion with the rate depending on the electrolyte and the nature of bath – – impurities (e.g., Cl , F , organics).

9.7.3.2.9 Platinized Titanium and Niobium Anodes (70/30 Pt/Ir) The improvement of the noble-metal-coated-titanium anodes was the starting point of the study and preparation of platinized titanium anodes by the thermal decomposition of 98,99 a precursor with the pioneering work of, for example, Angell and Deriaz, both from ICI. The precursor consisted of a given mixture of hexachloroplatinic (H2PtCl6) and hexachloroiridic acids (H2IrCl6) dissolved in an appropriate organic solvent (e.g., linalool, isopropanol, or ethyl acetoacetate). Prior to applying the painting solution, the titanium substrate was thoroughly sandblasted to increase roughness and chemically etched to remove the passivating layer. Etchants included various chemicals such as hot concentrated hydrochloric acid, hot 10 wt.% oxalic acid, and hot 30 wt.% sulfuric acid. After each application the treated piece underwent a long thermal treatment at high temperature in air between 400 and 500°C. At that temperature thermal oxidation of the underlying titanium substrate is negligible. This original protocol 100 was inspired by Taylor’s works used in the 1930s to obtain reflective coatings of Pt on glass for the manufacture of optical mirrors. The study of the thermal decomposition of these par101 102 ticular painting solutions was conducted by Hopper in 1923 and more recently by Kuo in 1974. Other companies interested in platinized titanium anodes prepared by thermal decom103 104 position were Engelhard and Ionics. After long-term trials, the formulation and procedure were finally optimized. These anodes were initially commercialized in 1968 by IMI (Marston) 105 under the trade name K-type® or 70/30 Pt/Ir. For optimum performance, the commercially pure titanium must be from ASTM grade 1 or 2 with equiaxed grain sizes ranging between 30 and 50 μm. The electrocatalytic coating consists of platinum and rhodium present in their metallic forms either as separate phases or as platinum-iridium intermetallic. In fact, after thermal decomposition titanium is coated with a highly divided mixture of metal oxides con–2 sisting essentially of 70 wt.% PtOx to 30 wt.% IrOx. The common anode loading is 10 g.m . 106 107 Later, Millington observed that niobium, tantalum, and even tungsten could also be used 108 as substrates, but they were only considered by certain suppliers when titanium showed deficiencies owing to their greater cost. These anodes were rapidly used in numerous processes requiring a long service life under severe conditions. For example, they were 97 98

99

100 101 102

103

104 105

106 107

108

Lowenheim, F.A. (1974) Modern Electroplating, 3rd ed. Wiley, New York. Angell, C.H.; Deriaz, M.G. (1961) Improvements in or relating to a method for the production of assemblies comprising titanium. British Patent 885,819; December 28, 1961. Angell, C.H.; Deriaz, M.G. (1965) Improvements in or relating to a method for the production of assemblies comprising titanium. British Patent 984,973; March 3, 1965. Taylor, J.F. (1929) J. Opt. Soc. Am., 18, 138. Hopper, R.T. (1923) Ceram. Ind. (June). Kuo, C.Y. (1974) Electrical applications of thin-films produced by metallo-organic deposition. – Solid State Technol. 17(2), 49–55. Anderson, E.P. (1961) Method for preparing anodes for cathodic protection systems. US Patent 2,998,359; August 29, 1961. Tirrel, C.E. (1964) Method for making non corroding electrode. US Patent 3,117,023; January 7, 1964. Hayfield, P.C.S.; Jacob, W.R. (1980) In: Coulter, M.O. (ed.) Modern Chlor-Alkali Technology. Ellis Horwood, London, Chap. 9, pp. 103–120. Millington, J.P. (1974) Lead dioxide electrode. British Patent 1,373,611; November 13, 1974. May, J.E.; Haley, Jr., A.J. (1970) Electroplating with auxiliary platinum-coated tungsten anodes. US Patent 3,505,178; April 7, 1970. Haley, Jr., A.J. (1967) Engelhardt Ind. Tech. Bull., 7, 157.

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Miscellaneous Electrical Materials

employed for the cathodic protection of immersed plants such as oil rigs, storage tanks, and 109,110 subterranean pipe-lines, in the electrolytic processes for the production of sodium hy111 112 pochlorite, electrodialysis, for regeneration of Ce(IV) in perchloric or nitric acid, and for 113 oxidation of sulfuric acid in peroxodisulfuric acid. It is interesting to note that De Nora registered a patent on a Pt-coated anode in which the base metal was a ferrosilicon with some 114 amounts of chromium. Other formulations consisted of clad platinum metal on a copperclad titanium or niobium core by roll bonding or a sandwich of platinum-titanium (or niobium)-copper. This technique, which provides a thick, dense, and impervious platinum coating, is now commercialized by Anomet in the USA for the cathodic protection of oil rigs. This continuous research effort, always developed under pressure from industry, resulted in the 1960s in a new generation of anodes that are still widely used in all electrochemical fields and are discussed below. Nevertheless, although platinized titanium electrodes were found active, they still were found to be unsatisfactory for chlorine production. It was for this reason that Beer patented a new type of anode, discussed in the next section.

9.7.3.2.10

Dimensionally Stable Anodes (DSA®) for Chlorine Evolution 115

In the 1960s, Henri Bernard Beer, who worked at Permelec and the Italian team of Bianchi, Vittorio De Nora, Gallone, and Nidola, started studying the electrocatalytic behavior of 116,117 mixed metal oxides and nitride coatings for the evolution of chlorine and oxygen. These oxides were obtained by the calcination of precursors but in an oxidizing atmosphere (i.e., air or pure oxygen). These RuO2-based anodes or so-called “ruthenized titanium anodes,” composed of mixed metal oxides (TiO2-RuO2) coated on a titanium metal, have been devel118 oped with great success since 1965, the year of Beer’s famous patent. At this stage, the selection of ruthenium was made only based on the low cost of the metal and its commercial 119,120,121,122 availability. These electrodes were later protected by several patents. It was the birth of the activated titanium anode (ATA), also called oxide-coated titanium anode (OCTA), designation now obsolete and modernized in the 1990 to mixed metal oxides (MMO). These anodes are characterized by a geometrical stability and a constant potential over a long time (more than 2 to 3 years). It is this dimensional stability in comparison with the graphite anodes that gives it its actual trade name: dimensionally stable anodes (the acronym DSA® is 109

110

111 112

113

114 115

116

117

118 119

120 121 122

Cotton, J.B.; Williams, E.C.; Barber, A.H. (1961) Improvements relating to electrodes and uses thereof. British Patent 877,901; September 20, 1961. Anderson, E.P. (1961) Method for preparing anodes for cathodic protection systems. US Patent 2,998,359; August 29, 1961. Adamson, A.F.; Lever, B.G.; Stones, W.F. (1963) J. Appl. Chem., 13, 483. Ibl, N.; Kramer, R.; Ponto, L.; Robertson, P.M. (1979) Electroorganic Synthesis Technology. AIChE Symposium Series No. 185 75, 45. Rakov, A.A.; Veselovskii, V.I.; Kasatkin, E.V.; Potapova, G.F.; Sviridon, V.V. (1977) Zh. Prikl. Khim. 50, 334. Bianchi, G.; Gallone, P.; Nidola, A.E. (1970) Composite anodes. US Patent 3,491,014; January 20, 1970. Beer, H.B. (1963) Noble metal coated titanium electrode and method for making and using it. US Patent 3,096,272; July 2, 1963. Bianchi, G.; De Nora, V.; Gallone, P.; Nidola, A. (1971) Titanium or tantalum base electrodes with applied titanium or tantalum oxide face activated with noble metals or noble metal oxides. US Patent 3,616,445; October 26, 1971. Bianchi, G.; De Nora, V.; Gallone, P.; Nidola, A. (1976) Valve metal electrode with valve metal oxide semiconductive face. US Patent 3,948,751; April 6, 1976. Beer, H.B. (1966) Electrode and method for making the same. US Patent 3,234,110; February 8, 1966. Beer, H.B. (1966) Method of chemically plating base layers with precious metals of the platinum group. US Patent 3,265,526; August 9, 1966. Beer, H.B. (1972) Electrode and coating therefor. US Patent 3,632,498; January 4, 1972. Beer, H.B. (1973) Electrode having a platinum metal oxide. US Patent 3,711,385; January 13, 1973. Beer, H.B. (1973) Electrode and coating therefor. US Patent 3,751,291; August 7, 1973.

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a trademark of Electronor Corp.). The classical composition of the composite anodes is 123 defined in Table 9.19 as follows : Table 9.19. Definition of dimensionally stable anodes A dimensionally stable anode is a composite electrode made of:

(1) Base metal or substrate

A base metal with a valve action property, such as the refractory metals (e.g., Ti, Zr, Hf, Nb, Ta, Mo, W) or their alloys (e.g., Ti-0.2Pd, Ti-Ru). This base metal acts as a current 124 collector. Sometimes it is possible to find in the claims of some particular patents unusual base materials (e.g., Al, Si-cast iron, Bi, C, Ti4O7, Fe3O4).

(2) Protective A thin and impervious layer (a few micrometers thick) of passivating layer a protective valve metal oxide (e.g., TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, NbO2 and TaO2). (3) Electrocatalyst

An electrocatalytic oxide of a noble metal or, more often, an oxide of the PGMs. This PGM oxide (e.g., RuO2, PtOx, IrO2) increases the electrical conductivity of the passivating film. Sometimes other oxides are added (e.g., SnO2, Sb2O5, Bi2O3) and also carbides (e.g., B4C) or nitrides.

As a general rule, these anodes are made from a titanium base metal covered by a rutile 125,126 layer TiO2 doped by RuO2 (30 mol.%). They were used extensively in the industry (e.g., De Nora, Magnetochemie, Permelec, Eltech Systems Corp., US Filter, and Heraeus) and 127 today they are used in all chlor-alkali processes and in chlorate production. The dimensionally stables anodes for chlorine evolution are described in the technical literature by the brand acronyms DSA®(RuO2) and DSA®-Cl2, and they enjoyed great success in industry for two reasons: first, ruthenium has the lowest price of all the PGMs and, second, its density is half that of its neighbors. Moreover, its electrocatalytic characteristics for the evolution of –2 chlorine are satisfactory. In industrial conditions (2 to 4 kA.m ) the service life of these electrodes is over 5 years. Therefore, today, titanium is the only base metal used for manufacturing dimensionally stable anodes for chlorine evolution. The contribution of Beer’s discovery to the development of industrial electrochemistry is very important. The reader can also find a complete story of the invention of DSA® as told by the inventor himself and 128 written on the occasion of his receiving the Electrochemical Society Medal award.

9.7.3.2.11

Dimensionally Stable Anodes (DSA®) for Oxygen

Several industrial processes require long-lasting anodes for evolving oxygen in an acidic medium. In comparison with the chlorine-evolution reaction, the evolution of oxygen leads 123

124 125

126

127

128

Nidola, A. In: Trasatti, S. (ed.) (1981) Electrodes of Conductive Metallic Oxides. Part B. Elsevier, Amsterdam, Chap. 11, pp. 627–659. De Nora, O.; Nidola, A.; Trisoglio, G.; Bianchi, G. (1973) British Patent 1,399,576. Vercesi, G.P.; Rolewicz, J.; Comninellis, C.; Hinden, J. (1991) Characterization of dimensionally stable anodes DSA-type oxygen evolving electrodes. Choice of base metal. Thermochimica Acta, 176, 31–47. Comninellis, Ch.; Vercesi, G.P. (1991) Characterization of DSA-type oxygen evolving electrodes: choice of a coating. J. Appl. Electrochem., 21(4), 335–345. Gorodtskii, V.V.; Tomashpol’skii, Yu.Ya.; Gorbacheva, L.B.; Sadovskaya, N.V.; Percherkii, M.M.; Erdokimov, S.V.; Busse-Machukas, V.B.; Kubasov, V.L.; Losev, V.V. (1984) Elektrokhimiya, 20, 1045. Beer, H.B. (1980) The invention and industrial development of metal anodes. J. Electrochem. Soc., 127, 303C−307C.

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Miscellaneous Electrical Materials

to higher positive potentials combined with an increase in the acidity leading to more severe conditions for the anode material. Hence most materials are put in their anodic dissolution or transpassive region. These conditions greatly restrict the selection of suitable materials. The only materials that withstand these conditions are gold and the PGMs, but their use is prohibited by their high densities and high prices when required in bulk. Today, when highly valuated chemicals are produced, these metals can be cladded onto common base metals and –2 polarized under low anodic current densities (1 kA.m ), while for more demanding conditions a hydrogen-diffusion anode must be used. Nevertheless, their high electrocatalytic activity dictates their use as electrocatalysts. As a general rule, the increasing electrochemical 129 activity could be classified as follows: Ir>Ru>Pd>Rh>Pt>Au. The carbon anodes, sometimes impregnated with a dispersion of PGMs, are now totally obsolete owing to their high oxygen overvoltage and a rapid failure during electrolysis. In fact, owing to their high porosity, an intercalation phenomenon occurs: the anions penetrate in the lattice and expand the 130 structure, leading rapidly to spalling of the electrode. Therefore most electrode materials described previously fail rapidly when operating at –2 high anodic current densities (e.g., 2 to 15 kA.m ) imposed by demanding electrochemical 132 processes such as high-speed gold plating, high-speed electrogalvanizing of steel (e.g., 133 Andritz Ruthner A.G. technology), and zinc electrowinning. Based on good results obtained with mixed metallic oxides (MMO) such as TiO2-RuO2 and Ta2O5-RuO2 for the chlorine reaction and the huge success of DSA® in the chlor-alkali industry, these anodes were optimized for the oxygen-evolution reaction. Several compositions of electrocatalysts and base metals were then actively studied. Many metal oxides exhibiting both a good electronic conductivity, multivalence states, and a low redox potential for the higher oxide versus the lower oxide couple have been reported as promising electrocatalysts. The experimental values for the standard redox potentials of oxide couples are presented in Table 9.20. These data show clearly that of the candidate electrocatalysts, Ir, Ru, Os, Ni, and Co have lower redox potentials than Rh, Pd, and Pt. Despite its excellent electrocatalytic activity, ruthenium dioxide (RuO2) is readily oxidized at 1.39V/SHE to give off the volatile ruthenium Table 9.20. Standard potentials for several oxide couples

131

Higher/lower oxide couple Standard electrode potential at 298.15 K (E/V vs. SHE)

129

130

131 132

133

IrO2/Ir2O3

0.930

RuO2/Ru2O3

0.940

OsO2/OsO4

1.00

NiO2/Ni2O3

1.43

CoO2/Co2O3

1.45

RhO2/Rh2O3

1.73

PtO3/PtO2

2.00

PdO3/PdO2

2.03

Miles, M.H.; Thomason, J. (1976) Periodic variations of overvoltages for water electrolysis in acid solutions from cyclic voltammetric studies. J. Electrochem. Soc., 123(10), 1459–1461. Jasinski, R.; Brilmyer, G.; Helland, L. (1983) Stabilization of glassy carbon electrodes. J. Electrochem. Soc., 130(7), 1634. Tseung, A.C.C.; Jasem, S. (1977) Oxygen evolution on semiconducting oxides. Electrochim. Acta, 22, 31 Smith, C.G.; Okinaka, Y. (1983) High speed gold plating: anodic bath degradation and search for stable low polarization anodes. J. Electrochem. Soc., 130, 2149–2157. Hampel, J. (1984) Process and apparatus for the continuous electroplating of one or both sides of a metal strip. US Patent 4,469,565; February 22, 1984.

Electrode Materials 134

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135,136

tetroxide (RuO4), and it is too sensitive to electrochemical dissolution. Osmium was excluded owing to the formation of volatile (b.p. 130°C) and hazardous tetroxide (OsO4), while nickel and cobalt oxides exhibit poor conductivity. Therefore, iridium dioxide (IrO2) is the most stable and active electrocatalyst coating, especially when prepared by the thermal decomposition of iridium-chloride precursors (e.g., H2IrCl6, IrCl4). Other studies demonstrated the important selection of the valve metal oxide (e.g., TiO2, Nb2O5, and Ta2O5). 137 De Nora showed that the best formulation was Ta2O5-IrO2. Later, Comninellis and cowork138 ers optimized the composition preparing a coating containing 70 mol.% IrO2. This product was later developed commercially by Eltech System Corp. under the trade name TIR-2000®. These anodes have achieved operation in high-speed electrogalvanizing at current densities –2 139 as high as 15 kA.m and with service lives exceeding 4300 h. In contrast to the coating wear limiting anode life in chlorine, the complex corrosion-passivation mechanism of the substrate beneath the coating is typically the limiting factor for oxygen-evolving anodes. Indeed, during coating preparation the thermal stresses transform the electrocatalyst layer 140 into a typical microcracked structure. The gaps between grains facilitate the penetration of 141,142,143 the corrosive electrolyte down to the base metal (i.e., undermining process). According to Hine et al., by analogy with the anodic deactivation mechanism of PbO2- and MnO2144 coated anodes, the failure mode involves the damage of the interface between the electrocatalyst and the base metal, forming a thin layer of insulating rutile. This insulating film decreases the anode active surface area, increasing the local anodic current density. This behavior ends up with the spalling of the coating. The deactivation can be easily monitored industrially because the operating cell voltage increases continuously up to the limiting potential delivered by the rectifier. At this stage the anode is considered to be deactivated and is returned to the supplier to be refurbished. The costly electrocatalyst coating is then removed from the substrate by chemical stripping. The etching operation is usually performed in a molten mixture of alkali-metal hydroxides (e.g., NaOH) containing small 145 amounts of an oxidizing salt. The precious catalyst is then recovered in the slimes at the bottom of the vessel, while the clean substrate is treated and reactivated by the classical procedure. Usually, the critical parameters that influence the service life of the anode are the anodic current density, the coating preparation, and impurities. Actually, several inorganic 146 and organic pollutants can lead to the dissolution of titanium (e.g., fluoride anions ), scaling (e.g., manganous cations), and the loss of coating (e.g. organic acids, nitroalcohols, etc.). For example, in organic electrosynthesis, the service life of these electrodes ranges from 134

135 136

137 138

139

140 141 142 143 144 145

146

Hine, F.; Yasuda, M.; Noda, T.; Yoshida, T. ; Okuda, J. (1979) Electrochemical behavior of the oxidecoated metal anodes. J. Electrochem. Soc., 126(9), 1439–1445. Manoharan, R.; Goodenough, J.B. (1991) Electrochim. Acta, 36, 19. Yeo, R.S.; Orehotsky, J.; Visscher, W.; Srinivasan,S. (1981) Ruthenium-based mixed oxides as electrocatalysts for oxygen evolution in acid electrolytes. J. Electrochem. Soc., 128(9), 1900–19004. De Nora, O.; Bianchi, G.; Nidola, A.; Trisoglio, G. (1975) Anode for evolution of oxygen. US Patent 3,878,083. Comninellis, Ch.; Vercesi, G.P. (1991) Characterization of DSA-type oxygen evolving electrodes: choice of a coating. J. Appl. Electrochem., 21(4), 335–345. Hardee, K.L.; Mitchell, L.K. (1989) The influence of electrolyte parameters on the percent oxygen evolved from a chlorate cell. J. Electrochem. Soc., 136(11), 3314–3318. Kuznetzova, E.G.; Borisova, T.I.; Veselovskii, V.I. (1968) Elektrokhimiya 10, 167. Warren, H.I., Wemsley, D., Seto, K. (1975) Inst. Min. Met. Branch Meeting, February 11, 1975, 53. Seko, K. (1976) Am. Chem. Soc. Centennial Meeting, New York. Antler, M.; Butler, C.A. (1967) J. Electrochem. Technol., 5, 126. Hine, F.; Yasuda, M.; Yoshida, T.; Okuda, J. (1978) ECS Meeting, Seattle, May 15, Abstract 447. Colo, Z.J.; Hardee, K.L.; Carlson, R.C. (1992) Molten salt stripping of electrode coatings. US Patent 5,141,563; August 25, 1992. Fukuda, K.; Iwakura, C.; Tamura, H. (1980) Effect of heat treatment of titanium substrate on service life of titanium-supported iridia electrode in mixed aqueous solutions of sulfuric acid, ammonium sulfate, and ammonium fluoride. Electrochim. Acta, 25(11), 1523–1525.

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Miscellaneous Electrical Materials 147

–2

500 to 1000 h in molar sulfuric acid at 60°C. Hence the high cost (10 to 30 k$.m ) forbids their industrial use in those conditions. In the late 1970s, as a consequence of work done on cathodically modified alloys initially conducted in the 1940s in the former Soviet Union by 148 the Tomashov group, followed in the 1960s by Stern and Cotton at ICI, there appeared a titanium-palladium alloy (i.e., ASTM grade 7) in which a small amount of palladium (0.12 to 0.25 wt.% Pd) greatly improved the corrosion resistance in reducing acids. Hence, several patents claimed a substrate made of Ti-Pd for preparing DSA® for oxygen. Nevertheless, despite a certain improvement, their limited service life led to the abandonment of several industrial projects. Moreover, Cardarelli and coworkers demonstrated that the service life of Ti/Ta2O5-IrO2 anodes was affected by impurities in commercially pure titanium and by alloy149 ing elements in titanium alloys. In addition, the influence of other reactive and refractory metals (i.e., Nb, Ta, Zr) as substrate on the service life has been studied, and it has been 150 observed by Vercesi et al. that the performance of tantalum-based anodes was better than that of titanium-based electrodes. This good behavior was due to the remarkable corrosion resistance of tantalum owing to the valve action property of its passivating and impervious film of anodically formed tantalum pentoxide. However, the development of a bulk tantalum-based electrode is not practical from the viewpoint of economics. Actually, the high –3 price of tantalum (461 US$/kg) combined with its high density (16,654 kg.m ), in compari–3 son with titanium metal (4540 kg.m ), which has a medium-range price (50 US$/kg), precludes any industrial applications. As a consequence, an anode of tantalum is 35 times more expensive than a titanium anode. Furthermore, owing to its high reactivity versus oxygen above 350°C, the preparation of tantalum anodes involves great difficulties during the thermal treatment required for the manufacture of electrodes. For these reasons, the tantalum anode does not enjoy widespread industrial use. To decrease the cost, a thin tantalum layer deposited onto a common base metal is a very attractive alternative. This idea appeared for 151 the first time in 1968 in a patent registered by the German company Farbenfabriken Bayer 152 and also in 1974 proposed by Jeffes in a patent of Allbright & Wilson. In this last patent a composite DSA®-Cl2 was made from a steel plate coated with 500 μm of tantalum prepared by chemical vapor deposition. Then the tantalum was coated with RuO2 (steel/Ta/RuO2). Twenty years later, the anodes made according to this process were not industrially devel153 oped. However, in 1990, in a European patent registered by ICI, Denton and Hayfield described the preparation of oxygen anodes made of a thin tantalum coating deposited onto 154 a common base metal using several techniques. Finally, in 1993, Kumagai et al. from DAIKI Engineering in Japan prepared an anode made of a thin intermediate layer of tantalum deposited onto a titanium base metal by sputtering (Ti/Ta/Ta2O5-IrO2). To select the most optimized method for depositing tantalum onto a common substrate, a comprehensive comparison of tantalum coating techniques used in the chemical process industry was 147

148

149

150

151 152 153

154

Savall, A. (1992) Electrosynthèse organique. In: Électrochimie 92, L’Actualité Chimique, Special issue, January 1992. Potgieter, J.H.; Heyns, A.M.; Skinner, W. (1990) Cathodic modification as a means of improving the corrosion resistance of alloys. J. Appl. Electrochem., 20(5), 711–15. Cardarelli, F.; Comninellis, Ch.; Savall, A.; Taxil, P.; Manoli, G.; Leclerc, O. (1998) Preparation of oxygen evolving electrodes with long service life under extreme conditions. J. Appl. Electrochem., 28, 245. Vercesi, G.P.; Rolewicz, J.; Comninellis, C.; Hinden, J. (1991) Characterization of dimensionally stable anodes DSA-type oxygen evolving electrodes. Choice of base metal. Thermochimica Acta, 176, 31–47. Farbenfabriken Bayer Aktiengesellschaft (1968) French Patent 1,516,524. Jeffes, J.H.E. (1974) Electrolysis of brine. British Patent 1,355,797; July 30, 1974. Denton, D.A.; Hayfield, P.C.S. (1990) Coated anode for an electrolytic process. European Patent 383,412; August 22, 1990. Kumagai, N.; Jikihara, S.; Samata, Y.; Asami, K.; Hashimoto, A.M. (1993) The effect of sputter-deposited Ta intermediate layer on durability of IrO2-coated Ti electrodes for oxygen evolution. In: Proceeding of the 183rd Joint International Meeting of the Electrochemical Society, 93–30(Corrosion, Electrochemistry, and Catalysis of Metastable Metals and Intermetallics), Abstract 324-33, Honolulu, HI, May 16-21, 1993.

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155

recently reviewed by Cardarelli et al. Moreover, the same authors developed anodes made from a thin tantalum layer deposited onto a common base metal (e.g. copper, nickel, or stainless steel) coated with an electrocatalytic mixture of oxides Ta2O5-IrO2 produced by calcination. The performances of these anodes (stainless steel/Ta/IrO2) are identical to that 156 obtained with solid tantalum base metal (Ta/IrO2).

9.7.3.2.12 Synthetic Diamond Electrodes Structure. The use of synthetic semiconductive diamond thin films in electrochemistry has 157 only recently been reported. Former designations such as diamondlike carbon (DLC) are now obsolete and so are not used in this book. By contrast with its other carbon allotropes, 3 in diamond each carbon atom is tetrahedrally bonded to four other carbons using sp -hybrid orbitals. Properties. Diamond has several attractive properties including the highest Young’s modulus, thermal conductivity, and hardness of all solid materials, high electrical resistance, excellent chemical inertness, high electron and hole mobilities, and a wide optical transparency range (Section 12.5.1). The pure material is a wide bandgap insulator (Eg = 5.5 eV) and offers advantages for electronic applications under extreme environmental conditions. Nevertheless, when doped with boron, the material exhibits p-type semiconductive properties (i.e., IIb type diamond). Actually, doped diamond thin films can possess electronic conductivity ranging from that of an insulator at low doping levels to those of a good semiconduc19 –3 tor for highly doped films (i.e., impurity level >10 atoms.cm ). For instance, synthetic diamond thin films grown using hot-filament or microwave-assisted chemical vapor deposition can be doped to as high as 10,000 ppm at. of boron per carbon atom, resulting in films 5 with resistivities of less than 10 μΩ.cm. Boron atoms that are electron acceptors form a band located roughly 0.35 eV above the valence band edge. At room temperature, some of the valence-band electrons are thermally promoted to this intermediate level, leaving free electrons in the dopant band and holes, or vacancies, in the valence band to support the flow of current. In addition, boron-doped diamond thin films commonly possess a rough, polycrystalline morphology with grain boundaries at the surface and a small-volume fraction of nondiamond carbon impurity. Hence, the electrical conductivity of the film surface and the bulk is influenced by the boron-doping level, the grain boundaries, and the impurities. Several interesting electrochemical properties distinguish boron-doped diamond thin films from conventional carbon-based electrodes. As a general rule, boron-doped diamond films exhibit voltammetric background currents and double-layer capacitances up to an order of magnitude lower than for glassy carbon. The residual or background current density in –2 0.1 M KCl measured by linear sweep voltammetry is less than 50 μA.cm between –1.0 and +1.0 V/SHE. This indicates that the diamond-electrolyte interface is almost ideally polarizable. The evolution of hydrogen starts at roughly –1.75 V/SHE. The electrochemical span or working potential window, defined as the potentials at which the anodic and cathodic cur–2 rents reach 250 μA.cm , is 3.5 V for diamond compared to 2.5 V for glassy carbon. The overpotentials for hydrogen and oxygen evolution reactions are directly related to the nondiamond carbon impurity content. The higher the fraction of nondiamond carbon present, the lower the overpotentials for both these reactions. The double-layer capacitance for BDD in 155

156

157

Cardarelli, F.; Taxil, P.; Savall, A. (1996) Tantalum protective thin coating techniques for the chemical process industry: molten salts electrocoating as a new alternative. Int. J. Refract. Metals Hard Mater., 14, 365. Cardarelli, F.; Comninellis, Ch.; Leclerc, O.; Saval, A.; Taxil, P.; Manoli, G. (1997) Fabrication of an anode with enhanced durability and method for making the same. PCT International Patent Application WO 97/43465A1. Swain, G.; Ramesham, R. (1993) The electrochemical activity of boron-doped polycrystalline diamond thin film electrodes. Anal. Chem., 65(4), 345–351.

9 Miscellaneous Electrical Materials

586

Miscellaneous Electrical Materials –2

1 M KCl ranges from 4 to 8 μF.cm over a 2-V potential window. There is a general trend toward increasing capacitance with more positive potentials, which is characteristic for p-type 158 semiconductor electrode-electrolyte interfaces. These capacitance values are comparable in magnitude to those observed for the basal plane of highly oriented pyrolytic graphite and –2 significantly lower than those for glassy carbon (25 to 35 μF.cm ). The capacitance versus potential profile shape and magnitude for diamond is largely independent of the electrolyte composition and solution pH. On the other hand, boron-doped diamond electrodes have good electrochemical activity without any pretreatment. Preparation. Diamond thin films can be prepared on a substrate from thermal decomposition of dilute mixtures of a hydrocarbon gas (e.g., methane) in hydrogen using one of several energy-assisted CVD methods, the most popular being hot-filament and microwave 159,160 The growth methods mainly differ in the manner in which the gas thermal discharge. activation is accomplished. Typical growth conditions are C/H ratios of 0.5 to 2 vol%, reduce pressures ranging from 1.33 to 13.3 kPa, a substrate temperature between 800 and 1000°C, and microwave powers of 1 to 1.3 kW, or filament temperatures of ca. 2100°C, depending on the method used. The film grows by nucleation at rates in the 0.1- to 1-μm/h range. For the substrates to be continuously coated with diamond, the nominal film thickness must be 1 μm. Wafer diameters of several centimeters can easily be coated in most modern reactors. Boron doping is accomplished from the gas phase by mixing a boron-containing gas such as diborane (B2H6) with the source gases, or from the solid state by gasifying a piece of hexagonal161 boron nitride (h-BN). Prior to deposition the substrate must be pretreated by cleaning it with a series of solvents, and nucleation sites are provided by embedding tiny diamond particles that are polished with a diamond paste. Hydrogen plays an important role in all of the 3 growth methods as it prevents surface reconstruction from a saturated sp -hybridized dia2 mond microstructure to an unsaturated sp -hybridized graphite microstructure; it also suppresses the formation of nondiamond carbon impurity, and it prevents several species from forming reactive radicals.

9.7.4 Electrodes for Corrosion Protection and Control Apart from batteries, fuel cells, and industrial electrolyzers, corrosion protection and control is another field in which electrode materials occupy an important place.

9.7.4.1 Cathodes for Anodic Protection 162

Anodic protection is a modern electrochemical technique for protecting metallic equipment used in the chemical-process industry against corrosion and handling highly corrosive chemicals (e.g., concentrated sulfuric and orthophosphoric acids). The technique consists in –2 impressing a very low anodic current (i.e., usually 10 μA.m ) on a piece of metallic equipment (e.g., tanks, thermowells, columns) to protect against corrosion. This anodic polarization puts the electrochemical potential of the metal in the passivity region of its Pourbaix 158

159

160

161

162

Alehashem, S.; Chambers, F.; Strojek, J.W.; Swain, G.M.; Ramesham, R. (1995) New applications of diamond thin film technology in electro chemical systems. Anal. Chem., 67, 2812. Angus, J.C.; Hayman, C.C. (1988) Low-pressure, metastable growth of diamond and “diamondlike” phases. Science 241, 913–921. Argoitia, A.; Angus, J.C.; Ma, J.S.; Wang, L.; Pirouz, P.; Lambrecht, W.R.L. (1994) Pseudomorphic stabilization of diamond on non-diamond substrates. J. Mater. Res., 9, 1849. Vinokur, N.; Miller, B.; Avyigal, Y.; Kalish, R. (1996) Electrochemical behavior of boron-doped diamond electrodes. J. Electrochem. Soc., 143(10), L238–L240. Riggs, Jr., O.L.; Locke, C.E. (1981) Anodic Protection: Theory and Practice in the Prevention of Corrosion. Plenum, New York.

Electrode Materials

587

diagram, i.e., where the dissolution reaction does not occur, and hence this leads to a negligible corrosion rate (i.e., less than 25 μm/year). The anodic protection method can only be used to protect metals and alloys exhibiting a passive state (e.g., reactive and refractory metals, stainless steels, etc.) against corrosion. Usually, the equipment required is a cathode, a reference electrode, or a power supply. The various cathode materials used in anodic protection are listed in Table 9.21. Table 9.21. Cathode materials for anodic protection

163

Cathode

Corrosive chemicals

Hastelloy®C

Nitrate aqueous solutions, sulfuric acid

Illium®G

Sulfuric acid (78–100 %wt.), oleum

Nickel-plated steel

Electroless nickel plating solutions

Platinized copper or brass

Acids

Silicon-cast iron (Duriron®) Sulfuric acid (89–100 %wt.), oleum ASTM A518 grade 3 Stainless steels (AISI 304, 316L)

Nitrate aqueous solutions

Steel

Kraft digester liquid

9.7.4.2 Anodes for Cathodic Protection Cathodic protection is the cathodic polarization of a metal to maintain its immunity in a corrosive environment. There are two ways to achieve an efficient cathodic polarization. Table 9.22. Sacrificial anode materials

164

Sacrificial anode material

Oxidation Electrode Capacity –1 reaction potential (Ah.kg ) at 298.15 K (E0/mV vs. SHE)

Magnesium

Mg /Mg

Zinc

0

0

Zn /Zn

2+

2+

–2360

1100

Consumption rate –1 –1 (kg.A .yr )

Notes

7.9

Buried soils, suitable for highresistivity environments. Unsuited for marine applications due to high corrosion rate of magnesium in seawater

–760

810

10.7

Used in fresh, brackish, and marine water

–1660

920–2600

3.0–3.2

AluminumZinc-Indium

1670–2400

3.6–5.2

Seawater, brines. Offshore and oil rigs, marine. Addition of In, Hg, and Sn prevent passivation

AluminumZinc-Tin

2750–2840

3.4–9.4

0

AluminumAl /Al Zinc-Mercury

163

164

3+

From Locke, C.E. (1992) Anodic Protection. In: ASM Metals Handbook, 10th ed. Vol. 9. Corrosion, ASM, Materials Park, OH, pp. 463–465. Dreyman, E.W. (1973) Selection of anode materials. Eng. Exp. Stn. Bull. (West Virginia University), 110, 83–89.

9 Miscellaneous Electrical Materials

588

Miscellaneous Electrical Materials

The first is a passive protection that consists in connecting electrically the metal to a less noble material that will result in a galvanic coupling of the two materials, which leads to the anodic dissolution of the sacrificial anode. The second method is an active protection that consists in using an impressed current power supply in order to polarize cathodically the workpiece versus a nonconsumable or inert anode. Table 9.23. Impressed-current anode materials Sacrificial anode material

Composition Typical anodic current density –2 (A.m )

Dimensionally Ti/IrO2 stable anodes Ti-Pd/IrO2 (DSA®) Nb/IrO2 Ta/IrO2

700 to 2000

165

Consump- Cost per unit Notes tion rate surface area –1 –1 2 (g.A .yr ) (US$/m ) 1-mm-thick anode Less than 1 9000 15,000 13,000 54,000

Cathodic protection of water tank and buried steel structures

200 to 500

500–1000

Both good corrosion and abrasion/wear resistance. Used extensively offshore, on oil rigs, and in other marine technology applications

2000–3000

Corrosion resistant to both alkaline and acid media. Brittle and shock-sensitive material. –3 Density 3600–4300 kg.m . Conductivity 30–300 S/cm

Silicon-cast iron (Duriron®)

Fe-14.5Si10 to 40 4.0Cr-0.8C1.50Mn0.5Cu-0.2Mo

Ebonex®

Ti4O7, Ti5O9

50 (naked) n.a. 2000 (IrO2 coated)

Graphite and carbon

Carbon

10–40

225–450

Lead-alloy anodes

Pb-6Sb1Ag/PbO2

160 to 220

45 to 90

15–20

Cathodic protection for equipment immersed in seawater

Platinized Ti/70PtOxtitanium 30IrO2 (K-type 70/30)

500 to 1000

18

15,000

Low consumption rate, high anodic current, but expensive

Platinized niobium and tantalum anodes

Nb/Pt-Ir, Ta/Pt-Ir

500 to 1000

1 to 6

40,000– 60,000

Low consumption rate, high anodic current, but expensive

Ebonex®/ Polymer composite

Ti4O7 with conductive polymer binder

n.a.

n.a.

1000

Cathodic protection of reinforced steel bars in salt-contaminated –3 concrete. Density 2300–2700 kg.m ; conductivity 1–10 S/cm

165

Brittle and shock-sensitive materials. Used extensively buried for cathodic protection of ground pipelines

Dreyman, E.W. (1973) Selection of anode materials. Eng. Exp. Stn. Bull. (West Virginia University), 110, 83–89.

Electrode Materials

589

9.7.5 Electrode Suppliers and Manufacturers Table 9.24. Industrial electrode manufacturers (continued) Electrode supplier

Typical products and brand names

Contact address

Anomet Products

Pt/Nb/Cu, Pt/Ti/Cu

830 Boston Turnpike Road, Shrewsbury, MA 01545, USA Telephone: +1 (508) 842-3069 Fax: +1 (508) 842-0847 E-mail: [email protected] URL: http://www.anometproducts.com/

Anotec Industries

High silicon cast iron anodes for impressed current

5701 Production Way, Langley, V3N 4N5 British Columbia, Canada Telephone: +1 (604 )514-1544 Fax: +1 (604 ) 514 1546 URL: http://www.anotec.com/

Atraverda Ltd. (formerly Ebonex Technology Inc.)

Andersson–Magnéli phases, Ti4O7, Ebonex®

Units A&B, Roseheyworth Business Park Abertillery, Gwent, NP13 1SX, UK Telephone:+44 (0) 1495 294 026 Fax:+44 (0) 1495 294 179 E-mail: [email protected] URL: http://www.atraverda.com

Chemapol Industries

Ti/RuO2, Ti/IrO2

Mumbai, India Telephone: +22 641 010 / 226 412 12 Fax: 22653636 E-mail: [email protected]

De Nora Elettrodi Spa

Ti/RuO2, Ti/IrO2, Nb/RuO2, Ta/IrO2

Via Bistolfi, 35, I-20134 Milan, Italy Telephone: (+39) 0221291 Fax: (+39) 022154873 E-mail: [email protected] URL: http://www.denora.it/

DISA Anodes

Ti/RuO2, Ti/IrO2, Nb/RuO2, Ta/IrO2

7 Berg Street, Jeppestown Johannesburg, Republic of South Africa Tel: +27 (0) 11 614 5238 / 5533 Fax: +27 (0) 11 614 0093 E-mail: [email protected] URL: http://www.disaeurope.it/products.html

Eltech Systems Corp.

DSA-Cl2 and DSA-O2 TIR®2000 TM MOL

Corporate Headquarters 100 Seventh Avenue, Suite 300, Chardon, OH 44024, USA Telephone: +1 (440) 285-0300 Fax: +1 (440) 285-0302 E-mail: [email protected] URL: http://www.eltechsystems.com/

Farwest Corrosion

Anodic, cathodic protection

1480 West Artesia Blvd., Gardena, CA 90248-3215, USA Telephone: +1 (310) 532-9524 Fax: +1 (310) 532-3934 E-mail: [email protected]

Magneto Special Anodes BV (formerly Magnetochemie)

MMO, Ti/RuO2, Ti/IrO2, Nb/RuO2, Ta/IrO2

Calandstraat 109, NL-3125 BA Schiedam, Netherlands Telephone: (+31) 10-2620788 Fax: (+31) 10-2620201 E-mail: [email protected] URL: http://www.magneto.nl

9 Miscellaneous Electrical Materials

590

Miscellaneous Electrical Materials

Table 9.24. (continued) Electrode supplier

Typical products and brand names

Contact address

Permascand AB

MMO, Ti/RuO2, Ti/IrO2

P.O. Box 42, Ljungaverk, S-840 10, Sweden Telephone: (+46) 691 355 00 Fax: (+46) 691 331 30 E-mail: [email protected] URL: http://www.permascand.com

Ti Anode Fabricators P (TAF)

MMO, Ti/RuO2, Ti/IrO2

# 48, Noothanchery, Madambakkam, Chennai - 600 073, India Telephone: +91 44 2278 1149 Fax: +91 44 2278 1362 E-mail: [email protected] URL: http://www.tianode.com

Titanium Equipment & MMO, Ti/RuO2, Ti/IrO2 Anode Manufacturing Company (TEAM)

TEAM House, Grand Southern Trunk Road, Vandalur, Chennai - 600 048, India Telephone: + 91 44 2 2750323 / 24 Fax: + 91 44 2 2750860 E-mail: [email protected] URL: http://www.team.co.in/

Titaninum Tantalum Products (TiTaN)

MMO, Ti/RuO2, Ti/IrO2, Nb/RuO2, Ta/IrO2

86/1, Vengaivasal Main Road Gowrivakkam, Chennai 601 302, Tamil Nadu, India Telephone: + 91 44 2278 1210 Fax: + 91 44 2278 0209 URL: http://www.titanindia.com/

US Filter Corp. (formerly Electrode Products)

MMO, Ti/RuO2, Ti/IrO2

2 Milltown Court, Union, NJ 07083, USA Telephone: +1 (908) 851-6921 Fax: +1 (908) 851-6906 E-mail: [email protected] URL: http://www.usfilter.com

9.8 Electrochemical Galvanic Series Table series of metals and alloys in seawater Table9.25. 9.25. Galvanic (continued) Metal or alloy Corroded end (anodic or least noble) Magnesium Magnesium alloys Zinc Aluminum alloys 5052, 3004, 3003, 1100, 6053 Cadmium Aluminum alloys 2117, 2017, 2024 Mild steel (AISI 1018), wrought iron Cast iron, low-alloy high-strength steel Chrome iron (active) Stainless steel, AISI 430 series (active) Stainless steels AISI 302, 303, 321, 347, 410, and 416(active)

Electrochemical Galvanic Series

591

Table 9.25. (continued) Metal or alloy Ni - Resist Stainless steels AISI 316, 317 (active) Carpenter 20Cb-3 (active) Aluminum bronze (CA 687) Hastelloy C (active), Inconel® 625 (active), titanium (active) Lead-tin solders Lead Tin Inconel® 600 (active) Nickel (active) 60 Ni-15 Cr (active) 80 Ni-20 Cr (active) Hastelloy® B (active) Brasses Copper (CDA102) Manganese bronze (ca 675), tin bronze (ca903, 905) Silicone bronze Nickel silver 90Cu-10Ni 80Cu-20Ni Stainless steel 430 Nickel, aluminum, bronze (ca 630, 632) Monel 400 and K500 Silver solder Nickel 200 (passive) 60Ni-15Cr (passive) Inconel 600 (passive) 80Ni- 20Cr (passive) Cr-Fe (passive) Stainless steel grades 302, 303, 304, 321, 347 (passive) Stainless steel grades 316 and 317 (passive) Carpenter 20 Cb-3 (passive), Incoloy® 825 and Ni-Mo-Cr-Fe alloy (passive) Silver Titanium (pass.), Hastelloy® C276 (passive), Inconel® 625(pass.) Graphite Zirconium Gold Platinum Protected end (cathodic or most noble)

9 Miscellaneous Electrical Materials

Ceramics, Refractories, and Glasses

10.1 Introduction and Definitions The word “ceramics” is derived from the Greek keramos, meaning solid materials obtained from the firing of clays. According to a broader modern definition, ceramics are either crystalline or amorphous solid materials involving only ionic, covalent, or ionocovalent chemical bonds between metallic and nonmetallic elements. Well-known examples are silica and silicates, alumina, magnesia, calcia, titania, and zirconia. Despite the fact that, historically, oxides and silicates have been of prominent importance among ceramic materials, modern ceramics also include borides, carbides, silicides, nitrides, phosphides, and sulfides. Several processes, namely calcining and firing, are extensively used in the manufacture of raw and ceramic materials, and they must be clearly defined. Calcining consists in the heat treatment of a raw material prior to being used in the final ceramic material. The purpose of calcination is to remove volatile chemically combined constituents and to produce volume changes. Firing or burning is the final heat treatment performed in a kiln to which a green ceramic material is subjected for the purpose of developing a strong chemical bond and producing other required physical and chemical properties. As a general rule ceramic materials can be grouped into three main groups: traditional ceramics, refractories and castables, and advanced or engineered ceramics. Before describing each class, a description of the most common raw materials used in the manufacture of traditional and advanced ceramics, refractories, and glasses is presented below.

594

Ceramics, Refractories, and Glasses

10.2 Raw Materials for Ceramics, Refractories and Glasses 10.2.1 Silica Silica, with the chemical formula SiO2 and relative molar mass of 60.084, exhibits a complex polymorphism characterized by a large number of reversible and irreversible phase transformations (Figure 10.1) usually associated with important relative volume changes (ΔV/V). At low temperature and pressure beta-quartz (β-quartz) [14808-60-7] predominates, but above 573°C, it transforms reversibly into the high-temperature alpha-quartz (α-quartz) [14808-60-7] with a small volume change (0.8 to 1.3 vol.%): β-quartz α-quartz

(573°C)

Quartz exhibits a very low coefficient of thermal expansion (0.5 μm/m.K) and an elevated Mohs hardness of seven. Large and pure single crystals of quartz of gem quality called lascas are used due to their high purity in the preparation of elemental silicon for semiconductors (see Section 5.8.1). At a temperature of 870°C, α-quartz transforms irreversibly into alpha-tridymite (α-tridymite, orthorhombic) [15468-32-3] with an important volume change of 14.4 vol.% as follows: α-quartz —> α-tridymite

(870°C)

But in practice, the kinetic of the above reaction is too slow, and tridymite never forms below 1250°C, and hence at 1250°C or 1050°C in the presence of impurities, α-quartz transforms irreversibly into alpha-cristoballite (α-cristoballite, tetragonal) [14464-46-1] with an important volume change (17.4 vol.%) as follows: α-quartz —> α-cristoballite

(1250°C)

However, if the temperature is raised to 1470°C, α-tridymite transforms also irreversibly into alpha-cristoballite (α-cristoballite) without any change in volume as follows: α-tridymite —> α-cristoballite

(1470°C)

On cooling α-cristoballite transforms reversibly into beta-cristoballite (β-cristoballite, cubic) at 260°C with a volume change 0 2.0 to 2.8 vol.%: α-cristoballite β-cristoballite (260°C) Finally, α-cristoballite melts at 1713°C while α-tridymite melts at 1670°C. Upon cooling silica melt yields amorphous fused silica [60676-86-0]. There also exist two high-pressure polymorphs of silica called coesite and stishovite (see Section 12.7) that occur in strongly mechanically deformed metamorphic rocks (e.g., impactites), but these two phases are usually not encountered in ceramics, refractories, and glasses. Industrially, silica products are classified into two main groups: natural silica products —quartzite, silica sand, and diatomite—and specialty silicas including fumed silica, silica gel, microsilica, precipitated silica, fused silica, and vitreous silica.

Figure 10.1. Polymorphs of silica (SiO2)

Raw Materials for Ceramics, Refractories and Glasses

595

10.2.1.1 Quartz, Quartzite, and Silica Sand Quartz is extensively found in nature either as a major mineral in most igneous (e.g., granite), sedimentary (e.g., sand and sandstone), and metamorphic rocks (e.g., quartzite and gneiss). In the case of ceramics, refractories, and glasses, raw quartz is essentially mined as round silica sand from glacial deposits, beach sands, crushed sandstones, or high-quality quartzite with a silica content of more than 97 wt.% SiO2. Quartzite can be either of sedimentary origin with detrital grains of quartz cemented by secondary silica or of metamorphic origin from the contact metamorphism of sandstones or tectonically deformed sandstones. For the most demanding applications, the run-of-mine is even washed with hydrochloric acid to remove traces of iron and aluminum sesquioxides and magnesium and calcium carbonates. Because quartzite consists mainly of beta-quartz, during firing, quartzite is subject to a behavior related to the polymorphism of silica. However, sedimentary quartzite transforms more rapidly than metamorphic equivalent. Price (2006). Silica sand is priced 15–40 US$/tonne.

10.2.1.2 Diatomite Diatomaceous earth, or simply diatomite, formerly called Kieselguhr, is a sedimentary rock of biological origin formed by the accumulation at the bottom of the ocean of siliceous skeletons of diatoms, or unicellular algae. Once-calcined diatomite is a white and lightweight –3 material with a mass density ranging from 190 to 275 kg.m . Diatomite is a highly porous material that exhibits high absorption capabilities and has a good chemical inertness. Major applications are filtering aids, metal polishing, thermal insulation, and Portland cement. Price (2006). Diatomite is priced 700–800 US$/tonne.

10.2.1.3 Fumed Silica Fumed silicas are submicrometric particles of amorphous silica produced industrially by burning silicon tetrachloride or tetrachlorosilane (SiCl4) using an oxygen-hydrogen burner. The continuous process requires high-purity silicon tetrachloride, which is a byproduct of the carbochlorination of zircon sand for the production of zirconium tetrachloride by companies like Western Zirconium and Wah Chang in the United States or CEZUS in France (see Section 4.3.3, Zirconium and Zirconium Alloys) Fumed silicas usually receives an after-treatment that consists in coating the surface of particles with silanes or silicones in order to enhance hydrophobicity or improve dispersion in aqueous solution. In 2004, the annual production of fumed silica worldwide reached ca. 100,000 tonnes. The German company Degussa-Hüls, with its brand name Aerosil®, is the world leader with half of the world production, followed by Cabot Corp. in the USA.

10.2.1.4 Silica Gels and Sol–Gel Silica Silica gels are dispersions of colloidal silica obtained by a sol–gel process. The process consists in precipitating colloidal silica from an aqueous solution of sodium silicate by adding hydrochloric or sulfuric acid. The colloidal precipitate or gel consists mainly of hydrated silica (SiO2.nH2O). After filtration the precipitated silica is washed in order to remove residual salts and stabilized by adding ammonia or sodium hydroxide. The stabilized gel is then dried and later calcined to obtain an activated material, usually in the form of small beads. Major producers are E.I. DuPont de Nemours, Akzo, and Nalco Chemicals Co.

10.2.1.5 Precipitated Silica Precipitated silica is obtained like silica gel by acidifying an aqueous solution of sodium silicate. Precipitated silica is used as filler in rubber for automobile tires and reinforcement particulate in elastomers, and as a flatting agent in paints and coatings for improving the

10 Ceramics, Refractories, and Glasses

596

Ceramics, Refractories, and Glasses

flatness of coatings. About 850,000 tonnes are produced annually worldwide. Major producers of precipitated silica are PPG Industries and Rhodia.

10.2.1.6 Microsilica Microsilica, also called silica-fume, is a submicronic amorphous silica with 90 to 98 wt.% SiO2 –3 and a low bulk density ranging from 200 to 450 kg.m . It forms most of the dust and other particulates in the off-gases produced during the electrothermal production of ferrosilicon (Fe-Si) or silicon (Si). The dust is collected in baghouses and bagged without further treatment. Due to its high surface area, microsilica reacts readily with hydrated calcium silicates forming strong bonds, and for that reason it is sometimes called reactive silica. Therefore the addition of microsilica to hydraulic cements improves their mechanical strength, reduces their permeability, and enhances their workability, cohesiveness, and flowing properties and hence is extensively used as an additive to cements and monolithic refractories. Annually, ca. 300,000 tonnes of microsilicas are produced worldwide. Major producers are obviously silicon or ferrosilicon producers such as Elkem in Canada and Norway and Fesil in Norway.

10.2.1.7 Vitreous or Amorphous Silica High-purity amorphous or fused silica, also called vitreous silica, when optically translucent is a high-performance ceramic obtained by electrothermal fusion of high-grade silica sand with a silica content above 99.5 wt.% SiO2 into an AC electric-arc furnace (EAF) at a temperature of around 1800 to 2100°C. The melt is then rapidly quenched to prevent crystallization. –3 Fused silica has a mass density of 2200 kg.m while vitreous silica is slightly denser with –3 a density of 2210 kg.m . Mechanically, fused silica is a relatively strong but brittle material with a tensile strength of 28 MPa, a compressive strength of 1450 MPa, and a Mohs hardness –6 –1 of 5. Both grades exhibit an extremely low coefficient of thermal expansion (e.g., 0.6 × 10 K from 20 to 1000°C) and a remarkable thermal shock resistance together with a low thermal –1 conductivity. Fused silica, with a dielectric field strength of 16 MV.m , exhibits also excellent electrical insulation capabilities up to 1000°C. When heated above 1150°C, fused silica converts irreversibly into α-cristoballite as follows: fused silica —> α-cristoballite

(1150°C)

Fused silica begins to soften at 1670°C and melt at 1755°C. From a chemical point of view, fused silica possesses an excellent corrosion resistance to most chemicals, especially strong mineral acids, molten metals, and molten glasses. Common industrial uses for fused silica are steelmaking, coke making, metallurgy, glass production, nonferrous foundries, precision foundries, ceramics, the chemical industry, the nuclear industry, and finally aeronautics.

10.2.2 Aluminosilicates From a geological point of view, clays are soft, fine-grained, and residual sedimentary rocks resulting from the weathering of feldspars (e.g., orthoclases and plagioclases) and ferromagnesian silicates (e.g., micas, amphiboles) contained in igneous and metamorphic rocks. Hence clays are always made of various hydrated aluminosilicates, mainly kaolinite but also illite and montmorillonite, all exhibiting the typical structure of sheet silicates (i.e., phyllosilicates). When a clay is fired, it loses its absorbed water between 100 and 200°C. Secondly, its major phyllosilicate mineral, kaolinite [Al4(Si4O10)(OH)8 = 2Al2O3·4SiO2·4H2O], dehydrates between 500 and 600°C, giving off its water to form metakaolin [Al2Si2O7 = 2Al2O3·2SiO2]: Al4[Si4O10(OH)8] —> 2Al2Si2O7 + 4H2O (500°C < T < 600°C).

Raw Materials for Ceramics, Refractories and Glasses

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Above 800°C an important chemical change takes place with the formation of one of the three aluminosilicate polymorphs (Al2SiO5), i.e., andalusite, kyanite, or sillimanite, and free silica according to the overall chemical reaction: 2Al2Si2O7 —> 2Al2SiO5+ 2SiO2 (at T > 800°C). If firing is carried out above 1595°C, the highly refractory mineral mullite then forms (see mullite) with an additional liberation of free silica that melts according to the following chemical reaction: 3Al2SiO5 —> Al6Si2O13 + SiO2 (at T >1600°C). Refractory fireclays embrace all types of clays commercially available. Because of the abundant supply of fireclay and its comparative cheapness, refractory bricks made out of it are the most common and extensively used in all places of heat generation. In fact, several technical designations are used in the ceramic industry for classifying refractory clays; these are fire clay, China clay, ball clay, flint clay, and chamotte.

10.2.2.1 Fireclay Description and general properties. Fireclay denotes a silica-rich natural clay that can withstand a high firing temperature above the pyrometric cone equivalent (PCE; Table 10.19) of 19 without melting, cracking, deforming, disintegrating, or softening. Typically, a good fireclay should have 24 to 26 vol.% plasticity, and shrinkage after firing should be within 6 to 8 vol.% maximum. Fireclays are mostly made of kaolinite, but some Fe2O3 and minor amounts of Na2O, K2O, CaO, MgO, and TiO2 are invariably present depending on the mineralogy and geology of the deposit, making it gray in color. Upon firing, fireclay yields a strong ceramic product with a composition close to the theoretical composition of metakaolin (i.e., 54.1 wt.% SiO2 and 45.9 wt.% Al2O3), but in practice it contains between 50 and 60 wt.% SiO2, 24 and 32 wt.% Al2O3, no more than 25 wt.% Fe2O3 and a loss on ignition of 9 to 12 wt.%. Fireclay is classified under acid refractories, that is, refractories that are not attacked by acid slags. In practice, refractoriness and plasticity are the two main properties required for the manufacture of refractory bricks; hence fireclays are grouped according to the maximum service temperature of the final product before melting in: low-duty fireclay (max. 870°C, PCE 18 to 28), mediumduty fireclay (max. 1315°C, PCE 30), high-duty fireclay (max. 1480°C, PCE 32), and super-duty fireclay (max. 1480°C–1619°C, PCE 35). In practice, it has been observed that the higher the alumina content in the fireclay, the higher the melting point. All fireclays are not necessarily plastic clays. In such cases, some plastic clay, like ball clay, is added to increase plasticity to a suitable degree. A good fireclay should have 24 to 26% plasticity, and shrinkage after firing should be within 6 to 8% maximum. It should also not contain more than 25% Fe2O3. Industrial preparation. Mined clay is stacked in the factory yard and allowed to weather for about 1 year. For daily production of different types of refractories, this weathered clay is taken and mixed in different percentages with grog (i.e., spent fireclay). The mixture is sent to the grinding mill from where it is transferred to the pug mill. In the pug mill a suitable proportion of water is added so as to give it proper plasticity. The mold is supplied to different machines for making standard bricks or shapes. Intricate shapes are made by hand. The bricks thus made are then dried in hot floor driers and after drying are loaded in kilns for firing. The firing ranges are, of course, different for different grades of refractories. After firing, the kilns are allowed to cool, then the bricks are unloaded. Upon burning fireclay is converted into a stonelike material that is highly resistant to water and acids, while manufacturing high aluminous fire-bricks bauxite is added along with grog in suitable proportions. Industrial applications and uses. As a general rule fireclays are used in both shaped refractories (i.e., bricks) and monolithic refractories (i.e., castables), while super-duty plastic fireclay is used in the preparation of castable recipes. Therefore, the major applications of

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fireclays are in power generation, such as in boiler furnaces, in glass-melting furnaces, in chimney linings, in pottery kilns, and finally in blast furnaces where the backup lining is done almost entirely with fireclay bricks. Pouring refractories like sleeves, nozzles, stoppers, and tuyers are also made of fireclay.

10.2.2.2 China Clay China clay or kaolin, the purest white porcelain discovered and used by the Chinese since ancient times, has always been a much-prized material. Outside of China, a few deposits were found in some parts of Europe and in the United States early in the 18th century. China clay occurs in deposits in the form of china clay rock, a mixture of up to 15 wt.% china clay and up to 10 wt.% mica muscovite, the remainder being free silica as quartz. But the terms china clay and kaolin are not well defined; sometimes they are synonyms for a group of similar clays, and sometimes kaolin refers to those obtained in the United States and china clay to those that are imported. Others use the term china clays for the more plastic of the kaolins. China clays have long been used in the ceramics industry, especially in whitewares and fine porcelains, because they can be easily molded, have a fine texture, and are white when fired. France’s clays are made into the famous Sèvres and Limoges potteries. These clays are also used as a filler in making paper. In the United States, deposits are found primarily in Georgia, North Carolina, and Pennsylvania; china clay is also mined in England (Cornwall) and France. Industrial preparation. The extraction of china clay from its deposits is usually performed in three steps: open-pit mining, mineral processing and beneficiation, and drying. Open-pit operations require the removal of ground overlying the clay (i.e., overburden). The exposed clay is then mined by a hydraulic mining process, that is, a high-pressure water jet from a water cannon called a monitor erodes the faces of the pit. This liberates from the quarry face the china clay, together with sand and mica. The slurry formed flows to the lowest part of the pit or sink, where it is pumped by centrifugal pumps to classifiers, where coarse silica sand is removed. The silica sand is later reused for landscape rehabilitation. The remaining suspension of clay is transported by underground pipeline to the mineral-processing and beneficiation plant, where a series of gravity separation techniques are used to remove particulate materials such as quartz, mica, and feldspars. Sometimes the purified clay slurry undergoes an additional chemical bleaching process that greatly improves its whiteness. The refined clay suspension is then filtrated, and the filtration cake with a moisture content of about 25 wt.% passes through a thermal drier fired by natural gas to yield a final product with 10 wt.% moisture. The end product is normally sold in pelletized form with a pellet size ranging from 6 to 12 mm.

10.2.2.3 Ball Clay Ball clay, like china clay, is a variety of kaolin. It differs from china clay in having a higher plasticity and less refractoriness. In chemical composition, ball and china clays do not differ greatly except that the former contains a larger proportion of silica. Its name is derived from the practice of removing it in the form of ball-like lumps from clay pits in the UK. The main utility of ball clay is its plasticity, and it is mixed with nonplastic or less plastic clays to make them acquire the requisite plasticity. The high plasticity of ball clay is attributed to the fact that it is fine-grained and contains a small amount of montmorillonite. Over 85% of the particle sizes present in ball clay are of 1 μm or less in diameter. It is light to white in color and on firing may be white buff. The pyrometric cone equivalent to ball clay hardly ever exceeds 33. Usually the following mass fractions of ball clay are commonly used in various types of ceramic compositions: vitreous sanitaryware 10 to 40 wt.%, chinaware 6 to 15 wt.%, floor and wall tiles 12 to 35 wt.%, spark plug porcelain 10 to 35 wt.%, semivitreous whiteware

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20 to 45 wt.%, and glass melting-pot bodies 15 to 20 wt.%. The wide use of ball clay is mainly due to its contribution of workability, plasticity, and strength to bodies in drying. Ball clay, on the other hand, also imparts high-drying shrinkage, which is accompanied by a tendency toward warping, cracking, and sometimes even dunting. This undesirable property is compensated by the addition of grog. Industrial applications. Filler for paper and board, coating clays, ceramics, bone china, hard porcelain, fine earthenware, porous wall tiles, electrical porcelain, semivitreous china, glazes, porcelain, enamels, filler for plastics, rubbers and paints, cosmetics, insecticides, dusting and medicine, textiles, and white cement.

10.2.2.4 Other Refractory Clays Flint clay or hard clay. This is a hardened and brittle clay material having a conchoidal fracture like flint that resists slacking in water but becomes plastic upon wet grinding. Chamotte. Chamotte denotes a mixture of calcined clay and spent ground bricks. It is also called fireclay mortar. Diaspore clay. This is a high-alumina material containing 70 to 80 wt.% Al2O3 after firing of a mixture of diasporic bauxite and clay.

10.2.2.5 Andalusite, Kyanite, and Sillimanite Andalusite, kyanite, and sillimanite are three polymorphs minerals that belong to the nesosilicate minerals. Hence they have the same chemical formula [Al2SiO5 = Al2O3·SiO2] and all contain theoretically 62.92 wt.% Al2O3 and 37.08 wt.% SiO2. They are distinguished from one another by their occurrence and physical and optical properties (see Section 12.7, Minerals and Gemstones Properties Table). Kyanite is easily distinguished from sillimanite or andalusite by its tabular, long-bladed, or acicular habit and by its bluish color and slightly lower hardness than sillimanite and andalusite. Sillimanite, kyanite, and andalusite are all mullite-forming minerals, that is, on firing they decompose into mullite and vitreous silica (see mullite) according to the chemical reaction: 3Al2SiO5 —> Al6Si2O13 + SiO2. However, each polymorph exhibits a different decomposition behavior. Actually, the decomposition of kyanite is unpredictable; it first starts to decompose slowly at 1310°C, and the reaction disrupts at about 1350 to 1380°C with an important volume expansion of 17 vol.%. For that reason, kyanite must always be calcined prior to being incorporated into a refractory in order to avoid blistering and spalling. By contrast, andalusite decomposes gradually from 1380 to1400°C with a low volume increase of 5 to 6 vol.%, while sillimanite does not change into mullite until the temperature reaches 1545°C with a volume expansion of 5 to 6 vol.%. In nature, these three minerals are originally found in metamorphic rocks, but, due to their high Mohs hardness and relative chemical inertness, they resist weathering processes and are also ubiquitous in mineral sands. For instance, sillimanite is extensively mined as a byproduct of beach mineral sand operations in South Africa and Australia. Sillimanite minerals are predominantly used in refractories and technical porcelains. Sillimanite refractories cut into various shapes and sizes or made out of bonded particles are used in industries like cement, ceramics, glass making, metal smelting, refinery and treatment, tar distillation, coal carbonization, chemical manufacture, and iron foundries. Kyanite in the form of mullite is widely used in the manufacture of glass, burner tips, spark plugs, heating elements, and high-voltage electrical insulations and in the ceramic industry. India is the largest producer of kyanite in the world.

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10.2.2.6 Mullite Mullite [Al6Si2O13 = 3Al2O3·2SiO2], with 71.8 wt.% Al2O3, is an important silicate mineral that occurs in high-silica alumina refractories. Mullite exhibits a high melting point of 1810°C –6 –1 combined with low thermal expansion coefficients (i.e., 4.5 × 10 K parallel to the a-axis –6 –1 and 5.7 × 10 K parallel to the c-axis), a good mechanical strength with a tensile strength of 62 MPa, and resilience at elevated temperatures that make mullite a highly suitable mineral for highly refractory materials. In nature, mullite is an extremely scarce mineral that occurs only in melted argillaceous inclusions entrapped in lavas from the Cenozoic Era on the Island of Mull, Scotland, but no deposit was found to be economically minable. Synthetic mullite is formed in high-silica alumina refractories during the firing process at high temperature, the major raw materials being kaolin, alumina, and clays and to a lesser extent kyanite, when available. Actually, when a fire clay is fired, its major phyllosilicate mineral, the kaolinite Al4(Si4O10)(OH)8, first gives off its water, and above 800°C an important chemical change takes place with the formation of one of the three aluminosilicate polymorphs (Al2SiO5), i.e., andalusite, kyanite, or sillimanite, and free silica according to the following chemical reaction: Al4(Si4O10)(OH)8 —> 2Al2SiO5 + 2SiO2 + 4H2O (at T > 800°C). If firing is carried out above 1595°C, the highly refractory mineral mullite then forms with an additional liberation of free silica that melts according to the following chemical reaction: 3Al2SiO5 —> Al6Si2O13 + SiO2 (at T >1600°C). For that reason, high-silica alumina refractories containing less than 71.8 wt.% Al2O3 are limited in their use to temperatures below 1595°C. Above 71.8 wt.% Al2O3, mullite alone or mullite plus corundum (α-Al2O3) coexists with a liquidus at 1840°C. Therefore, the use of high-alumina refractories is suited for iron- and steelmaking for firebrick and ladles and furnace linings. Two grades of synthetic mullite are available for refractories: sintered mullite is obtained by calcination of bauxitic kaolin or a blend of bauxite, aluminas, and kaolin or, to a lesser extent, kyanite; electrofused mullite is made by the electrothermal melting at 2200°C of a mixture of silica sand and bauxite or diasporic clay in an electric-arc furnace. Mullites are formulated to produce dense shapes, some in a glass matrix to yield maximum thermal shock resistance and good mechanical strength. Dense electrofused mullite in a glassy matrix formulated to offer a high-quality economical insulating tubing for thermocouple applications is an extremely versatile and economically viable material. Its workability allows for an extensive range and flexibility in fabrication. It is well suited for the casting of special shapes. Its typical applications are insulators in oxidizing conditions for noble-metal thermocouples used in conditions up to 1450°C, spark plugs, protection tubes, target and sight tubes, furnace muffles, diffusion liners, combustion tubes, radiant furnace tubes, and kiln rollers. Major producers of sintered mullite are C-E Minerals, Andersonville, GA in the USA, followed by several Chinese producers, while Washington Mills Electro Minerals Corp. in Niagara Falls, NY leads the production of electrofused mullite.

10.2.3 Bauxite and Aluminas 10.2.3.1 Bauxite Bauxite is the major source of aluminum sesquioxide (alumina, Al2O3) worldwide. Bauxite is a soft and red clay, rich in alumina, and its name originates from Les Baux de Provence, a small village located in the region of Arles in southeastern France, where it was first discovered in 1821 by P. Berthier. From a geological point of view bauxite is defined as a residual sedimentary rock in the laterite family that results from in situ superficial weathering in

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Table 10.1. Mineralogy and chemistry of bauxite Oxide

Chemical composition (wt.%) Mineralogy

Alumina (Al2O3)

35 to 65

Gibbsite, boehmite and diaspore

Silica (SiO2)

0.5 to 10

Quartz, chalcedony, kaolinite

Ferric oxide (Fe2O3) 2 to 30

Goethite, hematite and siderite

Titania (TiO2)

0.5 to 8

Rutile and anatase

Calcia (CaO)

0 to 5.5

Calcite, magnesite and dolomite

moist tropical climates of clays, clayey limestones, or high-alumina-content silicoaluminous igneous and metamorphic rocks containing feldspars and micas. Around the world there is a restricted number of geographical locations containing bauxite deposits of commercial interest. Their occurrence and origin can be explained by both plate tectonics and climatic conditions. Actually, during weathering water-soluble cations (e.g., Na, K, Ca, and Mg) and part of the silica (SiO2) are leached by rainwater acidified by the organic decomposition of humus, leaving only insoluble aluminum and iron sesquioxides and a lesser amount of titania (TiO2). Hence, insoluble cations such as iron (III) and aluminum (III) associated with clays and silica remain in the materials. Bauxite is a sedimentary rock, so it has neither a precise definition nor chemical formula. From a mineralogical point of view, bauxite is mainly composed of hydrated alumina minerals such as gibbsite [Al(OH)3 or Al2O3.3H2O, monoclinic] in recent tropical and equatorial bauxite deposits, while boehmite [AlO(OH) or Al2O3.H2O, orthorhombic] and, to a lesser extent, diaspore [AlO(OH) or Al2O3.H2O, orthorhombic] are the major minerals in subtropical and temperate bauxite old deposits. The average chemical composition of bauxite is 45 to 60 wt.% Al2O3 and 10 to 30 wt.% Fe2O3, the remainder consisting of silica, calcia, titanium dioxide, and water. The typical mineralogy and chemical composition of bauxite is presented in Table 10.1. The different types of bauxite are only distinguished according to their mineralogical composition. They are then called gibbsitic, boehmitic, or diasporic bauxite. Gibbsitic bauxite predominates. It is geologically the youngest and situated in tropical or subtropical regions, very close to the ground surface (e.g., laterites). The oldest deposits, which are mainly found in Europe (e.g., Gardanne in France, and Patras in Greece) and in Asia, mainly contain boehmite and diaspore. Most of the time they are underground deposits. According to the US Geological Survey, the world’s bauxite resources are estimated to be 55 to 75 billion tonnes located mainly in South America (33%), Africa (27%), Asia (17%), Oceania (13%), and elsewhere (10%). Today, Australia supplies 35% of the demand worldwide for bauxite, South America 25%, and Africa 15%. The current reserves are estimated at being able to supply worldwide demand for more than two centuries. Note that about 95% of bauxite is of the metallurgical grade and hence used for the production of primary aluminum metal. Bayer process. Because bauxite exhibits a high alumina content and its worldwide reserves are sufficient to satisfy demand for a few centuries, it is the best feedstock for producing alumina and then aluminum. Actually, today, more than 95% of alumina worldwide is extracted from bauxite using the Bayer process, which was invented in 1887, just one year after the invention of the Hall–Heroult electrolytic process. This Bayer process was implemented for the first time in 1893, in France, at Gardanne. However, the conditions for implementing the process strongly depend on the type of bauxitic ore used. For instance, refractory-type diasporic bauxite must be digested at a higher temperature than gibbsitic bauxite. Therefore, the selection of the type of bauxite to be used is a critical factor affecting the design of the alumina plant. A brief description of the Bayer process is given hereafter.

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Table 10.2. Digestion conditions for various bauxitic ore Bauxitic ore Digestion reaction

Conditions

Gibbsitic

2AlO(OH).H2O + 2NaOH —> 2NaAlO2 + 4H2O Atmospheric pressure 135°C < T < 150°C

Boehmitic

2AlO(OH) + 2NaOH —> 2NaAlO2 + 2H2O

Atmospheric pressure 205°C < T < 245°C)

Diasporic

2AlO(OH) + 2NaOH —> 2NaAlO2 + 2H2O

High pressure (3.5–4 MPa) T > 250°C

Comminution. First, bauxite run-of-mine ore is crushed using a jaw crusher to produce coarse particles below 30 mm in diameter. It is then washed with water in order to remove clay minerals and silica in an operation called desliming. The washed and crushed ore is then mixed with the recycled caustic liquor downstream from the Bayer process, then ground more finely providing a suspension or slurry of bauxite with 90% of particles with a size less than 300 μm (48 mesh Tyler). This grinding step is required to increase the specific surface area of the bauxite in order to improve the digestion efficiency. The recycled liquor comes from the filtration stage of the hydrate after it has been precipitated. This liquor is enriched in caustic soda (i.e., sodium hydroxide, NaOH) and slacked lime [calcium hydroxide, Ca(OH)2] before grinding to meet the digestion conditions and to be more aggressive toward the bauxite. The permanent recycling of the liquor and, more generally, of the water is at the origin of the synonym for the Bayer process, also called the Bayer cycle. The red bauxite-liquor slurry is preheated before being sent to the digesters for several hours. Digestion of bauxite. The conditions of digestion are strongly related to the mineralogical composition of the bauxitic ore, that is, whether gibbsite, boehmite, or diaspore is the dominant ore. For instance, a gibbsitic bauxite can be digested under atmospheric pressure, whereas high pressures in excess of 1 MPa and temperatures above 250°C are required to digest the alumina contained in refractory diasporic bauxite. The various digestion conditions are summarized in Table 10.2. Usually, the slurry is heated in an autoclave at 235 to 250°C under a pressure of 3.5 to 4.0 MPa. During the digestion stage, the hydrated alumina is dissolved by a hot and concentrated caustic liquor in the form of sodium aluminate (NaAlO2). During the dissolution reaction, the sodium hydroxide reacts with both alumina and silica but not with the other impurities such as calcium, iron, and titanium oxides, which remain as insoluble residues. These insoluble residues sink gradually to the bottom of the tank and the resulting red sludge, called red mud, concentrates at the bottom of the digester. The slurry is diluted after digestion to make settling easier. Slowly heating the solution causes the Na2Si(OH)6 to precipitate out, removing silica. The bottom solution is then pumped out and filtered and washed while the supernatant liquor is filtered to leave only the aluminum-containing NaAl(OH)4. The clear sodium tetrahydroxyaluminate solution is pumped into a huge tank called a precipitator. There are two objectives in washing the red mud that has been extracted from the settler: to recuperate the spent sodium aluminate, which will be reused in the Bayer cycle, and to remove sodium hydroxide from the red mud for safe disposal as an inert mining residue. Precipitation. The clear sodium aluminate liquor is cooled down, diluted with the water from the red-mud wash, and acidified by bubbling carbon dioxide (CO2) gas through the solution. Carbon dioxide forms a weak acid solution of carbonic acid, which neutralizes the sodium hydroxide from the first treatment. This neutralization selectively precipitates the aluminum hydroxide [Al(OH)3] but leaves the remaining traces of silica in solution; the precipitation or the crystallization of the hydrate is also called decomposition. The liquor is

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then sent into huge thickening tanks owing to the extremely slow precipitation kinetics. The alumina hydrate slowly precipitates from tank to tank as the temperature goes down. The floating suspension is recuperated in the last thickening tank. Fine particles of aluminum hydrate are usually added to seed the precipitation process of pure alumina particles as the liquor cools. In fact, 90% of the wet aluminum trihydrate recovered after filtration is recycled and used as a crystallization seed. The liquor is then filtered so as to separate the wet hydrate from the liquor. This liquid is then sent to the bauxite digestion tank, where it will be enriched in soda and in lime. The particles of aluminum hydroxide crystals sink to the bottom of the tank, are removed, and are then vacuum dewatered. The alumina trihydrate (ATH) or gibbsite [Al(OH)3] obtained can be commercialized as is or it can be calcined into various grades of alumina (Al2O3). Calcination. To produce calcined alumina (CA), the alumina trihydrate must be calcined into a rotary kiln or a fluidized-bed calciner operating at 1100 to 1300°C to drive off the chemically combined water. Usually, fluidized-bed calciners are restricted to transition aluminas used in the manufacture of metallurgical-grade alumina, while rotary kilns are used for non-metallurgical-grade alumina. All of the characteristics of calcined alumina are extremely variable and depend on the conditions of calcination. Sodium is the major impurity of the alumina produced in the Bayer process; this can be a hindrance for certain technical applications. Several methods for the removal of sodium exist to produce aluminas with a very low sodium content, such as water leaching or the use of silica to form a soluble sodium silicate phase. These reactions compete with the combination of sodium and alumina to form beta-aluminas. The transformation of gibbsite into alpha-alumina successively gives rise to the following phenomena while the temperature is rising: release of water vapor between 250 and 400°C that fluidizes the alumina and, at around 1000 to 1250°C, the exothermic transformation into alpha-alumina occurs. The appearance of alpha-alumina crystallites modifies the morphology of the grains, which become rough and friable. Completion of the transformation of gibbsite into alpha-alumina requires a residence time of at least 1 h. Some halogenated compounds called mineralizers are used to catalyze the transformation of the alpha-alumina crystallites. The mineralizers also form volatile sodium chloride. Calcined alumina consists of alpha-alumina crystallite clusters with a particle size ranging from 0.5 to 10 μm. The higher the calcinations, the larger the crystallites (Figure 10.2).

10.2.3.2 Alumina Hydrates Aluminum hydroxides and oxihydroxides, formerly called aluminas hydrates, are all produced during the Bayer process described in the preceding paragraphs. All the aluminum hydroxides exhibit the same molecular unit, which consists of an octahedron made of one 9– hexacoordinated aluminum cation surrounded by six oxygen anions [AlO6 ]. The great stability of this structure is due to the strong Al-O chemical bonds owing to the high polarization of aluminum cations. Three crystalline polymorphs of alumina trihydrates (ATH) or aluminum trihydroxide [Al(OH)3 = Al2O3.3H2O] exist: gibbsite or hydrargillite [γ-Al(OH)3], bayerite [α-Al(OH)3], and nordstrandite [β-Al(OH)3]. The octahedrons form a plane framework of hexagonal crowns of Al(OH)3 forming two planes of oxygen atoms in a compact hexagonal network wrapped around a plane of aluminum atoms two thirds of which is occupied. The three minerals differ by the sequence of these sheets. The sequence is (AB BA AB BA…) for gibbsite, (AB AB AB AB…) for bayerite, which is more compact and hence more stable and dense), and (AB BA BA AB…) for the intermediate case of nordstrandite. The sheets are linked together by hydrogen bonds. Two crystalline polymorphs of monohydrated alumina or aluminum oxihydroxide 9– [AlO(OH) = Al2O3.H2O], where the [AlO6 ] octahedrons share one edge: boehmite [γ-AlO(OH)];

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Figure 10.2. Aluminas production flowsheet

and diaspore [α-AlO(OH)]. The main characteristics of aluminum hydroxides are listed in Table 10.3. Among all the alumina hydrates, gibbsite or gamma-aluminum trihydroxide (ATH) is, after bauxite, by far the most common aluminum commodity. Actually, 85% of the total gibbsite produced by the Bayer process is used to produce metallurgical-grade alumina for the electrowinning of aluminum metal by the Hall–Heroult process, while 8–10 percent are used for preparing non-metallurgical-grade alumina required for the manufacture of high

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Table 10.3. Alumina hydrates (aluminum trihydroxides and oxihydroxides) Phase

Crystal system

Therm. stability range

Density –3 (kg.m )

Mohs Tenacity hardness

Average refractive index (nD)

Gibbsite α-Al(OH)3 (hydrargillite)

Monoclinic

κ-phase—1000°C—> α-Al2O3

Bayerite

Bayerite —280°C—> η-phase —830°C—> θ-phase—1000°C—> α-Al2O3

Boehmite

Boehmite—450°C—> γ-phase —800°C—> δ-phase—920°C—>θ-phase—1050°C—> α-Al2O3

Diaspore

Diaspore—500°C—> α-Al2O3

10.2.3.3 Transition Aluminas (TrA) During the thermal decomposition of alumina hydrates, the progressive loss of hydratation water leads to the formation of the so-called transition aluminas, denoted by the common acronym TrA. These are metastable aluminas with an intermediate crystallographic structure ranging between that of alumina hydrates and that of alpha-alumina. The family of transition aluminas includes all aluminas that are obtained by the thermal decomposition of aluminum hydroxides or oxihydroxides, with the exception of alpha-alumina. The different transition aluminas generally coexist, and their proportions depend on the type of precursor hydrate and on the decomposition conditions (i.e., temperature, heating rate, relative humidity). As a general rule, each intermediate alumina hydrate exhibits at least two phase transformations when the temperature rises before reaching the final structure of the alpha alumina: a very disordered low-temperature structure produced by the loss of hydratation water and a hightemperature, well-ordered structure (Table 10.5). The most important properties of all transition aluminas are their intrinsic microporosity and their high specific surface area that can 2 –1 reach up to 400 m .g . Because of their high specific surface areas, combined with their adsorptive capabilities, transition aluminas are able to adsorb huge quantities of polar, acidic, or basic compounds, but the adsorption is not selective. Moreover, transition aluminas are also very reactive chemically. Actually, the adsorption of acid in an aqueous medium always leads to the dissolution of part of the alumina and then the adsorption of the salt that has formed. Finally, when they undergo thermal decomposition above a temperature of 1100°C, all the transition aluminas are transformed irreversibly into calcined aluminas. Four main processes are used for preparing industrial transition aluminas: (i)

The dehydration of gibbsite performed in a rotary kiln at 400°C. The thermal decomposition of gibbsite at 250°C produces a transition alumina having a large specific surface area. If the process is performed under pressure, a hydrothermal transformation occurs, yielding boehmite. Further dehydration of the boehmite produces a gamma transition alumina with a low specific surface area. (ii) The activation of gibbsite by flash-firing that consists in firing the ATH in a few seconds at around 400°C. The activated alumina thus obtained is amorphous and very reactive. (iii) The activation of oxihydroxide gels that are first transformed into grains by various processes and are then activated at between 500 and 600°C in a fluidized bed. (iv) The activation of bayerite, which consists in agglomerating bayerite into a shaped material by means of an appropriate binder.

10.2.3.4 Calcined Alumina Aluminum sesquioxide, or α-alumina (α-Al2O3), also called calcined alumina (CA) or burned alumina in the ceramic and refractory industries, is the final product resulting from the thermal decomposition of all aluminum hydroxides. Actually, in the temperature range 1000–1250°C, the exothermic transformation of transition aluminas into α-Al2O3 occurs

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irreversibly. The rate of transformation into α-Al2O3 depends on the residence time of the aluminum hydroxide at these temperatures. The transformation is usually complete after a few hours at more than 1250°C. Calcined aluminas are prepared by calcination of aluminum hydroxide performed in rotary kilns, fluidized-bed kilns, or tunnel kilns. The α-Al2O3 crystallites give a polycrystalline product that becomes friable. Calcined aluminas are offered in a wide variety of technical grades from those containing 100 wt.% α-Al2O3 to grades containing some sodium such as soda-alumina, also called beta alumina [NaAl11O17 = Na2O·11Al2O3], the remaining component being unreacted transition alumina. Some halogenated compounds (e.g., BF3, BCl3) called mineralizers are used to catalyze the nucleation of the α-Al2O3 crystallites. The mineralizers also form volatile sodium chloride (NaCl), which removes the sodium. Calcined alumina consists of α-Al2O3 crystallite clusters with a particle size ranging from 0.5 to 10 μm, and it is hence a polycrystalline material with grains made of several crystallites. The higher the calcination temperature is, the larger the crystallites are. The morphology of crystallites is strongly influenced by the chemical nature of the mineralizer: fluorine produces tabular crystallites with a hexagonal shape, boron gives rounded crystallites, while boron chloride produces round and dense crystals. By contrast with transition aluminas, crystals in calcined alumina are free from micropores, and hence calcined alumina’s specific surface area equals the surface area of its crystallites, and the larger they are, the lower the surface area will be. Technical calcined aluminas are classified according to the particle size of their crystallites, the morphology of the crystallites (i.e., angular, rounded, tabular), their sodium content, and, to a lesser extent, the content of other impurities that result mainly from the Bayer process and bauxite. Commercially, four grades of calcined aluminas are distinguished based on their soda content: (i)

Standard calcined aluminas with a sodium content of between 3000 and 7000 ppm wt. Na2O. (ii) Intermediate calcined alumina with a sodium content of between 1000 and 3000 ppm wt. Na2O. The sodium content of this grade has been lowered by modifying the conditions of the precipitation of gibbsite or of the calcination. (iii) Low-sodium calcined aluminas with a sodium content of between 300 and 1000 ppm wt. Na2O. These aluminas are usually obtained by washing the precursor or by the extraction of sodium as a volatile compound with the mineralizer during calcination. (iv) High-purity aluminas with an extra-low sodium content below 100 ppm wt. Na2O. These aluminas obtained from an aluminum hydroxide produced by a process other than the Bayer process. The main applications for calcined aluminas are as feedstocks for refractories, glass and enamel, tiles and porcelain, and advanced ceramics. The diversity of applications for calcined aluminas can be explained by the wide range of properties: refractoriness, sinterability, chemical inertness in both oxidizing and reducing atmosphere and in both acid and alkaline media, hardness, wear and abrasion resistance, dimensional stability, high thermal conductivity, electrical resistivity, low dielectric loss and high permittivity, and high ionic conductivity in the case of betaalumina.

10.2.3.5 Tabular Alumina Tabular alumina (TA), also called sintered alumina, is produced by the sintering of calcined alumina, which occurs above 1600°C. Sintering is usually performed industrially in a tall shaft kiln equipped with gas burners in the median zone. First, 20-mm balls are made by pelletizing a mixture of ground calcined alumina, reactive micronized alumina, and an appropriate organic binder to ensure the highest green density. Usually boron trichloride is added for the proper removal of sodium as NaCl upon heating. Prior to being fed into the shaft kiln the balls are always dried. The sintering is performed continuously at a high

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operating temperature of between 1900°C and 1950°C to obtain the highest mass density of –3 3550 kg.m and a low porosity of 5 vol.% but always below the melting point of α-Al2O3 (2050°C). It takes about 15 h for the balls to exit from the bottom of the furnace. After sintering, the balls, which have shrunk by 20 vol.%, are crushed and ground, and iron-rich material is removed by magnetic separation and then sized in several grades. The high purity of tabular alumina (99.8 wt.% Al2O3) is due to its low soda content (Na2O < 1000 ppm wt.) and to the absence of nonvolatile mineral additions in the preparation of green balls. The resulting polycrystalline material exhibits large tabular crystals with a hexagonal shape and with a particle size of between 200 and 300 μm. Moreover, the commercial material contains a finer grain size and additives that lower the melting point in the range of 1700°C to 1850°C. The major properties of tabular alumina are a high density, a low open porosity, refractoriness, hardness, chemical inertness, thermal conductivity and dielectric rigidity at high temperatures, dimensional stability, creep and abrasion resistance, and exceptional resistance to thermal shock. These properties explain its development as a refractory raw material and its use in steelmaking and in electric furnaces, especially in Japan, as well as in ceramics, filters for molten metal, fillers for epoxy resins and polyester, inert catalyst supports, and heat conductors.

10.2.3.6 White Fused Alumina Above 2050°C, pure alumina (Al2O3) melts forming a covalent and nonconducting liquid that upon cooling yields a solidified mass of corundum. Corundum is also called in the ceramics and refractory industries white fused alumina. White fused alumina exhibits a fine-grained microstructure with euhedral crystals. Although the operation can be performed commercially on a small industrial scale by the Verneuil technique to produce kilogram-size single crystals (see Gemstones, Section 12.5), most of the large tonnage production uses a tilting electric-arc furnace with three electrodes operating in an AC mode. Once molten and homogeneous, the alumina melt is poured into molds and allowed to cool slowly until demolding. Beta-alumina represents the major impurity observed in white fused alumina due to the concentration of sodium occurring in certain regions. However, the volatilization of the sodium occurs at 2100°C and creates pores that are beneficial. To improve is mechanical strength, usually 2 wt.% of chromia (Cr2O3) is added to the melt. Actually, trivalent chromium substi3+ tutes isomorphically for the Al increasing the toughness of white fused alumina.

10.2.3.7 Brown Fused Alumina The electrothermal fusion of bauxite at 2100°C yields an impure and brown electrofused alumina product called brown fused alumina, sometimes simply brown corundum. Brown fused alumina exhibits coarse grains, and the major impurity in brown fused alumina is titania or titanium dioxide (TiO2) coming from the bauxite ore. Therefore, commercially, two grades of brown fused aluminas can be distinguished according to their titania content: the friable grade, with 1.5 wt.% TiO2, and the standard grade, with 3 wt.% TiO2, which exhibits a greater toughness than the friable grade. The toughness of brown fused alumina is higher than that of white fused alumina, and this is due to the titania content, which reduces the size of the crystallites. Brown electrofused alumina is obtained industrially by the simultaneous electrothermal fusion and reduction by coke in a tilting and triphased electric-arc furnace of a blend of bauxite and spent products of white and brown aluminas. During the process, the reduction of iron oxide, silica, and, to a lesser extent, titania produces a titanium-bearing ferrosilicon alloy (FeSi), which is an important byproduct. The dense droplets of ferrosilicon sink by gravity, settling at the bottom of the crucible, and coalesce to form a pool of liquid FeSi. After several castings of the electrofused brown alumina thus produced, the ferrosilicon that has accumulated at the bottom must be tapped by overturning the crucible; this represents an important byproduct. During electrofusion, the raw materials

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–2

float over the molten alumina, decreasing the thermal losses by radiation (ca. 900 kW.m at 2000°C). Because of the high temperature combined with the corrosiveness of the melt, no container can withstand such melts and skull melting is the only means to contain the molten materials. Actually, a frozen layer forms upon cooling on the inner wall and at the bottom of the crucible that are externally cooled by running water, forming a protective and self-lining skull. In practice, two distinct skulls are formed, on the inner side wall of the furnace the thick skull is made of solidified alumina, while at the bottom a thick skull forms containing titanium carbide (TiC). During the process, the gases resulting from the reduction of various metal oxides with the carbon are mainly CO and SiO. This aspect is of crucial importance both for reasons linked to the process and for safety reasons. Once molten alumina is poured into molds and allowed to cool slowly until demolding, it is crushed and ground while droplets of FeSi are removed by magnetic separation performed with a rotary drum equipped with rare-earth magnets. To ensure that the ferrosilicon is ferromagnetic and hence easily separated from corundum, its silicon content must be less than 21 wt.% Si, but in order to be easily crushed, its silicon content must be at least 13 wt.% Si. Proper operation of the process consists in maintaining a silicon content ranging between these two limits. Moreover, the titanium content is another important parameter to control. If the titanium content is too high, it forms a bed of TiC, reducing the useful depth of the crucible. On the other hand, if the titanium content is too low, the skull at the bottom of the crucible will be too thin. Apart from refractories, brown fused alumina is used in deburring, plunge cut grinding, and sandblasting.

10.2.3.8 Electrofused Alumina-Zirconia Electrofused alumina-zirconia (EFAZ) is obtained by a process similar to that used for preparing brown fused alumina by electrothermal fusion and reduction by metallurgical coke at 2100°C of a mixture of bauxite ore, zircon sand, and scrap iron in a tilting and triphased electric-arc furnace. After quenching the molten mass, the resulting product obtained is about five times stronger than brown fused alumina.

10.2.3.9 High-Purity Alumina High-purity alumina contains at least 99.99 wt.% Al2O3, with crystallites small in size and morphology. Nearly half the high-purity alumina produced annually is used to manufacture sapphires and, to a lesser extent, as polishing medium for metallographical and optical processes. Four manufacturing processes of ultrapure aluminas are used, using either Bayer gibbsite or aluminum metal. (i)

Alum process. Gibbsite from the Bayer process is dissolved in an excess of sulfuric acid (H2SO4). The resulting liquor is then neutralized by aqueous ammonia and cooled to yield crystals of the double ammonium aluminum sulfate, formerly called ammonium alum [NH4Al(SO4)2.12H2O]. After settling and drying, the dried crystals of alum are calcined above 1000°C, giving a white powder of pure Al2O3. (ii) Gel process. High-purity aluminum metal is dissolved in an alcoholic solution of KOH into isopropanol. Once dissolved, the aluminum propanolate produced is purified by distillation and hydrolyzed to yield a gel that is later calcined. (iii) Chloride process. This process consists in dissolving pure alumina into concentrated hydrochloric acid and precipitating hexahydrated aluminum chloride (AlCl3.6H2O). After calcination at 1000°C the residue consists of highly pure Al2O3. (iv) Alkaline process. This process consists in dissolving pure alumina into concentrated sodium hydroxide and precipitating the gibbsite either by Bayer precipitation or by neutralization. Sodium is removed from gibbsite by hydrothermal treatment. All these processes use a tunnel kiln for the final calcination.

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10.2.4 Limestone and Lime Description and general properties. Lime or calcia are common names for calcium oxide –3 [1305-78-8], whose chemical formula is CaO. Lime exhibits a medium density of 3340 kg.m and a high melting point of 2899°C. More specifically, quicklime is calcined calcium oxide (CaO). It reacts vigorously with water according to the following reaction: CaO(s) + H2O(l)—> Ca(OH)2(s). The hydratation of quicklime is highly exothermic and it releases circa 1.19 MJ per kilogram of lime. If not enough water is added, the heat released can increase the temperature of the water until it reaches its boiling point. Once the reaction is complete, the product obtained is calcium hydroxide, Ca(OH)2 [1305-62-0], also called hydrated lime or slaked lime. The solution saturated with calcium hydroxide is called milk of lime and has a pH of 12.25. Hydraulic lime is an impure form of lime that will harden under water. Lime has been used for thousands of years for construction. Archeological discoveries in Turkey indicate lime was used as a mortar as far back as 7000 years ago. Ancient Egyptian civilization used lime to make plaster and mortar. Industrial preparation. Most lime worldwide is obtained from quarries of carbonated rocks such as limestone, marble, chalk, and dolomite, or even from oyster shells. The suitable raw materials are usually selected because of their low silica and iron contents. After the rock is blasted away, the material is then crushed and sized before being calcined into vertical shaft furnaces (Europe) or rotary kilns (USA) at 1010 to 1345°C. During calcination, the carbon dioxide is driven off and leaves calcium oxide or quicklime according to the following reaction: CaCO3(s) —> CaO(s) + CO2(g). Theoretically, 100 kg of pure calcium carbonate yields 56 kg of quicklime. Industrial applications and uses. Today, nearly 90% of lime is used for chemical and industrial purposes. The largest use of lime is in steel manufacturing, where it is used as a flux to remove impurities such as phosphorus and sulfur. Lime is used in power-plant smokestacks to remove sulfur from emissions. Lime is also used in mining to neutralize acid-mine drainage, paper and paper-pulp production, water treatment and purification, and wastewater treatment. It is used in road construction and traditional building construction. Limestone is a sedimentary carbonated rock essentially made of calcite [CaCO3, rhombohedral] and hence can be used in place of lime for some industrial applications such as agriculture, as a flux in steelmaking, and in sulfur removal. Limestone is much less expensive than lime (60–100 US$/tonne); however, it is not as reactive as lime, so it may not be the best substitute in all cases. Magnesium hydroxide can be used for pH control. Lime resources are plentiful worldwide. Major producers of lime are the United States (Texas, Alabama, Kentucky, Missouri, Ohio, and Pennsylvania), Canada and Mexico, Belgium, Brazil, China, France, Germany, Italy, Japan, Poland, Romania, and the United Kingdom.

10.2.5 Dolomite and Doloma 10.2.5.1 Dolomite Description and general properties. Dolomite is a massive calcareous sedimentary rock made of the mineral dolomite [CaMg(CO3)2, rhombohedral], first identified by the French geologist D. Dolomieu in 1791 and named by H. Saussure after its discoverer. Dolomite occurs as huge geological formations such as in the northeastern Italian Alps called the Dolomiti. Usually dolomite as a rock contains, apart from dolomite, other carbonates (e.g., calcite,

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magnesite, and siderite), along with some silica and alumina, mostly as clays. For commercial purposes, the mass fraction of combined impurities must be below 7 wt.%, above which it becomes unsuitable for industrial use and is then used only for road ballasts and building stones. When the percentage of calcium carbonate (CaCO3) is above 10 wt.% or more over the theoretical composition, the rock is termed calcitic dolomite, while with a departure from theoretical magnesite content the rock is called dolomitic limestone. With variations in MgCO3 between 5 and 10 wt.%, it is called magnesian limestone, and when it contains up to 5 wt.% MgCO3 or less it is considered limestone for all purposes. Industrial applications and uses. Pure dolomite, without calcining, is chiefly used as refractory, ramming, and felting material in steel-melting shops and as fluxing material in blast-furnace operations in secondary steel and in the production of ferromanganese. Dolomite for use as flux in iron- and steelmaking should be hard, compact, and fine-grained so that it can withstand the burden of batches in blast furnaces as well as the basic steel converter. Dolomite bricks are kept in backup lining because it exhibits a lower thermal conductivity than magnesite. Chemical impurities must be as low as possible, especially phosphorus and sulfur, while silica and alumina are not deleterious for blast furnaces. Moreover, the magnesia in dolomite acts as desulfurizating agent in molten iron metal. Generally, two grades of dolomite are used, one is called blast furnace grade and the other steel melting shop grade. Dolomite is also used to a lesser extent in the glass industry, especially in sheetglass manufacture. For that application, dolomite should contain no more than 0.1 wt.% Fe2O3. It also finds use in the manufacture of mineral wool. Dolomite is also a useful source for the production of magnesite by reacting calcined dolomite with seawater (Section 10.2.6).

10.2.5.2 Calcined and Dead Burned Dolomite (Doloma) Description and general properties. Like other carbonates, upon heating above 900°C dolomite decomposes completely into a mixture of calcium and magnesium oxides, and carbon dioxide: CaMg(CO3)2(s) —> CaO(s) + MgO(s) + 2CO2(g). The product resulting from this relatively low-temperature calcination is highly porous and reactive and is known as calcined dolomite or simply doloma or dolime (i.e., CaO + MgO). Like lime, most dolime is produced either in vertical shaft kilns (Europe and UK) or rotary kilns (USA). Dolime is used in the extractive metallurgy of magnesium metal by the silicothermic process. Although pure magnesite decomposes at 700°C and calcite at 900°C, dolime is too porous for most refractory uses. Therefore, prior to use it is calcined at a higher temperature of ca. 1700°C. This harsh treatment allows the material to shrink thoroughly and render it less reactive than calcined dolomite. The product obtained is called dead burned dolomite and is generally used for the refractory made by firing dolomite, with or without additives, at high temperatures to produce dense, well-shrunk particles. Industrial preparation. Dead burned refractory dolomite is produced in vertical shaft or rotary kilns. Generally high-purity dolomite, with total impurities of less than 3 wt.%, is selected. As it is difficult to densify high-purity dolomite in a rotary kiln, it is customary to use some mineralizers to facilitate sintering. Iron sesquioxide is a common additive. The manufacturing process varies with the grade of dead burned dolomite needed. Most plants use rotary kilns lined in the hot zone with basic bricks and fired with powdered coal. The temperature reached in the hot zone is ca. 1760°C or above when iron oxide is added. After dead burning, dead burned dolomite is cooled in either rotary or reciprocating recuperative coolers. The air used for cooling gets heated and is again used as secondary air for combustion in the kilns. There is another product known as stabilized refractory dolomite. It is manufactured by a process similar to that of Portland clinker. Dolomite and serpentine, with small amounts of

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suitable stabilizing agents, are ground to a slurry in a ball mill. The slurry is fired into a dense mature clinker in a rotary kiln having a temperature on the order of 1760°C. Industrial applications and uses. Dead burned dolomite exhibits high refractoriness and can withstand temperatures up to 2300°C. It is widely used as a refractory material wherever steel is refined using basic slag. It is used for original hearth installations in open hearth furnaces as well as for hearth maintenance. These hearths are installed using tar-dolomite ramming mixes and rammed dolomite. Dolomite refractories are also used in electrical furnaces and in the cement industry during clinker manufacture.

10.2.6 Magnesite and Magnesia 10.2.6.1 Magnesite Description and general properties. Magnesite (MgCO3) is like alumina, that is, it is considered either as an ore for magnesium metal production or as an industrial mineral. When pure, magnesite contains 47.8 wt.% magnesium oxide (MgO) and 52.2 wt.% carbon dioxide. Natural magnesite almost always contains some calcite (CaCO3) and siderite (FeCO3). Magnesium also occurs in dolomite [FeMg(CO3)2], a sedimentary rock in which MgCO3 constitutes 45.65 wt.% (i.e., 21.7 wt.% MgO) and 54.35 wt.% CaCO3. Magnesite color varies from white, when pure, to yellowish or gray white and brown. Its Mohs hardness ranges from –3 3.5 to 4.5 and its density varies from 3000 to 3200 kg.m . A vitreous luster and very slow reaction with cold acids distinguishes magnesite from other carbonates. Magnesite, dolomite, seawater, and lake brines are used as major sources of magnesium metal with the most common source being lake brines and seawater. Occurrence. Magnesite occurs in two physical forms: as cryptocrystalline or amorphous magnesite and as macrocrystalline magnesite. It occurs in five different ways: as a replacement mineral in carbonate rocks; as an alteration product in ultramafic rocks (e.g., serpentinite, dunite); as a vein-filling material; as a sedimentary rock; and as nodules formed in a lacustrine environment. Replacement-type magnesite deposits involve magnesium-rich hydrothermal fluids entering limestone via openings to produce both magnesite and dolomite. The alteration-type deposits are formed by the action of carbon-dioxide-rich waters on magnesium-rich serpentinite. Sedimentary deposits usually occur as thin layers of variable magnesite quality. Lacustrine magnesite deposits consist of nodules of cryptocrystalline magnesite formed in a lake environment. Both vein filling and sedimentary magnesite occurrences are rarely mined on a large scale. Mining. All magnesite deposits are mined by open-cut methods. During mining the strip ratio, that is, the quantity of magnesite ore to waste material, may be high. The processing of magnesite ore begins with crushing, screening, and washing. The estimated world economic reserves of magnesite are about 8.60 billion tonnes expressed as MgCO3. China is ranked first, followed by Russia and North Korea. Industrial applications. Raw magnesite is used for surface coatings, landscaping, ceramics, and as a fire retardant.

10.2.6.2 Caustic Seawater and Calcined Magnesia Industrial preparation. Raw magnesite coming from the run-of-mine is calcined between 700 and 1000°C in a vertical shaft kiln and decomposes yielding magnesium oxide or magnesia (MgO) and giving off carbon dioxide gas: MgCO3(s) —> MgO(s) + CO2(g). The product obtained is called caustic-calcined magnesia (CCM), also called natural magnesia. The purity of CCM ranges usually between 75 and 96 wt.% MgO, with most of the impurities (e.g., Fe2O3, Al2O3, SiO2, etc.) coming from the raw material used.

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When a higher-purity magnesia is required, another more energy demanding route consists in preparing directly magnesium oxide from seawater or magnesium-rich brines. Prior to being processed, seawater is pumped and its impurities, mostly carbonates along with dissolved carbon dioxide, are removed. Usually, a hydrotreater removes CO2 as calcium carbonate by the addition of milk of lime, Ca(OH)2. Afterwards, the addition of hydrochloric acid removes the dissolved CO2 as gaseous carbon dioxide with an efficiency of 95%. On the 2 other hand, either quicklime (CaO) obtained from the calcination of pure limestone or, better, dolime (i.e., CaO and MgO) obtained from the calcination of dolomitic limestone is prepared in a vertical shaft kiln. Once cooled, quicklime or dolime is then slacked with water to yield milk lime, Ca(OH)2. The operation is performed in a rotary slacker from which any traces of calcium carbonate are removed by centrifugation. The milk of lime is added to the decarbonated seawater for precipitating magnesium as brucite [Mg(OH)2]. The milky slurry is filtrated to recover the magnesium hydroxide. The filtration cake is then sintered into a rotary kiln to obtain the so-called seawater magnesia clinker, also called synthetic magnesia, with a purity of at least 97 wt.% MgO. Both grades of caustic magnesia readily react with water to give magnesium hydroxide or brucite [Mg(OH)2], also called slacked or spent magnesia: MgO(s) + H2O(l) —> Mg(OH)2(s). Due to its alkaline properties and its poor solubility, when an excess of caustic magnesia is mixed with water, it gives a slurry called milk of magnesia with a pH of 10.25, and hence most heavy metals (e.g., Ni) are precipitated as metal hydroxides and then can be either removed by decantation, centrifugation, or filtration or stabilized in situ after drying of the slurry. Industrial applications and uses. Magnesium hydroxide or brucite is used in sugar refining, as a flame and smoke retardant, in wastewater treatment, and finally in pharmaceuticals. Caustic magnesia is extensively used in acid mine drainage and wastewater treatment to precipitate deleterious metals. On the other hand, caustic-calcined magnesite is used in agriculture as a food supplement in fertilizers, in environmental applications, and in the chemical industry for making magnesium oxychloride and oxysulfate cements that are resilient, fireproof, spark proof, and vermin proof; it is also used as filler in paints, paper, and plastic. The building industry consumes large quantities of caustic-calcined magnesite for use as a flooring material, in wall boards, and in acoustic tiles. Worldwide annual production is 1,000,000 tonnes of synthetic magnesia. Prices (2006). Prices are roughly 200 US$/tonne for natural magnesia and up to 400 US$/ tonne for synthetic magnesia.

10.2.6.3 Dead Burned Magnesia When caustic magnesia is further heated at temperatures of between 1530 and 2300°C, the grains of magnesia become sintered and the product obtained is nonhygroscopic and exhibits exceptional stability and strength at high temperatures. This fine-grained product, with a den–3 sity of 3400 kg.m , an average periclase grain size above 120 μm that contains at least 97 wt.% MgO, is known as dead burned magnesia or sintered magnesia. Worldwide circa 7.5 million tonnes of dead burned magnesia are produced annually. Dead burned magnesia and fused magnesia, due to their refractoriness, are used in the manufacture of basic refractories for iron- and steelmaking, nonferrous metallurgy, and finally in cement kilns. Eighty-five percent of the world production is used as refractory grade dead burned magnesia essentially as a refractory material because of its inertness and high melting point, while the remaining 15% is used in the cement industry, glassmaking, and the metallurgy of nonferrous metals. 2

In the early days of the Dow Chemical process for producing magnesium metal, tonnes of Oyster shells were used as a source of pure calcium carbonate for the preparation of magnesia from seawater.

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10.2.6.4 Electrofused Magnesia Electrofused magnesia is obtained when dead burned magnesia is melted in an electric-arc furnace at temperatures above the melting point of MgO (2800°C) and pouring the melt into a mold. After cooling and demolding and then crushing, so-called electrofused magnesia, or simply fused alumina, is obtained. It has a higher mechanical strength, high resistance to abrasion, and a higher chemical stability than dead burned magnesia. It is used in the manufacture of premium-grade refractory bricks used in the high wear hot spots of basic oxygen furnaces and electric-arc or similar furnaces where temperatures can approach 950°C.

10.2.6.5 Seawater Magnesia Clinker Magnesia is also produced from the processing of seawater and magnesium-rich brines. This is a much more complex and energy-demanding process than the processing of natural magnesite.

10.2.7 Titania Titanium dioxide [13463-67-7], chemical formula TiO2 and relative molecular molar mass of 79.8788, occurs in nature in three polymorphic crystal forms: anatase, rutile, and brookite. Moreover, under high pressure, the structure of all three polymorphs of titanium dioxide may be converted into that of α-PbO2. The main properties of the three polymorphs are summarized in Table 10.6.

10.2.7.1 Rutile Rutile [131-80-2], among other polymorphs of titanium dioxide, is the most thermodynamically stable structure, and thus rutile is the major naturally occurring mineral of pure titanium dioxide and is much more common than either anatase or brookite. It is usually colored red or brownish red by transmitted light owing to trace impurities such as Fe, Nb, Ta, and, to a lesser extent, Sn, Cr, and V. The preparation of single crystals of rutile at the laboratory 3 scale can be performed using Verneuil’s flame fusion method, while its large-scale industrial preparation is based on the sulfate and chloride processes (see Titanium). The crystallographic structure of rutile is a flat tetragonal prism where each tetravalent titanium cation is hexacoordinated to six almost equidistant oxygen anions, and each oxygen anion to three 8– titanium anions. The TiO6 octahedra are arranged in chains parallel to the c-axis. The oxygen atoms are arranged in the form of a somewhat distorted octahedron with each octahedron sharing one edge with adjacent members of the chain. The O-Ti-O bond angles are 90° by symmetry, 80.8°, and 99.2°, respectively. Highly pure rutile is an excellent electrical insulator at room temperature. However, its electrical conductivity, which is highly anisotropic, rises rapidly with temperature owing to the reversible lost of oxygen atoms that leads to a departure from ideal stoichiometry. Hence, upon heating rutile gives an n-type semicon4 –1 5 ductor and its conductivity can increase up to 100 S.cm for the composition TiO1.75. Expres–1 sion for the intrinsic conductivity expressed in S.cm of single crystals of rutile as a function 6,7 of temperature have been given by Cronmeyer, where the two subscript symbols // and + refer to the c-axis. 3 4 5 6 7

Verneuil, A. (1902) Compt. Rend. Acad. Sci., 135, 791. Grant, F.A. (1959) Rev. Mod. Phys., 31, 646. Verwey, E.J.W. (1947) Philips Tech. Rev. 9, 46. Cronmeyer, D.C. (1952) Phys. Rev., 87, 876. Cronmeyer, D.C. (1959) Phys. Rev., 113, 1222.

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Table 10.6. Properties of titanium-dioxide polymorphic phases Phase [CAS RN] 9

Anatase [1317-70-0]

10

Rutile [131-80-2]

12

Brookite [12188-41-9]

Crystal system, space group, and space lattice parameters

Refractive indices (for λD = 589.3 nm)

Miscellaneous properties 8 (density , etc.)

Tetragonal (I41/amd, Z = 4) a = 379.3 pm c = 951.2 pm Ti-O: 191 pm (2) – 195 pm (4) Packing fraction = 70%

Uniaxial (–) nε = 2.4880 nω = 2.5612

Black to red –3 ρcalc. = 3877 kg.m trans. temp. 700°C εr = 48 HM = 5.5 – 6.0

Tetragonal (P42/mnm, Z = 2) a = 459.37 pm c = 296.18 pm Ti-O: 194.4 pm (4) – 198.8 pm (2) Packing fraction = 77%

Uniaxial (+) nε = 2.6124 nω = 2.8993

Reddish brown –3 ρcalc. = 4245 kg.m m.p. = 1847°C –14 –1 σe = 10 S.cm –9 11 χm = +74 × 10 emu εr = 110 – 117 HM = 6.0 – 6.5

Orthorhombic (Pbca, Z = 8) a = 545.6 pm b = 918.2 pm c = 514.3 pm Ti-O: 184 pm – 203 pm

Biaxial () nα = 2.5831 nβ = 2.5843 nγ = 2.7004

ρcalc. = 4130 kg.m m.p. = 1900°C εr = 78 HM = 5.5 – 6.0

n.a.

n.a.

TiO2 II highOrthorhombic (Pbcn, oP12, Z = 4) pressure phase (40 a = 551.5 pm 13 kbar, 450°C) b = 549.7 pm c = 493.9 pm Ti-O: 191 pm (4) – 205 pm (2) TiO2 III highpressure phase

–3

Hexagonal hP48

ln σ+ = 7.92 – 17,600/T (623.15 K – 1123.15 K) = 11.10 – 21,200/T (1123.15 K – 1673.15 K) ln σ// = 8.43 – 17,600/T (773.15 K – 1223.15 K) = 11.30 – 21,200/T (1223.15 K – 1673.15 K) On the other hand, the electrical conductivity of single crystals of highly pure rutile is strongly affected by the doping of the crystal lattice with traces (i.e., less than 0.1 ppm wt.) of 3+ 4+ 4+ 5+ 3+ 2+ 2+ 3+ 2+ transition-metal cations (e.g., Cr , V , Nb , Nb , Fe , Co , Ni , Ni , and Cu ). From an optical point of view, rutile, which is uniaxial (-), exhibits a high refractive index even higher than that of diamond and is transparent from visible to near-infrared radiation with wavelengths ranging from 408 nm to 5000 nm. However, at the blue end of the visible spectrum the strong absorption band of rutile at 385 nm renders the rutile pigment slightly brighter than anatase, which explains its typical yellow undertone. For that reason it can be used efficiently as sunscreen. When heated in air to ca. 900°C the powdered material 8 9 10

11

12 13

Theoretical density calculated from crystal lattice parameters. Pascal, P. (1963) Nouveau Traité de Chimie Minérale, Tome IX. Masson & Cie, Paris. Meagher, E.P.; Lager, G.A. (1979) Polyhedral thermal expansion in the TiO2 polymorphs: refinement of the crystal structures of rutile and brookite at high temperature. Can. Mineral., 17, 77–85. –9 Wide range also reported in the litterature from –300 to +370 × 10 emu owing to slight departure from stoichiometry and doping with paramgnetic impurities leads to positive susceptibilities. Weyl, R. (1959) Z. Krist. 111, 401. Simons, P.Y.; Dachille, F. (1967) Acta Cryst., 23, 334.

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becomes lemon-yellow and exhibits a maximum absorption edge at 476 nm, but coloring disappears on cooling. In addition, doped rutile is phototropic, that is, it exhibits a reversible 14 darkening when exposed to light. On the other hand, rutile exhibits strong photocatalytic properties. As for electrical properties, metallic trace impurities strongly affect the whiteness of rutile. Even minute concentrations on the order of a few parts per million by weight may be sufficient to impart color. Thus in the industrial production of the whitest rutile, it is essential that other chromophoric transition elements not be present in the feedstock or be removed during the processing. Of these, chromium (Cr), vanadium (V), iron (Fe), and, to a lesser extent, niobium (Nb) are particularly deleterious in discoloring rutile. Generally, the colors are too intense to arise from crystal-field effects only but may arise from the excitation of the d-electrons of the impurity metal cation into the conduction band of the crystal lattice. From a chemical point of view, titanium dioxide is relatively inert chemically and resists attack from most chemical reagents. This property is further enhanced after titanium dioxide has been calcined at high temperatures.

10.2.7.2 Anatase The lattice structure of anatase [1317-70-0] is also tetragonal, but the lower packing fraction of the crystal lattice explains why anatase crystal exhibits both a lower hardness and refractive indices than rutile. Nevertheless, because the crystal lattice energies of the two phases are quite similar, anatase remains metastable over long periods of time despite being less thermodynamically stable. However, above 700°C, the irreversible and rapid monotropic conversion of anatase to rutile occurs. From an optical point of view, anatase exhibits a greater transparency in the near-UV than rutile. The absorption edge being at 385 nm, this explains why anatase absorbs less light at the blue end of the visible spectrum and has a blue tone. Although anatase was the first pigment to be produced commercially and represented a step-change in optical performance over the pigments that preceded it, rutile remains the preferred pigment because of its higher refractive index and lower photocatalytic activity. Actually, rutile ensures greater stability and durability of the paint made from it (less chalking). However, anatase is required in certain applications, especially where low abrasivity may be an issue. Thus anatase pigments were originally the preferred choice for paper filling and coating and also for delustring of synthetic fibers, where the color of the application may degrade by abrasion of metal during frequent rubbing contact with machinery during processing.

10.2.7.3 Brookite Brookite [12188-41-9], which exhibits an orthorhombic crystal lattice, is more difficult to produce than rutile and anatase, and for that reason it has never been used industrially, especially in the white pigment industry. Apart from the well-known titanium-dioxide phases mentioned above, other titanium oxides exists such as titanium hemioxide (Ti2O), titanium monoxide (TiO), titanium sesquioxide (Ti2O3), and anosovite (Ti3O5). See Table 10.6, page 615.

10.2.7.4 Anosovite 15

Anosovite [12065-65-5], chemical formula Ti3O5, was identified by Ehrlich in the Ti-O binary phase diagram, in the region between 62.3 and 64.3 at.% oxygen. It can be prepared in the following ways:

14 15

Weyl, W.A.; Forland, T. (1950) Ind. Eng. Chem., 42, 257. Ehrlich, P.Z. (1939) Elektrochem., 45, 362.

Raw Materials for Ceramics, Refractories and Glasses

(i)

16

By the hydrogen reduction of solid TiO2 at temperature around 1300°C according to the following reaction scheme: 3TiO2(s) + H2(g) —> T3O5(s) + H2O(g)

(ii)

617

(1300°C)

By mixing intimately stoichiometric quantities of titanium metal and titanium dioxide in an electric-arc furnace under an argon atmosphere according to the following reaction scheme: 5TiO2(s) + Ti(s) —> 2T3O5(s)

(1150°C)

followed by annealing in a vacuum of the crushed material for 2 weeks at 1150°C in a sealed silica tube. This oxide is dimorphic with a rapid phase transition from semiconductor to metal occurring at roughly 120°C. α-Ti3O5—> β-Ti3O5

(120°C)

The low-temperature form (α-Ti3O5), also called anosovite type I, crystallizes with a monoclinic unit cell with the Ti-O bond distances ranging from 178 to 221 pm. The structure can 8– be described in terms of TiO6 octahedra joined by sharing the edge and corners to form an infinite three-dimensional network. Anosovite I is obtained by the hydrogen reduction of pure rutile at 1300°C. The high-temperature form (β-Ti3O5), also called anosovite type II, is a slightly deformed pseudobrookite structure (AB2O5) with the Ti-O bond distances ranging from 191 to 210 pm. The type II is obtained by hydrogen reduction at 1500°C with magnesia 17 as a catalyst. The anasovite type II is similar to that identified in titanium slags. It can be stabilized at room temperature with a small amount of iron.

10.2.7.5 Titanium Sesquioxide Titanium sesquioxide [1344-54-3], chemical formula Ti2O3, exists within a rather narrow range of homogeneity, from 59.4 to 60.8 at.% oxygen (TiO1.49–TiO1.51). It has a corundum structure and is isomorphous with hematite and ilmenite. It may be prepared by reduction of titania by hydrogen gas at 1000°C or as powder by reacting titanium metal with a stoichiometric amount of TiO2 at 1600°C as follows: Ti(s) + 3TiO2(s) —> 2 Ti2O3(s)

(1600°C).

10.2.7.6 Titanium Monoxide or Hongquiite Titanium monoxide or hongquiite [12137-20-1], chemical formula TiO, exhibits a very wide range of composition, extending approximately from 42 to 54 at. % oxygen (TiO0.64 to TiO1.26). It may be prepared by direct reduction by mixing stoichiometric amounts of titanium metal and titanium dioxide into a molybdenum crucible at 1600°C or reduction of the titanium dioxide with hydrogen under pressure at 130 atm and 2000°C. Ti (s) + TiO2(s) —> 2 TiO(s)

(1600°C)

On heating the monoxide in air, the compound reverts to other titanium oxides as a function 18 of temperature increase :

16 17

18

TiO(s) —> Ti2O3(s)

(200°C),

TiO(s) —> Ti3O5(s)

(250–350°C),

TiO(s) —> TiO2(s)

(350°C).

Ehrlich, P. (1941) Z. Anorg. Allgem. Chem., 247, 53. Reznichenko, V.A.; Khalimov, F.B. (1959) Reduction of titanium dioxide with hydrogen. Titan i Ego Splavy, 2, 11–15. Wyss, R. (1948) Ann. Chim. 3, 215.

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Ceramics, Refractories, and Glasses

Its crystal structure has varying proportions of both titanium and oxygen vacancies. Density and y-ray lattice parameter measurements have shown that a third of the oxygen sites are vacant in TiO0.7, a quarter of the titanium sites are vacant in TiO1.25, and even in stoichiometric TiO about 15% of both sites are vacant. Above 990°C, the vacancies are arranged randomly, giving rise to diffraction patterns typical of the cubic NaCl-type structure.

10.2.7.7 Titanium Hemioxide Oxygen is soluble in alpha-titanium until the composition TiO0.5 (alpha-case) is formed, with the oxygen atoms supposedly being randomly distributed in the octahedral interstices of the 19 hexagonally close-packed titanium lattice.

10.2.7.8 Andersson–Magnéli Phases 20

In addition, a major series is represented by Andersson–Magnéli’s phases that consist of a continuous series of substoichiometric titanium oxides, characterized by the general formula TinO2n-1, where n is an integer greater than 4 (i.e., Ti4O7, Ti5O9, Ti6O11, Ti7O13, etc.). See Table 10.7, page 619.

10.2.8 Zircon and Zirconia 10.2.8.1 Zircon Zircon [10101-52-7], chemical formula ZrSiO4, is an accessory nesosilicate mineral found in granites and, due to its high Mohs hardness of 7.5 and chemical inertness, it concentrates in the weathering products of mother igneous rocks such as in alluvial placer deposits and beach sands. Because of its chemical inertness and high melting point, zircon is wetted less easily by molten metal, producing smoother surfaces on iron, high alloy steel, aluminum, and bronze casting. The largest use of zircon is as foundry sand, where zircon is used as the basic mold material, as facing material on mold cores, and in ram mixes. Zircon-sand molds have greater thermal shock resistance and better dimensional stability than quartz-sand molds. Zircon grains are usually bonded with sodium silicate. Major producers of zircon sand are Richards Bay Minerals (Rio Tinto plc-BHP Billiton) located on the coastline of the KwaZulu-Natal region of the Republic of South Africa, followed by the Australian mining company Iluka. Both produce zircon sand as coproduct during mineral dressing of weathered ilmenite and rutile from beach mineral sands.

10.2.8.2 Zirconia Description and general properties. Pure zirconium dioxide (ZrO2), also called zirconia, is –3 a dense material (5850 kg.m ) that exhibits a high temperature of fusion (2710°C) and a good –1 –1 thermal conductivity (1.8 Wm K ). Electrically speaking, zirconia is a dielectric at room temperature but becomes a good ionic conductor at high temperatures. Actually, cubic zirconia is a solid ionic electrolyte that allows oxygen anions to migrate through the crystal structure under an electric field at temperatures above 800°C. Optically, zirconia has a high index of refraction, which allows it to be used for increasing the refractive index of some optical glasses. Chemically, zirconia exhibits an excellent chemical inertness and corrosion resistance to many strong mineral acids, liquid metals, and molten salts up to high temperatures well above the melting point of alumina. Zirconia is not wetted by many metals and is therefore an excellent crucible material when corrosive melts (e.g., molten alumina and titanium slag) 19 20

McQuillan, A.D.; McQuillan, M.D. (1956) Titanium. Butterworths, London. Andersson, S.; Collen, B.; Kuylenstierna, U.; Magneli, A. (1957) Acta Chem. Scand., 11, 1641.

Raw Materials for Ceramics, Refractories and Glasses

619

Table 10.7. Properties of other titanium oxides Titanium oxide

Formula

Rel.molar mass (Mr)

wt.% Ti

Color, crystal lattice structure, space group (SG), Pearson symbol, lattice parameters, physical properties

Andersson– Magnéli phases

Ti10O19

780.6886

61.1

Triclinic

Ti9O17

701.0198

61.2

Triclinic; S.G. P1; aP52

Ti8O15

621.3510

61.4

Triclinic, S.G. A1; aC92

Ti7O13

541.6822

61.6

Triclinic; S.G. P1; aP40

Ti6O11

462.0134

61.9

Triclinic; S.G. A1; aC68

Ti5O9

382.3446

62.3

Triclinic; S.G. P1; aP28

Ti4O7

302.6758

63.0

Triclinic; S.G. P1; aP44

Anosovite [12065-65-5]

Ti3O5

223.0070

64.1

Dark blue; dimorphic (120°C) Low T: Anasovite-type I Monoclinic, C2/m, Z = 4 a = 975.2 pm; b = 380.2 pm; c = 944.2 pm; β = 91.55° High T: Pseudobrookite (orthorhombic) –3 ρcalc. = 4900 kg.m m.p. = 1777°C

Titanium sesquioxide [1344-54-3]

Ti2O3

143.3382

66.5

Dark violet to purple violet Corundum type a = 515.5 pm; c = 1361 pm –3 ρcalc. = 4486 kg.m m.p. = 1839°C –1 –1 cp = 679 J.kg .K –6 χm = +63 × 10 emu

Titanium monoxide or hongquiite [12137-20-1]

TiO

63.6694

74.9

Gold-bronze Halite-type (cubic) a = 417 pm –3 ρcalc. = 4888 kg.m m.p. = 1750°C –1 –1 cp = 628 J.kg .K α = 9.19 μ/m.K –6 χm = +88 × 10 emu

Titanium hemioxide

Ti2O

111.3394

85.6

Metallic gray

are absent. It can be used continuously or intermittently at temperatures up to 2200°C in neutral or oxidizing atmospheres. However, above 1600°C, zirconia reacts with alumina, and above 1650°C, in contact with carbon, zirconia forms zirconium carbide (ZrC). It has been used successfully for melting alloy steels and the noble metals. Nevertheless, zirconia in its chemically pure state exhibits poor mechanical and thermal properties that are inappropriate for use in structural and advanced ceramics. Actually, the polymorphism of pure zirconia exhibits deleterious phase transitions between room temperature and its melting point (Figure 10.3). These phase changes, accompanied by important relative volume changes, create a dense population of microcracks for the sake of toughness and thermal shock resistance.

Figure 10.3. Polymorphs of zirconia (ZrO2)

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Ceramics, Refractories, and Glasses

At room temperature, pure zirconia is essentially made of monoclinic baddeleyite with –3 –6 –1 a density of 5850 kg.m and a coefficient of linear thermal expansion of 6.5 × 10 K , which is stable up to the transition temperature of 1197°C, at which it transforms into tetragonal –3 zirconia (i.e., rutile type) with a density of 6045 kg.m . This inversion in crystalline structure causes an important volume change upon heating ( V/V = +7.0 vol.%). Due to the inversion, pure zirconia is highly sensitive to thermal shocks: ZrO2 (monoclinic) —> ZrO2 (tetragonal)

Tt = 1197°C.

Afterwards, above 2300°C, tetragonal zirconia transforms into high-temperature cubic zir–3 conia (i.e., fluorite type) with a mass density of 5500 kg.m and a coefficient of linear ther–6 –1 mal expansion of 10.5 × 10 K : ZrO2 (tetragonal) —> ZrO2 (cubic)

Tt = 2300°C.

Finally, at 2710°C zirconia melts, giving molten zirconia: ZrO2(cubic) —> ZrO2(l)

Tf = 2710°C.

However, to prevent the first disastrous phase transition, it is possible to stabilize hightemperature cubic zirconia introducing foreign bivalent, trivalent, and/or tetravalent cations into its structure. Once stabilized, zirconia is stable from room temperature up to its melting point without any phase changes, and its thermal expansion varies linearly with temperature. The doped material demonstrates superior mechanical, thermal, and electrical properties owing to the modification of its crystal structure. Major lattice stabilizers are, for instance, calcia (CaO), magnesia (MgO), ceria (CeO2), yttria (Y2O3), and lanthania (La2O3), which are introduced into the material prior to firing. The stabilized zirconia is then extremely resistant to thermal shock. Actually, white hot parts can be quenched in cold water or liquid nitrogen without break. Usually, calcia is the most widely used addition commercially, not only because it is a cheap raw material but also because the cubic form remains stable at all temperatures, whereas the magnesia-stabilized form may revert to the monoclinic structure at low temperature. Commercial zirconia grades. Usually unstabilized zirconia (i.e., fully monoclinic), partially stabilized zirconia, and stabilized zirconia (i.e., completely cubic) grades exist commercially and are available among advanced ceramic producers worldwide (e.g., Zircoa, Vesuvius, and Degussa), and they are briefly described below. (i)

(ii)

Unstabilized zirconia. As indicated previously, pure zirconia is monoclinic at room temperature and changes to the denser tetragonal form at 1100°C, which involves a large volume change and creates microcracks within its structure. However, pure zirconia is an important constituent of ceramic colors and an important component of lead-zirconia-titanate electronic ceramics. Pure zirconia can be used as an additive to enhance the properties of other oxide refractories. It is particularly advantageous when added to high-fired magnesia and alumina bodies. It promotes sinterability and, with alumina, contributes to abrasive characteristics. Partially stabilized zirconia. Partially stabilized zirconia (PSZ) is a mixture of various zirconia polymorphs, because insufficient cubic-phase-forming oxide has been added and a cubic plus metastable tetragonal ZrO2 mixture is obtained. A smaller addition of stabilizer to pure zirconia will bring its structure into a tetragonal phase at a temperature higher than 1100°C, and a mixture of cubic phase and monoclinic or tetragonal phase at a lower temperature. Therefore, partially stabilized zirconia is also called tetragonal zirconia polycrystal (TZP), which is usually a zirconia doped with 2 to 3 mol.% of yttria and which has a fine-grained microstructure (i.e., 0.5 to 0.8 μm) that exhibits most impressive mechanical properties at room temperature. Usually such PSZ consists of more than 8 mol.% MgO (2.77 wt.%), 8 mol% CaO (3.81 wt.%), or 3 to

Raw Materials for Ceramics, Refractories and Glasses

(3)

621

4 mol.% Y2O3 (5.4 to 7.1 wt.%). PSZ is a transformation-toughened material. Microcracks and induced stress may be two explanations for the toughening in partially stabilized zirconia. Microcracks arise due to the difference in the thermal expansion between the cubic-phase particle and monoclinic or tetragonal-phase particles in the PSZ. This difference creates microcracks that dissipate the energy of propagating cracks. The induced-stress explanation depends upon the tetragonal-to-monoclinic transformation, once the application temperature passes the transformation temperature at about 1000° C. The pure zirconia particles in PSZ can metastably retain the high-temperature tetragonal phase. The cubic matrix provides a compressive force that maintains the tetragonal phase. Stress energies from propagating cracks cause the transition from the metastable tetragonal to the stable monoclinic zirconia. The energy used by this transformation is sufficient to slow or stop propagation of the cracks. PSZ has been used where extremely high temperatures are required. PSZ is also used experimentally as heat engine components, such as cylinder liners, piston caps, and valve seats. Fully stabilized zirconia (CSZ). Fully stabilized zirconia, also called cubic stabilized zirconia (CSZ), is essentially a single-phase cubic material with large grain sizes of 10 to 150 μm that result when the stabilizer content and sintering temperature place it entirely in the cubic-phase region. Generally, the addition of more than 16 mol.% CaO (7.9 wt.%), 16 mol.% MgO (5.86 wt.%), or 8 mol.% Y2O3 (13.75 wt.%) to a zirconia structure is needed to form a fully stabilized zirconia. Its structure becomes cubic solid solution, which has no phase transformation from room temperature up to 2710°C. Fully yttria-stabilized zirconia (YSZ) is an excellent oxygen anion conductor that has been used extensively either as oxygen sensor or anion exchange membrane in solid oxide fuel cells (SOFCs). Other applications include grinding media and advanced ceramics due to its hardness and high thermal shock resistance.

Preparation of unstabilized zirconia. Zirconia is usually produced from zircon flour. Although the carbochlorination of zircon produces zirconium tetrachloride that can be oxidized to yield zirconia, such a method is only restricted to the production of zirconium metal (see Zirconium and Zirconium alloys). Therefore, to produce zirconia from zircon, the first step is to convert zircon to zirconyl chloride dihydrate. The process starts with the preparation of disodium metazirconate (Na2ZrO3) by digesting zircon into molten sodium hydroxide as follows: ZrSiO4(s) + NaOH(l) —> Na2ZrO3(s). Then the sodium zirconate is dissovled in concentrated hydrochloric acid: Na2ZrO3(s) + 2HCl(l) —> ZrOCl2 · 8H2O(s). There are two methods used to make zirconia from zirconyl chloride dihydrate (ZrOCl2.8H2O): thermal decomposition and precipitation. In the thermal decomposition method, upon heating above 200°C, zirconyl chloride dihydrate loses its hydratation water as follows: ZrOCl2 · 8H2O(s) —> ZrOCl2(s) + 8H2O(g). Afterwards, at a higher temperature anhydrous ZrOCl2 decomposes during calcination into chlorine gas and yields zirconia: ZrOCl2(s) + 1/2O2(g) —> ZrO2(s) + Cl2(g). The zirconia lumps obtained from the calcination then undergo a size-reduction process, such as ball milling, into the particle size range needed, usually up to –325 mesh. Thermal decomposition is hence an energy-demanding process from which it is not easy to produce zirconia powders with a high purity and fine particle size.

10 Ceramics, Refractories, and Glasses

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Ceramics, Refractories, and Glasses

In the precipitation method, zircornyl chloride dihydrate is dissolved into water, and after addition of aqueous ammonia a precipitate of zirconium hydroxide is obtained: +

–

+

–

ZrOCl2 + 4NH4 + 4OH —> Zr(OH)4(s) + NH4 + Cl . The precipitate of zirconium hydroxide (Zr(OH)4) is washed in order to obtain a chlorinefree product. The solid is recovered by filtration to yield a wet powder that after calcination and quenching into liquid nitrogen yield a high-quality zirconia powder: Zr(OH)4(s) —> ZrO2(s) + 2H2O(g). By this method, the grain size, particle shape, agglomerate size, and specific surface area can be modified within a certain degree by controlling the precipitation and calcination conditions. Furthermore, its purity is also more easily controlled. For the applications of zirconiain the slip casting, tape casting, mold injection, particle size, specific surface, etc. are important characteristics. Well-controlled precipitated zirconia powder can be fairly uniform and fine. Preparation of stabilized zirconia. In order to achieve the requirement of the presence of cubic and tetragonal phases in the microstructure of zirconia, stabilizers, i.e., magnesia, calcia, or yttria must be introduced into pure zirconia powders prior to sintering. Stabilized zirconia can be formed during a process called in situ stabilizing. Before the forming processes, such as molding, pressing, or casting, a blend of fine particles of stabilizer and monoclinic zirconia is prepared. Then the mixture is used for forming of green body. The phase conversion is accomplished by sintering the doped zirconia at 1700°C. During the firing (sintering), the phase conversion takes place. On the other hand, high-quality stabilized zirconia powder is made by a coprecipitation process. Stabilizers are then introduced before precipitation of zirconium hydroxide. Preparation of fused zirconia. Production of electrofused or simply fused zirconia consists in removing silica from zircon by melting zircon sand with coke into an electric arc furnace at temperatures of around 2800 to 3000°C. During the electrothermal process, silica is reduced to volatile silicon monoxide (SiO), which escapes the furnace and leaves molten zirconia. On rapid cooling, a granular material is produced that is screened and crushed. Usually, the monoclinic zirconia produced contains less than 0.2 wt.% silica. Preparation of zirconia by alkaline leaching. Zircon is roasted with sodium hydroxide and calcia at 600 to 1000°C. During the process silica reacts with calcium and sodium to yield calcium and sodium metasilicates. After acid leaching, the product is dyed and calcined to yield pure zirconia with less than 0.10 wt.% residual silica. The major producers of zirconia are listed in Table 10.8. Table 10.8. Major producers of zirconia Country

Company name

Plant location

Annual nameplate capacity (tonnes)

United States

Washington Mills Electro Minerals Corp.

Niagara Falls, NY

1500

Ferro Electronic Materials Systems

Niagara Falls, NY

4000

Universal America

Greeneville, TN

6000

Saint-Gobain Ceramic Materials

Huntsville, AL

6000

United Kingdom

Unitec Ceramics

Stattford

200

France

SEPZirPro

Le Pontet

8000

Australia

Australia Fused Materials

Rockingham, WA

4000

South Africa

Foskor

Phalaborwa

4000

Raw Materials for Ceramics, Refractories and Glasses

623

Table 10.8. (continued) Country

Company name

Plant location

Japan

JACO Co.

Osaka

Showa Denco Ceramics

Shiojiri

Fukushima Steel Works

Fukushima

JFE Material Co.

Imizu

1000

IDU Co.

Kochi

1500

Shanghai Zirconium Products

Shanghai

Yingkou Astron Chemical Co.

Bayuquan

9000

Zhenzou Fused Zirconia Co.

Zhengzou

5500

China

Annual nameplate capacity (tonnes) 1000

10.2.9 Carbon and Graphite 10.2.9.1 Description and General Properties Graphite [7440-44-0] is one of the two allotropic forms of the chemical element carbon, the other two being diamond (see Section 12.5). Graphite crystallizes in the hexagonal system. It has a black to steel gray color and usually leaves a black streak on the hand when touched because of its extreme softness and greasiness. It is opaque, even in the finest flakes. Graphite exhibits a high thermal conductivity close to that of copper alloys (Table 10.9). An important limitation of this material is its low tensile strength, and all components manufactured from carbon or graphite are highly susceptible to brittle fracture by mechanical shock or vibrations. Graphite is almost completely inert to all but the most severe oxidizing conditions, especially acids. Actually, graphite is recommended for use in 60 wt.% HF, 20 wt.% HNO3, 96 wt.% H2SO4, bromine, fluorine, or iodine. The excellent heat-transfer property of impervious graphite has made it very popular in heat exchangers handling corrosive media, but also for a number of other devices used in the chemical-process industries such as piping, pumps, valves, brick lining for process or storage vessels, anode materials in electrochemical processes, and ring packing for columns. Impervious graphite is also used for liquid metal-handling devices. It has high refractoriness; actually, graphite is highly refractory up to temperatures approaching 3000°C in an inert atmosphere or in a vacuum. However, if oxygen is present, it burns between 620 and 720°C. Graphite has an extraordinarily low coefficient of friction under practically all working conditions. This property is invaluable in lubricants. It diminishes friction and tends to keep the moving surface cool. Dry graphite, as well as graphite mixed with grease and oil, is used as a lubricant for heavy and light bearings. Graphite grease is used as a heavy-duty lubricant where high temperatures may tend to remove the grease. All grades of graphite, especially high-grade amorphous and crystalline graphite, can behave as colloids; for example, in suspension in an oil base, they are used as lubricants. Properties of selected commercial grades of graphite are listed in Table 10.10.

10.2.9.2 Natural Occurrence and Mining Graphite is usually found in metamorphic rocks as veins, lenses, and pockets and as thin laminae disseminated in gneisses, schists, and phyllites. Depending upon the mode of occurrence and origin, it is graded into three forms: flake graphite found in metamorphosed rocks as vein deposits, crystalline graphite found as fissure-filled veins, and cryptocrystalline graphite

10 Ceramics, Refractories, and Glasses

Ceramics, Refractories, and Glasses Table 10.9. Selected properties of different carbon products

Specific heat capacity –1 –1 (cP/J.kg .K )

Coeff. linear thermal –6 –1 expansion (α /10 K )

5–21

85–350

709

1.3–3.8 1385

HM 1

32

480–1950

707

4.5

1500

145

Diamond

3514

7000

n.a.

900–2300

506

2.16

10

8000

Vitreous carbon (treated at 1000°C)

1500–1550 28

300

100

4

710

3.2

5500

225

Vitreous carbon (treated at 2500°C)

1500–1550 22

150–200

60–80 8

710

3.2

4500

150–175

900

16

Vickers hardness (HV)

Young’s modulus (E/GPa)

–3

Graphite (industrial) 1400–2266 3–12

Electrical resistivity (ρ/μΩ.cm)

Thermal conductivity –1 –1 (k/W.m .K )

14–42

Pyrolitic carbon 1400–2210 16–30 72 (impervious graphite)

Density (ρ/kg.m )

Flexural strength (MPa)

21

Compressive strength (MPa)

Carbon derivate

Thermal expansion coefficient (20–200°C) (μm/m.K)

Specific electrical resistivity (ρ/μΩ.cm)

n.a.

15–18 37–44 7.4– 10.2

940– 105– 1.4– 1240 180 3.6

1000– 3000

MNC

1800

14

200

n.a.

n.a.

n.a.

n.a.

40

55–60 16

1000 130

1.5

1500

MNT

1750

16

400

n.a.

n.a.

n.a.

n.a.

20

28–30 15

1000 130

1

4000

R4340

1720

15

15

2

0.15

80

50

45

90

10.5

1200 90

2.9

200

R4500

1770

13

10

1.5

0.1

70

65

50

120

10.5

1400 80

3.9

200

R4550

1830

10

10

1.5

0.04

95

75

60

125

11.5

1300 100

4

20

R4820

1820

10

20

2.5

0.1

100

65

45

105

11

1150 125

4.2

50

R6300

1730

15

20

2

0.1

80

50

40

90

10

1700 65

3.8

n.a.

R6340

1720

15

15

2

0.15

80

50

45

90

10.5

1200 90

4

R6500

1770

13

10

1.5

0.1

70

65

50

120

10.5

1400 80

5

R6510

1830

10

10

1.5

0.04

95

75

60

125

11.5

1300 90

5.1

R6650

1840

10

7

0.8

0.03

95

75

65

150

12.5

1400 90

5

R6710

1880

10

3

0.6

0.01

110

80

85

170

13.5

1300 100

5.8

R6810

1800

11

20

2.5

0.3

95

75

45

100

10

1000 130

5.2

R6830

1820

9.5

20

2.5

0.1

95

75

50

100

10

1000 130

5

R8710

1880

10

3

0.6

0.01

110

80

85

170

13.5

1300 100

4.7

21

–3

Technical data from various producers such as Le Carbone Lorraine, Sigradur, SGL, and Tokkai.

Ash content (ppm wt.)

n.a.

Thermal conductivity –1 –1 (k/W·m ·K )

Shore hardness

Young’s modulus (E/GPa)

Rockwell hardness (HR)

n.a.

Flexural strength (MPa)

Dry air permeability 2 –1 at 20°C (cm .s )

n.a.

Average grain size (μm)

1700– 17–23 1.65 1780

Open porosity (vol.%)

HLM

Bulk density (ρ/kg.m )

Medium pore size (μm)

Compressive strength (MPa)

Table 10.10. Properties of industrial graphite grades from SGL Carbon

Graphite or carbon grade

624

200

Raw Materials for Ceramics, Refractories and Glasses

625

formed in metamorphosed coal beds. Natural graphite occurs in many parts of the world in fair abundance and it has been used in various applications. In nature, graphite is found usually in association with feldspars, mica, quartz, pyroxene, rutile, pyrites, and apatite. These impurities are associated with vein graphite. The impurities with amorphous graphite are shale, slate, sandstone, quartz, and limestone. Graphite is found in almost every country, but Ceylon, Madagascar, Mexico, western Germany, and Korea all possess particularly plentiful reserves. Major industrial producers of graphite are South Korea, the largest producer in the world, followed by Austria. Graphite is usually obtained by underground mining and, to a lesser extent, by hydraulic mining such as in Madagascar. Afterwards, beneficiation of the run-of-mine consists in using the intrinsic floatation ability of natural graphite without having to use a collector. However, the recovery of flake graphite from disseminated deposits is difficult, and several proprietary processes have been developed by many companies. This difficulty arises because fine grinding is not efficient and reduces the size and also lowers the price and value of the graphite.

10.2.9.3 Industrial Preparation and Processing Impervious graphite is manufactured by processing graphite at temperatures above 2000°C using Acheson furnaces (Section 10.2.10), evacuating the pores, and impregnating with a phenolic resin. The impregnation seals the porosity.

10.2.9.4 Industrial Applications and Uses Flake graphite containing 80 to 85 wt.% C is used for crucible manufacture; 93 wt.% C and above is preferred for the manufacture of lubricants, and graphite with 40 to 70 wt.% C is used for foundry facings. Natural graphite, refined or otherwise pure, having a carbon content of not less than 95%, is used in the manufacture of carbon rods for dry battery cells. Graphite crucibles are manufactured by pressing a mixture of graphite, clay, and silica sand (formerly called plumbago) and heating the pressed article at a high temperature in an inert atmosphere. Flake graphite is the best material, although crystalline graphite is also used. Crucibles made of graphite are used for melting nonferrous metals, especially brass and aluminum. Coarsegrained flake graphite from Malagasy is regarded as standard for crucible manufacture. The utility of graphite is dependent largely upon its type, i.e., flake, lumpy, or amorphous. The flake-type graphite is found to possess extremely low resistivity to electrical conductance. The electrical resistivity decreases with an increase in flaky particles. In addition, the bulk density decreases progressively as the particles become more and more flaky. Because of this property in flake graphite, it enjoys widespread use in the manufacture of carbon electrodes, plates, and brushes required in the electrical industry and dry-cell batteries. In the manufacture of plates and brushes, however, flake graphite has been substituted to some extent by synthetic, amorphous, crystalline graphite, and acetylene black. Graphite electrodes serve to give conductivity to the mass of manganese dioxide used in dry batteries.

10.2.10 Silicon Carbide 10.2.10.1 Description and General Properties Silicon carbide [409-21-2], chemical formula SiC and relative molar mass 40.097, is an important advanced ceramic with a high melting point (2830°C), a high thermal conductivity –1 –1 (135 Wm K ), and extremely high Mohs hardness of 9. Silicon carbide is also has a wide band gap for a semiconductor (2.3 eV). The preparation of silicon carbide involves the reaction of silica sand (SiO2) and carbon (C) at a high temperature (between 1600 and 2500°C). SiO2(s) + C(s) —> SiC(s) + CO(g)

10 Ceramics, Refractories, and Glasses

626

Ceramics, Refractories, and Glasses 22

The first observation of silicon carbide was made in 1824 by Jöns Jacob Berzelius. It was first prepared industrially in 1893 by the American chemist Edward Goodrich Acheson, who patented both the batch process and the electric furnace for making synthetic silicon-carbide 23 powder. In 1894 he established the Carborundum Company in Monongahela City, PA, to manufacture bulk synthetic silicon carbide commercialized under the trade name Carborundum™. Silicon carbide was initially used to produce grinding wheels, whetstones, knife sharpeners, and powdered abrasives. Despite being extremely rare in nature, when it occurs as a mineral it is called moissanite after the French chemist Henri Moissan who discovered it 24 in a meteorite in 1905. Polymorphism and polytypism. Silicon carbide has two polymorphs. At temperatures above 2000°C alpha silicon carbide (α-SiC), with a hexagonal crystal structure, is the more stable polymorph with iridescent and twinned crystals with a metallic luster. At temperatures lower than 2000°C, beta silicon carbide (β-SiC) exhibits a face-centered cubic (fcc) crystal structure. Moreover, α-SiC exists as different hexagonal polytypes with a carbon atom situated above the center of a triangle of Si atoms and underneath a Si atom belonging to the next layer. The difference between polytypes is the stacking sequence between succeeding double layers of carbon and silicon atoms. If the first double layer is called the A position, the next layer that can be placed according to a close-packed structure will be placed on the B position or the C position. The different polytypes will be constructed by permutations of these three positions. For instance, the 2H-SiC polytype will have a stacking sequence ABAB… The number thus denotes the periodicity and the letter the resulting structure, which in this case is hexagonal. The 3C-SiC polytype is the only cubic polytype and it has a stacking sequence ABCABC… or ACBACB… The cell lattice parameter a, between neighboring silicon or carbon atoms, is ca. 308 pm for all polytypes. The carbon atom is positioned at the center of mass of the tetragonal structure outlined by the four neighboring Si atoms so that the distance between the C atom and each of the Si atoms is the same. Geometrical considera1/2 tions require that the C-Si distance be exactly a(3/8) (189 pm). The distance between two 1/2 silicon planes is thus a(2/3) (252 pm). The height of a unit cell, c, varies between the different polytypes. The ratio (c/a) thus differs from polytype to polytype but is always close to the ideal for a close-packed structure. The actual ratio for the 2H-, 4H- and 6H-SiC polytypes is 1/2 1/2 1/2 closed to ideal ratios for these polytypes, that is, (8/3) , 2(8/3) , and 3(8/3) , respectively. The different polytypes exhibit different electronic and optical properties. The bandgaps at 4.2 K of the different polytypes range between 2.39 eV for 3C-SiC and 3.33 eV for the 2H-SiC polytype. The important polytypes 6H-SiC and 4H-SiC have bandgaps of 3.02 eV and 3.27 eV, respectively. All polytypes are extremely hard, chemically inert, and have a high thermal conductivity. Properties such as the breakdown voltage, the saturated drift velocity, and the impurity ionization energies are all specific for the different polytypes. Silicon carbide has long been recognized as an ideal ceramic material for applications where high hardness and stiffness, mechanical strength at elevated temperatures, high thermal conductivity, low coefficient of thermal expansion, and resistance to wear and abrasion are of primary importance. Moreover, because of its low density it offers greater advantages compared to other ceramics.

10.2.10.2 Industrial Preparation The Acheson process. This process, invented by Edward Goodrich Acheson in 1893, was extensively used for making silicon carbide and was the only industrial process available for 22 23

24

Berzelius, J.J. (1824) Ann. Phys., Leipzig, 1, 169. Acheson, E.G. (1893) Production of crystalline artificial carbonaceous materials. US Patent 492,767, February 28, 1893. Moissan, H. (1905) C.R. Acad. Sci. Paris, 140, 405.

Raw Materials for Ceramics, Refractories and Glasses

making bulk abrasive materials until the mid-1950s. The simplicity of the process makes it useful for production of huge quantities of silicon carbide suitable for grinding and cutting purposes. Some of the material produced by the Acheson process may, however, have adequate quality for electronic device production. A mixture of 50 wt.% silica, 40 wt. coke, 7 wt.% sawdust, and 3 wt.% rocksalt is heated in an electric resisting furnace. The heating is accomplished by a core made of graphite and coke called a resistor placed centrally in the furnace. The mixture of reactants is placed around this core. The mixture is then heated to reach a maximum temperature of ca. 2700°C, after which the temperature is gradually lowered. After the furnace has been fired, the outermost volume, which did not reach such high temperatures, consists of an unreacted mixture. Inside this is a volume where the temperature has not reached 1800°C. In this volume the mixture has reacted to form amorphous SiC. Close to the resistor, where the highest temperatures are obtained, SiC will be produced at first. As the temperature increases in the furnace, this will decompose again into graphite and silicon. The graphite will remain at the core; however, silicon reacts again with carbon to form SiC in colder parts of the furnace. The outer layer of graphite contains SiC in the form of threads of crystallites radiating from the core. The size of the crystallites decreases with increasing distance from the core. The purpose of the sawdust is to make the mixture porous in such a way that the huge amounts of carbon monoxide produced in the reaction may escape. High pressures of gas may locally be built up to form voids and channels to more porous parts of the mixture to eventually find its way out. The common salt serves as a purifier of the mixture. The chlorine reacts with metal impurities to form volatile metal chlorides (e.g., FeCl3, MgCl2), which escape. As a consequence of the furnace geometry, the material formed in the Acheson furnace varies in purity, according to its distance from the graphite resistor that is the heat source. The color changes to blue and black at a greater distance from the resistor, and these darker crystals are less pure and usually doped with aluminum, which increases electrical conductivity. A higher grade of silicon carbide for electronic application can be obtained from a more expensive process described below. Lely process. A major improvement to the Acheson process is the process developed by 25 J.A. Lely, a scientist at Philips Research Laboratories in Eindhoven, in 1955. The process is similar to that observed in the voids and channels of the Acheson process. Lumps of SiC are packed between two concentric graphite tubes. The inner tube is thereafter withdrawn, leaving a cylinder of SiC lumps inside the outer graphite tube called the crucible. The crucible is closed with a graphite or SiC lid and placed inside a furnace. The crucible is heated to ca. 2500°C in an inert atmosphere of argon at atmospheric pressure. At this temperature SiC sublimes appreciably, leaving a graphite layer at the outermost part of the cylinder, and small platelets start to evolve from the innermost parts of the SiC cylinder. These platelets successively grow to larger sizes during a prolonged heating at this temperature. Each platelet is attached on one edge to an original lump of SiC. On the top and bottom of the cylinder a thick dense layer of SiC is formed. The quality of these crystals can be very high; however, the yield of the process is low, the sizes are irregular, the shape of the crystals is normally hexagonal, and there exists no polytype control. The purity of the crystals is largely governed by the starting material, which may be obtained in a high-purity form. The use of highquality Lely grown material as substrate for a succeeding epitaxial growth is highly advantageous with regard to the high crystalline quality obtained from these substrates. The modified Lely process. Despite the high crystalline quality that may be obtained with the Lely method, it has never been considered an important technique for future commercial exploitation on account of the low yield and irregular sizes. In the modified Lely process, which is a seeded sublimation growth process, these problems are overcome, though at the price of a considerably lower crystalline quality. In the modified Lely technique, SiC powder or lumps of SiC are placed inside a cylindrical graphite crucible. The crucible is closed with 25

Lely, J.A. (1955) Berichte der Deutschen Keramischen Gesellschaft, 32, 229.

627

10 Ceramics, Refractories, and Glasses

628

Ceramics, Refractories, and Glasses

a graphite lid onto which a seed crystal is attached. The crucible is heated to ca. 2200°C normally in an inert argon atmosphere at a reduced pressure. A temperature gradient is applied over the length of the crucible in such a way that the SiC powder at the bottom of the crucible is at a higher temperature than the seed crystal. The temperature gradient is typically kept in a range on the order of 20 to 40°C/cm. The SiC powder sublimes at the high temperature and the volume inside the crucible is filled with a vapor of progressive composition (e.g., Si2C, SiC2, Si2, and Si). Since the temperature gradient is chosen such that the coldest part of the crucible is the position of the seed, the vapor will condense on this and the crystal will grow. The growth rate is largely governed by the temperature, the pressure, and the temperature gradient; however, experiments have shown that also the source-to-seed distance may have some influence. It has also been experimentally confirmed that different growth temperatures and the orientation of the seed crystal give rise to different polytypes.

10.2.10.3 Grades of Silicon Carbide Several commercial grades of SiC are available on the market: (i)

Electrically conductive sintered alpha silicon carbide. This is a dense type of SiC and has superior resistance to oxidation, corrosion, wear, and chemical attacks. The singlephase SiC also has high strength and good thermal conductivity. (ii) Black silicon carbide (98.5 wt.% SiC) is composed of premium-grade, medium-highdensity, high-intensity magnetically treated SiC in which most impurities have been removed from the carbide. (iii) CVD silicon carbide (99.9995 wt.% SiC) is a unique type of silicon carbide due to its purity, homogeneity, and chemical and oxidation resistance. It is thermally stable, is very cleanable and polishable, and is dimensionally stable. (iv) Green silicon carbide (99.5 wt.% SiC) is an extremely hard synthetic material that possesses very high thermal conductivity. It is also able to maintain its strength at elevated temperatures. General applications of green SiC are in aerospace, blasting, coatings, composites, refractories, compounds, and kiln furniture, and it is used as an abrasive as honing stones, lapping, polishing, sawing silicon and quartz, and in grinding wheels. Prices (2006). Silicon carbide is priced from 1150 to 1700 US$/tonne.

10.2.11 Properties of Raw Materials Used in Ceramics, Refractories, and Glasses Table 10.11. Selected properties and prices of raw materials used in ceramics and refractories 26

Raw material

Apparent density Bulk density Bond’s work index –3 –3 –1 (kg.m ) (kg.m ) (kWh/tonne )

Alumina (fused)

3480

961

58.18

0.6447

1250–1700

Bauxite (chunk)

2380

1200–1360

9.45

0.1200

125–200

Chrome ore

4060

9.60

0.1200

150–250

26

27

Abrasion Average price (2006) 27 index (US$/tonne)

The Bond’s index is the energy per unit mass of material required to grind it from until 80 wt.% pass 325 mesh, here it is expressed in KWh per short ton (2000 lb.). The abrasion index is defined as the mass fraction lost by a steel padle beating during 1 hour a charge of 1.6 kg of the material having pellets dimension 3/4 in x 1/2 in with 80 wt.% of the final final product passing 13.25 mm.

Traditional Ceramics

629

Table 10.11. (continued) Raw material

Apparent density Bulk density Bond’s work index –3 –3 –1 (kg.m ) (kg.m ) (kWh.tonne )

Abrasion Average price (2006) index (US$/tonne)

Coke

1510

400–720

20.70

0.3095

Dolomite (lump)

2820

1440–1600

11.31

0.016

Feldspar (ground) 2590

1050–1121

11.67

n.a.

Graphite

1750

450–640

45.03

420–1000

Hematite

5260

3600

12.68

30–50

Ilmenite

4270

2240

13.11

80–100

Kaolin

2600

2600

7.10

Lime

3340

960–1080

Limestone

2690

1340–1440

Magnesite Silicon carbide

60–100

11.61

0.0256

30–40

2980

16.80

0.075

130–180

2730

26.17

Quartzite (chunk) 2650

12.77

Zircon (flour)

1200–1700 0.6905

4600

n.a. 700–800

10.3 Traditional Ceramics Traditional ceramics are those obtained only from the firing of clay-based materials. The common initial composition before firing consists usually of a clay mineral (i.e., phyllosilicate minerals such as kaolinite, montmorillonite, or illite), fluxing agents or fluxes [e.g., feldspars: K-feldspars (orthoclases) and Ca-Na-feldspars (plagioclases)], and filler materials (e.g., silica, alumina, magnesia). The traditional ceramics can be prepared using two main groups of clays: kaolin or china clays made from the phyllosilicate kaolinite and, to a lesser extent, micas, but free of quartz; and ball clays containing a mixture of kaolinite, montmorillonite, illite, and micas. Table 10.12. Examples of traditional ceramics Type

Properties

Applications

Fired bricks Porosity: 15–30% Firing temperature: 950–1050°C Enameled or not

Bricks, pipes, ducts, walls, ground floors

China

Porosity: 10–15% Firing temperature: 950–1200°C Enamel, opacity

Sanitation, tile

Stoneware

Porosity: 0.5–3% Crucible, labware, Firing temperature: 1100–1300°C pipe Glassy surface

Porcelain

Porosity: 0–2% Insulators, labware, Firing temperature: 1100–1400°C cookware Glassy, translucent

10 Ceramics, Refractories, and Glasses

630

Ceramics, Refractories, and Glasses

The classical procedure for preparing traditional ceramics consists of the following operation sequence: raw material selection and preparation (i.e., grinding, mixing), forming (e.g., molding, extrusion, slip casting, and die pressing), drying, prefiring operations (i.e., glazing), firing, and postfiring operation (e.g., enameling, cleaning, and machining). The common classes of traditional ceramics are whitewares (e.g., stoneware, china, and porcelain), glazes, porcelain enamels, high-temperature refractories, mortars, cements, and concretes (see Chapter 15).

10.4 Refractories Refractories perform four basic functions: (i)

they act as a thermal barrier between a hot medium (e.g., flue gases, liquid metal, molten slags, and molten salts) and the wall of the containing vessel; (ii) they insure a strong physical protection, preventing the erosion of walls by the circulating hot medium; (iii) they represent a chemical protective barrier against corrosion; (iv) they act as thermal insulation, insuring heat retention. As a rule of thumb, an insulating material is considered a refractory material if its melting or solidus temperature is well above the melting point of pure iron (1539°C), i.e., if it exhibits a Seger’s pyrometric cone equivalent of No. 26 or more (Table 10.19). Moreover, the maximum operating temperature of a refractory material is usually 150°C lower than its pyrometric cone equivalent.

10.4.1 Classification of Refractories The classification of refractories can be approached in a number of different ways: chemical composition, type of applications, or operating temperature range. Table 10.13. Classification of refractory by end user Rank Refractory industry users

End user

1

Cement and lime production

Building industry

2

Iron and steelmaking

3

Glass industry

4

Nonferrous metals production

5

Oil and gas industries

6

Waste incineration

7

Basic industries

Automotive industry

Other

Refractories

631

Table 10.14. Classification of primary refractories by chemistry Category (definition)

Description

Basic refractories Dolomite (i.e., essentially made of calcined Dead burned magnesia (min. 95 wt.% MgO) magnesite or magnesia, MgO) Dead burned magnesia with chromite Fused magnesia Magnesia-carbon bricks High alumina (i.e., with an alumina content greater than 47.5 wt.% Al2O3)

50%, 60%, 70%, 80% Al2O3 (±2.5), 85%, 90% Al2O3 (±2.0), 99% Al2O3 (>97%), Mullite (3Al2O3.2SiO2) Chemically bonded bricks (75–85 wt.% Al2O3) Alumina-chrome bricks Alumina-carbon bricks

Fireclay (i.e., made of fired aluminum phyllosilicates or clays)

Super-duty (40–44 wt.% Al2O3) High-duty Medium-duty Low-duty Semisilica (18–25 wt.% Al2O3, 72–80 wt.% SiO2)

Silica

Silica bricks

Advanced

Graphite and carbon ceramics Silicon carbide Zircon (ZrSiO4) and fused zirconia (ZrO2) Fused silica Fused alumina (brown and white) Fused and cast refractories

10.4.2 Properties of Refractories Table 10.15. (continued) Selected physical properties of refractories

1842

1650–2030 4.67

Brick, fireclay

2000

1.0042

753

Brick, hard-fired silica (94–95 wt.% silica)

1800

1.6736

753.10

Brick, high alumina (53 wt.% alumina) (20% porosity)

2330

1.3807

753

Brick, high alumina (83 wt.% alumina) (28% porosity)

2570

1.5062

753

Brick, high alumina (87 wt.% alumina) (22% porosity)

2850

2.9288

753

Brick, kaolin insulating (heavy)

430

0.2510

774

Brick, kaolin insulating (light)

300

0.0837

774

Brick, magnesite (86 wt.% MgO) (17.8% porosity)

2920

3.6819

837

Brick, magnesite (87 wt.% MgO)

2530

3.8493

837

Specific heat capacity –1 –1 (cP/J.kg .K )

Melting point (°C)

Alumina brick (64–65 wt.% Al2O3)

Thermal conductivity –1 –1 (k/W.m .K )

Density –3 (ρ/kg.m )

Refractory materials

10 Ceramics, Refractories, and Glasses

Ceramics, Refractories, and Glasses

Thermal conductivity –1 –1 (k/W.m .K )

Specific heat capacity –1 –1 (cP/J.kg .K )

Refractory materials

Melting point (°C)

Table 10.15. (continued)

Brick, magnesite (89 wt.% MgO)

2670

3.4727

837

Brick, magnesite (90 wt.% MgO) (14.5% porosity)

3080

4.9371

837

Brick, magnesite (93 wt.% MgO) (22.6% porosity)

2760

4.8116

837

Brick, normal fireclay (22% porosity)

1980

1.2970

732

Brick, siliceous (25% porosity)

1930

0.9372

753

Brick, siliceous fireclay (23% porosity)

2000

1.0878

753

Brick, sillimanite (22% porosity)

2310

1.4644

711

Brick, stabilized dolomite (22% porosity)

2700

1.6736

837

Brick, vermiculite

485

0.1674

837

Calcium oxide (pressed)

3030

13.8070

753

Calcium oxide(packed powder)

1700

0.3180

753

Carbon brick (99 wt.% graphite)

1682

Carbon brick (fired)

1470

3.5982

Chrome brick (100 wt.% Cr2O3)

2900–3100 1900

2.3

Chrome brick (32 wt.% Cr2O3)

3200

1.1715

627.60

Chrome-magnesite brick

3000

2.0920

753.10

Chrome-magnesite brick (52 wt.% MgO, 23 wt.% Cr2O3)

3100

Diabasic glass (artificial)

2400

1.1715

753

Diatomaceous earth brick

440

0.0877

795.00

Diatomaceous earth brick (850°C)

440

0.0921

795.00

Diatomaceous earth brick (fused at 1100°C)

600

0.2218

795.00

Diatomaceous earth brick (high burn)

590

0.2259

795.00

Diatomaceous earth brick (molded)

610

0.2427

795.00

Dolomite (fired) (55 wt.% CaO, 37 wt.% MgO)

2700

Dolomite brick, stabilized (22 wt.% silica)

2700

1.6736

837

Egyptian fire (64–71 wt.% silica)

950

0.3138

732.20

Egyptian firebrick (64–71 wt.% silica)

950

0.3138

732

Fireclay brick (54 wt.% SiO2, 40 wt.% Al2O3)

2146–2243 1740

0.3–1.6

Fireclay brick, Missouri

2645

1.0042

960

Fireclay brick, normal (22 wt.% water)

1980

1.2970

732

Fireclay brick, siliceous (23 wt.% water)

2000

1.0878

753

Forsterite brick (58 wt.%MgO, 38 wt.%SiO2) (20% porosity)

2760

1.0042

795.00

Fused-alumina brick (96 wt.% alumina) (22% porosity)

2900

3.0962

753.10

Fused-alumina brick (96 wt.% alumina) (22% porosity)

2900

3.0962

753.10

High-alumina brick (90–99 wt.% Al2O3)

2810–2970 1760–2030 3.12

Kaolin brick, insulating (dense)

430

Density –3 (ρ/kg.m )

632

3500

3045

3.6 707

3.5

2000

0.2511

774

Refractories

633

Specific heat capacity –1 –1 (cP/J.kg .K )

Kaolin brick, insulating (light)

300

0.0837

774

Magnesite brick (95.5 wt.% MgO)

2531–2900 2150

3.7–4.4

Mullite brick (71 wt.% Al2O3)

2450

1810

7.1

Silica brick (95–99 wt.% SiO2)

1842

1765

1.5

Silicon carbide brick (80–90 wt.% SiC)

,595

2305

20.5

Vermiculite brick

485

0.1674

837

Vermiculite insulating powder

270

0.1213

837

Vermiculite, expanded (heavy)

300

0.0690

753

Vermiculite, expanded (light)

220

0.0711

753

Zircon brick (99 wt.% ZrSiO4)

3204

1700

2.6

Zirconia (stabilized) brick

3925

2650

2.0

Density –3 (ρ/kg.m )

Thermal conductivity –1 –1 (k/W.m .K )

Refractory materials

Melting point (°C)

Table 10.15. (continued)

Silica brick. The earliest silica bricks were composed of crushed minerals of 90 wt.% silica, with as much as 3.5 wt.% flux materials (i.e., usually CaO), and fired at about 1010°C. These bricks found use primarily in steel mills and coke-byproduct operations, from the second quarter of this century in chemical service, primarily in strong phosphoric acid exposures where shale and fireclay brick do not long survive. They can serve in highertemperature service to about 1093°C and are more resistant to thermal shock due to their greater porosity, as high as 16%. When used in chemical service, those of the highest silica content (not below 98 wt.% SiO2) should be used. The purity of the silica and its percentage of alkali, along with the manufacturing techniques, determine the uniformity or the wideness of ranges of the physical properties. Ranges of chemical composition of silica brick are 98.6 to 99.6 wt.% SiO2, 0.2 to 0.5 wt.% Al2O3, 0.02 to 0.3 wt.% Fe2O3, 0.02 to 0.1 wt.% MgO, 0.02 to 0.03 wt.%CaO, and 0.01 to 0.2 wt.% (Na2O, K2O, Li2O). Silica brick serves well and for long periods in acid service, except for hydrofluoric, without noticeable damage, showing greater resistance, especially to strong hot mineral acids, and particularly phosphoric rather than acid brick, and in halogen exposures, except fluorine, solvents, and organic chemical exposures. Silica bricks are not recommended for service in strong alkali environments. They also exhibit better shock resistance than shale or fireclay acid brick, but they have lower strength and abrasion resistance. Porcelain brick. Porcelain bricks are made from high-fired clays, the temperature of firing depending on the amount of alumina in the clay, 15% to 38% usually at ca. 1200 to 1300°C, 85% at 1500 to 1550°C, and 95 to 98% at 1600 to 1700°C. The bodies of these bricks are extremely dense and nonporous, with zero absorption, and a Mohs hardness ranging from 6 to 9 for 99 wt.% alumina. As alumina content increases, Mohs hardness, the maximum service temperature, and chemical resistance increase. Major uses of porcelain include: the lining of ball mills, where they will outlast almost all other abrasion-resistant linings, and employment (glazed) as pole line hardware for the power industry where, exposed to abrasion, weathering, and cycling temperature changes, they outlast all other materials in similar service. All chemists and laboratory personnel are familiar with glass and porcelain equipment, and so are aware of the fact that they give excellent service in hot chemicals except

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hydrofluoric acid and acid fluorides and strong sodium or potassium hydroxides, especially in the molten state. Due to the high cost of porcelain brick, they are used sparingly in the process industries, chiefly in dye manufacture, due to their density for the prevention of interbatch contamination and ease of cleaning. The use of porcelain brick is primarily limited by its cost.

10.4.3 Major Refractory Manufacturers Table 10.16. Major manufacturers of refractories worldwide Company (Brands)

Location and Address

Refractory applications

Minerals Technologies (MinteQ)

Chrysler Building, 405 Lexington Ave., New York, NY 10174-1901, USA Telephone: +1 (732) 257-1227 E-mail: [email protected] URL: http://www.minteq.com/

Monolithic refractories and castables

Resco Products (Resco and National)

2 Penn Center, West Suite 430, Pittsburgh, PA 15276, USA Telephone: (412) 494-4491 Fax: (412) 494-4571 URL: http://www.rescoproducts.com/

Iron- and steelmaking Nonferrous smelting (Cu, Al) Fireclays and bricks Glassmaking processes Waste incinerators Hydrocarbon processing Power generation

RHI AG Wienerbergstrasse 11 (Didier, Radex, A-1100 Vienna, Austria and Veitscher) Telephone: +43 (0) 50 213-0 Fax: +43 (0) 50 213-6213 E-mail: [email protected] URL: http://www.rhi.at/

Iron- and steelmaking Cement and lime kilns Glassmaking processes Nonferrous smelting (Cu, Al, Ni, Sn, Zn) Petrochemical and hydrocarbon processes Oil refineries

SANAC Spa

Viale Certosa, 249, I-20151 Milano, Italy Telephone: (+39) 02307 00335 Fax: (+39) 02380 11158 URL: http://www.sanac.com/

Iron and steelmaking Glassmaking processes Castables Resin-bonded alumina

Shinagawa Refractories

1-7,Kudan-kita 4-chome,Chiyodaku, Tokyo 102-0073 Japan Telephone: +81 3-5215-9700 Fax: +81 3-5215-9720 URL: http://www.shinagawa.co.jp/

Iron- and steelmaking Nonferrous metals (Cu, Zn, Pb,and Al) Cement and lime kilns Refractories for gas, petroleum, and chemical plants Refractories for cement and lime kilns Glassmaking processes and ceramic firing kilns Petrochemical and hydrocarbon processes Oil refineries Waste incinerators

Vesuvius USA Corp.

P.O. Box 4014, Newton Drive 1404 Champaign, IL 61822 USA Telephone: +1 (217) 351-5000 Fax: +1 (217) 351-5031 URL: http://www.vesuvius.com/

Iron and steelmaking Foundry Aluminum smelters Glassmaking processes

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10.5 Advanced Ceramics Advanced ceramics or engineered ceramics, also formerly called industrial ceramics, are various inorganic chemical compounds, not necessarily oxides and silicates, that exhibit improved physical and chemical properties and can be grouped according to their field of application: electrical (e.g., semiconductors, insulators, dielectrics, piezo- and pyroelectrics, and superconductors), optical (e.g., phosphors, lasing crystals, mirrors, and reflectors), magnetics (e.g., permanent magnets), and structural ceramics. The properties of these ceramic materials are extensively described in the section in the book relative to their properties (e.g., insulators in dielectrics materials and superconducting ceramics in the superconductor section). Hereafter, dedicated sections on selected advanced ceramic materials are presented, providing a brief description, the general physical and chemical properties, along with method of preparation, industrial applications, and major producers.

10.5.1 Silicon Nitride 10.5.1.1 Description and General Properties Silicon nitride [12033-89-5], chemical formula Si3N4 and relative molecular mass of 140.284, is –3 a medium-density ceramic material (3290 kg.m ). The high flexural strength (830 MPa), –1/2 high fracture toughness (6.1 MPa.m ), and creep resistance, even at elevated temperatures, ensure a high temperature strength to silicon nitride. Moreover, its low thermal expansion coefficient (3.3 μm/m.K), combined with a Young’s modulus of 310 GPa, confers upon silicon nitride a superior thermal shock resistance compared with most ceramic materials. This set of extreme properties, together with a good oxidation resistance, were the major reasons of its first development in the late 1960s for replacing superalloys in advanced turbine and reciprocating engines to give higher operating temperatures and efficiencies. Although the ultimate goal of ceramic engines has never been achieved, silicon nitride has been used extensively in a number of other industrial applications, such as engine components, bearings, and cutting tools. In general, silicon nitride exhibits higher temperature capabilities than most metals, combining high mechanical strength and creep resistance with oxidation resistance. From a chemical point of view, silicon nitride exhibits an excellent corrosion resistance to numerous molten nonferrous metals such as Al, Pb, Zn, Cd, Bi, Rb, and Sn and molten salts like NaCl-KCl, NaF, and silicate glasses. However, it is corroded by molten Mg, Ti, V, Cr, Fe, and Co, and salts like cryolite, KOH, and Na2O.

10.5.1.2 Industrial Preparation and Grades Pure silicon nitride is difficult to produce as a fully dense material because it does not readily sinter and cannot be heated above 1850°C because it decomposes into silicon and nitrogen. Dense silicon nitride can only be made using sintering aids or by the direct nitriding of silicon. Therefore, the final material properties strongly depend on the fabrication method, and hence commercial silicon nitride cannot be considered a single material. Three grades of silicon nitride are available commercially: (i)

Reaction bonded silicon nitride (RBSN) is a high-purity grade of silicon nitride prepared by direct nitriding of compacted silicon powder. The incomplete nitriding reaction leads to densities of only 70 to 80% of the theoretical density and usually ranges from 2300 to –3 2700 kg.m . It exhibits excellent thermal shock resistance and an outstanding corrosion resistance to molten nonferrous metals, especially aluminum metal. Reaction-bonded silicon nitride represents a cheaper alternative to the fully dense silicon nitride and can be machined to close tolerance (near-net shape) without the need for expensive diamond grinding.

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(ii)

Hot-pressed silicon nitride (HPSN) is obtained by applying both heat and pressure through a graphite die using sintering aids. However, most hot-pressed silicon nitride grades can be formulated with a minimum amount of densification aids. These compositions offer the highest mechanical strength of other silicon nitride grades. The major drawbacks are that only simple shaped billets can be produced by this process and the preparation of finished components requires expensive machining by utilizing diamond grinding. (iii) Sintered silicon nitride (SSN) consists of a family of fully dense materials having a range of compositions that can be produced in cost-effective, complex net shape. The green compacts, made of powders with a high surface area, are fired under a nitrogen atmosphere, without applying pressure. This grade of silicon nitride has the best combination of properties, making it the leading technical ceramic for a number of structural applications including automotive engine parts, bearings, and ceramic armor. (iv) Hot isostatically pressed silicon nitride (HIPSN) is obtained by glass-encapsulated parts that are placed in a high-pressure vessel or autoclave, with heat and pressure applied. The result is a slight decrease in strength but a substantial improvement in reliability. The material is used currently in niche market applications, for example, in reciprocating engine components and turbochargers, bearings, metal cutting and shaping tools, and hot metal handling.

10.5.2 Silicon Aluminum Oxynitride (SiAlON) Description and general properties. Sialon is the commercial acronym for silicon aluminum oxynitride (SiAlON), that is, an alloy of silicon nitride (Si3N4) and aluminum oxide (Al2O3). Sialon is in fact a fine-grained nonporous advanced ceramic material with less than 1 vol.% open porosities. Sialon is made of a silicon nitride ceramic with a small percentage of aluminum oxide. Its generally adopted chemical formula is Si6-xAlxOxN8-x. This superior refractory material has the combined properties of silicon nitride, i.e., high-temperature strength, hardness, fracture toughness, and low thermal expansion, and that of aluminum oxide, i.e., corrosion resistance, chemical inertness, high temperature capabilities, and oxi–3 dation resistance. Sialon exhibits a medium density of 3400 kg.m , a low Young’s modulus of 288 MPa, a bulk modulus of 220 GPa, and a shear modulus of 120 GPa with a Poisson ratio of 0.25. Moreover, it has a flexural strength of 760 MPa, an elevated Vickers hardness –1/2 (1430 to 1850 HV), and a good fracture toughness (6.0 to 7.5 MPa.m ). In addition, like pure silicon nitride, the combination of a low Young’s modulus of 288 GPa with a low coefficient of linear thermal expansion (3 μm/m.K) ensures an excellent thermal shock resis–1 –1 tance together with a low thermal conductivity of 15 to 20 W.m K . Most refractory products are capable of surviving one or two specific environments that typically involve high temperature, mechanical abuse, corrosion, wear, or electrical resistance. Sialon is perfect for molten-metal applications and high wear or high impact environments up to 1250°C. Moreover, sialon exhibits a good oxidation resistance in air up to 1500°C imparted by its alumina content, and it has an outstanding corrosion resistance to molten nonferrous metals. Moreover, it is neither wetted nor corroded by molten aluminum, brass, bronze, and other common industrial metals. Industrial applications. Typical uses are as protection sheath for immersion thermocouples used in nonferrous metal melting, immersion heater and burner tubes, degassing and injector tubes in nonferrous metallurgy, metal feed tubes in aluminum die casting, welding, and brazing fixtures and pins.

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10.5.3 Boron Carbide 10.5.3.1 Description and General Properties Boron carbide [12069-32-8], with its chemical formula B4C and its rhombohedral crystal lattice, –3 is a low-density black solid (2512 kg.m ) with a metallic luster. Its high refractoriness due to its high melting point (2450°C) allows it to be used for high-temperature applications. On the other hand, it is the hardest manmade solid (HK 3200) after synthetic diamond. Actually under high temperatures above 1300°C, its hardness exceeds that of diamond and cubic boron nitride. A Poisson ratio of 0.21 indicates its high anisotropy. It has a high compressive strength that may vary according to its density and percentage purity. It has a very low thermal conductivity (27 W/m.K). With such a strength-to-density ratio and low thermal conductivity, boron carbide looks promising and ideal for a wide variety of applications. Because of its high hardness, boron carbide succeeded in replacing diamond as a lapping material. Boron carbide is a material with excellent properties. It has a list of important properties such as ultimate strengthto-weight (density) ratio, exceptionally high hardness, and high melting and oxidation temperatures (500°C). In addition, it has a very low thermal expansion coefficient (5.73 μm/mK). However, owing to its high Young’s modulus, it possesses less thermal shock resistance. Boron carbide is stable toward dilute and concentrated acids and alkalis and inert to most organic compounds. It is slowly attacked by mixtures of hydrofluoric-sulfuric acids or hydrofluoric-nitric acids. It resists attack by water vapor at 200 to 300°C. However, it is attacked rapidly when put in contact with molten alkali and acidic salts to form borates. In addition, B4C is characterized by a very high oxidation temperature.

10.5.3.2 Industrial Preparation Boron carbide is either prepared from boron ores or from pure boron. The process involves the reduction of a boron compound. Usually, boron carbide is obtained by reacting boric acid or boron oxide and carbon at ca. 2500°C in an electric-arc furnace. 2B2O3(s) + 7C(s) —> B4C(s) + 6CO(g) Its composition is variable over a relatively wide range. The boron/carbon ratio ranges from 3.8 to 10.4. Technical-grade boron carbide values are typically between 3.9 and 4.3. Later, the powder obtained is transformed into dense parts by hot pressing or cold forming and sintering. The cold formed and sintered material is less expensive, but sintering aids or other added bonding agents seriously degrade the material properties.

10.5.3.3 Industrial Applications and Uses The applications of boron carbide are as wear-resistant components. Armor tiles in military applications such as in light hard bulletproof armor for helicopters and tanks or as thermal shield for the space shuttles. It is used in abrasives as lapping and polishing powders and in raw materials in preparing other boron compounds, notably titanium diboride. It is also us as an insert for spray nozzles and bearing liners and wire drawing guides. Finally, because of its boron content and elevated resistance to high temperatures, boron carbide is used as a shield for neutrons in nuclear reactors.

10.5.4 Boron Nitride 10.5.4.1 Description and General Properties Boron nitride [10043-11-5], chemical formula BN, exists as three different poly-morphs: –3 alpha-boron nitride (α-BN), a soft and ductile polymorph (ρ = 2280 kg.m and m.p. = 2700°C)

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with a hexagonal crystal lattice similar to that of graphite, also called hexagonal boron nitride (HBN) or white graphite; beta-boron nitride (β-BN), the hardest manmade material and dens–3 est polymorph (ρ = 3480 kg.m , m.p. = 3027°C), with a cubic crystal lattice similar to that of diamond, also called cubic boron nitride (CBN) or borazon; and (iii) pyrolitic boron nitride (PBN). From a chemical point of view, boron nitride oxidizes readily in air at temperatures above 1100°C, forming a thing protective layer of boric acid (H3BO3) on its surface that prevents further oxidation as long as it coats the material. Boron nitride is stable in reducing atmospheres up to 1500°C.

10.5.4.2 Industrial Preparation Cubic BN, or borazon, is produced by subjecting hexagonal BN to extreme pressure and heat in a process similar to that used to produce synthetic diamonds. Melting of either phase is possible only with a high nitrogen overpressure. The alpha-phase decomposes above 2700°C at atmospheric pressure and at ca. 1980°C in a vacuum. Hexagonal BN is manufactured using hot pressing or pyrolytic deposition techniques. These processes cause orientation of the hexagonal crystals, resulting in varying degrees of anisotropy. There is one pyrolytic technique that forms a random crystal orientation and an isotropic body; however, the density reaches only 50 to 60% of the theoretical density. Both manufacturing processes yield high purity, usually greater than 99 wt.% BN. The major impurity in the hot-pressed materials is boric oxide, which tends to hydrolyze in the presence of water, degrading the dielectric and thermal-shock properties of the material. The addition of calcia reduces the water absorption. Hexagonal hot-pressed BN is available in a variety of sizes and shapes, while the pyrolytic hexagonal material is currently available in thin layers only.

10.5.4.3 Industrial Applications and Uses The major industrial applications of hexagonal boron nitride rely on its high thermal conductivity, excellent dielectric properties, self-lubrication, chemical inertness, nontoxicity, and ease of machining. These are, for instance, mold wash for releasing molds, high-temperature lubricants, insulating filler material in composite materials, as an additive in silicone oils and synthetic resins, as filler for tubular heaters, and in neutron absorbers. On the other hand, the industrial applications of cubic boron nitride rely on its high hardness and are mainly as abrasives.

10.5.5 Titanium Diboride 10.5.5.1 Description and General Properties –3

Titanium diboride [12045-63-5], chemical formula TiB2, is a dense (4520 kg.m ) and highmelting-point (2980°C) advanced ceramic material. Due to its high elastic modulus of 510 to 575 GPa, titanium diboride exhibits an excellent stiffness-to-density ratio. It is also a hard material with a Vickers hardness (3370) superior to that of tungsten carbide, and its fracture 1/2 toughness (5 to 7 MPa.m ) is even greater than that of silicon nitride. The high flexural strength (350 to 575 MPa), combined with a high compressive strength (670 MPa), allows it to be used in military and ballistic applications. As expected from its hexagonal crystal lattice, it is highly anisotropic with a Poisson ratio of 0.18 to 0.20. It retains its mechanical strength up to very high temperatures. By contrast with most ceramics, it is a good electrical conductor, with an electrical resistivity of only 15 μΩ.cm, and has a good thermal conductiv–1 –1 ity (65 W m K ); its linear coefficient of thermal expansion is 6.4 μm/m K. From a chemical point of view, TiB2 is not attacked either by concentrated strong mineral acids such as hydrochloric acid or hydroflouric acids. Titanium diboride also has a very good oxidation

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resistance up to 1400°C. TiB2 has excellent wettability and stability in liquid metals such as aluminum and zinc and has many applications as a corrosion-resistant material such as crucibles and cutting tools in addition to some military applications.

10.5.5.2 Industrial Preparation and Processing The most common process for producing large quantities of titanium diboride is by reacting titania (TiO2) with carbon and boron carbide (B4C) or boron sesquioxide (B2O3) as follows: 2TiO2(s) + C(s) + B4C(s) —> 2TiB2(s) + 2CO2(g), 2TiO2(s) + 5C(s)+ 5B2O3(s) —> 2TiB2(s) + 5CO2(g). The final purity of the powder depends on the purity of the raw materials. Generally, several different grades of TiO2, carbon, B4C, and B2O3 can be used for the production of a wide panel of TiB2 products, depending on the required grain size, purity, and price. Vacuum-arc melting is used to produce a fully dense, single-phase titanium diboride. Graphite hearths are commonly used; the molten titanium diboride wets the graphite and exhibits excellent fluidity, and shapes are produced both by gravity and tilt-pour-casting methods. Sintered parts of titanium diboride are usually produced by either hot pressing or pressureless sintering, although hot isostatic pressing HIP has also been used. Quite a number of different sintering methods and sintering aids are used to produce fully dense parts of titanium diboride. Hot pressing of titanium diboride is performed at temperatures above 1800°C in a vacuum or 1900°C in an inert argon atmosphere. However, hot pressing is expensive and the net-shape fabrication is not possible, hence the required shape must still be machined from the hotpressed billet. Some usual sintering aids used for hot-pressed parts include iron, nickel, cobalt, carbon, tungsten, and tungsten carbide. Pressureless sintering of titanium diboride is a cheaper method for the production of net-shaped parts. Due to the high melting point of titanium diboride, sintering temperatures in excess of 2000°C are often required to promote sintering. Another method, called high-temperature synthesis (HTS), uses a powdered reducing metal such as magnesium or aluminum, and powders of titanium oxide and boron oxide. The materials are mixed and placed in a high-temperature crucible. This mixture is then ignited, and the self-sustaining reaction produces titanium diboride particles dispersed within a matrix of alumina or magnesia. After leaching the reaction mass, it remains as micrometric titanium diboride particles. The major producers of titanium diboride are Advanced Refractory Technologies, Advanced Ceramics Corp., and Cerac in the United States, H.C. Starck and Electroschmeltzwerk Kempten in Germany, Denka in Japan, and Borides Ceramics and Composites in the UK.

10.5.5.3 Industrial Applications and Uses Titanium diboride was originally developed to make lightweight armor for US and Soviet army tanks. It also has many commercial applications such as nozzles, seals, cutting tools, dies, wear parts due to its corrosion resistance, and also molten-metal crucibles and electrodes. It is used in crucibles due to its high melting point and chemical inertness.

10.5.6 Tungsten Carbides and Hardmetal 10.5.6.1 Description and General Properties Tungsten carbide, or hardmetal, was developed in the 1920s for wear-resistant dies to draw incandescent-lamp filament wire. Earlier efforts to manufacture the WC-W2C eutectic alloy was unsuccessful because of its inherent brittleness; therefore researchers diverted their attention to powder metallurgy techniques. At present, these powder metallurgy techniques are

10 Ceramics, Refractories, and Glasses

Ceramics, Refractories, and Glasses

Electrical resistivity (μΩ.cm)

15,700 707

296–490

2937

1800–2000

97WC–3Co

15,150 655

979–1175

5778

1600–1700

87.9

95.5WC–4.5Co

15,050 627

1172–1372

5681

1550–1650

83.7

3.4

94.5WC–5.5Co

14,800 607

1565–1765

4895

1500–1600

79.5

3.6

20

91WC–9Co

14,600 579

1469–1862

4702

1400–1500

75.3

89WC–11Co

14,150 565

1565–1958

4502

1300–1400

66.9

3.8

18

87WC–13Co

14,080 545

1662–2,55

4406

1250–1350

58.6

85WC–15Co

13,800 538

1765–2151

3820

1150–1250

6.0

80WC–20Co

13,300 490

1958–2544

3330

1050–1150

4.7

75WC–25Co

13,000 459

1765–2648

3130

900–1000

5.0

70WC–30Co

12,500

Thermal conductivity –1 –1 (k/Wm K )

Vickers hardness –2 (HV/kgf.mm )

100WC

Young’s modulus (E/GPa)

Compressive strength (MPa)

53

Transverse rupture strength (MPa)

5.7–7.2

Density –3 (ρ/kg.m )

Coefficient of linear thermal expansion –6 –1 (10 K )

Table 10.17. Properties of selected hardmetals

Hardmetal (wt.%)

640

850–950

being further developed and refined to reduce manufacturing costs and improve performance. Tungsten carbide is in fact a composite material called cermet or hardmetal made of tungsten carbides in a metal matrix of cobalt. Tungsten carbide is harder than most steels, has greater mechanical strength, transfers heat quickly, and resists wear and abrasion better than other metals. Among the materials that resist severe wear, corrosion, impact, and abrasion, tungsten –3 carbide is superior. Tungsten carbide is a dense (15,630 kg.m ) and very hard ceramic material (1700–2400 HK). It exhibits outstanding mechanical properties with a Young’s modulus of 668 GPa, a tensile strength of 344 MPa, and a compressive strength of 2683–2958 MPa. It has a high melting point of 2777°C and a thermal conductivity at 100°C of 86 W/mK.

10.5.6.2 Industrial Preparation Most cemented carbides are manufactured by powder metallurgy, which consists in the preparation of the tungsten-carbide powder, powder consolidation, sintering, and postsintering forming. Tungsten-carbide powder is usually obtained by a carburization process and mixed with a relatively ductile matrix material such as cobalt, nickel, or iron and paraffin wax in either an attrition or ball mill to produce a composite powder. Spray drying yields uniform, spheroidized particles that are 100 to 200 mm in diameter. The powder is then consolidated into net and near-net-shape green compacts and billets by pressing and extrusion. Pressed billets can also be machined to shape before sintering. The density of the green compacts is around 45 to 65% of the theoretical. The green parts are then dewaxed at a temperature between 200 and 400°C and are then presintered between 600 and 900°C to impart adequate strength for handling. An alternative technology is a combination sinter-HIP process that combines dewaxing, presintering, vacuum sintering, and low-pressure HIP to speed up the overall cycle time.

10.5.6.3 Industrial Applications and Uses Tungsten carbide can be used for a wide variety of applications. It has many applications that utilize its corrosion-resistant property such as wear plates, drawing dies, and wear parts for wire wearing machines. There are other applications that make use of its high hardness

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such as punches, bushings, dies, cylinders, discs, rings, and intricate shapes as well as performs and blanks. There are other minor applications such as in rusticator blades, sander nozzles, air jets, and sander guns. Tungsten carbide is also used primarily and extensively for making drill-tip tunneling, rock crushing, mining, and quarrying purposes, i.e., for most geological activities. Tungsten carbide is also made into tiles for wear and abrasion resistance. It is also very useful in rebuilding worn parts. The application of tungsten carbide on industrial wearing surfaces has been proven to greatly enhance the performance factors for a whole spectrum of industrial applications. The service life of many kinds of machinery can be greatly prolonged by surface coating of wear-prone materials with tungsten carbide.

10.5.7 Practical Data for Ceramists and Refractory Engineers 10.5.7.1 Temperature of Color In practice, the temperature of an incandescent body can be estimated roughly from the color of radiation emitted according to a practical scale described in Table 10.18. Table 10.18. Practical color scale for temperature of incandescent body Color

Temperature range (°C)

Lowest visible red

475

Lowest visible red to dark red

475–650

Dark red to cherry red

650–750

Cherry red to bright cherry red

750–815

Bright cherry red to orange

815–900

Orange to yellow

900–1090

Yellow to light yellow

1090–1315

Light yellow to white

1315–1540

White to dazzling white

1540 and higher

10.5.7.2 Pyrometric Cone Equivalents The pyrometric cone equivalent (PCE), a special ceramic material, was introduced by Segers and standardized by Edward Orton, Jr. It is determined by testing the refractory against a series of standardized test pieces, cone shaped and having a ceramic composition with different softening points, one withstanding a slightly higher temperature than the other. The test pieces are generally made to form triangular pyramids having a height four times the base. The softening point is reached depending upon the temperature and the rate of heat increase. Cones are numbered from 022, 021, 020, 02, 01, 1, and 2 to 42. Where the softening range in cones is too close, for example, in 21, 22, 24, and 25, they are omitted from the series, and where the temperature range is widely spaced, extra cones like 31.5, 32.5, etc. are added. At a temperature increase rate of 20°C per hour, the cones numbering 022 to 01 have softening points between 585 and 1110°C, and those numbered 1 to 35 have softening points between 1125 and 1775°C. Thus, the predetermined pyrometric cone equivalents of standard test pieces are placed along with cones made of the samples being tested in the furnace, and the PCE of the samples are determined by visual comparison. The softening point is noticed when the tip of the cone starts bending with the rise in temperature.

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Table 10.19. Temperature (continued) equivalents (°C) of pyrometric cones and pyrometric cone equivalents Cone No. Heating rate for large cones

Heating rate for small cones

Pyrometric cone equivalent (PCE)

300°C/h

150°C/h

60°C/h

150°C/h

022

585

600

021

602

614

643

020

625

635

666

019

668

683

723

018

696

717

752

017

727

747

784

016

767

792

825

015

790

804

843

014

834

838

013

869

852

012

866

884

011

886

894

010

887

894

919

09

915

923

955

08

945

955

983

07

973

984

1008

06

991

999

1023

05

1031

1046

1062

04

1050

1060

1098

03

1086

1101

1131

02

1101

1120

1148

01

1117

1137

1178

1

1136

1152

1179

2

1142

1162

1179

3

1152

1168

1196

4

1168

1186

1209

5

1177

1196

1221

6

1201

1222

1255

7

1215

1240

1264

8

1236

1260

1300

9

1260

1280

1317

10

1285

1305

1330

11

1294

1315

1366

12

1306

1326

1355

13

1321

1346

1349

14

1388

1366

1398

15

1424

1431

1430

16

1455

1473

1491

1337

Standards for Testing Refractories

643

Table 10.19. (continued) Cone No. Heating rate for large cones

Heating rate for small cones

Pyrometric cone equivalent (PCE)

300°C/h

150°C/h

60°C/h

150°C/h

17

1477

1485

1512

18

1500

1506

1522

19

1520

1528

1541

20

1542

1549

1564

23

1586

1590

1605

26

1589

1605

1621

27

1614

1627

1640

28

1614

1633

1646

29

1624

1645

1659

30

1636

1654

1665

1661

1679

1683

31 1

1706 1717

1717

32 /2

1

1718

1730

1724

33

1732

1741

1743

34

1757

1759

1763

35

1784

1784

1785

36

1798

1796

1804

31 /2 32

1699

37

1820

38

1835

39

1865

40

1885

41

1970

42

2015

Reference: Standard Pyrometric Cones. Edward Orton, Jr.Ceramic Foundation, Columbus, OH

10.6 Standards for Testing Refractories 10

Table 10.20. (continued) ASTM standards for testing refractories ASTM standard

Description

ASTM C-16

Load-testing refractory brick at high temperatures

ASTM C-20

Apparent porosity, water absorption, apparent specific gravity, and bulk density of burned refractory brick and shapes by boiling water

ASTM C-24

Pyrometric cone equivalent of fireclay and high-alumina refractory materials

ASTM C-67

Brick and structural clay-tile testing

ASTM C-92

Sieve analysis and water content of refractory materials

ASTM C-93

Cold crushing strength and modulus of rupture of insulating firebrick

Ceramics, Refractories, and Glasses

644

Ceramics, Refractories, and Glasses

Table 10.20. (continued) ASTM standard

Description

ASTM C-113

Reheat change of refractory brick

ASTM C-133

Cold crushing strength and modulus of rupture of refractories

ASTM C-134

Size and bulk density of refractory brick and insulating firebrick

ASTM C-135

True specific gravity of refractory materials by water immersion

ASTM C-167

Thickness and density of blanket or batt thermal insulations

ASTM C-179

Drying and linear change in refractory plastic and ramming mix specimens

ASTM C-181

Workability index of fireclay and high-alumina plastic refractories

ASTM C-182

Thermal conductivity of insulating firebrick

ASTM C-198

Cold bonding strength of refractory mortar

ASTM C-199

Pier test of refractory mortars

ASTM C-201

Thermal conductivity of refractories

ASTM C-202

Thermal conductivity of refractory brick

ASTM C-210

Reheat change in insulating firebrick

ASTM D-257

DC resistance or conductance of insulating materials

ASTM C-279

Chemical-resistant masonry units

ASTM C-288

Disintegration of refractories in an atmosphere of carbon monoxide

ASTM C-336

Annealing point and strain point of glass by fiber elongation

ASTM C-338

Softening point of glass by fiber elongation

ASTM C-356

Linear shrinkage of preformed high-temperature thermal insulation subjected to soaking heat

ASTM C-357

Bulk density of granular refractory materials

ASTM C-373

Water absorption, bulk density, apparent porosity, and apparent specific gravity of fired whiteware products

ASTM C-417

Thermal conductivity of unfired monolithic refractories

ASTM C-454

Disintegration of carbon refractories by alkali

ASTM C-491

Modulus of rupture of air-setting plastic refractories

ASTM C-559

Bulk density by physical measurements of manufactured carbon and graphite articles

ASTM C-561

Ash in a graphite sample

ASTM C-577

Permeability of refractories

ASTM C-583

Modulus of rupture of refractory materials at elevated temperatures

ASTM C-598

Annealing point and strain point of glass by beam bending

ASTM C-605

Reheat change of fireclay nozzles and sleeves

ASTM C-611

Electrical resistivity of manufactured carbon and graphite articles at room temperature

ASTM C-651

Flexural strength of manufactured carbon and graphite articles using four-point loading at room temperature

ASTM C-695

Compressive strength of carbon and graphite

ASTM C-704

Abrasion resistance of refractory materials at room temperature

ASTM C-747

Modulus of elasticity and fundamental frequencies of carbon and graphite materials by sonic resonance

ASTM C-767

Thermal conductivity of carbon refractories

Standards for Testing Refractories

645

Table 10.20. (continued) ASTM standard

Description

ASTM C-769

Sonic velocity in manufactured carbon and graphite materials for use in obtaining an approximate Young’s modulus

ASTM C-830

Apparent porosity, liquid absorption, apparent specific gravity, and bulk density of refractory shapes by vacuum pressure

ASTM C-831

Residual carbon, apparent residual carbon, and apparent carbon yield in coked-carboncontaining bricks and shapes

ASTM C-832

Measuring the thermal expansion and creep of refractories under load

ASTM C-838

Bulk density of as-manufactured carbon and graphite shapes

ASTM C-860

Determining and measuring consistency of refractory concrete

ASTM C-862

Preparing refractory concrete specimens by casting

ASTM C-863

Evaluating oxidation resistance of silicon carbide refractories at elevated temperatures

ASTM C-865

Firing refractory concrete specimens

ASTM C-885

Young’s modulus of refractory shapes by sonic resonance

ASTM C-892

Unfiberized shot content of inorganic fibrous blankets

ASTM C-914

Bulk density and volume of solid refractories by wax immersion

ASTM C-973

Preparing test specimens from basic refractory gunning products by pressing

ASTM C-974

Preparing test specimens from basic refractory castable products by casting

ASTM C-975

Preparing test specimens from basic refractory ramming products by pressing

ASTM C-1025

Modulus of rupture in bending of electrode graphite

ASTM C-1039

Apparent porosity, apparent specific gravity, and bulk density of graphite electrodes

ASTM C-1054

Pressing and drying refractory plastic and ramming mix specimens

ASTM C-1099

Modulus of rupture of carbon-containing refractory materials at elevated temperatures

ASTM C-1100

Ribbon thermal shock testing of refractory materials

ASTM C-1113

Thermal conductivity of refractories by hot wire

ASTM C-1161

Flexural strength of advanced ceramics at ambient temperature

ASTM C-1171

Quantitatively measuring the effect of thermal cycling on refractories

ASTM C-1259

Dynamic Young’s modulus, shear modulus, and Poisson ratio for advanced ceramics by impulse excitation of vibration

(continued) Table 10.21. ISO standards for testing refractories ISO standard

Description

ISO 10058: 1992

Magnesites and dolomites – chemical analysis

ISO 10059-1: 1992

Dense, shaped refractory products – determination of cold compressive strength. Part 1: Referee test without packing

ISO 10059-2: 2003

Dense, shaped refractory products – determination of cold compressive strength. Part 2: Test with packing

ISO 10060: 1993

Dense, shaped refractory products – test methods for products containing carbon

ISO 10080: 1990

Refractory products – classification of dense, shaped acid-resisting products

ISO 10081-1: 2003

Classification of dense shaped refractory products. Part 1: Alumina-silica

10 Ceramics, Refractories, and Glasses

646

Ceramics, Refractories, and Glasses

Table 10.21. (continued) ISO standard

Description

ISO 10081-2: 2003

Classification of dense shaped refractory products. Part 2: Basic products containing less than 7% residual carbon

ISO 10081-3: 2003

Classification of dense shaped refractory products. Part 3: Basic products containing from 7 to 50% residual carbon

ISO 10635: 1999

Refractory products – methods of testing for ceramic fiber products

ISO 1146: 1988

Pyrometric reference cones for laboratory use – specification

ISO 12676: 2000

Refractory products – determination of resistance to carbon monoxide

ISO 12677: 2003

Chemical analysis of refractory products by XRF – fused cast bead method

ISO 12678-1: 1996

Refractory products – measurement of dimensions and external defects of refractory bricks. Part 1: Dimensions and conformity to drawings

ISO 12678-2: 1996

Refractory products – measurement of dimensions and external defects of refractory bricks. Part 2: Corner and edge defects and other surface imperfections

ISO 12680-1: 2005

Methods of testing of refractory products. Part 1: Determination of dynamic Young’s modulus (MOE) by impulse excitation of vibration

ISO 13765-1: 2004

Refractory mortars. Part 1: Determination of consistency using the penetrating-cone method

ISO 13765-2: 2004

Refractory mortars. Part 2: Determination of consistency using the reciprocating-flowtable method

ISO 13765-3: 2004

Refractory mortars. Part 3: Determination of joint stability

ISO 13765-4: 2004

Refractory mortars. Part 4: Determination of flexural bonding strength

ISO 13765-5: 2004

Refractory mortars. Part 5: Determination of grain-size distribution (sieve analysis)

ISO 13765-6: 2004

Refractory mortars. Part 6: Determination of moisture content of ready-mixed mortars

ISO 1893: 2005

Refractory products – determination of refractoriness under load – differential method with rising temperature

ISO 1927: 1984

Prepared unshaped refractory materials (dense and insulating) – classification

ISO 20182: 2005

Refractory test-piece preparation – gunning refractory panels by pneumatic-nozzle mixing-type guns

ISO 2245: 1990

Shaped insulating refractory products – classification

ISO 2477: 2005

Shaped insulating refractory products – determination of permanent change in dimensions on heating

ISO 2478: 1987

Dense shaped refractory products – determination of permanent change in dimensions on heating

ISO 3187: 1989

Refractory products – determination of creep in compression

ISO 5013: 1985

Refractory products – determination of modulus of rupture at elevated temperatures

ISO 5014: 1997

Dense and insulating shaped refractory products – determination of modulus of rupture at ambient temperature

ISO 5016: 1997

Shaped insulating refractory products – determination of bulk density and true porosity

ISO 5017: 1998

Dense shaped refractory products – determination of bulk density, apparent porosity, and true porosity

ISO 5018: 1983

Refractory materials – determination of true density

ISO 5019-1: 1984

Refractory bricks – dimensions. Part 1: Rectangular bricks

ISO 5019-2: 1984

Refractory bricks – dimensions. Part 2: Arch bricks

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides)

647

Table 10.21. (continued) ISO standard

Description

ISO 5019-3: 1984

Refractory bricks – dimensions. Part 3: Rectangular checker bricks for regenerative furnaces

ISO 5019-4: 1988

Refractory bricks – dimensions. Part 4: Dome bricks for electric-arc furnace roofs

ISO 5019-5: 1984

Refractory bricks – dimensions. Part 5: Skewbacks

ISO 5019-6: 2005

Refractory bricks – dimensions. Part 6: Basic bricks for oxygen steelmaking converters

ISO 5022: 1979

Shaped refractory products – sampling and acceptance testing

ISO 528: 1983

Refractory products – determination of pyrometric cone equivalent (refractoriness)

ISO 5417: 1986

Refractory bricks for use in rotary kilns – dimensions

ISO 836: 2001

Terminology for refractories

ISO 8656-1: 1988

Refractory products – sampling of raw materials and unshaped products. Part 1: Sampling scheme

ISO 8840: 1987

Refractory materials – determination of bulk density of granular materials (grain density)

ISO 8841: 1991

Dense, shaped refractory products – determination of permeability to gases

ISO 8890: 1988

Dense shaped refractory products – determination of resistance to sulfuric acid

ISO 8894-1: 1987

Refractory materials – determination of thermal conductivity. Part 1: Hot-wire method (cross-array)

ISO 8894-2: 1990

Refractory materials – determination of thermal conductivity. Part 2: Hot-wire method (parallel)

ISO 8895: 2004

Shaped insulating refractory products – determination of cold crushing strength

ISO 9205: 1988

Refractory bricks for use in rotary kilns – hot-face identification marking

10.7 Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) See Table 10.22, pages 648–669.

10 Ceramics, Refractories, and Glasses

Table 10.22. Selected physical properties of advanced ceramics (borides, carbides, nitrides, silicides, and oxides)

IUPAC name (synonyms, common trade names)

n.a.

2460

Be4B [12536-52-6] 46.589

BeB2 Hexagonal [12228-40-9] a = 979 pm 30.634 c = 955 pm

Be2B Cubic [12536-51-5] a = 467.00 pm C1, cF12, Fm3m, CaF2 type (Z = 4)

BeB6 Tetragonal [12429-94-6] a = 1016 pm c = 1428 pm

BeB [12228-40-9]

Trigonal β-B [7440-42-8] (rhombohedral) a = 1017 pm 10.811 α = 65°12' hR105, R3m, β-B type

Beryllium diboride

Beryllium hemiboride

Beryllium hexaboride

Beryllium boride

Boron

2330

1890

2420

n.a.

4350

18,000

n.a.

n.a.

n.a.

1013

n.a.

n.a.

n.a.

n.a.

1000

10,000

n.a.

77

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2190

1970

2070

1520

1970

1160

2270

2421

1654

954.48

897.87

320

385

Young’s or elastic modulus (E/GPa)

Cubic a = pm D21, cP7, Pm3m CaB6 type (Z = 1)

Beryllium boride

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

BaB6 [] 202.193

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Barium hexaboride

Density (ρ/kg.m–3)

n.a.

n.a.

Dissipation or tangent loss factor (tanδ)

2580

Dielectric field strength (Ed/MV.m–1) n.a.

Melting point (m.p./°C)

AlB12 Tetragonal [12041-54-2] a = 1016 pm 156.714 c = 1428 pm

Dielectric permittivity [1MHz] (εr / nil) n.a.

Specific heat capacity (cP/J.kg–1.K–1)

Aluminum dodecaboride

Electrical resistivity (ρ/μΩ.cm)

n.a.

20.15 Brown or dark powder, (HM 11) unreactive to oxygen, water, acids, and alkalis. ΔHvap.= 480 kJ/mol

8.53

Better air oxidation resistance than any other beryllium boride (Be2B, BeB6) in temperature range 1000–1200°C

Black cubic crystals

23.55– Soluble in hot HNO3, insoluble 25.50 HK in other acids and alkalis. Neutron shielding material

9.61 HK Temp. transition to AlB12 at 920°C. Soluble in dilute HCl. Nuclear shielding material

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

AlB2 Hexagonal 3190 [12041-50-8] a = 300.50 pm 48.604 c = 325.30 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

Other physicochemical Properties, oxidation and corrosion resistance28, and major uses.

Aluminum diboride

Borides

648 Ceramics, Refractories, and Glasses

Fracture toughness (K1C/MPa.m1/2)

Compressive strength (σ/MPa)

Flexural strength (τ/MPa)

Ultimate tensile strength (σUTS/MPa)

Poisson ratio (ν)

Bulk or compression modulus (K/GPa)

Coulomb’s or shear modulus (G/GPa)

Coeff. linear thermal expansion (α /10–6K–1)

Thermal conductivity (k/W.m–1.K–1)

Co2B [12045-01-1] 128.677

CoB [12006-77-8] 69.744

HfB2 Hexagonal 11,190 [12007-23-7] a = 314.20 pm 200.112 c = 347.60 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

Cobalt hemiboride

Cobalt boride

Hafnium diboride

FeB2 Tetragonal [12006-86-9] 122.501

FeB Orthorhombic [12006-84-7] 66.656

Iron diboride

Iron boride

Cubic NaCl type

CrB Tetragonal [12006-79-0] a = 294.00 pm 62.807 c = 1572.00 pm Bf, oC8, Cmcm CrB type (Z = 4)

Chromium boride

Hafnium boride HfB [] 189.301

CrB2 Hexagonal 5160– [12007-16-8] a = 292.9 pm 5220 73.618 c = 306.6 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

Chromium diboride

n.a.

n.a.

n.a.

3249

7000

1389

n.a.

7300

n.a.

2899

n.a.

2100

12,800

8.8–11

n.a.

1850– 2200

1460

n.a.

n.a.

7250

n.a.

n.a.

1280

64.0

n.a.

8100

6200

21

1900

n.a.

6100

Cr5B3 Orthorhombic [12007-38-4] a = 302.6 pm 292.414 b = 1811.5 pm c = 295.4 pm D81, tI32, I4/mcm, Cr5B3 type (Z = 4)

Chromium boride

2235

2550

222

4870

CeB6 Cubic [12008-02-5] a = 4 pm 204.981 D21, cP7, Pm3m CaB6 type (Z = 1)

Cerium hexaboride

2460

CaB6 Cubic [12007-99-7] a = 413.77 pm 104.944 D21, cP7, Pm3m CaB6 type (Z = 1)

Calcium hexaboride

57.1

20.1

12.3

6.2– 7.5

13.7

6.48

247.11 6.3– 7.56

20–32 712

15.8

39.29

500

211

451

n.a.

n.a.

0.12

n.a.

n.a.

350

607

1300

n.a. n.a.

n.a.

Strongly corroded by molten metals such as Mg, Al, Na, Cu, Si, V, Cr, Mn, Fe, and Ni; corrosion resistant to liquid metals Cu, Zn, Sn, Rb, and Bi

Gray hexagonal crystals

28.44 Gray crystals. HfB2 exhibits the and greatest oxidation resistance of 23.54 HK all refractory group IV and V borides above 1090°C. Attacked by hydrogen fluoride gas (HF) but resists fluorine gas up to 590°C and is less resistant than zirconium diboride

17.65

Blue hexagonal crystals

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 649

Ceramics, Refractories, and Glasses

10

26–65

40–64.5

MoB2 117.59

Mo2B Tetragonal [12006-99-4] a = 554.3 pm 202.691 c = 473.5 pm C16, tI12, I4/mcm, CuAl2 type (Z = 4)

MoB 106.77

Hexagonal 6970 ε−NbB2 [12007-29-3] a = 308.90 pm c = 330.03 pm 114.528 C32, hP3, P6/mmm, AlB2 type (Z = 1)

Orthorhombic δ−NbB [12045-19-1] a = 329.8 pm b = 316.6 pm 103.717 c = 87.23 pm Bf, oC8, Cmcm, CrB type (Z = 4)

SiB6 Trigonal [12008-29-6] (rhombohedral)

IUPAC name (synonyms, common trade names)

Molybdenum diboride

Molybdenum hemiboride

Molybdenum boride

Niobium diboride

Niobium boride

Silicon hexaboride

Tetragonal a = 311.0 c = 169.5 Bg, tI4, I41/amd MoB type (Z = 2)

2430

200,000

n.a.

n.a.

n.a.

n.a.

n.a.

1950

2270– 2917

15.6

n.a.

418

12.9

8.0– 8.6

n.a.

637

n.a.

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

17– 23.5

368

5.0

7.7

n.a.

n.a.

Bulk or compression modulus (K/GPa)

2900

2180

377

527

672

n.a.

n.a.

Poisson ratio (ν)

n.a.

n.a.

2280

2100

8.6

n.a.

n.a.

Ultimate tensile strength (σUTS/MPa)

n.a.

n.a.

α−MoB 45, n.a. β−MoB 25

n.a.

n.a.

50

479

n.a. n.a.

n.a. n.a.

345

126

Compressive strength (σ/MPa)

n.a.

n.a.

n.a.

40

n.a.

1600

6.4

n.a.

Fracture toughness (K1C/MPa.m1/2)

7570

8770

9260

n.a.

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

45

n.a.

47.7

Corrosion-resistant film

Corroded by molten metals Al, Mg, V, Cr, Mn, Fe, Ni, Cu, Nb, Mo, and Ta; corrosion resistant to molten Cd, Sn, Bi, and Rb

Wear-resistant, semiconducting, thermoionic conductor film

Wear-resistant and semiconductive films, neutron-absorbing layer on nuclear fuel pellets

30.70 Corrosion resistant to molten (HM>8) Ta while corroded by molten rhenium

15.40

(HM 8–9)

12.55

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

Hexagonal 7780 a = 305.00 pm c = 311.30 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

Dielectric permittivity [1MHz] (εr / nil) n.a.

Dielectric field strength (Ed/MV.m–1)

25–55

Dissipation or tangent loss factor (tanδ)

7480

Melting point (m.p./°C) 2715

Thermal conductivity (k/W.m–1.K–1)

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

n.a.

Young’s or elastic modulus (E/GPa)

n.a.

Flexural strength (τ/MPa)

17.4

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

4760

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Mo2B5 Trigonal [12007-97-5] a = 301.2 pm 245.935 c = 2093.7 pm D8i, hR7, R3m Mo2B5 type (Z = 1)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Molybdenum boride

Density (ρ/kg.m–3)

LaB6 Cubic [12008-21-8] a = 415.7 pm 203.772 D21, cP7, Pm3m CaB6 type (Z = 1)

Electrical resistivity (ρ/μΩ.cm)

Lanthanum hexaboride

Table 10.22. (continued)

650 Ceramics, Refractories, and Glasses

TiB2 Hexagonal 4520 [12045-63-5] a = 302.8 pm 69.489 c = 322.8 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

W2B Tetragonal [12007-10-2] a = 556.4 pm 378.491 c = 474.0 pm C16, tI12, I4/mcm, CuAl2 type (Z = 4)

WB Tetragonal [12007-09-9] a = 311.5 pm 194.651 c = 1692 pm

Titanium diboride

Tungsten hemiboride

Tungsten boride

n.a.

n.a.

15,200– 4.1 16,000

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

16,720

16–28.4

TiB [] 58.678

Titanium boride

5260

n.a.

ThB4 Tetragonal 8450 [12007-83-9] a = 725.6 pm 275.53 c = 411.3 pm D1e, tP20, P4/mbm, ThB4type (Z = 4)

Thorium tetraboride

Cubic

n.a.

6800

ThB6 Cubic [12229-63-9] a = 411.2 pm 296.904 D21, cP7, Pm3m CaB6 type (Z = 1)

Thorium hexaboride

100

TaB Orthorhombic [12007-07-7] a = 327.6 pm 191.759 b = 866.9 pm c = 315.7 pm Bf, oC8, Cmcm CrB type (Z = 4)

Tantalum boride

33–75

n.a.

14,190

TaB2 Hexagonal 12,540 [12077-35-1] a = 309.80 pm 202.570 c = 324.10 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

Tantalum diboride

2400

SiB4 [12007-81-7] 71.330

Silicon tetraboride

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2660

2670

2980– 3225

2060

2500

2149

2340– 3090

3037– 3200

1870 (dec.)

510

7.9

7.8

168

6.9

6.7

64.4– 637.22 7.6– 96 8.64

25

44.8

246.85 n.a.

10.9– 237.55 8.2– 16.0 8.8

372– 551

148

n.a.

257

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.11

n.a.

n.a.

131

n.a.

n.a.

240– 669 400

137

n.a. n.a.

n.a. n.a.

6.2– 6.7

n.a.

n.a.

13.63 (HM 9)

23.73 (HM 9)

Black powder

Black powder

33.05 Gray crystals, superconducting (HM>9) at 1.26 K. High-temperature 31.87 HK electrical conductor, used as crucible material for handling molten metals such as Al, Zn, Cd, Bi, Sn, and Rb; strongly corroded by liquid metals such as Ti, Zr, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, and Cu. Begins to be oxidized in air above 1100–1400°C. Corrosion resistance in hot concentrated brines. Maximum operating temperature 1000°C (reducing) and 800°C (oxidizing).

21.57 Severe oxidation above (HM>8) 1100–1400°C in air

(HM>8) Gray metallic powder. Severe oxidation in air above 800°C. Corroded by molten metals Nb, Mo, Ta, and Re.

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 651

Ceramics, Refractories, and Glasses

10

UB4 Tetragonal 5350 [12007-84-0] a = 707.5 pm 281.273 c = 397.9 pm D1e, tP20, P4/mbm, ThB4type (Z = 4)

VB2 Hexagonal 5070 [12007-37-3] a = 299.8 pm 72.564 c = 305.7 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

ZrB2 Hexagonal 6085 [12045-64-6] a = 316.9 pm 112.846 c = 353.0 pm C32, hP3, P6/mmm, AlB2 type (Z = 1)

IUPAC name (synonyms, common trade names)

Uranium tetraboride

Vanadium diboride

Zirconium diboride

Electrical resistivity (ρ/μΩ.cm) 392.54 5.5– 8.3

343– 506

220

Coulomb’s or shear modulus (G/GPa)

57.9

268

n.a.

Bulk or compression modulus (K/GPa)

3060– 3245

647.43 7.6– 8.3

0.15

Poisson ratio (ν)

n.a.

42.3

n.a.

Ultimate tensile strength (σUTS/MPa)

n.a.

2450– 2747

440

305

413

n.a.

Compressive strength (σ/MPa)

n.a.

n.a.

7.0

4.6

n.a.

Fracture toughness (K1C/MPa.m1/2)

9.2

n.a.

4.0

Specific heat capacity (cP/J.kg–1.K–1)

n.a.

2495

1500

18.63– 33.34 (HM 8)

(HM 8–9)

24.52

Gray metallic crystals, excellent thermal shock resistance, greatest oxidation inertness of all refractory hardmetals. Hot-pressed crucible for handling molten metals such as Zn, Mg, Fe, Cu, Zn, Cd, Sn, Pb, Rb, Bi, Cr, brass, carbon steel, cast irons, and molten cryolithe, yttria, zirconia, and alumina. Readily corroded by liquid metals such as Si, Cr, Mn, Co, Ni, Nb, Mo, Ta and attacked by molten salts such as Na2O, alkali carbonates, and NaOH. Severe oxidation in air occurs above 1100–1400°C. Stable above 2000°C in inert or reducing atmosphere.

Wear-resistant and semiconductive films

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

23

n.a.

n.a.

9.0

Young’s or elastic modulus (E/GPa)

n.a.

n.a.

51.9

Flexural strength (τ/MPa)

n.a.

n.a.

2385

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

n.a.

n.a.

Dielectric permittivity [1MHz] (εr / nil)

5820

UB12 367.91

Dielectric field strength (Ed/MV.m–1) n.a.

Dissipation or tangent loss factor (tanδ)

n.a.

Melting point (m.p./°C)

n.a.

Thermal conductivity (k/W.m–1.K–1)

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

Cubic a = 747.3 pm D2f, cF52, Fm3m, UB12 type (Z = 4)

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Uranium dodecaboride

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

UB2 Hexagonal 12,710 [12007-36-2] a = 313.10 pm 259.651 c = 398.70 pm C32, hP3, P6/mmm, AlB2 type

Density (ρ/kg.m–3)

Uranium diboride

Table 10.22. (continued)

652 Ceramics, Refractories, and Glasses

B 4C Hexagonal [12069-32-8] a = 560 pm 55.255 c = 1212 pm D1g, hR15, R3m, B4C type

Cr7C3 400.005

Cr3C2 Orthorombic [12012-35-0] a = 282 pm 180.010 b = 553 pm c = 1147 pm D510, oP20, Pbnm, Cr3C2 type (Z = 4)

Boron carbide (Norbide®)

Chromium carbide

Chromium carbide

Hexagonal a = 1398.02 pm c = 453.20 pm

Cubic a = 433 pm C1, cF12, Fm3m, CaF2 type (Z = 4)

Be2C [506-66-1] 30.035

Beryllium hemicarbide

Cubic a = 740.8 pm D2f, cF52, Fm3m, UB12 type (Z = 4)

Al4C3 Trigonal [1299-86-1] (rhombohedral) 143.959 a = 333 pm c = 2494 pm D71

ZrB12 283.217

Aluminum carbide

Carbides

Zirconium dodecaboride

60–80

n.a.

n.a.

4500

109.0

75.0

3630

2360

1900

2512

6992

6680

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1895

1665

2350– 2427

2100

2798

2680

19.2

n.a.

27

21.0

n.a.

n.a.

n.a.

1854

1397

n.a.

523

10.3

11.7

n.a.

386

n.a.

n.a.

n.a.

184

314.4 n.a.

n.a.

2.63– 448– 5.6 470

10.5

n.a.

0.78

n.a.

490

96.5

n.a.

0.280

n.a.

0.207

0.100

n.a.

n.a.

n.a.

310– 350

155

n.a.

n.a.

n.a.

n.a.

n.a. 1041– n.a. 1350

n.a. n.a.

n.a. 1400– 3.2– 2900 4.2

n.a. 723

n.a. n.a.

Decomposes in water with evolution of CH4

25.99

13.10

31.38– 34.32 HK (HM 9.32)

Corroded by molten metals Ni, Zn, Cu, Cd, Al, Mn, and Fe. Corrosion resistant in molten Sn and Bi.

Resists oxidation in range 800–1000°C. Corroded by molten metals Ni and Zn.

Hard black shiny crystals, fourth hardest material known after diamond, cubic boron nitride, and boron oxide. Does not burn in an O2 flame if temperature is maintained below 983°C. Maximum operating temperature 2000°C (inert, reducing) or 600°C (oxidizing). Not attacked by hot HF or chromic acid. Used as abrasive, crucible container for molten salts except molten alkali hydroxides. In form of molded shape, used for pressure-blast nozzles, wire-drawing dies, and bearing surfaces for gauges. For grinding and lapping application available mesh sizes cover range 240 to 800.

23.63 HK Brick-red or yellowish-red octahedra. Nuclear reactor cores.

n.a.

–

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 653

Ceramics, Refractories, and Glasses

10

C Hexagonal [7782-42-5] a = 246 pm 12.011 b = 428 pm c = 671 pm A9, hP4,P63/mmc, graphite type (Z =4)

HfC Cubic 12,670 [12069-85-1] a = 446.0 pm 190.501 B1, cF8, Fm3m, rock salt type (Z = 4)

IUPAC name (synonyms, common trade names)

Hafnium carbide

Dielectric permittivity [1MHz] (εr / nil)

Electrical resistivity (ρ/μΩ.cm) n.a.

Dielectric field strength (Ed/MV.m–1)

45.0

n.a.

Dissipation or tangent loss factor (tanδ) n.a.

n.a.

Melting point (m.p./°C)

n.a.

3890– 3950

3650

Thermal conductivity (k/W.m–1.K–1)

n.a.

n.a.

22.15 n.a.

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

1385

Coeff. linear thermal expansion (α /10–6K–1)

2250

6.3

0.6– 4.3

Young’s or elastic modulus (E/GPa) 424

6.9

179

n.a.

n.a.

Coulomb’s or shear modulus (G/GPa)

930

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

2.16

0.17

n.a.

n.a.

Poisson ratio (ν)

n.a.

n.a.

28

n.a.

Ultimate tensile strength (σUTS/MPa)

900 (I) 2400 (IIa)

n.a. n.a.

n.a. n.a.

n.a. 7000

Flexural strength (τ/MPa)

3550

Compressive strength (σ/MPa)

n.a.

n.a.

n.a.

5.3– 6.7

Fracture toughness (K1C/MPa.m1/2)

n.a.

18.34– 28.44

(HM 2)

Dark gray brittle solid, most refractory binary material known. Controls rods in nuclear reactors, crucible container for melting HfO2 and other oxides. Corrosion resistant to liquid metals such as Nb, Ta, Mo, and W. Severe oxidation in air above 1100–1400°C and stable up to 2000°C in helium.

High-temperature lubricant, crucible container for handling molten metals such as Mg, Al, Zn, Ga, Sb, and Bi

78.45 HK Exists in two major varieties: (HM 10) those bearing nitrogen as an impurity (Type I) and those without nitrogen (Type II). These two subgroups are further subdivided into Types Ia, Ib, IIa, and IIb. Type Ia diamonds are the most common type of naturally occurring diamond; they exhibit 0.1 to 0.2 wt.% nitrogen present in small aggregates, including platelets. By contrast, nitrogen in Type Ib diamonds is dispersed substitutionally. Of the two Type II diamond types, Type IIb is a semiconductor due to minute amounts of boron impurities and exhibits a blue color, whereas Type IIa diamonds are comparatively pure. Electric insulator (Eg = 7 eV.). Burns in oxygen.

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

n.a.

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

3515.24 >1016 (I, IIa) >103 (IIb)

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Graphite

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

C Cubic [7782-40-3] a = 356.683 pm 12.011 A4, cF8, Fd3m, diamond type (Z =8)

Density (ρ/kg.m–3)

Diamond

Table 10.22. (continued)

654 Ceramics, Refractories, and Glasses

51.1–74.0

107–200

410,000

NbC Cubic 7820 [12069-94-2] a = 447.71 pm 104.917 B1, cF8, Fm3m, rock salt type (Z = 4)

3160

3160

Niobium carbide

Hexagonal a = 308.10 pm c = 503.94 pm B4, hP4, P63/mmc, wurtzite type (Z = 2)

n.a.

7800

Nb2C Hexagonal [12011-99-3] a = 312.70 pm 197.824 c = 497.20 pm L'3, hP3, P63/mmc, Fe2N type (Z = 1)

Niobium hemicarbide

Silicon carbide α−SiC (moissanite, [409-21-2] Carbolon®, 40.097 Crystolon®, Carborundum®)

50.0

9150

MoC Hexagonal [12011-97-1] a = 290 pm 107.951 c = 281 pm Bk, P63/mmc, BN type (Z = 4)

Molybdenum carbide

Cubic a = 435.90 pm B3, cF8, F43m, ZnS type (Z = 4)

71.0

9180

Hexagonal β−Mo2C [12069-89-5] a = 300.20 pm c = 427.40 pm 203.891 L'3, hP3, P63/mmc, Fe2N type (Z = 1)

Molybdenum hemicarbide

Silicon carbide β−SiC (Carbolon®, [409-21-2] Crystolon®, 40.097 Carborundum®)

68.0

LaC2 Tetragonal 5290 [12071-15-7] a = 394.00 pm 162.928 c = 657.20 pm C11a, tI6, I4/mmm, CaC2 type (Z = 2)

Lanthanum dicarbide

10.2

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2093 trans.

2093– 2400

3760

3090

2577

2687

2360– 2438

42.5

135

14.2

n.a.

n.a.

n.a.

n.a.

690– 715

1205

n.a.

n.a.

n.a.

29.4

n.a.

4.3– 4.6

4.5

6.84

n.a.

5.76

7.8

12.1

386– 414

262– 468

340

n.a.

197

221

n.a.

179

168

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

414

n.a.

n.a.

n.a.

n.a.

n.a.

0.16

0.192

n.a.

n.a.

0.204

n.a.

n.a.

450– 520

550

n.a.

n.a.

n.a.

n.a.

n.a.

359

500

n.a. 1000

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

3.1

3.1

n.a.

n.a.

n.a.

n.a.

n.a.

Decomposed by H2O

23.54– Semiconductor (Eg=3.03 eV) 24.52 soluble in fused alkali (HM 9.2) hydroxides

26.48– Green to bluish black, iridescent 32.85 crystals. Soluble in fused alkali (HM 9.5) hydroxides. Abrasives best suited for grinding low-tensilestrength materials such as cast iron, brass, bronze, marble, concrete, stone and glass, optical structural, and wear-resistant components. Corroded by molten metals such as Na, Mg, Al, Zn, Fe, Sn, Rb, and Bi. Resistant to oxidation in air up to 1650°C. Maximum operating temperature of 2000°C in reducing or inert atmosphere.

24.22 Lavender gray powder, soluble (HM>9) in HF-HNO3 mixture. Wearresistant film, coating graphite in nuclear reactors. Oxidation in air becomes severe only above 1000°C.

20.82

17.65 Oxidized in air at 700–800°C (HM>9)

14.70 Gray powder. Wear-resistant (HM>7) film. Oxidized in air at 700–800°C. Corroded in molten metals Al, Mg, V, Cr, Mn, Fe, Ni, Cu, Zn, and Nb. Corrosion resistant in molten Cd, Sn, and Ta

n.a.

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 655

Ceramics, Refractories, and Glasses

10

30–42.1

30.0

Tetragonal 8960– α−ThC2 9600 [12071-31-7] a = 585 pm c = 528 pm 256.060 C11a, tI6, I4/mmm, CaC2 type (Z = 2)

ThC Cubic 10,670 [12012-16-7] a = 534.60 pm 244.049 B1, cF8, Fm3m, rock salt type (Z = 4)

TiC Cubic 4938 [12070-08-5] a = 432.8 pm 59.878 B1, cF8, Fm3m, rock salt type (Z = 4)

IUPAC name (synonyms, common trade names)

Thorium dicarbide

Thorium carbide

Titanium carbide

52.5

Dielectric permittivity [1MHz] (εr / nil)

25.0

n.a.

n.a.

Dielectric field strength (Ed/MV.m–1) n.a.

n.a.

n.a.

Dissipation or tangent loss factor (tanδ)

n.a.

n.a.

n.a.

n.a.

Melting point (m.p./°C)

n.a.

2940– 3160

2621

2655

3880– 3920

Thermal conductivity (k/W.m–1.K–1)

n.a.

n.a.

n.a.

190

17–21 841

28.9

23.9

22.2

Specific heat capacity (cP/J.kg–1.K–1) 7.5– 7.7

6.48

8.46

310– 462

n.a.

n.a.

6.64– 364 8.4

172

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.172

n.a.

0.854 0.182

n.a.

n.a.

n.a.

n.a.

275– 450

n.a.

n.a.

n.a.

n.a.

n.a. 1310

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

1.7– 3.8

n.a.

n.a.

n.a.

n.a.

25.69– 31.38 (HM 9–10)

9.807

5.88

15.68– 17.65 (HM 9–10)

16.80– 19.61

Gray crystals. Superconducting at 1.1 K. Soluble in HNO3 and aqua regia. Resistant to oxidation in air up to 450°C. Maximum operating temperature 3000°C in helium. Crucible container for handling molten metals such as Na, Bi, Zn, Pb, Sn, Bi, Rb, and Cd. Corroded by liquid metals Mg, Al, Si, Ti, Zr, V, Nb, Ta, Cr, Mo, Mn, Fe, Co, and Ni. Attacked by molten NaOH

Readily hydrolyzes in water evolving C2H6.

α−β transition at 1427°C and β−γ at 1497°C. Decomposed by H2O with evolution of C2H6

Golden brown crystals, soluble in HF-HNO3 mixture. Crucible container for melting ZrO and similar oxides with high melting point. Corrosion resistant to molten metals such as Ta and Re. Readily corroded by liquid metals such as Nb, Mo, and Sn. Burning occurs in pure oxygen above 800°C. Severe oxidation in air above 1100–1400°C. Maximum operating temperature of 3760°C in helium

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

n.a.

Coeff. linear thermal expansion (α /10–6K–1) n.a.

Young’s or elastic modulus (E/GPa)

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

Bulk or compression modulus (K/GPa)

n.a.

Poisson ratio (ν)

3327

Ultimate tensile strength (σUTS/MPa)

n.a.

Flexural strength (τ/MPa)

n.a.

Compressive strength (σ/MPa)

n.a.

Fracture toughness (K1C/MPa.m1/2)

80.0

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

15,100

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

TaC Cubic 14,800 [12070-06-3] a = 445.55 pm 194.955 B1, cF8, Fm3m, rock salt type (Z = 4)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Tantalum carbide

Density (ρ/kg.m–3)

Ta2C Hexagonal [12070-07-4] a = 310.60 pm 373.907 c = 493.00 pm L'3, hP3, P63/mmc, Fe2N type (Z = 1)

Electrical resistivity (ρ/μΩ.cm)

Tantalum hemicarbide

Table 10.22. (continued)

656 Ceramics, Refractories, and Glasses

50.0

65.0–98.0

68

UC Cubic 13,630 [12070-09-6] a = 496.05 pm 250.040 B1, cF8, Fm3m, rock salt type (Z = 4)

V2C Hexagonal [12012-17-8] a = 286 pm 113.89 c = 454 pm L'3, hP3, P63/mmc, Fe2N type (Z = 2)

VC Cubic 5770 [12070-10-9] a = 413.55 pm 62.953 B1, cF8, Fm3m, rock salt type (Z = 4)

ZrC Cubic 6730 [12020-14-3] a = 469.83 pm 103.235 B1, cF8, Fm3m, rock salt type (Z = 4)

Uranium carbide

Vanadium hemicarbide

Vanadium carbide

Zirconium carbide

n.a.

n.a.

UC2 Tetragonal 11,280 [12071-33-9] a = 352.24 pm 262.051 c = 599.62 pm C11a, tI6, I4/mmm, CaC2 type (Z = 2)

Uranium dicarbide

5750

n.a.

12,880

U2C3 Cubic [12076-62-9] a = 808.89 pm D5c, cI40, I43d, Pu2C3 type (Z = 8)

Uranium carbide

81.0

17,340

W2C Hexagonal [12070-13-2] a = 299.82 pm 379.691 c = 472.20 pm L'3, hP3, P63/mmc, Fe2N type (Z = 2)

Tungsten hemicarbide

19.2

15,630

WC Hexagonal [12070-12-1] a = 290.63 pm 195.851 c = 283.86 pm L'3, hP3, P63/mmc, Fe2N type (Z = 1)

Tungsten carbide (Widia®)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

3540– 3560

2810

2166

2370– 2790

2350– 2398

1777

2730

2870

n.a.

n.a.

n.a.

147

n.a.

n.a.

n.a.

20.61 205

24.8

n.a.

23.0

32.7

n.a.

n.a.

121

6.82

4.9

n.a.

11.4

14.6

11.4

3.84

6.9

n.a.

n.a.

n.a.

n.a.

345

614

n.a.

123

435

n.a.

172.4 66.9

n.a.

179– 221

421

710

338

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.58

0.257

n.a.

n.a.

0.29

n.a.

n.a.

n.a.

0.26

110

790– 825

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. 1641

n.a. 613

n.a. n.a.

n.a. 351.6

n.a. n.a.

n.a. 434

n.a. n.a.

n.a. 530

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

7.5– 8.9

Transition tetragonal to cubic at 1765°C. Decomposes in H2O, slightly soluble in alcohol. Used in microsphere pellets to fuel nuclear reactors

Black. Resistant to oxidation in air up to 700°C. Corrosion resistant to Mo

Black crystals soluble in HNO3 with decomposition. Wearresistant film, cutting tools. Resistant to oxidation in air up to 300°C

Corroded by molten Nb, Mo, and Ta

17.95– Dark gray brittle solid, soluble 28.73 in HF solutions containing (HM >8) nitrate or peroxide ions. UCnuclear power reactor, crucible container for handling molten metals such as Bi, Cd, Pb, Sn, Rb, and molten zirconia ZrO2. Corroded by liquid metals Mg, Al, Si, V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Ni, and Zn. In air oxidizes rapidly above 500°C. Maximum operating temperature of 2350°C in helium

20.50

29.42

7.35– Gray crystals with metallic 9.17 appearance, reacts with oxygen. (HM>7) Corroded by molten metals Be, Si, Ni, and Zr

5.88

n.a.

29.42

26.48 Gray powder, dissolved by HF(HM>9) HNO3 mixture. Cutting tools, wear-resistant semiconductor film. Corroded by molten metals Mg, Al, V, Cr, Mn, Ni, Cu, Zn, Nb, and Mo. Corrosion resistant to molten Sn and Ta

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 657

Ceramics, Refractories, and Glasses

10

Table 10.22. (continued)

IUPAC name (synonyms, common trade names)

Density (ρ/kg.m–3)

Cr2N Hexagonal [12053-27-9] a = 274 pm 117.999 c = 445 pm L'3, hP3, P63/mmc, Fe2N type (Z = 1)

CrN Cubic 6140 [24094-93-7] a = 415.0 pm 66.003 B1, cF8, Fm3m, rock salt type (Z = 4)

Chromium heminitride

Chromium nitride

Cubic a = 361.5 pm

BN 24.818

6800

3430

2250

Boron nitride (Borazon®, CBN)

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

BN Hexagonal [10043-11-5] a = 250.4 pm 24.818 c = 666.1 pm Bk, hP8, P63/mmc, BN type (Z = 2)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Boron nitride

640

76

1900 (2000°C)

n.a.

n.a.

2.54

n.a.

1019

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1499 (dec.)

1661

0.0002 1540

0.0002 2730 (dec.)

Thermal conductivity (k/W.m–1.K–1) 1221

12.1

22.5

n.a.

795

630

n.a.

15.41 711

n.a.

2.34

9.36

n.a.

7.54

n.a.

n.a.

n.a.

n.a.

85.5

n.a.

346

Young’s or elastic modulus (E/GPa)

2200

Coeff. linear thermal expansion (α /10–6K–1) 5.3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

29.96 820

n.a.

n.a.

n.a.

0.11

n.a.

0.28

Bulk or compression modulus (K/GPa)

n.a.

Melting point (m.p./°C) 2230

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Poisson ratio (ν)

n.a.

Dissipation or tangent loss factor (tanδ) n.a.

n.a. n.a.

n.a. 2068

n.a.

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. 7000

41–62 n.a. 310

n.a.

270

Ultimate tensile strength (σUTS/MPa)

n.a.

Dielectric field strength (Ed/MV.m–1) n.a.

Flexural strength (τ/MPa)

Cubic 2710 [1304-54-7] a = 814 pm D53, cI80, Ia3, 55.050 Mn2O3 type (Z = 16)

Dielectric permittivity [1MHz] (εr / nil) n.a.

Compressive strength (σ/MPa)

α-Be3N2

Electrical resistivity (ρ/μΩ.cm)

1017

n.a.

n.a.

n.a.

5.0

n.a.

2.79

Fracture toughness (K1C/MPa.m1/2)

Beryllium nitride

3255

Hard white or grayish crystal. Oxidizes in air above 600°C. Slowly decomposes in water, quickly in acids and alkalis with evolution of NH3

Insulator (Eg=4.26 eV). Decomposes with water, acids, and alkalis to Al(OH)3 and NH3. Crucible container for GaAs crystal growth

10.69

11.77– 15.40

46.09– Tiny reddish to black grains. 49.00 Used as abrasive for grinding (HM 10) tool and die steels and highalloy steels when chemical reactivity of diamonds is a problem

2.26 Insulator (Eg=7.5 eV). Crucibles (HM 2.0) for melting molten metals such as Na, B, Fe, Ni, Al, Si, Cu, Mg, Zn, In, Bi, Rb, Cd, Ge, and Sn. Corroded by molten metals U, Pt, V, Ce, Be, Mo, Mn, Cr, V, and Al. Attacked by molten salts PbO2, Sb2O3, AsO3, Bi2O3, KOH, and K2CO3.Used in furnace insulation-diffusion masks and passivation layers

n.a.

11.77 (HM 9–10)

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

AlN Hexagonal [24304-00-5] a = 311.0 pm 40.989 c = 497.5 pm B4, hP8, P63mc, wurtzite type (Z = 2)

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

Aluminum nitride

Nitrides

658 Ceramics, Refractories, and Glasses

Thorium nitride ThN Cubic 11,560 [12033-65-7] a = 515.9 246.045 B1, cF8, Fm3m, rock salt type (Z = 4)

20

128–135

13,800

TaN Hexagonal [12033-62-4] a = 519.1 pm 194.955 c = 290.6 pm

Tantalum nitride (ε)

n.a.

n.a.

n.a.

263

15,600

Hexagonal a = 306 pm c = 496 pm L'3, hP3, P63/mmc, Fe2N type (Z=1)

Ta2N 375.901

Tantalum heminitride

9.4

1019

3184

Hexagonal α-Si3N4 [12033-89-5] a = 775.88 pm c = 561.30 pm 140.284 P31c

Silicon nitride (Nitrasil®)

n.a.

106

3170

Hexagonal β-Si3N4 [12033-89-5] a = 760.8 pm c = 291.1 pm 140.284 P6/3m

Silicon nitride

n.a.

78

n.a.

n.a.

n.a.

Niobium nitride NbN Cubic 8470 [24621-21-4] a = 438.8 pm 106.913 B1, cF8, Fm3m, rock salt type (Z = 4)

n.a.

9180

MoN Hexagonal [12033-19-1] a = 572.5 pm 109.947 c = 560.8 pm Bh, hP2, P6/mmm, WC type (Z = 1)

Molybdenum nitride

19.8

Mo2N Cubic [12033-31-7] a = 416 pm 205.887 L'1, cP5, Pm3m, Fe4N type (Z = 2)

Molybdenum heminitride

33

9460

HfN Cubic 13,840 [25817-87-2] a = 451.8 pm 192.497 B1, cF8, Fm3m, rock salt type (Z = 4)

Hafnium nitride

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2820

3093

2980

1900 (sub.)

1850

2575

1749

760– 899

3310

700

713

n.a.

n.a.

293

210

7.38

8.31

n.a.

210

10.04 126

17

28

3.63

n.a.

17.9

21.6

n.a.

3.2

5.2

2.5– 3.3

2.25

10.1

n.a.

6.12

6.5

n.a.

n.a.

n.a.

304

55

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.26

0.25

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

400– 580

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

750

850

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a.

n.a.

n.a.

7.0– 8.3

6.1

n.a.

n.a.

n.a.

n.a.

Temperature transition at 5.0 K

Most refractory of all nitrides

Decomposed by KOH with evolution of NH3

5.88

Gray solid; slowly hydrolyzed by water

10.89 Bronze or black crystals. (HM>8) Transition temperature 1.8 K. Insoluble in water, slowly attacked by aqua regia, HF, and HNO3

31.38

17 Gray amorphous powder or (HM>9) crystals. Resistant to thermal shock. Good oxidation resistance up to 1500°C but decomposes into nitrogen and silicon above 1850°C. Excellent corrosion resistance to molten nonferrous metals such as Al, 26–35 (HM>9) Pb, Zn, Cd, Bi, Rb, and Sn, and molten salts like NaCl-KCl, NaF, and silicate glasses. However, corroded by molten Mg, Ti, V, Cr, Fe, and Co, cryolite, KOH, and Na2O

13.73 Dark gray crystals. Transition (HM>8) temperature 15.2 K. Insoluble in HCL, HNO3, and H2SO4 but attacked by hot caustic, lime, or strong alkalis evolving NH3

650

16.68

16.08 (HM 8–9)

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 659

Ceramics, Refractories, and Glasses

10

Density (ρ/kg.m–3)

86

6102

Vanadium nitride

VN Cubic [24646-85-3] a = 414.0 pm 64.949 B1, cF8, Fm3m, rock salt type (Z = 4)

n.a.

Uranium nitride U2N3 Cubic 11,240 [12033-83-9] a = 1070 pm 518.259 D53, cI80, Ia3, Mn2O3 type (Z = 16)

n.a.

n.a.

208

17,700

n.a.

14,320

W2N Cubic [12033-72-6] a = 412 pm 381.687 L'1, cP5, Pm3m, Fe4N type (Z = 2)

Tungsten heminitride

Electrical resistivity (ρ/μΩ.cm)

7700

Dielectric permittivity [1MHz] (εr / nil)

Uranium nitride UN Cubic [25658-43-9] a = 489.0 pm 252.096 B1, cF8, Fm3m, rock salt type (Z = 4)

WN2 Hexagonal [60922-26-1] a = 289.3 pm 211.853 c = 282.6 pm

Tungsten dinitride

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Dielectric field strength (Ed/MV.m–1) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Dissipation or tangent loss factor (tanδ)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Melting point (m.p./°C)

21.7

2360

n.a.

2900

593

982

600 (dec.)

2930 (dec.)

Thermal conductivity (k/W.m–1.K–1)

5430

n.a.

188

n.a.

n.a.

n.a.

586

11.25 586

n.a.

12.5

n.a.

n.a.

n.a.

29.1

Specific heat capacity (cP/J.kg–1.K–1)

15,940

TiN Cubic [25583-20-4] a = 424.6 pm 61.874 B1, cF8, Fm3m, rock salt type (Z = 4)

IUPAC name (synonyms, common trade names)

Titanium nitride

Coeff. linear thermal expansion (α /10–6K–1) 8.1

n.a.

9.72

n.a.

n.a.

n.a.

9.35

n.a.

n.a.

149

n.a.

n.a.

n.a.

248

n.a.

Young’s or elastic modulus (E/GPa)

n.a.

n.a.

n.a.

60

n.a.

n.a.

n.a.

n.a.

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

n.a.

n.a.

n.a.

0.24

n.a.

n.a.

n.a.

n.a.

n.a.

Poisson ratio (ν)

1750

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Ultimate tensile strength (σUTS/MPa)

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 972

n.a. n.a.

Flexural strength (τ/MPa)

n.a.

Compressive strength (σ/MPa)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

5.0

n.a.

Fracture toughness (K1C/MPa.m1/2)

n.a.

14.91 (HM 9–10)

4.46

n.a.

n.a.

n.a.

n.a.

18.63 (HM 8–9)

n.a.

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

10,400

Black powder. Transition temperature 7.5 K. Soluble in aqua regia

Gray crystals

Brown crystals

Bronze powder. Transition temperature 4.2 K. Corrosion resistant to molten metals such as Al, Pb, Mg, Zn, Cd, and Bi. Corroded by molten Na, Rb, Ti, V, Cr, Mn, Sn, Ni, Cu, Fe, and Co. Dissolved by boiling aqua regia, decomposed by boiling alkalis evolving NH3

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

Tungsten nitride WN Hexagonal [12058-38-7]

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Th2N3 Hexagonal [12033-90-8] a = 388 pm c = 618 pm D52, hP5, 3m1, La2O3 type (Z = 1)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Thorium nitride

Table 10.22. (continued)

660 Ceramics, Refractories, and Glasses

21.5

50.4

8.5

MoSi2 Tetragonal 6260 [12136-78-6] a = 319 pm 152.11 c = 783 pm C11b, tI6, I4/mmm, MoSi2 type (Z = 2)

5290

9140

NbSi2 Hexagonal [12034-80-9] a = 479 pm 149.77 c = 658 pm C40, hP9, P6222, CrSi2 type (Z = 3)

TaSi2 Hexagonal [12039-79-1] a = 477 pm 237.119 c = 655 pm C40, hP9, P6222, CrSi2 type (Z = 3)

Ta5Si3 Hexagonal [12067-56-0] a = 747.4 pm 988.992 c = 522.5 pm P63/mcm

Molybdenum disilicide

Niobium disilicide

Tantalum disilicide

Tantalum silicide

13,060

n.a.

8030

HfSi2 Orthorhombic [12401-56-8] a = 369 pm 234.66 b = 1446 pm c = 364 pm C49, oC12, Cmcm, ZrSi2 type (Z = 4)

Hafnium disilicide

45.5

6430

Cr3Si Cubic [12018-36-9] a = 456 pm 184.074 A15, cP8, Pm3n, Cr3Si type (Z = 2)

1400

4910

Chromium silicide

13.6

7349

CrSi2 Hexagonal [12018-09-6] a =442 pm 108.167 c = 635 pm C40, hP9, P6222, CrSi2 type (Z = 3)

ZrN Cubic [25658-42-8] a = 457.7 pm 105.231 B1, cF8, Fm3m, rock salt type (Z = 4)

Chromium disilicide

Silicides

Zirconium nitride

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2499

2299

2160

1870

1699

1770

1490– 1550

2980

n.a.

n.a.

n.a.

58.9

n.a.

n.a.

106

20.9

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

377

n.a.

8.8– 9.54

n.a.

8.12

n.a.

10.5

13.0

7.24

n.a.

n.a.

n.a.

407

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

163

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.344 0.165

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

276

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a.

n.a.

n.a.

n.a. 2068– n.a. 2415

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 979

11.77– 14.71

11.77– 15.69

10.30

12.36

8.48– 9.12

9.86

9.77– 11.08

The compound is thermally stable in air up to 400°C

Corroded by molten Ni

The compound is thermally stable in air up to 1000°C. Corrosion resistant to molten metals such as Zn, Pd, Ag, Bi, and Rb. Corroded by liquid metals Mg, Al, Si, V, Cr, Mn, Fe, Ni, Cu, Mo, and Ce

14.51 Yellow solid. Transition (HM>8) temperature 9 K. Corrosion resistant to steel, basic slag, and cryolithe and molten metals such as Al, Pb, Mg, Zn, Cd, and Bi. Corroded by molten Be, Na, Rb, Ti, V, Cr, Mn, Sn, Ni, Cu, Fe, and Co. Soluble in concentrated HF, slowly soluble in hot H2SO4

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 661

Ceramics, Refractories, and Glasses

10

TiSi2 Orthorhombic [12039-83-7] a = 360pm 104.051 b = 1376 pm c = 360 pm C49, oC12, Cmcm, ZrSi2 type (Z = 4)

Ti5Si3 Hexagonal 4320 [12067-57-1] a = 747 pm 323.657 c = 516 pm D88, hP16, P63/mcm, Mn5Si3 type (Z = 2)

WSi2 Tetragonal 9870 [12039-88-2] a = 320 pm 240.01 c = 781 pm C11b, tI6, I4/mmm, MoSi2 type (Z = 2)

W5Si3 Hexagonal [12039-95-1] a = 719 pm 1003.46 c = 485 pm P63/mcm

Tetragonal a = 397 pm c = 1371 pm Cc, tI12, I4/amd, ThSi2 type (Z = 4)

Tetragonal 12,200 a = 733 pm c = 390 pm D5a, tP10, P4/mbm, U3Si2 type (Z = 2)

USi2 294.200

β−U3Si2 770.258

VSi2 Hexagonal [12039-87-1] a = 456 pm 107.112 c = 636 pm C40, hP9, P6222, CrSi2 type (Z = 3)

IUPAC name (synonyms, common trade names)

Titanium trisilicide

Tungsten disilicide

Tungsten silicide

Uranium disilicide

Uranium silicide

Vanadium disilicide

5100

9250

12,210

Electrical resistivity (ρ/μΩ.cm)

9.5

150

n.a.

n.a.

33.4

Dielectric permittivity [1MHz] (εr / nil) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Dielectric field strength (Ed/MV.m–1)

55

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Dissipation or tangent loss factor (tanδ) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Melting point (m.p./°C)

n.a.

1699

1666

1700

2320

2165

2120

1499

Thermal conductivity (k/W.m–1.K–1)

n.a.

n.a.

14.7

n.a.

n.a.

n.a.

n.a.

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

123

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

4150

11.2

14.8

n.a.

n.a.

8.28

11.0

10.4

Young’s or elastic modulus (E/GPa) n.a.

77.9

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

33.1

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

n.a.

n.a.

0.170

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Poisson ratio (ν)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Ultimate tensile strength (σUTS/MPa)

1850

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

Flexural strength (τ/MPa)

n.a.

Compressive strength (σ/MPa)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Fracture toughness (K1C/MPa.m1/2)

n.a.

13.73

7.81

6.86

7.55

10.69

9.67

10.19

10.98

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

n.a.

Corroded by molten Ni

Corrosion resistant to molten Cu; corroded by molten Ni

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

7790

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Titanium disilicide

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

ThSi2 Tetragonal [12067-54-8] a =413 pm 288.209 c =1435 pm Cc, tI12, I4/amd, ThSi2 type (Z = 4)

Density (ρ/kg.m–3)

Thorium disilicide

Table 10.22. (continued)

662 Ceramics, Refractories, and Glasses

α−Al2O3 [1344-28-1] [1302-74-5] 101.961

BeO Trigonal [1304-56-9] (hexagonal) 25.011 a = 270 pm c = 439 pm B4, hP4, P63mc, wurtzite type (Z = 2)

Aluminum sesquioxide (alumina, corundum, saphir)

Beryllium monoxide (beryllia)

Trigonal (rhombohedral) a = 475.91 pm c = 1298.94 pm D51, hR10, R-3c, corundum type (Z=2)

ZrSi2 Orthorhombic [12039-90-6] a = 372 pm 147.395 b = 1469 pm c = 366 pm C49, oC12, Cmcm, ZrSi2 type (Z = 4)

Zirconium disilicide

Oxides

V3Si Cubic [12039-76-8] a = 471 pm 180.9085 A15, cP8, Pm3n, Cr3Si type (Z = 2)

Vanadium silicide

9.1– 9.8

2 ∞ 1023

1.0∞1022

3987

3008– 3030

6.8– 7.66

n.a.

161

4880

n.a.

203

5740

n.a.

n.a.

1604

1732

11.8

0.0004 2550– 2565

28–47 0.0005 2054

n.a.

n.a.

n.a.

n.a.

8.6

8.0.

245– 250

996.5 7.5– 9.7

35.6– 795.5– 7.1– 39 880 8.3

n.a.

n.a.

162– 184

n.a.

n.a.

296.5– n.a. 345

365– 416

n.a.

n.a.

n.a.

234– 496

n.a.

n.a.

n.a.

n.a.

0.340

103.4

0.231– 206– 0.254 255

n.a.

n.a.

n.a.

n.a.

241– 1551 250

3.68

282– 2549– 3.5– 1084 3103 5.0

n.a. n.a.

n.a. n.a.

14.71 (HM 9)

20.59– 29.42 (HM 9)

10.10

14.71

It is the only material with diamond that combines both excellent thermal shock resistance, high electrical resistivity, and high thermal conductivity, and hence is used for heat sinks in electronics. Beryllia is very soluble in water, but slowly in concentrated acids and alkalis. Highly toxic. Exhibits outstanding corrosion resistance to liquid metals Li, Na, Al, Ga, Pb, Ni, and Ir. Readily attacked by molten metals such as Be, Si, Ti, Zr, Nb, Ta, Mo, and W. Maximum service temperature 2400°C.

White and translucent hard material used as abrasive for grinding. Excellent electric insulator and also wear resistant. Insoluble in water and in strong mineral acids, readily soluble in strong alkali hydroxides, attacked by HF or NH4HF2. Owing to its corrosion resistance, in inert atmosphere, in molten metals such as Mg, Ca, Sr, Ba, Mn, Sn, Pb, Ga, Bi, As, Sb, Hg, Mo, W, Co, Ni, Pd, Pt, and U it is used as crucible container for these liquid metals. Alumina is readily attacked in an inert atmosphere by molten metals such as Li, Na, Be, Al, Si, Ti, Zr, Nb, Ta, and Cu. Maximum service temperature 1950°C

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 663

Ceramics, Refractories, and Glasses

10

1.3 ∞ 109 (346°C)

Cr2O3 Trigonal [1308-38-9] (rhombohedral) 151.990 a = 538 pm, 54°50' D51, hR10, R3c, corundum type (Z = 2)

Dy2O3 Cubic 8300 [1308-87-8] D53, cI80, Ia3, 373.00 Mn2O3 type (Z = 16)

Eu2O3 Cubic 7422 [1308-96-9] D53, cI80, Ia3, 351.928 Mn2O3 type (Z = 6)

Gd2O3 Cubic 7630 [12064-62-9] D53, cI80, Ia3, 362.50 Mn2O3 type (Z =1 6)

HfO2 Monoclinic [12055-23-1] [1790°C] 210.489 a = 511.56 pm b = 517.22 pm c = 529.48 pm C43, mP12, P21/c, baddeleyite type (Z = 4)

Chromium oxide (eskolaite)

Dysprosium oxide (dysprosia)

Europium oxide (europia)

Gadolinium oxide (gadolinia)

Hafnium dioxide (hafnia)

IUPAC name (synonyms, common trade names)

9680

n.a.

n.a.

5 ∞1015

n.a.

n.a.

n.a.

Dielectric field strength (Ed/MV.m–1) n.a.

n.a.

n.a.

n.a.

n.a.

Dissipation or tangent loss factor (tanδ)

5220

n.a.

n.a.

n.a.

n.a.

n.a.

Melting point (m.p./°C) 2900

2420

2350

2408

2330

2340

Thermal conductivity (k/W.m–1.K–1)

n.a.

1.14

n.a.

n.a.

n.a.

n.a.

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

n.a.

n.a.

1010 10.6

121

276

n.a.

n.a.

5.85

10.44

7.02.

7.74.

921.1 10.90

389

Young’s or elastic modulus (E/GPa)

n.a.

n.a.

Electrical resistivity (ρ/μΩ.cm)

Cerium dioxide CeO2 Cubic 7650 (ceria, cerianite) [1306-38-3] a = 541.1 pm 172.114 C1, cF12, Fm3m, fluorite type (Z = 4)

57

124

n.a.

n.a.

103

181

Coulomb’s or shear modulus (G/GPa) n.a.

n.a.

n.a.

n.a.

n.a.

70.3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.311

n.a.

Poisson ratio (ν)

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Ultimate tensile strength (σUTS/MPa)

753.1 3.88

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

268

n.a. 589

n.a. n.a.

Flexural strength (τ/MPa)

8–16

Compressive strength (σ/MPa)

2927

n.a.

n.a.

n.a.

n.a.

3.9

n.a.

n.a.

Fracture toughness (K1C/MPa.m1/2)

n.a.

7.65– 10.30

4.71

n.a.

n.a.

29 (HM >8)

(HM 6)

Monoclinic (baddeleyite) below 1790°C, tetragonal above 1790°C

Pale yellow cubic crystals. Abrasive for polishing glass, interference filters, antireflection coating. Insoluble in water, soluble in H2SO4 and HNO3 but insoluble in diluted acid

5.49 White or grayish ceramics. (HM 4.5) Readily absorbs CO2 and water from air to form spent lime and calcium carbonate. Reacts readily with water to give Ca(OH)2. Volumic expansion coefficient 0.225 × 10–9.K–1. Exhibits outstanding corrosion resistance to liquid metals Li and Na

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

n.a.

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

3320

11.1

Density (ρ/kg.m–3)

Dielectric permittivity [1MHz] (εr / nil)

1.0 ∞ 1014

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

CaO Cubic [1305-78-8] a = 481.08 pm 56.077 B2, cP2, Pm3m, CsCl type (Z=1)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Calcium oxide (calcia, lime)

Table 10.22. (continued)

664 Ceramics, Refractories, and Glasses

2202– 2650

α−SiO2 [7631-86-9] [14808-60-7] 60.085

Silicium dioxide (silica, α−quartz)

Trigonal (rhombohedral) a = 491.27 pm c = 540.46 pm C8, hP9, R-3c, α−quartz type (Z=3)

Sm2O3 Cubic 7620 [12060-58-1] D53, cI80, Ia3, 348.72 Mn2O3 type (Z = 16)

Samarium oxide (samaria)

n.a.

3.79

n.a.

1∞1020 50

n.a.

n.a.

n.a.

5.5 ∞ 1012

4470

Nb2O5 Trigonal [1313-96-8] (rhombohedral) 265.810 a = 211.6 pm b = 382.2 pm c = 193.5 pm columbite type

Niobium pentaoxide (columbite, niobia)

9.65– n.a. 9.8

1.3 ∞ 1015

MgO Cubic 3581 [1309-48-4] a = 420 pm 40.304 B1, cF8, Fm3m, rock salt type (Z = 4)

Magnesium monoxide (magnesia, periclase)

n.a.

n.a.

1 ∞ 1014 (550°C)

6510

La2O3 Trigonal [1312-81-8] (hexagonal) 325.809 D52, hP5, P3m1), lanthania type (Z = 1)

Lanthanum dioxide (lanthania)

2350

1520

2852

2315

0.0002 1710

n.a.

n.a.

n.a.

n.a.

288.89 11.9

1.38

2.07

n.a.

787

331

0.55

10.3

502.41 n.a.

50–75 962.3 11.52

n.a.

n.a.

n.a.

n.a.

72.95 29.9

183

n.a.

303.4 117– 130

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.170

n.a.

n.a.

69– 276

n.a.

n.a.

0.33– 200– 0.36 300

n.a.

690– 1380

n.a. n.a.

310

n.a.

0.9– 1.2

n.a.

n.a.

1300– 1.8 1379

n.a. n.a.

441

n.a. n.a.

5.39– 12.36 (HM 7)

4.30

14.71

7.35 (HM 5.5–6)

n.a.

Colorless amorphous (i.e., fused silica) or crystalline (i.e., quartz) material having a low thermal expansion coefficient and excellent optical transmittance in far UV. Silica is insoluble in strong mineral acids and alkalis except HF, concentrated H3PO4, NH4HF2, concentrated alkali metal hydroxides. Owing to its good corrosion resistance to liquid metals such as Si, Ge, Sn, Pb, Ga, In, Tl, Rb, Bi, and Cd, it is used as crucible container for melting these metals, while silica is readily attacked in an inert atmosphere by molten metals such as Li, Na, K Mg, and Al. Quartz crystals are piezoelectric and pyroelectric. Maximum service temperature 1090°C

Dielectric used in film supercapacitors. Insoluble in water, soluble in HF and in hot concentrated H2SO4

White ceramics, with a high reflective index in the visible and near-UV regions. Used as linings in steel furnaces. Crucible container for fluoride melts. Very slowly soluble in pure water but soluble in diluted strong mineral acids. Exhibits outstanding corrosion resistance in liquid metals Mg, Li, and Na. Readily attacked by molten metals Be, Si, Ti, Zr, Nb, and Ta. MgO reacts with water, CO2, and diluted acids. Maximum service temperature 2400°C. Transmittance of 80% and n=1.75 in IR region 7 to 300 μm

Insoluble in water, soluble in diluted strong mineral acids

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 665

Ceramics, Refractories, and Glasses

10

TiO2 [13463-67-7] [1317-70-0] 79.866

TiO2 [13463-67-7] [12188-41-9] 79.866

IUPAC name (synonyms, common trade names)

Titanium dioxide (Anatase)

Titanium dioxide (brookite)

Orthorhombic 4130 a = 545.6 pm b = 918.2 pm c = 514.3 pm C21, oP24, Pbca brookite type, Z = 8 Ti-O: 184 pm – 203 pm

Dielectric field strength (Ed/MV.m–1) n.a.

Dissipation or tangent loss factor (tanδ)

n.a.

n.a.

Melting point (m.p./°C) 1750

n.a.

n.a.

14.19 272.14 9.54

700°C n.a. (rutile)

3390

Thermal conductivity (k/W.m–1.K–1)

n.a.

Specific heat capacity (cP/J.kg–1.K–1)

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

n.a.

n.a.

Electrical resistivity (ρ/μΩ.cm)

4 ∞ 1019

Young’s or elastic modulus (E/GPa) n.a.

n.a.

144.8 94.2

n.a.

Coulomb’s or shear modulus (G/GPa)

n.a.

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

301.5 n.a.

n.a.

0.280

n.a.

Poisson ratio (ν)

n.a.

n.a.

96.5

n.a.

Ultimate tensile strength (σUTS/MPa)

1882

n.a. n.a.

n.a. 1475

n.a. n.a.

Flexural strength (τ/MPa)

n.a.

Compressive strength (σ/MPa)

n.a.

n.a.

1.07

0.9

Fracture toughness (K1C/MPa.m1/2)

3900 [3890]

n.a.

Dielectric used in film supercapacitors. Tantalum oxide is a high-refractiveindex, low-absorption material used in making optical coatings in the near-UV (350 nm) to IR (8 μm). Insoluble in most chemicals except HF, HF-HNO3 mixtures, oleum, fused alkali hydroxides (e.g., NaOH, KOH), and molten pyrosulfates

(HM 5.5–6.0)

(HM 5.5–6)

Metastable over long periods of time despite being less thermodynamically stable than rutile. However, above 700°C, the irreversible and rapid monotropic conversion of anatase to rutile occurs. It exhibits a greater transparency in the near-UV than rutile. With an absorption edge at 385 nm, anatase absorbs less light at the blue end of the visible spectrum and has a blue tone

9.27 Corrosion-resistant container (HM 6.5) material for molten metals Na, Hf, Ir, Ni, Mo, Mn, Th, and U. Corroded by liquid metals Be, Si, Ti, Zr, Nb, and Bi. Radioactive

n.a.

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

Tetragonal a = 379.3 pm c = 951.2 pm C5, tI12, I41/amd, Anatase type (Z = 4) Ti-O: 191pm (2) 195 pm (4) Packing fraction: 70%

ThO2 Cubic 9860 [1314-20-1] a = 559.52 pm 264.037 C1, cF12, Fm3m, fluorite type (Z= 4)

Dielectric permittivity [1MHz] (εr / nil)

1.0 ∞ 1012

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

8200

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Thorium dioxide (thoria, thorianite)

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

Ta2O5 Trigonal [1314-61-0] (rhombohedral) 441.893 columbite type

Density (ρ/kg.m–3)

Tantalum pentaoxide (tantalite, tantala)

Table 10.22. (continued)

666 Ceramics, Refractories, and Glasses

1839

1847

4486

n.a.

Ti2O3 Trigonal [1344-54-3] (rhombohedral) 143.3382 a = 515.5 pm c = 1361 pm D51, hR10, R-3c corundum type (Z=2)

769

Titanium sesquioxide

110– 117

1750

1019

TiO Cubic 4888 [12137-20-1] a = 417 pm 63.6694 B1, cF8, Fm3m rock salt type (Z = 4)

4240 [4250]

Titanium monoxide (hongquiite)

Tetragonal a = 459.37 pm c = 296.18 pm C4, tP6, P4/mnm rutile type (Z =2) Ti-O: 194.4 pm (4) 198.8 pm (2), packing fraction 77%

TiO2 [13463-67-7] [1317-80-2] 79.866

Titanium dioxide (rutile, titania)

10.4 (// c) 7.4 (⊥ c)

679

628

711

9.19

7.14

248– 282

111

206– 282

0.278

69– 103

340

800– 940

2.8

10.89 (HM 7–7.5)

Dark-violet to purple-violet solid. It can be prepared by mixing stoichiometric amounts of Ti and TiO2 heated in a Mo-crucible at 1600°C. Slightly paramagnetic solid with χm = +63 × 10–6 emu

Gold-bronze solid. Prepared by mixing stoichiometric amounts of Ti and TiO2 heated in a Mo-crucible at 1600°C or by the reduction of TiO2 with H2 under pressure at 130 atm and 2000°C. Slightly paramagnetic solid with χm = +88 × 10–6 emu

White solid that exhibits a high refractive index, even higher than that of diamond. Transparent from visible to near-infrared radiation (i.e., 408 nm to 5000 nm). On the blue end of the visible spectrum the strong absorption band at 385 nm renders rutile powder slightly brighter than anatase, explaining its typical yellow undertone. When heated in air to 900°C the powdered material becomes lemon-yellow and exhibits a maximum absorption edge at 476 nm but coloring disappears on cooling. Doped rutile is phototropic, i.e., it exhibits a reversible darkening when exposed to light. Readily soluble in HF and in concentrated H2SO4 . Reacts rapidly in molten alkali hydroxides and fused alkali carbonates. Corrosion resistant to liquid Ni and Mo. Readily attacked in an inert atmosphere by molten Be, Si, Ti, Zr, Nb, and Ta

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 667

Ceramics, Refractories, and Glasses

10

Crystal system, lattice parameters, structure type, Strukturbericht, Pearson, space group, structure type (Z)

IUPAC name (synonyms, common trade names)

Zirconium ZrO2 Tetragonal dioxide [1314-23-4] C4, tP6 P42/mnm, [tetragonal 123.223 rutile type (Z=2) zirconia phase (TZP), >1170°C]

Monoclinic a = 514.54 pm b = 520.75 pm c = 531.07 pm 99.23° C43, mP12, P21/c, baddeleyite type (Z = 4)

ZrO2 [1314-23-4] [12036-23-6] 123.223

Zirconium dioxide (baddeleyite, monoclinic zirconia)

5680– 6050

5850

n.a.

n.a.

2.3 × 1010

7.7 × 107 n.a.

n.a.

n.a.

n.a.

2710

2710

Thermal conductivity (k/W.m–1.K–1)

2439

Specific heat capacity (cP/J.kg–1.K–1)

n.a.

n.a.

n.a.

n.a.

n.a.

711

74.2

241

n.a.

97

114.5 48.3

10–11 200– 210

7.56

439.62 8.10

Young’s or elastic modulus (E/GPa) 145

Coulomb’s or shear modulus (G/GPa)

n.a.

Coeff. linear thermal expansion (α /10–6K–1)

10.04 234.31 11.2

n.a.

n.a.

n.a.

n.a.

Bulk or compression modulus (K/GPa)

n.a.

2880

0.310

0.337

0.186

0.302

Poisson ratio (ν)

n.a.

Dissipation or tangent loss factor (tanδ) n.a.

n.a.

n.a.

n.a.

n.a.

Ultimate tensile strength (σUTS/MPa)

5030

Dielectric field strength (Ed/MV.m–1) n.a.

9.2

0.71

n.a.

800– >2900 7–12 1200

2068 n.a.

n.a. 393

n.a. n.a.

Flexural strength (τ/MPa)

Y2O3 Trigonal [1314-36-9] (Hexagonal) 225.81 D52, hP5, P3m1, lanthania type (Z = 1)

Dielectric permittivity [1MHz] (εr / nil) n.a.

Compressive strength (σ/MPa)

Yttrium oxide (yttria)

Electrical resistivity (ρ/μΩ.cm)

3.8 × 1010

Fracture toughness (K1C/MPa.m1/2)

UO2 Cubic 10,960 [1344-57-6] a = 546.82 pm 270.028 C1, cF12, Fm3m, fluorite type (Z= 4)

Yttria is a medium-refractiveindex, low-absorption material used for optical coating in the near-UV (300 nm) to IR (12 μm) regions and hence used to protect Al and Ag mirrors. Used for crucibles containing molten lithium

Used in nuclear power reactors as nuclear-fuel-sintered element containing either natural or enriched uranium

Dark blue crystals. Anasovite Type II is similar to that identified in titania slags.29 Can be stabilized at room temperature with a small amount of iron

11.77 Monoclinic zirconia (HM 6.5) (baddeleyite structure) stable below 1197°C, tetragonal zirconia (rutile structure) stable between 1197 and 2300°C, cubic zirconia (fluorine structure) stable above 2300°C or at lower temperature if stabilized by addition of magnesia, calcia or 12.5 yttria. Maximum service temperature 2400°C. Zirconia starts to act as an oxygen anion conductor at 1200°C. Highly

6.86

5.88 (HM 6–7)

Vickers or Knoop Hardness (HV or HK/GPa) (/HM)

Uranium dioxide (uraninite)

Melting point (m.p./°C) 1777

Other physicochemical Properties, oxidation and corrosion resistance, and major uses.

High temperature: pseudobrookite orthorhombic Cc mC32

Theoretical chemical formula, [CAS RN], relative molecular mass (12C = 12.000)

Ti3O5 Dimorphic (120°C) 4900 [12065-65-5] 223.0070 Low temperature: anasovite type monoclinic C2/m (Z = 4) mC32 a = 975.2 pm b = 380.2 pm c = 944.2 pm β = 91.55°

Density (ρ/kg.m–3)

Trititanium pentoxide (anasovite)

Table 10.22. (continued)

668 Ceramics, Refractories, and Glasses

28

29

n.a.

24.7

n.a.

n.a.

400– 480

n.a.

n.a.

n.a.

n.a.

2710

2710

n.a.

n.a.

1.8

n.a.

n.a.

400

n.a.

n.a.

10.1

n.a.

n.a.

200

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.230

n.a.

n.a.

700

n.a.

1850

n.a. n.a.

690

n.a. n.a.

9.2– 10

9.0– 9.5

n.a.

n.a.

15.69

n.a.

corrosion resistant to molten metals such as Bi, Hf, Ir, Pt, Fe, Ni, Mo, Pu, and V. Strongly attacked by liquid metals Be, Li, Na, K, Si, Ti, Zr, and Nb. Insoluble in water, but slowly soluble in HCl and HNO3; soluble in boiling concentrated H2SO4 and alkali hydroxides but readily attacked by HF

Corrosion data in molten salts from: Geirnaert, G. (1970) Céramiques et métaux liquides: compatibilités et angles de mouillages. Bull. Soc. Fr. Ceram. 106, 7–50. Reznichenko, V.A.; Khalimov, F.B. (1959) Reduction of titanium dioxide with hydrogen. Titan i Ego Splavy, 2, 11–15.

n.a.

n.a.

ZrO2 Cubic 5800– [1314-23-4] C1, cF12, Fm3m, 6045 [64417-98-7] fluorite type (Z = 4) 123.223

Zirconium dioxide [partially stabilized zirconia (PSZ) with MgO]

Zirconium ZrO2 Cubic 6045 dioxide TTZ [1314-23-4] C1, cF12, Fm3m, (stabilized Y2O3) [64417-98-7] fluorite type (Z = 4) 123.223

n.a.

ZrO2 Cubic 6045 [1314-23-4] C1, cF12, Fm3m, [64417-98-7] fluorite type (Z= 4) 123.223

Zirconium dioxide [yttriastabilized zirconia (YSZ) with 8–10 mol.% Y2O3]

Properties of Pure Ceramics (Borides, Carbides, Nitrides, Silicides, and Oxides) 669

Ceramics, Refractories, and Glasses

10

670

Ceramics, Refractories, and Glasses

10.8 Further Reading 10.8.1 Traditional and Advanced Ceramics ALPER, A.M. (ed.) (1970–1971) High Temperature Oxides, 4 volumes. Academic, New York. ARONSSON, B.; LUNDSTROM, T.; RUNDQUIST, S. (1965) Borides, Silicides, and Phosphides. Methuen, London. BILLUPS, W.E.; CIUFOLINI, M.A. (1993) Buckminsterfullerenes. VCH, Weinheim. BLESA, M.A.; MORANDO, P.J.; REGAZZONI, A.E. (1994) Chemical Dissolution of Metal Oxides. CRC Press, Boca Raton, FL. BRADSHAW, W.G.; MATTHEWS, C.O. (1958) Properties of Refractory Materials: Collected Data and References. Lockheed Aircraft, Sunnyvale, CA, U.S. Government Report AD 205 452. BRIXNER, L.H. (1967) High Temperature Materials and Technology. Wiley, New York. FREER, R. (1989) The Physics and Chemistry of Carbides, Nitrides and Borides. Kluwer, Boston. GOODENOUGH, J.B.; LONGO, J.M. (1970) Crystallographic and Magnetic Properties of Perovskite and Perovskite related Compounds. Springer, Berlin Heidelberg New York. KOSOLAPOVA, T.A. (1971) Carbides, Properties, Productions, and Applications. Plenum, New York. MATKOVICH, V.I. (ed.) (1977) Boron and Refractory Borides. Springer, Berlin Heidelberg New York. MATKOVICH, V.I.; SAMSONOV, G.V., HAGENMULLER, P.; LUNDSTROM, T. (1977) Boron and Refractory Borides. Springer, Berlin Heidelberg New York. PIERSON, H.O. (1996) Handbook of Refractory Carbides and Nitrides: Properties, Characteristics, Processing and Applications. Noyes, Westwood, NJ. SAMSONOV, G.V. (1974) The Oxides Handbook. Plenum, New York. SINGER, F.; SINGER, S.S. (1963) Industrial Ceramics. Chemical Publishing Company, New York. STORMS, E.K. (1967) The Refractory Carbides. Academic, New York. TOTH, L.E. (1971) Transition Metals Carbides and Nitrides. Academic, New York. TOROPOV, N.A. (ed.) Phase Diagrams of Silicates Systems Handbook. Document NTIS AD 787517.

10.8.2 Refractories ANDREW, W. (1992) Handbook of Industrial Refractories: Technology, Principles, Types and Properties. Noyes, Westwood, NJ. BANERJEE, S. (1998) Monolithic Refractories: A Comprehensive Handbook. World Scientific, Singapore. CAMPBELL, I.E.; SHERWOOD, E.M. (ed.) (1967) High-temperature Materials and Technology. Wiley, New York. CARNIGLIA, S.L.; BARNA, G.L. (1992) Handbook of Industrial Refractories Technology: Principles, Types, Properties, and Applications. Noyes, Park Ridge, NJ. CHESTERS, J.H. (1974) Refractories for Iron and Steelmaking. Metals Society, London. CHESTERS, J.H. (1973) Refractories: Production and Properties. Iron and Steel Institute (ISI), London. Collective (1984) Technology of Monolithic Refractories. Plibrico Japan Company, Tokyo. JOURDAIN, A. (1966) La technologie des produits céramiques réfractaires. Gauthier-Villars, Paris. KUMASHIRO, Y. (2000) Electric Refractory Materials. Marcel Dekker, New York. LETORT, Y.; HALM, L. (1953) Produits réfractaires et isolants: nature, fabrication, et utilisation. Centre d’études supérieures de la sidérurgie (CESS), Metz. NORTON, F.H. (1968) Refractories, 4th ed. McGraw-Hill, New York. OATES, J.A.H. (1998) Lime and Limestone: Chemistry and Technology, Production and Uses. Wiley-VCH, Weinheim. PINCUS, A.G. (1980) Refractories in the Glass Industry. Books for Industry, Glass Industry Magazine, New York. SCHACHT, C. (2004) Refractories Handbook. CRC Press, Boca Raton, FL. SCHWARZKOPF, P.; KIEFFER, R. (eds.) (1953) Refractory Hard Metals: Borides, Carbides, Nitrides, and Silicides. Macmillan, New York. STORMS, E.K. (1967) The Refractory Carbides. Academic, New York. TAKAMIYA,Y.; ENDO,Y.; HOSOKAWA, S. (1998) Refractories Handbook. American Ceramic Society (ACerS) Westerville, OH.

Glasses

671

10.9 Glasses 10.9.1 Definitions Glass is, from a thermodynamic point of view, a supercooled liquid, i.e., a molten liquid cooled at a rate sufficiently rapid to fix the random microscopic organization of a liquid and avoid the crystallization process to operate. Therefore, by contrast with crystallized solids, glasses do not exhibit a clear melting temperature and the structural change is only reported by an inflection in the temperature-time curve. This change is called the glass transition temperature. As a general rule, glasses are amorphous inorganic solids usually made of silicates, but other inorganic or organic compounds can exhibit a vitreous structure (e.g., sulfides, polymers). As a general rule, commercial glasses are hard but both brittle and thermal-shock-sensitive materials, excellent electrical insulators, optically transparent media, and exhibit for certain particular chemical compositions (e.g., Vycor® and borosilicated glasses, such as Pyrex®) an excellent corrosion resistance to a wide range of chemicals except hydrofluoric acid, ammonium fluoride, and strong alkali-metal hydroxides and other strong alkalis. Owing to their good transmission in the visible range, glasses are extensively used for optical lenses, sight lenses, and windows. while corrosion-resistant glasses are widely used for cookware and laboratory glassware. The basic components of silicate glasses are silica, SiO2 (e.g., from siliceous sand), lime, CaO (i.e., from fired limestone, CaCO3), and soda, Na2O (i.e., from soda ash, Na2CO3). Other oxides are used for special purposes such as boric acid (B2O3), potash (K2O), baria (BaO), and lithia (Li2O), while colored glasses require minute additions of transition-metal oxides (e.g., FeO, Co2O3). Silicate glasses can be grouped into the following categories: A-glass (i.e., high alkali or soda-lime), C-glass (i.e., chemical resistant), E-glass (i.e., calcium alumino borosilicate or borosilicated glasses), and S-glass (i.e., high strength magnesium alumino silicate).

10.9.2 Physical Properties of Glasses See Table 10.23, pages 672–675.

10.9.3 Glassmaking Processes The majority of industrial glass is produced by continuous melting processes, while batchtype processes are restricted to customized formulations for special purposes. Large-scale production of industrial glasses utilizes huge melting crucibles with a rectangular shape called glass tanks that are heated from the bottom and sidewalls by natural gas or oil burners; sometimes auxiliary electric heaters immersed in the melt (i.e., booster electrodes) are used to provide additional heat. The temperature of the melt can be as high as 1660°C to ensure the complete melting of alumina-rich raw materials (Ca-feldspars); the specific energy consumption is about 2.8 kWh/kg of glass. Commercial glass tanks can hold up to 1200 tonnes of molten glass. The thick bottom and sidewalls are built with refractory materials, usually mullite bricks, while electrofused alumina-silica-zirconia bricks are used for the inner layer, which is in direct contact with the melt. The vault or cupola is usually made of silica bricks. The glass tank is divided into two distinct sections called the melting end where the feed (i.e., cullet and raw materials) is introduced, while in the second section, called the working or refining end, the molten glass reaches its working viscosity. The division between the two sections can be either permanent with a refractory barrier or using mobile baffles.

10 Ceramics, Refractories, and Glasses

Chemical composition (wt.%)

73SiO2-17Na2O-5CaO-4MgO-1Al2O3

56SiO2-29PbO-9K2O-4Na2O-2Al2O3

52.5SiO2-28PbO-13K2O-5SrO1Al2O3-0.5Na2O

54SiO2-23PbO-8K2O-6Na2O-5SrO2Al2O3-3CaO-2MgO

56SiO2-31PbO-8Na2O-5SrO-4K2O1Al2O3-1Li2O-1Sb2O3-1As2O3

74SiO2-14Na2O-9CaO-1Al2O3-1B2O30.3Sb2O3-0.1As2O3

61SiO2-17Al2O3-13Na2O-3K2O3MgO-1TiO2-1As2O3-0.4CaO

63SiO2-12Al2O3-13B2O3-6Na2O-5Li2O

66SiO2-21Al2O3-9Na2O-4Li2O1MgO-0.2K2O

60SiO2-10Al2O3-10ZnO-8Na2O5CaO-2K2O-1B2O3

74PbO-12B2O3-11Al2O3-3SiO2

Glass trade name

Corning® 0080 (light bulb)

Corning® 0120 (potash soda lead glass)

Corning® 0137 (potash soda lead glass)

Corning® 0138 (potash soda lead glass)

Corning® 0160 (crystal glass)

Corning® 0281 (glassware)

Corning® 0317 (aircraft window)

Corning® 0320 (tape reel)

Corning® 0331 (centrifuge tubes)

Corning® 6720 (tableware)

Corning® 7570 (high leaded glass)

Table 10.23. Physical properties of selected commercial glasses Thermal conductivity –1 –1 (k/W.m .K )

Knoop hardness (HK) 30

Poisson ratio (ν/nil)

Young’s modulus (E/GPa)

Density (kg.m ) –3

0.22

0.22

5420 56 0.28 n.a. n.a.

2410

2380

2450

2480 73 0.22

0.22

Coefficient linear thermal –6 –1 expansion (0–300°C) (10 K )

2570

8.40

7.55

7.07

8.7

8.7

31

9.30

32

3090 n.a. 0.22

Annealing point (°C)

9.85

Strain point (/°C) 33

3020 n.a. 0.22

Softening point (°C)

9.70

34

3180 n.a. 0.22

Working point (°C)

342 363 440 558 100

510 548

463 493 638

574 624 871

500 540 719

367 405 583

450 490 670

436 478 661 977

395 435 630 985

Refractive index at 589.3nm (nD/nil)

8.95

Relative permittivity at 1MHz (εr/nil)

1.860 15

1.506

1.515

1.569

1.563

1.570

1.560 6.7

1.512 7.2

n.a.

Dielectric field strength –1 (Ed/MV.m )

3050 59 0.22 382

Continuous operating temperature (°C)

473 514 696 1005 110

12.8

17

0.0022 10

0.008 10

17

0.009 10

Loss factor (tanδ/nil)

9.35

Electrical volume resistivity (Ω.m)

2470 71 0.22 465 n.a.

672 Ceramics, Refractories, and Glasses

Specific heat capacity –1 –1 (cP/J.kg .K )

54SiO2-14Al2O3-10B2O3-17.5CaO4.5MgO

E-Glass (electrical glass)

4.60 3.20

2570 76 0.22 593 0.98

2230 76 0.20 418 1.13 2220 64.3 n.a. n.a. n.a. 2470 2340 n.a. n.a.

46SiO2-17MgO-16Al2O3-10K2O7B2O3-4F (55 wt.% fluorophlogopite and 45 wt.% borosilicate glass)

65SiO2-2Al2O3-5.9CaO-7ZnO-9B2O37Na2O-7K2O-3TiO2

49SiO2-25BaO-15B2O3-10Al2O3-1As2O3 2760 2130 52 0.22 n.a.

Leaded glass

72SiO2-25B2O3-1Al2O3-1K2O-0.5Li2O0.5Na2O

80.6SiO2-13B2O3-4Na2O-2.3Al2O30.1K2O

81SiO2-13B2O3-3Na2O-2Al2O3-1K2O

70SiO2-10B2O3-9Na2O-6Al2O3-2BaO1K2O-1CaO-0.5MgO-0.5ZnO

72SiO2-11B2O3-7Na2O-6Al2O3-2CaO1K2O-1BaO

Kimble®EG11

Macor® (machinable glass)

Pyrex® 0211 (microsheet glass)

Pyrex® 7059 (substrate glass)

Pyrex® 7070

Pyrex®7740 (Labware)

Pyrex®7789

Pyrex®7799

Pyrex®7800 (pharmaceutical glass)

790

2520 66.9 0.29

74SiO2-15Na2O-5CaO-4MgO-1Al2O3

Float glass (soda lime glass) 1.46

2850 n.a n.a. n.a.

65SiO2-10SrO-9K2O-7Na2O-2Al2O32CaO-2BaO-2PbO-1MgO-1TiO2-1CeO2

Corning® 9068 (color TV panel)

6.20

3.25

3.25

7.38

9.30

10.80

8.90

2530 72 0.23 n.a. 0.937

68SiO2-12B2O3-4Al2O3-6K2O-5Na2O3Li2O-1TiO2-1CeO2

Corning® 9025 (cathodic ray tube panel)

5.6

5.0

65SiO2-25Al2O3-10MgO

2490 87

2600 72

S-Glass (high-strength glass)

C-Glass 65SiO2-4Al2O3-5.5B2O3-14CaO-3MgO(chemically resistant glass) 8Na2O-0.5K2O

44SiO2-24PbO-21BaO-6Na2O-4ZnO1CaO-5ZrO2-3TiO2-2La2O3-0.1Sb2O30.1As2O3

Corning® 8078 (ophthalmic glass)

525 560 740

510 560 815 n.a. n.a.

510 560 821 1252 230

456 496 n.a. n.a. 230

593 639 844

508 550 720 1008

800 (1000)

394 434 626 980 n.a.

514 546 726 n.a. 230

760

600

1.474

1.474 4.6

1.469 4.1

1.533

1.523 6.7

6.03

1.540 n.a.

1.523 n.a.

5.2

6.1

n.a.

n.a.

9.40

n.a.

n.a.

16

10

9

n.a.

17

0.005 10

17

0.006 10

0.005

0.0047 10

n.a.

n.a.

Glasses 673

Ceramics, Refractories, and Glasses

10

Specific heat capacity –1 –1 (cP/J.kg .K )

Thermal conductivity –1 –1 (k/W.m .K )

Knoop hardness (HK) 30

Poisson ratio (ν/nil)

Young’s modulus (E/GPa)

Density (kg.m ) –3

Glass trade name 2460 74 0.210 560 1.069 825 2510 82 0.206 610 1.114 858 2270 46 0.243 380 0.90

2450 62 0.232 520 0.925 808 3730 81 0.293 430 0.911 636 3640 78 0.291 400 0.861 716 3180 76 0.286 390 n.a.

2590 71 0.224 530 0.950 783

Schott®BK1 (borosilicate crown)

Schott®BK7 (borosilicate crown)

Schott®FK3 (fluoro crown)

Schott®FK5 (fluoro crown)

Schott®FK51 (fluoro crown)

Schott®FK52 (fluoro crown)

Schott®FK54 (fluoro crown)

Schott®K5 (crown)

n.a.

840

3190 73 0.252 530 0.795 687

Coefficient linear thermal –6 –1 expansion (0–300°C) (10 K )

Schott®BaK1 (barium crown)

31

3980 379 0.29 1500 16–23

32

fused Al2O3

Strain point (/°C) 33

Sapphire glass

Annealing point (°C)

800

Softening point (°C)

438

34

2580 93 0.25 n.a. 1.6

Working point (°C)

2302

Continuous operating temperature (°C)

Pyroceramics

9.60

16.50

16.00

15.30

10.00

9.40

8.30

8.80

8.60

n.a.

0.5

5.70 n.a.

467 502 676 680

Refractive index at 589.3nm (nD/nil) 1.5225

1.4370

1.4861

1.4866

1.4875

1.4650

1.5168

1.5101

1.5725

1.492

9–11

1.458 3.8

Relative permittivity at 1MHz (εr/nil)

0.552–0.75 890 1020 1530 n.a. 900

n.a.

Dielectric field strength –1 (Ed/MV.m )

2180 89 0.19 487 0.19

17

48

18

10

0.0015 10

Loss factor (tanδ/nil)

Robax® (fire-resistant glass)

96.5SiO2-3B2O3-0.5Al2O3

Electrical volume resistivity (Ω.m)

Pyrex®plus

Chemical composition (wt.%)

Pyrex®7913 (Vycor® HT)

Table 10.23. (continued)

674 Ceramics, Refractories, and Glasses

34

33

32

31

30

Microhardness 100-g-force load 15.5 For a dynamic viscosity of 10 Pa.s 13 For a dynamic viscosity of 10 Pa.s 8.6 For a dynamic viscosity of 10 Pa.s 4 For a dynamic viscosity of 10 Pa.s

Schott®ZKN7

Schott®SK2 (heavy crown)

Schott®SF63 (heavy flint)

Schott®SF11 (heavy flint)

Schott®PSK3 (heavy phosphate crown)

Schott®PK50 (phosphate crown)

Schott®PK3 (phosphate crown)

Schott®LF5 (lanthanum flint)

Schott®LaK9 (lanthanum flint)

Schott®KF9 (crown flint)

7.90 7.50 10.60 8.30 10.30 7.30 6.80 9.00 7.10 5.20

2710 67 0.202 490 1.160 490 3510 110 0.285 700 0.908 649 3220 59 0.223 450 0.866 657 2590 84 0.209 640 1.193 779 2590 66 0.235 430 0.772 812 2910 84 0.226 630 0.990 682 4740 66 0.235 450 0.744 450 4620 58 0.235 390 0.744 431 3550 78 0.263 550 0.776 595 2490 70 0.214 530 1.042 770

1.5085

1.6074

1.7484

1.7845

1.5523

1.5205

1.5254

1.5814

1.6910

1.5474

Glasses 675

Ceramics, Refractories, and Glasses

10

676

Ceramics, Refractories, and Glasses

Float glass (annealed glass). Historically, two techniques were used to produce sheets of glass. Flat glass was obtained by extruding and rolling a softened mass of glass, while cylinder glass was obtained by blowing molten glass into a cylindrical iron mold. The ends were cut and removed while a cut was made on the overall length of the cylinder. The cut cylinder was then placed in an oven, where the cylinder bent flat into a glass sheet. In both processes, from an optical point of view, the surfaces were rarely parallel, leading to optical distortions. By contrast, today 90% of the flat glass produced worldwide is obtained by the float glass process invented in the 1950s by Sir Alastair Pilkington of Pilkington Glass Co. In the float glass process, molten glass exiting a melting furnace is poured onto a bath of molten tin metal. The glass floats on the specular surface of the molten tin and levels out as it spreads along the bath, providing a smooth finish on both sides. The glass cools and slowly solidifies as it travels over the molten tin and leaves the tin bath in a continuous ribbon. The glass is then fire-polished. The finished product has near-perfect parallel surfaces.The only drawback of annealed glass is that upon mechanical stress it breaks into large and sharp pieces that can cause serious injury. For that reason, building codes worldwide prohibit the use of annealed glass where there is a high risk of breakage and injury. Tempered glass (toughened glass, safety glass). Tempered glass is obtained after applying a thermal tempering process to annealed glass. The glass is cut to the required size and any required processing such as polishing or drilling is carried out before the tempering process begins. The hot glass at 600°C coming from an annealing furnace is placed onto a roller table. The glass is then quenched with forced cold air convection. This rapidly cools the glass surface below its annealing point, causing it to harden and contract, while the inner core of the glass remains free to flow for a short time. The final contraction of the inner layer induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. This typical pattern of cooling can be observed under polarized light. Tempered glass exhibits typically a mechanical strength six times that of annealed glass and hence it is also called toughened glass. However, this increased mechanical strength has a drawback. Due to the balanced stresses in the glass, any damage to the glass edges will result in the glass shattering into small sized pieces, and for that reason it is also called safety glass under the tradename Securit®. Therefore, the glass must be cut to size before toughening and cannot be reworked once tempered. Moreover, the toughened glass surface is less hard than annealed glass and more prone to scratching. Laminated glass. This multilayered composite material was first invented in 1903 by the French chemist Edouard Benedictus, who had been inspired by the breaking resistance of a glass flask coated with a layer of cellulose nitrate. Today, laminated glass is currently produced by bonding two or more layers of ordinary annealed glass together with a plastic interlayer of polyvinyl butyral (PVB). The polymer is sandwiched by the glass, which is then heated to around 70°C and passed through rollers to expel any air pockets and form the initial bond. A typical laminate has a 3-mm layer of glass, 0.38-mm interlayer, and another 3-mm layer of glass. This gives a final product that would be referred to as 6.38 laminated glass. The plastic interlayer keeps the two sheets of glass tightly bound even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. Multiple laminates and thicker glass increase the strength. Bulletproof glass panels, made up of thick glass and several interlayers, can be as thick as 50 mm. The plastic interlayer also gives the glass a much higher acoustic insulation rating due to the damping effect.

10.9.4 Further Reading BACH, H; NEUROTH, N. (1998) The Properties of Optical Glass. Springer, Berlin Heidelberg New York. EITEL, W. (ed.) (1964–1973) Silicate Science, 6 volumes. Academic, New York. FELTZ, A. (1993) Amorphous Inorganic Materials and Glasses. VCH, Weinheim.

Proppants

677

JONES, G.O. (1956) Glass. Wiley, New York. MOREY, G.W. (1954) The Properties of Glasses, 2nd. ed. Reinhold-Van Nostrand, New York. SHAND, E.B. (1958) Glass Engineering Handbook. McGraw-Hill, New York. STANWORTH, J.E. (1950) The Physical Properties of Glasses. Clarendon, Oxford. ZARZYCKY, J. (1981) Les verres et l’état vitreux. Masson, Paris.

10.10 Proppants 10.10.1 Fracturing Techniques in Oil-Well Production Under the constant pressure of the market and the prediction of long-term depletion of oil resources, the oil and gas industry has constantly increased the productivity and injectivity of production wells. For instance, today, by increasing the drilling depth, it is possible to recover oil and natural gas from remote and shallow reservoirs. However, to recover fossil fuels more efficiently from existing or new oil fields exhibiting low original permeability, some additional techniques must be used for better results. Actually, in many cases including severe damage around well-bore, complex beds, layered unconnected reservoirs, or laminated reservoirs with low permeability, the best known techniques for the treatment of reservoir beds are the fracturing technologies, which provide the only stimulation method possible. These techniques will be briefly described in the next several paragraphs. There are basically two methods in the industry to stimulate well production by extensive improve35 ment of the inflow conditions in a reservoir bed : hydraulic fracturing and, to a lesser extent, pressure acidizing, which is restricted to carbonated rocks (e.g., limestones and dolomites). As mentioned previously, the aim of both types of stimulation is to improve the cumulative production versus time behavior of an oil well.

10.10.1.1 Hydraulic Fracturing 36

This technique was developed by the oil industry in the 1940s for opening up tight reservoir rocks to improve product recovery. It consists in pumping and injecting a fluid into the production well until the hydrostatic pressure increases to a level sufficient to expand the strata and fracture the rock, which results in the creation of a network of cracks in the rock formation. The pumping rate is high enough to overcome the maximum rate of fluid loss in the medium to be fractured. The fractures produced are generally only a few millimeters wide, but they may be either horizontal or vertical depending on the path of least resistance. With a widening fracture, the oil increasingly migrates into the pore space of the rocks. Therefore, the presence of high-conductivity fractures affects the overall oil mass transfer efficiency, and they have a significant impact on reservoir performance. To insure the success of reservoir-bed treatment, a sufficient depth of penetration must be achieved originating at the well bore and extending into the rock mass. Usually, a penetration depth of 40 to 70 m is common. After the porous rock has been fractured, it is necessary to prop open the newly formed cracks to act against the closure stress in order to facilitate the continued flow of gas and oil and to avoid the catastrophic collapse of reservoir walls due to the elevated surrounding lithostatic pressure. If the cracks were not propped open, they would close under the overburden. The most common technique consist in pumping a slurry made of a mixture of viscous carrier fluid (i.e., frac fluid: water or brines) and solid particulate materials into the 35

36

Rischmuller, H. (1993) Resources of Oil and Gas. In: Ullmann’s Encyclopedia of Industrial Chemistry, Vol. A23. VCH, Weinheim, p. 183. The reservoir is the underground formation where oil and gas has accumulated. It consists of a porous rock to hold the oil or gas, and an impervious cap rock that prevents them to escape.

10 Ceramics, Refractories, and Glasses

678

Ceramics, Refractories, and Glasses

fractured formation. The particulate materials are called propping agent or, most commonly, proppants. Note that at the end of the treatment, the proppant slurry is displaced from the well bore and tubing by a clean flush fluid. However, the volume of flush fluid must be accurately determined so as not to release the proppants into the reservoir. In conclusion, proppants are agents that keep cracks open against closure stresses, avoid the collapse of reservoir walls, and insure an efficient mass transfer for both oil and gas while the production well is moved to another location. Note that hydraulic fracturing is used not only in oil and gas industry but also in hydrogeology to improve the performance of aquifers.

10.10.1.2 Pressure Acidizing This method uses an aqueous acidic solution instead of brines or water for creating unpropped fractures. To do this, a greater increase in permeability than with common hydraulic fracturing is achieved by chemical dissolution of a part of the carbonate matrix along the fracture walls. Obviously, this treatment can only be used in the case of carbonated formations, such as limestones or dolomites. The most common acidic agents are aqueous solutions of hydrochloric acid (5 to 15 wt.% HCl), hydrofluoric acid (1 to 6 wt.% HF), acetic acid, citric acid, and surfactants. The surfactants are used as dispersing agents to promote the dispersion of solids, to improve the wettability of the rock, and to prevent emulsification. To determine whether acidizing or fracturing will yield the greatest economic benefit, the current condition of the well must be known. This includes knowledge of the undamaged production capacity of the reservoir and the type of damage in existence including the severity and cause of the damage. Worldwide, acidizing has about a 50% success rate, which is believed to be due to a lack of knowledge about the true well condition. On the other hand, fracturing can result in substantially greater improvement in productivity than acidizing just to remove the skin damage, but at a much higher cost. Acidizing is a good stimulation candidate in moderate to high permeability reservoirs that show substantial damage after completion. If there is a damaged zone around the well bore where effective permeability is reduced, acidizing can increase productivity by as much as fivefold, depending on the degree and depth of damage. On the other hand, if acidizing is used to increase permeability above the average reservoir effective permeability, very little stimulation benefit results. Increasing near-well-bore permeability by even an order of magnitude results in a less than twofold productivity improvement. In conclusion, these two techniques increase economically recoverable reserves and improve vertical communication in layered and unconnected reservoirs. Reserves can be increased either by increasing the flow capacity of an uneconomic well or by increasing the drainage radius of a well or by contacting producing layers that are not connected to the well through perforations. Economic benefit can also be obtained by accelerating production from low-permeability reservoirs. Sweep efficiency can be increased by forming line sources or sinks for injection or production.

10.10.2 Proppant and Frac Fluid Selection Criteria 10.10.2.1 Proppant Materials As a general rule, not all materials can be used as efficient propping agents. Actually, due to the existing geothermal gradient (e.g., 30°C/km) and lithostatic pressure (e.g., 23 MPa/km) in sedimentary basins, a suitable proppant material must withstand both these harsh conditions (i.e., high bottom temperature and elevated pressure) encountered in deep wells (up to 6 km) and insure the good mass transfer of oil and gas. Hence, the critical characteristics and properties that must be taken into account for the proper selection of proppants are listed below:

Proppants

679

• high crushing or compressive strength; • both elevated hardness and fracture toughness; • high gas and oil permeability; • narrow particle-size distribution; • low specific surface area; • low bulk and tap densities; • chemical inertness in hot acidic solutions and hot brines; • good thermal stability; • good flowability and rheology in frac fluids; • low abrasiveness; • low cost and large commercial availability.

10.10.2.2 Frac Fluids The above-mentioned proppants can only be used successfully when mixed with a viscous fluid to form a pumpable slurry; hence the carrying fluid also plays an important rheological role in the final fracturing job. Many fluids have been used in fracturing operations, including lease crude oil, water, brines, linear gels, foams, cross-linked polymer gels, emulsions, and even carbon dioxide. Most fracturing fluids used today are either linear or cross-linked aqueous polymer gels or foams. These fluids are extremely complex and exhibit rheological properties that are sensitive to several critical operating parameters. Some of their properties, such as their shear rate, are also time and temperature dependent. The most common fracturing fluids used today include guar cross-linked with borate or zirconium, carboxymethyl-hydroxypropyl guar (CMHPG) cross-linked with zirconium, foams of guar-based fluids and nitrogen or carbon dioxide for gas assist, and gelled oils made of phosphate esters and sodium aluminate. When pH adjustment is required, this can be achieved by adding sodium hydroxide (NaOH) or magnesium oxide (MgO) directly to the frac fluid. Other additives include fluid loss additives, breakers, and surfactants. Breakers are typically enzymes or oxidizers for guar-based products. For gelled oil, acids and bases are used to break the association polymer structure including magnesium oxide.

10.10.2.3 Properties and Characterization of Proppants To select a suitable propping agent, the properties of the material must be characterized according to well-known standards, e.g., the standards edited by the American Petroleum Institute (API) or other professional societies involved in the oil and gas industry (e.g., IoP, IFP, or ASTM). The critical properties that must be measured to qualify a suitable propping agent with the explanation of the critical values are listed in Table 10.24.

10.10.2.4 Classification of Proppant Materials The materials commonly used as proppants can be grouped into three main categories, listed in Table 10.25. The first proppant material used was rounded silica sand mined from glacial deposits. This material was initially selected owing to both its wide availability near production wells and its low cost, but since the early days several other industrial materials have been selected and used as proppants, and today we observe the increased use of synthetic materials, especially sintered and fused ceramics. The main impetus in focusing on ceramics was driven by the fact that ceramic materials offer suitable properties for use in modern deep wells today.

10 Ceramics, Refractories, and Glasses

Ceramics, Refractories, and Glasses

(continued) Table 10.24. Critical properties for proppants Critical properties

Mechanical properties

680

37

Description

Requirements

Benefits

High crushing strength (σc/MPa)

The crushing strength is the compressive strength of a material, i.e., its ability to resist compaction or compression under axial load.

σc > 35 MPa

Insures prop of cracks and avoids the collapse of cap rock if crushing strength is above the lithostatic pressure at the given depth.

Crushing resistance (wt.%)

A series of crushing resistance tests consists in determining the stress at which the proppant material shows excessive generation of fines. Tests are conducted on samples that have been sieved. Four specific stress levels (i.e., 7.5, 10, 12.5, and 15 ksi) are used in the recommended practice (see API RP-61).

Suggested fine limit (API): 12/20 25 wt.% 16/20 25 wt.% 20/40 10 wt.% 40/70 8 wt.%

The lower the fine generation, the better the permeability of the reservoir; moreover; this avoids fooling of cavities and porosities.

Suggested fine limit (Stim. Lab.) All 5 wt.%

Pycnometer density –3 (ρpyc/kg.m )

The pycnometer density measures ρpyc < 2800 kg.m the true skeletal density including closed internal porosity. Its knowledge is required for the determination of the specific surface area. It is usually measured with a helium pycnometer because helium gas will penetrate all open pores and intricate channels.

Bulk density –3 (ρbulk/kg.m )

The bulk density corresponds to the mass of proppants that fill a unit volume and includes both proppant and porosity void volume.

Tap density –3 (ρtap/kg.m )

The tap density corresponds to the ρtap < 1800 kg.m volume occupied by a weighed powder after a set number of taps, usually 10, have been applied to the bottom of its container. As such, the tap density provides a measure of the compactability of a powder.

Permeability coefficient (darcy)

Characterizes the volume flow rate of a fluid into a porous medium exhibiting a cross-section area, A, and a thickness, l, under a given pressure differential ΔP (see standard API RP-61). Conductivity is kA/l.

–3

ρbulk < 1600 kg.m

–3

–3

k > 340 darcies P > 6 darcy-ft

37

A low-pycnometer-density material allows the use of low-viscosity carrying fluids, leading to both lower power consumption and pumping rates during well injection.

A low-bulk-density material leads to the use of less mass of proppant for a given volume of reservoir bed or storage tank to fill. A low-tap-density material allows one to use less mass of proppant for a given volume of reservoir bed to fill.

A high permeability coefficient insures a good mass transfer of oil and gas into the fractured rock.

The darcy corresponds to the volume flow rate of one cubic centimeter per second of a liquid having a dynamic viscosity of 1 centipoise, which flows through an area of one square centimeter of a porous medium in 1 s when it undergoes a pressure gradient of one atmosphere per centimeter of length. Hence, –13 2 1 darcy = 9.869232266 × 10 m .

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681

Table 10.24. (continued) Description

Requirements

Benefits

Particle size distribution (PSD)

Distribution of the particle size is determined by sieving according to ASTM C429-82(1996).

425 < D < 850μm (40 < mesh < 20)

A narrow grain size distribution insures a good intercalation of grains into tight fractures and excellent packing ability. The sizes used in hydraulic fracturing are typically in US mesh: 20/40, 16/20, and 16/30. Some 30/50 and 12/20 is used in specialty applications.

Sphericity and roundness indices (S, RI)

Dimensionless quantities that S > 0.9 measure the ellipsoidal shape and RI > 0.9 particle smoothness, respectively. It gives the ratio of the smaller diameter to the larger diameter, and the ratio of actual area to theoretical area.

Porosity (ε/vol.%)

Dimensionless quantity equal to the void volume fraction, i.e., ratio of volume of voids to the overall volume of material.

ε < 30 vol.%

The lower the porosity, the better the crushing strength, the lower the brittleness.

Chemical composition

Chemical composition of the dried solid, expressed as oxides or elements, indicates also the oxidation degree of multivalent species (e.g., Fe, Mn, Cr, Co, and V).

No hazardous substances, low Fe(II) and Fe(III).

Soluble hazardous substances must be avoided so as not to contaminate aquifers, and release of iron cations is not recommended for well control.

Weight loss in acidic media and boiling water

Weight loss during dissolution of a representative sample in an acidic mixture of 12 wt.% HCl and 3 wt.% HF at a given temperature of 100°C and/or in boiling water.

Less than 2 wt.% in acid mixture, and no dissolution in boiling water.

Chemical inertness allows it to resist the dissolution of beads into acidic frac fluids, brines, and corrosive agents used in chemical fracturing (e.g., HCl, HF, etc.).

Maximum operating temperature (°C)

Capability to withstand maximum temperatures encountered in the deepest production wells owing to the usual geothermal gradient encountered in sedimentary basins (i.e., 30°C/km)

At least above 250°C with no phase changes

Helps to avoid creep phenomena and softening of the material under permanent load.

Price (US$/tonne)

Specific cost, i.e., cost per unit mass of material including raw material cost, production cost, and distribution cost.

Less than 500 US$/tonne

Allows for competitive product on the market.

Other

Chemical properties

Size and dimensions

38

Critical properties

38

ASTM F1877-98 – Standard Practice for Characterization of Particles.

Beadlike particles allow a good flowability of the slurry during pumping operation.

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Ceramics, Refractories, and Glasses

Table 10.25. Major materials used as proppants Material

Description

Characteristics

Rounded silica sand (e.g., Arizona Sand, Badger Mining, Borden, Colorado Silica, Hepworth, Oglebay Norton, Uninim)

Naturally occurring sand usually mined from glacial deposits, sometimes called Ottawa sands. Silica sand is essentially made of quartz (SiO2) grains.

Pressure range: 28 < σc < 35 MPa (4 < σc < 5 ksi) Advantages: Low cost, low density, wide availability, and excellent chemical resistance in acidic media except those containing free HF Drawbacks: Low permeability, low crushing strength, and poor resistance to flow back

Resin-coated sand (e.g., Borden, Santrol, Hepworth)

The first application of a phenolic resin coating was to particles such as silica sand, glass beads, and ceramics. The concept was to inject a partially cured resin-coated proppant into a well and let the elevated bottom hole temperature finish the resin polymerization and bond the coated particles together, forming a down-hole filter. When a proppant is coated with a phenolic formaldehyde resin that is securely attached to the proppant surface by a silane or other coupling agent, the former brittle material becomes crush resistant. Actually, the resin coating helps to provide a smooth and round substrate surface. In addition, it reduces stress between grains and maintains particle integrity. The coated grains are less sensitive to embedment and generate fewer fines. Finally, it increases the chemical resistance of particles.

Pressure range: 35 < σc < 69 MPa (7 < σc < 10 ksi) Advantages: Better resistance to flow back and improved crushing strength Drawbacks: Higher tendency to produce dust under high shear conditions (dust explosions)

Ceramics (e.g., Carbo-Ceramics Inc., Norton Alcoa, Sintex Minerals Inc.)

Synthetic materials made by sintering of bauxite and kaolinite clay. After processing, the final material mineralogical composition consists of a mixture of mullite and corundum. Sometimes less common ceramics are also used, e.g., carborundum, stabilized cubic zirconia, other oxides, and silicates.

Pressure range: σc up to 140 MPa (σc up to 20 ksi) Advantages: High crushing strength Drawbacks: High density, high cost

10.10.2.5 Production of Synthetic Proppants All ceramic proppant producers use as feedstock essentially bauxite and, to a lesser extent, other industrial minerals with a high alumina content such as kaolin, nepheline syenite, wollastonite, talc, and feldspars. The final spherical shape is obtained by several processing routes currently used in the ceramics industry for producing beads and other particulate materials. The most common of these processes are pelletizing and sintering, atomization, fire polishing, and flame spraying. Pelletizing and sintering. In this process, which is the most common among ceramic proppant producers, raw material with a high alumina content (i.e., bauxite, or kaolin clay) is ground to a final particle size of several micrometers by ball milling prior to formation of the pellets. Then the material is calcined at 1000°C to drive off moisture and water from hydratation and reground to less than a micrometer to obtain through granulation as high

Proppants

a green density as possible. Afterwards, various pelletizing techniques can be used to agglomerate the material. Usually, ball forming consists in finely grounding the fired material and mixing it in a rotary dryer with water and a binder that gives them temporary cohesion and that does not affect the final strength of the material (e.g., molasses, starch, cellulose gum, polyvinyl alcohol, bentonite, sodium metasilicate, and sodium lignosulfonate). Until the final desired size of green pellets is obtained, the binder is continuously added. Finally, the green pellets are fired with a suitable parting agent (e.g., pure alumina powder) into a kiln between 1200 and 1650°C for a sufficient amount of time for vitrification to occur. After sintering the balls are made of alpha-alumina (i.e., corundum) and mullite grains with a diameter of 50 to 300 μm formed by crystalline growth during sintering together with a glassy phase. Hence sintered bauxite exhibits only a low residual porosity (3550 kg.m ) and strong. Atomization. This technique involves the melting at high temperatures (i.e., above 1800°C) of raw material particles together to obtain a molten bath of bulk liquid. Usually, the bulk liquid contains more than thousands of times the amount of raw material required to make a single product particle. A thin stream of molten material is atomized by dropping it into a disruptive air jet, subdividing the stream into fine, molten droplets. The droplets are then kept away from one another and from other objects until they have been cooled and solidified. Then they can be recovered as substantially discrete ellipsoidal glassy (i.e., amorphous) particles. Fire polishing. In this techniques, discrete solid particles are heated to the softening or melting temperature of the material, usually between 1200 and 1650°C, while suspended and dispersed in a hot gaseous medium (e.g., fluidized bed). As particles become soft or molten, surface tension forms them into an ellipsoidal shape. If kept in suspension until cooled below softening temperature, the particles may be recovered as spherical grains. Flame spraying. In this technique, finely ground raw particles are premixed with a combustible gas mixture, i.e., fuel and oxidant, and the mixture is then introduced into a burner. Hence, in the hot flame, the tiny particles melt or soften, and the surface tension leads them to exhibit an ellipsoidal shape. To prevent molten droplets or soften particles from contacting any surface before cooling, the flame must be allowed to move freely in a large combustion chamber. The droplets or softened particles are then kept away from one another and from the reactor walls until they have been cooled and solidified. It is important to point out that, despite the wide availability of industrial minerals for preparing commercial ceramic proppants (e.g., bauxite, kaolin clay), all the major proppant producers must overcome technical issues for obtaining crush-resistant beads made of tough and hard corundum or mullite minerals. Actually all the above-mentioned processes require at least a comminution step and also a firing or sintering step conducted at high temperature. Hence, the overall process for obtaining suitable ceramic proppants is always energy demanding and accounts for 60% of the cost of the final product. Hence, the process represents a major pitfall for obtaining competitive ceramic proppants at low prices.

10.10.2.6 Properties of Commercial Proppants The properties of most common commercial proppants measured according to standardized tests are summarized in Table 10.26.

683

10 Ceramics, Refractories, and Glasses

1530

12/20, 16/30, 20/40 (730μm)

12/20, 16/30, 20/40 (710μm)

12/20, 16/30, 20/40 (720μm)

Precured resin-coated sand (Tempered HS®, Santrol)

Precured resin-coated sand (Tempered DC®, Santrol)

Precured resin-coated sand (Tempered LC®, Santrol)

Resin-coated sand

1530

1540

1490

Precured resin-coated sand 12/20, (Tempered Econoflex®, Santrol) 16/30, 20/40 (620μm)

2600

2570

2530

2590

2650

0.00 ........ •

•

RM n–2 + M —> RM n–1 (iii) Termination, which consists of the completion of the reaction by combination of last radical monomers to form the final macromolecule •

•

RM n–1 + M —> RM n Ionic polymerization involves ions. Polycondensation. A chemical reaction (e.g., esterification) occurring between two monomers with complementary function, for instance alcohols and carboxylic acids, with the removal of a small molecule (e.g., water, hydroacid, ammonia, formol, etc.) as a byproduct. Esterification:

R1—CO—OH + HO—R2 —> R1—CO—O—R2 + H2O R1—CO—OH + X—R2 —> R1—CO—O—R2 + HX

Peptide formation: R1—CO—OH + H2N—R2 —> R1—CO—NH—R2+ H2O Copolymerization. Copolymerization involves two or more different monomers, and the resulting macromolecule is named a dipolymer, terpolymer, etc.

11.2 Properties and Characteristics of Polymers 11.2.1 Molar Mass and Relative Molar Mass The molecular molar mass or simply the molar mass, denoted M, corresponds to the mass per amount of substance of the macromolecule. For a macromolecule containing a number n of monomer units or residues R its molar mass is simply given by: M = n × MR –1

with M molecular molar mass of the polymer in kg.mol , n dimensionless number of monomers or residues, –1 MR molecular molar mass of the monomer in kg.mol . Note that in some old textbooks dealing with macromolecular chemistry and polymer science, the molar masses were expressed in an old unit called the Dalton (Da) which is the old –27 name for the atomic mass unit (1 u = 1.66054021 × 10 kg). The relative molecular molar mass or simply the relative molar mass, denoted Mr (formerly the molecular weight, MW) is a dimensionless quantity that corresponds to the ratio 12 of the mass of the macromolecule to 1/12 of the mass of an atom of the nuclide C. It is the most important property of a macromolecule, because it is directly related to its physical

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695

properties such as mechanical, thermal and electrical properties. For instance, for a simple macromolecule —[R]n— made of n monomer units or residues, R, its relative molar mass is simply given by: Mr = n × MR with Mr relative molar mass of the polymer, n degree of polymerization, MR relative molar mass of the monomer.

11.2.2 Average Degree of Polymerization The average degree of polymerization, denoted Xk, were k represent the type of average (i.e., arithmetic, geometric), represents the dimensionless number of monomer units or residues R constitutive of a macromolecular chain. It can be defined as the ratio of the relative molar mass of the macromolecule to the relative molar mass of the monomer unit: Xk = Mr/MR Depending of the degree of polymerization, it is possible to distinguish several subgroups of polymers listed in Table 11.2. Table 11.2. Degree of polymerization and polymer subgroups Degree of polymerization Subgroups

Examples

2 < Xk < 10

Oligomers

Polysacharides, polypeptides

10 < Xk < 100

Low-mass polymers

100 < Xk < 1000

Medium-mass polymers

1000 < Xk

High-mass polymers

Most of the commercial plastics

11.2.3 Number-, Mass- and Z-Average Molar Masses During polymerization, the length of each macromolecule produced is determined entirely by random events. Therefore, the random nature of the growth process requires that the final polymer consists of a mixture of chains of macromolecules having a different length and hence a different relative molar mass. Consequently, a polymer is better defined by a statistical distribution that plots the number fraction of the polymer having a given molar mass rather than a definite molar mass. Therefore, polymer scientists soon introduced several quantities called molar-mass averages. In practice, the most important molar mass averages are defined by simple moments of the distribution functions. The first quantity is a colligative property called the number-average relative molar mass or simply the number-average molar mass denoted Mn and defined as the weighed average of the number fraction of each macromolecule by the following equation. with

Mn = ΣiNi Mi /ΣiNi = ΣiniMi = Σiwi /Σi(wi/Mi) Mn averaged relative molar mass, Ni number fraction of the macromolecule i, relative molar mass of the macromolecule i. Mi

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Because the number-average molar mass is a colligative property, it can be determined experimentally by techniques which are able to count the number of macromolecules such as osmotic pressure measurements. The second quantity is a constitutive property called the mass-average relative molar mass or simply the mass-average molar mass denoted Mw and defined as the weighed average of the mass fraction of each macromolecule having a given molecular mass. Mw = Σiwi Mi /Σiwi = ΣiNi Mi /ΣiNi Mi with Mw weighed relative molar mass, mass fraction of the macromolecule i, wi Mi relative molar mass of the macromolecule i. 2

The mass-average molar mass is determined by optical methods such as Rayleigh light scattering measurements. The third quantity is called the z-average relative molar mass or simply the z-average molar mass denoted MZ and defined as the weighed average of the mass fraction of each macromolecule having a given molecular mass. Mz = ΣiwiMi with Mz wi Mi

2

/ΣiwiMi = ΣiNi Mi /ΣiNi Mi z-average relative molar mass, mass fraction of the macromolecule i, relative molar mass of the macromolecule i. 3

2

It can be measured by ultracentrifugation. The fourth quantity is called the (z+1)-average relative molar mass or simply the (z+1)average molar mass denoted MZ and defined as the weighed average of the mass fraction of each macromolecule having a given molecular mass. Mz = ΣiwiMi with Mz wi Mi

3

/ΣiwiMi = ΣiNi Mi /ΣiNi Mi z-average relative molar mass, mass fraction of the macromolecule i, relative molar mass of the macromolecule i. 2

4

3

A schematic plot representing the above three quantities is presented in Figure 11.1. The width of the distribution can be measured by introducing the heterogeneity index which is the dimensionless ratio (Mw/MN). For most polymers the most probable value is ca. 2.0.

Figure 11.1. Schematic plot of molar masses of polymers

Thermoplastics

697

11.2.4 Glass Transition Temperature Pure crystalline materials possess a well-defined temperature of fusion or melting point. By contrast, most polymers exhibit a temperature range over which the crystalline order progressively disappears. Actually, upon cooling, molten polymers begin to crystallize below their melting point with a contraction of volume. For amorphous polymers, the volume contraction continues until a given temperature, called the glass transition temperature denoted Tg, at which the supercooled liquid polymer exhibits enormous viscosity, is reached. Below Tg all polymers are rigid. Many physical properties of polymers such as the dynamic viscosity, the specific heat capacity, the coefficients of thermal expansion and elastic moduli, change abruptly at Tg.

11.2.5 Structure of Polymers A homopolymer is a polymer made of the same monomer while a heteropolymer is made of at least two or more distinct monomers. Copolymer. A copolymer is a heteropolymer formed when two or more different types of monomer are linked in the same polymer chain. Graft polymer. A graft polymer is a heteropolymer with polymer chains of one monomeric composition branching out of the sides of a polymeric back-bone with a different chemical composition. Block copolymer. A block copolymer denotes a heteropolymer having a great regularity of structure with large repeating unit containing dozens of monomers. Tacticity. The orderliness of the succession of configurational repeating units in the main chain of a polymer molecule. Tactic polymer. A regular polymer, the molecules of which can be described in terms of only one species of configurational repeating unit in a single sequential arrangement. Isotactic polymer. A regular polymer, the molecules of which can be described in terms of only one species of configurational base unit having chiral or prochiral atoms in the main chain in a single sequential arrangement. Syndiotactic polymer. A regular polymer, the molecules of which can be described in terms of alternation of configurational base units that are enantiomeric. Atactic polymer. A regular polymer, the molecules of which have equal numbers of the possible configurational base units in a random sequence distribution.

11.3 Classification of Plastics and Elastomers See Table 11.3, page 698.

11.4 Thermoplastics 11.4.1 Naturally Occurring Resins 11.4.1.1 Rosin Rosin, formerly called colophony, is a solid form of resin obtained from several pine trees extensively found in Asia, Europe and North America and to a lesser extent from other conifers

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Table 11.3. Classification of thermoplastics, thermosets and elastomers Derivatives of natural products

Polyaddition resins

Polycondensation resins

1. – – – –

Naturally occurring resins Amber and succinite Rosin Shellac Lignin

4. – – –

Polyolefins Polyethylene (PE) Polypropylene (PP) Polybutylene (PB)

12. Phenolics – Phenol-formaldehyde – Resorcinolformaldehyde

2. Derivative of cellulose: 2.1 Cellulose esters – Cellulose acetate (CA) – Cellulose propionate (CP) – Cellulose acetobutyrate (CAB) – Cellulose acetopropionate (CAP) – Cellulose nitrate (CN) 2.2 Cellulose ethers – Methyl cellulose (MC) – Ethyl cellulose (EC) – Carboxymethyl cellulose (CMC) 2.3 Regenerated cellulose – Viscose, rayon

5. – – – – –

Polyvinyls Polyvinyl ethers Dipolyvinyls Polyvinyl chloride (PVC) Polyvinyl fluoride (PVF) Chlorinated polyvinyl chloride (CPVC)

13. Aminoplastics – Urea-formaldehyde – Melamine-formaldehyde – Melamine-phenolics

3. Derivatives of vegetal proteins – Caseine-formaldehyde – Zein-formaldehyde

14. Furan resins – Phenol-furfural

6. Polyvinylidenes – Polyvinylidene chloride (PVDC) – Polyvinylidene fluoride (PVDF)

15. Polyesters – Alkyd resins – Polycarbonates (PC)

7. Polyvinyl derivatives – Polyvinyl alcohol (PVA) – Polyacetals (PAc)

16. Polyethers – Polyformaldehydes – Polyglycols

8. – – – –

Styrenics Polystyrene (PS) Acrylonitrile-butadiene-styrene (ABS) Styrene-acrylonitrile (SAN) Styrene-butadiene

17. Polyurethanes (PU)

9. – – – – –

Fluorocarbons Polytetrafluoroethylene (PTFE) Polytrichlorofluoroethylene (PTCFE) Fluorinated ethylene propylene (FEP) Perfluoroalkoxy (PFA) Ethylenetetrafluoroethylene (ETFE)

18. Polyamides (PA) 19. Polyimides (PI) 20. Polyaramides (PAR) 21. Sulfones – Polysulfones (PSF) – Polyethersulfone – Polyphenylsulfone

10. Acrylics – Polymethylmethacrylate (PMMA)

22. Epoxy resins

11. Coumarone-indenes

23. Polysiloxanes – Silicones

conifers. It is prepared by cutting a long slice in the tree to allow exudation and to collect the liquid resin in containers. Afterwards the liquid resin is steam heated to remove volatile terpene and turpentine and leaving gum rosin as residue. It is semi-transparent and varies in color from yellow to black. It chiefly consists of different organic acids, among those abietic acid (C19H29COOH) is the most important. Rosin is a brittle and friable resin, with a faint piney odor; the melting-point varies with different specimens, some being semi-fluid at the temperature of boiling water, while others melt between 100°C to 120°C. It is very flammable, burning with a smoky flame. It is soluble in alcohol, ether, benzene and chloroform. Rosin combines with caustic alkalis to yield salts called rosinates or pinates that are known as rosin soaps. In addition to its extensive use in soap making, rosin is largely employed in making inferior varnishes, sealing-wax and various adhesives.

Thermoplastics

699

11.4.1.2 Shellac Shellac is a brittle or flaky secretion produced by the lac insect Tachardia lacca, commonly found in the rain-forests of Southern Asia (e.g., Thailand). Actually, the larvae of the insect settle on the branches, pierce the bark and feed from the sap. The female insect produces a protective coating over their bodies that produce a thick incrustation over the twig. When larvae emerge, the thick incrustation is scraped off and dried to yield the stick lac which still contains wood, lac resin, lac dye and various organic debris. After grinding, screening and washing the stick lac, the purified product called seed lac is obtained. Shellac is a naturally occurring polymer and it is chemically similar to synthetic polymers, thus it is considered as a natural plastic. It can be molded by heat and pressure methods, so it is classified as a thermoplastic. It is soluble in alkaline solutions such as ammonia, sodium borate, sodium carbonate, and sodium hydroxide, and also in various organic solvents. When dissolved in acetone or alcohol, shellac yields a coating of superior durability.

11.4.2 Cellulosics Cellulosic materials are thermoplastics derivatives of cellulose. The raw material for the industrial preparation of cellulosics is natural cellulose, itself a natural polymer, i.e., a polysaccharide chain (C6H10O5)n, with ca. 3500 glucosidic monomer units which is found extensively in plants and woods. In plants, cellulose acts as a structural reinforcement material. Actually, natural cellulose exhibits no plasticity because of the cross-linking existing between two polysaccharide chains. This reticulation is ensured by hydrogen bonds between two adjacent alcohol functions. Therefore, in order to become plastic, the alcohol functions of the cellulose must be converted either by esterification by an organic acid or by etherification with another alcohol. The most common esters of cellulose used commercially are the nitrate, acetate, butyrate, acetobutyrate, and propionate while major ethers are methylcellulose, ethylcellulose and benzylcellulose; finally xanthate of cellulose, called rayon, is also produced. Cellulose used for making cellulosics comes either from linters by-produced during the extraction of cotton or from wood pulp. However, before use, the raw cellulose must be carefully purified by removing pectine and fatty acids. Therefore, the raw cellulose is first treated by a strong caustic solution of NaOH followed by washing with water and finally bleaching is performed by sodium hypochlorite (NaOCl). As a general rule, cellulosics do not constitute any major use but are encountered daily in a number of smaller items such as name plates, electrical component cases, high impact lenses, and other applications requiring a transparent plastic with good impact resistance. Weathering properties of the materials are good, particularly that of propionate, but overall chemical resistance is not comparable to other thermoplastics. Water and salt solutions are readily handled, but any appreciable quantity of acid, alkali, or solvent can have an adverse effect on the plastic.

11.4.2.1 Cellulose Nitrate Cellulose nitrate or pyrolyxin was the first synthetic thermoplastic of industrial significance, 2 and was first discovered in 1833 by H. Bracconot after the nitration of wood flour and paper 3 and later by Friedrich Schonbein in 1846. In 1870 the American chemist J.W. Hyatt invented its gelification in order to find a substitute for ivory. It is obtained by nitration of purified

2 3

Braconnot, H. Ann., 1(1833)242–245. Hyatt, J.W.; Hyatt, I.S. US Patent 105,388, 1870.

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Polymers and Elastomers

cellulose with the sulfo-nitric mixture (i.e., conc. HNO3 + fuming H2SO4). Actually, if concentrated nitric acid is used alone the by-produced water stops nitration by diluting the acid: (C6H10O5)n + 2n HNO3 —> –[C6H8O3(NO3)2]n– + 2n H2O After nitration, the cellulose nitrate paste is carefully washed with water, bleached with sodium hypochlorite, washed with hydrochloric acid and washed again with water. Afterwards, the wet paste is progressively dried by mixing it with camphor or excess ethanol in order to replace the water by the alcohol which acts both as a platicizer and stabilizer. Actually, dry nitrate of cellulose is highly flammable, poorly stable towards heat and sunlight, and even choc sensitive. Addition of camphor up to 20–25 wt.% yields a safer material, called celluloid, having good dimensional stability, low absorption of moisture and toughness. It can be laminated and colored providing a huge variety of material textures. The upper temperature of usefulness is 60°C. First uses of celluloid were to produce imitations of the expensive tortoise shell, the manufacture of photographic and cinematographic films and fabrication of varnishes by dissolving it into acetone or ethanol to yield collodions. But today, due to its high flammability, it has been abandoned in favor of other esters of cellulose.

11.4.2.2 Cellulose Acetate (CA) Industrially, cellulose acetate is made quite exclusively from pure cellulose obtained from linters of cotton because purified cellulose obtained from wood pulp still contains deleterious impurities. Cellulose is esterified by using a mixture of acetic anhydride and concentrated sulfuric acid, the latter acting as dehydrating agent for removing by-produced water, and also zinc (II) chloride acting as a catalyst. (C6H10O5)n + 3n CH3COOH —> [C6H7O2(OOCCH3)3]n + 3n H2O Usually, glacial acetic acid is introduced gradually in the reactor to dissolve the newly formed cellulose acetate. The product obtained is the nonflammable cellulose triacetate which is insoluble in most organic solvents including acetone, and ether but it is soluble in chloroform, dichloromethane, glacial acetic acid and nitrobenzene. Cellulose triacetate exhibits good dimensional stability and heat resistance, possesses a dielectric constant, resistance to water and good optical transparency. Mechanically, cellulose triacetate has good folding endurance and burst strength. In order to render it soluble, a retrogadation (reverse) reaction, in which one ester functional group is partially saponified, is used to yield the cellulose diacetate or simply cellulose acetate which is soluble in acetone but not in chloroform. Afterwards, its dissolution into a solvent and addition of a plasticizer yields commercial cellulose acetate. Commercially, the product contains between 38 and 40% of acetyl groups. Cellulose acetate can be used up to 70°C, it is resistant to water and transparent to UV radiation. Dissolved in solvent it is used as a varnish. Cellulose acetate replace the highly hazardous cellulose nitrate for the manufacture of photographic and cinematographic films.

11.4.2.3 Cellulose Propionate (CP) Cellulose propionate is the ester of cellulose with propionic acid and it is similar to cellulose acetate but with a higher plasticity. Cellulose propionate is a tough, strong, stiff, with a greater hardness that cellulose acetate and has excellent impact resistance. Articles made from it have a high gloss and are suitable for use in contact with food.

11.4.2.4 Cellulose Xanthate Cellulose xanthate is obtained by reacting first pure cellulose with a strong caustic solution of NaOH to yield alkali-cellulose. Then, alkali-cellulose is reacted with carbon disulfide (CS2). The commercial product is called rayon.

Thermoplastics

701

11.4.2.5 Alkylcelluloses These ethers of cellulose are all prepared industrially in the same manner. The pure cellulose is digested into a strong caustic solution of 50 wt.% NaOH to yield the alkali-cellulose. Afterwards, the alkali-cellulose is alkylated by mixing it with an etherification agent such as methyl, ethyl or benzyl chloride or sulfate. The resulting products are alkylcelluloses in which the hydrogen in the hydroxyl groups is replaced by a methyl-, ethyl- or benzyl-group. Outstanding properties are unusually good low-temperature flexibility and toughness, wide range of compatibility, heat stability, and dielectric properties. The three ether groups are usually distinguished according to their solubilities. Methylcelluloses are soluble in water, aqueous alkaline solutions and organic solvents. They are used for forming emulsions of given viscosities or as gelifying agent for electrolytes in batteries. –3 Ethylcelluloses are low density polymers (1070–1180 kg.m ) with solubilities depending on the degree of ethylation; usually commercial grade contains 44–48% ethoxyl functional groups. Solid masses of ethylcellulose exhibit low absorption of moisture, excellent dimensional stability and low temperature toughness and impact resistance. Chemically they are less resistant towards acids than cellulose esters but much more resistant to alkalis. They can be processed by injection molding. Because ethylcellulose is soluble in a wide variety of solvents, it provides a wide variety of varnish formulations. Benzylcelluloses yield plastics with excellent dielectric properties and chemical stability.

11.4.3 Casein Plastics The casein plastics first produced in 1885 are a particular class of thermoplastic materials made from the rennet casein extracted from milk. With cellulosics they were the first synthetic thermoplastics produced industrially. The purified casein is reacted with formaldehyde to yield by condensation a casein-formaldehyde thermoplastics also known commercially as Galathite®, meaning milkstone. By contrast with other condensation resins, casein-formaldehyde is obtained by impregnating the semi-products or preforms (e.g., rod, sheet, and plates) made by compressing an aqueous slurry of casein powder with formaldehyde until the compound penetrates inside the material. The raw material, that is, casein, can be prepared from milk by several routes. Actually, milk that contains between 2.7 and 3.5 wt.% casein also contains fatty acids that must be removed prior to precipitation. Therefore, the raw milk is strongly mixed to promote the coalescence of lipid droplets, that are removed by centrifugation. Then, the casein from the fat-free milk can be coagulated either by adding rennet, or by promoting the lactic fermentation using yeast or by adding a mineral acid. However, for the industrial preparation of casein-formaldehyde resins, only the precipitation by rennet provides a suitable product. Precipitation is performed in large jacketed vessels in order to maintain the temperature at 37°C at the beginning, ending at 65°C when coagulation is complete. The casein is removed by filtration, washed, dried, ground, and gelatinized with water before molding into semi-products. The complete reaction of semi-products with formaldehyde takes months but it yields an easily machinable and molded, nonflammable material. However, galathite exhibits a high water absorption and is attacked by alkalis. On the other hand, artificial wool can be obtained by dissolving casein into sodium hydroxide and then forcing the viscous solution through nozzles into a coagulating bath of acidified formaldehyde. The synthetic fiber produced resembles wool and was sold under the trade names Lanital and Aralac.

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11.4.4 Coumarone-Indene Plastics Coumarone-indene plastics along with cellulose nitrate were the first synthetic resins developed commercially in the middle of the nineteenth century. Industrially, they are produced from coal-tar light oils by-produced either during coking or petroleum cracking operations. By treating the fraction distilling between 150 and 200°C that contains mainly indene and coumarone, with concentrated sulfuric or phosphoric acid, polymerization occurs readily. The synthetic resins obtained are mixtures of polyindene and polycoumarone, that are called cumar gum and commercialized under the trade name Nevindene with properties varying from a soft gum melting at 4°C to a hard brown solid with a melting point of ca. 150°C depending of the ratio of the two monomers. In all cases, the density is usually close to –3 1080 kg.m . These resins are resistant towards alkalis but are easily soluble in organic solvents and hence are used as lacquers, varnishes, or waterproofing compounds.

11.4.5 Polyolefins or Ethenic Polymers These thermoplastics have in common all the same basic monomer structure of the ethylene (i.e., H2C=CH2).

11.4.5.1 Polyethylene (PE) Polyethylene also named polythene (PE) with the basic ethylene molecule [—H2C—CH2—]n as monomer was first produced on a commercial basis in 1934. Polyethylene is prepared directly from the polymerization of ethylene (C2H4). Ethylene is obtained from a refinery or from the steam cracking of naphtha or natural gas. Two industrial processes are today used: (i) (ii)

high pressure synthesis; and low pressure synthesis.

In the high pressure process, the high purity ethylene is compressed under pressures ranging from 150 to 300 MPa at 300°C in the presence of traces of oxygen acting as a catalyst. The polymerization reaction is very simple and can be written as follows: n CH2=CH2 —> [—CH2—CH2—]n The majority of the polyethylene macromolecules produced are mostly linear and they have the same chain length. To a lesser extent however, some macromolecules have lateral chains (ramification). As a general rule, the longer the chain, the higher the mechanical strength and the lower the heterogeneity ratio. In the low pressure process, a stiffer product with a high softening point is obtained. Pure polyethylene solid crystallizes in the orthorhombic system with the crystal lattice parameters a = 741 pm, b = 494 pm and c = 255 pm respectively with 2 molecules (C2H4) per formula unit. Therefore the theoretical density of polyeth–3 ylene is 996 kg.m which is only approached by the UHMW grade (see below). Hence polyethylene is a low density thermoplastics that floats on water. Polyethylene is a thermoplastic material which varies from type to type according to the particular molecular structure of each type. Actually, several products can be made by varying the molecular weight (i.e., the chain length), the crystallinity (i.e., the chain orientation), and the branching characteristics (i.e., chemical bonds between adjacent chains). Polyethylene can be prepared in four commercial grades: (i) (ii)

low density (i.e., LDPE) and linear low density polyethylene (LldPE); medium density (i.e., MDPE);

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(iii) high density (i.e., HDPE); and (iv) ultra-high molecular weight (i.e., UHMWPE) polyethylene. Low density polyethylene (LDPE) exhibits a melting point of 105°C, toughness, stress cracking resistance, clarity, flexibility, and elongation. Hence, it is used extensively for piping and packaging, because of its ease of handling and fabrication. The chemical resistance of the product is outstanding, although not as good as high density polyethylene or polypropylene but it is resistant to many strong mineral acids (e.g., HCl, HF) and alkalis (e.g., NaOH, KOH, NH4OH), it can be used for handling most organic chemicals but alkanes, aromatic hydrocarbons, chlorinated hydrocarbons, and strong oxidants (e.g., HNO3) must be avoided. Assembly of parts made of PE can be achieved by fusion welding of the material which is readily accomplished with appropriate equipment. For instance, installations of piping made in this manner are the least expensive and most durable of any material available for waste lines, water lines, and other miscellaneous services not subjected to high pressures or temperatures. Nevertheless several limitations avoid its uses in some applications. These limitations are: a low modulus, a low strength, a low heat resistance, actually the upper temperature limit for the material is 60°C, combined with a tendency to degrade under UV irradiation (e.g., sunlight exposure). However, the polyethylene can be compounded with a wide variety of materials to increase strength, rigidity, and other suitable mechanical properties. It is now available in a fiber reinforced product to further increase the mechanical properties. Stress cracking can be a problem without careful selection of the basic resin used in the product or proper compounding to reduce this effect. Compounding of the product is also recommended to reduce the effect of atmospheric exposures over long periods. Linear low density polyethylene (LldPE) is produced by adding alpha-olefins (e.g., butene, 4-methyl-pentene-1, hexene, or octene) during ethylene polymerization to give a polymer with a similar density to LdPE but with the linearity of the HdPE. High density polyethylene (HDPE) has considerably improved mechanical properties, has better permeation barrier properties, and its chemical resistance is also greatly increased compared to the low density grade with a superior temperature limit of 75°C. Only strong oxidants will attack the material appreciably within the appropriate temperature range. Stress cracking of the HDPE can again be a problem if proper selection of the resin is not made. The better mechanical properties of this product extend their use into larger shapes, the application of sheet materials on the interior of appropriately designed vessels, such as packing in columns, and as solid containers to compete with glass and steel. Fusion welding can be achieved with a hot nitrogen gun. HdPE is produced by the catalytic polymerization of ethylene either in suspension, solution or gas phase reactors using traditional Ziegler–Natta, chromium or metallocene catalysts. Ultra-high molecular weight polyethylene (UHMWPE) is a linear polyethylene with an average relative molecular mass 6 6 ranging from 3x10 to 5 x10 . Its long linear chains provide great impact strength, wear resistance, toughness, and freedom stress cracking in addition to the common properties of PE such as chemical inertness, self-lubricant, low coefficient of friction. Therefore, this thermoplastic is suitable for applications requiring high wear/abrasion resistance for components used in machinery. As a general rule, polyethylenes are highly sensitive to UV irradiation, especially sunlight exposure. Nevertheless, it is possible to avoid UV-light sensitivity by adding particular UV stabilizers. 11

11.4.5.2 Polypropylene (PP) Polypropylene with the basic methyl substituted ethylene (i.e., propylene) as monomer is prepared industrially by the polymerization of propylene (C3H6) in a low pressure process using a mixture of aluminum triethyl [(C2H5)3Al] and titanium tetrachloride (TiCl4) as catalysts. The polymerization reaction is very simple and can be written as follows: n (CH2=CH2—CH2) —> [—CH(CH2)—CH2—]n

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In fact, the reaction mechanism induces a chain having a helical structure that exhibits the same asymmetrical stereochemical configuration of carbon atoms. This leads to a macromolecule having a high degree of crystallinity. Hence, polypropylene has considerably improved mechanical properties compared to polyethylene; actually it has a low density –3 (900–915 kg.m ), it is stiffer, harder, and has a higher strength than many polyethylene grades. Moreover, due to its higher melting point (160°C), it can be used at higher temperatures than PE with a superior temperature limit of 100°C. Its chemical resistance is also greatly increased, and it is only attacked by strong oxidants. Stress cracking of the PP can be a problem if proper selection of the resin is not made. In comparison with PE it exists in few commercial grades but the plastic is stereospecific and can be isotactic and atactic. The better mechanical properties of this products extend their use into larger shapes, the application of the sheet materials on the interior of appropriately designed vessels, such as packing in columns, and as solid containers to compete with glass and steel. The modulus of the polypropylene is somewhat higher, which is beneficial in certain instances. The coefficient of thermal expansion is less for polypropylene than for the high density polyethylene. Fusion welding with a hot nitrogen gun is practical in the field for both materials when the technique is learned. The two main applications of polypropylene are injected molded parts and fibers and filaments. Polypropylene is prepared either by the Spherisol process licensed by Basell that combines both liquid and gas phase polymerization with a Ziegler–Natta catalyst or the Borstar process introduced by Borealis.

11.4.5.3 Polybutylene (PB) The linear macromolecule of polybutylene is made of the following monomer unit [—CH2— CH(CH2-CH3)—]n. The ethyl groups are all located on the same side of the chain leading to an isotactic structure. Polybutylene is made from isobutylene, a distillation product of crude oil. Polybutylene exhibits high tear, impact, and puncture resistance. It also has low creep, excellent chemical resistance, and abrasion resistance.

11.4.6 Polymethylpentene (PMP) Polymethylpentene (PMP) is a transparent thermplastic obtained industrially by means of a Ziegler-type catalytic polymerization of 4-methyl-1-pentene. Polymethylpentene exhibits both a high stiffness and impact resistance, good dielectric properties similar to those of fluorocarbons, and a good resistance towards chemicals and to high temperatures. Actually, it withstands repeated autoclaving, even at 150°C.

11.4.7 Polyvinyl Plastics 11.4.7.1 Polyvinyl Chlorides (PVCs) Polyvinyl chloride [—CH2—CHCl—]n was the first thermoplastic to be used in any quantity in industrial applications. It is prepared by reacting acetylene gas with hydrochloric acid in the presence of a suitable catalyst. PVC has grown steadily in favor over the years, primarily because of the ease of its fabrication. It is easily worked and can be solvent welded or machined to accommodate fittings. It is very resistant to strong mineral acid and bases, and as a consequence, the materials have been extensively used for over 40 years as piping for cold water and chemicals. However, in the design of a piping structure, the thermal coefficient of linear expansion must be taken into consideration, and the poor elastic modulus of the material must be considered. With these limitations, the product as a piping material can

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accommodate a wide range of products found in the chemical process industries. The industrial production of polyvinylchloride utilizes several polymerization processes depending on the final application. In the mass polymerization, liquid vinyl chloride monomer (VCM) is polymerized in a pressurized batch reactor at an operating temperature ranging from 40 to 70°C. This process yields PVC resins with a high clarity. On the other hand, suspension polymerization is the most common industrial process because of the versatility of PVC grades obtained while emulsion polymerization is conducted in aqueous solution and yields colloidal PVC more suitable for preparing paints and printing inks. Two grades of the primary PVC material are available: rigid PVC grade which accounts for 65% of demand is extensively used in the construction industry for piping used for water drainage, while flexible PVC grade that contains a plasticizer is used in calendered sheet, wire and cable coating.

11.4.7.2 Chlorinated Polyvinylchloride (CPVC) Polyvinyl chloride can be modified through chlorination to obtain a vinyl chloride plastic with improved corrosion resistance and the ability to withstand operating temperatures that are 20–30°C higher. Hence, CPVC, which has about the same range of chemical resistance as rigid PVC, is extensively used as piping, fittings, ducts, tanks, and pumps for handling highly corrosive liquids and for hot water. For instance, it has been determined that the chemical resistance is satisfactory for CPVC in comparison with PVC on exposure for 30 days in such environments as 20wt.% acetic acid, 40–50 wt.% chromic acid, 60 to 70 wt.% nitric acid, at 30°C and 80 wt.% sulfuric acid, hexane, at 50°C and 80 wt.% sodium hydroxide until 80°C.

11.4.7.3 Polyvinyl Fluoride (PVF) The linear macromolecule of polyvinyl fluoride (PVF) is based on the monomer unit: [—CH2—CHF—]n. PVF which is only used industrially as a thin film, exhibits good resistance to abrasion and resists staining. It also has outstanding weathering resistance and maintains useful properties from –100 to 150°C.

11.4.7.4 Polyvinyl Acetate (PVA) The macromolecule of polyvinyl acetate (PVA) is based on a monomer where an acetate group replaces a hydrogen atom in the ethylene monomer. It is not used as a structural polymer because it is a relatively soft thermoplastic and hence it is only used for coatings and adhesives.

11.4.8 Polyvinylidene Plastics 11.4.8.1 Polyvinylidene Chloride (PVDC) Polyvinylidene chloride identified as PVDC or polyvinyl dichloride is based on a dichloroethylene monomer [—CH2—CCl2—CH2—CHCl—]n. It has improved chemical resistance and mechanical properties. Actually, it has better strength than common PVC. The material has an upper temperature limitation of 65°C for the normal (Type I) and 60°C for the high impact (Type II) products. The chemical resistance is good in inorganic corrosive media with an outstanding resistance to oxidizing agents. However, contamination by solvents of almost all types must be avoided. This material has had great significance in chemical industry applications over the years. The product has been made into a number of specific items designed to serve the chemical process industry. Among these are valves, pumps, piping, and liners particularly on the inside of the pipe. The latter product was the first thermoplastic to be used for this purpose and found extensive and useful service as its trade-name Saran®. Also, the material is available as a rigid or pliable sheet liner for application on the interior

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of vessels. It must be recognized that many modifications of the PVC can be made. Fiber reinforced products are also available.

11.4.8.2 Polyvinylidene Fluoride (PVDF) The macromolecule of polyvinylidene fluoride (PVDF) consists of a linear chain in which the predominant monomer unit is [—CH2—CF2—]n. PVDF has good weathering resistance and it is resistant to most chemicals and solvents but less inert than PTFE, PFA and FEP in the same conditions. PVDF is nonflammable and exhibits greater mechanical strength, wear and creep resistance than other fluorocarbons. PVDF is heat resistant up to 150°C. However, the material is much more workable and has been made into essentially any shape necessary for the chemical process industry. Complete pumps, valves, piping, smaller vessels, and other hardware have been made and have served successfully. The material may also be applied as a coating or as a liner.

11.4.9 Styrenics 11.4.9.1 Polystyrene (PS) Polystyrene is based on the monomer of styrene (i.e., phenylethene). Polystyrene [—CH(C6H5)—CH2—]n is essentially a light amorphous and atactic thermoplastic. The aromatic ring confers stiffness on the plastic and avoids chain displacement which would render the plastic brittle. The material is not recommended for applications handling corrosive chemicals because its chemical resistance by comparison with other available thermoplastics is poor and the material will stress crack in certain specific media. However, it has a high light transmission in the visible region, it has an excellent moldability rendering the ease of fabrication and possesses a low cost of the material so that it will always be considered if the properties are adequate for the use. Nevertheless, polystyrene is sensitive to UV irradiation (e.g., sunlight exposure) which gives a yellowish color to the material and the heat resistance of the material is only 65°C. The plastic will be encountered as casings for equipment and in various electrical applications. Fittings for piping have been made from the plastic, and many containers may be found made of the modified polystyrene. Joining can be achieved by solvent welding of the product to fabricate devices but restricts its use to waters and services not containing organic and inorganic chemicals. Polystyrene is prepared industrially by three different polymerization processes: (i)

the suspension polymerization produces polymers of different molecular weights and it can produce crystal polystyrene and high impact grades; (ii) the solution polymerization that can be either a batch or a continuous process yields the purest polystyrene grades; while (iii) bulk polymerization yields a high transparency and colorless polystyrene. Polystyrene is available commercially in several grades: general purpose polystyrene (GPPS), medium impact (MIPS) and high impact (HIPS) polystyrenes and finally expandable polystyrene (EPS). Polystyrene is the third largest consumed thermoplastic in use today after PE and PP with 20% of the market.

11.4.9.2 Acrylonitrile Butadiene Styrene (ABS) This is a terpolymer: the first monomer is butadiene; the second, acrylonitrile, consists of an ethylene molecule in which a hydrogen atom is replaced by a nitrile group (i.e., CN); and the third is styrene (i.e., an ethylene molecule with a phenyl group replacing a hydrogen atom).

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The material can be varied considerably in properties by changing the ratio of acrylonitrile to the other two components of the terpolymer. This offshoot of the original styrene resins has achieved a place in industrial work of considerable importance. Actually, the strength, toughness, dimensional stability and other mechanical properties were improved at the sacrifice of other properties. Although the material has poor heat resistance (90°C), a relatively low strength, and a restricted chemical resistance, the low price, ease of joining, and ease of fabrication make the material most attractive for distribution piping for gas, water, waste and vent lines, automotive parts, and numerous consumer service items ranging from the telephones to automobile parts. Actually, the plastic withstands attack by very few organic compounds, but is readily attacked by oxidizing agents and strong mineral acids. Moreover, stress cracks can occur in the presence of certain organic products.

11.4.10 Fluorinated Polyolefins (Fluorocarbons) Fluorocarbons represent certainly the most versatile and important group of thermoplastics for use in the chemical process industries (CPI). Most of these fluorinated polymers are able to handle, without any corrosion, extremely harsh environment and highly corrosive chemicals that only refractory, noble or precious metals or particular ceramics can tolerate. Nevertheless, owing to the presence of the most electronegative fluorine in the chain, the fluorocarbons are seldom attacked by molten alkali metals such as sodium and lithium forming graphite. As with other products, when such inertness is obtained in the material, certain other properties must be sacrificed. In this case, the fluorocarbon materials are more difficult to work in any manner and are much more limited in design and application than are other thermoplastic materials. The materials are porous and the permeation of specific chemicals must be considered to insure the proper selection of the proper fluorocarbon for the intended service. There are currently six types of commercial fluorocarbon thermoplastics. All have exceedingly good chemical stability, but there are differences which should be noted. These materials have been designed into a number of solid items for chemical service, such as impellers, mixers, spargers, packing, smaller containers, and a few more intricate shapes. However, the vast proportion of the use of fluorocarbons in the chemical process industry is as linings in steel or ductile iron. All shapes of lined pipe can be obtained. In addition, certain of the thermoplasts can be cut and jointed in the field using appropriate tools. Lined pumps and valves are available.

11.4.10.1 Polytetrafluoroethylene (PTFE) The basic monomer unit is a totally fluorinated ethylene molecule (—CF2—CF2—). It is well known under its common trade name Teflon®. It was discovered in 1938 by Roy J. Plunkett a DuPont scientists. Industrially, polytetrafluoroethylene is obtained from several consecutive of steps. First, chloroform reacts with hydrofluoric acid to yield chlorodifluoromethane. The chlorodifluoromethane is then pyrolized at 800–1000°C to yield the monomer, i.e., tetrafluoroethylene (CF2=CF2, TFE) which is purified and polymerized in aqueous emulsion or suspension using organic peroxides, persulfates or hydrogen peroxide as catalysts. The simple polymerization reaction is as follows. n (CF2=CF2) —> (—CF2—CF2—)n The macromolecule exhibits a structure with a high crystallinity that explains its unusually high melting point of 327°C. This characteristics ensures the highest useful temperature limit among plastics of 260°C. PTFE exhibits also good mechanical strength and an extremely low coefficient of friction that imparts to the material excellent self-lubricating abilities similar to

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those of graphite and molybdenum disilicide. PTFE exhibits the strongest anti-adhesive properties and no compound is known to adhere durably to PTFE. However, PTFE remains the most difficult of the fluorocarbons to work because of its high viscosity in the molten state; it cannot be cast and extrusion requires particular procedures. Therefore shapes and parts are usually made using powder metallurgy techniques such as sintering to produce it in usable forms. During sintering the PTFE powder or granules filling a mold of the desired shape are compressed under 14–70 MPa at a temperature well above 327°C and after cooling the PTFE exhibits the desired shape. From a chemical point of view, PTFE is one of the most chemically inert materials known apart from glass, tantalum, platinum and iridium for servicing (possessing a long service life) in various severely corrosive chemicals even at high temperatures. Moreover, no organic or mineral solvent dissolves PTFE. The only chemicals that are known to attack PTFE readily are molten alkali metals (e.g., Li, Na, K) and nascent fluorine gas. Finally, PTFE has excellent insulating properties with a low loss tangent factor at high frequencies. Nevertheless, permeation is an issue depending on the specific exposure but sometimes no better than many of the newer materials. Some problems associated with thermal cycling which can cause fatigue due to repeated expansion and contraction over a period of time when going through high temperatures were reported. Nevertheless, owing to their porosity, one particular mode of deterioration for fluorocarbons is the adsorption of a chemical, followed either by reaction with another component inside the thermoplastic or by polymerization of the product within the plastic. When this phenomena occurs, it leads to the surface degradation such as blistering. The material has also a definite heat limitation and overheating should be avoided. Cold flow of the resins is well known implies that the design and use of the fluorocarbon should be such that excessive compressive stresses are not imposed to create a cold flow condition. PTFE is now largely used in consumer goods as anti-stick materials. Industrially, its chemical inertness favors PTFE in applications involving harsh environments such as piping, pump parts and protective lining in the chemical process industry, while its self-lubricating properties allow its use in moving parts such as braking-pads on machinery, rotors and shafts packing etc., where lubrication is an issue.

11.4.10.2 Fluorinated Ethylene Propylene (FEP) The fluorinated ethylene propylene (FEP) macromolecule consist mainly of a linear chain with the basic monomer unit [—(CF2)3—CF(CF3)—]n.This translucent fluorocarbon is flexible and more workable than PTFE, and like PTFE it resists to all known chemicals except molten alkali metals, elemental fluorine, fluorine precursors, and concentrated perchloric acid. It withstands temperatures up to 200°C and may be sterilized by all known chemical and thermal methods. Certain carefully prepared films of FEP can be used as windows in equipment when necessary. The product has found extensive use as a pipe fitting liner as well as a liner in small vessels.

11.4.10.3 Perfluorinated Alkoxy (PFA) The macromolecule of perfluorinated alkoxy (PFA) or simply perfluoroalkoxy is based on the monomer unit: [—(CF2)2—CF(O—CnF2n+1)—(CF2)2—]n. Perfluoroalkoxy is similar to other fluorocarbons such as polytetrafluoroethylene and fluorinated ethylene propylene regarding its chemical resistance, dielectric properties, and coefficient of friction. Its mechanical strength, Shore hardness, and wear resistance are similar to PTFE and superior to that of FEP at temperatures above 150°C. PFA has a good heat resistance from –200°C up to 260°C near to that of PTFE but having a better creep resistance.

11.4.10.4 Polychlorotrifluoroethylene (PCTFE) Polychlorotrifluoroethylene (PCTFE) consists of a linear macromolecule with the following monomer unit [—CF2—CF(Cl)—]n. PCTFE possesses outstanding barrier properties to gases,

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especially water vapor. Its chemical resistance is surpassed only by PTFE and few solvents dissolve it at temperatures above 100°C, and it swells in chlorinated solvents. It is harder and stronger than perfluorinated polymers but its impact strength is much lower. PCTFE has heat resistance up to 175°C. It is commercialized under the common trade name Kel-F®. The working properties of PCTFE are relatively good, and it can be formed by injection molding, and hence the material is used as a coating as well as a prefabricated liner for severe chemical applications.

11.4.10.5 Ethylene-Chlorotrifluoroethylene Copolymer (ECTFE) Ethylene-chlorotrifluoroethylene copolymer (ECTFE) has a linear macromolecule in which the predominant alternating copolymer is [—(CH2)2−CF2—CFCl—]n. This copolymer exhibits useful properties for a wide range of temperatures, that is, from cryogenic temperatures up to 180°C. Its permittivity is low but stable over a broad temperature and frequency range.

11.4.10.6 Ethylene-Tetrafluoroethylene Copolymer (ETFE) Ethylene-tetrafluoroethylene copolymer (ETFE) is a linear macromolecule with the monomer unit: [—(CH2)2—(CF2)2—]n. ETFE exhibits physical properties similar to those of ethylene-chlorotrifluoroethylene copolymer.

11.4.11 Acrylics and Polymethyl Methacrylate (PMMA) The polymethyl methacrylate (PMMA) macromolecule is based on a monomer that corresponds to an ethylene molecule with one hydrogen atom substituted by a methyl group (i.e., CH3—) while the second hydrogen atom on the same carbon is replaced by an acetyl group (i.e., CH3COO—) giving the basic monomer unit [—CH3—C(CH3)(COOCH3)—]n. The raw chemical intermediate used for making polymethyl methacrylate is 2-hydroxy-2-methylpropanenitrile, which is prepared by reacting acetone with hydrocyanic acid according to the following reaction: CH3COCH3 + HCN —> (CH3)2C(OH)CN Afterwards, the 2-hydroxy-2-methylpropanenitrile produced is reacted with methanol (CH3OH) to yield the methacrylate ester. Another former route consisted of reacting methylacrylic acid [CH2=C(CH3)COOCH3] directly with methanol. The polymerization reaction is initiated either by organic peroxides or azo catalysts to finally produce the polymethyl methacrylate macromolecule. The polymerization is highly exothermic as indicated by the –1 elevate enthalpy of the reaction (58 kJ.mol ). Therefore, the process requires fast heat removal from the reactor vessel by efficient cooling. Continuous or batch processes are used. Batch process yield higher molecular weight PMMA while continuous process leads to copolymers. The commercial product is well known under the common trade name Plexiglas®. PMMA is a clear and rigid thermoplastic and in addition it is readily formed by injection molding. Main applications are guards and covers. As a general rule, the good atmospheric stability and clarity of acrylics have made them useful as high impact window panes and other see-through barriers important in industry. Various modifications are being made to alter the properties of the basic acrylic resins for specific services. However, these are not found in any great use in the industrial area to date. The upper temperature of usefulness is approximately 90°C. The loss in light transmission is only 1% after five years’ exposure in locations with high sunlight exposure.

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11.4.12 Polyamides (PA) Polyamides thermoplastics are prepared by condensation by reacting a carboxylic acid (i.e., RCOOH) and an amine (i.e., R'NH2) giving off water. Hence, the basic monomer unit in polyamides is [—NH—(CH2)2—CO—]n. These resins are well known under the common trade name Nylon®. Nylon was one of the first resinous products to be used as an engineering material. Actually, their excellent mechanical properties combined with their ease of fabrication have assured their continued growth for mechanical applications. Excellent strength, toughness, abrasion/wear resistance, and a high Young’s modulus are the chief valuable properties of nylons and explained the important applications as mechanical parts in various operating equipment such as gears, electrical fittings, valves, fasteners, tubing, and wire coatings. Actually, some nylon grades have tensile properties comparable to that of the softer aluminum alloys. In addition, coatings and structural items can be obtained. The heat resistance of the nylon can be varied, but must be considered in the range of 100°C. The chemical resistance is remarkably good for a thermoplastic, the most notable exception being the poor resistance to strong mineral acids. Moreover, stress corrosion cracking of nylon parts can occur, particularly when in contact with acids and alkaline solutions. Owing to the wide diversity of different additives or copolymer as starting materials, there are several commercial grades of nylon resins available. each of them with particular properties. The main grades are nylon®6 and nylon®66, these being the two grades having the highest strength. Industrially, nylon 6 is obtained in a batch process by mixing caprolactam, water and ethanoic acid in a reaction vessel heated under inert nitrogen atmosphere at 230°C, while nylon 66 is prepared from adiponitrile, itself obtained from butadiene or propylene, which is converted into hexamethylene diamine (HMD). HMD is then reacted with adipic acid to yield nylon by a condensation reaction.

11.4.13 Polyaramides (PAR) More recently, new commercial grades of nylon resins were developed in order to overcome the limitation of the previously discussed nylons grades. These products consist of polyamides that contain an aromatic functional group in their monomer, and hence are called aramid resins, aramid nylons after the acronym of aromatic and amides. The basic monomer units in polyaramides is [—NH—C6H4—CO—]n.They are well know under the trade names Kevlar® and Nomex® from E.I. DuPont de Nemours or Twaron® and Technora® from Teijin, the two companies that have 50% of the market. In practice, the basic difference between Kevlar and Nomex is the orientation of the aromatic rings, Kevlar being para-oriented while Nomex is meta-oriented. In both cases, this leads to a typical rod-like structure resulting in a high temperature of glass transition, and poor solubility in organic solvents along with an improved clarity.

11.4.14 Polyimides (PI) These plastics offer the most unique combinations of properties available for use in industrial service. The plastics are usable from –190°C to 370°C. These excellent low temperature properties are often overlooked where a plastic is required to retain some ductility and toughness at such low temperatures. Some combinations of the resins can be taken to 510°C for short periods without destroying the parts. The plastic has excellent creep and abrasion resistance, excellent elastic modulus for a thermoplastic, and good tensile strength that does not drop off rapidly with temperature. The chemical resistance must be rated as good.

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11.4.15 Polyacetals (PAc) Polyacetals or simply acetals under the common trade name Delrin® differ from other polymers due to the presence of an oxygen heteroatom in their monomer giving an heterochain polymer. The basic polymer unit is usually formaldehyde [—CH—O—]n.Polyacetals resins are obtained by the polymerization of formaldehyde using trioxanes to give the homopolymer while copolymers are usually prepared by incorporating other monomers. The main properties of acetals include high melting point, elevate strength and stiffness, low friction coefficient, and high resistance to fatigue. Higher molecular weight increases toughness but reduces melt flow. The excellent dimensional stability and toughness of the acetal resins recommends their use for gears, pump impellers, other types of threaded connections such as plugs, mechanical uses. The material has an upper useful temperature limitation of ca. 105°C. The chemical resistance indicated in the literature shows a wide range of tolerance for various inorganic and organic products. As with many other resins, this formaldehyde polymer will not withstand strong acids, strong alkalis, or oxidizing media.

11.4.16 Polycarbonates (PC) Polycarbonate (PC) is prepared by reacting bisphenol A and phosgene or by reacting a polyphenol with dichloromethane and phosgene. The basic monomer unit is [—OC6H4C(CH3)2C6 H4COO—]n. Polycarbonate is a linear, low crystalline, transparent, high molecular mass thermoplastic commonly know under the commercial trade name Lexan®. It exhibits a good chemical resistance to greases, and oils but has a poor organic solvent resistance. Moreover, it is greatly restricted in its resistance by a severe propensity to stress crack. This property can be modified greatly by proper compounding but remains the most serious problem when considering the polycarbonate for chemical exposures. The exceedingly high impact resistance of this thermoplastic (30 times that of safety glass) combined with high electrical resistivity, ease of fabrication, fire resistance, and light transmission (90%) has promoted its use into a wide range of industrial applications. The most notable of these for industrial applications is the use of the sheet material as a glazing product. Where a high impact, durable, transparent shield is required, the polycarbonate material is used extensively. In addition, many smaller mechanical parts for machinery, particularly those with very intricate molding requirements, impellers in pumps, safety helmets, and other applications requiring light weight and high impact resistance have been satisfied by the use of polycarbonate plastics. The material can be used from –170°C up to a temperature of 121°C.

11.4.17 Polysulfone (PSU) Polysulfone plastics comprise polysulfone [—Ph—C(CH3)2—Ph—O—Ph—SO2—O—]n, polyester sulfone [—O—Ph—SO2—O—]n and polyphenylsulfone [—O—Ph—SO2—Ph— O—Ph—Ph—]n with the aryl radical Ph = C6H4. The isopropylidene linkage imparts chemical resistance, the ether bond imparts temperature resistance, while the sulfone linkage imparts impact strength. The brittleness temperature of polysulfones is –100°C. Polysulfones are clear, strong, nontoxic, and virtually unbreakable. However, stress cracking can be a problem and should be considered before use. PSU do not hydrolyze during autoclaving and they are resistant to acids, alkalis, aqueous solutions, aliphatic hydrocarbons, and alcohols. Hence they have added another dimension to thermoplastics in heat resistance and strength at high temperature. The ease of molding the material, and its retention of properties as

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temperatures increase, has made it one of the faster growing resins in the market place. Use of the product for chemical equipment applications has not been noted to date but is anticipated.

11.4.18 Polyphenylene Oxide (PPO) PPO is a thermoplastic with excellent heat and dimensional stability, and satisfactory chemical resistance. The material may be found primarily in pump parts and certain other applications where impact strength, good modulus, and reasonable abrasion resistance are required. The chemical resistance of the material is good and the allowable temperature limit of 120°C, under appropriate conditions, extends the attractiveness for use of the product. The cost requires specific need for an identifiable application before choosing the product over many less costly thermoplastics.

11.4.19 Polyphenylene Sulfide (PPS) The macromolecule of polyphenylene sulfide (PPS) consists of the basic monomer of parasubstituted benzene rings [—C6H5—S—]n. The high crystallinity and thermal stability of the chemical bond existing between the aromatic ring and the sulfur atom are responsible for the high melting point, thermal stability, inherent flame-retardance, and good chemical resistance of polyphenylene sulfide. There are no known solvents of polyphenylene sulfide below 205°C. Chemical resistance is outstanding and the temperature usefulness ranges from –170°C to 190°C. Coatings prepared from the resin are available. Considerable strength with high elastic modulus can be obtained by the addition of glass or other mineral fillers to the material.

11.4.20 Polybutylene Terephthalate (PBT) Polybutylene terphthalate (PBT) is a semicrystalline thermoplastic polyester considered as a medium performance engineering polymer. It is produced industrially in a two-step batch or continuous process. The first step involves the transesterification of dimethyl terephthalate (DMT) with 1,4-butanediol (BDO) to produce hydrobutyl terephtlate (bis-HBT) at a temperature of 200°C. The second step consists to the polycondensation of bis-HBT at 250°C to yield PBT. It exhibits both excellent electrical properties and chemical resistance. When reinforced with glass fibers, it has improved stiffness and mechanical strength. Typical uses include connectors, capacitors and cable enclosures. PBT is also used in hot appliances such as iron and kettles.

11.4.21 Polyethylene Terephthalate (PET) Polyethylene terephthalate (PET) is obtained by reacting purified terephthalic acid (PTA) and monoethylene glycol (MEG) and melting the reaction product to initiate the polycondensation. The molten polymer is then extruded, cut into chips and cooled. PET main use is in the soft drinks and water bottles, other applications include thick-walled containers for cosmetics and pharmaceuticals.

Thermosets

713

11.4.22 Polydiallyl Phthalate (PDP) Polydiallyphthalate (PDP) is prepared from the diallyl 1,3-phthalate [C6H4(CH2—CH=CH2)]. The linear polymer obtained is a solid thermoplastic still containing unreacted allylic groups spaced at regular intervals along the polymer chain. When mixed with various fillers such as mineral, glass, or synthetic fibers it exhibits good electrical properties under high humidity and high temperature conditions, stable low-loss factors, high surface and volume resistivity, and high arc resistance.

11.5 Thermosets 11.5.1 Aminoplastics These thermosetting polymers are synthetic resins containing the amine group (–NH2) in their macromolecules. The major commercial resins in this group are: (i) urea-formaldehyde; (ii) melamine-formaldehyde; and (iii) aniline-formaldehyde. Urea-formaldehyde first appeared in 1929 in the USA as a substitute of glass for windows while melamine-formaldehyde was first commercialized by the American Cyanamid Co. in 1939. Urea-formaldehyde. This thermoset is obtained by the condensation of urea [(NH2)2CO] or derivatives such as hydroxymethylurea and formaldehyde (HCHO) in the presence of a proper catalyst either basic or acid. The general equation of the first reaction is given below: NH2-CO-NH2 + HCHO —> NH2-CO-NH-CH2OH + OHCH2-NH-CO-NH-CH2OH A wide variety of urea-formaldehyde resins can be obtained by careful selection of the pH, reaction temperature, reactant ratio, amino monomer, and degree of polymerization. If the reaction is carried far enough, an infusible polymer network is produced. The condensation proceeds in several consecutive stages: First it yields a liquid and transparent resin easily soluble in organic solvents. Secondly, the condensation continues and the resin becomes easy to mold. Thirdly, upon heating, the resin hardens yielding a hard solid, non fusible and insoluble in organic solvents. Industrially, the condensation is maintained in the second state in order to be able to mold the resin easily. The major fillers consist of pure cellulose, caseine or cotton flocks, in order to not alter the whiteness. Once cured, urea-formaldehyde exhibits good mechanical and dielectric properties and good chemical resistance. Melamine-formaldehyde. The monomer used for preparing melamine formaldehyde is formed by reacting melamine with formaldehyde to yield hexamethylolmelamine. The monomer can further condense in the presence of an acid catalyst; ether linkages can also form. A wide variety of resins can be obtained by careful selection of pH, reaction temperature, reactant ratio, amino monomer, and extend of condensation. Liquid coating resins are prepared by reacting methanol or butanol with the initial methylolated products. These can be used to produce extreme surface hardness, discoloration and solvent-resistant coatings by heating with a variety of hydroxy, carboxyl, and amide functional polymers to produce a cross-linked film.

11 Polymers and Elastomers

714

Polymers and Elastomers

11.5.2 Phenolics Phenol-formaldehyde resins or simply phenolics are prepared from the condensation of a mixture of phenol (i.e., carbolic acid) and cresols with formaldehyde as follows: n C6H5OH + n HCHO —> [—C6H2(OH)CH2—]n + nH2O Addition of formaldehyde ensures the formation of di- and trimethylolphenol, which later condense and polymerize rapidly. Industrial preparation. Two processes are currently used: (i)

(ii)

In the one-stage process, formaldehyde, phenol and an alkaline catalyst are introduced into a stainless steel vessel and reacted together. The elevated ratio of formaldehyde to phenol allows the thermosetting process to take place without any addition of another cross-linking agent. After discharge, further heating terminates the polymerization yielding an insoluble and non fusible resin. In the two-stage process, formaldehyde, phenol and concentrated sulfuric acid are introduced in a stainless steel vessel with a low ratio of formaldehyde to phenol in order to prevent the thermosetting reaction from occurring during manufacture of the resin. After 4 hours at 150°C, separation of condensation water and resin occurs and overlying water is simply removed by vacuum pumping. At this point the resin is a viscous liquid termed novolac resin. Subsequently, an activator, hexamethylenetetramine, is incorporated into the material to complete the polymerization and yields the final thermoset in the cured state. Ground phenolic resin can be mixed with a plasticizer and fillers such as asbestos, graphite, or silica to give materials with desired properties.

Properties. Phenolics are cheap thermosets that exhibit good strength, heat stability, and impact resistance along with a good machinability. Chemically speaking, phenolics demonstrate high chemical resistance and moisture penetration, except towards strong alkalis. Industrial applications. Due to their chemical resistance, phenolics are widely used as linings and impregnating resins for chemical process equipment for handling strong acids. Other uses include brake linings, electrical components, laminates, glues, adhesives, molds and binders.

11.5.3 Acrylonitrile-Butadiene-Styrene (ABS) Acrylonitrile-butadiene-styrene (ABS) is the largest volume engineering resin mainly used in the automotive industry and electronic appliances. ABS is made by the polymerization of styrene with acrylonitrile and butadiene. Three main processes are used industrially: (i) (ii)

the oldest process which is performed by emulsion polymerization is the more polluting; suspension polymerization consists of blending together a rich-rubber medium with styrene-acrylonitrile; and finally (iii) the continuous mass polymerization which does not use an aqueous medium is the preferred route because it generates less waste. ABS is usually sold as odorless solid pellets. From a health and safety point of view, when burning ABS produces dense fumes containing noxious gases such as carbon monoxide (CO) and hydrogen cyanide (HCN).

Rubbers and Elastomers

715

11.5.4 Polyurethanes (PUR) Polyurethanes are thermosets prepared by a condensation reaction involving diisocyanate (e.g., toluene diisocyanate, polymethylene diphenylene diisocyanate) with an appropriate polyol. They were first discovered by Wurtz in 1848. The polymers can be used in several forms such as flexible and rigid foams, elastomers, and liquid resin. The polyurethanes exhibit low corrosion resistance to strong acids and alkalis, and to organic solvents. Flexible foams are extensively used for domestic applications (e.g., bedding, and packaging), while rigid foams are used as thermal insulation material for transportation of cryogenic fluids, and frozen food products.

11.5.5 Furan Plastics Furan plastics or simply furans are the collective names for a wide range of thermosetting resins made either from furfuraldehyde (i.e., furol, furfural) or furfuryl alcohol. All these raw materials can be prepared from agricultural wastes (e.g., cornstalks, corncobs, oats husks, bagasse, and rice). Furfuryl alcohol resins are made by reacting furfuryl alcohol with an acid catalyst. They form low cost liquid resins having a good chemical resistance. They are used for making corrosion resistant coatings, industrial tank linings for protecting against various corrosives and finally mixed with silica sand they provide acid-proof cements (e.g., Alkor® cement). On the other hand, furfuraldehyde condenses with phenol to yield self-curing furalphenol resins. These resins possess excellent heat resistance up to 177°C and chemical resistance (e.g., acids, alkalis, alcohol, hydrocarbons) together with good dielectric properties. Moreover, their excellent adhesion capabilities onto metals and other materials make them highly suitable for making protective coatings for the CPI such as tank linings. As a general rule, they are more expensive than the phenolic resins but also offer somewhat higher tensile strengths. Furan plastics, filled with asbestos, have much better alkali resistance than phenolic asbestos. Some special materials in this class, based on bisphenol, are more alkali resistant.

11.5.6 Epoxy Resins (EP) Glycidal ether-based epoxies represent perhaps the best combination of corrosion resistance and mechanical properties. Epoxy novolac resins are produced by glycidation of the lowmolecular-weight reaction products of phenol or cresol with formaldehyde. Highly crosslinked systems are formed that have superior performance at elevated temperatures. Epoxies reinforced with fiberglass have very high strengths and excellent resistance to heat. Chemical resistance of the epoxy resin is excellent in non-oxidizing and weak acids but not good against strong acids. Alkali resistance is excellent in weak solutions. Chemical resistance of epoxy-glass laminates may be affected by any exposed glass in the laminate. Epoxies are available as castings, extrusions, sheet, adhesives, and coatings. They are used as pipes, valves, pumps, small tanks, containers, sinks, bench tops, linings, protective coatings, insulation, adhesives, dies for forming metal. When epoxies are used as adhesive, the epoxy resin and the aliphatic polyamine are packaged separately and mixed just before use.

11 Polymers and Elastomers

11.6 Rubbers and Elastomers Rubber and elastomers are widely used as lining materials for columns, vessels, tanks, piping. The chemical resistance depends on the type of rubber and its compounding. A number

716

Polymers and Elastomers

of synthetic rubbers have been developed to meet the demands of the chemical industry. Despite the fact that none of these has all the properties of natural rubber, they are superior in one or more ways. (trans-) polyisoprene and (cis-) Polybutadiene synthetic rubbers are close duplicates of natural rubber. A variety of rubbers and elastomers has been developed for specific uses.

11.6.1 Natural Rubber (NR) Natural rubber (NR) or cis-1,4-polyisoprene has as basic monomer unit a cis-1,4-isoprene (it is sometimes called caoutchouc). Natural rubber is made by processing the sap of the rubber tree (i.e., Hevea brasiliensis) with steam, and compounding it with vulcanizing agents, antioxidants, and fillers. If a color is desired, it can be obtained by incorporation of suitable pigments (e.g., red: iron oxide, Fe2O3, black: carbon black and white: zinc oxide, ZnO). Natural rubber have good dielectric properties, an excellent resilience, an elevate damping capacity and a good tear resistance. As a general rule, natural rubbers are chemically resistant to non-oxidizing dilute mineral acids, alkalis, and salts. However, they are readily attacked by oxidizing chemicals, atmospheric oxygen, ozone, oils, benzene, and ketones and as a general rule they have also poor chemical resistance to petroleum and its derivatives and many organic chemicals in which the material soften. Moreover, natural rubbers are highly sensitive to UV-irradiation (e.g., sunlight exposure). Hence, natural rubber is a general-purpose material for applications requiring abrasion/wear resistance, electric resistance, and damping or shock absorbing properties. Nevertheless, owing to their mechanical limitations, natural as well as many synthetic rubbers are converted into a harder and more stable product by vulcanization and compounding with additives. The vulcanization process consists of mixing crude natural or synthetic rubber with 25 wt.% sulfur and to heat the blend at 150°C in a steel mold. The resulting rubber material is harder and stronger than the previous raw material due to the cross-linking reaction between adjacent carbon chains. Therefore, industrial applications of natural rubber include components such as internal lining for pumps, valves, piping, hoses, and for machined components when hardened by vulcanization. However, because natural rubber has a low chemical resistance and is sensitive to exposure to sunlight, unsuitable properties in many industrial applications, it is today replaced by newer improved elastomers.

11.6.2 Trans-Polyisoprene Rubber (PIR) Trans-1,4-polyisoprene rubber (i.e., PIR, sometimes called Gutta Percha in the past) is a synthetic rubber with properties similar to those of its natural counterpart. It was first industrially prepared during World War II because of a lack of supply of natural rubber but despite containing fewer impurities than natural rubbers and having a simpler preparation process it is not widely used because it is also more expensive. Mechanical properties and chemical resistance is identical to that of natural rubber. As with many other rubbers its mechanical properties can be also improved by the vulcanization process.

11.6.3 Polybutadiene Rubber (BR) Polybutadiene rubber (BR) is similar to natural rubber in its properties but it is more costly to process into intricate shapes than rubbers such as styrene butadiene rubber. Hence, it is essentially used as an additive in order to increase the tear resistance of other rubbers.

Rubbers and Elastomers

717

11.6.4 Styrene Butadiene Rubber (SBR) Styrene butadiene rubber (SBR) is obtained by copolymerization of styrene and butadiene as basic monomer units usually mixed in the 3:1 mass ratio. It is well known commercially under the common trade name Buna®S. SBR exhibits a superior abrasion resistance than polybutadiene and natural rubber that explains its extensive use in automobile tires. Its chemical resistance is similar to that of natural rubber, that is, a poor resistance to oxidizing media, hydrocarbons and mineral oils. Hence, it offers no particular advantages in chemical service in comparison with other rubbers. Two main industrial processes are used for producing SBR: in the emulsion process, feedstocks are suspended in water together with a catalyst and a stabilizer; in the continuous-solution process, feedstocks are solubilized in a hydrocarbon solvent with an organometallic complex acting as a catalyst. SBR is the largest volume synthetic rubber used extensively in automobile tires, belts, gaskets, hoses, and other miscellaneous products.

11.6.5 Nitrile Rubber (NR) Nitrile rubber (NR) is a copolymer of butadiene and acrylonitrile. It is produced in different ratios varying from 25:75 to 75:25. The manufacturer’s designation should identify the percentage of acrylonitrile. Nitrile rubber under the common trade name Buna® N is well known for its excellent resistance to oils and solvents owing to its resistance to swelling when immersed in mineral oils. Moreover, its chemical resistance to oils is proportional to the acrylonitrile content. However, it is not resistant to strong oxidizing chemicals such as nitric acid, and it exhibits fair resistance to ozone and to UV irradiation which severely embrittles it at low temperatures. Nitrile rubber is used for gasoline hoses, fuel pumps diaphragm, gaskets, seals and packings (e.g., o-rings) and finally oil-resistant soles for safety work shoes.

11.6.6 Butyl Rubber (IIR) Butyl rubber (IIR) is a copolymer of isobutylene and isoprene as basic monomer units. Butyl rubber is chemically resistant to non-oxidizing dilute mineral acids, salts and alkalis, and a good chemical resistance to concentrated acids, except sulfuric and nitric acids. Moreover, it has a low permeability to air and an excellent resistance to aging and ozone. However, it is readily attacked by oxidizing chemicals, oils, benzene, and ketones and as a general rule it has also poor chemical resistance to petroleum and its derivatives and many organic chemicals. Moreover, butyl rubbers are sensitive to UV-irradiation (e.g., sunlight exposure). As with other rubbers, its mechanical properties can be largely improved by the vulcanization process. Industrial applications are the same as for natural rubber. Butyl rubber is used for tire inner tubes and hoses. 11

11.6.7 Chloroprene Rubber (CPR) Polycholoroprene is a chlorinated rubber material well-known under its common tradename Neoprene® or grade M. This elastomer is an extremely versatile synthetic rubber with nearly 70 years of proven performance in a broad spectrum of industry. It was the first commercial synthetic rubber originally developed in 1930s as an oil resistant substitute for

Polymers and Elastomers

718

Polymers and Elastomers

natural rubber. The polymer structure can be modified by copolymerizing chloroprene with sulfur and/or 2,3 dichloro-1,3-butadiene to yield a family of materials with a broad range of chemical and physical properties. By proper raw material selection and formulation of these polymers, the compounder can achieve optimum performance for a given end-use. Initially developed for resistance to oils and solvents it may resist various organic chemicals including mineral oils, gasoline, and some aromatic or halogenated solvents. It also exhibits good chemical resistance to aging and attack by ozone, and good resistance to UV irradiation (e.g., exposure to sunlight), until moderately elevated temperatures. Moreover, it has outstanding resistance to damage caused by flexing and twisting, an elevated toughness, and it resists burning but its electrical properties are inferior to that of natural rubber. Therefore, neoprene is noted for a unique combination of properties which has led to its use in thousands of applications throughout industry. It is extensively used as wire and cable jacketing, hose, tubes and covers. In the automotive industry, neoprene serves as gaskets, seals, boots, air springs, and power transmission belts, molded and extruded goods, cellular products adhesives and sealants, both solvent- and water-based foamed wet suits, latex dipped goods (e.g., gloves, balloons), paper, and industrial binders (e.g., shoe board). In civil engineering and construction applications, neoprene is used for bridge pads/seals, soil pipe gaskets, waterproof membranes, and asphalt modification.

11.6.8 Chlorosulfonated Polyethylene (CSM) Chlorosulfonated polyethylene (CSM) is well known under its common trade name Hypalon®. It is prepared by reacting polyethylene with sulfur dioxide and chlorine. This elastomer has outstanding chemical resistance to oxidizing environments including ozone, but it is readily attacked by fuming nitric and sulfuric acids. It is oil-resistant but it has poor resistance to aromatic solvents and most fuels. Except for its excellent resistance to oxidizing media, its physical and chemical properties are similar to that of neoprene with however improved resistance to abrasion, heat and weathering.

11.6.9 Polysulfide Rubber (PSR) Polysulfide rubbers are usually prepared by reacting dichloroalkyls with sodium polysulfide as follows: 2nCl—R—Cl + nNa2S4 —> [—R—S4—R—]n + 2nNaCl Polysulfide rubbers exhibit excellent chemical resistance towards oils and greases and they have very good dielectric properties. They are commercialized under the trade name Thiokol®.

11.6.10 Ethylene Propylene Rubbers Ethylene propylene rubber (EPR, or EPDM,) is a copolymer of ethylene and propylene. It has much of the chemical resistance of the related plastics: excellent resistance to heat and oxidation; good resistance to steam and hot water. It is used as a standard lining material for steam hoses; widely used in chemical services as well, having a broad spectrum of resistance.

Rubbers and Elastomers

719

11.6.11 Silicone Rubber Polysiloxanes are inorganic polymeric materials well known under the common name of silicone rubbers or simply silicones. Instead of the classic carbon chain skeleton, these particular class of polymers are based on a chemical bond occurring between silicon and oxygen (Si—O) similar to that found in silicates. Silicones are usually prepared from the hydrolysis of chlorosilanes such as dimethyl dichlorosilane that yields a silanol according to the chemical reaction listed below: (CH3)2SiCl2 + 2H2O —> (CH3)2Si(OH)2 + 2HCl Afterwards, in a second step, the unstable silanol formed yields by condensation a polysiloxane: n (CH3)2Si(OH)2 —> [—Si(CH3)2—O—]n Polysiloxanes are characterized by a three-dimensional branched-chain structure. Various organic groups introduced within the polysiloxane chain impart peculiar characteristics and properties to silicones. For instance, methyl groups impart water repellency, surface hardness, and nonflammability, while aromatic functions impart heat and wear resistance, and compatibility with organic chemicals. On the other hand, vinyl groups improve the stiffness of the macromolecule by reticulation. Finally, methoxy and alkoxy groups facilitate crosslinking at low temperatures. As a general rule, silicones have outstanding temperature resistance over an unusually wide temperature range (e.g., –75°C to +200°C). Silicones have relatively poor abrasion resistances and fair chemical resistance towards aromatic hydrocarbons (e.g., benzene, toluene), and to high-pressure steam, but withstand aging and ozone, as well as aliphatic solvents, oils and greases.

11.6.12 Fluoroelastomers Fluoroelastomers combine excellent chemical resistance (e.g. oxidizing acids, and alkalis) and high-temperature resistance (i.e., up to 275–300°C for short periods of time); excellent oxidation resistance; good resistance to fuels containing up to 30% aromatics; mostly poor resistance in solvents or organic media by contrast with fluorinated plastics. Viton® fluoroelastomers. There are three major general use families of Viton fluoroelastomer: A, B, and F. They differ primarily in their resistance to fluids, and in particular aggressive lubricating oils and oxygenated fuels, such as methanol and ethanol automotive fuel blends. There is a full range of Viton® grades that accommodates various manufacturing processes including transfer and injection molding, extrusion, compression molding, and calendering. There is also a class of high performance Viton® grades such as GB, GBL, GF, GLT, and GFLT. Viton®A is a family of fluoroelastomer dipolymers, that is they are polymerized from two monomers, vinylidene fluoride (VF2) and hexafluoropropylene (HFP). Viton®A fluoroelastomers are general purpose types that are suited for general molded goods such as o-rings and v-rings, gaskets, and other simple and complex shapes. Viton®B is a family of fluoroelastomer terpolymers, that is they are polymerized from three monomers, vinylidene (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). Viton®B fluoroelastomers offer better fluid resistance than A type fluoroelastomer. Viton®F is a family of fluoroelastomer terpolymers, that is they are polymerized from three monomers, vinyl fluoride (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). Viton®F fluoroelastomers offer the best fluid resistance of all Viton types. F types are particularly useful in applications requiring resistance to fuel permeation.

11 Polymers and Elastomers

720

Polymers and Elastomers

Viton®GBL is a family of fluoroelastomer terpolymers, that is they are polymerized from three monomers, vinyl fluoride (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). Viton GBL uses peroxide cure chemistry that results in superior resistance to steam, acid, and aggressive engine oils. Viton®GLT is a fluoroelastomer designed to retain the high heat and the chemical resistance of general use grades of Viton fluoroelastomer, while improving the low temperature flexibility of the material. Viton GLT shows a glass transition temperature 8–12°C lower than general use Viton grades. Viton®GFLT is a fluoroelastomer designed to retain the high heat and the superior chemical resistance of the GF high performance types, while improving the low temperature performance of the material. Viton GFLT shows a glass transition temperatures 6–10°C lower than general use Viton grades.

11.7 Physical Properties of Polymers Physical properties of common polymers and elastomers are reported in Tables 11.4 and 11.5, while physical quantities commonly used in the previous table to describe polymers characteristics are listed in Table 11.6 with the corresponding ASTM standards. On the other hand, particular mechanical properties are briefly described below. Shore hardness. Durometer hardness is a property that, as applied to elastomers, measures resistance to indentation. Shore A scale is used for soft elastomers, with shore D scale for harder materials. Compression modulus. Compression modulus is the stress required to achieve a specific deflection, typically 50% deflection. This test measures the polymer rigidity or toughness. Flexural or tear strength. Tear strength measures the resistance to growth of a nick or cut when tension is applied to a test specimen. Tear strength is critical in predicting an elastomer’s working life in demanding and abusive applications. Tensile strength. Tensile strength describes the ultimate strength of a material when enough stress is applied to cause it to break. In combination with elongation and modulus, tensile strength can predict a material’s toughness. Elongation at break. Elongation relates to the ability of an elastomer to stretch without breaking. Ultimate elongation is the percentage of the original length of the sample and is measured at the point of rupture. This property is useful in identifying the appropriate elastomer for stress or stretching applications.

CA

CAB

Protectoid

Tenite®

–3

Category

Usual chemical name

Epoxy resin

n.a.

n.a.

n.a. n.a.

n.a.

2.6– 3.15

0.69– 1.93

TS 1120– 1.5–3.6 n.a. 1180

EM 1270

ECO

Novalac®

EM n.a.

CSM

Epichloridrin rubber

Chlorofluorinated polyethylene Hypalon®

TP 1490– 2.48– 1500 3.30

CPVC

TP 1350– 1.03– 1600 2.76

TP 1150– 0.34– 1220 1.38

TP 1150– 0.3–2.0 0.62– 1220 4.14

Chlorinated polyvinyl chloride

CN

Density (ρ/kg.m )

Cellulose nitrate

Elastic or Young’s modulus (E/GPa)

Cellulose acetopropionate

Flexural modulus (G/GPa)

Cellulose acetobutyrate

Compressive modulus (K/GPa)

TP 1270– 1.0–4.0 8.3– 1340 27.6

Poisson’s ratio (ν/nil)

Cellulose acetate

Yield tensile strenght (σYS/MPa)

TP 1340– 3.5–3.9 1350

Ultimate tensile strenght (σUTS/MPa)

Celluloid®

GAT

Galathite®, Ameroid®

Elongation at break (Z/%)

Casein-formaldehyde

Ultimate compressive strenght (σUCS/MPa)

0.3–3.4 n.a.

Flexural yield strenght (/MPa)

EM 917

Notched Izod impact energy –1 per unit width (/J.m )

CAP

IIR

Kalar®, GR-1

Hardness Rockwell (or Shore SHD)

n.a.

n.a.

n.a.

2.3– 4.14

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

35–60

400

600

n.a.

69–121 n.a.

17

21

n.a.

35–83 4–60

n.a. 10.3– 13.8– 48.3 51.7

n.a. 10.3– 20–60 38.74 48.3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

42–75 53– 299

0.4– 0.9

n.a.

n.a.

n.a.

138– 62–75 2.7– 207 11.6

21–79 21–75 182

0.5

n.a.

SHA60-90

SHA40-90

R112-117

R95-R115

R20-R120

R31-99

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

SHA30-100 n.a.

100– R34-125 450

4.4

n.a.

14.5– 12.4– 260 52 110

20–55 14– 110

186– 365

700–950 n.a.

52–69 2.5

17

n.a. 17–43 12–110 6–70

n.a. n.a.

1.03– n.a. 32–45 41–62 20–100 36–69 28–97 105– R75-115 2.90 440

Static friction coefficient (µ/nil)

TP 1040– 1.7–2.6 0.92– 1180 3.03

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

65

n.a.

n.a.

Wear resistance (i.e., weight loss per 1000 cycles) (/mg)

Butyl rubber

ABS

Trade Names

Cycolac®

Acronym, Abreviation or Symbol

Acrylonitrile butadiene styrene

Table 11.4. Polymers Physical Properties 1

Physical Properties of Polymers 721

Polymers and Elastomers

11

Table 11.4. (continued) Elastic or Young’s modulus (E/GPa)

Density (ρ/kg.m ) –3

Category

Acronym, Abreviation or Symbol

Trade Names

Usual chemical name

Nylon®11

Nylon®12

Nylon®46

Nylon®6

Polyamide nylon 11

Polyamide nylon 12

Polyamide nylon 4,6

Polyamide nylon 6

PA

PA

PA

PA

Torlon®, Ultem® PAI

ABR

Polyacrylic butadiene rubber

Polyamide-imide

PF

Phenol formaldehyde

Buna®N, Nytek® NBR

Butadiene acrylonitrile rubber

PFA

NR

Caoutchouc

Natural rubber (cis-1,4-polyisoprene)

Perfluorinated alkoxy

MF

Melamine formaldehyde

n.a.

n.a.

n.a. n.a.

n.a.

0.66

n.a.

3.3–5.9 n.a.

TP 1130

TP 1180

TP 1010

TP 1040

n.a.

n.a.

2.6–3.0 0.97

3.1–3.3 3.1

2.0

1.5

TP 1420– 4.5–6.8 2 1460

EM n.a.

TS 1360

0.62

1.7

n.a.

7.6–10 n.a.

n.a.

1.7

n.a.

TP 2140– 0.66 2150

EM 1000

EM 920– 1037

TS 1500

TP 2150

FEP

Fluorinated ethylene propylene

Neoflon®

ECTFE TP 1680

EM n.a.

EBR

Flexural modulus (G/GPa)

Ethylene chlorotrifluoroethylene Halar®

Compressive modulus (K/GPa)

Ethylene-propylene rubber

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

2.2

n.a.

n.a.

1.7

n.a.

Poisson’s ratio (ν/nil) n.a. 44

n.a. 95

n.a. 45

n.a. 38

0.38 n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a.

300 n.a.

n.a.

100–300 n.a.

n.a.

23

510

320

7–15

n.a.

n.a.

78

300

55–100 50

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

170– 76– 220 200

n.a.

n.a.

n.a.

100– n.a. 600

50–55 290–300 n.a.

54

110– 190

n.a.

n.a.

21–29 300

21

18

48

n.a.

38

n.a.

36–90 n.a.

21

660–850 n.a.

n.a.

325

31–48 200–300 n.a.

n.a.

44.85

21

0.50 17.1– 29 31.7

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 45

n.a. n.a.

Yield tensile strenght (σYS/MPa)

n.a.

Ultimate tensile strenght (σUTS/MPa)

1.2–1.4 n.a.

Elongation at break (Z/%)

n.a.

Ultimate compressive strenght (σUCS/MPa)

1.4

Flexural yield strenght (/MPa)

n.a.

SHA30-90

SHD50-65

R93

n.a.

30– 250

80

n.a.

96

60– 140

n.a.

n.a.

nil

n.a.

n.a.

M82

M92

R84-107

M60

E72-86

n.a.

n.a.

SHD60

SHA30-90

SHA30-95

11–21 M115-125

nil

nil

n.a.

1000 SHD67-75

n.a.

Notched Izod impact energy –1 per unit width (/J.m )

TP 1700

Hardness Rockwell (or Shore SHD)

Tefzel®, Halon® ETFE

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.2–0.3 5

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.2

n.a.

n.a.

n.a.

0.27

n.a.

n.a.

0.4

n.a.

Static friction coefficient (µ/nil)

Ethylene tetrafluoroethylene

Wear resistance (i.e., weight loss per 1000 cycles) (/mg)

Ethylene propylene diene rubber Dutral®, Nordel® EPDM EM 850

722 Polymers and Elastomers

TP 1210

PA

PAR

PAR

PAR

Nylon®66

Kevlar®

Nomex®

Durel®

TP 935

PB

PEEK

Neoprene®

Victrex®

Ultem®

Polychloroprene rubber

MDPE TP 926– 940

UHMW TP 940

Polyethylene (medium density)

Polyethylene (ultra-high molecular weight)

PEN

LDPE

Polyethylene (low density)

Polyethylene naphtalate

HDPE

Polyethylene (high density)

Lennite®

TP 1370

PESV

TP 1360

TP 912– 925

TP 950– 968

TP 1270

PEI

TP 1320

1.207

1.241

n.a.

0.75

2.5

n.a.

7

13.80

n.a.

n.a. n.a.

2.9

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

6

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.240– n.a. 0.790

0.069– n.a. 0.207

5.0–5.5 n.a.

5.5

0.135– 0.520– n.a. 6.90 0.970

0.17– 0.38

0.14– 1.86

0.414– 0.062– n.a. 1.24 0.105

2.4–2.6 n.a.

2.9

3.7–4.0 n.a.

n.a.

2.3–2.4 2.2

0.3

2.6

2.1– 10.3

6

16.60

n.a.

59–124 n.a.

3.3

2.1

n.a.

EM 1230– 0.7– 1250 20.1

Polyether sulfone

Polyether imide

Polyether ether ketone

CPR

Lexan®, Macrolon®

Polycarbonate

TP 1200

TP 1310

PBT

Polybutadiene terephtalate

PC

EM 910

BR

Polybutylene

TP 1300

PBI

TP n.a.

TP 1440

TP 1140

TP 1060

PA

Nylon®612

TP n.a.

PA

Nylon®610

Polybutadiene rubber

Polybenzene-imidazole

Polyarylate resins

Polyaramide

Polyaramide

Polyamide nylon 6,6

Polyamide nylon 6,12

Polyamide nylon 6,10

n.a.

2760

82

156

50

n.a. n.a.

n.a. n.a.

n.a.

n.a.

n.a.

344

n.a.

n.a.

n.a.

103

60

70–95 40–80

85

5–26

20–40

200

60

20–40 500

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

140

n.a.

100–800 n.a.

70–100 50

n.a.

n.a. 10–19 10–19 10–20

n.a. 0.2– 11.5

n.a.

55–75 100–150 80

n.a.

250

450

3

50

n.a.

n.a.

300

n.a. 25–40 16–40 5–12

n.a. n.a.

n.a. n.a.

0.4 n.a.

n.a. 3.4– 24.1

n.a. 62

n.a. 16–18 n.a.

n.a. 52

n.a. 13.8– n.a. 17.2

n.a. n.a.

n.a.

52–61 100–250 n.a.

n.a.

n.a. 68.9– 138 75.8

n.a. n.a.

n.a. n.a.

n.a. 59

n.a. 51

n.a. 55

R107

n.a.

n.a.

40– 110 n.a.

n.a.

M89

5–70 R95-120

n.a.

n.a.

n.a.

n.a.

n.a.

M70

SHA45-80

E105

85

50

85

n.a.

n.a.

n.a.

1000 R50-70

1000 SHD45-60

1000 SHD41-46

SHD60-73

M88

R125

M99

SHA30-95

600– M70 850

640– SHD60 800

60

n.a.

26

20–38 20– 210

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

130.90 117– n.a. 294

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a.

n.a.

n.a.

n.a.

6

10

n.a.

n.a.

10– 15

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.27

n.a.

0.1–0.2 n.a.

n.a.

n.a.

0.29

n.a.

n.a.

0.18

n.a.

0.31

n.a.

n.a.

n.a.

0

n.a.

n.a.

n.a.

0.2–0.3 3–5

n.a.

n.a.

Physical Properties of Polymers 723

Polymers and Elastomers

11

Table 11.4. (continued)

Acronym, Abreviation or Symbol

Trade Names

Usual chemical name

Gutta Percha

Polyisoprene (trans-1,4-polyisoprene)

Delrin®500

Noryl®

Milkon®, Ryton® PPS

Propylux®

Polyoxymethylene (Homopolymer)

Polyphenylene Oxide

Polyphenylene sulfide

Polypropylene (atactic)

TP 1400

PP

PPO TP 850– 900

TP 1350

TP 1090

POMH TP 1420

POM

n.a.

2.24– 3.17

3.7– 3.83

n.a.

3.8

2.59

2.62– 3.585

0.689– 0.9 1.520

1350

2.5

3.6

2.9–3.2 2.41– 3.10

1.5

Acetal®

Polyoxymethylene (Heteropolymer)

TP 835

TPX®

Polymethyl pentene

PMP

PMMA TP 1180– 3.036 1190

Plexiglas®

n.a.

Polymethyl methacrylate

TP 1250

n.a.

2.0–3.0 3.1– 3.45

PLA

EM n.a.

TP 1420

3.5

Polylactic acid

PIP

PI

Category

Vespel®

–3

Polyimide

Density (ρ/kg.m )

TP 1250

Elastic or Young’s modulus (E/GPa)

PHB

Flexural modulus (G/GPa)

Polyhydroxybutyrate (biopoloymer)

Compressive modulus (K/GPa) n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 81

n.a. n.a.

n.a.

n.a.

n.a.

3.11

4.62

n.a.

48.3– 145

n.a.

25.5

15

2.5–4

2.5–100

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

15–75

21.4

65.5

300

1.6

55–65 50

n.a. 57–70 72

n.a. 65–69 69–83 40–75

n.a. n.a.

n.a.

70

n.a.

70–150 8–70

40

80

n.a.

2.55– n.a. 54–73 72.4 3.17

n.a.

n.a.

n.a.

n.a.

n.a.

Poisson’s ratio (ν/nil)

n.a.

Yield tensile strenght (σYS/MPa)

2.0–4.0 3.0

Ultimate tensile strenght (σUTS/MPa)

n.a.

Elongation at break (Z/%)

TP 1560

90

n.a.

72– 131

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

110

110

n.a.

96

n.a.

107– 94– 124 110

110

n.a.

72– 124

n.a.

n.a.

n.a.

n.a.

n.a.

Ultimate compressive strenght (σUCS/MPa)

TP n.a.

Flexural yield strenght (/MPa)

PET

n.a.

n.a.

E52-99

R85

763

16

200

75– 130

R95

R120

M78-R115

M94-101

53–80 R120-M78

49

16–32 M92-100

12.8– 29

n.a.

80

35–60 n.a.

13–35 M94-101

n.a.

Notched Izod impact energy –1 per unit width (/J.m )

PEO

Hardness Rockwell (or Shore SHD)

Mylar®

n.a.

0.10– 0.30

n.a.

0.35

0.20– 0.35

n.a.

n.a.

n.a.

n.a.

0.42

n.a.

13– 16

n.a.

20

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.2–0.4 n.a.

n.a.

Static friction coefficient (µ/nil)

Polyethylene terephtalate

Wear resistance (i.e., weight loss per 1000 cycles) (/mg)

Polyethylene oxide

724 Polymers and Elastomers

TP 1380– 4.4–11 n.a. 1720

PSR

PSU

PVDC

PVDF

PVF

Thiokol®

Udel®, Thermalux®

Teflon®

Kel-F®

Saran®

Kynar®, Foraflon®

Polysulfone

Polytetrafluoroethylene

Polytrifluorochloroethylene

Polyvinyl alcohol

Polyvinylidene chloride

Propylene-vynilidene hexafluoride

Polyvinyl chloride

Polyvinyl fluoride

Polyvinylidene fluoride

Polyvinyl acetate

Polyurethane

Polysulfide rubber

1.6–2.4 2.07

2.48

n.a.

PVC

TP n.a.

PVAL n.a.

n.a.

n.a.

1.0–3.0 1.17– 8.3

0.3– 0.55

n.a.

n.a.

1.17– 1.38

0.19– 0.55

2.69

n.a.

EM 1800– 2.07– 1860 15.17

n.a.

TP 1160– 2.1–2.7 1.0 1550

TP 1630

TP 1191

PVA

0.6

TS 1050– n.a. 1250

PUR

1.3

TP 2130– 0.48– 2220 0.76

TP 1240

EM 1340

TP 1054– 2.3–4.1 3.17 1070

TP 1040

PTFCE TP 2100

PTFE

Viton®, Fluorel® PVHF

Vinyl®

TP 1760

PS

Crystal®

Polystyrene (normal)

HIPS

0.689– n.a. 1.520

Propylux®

TP 890– 915

Polystyrene (high-impact)

PP

n.a.

4.83– 8.63

n.a.

n.a.

n.a.

83– 117

n.a.

n.a.

75

96

100–400 n.a.

27–69 1.6–3

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

48

n.a.

n.a.

n.a. 8.96– 4.8– 18.62 11.0

7–27

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

100–700 n.a.

4.5–65

n.a.

50–300 55– 110

200

n.a.

n.a.

29–49 10–21

0.4 33–41 n.a. n.a. 55

nil

106

n.a.

90

35– 39.3

n.a.

n.a.

160

69

n.a.

n.a.

n.a.

n.a.

R75-112

16–53 R98-106

n.a.

n.a.

102

n.a.

n.a.

n.a.

n.a.

21

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

SHA50-95

SHD65-85

n.a.

n.a.

n.a.

n.a.

0.20– 0.40

0.24

n.a.

n.a.

n.a.

n.a.

R45(SHD50) 0.05– 0.20

M69

n.a.

67–94 120– R77-83 320

n.a.

n.a.

n.a.

n.a.

L73

R95

19–24 M60-90

133

n.a.

20–53 R95

32–35 80–250 32–51 51–76 65

2.09– n.a. 20–57 5–25 2.90

n.a.

n.a.

n.a.

n.a.

n.a.

35–100 36–50

35

31–41 100–600 n.a.

n.a. 17–27 10–40 200–400 11.7

0.37 70.3

n.a. n.a.

n.a. n.a.

0.34 24.8

n.a. n.a.

n.a. n.a.

1.03– n.a. 37 2.07

0.41

2.58

n.a.

n.a.

n.a.

n.a.

0.689– 1.2–1.7 n.a. 1.520

Propylux®

TP 920– 940

Polypropylene (syndiotactic)

PP

Propylux®

Polypropylene (isotactic)

n.a.

n.a.

n.a.

24

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Physical Properties of Polymers 725

Polymers and Elastomers

11

Acronym, Abreviation or Symbol

UF

Urea formaldehyde

Category

UP

–3

Unsaturated polyester

Density (ρ/kg.m )

SBR n.a.

2.1– 10.3 n.a.

n.a.

5.5

TS 1470– n.a. 1520

TS 1780 n.a.

n.a.

TP 1300– 24–40 n.a. 1450

EM 940

EM 940

Elastic or Young’s modulus (E/GPa)

UPVC

Buna®S, GR-S

Styrene-butadiene rubber

Flexural modulus (G/GPa) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Compressive modulus (K/GPa)

n.a.

n.a.

6.5

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a.

41

n.a.

n.a.

750

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

450–500 n.a.

n.a.

38–62 2–40

25

n.a. 12.4– 21 20.7

n.a. n.a.

n.a. n.a.

Poisson’s ratio (ν/nil)

n.a.

Yield tensile strenght (σYS/MPa)

n.a.

Ultimate tensile strenght (σUTS/MPa)

n.a.

Elongation at break (Z/%)

EM n.a.

Ultimate compressive strenght (σUCS/MPa)

EM n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Flexural yield strenght (/MPa)

SBS

n.a.

32

21

n.a.

n.a.

n.a.

n.a.

Notched Izod impact energy –1 per unit width (/J.m )

SR

n.a.

M88

n.a.

SHA30-95

SHA30-90

n.a.

SHD60A

Hardness Rockwell (or Shore SHD)

Unplastified polyvinyl chloride

Kraton-D®

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Static friction coefficient (µ/nil)

IR

Rhodorsil®

Usual chemical name

Styrene-butadiene styrene rubber

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Wear resistance (i.e., weight loss per 1000 cycles) (/mg)

Synthetic isoprene rubber

Trade Names

Silicone rubber (polysiloxane)

Table 11.4. (continued)

726 Polymers and Elastomers

55–95

60–100 n.a.

60

110

n.a.

121

200–260 n.a.

–20

–40

n.a.

n.a.

n.a.

–46

n.a.

Usual chemical name

Cellulose acetobutyrate

Cellulose acetopropionate

Cellulose nitrate

Chlorinated polyvinyl chloride

Chlorofluorinated polyethylene

Epoxy resin

Epichloridrin rubber

n.a.

n.a.

n.a.

90

60–105 n.a.

Glass transition temperature (Tg/°C)

n.a.

Melting point or range (m.p./°C)

Cellulose acetate

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

110

n.a.

140

230

Specific heat capacity –1 –1 (cP/J.kg .K )

94

Thermal conductivity –1 –1 (k/W.m .K )

Casein-formaldehyde

Coefficient of linear thermal –6 –1 expansion (α/10 K )

n.a.

n.a.

n.a.

n.a.

43

n.a.

73

52–105

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.140 68–78 n.a.

1422– 0.180 65– 1590 160

1200– 0.16– 120– 1600 0.33 160

1464 0.16– 140 0.32

1200– 0.16– 80– 1900 0.36 180

50

1950 0.13– n.a. 0.23

Heat deflection temperature under 1.82 MP a flexural load (T/°C) Deflection temperature under 0.455 MP a flexural load (T/°C)

–75 to n.a. –67 6.1– 6.8

n.a.

6.7– 8.8

n.a.

n.a.

n.a.

n.a.

n.a.

1,E+15 3.3– 3.8

10 11 10

10–

1,E+13 n.a.

1,E+11 2.5– 6.2

1,E+12 5

n.a.

230–260 n.a.

n.a.

n.a.

n.a.

66

n.a.

62

73

n.a.

Electrical resistivity (ρ/ohm.cm)

n.a.

150

Minimum operating temperature range (/°C)

–45

Relative electric permittivity (@1MHz) (ερ/nil) n.a.

n.a.

n.a.

n.a. 1.9– 7.0

7–14

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 0.1

1.478 n.a. 1.0– 3.0

0.0400 1.478 n.a. 0.9– 2.2

0.0600 1.49

480– 0.0019 n.a. 590 n.a.

92 0.3– 0.7 1.5081 n.a. n.a.

118– 0.0700 1.46– 590 1.58

n.a.

100

110

157– 0.052 276

n.a.

140– 0.0200 1.49 250

Dielectric field –1 strenght (Ed/kV.cm )

1,E+15 2.4– 3.3

Loss factor

99–112

Refractive index (nD/nil)

77–98

Transmittance (T/%)

1506 0.17– 53– 0.34 110

Water absorption per –1 24 hours (/%wt.day )

88– 120

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Water absorption at saturation (/%wt.)

n.a.

n.a.

n.a.

n.a.

n.a.

Comb.

Comb.

Comb.

n.a.

HB

Flame rating ASTM UL94

Butyl rubber

70–110 n.a.

Maximum operating temperature range (/°C)

n.a.

Vicat softening temperature (/°C)

Acrylonitrile butadiene styrene

Table 11.5. Polymers Physical Properties 2

Physical Properties of Polymers 727

Polymers and Elastomers

11

0

n.a.

n.a.

n.a.

n.a.

–56

–40

n.a.

n.a.

n.a.

–200 200–260 n.a.

–50

n.a.

Usual chemical name

Ethylene-propylene rubber

Ethylene chlorotrifluoroethylene

Fluorinated ethylene propylene

Melamine formaldehyde

Natural rubber (cis-1,4-polyisoprene)

Butadiene acrylonitrile rubber

Perfluorinated alkoxy

Phenol formaldehyde

Polyacrylic butadiene rubber

Polyamide-imide

Polyamide nylon 11

Polyamide nylon 12

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

70–130 n.a.

n.a.

n.a.

260

121

82

120–200 n.a.

204

n.a.

n.a.

Glass transition temperature (Tg/°C)

150

n.a.

n.a.

280

104

n.a.

n.a.

n.a.

–70

n.a.

n.a.

n.a.

n.a.

Melting point or range (m.p./°C)

n.a.

n.a.

n.a.

n.a.

317

n.a.

305

n.a.

n.a.

n.a.

260

245

n.a.

Specific heat capacity –1 –1 (cP/J.kg .K )

270

n.a.

0.16

n.a.

n.a.

135

80

n.a.

90

n.a.

0.25

0.25

n.a.

n.a.

16

n.a.

n.a.

n.a.

1226 0.19

1226 0.3

100– 120

125

1000 0.26– n.a. 0.54

n.a.

n.a.

n.a.

n.a.

1830 0.15

1674 0.167 22

n.a.

n.a.

n.a.

n.a.

Thermal conductivity –1 –1 (k/W.m .K )

n.a.

Coefficient of linear thermal –6 –1 expansion (α/10 K )

n.a.

Heat deflection temperature under 1.82 MP a flexural load (T/°C) Deflection temperature under 0.455 MP a flexural load (T/°C)

150

55

278

n.a.

163

n.a.

n.a.

n.a.

183

n.a.

77

n.a.

70

130–135 48–55

150

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

115

n.a.

105

Electrical resistivity (ρ/ohm.cm) 2.5

2.6

n.a.

n.a.

2.6

n.a.

n.a.

1,E+13 3.5

1,E+13 3

1,E+17 3.9– 5.4

n.a.

1,E+12 5.0– 6.5

1,E+18 2.1

n.a.

n.a.

n.a.

1,E+18 2.1

n.a.

n.a.

1,E+17 2.6

n.a.

Relative electric permittivity (@1MHz) (ερ/nil)

n.a.

n.a.

n.a.

n.a.

n.a.

0.0001 n.a.

n.a.

n.a.

n.a.

0.0007 n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a. 0.2

n.a. 0.03

n.a. n.a.

n.a. n.a.

n.a. 0.1

n.a. 0.01

n.a. 0.01

n.a. n.a.

260– 0.0600 n.a. 300

n.a. 1.1

n.a. 1.1

0.0420 1.42– n.a. 0.3 1.46

n.a.

160– 0.0500 n.a. 200

230

n.a.

120– 0.0060 n.a. 160

800

n.a.

n.a.

1.474 n.a. n.a.

0.0050 1.4028 n.a. 0.03

n.a.

110– n.a. 160

n.a.

190

n.a.

800

n.a.

Dielectric field –1 strenght (Ed/kV.cm )

n.a.

Loss factor

2.22

Refractive index (nD/nil)

n.a.

Transmittance (T/%)

n.a.

Water absorption per –1 24 hours (/%wt.day )

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Water absorption at saturation (/%wt.)

n.a.

V2

V2

V0

n.a.

n.a.

V0

n.a.

n.a.

n.a.

V0

V0

n.a.

V0

n.a.

Flame rating ASTM UL94

150

Minimum operating temperature range (/°C)

Ethylene tetrafluoroethylene

Maximum operating temperature range (/°C)

–51

Vicat softening temperature (/°C)

Ethylene propylene diene rubber

Table 11.5. (continued)

728 Polymers and Elastomers

80–160 n.a.

n.a.

n.a.

80–180 n.a.

–40

n.a.

n.a.

–30

250

n.a.

n.a.

n.a.

–60

n.a.

Polyethylene (low density)

Polyethylene (medium density)

93

50–70

n.a.

n.a.

n.a.

n.a.

334

80

n.a.

127

223

n.a.

n.a.

n.a.

640

640

255

212

n.a.

223

290

0.3

n.a.

n.a.

n.a.

0.22

13

45

n.a.

23

n.a.

n.a.

320

110 to 1900 n.a. 120

–110 102 to 1900 0.33 to –20 112 –118

n.a.

n.a.

235

100– 200

100– 200

60

n.a.

426

174

n.a.

n.a.

90–100

147

n.a.

n.a.

50

75

260

3.1– 3.8

n.a.

n.a.

n.a.

n.a.

2.53

1,E+15 3.2

1,E+15 2.5

1,E+13 3.20

1,E+16 3.1

1,E+11 2.0– 6.3

n.a.

35

46

203

n.a.

n.a.

n.a. n.a.

n.a.

0.2000 n.a.

0.0280 n.a.

n.a.

0.2000 1.53

0.3500 n.a.

n.a.

n.a.

0.0005 n.a.

0.0020 n.a.

n.a.

n.a.

n.a. 0.03

n.a. n.a.

n.a. 0.01

n.a. 0.4

n.a. 0.0030 n.a.

n.a.

160

0.0030 1.65

280– 0.0013 n.a. 330

190

n.a.

n.a. 1.0

n.a. 0.25

n.a. 0.3

n.a. n.a.

150– 0.0010 1.585 n.a. 0.1 670

n.a.

200

n.a.

n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 2.3

n.a. 3.0

n.a. n.a.

n.a. 2.7

n.a. 1.3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.6

n.a.

n.a.

5.0

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1,E+17 2.25– 180– 0.0010 1.52– n.a. 0.01 2.35 390 1.53

n.a.

1,E+15 2.25– 270– 0.0005 1.51– n.a. 0.015 n.a. 2.35 390 1.52

1,E+15 2.30– 420– 0.0010 1.53– n.a. 0.01 2.40 520 1.54

1,E+17 3.7

190–210 1,E+15 3.1

142

n.a.

n.a.

n.a.

250

270

n.a.

250

200

1,E+12 2.93– 134– 0.0220 n.a. 3.30 183.1

n.a.

n.a.

1,E+13 3.4

n.a.

5,E+12 3.6

1,E+13 3.8– 4.3

128–138 1,E+16 2.92

102–113 54–60

150

n.a.

n.a.

31–56 210

26– 108

0.13– 55 0.18

0.22

0.25

2170 0.192 n.a.

n.a.

65–80

160

130–180 55–90

n.a.

200

1200 0.19– 38–70 140 0.22

n.a.

n.a.

2//

40

120– 130

n.a.

45

25–50 220

0.178 50.4– 355 72.0

n.a.

1350 0.21

n.a.

n.a.

n.a.

n.a.

1400 0.04

1670 0.25

1670 0.22

n.a.

1600 0.23

n.a.

–90 to 125 to 1900 0.42– 100– –200 137 0.52 200

n.a.

Polyethylene (high density)

55–120 n.a.

225

–110 180–200 n.a.

Polyether sulfone

143 215

n.a.

n.a.

Polyether imide

Polyether ether ketone

–50

107

–43

Polychloroprene rubber

n.a.

n.a.

–135 115–130 n.a.

50

Polycarbonate

210 n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

113

120

n.a.

Polybutadiene terephtalate

Polybutylene

–100 95

n.a.

n.a.

n.a.

n.a.

n.a.

375

n.a.

n.a.

n.a.

–150 100

375

49.85

45.85

49.85

53

42.85

–200 180–245 n.a.

n.a.

n.a.

100–200 n.a.

–40

Polybutadiene rubber

Polybenzene-imidazole

Polyarylate resins

Polyaramide

Polyaramide

Polyamide nylon 6,6

Polyamide nylon 6,12

Polyamide nylon 6,10

Polyamide nylon 6

Polyamide nylon 4,6

Comb.

Comb.

Comb.

V0

V0

V0

n.a.

V0–V2

n.a.

HB

n.a.

V0

V0

n.a.

n.a.

Self-E

HB-V2

V2

Self-E

V2

Physical Properties of Polymers 729

Polymers and Elastomers

11

n.a.

–40 to 115–170 235 –60

n.a.

–270 250–320 n.a.

n.a.

Usual chemical name

Polyethylene oxide

Polyethylene terephtalate

Polyhydroxybutyrate (biopoloymer)

Polyimide

Polyisoprene (trans-1,4-polyisoprene)

n.a.

n.a.

Polyoxymethylene (Heteropolymer)

Polyoxymethylene (Homopolymer)

80–120 n.a.

n.a.

–20 to 75–115 n.a. –40

Polymethyl pentene

105

–40

n.a.

n.a.

n.a.

Polymethyl methacrylate

50–90

n.a.

95

Glass transition temperature (Tg/°C) n.a.

255

n.a.

n.a.

n.a.

n.a.

n.a.

29

175

175

250

104.85 45

n.a.

280 to 365 330

n.a.

68.85

n.a.

Melting point or range (m.p./°C)

n.a.

Specific heat capacity –1 –1 (cP/J.kg .K )

n.a.

Thermal conductivity –1 –1 (k/W.m .K )

n.a.

Coefficient of linear thermal –6 –1 expansion (α/10 K )

n.a. n.a.

n.a. n.a.

n.a.

20–21 n.a.

n.a.

n.a.

n.a.

n.a.

n.a. 55

n.a.

85

117

1464 0.22– 122 0.24

1464 0.37

2000 0.17

170

n.a.

100

1450 0.17– 34–77 105 0.19

n.a.

1090 0.10– 30–60 n.a. 0.36

n.a.

1200 0.17– 15–65 115 0.40

n.a.

n.a.

Heat deflection temperature under 1.82 MP a flexural load (T/°C) Deflection temperature under 0.455 MP a flexural load (T/°C)

155

136

136

40

74–95

n.a.

360

n.a.

80

n.a.

n.a.

Electrical resistivity (ρ/ohm.cm)

Polylactic acid

n.a.

Relative electric permittivity (@1MHz) (ερ/nil) n.a.

1,E+15 3.7

1,E+15 3.8

1,E+16 2.12

1,E+15 2.76

1,E+15 2.5

1,E+18 3.4

1,E+16 3.0

1,E+14 3.0

n.a.

1,E+15 3.2

200

200

n.a.

150

n.a.

220

n.a.

170

n.a.

n.a.

n.a. n.a.

84 n.a.

n.a. 0.01

n.a.

n.a.

0.0050 n.a.

0.0048

0.0020 n.a.

0.0140 1.49

n.a.

0.0018 1.42

n.a.

n.a. 0.25

0.2

n.a. 0.01

92 0.2– 0.3

n.a. n.a.

n.a. 0.2– 2.9

n.a. n.a.

0.0020 1.58– n.a. 0.1 1.64

n.a.

1600 0.0048 n.a.

190– 0.0010 n.a. 280

Dielectric field –1 strenght (Ed/kV.cm )

1,E+18 2.3

Loss factor

42

Refractive index (nD/nil)

69

Transmittance (T/%)

125 to 1900 0.45– 130– 135 0.52 200

Water absorption per –1 24 hours (/%wt.day )

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Water absorption at saturation (/%wt.)

n.a.

HB

HB

Comb.

HB

n.a.

V0

n.a.

HB

n.a.

n.a.

Comb.

Flame rating ASTM UL94

55–95

Minimum operating temperature range (/°C)

Polyethylene naphtalate

Maximum operating temperature range (/°C)

n.a.

Vicat softening temperature (/°C)

Polyethylene (ultra-high molecular weight)

Table 11.5. (continued)

730 Polymers and Elastomers

50–95

n.a.

n.a.

n.a.

Polypropylene (syndiotactic)

Polystyrene (high-impact)

–260 180–260 n.a.

175

n.a.

n.a.

n.a.

80–100 n.a.

135–150 n.a.

175

n.a.

n.a.

n.a.

n.a.

n.a.

–40

–70

Polytetrafluoroethylene

Polytrifluorochloroethylene

Polyvinyl alcohol

Polyvinylidene chloride

Polyvinyl fluoride

Polyvinylidene fluoride

Polyvinyl acetate

Polyurethane

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

100–400 n.a.

n.a.

109

98

n.a.

–54

140

160

Polysulfone

Polysulfide rubber

Polystyrene (normal)

n.a.

n.a.

Polypropylene (isotactic)

n.a.

n.a.

240

n.a.

Polypropylene (atactic)

80–120 n.a.

n.a.

–40

–170 190

Polyphenylene sulfide

Polyphenylene Oxide

176

285

267

258

n.a.

n.a.

215

327

n.a.

n.a.

115

n.a.

0.22

n.a.

n.a.

–20 to 200 41

n.a.

90

0.159 100– 200

100– 200

1339 0.13

190

1255 0.795 n.a.

n.a.

100– 160

0.19– 126– 0.22 216

1800 0.21

920

1000 0.25

n.a.

0.17

50

n.a.

n.a.

n.a.

n.a.

75

54

174

n.a.

80

82

n.a.

n.a.

n.a.

120–150 80–115

n.a.

n.a.

n.a.

n.a.

130

120

1255 0.259 31–51 n.a.

n.a.

1250 0.10– 30– 0.13 210

91

1960 0.154 60–90 n.a. 1250 0.124 90

43

110–120 50–60

68–95 85

1960 0.154 81– 100

1960 0.12

135

2.46

n.a.

3.5

1,E+09 6.2– 7.7

1,E+14 6.4– 8.9

1,E+12 3.2– 6.0

n.a.

n.a.

1,E+12 n.a.

n.a.

1,E+18 2.0– 2.1

1,E+16 3.14

1,E+08 1.3

1,E+16 2.4– 3.1

1,E+16 2.3– 2.5

1,E+16 2.2– 2.3

1,E+16 2.2– 2.3

1,E+16 2.2– 2.3

1,E+14 3.8

38–60 137–179 100–125 2,E+17 2.59

1090 0.17– 30–49 260 0.28

n.a.

–40 to 141– 1381 0.10– 80– –35 178 0.25 140

–18.15 198

84.85

29

n.a.

45

–97

193

n.a.

100

100

–10 to 135 –8.2

–1.5 to 165 –10

–18

85

84.9

0.01

n.a. 0.01

n.a. 0.01

n.a. 0.05

n.a. 0.1– 0.5

n.a. 0.0050 1.63

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1.46

100– 0.0490 1.42 130 80– 130

n.a. 1

n.a. nil

nil 0.01

99 0.22

n.a. n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. n.a.

n.a.

n.a. 0.04– n.a. 0.06

n.a. 0.1

n.a. n.a.

1.4669 n.a. 3.6

n.a.

n.a.

160– 0.0450 1.63 240

n.a.

394

n.a.

197– n.a. 230

400– 0.0001 1.38 800

166

n.a.

180– 0.0002 1.59– n.a. 0.4 240 1.60

177– 0.0004 1.59– n.a. 0.1 240 1.60

200– 0.0005 260

200– 0.0005 n.a. 260

200– 0.0005 n.a. 260

177– 0.0014 n.a. 240

160– 0.0040 n.a. 200

Self-E

V0

Self-E

n.a.

n.a.

n.a.

V0

V0

V0

n.a.

V0

V0

Comb.

Comb.

Comb.

V0

V0

Physical Properties of Polymers 731

Polymers and Elastomers

11

232

–29

–60

Usual chemical name

Propylene-vynilidene hexafluoride

Silicone rubber (polysiloxane)

Vicat softening temperature (/°C)

120

–54

n.a.

n.a.

n.a.

Synthetic isoprene rubber

Unplastified polyvinyl chloride

Unsaturated polyester

Urea formaldehyde

n.a.

n.a.

n.a.

82

n.a.

–60

Styrene-butadiene rubber

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Glass transition temperature (Tg/°C)

Styrene-butadiene styrene rubber n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Melting point or range (m.p./°C) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Specific heat capacity –1 –1 (cP/J.kg .K )

n.a.

Thermal conductivity –1 –1 (k/W.m .K )

n.a.

Coefficient of linear thermal –6 –1 expansion (α/10 K )

n.a.

Heat deflection temperature under 1.82 MP a flexural load (T/°C) Deflection temperature under 0.455 MP a flexural load (T/°C)

n.a.

250

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

16

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.30– 22–96 n.a. 0.42

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Electrical resistivity (ρ/ohm.cm)

n.a.

Relative electric permittivity (@1MHz) (ερ/nil)

204

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1,E+15 2.4

1,E+14 2.4

n.a.

n.a.

n.a.

Dielectric field –1 strenght (Ed/kV.cm ) n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

120– 0.0350 n.a. 160

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

160– 0.0070 1.54 590

Loss factor

1,E+16 2.9– 3.6

Refractive index (nD/nil)

n.a.

n.a. 0.5

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. 0.1

n.a. n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a. 0.15–1 n.a.

Transmittance (T/%)

1674 0.167 60–70 n.a.

Water absorption per –1 24 hours (/%wt.day )

212

Water absorption at saturation (/%wt.)

81 to 87

n.a.

HB

Self-E

n.a.

n.a.

n.a.

n.a.

Self-E

Self-E

Flame rating ASTM UL94

60–105 n.a.

Minimum operating temperature range (/°C)

n.a.

Maximum operating temperature range (/°C)

Polyvinyl chloride

Table 11.5. (continued)

732 Polymers and Elastomers

Physical Properties of Polymers

733

Table 11.6. Polymers physical quantities and ASTM standards (continued)

Electrical

Thermal properties

Mechanical

Processing

Physical quantities

ASTM standard

SI unit

U.S. customary unit

Processing temperature range

°C

°F

Molding pressure range

Pa

psi

Compression ratio

nil

nil –1

Melt mass flow rate

ASTM D1238

kg.s

Mold linear shrinkage

ASTM D955

nil

lb./h

Density (ρ)

ASTM D792

kg.m

lb.ft

Specific gravity (d)

ASTM D792

nil

nil

Poisson’s coefficient (ν)

n.a.

nil

nil

Yield tensile strength (σYS)

ASTM D638

Pa

psi

Ultimate tensile strength (σUTS)

ASTM D638

Pa

psi

Tensile strength at break

ASTM D412

Pa

psi

Elongation at yield (Z)

ASTM D638

nil

%

Elongation at break (Z)

ASTM D638

nil

%

Compressive strength

ASTM D695

Pa

psi

Flexural yield strength

ASTM D790

Pa

psi

Tensile or elastic modulus (E)

ASTM D638

Pa

psi

Compressive or bulk modulus (K)

ASTM D695

Pa

psi

Flexural or shear modulus (G)

ASTM D790

Pa

Unotched Izod impact strength (i.e., impact energy per unit width)

ASTM D256A

J.m

ft.lb/in

Abrasion resistance per 1000 cycles

ASTM D1044

kg.Hz

lb.cycles

Hardness Rockwell (HR) scale M and R

ASTM D785

nil

nil

Hardness Durometer Shore (SH) scale A and D

ASTM D2240

nil

nil

Hardness Durometer Barcol

ASTM D2583

nil

nil

Minimum operating temperature (Tmin)

n.a.

°C

°F

Maximum operating temperature (Tmax)

n.a.

°C

°F

Brittle temperature (Tbrit)

ASTM D746

°C

°F

Glass transition temperature (Tg)

ASTM D3418

°C

°F

Vicat softening point (Tvicat)

ASTM D1525

°C

°F

Melting point (m.p.)

ASTM D3418

°C

Thermal conductivity (k)

ASTM C177

Wm K

in/in –3

–3

psi –1

–1

°F –1

–1

–1

Btu.ft .h .°F

–1

–1

–1

–1

Specific heat capacity (cP)

n.a.

J.kg .K

Coefficient of linear thermal expansion (a)

ASTM E831

K

Deflection temperature under flexural load (0.455MPa)

ASTM D648

°C

°F

Deflection temperature under flexural load (1.82MPa)

ASTM D648

°C

°F

Dielectric permitivity (er) (1MHz)

ASTM D150

nil

Dielectric field strength (Ed)

ASTM D149

V.m

V.mil

Dissipation or loss factor (δ)

ASTM D149

nil

nil

Electrical volume resistivity (ρ)

ASTM D257

Ω.m

Ω.cirft/in

Surface resistivity

ASTM D257

Ω.m

Ω.cirft/in

–1

Btu.lb .°F

–1

–1

°F-1

nil –1

–1

11 Polymers and Elastomers

Polymers and Elastomers

Table 11.6. (continued)

Chemical

Miscellaneous

Physical quantities

Molten state

734

ASTM standard

SI unit

U.S. customary unit

Refractive index (nD) (589 nm)

n.a.

nil

nil

Optical transmission (T) (visible light)

n.a.

nil

%

Nuclear radiation resistance (e.g., α, β. γ, and X-rays)

n.a.

nil

nil

Water absorption in 24 hours

ASTM D570

s

Water absorption at saturation

ASTM D570

nil

wt.%

Chemical resistance

n.a.

nil

nil

Flammability rating index

ANSI/UL-94

nil

Oxygen permeability

ASTM D3985

m s Pa

barrers

Water vapor transmission

ASTM E96

s

perm-inch

Water vapor transmission rate

ASTM F1249

s

perm-inch

Apparent viscosity

ASTM D3835

nil

Melt specific heat

ASTM C351

mPa.s

Melt thermal conductivity

ASTM C177

mPa.s

Melt viscosity

ASTM D3835

mPa.s

–1

2 –1

wt.%day

nil –1

11.8 Gas Permeability of Polymers Table 11.7. Gas permeability coefficients of most common polymers (in barrers) Polymer

O2

N2

H2

He

CO2

H 2O

PAN

0.0002

–

–

–

0.0008

300

Cellophane

0.0021

0.0032

0.0065

0.005

0.005

1900

PVDC

0.0053

0.00094

–

0.31

0.03

0.5

PVA

0.0089

0.001

0.009

0.001

0.001

–

TFE

0.025

0.003

0.94

6.8

0.048

0.29

PETP

0.035

0.0065

3.70

1.32

0.17

130

PA (Nylon 6)

0.038

0.0095

–

0.53

0.10

177

PVC

0.0453

0.0118

1.70

2.05

0.157

275

HDPE

0.403

0.143

3.0

1.14

0.36

12.0

CA

0.78

0.28

3.5

13.6

23

5500

PP

2.3

0.44

41

38

9.2

51

PTFE (Teflon)

2.63

0.788

23.3

18.7

10.5

1200

PS

2.63

23.2

23.2

18.7

10.5

1200

LDPE

2.88

0.969

12.0

4.9

12.6

90

–10

3

2

Conversion factors: 1 barrers = 10 cm (STP).cm /(cm .s.cmHg) (E)

11.9 Chemical Resistance of Polymers See Table 11.8, pages 735–744.

–1

HDPE

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

Ammonium acetate (std.)

Ammonium phosphate

Ammonium nitrate

Ammonium hydroxide (28 wt.%)

Ammonium glycolate

Ammonium chloride

Ammonium carbonate

A

A

A

A

A

A

A

A

A

Ammonia (anhydrous)

Amino acids

A

A

A

A

A

A

A

A

A

C

NR

B

A

A

A

A

A

A

NR B

B

A

Aluminum sulfate

PP

PS

PMP PC

PEEK PSU

A

A

A

A

A

A

A

A

C

A

A

A

A

A

A

A

A

A

C

C

A

B

A

A

A

B

A

A

A

A

A

B

A

A B

B A

A

A

B

B

A

B

A

B

A

B

B

A

A

NR

NR

B

C

C

A

C

A

A

A

A

A

A

A

A

A

A

C

NR NR A

NR

B

A

A

NR NR NR B

A/A

A/A

A/A

A/A

A/A

A/A

NR A/A

B

A

A/A

B

A

C

A/A

B

A

C

A/A

B

A

C

NR

C/C

NR

NR

C/NR B

A/B

B

B

NR

A

A

NR

NR

B/NR B

A

A

B

B/C

A/B

A/A

A

B

B/C

A/B

B A

NR

C/C

B/C

B

A/A A/A A/A

A/A A/A A/A

A/A A/A NR

A

A

A

A

A

A

B

NR

A

NR

NR

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A NR

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

NR A/A A/A NR

NR

A

NR

B

A/B

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A A/A

A/A A/A

A/C

A/A B

A/A B

A/A B

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/B

B

B

B

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

A/A

A/A

NR A/A

A

C

B

NR

A

NR

NR

NR A/A

NR

A

NR

A

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

A

Aluminum hydroxide

Aluminum chloride

Allyl alcohol

Alanine

Adipic acid

Acrylonitrile

Acetonitrile

Acetone

Acetic anhydride

Acetic acid (50 wt.%)

Acetic acid (5 wt.%)

Acetamide (std.)

Acetaldehyde

Chemical

Table 11.8. Chemical resistance of polymers. A ≡ satisfactory; B ≡ fairly; C ≡ poor and NR ≡ nonresistant

Chemical Resistance of Polymers 735

Polymers and Elastomers

11

A

A

B

Ammonium sulfate

n-Amyl acetate

PP

PS

PMP PC

PEEK PSU

NR

B

B B

NR A/A

C

NR NR C

A/A

C/NR

B/B

A/A

NR

C/C

B/B

A/A

NR

B

B

B

B

NR

NR

A

C

A

B

B

B

NR

A

NR

A

NR

A

C

A

NR

B

NR A

C

B

B

B

C

B

NR

B

B

A

NR

NR NR C

Butyl chloride

B

NR

C

Butyl alcohol

A

NR

NR NR NR

B

n-Butyl acetate

C

NR

NR NR

NR

NR

NR

Butadiene

NR

NR

NR

C

NR

Bromoform

NR

B

Bromobenzene

NR

A/A

NR

B

NR NR NR NR NR NR NR NR NR C

A

Bromine

A

NR

B

NR

A

B

C

Bromic acid

A

A

A/A

C

NR

A

NR

A

B/B

NR

A

A

NR NR

B

NR NR NR NR NR NR B

C

C/C

NR

Boric acid

A

B

A

NR/NR C/C

NR/NR C/C

Borax

A

A

Benzyl alcohol

B

Benzyl acetate

B

A

C

N

A

Benzine

NR A/A

Benzoic acid (std.)

NR NR NR B

NR NR C

Benzene

C

A

C

A A

NR NR

C

A

NR

NR

NR NR B

Benzaldehyde

A

NR

B

A/A

NR

NR

C

B

Barium chloride

A

NR

A

A

NR

NR

B

A

A

NR NR NR NR NR NR NR

A

A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

C

B

A/A A/A A/A

NR A/A A/A B

C

NR

NR

B

B

NR

A

NR A/A A/A A/A

NR A/A A/A C

NR

NR

NR A/A A/A A/A

A/A A/A A/A

NR A/A A/A A/C

A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A A/A

A/A A/A

A/C

A/A A/A

A/A A/A

A/A A/A

A/A

B/NR

A/A

A/A

A/A

A/A

A/A B/NR B/NR

A/A A/A

A/A B/NR B/NR

A/A A/A

A/A A/A

A/A A/A

A/A

A/A A/A

A/A A/A

A/A A/NR A/NR

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

Barium carbonate

Aqua regia

B

B

Antifreeze (Prestone)

Aniline

B

A

A

NR NR C

A

A

A

Amyl chloride

Amyl alcohol

HDPE

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

Ammonium oxalate

Chemical

Table 11.8. (continued)

736 Polymers and Elastomers

A

A

A

Calcium hypochlorite (std.)

A

A

Cyclohexanone

Cyclohexane

Cresol

Copper (II) sulfate

Copper (II) nitrate

Copper (II) fluoride

Copper (II) chloride

Citric acid (10 wt.%)

A

C

NR

A

A

A

A

A

C

A

NR

C

C

B

C

C

C

A

B

C

A

A

A

A

A

C

B

NR B

A

A

A

C

C

NR NR C

A

A

Chromic acid (50 wt.%)

Chromic acid (80 wt.%)

A

Chromic acid (10 wt.%)

A

A

A

A

A

A

p-Chloroacetophenone

Chloroacetic acid

A

NR B

B

B

Chlorine 10 wt.% in water

N

C

Chlorine gas

C

A

A

A

C

NR

A

B

B

B

A

B

B

A

NR

C

NR

NR NR

A

A

A

NR

A

C

C

A

C

A

NR

B

C

A

A

B

A

A

A

C

NR

C

NR

C B

NR

NR NR A

NR NR NR NR

A

C

A

NR

B

B

NR NR NR NR

NR NR NR B

C

C

NR NR NR NR NR

A

A

A

NR NR NR NR C

NR NR NR NR NR NR NR NR C

NR C

NR

NR

C

A

A

A

A

Chloroform

Chlorobenzene

Cetyl alcohol

Cellosolve acetate

Caustic soda

Carbon tetrachloride

Carbon disulfide

Carbazole

Calcium sulfate

Calcium nitrate

A

A

Calcium hydroxide (std.)

A

A

A

A

NR B

C

Calcium chloride

Butyric acid

A/A

A/A

A/A

A/A

B

NR

NR

B

A/A

A

B

B

NR

A

A/A

B/NR

NR

NR

NR

NR

NR

NR

A/A

B

NR

NR

B

NR

B

B

NR

A/A

A/A

A/A

B

NR

NR

B

NR

B/B

B/B

A/A

B

NR

NR

C/C

NR

A/A

A/A

C

B

A

NR

A

A/A

NR

B

NR

B

A

NR

C

A

NR

NR

C

B

NR

NR

B

A

B

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A

A/A A/A A/C

A/A A/A A/A

A/A A/A A/A

A/A A/A N/T

A/A A/A N/T

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A

A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/C

A/A A/A

A/A A/A

A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

Chemical Resistance of Polymers 737

Polymers and Elastomers

11

HDPE

PP

PS

PMP PC

PEEK PSU

NR

C

C

C

C

NR

NR

NR

NR

B

A

NR

A

A

C

A

A

B

A

NR

A

A

C

C

B

C

n-Decane

Diacetone alcohol

o-Dichlorobenzene

p-Dichlorobenzene

1,2-Dichloroethane

2,4-Dichlorophenol

Diethyl benzene

Diethyl ether

Diethyl ketone

Diethyl malonate

Diethylamine

Diethylene glycol

Diethylene glycol ethyl ether

Dimethyl acetamide

Dimethyl formamide

Dimethylsulfoxide

1.4-Dioxane

Dipropylene glycol

Ether

Ethyl acetate

Ethanol (95 wt.%)

Ethyl benzene

Ethyl benzoate

Ethyl butyrate

Ethyl chloride

A

A

C

A

B

A

A

A

A

A

C

A

B

C

B

B

NR B

A

C

C

A

C

C

C

NR

NR

B

C

A

C

C

C

A

B

B

A

B

C

B

B

C

A

A

NR

A

C

A

A

A

A

A

B

A

B

NR

NR

NR

NR

B

C

A

C

C

B

A

A

C

A

A

C

A

A

A

NR

NR

NR

B

A

C

C

B

NR

NR

NR

NR

A

NR

NR NR

A

NR NR C

NR

A

B

NR

NR

NR

C

B

NR

C

NR

NR NR

NR NR B

A

NR

NR

NR

B

B

NR

NR C

C

NR NR B NR

NR

NR

NR

C

NR

NR NR

B

C

A

C

C

NR NR NR C

A

C

C

A

B

NR

NR

NR

NR

NR

NR

B

C

NR

A/A

NR

NR

NR

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

Cyclopentane

Chemical

Table 11.8. (continued)

NR

B/C

NR

NR

B

B/NR B/NR C/C

NR

NR

NR

NR

NR

A/A A/A A/C

A/A A/A A/A

NR A/A A/A A/A

NR

NR

NR

A

NR A/A A/A NR

C

B

C

NR

C

NR

C

C

NR

B

NR

C

NR

NR

C

NR

NR

NR

A

C

A/A

A/A A/A

A/A A/A

A/C

A/A

A/A

A/A

C/C

NR

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

738 Polymers and Elastomers

B

A

A

B

B

A

A

C

Ethylene glycol

Ethylene glycol methyl ether

A

A

B

B

A

A

C

C

A

A

A

A

hydrochloric acid (20 wt.%)

hydrochloric acid (35 wt.%)

B

C

hydrochloric acid (5 wt.%)

B

C

A

A

A

A

A

A

NR

NR B

C

NR

A

C

A

A

A

B

A

Hydrazine

Hexane

n-Heptane

Heating oil

Glycerol

Glutaraldehyde

Glacial acetic acid

Gasoline

Fuel oil

Freon TF

A

A

A

C

C

A

A

B

A

A

A

NR

B

C

A

A

A

A

B

A

A

A

A

B

A

A

C

B

A

B

B

B

B

C

A

A C

A

C

C

A

A

NR

C

A

A A

A/A

A

A/A

A/A

C

A

A

A

NR A/A

A/A

A/A

A

A

A/A

NR A/A

C

A

B

A

A

NR NR

NR NR C

NR

NR NR

A

A

NR NR A

NR

NR

C

C

NR NR A

NR

NR

NR

C

NR

NR

B/C

NR

NR

NR

B/B

NR

NR

A

B

NR

B/C

NR

C

B

B

NR

NR

A

B

NR

B/C

NR

C

B

B

A

A

A

C

A

Formic acid (98–100 wt.%)

C

A

NR A/A

B

A

B

A

Formaldehyde (40 wt.%)

A

A

C

A

B NR

A

B

NR NR NR C

A

A

NR C

A

NR

NR

NR

B/C

A/A

B

NR

B/C

B

NR

B

NR

A

B

C

C

NR

B

A

C

NR

B/C

C

B

NR

B

B

A

A

A

B

A

B

C

B

A

C

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

C

A/A A/A A/A

A/A A/A A/C

A/A A/A A/A

NR NR C

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A C

A

C

C

A

NR A/A A/A A/A

A/A

B

Formaldehyde (10 wt.%)

A/A

B

B

Fluosilicic acid

A/A

B

B

B

NR B

A/A

A/B

C

C

A

C/C

A/A

A/B

C

A

B

C/C

Fluorine gas

A

A

A

A

A/A

C

A

A

A

C

C

B

C

A

Fluorides

Ferric sulfate

Ferric nitrate

A

A

A

A

C

A

A

A

NR NR C

NR

A

NR

A

C

A

C

C

NR NR

A

A

A

Ferric chloride

A

C

A

A

NR

C

B

A

C

A

C

A

A

A

Fatty acids

Ethylene oxide

Ethylene chloride

C

A

A

A

A

A

Ethyl lactate

Ethyl cyanoacetate

NR

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A B

A/A A/A

A/A NR

A/A A/A

A/A A/A

A/A A/A

C

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A

A/A

NR

A/A

A/A

B

A/A

NR

A/A

A/A

A/A

NR

A/A

A/A

A/A

A/A

NR

A/A

A/A

Chemical Resistance of Polymers 739

Polymers and Elastomers

11

HDPE

PP

PS

PMP PC

PEEK PSU

A

Hydrogen peroxide (3 wt.%)

A

B

A

C

NR

C

C

NR

A

A

A

A

Isobutanol

Isopropyl acetate

Isopropyl alcohol

Isopropyl benzene

Isopropyl ether

Jet fuel

Kerosene

Lacquer thinner

Lactic acid (10 wt.%)

Lactic acid (85 wt.%)

Lactic acid (90 wt.%)

Lead (II) acetate

C

NR

B

A

A

A

A

NR

NR

A

B

B

A

B

B

B

NR

A

B

B

A

C

A

A

C A

NR

A

NR

NR

NR NR

A

NR NR B

B

NR

NR

B

NR

A

A/A

A/A

A/A

A

A

NR B/C

A/A

B/B

NR

NR

NR

NR

C

NR

B/B

B

B

NR

NR

B

C

B/B

B

B

NR

NR

B

C

B

A/A

B/B

B

NR

NR

C

NR

B

B

NR

C

NR

NR

C

NR

A/A A/A A/A

A/A A/A C

A/A A/A A/A

A/A A/A A/A

B

NR

A

A

NR

NR

A

NR

A

A/A A/A A/A

A/A A/A A/C

A/A A/A A/A

A/A A/A A/B

NR A/A A/A A/B

A

B

A/A A/A A/A

A/A A/A A/A

A

A

A

B

B

NR NR B

B

NR

A

A

A

NR NR A

C

A/A A/A A/A

A

A

A

C

A

C

B

A

B

B

Magnesium sulfate

A

A

A

C

B

C

NR

C

A

B

A

C

A

A

A

A

B

NR NR NR

B

Magnesium nitrate

A

A

A

A

B

A

B

A

A

A

A

B

A/A A/A A/A

A

A

A

A

C

NR B

A

C

A

NR

A

A

A

A

A

NR C

A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

B

A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A

A/A

A/A

A/A

B

A/A

A/A

A/A

A/A

A/A

A/A

A/A

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

Magnesium hydroxide

Magnesium chloride

NR

Iodine crystals

Hydrogen sulfide

Hydrogen peroxide (90 wt.%) A

A

A

B

A

A

A/A

A

Hydrofluoric acid (48 wt.%)

B

NR B

A

A/A

A

Hydrofluoric acid (4 wt.%)

A

Hydrogen peroxide (30 wt.%) A

C

Hydrofluoric acid

A

Hydrogen peroxide (10 wt.%)

A

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

Hydrocyanic acid

Chemical

Table 11.8. (continued)

740 Polymers and Elastomers

Nitromethane

Nitrobenzene

Nitric acid (fuming)

Nitric acid (70 wt.%)

Nitric acid (50 wt.%)

Nitric acid (10 wt.%)

n-butyl alcohol

n-amyl acetate

Nickel (II) sulfate

Nickel (II) nitrate

Nickel (II) chloride

Naphtha

Mineral spirits

Mineral oil

Methylene chloride

Methyl-t-butyl ether

Methyl propyl ketone

Methyl isobutyl ketone

Methyl ethyl ketone

Methyl chloride

Methanol

Methyl acetate

Methoxyethyl oleate

2-Methoxyethanol

A

A

C

A

B

C

B

B

C

B

A

C

NR B

C

A

A

B

C

C

C

NR

NR

B

A

A

C

C

A

NR B

C

C

A

B

NR

A

B

C

C

C

B

A

A

A

A

B

A

A

A

Methanoic acid (100 wt.%)

Mercury (II) nitrate

Mercury (II) chloride

A

Mercury

Malic acid

C

A

A

C

A

C

B

B

B

A

B

A

A

A

A

A

A

NR A

C

C

NR

A

NR NR C

NR

A

B

B

A

A

NR A

B

NR NR

C

A

NR NR NR B

A

B

C

A

C

NR

B

NR

C

NR

NR

A

A/A

A/A

A/A

NR

NR

NR

NR NR A

NR

A/A

NR NR

NR

NR

NR NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

B

B

NR

NR

C

C

C

A/A

B

A/B

B

C

B

B/NR NR

NR

B

C

NR

NR

B

A/A

B

C

NR

NR

B

C

NR

C/C

NR

NR

NR A/A A/A A/A

A/A A/A A/A

NR

NR

C

B

A

B

A

A/A A/A NR

A/A A/A NR

A/A A/A A/C

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

NR A/A A/A A/C

NR

NR

NR

NR A/A A/A NR

A

NR

NR

B

A/A A/A A/A

C

A/A A/A A/A

A/A A/A A/A A/A A/A A/A

A

B

NR

A/A

A/A

A/A

NR A

B

A

NR

A

NR A/A

NR

NR

NR

NR NR NR NR A/A

C

NR

NR

NR

C

A

NR NR NR C

C

C

A

B

NR

NR NR NR NR NR B

B

A

A

C

C

A

C

C

B

B

A

A

A

B

A/A

A/A

A/A

A/A

A/A

NR

NR

A/C

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

B/NR B/NR

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A B/NR B/NR

A/A B/NR B/NR

A/A B

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

Chemical Resistance of Polymers 741

Polymers and Elastomers

11

HDPE

PP

PS

PMP PC

A

A

A

A

B

NR

B

A

A

A

Phosphoric acid (10 wt.%)

Phosphoric acid (85 wt.%)

Phosphorus trichloride

Picric acid

Pine oil

Potassium acetate

Potassium bromide

Potassium carbonate

Potassium hydroxide (5 wt.%) A

Potassium hydroxide, concentrated

C

A

A

C

A

Propylene glycol

Propylene oxide

Pyridine

Resorcinol, Sat.

A

Propionic acid

Propanol

Potassium permanganate

A

A

C

A

A

A

A

A

A

A

A

A

A

NR

B

A

A

A

NR B

A

A

A

A

C

A

A

NR B

C

A

A

A

A

A

A

A

A

B

A

A

B

A

C

A

A

A

A

A

A

A

A

A

NR

B

A

A

B B

B

NR

A

B

C

B

B

A

A

A

NR

B

A

C

B

B

A

A

A

NR NR

A

B

B

A

A

A

A

A

B

A

A

NR NR A

NR NR NR

A

A

A

A

A

A

A

C

B

A

C

B

A/A

A

A

A/A

A/A

A/A

B

B

B

NR

A

A/A

NR A/A

B

NR

A

NR

NR A/A

A

NR NR NR NR NR NR NR NR NR NR

C

NR NR A

NR B

C

B

B

Phenol

C

NR B

C

A

B

Perchloroethylene

B

NR B

C

A

C

B

A

B

C

A

B

B

Perchloric acid

A

NR NR A

Ozone

A

NR B

A

A

A

C

A

Oxalic acid

A

Oleic acid

A

A

Potassium sulfide

PEEK PSU

B/B

B/C

A/A

NR

NR

B

C

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

n-Octane

Chemical

Table 11.8. (continued)

B

B/C

B

C

C

B

C

B

B/C

B

C

C

B

C

B

B

B

NR

NR

NR

NR

B/B

NR

B

A

B

B

B

C

C

C

B

A

C

NR

C/NR A

C/NR C

C

B

NR

C

A/A A/A A/B

A/A A/A A/A

A/A A/A A/C

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/C

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/B

A/A A/A

A/A A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

742 Polymers and Elastomers

A

A

B

A

A

A

A

A

A

A

A

A

A

A

A

A

Sodium dichromate

Sodium hydroxide (1 wt.%)

Sodium hydroxide (50 wt.%)

Tetrahydrofuran

Tartaric acid

Tannic acid

Sulfur dioxide

Sulfuric acid (98 wt.%)

Sulfuric acid (60 wt.%)

Sulfuric acid (20 wt.%)

Sulfuric acid (6 wt.%)

Sucrose

Stearic acid (crystals)

Sodium sulfate

Sodium phosphate

Sodium nitrate

Sodium hypochlorite (15 wt.%)

Sodium Flouride

A

A

B

B

A

A

A

B

A

NR C

C

A

A

A

A

B

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

Sodium chloride (std.)

Sodium Bromide

Sodium Bisulfite

A

A

A

A

Sodium carbonate

A

A

A

A

A

A

A

A

A

A

Sodium acetate (std.)

Silver nitrate

Silver acetate

Silicone oil

Salicylic acid (std.)

Salicylaldehyde

C

A

B

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

C

A

A

A

C

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

B

A

A

A

A

A

A

B

B

B

A

A

A

B

B

B

A

A

NR

A

A

A

A

A

A

A

A

A

A

NR A

B

B

A

A

A

B

B

B

A

A

A

C

B

B

C

A

B A

A

NR NR C

B

B

C

NR NR NR B

B

B

A

A

A

A

A

A

A

A

A

A

B

A

A

A/A

A

A

A/A

A/A

NR

A/A

A/A

A/A

NR

A

A A/A

NR NR

B

A

B

NR A/A

C

A

A

A

A

A

B

NR

C/C

B/C

C

A/B

B

B

C

NR

C/C

B/C

B

B

B

B

B

NR

C/C

B/C

B

B

B

B

B

B

NR

NR

NR

B

NR

A/B

A

NR

NR

NR

B

NR

A

A

B

A

A

A/A A/A A/A

A/A A/A A/B

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A NR

A/A A/A A/A

A/A A/A A/A

NR

A

NR A/A A/A A/C

A/A A/A A/A

A/A A/A A/A

C

B

C

B

A/A A/A A/A

C

A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

A/A A/A A/A

B

B

C/NR A

B

C/NR A

NR

B/B

C

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

A/A

Chemical Resistance of Polymers 743

Polymers and Elastomers

11

HDPE

PP

PS

PMP PC

PEEK PSU

C

B

C

NR

NR NR C

NR

C

A

C

A

A

NR

C

A

A

Toluene

Tributyl citrate

Trichloracetic acid

1,2,4-Trichlorobenzene

Trichloroethane

Trichloroethylene

2,2,4-Trimethylpentane

Tris buffer solution

Turpentine oil

Undecanol

Urea

Vinylidene chloride

Xylene

Zinc chloride

Zinc stearate

C

A

A

A

A

NR C

A

A

NR B

A

C

C

NR

NR B

A

NR B

NR NR NR

NR

C

B

C B

NR

B

NR NR NR A

NR

NR NR NR C

NR

C

NR

C

NR NR

A

C

A

C

A

A

C

NR

A

A

B

A

C

NR A

C

NR

A

B

A A

A

A

NR

B

C

B

NR

A

A

A

A/A

A/A

NR A

NR NR

A

A

NR NR C B

A

NR NR A/A

NR NR NR C

A

C

B

NR

NR

NR NR NR NR NR NR NR

C

B

NR

A/A

NR

NR

NR

NR

20°C 60°C 20°C 60°C 20°C 60°C 20°C 60°C 20°C 20°C 20°C/60°C

LDPE

Thionyl chloride

Chemical

Table 11.8. (continued)

A/A

C

NR

B

NR

A/A

C

NR

B

NR

B

B

B

NR

B/C

B

B

NR

A/A A/A A/A

A

A/A A/A A/A

A/A A/A A/A

NR A/A A/A A/A

NR

B

A

B

B

NR

NR A/A A/A A/A

NR

NR

C

C

NR A/A A/A A/B

NR

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A A/A

A/A

A/A

B/NR

A/A

NR

A/A B/NR B/NR

Ulltem Radel Acetal ABS PVC FEP PFA PVDF ETEE ECTFE PCTFE

744 Polymers and Elastomers

IUPAC Acronyms of Polymers and Elastomers

745

11.10 IUPAC Acronyms of Polymers and Elastomers Table 11.9. IUPAC acronyms of polymers and elastomers Acronym

Polymer name

A/EPDM/S acrylonitrile/ethylene-propene-diene/styrene A/MMA

acrylonitrile/methyl methacrylate

ABS

acrylonitrile/butadiene/styrene

ASA

acrylonitrile/styrene/acrylate

CA

cellulose acetate

CAB

cellulose acetate butyrate

CAP

cellulose acetate propionate

CF

cresol-formaldehyde

CMC

carboxymethylcellulose

CN

cellulose nitrate

CP

cellulose propionate

E/EA

ethylene/ethyl acrylate

E/P

ethylene/propene

E/VAC

ethylene/vinyl acetate

EC

ethylcellulose

EP

epoxide;epoxy

EPDM

ethylene/propene/diene

FEP

perfluoro(ethylene/propene); tetrafluoroethylene/hexafluoropropene

MF

melamine-formaldehyde

MPF

melamine/phenol-formaldehyde

PA

polyamide

PAN

polyacrylonitrile

PB

poly(l-butene)

PBA

poly(butylacrylate)

PBT

poly(butyleneterephthalate)

PC

polycarbonate

PCTFE

poly(chlorotrifluoroethylene)

PDAP

poly(diallylphthalate)

PE

polyethylene

PEO

poly(ethylene oxide)

PETP

poly(ethylene terephthalate)

PF

phenol-formaldehyde

PIB

polyisobutylene

PMMA

poly(methylmethacrylate)

POM

poly(oxymethylene); polyformaidehyde

pp

polypropene

PS

polystyrene

11 Polymers and Elastomers

746

Polymers and Elastomers Table 11.9. (continued) Acronym

Polymer name

PTFE

poly(tetrafluoroethylene)

PUR

polyurethane

PVAC

poly(vinyl acetate)

PVAL

poly(vinyl alcohol)

PVB

poly(vinylbutyral)

PVC

poly(vinyl chloride)

PVDC

poly(vinylidene dichloride)

PVDF

poly(vinylidene difluoride)

PVF

poly(vinyl fluoride)

PVFM

poly(vinylformal)

PVK

polyvinylcarbazole

PVP

polyvinylpyrrolidinone

S/B

styrene/butadiene

S/MS

styrene/a-methylstyrene

SI

silicone

UF

urea-formaldehyde

UP

unsaturated polyester

VC/E

vinyl chloride/ethylene

VC/E/MA

vinyl chloride/ethylene/methylacrylate

VC/E/VAC vinyl chloride/ethylene/vinylacetate

11.11 Economic Data on Polymers and Related Chemical Intermediates 11.11.1 Average Prices of Polymers Table 11.10. Average prices of polymers (2006) Polymer

Price (US$/kg)

Acetal (copolymer)

3.60

Acetal (homopolymer)

2.70

Acrylonitrile styrene acrylate (ASA)

3.90

Acrylonitrile-butadiene-styrene (ABS)

2.50

Acrylonitrile-butadiene-styrene (ABS) (high impact grade)

2.70

Acrylonitrile-butadiene-styrene (ABS) (medium impact grade)

1.90

Acrylonitrile-butadiene-styrene (ABS) (reinforced 30 vol.% glass) 2.80 Ethylene vinyl acetate

3.70

High density polyethylene (HDPE)

0.90

Economic Data on Polymers and Related Chemical Intermediates

747

Table 11.10. (continued) Polymer

Price (US$/kg)

Low density polyethylene (LDPE)

1.90

Polyamide (Nylon 11)

8.30

Polyamide (Nylon 12)

6.60

Polyamide (Nylon 46)

9.00

Polyamide (Nylon 6 )

3.10

Polyamide (Nylon 66)

3.70

Polycarbonate (PC)

5.50

Polycarbonate (PC)(high impact)

1.90

Polyester

2.40

Polyethyleneterephthalate (PET)

1.25

Polymethylmethacrylate (PPMA)

4.90

Polypropylene (PP)

1.40

Polystyrene (GPPS)

1.56

Polystyrene (HIPS)

1.60

Polyvinylchloride (PVC) Flexible

3.79

Polyvinylchloride (PVC) Rigid

1.72

PPA

8.09

Silicone

9.92

11.11.2 Production Capacities, Prices and Major Producers of Polymers and Chemical Intermediates (continued) Table 11.11. Annual production capacities and prices of polymers and related chemical intermediates 3

Polymer or chemical intermediate

Major producers worlwide (annual capacity /10 tonnes)

Price 2004 (US$/tonne)

Acrylonitrile (ACN)

British Petroleum-BP (955); Solutia (490); Sterling Chemicals (335); BASF (280); Cytec Industries (227); DSM (200); DuPont (185); Saratovorgsintez (150); Repsol (125); PetKim (92); Arpechim (75)

1400–1510

AcrylonitrileButadiene-Styrene (ABS)

Chi Mei (1000); Bayer (679); GE Plastics (615); LG Chem (500); BASF (460); Dow Chemical (382); Cheil Industries (330); Formosa Chemicals (240); Korea Kumo Petrochemical (200); UMG ABS (175); Thai ABS (100); Polimeri Europa (80)

1525–1830

Adipic acid

DuPont (1045); Rhodia (470); Solutia (400); BASF (260); Radici (150); 1320–1460 Asahi Kasei (120)

Adiponitrile

Invista (615); Butachimie (468); Solutia (300); BASF (140); Asahi Kasei (41); Liaoyang Petrochemical (24)

Butadiene

BP (315); Polimeri Europa (320); Dow Chemical (275); Shell (195); Oxeno (180); Basell (170); Repsol (162); Sabic (130); DSM (120); Naphthachimie (120); BASF (105); HICI (100); Huntsman Petrochemicals (100); Atofina (60)

11 Polymers and Elastomers

490

748

Polymers and Elastomers

Table 11.11. (continued) 3

Polymer or chemical intermediate

Major producers worlwide (annual capacity /10 tonnes)

Price 2004 (US$/tonne)

Caprolactam

Solutia (500); BASF (420); DSM (250); Bayer (180); Radici (130);

950–970

Cellulose

780–800

Cellulose acetate

450

Dimethyl terephthalate (DMT)

KoSa (1120); DuPont (610); Vorridian (550); Petrocel (500); Oxxynova (480); Teijin (250); Khimvolokno Mogilev (305); Bombay Dyeing (165); Elana (105); Interquisa (90)

740

Ethylene

Dow (2825); BP (2270); Polimeri Europa (2190); BASF (1520); Fina (1500); Rühr Oel (1300); Borealis (1280); Sabic (1215); Basell (1050); Atofina (1040); Shell (900); Repsol (880); Huntsman (865); Naphthachimie (725); OMV (655); Exxon (545); Noretyl (450); Copenor (380); Enichem (250)

420–440

Ethylene dichloride (EDC)

SolVin (2130); EVC (1355); Atofina (980); Hydropolymers (975); LVM (930); Shin-Etsus (840); Vestolit (590); Ineos (550); ViniChlor (490); Wacker-Chemie (410); Enichem (355); Aiscondel (272); Dow (260); BSL (255)

225–235

Ethylene-prolypene diene monomer (EPDM)

DuPont-Dow (190); Exxon Mobil Chemical (180); DSM (170); Lanxess (115); Crompton (91); Polimeri Europa (85); Société du Caoutchouc (85); Japan Synthetic Rubber (70); Mitsui (60); Sumitomo (40); Petrochima (30)

850–900

Expandable polystyrene (EPS)

Nova Chemicals (320); BASF (260); BP (175); StyroChem (105); Polimeri Europa (70); Kaucuk (70); Dwory (65); SunPor (55); Unipol (55); Dow Chemical (40)

1580–1620

Formaldehyde

Dynea (720); BASF (650); Perstorp Formox (550); Degussa (519); Borden (380); Total (370); Formol y Derivados (280); Sadepan Chimica (250); Caldic Chemie (215); Krems Chemie (170); Akzo Nobel (110)

260

High density polyethylene (hdPE)

BP (1375); Borealis (1240); Basell (1200); Dow (950); Atofina (940); Sabic (855); Polimeri Europa (390); Repsol (245)

850–880

Isophthalic acid (PIA) BP (325); AG International (120); Eastman Chemical (68); Lonza (70); 940–1020 KP Chemical (60); Interquisa (50); Linear low density polyethylene (LldPE)

Dow Chemical (800); Borealis (600); Polimeri Europa (590); BP (530); 950–1000 Cipen (420); Sabic (370); BSL (210);

Low density polyethylene (LdPE)

Basel (1030); Polimeri Europa (830); Borealis (800); Exxon Mobil (665); Atofina (590); Sabic (565); Dow Chemical (520); BP (370); Repsol (230); TDSEA (170); Specialty Polymers (130)

1145–1160

Methyl Diphenyl diisocyanate (MDI)

BASF (715); Dow Chemical (760); Bayer (710); Rubicon (390); Huntsman (300); Nippon Polyurethane Industry (170)

2320–2500

Methyl methacrylate (MMA)

Rohm and Haas (640); Lucite (525); Mitsubishi Rayon (265); Atofina 1465–1525 (180); Cyro Industries (132); Asahi Kasei (70); Repsol (45); BASF (36)

Nylon

Solutia; DSM; Rhodia (280); DuPont (150); Radici (90)

9760

Phenol

Ineos Phenol (1060); Polimeri Europa (480); Ertisa (370); Borealis (130)

950–1100

Polyacetals

DuPont (150); Polyplastics (150); Ticona (150); Ultraform (70); Korea 2920–3490 Engineering Plastics (55); Asahi Kasei (44); Mitsubishi Engineering (20); Thai Polyacetal (20); Zaklady Azotowe Tarnowie (10)

Economic Data on Polymers and Related Chemical Intermediates

749

Table 11.11. (continued) 3

Polymer or chemical intermediate

Major producers worlwide (annual capacity /10 tonnes)

Price 2004 (US$/tonne)

Polyacrylamide (PAM)

SNF (166); Ciba (115); CNPC (60); Cytec (47); Sinopec (32); Nalco (30); Stockhausen (26); Dia-Nitrix (12); Harima Chemical Japan (11)

3050–4300

Polyacrylic acid

Rohm and Haas (85); BASF (70); Nalco (30); Coatex (24); Ciba (18); National Starch (18); Protex (18); Kemira (16)

1950–4920

Polyaramides

DuPont (100); Teijin (100)

Polybutylene terephthalate (PBT)

GE Plastics (120); BASF-GE (100); DuBay Polymer (80); DuPont (70); Chang Chung Plastics (66); Shinkong Synthetic Fibers (40); DSM (30); Ticona (30); Toray (24)

n.a.

Polycarbonate (PC)

Bayer (830); GE Plastics (780); Teijin Chemical (300); Dow Chemical (205); Mitsubishi Engineering Plastics (90); Sam Yang (85); LG Dow (70); Thai Polycarbonate (60); Sumitomo (50); Asahi Kasei (50); Formosa (50); Idmetsu Petrochemical (47)

2990–3600

Polychloroprene

DuPont (100); Lanxess (65); Denki Kagaku Kogyo (48); Enichem (43); Tosoh (30); Shanxi Synthetic Rubber (25); Showa Denko (20)

4000–5000

Polyester polyols

Dow (580); Bayer (565); BASF (290); Shell (250); Repsol (200); ICI (45); DuPont (40);

1700–1830

Polyethylene terephthalate (PET)

Voridian (465); DuPont (280); Dow (270); M&G Polimeri (195); Elana (120)

1400–1464

Polymethyl methacrylate (PMMA)

Rohm and Haas (640); Lucite (525); Mitsubishi Rayon (265); Atofina 2260–2685 (180); Cyro Industries (132); Asahi Kasei (70); Repsol (45); BASF (36)

Polypropylene (PP)

Basell (2700); Borealis (1500); Atofina (1260); BP (1180); Sabic (1100); 900–1000 Exxon (500); BSL (210)

Polystyrene (PS)

Dow (630); BASF (605); BP (340); Polimeri Europa (335)

Polytetrafluoroethylene (PTFE)

DuPont (25); Daikin (11); Dyneon (9.8); Asahi Glass (7); Solvay (6.5); AGC Chemicals (4)

Polyvinylchloride (PVC)

Solvay (815); Atofina (700); HydroPolymers (610); Vinnolit (600); Shin-Etsu (295); JSC (255); Aiscondel (200)

Propylene

BP (1925); Dow Chemical (1335); Polimeri Europa (1145); Shell (840); 750–780 BASF (810); Sabic (675); Borealis (620); Atofina (600); Repsol (500); Basell (475)

1040–1060 1085–1110

770–780

Propylene glycol (PG) Dow Chemical (570); Lyondell (400); BP (90); BASF (80); Seraya Chemicals (65); Huntsman (60); Repsol (52); SKC (50); Arch Chemicals (35); Jin Hua Chemical (20); Sasol (18)

1080–1110

Propylene oxide (PO) Lyondell (1900); Dow (1810); Elba (500); Huntsman (240); Repsol (220); BP (205); Sumitomo (200); Shell (200); Nihon Oxirane (180); BASF (125); Asahi Glass (110)

1410–1490

Purified phthalic anhydride (PPA)

BASF (210); Lonza (110); Proviron (100); Atofina (90); Bayer (85)

850–890

Purified terephthalic acid (PTA)

BP (3390); DuPont (570); Interquisa (1275); Tereftalatos Mexicanos (1050); Voridian (940); DAK (550); Rhodiaco (285); Invista (180); Dow (180)

980–1100

Styrene

Dow Chemical (1280); BASF (1050); Atofina (720); EniChem (660); Lyondel (640); Elba (550); Repsol (480); Shell (440); BP (380)

920

11 Polymers and Elastomers

750

Polymers and Elastomers

Table 11.11. (continued) 3

Polymer or chemical intermediate

Major producers worlwide (annual capacity /10 tonnes)

Price 2004 (US$/tonne)

Styrene butadiene rubber (SBR)

Polimeri Europa (230); Petro Borzesti (150); Dow (160); Lanxess (140); Michelin (40);

1520–1830

Toluene diisocyanate (TDI)

Bayer (420); BASF (370); Dow (215); Lyondell (260); Mitsui Chemicals (243);

1950–2074

Urea

Yara (2335); SKW (1070); Zaklady Azotowe (960); Togliatti Azot (900); Chimco (800); Ammonil (720); Ege Gubre Sanayii (600); Agrolinz (570); BASF (540); Fertiberia (500); Petrochemija (495);

200–205

Vinyl chloride monomer (VCM)

EVC (1090); Solvay (925); Vinnolit (660); Atofina (615); Shin-Etsu (600); HydroPolymer (590); LVM (550); Dow (300);

740–750

References: Chemical Week (CheW), European Chemical News (ECN), Chemical Engineering and News (CEN), and Chemical Engineering (CE).

11.12 Further Reading ASH, M.B.; ASH, I.A.(1992) Handbook of Plastic Compounds, Elastomers, and Resins, An International Guide by Category, Tradename, Composition, and Suppliers. VCH, Weinheim. BOST, J. (1985) Matières plastiques, Vol. 1 & 2. Techniques & Documentation, Paris. ELIAS, H.-G. (1993) An Introduction to Plastics. VCH, Weinheim. FIZ Chemie (1992) Parat - Index of Polymer Trade Names, 2nd. ed. VCH, Weinheim. VAN KREVELEN, D.W. (1994) Properties of Polymers. Elsevier, Amsterdam.

Minerals, Ores and Gemstones

12.1 Definitions In this section the main definitions, properties of minerals are detailed and explained. Crystal. A crystal is a homogeneous solid with an ordered atomic space lattice which has developed a crystalline morphology when external crystallographic planes have had the possibility to grow freely without external constraints and under favorable conditions. Moreover, it is a chemical substance with a definite theoretical chemical formula. Nevertheless, the theoretical chemical composition is usually variable within a limited range owing to the isomorphic substitutions (i.e., diadochy), or/and low presence of traces of impurities. Minerals. A mineral is defined as a naturally occurring, inorganic, and homogeneous crystal that has been formed as a result of geological processes with a definite but generally not fixed chemical composition. Therefore, minerals are the basic building entities of Earth’s crust materials, i.e., rocks and soils. On the other hand, among the 4000 minerals species, the most abundant minerals found in common rocks (i.e., igneous, sedimentary, metamorphic and meteorites) are called by petrologists the rock forming minerals. Mineraloids. The mineraloids are naturally occurring substances having a structure which can be partially crystalline or noncrystalline, i.e., solids with an irregular atomic arrangement within the solid. For instance, compounds such as obsidian, opal, amber or succinite are defined as mineraloids. Ores. An ore is a natural occurring mineral or association of minerals containing a high percentage of a metallic element, which form deposits from which this metal can be mined, extracted, and processed at a profit under favorable conditions. Therefore, it is

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Minerals, Ores and Gemstones

Table 12.1. Common gangue minerals Class

Mineral

Oxides

Quartz Limonite

Carbonates

Calcite Dolomite Rhodocrosite

Sulfates

Baryte Gypsum

Halides

Fluorspar

Phosphates

Apatite

Silicates

Feldspars Clays Chlorites

economically defined. However, a distinction must be made between ore and ore minerals. A deposit of ore minerals in geological terms is not always an ore deposit, while an ore mineral is a mineral from which a metal can feasibly be extracted, and an ore deposit (or an orebody) is a mass of rock from which a metal or mineral can be profitably produced. What is, or is not, becomes dependent upon economic, technological, and political factors as well as geological criteria. A protore is a low-grade metalliferous material which is not in itself valuable but from which ore may be formed by superficial enrichment. Gangue. The gangue is an earthy or nonmetallic mineral associated with the ore minerals of a deposit, i.e., a worthless material in which the ore mineral is disseminated and must be concentrated by classical ore beneficiation techniques (e.g., gravity separation, flotation, leaching). The most common gangue minerals are listed in Table 12.1. Vein deposits. A vein is a mineral mass, more or less tabular, deposited by solutions in or along fracture of group of fractures. The country rock is the rock that encloses a metalliferous deposit. Vein walls are the rock surfaces on the borders of the veins. The footwall is the rock below an inclined vein, a bed, or a fault. The hanging wall is the rock above an inclined vein, bed or fault. A druse or vug is an unfilled portion of a vein usually lined with crystals. Gouge (salbandes in French) is a soft claylike material that occurs at some places as a selvage between a vein and country rock or in a vein. Along with scientific and technical terms, prospectors, geologists and mining engineers have established various terms to describe and classify mineral resources. Some of these terms are defined hereafter based on standardized definitions introduced by the U.S. Geo1 logical Survey (USGS) . Reserves. Amount of ore deposits economically recoverable at current prices using existing technologies. Because reserves include only recoverable materials, terms such as extractable or recoverable are redundant adjectives. Marginal reserves. Part of the reserve base which, at the time of determination, borders on being economically producible.

1

U.S. Geological Survey Circular 831, 1980.

Definitions

Figure 12.1. McKelvey diagram

753

2

Subeconomic resources. Part of identified resources that does not meet the economic criteria of reserves and marginal reserves. Reserve base. Part of an identified resource that meets specified minimum physical and chemical criteria related to current mining and production practices, including those of grade, quality, thickness and depth. The reserve base includes those resources that are currently economic (reserves), marginally economic (marginal reserves) and finally those that are currently subeconomic (subeconomic resources). Reserve base = Reserves + Marginal Reserves + Subeconomic Reserves A schematic illustration of the economic viability of ore deposits based on the previous definitions is provided by the McKelvey diagram (see Figure 12.1). Industrial minerals or nonmetallics. This designation includes all the minerals with economic importance, except those defined as ore, which are processed industrially. In fact, industrial minerals class also includes (i)

sedimentary rocks such as: limestone, dolomite, clays, sand, gravel, diatomite, and phosphates; (ii) metamorphic rocks such as marble or slate; and (iii) igneous rocks such as granite and basalt. However in order to be rigorous from a mineralogical and petrological point of view it is preferable to split the previous group into two distinct subgroups: (i) (ii)

industrial minerals, sensu stricto; and industrial rocks, sensu stricto.

A conventional listing of the more important nonmetallics is presented in Table 12.2. Gemstones. A gemstone is a semi-precious or precious natural mineral with exceptional physical properties which, when cut and polished, can be used in jewelry. Only four minerals are considered as precious gemstones sensu stricto: diamond, one gem variety of beryl (i.e., emerald: green), and the two gem varieties of corundum (i.e., ruby: deep red, and sapphire: deep blue). Beside natural minerals synthetic gemstones and their simulants are also found in jewelry. 2

McKelvey, V.E. – “Mineral Potential of the United States” in the Mineral Position of the United States 1975–2000 E.N. Cameron (Ed.) (1973) Univ. of Wisconsin Press, Madisson, Wi.

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Minerals, Ores and Gemstones

Table 12.2. Industrial minerals and rocks Nonmetallics

Material

Industrial applications and uses

Industrial minerals s.s.

Asbestos (chrysotile, crocidolite, amosite, anthophyllite, tremolite, and actinolite)

(i) Spinning fibers: woven brake lining, clutch facing, fireproof and safety clothing, and blankets. (ii) Nonspinning fibers: roofing shingles, millboard, and corrugated panels for thermal insulation.

Apatite (see also phosphate rock)

Fertilizers and chemical industry.

Barite (baryte, heavyspar)

Oil-well drilling muds, filler in rubbers, paint extender, aggregate in speciality heavy weight concretes, flux in the glass industry, and barium chemicals

Beryl and bertrandite

Beryllia, and beryllium chemicals

Borax and borates (kernite, tincal, colemanite, and ulexite)

Fluxing agents in the manufacture of glass and vitreous enamel, borosilicated glasses (i.e., Pyrex®), borate fertlizers in agriculture, detergents and soaps, flame retardants, and in a lesser extent synthetic cubic boron nitride (i.e., Borazon®) for industrial abrasives, boron-doped semiconductors.

Chalk

Aggregate

Chromite Only commercial source of chromium used in the (podiform and stratiform) metallurgical industry (85%) mainly as Fe–Cr for steelmaking, in the refractory and foundry market (8%) and in the chemical industry (7%). Cryolithe (cryolite)

Fluxing agent in the Hall–Heroult process in the aluminum industry.

Diamond (bort varieties)

Abrasives, diamond drill in the mining industry, wire-drawing dies.

Emery (corundum, magnetite, and spinel)

Abrasive for paper grit

Feldspars (microcline, orthose, plagioclases)

Glass Industry for porcelain, enamels and glazes.

Fluorspar (fluorite)

Foundry fluxes in steel making (metallurgical grade), preparation of hydrofluoric acid (acid grade), glass industry (ceramic grade).

Garnets (pyrope, almandine, spessartine, uvarovite, grossular, spessartine)

Abrasives, blasting media, water jet cuttings, and water filtration.

Graphite

Foundry molds facing (70%), crucibles, and lubricant.

Gypsum and anhydrite

Gypsum wallboads for building purposes, fertilizers, sulfates and sulfuric acid.

Kyanite

Refractories

Magnesite

After calcination give periclase (MgO) used for refractories

Manganese dioxide (psilomelane)

Primary batteries

Micas (muscovite, phlogopite)

Electrical sheet insulators, furnaces windows, roofing materials.

Nitrates (salpeter, niter, ammonium nitrate)

Fertilizers in agriculture, raw material for the chemical industry (i.e., pyrotechnics and explosives)

Definitions

755

Table 12.2. (continued) Nonmetallics

Material

Industrial applications and uses

Olivine

Slag conditioner, refractories (brick, mortars and monolithic castables), foundry sands.

Potash (sylvite, carnalite)

Fertilizer in agriculture and potassium chemicals (e.g., soaps, detergents, dyes, explosives).

Pyrophillite (Rozeckite)

Refractories (e.g., firebricks, monolithics), whiteware ceramics, filler applications.

Quartz

Piezoelectric crystals, optical lens, speciality glassware, optical fibers, silicon for semiconductors.

Sillimanite

Refractories

Staurolite

Sandblasting abrasives (90%), foundry sand

Sulfur (native)

Chemical industry for the manufacture of sulfuric acid

Talc (steatite)

Manufacture of whiteware and porcelain, inert extender in paint, lubricant in paper-making, absorbant in pharmaceutical and chemical Industry.

Trona and nahcolite

Glass industry, raw material for the chemical industry, soaps and detergents.

Vermicullite

Loose-fill insulation, and lightweight concrete.

Aplite

Glassmaking and ceramic industry.

Basalt and diabase (crushed)

Concrete aggregate, railroad ballast, and roofing granules.

Granite and granodiorite

Monuments and memorials, building foundation blocks, steps, cubstones and paving blocks.

Industrial rocks Igneous rocks

Perlite (rhyolitic obsidian) Aggregate in plasters, loose-fill insulation, filtration medium, paint filler, oil-well drilling muds, inert packing materials.

Sedimentary rocks

Pumice

Abrasives, concrete building blocks, stone washing, polishing metals and woodworking.

Attapulgite and sepiolite (i.e., palygorskite or Fuller’s earth)

Owing to its excellent sorbtive capabilities, decolorizing agent, binding and thickening together with non swelling behavior when wet and non floculating with electrolytes major uses are: pet litter, animal bedding, floor absorbents, oil spill-clean-up materials, tank cleaning

Clays (bentonite, kaolinite, montmorillonite)

Filler material, oil-well drilling mud, waxes, fats and oils adsorbents, Portland-cement, enamels and ceramics, refractories, potery.

Bauxite (i.e., gibbsite, boehmite, and diaspore)

(i) (ii)

Metallugical grade (85%): Hall–Heroult process for aluminum metal. Non metallurgical grade (15%): High alumina refractories (briclks and monolithic castables), abrasives, welding flux, ceramic proppants, Bayer’s alumina, aluminum based chemicals

Diatomite (kieselguhr)

Filter aid, filler material.

Dolomite

(i) (ii)

crushed: aggregate in concrete, railroad ballast, sewage filter beds; fluxing agent in smelting and refining of steel;

12 Minerals, Ores and Gemstones

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Minerals, Ores and Gemstones

Table 12.2. (continued) Nonmetallics

Material

Industrial applications and uses

Sedimentary rocks

Dolomite

(iii) (iv) (v) (vii) (viii)

Gypsum and anhydrite

Gypsum plasters for building purposes, fertilizers, sulfates and sulfuric acid.

Limestone

(i)

Phosphate rocks (phosphorites)

Fertilizer in agriculture, raw material for the chemical and pharmaceutical industry for the manufacture of orthophosphoric acid, steelmaking and pyrotechnics.

Quartzite

Ferrosilicon, refractories, abbrasives, potery and enamels.

Rocksalt (halite)

Raw material for the chemical industry (e.g., chlor-alkali process)

Sand and gravel (silica sand)

Aggregate in Portland-cement concrete, foundry sands, glass sands.

Marble

Achitectural and statuary, dimension stone

Slate

Roofing stales and flagstones.

Metamorphic rocks

soil conditioner; source of lime and magnesia (dolime); chemical raw material; high grade refractories; and dimension stone.

crushed: aggregate in concrete, railroad ballast, sewage filter beds; (ii) fluxing agent in smelting and refining of steel; (iii) soil conditioner; (iv) source of lime; (v) raw material for Portland-cement; (vi) chemical raw material; and (vii) dimension stone.

12.2 Mineralogical, Physical and Chemical Properties Among the approximate 4000 minerals species found in nature, only the major rock forming minerals, chief metals ores and gemstones are listed in the Mineral Properties Table (roughly 400 minerals species) presented in Section 12.7, Mineral and Gemstone Properties, with their common physical and chemical properties useful for mineralogical identification. These properties are sufficient to identify common rock-forming and ore minerals occurring in common geological materials (e.g., rock, and soils) with common field laboratory equipment (i.e., magnification lenses, polarizing microscope, pycnometer, microchemical analysis spot tests). The selected properties of minerals detailed in the table are explained in detail the following paragraphs.

12.2.1 Mineral Names Minerals are most commonly classified on the basis of the presence of a major chemical component (i.e., anion or anionic complex) into several mineral classes such as, for instance, native elements, sulfides and sulfosalts, oxides, carbonates, sulfates, phosphates, silicates, etc. Today, there exist two main mineralogical classifications of minerals according to either

Mineralogical, Physical and Chemical Properties

757

the modernized Dana’s classes (Table 12.16) or the Strunz’s classes (Table 12.15). However, the naming of minerals is not based on such a logical scheme. The careful description and identification of minerals often requires highly specialized physical or/and chemical techniques such as inorganic spectrochemical analysis (i.e., AAS, AES, XRF) and measurement of common physical properties (e.g., density, microhardness, optical properties, X-ray lattice parameters, etc.). However, because of historical reasons, the names of minerals were not arrived at in an analogous scientific manner. Minerals may be given names on the basis of some physical property (e.g., barite from the Greek, baryos, meaning heavy due to its elevate density) or chemical composition (e.g., germanite from its germanium content), or they may be named after the locality of discovery (e.g., aragonite from the Spanish region of Aragon), a public figure (e.g., perovskite after the Russian Count Perowski), a mineralogist (e.g., haüyne after the French mineralogist René-Just d’Haüy), or almost any other subject considered appropriate. An international committee, the Commission on New Minerals and New Mineral Names of the International Mineralogical Association (IMA), now reviews all new mineral descriptions and judges the appropriateness of new mineral names as well as the scientific characterization of newly discovered mineral species. As for all the chemical compounds, each mineral can also be identified by its chemical abstract registered number [CAS RN].

12.2.2 Chemical Formula and Theoretical Chemical Composition The theoretical chemical formula of a mineral is unique and identifies only one species. Nevertheless, the actual chemical composition is usually variable within a limited range owing to the isomorphic substitutions (i.e., diadochy), or/and low presence of traces of im12 purities. The relative atomic or molecular mass (based on C = 12.000) of minerals is calculated from the theoretical formula using the last value of atomic masses adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 2001, and the theoretical chemical composition is commonly expressed in percentage by weight (wt.%) of elements and sometimes oxides for oxygenated minerals.

12.2.3 Crystallographic Properties Minerals, with few exceptions (i.e., amorphous species), possess the internal, ordered arrangement that is characteristic of crystalline solids. When conditions are favorable, they may be bounded by smooth plane surfaces and assume regular geometric forms known as crystals. The study of crystalline solids and the principles that govern their growth, external shape, and external structure is called crystallography. Morphological crystallography refers to the study of the external form, or morphology of crystals. Crystals are formed from solutions, melts, and vapors. The atoms in these disordered states have a random distribution but with changing temperature and pressure (T, P), and concentration they may join in an ordered arrangement characteristic of the crystalline state. Most well-formed mineral crystals are the result of chemical deposition from a solid (or a melt) into an open space, such as a vug, or a cavity in a rock formation. The main crystallographic properties are the crystal –12 system, the space lattice parameters expressed in picometers (1 pm = 10 m) and plane angle in degrees (°), the strukturbericht designation, the Pearson’s notation and the number of atoms or molecules per unit space lattice are listed. Finally, the space group and point group according to the international Hermann–Mauguin notation and the crystal space lattice structure type are also given when known.

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Minerals, Ores and Gemstones

12.2.4 Habit or Crystal Form Some crystals grow in a characteristic morphological form called their crystal habit or habit. For example, quartz may grow to form crystals with a hexagonal outline and pyramid-like ends. Habit is generally well-developed only if a mineral is allowed to grow in an environment without space limitations and in this case it is called euhedral (i.e., idiomorph or automorph). On the contrary, it is called anhedral (i.e., xenomorph, or allotriomorph) if no external form can be identified. If the habit is partially developed, the mineral is called subhedral (i.e., subautomorph or hypidiomorph). The habit or appearance of single crystals as well as the manner in which crystals grow together in aggregates are of considerable aid in mineral recognition. Terms used to express habit and state of aggregation are given below. Single crystals, i.e., minerals in isolated or distinct crystals may be described as: (i) (ii) (iii) (iv)

acicular (i.e., needlelike); capillary or filiform (i.e., hairlike or threadlike); bladed (i.e., lamellar, tabullar); and columnar (i.e., prismatic).

For aggregates, i.e., groups of distinct crystals the following terms are used: (v) (vi) (vii) (viii)

dendritic (i.e., branching); reticulated (i.e., lattice-like); divergent or radiated (i.e., radiating); drusy (i.e., layer of small crystals on a surface).

Parallel or radiating groups of individual crystals are described as: (ix) (x) (xi) (xii) (xiii) (xiv) (xv) (xvi) (xvii)

columnar; bladed; fibrous; stellated (i.e., starlike); globular; botryroidal (i.e., bunch of grapes); reniform (i.e., kidney-shaped masses); mammillary; colloform.

A mineral aggregate composed of scales or lamellae is described as: (xviii) (xix) (xx) (xxi)

foliated; micaceous; lamellar or tabular; and plumose.

Miscellaneous terms are: (xxii) (xxiii) (xxiv) (xxv) (xxvi)

stalactitic; concentric; pisolitic; oolitic; banded;

Mineralogical, Physical and Chemical Properties

759

Table 12.3. Crystal habits grouped by the ratio of their longitudinal and transversal dimensions Group

Crystal habit

Equant or equiaxed crystal habits (i.e., form Equiaxed similarly developed in all three directions) Fluorite

Granular

Elongated crystal habits (i.e., one dimension dominates)

Fibrous (hair-like)

Acicular (needle-like)

Columnar (pilar-like)

Prismatic (barrel-like)

Actinolite, Chrysotile

Stibnite

Beryl, tourmaline

Quartz, apatite

Tabular

Platy

Bladed

Lamellar

Baryte

Baryte, gypsum

Ilmenite

Muscovite, graphite

Flattened crystal habits

Olivine

(xxvii) massive; (xxviii) mygdaloidal; and (xxix) geode.

12.2.5 Color The color variations of a nonmetallic mineral are often the result of ionic trace impurities in the crystal space lattice structure. Since the impurities vary from sample to sample, the color may vary. Some nonmetallic minerals have no color and are referred to as colorless. This variability in color, which can sometimes be extreme, means that color is one of the least useful properties for identifying nonmetallic minerals even though it is probably the most obvious. The origin of a mineral’s color can be explained by three types of electronic transitions in the crystalline solids. (i)

According to the Crystal Field Theory (CFT) the color of nonmetallic minerals is often due to traces of transition element cations inside the crystal lattice of minerals. Actually, all the first group of first transition elements (i.e., from Ti to Cu) have partially filled 3d electron shell orbitals. The electrostatic interactions between the 3d electrons with the electric field imposed by the lattice of surrounding coordinating anions is responsible of the degenerescence of the electron energy levels found in the free atom. (ii) Another possible origin of the color of nonmetallic minerals is due to the Charge Transfer Transitions (CTT). The charge transfer electronic transitions occur when valence electrons transfer back and forth between adjacent cations. Several important charge transfer transitions have energies within the visible region and therefore cause selective absorption. A characteristic of the absorption spectrum is that the intensity of absorption depends of particular orientations. This phenomenon gives rise to the important property of pleochroism discussed in the optical properties paragraph. (iii) Finally, the third important electronic transition within minerals which causes color are both electron color centers and hole color centers. Actually, in some ionic solids having lattice defects such as anion vacancies, electrons occupy vacancies in order to preserve the overall electric neutrality. For instance, fluorite, and rock salt are common minerals exhibiting F-centers (from German, Farben, meaning color). In contrast, hole color centers arise when an electron is missing from a location normally occupied by an electron pair. Smoky quartz and amethyst are common examples of minerals

12 Minerals, Ores and Gemstones

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Minerals, Ores and Gemstones

exhibiting hole color centers. On the contrary, color is much more useful in identifying metallic minerals. Actually the origin of color in metallic minerals depends on the energy involved in the electronic transition between the conduction band and valence band described in the theory of bands (see the chapter on semiconductors). Therefore, it directly depends of the energy gap of the minerals.

12.2.6 Diaphaneity or Transmission of Light The interaction of electromagnetic radiation with minerals only depends on the particular region of the spectra considered. As a general rule, the visible region (i.e., light wavelength comprises between 380 nm and 780 nm) is considered in optical mineralogy. Two main categories of mineral can be clearly identified, (i) (ii)

transparent and translucent minerals which may transmit light to varying degrees; and opaque minerals which do not transmit visible light at all.

Actually, minerals which are transparent transmit light much like glass. These minerals are essentially solids with ionic or covalent bond such as oxides, carbonates, silicates (e.g., calcite, quartz), or native element (e.g., diamond). Minerals which are translucent transmit light on thin edges or in thin section. By contrast, opaque minerals do not transmit light even in thin section and comprise solids with metallic or partially metallic bond characterized by a free electron cloud (i.e., Fermi gas) such as native element (e.g., Cu, Ag, Au), most iron and copper bearing sulfides (e.g., CuS, FeS2), and several transition metal oxides (e.g., Fe3O4. FeTiO3, FeCr2O4). As a general rule, all minerals with a metallic luster are commonly opaque.

12.2.7 Luster The term luster refers to the external appearance of the mineral owing to the reflection of light by its surface. The most important distinction to be made is between minerals with a metallic luster and a non-metallic luster. Minerals with a metallic luster (e.g., pyrite) reflect visible light like polished metals and alloys, and are often very shiny. Nevertheless, some minerals with a metallic luster may tarnish on exposure to moist air and become less shiny taking on a darker color. Minerals with a nonmetallic luster do not reflect light such as metals. There are a variety of nonmetallic lusters, each being descriptive of its appearance. A luster resembling light reflected from the surface of broken window glass is termed glassy or vitreous (e.g., quartz). A mineral which reflects light as if it were coated by a thin film of oil has a greasy luster (e.g., calcite). A dull luster resembling the appearance of dry soil is termed earthy (e.g., limonite). Other non-metallic lusters include pearly (e.g., moonstone), resinous (e.g., garnets, and realgar), waxy (e.g., turquoise), silky (e.g., tigers eye quartz), and adamantine such a diamond luster.

12.2.8 Cleavage and Parting Some minerals tend to break repeatedly along certain planes parallel to atomic planes (i.e., flat crystallographic surfaces) owing to the weakness in their atomic structure because of the lowest binding energy between adjacent atoms. These planes are referred to as cleavage surfaces quantified by Miller indices (hkl) with cleavage directions perpendicular to them [hkl].

Mineralogical, Physical and Chemical Properties

761

The result is flat regular surfaces. Parallel cleavage surfaces represent a single cleavage direction.which may be very well developed (i.e., perfect) in some crystals (e.g. micas, calcite), or may be fairly obscure (e.g. beryl). Cleavage surfaces which are not parallel represent different cleavage directions. While cleavage surfaces tend to reflect light all in the same direction, rougher fracture surfaces scatter light reflected off of them. As a result, cleavage surfaces are generally shinier than fracture surfaces. Sometimes cleavage may appear as a series of surfaces on one side of a sample which are parallel to each other but at different heights somewhat like stair steps. Such parallel surfaces can be recognized as a cleavage direction by the fact that they will reflect light all at once. Many minerals may be identified by their number of cleavage directions and plane angle(s) between cleavage directions. Parting is like cleavage, but only occurs along planes of structural weakness in twinned crystals.

12.2.9 Fracture The way in which a mineral breaks is determined by the arrangement of atoms in its crystal structure and the strength of the different types of chemical bonds between atoms. All minerals may break somewhat randomly in any direction across a crystal. This type of breakage is called fracture and this word refers to the way minerals break along an uneven surface when they do not yield along cleavage or parting surfaces. Different kinds of fracture are designated as: (i)

conchoidal – a curving shell-like fracture similar to the way glass breaks with concentric rings. It is named after the smooth curving surface of a conch shell. (ii) fibrous or splintery – fracture producing long splintery fibers (e.g., nephrite); (iii) hackly; and (iv) uneven or irregular – fracture simply producing a rough, broken, and irregular surface.

12.2.10 Streak Streak is the color of a mineral when finely powdered, found by rubbing the mineral against an unglazed, typically white, porcelain plate called a streak plate. Minerals with a Mohs hardness much greater than 6 do not give a streak owing to their hardness being higher than that of the silicate solids found in porcelain. Instead, they scratch the streak plate. Most soft colorless or pale colored minerals have a white streak which is only visible against a darkcolored streak plate or if the mineral is rubbed against a hard, dark-colored mineral such as pyroxene or amphibole. Although the color of a mineral may vary, the streak is usually constant and is thus useful in mineral identification. Actually, the streak color of a mineral is usually the same regardless of the color of the whole mineral (and may or may not be the same as the color of the whole mineral). Thus streak is a more reliable property than the color of the mineral. Streak is particularly useful for identifying metallic minerals. For instance, the mineral pyrite which is often referred to as “fools’ gold” because of its resemblance to true gold has a black streak while the streak of true gold is yellow.

12.2.11 Tenacity The cohesiveness of a mineral is known as tenacity. The following terms are used to describe tenacity in minerals:

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(i) (ii) (iii) (iv) (v) (vi)

brittle (i.e., breaks and powders easily); malleable (i.e., may be hammered into thin sheets); sectile (i.e., can be cut into thin shavings with a knife); ductile (i.e., can be drawn into a wire); flexible (i.e., can be bent without breaking); finally elastic (i.e., will spring back after being bent, e.g. mica).

12.2.12 Density and Specific Gravity Density (symbol d or ρ) is a physical quantity equal to the ratio of mass to volume expressed –3 in SI as kg.m while specific gravity or relative density (SG, D) is a dimensionless physical quantity equal to the ratio of the density of a mineral at a given temperature to the density of water at a reference temperature, usually defined as the temperature of its maximum density (3.98°C). Qualitatively mineral specific gravities can be classified in petrology as: barylites –3 (i.e., heavy or dense with a density above that of quartz i.e., 2650 kg.m ), and coupholites –3 (i.e., light with a density below that of quartz i.e., 2650 kg.m ). The specific gravity of a mineral is frequently an important aid in its identification, particularly in working with fine crystals or gemstones, when other tests would injure the specimens. The specific gravity of a crystalline substance depends on: (i) (ii)

its chemical composition; and its crystal space lattice structure type.

For instance, the two allotropic forms of carbon, such as diamond, and graphite, owing to their different space lattice structure exhibit different densities. Actually, diamond owing to its closely packed cubic structure has a specific gravity of 3.512 while the graphite with its loosely hexagonal lamellar packed structure has specific gravity 2.230.

12.2.13 Mohs Hardness The resistance of a mineral to scratching and abrasion is called its hardness. Hardness is a direct measure of the binding energy of atoms in the solid. In mineralogy, a series of 10 common standard minerals was chosen arbitrarily by the German mineralogist Friedrich 3, 4 Mohs in 1824 as a relative scale, by which the relative hardness of any mineral can be told. Hence, the following minerals arranged in order of increasing hardness comprise what is known as the Mohs scale of hardness: 1. 2. 3. 4.

3 4

talc; gypsum; calcite; fluorite;

Mohs, F. Grundriss der Mineralogie, 1824. Staples, L.F. Friedrich Mohs and the scale of Hardness J. Geol. Education, 12 (1964) 98–101.

Mineralogical, Physical and Chemical Properties

5. 6. 7. 8. 9. 10.

763

apatite; orthoclase; quartz; topaz; corundum; diamond.

However, the numbers of the Mohs scale do not have a linear relationship to hardness. Diamond is actually much more than 10 times the hardness of talc. The numbers only represent a simple qualitative ordering of minerals by hardness. A mineral’s hardness may be determined by attempting to scratch an object of known hardness such as glass or a coin with the mineral. Alternately, one may attempt to scratch a mineral sample with an object of known hardness. A harder mineral can scratch a softer mineral, but a softer mineral cannot scratch a harder mineral. Often a powder is produced when attempting to make a scratch. This powder may be mistaken for a scratch. Remember that while a powder can be wiped away, a scratch must remain after the removal of powder. Usually, the groove of a scratch in glass can be felt with a fingernail. The following common materials serve in addition to the above scale: the hardness of the fingernail is roughly 2.5, a U.S. copper coin about 3, the stainless steel AISI 440C grade of a pocket knife blade a little over 6, window glass 5.5, and the quenched carbon steel of a knife blade file 6.5. A grit paper made of carborundum® (i.e., silicon carbide) 9.25. For more accurate and quantitative measurements, hardness of minerals can be measured such as for metal and alloys by micro-indentation testing such as microhardness Vickers and Knoop tests (see hardness tests definitions and scales in the appendices). Nevertheless, since 1824 several other scales for reporting hardness of minerals were established in order to improve the reliability and accuracy of hardness measurements. The Rosival scale is an improved version of the original Mohs scale using corundum in place of diamond as reference mineral, with a hardness number defined as 1000. Later in 1933, 5 Ridgeway et al. suggested an extended Mohs hardness. For this purpose, he had introduced the hardness of fused silica between those of feldspar and quartz and the hardness of garnet between those of quartz and topaz respectively. However, in the 1960s more precise scientific 6, 7 studies were performed, in the former Soviet Union, by Povarennykh . His rational scale of hardness was established from accurate measurements of the hardness of minerals by the micro-Vickers diamond indenter. Hence, the original Mohs scale was increased by five additional synthetic minerals in order to decrease the gap existing between the hardness of corundum and that of diamond. Moreover, he had also reported the crystallographic plane used in the measurement in order to take into account the anisotropy of mechanical properties of crystals. A brief comparison of these scale is reported in Table 12.4.

5 6

7

Ridgeway, R.R.; Ballard, A.H.; and Bailey, B.L. Trans. Electrochem. Soc. 63 (1933) 267. Povarennikh, A.S. A Fifteen Division Mohs Scale of Hardness Zap. Ukr. Otd. Vses. Mineralog. Obshchestva Akad. Nauk. Ukr. SSSR 1 (1962) 67–74. Povarennikh, A.S. Necessary Revisions to be made in the Mohs Scale of Hardness. Dopovidi Akad., Nauk. Ukr. SSSR, 6 (1964) 804–806.

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Minerals, Ores and Gemstones Table 12.4. Comparison of scales hardness of minerals Mineral or material (in bold the original Mohs minerals)

Mohs Rosival Ridgeway Povarennyk scale scale scale h scale (1822) (1933) (1962)

Vickers hardness kgf /mm GPa

kgf /mm

GPa

Talc

1

0.033

1

1 (001)

n.a.

n.a.

65

0.64

Graphite

1.5

n.a.

n.a.

n.a.

32.5

0.32

n.a.

n.a.

Gypsum

2

1.25

2

n.a.

68

0.67

32–125

0.31–1.23

Halite

2–2.5

n.a.

n.a.

2

n.a.

n.a.

n.a.

n.a.

Finger nail

2.5

n.a.

n.a.

n.a.

n.a.

n.a.

150

1.47

Galena

2.5

n.a.

n.a.

3 (100)

71–84

0.70–0.82

n.a.

n.a.

Calcite

3

4.5

3

n.a.

110

1.07

135–190

1.32–1.86

Fluorite

4

5

4

4 (111)

n.a.

n.a.

163–310

1.60–3.04

Scheelite

4.5–5

n.a.

n.a.

5 (111)

285–429 2.79–4.21

n.a.

n.a.

Apatite

5

6.5

5

n.a.

n.a.

n.a.

430–435

4.22–4.27

Knife blade

5.5

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Feldspar (Orthoclase)

6

37

6

n.a.

n.a.

n.a.

560–625

5.49–6.13

Magnetite

5.5–6

n.a.

n.a.

6 (111)

530–599 5.20–5.87

n.a.

n.a.

Pyrex glass

6.5

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Silica (fused)

n.a.

n.a.

7

n.a.

n.a.

n.a.

n.a.

n.a.

Quartz

7

120

8

7 (1011)

n.a.

n.a.

820–875

8.04–8.58

Garnet

6

n.a.

9

n.a.

n.a.

n.a.

1360

13.34

Stellite®

n.a.

n.a.

8

n.a.

n.a.

n.a.

n.a.

n.a.

Zircon

7.5

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Porcelain (hard)

8

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Topaz

8

175

10

8 (001)

n.a.

n.a.

1340

13.14

Zirconia (fused)

9

n.a.

11

n.a.

n.a.

n.a.

1160

11.38

Tantalum carbide

n.a.

n.a.

11

n.a.

n.a.

n.a.

2000

19.61

Alumina (fused)

n.a.

n.a.

12

n.a.

n.a.

n.a.

n.a.

n.a.

Tungsten n.a. carbide (WC+Co cermet)

n.a.

12

n.a.

n.a.

n.a.

1400– 1800

13.73– 17.65

2

Knopp hardness 2

Corundum

9

1000

n.a.

9 (1120)

2100

20.60

2100

20.59

Carborundum®

n.a.

n.a.

13

n.a.

n.a.

n.a.

2400

23.55

Titanium carbide n.a.

n.a.

n.a.

10

n.a.

n.a.

n.a.

n.a.

Aluminum boride

n.a.

n.a.

n.a.

11

n.a.

n.a.

2470

24.22

Sialon®

9

n.a.

n.a.

12

n.a.

n.a.

2500

24.52

Boron carbide

n.a.

n.a.

n.a.

13

n.a.

n.a.

2750

26.97

Borazon®

n.a.

n.a.

14

14

n.a.

n.a.

4700

46.09

Diamond

10

140,000 15

15

8000

78.45

7000

68.65

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765

12.2.14 Optical Properties In optical mineralogy, transparent and translucent minerals are classified according to five possible classes (i.e., with different indicatrices) to which a crystal can belong: isotropic, uniaxial (+/–), or biaxial (+/–).The main physical quantity is the index of refraction or the refractive index (RI), denoted n. The refractive index of a substance at a given wavelength is the dimensionless ratio of the celerity of light in vacuum, c, to the celerity of light in the crystal, v, n = c/v. In most tables and databases, this index is measured, unless otherwise specified, for monochromatic radiation having a standardized wavelength usually taken equal to that of the D-line of the resonance atomic transition of the sodium metal vapor (λD = 589.3 nm). Therefore, the right symbol is nD. The three-dimensional surface describing the variation in refractive index with relationship to the vibration direction of incident light is called the indicatrix. Isotropic materials have the same refractive index regardless to vibrations directions and, the indicatrix is a sphere. Isotropic materials are: (i) crystals with a cubic crystal lattice; (ii) amorphous materials (i.e., vitreous or glassy); or (iii) fluids (e.g., liquids and gases). On the contrary, a solid material with more than one principal refractive index is called anisotropic. Anisotropic materials are divided into two subgroups: (i) (ii)

solid materials having a tetragonal, hexagonal, and rhombohedral crystal space lattice structure are called uniaxial; solid materials having an orthorhombic, monoclinic, and triclinic crystal space lattice structure are called biaxial.

Uniaxial crystals belong to either the rhombohedral, the hexagonal or tetragonal crystal systems and possess two mutually perpendicular refractive indices, ε, and ω, which are called the principal refractive indices. Intermediate values occur and are called ε ', a nonprincipal refractive index. The uniaxial indicatrix is an ellipsoid, either prolate (ε > ω), termed positive (+), or oblate (ε < ω), termed negative (–). In either case, ε coincides with the single optic axis of the crystal, yielding the name uniaxial. The optic axis also coincides with the axis of highest symmetry of the crystal, either the 4-fold for tetragonal minerals or the 3- or 6-fold of the hexagonal class. Because of the symmetry imposed by the 3-, 4-, or 6-fold axis, the indicatrix contains a circle of radius ω perpendicular to ε (i.e., perpendicular to the optic axis). Light vibrating parallel to any of the vectors would exhibit the refractive index ω. Light vibrating parallel to the optic axis would exhibit ε. Light that does not vibrate parallel to one of these special directions within the uniaxial indicatrix would exhibit a refractive index intermediate between ε and ω and is termed ε '. Biaxial crystals belong to the orthorhombic, monoclinic, or triclinic crystal systems and possess three mutually perpendicular refractive indices (α, β, and γ ), which are the principal refractive indices. Intermediate values also occur and are labeled α ' and γ '. The relationship between these values are α < α ' < β < γ ' < γ. The three principal refractive indices coincide with three mutually perpendicular lattice vectors directions, a, b, and c, which form the framework for the biaxial indicatrix. The point group symmetry of the biaxial indicatrix is 2/m 2/m 2/m. In orthorhombic minerals the a, b, and c vectors coincide with either the 2-fold axes or normals to mirror planes. In monoclinic minerals, one of the a, b, or c axes coincides with the single symmetry element. In triclinic minerals, no symmetry elements necessarily coincide with the axes of the indicatrix. The birefringence (i.e., double refraction), δ, is the physical quantity equal to the mathematical difference between the largest and smallest refractive index for an anisotropic mineral. The pleochroism is the property of exhibiting different colors as a function of

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the vibration direction. Dichroism refers to uniaxial minerals while trichroism refers to biaxial minerals. Dispersion is the variation of the refractive index with the wavelength of incident light. Opaque minerals are more commonly studied in reflected light and that study is generally called ore microscopy or ore-metallography, the main parameter is the reflective index (Rλ) for a given wavelength, λ (generally taken as 650 nm), expressed in percentage of intensity of light reflected to intensity of incident light.

12.2.15 Static Electricity and Magnetism The electrostatic charging properties of insulating materials were historically split into vitreous electricity, that is, materials that acquire a positive charge (+) due to a loss of electrons upon friction with a wool fabric (e.g., quartz, glass), and resinous electricity, those acquiring a negative charge (–) , that is a gain of electron upon friction (e.g., ebonite, amber). Some minerals could be strongly ferromagnetic, i.e., readily attracted by a permanent magnet. For instance, lodestone or magnetite, ilmenite and pyrrhotite are the most common ferromagnetic minerals found both in igneous and sedimentary rocks. Sometimes, hematite may be contaminated by magnetite and appear to be ferromagnetic.

12.2.16 Luminescence The effect is noticed when some minerals when submitted to long (366 nm, Wood’s light) or short (256 nm) wavelength UV-light irradiation could simultaneously emit visible light (i.e., fluorescence) or emit light after the irradiation has stopped (i.e., phosphorescence). In particular case, minerals owing to the relaxation of point defects (e.g., Schottky, Frenkel, or F-center) in their crystal lattices can also emit light when submitted to heating (i.e., thermoluminescence), or when scratched or rubbed to a rough surface (i.e., triboluminescence). Cathodoluminescence is displayed by some particular minerals when they are irradiated by a beam of high-energy charged particles (i.e., electrons, protons, etc.). For instance, several uranium ores are fluorescent, while sphalerite bombarded by an electron beam is cathodoluminsecent and was the first compound used as screen-phosphor is spynthariscopes, while fluorspar (i.e., fluorite) is thermoluminescent and was used in the dating of archeological stoneware.

12.2.17 Piezoelectricity and Pyroelectricity The property of piezoelectricity refers to the development of a momentary electric current when crystals are squeezed suddenly in certain crystallographic directions. The strain caused by squeezing is very small and purely elastic. Some common rock-forming minerals exhibit piezoelectricity such as low temperature quartz, tourmaline, sphalerite, boracite and topaz. The property of pyroelectricity refers to the development of a momentary electric charge displacement when crystals are submitted of a sudden change in temperature. The effect is proportional to the magnitude of the temperature change. Like piezoelectricity, pyroelectricity is strongly dependent on the crystal symmetry. Tourmaline is the most common pyroelectric mineral.

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12.2.18 Play of Colors and Chatoyancy Interference of light either at the surface or in the interior of a mineral may produce a series of colors as the angle of incident light changes. Iridescence: when an incident ray of light falls upon a thin transparent layer, some fraction of incident light is reflected, whilst the remainder fraction is refracted and is subsequently reflected back along a different path parallel to the first. Owing to the path difference between the two rays, interference occur with either cancelation when in phase opposition or intensification when in phase. The color effects caused by this phenomena are called iridescence. Opalescence consists of the reflection of incident light by small lamellar, or spherical inclusions in the mineral giving a milky or pearly aspect (e.g. precious opal). Some specimens of labradorite show colors ranging from blue to green or yellow with changing angle of incident light. This iridescence, also called schiller and labradorescence, is the result of light scattered by extremely fine exsolution lamellae. Chatoyancy consists of a wavy band of light that is seen to pass accross the mineral at right angles to the direction of the fibers. Asterism is a star-like effect of minerals cut in cabochon, caused by the reflection of light from fibers or fibrous cavities crossing at 60° (six-rayed star) or 90° (four-rayed star).

12.2.19 Radioactivity Several uranium and thorium containing minerals and ores are obviously radioactive owing to the decay of the actinides and particularly uranide elements that they contain, while some minerals such as zircon which should not be radioactive, owing to the isomorph (i.e., diadochy) substitution of cations Zr(IV) by U(IV) and Th(IV), are often radioactive. The metamict (i.e., amorphization) habit is due to the destruction of the crystal lattice structure by selfirradiation and atom recoil following emmission of an alpha particle.

12.2.20 Miscellaneous Properties Halite tastes salty, while epsomite exhibit a bitter taste. Some sulfides when rubbed exhibit the odor of sulfur. Talc feels slippery like soap. Plagioclase may have tiny parallel grooves called striations on cleavage surfaces. Striations are best seen when a cleavage surface is oriented to reflect light. Micas break into thin sheets which are elastic. The sheets may be bent and will spring back. Transparent varieties of gypsum with obvious cleavage may be flexible. They can be bent but will not spring back. Some varieties of alkali feldspar may have an irregular pattern of veins.

12.2.21 Chemical Reactivity Reaction to common strong mineral acids (e.g., HCl, HNO3, H2SO4, HF, or aqua regia) either diluted or concentrated is another important and rapid identification test. A few minerals effervesce, i.e., they produce bubbles, when a few drops of dilute hydrochloric acid are placed on a sample. Calcite vigorously evolves carbon dioxide and can easily be detected using this test, while dolomite must be powdered (i.e., streak powder) or the acid must be concentrated and heated to produce the same strong effervescence. When fluorite is heated in concentrated sulfuric acid it evolves hazardous hydrogen fluoride gas which strongly corrodes the test tube glassware.

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12.2.22 Pyrognostic Tests or Fire Assays The pyrognostic tests also called fire assays are simple qualitative laboratory techniques used by mineralogists in the field or in a laboratory to indentify quickly without complex equipment the chemical elements present in an unknown mineral sample. Five major types of fire assays are used: (i) (ii) (iii) (iv) (v)

the flame test; the fusibility or blowpipe test; the reduction on charcoal; the open and closed tube tests; and finally the bead test.

12.2.22.1 The Flame Test The vapor of certain chemical elements imparts a characteristic color to the flame of burning gas (e.g., Bunsen burner). This property is used for identifying qualitatively various metallic elements. The flame coloration is caused by electronic transitions occurring between the energy levels of the atoms of the chemical element. For a particular chemical element the flame coloration is always the same, regardless of whether the chemical element is in the free atomic state or chemically in molecules. For example, free sodium metal, sodium chloride, sodium carbonate and sodium sulfate all impart an intense yellow color to the flame (D-line of 589 nm). This yellow color is characteristic of sodium in any form, and hence can be used as a test for sodium. In the making of flame tests, chlorides of the metals are commonly used, since chlorides are more volatile than other salts. Procedure. Usually a thin wire of pure platinum metal is embeded into the tip of a borosilicated glass rod. Prior to conduct the test the Pt-wire must be cleaned thoroughly. Hence the Pt-wire is dipped into a solution of dilute hydrochloric acid (HCl) and placed into the hottest part of the Bunsen flame to burn off impurities. This operation must be repeated until no color is imparted to the flame. The unknown mineral is ground in an agate mortar and its powder is dissolved into an appropriate strong mineral acid (e.g., HNO3, HCl) and the resulting solution is analyzed. The Pt-wire is dipped into the solution and the test is conducted by holding the Pt-wire in the hottest part of a non-luminous Bunsen burner flame. It is important to observe if sodium is present through a cobalt-glass filter. Insoluble mineral samples are only ground and a pinch of the finely ground solid is put on a watch glass. A few drops of 6 M hydrochloric acid are added to moisten the powder and stirred with a clean platinum wire and hold in the hottest part of a non-luminous Bunsen burner flame. Note that a trace of sodium is found as an impurity in practically all substances, especially in solutions that have been standing in glass bottles. Do not report sodium unless a very vigorous yellow flame is observed. For comparison draw the cold wire between your fingers. The sodium flame should be more intense than that obtained from the trace of sodium on the fingers. The chemical elements which impart characteristic colors to flame are listed in Table 12.5.

Mineralogical, Physical and Chemical Properties

769

Table 12.5. Flame coloration tests Flame Wavelength coloration lines (intensity)

Chemical element

Comments

Red 610.36 nm (Crimson) (orange) 670.78 nm (red, m)

Lithium (Li)

The lithium minerals, which are either silicates or phosphates, do not become alkaline after ignition. If strontium is suspected it can be detected using a blue cobalt glass. Masked by Ba and Na. Violet through blue cobalt-glass and invisible through green glass.

Red (Carmin)

605.0 nm (orange, m) 460.73 nm (blue)

Strontium (Sr)

Carbonates and sulfates show the strontium reaction, and become alkaline after ignition. Silicates and phosphates do not give the strontium flame. Masked by Ba. Greenish through blue cobalt-glass and yellowish through green glass.

Red yellowish or orange

622.0 nm (red, m) 553.5 nm (green)

Calcium (Ca)

Only a few minerals give this calcium color decisively when heated alone. Often, however, the color shows distinctly after moistening the assay with hydrochloric acid. Masked by Ba. Greenish through blue cobalt-glass and green through green glass.

Yellow intense

597.3 nm (yellow) 589.2 nm (yellow, s)

Sodium (Na)

This test for sodium is so delicate that great care must be exercised in using it. Glass blowers Didymium Safety Glasses may be used to block out this emission to observe the less intense colors while the blue cobalt glass masks the color.

Green bright

Boron (B)

The addition of 3 parts potassium hydrogenosulfate (KHSO4) and 1 part calcium fluoride (CaF2) impart an emerald green coloration. Boron compounds rarely show an alkaline reaction after ignition. Green color is due to the blue and orange in the spectrum.

Green 535.05 nm (emerald) (green)

Thallium (Tl)

Presence of sodium impart a pale green color. Not often observed due to the rarity of thallium-bearing minerals.

Green yellowish

Barium (Ba)

Carbonates and sulfates show the reaction, and become alkaline after ignition. Silicates and phosphates do not give the barium flame. The flame appears bluish through a green glass.

Molybdenum (Mo)

If the molybdenum is in the form of the oxide or the sulfide.

Green pale

524.2 nm (green, w) 513.7 nm (green)

451.1 nm 410.1 nm

Green bluish

Tellurium (Te) Antimony (Sb) Phosphorus (P) The phosphorus color is not very decisive, but often aids in the identification of a phosphate. Adding concentrated sulfuric acid it gives a yellowish flame. Zinc (Zn)

Violet pale

Zinc appears as bright streaks in the flame.

769.90 nm (red) Potassium (K) 766.5 nm (red) 404.5 nm (violet, w)

The potassium color is often masked by the more prominent yellow from sodium. Silicates, phosphates and borates do not give the potassium flame. Purple-red through blue glass and bluish green through green glass.

794.76 nm (red) 780.0 nm (red) 775.8 nm (red) 740.8 nm (red) 421.56 nm (violet) 420.2 nm (indigo)

The rubidium color is often masked by the more prominent yellow from sodium.

Rubidium (Rb)

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Table 12.5. (continued) Flame Wavelength coloration lines (intensity)

Chemical element

Comments

Violet pale

697.3 nm (red) 672.3 nm (red) 621.3 nm (orange) 459.3 nm (blue) 455.54 nm (indigo)

Caesium (Cs)

The cesium color is often masked by the more prominent yellow from sodium. The first element found using a spectroscope.

Blue azure

510.55 nm (green, m)

Copper (II) chloride

The copper flame color is dependent on the presence of halide (i.e., F, Cl, Br, or I). The color can be used to detect halides by using copper oxide moistened with the test solution (e.g., flame blue-purple with Cl, blue-green with Br, and emerald-green with I). The outer darts of the flame are tinted with emerald-green.

(weak)

Selenium (Se)

The selenium color is accompanied by the characteristic odor of rotting radishes.

(weak)

Lead (Pb)

In reducing flame.

Indium (In)

The element Indium is named for the prominent blue lines in its spectrum.

Arsenic (As)

The arsenic color is accompanied by the characteristic odor of garlic.

Blue

12.2.22.2 The Fusibility Test The fusibility test is also a qualitative assay that consists of observing the melting ability of a tiny mineral fragment held in the dart of the blowpipe flame. Historically this simple test was based on the experimental observation made by the first mineralogists and chemists that Table 12.6. Von Kobell’s fusibility scale of minerals Classification

No. Melting Mineral point

Description

Easy fusible

1

525°C

Stibnite [Sb2S3]

Coarse splinters that fuse easily in the flame of a candle or a match.

2

800°C

Chalcopyrite [CuFeS2]

Small fragments that fuse slowly in the Bunsen burner flame or in a closed glass tube at red heat.

3

1050°C

Almandine [Fe3Al2(SiO4)3]

Coarse splinters easily fuse to give a globule at the tip of the blowpipe, and only finest splinters rounded in a Bunsen burner.

4

1200°C

Actinolite Fine splinters rounded under the blowpipe and [Ca2(Fe,Mg)5(Si8O22)(OH,F)2] only fine splinter form a globule.

5

1300°C

Orthoclase [KAlSi3O8]

Fused only in fine splinters or on thin edges underthe blowpipe.

6

1400°C

Hemimorphite [Zn4Si2O7(OH)2] Bronzite [(Mg,Fe)2(Si2O6)]

Finest edge only rounded in the hottest part of the dart of the blowpipe.

7

1760°C

Quartz [SiO2]

Entirely infusible under the dart of the blowpipe, and retaining the edge in all its sharpness.

Fusible

Fusible with difficulties

Infusible

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every mineral like any other chemical compound with a definite chemical composition exhibits a fixed melting point which is observed and compared to other reference minerals. Actually, some minerals melt under the flame of the blowpipe as easily as wax (e.g., stibnite) while others are quite infusible (e.g., quartz) even when exposed to the hottest, most oxidizing region of the flame (ca. 1500°C). Moreover, there are other special mineral characteristics that can be determined from the fusibility test and these are discussed in Section 12.2.22.5. Table 12.6 presents the practical scale of fusibility first devised by Von Kobell to differentiate how fusable some minerals are compared to others.

12.2.22.3 The Reduction on Charcoal The reduction test on charcoal involves the heating of a powdered mineral mixed with a flux made of sodium carbonate (Na2CO3) and powdered charcoal on a cube of charcoal. During this test most sulfidic minerals give off a metal globule after reduction, and the coating color is related to the metal.

12.2.22.4 Tests with Cobalt Nitrate and Sulfur Iodide During the charcoal test is possible to add a drop of reagent to produce a typical coloration related to a particular chemical element. The most common reagents are: (i) (ii)

an aqueous solution containing 5 wt.% of cobalt nitrate used on charcoal; sulfur iodide produced in situ by mixing stoichiometric amounts of iodine and sulfur with the powdered mineral that must be used on a plate of Plaster of Paris. Table 12.7. Coloration obtained with Co(NO3)2 on charcoal Coloration

Chemical elements

Gray to black

Baryum, strotium, calcium and niobium

Bluish-gray

Beryllium

Pinkish-gray

Tantalum

Pink

Magnesium

Blue

Aluminum (Thenard blue)

Dark blue

Silicium

Yellowish green Titanium Greenish blue

Tin

Grayish green

Antinony

Emerald green

Zinc

Dark violet

Zirconium, arsenic, boron, and phosphorus

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Table 12.8. Coloration obtained with sulfur iodide on plaster Coloration

Chemical elements

Ultramarine

Molybdenum

Blue-green

Tungsten

Orange

Arsenic, antimony

Reddish brown

Selenium

Purple-brown

Tellurium

Chocolate

Bismuth

Brownish-Green

Cobalt

Gold

Lead

Yellow

Silver

Yellow-brown

Tin

Yellow and red

Mercury

12.2.22.5 The Closed Tube Test In the closed tube test, a powdered mineral sample is placed at the bottom of a glass test tube and heated. The following characteristics must be reported: (i) the change in the appearance; (ii) the formation of gases which collect in the tube; (iii) the formation of sublimates or condensed liquids on the cold walls of the tube. Table 12.9. Mineral changes during the closed tube test Characteristics

Reactions

Boiling

Some hydrayed minerals containing hydratation water release their water and gives the filling of boiling. Zeolithes are the most common examples.

Discoloration or darkening

The color of a mineral can changes due to the healing of lattice defects on moderate heating, mostly from dark colors to lighter ones. Such bleaching is a common practice used for treating raw gemstones, especially metamict zircons. But minerals may also change color after heating, owing to decomposition. For example the carbonates of copper, iron, and manganese become black on heating, due to the formation of black oxides. A dark red color frequently occurs when hematite is formed.

Decrepitation

Minerals containing liquid inclusions may explode owing to the evolution of steam during heating. Other such as baryte break into smaller crystal while milky quartz breaks into very fine powder or dust.

Exfoliation

Several minerals having a lamellar structure, including many phyllosilicates delaminate or exfoliate.

Melting

Only minerals having a low melting point melt in the closed tube.

Thermoluminescence

Some minerals emit a bright, often colored light (e.g., fluorescence and phosphorescence) when heated below redness, that is, above 300°C. The effect can be observed only in darkness. It is caused by the relaxation of lattice defects upon heating. The lattice defects are always due to radiation dammage that the crystal undergoes since its formation. This effect is called thermoluminescence, it is often found on fluorite, quartz, calcite, apatite, zircon, and diamond.

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Table 12.10. Gases evolved during the closed tube test Gases

Reactions

Arsenic and A garlic-like odour points to the presence of arsenic, while selenium causes a peculiar odour antimony resembling the smell of a rotten radishes. oxides Carbon dioxide (CO2)

Carbon dioxide is originates from the decomposition of most carbonates during firing. The gas can be identified by introducing a drop of a clear solution of barium hydroxide or calcium hydroxide onto the inner wall of the tube next to the open side. The drop becomes white owing to the formation of the respective carbonates.

Hydrogen fluoride (HF)

Minerals containing fluorine along with hydroxyl groups (e.g., topaz) can evolves hydrogen floride upon intense heating at high temperature. The HF gas has a pungent odor, etches the glass and gives an acidic reaction with litmus paper.

Organic vapors

Mineraloids develop upon heating a brown smoke, mostly accompanied by dark distillation products and an empyreumatic odour. Only amber or natural resins produce an aromatic odour.

Oxygen (O2)

Oxygen gas may be formed by the decomposition of pyrolusite and other manganese oxides. To detect it, light a wooden toothpick with a torch flame, blow out the flame of the burning wood and insert the still glowing end of the toothpick into the tube. The presence of oxygen causes the glow to intensify or the flame to re-appear.

Sulfur dioxide (SO2)

Sulfur dioxide exhibits a strong pungent odour and it may be formed by the decomposition of sulfates or the partial oxidation of sulfides. It is detectable by the acid reaction it imparts to moistened litmus paper or by the decoloration of wet brown permanganate paper.

Water (H2O)

Water is given off under moderate heating from zeolites and mineral hydrates like gypsum Minerals containing the hydroxyl group, like clay minerals, micas or amphiboles lose their water under firing only at higher temperatures.

Table 12.11. Sublimates during the closed tube test Sublimates Reactions Black-like

Black like a black mirror, next to the assay dark gray crystals indicates As Black similar to As, transferred to a streak plate and rubbed it turns red indicates HgS Black fusible globules indicates Se or Te, small globules of Se transmit a reddish light

Gray

Gray metallic globules, which may be united by rubbing with a strip of paper indicates mercury.

Oily

When sulfates decompose, small drops of concentrated sulfuric acid may sometimes occur, they look like oil.

Red to brown

They oint to sulfides of As or Sb , hot they look nearly black, the As compounds are readily volatile

White

White sublimates could be either ammonium salts or As2O3 or Sb2O3 or lead chloride or Hg2Cl2. Repeat the test adding five times the amount of dry sodium carbonate to the assay, ammonium salts give off ammonia (NH3) while mercury chloride decomposes to metallic mercury. To distinguish between As- and Sb-oxides use the open tube test.

Yellow

Sublimates that appears orange-red on heating and then yellow after cooling indicates the presence of sulfur as that produced by heating minerals such as pyrite or marcasite.

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Borosilicate glass test tube 8–12 cm long, and 3–6 mm inside diameter are commonly used. The ground mineral sample is introduced at the bottom of the tube. The tube held by a wooden clamp is put near the vertical position and placed over a Bunsen burner. If any water condenses in the upper part, put some cotton wool in the upper part to avoid water drops rolling back to the hot parts and causing cracks due to thermal shock. The mineral changes, the gases evolved, the colors of the coating and sublimates that form on the cold sides of the tube are all important characteristics to identify mineral classes.

12.2.22.6 The Open Tube Test In the open tube test a powdered mineral sample is placed inside a glass tube, open at both ends, and heated. The combination of heat and the circulation of air leads to the roasting of the mineral, thus bringing it to oxidation. Oxygen from the air oxidizes the mineral and the reaction products (e.g., As2O3, SbO3, SO2, H2O, etc.) escape as gases. Therefore, heating in an open tube is one of the most important tests for minerals which are suspected to belong to the sulfides and sulfosalts; the test will give a reliable proof if S, As, Sb, Hg, Te, or Se are main constituents. The borosilicated glass tubes used are 12 cm long and 4 mm in diameter with

Table 12.12. Open tube test characteristics Element

Reaction

Antimony Antimonides are oxidized to Sb2O3, which is white and slowly volatile. The sublimate forms as (Sb) a dense, white smoke, which passes up the tube and partly settles on the upper side, partly it leaves the tube. It is volatile, but on further heating it changes to Sb2O4, this compound is nonvolatile, infusible, and its color is pale straw-yellow when hot. Arsenic (As)

All arsenides are oxidized to give off arsenic trioxide (As2O3) which is white and readily volatile. The sublimate forms as a ring in the cold part of the tube, and where it deposits on the warm glass it is distinctly crystalline. With a good magnifying lens tiny octahedrons can be visually observed. The typical garlic odour should not occur, since this is an indication of incompletely oxized samples.

Bismuth (Bi)

When sulfides are present, bismuth combines with SO2 forming a small white sublimate of bismuth sulfate. When heated it melts to brown drops, the cooled drops are yellow and opaque. On increased heating they vanish due to the formation of Bi-silicates. The test for Bi is not very reliable and should be confirmed by heating on charcoal

Lead (Pb)

Sulfides with a considerableamount of lead such as galena may give a small amount of a sublimate of PbSO4. The color is white when cold, on strong heating it vanishes due to the formation of colorless lead silicate. The test for Pb is not very reliable and should be confirmed by heating on charcoal.

Mercury (Hg)

Mercury minerals produce gray metallic globules of free mercury which are volatile on further heating. By rubbing the minute globules with a strip of paper, they may be made to unite.

Selenium (Se)

Selenides gives-off SeO2 has a typical odour of rotten radish. Only large amounts produce a gray sublimate of Se next to the sample. It may turn to red at a distance, and, far from the sample there appears a sublimate of SeO2 made up of white, radiating, prismatic crystals, which are readily volatile on heating.

Sulfur (S)

All sulfide minerals are oxidized and sulfur dioxide (SO2) is formed, which can be detected by its odour or by the color change of wet pH-paper. Again brown moistened pyrolusite paper can be used to detect the formation of sulfur dioxide, which will bleach the brown paper. Sphalerite (ZnS) and molybdenite (MoS2) are difficult to roast, and they should be finely ground for this test.

Tellurium Tellurides produce a dense white smoke, part of which passes through the tube and part of (Te) which settles as a thick, white sublimate on the lower side. On heating of the sublimate of TeO2 small oil-like drops are formed.

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775

both open sides. They should be held in a standing position of 30° in order to ensure a sufficient draft of air on heating. Straight tubes may be used, but the powder of the assay tends to fall out of the tube hence bent tubes are preferred. The coarsely powdered sample is placed next to the open end. The flame of the Bunsen burner is moved under the mineral and allows oxidization to take place. The most important reactions occurring in the open tube test are summarized in Table 12.12.

12.2.22.7 The Bead Tests The bead tests, sometimes called the borax bead or blister tests, are an old and straightforward qualitative analytical method first introduced by Berzelius in 1812 and widely used to test for the presence of certain metals in minerals and inorganic compounds since then. Historically, they were conducted with fluxing salts such as borax [i.e., sodium tetraborate, Na2B4O7.10H2O] which melts at 742°C. Actually, when a minute amount of borax is heated to redness it loses its water of crystallization and it forms a transparent glass bead. Small amounts of metal oxides dissolve readily in fused borax to form a colored glass. Upon cooling many chemical elements produce a characteristic color in the borax glass bead. Since then other salts were also used as fluxing agent such as sodium carbonate (Na2CO3), sodium fluoride (NaF). Among them the salt of phosphorus also called microcosmic salt [sodium ammonium hydrogenophosphate, NaNH4HPO4.4H2O] which after losing water and ammonia form NaPO3 which melts at 628°C is the most important after borax. Bead test procedure. Make a loop in the end of a platinum wire. Heat the Pt-wire to redness and then dip it into borax or microcosmic salt powder. A small amount of salt is coated

Table 12.13. Bead test made with borax (Na2B4O7.10 H2O) Bead coloration

Oxidizing

Reducing

Colorless

hc: Al, Si, Sn, Bi, Cd, Mo, Pb, Sb, Ti, V, W ns: Ag, Al, Ba, Ca, Mg, Sr

Al, Si, Sn, alk. earths, earths h: Cu hc: Ce, Mn

Gray/Opaque

sprs: Al, Si, Sn

Ag, Bi, Cd, Ni, Pb, Sb, Zn s: Al, Si, Sn sprs: Cu

Blue

c: Cu hc: Co

hc: Co

Green

c: Cr, Cu h: Cu, Fe+Co

Cr hc: U sprs: Fe c: Mo, V

Red

c: Ni h: Ce, Fe

c: Cu

Yellow/Brown

h, ns: Fe, U, V h, sprs: Bi, Pb, Sb

W h: Mo, Ti, V

Violet

h: Ni+Co hc: Mn

c: Ti

The following abbreviations are used in the tables: h: hot; c: cold; hc: hot or cold; ns: not saturated; s: saturated; sprs: supersaturated. References: (i) Haller, A.; Girard, Ch. (1907) Mémento du chimiste (Ancien agenda du Chimiste). Recueuil de tables et documents divers indispensables aux laboratoires officiels et industriels. H. Dunod & E. Pinat Ed., Paris, pp. 200–210. (ii) Brush, G. (1926) Manual of Determinative Mineralogy with an Introduction on Blowpipe Analysis. John Wiley & Sons, New York.

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Table 12.14. Bead test made with microcosmic salt (NaNH4HPO4) Bead coloration

Oxidizing zone

Reducing zone

Colorless

Si (undissolved) h: Mg, Ca, Sr, Ba, Al, Sn ns: Bi,Cd,Mo,Pb,Sb,Ti, Zr,Zn, Y, La, Th

Si (undissolved) Ce, Mn, Sn, Al, Ba, Ca, Mg Sr (sprs, not clear)

Gray/Opaque

s: Al, Ba, Ca, Mg, Sn, Sr

Ag, Bi, Cd, Ni, Pb, Sb, Zn

Blue

c: Cu hc: Co

c: W hc: Co

Green

U c: Cr h: Cu, Mo, Fe+(Co or Cu)

c: Cr h: Mo, U

Red

h, s: Ce, Cr, Fe, Ni

c: Cu h: Ni, Ti+Fe

Yellow/Brown

c: Ni h, s: Co, Fe, U

c: Ni h: Fe, Ti

Violet

hc: Mn

c: Ti

The following abbreviations are used in the tables: h: hot; c: cold; hc: hot or cold; ns: not saturated; s: saturated; sprs: supersaturated. References: (i) Haller., A; Girard, Ch. (1907) Mémento du chimiste (Ancien agenda du Chimiste). Recueuil de tables et documents divers indispensables aux laboratoires officiels et industriels. H. Dunod & E. Pinat Ed., Paris, pp. 200–210. (ii) Brush; Penfield (1906) Determinative Mineralogy and Blowpipe Analysis.

onto the Pt-wire loop and the loop is then heated again in the flame of a Bunsen burner until it melts down into a small transparent bead. If the bead is too small repeat the procedure until a bead of about 1–2 mm in diameter is obtained. A very small amount of the crushed substance to be tested and previously roasted in the case of sulfide minerals is touched by this hot bead, which is then heated again to redness in the oxidizing flame and then in the reducing flame of dart of the blowpipe. If the bead is black in color, dip it into more salt and reheat to dilute the concentration of metal. The bead is allowed to cool and is examined. The element present is determined by matching the color of the glass bead thus formed with known color according to the the zone of the flame. Coloration of borax and microcosmic salt are given in Tables 12.13 and 12.14 respectively.

12.2.23 Heavy-Media or Sink-float Separations in Mineralogy The separation of heavy minerals by the sink-float techniques is usually performed by immersing a mixture of mineral grains into a glass separatory funnel containing a dense liquid (heavy liquor or medium) of known specific gravity. Under the standard acceleration of gravity the minerals distribute according to their own density, i.e., light minerals float while heavy 8 minerals sink to the bottom of the flask . The most common dense liquids in commonest use are brominated and iodided organic liquids usually diluted with a solvent to adjust the density, to a lesser extent aqueous solutions of inorganic salts and low temperature molten salts are also used for specific purposes. For high density solutions, slurries made by a suspension of a dense solid in a liquid of the same density have been especially studied by Retgers and Gossner in view of their applicability to density determinations of crystals. 8

Browning, J.S. (1961) Heavy Liquids and Procedures for Laboratory Separation of Minerals. U.S. Bureau of Mines, Inform. Circ. No. 8007.

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777

12.2.23.1 Selection of Dense Media The appropriate liquid used as dense media must meet the following requirements: -3

• elevate density at least above that of quartz (i.e., 2.650 g.cm ); • no chemical reactivity with most common minerals; • thermal and photochemical stability; • miscibility with usual solvents and diluents (e.g., acetone, benzene, ethanol); • transparent; • low dynamic viscosity, i.e., close to that of water at room temperature (1 mPa.s); • non-hazardous properties (toxic, flammable) and easy to dispose; • low cost.

12.2.23.2 Common Heavy Liquids Used in Mineralogy The three most common heavy liquids used in routine mineralogical identification are brominated and iodided organic compounds, among which the three solvents listed below are the most common: • tribromomethane (syn. bromoform) with chemical formula CHBr3 and d

20

= 2.89; • tetrabromo-1,1,2,2-ethane (syn. acetylene tetrabromide) with chemical formula C2H2Br4 20 and d 4 = 2.965); 20 • diiodomethane (syn. methylene iodide) with chemical formula CH2I2 and d 4 = 3.325. 4

These dense liquors allow us to separate grains of minerals easily into two distinct groups: (i)

(ii)

–3

a light fraction with minerals exhibiting a density lower than 2.9 g.cm that includes the light igneous-rock-forming silicates, e.g., quartz, feldspars, and feldspathoids (coupho9 lites ); –3 two heavy fractions with minerals exhibiting densities greater than 2.9 g.cm (barylites). The heavy fractions are: –3 (1) a medium-density fraction with minerals having a density ranging from 2.9 g.cm –3 to 3.3 g.cm that corresponds to major silicate minerals; –3 (2) a denser fraction with heavy minerals having densities greater than 3.3 g.cm and that are of economic importance (ores).

Detailed physical properties of these heavy media along with other less common dense organic and inorganic liquids are described in Chapter 20.

12.3 Strunz Classification of Minerals The modern systematic classification of minerals was introduced by Prof. Hugo Strunz and is briefly listed in Table 12.15.

9

According to the French Mineralogist Eugène Lacroix, the coupholites denote the light rock forming –3 minerals having an apparent density lower than 2.77g.cm (e.g., quartz, feldspaths, feldspathoids). By contrast heavier minerals having a density greater than the previous values are baylites named after Greek, baryos, heavy and lithos, stones.

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Minerals, Ores and Gemstones Table 12.15. Strunz classification of minerals Strunz class

Subclass

1/Class I: 1/A1 Metals and intermetallic alloys Native elements 1/A2 Semimetals and nonmetals 2/Class II: Sulfides and sulfosalts

2/A1 Alloys and alloylike compounds 2/B1 Sulfides, selenides, and tellurides (M:S,Se,Te > 1:1) 2/C1 Sulfides, selenides, and tellurides (M:S,Se,Te = 1:1) 2/D1 Sulfides, selenides, and tellurides (M:S,Se,Te 2 VIII – 68 Inosilicates with structures with chains of more than one width VIII – 69 Inosilicates with chains with side branches or loops VIII – 70 Inosilicates with column or tube structures VIII – 71 Phyllosilicate minerals VIII – 72 Phyllosilicates with 2D infinite sheets with other than six-membered rings VIII – 73 Phyllosilicates with condensed tetrahedral sheets VIII – 74 Phyllosilicates with modulated layers VIII – 75 Tektosilicate minerals

IX – 50 Organic minerals

IX – 50 Organic minerals

12.5 Gemstones A gemstone is a natural mineral that can be cut and polished or otherwise treated for use as jewelry or other ornament. A precious gemstone has beauty, durability, and rarity, whereas a semiprecious gemstone has only one or two of these qualities. A gem is a gemstone that has been cut and polished. Diamond, corundum (i.e., ruby and sapphire varieties) and beryl (i.e., emerald and aquamarine varieties) are generally classified as precious gemstones while all other gemstones are usually classed as semiprecious. A gemmologist or gemologist is a mineralogist with proven skills in identifying and evaluating gemstones. A lapidary is a cutter, polisher, or engraver of precious stones. From a geological point of view, gemstones occur in various geologic materials but most gemstones are found in particular igneous rocks (e.g., pegmatites, kimberlites, and lamproites) and in sedimentary alluvial gravels (e.g., placers deposits), but metamorphic rocks may also contain gem materials. The major precious and semiprecious gemstones are listed in Table 12.17. Table 12.17. Precious and semiprecious gemstones Mineral

Gem varieties

Color

Benitoite

Benitoite

Deep blue color

Beryl

Emerald

Intense green or bluish green

Aquamarine

Greenish blue or light blue

Morganite

Pink, purple pink, or peach

Heliodore

Golden yellow to golden green

Goshenite

Colorless, greenish yellow, yellow green, brownish

Chrysoberyl

Transparent yellowish green to greenish yellow and pale brown

Alexandrite

Red in incandescent light and green in daylight

Ruby

Intense red

Sapphire

Blue

Diamond

Colorless, yellow canary, green, deep blue

Chrysoberyl Corundum Diamond

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Table 12.17. (continued) Mineral

Gem varieties

Color

Plagioclases

Labradorite

Colorful, iridescent, also transparent stones in yellow, orange, red, and green

Sunstone

Gold spangles from inclusions of hematite

Peristerite

Blue white iridescence

Amazonite

Yellow green to greenish blue

Moonstone

Colorless; also white to yellowish, and reddish to bluish gray

Almandine

Orange red to purplish red

Andradite

Yellowish green to orangy yellow to black:

Demantoid

Green to yellow green

Grossular

Colorless; also orange, pink, yellow, and brown

Hessonite

Yellow orange to red

Malaia

Yellowish to reddish orange to brown

Pyrope

Colorless also pink to red

Rhodolite

Purplish red to red purple

Spessartine

Yellowish orange

Topazolite

Yellow to orangy yellow

Tsavorite

Green to yellowish green

Uvarovite

Emerald green

Jadeite

Nephrite

White, leafy and blue green, emerald green, lavender, dark blue green and greenish black, deep emerald-green

Lazurite

Lapis lazuli

Opal

White opal

Opaque, porcelain-like white material; colors resemble flashes or speckles

Black opal

Flashes and speckles appear against black background

Water opal

A transparent, colorless opal is the background for brilliant flashes of color

Orthoclases Garnets

10

Deep blue, azure blue, greenish blue (bluish color with flecks of white and gold)

Fire opal

Reddish or orange opa

Olivine

Peridot

Olive to lime green

Quartz

Rock crystal

Colorless

Amethyst

Violet

Citrine

Yellow to amber

Morion

Black

Smoky quartz

gray to brown

Rose quartz

Translucent pink

Silica Chalcedony (cryptocrystalline) and Jasper

10

White to black

Agate

Various

Onyx

Black

Bloodstone

Red

An aggregate of lazurite with variable amounts of pyrite and calcite

Gemstones

783

Table 12.17. (continued) Mineral

Gem varieties

Color

Spinels

Balas ruby

Red

Almandine spinel Purple red

Spodumene

Rubicelle

Orange

Sapphire spinel and ghanospinel

Blue

Chlorspine

Green

Kunzite

Pink to lillac

Hiddenite

Yellow to green

Tanzanite

Tanzanite

Topaz

Topaz

Wine yellow, pale blue, green, violet, or red

Tourmaline

Achorite

Colorless

Brazilian emerald Green Dravite

Brown

Indicolite

Dark blue

Rubellite

Pink to red

Siberite

Violet

Verdilite

Green

Turquoise

Turquoise

Deep blue to greenish blue

Zircon

Jargon

Brown

Malacon

Metamict

Matura diamond

Colorless

Hyacinth

Yellow, orange, red, brown

Note: amber, coral and pearl are organic materials also considered with gem materials

12.5.1 Diamond 12.5.1.1 Introduction Diamond [7782-40-3] with the relative atomic molar mass of 12.0107 is the high-pressure and high-temperature allotrope of carbon (i.e., P >20 GPa and T >4000 K), but at ambient pressure it is metastable owing to the high temperature (2000 K) needed to initiate the phase change to graphite. The word diamond originates from the Greek, adamas, meaning invincible due to its hardness. Diamond crystallographic structure consists to a face centered cubic crystal lattice where the carbon atoms occupy the eight corners, the centers of the six faces and half of the tetrahedral crystallographic sites (Z = 8). The most common crystal habits for euhedral crystals found in nature are the octahedron {111}, the cube {100}, and the dodecahedron {110} sometimes rounded due to etching. Diamond normally cleaves on the (111) plane but cleavage has been observed on the (110) plane and to a lesser extent some other crystallographic planes. Diamond luster is adamantine by definition and depending of the diamond type and impurities diamonds can be colorless, yellow, blue, or green. Polycrystalline diamond is also found in nature as multigranular masses called boart or bort. These polycrystalline aggregates are especially named carbonado after the Portuguese word meaning burned for black polycrystalline aggregates coming from the Congo-Kasai craton in the Central African Republic and in the São Francisco craton in Brazil, while framesite denotes randomly oriented microcrystalline diamonds found in kimberlites worldwide.

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12.5.1.2 Diamond Types Depending on the levels of trace impurities occurring in their crystal lattice, diamonds are classified into two major types, that is, those bearing nitrogen as major impurity (Type I) and those without nitrogen (Type II). These two subgroups are further subdivided into Types Ia, Ib, IIa, and IIb respectivelly. A brief description of these various types is presented in Table 12.18. Table 12.18. Classification of major types of diamonds

Type I (with nitrogen)

Main type

Type II (without nitrogen)

784

Subdivision Description Type Ia

Type Ia diamonds with an occurrence of 98%, the are the most common type of naturally occurring diamonds. They contain nitrogen (10–3000 ppm at. N) which is present into small aggregates of two to four atoms, including platelets.

Type Ib

Type Ib diamonds are naturally scarce (ca. 0.1 %). They have a low nitrogen content (25–30 ppm at. N) which is dispersed substitionally. Usually, most synthetic diamonds tend to be of the Type Ib, with up to 0.05 wt.% N as single atoms, often giving rise to a brilliant yellow color (e.g., canary diamonds).

Type IIa

Type IIa diamonds are relatively free of nitrogen imputity and they contain less than 10 ppm at. N. They are all colorless (e.g., the Cullinan and the Koh-i-Noor) and exhibit enhanced optical and thermal properties.

Type IIb

Type IIb diamonds are extremely rare. Due to minute amounts of boron impurities and with nitrogen below 0.1 ppm at. N they behave as a p-type semiconductors. They exhibits a blue color (e.g., the blue Hope diamond) due to the absorption band in the tail of the infrared absorption spectrum combined with the acceptor center.

Notes: about 22 mineral species have been identified as tiny inclusions in diamonds among those majorite garnet, ferropericlase, magnesioperovskite, and stishovite.

Recently, a classification based on the measure of the variation of the carbon and nitrogen 11 stable isotopes was introduced as a geochemical fingerprint of the deep origin of natural diamonds. The classification utilizes the delta isotopic function (δ‰) of a given stable iso13 15 18 34 tope (e.g., C, N but also O and S). The delta isotopic function expresses the deviation of 13 12 15 14 a given isotopic ratio for instance ( C/ C) or ( N/ N) relative to a standard reference material such as the Standard Pee Dee Belemnite (SPDB) the standard mean ocean water (SMOW) or the Cañon Diablo Troilite (CDT) and expressed in parts per thousand (‰). Geochemists have analyzed the isotopic composition of carbon (the ratio of carbon-13 to carbon-12) in diamonds and compared it to carbon in other minerals and rocks. Their work suggests diamonds are made of carbon that comes from two sources. Some diamonds have carbon that is identical to that in carbonate minerals (e.g., calcite in limestone) and hydrocarbons, suggesting they were derived from ocean floor or near-surface sediments that were recycled, through the process of subduction, into the mantle. Others contain carbon that is more like that expected if it were derived directly from parts of the mantle (peridotite) that still contain carbon from when the Earth first formed, 4.5 billion years ago.

12.5.1.3 Diamond Physical and Chemical Properties The properties of diamond require many superlatives to describe them as diamond exhibits a unique set of physical and chemical properties, among those the most remarkable characteristics are: 11

Cartigny, P. Stable isotopes and the origin of diamond. Elements, 1 (2) (2005) 79–84.

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(i) Diamond is the hardest known natural solid still unsurpassed. (ii) Diamond has the highest Young’s modulus. (iii) Diamond exhibits the highest thermal conductivity near room temperature of all the known materials. (iv) Diamond has the lowest coefficient of linear thermal expansion. (v) Diamond is an excellent electrical insulator due to the strong covalent bonding except for the type IIb doped with boron which is a p-type semiconductor. (vi) Diamond is corrosion-resistant to strong acids, alkalis, and molten salts and resist graphitization up to high temperatures. (vii) Diamond is transparent from near-UV until far IR electromagnetic radiation. Table 12.19. Diamond physical properties and characteristics Value

Crystal lattice

Cubic

Strukturbericht and Pearson’s symbol (atoms per formula unit)

A4, cF8 (Z = 8)

Lattice parameter (a/pm)

356.71

General properties

Properties (SI unit)

Space group (Hermann–Mauguin)

Fd3m

12

Relative atomic molar mass ( C = 12)

12.0107

Mechanical properties

–3

Density (ρ/kg.m )

3515

Young’s or elasticity modulus (E/GPa)

1050

Coulomb’s or shear modulus (G/GPa)

300

Bulk or compression modulus (K/GPa)

500

Poisson’s ratio (v/nil)

0.100 –1

Sound longitudinal velocity (Vl/m.s )

17,500

Tensile strength (/MPa)

>1200

Compressive strength (/GPa)

>110

Dynamic friction coefficient (μ)

0.1

Mohs hardness (HM)

10 (definition)

Knoop hardness (HK/GPa)

56–115 –1

–1

Thermal

Thermal conductivity (k/Wm K ) –1

500–2500 (300)

–1

Specific heat capacity (cP/J.K .kg )

502 –6

–1

Coefficient linear thermal expansion (α/10 K )

0.8 (300 K)

Optical

Electrical

4.4 (700 K) 11

14

Electrical resistivity (ρ/Ω.m)

10 –10

Energy band gap (Eg/eV)

5.45

Relative electric permittivity (at 27°C and 0.3 kHz) 5.58–5.70 Loss tangent factor (tanδ at 140 GHz)

30 km) having roughly 2–3 kilometer diameter (e.g., Kimberley, South Africa). The walls of the diatreme dip at angles of 75–85° from the horizontal; the crater walls exhibit shallower dip. The crater is the widest part of the pipe, but it seldom exceeds 2 km in diameter. The concentration of diamond is usually low and ranges from 0.5 to 5 carat per tonne among which less than 5% are of gem quality. From the nature of the silicate inclusions (e.g., coesite) found in diamonds it was found that kimberlites form usually in the region of maximum thickness of the lithosphere which is only found beneath cratons older than 2.5 Ga (Clifford’s rule) also called archons. Kimberlite diatremes are known on every continent but most do not contain diamonds. Southern and Western Africa (e.g., Democratic Republic of Congo, Botswana, Namibia, and South Africa) contains the largest concentrations of diamond-bearing kimberlites. Other important sources are in Northern Russia, Australia, Brazil and, since 1997, the Northwest Territories in Canada. By contrast, lamproites (e.g., Argyle, Australia) are phaneritic igneous rocks with olivine, leucite, and phlogopite forming wider crater than kimberlite having fewer than 500 metres in depth. Some diamonds also originates during metamorphism or impact from meteorites. Once these primary diamond

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Figure 12.2. Major diamond deposits

deposits are eroded by means of meteoric and geomorphological processes, the diamonds due to their outstanding hardness and chemical inertness are transported by rivers and finally forms detrital placer grains that concentrate with other heavy minerals in alluvial placer deposits (e.g., Sierra Leone) or even beach mineral sands (e.g., Namibia) derived from the parent kimberlite or lamproite rocks. Kimberlite and lamproite craters and kimberlite diatremes are usually mined as open-pit operations because the host rocks are usually friable. Underground production is frequently initiated with increases at depth. Alluvial sources are mined as open-pit operations. Most of the production of diamond is concentrated geographically in a few regions worldwide (see Figure 12.2) usually in the oldest continents: Africa (e.g., Angola, Botswana, Congo, Namibia, and Republic of South Africa), Asia (e.g., northeastern Siberia and Yakutia in Russia), Australia, North America (e.g., Northwest Territories in Canada), and South America (e.g., Brazil and Venezuela). Botswana is the world’s leading diamond producer in terms of output value and quantity and the total diamonds produced worldwide both indusrial and gems reached 150 million carats (30 tonnes).

12.5.1.5 Industrial Applications Because it is the hardest substance known, diamond has been used for centuries as an abrasive in cutting, drilling, grinding, and polishing. Industrial grade diamond continues to be used as a superabrasive for many industrial applications. Despite being expensive, diamond has proven to be more cost-effective in many industrial processes even compared to cubic boron nitride or borazon (cBN) and silicon nitride (Si3N4) because it cuts faster and lasts longer than alternative superabrasive materials. More recently, CVD of thin diamond films has opened the way to a range of new applications. The space shuttle uses diamond-coated parts to produce wear-resistant, lubricant-free bearings, and similar technology is expected to be used before long in terrestrial vehicles. But the use of diamond as both an abrasive and a wear-resistant coating is limited by the solubility of carbon in ferrite. In 2004 according to 12 D.W. Olson from the USGS, circa 800 millions carats (i.e., 160 tonnes) were used for superabrasives and the United States remained the world’s leading market for the production of industrial diamond. 12 Minerals, Ores and Gemstones 12

1 carat = 200 mg (E)

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12.5.1.6 Diamond Prices According to the U.S. Geological Survey, natural industrial diamond normally has a more limited range of values. Its price varies from about 0.30 US$/carat for bort-size material to about 7–10 US$/carat for most stones, with some larger stones of gem quality selling for up to 200 US$/carat. Synthetic industrial diamond has a much larger price range than natural diamond. Prices of synthetic diamond vary according to particle strength, size, shape, crystallinity, and the absence or presence of metal coatings. In general, synthetic diamond prices for grinding and polishing range from as low as $0.40–$1.50 per carat. Strong and blocky material for sawing and drilling sells for $1.50–$3.50 per carat. Large synthetic crystals with excellent structure for specific applications sell for many hundreds of dollars per carat. There are more than 14,000 categories used to assess rough diamond and more than 100,000 different combinations of carat, clarity, color, and cut values used to assess polished diamond.

12.5.1.7 Treatments Color in diamonds arises from trace amounts of nitrogen (yellow) and/or boron (blue) that substitute for carbon and act as either electron donors or acceptors with electron energy transition levels that are within the visible spectrum. Color can be induced or changed by irradiation and/or heating. Irradiation by high energy particles (e.g., electrons, neutrons, protons, gamma rays, alpha particles) is known to change pale yellow stones to fancy blue, green, brown, orange, very dark green, and yellow. Heating following irradiation can further modify the color. Treatment by all but gamma rays and neutrons colors only the outer few microns of a diamond’s surface, producing an umbrella-like color zonation near the culet or an unevenness of color elsewhere. Heating changes the absorption spectra and can usually be detected with a spectroscope. Color change induced by bombardment of neutrons (e.g., nuclear reactor) is most difficult to detect; most stones turn green but show no color zoning or characteristic change in their absorption spectra. Coatings or backings have also been used to improve color. Coating applied to the pavilion girdle area can be used to mask a pale yellow color or give a blue or pink tint. Well applied coatings can be difficult to detect but sometimes give a grayish tint to the stone’s color.

12.5.1.8 Diamond Shaping and Valuation Because of its extreme hardness, diamond cutting is a highly specialized process. Preforming usually involves cutting but not cleaving with a diamond-impregnated saw, followed by further rough-shaping by a process known as bruting. Bruting is done by affixing the diamond to a dop stick, and shaping the stone with a diamond-tipped cutting tool called the brute. The principal cutting centers for diamond are in New York, Antwerp, and Tel Aviv. Most cutting of very small diamonds called melee is done in India. Smaller cutting centers exist in Amsterdam, London, Johannesburg, San Juan, and Puerto Rico. Unlike colored stones, the wide availability of diamonds over a large range of quality has led to highly standardized grading practices. One of the most widely used rating schemes is the grading system introduced by the GEMOLOGICAL INSTITUTE OF AMERICA (GIA) known as the 4 C’s standing for Color, Cut proportions, Clarity, and Caratage. This system yields highly reproducible results, is easily understood, and requires little subjectivity. Color. The GIA color grading scale is used to grade “colorless” diamonds, those showing varying shades of yellow, gray or brown tint. The most desirable are the truly colorless stones, which receive a grade of D. Color differences are extremely slight, so much so that the difference between a D and G-rated diamond is not discernable to the untrained eye. To grade color accurately requires comparisons with a set of pre-graded, “master stones”. The highest master stone is an E; any stone that falls on or above an E is a D. Without masters,

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a loose diamond can only be approximated within two grades. A mounted stone can only be approximated within three grades, with or without a master. Clarity. Inclusions, fractures, and incipient cleavage cracks all fall under the general heading of “flaws” that affect a diamond’s clarity. In grading, no distinction is made among them, except with respect to the extent each affects appearance. White inclusions are preferred to black, and those near the girdle are not of the consequence of flaws near the table or culet. The scale is characterized by a series of abbreviations: flawless (FL), internally flawless (IF), very, very slightly included (VVSI), etc. By most definitions, no flaws are visible to the naked eye until a grade of I1. Flaws in stones above this grade are visible only with a 10X loupe. Cut proportions. Although a wide variety of cuts have been used and continue to be used to facet diamond, by far the standard in this country is the Standard Brilliant Cut or American Cut. The cut proportions are extremely important to the value of a diamond. For standard brilliants, the table percentage, that is, the diameter of table vs. the diameter of girdle, should be 52–58%. The depth percentage, that is, the distance from table to culet vs. diameter of girdle should ideally be between 61% and 63% for standard round brilliants. The depth percentage parameter includes the girdle thickness, which is less than desirable inasmuch as all girdles are not a uniform percentage of the diameter.The girdle should be thick enough to prevent chipping during mounting and wear and no thicker, and should be of uniform thickness around the stone. A guideline for maximum girdle thickness is 3% of the stones diameter with a minimum of 0.05 mm. Caratage. The mass of diamond is expressed in carat (200 mg). In practice, the girdle diameters can be used to estimate weights. For instance, 0.5 carat diamonds have a girdle diameter close to 5 mm, 0.75 close to 6 mm, 1 carat close to 6.5 mm, 1.5 carats close to 7.5 mm, 2 carats close to 8 mm, and 2.5 carats close to 9 mm. A fairly precise formula that can be used to estimate the weight of a mounted standard round brilliant diamond with a girdle diameter, D, in mm and depth h, in mm is given belows: 2

Caratage of diamond = 0.0061·D · h Another useful formula for well proportioned stones when the depth is unknown is: 3

Caratage of diamond = 0.0037 · D

12.5.2 Beryl Gem Varieties Beryl [1302-52-9] named after the Greek, beryllos, a word designating various green gemstones with the chemical formula Be3Al2[Si6O18] and the relative molar mass of 537.50182 is a hexagonal cyclosilicate mineral that occurs exclusively in high-temperature hydrothermal veins, in granitic pegmatites, at the contact zone of intrusive mafic igneous rocks with aluminous schists, shales or limestones and in a lesser extent in vugs inside rhyolites. The departure from its theoretical chemical formula is common due to the isomorphous substi3+ tution of the hexacoordinated aluminum cations (Al ) in the crystal lattice by chromophoric metal cations. These substitutions impart a wide variety of vivid allochromatic colors, each of which is responsible of a particular beryl gem variety. For instance, substitution by chro3+ 3+ mium (Cr ) or rarely vanadium (V ) imparts a medium to dark green color and the result2+ ing gem beryl is called emerald. Ferrous iron (Fe ) imparts a blue color and the gem variety 3+ is called aquamarine while ferric iron (Fe ) imparts a golden yellow color and is named 2+ heliodor. Manganous cations (Mn ) furnishes a pink hue to morganite or a deep red color such as in red beryl, while goshenite is the colorless gem variety of beryl. The distinguishing physical properties of beryl are:

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(i) (ii) (iii) (iv)

a low mass density; low refractive indices; dichroism; and a low birefringence.

On the other hand, the main properties of the gem varieties of beryl are summarized in Table 12.20. Table 12.20. Major properties of the gem varieties of beryl Properties

Emerald

Crystal space lattice

Hexagonal a = 920.5 pm – 927.4 pm c = 918.7 pm – 924.9 pm

Symmetry

Space group: P6/mmc Atoms per formula unit: Z = 2 apfu

Habit

Well formed prismatic or tabullar hexagonal crystals, with pinacoidal {1010}, {0001}, or prism {1120} or pyramidal terminations

Color (dopant)

Dark green 3+ 3+ (Cr , V )

Blue 2+ (Fe )

Pink 2+ (Mn )

Golden yellow 3+ (Fe )

Colorless (none)

Pleochroism (weak)

Green to blue green

Blue to darker blue

Light red to light viole

Greenish yellow to yellow

none

Crystalline optics

Uniaxial (–) ε = 1.568 ω = 1.564

Uniaxial (–) ε = 1.576–1.593 ω = 1.569–1.586

Uniaxial (–) ε = 1.576 ω = 1.570

Uniaxial (–) ε = 1.567 ω = 1.590

Uniaxial (–) ε = 1.568 ω = 1.564

Birefringence (δ)

0.004

0.005–0.007

0.006

Dispersion

0.014

Fluorescence under none to weak UV light orange-red or green –3

Density (/kg.m )

2670–2780

Mohs hardness (HM)

7.5–8

Vickers hardness (HV/GPa)

11.7–14.2

Aquamarine

Morganite

Heliodore

Goshenite

0.004

very weak to none

2680–2700

2710–2900

2680–2700

2630–2970

12.5.2.1 Emerald Description. The emerald is a gem variety of beryl doped by either chromium or vanadium providing its green color. The velvety appearance and lime color of the best emeralds is unique among all natural gems. Nearly all emeralds contain tiny inclusions, with the best colored stones sometimes being the most included. The term jardin named after the French word for garden, is used for the mossy-appearing, densely included gemstones. Emeralds with high clarity and color are extremely rare in sizes above 2–3 ct. Unlike other beryl gem varieties, emeralds are nearly always mined in situ except in Brazil where placer deposits exist. Actually, due to the abundance of inclusions, which decreases their toughness, most crystals are too fragile to survive the mechanical stresses encountered during fluvial transport.

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Natural occurrence and deposits. About 60% of the world production of emerald comes from Colombia. The production is mainly located in two mining districts, i.e., northeast and east of Bogota, called Muzo and Chivor respectivelly. These two gem deposits were originally mined by Aztecs and then rediscovered by Spanish in 1537 (Chivor) and 1559 (Muzo). The Muzo mine was once the most prolific emerald mine in the world. At Muzo, emerald beryl occurs in calcite veins through black shale. At Chivor, the emerald beryl occurs in quartzalbite-apatite veins that invade a gray calcareous shale. Both Muzo and Chivor emeralds are characterized by three-phase inclusions, that is, entrapped fluid and gas bubbles with tiny crystals of halite (NaCl). Muzo emeralds often contain inclusions of calcite and yellow-brown needles of the mineral parisite. Emeralds are also mined in Brazil from alluvial placer deposits where the major producing areas are: the Salininha and Carnaibu Districts (State of Bahia); the Santa Terezinha District (State of Goias); the Nova Era and Itabira Districts (State of Minas Gerias). The majority of Brazilian gemstones contain vanadium as chromophore and are typically lighter-toned and much yellower compared to other sources. In Africa emeralds come from two major locations: in the Sandawana Valley (Zimbabwe) the emerald occurs in schists crossed by pegmatites veins and quartz stockwerks. In the Miku deposit near Kitwe (Zambia) that was once a major producer, the emerald also occurred in schists adjacent to pegmatites. Others minor production worldwide is also reported in the Ural Mountains (Russia), India, Tanzania, Australia, Pakistan (Swat Valley), Afghanistan (Panjshir Valley), in the United States in North Carolina near Hiddenite, South Africa, Austria, and Madagascar. Shaping and treatment. Usually the step-cuts called the emerald cut are used. Heavily flawed stones are sometimes cut en cabochon. Some emerals are oiled to improve their clarity. Canada balsam and cedarwood oil fill cracks and cavities, and due to the refractive index close to that of the gemstone, cracks vanished. Synthetic emeralds. Emeralds can be synthesized either by flux-growth or hydrothermal processes. The flux-growth techniques is used by Chatham Research Laboratories in San Francisco, United States and Les Établissements Céramiques Pierre Gilson, while the hydrothermal synthesis once utilized by Union Carbide (1965–1970) is currently employed by Biron and Vacuum Ventures. Synthetic emeralds are easily distinguished from naturals by their lower indices of refraction and densities, and by their distinct inclusions.

12.5.2.2 Aquamarine Description. Aquamarine is a greenish-blue to bluish-green gem variety of beryl. The color is imparted by ferrous cations. It is important to note that most raw aquamarines especially those mined in Brazil exhibit a strong yellow component and thus they appear green when viewed. Therefore, most commercial aquamarine with a deep blue color have followed a heat treatment between 250°C and 720°C in order to deepen the color and to drive off green overtones. Aquamarine can be distinguished from blue topaz by its hardness, the indices of refraction and its density. Aquamarine occurs exclusively in granitic pegmatites, or pebbles or cobbles in stream gravels. Single giant crystals weighing up to 110 kg are also known. Natural occurrence and deposits. Brazil is the most important source of aquamarine. The most famous gem deposits are all located in the pegmatite region of the state of Minas Gerais. Four districts have produced major amount of aquamarine: (i) (ii) (iii) (iv)

Teofilo Otoni-Marambaia; Jequitinhonha river valley; Araçuai river-Capelinha-Malacacheta; and 13 Governador Valadares. 12

13

Proctor, K. Gem pegmatites of Minas Gerais, Brazil: eploration, Occurrence, and aquamarine deposits. Gems & Gemology, Summer 1994, pp. 78–100.

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The Brazilian aquamarine is found either in primary or secondary gem deposits. In primary deposits, aquamarine is found in gem pockets hosted by granitic pegmatites. In secondary deposits, aquamarine along with other gem varieties of beryl, topaz, and tourmaline is found in the weathered material coming from the parent pegmatite and they can be subdivided into: (i) eluvial; (ii) colluvial; and (iii) alluvial type gem deposits. Eluvial deposits usually lie on hilltops close to parent granitic pegmatite dykes. The aquamarine crystals are found in in situ moderatly decomposed and eroded host rock. Colluvial deposits are found usually on the hillsides and are covered by a thick lateritic soil, aquamarine is found in the clay-like softened material produced by the intense meteoric weathering of the host rock common under the tropical climate. Finally, alluvial type deposits are found in the valleys far away from the original host pegmatite, and aquamarine along with other hard gem minerals are found as rounded stones into the gravel. Aquamarines are also found in Africa at Kleine Spitzkopje (Namibia), in Nigeria, Zambia, Zimbabwe, in Madagascar and in a lesser extent in Afghanistan, Northern Ireland, Russia, Sri Lanka, Pakistan, India, and United States.

12.5.2.3 Morganite Description. Morganite is a pink to peach-colored gem variety of beryl, named after J.P. Morgan, the famous financier and banker. The color is due to the doping by manganous cations. A deep red gem variety of beryl occurring at the Ruby Violet Mine in the Wah Wah mountains Utah, is not called morganite, but red beryl. Heat treatment of some specimens renders them colorless, in others heating may be used to drive off a yellow overtone produced by a yellow color center to yield a nice pink. Natural occurrence and deposits. Morganite occurs in granitic pegmatites along with tourmaline. The major locations are in the United States at Pala and Mesa Grande districts in San Diego County, California; in Brazil in the State of Minas Gerias, Brazil at Urucum and Bananal Mines and finally in Madagascar in the Mount Bity region in Madagascar.

12.5.2.4 Heliodor Heliodor is the golden yellow gem variety of beryl due to the isomorphous substitution of aluminum by ferric cations. It is also known as yellow beryl if the golden tint lacking. Good colored material is relatively rare. As other gem varieties of beryl it is found in granitic pegmatites in Brazil; in the Ural Mountains (Russia), and Namibia.

12.5.2.5 Goshenite Goshenite is the colorless gem variety of beryl. It occurs in the Ural Mountains (Russia), in Brazil and Madagascar.

12.5.3 Corundum Gem Varieties Corundum [1344-28-1] with the chemical formula Al2O3 and the relative molar mass of 101.96127 is named after the Hindi, kurund, or the Tamil, kurundam. Corundum with a trigonal space lattice is the second hardest mineral on the Mohs scale just after diamond. The well-known gem varieties are the blood-red ruby while all other colors are named sapphire (e.g., pink sapphire, yellow sapphire) despite it is commonly used to denote the blue

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gem variety. The name star sapphire denotes asteriated blue corundum. Paradoxically, star stones that are not blue are sometimes referred to as star ruby, even those that are not red. Padparadscha, meaning the lotus flower is an ill-defined name for rare pinkish orange sapphire. Because pure corundum is a colorless crystal, the colors of the gem varieties are due to 3+ 3+ the presence of chromophore. For instance, chromium (Cr ) and ferric iron (Fe ) impart 2+ the blood red color of ruby, ferrous iron (Fe ) is responsibles of the color of blue sapphire, 3+ 4+ ferric iron (Fe ) and titanium (Ti ) impart the color of the yellow sapphire. Padparadscha is colored by trace impurities of chromium and iron, with or without a yellow color center. 2+ Some green sapphire contains trace amounts of nickel (Ni ) as chromophore. Due to its hardness and toughness, gem varieties of corundum are mined almost exclusively from gem gravel deposits. These deposits are derived from the weathering of high temperature metamorphic (e.g., marble, gneiss) or volcanic igneous rocks (e.g., basalts). Historically, the most famous and prolific production has been mined from Myanmar, Thailand, India and Sri Lanka. Today important gem deposits are found in Australia and the East African countries of Tanzania and Kenya. Synthetic corundum was the first gem mineral to be synthesized in in 1902 at the laboratory scale by a process known today as flame fusion or Verneuil’s process. A somewhat more difficult process, flux growth, is also used to synthesize gem corundum. Synthetic rubies and sapphires are presently manufactured in enormous quantities for both industrial and gem application. Table 12.21. Major properties of the gem varieties of corundum Properties

Corundum

Crystal space lattice

Rhombohedral (Trigonal) a = 513.29 pm and 55°17'

Symmetry

Strukturbericht: D51 Pearson’s symbol: hR10 Space Group: R3c

Habit

well-formed hexagonal prisms with or without rhombohedral terminations. Sapphire often as elongate prisms; ruby usually stubby, flat prisms

Color (dopant)

Colorless

Pleochroism (weak) Crystalline optics

Uniaxial (–) ε = 1.765–1.776 ω = 1.757–1.767

Birefringence (δ)

0.008–0.009

Dispersion

0.018

Fluorescence under UV light

Moderate light red to orange

–3

Density (/kg.m )

3980–4020

Mohs hardness (HM)

9

Vickers hardness (HV/GPa)

19.6

Sapphire

Ruby

Violet-blue to lighter greenish-blue 2+ 3+ (Fe , Fe )

Intense blood-red to lighter orange-red 3+ (Cr )

Indogo blue to light blue

Deep purple to light yellow

None to red or orange in LWUV

Strong red under LWUV

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12.5.3.1 Ruby Description. Ruby is the red gem variety of corundum, the deep red color is imparted by 3+ 3+ chromium (Cr ) and sometimes also by ferric iron (Fe ). Burmese gemstones of the highest quality are the most expensive of all gemstones. Color is of principal importance in pricing for rubies. The ill-defined adjective pigeon blood has been used to describe the intense, medium, pure to slightly purplish red color of Burmese rubies. These true Burmese rubies show a red, warm glow in direct sunlight, a consequence of strong ultraviolet fluorescence peculiar to these stones that are colored only by chromium without any trace of iron. Thai ruby is commonly darker, with a more brownish- or purplish-red color imparted by traces of iron. Ceylon ruby was once a common term for light red to pinkish ruby that in most cases could more properly be referred to as pink sapphire. It should be emphasized that these names today have very little to no meaning with regard to a ruby’s origin. Natural occurrence and deposits. These deposits of ruby are derived from the weathering of high temperature metamorphic (e.g., marble) or volcanic igneous rocks. Historically, the ruby was mined in several geographical area worldwide mainly concentrated in the far-east. Since at least 1597 A.D. ruby was mined from the Mogok Stone tract in Myanmar (formerly Burma). This gem deposit yield the worlds finest rubies. The rubies originated from a marble resulting of contact metamorphism of impure limestones. The rubies were mined from gravel deposits derived from marble. Thailand (formerly the Kingdom of Siam) which represented once about 70% of world production was also an important location. The rubies were found in lateritic soils above a Plio-Pliestocene basalt, or in gem gravels derived from basalt. Finally, in Sri Lanka (formerly Ceylon) rubies were mined from gem gravels in the Ratnapura district near Colombo, and Elahera district. Ruby is also mined in Cambodia at the Pailin Gem Fields. Others locations include Vietnam, Kenya, Tanzania, India, Madagascar, Pakistan, Afghanistan, and Nepal. Shaping and treatment. Step or brilliant cut; heavily flawed or star stones are cut en cabochon. Heating is used to remove dark brownish or purplish overtones and lighten the color. CO2 inclusions will not survive high temperature treatment; their presence is good indication of no heat treatment. Discoid fracture patterns around natural mineral inclusions are also a sign of heating. Asterism can be induced in stones containing sufficient titanium by heating for an extended period at about 1300°C to form needle-like crystals of rutile. A surface diffusion process is also used to enhance color in weakly colored material.

12.5.3.2 Sapphire Description. Sapphire occurs in a wide range of colors such as blue, pink, padparadscha 2+ 3+ orange, yellow, green, purple, black. Color is due to trace impurities of Fe , Fe , Ti, and yellow color centers. The most expensive color is an intense cornflower blue; these are sometimes referred to as “Kashmir” sapphires having a highly saturated, slightly milky, violet blue color. Padparadscha is next in value, followed by pink, then orange, purple and yellow, respectively. Nowadays 400–500 tonnes of synthetic sapphire are produced by the Verneuil process each year. Natural occurrence and deposits. Sapphire is exclusively mined from gem gravels or clay resulting of the weathering of basalt. Major deposits are similar to those for mining ruby, that is, Myanmar, Thailand, Sri Lanka, Australia and East Africa (i.e., Tanzania, Kenya, Nigeria, with lesser amounts from Malawi and Burimundi). Historically, sapphire have been mined from pegmatite veins in marble in the Jamu-Kashmir region (India) since 1881. Thermal treatment. Thermally treated sapphires are widespread while gamma irradiated stones are less common. Usually, pale yellow or colorless sapphires are heat treated in air in the temperature range 1500–1900°C to yield a dark yellow, golden, golden-brown, orange, or 2+ 3+ reddish-brown color due to the oxidation of Fe into to Fe . Pink sapphire containing traces of chromium can be heat treated to yield a padparadscha orange-pink color, while dark blue

Gemstones

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stones can be clarified by heating them briefly at 1200°C in air. On the other hand, pale blue sapphire containing embeded rutile needles can be heat treated in air at 1200°C to remove blue; while heating them up to 1900°C will restore the blue color and dissolve rutile forming a solid solution of tialite (Al2TiO5). Heating irradiated sapphires will restore their original color. Another treatment, to darken the color of pale blue sapphire consists to coat a thin 4+ 3+ layer of TiO2 and Fe2O3 powders and heat up to 1950°C. At that temperatures, Ti and Fe cations diffuse fastly in the outer layer of the sapphire, yielding a very thin, skin-like layer of blue color.

12.5.4 Synthetic Gemstones Almost all gems can be synthesized, either from melts, from molten salts, ceramic and other techniques, and at high temperature and pressure. These techniques are briefly described here.

12.5.4.1 Synthesis from Melts The Verneuil melt growth technique (flame fusion). This containerless process was first developed on a commercial scale in 1902 in Paris (France) by Auguste Victor Louis Verneuil especially for producing synthetic ruby, sapphire and spinel required at that time for the large scale fabrication of jewel bearings. The flame-fusion technique now called the Verneuil method consists to melt powdered high purity aluminum oxide (alumina) into the intense flame (2200°C) of an inverted vertical oxygen-hydrogen torch. The alumina powder is contained into a perforated basket. Periodically a small hammer hits the basket leading to the regular delivery of a given amount of alumina that passes through the coaxial tubes of the torch and melts into the high temperature oxygen-hydrogen flame. The molten dropplets fall onto a fire-clay support and crystallize in a cone-shaped crystal called the boule that is lowered as it grows. After the boule reaches several hundred carats, the torch is shut down and the boule allowed to cool rapidly and it is then removed still hot. The final color is controlled by careful addition of chemical additives (e.g., Cr2O3). Gems produced by this technique is rather easy to distinguish from natural gemstones by the presence of curved growth striations and spherical gas bubbles or by the Plato method, in which repeated twinning lines appear when the material is immersed in high refractive index liquid and examined under magnification between crossed polars. The Czochralski (CZ) melt growth technique (crystal pulling). The Czochralski pulledgrowth method first devised in 1917 by J. Czochralski is often used to make rod-shaped single crystals especially ruby, sapphire, spinel, yttrium-aluminum-garnet (YAG), gadolinium-gallium-garnet (GGG), and alexandrite. In the Czochralski method, inorganic powders and doping agents are first melted in a large platinum, iridium, graphite, or advanced ceramic crucible depending on the corrosiveness of the molten material. Afterwards, a seed crystal is attached to the tip of a rotating rod, the rod is then lowered into the crucible until the seed just touches the surface of the melt, and then the rod is slowly withdrawn. The crystal grows as the seed pulls materials from the melt, and the material cools and solidifies. Due to the interfacial tension between the melt and the seed crystal, the growing crystal remains in contact with the molten material and it continues to grow until the melt is depleted. Typically, the seed is pulled from the melt at a rate of 1–100 millimeters per hour. Crystals grown using this method can be very large, more than 50 millimeters in diameter and one meter in length, and of very high purity (see chapter on processing single crystals for semiconductors). The Bridgman–Stockbarge melt growth technique. This method is named after P.W. Bridgman (United States) and D.C. Stockbarge (Germany) with the collaboration of three

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Russian scientists, J. Obreimov, G. Tammann, and L. Shubnikov, who discovered and perfected the process between 1924 and 1936. Currently, the method is used primarily for growing inorganic halides, sulfides, and various metallic oxide crystals, one of the metallic oxides being aluminum oxide or sapphire. The Bridgman–Stockbarge process uses a specially shaped crucible, which is a cylindrical tube open at one end and capped at the other by a small, pointed cone. The crucible is filled with the powdered mineral to grow and is lowered slowly through a heat resisting furnace. The small, pointed end of the cone cools first because it is the first part of the crucible that moves from the hottest part of the furnace into cooler regions and it is the first part to emerge from the furnace. As the crucible cools, the molten materials solidify, hopefully in a single crystal, in the point of the crucible. The crystal then acts as a seed around which the remainder of the molten material solidifies until the entire melt has frozen, filling the container with a single crystal. This process is simple, and crystals of various sizes can be grown. The crystals are typically about 50 millimeters in diameter and 15 millimeters in length, but large ones exceeding 890 millimeters in diameter and weighing more than 1000 kilograms have been grown. The crystals exhibit the same shape as the crucible. The floating zone (FZ) melt growth technique. This technique was developed in the 1950s for the production of high-purity silicon, it is also used to grow gems from a sintered rod of fine powder. The rod is held vertically at the top and rotated clockwise while a seed crystal is held vertically at the bottom and rotated counterclockwise. Both are partially melted at the molten interface either by induction heating or by infrared heating provided by glass mirrors combined to a high pressure xenon lamp. At the next step, this molten zone is gradually upwards rotating with the seed crystal until the entire polycrystalline rod has been converted to single crystal. High purity rutile single crystals are commonly produced by this technique. Skull melting melt growth technique. This technique ressembles that used to melt titanium and other refractory metals, and it is only used for preparing synthetic gems that exhibit exceptionally high melting points or that are highly chemically reactive (e.g., cubic zirconia). The set-up consists to a water-cooled jacketed copper mold filled with the powdered material and heated by induction until the powders melt. Due to the intense heat transfer provided by the water cooling, the powdered materials next to the walls forms a frozen layer or skull. Therefore, the highly reactive or high-temperature melt is contained within itself. When the heat source is removed and the system is allowed to cool, crystals form by nucleation and grow until the entire melt solidifies. Crystals grown using this system vary in size, depending on the number of nucleations. In growing cubic zirconia, a single skull yields about 1 kg of material per cycle.

12.5.4.2 Synthesis from Solutions In these techniques the crystals precipitate from a saturated or supersaturated solution. Hydrothermal growth technique. The principle is to increase the solubility of an inorganic compound using the same supercritical conditions encountered during the formation of gem-bearing pegmatites. The set-up consists of a pressure vessel called an autoclave or bomb capable to withstand both high pressure and temperature. At the begining water and feed material along with seed crystals are introduced into the autoclave. The seed is suspened to a fixture in the upper part of the autoclave while water and the crystal feed remain at the bottom. In the hotter regions of the autoclave the feed material dissolves while the crystallization occurs in cooler areas., that is on seed crystals, located in the cooler portion, forming synthetic crystals. This technique is especially suited for synthesis of high purity quartz for piezoelectric components, and in a lesser extent emerald, and some unusual beryls. In the particular case of quartz, the feed material is known as lascas and it consists of natural quartz crystals of gem quality found in Brazil. The process usually takes 30–60 days

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for the crystals to reach the desired size. The process can produce rock crystal, amethyst, and citrine, or in some cases blue or green quartz with no natural counterpart. Flux growth technique. This technique consists of dissolving the feed mineral having a high melting point into an appropriate molten salt called flux due to its ability to dissolved oxides. The contents are melted until a homogeneous melt is obtained and then the molten material is allowed to cool very slowly. Upon cooling the supersaturation of the melt occurs and the crystals of the high-melting compound crystallizes while the flux is still molten. Sometimes seed crystals are used to initiate the nucleation. Flux growth is especially useful for synthesis of refractory compounds having a high melting point. Common fluxing agents are lithium molybdate (Li2Mn2O7) or lead fluoride (PbF2) mixed with the mineral powder into a crucible (e.g., Pt, Ir, Au-lined crucible). Common gemstones produce by this technique are ruby, sapphire, emerald, and alexandrite. Sol–gel growth techniques. The most common example is the production of synthetic opal. The first step consists to produce a suspension of monodisperse silica nanospheres in ethanol obtained by the direct hydrolysis of tetraethyl ester of orthosilicic acid, Si(OC2H5)4 with ethanol using ammonia as a catalyst according to the following reaction: Si(OC2H5)4 + 4H2O —> Si(OH)4 + 4C2H5OH Simultaneously, the polymerization of orthosilicic acid occurs by the reaction: nSi(OH)4 —> (SiO2)n + 2nH2O By adding further amounts of reactant, the particles of silica grow up to the diameter desired-that is to about 300 nm size. Secondly, the raw opal precursor is precipitated either by spontaneous sedimentation or by centrifugation. Finally, the opal precursor is then dried in order to remove liquid from its pores. Afterwards, the dried opal precursor is sintered by thermal treatment at 400–800°C in a furnace. For the production of synthetic opal of gem quality, it is then necessary to complete the process by filling pores in the opal substance with a silica gel.

12.5.4.3 Diamond Synthesis High pressure high temperature (HPHT). The first commercial synthesis of diamonds occured in 1955 by the GE Corporation using high P, T synthesis techniques. Today, 100 million carats of industrial quality diamond are produced by synthesis. Flawless gem-quality crystals are produced in pressure chambers. Today’s method uses C source (crystals) and a seed crystal and Fe catalyst. These are kept in a pressure vessel (high temperature and pressure) for some time. Synthetic diamonds have been produced industrially since the first commercialization in 1955 of a proprietary High Pressure and High Temperature Process (HPHTP) from General Electric (GE). Today GE Superabrasives, Worthington, OH is one of the world’s largest producers of industrial diamond with in a lesser extent Mypodiamond, Inc. located in Smithfield, PA. Since 2003 by Chemical Vapor Deposition (CVD) by Apollo Diamond Inc. Chemical vapor deposition (CVD). The fundamental problem of diamond synthesis is the allotropic nature of carbon. Under ordinary conditions graphite, not diamond, is the thermodynamically stable crystalline phase of carbon. Hence, the main requirement of diamond CVD is to deposit carbon and simultaneously suppress the formation of graphitic sp2-bonds. This can be realized by establishing high concentrations of non-diamond carbon etchants such as atomic hydrogen. Usually, those conditions are achieved by admixing large amounts of hydrogen to the process gas and by activating the gas either thermally or by a plasma. The common CVD deposition conditions are: 1 vol.% methane in hydrogen as source gas, an operating temperature 700–1000°C deposition temperature and gas pressures in the range 30–300 torr.

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12.6 IMA Acronyms of Rock-forming Minerals Table 12.22. IMA acronyms of rock-forming minerals Acronym

Mineral name

Acronym

Mineral name

Acronym

Mineral name

Ab

Albite

Brk

Brookite

Dol

Dolomite

Act

Actinolite

Brl

Beryl

Drv

Dravite

Adr

Andradite

Brt

Barite

Dsp

Diaspore

Ae

Aegirine

Bry

Beryllonite

Dum

Dumortierite

Ak

Akermanite

Bst

Bustamite

Eck

Eckermannite

Alm

Almandine

Bt

Biotite*

Ed

Edenite

Aln

Allanite

Cal

Calcite

Elb

Elbaite

Amp

Amphibole*

Cbz

Chabazite

En

Enstatite

An

Anorthite

Cc

Chalcocite

Ep

Epidote

And

Andalusite

Ccl

Chrysocolla

Fa

Fayalite

Anh

Anhydrite

Ccn

Cancrinite

Fac

Ferro-actinolite

Ank

Ankerite

Ccp

Chalcopyrite

Fcl

Ferrocolumbite

Anl

Analcime

Chl

Chlorite*

Fed

Ferro-edenite

Ann

Annite

Chn

Chondrodite

Fl

Fluorite

Ant

Anatase

Chr

Chromite

Fo

Forsterite

Ap

Apatite

Chu

Clinohumite

Fs

Ferrosilite

Apo

Apophyllite

Cld

Chloritoid

Ftn

Ferrotantalite

Apy

Arsenopyrite

Cls

Celestite

Fts

Ferrotschermakite

Arf

Arfvedsonite

Coe

Coesite

Gbs

Gibbsite

Arg

Aragonite

Cpx

Clinopyroxene*

Gdd

Grandidierite

Asp

Aspidolite

Crd

Cordierite

Ged

Gedrite

Atg

Antigorite

Crn

Corundum

Gft

Graftonite

Ath

Anthophyllite

Crs

Cristobalite

Gh

Gehlenite

Aug

Augite

Cst

Cassiterite

Gln

Glaucophane

Bet

Betatife

Ctl

Chrysotile

Glt

Glauconite

Beu

Beusite

Cum

Cummingtonite

Gn

Galena

Bhm

Boehmite

Cv

Covellite

Gp

Gypsum

Bn

Bornite

Czo

Clinozoisite

Gr

Graphite

Bor

Boralsilite

Dg

Digenite

Gre

Greenalite

Brc

Brucite

Di

Diopside

Grs

Grossular

Grt

Garnet*

Lop

Loparite

Opx

Orthopyroxene*

Gru

Grunerite

Lpd

Lepidolite*

Or

Orthoclase

Gt

Goethite

Ltp

Latrappite

Osm

Osumilite

Ham

Hambergite

Lue

Lueshite

Pct

Pectolite

Hbl

Hornblende

Lws

Lawsonite

Per

Periclase

Hc

Hercynite

Lz

Lizardite

Pg

Paragonite

IMA Acronyms of Rock-forming Minerals

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Table 12.22. (continued) Acronym

Mineral name

Acronym

Mineral name

Acronym

Mineral name

Hd

Hedenbergite

Mc

Microcline

Pgt

Pigeonite

Hem

Hematite

Mcl

Manganocolumbite

Phk

Phenakite

Hl

Halite

Mel

Melilite

Phl

Phlogopite

Hlv

Helvite

Mgh

Maghemite

Pl

Plagioclase*

Hrd

Herderite

Mgs

Magnesite

Pmc

Plumbomicrolite

Hs

Hastingsite

Mgt

Magnetite

Pmp

Pumpellyite

Hu

Humite

Mic

Microlite

Pn

Pentlandite

Hul

Heulandite

Min

Minnesotaite

Po

Pyrrhotite

Hyn

Haüyne

Mkt

Magnesiokatophorite

Pol

Pollucite

Ill

Illite*

Mlb

Molybdenite

Prg

Pargasite

Ilm

Ilmenite

Mnt

Montmorillonite

Prh

Prehnite

Jd

Jadeite

Mnz

Monazite

Prl

Pyrophyllite

Jh

Johannsenite

Mrb

Magnesioriebeckite

Prm

Prismatine

Jsv

Johnsomervilleite

Mrg

Margarite

Prp

Pyrope

Kfs

Orthoclase*

Ms

Muscovite

Prv

Perovskite

Kin

Kaolinite

Mtc

Monticellite

Py

Pyrite

Kis

Kalsilite

Mtn

Manganotantalite

Qtz

Quartz

Km

Kornerupine

Mul

Mullite

Rbk

Riebeckite

Krs

Kaersutite

Ne

Nepheline

Rdn

Rhodonite

Ktp

Katophorite

Nrb

Norbergite

Rds

Rhodochrosite

Ky

Kyanite

Nsn

Nosean

Rt

Rutile

Lct

Leucite

Ntr

Natrolite

Sa

Sanidine

Lmt

Laumontite

Ol

Olivine*

Sar

Sarcopside

Lol

Löllingite

Omp

Omphacite

Scp

Scapolite

Sd

Siderite

Sti

Stishovite

Ttn

Titanite

Sdl

Sodalite

Stl

Stellerite

Tur

Tourmaline

Sil

Sillimanite

Stm

Stibiomicrolite

Umc

Uranmicrolite

Skn

Sekaninaite

Stp

Stilpnomelane

Usp

Ulvöspinel

Sp

Sphalerite

Str

Strontianite

Ves

Vesuvianite

Spd

Spodumene

Tap

Tapiolite

Vrm

Vermiculite

Spl

Spinel

Tep

Tephroite

Vtm

Viitaniemiite

Spr

Sapphirine

Thm

Thomsonite

Wai

Wairakite

Sps

Spessartine

Toz

Topaz

Wo

Wollastonite

Srl

Schorl

Tph

Triphylite

Wrd

Werdingite

Srp

Serpentine*

Tr

Tremolite

Wth

Witherite

St

Staurolite

Trd

Tridymite

Wus

Wüstite

Stb

Stibiobetafite

Tro

Troilite

Zo

Zoisite

Stb

Stilbite

Ts

Tschermakite

Zrn

Zircon

Notes: (*) denotes a mineral series.

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12.7 Mineral and Gemstone Properties Table In this section a table containing the description of the most common minerals and gemstones (ca. 400 species among the 3700 mineral species known today) is presented with their main physical, chemical and mineralogical properties. • Column 1 presents the mineral name accoring to the International Mineralogical Associa-

•

•

•

• • •

tion (IMA), moreover, its Chemical Abstract Registered Number in brackets [CAS RN], the synonym(s) (syn.), its etymology and the Powder Diffraction File (PDF) and in the Inorganic Crystal Structure Datafile (ICSD) are also indicated when available, Column 2 presents: (1) the theoretical chemical formula, (2) the relative atomic or mo12 lecular mass ( C=12.000) of minerals based on the previous theoretical formula using the last value of atomic masses adopted by the IUPAC in 2001, (3) the theoretical chemical composition expressed in mass percentage (wt.%), (4) the common traces impurities, (5) the coordinence number of major cations, and finally (6) the Strunz’s mineralogical class, Column 3 present the main crystallographic properties: (1) the crystal system, (2) the –12 space lattice parameters expressed in picometers (1 pm = 10 m) and plane angle in degrees (°), (3) the strukturbericht designation, (4) the Pearson’s notation, (5) the number of atoms or molecules per unit space lattice (Z). Finally, (6) the space and (7) point group according to the international Hermann–Mauguin notation and the crystal space lattice structure type are also listed when known, Column 4 lists the mineral optical properties either in transmisted light with refractive index for isotropic (nD), uniaxial (ε, ω), or biaxial (α, β, γ, 2V), with the birefringence (δ), at 589 nm or in reflected light the reflective index (R) at 650 nm, 2 Column 5 lists the Mohs hardness and Vickers hardness (kgf /mm ) in brackets when available, –3 Column 6 lists the density or range of density in kg.m (X-ray density or calculated in brackets), Column 7 details the common habit, the color, the diaphaneity, the luster, the luminescence, the streak, the cleavage planes, the fracture, the tenacity, the twinning planes, the chemical reactivity, the deposits and other miscellaneous chemical and physical properties of the mineral.

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Ag2S M = 247.8024 87.06 wt.% Ag 12.94 wt.% S Coordinence Ag(4) (Sulfides and sulfosalts)

Ca2Mg3Fe2Si8O22(OH)2 M = 875.45 9.16 wt.% Ca 8.33 wt.% Mg 12.76 wt.% Fe 27.66 wt.% Si 0.23 wt.% H 43.86 wt.% O Traces Mn and Al. (Inosilicates, double-width unbranched chains and band)

NaFe[Si2O6] M = 231.00416 9.95 wt.% Na 24.18 wt.% Fe 24.32 wt.% Si 41.56 wt.% O (Inosilicates, double-width unbranched chains and band)

SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O Coordinence Si(4) (Oxides, and hydroxides)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Acanthite [21548-73-2] (syn., silver glance, argentite) [Named from the Greek, akanta, arrow, and after the Latin, argentum, silver] (ICSD 30445 and PDF 14-72)

Actinolite (syn., byssolite, nephrite, smaragdite: emerald green, abestos) [Named from the Greek, aktinos, meaning, ray, and lithos meaning stone in reference to its fibrous nature that forms bundles of radiating needles] (ICSD 24900 and PDF 41-1366)

Aegirine (syn., acmite) [Named after the Teutonic god of the sea. Acmite is from the Greek, point, in allusion to the pointed crystals] (ICSD 9671 and PDF 34-185)

Agate (syn., chalcedony) [Named after the River Achates, now Drillo in Sicily, where it was originally found]

Amorphous

Monoclinic a = 965.8 pm b = 879.5 pm c = 529.4 pm 107.42° (Z = 4) Diopside type

Monoclinic a = 984 pm b = 1810 pm c = 5278 pm β = 104.75° (Z = 2) P.G. 2/m S.G. C2/m Amphibole group Tremolite series

Isotropic

Biaxial (–) α = 1.72–1.778 β = 1.74–1.819 γ = 1.757–1.839 δ = 0.037–0.061 2V = 60–90° O.A.P. (010)

Biaxial (–) α = 1.613–1.628 β = 1.627–1.644 γ = 1.638–1.655 δ = 0.017–0.0270 2V = 84–73°

6

6–6.5

5–6

2–2.5 (HV 20–30)

Mohs hardness (/HM) (Vickers)

Biaxial (n.a.) R = 29.0%

Optical properties

2600

3550

3020– 3440 (3200)

7300

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 422.9 pm b = 692.8 pm c = 786.2 pm β = 99.58° C34, mC6 (Z = 4) S.G. P2/m AuTe2 type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Table 12.23. Properties of selected minerals by alphabetical order

Mixture of cryptocrystalline and amorphous silica consisting mainly of chalcedony.

Habit: acicular. Color: blackish green or reddish brown. Diaphaneity: transparent to opaque. Luster: vitreous, resinous. Streak: yellowish gray. Fracture: brittle. Occurrence: sodium-rich igneous nepheline syenites.

Habit: acicular, splintery and bladed crystals to fibrous mass (asbestos). Color: colorless to pale green, green with a blue hue. Luster: glassy. Diaphaneity: transparent to translucent. Cleavage: (110) perfect with angle of 124°. Fracture: subconchoidal to uneven. Streak: white. Others: not attacked by hot HCl, dielectric permittivity of 6.60 to 6.82. Not fluorescent under UV radiation. Magnetic susceptibility between 15 to 25 × 10–6 cgsemu. Occurrence: regional metamorphism in schists talc-bearing rocks and marbles, altered into chlorite.

Habit: acicular, octahedral, blocky, skeletal, arborescent. Color: black or lead gray. Streak: shining black. Diaphaneity: opaque. Luster: metallic. Fracture: subconchoidal, sectile. Cleavage: {001} poor, {110} poor. Argentite (cubic) is stable above 179°C while acanthite is stable below 179°C. melt at 825°C. Electric resistivity 1.5–2.0 × 105 μΩ.cm.

Other relevant mineralogical, physical, and chemical properties with occurrence

Mineral and Gemstone Properties Table 801

Minerals, Ores and Gemstones

12

KAl3(SO4)2(OH)6 M = 414.214334 9.44 wt.% K

Alunite [Named from French alun itself from Latin, alumen, meaning alum]

Trigonal (Rhombohedral) a = 697 pm

Cubic a = 1152.6 pm (Z = 8) P.G. 432 S.G. Ia3d Garnet group (Pyralspites series)

Triclinic a = 814.4 pm b = 1278.7 pm c = 716 pm α = 93.17° β = 115.85° γ = 87.65° (Z = 4) P.G. 1 S.G. P1

Fe3Al2(SiO4)3 M = 497.75338 10.84 wt.% Al 33.66 wt.% Fe 16.93 wt.% Si 38.57 wt.% O Coordinence Fe(8), Al(6), Si(4) (Nesosilicates)

Na[Si3AlO8] An0-Ab100 M = 263.02222 8.30 wt.% Na 0.76 wt.% Ca 10.77 wt.% Al 31.50 wt.% Si 48.66 wt.% O Coordinence Na(7), Si(4), Al(4) (Tectosilicates, framework)

Albite (syn., clevelandite) [from the Latin, alba, in allusion to the common white color] Albite high (ICSD 100496 and PDF 10-393) Albite low (ICSD 201649 and PDF 19-1184) Albite Ca (ICSD 34916 and PDF 41-1480)

Cubic a = 521 pm (Z = 4) P.G. 432 S.G. Fm3m Galena group

Almandine (syn., almandite) [Named after the locality, Alabanda, in Asia Minor] (ICSD 28030 and PDF 41-1423)

MnS M = 87.00 63.14 wt.% Mn 36.86 wt.% S May contains up to 22 wt.% Fe and 7 wt.% Mg (Sulfides and sulfosalts)

Alabandite [Named after its locality Alabanda] (ICSD 18007 and PDF 6-518)

Tetragonal a = 784.35 pm c = 501.0 pm (Z = 2) P.G. 42m S.G. P421m Melilite-Fresnoite group

Uniaxial (+) ε = 1.592 ω = 1.572

Isotropic nD = 1.830

Biaxial (–/+) α = 1.690–1.791 β = 1.700–1.815 γ = 1.706–1.828 2V = 40–123° O.A.P. (010)

Biaxial (+) α = 1.527–1.533 β = 1.531–1.536 γ = 1.538–1.542 δ = 0.009–0.010 2V = 76–82°

Isotropic R = 22.8%

Uniaxial (+) ε = 1.638 ω = 1.631 δ = 0.007

Optical properties

3.5–4

7–8

5–6.5

6–6.5

3.5–4 (HV 240– 251)

5–6

Mohs hardness (/HM) (Vickers)

Monoclinic a = 898 pm b = 575 pm c = 1023 pm 115° Epidote group

Ca2Mg[Si2O7] M = 272.63 29.40 wt.% Ca 8.92 wt.% Mg 20.60 wt.% S 41.08 wt.% O (Sorosilicates)

Akermanite [Named after the Swedish metallurgist Anders Richard Akerman (1837–1922)] (ICSD 39924 and PDF 35-592)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

2600– 2900

4318

3400– 4200

2620

4000– 4100 (4080)

2944

Density (ρ/kg.m–3) (calc.)

Allanite (Ca,Ce,Th)2(Al,Fe,Mn,Mg)(Al,Fe)2O. [Named after the Scottish mineralogist OH[Si2O7][SiO4] Thomas Allan (1777–1833)] (Neso-Sorosilicates) (ICSD 15190 and PDF 25-169)

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: rhombohedral. Color: white, gray. Streak: white, gray. Diaphaneity: transparent to translucent. Luster: vitreous. Fracture: conchoidal. Cleavage: good (001), poor (101).

Habit: massive, lamellar, granular. Color: reddish black or brownish red. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), resinous. Fracture: brittle, conchoidal. Parting: {110}. Chemical: soluble in HF. Occurrence: metamorphic and pegmatitic rocks.

Habit: massive granular grains. Color: brown to reddish brown and black. Luster: vitreous to greasy. Diaphaneity: translucent to opaque. Cleavage: (001) and (100). Fracture: conchoidal. Streak: grayish-brown. Occurrence: near-end members rare and only intermediate members are found in volcanic rocks but they are commonly found in metallurgical slags and synthetic products.

Habit: blocky, striated, granular. Color: white, gray, greenish gray, bluish green, or gray. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Cleavage: (001) perfect, (010) good. Twinning: Albite [010], Pericline [010]. Fracture: uneven. Streak: white. Occurrence: magmatic and pegmatitic rocks.

Habit: massive or granular. Color: Brownish black to black, tarnish upon exposure to moist air. Luster: submetallic. Diaphaneity: opaque. Cleavage: (110) perfect. Fracture: uneven. Streak: green. Occurrence: epithermal sulfide vein deposits.

Habit: anhedral equant grains. Color: colorless to green. Luster: vitreous to resinous. Diaphaneity: transparent to translucent. Cleavage: (001) and (110). Fracture: uneven. Streak: white. Others: it gelatinizes in conc. HCl. Occurrence: near-end members rare and only intermediate members are found in volcanic rocks but they are commonly found in metallurgical slags and synthetic products.

Other relevant mineralogical, physical, and chemical properties with occurrence

802 Minerals, Ores and Gemstones

19.54 wt.% Al 15.48 wt.% S 54.08 wt.% O 1.46 wt.% H Coordinence K(12), Cu(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

C10H16O M = 152.23692 10.59 wt.% H 78.90 wt.% C 10.51 wt.% O (Mineraloids)

(Li, Na)PO4(F,OH) Coordinence Li(6), Na(6), P(4) (Phosphates, arsenates, and vanadates)

NaAlSi2O6·H2O M = 220.15398 10.44 wt.% Na 12.26 wt.% Al 25.51 wt.% Si 0.92 wt.% H 50.87 wt.% O Coordinence Na(6), Si(4), Al(4) (Tectosilicates)

TiO2 M = 79.8788 59.94 wt.% Ti 40.06 wt.% O Traces Fe, Sn Coordinence Ti(6) (Oxides and hydroxides)

Al2O[SiO4] = Al2SiO5 M = 162.04558 33.30 wt.% Al 17.33 wt.% Si 49.37 wt.% O Traces of Fe, Mn Coordinence Al(5), Al(6), Si(4) (Nesosubsilicates)

(ICSD 12106 and PDF 13-136)

Amber (syn., succinite, bernstein) [Named from French ambre itself from Arabic anbar meaning ambergris]

Amblygonite [Named from the Greek, amblys, obtuse and gonia meaning angle, in reference to cleavage angle] (ICSD 26513 and PDF 22-1138)

Analcime (syn., analcite, analcidite) [from the Greek, analcis, weak, referring to a weak electrical charge developed on rubbing or heating] (ICSD 2930 and PDF 42-1378)

Anatase [1317-70-0] [from the Greek, anatasis, tall direction owing to the great vertical space lattice parameter c compared with other tetragonal minerals] (ICSD 9852 and PDF 21-1272)

Andalusite [12183-80-1] (syn., chiastolite: carbonaceous inclusions) [Named after the province of Andalucia, Spain] (ICSD 24275 and PDF 39-376)

Orthorhombic a = 779.59 pm b = 789.83 pm c = 555.83 pm (Z = 4) P.G. mmm S.G. Pnnm

Tetragonal a = 379.3 pm c = 951.2 pm C4, tP6 (Z = 4) P.G. 422 S.G. I41/amd Anatase type Packing fraction = 70%

Cubic a = 1373.3 pm (Z = 16) P.G. 432 S.G. I41ad

Triclinic a = 519 pm b = 712 pm c = 504 pm α = 112.02° β = 97.82° γ = 68.12° (Z = 2) P.G. 1 S.G. P1

Amorphous

c = 1738 pm (Z = 3) P.G. 3m S.G. P3m

Biaxial (–) α = 1.629–1.640 β = 1.633–1.644 γ = 1.638–1.650 δ = 0.009–0.010 2V = 73–86°

Uniaxial (+) ε = 2.4880 ω = 2.5612 δ = 0.073 Dispersion strong

Isotropic nD = 1.479–1.493

Biaxial (–) α = 1.590 β = 1.600 γ = 1.620 δ = 0.03 2V = 52–90°

Isotropic nD = 1.539–1.545

δ = 0.020

6.5–7.5

5.5–6.0

5.5

6

2–2.5

3130– 3160

3877

2260

3000

1050– 1090

Habit: acicular, blocky, prismatic, euhedral crystals. Color: usually pink, white, rose, dark green, gray, brown, red, or green or with clouded inclusions. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Cleavage: (110) distinct, (100) indistinct, (010) poor. Fracture: uneven, splintery, brittle. Streak: white. Chemical: insoluble in strong mineral acids but attacked by molten alkali-metal hydroxides (e.g., NaOH) and carbonates (e.g., Na2CO3). Heated in Co(NO3)2 give the Thénard blue color. Non fusible but transforms to sillimanite on heating. Other properties: Unfusible but when heated above 1200°C transforms to a mixture of silica and mullite (Al6Si2O13). Dielectric constant of 8.28. Diamagnetic with a specific magnetic susceptibility of –10–10 m3.kg–1. Occurrence: metamorphosed peri-aluminous sedimetary rocks.

Habit: acicular, prismatic, massive. Color: reddish brown, yellowish brown, black or bluish violet. Diaphaneity: transparent, translucent to opaque. Luster: adamantine. Streak: grayish black. Fracture: uneven. Cleavage: [111]. Chemical: insoluble in water, slightly soluble in HCl, HNO3, sol. HF and in hot H2SO4 or KHSO4. Attacked by molten Na2CO3. Other properties: dielectric constant 48. Transition temperature to rutile 700°C.

Habit: euhedral crystals, granular, massive. Color: white, grayish white, greenish white, yellowish white, or reddish white. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Luminescence: fluorescent. Streak: white. Cleavage: (100) poor. Fracture: Subconchoidal, uneven. Twinning: {100}, {110}. Occurrence: occurs frequenty in basalts and other basic igneous rocks associated with other zeolites.

Habit: equant. Color: white, green. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous, greasy. Fracture: subconchoidal. Cleavage: (100) perfect, (110) good, (011) perfect. Twinning: (111).

Fossil resin found buried in the countries along the Baltic sea and in Madagascar. Fluorescence: bluish white to yellow green

Mineral and Gemstone Properties Table 803

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

(Na,Ca)(Si,Al)4O8 An40-Ab60 M = 268.61671 5.14 wt.% Na 5.97 wt.% Ca 14.06 wt.% Al 27.18 wt.% Si 47.65 wt.% O (Tectosilicates, framework)

Ca3Fe2(SiO4)3 M = 508.1773 23.66 wt.% Ca 21.98 wt.% Fe 16.58 wt.% Si 37.78 wt.% O Coordinence Ca(8), Fe(6), Si(4) (Nesosilicates)

PbSO4 M = 303.2636 68.32 wt.% Pb 10.57 wt.% S 21.10 wt.% O Coordinence Pb(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

CaSO4 M = 136.1416 29.44 wt.% Ca 23.55 wt.% S 47.01 wt.% O Coordinence Ca(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Ca(Mg,Fe, Mn)(CO3)2 M = 206.39 19.42 wt.% Ca 3.53 wt.% Mg 2.66 wt.% Mn 16.24 wt.% Fe 11.64 wt.% C 46.51 wt.% O

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Andesine (syn., acmite) [Named after Andes Mountains, South America]

Andradite (syn., demantoid: green, melanite: black, topazolite: yellow) [Named after the Brazilian mineralogist J.B. de Andrada e Silva (1763–1838). Demantoid is named after its adamantine luster] (ICSD 27370 and PDF 10-288)

Anglesite [7446-14-2] (syn., lead spar, lead vitriol) [Named after the island of Anglesey, Wales, UK] (ICSD 100625 and PDF 36-1461)

Anhydrite [7778-18-9] (From the Greek, anhydros, meaning dry, in contrast to gypsum, which is hydrated) (ICSD 16382 and PDF 37-1496)

Ankerite [Named after Austrian mineralogist, Mathias Joseph Anker (1771–1843)] (ICSD 100417 and PDF 41-586)

Table 12.23. (continued)

Trigonal (Rhombohedral) a = 482 pm c = 1614 pm aRh = 605.0 pm 47°00' (Z = 3) P.G. 3

Orthorhombic a = 699.1 pm b = 699.6 pm c = 623.8 pm (Z = 4) P.G. mmm S.G. Ccmm Anhydrite type

Orthorhombic a = 848.0 pm b = 539.8 pm c = 695.8 pm (Z = 4) P.G. mmm S.G. P21nma Barite type

Cubic a = 1204.8 pm (Z = 8) P.G. 432 S.G. Ia3d Garnet group (Ugrandite series)

Uniaxial (–) ε = 1.500–1.548 ω = 1.690–1.750 δ = 0.182–0.202 Dispersion strong

Biaxial (+) α = 1.569–1.574 β = 1.574–1.579 γ = 1.609–1.618 δ = 0.040–0.045 2V = 36–45°

Biaxial (+) α = 1.878 β = 1.883 γ = 1.894 δ = 0.017 2V = 68–75° Dispersion strong

Isotropic nD = 1.887

3.5–4

3–3.5

2.5–3

6.5–7

7

Mohs hardness (/HM) (Vickers)

Biaxial (+/–) α = 1.543–1.554 β = 1.547–1.559 γ = 1.552–1.562 δ = 0.008–0.009 2V = 78–84°

Optical properties

2930– 3100

2980

6380

3859

2670

Density (ρ/kg.m–3) (calc.)

Triclinic a = 815.5 pm b = 129 pm c = 916 pm Z=6

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: crystalline, massive. Color: white, gray, reddish white, brownish white, or gray. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Streak: white. Fracture: brittle, subconchoidal. Cleavage: (1011) perfect. Twinning: {0001}, and {1010}.

Habit: massive, granular, fibrous, plumose. Color: colorless, white, bluish white, violet white, or dark gray. Luster: vitreous, pearly. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (010) perfect, (001) good. Fracture: conchoidal, brittle. Chemical: decomposes at 1200°C into CaO and SO3. Occurrence: sedimentary beds, gangue in ore veins, and in traprock zeolite occurrences.

Habit: tabular, prismatic, granular, stalactitic. Color: white, gray, gray, or yellow. Diaphaneity: transparent to translucent. Luster: adamantine. Streak: white. Cleavage: perfect (001) good, (210). Twinning: {011}. Fracture: conchoidal, brittle. Decomposes upon heating in air above 637°C yielding PbO and SO3 fumes. Occurrence: secondary, weathered deposits of lead ore.

Habit: Dodecahedral crystals, massive. Color: black, yellowish brown, red, greenish yellow, or gray. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Fracture: subconchoidal. Occurrence: igneous and metamorphic rocks.

Habit: granular, crystalline. Color: white, gray, or gray. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (001) perfect, (010) good. Fracture: uneven. Occurrence: magmatic and metamorphic rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

804 Minerals, Ores and Gemstones

Orthorhombic Distorded pseudobrookite TiO 191–210 pm mC32 (Z = 4) S.G. C2/m

β-Ti3O5 M = 223.0070 64.1 wt.% Ti 35.9 wt.% O (Oxides and hydroxides)

Mg6(OH)8Si4O10 M = 300.77 18.18 wt.% Mg 13.93 wt.% Fe 18.68 wt.% Si 1.34 wt.% H 47.88 wt.% O Coordinence Mg(6), Si(4) (Phyllosilicates, layered)

Mg7[Si8O22](OH)2 MM = 780.82 21.79 wt.% Mg 28.78 wt.% Si 0.26 wt.% H 49.18 wt.% O Inosilicates

Anosovite (type II) [12065-65-5]

Antigorite (2M1) (fibrous chrysotile) [Named after its locality Antigorio, Italy] (ICSD 654 and PDF 41-1486)

Anthophyllite [Named from Latin anthophyllum, clove for its brown color, and Greek lithos for stone] (ICSD 30254 and PDF 42-544)

*Note: Where the optical sign is listed as “(?)” it is not known or has not been determined.

Orthorhombic a = 1855.40 pm b = 1802.26 pm c = 528.2 pm (Z = 4) P.G. 2/m2/m2/m S.G. Pnma Amphibole group

Monoclinic a = 532 pm b = 950 pm c = 1490 pm 101.9° (Z = 2) P.G.2/m S.G. C2/m

Monoclinic a = 975.2 pm b = 380.2 pm c = 944.2 pm β = 91.55° mC32 (Z = 4) S.G. C2/m

α-Ti3O5 M = 223.0070 64.1 wt.% Ti 35.9 wt.% O (Oxides and hydroxides)

Anosovite (type I) [12065-65-5]

Triclinic a = 817.7 pm b = 1287.7 pm c = 1416.9 pm α = 93.33° β = 115.60° γ = 91.22° (Z = 8) P.G. 1 S.G. P1

Ca2[Si2Al2O8] An100 Ab0 M = 277.40806 0.41 wt.% Na 13.72 wt.% Ca 18.97 wt.% Al 20.75 wt.% Si 46.14 wt.% O Coordinence Ca(7), Si(4), Al(4) (Tectosilicates, framework)

Anorthite (syn., Indianite) [from the Greek, an, and orthos, not upright in allusion to the oblique crystals] (ICSD 654 and PDF 41-1486)

Monoclinic P.G. 2/m

Ni3(AsO4)2·8H2O M = 598.03064 29.44 wt.% Ni 25.06 wt.% As 2.70 wt.% H 42.81 wt.% O (Phosphates, arsenates and vanadates)

S.G. R3 Dolomite type

Annabergite (syn., Nickel Bloom) [Named after the locality Annaberg, Germany) (ICSD 81386 and PDF 35-568)

Coordinence Ca(6), Fe(6), C(3) (Nitrates, carbonates, and borates)

Biaxial (+) α = 1.598–1.674 β = 1.605–1.685 γ = 1.615–1.697 δ = 0.017–0.0230 2V = 57–90°

Biaxial (–) α = 1.560 β = 1.570 γ = 1.570 δ = 0.007 2V = 20–60° Dispersion weak

Biaxial (?)

Biaxial (?)*

Biaxial (–) α = 1.577 β = 1.585 γ = 1.590 δ = 0.013 2V = 78° Dispersion weak

Biaxial (–) α = 1.622 β = 1.658 γ = 1.687 δ = 0.065 2V = 78° Dispersion weak

5.5–6

3–4

n.a.

n.a.

6

2

2850– 3570 (3090)

2600

4900

4900

2760

3000– 3100

Habit: prismatic crystals, columnar to fibrous even asbestiform. Color: clove-brown to dark brown. Diaphaneity: translucent to nearly opaque. Luster: vitreous to silky. Fracture: subconchoidal. Cleavage: perfect [210]. Streak: colorless. Others: infusible and insoluble in HCl. Occurrence: metamorphic rocks.

Habit: platy, massive. Color: green yellow. Diaphaneity: transparent to translucent. Luster: resinous, silky. Cleavage: (001) perfect. Fracture: uneven, flexible. Streak: white.

Habit: acicular crystals. Color: blue-dark. Diaphaneity: opaque. Luster: metallic. Streak: black. Type II can be prepared by the hydrogen reduction of solid TiO2 at temperature around 1500°C with magnesia as a catalyst. Anosovite type II is similar to that found in artificial titania slags and it is stabilized at room temperature with small amount of iron. This oxide is dimorphic with a rapid phase transition from semiconductor to metal occuring at roughly 120°C.

Habit: needle-like crystals. Color: blue-dark. Diaphaneity: opaque. Luster: metallic. Streak: black. Other properties: melting point 1777°C. It can be prepared by the hydrogen reduction of solid TiO2 at temperature around 1300°C or by mixing intimatelly stoichiometric quantities of titanium metal and titanium dioxide in an electric arc furnace under argon atmosphere. This oxide is dimorphic with a rapid phase transition from semiconductor to metal occuring at roughly 120°C.

Habit: granular, euhedral crystals, striated. Color: white, gray, or reddish white. Diaphaneity: transparent to translucent. Luster: pearly, vitreous (i.e., glassy). Cleavage: (001) perfect, (010) good. Twinning: Albite [010], Pericline [010]. Fracture: uneven. Streak: white. Occurrence: magmatic and metamorphic rocks.

Habit: earthy, encrustations, massive. Color: green, green white, apple green, or green. Luster: pearly. Diaphaneity: transparent to translucent. Streak: light green. Cleavage: [010] perfect. Fracture: brittle.

Mineral and Gemstone Properties Table 805

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Sb M = 121.75 Coordinence Sb(3) (Native elements)

Cu3SO4(OH)4 M = 354.73108 53.74 wt.% Cu 9.04 wt.% S 36.08 wt.% O 1.14 wt.% H Coordinence Cu(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Ca5(PO4)3(OH,F,Cl) M = 504.30248 39.74 wt.% Ca 18.43 wt.% P 38.07 wt.% O 3.77 wt.% F Coordinence Ca(6), P(4) (Phosphates, arsenates, and vanadates)

(K,Na)3Na(SO4)2 M = 320.33 27.46 wt.% K 12.56 wt.% Na 20.02 wt.% S 39.96 wt.% O (Sulfates, chromates, molybdates, and tungstates)

CaCO3 M = 100.0872 40.04 wt.% Ca 12.00 wt.% C 47.96 wt.% O Traces of Sr (up to 5.6 wt.% ), Mg,

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Antimony (syn., stibium) [from the Arabic, aluthmud, the medieval Latin, antimonium, originally applied to stibnite] (ICSD 64695 and PDF 35-732)

Antlerite [Named after the Antler mine, Mojave Company, Arizona USA] (ICSD 203067 and PDF 7-407)

Apatite [Named from the Greek, apatos, misleading, owing to the confusion with beryl, tourmaline, and olivine owing to its wide variety of forms and colors)

Aphthitalite (syn., glaserite) [Named from Greek aphthitos, indestructible, halos, salt, and lithos for stone since the mineral is very stable in air] (ICSD 26014 and PDF 20-928)

Aragonite [471-34-1] [Named after the Spanish locality of Aragon where the mineral was first discovered) (ICSD 15194 and PDF 41-1475)

Table 12.23. (continued)

Orthorhombic a = 574.1 pm b = 796.8 pm c = 495.9 pm (Z = 4) S.G. Pmcn

Trigonal (Rhombohedral) a = 565 pm c = 729 pm (Z = 1) P.G. 32/m S.G. P3m1

Hexagonal a = 938 pm c = 686 pm (Z = 2) P.G. 6/m S.G. P63/m Apatite type

Orthorhombic a = 824 pm b = 1199 pm c = 603 pm (Z = 4) P.G. mmm S.G. P21/aam

Biaxial (–) α = 1.530–1.531 β = 1.680–1.681 γ = 1.685–1.686 δ = 0.155–0.156 2V = 18–19°

Uniaxial (+) ε = 1.490 ω = 1.496 δ = 0.006

Uniaxial (–) ε = 1.624–1.666 ω = 1.629–1.667 δ = 0.001–0.007 Dispersion moderate

Biaxial(+) α = 1.726 β = 1.738 γ = 1.789 δ = 0.063 2V = 53°

3.5–4 (HV 280)

3

5

3.5–4

3–3.5 (HV 83–99)

Mohs hardness (/HM) (Vickers)

Uniaxial (n.a.) nD = 1.70–1.80 R = 72.0–77.1%

Optical properties

2940– 2950

2700

3100– 3350

3900

6660

Density (ρ/kg.m–3) (calc.)

Trigonal (Rhombohedral) a = 429.96 pm c = 1125.16 pm A7, hR2 (Z = 6) P.G. 3m S.G. R3m α-Arsenic type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: pseudo hexagonal, columnar, globular, reniform, fibrous. Color: colorless, white, gray, yellowish white, or reddish white. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Streak: white. Cleavage: (010) distinct. Twinning: {110}. Fracture: subconchoidal. Chemical: readily dissolved by cold diluted strong mineral acids (e.g., HCl) with evolution of CO2. Decomposed at 825°C giving off CO2 and CaO. Meigen’s spot test: it exhibits a pink to violet color after immersion in boiling Co(NO3)2 solution.

Habit: massive, encrustations. Color: blue, colorless. Luster: vitreous to resinous. Diaphaneity: translucent. Cleavage: (1011) fair. Fracture: conchoidal. Streak: white. Occurrence: encrustation in volcanoes and fumaroles, and lacustrine salt deposits (e.g., Searles Lake, California, USA).

Habit: prismatic, colloform, massive, granular, earthy. Color: white, yellow, green, red, or blue (the color is often due to the presence of rare earths). Diaphaneity: transparent to translucent. Luster: subresinous. Streak: white. Cleavage: (0001) indistinct, (1010) indistinct. Fracture: conchoidal. Chemical: soluble in HCl, and HNO3. Occurrence: found in all type of rocks (igneous, sedimentary, and metamorphic).

Habit: prismatic, tabular. Color: white, gray. Streak: green, gray. Diaphaneity: transparent to translucent. Luster: vitreous. Fracture: uneven. Cleavage: perfect (010).

Habit: massive, lamellar, massive, reticulate. Color: tin white. Diaphaneity: opaque. Luster: metallic. Streak: lead gray. Cleavage: (0001) perfect. Fracture: brittle.

Other relevant mineralogical, physical, and chemical properties with occurrence

806 Minerals, Ores and Gemstones

Mg0.75Fe0.25Ti2O5 M = 207.95 8.77 wt.% Mg 46.05 wt.% Ti 6.71 wt.% Fe 38.47 wt.% O (Oxides and hydroxides)

As M = 74.9216 Coordinence As(3) (Native elements)

FeAsS M = 162.8346 34.30 wt.% Fe 46.01 wt.% As 19.69 wt.% S (Sulfides and sulfosalts) Coordinence Fe(6)

Cu2Cl(OH)3 M = 213.56672 59.51 wt.% Cu 1.42 wt.% H 16.60 wt.% Cl 22.47 wt.% O (Halides)

Al2PO4(OH)3 M = 199.956547 26.99 wt.% Al 15.49 wt.% P 56.01 wt.% O 1.51 wt.% H Coordinence Al(5, and 6), P(4) (Phosphates, arsenates, and vanadates)

Armalcolite [64476-39-7] (syn., Kennedyite) [Named after the three astronauts Neil Alden Armstrong, Edwin Eugene Aldrin, and Michael Collins] (ICSD 15845 and PDF 41-1444)

Arsenic (syn., arsenicum) [from the Greek, arsenikon, a name originally applied to the mineral orpiment] (ICSD 16516 and PDF 5-632)

Arsenopyrite (syn., arsenical pyrite, mispickel) [Named after the minerals chemical composition] (ICSD 62400 and PDF 42-1320)

Atacamite [Named after the Atacama desert province in Northern Chile] (ICSD 61252 and PDF 25-269)

Augelite [Named after the Greek for luster, for its pearly luster on the cleavage] (ICSD 24430 and PDF 34-151)

Fe and Zn Coordinence Ca(6), C(3) (Carbonates, aragonite group)

Monoclinic a = 1312 pm b = 799 pm c = 507 pm β = 112.25° (Z = 4) P.G. 2/m S.G. C2/m

Orthorhombic a = 602 pm b = 915 pm c = 685 pm P.G. 222 S.G. P21/nam (Z = 4)

Monoclinic a = 576.0 pm b = 569.0 pm c = 578.5 pm 112.23° E07, mP24 (Z = 8) S.G. B21/d P.G. 2/m Arsenopyrite type

Trigonal (Rhombohedral) a = 413.19 pm 54.12° A7, hR2 (Z = 2) P.G. 3m S.G. R3m α-Arsenic type

Orthorhombic a = 977.62 pm b = 1002.14 pm c = 374.85 pm (Z = 4) P.G. 2/m 2/m 2/m S.G. Bbmm Karrooite type

P.G. mmm Aragonite type

Biaxial(+) α = 1.574 β = 1.588 γ = 1.576 δ = 0.014 2V = 51°

Biaxial (–) α = 1.831 β = 1.861 γ = 1.880 δ = 0.049 2V = 75° Dispersion strong

Biaxial R = 53.7%

Uniaxial (n.a.) R = 48–51%

Biaxal (?) R = 13–14%

Dispersion weak

5

3–3.5

5.5–6 (HV 1048– 1127)

3.5 (HV 57–69)

4

2700

3760– 3780

6100

5700

3904

Habit: tabular, massive. Color: colorless, white. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous. Fracture: uneven. Cleavage: (101) good.

Habit: acicular, striated prisms, euhedral crystals, fibrous, granular. Color: green, dark green, or blackish green. Luster: adamantine. Diaphaneity: transparent to translucent. Streak: apple green. Cleavage: [010] perfect. Fracture: conchoidal. Occurrence: arid climates with oxidizable copper minerals.

Habit: faces striated, euhedral crystals, prismatic. Color: tin white or light steel gray. Luster: metallic. Diaphaneity: opaque. Streak: black. Cleavage: {110} distinct. Twinning: {100}, {101}, {012}. Fracture: uneven, brittle. Electrical resistivity 20 to 300 μΩ.cm.

Habit: nodular, reniform, lamellar. Color: tin white or gray. Diaphaneity: opaque. Luster: metallic. Streak: black. Cleavage: (0001) perfect. Fracture: uneven. Occurrence: In ore veins in igneous crystalline rocks.

Habit: granular anhedral to subhedral crystals. Color: gray to tan. Diaphaneity: opaque. Luster: metallic. Occurrence: extraterrestrial materials such as in the lunar regolith (Tranquility base, Moon), in Ti-rich basalts (Ovifalk, Disco Islang, Greenlan) and in artificial titania rich slags resulting from the EAF smelting of hemo-ilmenite or ilmenite with anthracite coal. Melting point: 1550°C.

Other: dielectric constant 7.4. Occurrence: fossil skeletons, with gypsum and celestine in marl and clays, near geysers and stalactites in caverns.

Mineral and Gemstone Properties Table 807

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6 M = 236.35 0.97 wt.% Na 15.26 wt.% Ca 9.26 wt.% Mg 2.03 wt.% Ti 4.57 wt.% Al 4.73 wt.% Fe 22.58 wt.% S 40.62 wt.% O (Inosilicates, double chains)

Ca(UO2)2(PO4)2.10H2O M = 986.26 4.06 wt.% Ca 48.27 wt.% U 6.28 wt.% P 2.45 wt.% H 38.93 wt.% O Coordinence Ca(6), U(2), P(4) (Urano-phosphates)

Cu3(CO3)2(OH)2 M = 344.67108 55.31 wt.% Cu 0.58 wt.% H 6.97 wt.% C 37.14 wt.% O Coordinence Cu(5), C(3) (Nitrates, carbonates, and borates)

ZrO2 M = 123.2228 74.03 wt.% Zr 25.97 wt.% O (Oxides, and Hydroxides)

BaSO4 M = 233.3906 58.84 wt.% Ba 13.74 wt.% S 27.42 wt.% O Coordinence Ba(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Augite (syn., fassaite) [Named from the Greek, auge, luster) (ICSD 9257and PDF 24-203)

Autunite [Named in 1852 after Autun, Saône-et-Loire (France) locality where the mineral was first discovered]

Azurite (syn., chessylite) [from the Persian, lazhward, blue] (ICSD 2934 and PDF 11-682)

Baddeleyite [1314-23-4] [after J. Baddeley who first brought the original specimens from Ceylon (Sri Lanka)] (ICSD 18190 and PDF 37-1484)

Barite [7727-43-7] (syn., heavy spar, barytine, baryte) [Named from the Greek, baryos, meaning heavy] (ICSD 16904 and PDF 24-1035)

Table 12.23. (continued)

Orthorhombic a = 887.8 pm b = 545.0 pm c = 715.2 pm (Z = 4) P.G. mmm S.G. P21nma Barite type

Monoclinic a = 514. 54 pm b = 520. 75 pm c = 531. 07 pm 99.23° (Z = 4) Baddeleyite type

Monoclinic a = 500.8 pm b = 584.4 pm c = 1033.6 pm β = 92.45° (Z = 2)

Tetragonal a = 700.9 pm c = 2073.6 pm (Z = 4) P.G. 422 S.G. I4/mmm

Biaxial (+) α = 1.634–1.637 β = 1.636–1.639 γ = 1.647–1.649 δ = 0.011–0.012 2V = 37–40° Dispersion weak

Biaxal (–) α = 2.13 β = 2.19 γ = 2.2 δ = 0.070 2V = 30°

Biaxial (+) α = 1.730 α = 1.756 γ = 1.836 δ = 0.108 2V = 68° Dispersion weak

Biaxial (–) ε = 1.553 ω = 1.577 δ = 0.024

3–3.5

6.5

3.5–4

2–2.5

5–6.5

Mohs hardness (/HM) (Vickers)

Biaxial (+) α = 1.68–1.703 β = 1.684–1.711 γ = 1.706–1.729 δ = 0.026 2V = 40–52° Dispersion weak

Optical properties

4490

5500– 6000

3770

3150 (3100)

3400

Density (ρ/kg.m–3) (calc.)

Orthorhombic a = 980 pm b = 900 pm c = 525 pm (Z = 4) P.G. 2/m S.G. C2/c

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: tabular, prismatic, lamellar, massive, fibrous, cockscomb aggregates. Color: white, yellowish white, grayish white, brownish white, or dark brown. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: transparent, translucent, opaque. Fracture: uneven. Streak: white. Cleavage: (001) perfect, (210) perfect. Twinning: {011}. Luminescence: phosphorescent. Chemical: Insoluble in hot HCl. Decomposes at 1580°C into BaO and SO3. Can be reduced by carbon at 1000°C yielding BaS and CO2. Occurrence: sedimentary rocks and late gangue mineral in ore veins.

Habit: tabular, crystalline. Color: brown, colorless, black. Diaphaneity: transparent, translucent, opaque. Luster: adamantine. Streak: white. Fracture: uneven. Cleavage: (001). Slightly sol. HCl, HNO3, and dil. H2SO4, sol. hot conc. H2SO4, and HF. Attacked by molten KHSO4, NaOH, and Na2CO3. Melting point: 2710°C.

Habit: tabular, massive, prismatic, stalactitic. Color: azure blue or very dark blue. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: light blue. Cleavage: (011) perfect, (100) good. Fracture: conchoidal, brittle. Occurrence: secondary mineral in the oxidized zone of copper ore deposits in association with malachite.

Habit: thin tabular crystals according to {001}, scaly foliated aggregates. Color: lemon yellow to greenish yellow to pale green. Diaphaneity: transparent to translucent. Luster: vitreous to pearly on {001}. Streak: yellowish. Cleavage: (001) perfect, (100) good, (010) good. Fracture: uneven. Other: radioactive, strongly fluorescent yellow-green.

Habit: massive, fibrous, columnar. Color: white, green, or black. Diaphaneity: translucent to opaque. Luster: vitreous, resinous. Cleavage: (110) perfect, (010) indistinct. Fracture: brittle, conchoidal. Streak: greenish gray. Occurrence: basic igneous and metamorphic rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

808 Minerals, Ores and Gemstones

Monoclinic a = 506.26 pm b = 867.19 pm c = 471.3 pm β = 90.45°, (Z = 4) P.G. 2/m S.G. P21/a

α-Al(OH)3 M = 78.00 34.59 wt.% Al 3.88 wt.% H 61.53 wt.% O Coordinence Al(6) (Oxides and hydroxides)

V2TiO5 M = 229.747 44.35 wt.% V 20.83 wt.% Ti 34.82 wt.% O Coordinence Ti(6)

Be4[Si2O7(OH)2] M = 238.2302 15.13 wt.% Be 23.58 wt.% Si 0.85 wt.% H 60.44 wt.% O (Sorosilicates, pair)

Be3Al2[Si6O18] M = 537.50182 5.03 wt.% Be 10.04 wt.% Al 31.35 wt.% Si 53.58 wt.% O Coordinence Al(6), Si(4), and Be(4) Traces of Fe, Cr, Mg, Li, Na, K, Cs. (Cyclosilicates, ring)

Bayerite [Named after the German metallurgist Karl J. Bayer()] (ICSD 200413 and PDF 20-11)

Berdesinskiite [85270-10-6] [Named after the German mineralogist,Waldemar Berdesinski (1911–1990), University of Heidelberg]

Bertrandite [Named after the French mineralogist, M.A. Bertrand (1847–1907)] (ICSD 202360 and PDF 24-509)

Beryl [1302-52-9] (syn., emerald: green, aquamarine: blue, morganite: pink, goshenite: colorless, heliodor: yellow) [Named from the Greek, beryllos, signifying a blue-green color of a gemstone] (ICSD 2791 and PDF 9-430)

Hexagonal a = 921.5 pm c = 919.2 pm (Z = 2) P.G. 6/mmm S.G. P6/mcc Beryl type

Orthorhombic a = 1522 pm b = 869 pm c = 454 pm (Z = 4) P.G. mm2 S.G. Ccm21

Monoclinic a = 1011 pm b = 508.4 pm c = 703 pm β = 111.6°, (Z = 4) P.G. 2/m 2/m 2/m S.G. Bbmm Pseudobrookite type

Hexagonal a = 712 pm c = 976 pm (Z = 6) S.G. 6m2 P.G. 6m2 (Ditrigonal dipyramidal)

Ce(CO3)F M = 219.12 63.94 wt.% Ce 5.48 wt.% C 21.90 wt.% O 8.67 wt.% F La(CO3)F M = 217.91 63.74 wt.% La 5.51 wt.% C 22.03 wt.% O 8.72 wt.% F Both contain Th (Carbonates, nitrates and borates)

Bastnaesite (syn., hamartite) [Named after the Swedish locality Bastnas Mine, Riddarhyttan, Vastmanland] Ce-rich (ICSD 81673 and PDF 11-340) La-rich (ICSD 36180 and PDF 41-595)

Uniaxial (–) ε = 1.564–1.598 ω = 1.565–1.602 δ = 0.003–0.008

Biaxial (–) α = 1.589 β = 1.602 γ = 1.614 δ = 0.023 2V = 76° Dispersion none

Biaxial (?) R = 20.6–21.6%

Biaxial (+) α = 1.565–1.574 β = 1.583 γ = 1.580–1.584 δ = 0.023 2V = small

Uniaxial (+) ε = 1.717 ω = 1.818 δ = 0.1010

7.5–8.0

6

6.5–7

n.a.

4–5

2640

2590

4540

2540– 3050 (3060)

4970

Habit: crystalline, prismatic, columnar. Color: green, blue, yellow, colorless, or pink. Luster: vitreous, resinous. Diaphaneity: transparent to subtranslucent. Streak: white. Cleavage: [0001] imperfect. Twinning: {311}, {110}. Fracture: brittle, conchoidal. Chemical: insoluble in strong mineral acids. Other: dielectric constant 3.9 to 7.7. Occurrence: occurs exclusively in high-temperature hydrothermal veins, in granitic pegmatites, at the contacts zone of intrusive mafic igneous rocks with aluminous schists, shales or limestones and to a lesser extent in vugs inside rhyolites.

Habit: well formed prismatic or tabullar hexagonal crystals, with pinacoidal {1010}, {0001}, or prism {1120} or pyramidal terminations. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Color: colorless or pale yellow. Streak: white. Cleavage: [001] perfect, [110] distinct, [101] distinct. Fracture: brittle. Occurrence: commonly found in Be-bearing pegmatites and may be derived from the alteration of beryl.

Habit: tiny grains. Color: black. Luster: metallic. Diaphaneity: opaque. Occurrence: weathered gneiss associated with schreyerite, tourmaline and kornerupine. Melts at 1750°C.

Habit: fine fibers. Color: colorless. Luster: silky. Diaphaneity: translucent to transparent. Streak: white. Occurrence: precipitates of aluminum hydroxide gels onto carbonates at pH > 5.8.

Habit: prismatic, granular. Color: yellow or reddish brown. Luster: vitreous, greasy. Cleavage: (1011) imperfect, (0001) poor. Fracture: uneven. Streak: white.

Mineral and Gemstone Properties Table 809

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Pb2Sb2O6(O,OH) M = 770.15 3.81 wt.% Pb 31.62 wt.% Sb 514.54 wt.% O 0.03 wt.% H (Oxides and hydroxides)

K(Mg,Fe)3Si3(Al,Fe)O10(OH,F)2 Coordinence K(6), Fe(6), Mg(6), Si(4), Al(4) (Phyllosilicates, layered)

MgCl2·6H2O M = 203.301 11.96 wt.% Mg 34.88 wt.% Cl 5.95 wt.% H (Halides)

Bi M = 208.9804 Coordinence Bi(3) (Native elements)

Na2Mg(SO4)2.4H2O M = 334.47 13.75 wt.% Na 7.27 wt.% Mg 2.41 wt.% H 19.17 wt.% S 57.40 wt.% O (Sulfates, chromates, molybdates, and tungstates)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Bindheimite [Named after the German chemist, J.J. Bindheim] (ICSD 27120 and PDF 42-1355)

Biotite (1M) (syn., manganophyllite: Mn, lepidomelane: Fe) [Named after the French physicist, J.B. Biot] (ICSD 68928 and PDF 42-1437)

Bischofite [7791-18-6] [Named after the German chemist and geologist G. Bischof (1792–1870)] (ICSD 47161 and PDF 25-515)

Bismuth [Named from the Arabic, biismid, having the properties of antimony] (ICSD 64703 and PDF 5-519)

Bloedite (syn., blödite) (ICSD 48017 and PDF 19-1215)

Table 12.23. (continued)

Monoclinic a = 1113 pm b = 824 pm c = 554 pm β = 100.84° (Z = 2) P.G. 2/m S.G. P21/a

Trigonal (Rhombohedral) a = 474.60 pm 57.23° A7, hR2 (Z = 2) P.G. 3m S.G. R3m α-Arsenic type

Monoclinic a = 990 pm b = 715 pm c = 610 pm β = 93.7° (Z = 2) P.G. 2/m S.G. C2/m

Monoclinic a = 533 pm b = 931 pm c = 1016 pm β = 99.3° (Z = 2) P.G. 2/m S.G. C2/m

Biaxial (–) α = 1.48 β = 1.48 γ = 1.48 δ = 0.00 2V = 71° Dispersion strong

Uniaxial (n.a.) nD = 2.26 R = 67.9%

Biaxial (+) α = 1.498 β = 1.505 γ = 1.525 2V = 79°

Biaxial (–) α = 1.565–1.625 β = 1.605–1.696 γ = 1.605–1.696 δ = 0.040–0.080 2V = 0–32° Dispersion weak

3

2–2.5 (HV 16–19)

1–2

2.5–3

4–5

Mohs hardness (/HM) (Vickers)

Isotropic nD = 1.84–1.87.

Optical properties

2230

9750

1604 (1585)

2700– 3300

4600– 7300

Density (ρ/kg.m–3) (calc.)

Cubic a = 1041 pm (Z = 6) P.G. 432 S.G. Fd3m

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: massive, granular. Color: colorless, green, yellow, or red. Diaphaneity: transparent to translucent.

Habit: platy, lamellar, granular, reticulated. Color: silver white, pinkish white, or red. Diaphaneity: opaque. Luster: metallic. Streak: lead gray. Cleavage: [0001] perfect. Fracture: uneven.

Habit: fibrous, deliquescent, massive, granular Color: colorless or white. Luster: vitreous, greasy. Diaphaneity: translucent to transparent. Streak: white. Occurrence: marine evaporites. Dehydratation occurs at 120°C. Soluble in water.

Habit: micaceous, foliated, lamellar, pseudo hexagonal. Color: dark brown, greenish brown, blackish brown, yellow, or white. Diaphaneity: transparent to opaque. Luster: vitreous, pearly. Streak: white gray. Cleavage: (001) perfect. Twinning: [310]. Fracture: uneven, elastic. Occurrence: granitic rocks. Forms a series with phlogopite.

Habit: encrustations, earthy, encrustations. Color: yellow, greenish yellow, green, brownish white, or grayish white. Luster: greasy. Streak: light greenish brown. Fracture: conchoidal.

Other relevant mineralogical, physical, and chemical properties with occurrence

810 Minerals, Ores and Gemstones

γ-AlO(OH) M = 59.98828 44.98 wt.% Al 1.68 wt.% H 53.34 wt.% O Coordinence Al(6) (Oxides and hydroxides)

Mg6B14O25Cl2 M = 768.0744 18.99 wt.% Mg 19.71 wt.% B 9.22 wt.% Cl 52.08 wt.% O Coordinence Mg(6), B(3 and 4) (Nitrates, carbonates, and borates)

Na2B4O5(OH)4·10H2O M = 381.36813 12.06 wt.% Na 11.34 wt.% B 5.29 wt.% H 71.32 wt.% O Coordinence Na(6), B(3 and 4) (Nitrates, carbonates, and borates)

Cu5FeS4 M = 501.823 63.31 wt.% Cu 11.13 wt.% Fe 25.56 wt.% S (Sulfides ans sulfosalts) Coordinence Cu(4), Fe(4)

Pb5CuSb4S11 M = 1887.90 26.44 wt.% Sb 54.88 wt.% Pb 18.68 wt.% S (Sulfides and sulfosalts) Coordinence Pb(7), Sb(3)

PbCuSbS3 M = 974.348 13.04 wt.% Cu 12.18 wt.% Sn 12.50 wt.% Sb 42.53 wt.% Pb 19.75 wt.% S (Sulfides and sulfosalts)

Boehmite [14457-84-2] [Named after the German geologist and paleontologist J. Böhm (1857–1938)] (ICSD 200599 and PDF 21-1307)

Boracite [Named after its chemical composition containing boron] (ICSD 9290 and PDF 5-710)

Borax [1303-96-4] (syn., tincal) [from the Arabic, buraq, white] (ICSD 30506 and PDF 33-1215)

Bornite [Named after the Austrian mineralogist I. von Born (1742–1791)] (ICSD 1963 and PDF 42-1405)

Boulangerite (syn., mullanite) [Named after the French mining engineer, C.L. Boulanger (1810–1849)] (ICSD 300107 and PDF 42-1407)

Bournonite (syn., wheel ore endellionite) [Named after the French mineralogist, J.L. de Bournon] (ICSD 14303 and PDF 42-1407)

Orthorhombic a = 816 pm b = 870 pm c = 780 pm (Z = 4)

Monoclinic a = 215.6 pm b = 235.1 pm c = 80.9 pm 100.8° (Z = 8) S.G. P2/a P.G. 2/m

Cubic a = 1094 pm (Z = 8) S.G. Fm-3m P.G. 4-32

Monoclinic a = 1185.8 pm b = 1067.4 pm c = 1267.4 pm 106.58° (Z = 4) P.G. 2/m S.G. C2/c

Orthorhombic a = 854 pm b = 854 pm c = 1270 pm (Z = 2) P.G. m2m S.G. Pc2a

Orthorhombic a = 286.8 pm b = 1222.7 pm c = 370 pm (Z = 4) P.G. mmm S.G. A2/mam Lepidocrite type

Biaxial R = 36.0–38.2% α = 1.487 β = 1.546 γ = 1.560 2V = 49°

Biaxial (?) R = 37.0–44.1%

Isotropic R = 21.9%

Biaxial (–) α = 1.447 β = 1.469 γ = 1.472 δ = 0.025 2V = 39–40°

Biaxial (+) α = 1.662 β = 1.647 γ = 1.673 δ = 0.011 2V = 82°

Biaxial (+) α = 1.646–1.650 β = 1.652–1.660 γ = 1.650–1.670 δ = 0.015 2V = 80°

1730– 1900

2950

3440

3 (HV 185– 199)

2.5–3 (HV 157– 183)

5800

6000– 6200

3 6000 (HV 97–105)

2–2.5

7

3.5–4

Habit: tabular, pseudo cubic, cog-wheel. Color: lead gray or black. Diaphaneity: opaque. Luster: metallic. Cleavage: (010) imperfect. Fracture: subconchoidal. Streak: gray.

Habit: prismatic, tabular. Color: purple gray. Luster: metallic. Diaphaneity: opaque. Streak: gray. Fracture: conchoidal. Cleavage: {100}. Electrical resistivity 2000 to 40,000 Ω.m.

Habit: cubic euhedral crystals, tarnishes to purple. Color: bronze. Luster: metallic. Diaphaneity: opaque. Cleavage: {111}. Twinning: {111}. Fracture: conchoidal. Others: p-type semconductor with ΔEg = 0.1 eV due to covellite or digenite inclusions; electrical resistivity 3 to 570 Ω.m.

Habit: prismatic, tabular, massive. Color: colorless, white, gray, or greenish white. Diaphaneity: translucent to opaque. Luster: resinous, greasy. Streak: white. Cleavage: (100) perfect, (110) perfect. Fracture: conchoidal, brittle. Sweet alkaline taste. Easy fusible acting as flux for several metal oxides (m.p. 75°C).

Habit: pseudocubic. Color: white, yellow. Diaphaneity: transparent to translucent. Luster: vitreous. Streak: white. Cleavage: (111). Fracture: conchoidal. pyroelectric.

Habit: flaky, nodular, pistolitic, massive. Color: white, light yellow, or yellowish green. Diaphaneity: transparent to translucent. Luster: vitreous, pearly. Streak: white. Cleavage: perfect (010). Fracture: brittle. Occurrence: subtropical areas, lateritic soils develop on Al-bearing igneous rocks, major constituent of most bauxite ore.

Mineral and Gemstone Properties Table 811

Minerals, Ores and Gemstones

12

Monoclinic a = 981pm b = 377 pm c = 693 pm β = 118.97° (Z = 2) S.G. C2/m Brannerite-Thorutite series

Tetragonal a = 940.8 pm c = 1866.8 pm S.G. I41/acd P.G. 422 (Z = 8)

(U, Ca,Ce)(Ti,Fe)2O6 M = 354.80 33.54 wt.% U 3.39 wt.% Ca 7.90 wt.% Ce 20.24 wt.% Ti 7.87 wt.% Fe 27.06 wt.% O Coordinence Ti(6)

MnIIMnIII6SiO12=Mn7SiO12 M = 604.645 63.60 wt.% Mn 4.63 wt.% Si 31.77 wt.% O (Silicates)

Cu4(SO4)(OH)6 M = 452.29164 56.20 wt.% Cu 1.34 wt.% H 7.09 wt.% S 35.37 wt.% O (Sulfates, chromates, molybdates, and tungstates)

AgBr M = 187.7722 57.45 wt.% Ag 42.55 wt.% Br (Halides)

BeO M = 25.011582 36.03 wt.% Be

Brannerite (syn., orthobrannerite) [Named after the American geologist, G. Branner (1850–1922)] (ICSD 201342 and PDF 12-477)

Braunite [Named in 1831 after K.W. Braun (1790–1872)] (ICSD 4347 and PDF 41-1367)

Brochantite (syn., Blanchardite) [Named after the French geologist and mineralogist, A.J.M. Brochant de Villiers) (ICSD 64688 and PDF 43-1488)

Bromargyrite [7785-23-1] (syn., Bromyrite) [from Greek, bromos, stench and argyros, silver] (ICSD 65061 and PDF 6-438)

Bromellite [1304-56-9] [Named after the Swedish physician

Hexagonal a = 269.83 pm c = 436.76 pm

Cubic a = 577.45 pm (Z = 4) Rock salt type

Monoclinic Prismatic (2/m) a = 1306.7 pm b = 985.0 pm c = 602.2 pm (Z = 4)

Uniaxial (+) ε = 1.733 ω = 1.705–1.719

Isotropic nD = 2.25

Biaxial (–) α = 1.728 β = 1.771 γ = 1.8 δ = 0.072 2V = 72° Dispersion weak

Uniaxial () R = 18.4–19.7

Isotropic when metamict nD = 2.33 R = 14.8%

9

1.5–2

3.5–4

6–6.5 (HV 920– 1196)

4.5–5.5 (HV 710– 730)

3.5

Mohs hardness (/HM) (Vickers)

Biaxial

Optical properties

3017 (3044)

5800

3970

4800 (4860)

4500– 6350 (6370)

2720– 2734 (2720)

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 885 pm b = 663 pm c = 516 pm 90.15° (Z = 2) S.G. P21/m P.G. 2/m

Na3Mg(PO4)(CO3) M = 248.25 27.78 wt.% Na 9.79 wt.% Mg 12.48 wt.% P 4.84 wt.% C 45.11 wt.% O (Nitrates, carbonates, and borates)

Bradleyite [Named after American geologist Wilmot Hyde Bradley (1899–1979)]

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: prismatic, pyramidal hemimorphic crystals. Color: white to cream. Diaphaneity: transparent. Luster: vitreous. Streak: n.a. Fracture: n.a. Cleavage:{1010}. Others: pyroelectric, fluorescence. Occurrence: in calcite veins and skarns.

Color: bright yellow or amber yellow. Luster: adamantine-greasy. Diaphaneity: transparent to translucent. Occurrence: oxidized portions of silver deposits.

Habit: acicular, prismatic, druse. Color: emerald green or blackish green. Luster: vitreous, pearly. Diaphaneity: transparent to translucent. Streak: pale green. Cleavage: [100] perfect. Fracture: conchoidal, brittle. Occurrence: secondary, formed in arid climates or in rapidly oxidizing copper sulfide deposits.

Habit: pyramidal crystals also dense granular. Color: brownish black to steel-gray. Diaphaneity: opaque. Luster: submetallic. Streak: brownish black to steel gray. Fracture: uneven to conchoidal. Cleavage: (112) perfect. Twinning: (112). Other: weakly ferromagnetic. Chemical: soluble in HCl with evolution of nascent chlorine gas leaving a gelatinous silica residue. Occurrence: product of weathering occuring along with pyrolusite and psilomelane (romanechite) in manganese ore deposits.

Habit: prismatic crystals, metamict. Color: brown, brown green, olive green, black. Diaphaneity: opaque to translucent. Luster: adamantine, resinous. Fracture: conchoidal. Streak: dark greenish brown. Insoluble in cold H2SO4 or HCl but dissolves in mixture of H2SO4 and H3PO4. Strongly radioactive.

Habit: rare minute crystals, extremely fined grained masses. Color: light gray. Diaphaneity: translucent. Luster: vitreous. Soluble in water and in sodium phosphate. Occurrence: oil shales.

Other relevant mineralogical, physical, and chemical properties with occurrence

812 Minerals, Ores and Gemstones

63.97 wt.% O Coordinence Be(4)

TiO2 M = 79.8788 59.94 wt.% Ti 40.06 wt.% O Coordinence Ti(6) (Oxides and hydroxides)

Mg(OH)2 M = 58.31974 Coordinence Mg(6) (Oxides and hydroxides)

NiO M = 74.6928 78.58 wt.% Ni 21.42 wt.% O (Oxides and hydroxides) Coordinence Ni(6)

(Ca,Na)(Si,Al)4O8 An80-Ab20 M = 275.01042 1.67 wt.% Na 11.66 wt.% Ca 17.66 wt.% Al 22.47 wt.% Si 46.54 wt.% O (Tectosilicates, framework)

AuTe2 M = 452.17 56.44 wt.% Te 43.56 wt.% Au (Sulfides and sulfosalts)

and mineralogist Magnus von Bromell (1679–1731)] (ICSD 62726 and PDF 35-818)

Brookite [12188-41-9] [Named after the English mineralogist, Henry James Brooke (1771–1857)] (ICSD 36408 and PDF 29-1360)

Brucite [1309-42-8] [Named after the American mineralogist, Archibald Bruce (1777–1818)] (ICSD 64722 and PDF 7-239)

Bunsenite [1313-99-1] [Named after the German chemist and spectroscopist Robert Wilhelm Bunsen (1811–1899)] (ICSD 9866 and PDF 4-835)

Bytownite [Named after Bytown, ancient name of Ottawa, Ontario, Canada] (ICSD 34791 and PDF 41-1481)

Calaverite [Named after Staislaus mine, Carson Hill, Calaveras Co. California) (ICSD 64681 and PDF 7-344)

Monoclinic a = 718 pm b = 440 pm c = 507 pm 90°13' C34, mC6 (Z = 2) P.G. 2/m S.G. C2/m

Triclinic a = 817 pm b = 1285 pm c = 1316 pm (Z = 7) P.G. 1

Cubic a = 417.69 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 432 Rock salt type Periclase group

Trigonal (Hexagonal) a = 314.7 pm c = 476.9 pm C6, hP3 (Z = 1) P.G. 32 S.G. P-3m1 CdI2 type

Orthorhombic a = 545.6 pm b = 918.2 pm c = 514.3 pm C2I, oP24 (Z = 8) P.G. mmm S.G. Pbca Brookite type

B4, hP4 (Z = 2) S.G. P63mc P.G. 6mm Wurtzite type

Biaxial R = 63.2%

Biaxial (+/–) α = 1.563–1.572 β = 1.568–1.5784 γ = 1.573–1.583 δ = 0.010–0.011 2V = 80–88

Isotropic nD = 2.37

Uniaxial (+) ε = 1.560–1.590 ω = 1.580–1.600 δ = 0.012–0.020 Dispersion strong

Biaxal (+) α = 2.5831–2.584 β = 2.5843–2.586 γ = 2.7004–2.741 δ = 0.117–0.158 2V = 0–30° Dispersion strong

δ = 0.014

2.5

7

5.5

2.5

5.5–6.0

9040

2710

6898 (6806)

2390

4100– 4140 (4130)

Habit: striated, massive, crystalline, fine. Color: white. Luster: metallic. Diaphaneity: opaque.

Habit: granular, euhedral, striated. Color: white or gray. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy). Cleavage: (001) perfect, (010) good. Fracture: uneven. Streak: white. Occurrence: magmatic and metamorphic rocks.

Habit: octahedral crystals. Color: dark pistachio green. Luster: vitreous. Diaphaneity: transparent. Streak: brownish black. Clivage: unknown. Fracture: uneven. Chemical: soluble with difficulty in strong mineral acids. Occurrence: found in the oxidized zone of hydrothermal nickel–uranium veins along with nickel and cobalt arsenates.

Habit: tabulated, foliated. Color: white, green. Diaphaneity: transparent to translucent. Luster: pearly, vitreous. Streak: white. Fracture: sectile. Cleavage: (001). Melting point: 350°C.

Habit: tabular. Color: reddish brown, yellowish brown, dark brown, black. Diaphaneity: transparent, translucent, opaque. Luster: submetallic, adamantine. Streak: yellowish white. Fracture: subconchoidal. Cleavage: (120). Chemical: insoluble in water, slightly soluble in HCl, HNO3, soluble in HF and in hot H2SO4 or KHSO4. Attacked by molten Na2CO3. Other properties: dielectric constant of 78.

Mineral and Gemstone Properties Table 813

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

CaCO3 M = 100.0872 40.04 wt.% Ca 12.00 wt.% C 47.96 wt.% O Traces of Mg, Fe, Mn, and Zn Coordinence Ca(6), C(3) (Nitrates, carbonates, and borates)

Hg2Cl2 M = 472.0854 84.98 wt.% Hg 15.02 wt.% Cl Coordinence Hg(5) (Halides)

KMgCl3·6H2O M = 277.85308 14.07 wt.% K 8.75 wt.% Mg 4.35 wt.% H 38.28 wt.% Cl 34.55 wt.% O (Halides) Coordinence K(6), Mg(6)

K2(UO2)2(VO4)2·3H2O M = 902.17604 8.67 wt.% K 52.77 wt.% U 11.29 wt.% V 0.67 wt.% H 26.60 wt.% O Coordinence V(5), V(4), K(9), U(2) (Uranylphosphates and uranylvanadates)

SnO2 M = 150.7088 78.77 wt.% Sn 21.23 wt.% O Coordinence Sn(6) (Oxides and hydroxides)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Calcite [471-34-1] (syn., travertine, nicols, calcareous spar) [Named from the Latin, calx, meaning quicklime) (ICSD 73446 and PDF 5-586)

Calomel [10112-91-1] (syn., horn quicksilver) [from the Greek, kalos, beautiful, and melas, black] (ICSD 64683 and PDF 26-312)

Carnallite [Named after the German mining engineer, Rudolph von Carnall (1804–1874)] (ICSD 64691 and PDF 24-869)

Carnotite [Named after the French chemist, M.A. Carnot] (ICSD 15839 and PDF 11-338)

Cassiterite [18282-10-5] (syn., tin ore, wood tin) [from the Greek kassiteros, tin] (ICSD 39173 and PDF 41-1445)

Table 12.23. (continued)

Tetragonal a = 473.8 pm c = 318.8 pm C4, tP6 (Z = 2) P.G. 422 S.G. P4/mnm Rutile type

Orthorhombic a = 1047 pm b = 841 pm c = 691 pm (Z = 1) P.G. 2/m S.G. P21/a

Orthorhombic a = 956 pm b = 1605 pm c = 2256 pm (Z = 12) P.G. mmm S.G. Pban

Tetragonal a = 447.8 pm c = 1091.0 pm (Z = 4) S.G. I4/mmm P.G. 4/mmm

Uniaxial (+) ε = 1.990–2.010 ω = 2.093–2.100 δ = 0.096–0.098 Dispersion strong R = 12.0%

Biaxial (–) α = 1.75 β = 1.92 γ = 1.95 δ = 0.20 2V = 38–44°

Biaxial (+) α = 1.467 β = 1.474 γ = 1.496 δ = 0.029 2V = 70°

Uniaxial (+) ω = 1.973 ε = 2.656 δ = 0.683

6–7 (HV 1027– 1075)

1.5–2

2.5

1.5–2

3.0 (HV 110)

Mohs hardness (/HM) (Vickers)

Uniaxial (–) ε = 1.486–1.550 ω = 1.658–1.740 δ = 0.172–0.190 Dispersion strong

Optical properties

6994

4200

1602

6480

2715– 2940

Density (ρ/kg.m–3) (calc.)

Trigonal (Rhombohedral) a = 498.9 pm c = 1706.2 pm (Z = 6) P.G. -32/m S.G. R-3c Calcite type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: acicular, prismatic, massive, botryroidal, fibrous ‘wood tin’. Color: yellow, reddish brown, brownish black, or white. Diaphaneity: transparent to opaque. Luster: adamantine. Streak: brownish white. Fracture: subconchoidal, irregular. Cleavage: [100] perfect, [110] indistinct. Twinning: {101}. Occurrence: granite, pegmatites and alluvial placer deposits. Melting point: 1630°C.

Habit: earthy, encrustations, platy. Color: canary yellow or greenish yellow. Luster: dull, earthy. Diaphaneity: translucent. Streak: light yellow. Cleavage: (001) perfect. Fracture: uneven. Radioactive.

Habit: massive, granular, pseudo hexagonal, fibrous. Color: colorless, milky white, reddish white, or yellowish white. Luster: greasy (i.e., oily), vitreous. Luminescence: fluorescent. Streak: white, red. Cleavage: none. Fracture: conchoidal. Occurrence: marine evaporites.

Habit: tabular, pyramidal, prismatic, earthy. Color: white, yellowish gray, gray, yellowish white, or brown. Luster: adamantine, resinous. Luminescence: fluorescent. Diaphaneity: translucent to subtranslucent. Streak: pale yellowish white. Cleavage: [100], [011]. Twinning: [110]. Fracture: conchoidal, sectile. Occurrence: oxidized mercury deposits. Easy fusible (m.p. 525°C). Insoluble in water.

Habit: crystalline, coarse, stalactitic, massive. Color: colorless, white, pink, yellow, or brown. Luster: vitreous (i.e., glassy). Diaphaneity: transparent, translucent, to opaque. Streak: white. Cleavage: (1011) perfect. Twinning: {0001}, {1014}, {0118}. Fracture: brittle, conchoidal. Luminescence: fluorescent. Chemical: decomposed at 1330°C giving CaO and readily dissolved in diluted acids with evolution of carbon dioxide. Alizarine’s spot test: a soln. of 0.5 wt.% Alizarine S in dil. HCl colors the calcite crystal in deep pink, while dolomite, ankerite and magnesite remain colorless. Occurrence: sedimentary rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

814 Minerals, Ores and Gemstones

SrSO4 M = 183.6836 47.70 wt.% Sr 17.46 wt.% S 34.84 wt.% O Coordinence Sr(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Ba[Si2Al2O8] M = 375.46 36.58 wt.% Ba 14.37 wt.% A 14.96 wt.% Si 34.09 wt.% O (Tectosilicates, framework)

PbCO3 M = 267.2092 77.54 wt.% Pb 4.49 wt.% C 17.96 wt.% O Coordinence Pb(6), C(3) (Nitrates, carbonates, and borates)

Sb2O4 M = 307.4976 79.19 wt.% Sb 20.81 wt.% O (Oxides and hydroxides)

CaSi4Al2O12.6H2O Coordinence Ca(7), Si(4), and Al(4) (Tectosilicates, framework)

CuSO4·5H2O M = 249.686 25.45 wt.% Cu 4.04 wt.% H 12.84 wt.% S 57.67 wt.% O Coordinence Cu(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Celestite [7759-02-6] (syn., celestine) [from the Latin, caelestis, meaning celestial] (ICSD 28055 and PDF 5-593)

Celsian [Named after the Swedish astronomer and natural scientist, A. Celsius] (ICSD 25836 and PDF 38-1450)

Cerussite [598-63-0] (syn., white lead ore) [from the Latin, cerussa, meaning white lead] (ICSD 36558 and PDF 47-1734)

Cervantite [Named after the locality Cervantes, Spain] (ICSD 63271 and PDF 11-6945)

Chabasite [Named after the Greek, chabazios, an ancient name of a stone celebrated in a poem ascribed to Orpheus] (ICSD 31263 and PDF 34-137)

Chalcanthite [7758-99-8] (syn., copper vitriol, blue vitriol) [Named from the Greek, chalkos, copper, and, anthos, flower] (ICSD 20657 and PDF 11-646)

Triclinic a = 610.45 pm b = 1072.0 pm c = 594.9 pm α = 97.57° β = 107.28° γ = 77.43° (Z = 2) P.G. 1 S.G. P1

Trigonal (Rhombohedral) a = 1317 pm c = 1506 pm (Z = 6) P.G. 32/m S.G. R32/m Zeolite group

Orthorhombic a = 543pm b = 481 pm c = 1176 pm (Z = 4) P.G. mm2 S.G. Pbn21

Orthorhombic a = 615.2 pm b = 843.6 pm c = 519.5 pm (Z = 4) P.G. mmm S.G. Pmcn Aragonite type

Monoclinic a = 863pm b = 1305 pm c = 1441 pm β = 115.2° (Z = 8) P.G. 2/m S.G. I21/c Feldspars group

Orthorhombic a = 835.9 pm b = 535.2 pm c = 686.6 pm (Z = 4) P.G. mmm S.G. P21nma Barite type

Biaxial (–) α = 1.514 β = 1.537 γ = 1.543 δ = 0.029 2V = 56° Dispersion none

Uniaxial (–) ε = 1.481 ω = 1.484 δ = 0.003

Biaxial α = 2.0 β = 2.076 γ = 2.1 δ = 0.274

Biaxial (–) α = 1.804 β = 2.076 γ = 2.079 δ = 0.274 2V = 8–14° Dispersion strong

Biaxial (+) α = 1.58–1.584 β = 1.585–1.587 γ = 1.594–1.596 δ = 0.012–0.014 2V = 86–90°

Biaxial (+) α = 1.622 β = 1.624 γ = 1.631 δ = 0.009 2V = 51° Dispersion moderate

2.5

4–5

4–5

3–3.5

6–6.5

3–3.5

2120– 2300

2100

4000– 6600 (6641)

6580

3250

3970

Habit: tabular, encrustations, stalactitic, reniform. Color: berlin blue, sky blue, or greenish blue. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Streak: white. Fracture: conchoidal. Cleavage: (110) good, (111) indistinct. Others: loss two water molecules at 27°C giving CuSO4.3H2O, that loss two additional water molecules at 93°C yielding the pale blue CuSO4.H2O, that finally yields the anhydrous white CuSO4 at 110°C. Finally, it decomposes into black CuO and SO3 fumes at 702°C. Occurrence: secondary, formed in arid climates or in rapidly oxidizing copper deposits.

Habit: euhedral. Luster: vitreous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (101) perfect. Twinning: {100}, and {001}. Fracture: uneven.

Habit: reniform, earthy, acicular. Color: yellow, yellowish orange, white, or cream. Luster: vitreous-pearly. Diaphaneity: transparent to translucent. Streak: light yellow. Cleavage: [001] perfect. Fracture: conchoidal. Occurrence: alteration product of stibnite.

Habit: reticulate, tabular, massive, granular, crystalline, clustered. Color: colorless, gray, smoky gray, or grayish white. Diaphaneity: transparent to translucent. Luster: adamantine. Streak: white. Cleavage: (110) distinct, (021) distinct. Twinning: {110}, {130}. Fracture: conchoidal, brittle. Chemical: decomposed at 315°C giving off PbO and CO2. Soluble in strong mineral acids with evolution of CO2

Habit: massive, granular, euhedral. Color: white or yellow. Diaphaneity: transparent. Luster: vitreous (i.e., glassy). Cleavage: [001] perfect, [010] good. Fracture: brittle, uneven. Streak: white. Occurrence: contact metamorphic rocks with significant barium.

Habit: tabular, radiated fibrous, crystalline, massive, granular. Color: colorless, bluish white, yellowish white, or reddish white. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (001) perfect, (210) good. Fracture: uneven to conchoidal, brittle. Chemical: decomposed at 1607°C. Occurrence: sedimentary rocks.

Mineral and Gemstone Properties Table 815

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Cu2S M = 159.158 79.85 wt.% Cu 20.15 wt.% S (Sulfides and sulfosalts)

CuFeS2 M = 183.525 30.43 wt.% Fe 34.63 wt.% Cu 34.94 wt.% S Traces of Ag, Au, Pt, Co, Ni, Pb, Sn, Zn, As, and Se (Sulfides and sulfosalts) Coordinence Cu(4), Fe(4)

(Ni,Co)As3

AgCl M = 143.321 75.26 wt.% Ag 24.74 wt.% Cl Coordinence Ag(6) (Halides)

(Mg,Fe, Al)6(Si,Al)4O10(OH)8 Coordinence Mg(6), Fe(6), Si(4), Al(4) (Phyllosilicates, layered)

FeAl4O[SiO4]2(OH)4 26–28 wt.% FeO 2–4 wt.% MgO 39–41 wt.% Al2O3 24–26 wt.% SiO2 2–7 wt.% H2O Coordinence Fe(6), Mg(6), Al(6), Si(4) (Phyllosilicates, layered)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Chalcocite [22205-45-4] [Named from the Greek, chalkos, copper] (ICSD 100333 and PDF 33-490)

Chalcopyrite [1308-56-1] [Named from the Greek, chalkos, copper, hence copper pyrite] (ICSD 2518 and PDF 35-752)

Chloanthite (syn., white nickel) [Named from Greek, chloantos, greenish] (ICSD 2518 and PDF 35-752)

Chlorargyrite [7783-90-6] [Named after Greek, chloros, pale green, and Latin, argentum, silver] (ICSD 64734 and PDF 31-1238)

Chlorite (1M) (syn., alushite, tosudite) [from the Greek, chloros, green]

Chloritoid (2M) (syn., ottrelite: contains MnO) [from its similarity with chlorite] (ICSD 1850 and PDF 14-62)

Table 12.23. (continued)

Monoclinic a = 948 pm b = 548 pm c = 1818 pm β = 101.77° (Z = 8) P.G. 2/m S.G. C2/c

Monoclinic a = 537 pm b = 930 pm c = 1425 pm β = 101.77° (Z = 2)

Cubic a = 554.91 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4-32 Rock salt type

Cubic 432

Tetragonal a = 529.88 pm c = 1043.4 pm E11, tI16 (Z = 4) S.G. I42d P.G. 42m Chalcopyrite type

2.5

5.5

3.5–4 (HV 186– 219)

Biaxial (+) α = 1.713–1.730 β = 1.719–1.734 γ = 1.723–1.740 2V = 45–68° O.A.P. ⊥ (010) Dispersion strong

6.5 (HV 178– 218)

Biaxial (–) 2–3 α = 1.56–1.60 β = 1.57–1.61 γ = 1.58–1.61 2V = 0–40° δ = 0.006–0.020 Dispersion strong

Isotropic nD = 2.071

Isotropic

Uniaxial R = 42.0–46.1%

2.5–3 (HV 68–98)

Mohs hardness (/HM) (Vickers)

Biaxial R = 32.2%

Optical properties

3510– 3800

3000

5550

6400– 6600

4190

5800

Density (ρ/kg.m–3) (calc.)

Orthorhombic a = 1188.1 pm b = 273.23 pm c = 1349.1 pm (Z = 96) Cuprite type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: similar to that of micas, lamellar. Color: dark green, colorless to green in thin section. Luster: vitreous (i.e., glassy) and submetallic for dark varieties. Diaphaneity: transparent to translucent. Twinning: {001} simple, lamellar {221}, common. Fracture: uneven in steps, brittle. Cleavage: (001) perfect. Chemical: insol. In HCl but attacked by H2SO4. Slightly fusible on thin edges. Dielectric constant: 6.9. Deposits: metamorphic rocks, weathering of Al-rich sedimentary rocks.

Habit: foliated, scaly, lamellar. Color: green. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Twinning: (001) simple, lamellar, common. Fracture: uneven in steps, brittle. Cleavage: (001) perfect. Twinning: [310]. Deposits: metamorphic rocks, weathering of Al-rich sedimentary rocks.

Habit: massive, cubic euhedral crystals. Color: colorless gray, violet tarnish. Luster: resinous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: [100]. Fracture: subconchoidal, sectile.

Habit: massive, granular, euhedral crystals. Color: tin white or dark gray. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Fracture: uneven.

Habit: rare tetrahedral disphenoidal crystals, botryoidal, striated, druse, usually zoned. Color: brass yellow or honey yellow. Luster: metallic. Diaphaneity: opaque. Streak: greenish black. Cleavage: {011}, {111}. Fracture: uneven, brittle. Twinning: {112}. Chemical: attacked by HNO3, corroded by a mixture of KOH + KMnO4. Occurrence: veins and disseminated in metamorphic and igneous rocks (e.g., gabbros, norites). Others: n-type semiconductor with ΔEg = 0.01 eV–0.03 eV. Electrical resistivity 150 to 9000 μΩ.cm., melting point 950°C.

Habit: massive, granular, euhedral crystals. Color: black or iron black. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Cleavage: {110} indistinct. Twinning: {110}, {032}, {112}. Fracture: Conchoidal. Occurrence: secondary mineral in/near the oxidized zone of copper sulfide ore deposits. Others: p-type semiconductor with ΔEg = 0.06 eV–0.13 eV. Electrical resistivity 80 to 100 μΩ.cm., melting point of 1100°C.

Other relevant mineralogical, physical, and chemical properties with occurrence

816 Minerals, Ores and Gemstones

Mg(OH,F)2.2Mg2[SiO4] M = 382.12 23.85 wt.% Mg 18.27 wt.% Fe 14.70 wt.% Si 0.13 wt.% H 35.59 wt.% O 7.46 wt.% F Coordinence Mg(6), Si(4) (Nesosilicates)

FeCr2O4 M = 223.8348 46.46 wt.% Cr 24.95 wt.% Fe 28.59 wt.% O Coordinence Fe(4), Cr(6) (Oxides and hydroxides)

BeAl2O4 M = 126.97286 7.10 wt.% Be 42.50 wt.% Al 50.40 wt.% O Coordinence Al(6), Be(4) (Oxides and hydroxides)

(Cu,Al)2H2Si2O5(OH)4·nH2O M = 328.42 (n = 0.25) 2.05 wt.% Al 33.86 wt.% Cu 17.10 wt.% S 1.92 wt.% H 45.06 wt.% O (Cyclosilicates, ring)

Mg6Si4O10(OH)8 M = 554.22 26.31 wt.% Mg 20.27 wt.% Si 1.45 wt.% H 51.96 wt.% O Phyllosilicates

HgS M = 232.656 86.22 wt.% Hg 13.78 wt.% S (Sulfides and sulfosalts) Coordinence Hg(6)

Chondrodite [Named from the Greek, chondros, grain] (ICSD 15180 and PDF 12-527)

Chromite [1308-31-2] (syn., chromic iron, chrome iron ore) [Named from the Greek, chroma, color for the brilliant hues of its compounds] (ICSD 20819 and PDF 34-140)

Chrysoberyl [12004-06-7] (syn., alexandrite: green) [from the Greek, chrysos, golden and the mineral beryl and Czar Alexander II (1818–1881) of Russia] (ICSD 62501 and PDF 11-448)

Chrysocolla (syn., bisbeeite) [Named from the Greek, chrysos, gold, and kolla, glue in allusion to the name of the material used to solder gold)

Chrysotile [Named from Greek, chrysotos, guilded in reference to its color and nature]

Cinnabar [1344-48-5] [from the Latin, cinnabaris] (ICSD 70054 and PDF 42-1408)

Trigonal (Hexagonal) a = 414.9 pm c = 949.5 pm B9, hP6 (Z = 3) S.G. P3121 P.G. 32 Cinnabar type

Monoclinic a = 531.3 pm b = 912 pm c = 1464 pm β = 93.167° (Z = 4) P.G. 2/m S.G. A2/m Kaolinite-serpentinite group

Monoclinic a = 570 pm b = 890 pm c = 670 pm β = 93.167° (Z = 1)

Orthorhombic a = 547.56 pm b = 940.41 pm c = 442.67 pm (Z = 4) P.G. mmm S.G. P21/bnm Olivine type

Cubic a = 839.40 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type (Chromite Series)

Monoclinic a = 789 pm b = 474.3 pm c = 1029 pm 109.03° (Z = 2) P.G. 2/m S.G. P21/b (Humite group)

Uniaxial (+) ω = 2.814 ε = 3.143 δ = 0.351 R = 26.3%

Biaxial (–) α = 1.545–1.569 β = 1.546–1.569 γ = 1.553–1.570 δ = 0.0010 2V = 50°

Biaxial (–) α = 1.575 β = 1.587 γ = 1.600 δ = 0.025

Biaxial (+) α = 1.747 β = 1.748 γ = 1.757 δ = 0.010 2V = 45° Dispersion none

Isotropic nD = 2.16 R = 14.1%

Biaxial α = 1.592–1.615 β = 1.602–1.627 γ = 1.621–1.646 δ = 0.028–0.038 2V = 71–85° O.A.P (010)

2–2.5

2.5

2.5–3.5

8.5

5.5 (HV 1195– 1210)

6.5

8170

2530– 2550 (2600)

2200– 2400

3699

5090

3150– 3180

Habit: druse, disseminated, tabular, massive. Color: intense red, brownish red, or gray. Diaphaneity: transparent, translucent to opaque. Luster: adamantine. Streak: scarlet, bright red. Cleavage: {1010} perfect. Twinning: {0001}. Fracture: subconchoidal, brittle, sectile. Decomposed at 386°C in HgO.

Habit: acicular crystals making fibrous aggragates. Color: green to pale green. Diaphaneity: translucent. Luster: silky. Streak: white. Others: infusible and insoluble in HCl. Occurrence: metamorphic rocks.

Habit: botryoidal, earthy, stalactitic. Color: green, bluish green, blue, blackish blue, or brown. Diaphaneity: translucent to opaque. Luster: vitreous, dull. Cleavage: none. Fracture: sectile. Streak: light green. Occurrence: mineral of secondary origin commonly associated with other secondary copper minerals.

Habit: twinning, prismatic, tabular, striated (001). Color: green, white, brown, or yellow. Streak: white. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Cleavage: (110) distinct, (010) imperfect. Twinning: {031}. Fracture: brittle. Occurrence: granitic pegmatite dikes.

Habit: massive, granular, nuggets. Color: black or brownish black. Luster: metallic. Diaphaneity: opaque. Streak: brown. Cleavage: none. Twinning: {111}. Fracture: uneven to conchoidal. Others: weakly magnetic. Thermal conductivity of 1.73–2 W.m–1K–1

Habit: massive. Color: brown, yellow, orange, red, colorless. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Cleavage: (100) poor. Twinning: {001}. Fracture: uneven, brittle. Chemical: attacked by strong mineral acids giving a silica gel. Occurrence: dolomites, limestones, skarns.

Mineral and Gemstone Properties Table 817

Minerals, Ores and Gemstones

12

Cubic a = 557 pm F01, cP12 (Z = 4) S.G. P213 P.G. 23 NiSbS type

Monoclinic a = 715.2 pm b = 1237.9 pm c = 717.0 pm (Z = 16) P.G. 2/m S.G. C2/c

Ca2Al.Al2O(OH)[SiO4][Si2O7] M = 427.37572 18.76 wt.% Ca 12.63 wt.% Al 19.71 wt.% Si 0.24 wt.% H 48.67 wt.% O Traces of Fe(III) Coordinence Ca(7), Al(6), Si(4) (Sorosilicates and nesosilicates)

CoAsS M = 197.9868 29.77 wt.% Co 37.84 wt.% As 32.39 wt.% S (Sulfides and sulfosalts) Coordinence Co(6)

α-SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

U[SiO4].nH2O (Nesosilicates) Thorium and rare earths can substitute to uranium

Clinozoïsite [Named after the Austrian natural scientist, S. Von Zoïs, and clinos for its monoclinic lattice structure] (ICSD 66923 and PDF 44-1400)

Cobaltite [12254-82-9] [from the German, Kobold, underground spirit, or goblin, in allusion to the refusal of cobaltiferous ores to smelt properly, hence bewitched] (ICSD 31189 and PDF 42-1345)

Coesite [Named after the American chemist, Loring Coes, Jr. (1915–1973), from Norton Company, who first synthesized the mineral] (ICSD 18112 and PDF 14-654)

Coffinite [Named after the American mineralogist, Reuben Clare Coffin (1886–1972)] (ICSD 15484 and PDF 11-420)

Tetragonal a = 697.9 pm c = 625.3 pm I41/amd (Z = 4) P.G. 4/mmm S.G. I41/amd Zircon type

Monoclinic a = 888.7 pm b = 558.1 pm c = 1014.0 pm 115°93 (Z = 2) P.G. 2/m S.G. P21/m (Epidote group)

Uniaxial (+/–) Metamict R = 9.9%

Biaxial (+) α = 1.590 β = 1.600 γ = 1.600 δ = 0.010 2V = 64°

Isotropic R = 52.7%

Biaxial (+) α = 1.670–1.715 β = 1.674–1.725 γ = 1.690–1.734 δ = 0.005–0.015 2V = 14–90° Dispersion strong

5–6 (HV 236– 333)

7–8

5.5 (HV 1176– 1226)

6–6.5 (HV 680)

6

Mohs hardness (/HM) (Vickers)

Biaxial () α = 1.629–1.638 β = 1.641–1.643 γ = 1.662–1.674 δ = 0.028–0.041 2V = 65–84° O.A.P (100)

Optical properties

3500– 5100 (6900)

2930

6330

3120– 3380

3210– 3350

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 475 pm b = 1027 pm c = 1368 pm 100.83° (Z = 2) P.G. 2/m S.G. P21/b (Humite group)

Mg(OH,F)2.2Mg2[SiO4] Coordinence Mg(6), Si(4) (Nesosilicates)

Clinohumite [Named after the British mineralogist Sir Abraham Hume, and clinos, for its monoclinic crystal system] (ICSD 70054 and PDF 42-1408)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: aggregates of micrometric grains and masses rarely prismatic crystals. Usually metamict due its radioctivity. Color: black but yellow to brown in thin sections. Diaphaneity: opaque to transucent in thin sections. Luster: dull to adamantine. Streak: brownish-black. Radioactive. Occurrence: in sedimentary rocks from the weathering of uraninite in a supergene, reducing and alkaline environment.

Habit: tabular, high pressure. Color: colorless. Luster: vitreous (i.e., glassy). Streak: white. Fracture: conchoidal. Twinning: {011}, {021}. Diaphaneity: transparent to translucent. Chemical: resistant to strong mineral acids, attacked by HF and molten alkali-metal hydroxides.

Habit: massive, granular, faces striated. Color: reddish silver white, violet steel gray, or black. Diaphaneity: opaque. Luster: metallic. Streak: grayish black Cleavage: {100} good, {010} good, {001} good. Fracture: uneven, brittle. Electrical resistivity 6.5 to 130 mΩ.m.

Habit: prismatic according to b, striated, columnar. Color: pale-yellow, cream yellow, pink, greenish, colorless. Diaphaneity: transparent to opaque. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (001) perfect. Twinning: {100}. Fracture: uneven. Chemical: insoluble in HCl. Other: dielectric constant 8.51. Occurrence: regional metamorphic and pegmatite rocks.

Habit: massive. Color: brown, yellow, orange, red, colorless. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Cleavage: (100) poor. Twinning: {010}. Fracture: uneven, brittle. Chemical: attacked by strong mineral acids giving a silica gel. Deposits: dolomites, limestones, skarns.

Other relevant mineralogical, physical, and chemical properties with occurrence

818 Minerals, Ores and Gemstones

Orthorhombic a = 1713 pm b = 980 pm c = 935 pm (Z = 4) P.G. 2/mmm S.G. C2/ccm

Trigonal (Rhombohedral) a = 513.29 pm 55°17' D51, hR10 (Z = 2) S.G. R3c P.G. 32/m Corundum type

(Fe,Mn)(Nb,Ta)2O6 Coordinence Fe(6), Mn(6), Nb(6), Ta(6) (Oxides and hydroxides)

Cu M = 63.546 Coordinence Cu(12) (Native elements)

Mg2Si5Al4O18 M = 584.95 8.31 wt.% Mg 18.45 wt.% Al 24.01 wt.% Si 49.23 wt.% O Coordinence Mg(6), Si(4), Al(4) (Cyclosilicate, ring)

α-Al2O3 M = 101.961 52.93 wt.% Al 47.07 wt.% O (Oxides, and hydroxides) Coordinence Al(6)

PbCl2 M = 278.11 74.50 wt.% Pb 25.50 wt.% Cl (Halides)

Columbite (syn., niobite) [Named after its niobium (columbium) content] (ICSD 31943 and PDF 16-337)

Copper (syn., cuprum) [from the Greek, kyprios, the name of the island of Cyprus, once producing this metal] (ICSD 64699 and PDF 4-836)

Cordierite [Named after the French mining engineer and geologist Pierre Louis A. Cordier (1777–1861)] (ICSD 100250 and PDF 12-303)

Corundum [1344-28-1] (syn., alumina, saphirre: blue, ruby: red) [Named from the Hindi, kurund, or the Tamil, kurundam, name of the mineral] (ICSD 31545 and PDF 43-1484)

Cotunnite [7758-95-4] (syn., plumbous chloride) [Named after the Italian physicist Domenico Cotugno (1736–1822), University of Naples] (ICSD 27736 and PDF 26-1150)

Orthorhombic a = 762.2 pm b = 904.5 pm c = 453.5 pm (Z = 4) P.G. 2/m S.G. A2/m

Cubic a = 361.5 pm A1, cF4 (Z = 4) P.G. m3m S.G. Fm3m Copper type

Orthorhombic a = 510 pm b = 1427 pm c = 574 pm (Z = 2) P.G. mmm S.G. P21bcn

Cubic a = 646.0 pm B3, cF8 (Z = 4) S.G. F43m P.G. 43m Blende type

HgTe M = 328.19 61.12 wt.% Hg 38.88 wt.% Te (Sulfides and sulfosalts)

Coloradoite [Named after its occurrence in Smuggler mine, Boulder, Colorado] (ICSD 31086 and PDF 32-665)

Monoclinic a = 874.3 pm b = 1126.4 pm c = 610.2 pm β = 110.12° (Z = 4) P.G. 2/m S.G. P21/a

Ca2B6O11.5H2O M = 411.09 19.50 wt.% Ca 14.78 wt.% B 2.45 wt.% H 62.27 wt.% O Coordinence Ca(7), B(3, and 4) (Nitrates, carbonates and borates)

Colemanite (syn., neocolmanite) [Named after William Tell Coleman (1824–1893) owner of the Death Valley, California mine where this species was first found] (ICSD 16764 and PDF 33-267)

Biaxial (+) α = 2.199 β = 2.217 γ = 2.260 2V = 67°

Uniaxial (–) ε = 1.765–1.776 ω = 1.757–1.767 δ = 0.008 Dispersion moderate

Biaxial (+/–) α = 1.54 β = 1.55 γ = 1.56 2V = 65–105°

Isotropic nD = 0.641 R = 81.2%

Biaxial (+) α = 2.44 β = 2.32 γ = 2.38 2V = 75°

Isotropic R = 35.4

Biaxial (–) α = 1.586 β = 1.592 γ = 1.614 δ = 0.028 2V = 55–56° Dispersion weak

1.5–2

9 (HV 2000)

7

2.5–3 (HV 120– 143)

5 (HV 724– 882)

2.5 (HV 25–28)

4–4.5

5300– 5800 (5908)

3980– 4020 (3987)

2500– 2800

8935

6000

8070

2420 (2430)

Habit: acicular, massive, granular. Color: white or yellowish white. Luster: adamantine. Diaphaneity: transparent to translucent. Streak: white. Cleavage: [001] perfect. Fracture: conchoidal, sectile. Slightly soluble in hot water releasing Pb2+ that give a bright yellow precipitate of PbCrO4 with K2CrO4. Occurrence: oxidized lead deposits.

Habit: prismatic, crystal often barrel-shaped, also tabular or rhombohedral, Color: colorless, yellow, red, blue green, violet, black. Luster: vitreous to adamantine. Diaphaneity: transparent to opaque. Streak: white. Cleavage: none. Twinning: (101). Parting: (101). Fracture: uneven. Chemical: soluble in strong minerals acids only after fusion with KHSO4 or CaSO4. Melting point: 2054°C. Deposits: metamorphic rocks, sedimentary rocks.

Habit: prismatic. Color: white. Luster: vitreous. Diaphaneity: transparent to translucent. Fracture: even. Cleavage: (010) good, (100) poor. Twinning: {110}, {130}. Occurrence: alumina-rich metamorphic rocks.

Habit: nodular, dendritic, arborescent. Color: light rose, copper red, or brown. Diaphaneity: opaque. Luster: metallic. Streak: rose. Cleavage: none. Fracture: hackly. Chemical: readily dissolved in nitric acid, HNO3, giving a blue solution of Cu(NO3)2 which deposits copper onto a pure zinc rods immersed in the solution. Occurrence: Cap rock of copper sulfide veins and in some types of volcanic rocks.

Habit: prismatic. Color: black, brown. Luster: submetallic. Diaphaneity: translucent to opaque. Fracture: subconchoidal. Cleavage: {010}.

Habit: massive, granular. Color: iron black. Luster: metallic. Diaphaneity: opaque. Streak: black. Fracture: conchoidal.

Habit: blocky, crystalline, coarse, massive, granular. Color: white, yellowish white, gray, or yellowish white. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (010) perfect, (001) distinct. Fracture: subconchoidal, brittle. Diaphaneity: transparent to translucent. Soluble in hot HCl. Occurrence: ancient quaternary lacusterine limestone hosted borate deposits, Furnace Creek Death Valley, California.

Mineral and Gemstone Properties Table 819

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

FeV2O4 M = 221.73 25.19 wt.% Fe 45.95 wt.% V 26.86 wt.% O Coordinence Fe(4), V(6) (Oxides and hydroxides)

CuS M = 95.61 66.46 wt.% Cu 33.54 wt.% S (Sulfides and sulfosalts) Coordinence Cu(3), Cu(4)

SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

PbCrO4 M = 327.1937 63.33 wt.% Pb 15.89 wt.% Cr 19.56 wt.% O Coordinence Pb(6), Cr(4) (Sulfates, chromates, molybdates, and tungstates)

Na3AlF6 M = 209.94126 32.85 wt.% Na 12.85 wt.% Al 54.30 wt.% F (Halides) Coordinence Na(12), Na(6), Al(6)

CuFe2S3 M = 271.44 41.15 wt.% Fe 23.41 wt.% Cu 35.44 wt.% S

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Coulsonite [12418-94-9] [Named after A.L. Coulson] (ICSD 28962 and PDF 15-122)

Covellite [1317-40-4] (syn., covelline) [Named after the Italian mineralogist, Niccolo Covelli (1790–1829)] (ICSD 63327 and PDF 6-464)

Cristobalite (alpha) [14464-46-1] [Named after Cerro San Cristóbal near Pachuca, Mexico] (ICSD 47219 and PDF 39-1425)

Crocoite [7758-97-6] [Named from the Greek, krokos, meaning crocus or saffron] (ICSD 24607 and PDF 8-209)

Cryolite [13775-53-6] [from the Greek, kryos, frost, and lithos, stone for its icy appearance] (ICSD 4029 and PDF 23-772)

Cubanite [Named after Barracanao, Cuba] (ICSD 67529 and PDF 47-1749)

Table 12.23. (continued)

Orthorhombic a = 646 pm b = 1112 pm c = 623 pm E9e, oP24 (Z = 4)

Monoclinic a = 546 pm b = 560 pm c = 778 pm 90.18° (Z = 2) S.G. P21/n P.G. 2/m Prismatic

Monoclinic a = 711 pm b = 741 pm c = 681 pm β = 102.55° (Z = 4) P.G. 2/m S.G. P21/n Crocoite type

Tetragonal a = 497.1 pm c = 691.8 pm (Z = 4) P.G. 422 S.G. P43212

Trigonal (Hexagonal) a = 380 pm c = 1636 pm B18, hP12 (Z = 6) S.G. P63/mmc P.G. 622 Covellite type

Biaxial R = 41.2%

Biaxial (+) α = 1.3385 β = 1.3389 γ = 1.3396 δ = 0.0011 2V = 43°

Biaxial(+) α = 2.31 β = 2.37 γ = 2.66 δ = 0.35 2V = 54°

Uniaxial (–) ε = 1.482 ω = 1.489 δ = 0.007

Uniaxial (+) ε = 1.450 ω = 1.600 R = 14.5%

3.5 (HV 199– 228)

2.5–3

2.5–3

6–7

1.5–2 (HV 69–78)

4.5–5

Mohs hardness (/HM) (Vickers)

Isotropic nD = R = 23%

Optical properties

4100

2970

6000

2330

4600

5170– 5200 (5150)

Density (ρ/kg.m–3) (calc.)

Cubic a = 829.7 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: lamellar. Color: gray, black. Luster: metallic. Diaphaneity: opaque. Streak: gray. Cleavage: {110}. Twinning: {110}. Fracture: subconchoidal. Magnetic.

Habit: massive, granular, pseudocubic euhedral crystals. Color: snow white, gray, reddish white, or brownish white. Diaphaneity: transparent to translucent. Luster: vitreous, greasy. Streak: white. Cleavage: [001], [110], [101]. Fracture: uneven. Occurrence: large bed in a granitic vein in gray gneiss. Melting point: 1009°C.

Habit: acicular, striated //c. Color: red orange. Streak: orange. Diaphaneity: translucent. Luster: adamantine. Fracture: subconchoidal. Cleavage: (010). Twinning: (011). Melting point: 844°C.

Habit: coarse aggregate. Color: colorless. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous( i.e., glassy). Fracture: conchoidal. Twinning: (111). Chemical: resistant to strong mineral acids, attacked by HF and molten alkali-metal hydroxides. Melting point: 1713°C.

Habit: tabular, tarnishes purple. Color: blue. Luster: submetallic. Diaphaneity: opaque. Streak: dark gray. Fracture: conchoidal. Cleavage: {0001}. Electrical resistivity 3 to 83 μΩ.cm. Melting point: 507°C.

Habit: microscopic subhedral crystals. Cleavage: none Color: bluish gray. Diaphaneity: opaque. Luster: metallic. Streak: dark brown to balck.

Other relevant mineralogical, physical, and chemical properties with occurrence

820 Minerals, Ores and Gemstones

Cu2O M = 143.0914 88.82 wt.% Cu 11.18 wt.% O Coordinence Cu(2) (Oxides and hydroxides)

CaB[SiO4(OH)] M = 159.98 25.05 wt.% Ca 17.56wt.% Si 6.76wt.% B 0.63wt.% H 50.00wt.% O (Nesosilicates)

NaAl(CO3)(OH)2 M = 144.00 15.97 wt.% Na 8.34 wt.% C 18.74 wt.% Al 1.40 wt.% H 55.56 wt.% O

C M = 12.0107 Coordinence C(4) (Native elements)

AlO(OH) M = 59.98828 44.98 wt.% Al 1.68 wt.% H 53.34 wt.% O Coordinence Al(6) (Oxides and hydroxides)

Cuprite [1317-39-1] (syn., chalcotrichite) [from the Latin, cuprum, copper, while chalcotrichite from the Greek, khalkos, hairy copper) (ICSD 63281 and PDF 5-667)

Datolite [Named after the Greek, datos, to divide because of granular character of some varieties] (ICSD 22026 and PDF 36-429)

Dawsonite [Named after the Canadian geologist John William Dawson (1820–1899), principal of McGill University, Montreal, Canada] (ICSD 100140 and PDF 42-1346)

Diamond [7782-40-3] (syn., boart, carbonado) [from the Greek, adamas, invincible, or hardest first used in Manilius (AD 16)] (ICSD 29325 and PDF 6-675)

Diaspore [14457-84-2] [from the Greek, dia, through and speirein, to scatter in reference to its characteristic decrepitation on heating n in the bunsen flame] (ICSD 200952 and PDF 5-355)

Coordinence Cu(4), Fe(4) (Sulfides and sulfosalts)

Orthorhombic a = 440.1 pm b = 942.1 pm c = 284.5 pm (Z = 4) P.G. mmm S.G. P21/bnm Geothite type structure

Cubic a = 356.68 pm A4, cF8 (Z = 8) P.G. m3m S.G. Fd-3m Diamond type

Orthorhombic a = 673 pm b = 1036 pm c = 558 pm P.G. 2/m2/m2/m S.G. Imam (Z = 4) Barentsite type

Monoclinic a = 962 pm b = 760 pm c = 484 pm 90.15° (Z = 4)

Cubic a = 426.96 pm C3, cP6 (Z = 2) P.G. 432 S.G. Pn3m Cuprite type

S.G. Pnma P.G. mmm

Biaxial (+) α = 1.682–1.706 β = 1.705–1.725 γ = 1.730–1.752 δ = 0.047–0.050 2V = 85–88° Dispersion weak

Isotropic nD = 2.4175– 2.4178

Biaxial (–) α = 1.462 β = 1.542 γ = 1.596 δ = 0.130 2V = 76.75° Dispersion weak

Biaxial (–) α = 1.622–1.626 β = 1.649–1.654 γ = 1.666–1.670 δ = 0.044–0.046 2V = 72–75° O.A.P. (010) Dispersion weak

Isotropic nD = 2.849 R = 27.1%

6.5–7

10

30 km) and alluvial placer deposits derived from the Kimberlite rocks. Melting point: 4440°C under 12 GPa. Diamond exists in two major varieties, those bearing nitrogen as an impurity (Type I) and those without (Type II). These two subgroups are further subdivided into Types Ia, Ib, IIa, and IIb. Type Ia diamonds are the most common type of naturally occurring diamond (98%) and they contain between 10 to 3000 ppm wt. nitrogen present into small aggregates, including platelets. By contrast, type Ib diamonds are scarce (0.1%) with a low nitrogen content (25–30 ppm wt.) dispersed substitionally. Of the two type II diamond types, Type IIb which is extremely rare is a semiconductor due to minute amounts of boron impurities and with nitrogen below 0.1 ppm wt. N, it exhibits a blue color, whereas Type IIa diamonds are comparatively pure and contain less than 10 ppm wt. N.

Habit: thin encrustations, bladed, needle-like or radial crystals. Color: colorless to white. Diaphaneity: transparent. Luster: vitreous to silky. Fracture: uneven. Cleavage: [110] Perfect. Streak: colorless. Other: fluorescent under short-wavelength UV with dull white. Occurrence: low-temperature hydrothermal mineral.

Color: colorless or white, yellow, green, pink. Cleavage: none. Twinning: none. Chemical: insoluble in HCl but gelatinize. Gives intense yellowish color to bunsen flame when moistened with H2SO4. Deposits: in cavities and veins in hyapbyssal and volcanic igneous rocks. Skarns. Serpentine and hornblende schists. Secondary mineral associated with calcite, prehnite, zeolites and axinite. Melting point: 1235°C.

Habit: cubic, octahedral, massive, granular, capillary. Color: brownish red or dark red. Diaphaneity: transparent to translucent. Luster: submetallic to adamantine. Streak: brownish red. Cleavage: (111) imperfect. Fracture: brittle, conchoidal. Other: Electrical resistivity 10 to 50 Ω.m. Occurrence: oxidized zone of copper deposits.

Mineral and Gemstone Properties Table 821

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

CaMg[Si2O6] M = 216.5504 18.51 wt.% Ca 11.22 wt.% Mg 25.94 wt.% Si 44.33 wt.% O Coordinence Ca(8), Mg(6), Si(4) (Inosilicates, double chains)

CuSiO2(OH)2 (Cyclosilicates, ring)

CaMg(CO3)2 M = 184.4014 21.73 wt.% Ca 13.18 wt.% Mg 13.03 wt.% C 52.06 wt.% O Coordinence Mg(6), Ca(6), C(3) (Nitrates, carbonates, and borates)

NaMg3Al6(OH)4B3O9[Si6O18] Coordinence Na(6), Mg(6), Al(6), B(3), Si(4) (Cyclosilicates, ring)

Hg6Cl3O(OH) M = 1342.90 89.62 wt.% Hg 0.08 wt.% H 7.92 wt.% Cl (Halides)

NaLi3Al6(OH)4B3O9[Si6O18] M = 916.68 2.51 wt.% Na 1.89 wt.% Li 19.13 wt.% Al 18.38 wt.% Si 3.54 wt.% B 0.44 wt.% H 54.11 wt.% O

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Diopside (syn., diallage) [Named from the Greek, dis, two kinds, and opsis, opinion] (ICSD 100738 and PDF 41-1370)

Dioptase [Named from the Greek, dia, through, and optomai, vision] (ICSD 100077 and PDF 33-487)

Dolomite [Named after the French mineralogist and geologist, Deodat Guy Silvain Tancrède Gratet de Dolomieu] (ICSD 31336 and PDF 36-426)

Dravite [Named after the Drava River, Austria] (ICSD 72937 and PDF 44-1457)

Eglestonite [Named after the American mineralogist, Thomas E. Egleston (1832–1900)] (ICSD 12102 and PDF 29-909)

Elbaite [Named after the Island of Elba, Italy] (ICSD 9252 and PDF 26-964)

Table 12.23. (continued)

Trigonal a = 1646 pm c = 1625 pm (Z = 3) P.G. 3m S.G. R3m Tourmaline group

Cubic a = 1603.6 pm (Z = 16) S.G. Ia3d

Trigonal a = 1594 pm c = 722 pm (Z = 3) P.G. 3m S.G. R3m Tourmaline group

Trigonal (Rhombohedral) a = 480.79 pm c = 1601.00 pm aRh = 601.5 pm, 47°07' (Z = 3) P.G. 3 S.G. R3 Dolomite type

Trigonal

Uniaxial (–) ε = 1.650 ω = 1.628 δ = 0.022

Isotropic nD = 2.49

Uniaxial (–) ε = 1.650 ω = 1.628 δ = 0.022

Uniaxial (–) ε = 1.500–1.520 ω = 1.679–1.703 δ = 0.179–0.185

Uniaxial (+) ε = 1.644–1.658 ω = 1.697–1.709 δ = 0.051–0.053

7–7.5

2–3

7–7.5

3.5–4

5

6

Mohs hardness (/HM) (Vickers)

Biaxial (+) α = 1.665 β = 1.672 γ = 1.695 δ = 0.030 2V = 56–63° Dispersion weak

Optical properties

2900

8300– 8450 (8650)

3020

2860– 2930

3331

3400

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 970 pm b = 890 pm c = 525 pm β = 105.83° P.G. 2/m S.G. C2/c (Z = 4)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: prismatic. Color: white. Luster: resinous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (101) poor, {110} poor. Twinning: {101}. Fracture: subconchoidal.

Color: yellow or brownish yellow. Luster: adamantine, resinous. Diaphaneity: transparent to translucent.

Habit: prismatic. Color: brown, yellow. Luster: resinous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (101) poor, {110} poor. Twinning: {101}. Fracture: subconchoidal.

Habit: rhombohedral, crystalline, massive, botryoidal, globular, stalactitic. Color: white, gray, reddish white, brownish white, or gray. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Streak: white. Cleavage: (1011) perfect. Twinning: {0001}, {1010}, {1110}, {0112}. Fracture: brittle, subconchoidal. Chemical: readily dissolved by strong mineral acids with evolution of carbon dioxide. Occurrence: sedimentary rocks.

Habit: massive, cryptocrystalline. Color: dark green or emerald green. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Cleavage: (1011) good. Fracture: conchoidal. Streak: green. Occurrence: secondary mineral in oxidized zones of copper deposits.

Habit: Prismatic, Blocky, Granular. Color: white, yellowish green, black, or grayish blue. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white green. Cleavage: (110) good. Twinning: {001}, {100}. Fracture: brittle, conchoidal. Occurrence: basic and ultrabasic igneous and metamorphic rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

822 Minerals, Ores and Gemstones

(Au, Ag) (Native elements)

Ag(Br,Cl) M = 165.55 65.16 wt.% Ag 24.13 wt.% Br 10.71 wt.% Cl (Halides)

Cu3AsS4 M = 398.806 47.80 wt.% Cu 20.04 wt.% As 32.16 wt.% S (Sulfides and sulfosalts) Coordinence Cu(4), As(4)

Mg2[Si2O6] M = 200.778 60 wt.% SiO2 40 wt.% MgO Traces of Ca, Fe, Mn, Ni, Cr, Al and Ti Coordinence Mg(6, 8), Si(4) (Inosilicates, single chain)

Ca2Fe.(Al, Fe)2O(OH)[SiO4][Si2O7] M = 519.30 15.44 wt.% Ca 3.90 wt.% Al 24.20 wt.% Fe 16.22 wt.% Si 0.19 wt.% H 40.05 wt.% O (Sorosilicates and nesosilicates)

MgSO4.7H2O M = 246.47598 9.86 wt.% Mg 13.01 wt.% S 71.40 wt.% O 5.73 wt.% H Coordinence Mg(6), S(4) (Sulfates, chromates, molybdates, and tungstates)

Co3(AsO4)2.8H2O M = 598.76072 29.53 wt.% Co 25.03 wt.% As 42.75 wt.% O 2.69 wt.% H Coordinence Co(6), As(4) (Phosphates, arsenates, and vanadates)

Electrum

Embolite [Named from the Greek for intermediate, alluding to the 1:1 ratio of chloride and bromide] (ICSD 9252 and PDF 26-964)

Enargite [Named from the Greek, enargis, distinct] (ICSD 75556 and PDF 35-580)

Enstatite [13776-74-4] (syn., bronzite) [from the Greek, enstates, opponent or resistant owing to the unfusibility of the mineral and bronze brown] (ICSD 37313 and PDF 19-768)

Epidote [from the Greek, epidosis, increase, owing to the high lattice parameter] (ICSD 10268 and PDF 45-1446)

Epsomite [Named after Epsom, a town near London, England] (ICSD 29384 and PDF 36-419)

Erythrite (syn., cobalt bloom) (ICSD 81385 and PDF 33-413)

Coordinence Na(6), Li(6), Al(6), B(3), Si(4) (Cyclosilicates, ring)

Monoclinic a = 1026 pm b = 1337 pm c = 474 pm β = 105.1° (Z = 2) P.G. 2/m S.G. C2/m Vivianite type

Orthorhombic a = 1196 pm b = 1199 pm c = 685.8 pm (Z = 4) P.G. 222 S.G. P212121 Epsomite type

Monoclinic a = 889.0 pm b = 563.0 pm c = 1019.0 pm 115°40 (Z = 2) Epidote group

Orthorhombic a = 1822.0 pm b = 882.9 pm c = 519.2 pm (Z = 4) P.G. mmm S.G. P21bca Enstatite type

Orthorhombic a = 642.6 pm b = 742.2 pm c = 614.4 pm (Z = 2) S.G. Pn2m P.G. m2m

Cubic

Cubic

Biaxial(–) α = 1.626 β = 1.661 γ = 1.699 δ = 0.073 2V = 90°

Biaxial(+) α = 1.433 β = 1.455 γ = 1.461 δ = 0.028 2V = 52

Biaxial (–) α = 1.715–1.751 β = 1.725–1.784 γ = 1.734–1.797 δ = 0.015–0.049 2V = 90–116° Dispersion strong

Biaxial (+) α = 1.650–1.668 β = 1.652–1.673 γ = 1.658–1.680 δ = 0.008–0.011 2V = 54–90° Dispersion weak

Biaxial R = 25–28%

Isotropic nD = 2.15

Isotropic R = 83%

1–2

2–2.5

6–6.5 (HV 680)

5–6

3 (HV 133– 185 and 245– 346 //)

(HV 34–44)

3060

1680

3380– 3490

3190– 3500

4500

Habit: reniform, fibrous. Color: purple red. Streak: pale purple. Diaphaneity: translucent. Luster: adamantine. Fracture: sectile. Cleavage: (010) perfect.

Habit: botryoidal, prismatic. Color: colorless. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous. Fracture: conchoidal.

Habit: prismatic according to b, striated, columnar. Color: gray, apple green, brown, blue, or rose red. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), resinous, pearly. Streak: white. Cleavage: [001] perfect, [100] imperfect. Fracture: uneven. Chemical: insoluble in strong mineral acids, but attacked by HCl after calcination giving a gel of silica, fusible giving a dark green globule. Occurrence: regional metamorphic and pegmatite rocks.

Habit: massive, tabular, lamellar, prismatic. Color: white, yellowish green, brown, greenish white, or gray. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: translucent to opaque. Streak: gray. Cleavage: (100) distinct, (010) distinct. Twinning: {101}. Fracture: uneven, brittle. Chemical: insoluble in HCl but sol. in HF. Decomposed at 1550°C. Other: dielectric constant 8.23. Occurrence: magmatic mafic rocks.

Habit: striated tabular crystals. Color: bronze. Luster: metallic. Diaphaneity: opaque. Streak: dark gray. Fracture: uneven. Electrical resistivity 0.2 to 40 mΩ.m

Habit: massive. Color: yellowish green or grayish yellow. Luster: adamantine, greasy. Diaphaneity: transparent to translucent. Streak: white. Occurrence: oxidized portions of silver deposits.

Mineral and Gemstone Properties Table 823

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Cr2O3 M = 151.9904 68.42 wt.% Cr 31.56 wt.% O (Oxide and hydroxides) Coordinence Cr()

Na4(Ca,Ce)2(Fe,Mn,Y)Zr[Si8O22] (OH,Cl)2 M = 992.15 9.27 wt.% Na 6.06 wt.% Ca 7.06 wt.% Ce 0.90 wt.% Y 9.19 wt.% Zr 1.66 wt.% Mn 3.38 wt.% Fe 22.65 wt.% Si 0.15 wt.% H 1.79 wt.% Cl 37.90 wt.% O (Cyclosilicates, ring)

(Y,Ca,Ce)(Nb,Ta,Ti)2O6 M = 392.28 2.04 wt.% Ca 3.57 wt.% Ce 15.86 wt.% Y 18.45 wt.% Ta 2.44 wt.% Ti 33.16 wt.% Nb 24.47 wt.% O

(Ni,Mg)4[Si6O15](OH)2·6H2O M = 750.99 3.24 wt.% Mg 22.44 wt.% Si 23.45 wt.% Ni 1.88 wt.% H 49.00 wt.% O (Phyllosilicates, layered)

(Na2,Ca,Mg)3.5[Al7Si17O48]·32H2O (Tectosilicates, network)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Eskolaite [1308-38-09] [Named after the Finnish geologist, Pentti Eskola (1883–1964)] (ICSD 201102 and PDF 38-1479)

Eudialyte (syn., eucolite) [from the Greek, eu, well, and dialytos, decomposable] (ICSD 68157 and PDF 41-1465)

Euxenite [Named from the Greek euxenos, hospitable, in allusion to the rare earth elements it hosts] (ICSD 100175 and PDF 14-463)

Falcondoite (syn., garnierite, genthite) [Named from the contraction of Falconbridge Dominica C. Por A., Loma Peruera laterite deposit at Bonao, Dominican Republic]

Faujasite [Named after Barthelemy Faujas de

Table 12.23. (continued)

Cubic a = 247 pm

Orthorhombic a = 1350 pm b = 269 pm c = 524 pm (Z = 4) P.G. 2/m2/m2/m S.G. Pncn

Orthorhombic a = 1464.3 pm b = 555.3 pm c = 519.5 pm (Z = 4) P.G. 2/m2/m2/m S.G. Pbcn

Trigonal (Rhombohedral) a = 1434 pm c = 3021 pm (Z = 12) P.G. 32/m S.G. R3m

Isotropic nD = 1.47–1.48

Biaxial n ~ 1.55

Biaxial (?) Often metamict but recrystallize after heat treatment at 1000°C nD = 2.25 R = 15.0%

Uniaxial (+) ω = 1.593–1.643 ε = 1.597–1.634 δ = 0.001–0.010

5

3–4

5.5–6.5 (HV 530– 767)

5–5.5

9–9 (HV 3200)

Mohs hardness (/HM) (Vickers)

Uniaxial (–) R = 19.6%

Optical properties

1923– 1940

2410 (2620)

4300– 5870 (5130)

2900

5180 (5245)

Density (ρ/kg.m–3) (calc.)

Trigonal (Rhombohedral) a = 497.3 pm c = 1358.4 pm D51, hR10 (Z = 2) S.G. R3c P.G. 32/m Corundum type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: euhedral. Color: colorless, white, or pale brown. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (111) perfect, (111)

Habit: stalactitic. Color: green or yellowish green. Luster: resinous.

Habit: rare prismatic or flattened crystals. Color: Brownish black, brown, yellow, olive green. Luster: submetallic. Diaphaneity: opaque. Cleavage: (101). Fracture: subconchoidal to conchoidal. Streak: black to reddish brown. Radioactive. Occurrence: granite pegmatites, syenites, yellow and orange weathering products.

Habit: Massive-Granular, Tabular. Cleavage: [0001] Imperfect. Fracture: Uneven. Luster: vitreous (i.e., glassy). Color: pinkish red, red, yellow, yellowish brown, or violet. Streak: white. Occurrence: Nepheline–syenite rocks.

Habit: hexagonal prismatic crystals, rarely platty with (0001) and (1010). Color: black to dark green. Luster: vitreous. Diaphaneity: opaque but transparent on thin edges. Streak: light green. Chemical: insoluble in mineral acids and alkalis. Other: nonmagnetic, infusible. Occurrence: occurs in skarn associated with sulfide of igneous origin or as rounded grains in sedimentary detrital deposits such as beach mineral sands.

Other relevant mineralogical, physical, and chemical properties with occurrence

824 Minerals, Ores and Gemstones

Orthorhombic a = 481.7 pm b = 1047.7 pm c = 610.5 pm (Z = 4) P.G. mmm S.G. Pbnm Olivine group

Fe2[SiO4] Fe-pole: Fo10-0 M = 203.7771 54.81 wt.% Fe 13.78 wt.% Si 31.41 wt.% O Traces of Mg, Ca, and Mn Coordinence Fe(6), Si(4) (Nesosilicates)

FeWO4 M = 303.6826 18.39 wt.% Fe 60.54 wt.% W 21.07 wt.% O Coordinence Fe(6), W(4) (Sulfates, chromates, molybdates, and tungstates)

YNbO4 M = 245.80983 36.17 wt.% Y 37.80 wt.% Nb 26.04 wt.% O (Oxides and hydroxides)

Ca2FeAl2[Si4BO15](OH) M = 570.12 14.06 wt.% Ca 9.80 wt.% Fe 9.47 wt.% Al 19.71 wt.% Si 1.90 wt.% B 0.18 wt. H 44.90 wt.% O

FeTi2O5 M = 231.576 24.12 wt.% Fe 41.34 wt.% Ti 34.54 wt.% O Coordinence Ti(6)

CaF2 M = 78.0748 51.33 wt.% Ca 48.67 wt.% F Traces of Y and Ce (Halides) Coordinence Ca(8)

Fayalite [10179-73-4] (syn., hortonolite: Mn,Mg, knebelite: Mn) [Named after the locality, Fayal, one of the island of the Acores archipel] (ICSD 26375 and PDF 31-633)

Ferberite [13870-24-1] [Named after the German chemist, Moritz Rudolph Ferber (1805–1875)] (ICSD 64733 and PDF 46-1446)

Fergusonite [Named after the Scottish physician Robert Ferguson (1799–1865)] (ICSD 100836 and PDF 32-680)

Ferroaxinite [Named from Greek axine, ax in reference to its wedge-shaped crystals] (ICSD 4343 and PDF 27-76)

Ferropseudobrookite [12449-79-5]

Fluorite [7789-75-5] (syn., fluor spar) [Named from Latin, fluere, to flow] (ICSD 60559 and PDF 35-816)

Cubic a = 546.36 pm C1, cF12 (Z = 4) S.G. Fm3m P.G. 4-32 Fluorite type

Monoclinic (Z = 4) P.G. 2/m S.G. A2/m Karrooite type

Triclinic a = 896 pm b = 922 pm c = 716 pm α = 102.7° β = 98.03° γ = 88.03° S.G. P1 (Z = 2) Axinite group

Tetragonal a = 517 pm c = 530 pm (Z = 2) S.G. I41/a

Monoclinic a = 473.2 pm b = 570.8 pm c = 496.5 pm β = 90.00° (Z = 2) P.G. 2/m S.G. P2/c Wolframite type

(Z = 8) P.G. 432 S.G. Fd3m

Saint Fond (1741–1819), French geologist and writer on the origin of volcanoes] (ICSD 4392 and PDF 39-1380)

Isotropic nD = 1.434

Biaxial (?)

Biaxial (–) α = 1.674–1.683 β = 1.682–1.691 γ = 1.685–1.694 δ = 0.00090– 0.0110 2V = 67–73°

Isotropic nD = 2.190

Biaxial (+) α = 2.31 β = 2.40 γ = 2.46 δ = 0.15 2V = 79°

Biaxial (–) α = 1.827 β = 1.869 γ = 1.879 δ = 0.052 2V = 47–54° Dispersion weak O.A.P (001)

4

6.5–7

5.5–6

4–4.5

6.5–7 (HV 820)

3180

3290– 3320

5050

7600

4390

Habit: crystalline, massive, granular, octahedral crystals. Color: white, yellow, green, red, or blue. Luster: vitreous (i.e., glassy). Luminescence: fluorescent blue under short and long UV light. Diaphaneity: transparent to translucent. Streak: white. Cleavage: [111]. Fracture: conchoidal, splintery. Insoluble in water, dissolved in hot conc. H2SO4 evolving gaseous HF, slightly soluble in HCl and HNO3. Decrepitation when fired. Fusible (m.p. 1418°C) giving a white enamel. Sometimes radioactive owing to traces of Th. Occurrence: low-temperature vein deposits, guangue materials, sedimentary rocks.

Melt at 1500°C

Habit: thin wedge-shaped axehead crystals. Color: gray to bluish gray. Diaphaneity: opaque to translucent. Luster: vitrous. Cleavage: good (100). Fracture: uneven to conchoidal. Streak: colorless.

Color: brown or brownish black. Diaphaneity: translucent to opaque. Luster: submetallic. Cleavage: indistinct. Fracture: subconchoidal. Streak: brown.

Habit: short prismatic. Color: brown, black. Luster: submetallic. Diaphaneity: opaque. Streak: black. Cleavage: (010) poor. Twinning: {100}, {023}. Fracture: uneven.

Habit: massive, granular. Color: brown black, or black. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Streak: white. Cleavage: (010) distinct, (001) poor. Twinning: {100}, {011}, {012}. Fracture: conchoidal. Chemical: attacked by strong mineral acids giving a gel of silica. Fusible giving a magnetic globule. Occurrence: ultramafic silica-poor igneous rocks such as gabbros, basalts, peridotites.

perfect, (111) perfect. Fracture: brittle, uneven. Occurrence: usually occurs in basaltic volcanics, metapyroxenite, also with augite in limburgite.

Mineral and Gemstone Properties Table 825

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mg2[SiO4] Mg-pole: Fo90-100 57.1 wt.% MgO 42.9 wt.% SiO2 Traces Fe, Mn Coordinence Mg(6), Si(4) (Nesosilicates)

ZnFe2O4 M = 241.0776 Coordinence Zn(4), Fe(6) (Oxides and hydroxides)

ZnAl2O4 M = 183.35 29.43 wt.% Al 35.66 wt.% Zn 34.90 wt.% O Coordinence Zn(4), Al(6) (Oxides and hydroxides)

(Mn,Mg)(Al,Fe)2O4 M = 172.72 1.41% Mg 28.63% Mn 29.68% Al 3.23% Fe 37.05% O (Oxides and hydroxides)

PbS M = 239.266 86.60 wt.% Pb 13.40 wt.% S Traces Ag, Bi, As, Sb, Zn, Cd, Cu. (Sulfides and sulfosalts) Coordinence Pb(6)

Na2Ca(CO3)2.5H2O M = 296.15233 15.53 wt.% Na 13.53 wt.% Ca

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Forsterite [26686-77-1] (syn., olivine, chrysolite, peridot) [Named after the English mineralogist Adolarius Jacob Forster (1739–1806)] (ICSD 9334 and PDF 34-189)

Franklinite [1317-55-1] [Named after the American scientist, Benjamin Franklin (1706–1790)] (ICSD 81205 and PDF 22-1012)

Gahnite [Named after the Swedish chemist and mineralogist, J.G. Gahn (1745–1818)] (ICSD 9559 and PDF 5-669)

Galaxite [Named after locality Bald Knob, Sparta near the town of Galax, NC, USA] (ICSD 66855 and PDF 29-880)

Galena [1314-87-0] (syn., lead glance, blue lead) [the Roman naturalist, Pliny, used the Latin name, galena, to describe lead ore] (ICSD 38293 and PDF 5-592)

Gaylussite (syn., natrocalcite) [Named after the French chemist and physicist, Joseph Louis Gay-Lussac

Table 12.23. (continued)

Monoclinic a = 1159 pm b = 778 pm c = 1121 pm

Cubic a = 593.6 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4-32 Rock salt type

Cubic a = 827.1 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

Cubic a = 808 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

Cubic a = 842.0 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

Biaxial (–) α = 1.444 β = 1.5155 γ = 1.523

Isotropic nD = 3.921 R = 43.2%

Isotropic nD = 1.923

Isotropic nD = 1.805

Isotropic nD = 2.36 R = 18.9%

2.5

2.5–3 (HV 71–84)

7.5

7.5–8

5.5

6.5–7 (HV 820)

Mohs hardness (/HM) (Vickers)

Biaxial (+) α = 1.635 β = 1.651 γ = 1.670 δ = 0.035 2V = 82° Dispersion weak O.A.P. (001)

Optical properties

1930– 1990

7597

4230 (4040)

4570– 4620

5320

3220

Density (ρ/kg.m–3) (calc.)

Orthorhombic a = 475.8 pm b = 1021.4 pm c = 598.4 pm (Z = 4) P.G. mmm S.G. Pbnm Olivine group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: disseminated, tabular. Color: colorless, white, or yellowish white. Luster: vitreous (i.e., glassy). Diaphaneity: translucent. Streak: white. Cleavage: [110] perfect, [001] indistinct. Fracture: conchoidal.

Habit: octahedral crystals, massive, granular. Color: light lead gray or dark lead gray. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Cleavage: {001}, {010}, {100}. Twinning: {111}, {114}. Fracture: subconchoidal, brittle. Chemical: attacked by HNO3 with evolution of H2S, with sulfur and precipitate of PbSO4 soluble in hot HCl. Yellow precipitate of lead iodide with KI. Electrical resistivity 6.8 to 90,000 μΩ.cm. Melting point: 1118°C. Occurrence: veins, and disseminated in igneous and sedimentary rocks.

Habit: granular, generally occurs as anhedral to subhedral crystals in matrix. Color: brown red, black. Luster: metallic. Diaphaneity: opaque. Streak: brownish red. Fracture: conchoidal, uneven fracture producing small, conchoidal fragments.

Habit: octahedral crystals or irregular grains. Color: dark green, yellow. Diaphaneity: translucent. Luster: vitreous. Streak: brown to yelow. Fracture: conchoidal. Occurrence: metamorphic rocks (schists) or lithium-rich granite pegmatites.

Habit: octahedral. Color: black, red brown. Diaphaneity: opaque. Luster: metallic. Cleavage: none. Parting: {111}.

Habit: prismatic, tabular. Color: white, yellow, or greenish yellow. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (010) good, (001) poor. Fracture: conchoidal. Chemical: attacked by concentrated HCl with formation of a gel of silica. Melting point: 1898°C.

Other relevant mineralogical, physical, and chemical properties with occurrence

826 Minerals, Ores and Gemstones

3.40 wt.% H 8.11 wt.% C 59.43 wt.% O (Nitrates, carbonates, and borates)

Ca2Al[SiAlO7] M = 274.20 29.23 wt.% Ca 19.68 wt.% Al 10.24 wt.% Si 40.84 wt.% O (Sorosilicates, pair)

MgTiO3 M = 120.180 20.22 wt.% Mg 39.84 wt.% Ti 39.94 wt.% O (Oxides and hydroxides)

NiAsS M = 165.6776 35.42 wt.% Ni 45.22 wt.% As 19.35 wt.% S (Sulfides and sulfosalts)

Al(OH)3 M = 78.991618 34.59 wt.% Al 61.53 wt.% O 3.88 wt.% H Coordinence Al(6) (Oxides and hydroxides)

Na2Ca(SO4)2 M = 278.18 16.53 wt.% Na 14.41 wt.% Ca 23.05 wt.% S 46.01 wt.% O (Sulfates, chromates, molybdates, and tungstates)

(Co,Fe)AsS M = 165.15 8.45% Fe 26.76% Co 45.37% As 19.42% S (Sulfides and sulfosalts)

(1778–1850)] (ICSD 26969 and PDF 21-343)

Gehlenite [Named after the German chemist, Adolph F. Gehlen (1775–1815)] (ICSD 39921 and PDF 35-755)

Geikielite [9312-99-8] [Named after the Scottish geologist Sir Archibald Geikie (1835–1924)] (ICSD 65794 and PDF 6-494)

Gersdorffite (syn., gray nickel pyrite, nickel glance) [Named after Herr von Gersdorff, owner of Schladming Mine, Austria) (ICSD 16980 and PDF 42-1343)

Gibbsite [21645-51-2] [Named after George Gibbs (1776–1833)] (ICSD 36233 and PDF 33-18)

Glauberite (syn., Glauber’s salt) [Named after Glauber’s salt, of alchemist origin itself from the German chemist Johann Wilhelm Glauber (1603–1668)] (ICSD 26773 and PDF 19-1187)

Glaucodot [Named from the Greek, glaucos, blue, in reference to its use in the dark blue glass called smalt]

Orthorhombic a = 663 pm b = 2833 pm c = 563 pm (Z = 24) P.G. 2/m2/m2/m S.G. Cmmm

Monoclinic a = 1013 pm b = 831 pm c = 853 pm β = 112.183° (Z = 4) P.G. 2/m S.G. C2/c

Monoclinic a = 971.9 pm b = 507.05 pm c = 864.12 pm β = 94.57° (Z = 8) P.G. 2/m S.G. P21/n

Cubic a = 517.9 pm (Z = 4) P.G. 23 S.G. P213 Cobaltite group

Hexagonal a = 505.478 pm c = 1389.92 pm (Z = 6) S.G. R3m P.G. 3 Ilmenite type

5–6

Biaxial (?) R = 52.5%

Biaxial (–) α = 1.507–1.515 β = 1.527–1.535 γ = 1.529–1.536 δ = 0.021–0.022 2V = 24–34° Dispersion strong

Biaxial (+) α = 1.560–1.580 β = 1.560–1.580 γ = 1.580–1.600 δ = 0.02 2V = 0–40° Dispersion strong

Isotropic R = 45.0

5 (HV 1071– 1166)

2.5–3

2.5–3.5

5.5

Uniaxal (–) 5–6 ω = 1.95–1.98 ε = 2.31–2.35 δ = 0.3600– 0.3700 Dispersion strong Pleochroism moderate to weak

Uniaxial (–) ε = 1.667 ω = 1.657 2V = small

2V = 34° Dispersion strong

(Z = 4) P.G. 2/m S.G. I2/a

Tetragonal a = 769.0 pm c = 506.75 pm (Z = 2) Melilite type

δ = 0.0790

β = 102°

5900– 6100 (6220)

2700– 2850

2400

5900– 6330

3790– 4200 (3895)

3054

Habit: prismatic crystals often twinned. Color: silver- to gray-white. Luster: metallic. Diaphaneity: opaque. Cleavage: (010) perfect. Fracture: brittle, uneven. Streak: black. Occurrence: high-temperature sulfide vein deposits.

Habit: tabular, prismatic. Color: yellow, reddish gray, or red. Luster: vitreous (glassy). Diaphaneity: transparent to translucent. Streak: white. Fracture: brittle–conchoidal. Cleavage: [001] perfect. Occurrence: dry salt-lake beds in desert climates.

Habit: tabular, foliated. Color: white, gray. Luster: pearly, vitreous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (001). Twinning: {310}, and {001}. Fracture: uneven, tough.

Habit: massive, granular, euhedral crystals, tabular. Color: tin white or white. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Cleavage: (100) good, (010) good, (001) good. Fracture: brittle. Antiferromagnetic.

Habit: tabullar or small prismatic crystals. Color: bluish black, brownish black, ruby-red. Diaphaneity: translucent to opaque. Luster: metallic to submetallic. Streak: purple brown. Fracture: conchoidal to subconchoidal. Cleavage: [1011] distinct. Other: melting point at 1630°C. Deposits: metamorphosed magnesian limestones. Also in ultramafic igneous rocks such as carbonatites, kimberlites, and serpentinized ultramafic rocks.

Habit: short prismatic to equant crystals. Color: colorless to straw-yellow and even brown. Diaphaneity: translucent to transparent. Luster: vitreous. Cleavage: (001) distinct. Chemical: gelatinizes in conc. HCl. Occurrence: skarns.

Mineral and Gemstone Properties Table 827

Minerals, Ores and Gemstones

12

Monoclinic a = 974.80 pm b = 1791.50 pm c = 527.70 pm 102°78 (Z = 2) P.G.: 2/m S.G. C2/m Tremolite type

Orthorhombic a = 459.6 pm b = 995.7 pm c = 302.1 pm (Z = 4) P.G. mmm S.G. P21/bnm

Na2(Mg,Fe)3Al2Si8O22(OH)2 (Inosilicates, chain, ribbon) Coordinance Na(8), Mg(6), Al(6), and Si(4)

α-FeO(OH)=0.5Fe2O3 2H2O M = 88.85177 62.85 wt.% Fe 36.01 wt.% O 1.13 wt.% H Coordinence Fe(6) (Oxides and hydroxides)

Au M = 196.96655 Coordinence Au(12) (Native elements)

ZnSO4·7H2O M = 287.56056 22.74 wt.% Zn 4.91 wt.% H 11.15 wt.% S 61.20 wt.% O (Sulfates, chromates, molybdates and tungstates)

Glaucophane [Named from the Greek, glaukos, blue, and fanos, appearing] (ICSD 24433 and PDF 20-453)

Goethite [1309-37-1] (syn., needle iron stone, acicular iron ore, limonite, groutite: Mn-varieties) [Named after the German poet, Johann Wolfgang von Goethe (1749–1832), groutite after the American petrologist Frank Fitch Grout (1880–1958)] (ICSD 28247 and PDF 29-713)

Gold [7440-57-5] (syn., aurum) (ICSD 64701 and PDF 4-784)

Goslarite [7446-20-0] [Named after the locality of Goslar, Germany]

Orthorhombic a = 1180 pm b = 1205 pm c = 682 pm (Z = 24) P.G. 222 S.G. P212121 Epsomite-Goslarite series

Cubic a = 407.86 pm A1, cF4 (Z = 4) P.G. m3m S.G. Fm3m Copper type Biaxial (–) α = 1.457 β = 1.480 γ = 1.484 2V = 46°

Isotropic nD = 0.368 R = 74%

Biaxial (–) α = 2.260–2.275 β = 2.393–2.409 γ = 2.398–2.515 δ = 0.138–0.140 2V = 0–27° Dispersion strong R = 17.3%

Biaxial (–) α = 1.606–1.661 β = 1.622–1.667 γ = 1.627–1.670 δ = 0.009–0.021 2V = 0–50° Dispersion strong

2–2.5

2.5–3 (HV 50–52)

5–5.5 (HV 525– 824)

6–6.5

2

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 1.590–1.612 β = 1.609–1.643 γ = 1.610–1.644 δ = 0.020–0.032 2V = 0–20°

Optical properties

2000

19,287

4269

3080– 3300

2400– 2950 (2900)

Density (ρ/kg.m–3) (calc.)

Monoclinic P.G. 2/m Mica type

(K,Na)(Fe,Al,Mg)2(Si,Al)4O10 (OH)2 (Phyllosilicates, layered)

Glauconite [Named from the Greek, glaucos, originally gleaming, later bluish green, silvery, or gray]

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: stalactitic, massive, acicular. Color: white, yellowish white, or reddish white. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: [010] perfect. Fracture: conchoidal.

Habit: octahedral, dendritic, arborescent, platy, granular. Color: yellow, pale yellow, orange, yellow white, or reddish white. Diaphaneity: opaque. Luster: metallic. Streak: yellow. Cleavage: none. Twinning: {111}. Fracture: hackly. Occurrence: Quartz veins and alluvial placers deposits. Chemical: inert to most strong mineral acids (e.g., HCl, H2SO4, HF) but readily dissolved by aqua regia (i.e., 3 vol. HCl + 1 vol. HNO3).

Habit: acicular, reniform, radialor fibrous. Color: brown, black, reddish brown, or yellowish brown. Luster: subadamantine, silky. Diaphaneity: translucent to opaque. Streak: yellowish brown. Cleavage: (010), (100). Fracture: uneven, hackly (looking notched or hacked). Occurrence: iron ore deposits.

Habit: massive, fibrous, columnar, granular. Color: colorless, grayish blue, bluish black, or lavender blue. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: translucent. Streak: grayish blue. Cleavage: [110] good, [110] good. Fracture: conchoidal, uneven, brittle. Chemical: insoluble in strong mineral acids. Easy fusible giving a green enamel. The powdered mineral colors the bunsen flame in yellow (Na). Slightly attracted by electromagnet. Occurrence: metamorphic blue schists.

Habit: rounded aggregates and pellets. Color: yellow-green to blue-green. Diaphaneity: translucent to opaque. Luster: dull to earthy. Cleavage: (001) perfect. Chemical: readily decomposed by HCl. Occurrence: sedimentary rocks such as limestones, siltstones and sandstones.

Other relevant mineralogical, physical, and chemical properties with occurrence

828 Minerals, Ores and Gemstones

Monoclinic a = 957 pm b = 1822 pm c = 533 pm β = 102.1° P.G. 2/m S.G. C2/n

Amorphous

CdS M = 144.48 77.81 wt.% Cd 22.19 wt.% S (Sulfides and sulfosalts)

Ca3Al2(SiO4)3 M = 450.44638 26.69 wt.% Ca 11.98 wt.% Al 18.71 wt.% Si 42.62 wt.% O Coordinence Ca(8), Al(6), Si(4) (Nesosilicates)

Fe7Si8O22(OH)2 M = 1000.61 39.03 wt.% Fe 22.43 wt.% Si 0.20 wt.% H 38.34 wt.% O Inosilicates

UO3.nH2O M = 304.043

CaSO4·2H2O M = 172.17216 23.28 wt.% Ca 2.34 wt.% H 18.62 wt.% S 55.76 wt.% O Coordinence Ca(8), S(4) (Sulfates, chromates, molybdates, and tungstates)

Greenockite [Named after Lord Greenock, i.e., Charles Murray Cathcart (1783–1859)] (ICSD 60629 and PDF 41-1049)

Grossular (syn., grossularite, hessonite: brownish orange) [from the Latin, grossularia, gooseberry, hessonite is from the Greek, hesson, slight, in reference to the smaller specific gravity] (ICSD 24944 and PDF 39-368)

Grunerite (syn., amosite) [Named after the Swiss-French chemist Louis Emmanuel Gruner (1809–1883)] (ICSD 24590 and PDF 44-1401)

Gummite [12326-21-5]

Gypsum [10101-41-4] (syn., selenite, alabaster, satin spar) [from the Greek, gypsos, meaning burned mineral. Selenite from the Greek, selenos, in allusion to its pearly luster (moon light) on cleavage fragments] (ICSD 2057 and PDF 33-311)

Monoclinic a = 568.0 pm b = 1551.8 pm c = 629.0 pm β = 113°83' (Z = 4) P.G. 2/m S.G. A2/n

Cubic a = 1185.1 pm (Z = 8) P.G. 432 S.G. Ia3d Garnet group (Ugrandite series)

Hexagonal a = 413.6 pm c = 671.3 pm B4, hP4 (Z = 2) S.G. P63mc P.G. 6mm Wutzite group

Monoclinic a = 554 pm b = 955 pm c = 744 pm β = 104.2° (Z = 2) Sphenoidal 2

Fe2Fe3Si2O5(OH)4 M = 354.28 44.14 wt.% Fe 17.44 wt.% Si 0.94 wt.% H 37.48 wt.% O (Phyllosilicates, layered)

Greenalite [Named after its green color]

Hexagonal a = 246.4 pm c = 673.6 pm A9, hP4 (Z = 4) P.G. 6/mmm S.G. P63/mmc Graphite type

C M = 12.0107 Coordinence C(3) (Native elements)

Graphite [7440-44-0] (syn., plumbago, black lead) [from the Greek, graphein, to write due to its use in making pencils] (ICSD 31170 and PDF 42-1487)

Biaxial (+) α = 1.510 β = 1.523 γ = 1.529 δ = 0.009 2V = 58° Dispersion strong

Isotropic

Biaxial (–) α = 1.662–1.687 β = 1.678–1.709 γ = 1.698–1.729 δ = 0.0010 2V = 82–83°

Isotropic nD = 1.734

Uniaxial (+) ε = 2.506 ω = 2.529 δ = 0.023 R = 19.6%

Isotropic when fined-grained nD = 1.65–1.675

Uniaxial (n.a.) nD = 1.93–2.07 R = 12.5%

2.0

n.a.

5–6

6.5–7.5

3–3.5 (HV 98)

3

1.5–2 (HV 12)

2320

n.a.

3100– 3600 (3660)

3420– 3800 (3594)

4800– 4900 (4820)

2850– 3150 (3150)

2230

Habit: tabular, crystalline, massive,reniform, fibrouscockscomb aggregates: ‘desert roses’. Color: white, colorless, yellowish white, greenish white, or brown. Luster: vitreous, pearly. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (010), (100). Twinning: {100}. Fracture: conchoidal, fibrous. Chemical: start to decomposes at 38°C yielding CaSO4.H2O that decomposes at 80°C into CaSO4.0.5H2O that finally decomposes at 150°C giving off water and yielding CaSO4. Occurrence: sedimentary evaporites.

Generic name for a mixture of uranium and lead oxides of intense yellow color resulting from the weathering of uraninites.

Habit: acicular crystals making fibrous aggragates. Color: brown to dark green. Diaphaneity: translucent to nearly opaque. Luster: vitreous to silky. Fracture: subconchoidal. Cleavage: perfect [110]. Streak: colorless. Others: infusible and insoluble in HCl. Occurrence: contact metamorphic rocks.

Habit: dodecahedral, massive, granular, euhedral crystals, crystalline. Color: colorless, white, green, or yellow. Streak: brownish white. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), resinous. Cleavage: none. Fracture: conchoidal. Chemical: soluble in HCl, and HNO3. Occurrence: contact metasomatic deposits.

Habit: hemimorphic pyramidal crystals. Color: yellow to red. Luster: resinous to adamantine. Diaphaneity: translucent. Cleavage: (1122). Fracture: brittle, uneven. Streak: yellow to orange. Occurrence: sulfide ore veins.

Habit: rounded pellets with fibrous texture ressembling glauconite. Color: olive-green to dark-green. Diaphaneity: translucent to opaque. Luster: weakly ferromagnetic. Occurrence: banded iron formations.

Habit: foliated, tabular, earthy. Color: dark gray, black, or steel gray. Diaphaneity: opaque. Luster: submetallic. Streak: black Cleavage: (0001) perfect. Fracture: sectile. Occurrence: metamorphosed limestones, organic-rich shales, and coal beds. Melting point: 4492°C (10MPa).

Mineral and Gemstone Properties Table 829

Minerals, Ores and Gemstones

12

Hexagonal a = 1047pm c = 2120 pm (Z = 2) P.G. 6/m S.G. P63/m

Tetragonal a = 813.6 pm c = 944.2 pm (Z = 8) P.G. 4/mmm S.G. I41/amd Distorded spinel type

NaCl M = 58.44246 39.34 wt.% Na 60.66 wt.% Cl (Halides) Coordinence Na(6)

Al2[Si4O4(OH)8].2H2O M = 258.16 20.90 wt.% Al 21.76 wt.% Si 1.56 wt.% H 55.78 wt.% O Phyllosilicates

KNa22(SO4)9(CO3)2Cl M = 1564.92 2.50 wt.% K 32.32 wt.% Na 1.54 wt.% C 18.44 wt.% S 2.27 wt.% Cl 42.94 wt.% O (Sulfates, chromates, chromates, molybdates, and tungstates)

Mn3O4=MnIIMnIII2O4 M = 228.81175 72.03 wt.% Mn 27.97 wt.% O Coordinence Mn(4, and 6) (Oxides and hydroxides)

(Na,Ca)4–8[Al6Si6O24](SO4,S,Cl)1–2 M = 1032.43 8.91 wt.% Na 7.76 wt.% Ca

Halite [7647-14-5] (syn., rock salt) [from the Greek, halos, salt, and lithos, rock] (ICSD 18189 and PDF 5-628)

Halloysite [Named after the Belgian geologist, Baron Omalius d’Halloy (1707–1789)] (ICSD 26716 and PDF 29-1489)

Hanksite [Named after the American mineral collector, Elwood P. Hancock (1836–1916)] (ICSD 2852 and PDF 25-1348)

Hausmannite [Named after the German mineralogist, Johann Friedrich Ludwig Hausmann (1782–1859)] (ICSD 68174 and PDF 24-734)

Haüyne (syn., hauynite) [Named after the French crystallographer, R.J. Hauy]

Cubic a = 913 pm (Z = 1) Sodalite type

Monoclinic a = 514 pm b = 892 pm c = 725 pm β = 99.7° (Z = 2) S.G. Cc

Cubic a = 564.02 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4-32 Rock salt type

Isotropic nD = 1.496–1.505

Uniaxial (–) ε = 2.15 ω = 2.46 δ = 0.31 R = 17.5%

Uniaxial (–) ε = 1.46 ω = 1.48 δ = 0.02

Biaxial (–) α = 1.559 β = 1.564 γ = 1.565 2V = 37°

Isotropic nD = 1.5446

5.5–6

5–5.5 (HV 541– 613)

3

1–2

2.5

6.5–7

Mohs hardness (/HM) (Vickers)

Uniaxal (+) ε=? ω=? δ=? Dispersion very strong

Optical properties

2440– 2500

4863

2500

2580– 2620

2160– 2170

6970

Density (ρ/kg.m–3) (calc.)

Tetragonal a = 657.25 pm c = 596.32 pm c/a = 1.102 (Z = 4) P.G. 4/mmm S.G. I41/amd Zircon type

HfSiO4 M = 270.5731 65.97 wt.% Hf 10. 38 wt.% Si 23.65 wt.% O (Nesosilicates)

Hafnon [13870-13-8] (hafnium orthosilicate) [Named after its hafnium content] (ICSD 59111 and PDF 20-467)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: euhedral crystals. Color: white, gray, blue, green, red, yellow. Luster: vitreous (i.e., glassy), greasy. Diaphaneity: transparent to translucent. Streak: bluish white. Cleavage: (110) perfect, (011) perfect, (101) perfect. Twinning: {111} common. Fracture: conchoidal. Occurrence: igneous rocks low in silica and rich in alkalis.

Habit: pseudo-octahedral. Color: brown, black. Diaphaneity: translucent to opaque. Luster: submetallic. Streak: light brown. Fracture: uneven. Cleavage: perfect (001). Twinning: {112}, {101}.

Habit: crystalline, coarse. Color: white or yellow. Diaphaneity: transparent. Luster: vitreous, or greasy. Streak: white. Fracture: conchoidal. Occurrence: continental evaporitic deposits under desert climates.

Habit: earthy to waxy mineral. Color: white to tan. Diaphaneity: opaque but becomes translucent when immersed in water. Luster: dull. Fracture: conchoidal. Cleavage: {001} probable. Occurrence: alteration of basaltic rocks or hydrothermally altered monzonites.

Habit: euhedral crystals, granular, crystalline. Color: white, clear, light blue, dark blue, or pink. Luster: vitreous (i.e., glassy). Diaphaneity: transparent. Streak: white. Cleavage: [100], [010], [001]. Fracture: conchoidal, brittle. Occurrence: marine or continental evaporite. Soluble in water, the soln. Color the flame of a bunsen in yellow. Fusible (m.p. 801°C).

Habit: tiny millimeter prismatic, tabular, crystals. Color: amber, brown, reddish brown, colorless. Diaphaneity: transparent to translucent or opaque (metamict). Luster: adamantine. Streak: white. Fracture: uneven. Cleavage: (110). Twinning: {111}. Other: radioactive due to U isomorphic substitution. Chemical: insoluble in HCl and HNO3, slightly soluble in conc. H2SO4, readily dissolved by conc. HF. Radioactive owing to the isomorphic substitution of Zr(IV) cations by U(IV) and Th(IV) can contain some Pb from decaying. at high pressure and temperature adopt a scheelite type structure. Occurrence: in tantalum-bearing granite pegmatites.

Other relevant mineralogical, physical, and chemical properties with occurrence

830 Minerals, Ores and Gemstones

Trigonal (Rhombohedral) a = 503.29 pm 13.749° D51, hR10 (Z = 2) S.G. R-3c P.G. -32/m Corundum type

CaFe[Si2O6] M = 248.09 16.15 wt.% Ca 22.51 wt.% Fe 22.64 wt.% Si 38.69 wt.% O Coordinence Ca(8), Fe(6), Si(4) Traces Al, Mn, Ti (Inosilicates, simple chain)

α-Fe2O3 M = 159.6922 69.94 wt.% Fe 30.06 wt.% O (Oxides, and Hydroxides) Traces Ti, Mg. Coordinence Fe(6)

FeAl2O4 M = 173.80768 31.05 wt.% Al 32.13 wt.% Fe 36.82 wt.% O (Oxides and hydroxides)

Ag2Te M = 235.4682 45.81 wt.% Ag 54.19 wt.% Te (Sulfides and sulfosalts)

(Ca,Na)Si7Al2O18.6H2O Coordinence Ca(6), Na(6), Si(4), Al(4) (Tectosilicates, framework)

TiO M = 63.8664 74.95 wt.% Ti 25.05 wt.% O (Oxides and hydroxides)

Hedenbergite [Named after the Swedish mineralogist, M.A.L. Hedenberg] (ICSD 10226 and PDF 41-1372)

Hematite [1309-37-1] (syn., Kidney ore, specularite, martite) [from the Greek, haematites, bloodlike, in allusion to vivid red color of the powder] (ICSD 64599 and PDF 33-664)

Hercynite [from Latin, Hercynia Silva, Forested Mountains] (ICSD 74611 and PDF 34-192)

Hessite (syn., telluric silver) [Named after the Swiss chemist, G.H. Hesse) (ICSD 73230 and PDF 34-142)

Heulandite [Named after the English mineralogist, John Henry Heuland (1778–1856)] (ICSD 31278 and PDF 41-1357)

Hongquiite [100100-26-3] [Named after locality of first discovery in 1976 Tao district, Hongqui, China] (ICSD 28955 and PDF 43-1296)

Cubic a = 429.3 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 432 Rock salt type

Monoclinic a = 1773 pm b = 1782 pm c = 743 pm β = 116.3° (Z = 4) P.G. m S.G. Cm Zeolite group

Monoclinic a = 813 pm b = 448 pm c = 809 pm β = 112.9° (Z = 2) S.G. P21/c P.G. 2

Cubic a = 813.5 pm H11, cF56 (Z = 8) S.G. Fd3m Spinel type (Spinel Series)

Monoclinic a = 985.4 pm b = 902.4 pm c = 526.3 pm 104.33° (Z = 4) P.G. 2/m S.G. C2/c Diopside type

15.68 wt.% Al 16.32 wt.% Si 9.32 wt.% S 1.72 wt.% Cl 40.29 wt.% O (Tectosilicates, network)

(ICSD 39952 and PDF 37-473)

Isotropic R = 32.6%

Biaxial (+) α = 1.490 β = 1.500 γ = 1.500 δ = 0.005 2V = 35°

Biaxial R = 38.5%

Isotropic nD = 1.835

Uniaxis (–) ε = 2.96 ω = 3.22 δ = 0.28 Dispersion strong R = 28%

Biaxial (+) α = 1.699–1.739 β = 1.705–1.745 γ = 1.728–1.757 δ = 0.018–0.029 2V = 52–63° Dispersion strong

HV 710

3.5–4

1.5–2 (HV 28–41)

7.5

5.5–6.5 (HV 739– 1062)

5.5–6.5

4950 (4888)

2150

7200– 7900

3950– 4400

5256

3550

Habit: cuboctahedral crystals. Color: gold. Diaphaneity: opaque. Luster: metallic. Cleavage: none. Other: paramagnetic with χm = +88 × 10–6 emu, melting point of 1750°C; specific heat capacity of 628 J.kg–1.K–1, coefficient of linear thermal expansion of 9.19 × 10–6 K–1. Occurrence: high-temperature metamorphic rocks of the garnethornblende-pyroxenite facies along with platinum group metals ores.

Habit: platy. Color: white. Luster: vitreous. Diaphaneity: transparent to translucent. Cleavage: (010) perfect. Fracture: subconchoidal. Occurrence: volcanic tuffs and volcano-clastic sediments.

Habit: euhedral crystals, granular. Color: lead gray or steel gray. Luster: metallic. Diaphaneity: opaque. Streak: light gray. Cleavage: [100] indistinct. Fracture: uneven.

Habit: euhedral crystals, massive, granular. Color: black. Luster: vitreous (i.e., glassy). Diaphaneity: opaque. Streak: dark green. Cleavage: [111]. Fracture: uneven. Occurrence: magmatic rocks.

Habit: tabular, blocky, earthy, botryoidal. Color: reddish gray, black, or blackish red. Luster: metallic, greasy. Diaphaneity: translucent to opaque. Streak: reddish brown. Cleavage: none. Twinning: (001),(101). Fracture: subconchoidal. Chemical: soluble in hot HCl.Becomes magnetic after firing in reducing flamme. Antiferromagnetic. Occurrence: magmatic, hydrothermal, metamorphic and sedimentary rocks.

Habit: granular, crystalline, lamellar. Color: grayish green, brownish green, dark green, black. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: translucent to opaque. Streak: white green. Cleavage: (110) perfect, (110) indistinct. Twinning: {100}, {001} simple, multiple, common. Fracture: conchoidal, brittle. Chemical: insoluble in strong mineral acids, fusible giving a magnetic globule. Other: dielectric constant 8.99, attracted by a strong permanent magnet. Occurrence: contact metamorphic rocks.

Mineral and Gemstone Properties Table 831

Minerals, Ores and Gemstones

12

Hexagonal a = 459 pm c = 751 pm (Z = 2) P.G. 6mm S.G. P 63mc

Cubic a = 286.645 pm A2, cI2 (Z = 2)

Mg(OH,F)2.3Mg2[SiO4] (Nesosilicates)

(K,H)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,H2O] (Phyllosilicates, layered)

FeTiO3 M = 151.7252 31.56 wt.% Ti 36.81 wt.% Fe 31.63 wt.% O (Oxides and hydroxides) Coordinence Fe(6), Ti(6)

AgI M = 234.77267 45.95 wt.% Ag 54.05 wt.% I (Halides)

α-Fe M = 55.845 (Native elements)

Humite [Named after the British mineralogist Sir Abraham Hume (1749–1838)] (ICSD 34847 and PDF 12-755)

Illite (syn., hydromuscovite, hydromica, gumbelite) [Named after Illinois, USA]

Ilmenite [12168-52-4] (syn., mannacanite) [after the lake Ilmen, Russia] (ICSD 30664 and PDF 29-733)

Iodargyrite [7783-96-2] (syn., Iodyrite) [Named after Greek, iodos, violet, and Latin, argentum, silver) (ICSD 65063 and PDF 9-374)

Iron (native telluric and meteoritic) [7439-89-6] (syn., ferrum, ferrite)

Trigonal (Rhombohedral) a = 508.84 pm c = 1408.85 pm (Z = 6) S.G. R3m P.G. 3 Ilmenite type

Monoclinic a = 518 pm b = 898 pm c = 1032 pm β = 101.83° (Z = 2) S.G. C2/m P.G. 2/m

Orthorhombic a = 1024 pm b = 2072 c = 473.5 (Z = 4) P.G. 2/m2/m2/m S.G. Pnma (Humite group)

Isotropic R = 60%

Uniaxial (+)

Uniaxal (–) ω = 2.700 ε = 2.700 Dispersion strong R = 19.4%

Biaxial (–) α = 1.535–1.57 β = 1.555–1.6 γ = 1.565–1.605 δ = 0.030–0.035 2V = 5–25° Dispersion none

Biaxial α = 1.607–1.643 β = 1.619–1.653 γ = 1.639–1.675 δ = 0.029–0.031 2V = 65–84° O.A.P (001)

4 (HV 160)

1.5–2

5.0–5.5 (HV 519– 703)

1–2

6

4–4.5

Mohs hardness (/HM) (Vickers)

Biaxial (+) α = 2.17 β = 2.22 γ = 2.30 δ = 0.13 2V = 73°

Optical properties

7300– 7870 (7890)

5500– 5700

4720– 4780

2820– 2610

3200– 3420

7250

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 483.4 pm b = 575.8 pm c = 499.9 pm β = 91.18° (Z = 2) P.G. 2/m S.G. P2/c Wolframite type

MnWO4 M = 302.775649 18.14 wt.% Mn 60.72 wt.% W 21.14 wt.% O Coordinence Mn(6), W(4) (Sulfates, chromates, molybdates, and tungstates)

Hubnerite (syn., huebnerite) [Named after the German mineralogist, Adolph Huebner] (ICSD 15850 and PDF 13-434)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: tiny magnetic globules. Color: steel gray for freshly exposed surfaces to iron black. Diaphaneity: opaque. Luster: metallic. Streak: gray. Fracture: hackly. Ferromagnetic with a Curie temperature of 770°C. Occurrence: in basalts in the Disko Island, Greeland.

Habit: platy. Color: pale yellow or green. Luster: adamantine-greasy. Diaphaneity: transparent to translucent.

Habit: tabullar, lamellar, massive. Color: iron black. Diaphaneity: opaque. Luster: submetallic. Streak: brownish black. Fracture: subconchoidal. Cleavage: none. Chemical: insol. in HCl, or HNO3 but attacked by boiling H2SO4. Slightly antiferromagnetic with a specific magnetic susceptibility of +10–6 m3.kg–1. Nonfusible with a melting point of 1365–1470°C. Semiconductive with an electrical resistivity ranging from 0.001 to 4 Ω.m. Deposits: massive hard rock hemo-ilmenite deposits in ultramafic igneous rocks (e.g., anorthosites, peridotites, gabbros, diorites, syenites) such as the large deposits of Allard lake (Québec, Canada) or Tellnes (Norway). Sedimentary deposits as heavy mineral sands in South Africa (Richards Bay), Australia, India and Brazil.

Habit: fined grained clay sometimes indurated. Color: gray-white to graish-green. Diaphaneity: translucent to opaque. Luster: waxy. Streak: white. Cleavage: (001) perfect. Decomposed by conc. HCl. Occurrence: weathering of orthoclase associated with other clay minerals such as kaolinite.

Habit: massive. Color: brown, yellow, orange, red, colorless. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Cleavage: (100) poor. Fracture: uneven, brittle. Chemical: attacked by strong mineral acids giving a silica gel. Deposits: dolomites, limestones, skarns.

Habit: long prismatic. Color: red brown. Luster: submetallic. Diaphaneity: opaque. Cleavage: (010) perfect. Fracture: uneven, brittle.

Other relevant mineralogical, physical, and chemical properties with occurrence

832 Minerals, Ores and Gemstones

Cubic a = 383.92 pm A1, cF4 (Z = 4) Fm3m Copper type

(Ir,Os,Ru) (Native elements)

IrxOsyRuz Native elements (Platinum group metals, PGMs)

MnFe2O4 (Oxides, and hydroxides)

Na(Al,Fe)[Si2O6] M = 202.1387 11.37 wt.% Na 13.35 wt.% Al 27.79 wt.% Si 47.49 wt.% O Coordinence Na(8), Al(6), Si(4) Traces of Mg, Ca, and Fe (Inosilicates, chain, ribbon)

K[Fe3(SO4)2(OH)6] M = 692.9319 5.642 wt.% K 24.178 wt.% Fe 18.510 wt.% S 50.797 wt.% O 0.873 wt.% H Coordinence K(12), Fe(6), S(4) (Sulfates, chromates, molybdates, and tungstates) and tungstates); Al can substitute to Fe (AluniteJarosite solid solution)

MgSO4.KCl.3H2O M = 248.96544 15.70 wt.% K 9.76 wt.% Mg 2.43 wt.% H 12.88 wt.% S 14.24 wt.% Cl 44.98 wt.% O (Sulfates, chromates, molybdates, and tungstates)

Iridium [Named from the Latin, iris, rainbow, in allusion to the colored salts derived from its compounds] (ICSD 64992 and PDF 6-598)

Iridosmine (syn., siserskite, nevyanskite)

Jacobsite [1310-36-7] [Named after Jacobsberg, Wermland, Sweden] (ICSD 66851 and PDF 10-319)

Jadeite [from the Spanish, piedra de ijada, stone of the side, because its supposed to cure kidney ailments if applied to the side of the body] (ICSD 10232 and PDF 22-1338)

Jarosite [Named in 1852 after the Barranco del Jaroso Ravine in the Sierra Almagrera, Spain] (ICSD 12107 and PDF 36-427)

Kainite [from the Greek, kainos, contemporary] (ICSD 26003 and PDF 25-660)

Monoclinic a = 1972 pm b = 1623 pm c = 953 pm β = 94.92° (Z = 4) S.G. C2/m P.G. 2/m

Trigonal (Rhombohedral) a = 730.4 pm c = 1726.8 pm (Z = 3) P.G. 32/m S.G. R3m Alunite group

Monoclinic a = 940.9 pm b = 856.4 pm c = 522.0 pm 107.43° (Z = 4) P.G. 2/m S.G. C2/c Diopside type

Cubic a = 851 pm H11, cF56 (Z = 8) Fd3m Spinel type

Hexagonal a = 273 pm c = 432 pm (Z = 2) S.G. P63 /mmc

S.G. Im3m P.G. 432

(ICSD 64795 and PDF 6-696)

Biaxial (–) α = 1.494 β = 1.505 γ = 1.516 δ = 0.022 2V = 88°

Uniaxial (–) ε = 1.705–1.715 ω = 1.791–1.820 δ = 0.660

Biaxial (+) α = 1.640–1.658 β = 1.645–1.663 γ = 1.652–1.673 δ = 0.012–0.013 2V = 67–75° Dispersion moderate

Isotropic nD = 2.30 R = 18.5%

Uniaxial R = 55%

Isotropic R = 68%

3

2.5–3.5

6–6.5

5.5 (HV 724– 745)

6–7 (HV 1206– 1246)

6–7

2100

2910– 3260 (3250)

3240– 3430

4870

17,600– 22,400

22,600– 22,800

Habit: massive, granular, encrustations. Color: white, yellow, reddish gray, or dark flesh red. Luster: vitreous, greasy. Streak: white. Fracture: conchoidal. Cleavage: [001] good.

Habit: minute pseudocubic crystals or tabular, also granular, massive, earthy cryptocristalline crust and coatings. Color: ocherous, amber-yellow or dark brown. Diaphaneity: opaque. Luster: subadamantine to vitreous or resinous. Streak: pale yellow. Fracture: uneven to conchoidal. Cleavage: distinct (0001). Other: Pyroelectric. Chemical: insoluble in water but dissolves in HCl. Occurrence: widespread secondary mineral as encrustation and coating in the oxidizing zone of sulfidic ore deposits along with limonite and goethite. Forms from the aerobic alteration of pyrite.

Habit: granular, fibrous, massive. Color: green, white, pale bluish gray, grayish green, or pale purple. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: translucent. Streak: white. Cleavage: (110) good. Twinning: {100}, {001}. Fracture: tough. Chemical: insoluble in strong mineral acids. Occurrence: strongly metamorphosed sodium-rich serpentinous rocks.

Habit: massive. Color: black. Diaphaneity: opaque. Luster: metallic to submetallic. Streak: brownish-black. Cleavage: none. Ferromagnetic.

Habit: hexagonal tabular crystals to flattened grains. Color: tin white to iron black. Luster: metallic. Diaphaneity: opaque. Cleavage: [0001] perfect. Fracture: subconchoidal to uneven. Streak: white. Does not dissolve into aqua regia (3 vol.HCl + 1 vl. HNO3). Occurrence: mafic and ultramafic igneous rocks (e.g., gabbros, peridotites, pyroxenolites) along with magnetite and ilmenite and placer deposits.

Color: white. Diaphaneity: opaque. Luster: metallic. Cleavage: none. Streak: white.

Mineral and Gemstone Properties Table 833

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Al4[Si4O10(OH)8] M = 516.32088 20.90 wt.% Al 21.76 wt.% Si 1.56 wt.% H 55.78 wt.% O Coordinence Al(6), Si(4) (Phyllosilicates, layered)

V2O3 M = 149.880 67.98 wt.% V 32.02 wt.% O (Oxides and hydroxides)

MgTi2O5 M = 200.036 12.15 wt.% Mg 47.85 wt.% Ti 40.00 wt.% O Coordinence Ti(6)

Na2B4O6(OH)2.3H2O M = 290.28379 15.84 wt.% Na 14.90 wt.% B 3.13 wt.% H 66.14 wt.% O Coordinence Na(5), B(3, and 4) (Carbonates and borates)

AuTe2 M = 452.17 43.56 wt.% Au 56.44 wt.%Te (Sulfides and sulfosalts)

Al2O[SiO4] = Al2SiO5 M = 162.04558 33.30 wt.% Al

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Kaolinite (1Tc) [Named after the locality, Kao-Ling, China, where clay was extracted, from the Chniese, kao high, ling, mountain] (ICSD 63315 and PDF 14-164)

Karelianite [1314-24-7] [Named after Karelia, Finland] (ICSD 201106 and PDF 34-187)

Karrooite [12032-35-8] [Named after the South African Karroo desert]

Kernite (syn., rasorite) [Named after locality of Kern County, California, the location of the borate deposits at Kramer] (ICSD 10378 and PDF 25-1322)

Krennerite [Named after the Hungarian mineralogist Joseph A. Krenner (1839–1920)] (ICSD 30902 and PDF 8-20)

Kyanite (syn., cyanite, disthene) [from the Greek, kyanos, blue, and dis,

Table 12.23. (continued)

Triclinic a = 712.3 pm b = 784.8 pm

Orthorhombic a = 1654 pm b = 882 pm c = 446 pm C46, oP24 (Z = 8) S.G. Pma

Monoclinic a = 702.2 pm b = 915.1 pm c = 1567.6 pm β = 108.88° (Z = 4) P.G. 2/m S.G. P21/c

Orthorhombic a = 975 pm b = 1000 pm c = 375 pm P.G. 2/m 2/m 2/m S.G. A2/m Karrooite type

Trigonal (Rhombohedral) a = 499 pm c = 1398 pm D51, hR10 (Z = 2) S.G. R3c P.G. 32/m Corundum type

Biaxial (–) α = 1.712–1.718 β = 1.721–1.723

Biaxial R = 60.9%

Biaxial (–) α = 1.454 β = 1.472 γ = 1.488 δ = 0.034 2V = 80° Dispersion distinct

Biaxial (?)

Uniaxial (–)

5.5 (100) 7.0

2.5

2.5–3

n.a.

8–9

2–2.5

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 1.553–1.563 β = 1.559–1.569 γ = 1.565–1.570 δ = 0.007 2V = 40–44° Dispersion none

Optical properties

3530– 3650

8530

1900– 1920 (1905)

3630

4870 (4950)

2600

Density (ρ/kg.m–3) (calc.)

Triclinic a = 515 pm b = 892 pm c = 738 pm α = 91.8° β = 104.8° γ = 90.0°, (Z = 1) P.G. 1 S.G. P1

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: blady, columnar, tabular, fibrous. Color: blue, white, yellowish, gray, green, or black. Luster: vitreous (i.e., glassy), pearly. Diaphaneity: translucent to transparent. Streak: white. Fracture: uneven, brittle. Luminescence: pink to red. Cleavage: (100)

Habit: striated. Color: white or blackish yellow. Luster: metallic. Diaphaneity: opaque.

Habit: crystalline, coarse, acicular, massive. Color: colorless or white. Luster: vitreous, pearly. Diaphaneity: transparent to translucent. Cleavage: (100) perfect, (001) perfect, (201) good. Fracture: uneven, brittle. Streak: white. Occurrence: Weathered buried salty lake deposits.

Melts at 1630°C

Habit: granular anhedral crystal or prismatic crystals. Color: black. Diaphaneity: opaque. Luster: metallic. Cleavage: none. Fracture: conchoidal. Streak: black. Occurrence: found in sulfide-rich glacial boulders derived from high-grade metamorphic rocks (schists and quartzites).

Habit: platy, massive. Color: white, brownish white, grayish white, yellowish white, or grayish green. Diaphaneity: transparent to translucent. Luster: earthy (i.e., dull). Streak: white. Cleavage: (001) perfect. Fracture: flexible.

Other relevant mineralogical, physical, and chemical properties with occurrence

834 Minerals, Ores and Gemstones

17.33 wt.% Si 49.37 wt.% O Traces of Fe, Ca, Cr Coordinence Al(6), Si(4) (Nesosubsilicates)

V2Ti3O9 M = 389.4786 26.16 wt.% V 36.87 wt.% Ti 36.97 wt.% O Coordinence Ti(6) (Oxides, and hydroxides)

(Ca,Na)(Si,Al)4O8 An60 Ab40 M = 271.81357 3.38 wt.% Na 8.85 wt.% Ca 15.88 wt.% Al 24.80 wt.% Si 47.09 wt.% O (Tectosilicates, framework)

K2Mg2(SO4)3 M = 1291.77 0.93 wt.% Ca 47.63 wt.% Mn 6.05 wt.% Fe 4.35 wt.% Si 11.31 wt.% Sb 29.73 wt.% O (Sulfates, chromates, molybdates, and tungstates)

Ca2[SiO4] M = 172.24 46.54 wt.% Ca 16.31 wt.% Si 37.16 wt.% O (Nesosilicates)

CaSi4Al2O12.4H2O M = 470.44 8.52 wt.% Ca 11.47 wt.% Al 23.88 wt.% Si 1.71 wt.% H 54.42 wt.% O Coordinence Ca(6), Si(4), Al(4) (Tectosilicates, zeolite group)

two-fold, and sthenos, force, owing to the variation of hardness according to crystal planes] (ICSD 27771 and PDF 11-46)

Kyzylkumite [80940-68-7] [Named after Kyzyl-Kum, Uzbekistan]

Labradorite (syn., spectrolite) [Named after the Isle of Paul, Labrador, Canada where the mineral was first discovered about 1770]

Langbeinite [Named after the German chemist of Leopoldshall A. Langbein] (ICSD 100420 and PDF 19-975)

Larnite [Named after Scawt Hill, near Larne, Co., Antrim, Ireland] (ICSD 39006 and PDF 33-302)

Laumontite [Named after the French mineralogist, François Pierre Nicolas Giller de Laumont (1747–1834)] (ICSD 72914 and PDF 45-1325)

Monoclinic a = 1475 pm b = 1310 pm c = 755 pm β = 111.5° (Z = 4) P.G. m S.G. Cm

Monoclinic a = 548 pm b = 676 pm c = 928 pm 94.55° (Z = 4)

Cubic a = 992 pm (Z = 4) P.G. 2/m S.G. P213

Triclinic a = 815.5 pm b = 1284 pm c = 1016 pm Z=6

Monoclinic a = 3380 pm b = 457.8 pm c = 1999 pm β = 93.40° (Z = 4) Pseudorutile type

c = 556.4 pm α = 90°5.5 β = 101°25 γ = 105°44.5 (Z = 4) P.G. 1 S.G. P1

Biaxial (–) α = 1.510 β = 1.520 γ = 1.520 δ = 0.010 2V = 25–45°

Biaxial (+) α = 1.707 β = 1.715 γ = 1.730 δ = 0.023 2V = 13–14° Dispersion strong

Isotropic nD = 1.533–1.535

Biaxial (+) α = 1.554–1.563 β = 1.559–1.568 γ = 1.562–1.573 α = 0.008–0.010 2V = 78–86°

Biaxial (?)

2V = 82–83° Dispersion weak

γ = 1.727–1.734 δ = 0.012–0.016

3–4

6

3.5–4

7

n.a.

(010)

2300

3280

2824

2690

3750 (3770)

Habit: prismatic. Color: white. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (010) perfect, (110) perfect. Fracture: uneven. Pyroelectric. Deposits: volcanic tuffs.

Habit: tabullar crystals, granular or massive aggregates. Color: colorless to white. Diaphaneity: translucent to transparent. Luster: vitreous. Streak: white. Cleavage: (100). Fracture: conchoidal to uneven. Twinning: polysynthetic (100). Chemical: gelatinizes by dil. HCl. Occurrence: metamorphic and ingneous rocks.

Habit: nodules or grains. Color: colorless. Diaphaneity: translucent to transparent. Luster: vitreous. Cleavage: none. Fracture: conchoidal. Phosphorescent. Occurrence: marine evaporite deposits.

Habit: euhedral crystals, striated. Color: white or gray. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy). Cleavage: (001) perfect, (010) good, (110) distinct. Fracture: uneven. Streak: white. Occurrence: magmatic and metamorphic rocks.

Habit: prismatic crystals. Color: black. Luster: vitreous to resinous.

perfect, (010) imperfect. Twinning: {100}. Chemical: insoluble in strong mineral acids. Other properties: Unfusible but when heated above 1200°C transforms to a mixture of silica and mullite (Al6Si2O13). Dielectric constant of 5.7 to 7.18. Diamagnetic with a specific magnetic susceptibility of –10–10 m3.kg–1. Occurrence: metamorphosed peri-aluminous sedimentary rocks.

Mineral and Gemstone Properties Table 835

Minerals, Ores and Gemstones

12

K(Li,Al)3(Si,Al)4O10(F,OH)2 M = 386.31252 10.12 wt.% K 3.59 wt.% Li 6.98 wt.% Al 29.08 wt.% Si 0.52 wt.% H 49.70 wt.% O (Phyllosilicates, layered)

Lepidolite M1 [Named from the Greek lepidion, scale, and lithos, stone] (ICSD 30785 and PDF 38-425)

Monoclinic a = 521 pm b = 897 pm c = 2016 pm β = 100.8° (Z = 4) P.G. 2/m S.G. C2/m Mica group

Orthorhombic a = 386.8 pm b = 1252.5 pm c = 306.6 pm (Z = 4) P.G. mmm S.G. A2/mam Lepidocrite type

FeO(OH) M = 88. 8517 62.85 wt.% Fe 36.01 wt.% O 1.13 wt.% H Coordinence Fe(6) (Oxides and hydroxides)

Monoclinic a = 716 pm b = 726 pm c = 724 pm β = 120.67° (Z = 2) P.G. 2/m S.G. P21/c

Lepidocrocite [20344-49-4] [from the Greek, lipis, scale, and krokis, fibre] (ICSD 27846 and PDF 8-98)

MgAl2(PO4)2(OH)2 M = 302.23 8.04 wt.% Mg 17.86 wt.% Al 20.50 wt.% P 0.67 wt.% H 52.94 wt.% O Coordinence Fe(6), Mg(6), Al(6), P(4) (Phosphates, arsenates, and vanadates)

Lazulite (syn., scorzalite: Fe, Ni) [Named from the Arabic, azul, meaning sky and the Greek, lithos, stone] (ICSD 31259 and PDF 34-136)

Orthorhombic a = 878.7 pm b = 1312.3 pm c = 583.6 pm (Z = 4) P.G. mmm S.G. Ccmm

Biaxial (–) α = 1.525–1.548 β = 1.551–1.58 γ = 1.554–1.586 δ = 0.029–0.038 2V = 25–58° Dispersion weak

Biaxial (–) α = 1.94 β = 2.20 γ = 2.51 δ = 0.57 2V = 83° Dispersion weak R = 20.4%

Isotropic nD = 1.5

Biaxial(–) α = 1.612 β = 1.634 γ = 1.643 δ = 0.031 2V = 70°

Biaxial (+) α = 1.665 β = 1.674 γ = 1.685 δ = 0.020 2V = 76–87° O.A.P. (100) Dispersion strong

Optical properties

2.5–3

5 (HV 690– 782)

5.5

6

7–8

Mohs hardness (/HM) (Vickers)

Cubic a = 891 pm (Z = 1) Sodalite type

CaAl2[Si2O7(OH)2]·H2O M = 314.24 12.75 wt.% Ca 7.17 wt.% Al 17.88 wt.% Si 1.28 wt.% H 50.91 wt.% O Coordinence Ca(8), Al(6), Si(4) (Sorosilicates, pair)

Lawsonite [Named after the American mineralogist Prof. A.C. Lawson] (ICSD 80835 and PDF 13-533)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

2800– 2900 (2830)

4090

2380– 2420

3000

3050– 3120

Density (ρ/kg.m–3) (calc.)

Lazurite (Na,Ca)7–8(Al,Si)12(O,S)24[(SO4),Cl2, (OH)2] (syn., lapis lazuli, lasurite, ultamarine) (Tectosilicates, network) [Named from the Persian lazward, blue] (ICSD 49760 and PDF 42-1312)

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: massive, tabular, lamellar. Color: pale lilac blue, light red, colorless, or gray. Cleavage: (001) perfect. Diaphaneity: translucent. Luster: vitreous, pearly. Fracture: uneven. Streak: white. Occurrence: lithia-bearing pegmatites.

Habit: scaly, fibrous, blady, tabular, pulverulent. Color: red, yellowish brown, or blackish brown. Luster: submetallic. Diaphaneity: opaque. Streak: dark yellow brown, or orange. Cleavage: perfect (010), good (001). Fracture: uneven. Occurrence: iron ore deposits.

Habit: massive, granular. Color: dark blue or greenish blue. Diaphaneity: translucent. Luster: greasy. Luminescence: fluorescent. Cleavage: (110) imperfect. Fracture: conchoidal. Streak: light blue.

Habit: massive, prismatic. Color: azure blue. Streak: white. Diaphaneity: translucent. Luster: vitreous. Fracture: uneven. Cleavage: (011) perfect.

Habit: prismatic, tabular. Color: colorless, pale blue, or grayish blue. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy), greasy. Streak: white. Cleavage: (010) perfect, [100] perfect. Twinning: {110}. Fracture: uneven brittle. Deposits: originally described from a crystalline schist associated with serpentine. Also found as a secondary mineral in altered gabbros and diorites.

Other relevant mineralogical, physical, and chemical properties with occurrence

836 Minerals, Ores and Gemstones

Cubic a = 943 pm (Z = 8) P.G. 23 S.G. Fd3m Lannaeite group

Tetragonal a = 397.6 nm c = 502.3 nm (Z = 2) P.G. S.G. P4/nmm Litharge type

Cubic a = 389 pm S.G. Pm3m Perovskite type

Cubic a = 834 pm H11, cF56 (Z = 8) S.G. Fd3m Spinel type

Co3S4 M = 305.0636 57.95 wt.% Co 42.05 wt.% S (Sulfides and sulfosalts)

α-PbO M = 223.1994 92.83 wt.% Pb 7.17 wt.% O (Oxides and hydroxides)

HgSb4S8 M = 944.118 21.25 wt.% Hg 51.58 wt.% Sb 27.17 wt.% S (Sulfides and sulfosalts)

(Ce,Na,Ca)(Ti,Nb)O3 M = 164.60 8.38 wt.% Na 2.43 wt.% Ca 8.44 wt.% La 17.03 wt.% Ce 23.27 wt.% Ti 11.29 wt.% Nb 29.16 wt.% O (Oxides and hydroxides)

γ-Fe2O3 M = 159.69 69.94 wt.% Fe 30.06 wt.% O (Oxides and hydroxides)

Linnaeite (syn., Linneite) [Named in 1845 after the Swedish botanist, C. Linnaeus (1707–1778)] (ICSD 24212 and PDF 42-1448)

Litharge [1317-36-8] [Named in 1917 after Greek word meaning a pyrometallurgical process to separate lead from silver] (ICSD 62842 and PDF 5-561)

Livingstonite [Named after the missionary, David Livingstone (1813–1873)] (ICSD 60144 and PDF 36–416)

Loparite [Named after the Russian name of inhabitants of the Kola Peninsula] (ICSD 24444 and PDF 35-618)

Maghemite [Named from the fisrt syllables of magnetite and hematite referring to the magnetism and and composition] (ICSD 70048 and PDF 25-1402)

Monoclinic a = 3025 pm b = 398 pm c = 2160 pm β = 104.17° (Z = 8) P.G. 2/m S.G. A2/a

Amorphous or cryptocrystalline

FeO.OH.nH2O (Oxides and hydroxides)

Limonite [Named from the Greek leimon, meadow since it often occurs in bogs and swamps]

Tetragonal (pseudo-Cubic) a = 1343 pm c = 1370 pm (Z = 16) P.G. 4/m S.G. I41a

K[Si2AlO6] M = 218.24724 17.91 wt.% K 12.36 wt.% Al 25.74 wt.% Si 43.99 wt.% O Coordinence K(12), Si(4), Al(4) (Tectosilicates, framework)

Leucite (syn., amphigene) [from the Greek, leukos, white] (ICSD 9826 and PDF 38-1423)

Isotropic nD = 2.52–2.74 R = 25.0%

Isotropic nD = 2.33

Biaxial (–)

Uniaxial (–) α = 2.535 β = 2.665

Isotropic R = 43.6–47.4%

Isotropic nD = 2.0–2.1

Isotropic nD = 1.508–1.511

5.5–6 (HV 894– 988)

5.5

2

2

4.5–5.5 HV 492

4–5.5

5.5–6

5170

4860 (5250)

4810– 4900

9140 (9355)

4500– 4850 (4830)

2700– 4300

2470

Habit: massive, granular, crystalline. Color: black. Luster: metallic. Diaphaneity: opaque. Streak: black. Cleavage: none. Fracture: conchoidal. Ferromagnetic materials.

Habit: tiny cubes. Color: black. Luster: metallic. Streak: brownish. Fracture: conchoidal. Diaphaneity: translucent in this section. Occurrence: greisens and granites.

Habit: radial, fibrous, columnar. Color: steel gray or lead gray. Luster: sub metallic. Diaphaneity: opaque to subtranslucent. Streak: red. Cleavage: [010] perfect, [100] perfect. Fracture: uneven.

Habit: massive, scaly, earthy. Color: red. Luster: greasy to dull. Cleavage: (110). Dimorphous with massicot. Other properties: insoluble in water (ca. 17 mg/L at 20°C) but soluble in acetic acid, dilute HNO3 and in warm solutions of alkali-metal hydroxides. Heated at 300–450°C in air, it convert slowly to minium (Pb3O4) but at higher temperatures it reverts to PbO finally it melts at 888°C and finally decomposes at 1472°C. Occurrence: rare mineral of secondary origin associated with galena.

Habit: octahedral crystals crystalline, fine, encrustations, granular. Color: white or pinkish white. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Cleavage: {001} imperfect. Fracture: uneven to subconchoidal. Other: fuse on the charcoal giving a magnetic globule of Co3O4. Soluble in hot concentrated HNO3 giving sulfur. Occurrence: hydrothermal veins and with other sulfidic Co and Ni ores.

Habit: crystalline, coarse. Color: colorless, white, or gray. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (110) indistinct. Twinning: {100}, {112}. Fracture: brittle, conchoidal. Occurrence: acid volcanic rocks.

Mineral and Gemstone Properties Table 837

Minerals, Ores and Gemstones

12

Trigonal a = 463.30 pm c = 1501.60 pm R3¯c (Z = 6) P.G. -32/m S.G. R-3c Calcite type

Cubic a = 839.4 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

MgFe2O4 M = 200.00 12.15 wt.% Mg 55.85 wt.% Fe 32.00 wt.% O (Oxides and hydroxides)

MgCO3 M = 84.3142 28.83 wt.% Mg 14.25 wt.% C 56.93 wt.% O Coordinence Mg(6), C(3) (Nitrates, carbonates, and borates)

Fe3O4=FeIIFeIII2O4 M = 231.5386 72.36 wt.% Fe 27.64 wt.% O Coordinence Fe(4 and 6) (Oxides and hydroxides)

Cu2(CO3)(OH)2 M = 221.11588 57.48 wt.% Cu 0.91 wt.% H 5.43 wt.% C 36.18 wt.% O Coordinence Cu(4), C(3) (Nitrates, carbonates, and borates)

MnO(OH) M = 87.94482 62.47 wt.% Mn

Magnesioferrite (syn., ceylonite) (ICSD 49551 and PDF 36-398)

Magnesite [546-93-0] (syn., giobertite, bitter spar) [Named after the Greek city of Magnesia] (ICSD 80870 and PDF 8-479)

Magnetite [1309-37-1] (syn., lodestone, magnetic iron ore) [Named from Middle Latin magnes meaning magnet in reference to its magnetic properties; or after Magnes, a shepherd who from discovered the mineral on Mount Ida when the rock was attracted to the nails in his shoes] (ICSD 24830 and PDF 19-629)

Malachite [Named from the Greek, malachis, mallow in reference to green leaf color] (ICSD 100150 and PDF 41-1390)

Manganite (syn., brown manganese) [Named after its chemical

Monoclinic a = 884 pm b = 523 pm

Monoclinic a = 950.2 pm b = 1197.4 pm c = 324.0 pm β = 98.75° (Z = 4) P.G. 2/m S.G. P21/a

Cubic a = 838.3 pm H11, cF56 (Z = 8) S.G. Fd3m Spinel type (Magnetite series)

Biaxial (+) α = 2.24 β = 2.24

Biaxial (–) α = 1.655 β = 1.875 γ = 1.909 δ = 0.254 2V = 43° Dispersion strong.

Isotropic nD = 2.42 R = 21.1%

Uniaxial (–) ε = 1.509–1.563 ω = 1.700–1.782 δ = 0.190–0.218 Dispersion strong

Isotropic nD = 2.380

4 (HV 367– 459)

3.5–4

5.5–6.5 (HV 530– 599)

3.5–4.5

7.5

5.5

Mohs hardness (/HM) (Vickers)

Isotropic nD = 2.00–2.22

Optical properties

4200– 4400

3700– 4000 (4050)

5201

2980– 3500

4520

4200– 4430

Density (ρ/kg.m–3) (calc.)

Cubic a = 827.7pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type (Chromite series)

MgCr2O4 M = 192.29480 12.6395 wt.% Mg 33.2809 wt.% O 54.0796 wt.% Cr Coordinence Mg(4), Cr(6) (Oxides and hydroxides)

Magnesiochromite (syn., picotite) (ICSD 20819 and PDF 10-351)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: prismatic. Color: black, gray. Luster: submetallic. Diaphaneity: opaque. Streak: red brown. Cleavage: perfect (010), good (110). Twinning: {011}. Fracture: conchoidal.

Habit: botryoidal, stalactitic, massive, fibrous. Color: bright green or blackish green. Luster: vitreous, silky, earthy or adamantine. Diaphaneity: translucent to subtranslucent to opaque. Streak: pale green. Cleavage: [201] perfect, [010] fair. Fracture: uneven or subconchoidal. Chemistry: readily dissolved by HCl, and HNO3 evolving carbon dioxide (i.e., effervescence). Other: dielectric constant 6.23 to 4.4. Occurrence: secondary mineral in the oxidized zones of copper ore deposits, in sandstones. Weathering gives cuprite or azurite.

Habit: octahedral, massive, granular, crystalline. Color: black. Luster: metallic. Diaphaneity: opaque. Streak: black. Cleavage: none. Twinning: {111}. Fracture: subconchoidal. Other: highly ferromagnetic, electrical resistivity 56 μΩ.cm.

Habit: rhombohedral, massive, granular, earthy, fibrous. Color: colorless, white, grayish white, yellowish white, or brownish white. Luster: vitreous (i.e., glassy). Diaphaneity: transparent, translucent, to opaque. Streak: white, gray. Cleavage: (1011) perfect. Fracture: brittle, conchoidal. Chemical: decomposed at 990°C giving MgO and readily soluble in diluted acids with evolution of carbon dioxide.

Habit: octahedron or massive. Color: black. Diaphaneity: opaque. Luster: submetallic to metallic luster. Streak: black. Cleavage: none. Fracture: uneven. Ferromagnetic. Occurrence: metamorphic rocks.

Habit: massive granular. Cleavage: none. Color: black. Diaphaneity: opaque. Luster: metallic. Streak: dark red. Fracture: uneven.

Other relevant mineralogical, physical, and chemical properties with occurrence

838 Minerals, Ores and Gemstones

Tetragonal a = 1206.4 pm c = 751.4 pm (Z = 2) S.G. 4/m P.G. I4/m Scapolite type

Orthorhombic a = 589.1 nm b = 548.9 nm c = 475.5 nm (Z = 4) P.G. 222 S.G. Pbcm

FeS2 M = 119.979 46.55 wt.% Fe 53.45 wt.% S (Sulfides and sulfosalts) Coordinence Fe(6)

CaAl2(OH)2Si2Al2O10 M = 398.18 10.07 wt.% Ca 27.10 wt.% Al 14.11 wt.% Si 0.51 wt.% H 48.22 wt.% O Coordinence Ca(6), Al(6), Al(4), Si(4) (Phyllosilicates, layered)

Na4ClSi9Al3O24 M = 845.11 10.88 wt.% Na 9.58 wt.% Al 29.91 wt.% Si 4.20 wt.% Cl 45.44 wt.% O (Tectosilicates, framework) Coordinence Na(6), Si(4), Al(4)

β-PbO M = 223.1994 92.83 wt.% Pb 7.17 wt.% O (Oxides and hydroxides)

Marcasite [Named after Arabic or Moorish for pyrite and similar substances] (ICSD 26756 and PDF 37-475)

Margarite (2M1) [Named from the Greek, margaritos, meaning pearl] (ICSD 31365 and PDF 18-276)

Marialite [Named by von Rath in honor of his wife, Maria Rosa vom Rath (1830–1888)] (ICSD 39963 and PDF 31-1279)

Massicot [1317-36-8] [Named from Spanish mazacote] (ICSD 15402 and PDF 38-1477)

Monoclinic a = 514 pm b = 900 pm c = 981 pm 100.8° (Z = 4) P.G.2/m S.G. C2/c

Orthorhombic a = 444.3 pm b = 542.3 pm c = 338.76 pm C18, oP6 (Z = 2) S.G. Pnnm P.G. 222 Marcasite type

Cubic a = 444.5 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 432 Rock salt type Periclase group

MnO M = 70.93745 77.45 wt.% Mn 22.55 wt.% O Coordinence Mn(6) (Oxides, and hydroxides)

Manganosite [1344-43-0] [Named in 1874 after its manganese content] (ICSD 9864 and PDF 7-230)

c = 574 pm β = 90.0° P.G. 2/m S.G. B21/d, (Z = 8)

36.39 wt.% O 1.15 wt.% H Coordinence Mn(6) (Oxides and hydroxides)

composition] (ICSD 27456 and PDF 41-1379)

Biaxial (+) α = 2.510 β = 2.610 γ = 2.710 2V = 90°

Uniaxial (–) ε = 1.536 ω = 1.540 δ = 0.004

Biaxial (–) α = 1.635 β = 1.645 γ = 1.648 δ = 0.013 2V = 45° Dispersion weak

Isotropic R = 48.9–55.5%

Isotropic nD = 2.19 R = 13.6

R = 19.0–31.4%

γ = 2.24 δ = 0.29

2

5–6

3.5–4.5

6–6.5 (HV 941– 1288)

5.5

9640 (9560)

2550

3100

4900

5364 (5370) (HV 317– 328)

Habit: massive, scaly, earthy. Color: sulfur yellow or reddish yellow. Luster: greasy to dull. Cleavage: (100) and (010). Dimorphous with litharge. Other properties: insoluble in water (ca. 17 mg/L at 20°C) but soluble in acetic acid, dilute HNO3 and in warm solutions of alkali-metal hydroxides. Heated at 300–450°C in air, it convert slowly to minium (Pb3O4) but at higher temperatures it reverts to PbO finally it melts at 888°C and finally decomposes at 1472°C. Occurrence: rare mineral of secondary origin associated with galena.

Habit: prismatic. Color: colorless. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Fracture: conchoidal. Cleavage: {110}. Streak: white. Fluorescent under UV-light: yellow, orange.

Habit: foliated. Color: gray yellow. Diaphaneity: transparent to translucent. Luster: vitreous. Cleavage: (001) perfect. Fracture: uneven, flexible. Streak: white.

Habit: tabular, cickscomb aggregate, faces curved. Color: white green. Luster: metallic. Diaphaneity: opaque. Fracture: conchoidal. Cleavage: {101}. Twinning: {101}. Streak: black. Pyroelectric. Occurrence: sedimentary, magmatic, metamorphic, and hydrothermal.

Habit: octahedral crystals, irregular grains or masses. Color: emerald green to brown upon exposure to sunlight. Luster: vitreous to adamantine becomes dull on exposure to air and sunlight. Diaphaneity: translucent. Streak: brown. Fracture: fibrous. Cleavage: fair {001}. Chemical: poorly attacked by HCl or HNO3 giving a colorless solution. Melting point at 1840°C. Occurrence: alteration product of other manganese minerals and ores under reducing conditions.

Mineral and Gemstone Properties Table 839

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Ca4CO3Si6Al6O24 M = 934.71 17.15 wt.% Ca 17.32 wt.% Al 18.03 wt.% S 1.28 wt.% C 46.22 wt.% O (Tectosilicates, framework) Coordinence Ca(6), Si(4), Al(4)

FeSO4·7H2O M = 278.01756 20.09 wt.% Fe 5.08 wt.% H 11.53 wt.% S 63.30 wt.% O (Sulfates, chromates, molybdates, and tungstates)

(Ca,Na)2(Mg,Fe,Al)[Si3O7] (Sorosilicates, pair)

Hg M = 200.59 (Native elements)

Ca3Mg(SiO4)2 M = 328.71 36.58 wt.% Ca 7.39 wt.% Mg 17.09 wt.% Si 38.94 wt.% O

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Meionite [Named from the Greek, meios, less, referring to its less acute pyramidal form compared with vesuvianite] (ICSD 2628 and PDF 44-1399)

Melanterite [7782-63-0] (syn., Green Vitriol, Pistanite, copperas, ferrous sulfate heptahydrate) [Named after the Greek and meaning black metallic dye] (ICSD 16589 and PDF 22-633)

Melilite [Named from the Latin mel for honey and lithos, stone]

Mercury (syn., hydrargyrum, quicksilver) [Named from the Arabic]

Merwinite [Named after the American mineralogist Herbert Eugene Merwin (1878–1963)] (ICSD 26002 and PDF 35-591)

Table 12.23. (continued)

Monoclinic a = 1325.4 pm b = 529.3 pm c = 932.8 pm β = 91.9° (Z = 4) P.G. 2/m S.G.: P 21/a

Trigonal (Rhombohedral) a = 300.5 pm, 70.53° A10, hR1 (Z = 1) S.G. R3m Mercury type

Tetragonal a = 780 pm c = 500 pm (Z = 2) Melilite type

Monoclinic a = 1407 pm b = 650.9 pm c = 1105.4 pm β = 105.60° (Z = 4) P.G. 2/m S.G. P21/c Melanterite type

Biaxial (+) α = 1.702–1.710 β = 1.710–1.718 γ = 1.718–1.726 δ = 0.008–0.023 2V = 52–76°

Isotropic

Uniaxial (+/–) ε = 1.638–1.657 ω = 1.631–1.667 δ = 0.010

Biaxial (+) α = 1.470–1.471 β = 1.477–1.480 γ = 1.486 δ = 0.015–0.016 2V = 85°27' Dispersion none.

6

liquid

5–5.5

2

5–6

Mohs hardness (/HM) (Vickers)

Uniaxial (–) ε = 1.558 ω = 1.595 δ = 0.037

Optical properties

3150– 3310 (3340)

13,596

2950

1890 (1893)

2760

Density (ρ/kg.m–3) (calc.)

Tetragonal a = 1217.4 pm c = 765.2 pm (Z = 2) S.G. 4/m P.G. I4/m Scapolite group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: granular or rarely euhedral tabular or prismatic crystals. Color: colorless to light green. Diaphaneity: translucent. Luster: oily to vitreous. Streak: white. Cleavage: (100). Fracture: uneven. Chemical: readily soluble in HCl. Occurrence: high-pressure low-temperature metamorphism of carbonated rocks.

Occurrence: Secondary mineral resulting from oxidation of cinnabar deposits.

Habit: equant or short prismatic crystals. Color: colorless, yellow to light brown. Diaphaneity: translucent. Luster: vitreous. Streak: white. Cleavage: (001). Fracture: conchoidal. Chemical: gelatinizes in cold and dilute HCl. Occurrence: ultramafic igneous rocks and skarns.

Habit: rare euhedral short prismatic crystals, equant, sometimes pseudo-octahedral forming fibrous and capillary aggregates in efflorescences and encrustations. Color: colorless to green, yellow green, brownish black, bluish green, or greenish white. Luster: vitreous (glassy). Diaphaneity: subtransparent to translucent. Streak: white. Cleavage: [001] perfect, [110] distinct. Fracture: conchoidal. Other: readily soluble in water giving solutions that taste sweetish astringent and iron, insoluble in ethanol. Easily fusible. Loss of three water molecules above 21°C giving pale apple-green FeSO4.4H2O. Then loss of another three water molecules above 80°C, to give the white monohydrate: FeSO4.H2O. The complete dehydratation occurs above 406°C forming the yellowish green crystals of orthorhombic anydrous sulfate: FeSO4. Finally, it decomposes above 480°C on intense heating giving-off Fe2O3 with strong evolutions of corrosive white fumes of SO2/SO3. Occurrence: secondary product formed during weathering of pyrite, marcassite, and other iron sulfides; effloresnce and crusts on mining walls. Large amount of synthetic material by-produced during the industrial manufacture of white pigment titanium dioxide by the sulfate process. The synthetic mineral is extensively used as flocculating agent in waste water treatment, as feedstock in inks and plant fertilizers.

Habit: prismatic. Color: colorless. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Fracture: conchoidal. Cleavage: {110}. Streak: white. Fluorescent under UV-light: yellow, orange.

Other relevant mineralogical, physical, and chemical properties with occurrence

840 Minerals, Ores and Gemstones

HgS M = 232.656 86.22 wt.% Hg 13.78 wt.% S (Sulfides and sulfosalts)

K[Si3AlO8] M = 278.33154 14.05 wt.% K 9.69 wt.% Al 30.27 wt.% Si 45.99 wt.% O Coordinence K(10), Si(4), Al(4) (Tectosilicates, framework)

NiS M = 114.537 48.76 wt.% Fe 51.24 wt.% Ni (Sulfides and sulfosalts) Coordinence Ni(5)

Pb2PbO4 M = 685.5976 90.67 wt.% Pb 9.33 wt.% O (Oxides and hydroxides)

MoS2 M = 160.072 59.94 wt.% Mo 40.06 wt.% S (Sulfides and sulfosalts) Coordinence Mo(6)

(Ce0.50La0.25Nd0.20Th0.05)PO4 Coordinence Ce(8), P(4) M = 240.21 14.46 wt.% La 29.17 wt.% Ce 4.83 wt.% Th 12.89 wt.% P 12.01 wt.% Nd 26.64 wt.% O (Phosphates, arsenates, and vanadates)

Metacinnabar (syn., Onofrite(Se) Guadalcazarite(Zn) Saukovite(Cd)) [Named from Greek, meta, and cinnabar similar chemical composition and association with cinnabar] (ICSD 24094 and PDF 6-261)

Microcline (syn., amazonite green) [from the Greek, mikron, little and klinein, to stoop in reference to its characteristic variation of cleavage angle and amazonite after Amazon River, South America] (ICSD 34790 and PDF 19-932)

Millerite [Named after the British crystallographer William H. Miller] (ICSD 40054 and PDF 12-41)

Minium (syn., red lead oxide) [Named after the river Minius located in northwest of Spain] (ICSD 22325 and PDF 41-1494)

Molybdenite (2H) [1317-33-5] (syn., molybdic ochre) [Named from the Greek, molybdos, lead] (ICSD 49801 and PDF 37-1492)

Monazite [Named from the Greek, monazeis, to be alone in allusion to its isolated crystals and their rarity when first found] (ICSD 79746 and PDF 32-199)

Monoclinic a = 679.0 pm b = 701 pm c = 646 pm β = 104.4° (Z = 4) P.G. 2/m S.G. P21/n Crocoite type

Hexagonal a = 316.04 pm c = 1229.50 pm C7, hP6 (Z = 2) S.G. P63/mmc P.G. 622 Molybdenite type

Tetragonal P.G. –4 Spinel type

Trigonal (Rhombohedral) a = 961.6 pm c = 315.2 pm B13, hR6 (Z = 3) S.G. R3m P.G. 3m Millerite type

Triclinic a = 857.7 pm b = 1296.7 pm c = 722.3 pm α = 89.7° β = 115.97° γ = 90.87° (Z = 4) P.G. 1 S.G. P1

Cubic a = 585.3 pm (Z = 4)

Biaxial (+) α = 1.785–1.800 β = 1.786–1.801 γ = 1.838–1.851 δ = 0.045–0.075 2V = 10–19°

Uniaxial (–) ω = 4.33 ε = 2.03 δ = 2.3 R = 15.0–37.0%

Uniaxial n ~ 2.42

Uniaxial R = 54–60%

Biaxial (–) α = 1.518 β = 1.522 γ = 1.525 δ = 0.007 2V = 77–84° Dispersion weak

Isotropic R = 26.8%

8200

5500

2560

7700– 7800

5–5.5

5150– 5300 (5340)

1–1.5 5060 (HV 16–19 and 21– 28 //)

2.5–3

3–3.5 (HV 225– 256 and 235– 280 //)

6

3

Habit: crystalline, tabular, prismatic. Color: black, gray, brown, red, yellow, green, or orange. Diaphaneity: transparent to opaque. Luster: adamantine, resinous (Th rich). Streak: grayish white. Cleavage: (001) distinct, (100) indistinct. Twinning: {100} common. Fracture: uneven, subconchoidal. Chemical: slightly soluble in hot conc. H2SO4. When wetted by H2SO4, color the Bunsen flame in blue-green. Unfusible. Deposits: granodiorites, syenites, granitic pegmatites, heavy mineral sands. Other properties: slightly paramagnetic with a specific magnetic susceptibility of 10–7 m3.kg–1. Owing to its thorium content that can reach 10 wt.% in some cases (e.g., Madagascan monazite), monazite is considered as a radioactive material as defined in 49 CFR 173.403, that is, with a specific activity greater than 70 kBq /kg.

Habit: foliated, massive, disseminated. Luster: metallic. Diaphaneity: opaque. Color: bluish lead gray or lead gray. Streak: greenish gray. Cleavage: {0001} perfect. Fracture: sectile and flexible. Sol. conc. Acids. Electrical resistivity 0.12 to 7.5 Ω.m.

Habit: scaly, massive, granular, striated. Color: light red, brownish red, vivid red, or yellowish red. Luster: adamantine. Diaphaneity: subtransparent to opaque. Streak: yellowish orange. Cleavage: [110] perfect, [010] perfect. Fracture: earthy. Occurrence: Oxidized portions of lead ore deposits.

Habit: acicular, fibrous. Color: brass yellow. Luster: metallic. Diaphaneity: opaque. Streak: greenish gray. Fracture: uneven. Electrical resistivity 20 to 40 μΩ.cm.Antiferromagnetic.

Habit: blocky, crystalline, coarse, prismatic. Color: white, cream, bright green, or green. Diaphaneity: translucent to transparent. Luster: vitreous (i.e., glassy). Cleavage: (001) perfect, (010) good. Twinning: albite [010], pericline [010]. Fracture: uneven. Streak: white. Occurrence: granitic pegmatites, hydrothermal and metamorphic rocks.

Habit: granular, encrustations. Color: black or gray black. Luster: metallic. Diaphaneity: opaque. Streak: black. Fracture: uneven.

Mineral and Gemstone Properties Table 841

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

CdO M = 128.4104 87.54 wt.% Cd 12.46 wt.% O

CaMg[SiO4] M = 156.4 25.61 wt.% Ca 15.53 wt.% Mg 17.95 wt.% Si 40.90 wt.% O Coordinence Ca(6), Mg(6), Si(4) (Nesosilicates)

Na0.2Ca0.1Al2[Si4O10](OH)2.10H2O 0.84 wt.% Na 0.73 wt.% Ca 9.83 wt.% Al 20.46 wt.% Si 4.03 wt.% H 64.12 wt.% O Phyllosilicates

HgO M = 216.5894 92.61 wt.% Hg 7.39 wt.% O (Oxides and hydroxides)

Al6Si2O13 M = 322.38 34.31 wt.% Al 16.55 wt.% Si 49.13 wt.% O (Nesosubsilicates)

KAl2(Si3Al)O10(OH,F)2 M = 398.3081 9.82 wt.% K 20.32 wt.% Al 21.15 wt.% Si

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Monteponite [1306-19-0] (syn. cadmium oxide) [Named after the Sardinian locality Monte Poni, Italy] (ICSD 29289 and PDF 5-640)

Monticellite [Named after the Italian mineralogist Teodoro Monticelli (1759–1846)] (ICSD 79792 and PDF 35-590)

Montmorillonite (syn. bentonite) [Named after Montmorillon, Vienne, France]

Montroydite [Named after theTexan mine owner Montroyd Sharp] (ICSD 15890 and PDF 34-1469)

Mullite (syn., mullite 3:2) [Named from the Island of Mull, Scotland] (ICSD 66444 and PDF 15-776)

Muscovite 2M1 (syn., isinglass, potash mica, fuchsite: Cr, sericite) [from Latin, vitrum muscoviticum, Muscovy glass, alluding to the Russian

Table 12.23. (continued)

Monoclinic a = 520.3 pm b = 899.5 pm c = 2003.0 pm β = 94.47°

Orthorhombic a = 757.8 pm b = 768.76 pm c = 288.42 pm (Z = 1) P.G. 2/m2/m2/m S.G. Pbam

Orthorhombic a = 661 pm b = 552 pm c = 352 pm (Z = 4) P.G. 222 S.G. Pnma

Monoclinic a = 493–520 pm b = 894–902 pm c = 1240 pm β = 99.54° (Z = 1) S.G. C2/m

Orthorhombic a = 481.5 pm b = 1108.4 pm c = 637.6 pm (Z = 4) P.G. mmm S.G. Pbnm (Olivine group)

Biaxial (–) α = 1.552–1.574 β = 1.582–1.610 γ = 1.587–1.616 δ = 0.034–0.042

Biaxial (+) α = 1.642–1.653 β = 1.644–1.655 γ = 1.654–1.679 δ = 0.012–0.026 2V = 20–50° O.A.P. (010)

Biaxial (+) α = 2.37 β = 2.50 γ = 2.65 δ = 0.280

Biaxial (–) α= 1.480–1.503 β = 1.500–1.534 γ = 1.500–1.534 2V = 10–25°

Biaxial (–) α = 1.639–1.653 β = 1.645–1.664 γ = 1.653–1.674 δ = 0.014–0.017 2V = 72–82° Dispersion weak

2.5–3 (HV 85)

6–7

1.5–2

1–2

5.5

3

Mohs hardness (/HM) (Vickers)

Isotropic nD = 2.49

Optical properties

Habit: tabular crystals. Color: pale yellow to olive green. Diaphaneity: translucent. Luster: waxy to resinous. Fracture: conchoidal to fibrous. Cleavage: (001) perfect. Other: Expands with ethylene glycol but not with water. Decomposed by HCl with formation of a gel. Occurrence: found in weathering products of basic igneous rocks along with other phyllosilicates such as kaolinite, glauconite, chlorite and vermiculite. Found in vertisols.

Habit: crystalline, fine, prismatic. Color: colorless or gray. Diaphaneity: transparent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (010) good, (100) poor. Twinning: {031}. Occurrence: metamorphosed siliceous dolomitic limestones.

Habit: coating. Color: black but orange-red in transmitted light. Luster: metallic. Diaphaneity: transparent. Others: Soluble in strong mineral acids, melting point of 1555°C.

Other relevant mineralogical, physical, and chemical properties with occurrence

2770– 2880

3150– 3260 (3050)

Habit: massive, lamellar, foliated, micaceous. Color: white, gray, silver white, brownish white, or greenish white. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: (001) perfect. Fracture: brittle, sectile. Chemical: insoluble in strong mineral acids. Unfusible. Dielectric properties. Relative permittivity: 5 to 8, dielectric field strength: 10–20 kV/mm, loss tangent 0.001 to 0.004 , electrical resistivity

Habit: well-formed fine sized crystals, prismatic crystals shaped like slender prisms. Color: colorless, violet, yellow, white, light pink. Diaphaneity: transparent to translucent. Luster: vitreous (glassy). Streak: white. Fracture: brittle. Occurrence: Originally found in melted argillaceous inclusions in lavas from cenozoic on the Island of Mull, Scotland but usually found in artificial melts in porcelain and refractories as a result of the heating of andalusite, kyanite and sillimanite to high temperatures (1400°C) according to reaction: 3 Al2SiO5 = Al6Si2O13 + SiO2.

11,300 Habit: crystalline, fine. Color: reddish orange. Luster: adamantine. Streak: reddish orange. (11,209) Cleavage: [010] perfect. Occurrence: oxidized mercury deposits.

2290– 2360

3080– 3270

8100– 8200 (8238)

Density (ρ/kg.m–3) (calc.)

Cubic a = 469.53 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4–32 Rock salt type Periclase group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

842 Minerals, Ores and Gemstones

0.51 wt.% H 48.20 wt.% O Coordinence K(6), Al(6), Si(4), and Al(4) (Phyllosilicates, layered)

NaHCO3 M = 84.007 52.39 wt.% CO2 36.89 wt.% Na2O 10.72 wt.% H2O (Carbonates)

Na2Si3Al2O10.2H2O M = 380.22 12.09 wt.% Na 14.19 wt.% Al 22.16 wt.% Si 1.06 wt.% H 50.49 wt.% O Coordinence Na(6), Si(4), and Al(4). (Tectosilicates, framework)

KNa3Si4Al4O16 M = 146.08 6.69 wt.% K 11.80 wt.% Na 18.47 wt.% Al 19.23 wt.% Si 43.81 wt.% O Coordinence Na(8), K(9), Si(4), Al(4) (Tectosilicates, framework)

NiAs M = 133.61159 43.92 wt.% Ni 56.08 wt.% As Traces of Fe, S, Co, Sb, Bi, and Cu (Sulfides and sulfosalts) Coordinence Ni(6)

KNO3 M = 101.10324 38.67 wt.% K 13.85 wt.% N 47.47 wt.% O Coordinence K(6), N(3) (Nitrates, carbonates, and borates)

province of Muscovy] (ICSD 34406 and PDF 6-263)

Nahcolite [144-55-8] (sodium bicarbonate) [Named in 1929 from an acronym of Na, H, C, O and the Greek, lithos, stone] (ICSD 18183 and PDF 15-70)

Natrolite [Named from Latin natrium or Greek, natron, native soda and lithos, stone] (ICSD 16033 and PDF 15-800)

Nepheline (syn., nephelite, elaeolite) [from the Greek, nephele, cloud, because it becomes clouded when put in strong acid] (ICSD 2937 and PDF 9-338)

Niccolite (syn., nickeline) [Named from the old German, nickel, meaning an ore which is not usefull] (ICSD 31062 and PDF 47-1737)

Niter (syn., salpeter nitre) [Named from Latin, nitrum, the Greek, nitron, or the Hebrew, nether; perhaps originally from Nitria, a city in Upper Egypt] (ICSD 10289 and PDF 5-377)

Orthorhombic a = 643.1 pm b = 916.4 pm c = 541.4 pm (Z = 4) P.G. mmm S.G. Pmcn Aragonite type

Hexagonal a = 360.9 pm c = 501.9 pm B81, hP4 (Z = 2) S.G. P63/mmc P.G. 622 Niccolite type

Hexagonal a = 1001 pm c = 840.5 pm (Z = 2) P.G. 6 S.G. P63

Orthorhombic a = 1830.0 pm b = 1863.0 pm c = 660.0 pm (Z = 8) P.G. m2m S.G. Fd2d (Zeolite group)

Monoclinic a = 752.5 pm b = 972 pm c = 353 pm β = 93°19' (Z = 4) S.G. P21/n P.G. 2/m

(Z = 4) Type 2M1 mica (Micas group)

Biaxial (–) α = 1.333 β = 1.505 γ = 1.505 δ = 0.172 2V = 7°

Uniaxial R = 52.0–58.3%

Uniaxial (–) ε = 1.528–1.544 ω = 1.531–1.549 δ = 0.003–0.005

Biaxial (+) α = 1.480 β = 1.480 γ = 1.490 δ = 0.012 2V = 38–62°

Biaxial (–) α = 1.375 β = 1.498–1.503 γ = 1.583 δ = 0.208 2V = 75°

2V = 30–47° Dispersion weak

2

5–5.5 (HV 308– 455)

6

5–5.5

2.5

2100

7780

2600

2230

2210– 2238 (2160)

Occurrence: efflorescence on cavern walls.

Habit: massive, reniform, columnar. Color: dark tarnish red or pale copper red. Luster: metallic. Diaphaneity: opaque. Streak: brownish black. Cleavage: {1010} imperfect, {0001} imperfect. Fracture: uneven, brittle. Chemical: dissolved by aqua regia. Electrical resistivity 0.1 to 2 mΩ.cm. Occurrence: in ore veins with silver, copper, and nickel arsenides and sulfides.

Habit: massive, granular, prismatic. Color: white, gray, brown, brownish gray, or reddish white. Diaphaneity: transparent to opaque. Luster: vitreous, greasy. Streak: white. Cleavage: (1010) poor. Twinning: {100}, {112}, and {335}. Fracture: Subconchoidal. Occurrence: Silica-poor igneous rocks. Other: Cp = 123 J.K–1.mol–1.

Habit: acicular. Color: colorless, gray. Diaphaneity: transparent to translucent. Luster: vitreous. Streak: white. Cleavage: (110) perfect. Fracture: uneven. Other: Cp = 381 to 425 J.K–1.mol–1.

Habit: elongated crystals, fibrous masses and friable porous aggregates. Color: colorless, white, yellow, gray even reddish brown to black due to chromophoric impurities (Fe). Diaphaneity: transparent. Luster: vitreous to resinous. Cleavage: perfect on {101}, good on {111}, fair on {100}. Twinning: common on {101}. Streak: white. Fracture: conchoidal. Chemical: soluble in water, ethanol, and glycerol. On heating aqueous solutions decomposes from 20°C and the solid begins to decomposes at 50°C loosing CO2 and giving Na2CO3. Evolves CO2 on contact with weak acids (e.g., acetic). Occurrence: precipitates from hot mineral springs, efflorescences around saline lakes in arid regions.

1011 to 1012 ohm.m. Occurrence: granites and pegmatites.

Mineral and Gemstone Properties Table 843

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

NaNO3 M = 84.9947 27.05 wt.% Na 16.48 wt.% N 56.47 wt.% O Coordinence Na(6), N(3) (Nitrates, carbonates, and borates)

Mg(OH,F)2.Mg2[SiO4] M = 202.00 36.10 wt.% Mg 13.90 wt.% Si 0.25 wt.% H 35.64 wt.% O 14.11 wt.% F Coordinence Mg(6), Si(4) (Nesosilicates)

Na3Mg(CO3)2Cl M = 248.75 27.73 wt.% Na 9.77 wt.% Mg 9.66 wt.% C 14.25 wt.% Cl 38.59 wt.% O (Carbonates, nitrates and borates)

Na8[Al6Si6O24](SO4) M = 1012.38486 18.17 wt.% Na 15.99 wt.% Al 16.65 wt.% Si 0.20 wt.% H 3.17 wt.% S 45.83 wt.% O Traces of Ca, Fe (Tectosilicates, framework)

Cr1.5V0.5Ti3O9 M = 391.10 19.94 wt.% Cr 6.51 wt.% V 36.73 wt.% Ti 36.82 wt.% O Coordinence Ti(6)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Nitratite (syn., nitratine, soda niter, nitronatrite) [Named after its composition of containing nitrates]

Norbergite [Named after the Ostanmosoa iron mine, Norberg, Vastmanland, Sweden] (ICSD 15203 and PDF 11-686)

Northupite [Named after the American amateur mineralogist, Charles H. Northup] (ICSD 4237 and PDF 19-1213)

Nosean (syn., noselite) [Named after the German mineralogist, K.W. Nose] (ICSD 203102 and PDF 17-538)

Olkhonskite [165467-07-2] [Named after Olkhon Island, Lake Baikal, Russia]

Table 12.23. (continued)

Monoclinic a = 703 pm b = 502 pm c = 1883 pm β = 119.6° S.G. Unknown Pseudorutile type

Cubic a = 905 pm (Z = 1) Sodalite type

Cubic a = 1401 pm (Z = 16) P.G. 2/m3 S.G. Fd3

Orthorhombic a = 470 pm b = 1022 pm c = 872 pm (Z = 4) P.G. mmm S.G. Pbnm (Humite group)

Biaxial (?) R = 18.6–20%

Isotropic nD = 1.495

Isotropic nD = 1.514

Biaxial (+) α = 1.563–1.567 β= 1.567–1.579 γ = 1.590–1.593 δ = 0.026–0.027 2V = 44–50°

(HK 1412)

5.5

3.5–4

6–6.5

1.5–2

Mohs hardness (/HM) (Vickers)

Uniaxial (–) ε = 1.587 ω = 1.336 δ = 0.251

Optical properties

(4480)

2300– 2400

2380

3200– 3320

2240– 2290

Density (ρ/kg.m–3) (calc.)

Trigonal (Rhomboedral) a = 507 pm c = 1682 pm (Z = 6) P.G. 32/m S.G. R3c Calcite type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: platy inclusions in rutile. Color: black. Luster: metallic. Occurrence: paragenesis with schreyerite, eskolaite, and karelianite.

Habit: massive, granular. Color: white, gray, blue, green, or brown. Luster: vitreous (i.e., glassy), greasy. Luminescence: fluorescent. Streak: bluish white. Cleavage: [110] poor. Twinning: {111}. Fracture: brittle, conchoidal. Occurrence: igneous rocks low in silica and rich in alkalis.

Habit: crystalline-coarse, pyramidal. Color: white, yellow, or gray. Diaphaneity: transparent to translucent. Luster: vitreous (glassy). Occurrence: continental evaporite deposits.

Habit: massive, tabular. Color: white, yellow, colorless. Luster: vitreous (i.e., glassy). Diaphaneity: translucent to transparent. Streak: white. Cleavage: (100) poor. Twinning: {001}. Fracture: uneven, brittle. Chemical: attacked by strong mineral acids giving a silica gel. Deposits: dolomites, limestones, skarns.

Habit: massive. Color: white, reddish brown, gray, or lemon yellow. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Cleavage: perfect (1014). Twinning: {0001}. Fracture: uneven, sectile. Occurrence: residual water-soluble surface deposits in extremely arid deserts. Nitrates occur in clay rich caliche deposits replenished by occasional desert thunderstorms which fix N2 from the air.

Other relevant mineralogical, physical, and chemical properties with occurrence

844 Minerals, Ores and Gemstones

Monoclinic a = 862.5 pm b = 1299.6 pm c = 719.3 pm β = 116.01° (Z = 4) P.G. 2/m S.G. C2/m

Orthorhombic a = 908.1 pm b = 1843.1 pm c = 523.8 pm (Z = 16) P.G. 222 S.G. Pbca

As2S3 M = 246.0412 60.90 wt.% As 39.10 wt.% S Traces of Se, Sb, V, and Ge (Sulfides and sulfosalts)

K[Si3AlO8] M = 278.33154 14.05 wt.% K 9.69 wt.% Al 30.27 wt.% Si 45.99 wt.% O Coordinence K(10), Si(4), Al(4) (Tectosilicates, framework)

(Fe,Mg)2[Si2O6] Traces of Ca, Fe, Mn, Ni, Cr, Al and Ti (Inosilicates, single chain)

Pd or (Pd,Hg) M = 106.42 (Native elements)

Orpiment [from the Latin, auri pigmentum, given by Pliny in allusion to the vivid golden hue] (ICSD 15239 and PDF 24-75)

Orthoclase (syn., orthose, adularia) [Named from the Greek, orthos, right, and kalos, I cleave in allusion to the mineral’s right angle of good cleavage] (ICSD 9544 and PDF 31-966)

Orthoferrosilite (syn., ferrosilite)

Palladium [Named after the discovery of the asteroid, Pallas] (ICSD 64922 and PDF 46-1043)

Cubic a = 389.03 pm A1, cF4 (Z = 4) S.G. Fm3m Copper type

Monoclinic a = 1149 pm b = 959 pm c = 425 pm D5f, mP20 (Z = 4) S.G. P21/c P.G. 2/m Orpiment type

Orthorhombic

(Mg,Fe)2[SiO4] (Nesosilicates)

Olivine (syn., peridot, chrysolite light yellowish green) [Named after the green color]

Triclinic a = 815 pm b = 1278 pm c = 850 pm (Z = 5)

(Na,Ca)(Si,Al)4O8 An20-Ab80 M = 265.41986 6.93 wt.% Na 3.02 wt.% Ca 12.20 wt.% Al 29.63 wt.% Si 48.22 wt.% O (Tectosilicates, framework)

Oligoclase (syn., sunstone) [Named from the Greek, oligos, and kasein, little, cleavage]

Isotropic R = 70%

Biaxial (+)

Biaxial (–) α = 1.518–1.521 β = 1.523–1.525 γ = 1.526–1.528 δ = 0.005–0.006 2V = 65–75° Dispersion strong

Biaxial (+) α = 2.40 β = 2.81 γ = 3.02 δ = 0.62 2V = 76° R = 22.6%

Biaxial (+/–) α = 1.635–1.827 β = 1.651–1.869 γ = 1.670–1.879 δ = 0.035–0.052 2V = 82–134° Dispersion weak

Biaxial (+) α = 1.533–1.543 β = 1.537–1.548 γ = 1.542–1.552 δ = 0.009 2V = 82–86°

4.5–5

5–6

6

1.5–2 (HV 23–52)

6.5–7

7

11,550

3300– 3500

2560

3490– 3520

3220– 4390

2650

Habit: granular. Color: gray. Diaphaneity: opaque. Luster: metallic.

Habit: phenocrystals. Color: brown to black. Diaphaneity: translucent. Luster: vitreous. Streak: brown. Cleavage: (210). Fracture: uneven. Occurrence: basic and ultrabasic rocks.

Habit: prismatic, massive, granular, blocky. Color: white, pink, yellow, or red. Diaphaneity: transparent to translucent. Luster: pearly, vitreous (i.e., glassy). Streak: white. Cleavage: (001) perfect, (010) good, (110) poor. Twinning: Carlsbad [001], Baveno [021]. Fracture: uneven. Occurrence: intrusive and extrusive igneous, and metamorphic rocks.

Habit: prismatic, massive, fibrous, foliated, flexible crystals. Color: lemon yellow, brownish yellow, or orange yellow. Diaphaneity: transparent to opaque. Luster: resinous. Streak: pale yellow. Cleavage: [010] perfect. Fracture: even, sectile. Chemical: dissolved by the aqua regia. Occurrence: in hydrothermal veins with realgar, stibine and pyrite. Other: dielectric constant

Habit: massive. Color: yellowish green, olive green, greenish black, or reddish brown. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Cleavage: (001) good, (010) distinct. Fracture: conchoidal, brittle. Streak: white. Occurrence: basic and ultrabasic igneous rocks

Habit: euhedral crystals. Color: white or gray. Luster: vitreous (i.e., glassy). Luminescence: fluorescent. Cleavage: (001) perfect, (010) good. Fracture: uneven. Streak: white. Occurrence: magmatic and pegmatitic rocks.

Mineral and Gemstone Properties Table 845

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mg1.5Al0.5[(Si4O10)(OH)4].H2O M = 411.35 8.86 wt.% Mg 3.28 wt.% Al 27.31 wt.% Si 2.21 wt.% H 58.34 wt.% O Phyllosilicates

VS4 M = 179.21 28.44 wt.% V 71.57 wt.% S Sulfides and sulfosalts

Ag16As2S11 M = 2228.4604 77.45 wt.% Ag 6.72 wt.% As 15.83 wt.% S (Sulfides and sulfosalts)

Ca2Na[Si3O8](OH) M = 332.40 6.92 wt.% Na 24.11 wt.% Ca 25.35 wt.% Si 0.30 wt.% H 43.32 wt.% O Coordinence Ca(6), Na(6), Si(4) (Inosilicates, ribbon)

(Fe,Ni)9S8 M = 771.94 32.56 wt.% Fe 34.21 wt.% Ni 33.23 wt.% S (Sulfides and sulfosalts) Coordinence Ni(6),Fe(6), and Fe(4)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Palygorskite (syn., attapulgite, Fuller’s earth) [Named after locality Palygorskaya in the Urals Mountains, Russia and after Attapulgus, Georgia, USA] (ICSD 75974 and PDF 21-958)

Patronite [Named after the Peruvian engineer Antenor Rizo-Patron (1866–1948), who discoverer the Minasragra deposit near Cerro de Pasco, Peru] (ICSD 64770 and PDF 19-1408)

Pearceite [Named after the American chemist, R. Pearce (1837–1927)]

Pectolite [Named from the Greek, pektos, compacted, and lithos, stone] (ICSD 34945 and PDF 33-1223)

Pentlandite [Named after the Irish natural historian, Joseph Barclay Pentland (1797–1873)] (ICSD 61021 and PDF 8-90)

Table 12.23. (continued)

Cubic a = 1009.5 pm D89, cF68 (Z = 4) S.G. Fm-3m P.G. 4-32 Co9S8 type

Triclinic a = 799 pm b = 704 pm c = 702 pm α = 90.05° β = 92.58° γ = 102.47° P.G. 1 S.G. P1 Pyroxenoid group

Monoclinic a = 1261 pm b = 728 pm c = 1188 pm β = 90° (Z = 2) P.G. 2/m S.G. C2/m

Monoclinic a = 678 pm b = 1042 pm c = 1211 pm β = 100.8° (Z = 8) P.G. 2/m S.G. I2/a

Isotropic R = 52%

Biaxial (–) α = 1.590 β = 1.610 γ = 1.630 δ = 0.04 2V = 35–63°

Biaxial R = 29.3–32.3%

Biaxial (?) R = 20–30%

3.5–4 (HV 202– 230)

4.5–5

2.5–3 (HV 153– 164)

2

2–2.5

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 1.522–1.528 β = 1.530–1.546 γ = 1.533–1.548 2V = 36°–61°

Optical properties

5000

2900

6790

2820 (2834)

2290– 2360

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 1278 pm b = 1789 pm c = 524 pm β = 105.2° (Z = 4) S.G. C2/m Paligorskite group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: massive, granular. Color: light bronze yellow. Diaphaneity: opaque. Luster: metallic. Streak: greenish black. Cleavage: perfect {100}, good {111}. Fracture: uneven, conchoidal. Electrical resistivity 1 to 11 μΩ.cm. Deposits: mafic intrusives igneous rocks.

Habit: radiating, fibrous. Color: white. Luster: silky. Diaphaneity: transparent to translucent. Streak: white. Fracture: uneven. Cleavage: (100) perfect, (001) distinct. Twinning: {010}.

Habit: massive, granular. Color: black. Luster: submetallic. Diaphaneity: opaque. Streak: reddish black. Cleavage: [001] poor. Fracture: uneven.

Habit: massive to fine grains. Color: lead gray to black. Diaphaneity: opaque. Luster: metallic. Occurrence: asphaltite deposits.

Habit: aggregates or masses of lath-shaped crystals. Color: white to tan. Diaphaneity: opaque but becomes translucent in thin sections. Luster: dull. Fracture: conchoidal. Cleavage: {110 } good. Insoluble in HCl and infusible. Occurrence: hydrothermal veins.

Other relevant mineralogical, physical, and chemical properties with occurrence

846 Minerals, Ores and Gemstones

MgO M = 40.2990 60.31 wt.% Mg 39.69 wt.% O Coordinence Mg(6) (Oxides and hydroxides)

CaTiO3 MM = 135.9562 35.22 wt.% Ti 35.30 wt.% O 29.48 wt.% Ca Traces of rare earths, Nb, Ta, Th. Coordinence Ca(12), Ti(6) (Oxides and hydroxides)

LiAlSi4O10 M = 305.15 2.09 wt.% Li 8.75 wt.% Al 36.72 wt.% Si 52.43 wt.% O Phyllosilicates

Ag3AuTe2 M = 667.90294 32.30 wt.% Ag 38.21 wt.% Te 29.49 wt.% Au (Sulfides and sulfosalts)

Cs(Be2Li)Al2Si6O18 M = 658.80 14.93 wt.% Cs 0.99 wt.% Li 4.19 wt.% Be 8.35 wt.% Al 25.58 wt.% Si 43.96 wt.% O

KMg3(Si3Al)O10(F,OH)2 M = 417.26002 9.37 wt.% K 17.47 wt.% Mg 6.47 wt.% Al 20.19 wt.% Si 0.48 wt.% H 46.01 wt.% O Coordinence K(12), Mg(6), Si(4), Al(4) (Phyllosilicate, layered)

Periclase [1309-48-4] (syn., magnesia) [from the Greek, peri, around, and klao, to cut in reference to its perfect cubic cleavage] (ICSD 9863 and PDF 43-1022)

Perovskite or Perowskite [12049-50-2] [Named after the Russian mineralogist, count L.A. Perowski] (ICSD 37263 and PDF 42-423)

Petalite [Named from the Greek petalon, leaf and lithos, stone alluding to its leaflike cleavage] (ICSD 100348 and PDF 35–463)

Petzite [Named after the chemist, W. Petz] (ICSD 27539 and PDF 44-1420)

Pezzottaite [Named for Federico Pezzotta of the Museo Civico, Milano, Italy for his work on the granitic pegmatites of Madagascar]

Phlogopite (1M) [Named from the Greek, phlogopos, to burn or inflame alluding to its reddish tinge resembling fire] (ICSD 21102 and PDF 10-495)

Monoclinic a = 531 pm b = 923 pm c = 1015 pm β = 95.18° (Z = 2) P.G. 2/m S.G. C2/m Mica type

Trigonal a = 1595 pm c = 2780 pm (Z = 18) P.G. 3m S.G. R3c Beryl group

Cubic P.G. 23

Monoclinic a = 1175 pm b = 514 pm c = 763 pm β = 113.01° (Z = 2) S.G. P2/a

Orthorhombic (pseudocubic) a = 536.70 pm b = 764.38 pm c = 544.39 pm E21, cP5, (Z = 4) P.G. mmm S.G. Pm3m Perovskite type

Cubic a = 421.17 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4-32 Rock salt type

Biaxial (–) α = 1.53–1.573 β = 1.557–1.617 γ = 1.558–1.618 δ = 0.028–0.045 2V = 0–12° Dispersion weak

Uniaxial (–) ε = 1.615–1.619 ω = 1.607–1.610 δ = 0.0080–0.009

Isotropic R = 45%

Biaxial (–) α = 1.504–1.507 β = 1.510–1.513 γ = 1.516–1.523 2V = 83°

Biaxial (–) α = 2.34 β = 2.34 γ = 2.34 δ = 0.002 2V = 90° R = 16.7%

Isotropic nD = 1.736

2–2.5

8

2.5

6–6.5

5.5 (HV 988– 1131)

5.5

2800

3090– 3110 (3220)

8700– 9140

2300– 2500 (2398)

4044

3560

Habit: micaceous, scaly, lamellar. Color: brown, gray, green, yellow, or reddish brown. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous, pearly. Cleavage: (001) perfect. Fracture: uneven. Twinning: [310]. Dielectric properties. Relative permittivity: 6.5 to 8.7, dielectric field strength: 50–150 kV/mm, loss tangent 0.004 to 0.070, electrical resistivity 1012 to 1015 ohm.m. Occurrence: contact and regional metamorphic limestones and dolomites.

Habit: hexagonal tabular crystals. Color: raspberry to purplish pink. Diaphaneity: translucent to transparent. Luster: vitreous. Clivage: [001] imperfect. Streak: white. Fracture: conchoidal. Occurrence: Late-stage pocket mineral formed in a granitic pegmatites.

Habit: massive, granular. Color: iron black or steel gray. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Fracture: brittle, sectile.

Habit: massive and blocky aggregates. Color: colorless, gray, yellow, yellow gray, white. Diaphaneity: transparent to translucent. Luster: vitreous. Cleavage: [001] perfect. Fracture: conchoidal. Streak: colorless. insoluble in HCl. Occurrence: granite pegmatites.

Habit: faces striated, reniform, pseudocubic, pseudohexagonal. Color: black, reddish brown, pale yellow, yellowish orange. Diaphaneity: transparent to translucent or opaque. Luster: adamantine, submetallic. Streak: light brown. Fracture: subconchoidal. Cleavage: (100). Twinning: {111}. Chemical: attacked by hot H2SO4, and HF. Nonfusible: m.p. 1980°C. Deposits: ultramafic igneous rocks, metamorphosed limestone in contact with mafic igneous rocks.

Habit: granular, octahedral crystals. Color: white, gray, or green. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Luminescence: fluorescent, long uv-light yellow. Streak: white. Cleavage: [001], [010], [100]. Fracture: uneven, brittle, conchoidal. Occurrence: contact metamorphism of dolomites and magnesites.

Mineral and Gemstone Properties Table 847

Minerals, Ores and Gemstones

12

Cubic a = 392.36 pm A1, cF4 (Z = 4) P.G. m3m S.G. Fm3m Copper type

Tetragonal a = 495.25 pm c = 338.63 pm C4, tP6 (Z = 2) P.G. 422 S.G P42/mnm Rutile type

Na2Ca(CO3)2.2H2O (Nitrates, carbonates, and borates)

U3O8 M = 841.995 84.80 wt.% U 15.20 wt.% O Oxides and hydroxydes

Pt M = 195.08 Coordinence Pt(12) (Native elements)

β-PbO2 M = 239.1988 86.62 wt.% Pb 13.38 wt.% O (Oxides and hydroxides)

MgFe2O4 M = 200.00 12.15 wt.% Mg 55.85 wt.% Fe 32.00 wt.% O Coordinence Mg(4), Fe(6) (Oxides and hydroxides)

Pirssonite [Named after the American mineralogist, Louis Valentine Pirsson (1860–1919)] (ICSD 9012 and PDF 22-476)

Pitchblende [Named after pitch and blende]

Platinum [7440-06-4] [from Spanish, platina, silver] (ICSD 64917 and PDF 4-802)

Plattnerite [Named after the German Professor of metallurgy, Karl Friedrich Plattner (1800–1858)] (ICSD 34234 and PDF 41-1492)

Pleonaste (syn. ceylonite, magnesioferrite) (ICSD 49551 and PDF 36-398)

Cubic a = 836.6 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type (Ferrite series)

Amorphous

Orthorhombic

Mohs hardness (/HM) (Vickers)

Isotropic nD = 2.38 R=%

Uniaxial (–) ε = 2.25 ω = 2.35 δ = 0.100 R = 16.7–17.1%

Isotropic nD = 4.28 R = 70%

Isotropic R = 16.0%

Biaxial (+) α = 1.5 β = 1.5 γ = 1.57 δ = 0.070 2V = 33° Dispersion weak

6–6.5

5.5

4–4.5 (HV 125– 127)

3–5 (HV 673– 803)

3

Biaxial (–) 6–6.5 α = 1.732–1.794 (HV 680) β = 1.750–1.807 γ = 1.762–1.829 δ = 0.025–0.088 2V = 64–85° Dispersion strong

Optical properties

4650

85009630 (9563)

21,452

8000– 9000

2350

3450– 3520

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 895.0 pm b = 570.0 pm c = 941.0 pm 115°70 (Z = 2) Epidote group

Ca2(Mn,Fe,Al)2AlO(OH)[SiO4][Si2O7] 23.5 wt.% CaO 24.1 wt.% Al2O3 12.6 wt.% Fe2O3 37.9 wt.% SiO2 1.9 wt.% H2O (Sorosilicates and nesosilicates)

Piemontite (syn. piedmontite) [Named from the Piedmont region, Italy] (ICSD 24425 and PDF 29-288)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: massive granular and also as well-formed fine sized crystals. Color: brownish black, black. Diaphaneity: opaque. Luster: metallic. Streak: dark red. Fracture: uneven. Occurrence: igneous volcanic rocks, Vesuvius and Stromboli, Italy.

Habit: prismatic crystals, nodular, botryoidal, massive, encrustations. Color: black or grayish black. tarnish on sunlight exposure. Luster: submetallic to adamantine. Diaphaneity: subtranslucent to opaque. Streak: chestnut brown. Cleavage: none. Twinning: (001). Fracture: brittle. Chemical properties: easily fusible and decomposed at red-heat into minium (Mn3O4). Soluble in hot conc. HCl with chlorine evolution, and slightly soluble in sulfuric and nitric acids with oxygen evolution. Dimorphous with scrutinyite.

Habit: granular, nuggets. Color: grayish white. Diaphaneity: opaque. Luster: metallic. Streak: grayish white. Cleavage: none. Twinning: {111}. Fracture: hackly, malleable, ductile. Chemical: inert in most concentrated mineral acids (e.g., HCl, H2SO4, HF, HNO3), but readily dissolved in aqua regia (i.e., 3 vol. HCl + 1 vol. HNO3). Occurrence: mainly in grains and nuggets in alluvial placer deposits.

Habit: amorphous botryoidal mass. Color: black. Luster: submetallic. Contains up to 20 wt.% PbO from decaying.

Color: colorless or white. Diaphaneity: transparent to translucent. Occurrence: continental evaporite deposits under desert climates.

Habit: prismatic according to b, striated, columnar. Color: reddish-brown to dark red. Diaphaneity: transparent to opaque. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: [001] perfect. Fracture: uneven, conchoidal. Chemical: insoluble in strong mineral acids, fusible giving a black globule. Occurrence: regional metamorphic and pegmatite rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

848 Minerals, Ores and Gemstones

(Cs,Na)2Al2Si4O12·H2O (Tectosilicates)

(Ag,Cu)16Sb2S11 M = 2144.83 11.85 wt.% Cu 60.35 wt.% Ag 11.35 wt.% Sb 16.45 wt.% S (Sulfides and sulfosalts)

K2Ca2Mg(SO4)4.2H2O M = 410.81536 19.03 wt.% K 19.51 wt.% Ca 5.92 wt.% Mg 0.98 wt.% H 15.61 wt.% S 38.95 wt.% O (Sulfates, chromates, molybdates, and tungstates)

CaMoO4 M = 200.02 20.04 wt.% Ca 47.97 wt.% Mo 32.00 wt.% O (Sulfates, chromates, molybdates, and tungstates)

Ag3AsS3 M = 494.72 65.41 wt.% Ag 15.14 wt.% As 19.44 wt.% S (Sulfides and sulfosalts) Coordinence Ag(2), As(3)

Fe2TiO5 M = 238.41 1.02 wt.% Mg 15.06 wt.% Ti 50.36 wt.% Fe 33.55 wt.% O (Oxides and hydroxides)

Pollucite [Named after Pollux, a figure from Greek mythology, the twin brother of Castor, in reference to its association with the mineral castor (old name for petalite] (ICSD 39895 and PDF 25-194)

Polybasite [Named from the Greek, poly, many and basis, base, in allusion to the basic character of the compound]

Polyhalite [Named from the Greek, polys, much and halos, salt] (ICSD 6303 and PDF 21-982)

Powellite [7789-82-4] [Named after the American geologist, W. Powell] (ICSD 60552 and PDF 29-351)

Proustite (syn., ruby silver) [Named after the French chemist, J.L. Proust (1755–1826)] (ICSD 38388 and PDF 42-553)

Pseudobrookite [1310-39-0] [from the Greek, pseudo, mislead and the mineral brookite] (ICSD 69038 and PDF 41-1432)

Orthorhombic a = 976.7 pm b = 994.7 pm c = 371.7 pm (Z = 4) P.G. 2/m 2/m 2/S.G. Bbmm Pseudobrookite type

Trigonal (Rhombohedral) a = 1081.6 pm c = 869.48 pm (Z = 6) S.G. R3c P.G. 3m

Tetragonal a = 552.60 pm c = 1143.00 pm (Z = 4) Scheelite type

Triclinic a = 1169 pm b = 1633 pm c = 760 pm α = 91.6° β = 90° γ = 91.9° (Z = 4) P.G. -1 S.G. P1

Monoclinic a = 2612 pm b = 1508 pm c = 23.89 β = 90° (Z = 16) P.G. 2/m S.G. C 2/m

Cubic a = 1368.2 pm (Z = 16) P.G. 432 S.G. I a3d

2–2.5 (HV 109– 135)

3.8

2.5–3.5

2.5–3

6.5

Biaxial (+) 6 α = 2.35–2.38 β = 2.36–2.39 γ = 2.38–2.42 δ = 0.0300–0.0400 2V = 62–72° R = 15.6%

Uniaxial (–) ω = 2.98 ε = 2.71 δ = 0.17 R = 25.0–27.7%

Uniaxial (+) ε = 1.971 ω = 1.980 δ = 0.010

Biaxial (–) α = 1.546–1.548 β = 1.558–1.562 γ = 1.567 δ = 0.019–0.02 2V = 60–62°

Biaxial R = 30.8–32.8%

Isotropic nD = 1.525

4406

5570

4350

2770– 2780

4600– 5000

2900

Habit: well formed fine crystals. Color: brownish black, reddish brown, black. Diaphaneity: opaque. Luster: adamantine to submetallic. Streak: brown. Fracture: uneven. Occurrence: recent volcanic igneous rocks. m.p. 1375°C

Habit: prismatic, rhomboedral crystals. Color: ruby red. Luster: adamantine. Diaphaneity: translucent to opaque. Streak: red. Fracture: subconchoidal. Cleavage: {101}. Twinning: {101}, {104}.

Habit: euhedral crystals. Color: yellow or greenish yellow. Luster: adamantine, resinous. Cleavage: (111) distinct. Fracture: conchoidal, brittle. Streak: light yellow.

Habit: massive, lamellar, fibrous. Color: white, yellowish white, gray, or flesh pink. Luster: vitreous (glassy). Streak: white. Cleavage: [101] perfect. Fracture: conchoidal, brittle. Occurrence: sedimentary marine evaporite deposits.

Habit: massive, granular, granular, pseudo hexagonal. Color: black. Streak: reddish black. Luster: sub metallic. Diaphaneity: opaque. Cleavage: [001] poor. Fracture: uneven.

Habit: massive. Color: colorless, gray, or white. Diaphaneity: transparent. Luster: vitreous, dull. Cleavage: none. Fracture: uneven, brittle. Streak: white. Occurrence: granitic pegmatites

Mineral and Gemstone Properties Table 849

Minerals, Ores and Gemstones

12

Monoclinic a = 1392.9 pm b = 284.6 pm c = 967.8 pm β = 92.65° (Z = 2) P.G. 2/m S.G. C2/m

BaMnIIMnIV8O16(OH)4 M = 955.74568 Coordinence Ba(10), Mn(6) (Oxides and hydroxides)

Ag3SbS3 M = 541.5526 59.75 wt.% Ag 22.48 wt.% Sb 17.76 wt.% S Coordinence Ag(2), Sb(3) (Sulfides and sulfosalts)

FeS2 M = 119.979 46.55 wt.% Fe 53.45 wt.% S (Sulfides and sulfosalts) Coordinence Fe(6)

(Na4,Ca2,U,Th,Ln)(Nb,Ta)2O11(OH, F)2.nH2O (Oxides and hydroxides)

MnO2 M = 86.93685 63.19 wt.% Mn 36.81 wt.% O Traces of rare earths Coordinence Mn(6) (Oxides and hydroxides)

Psilomelane (syn., Romanechite) [from Greek, psilos, smooth, and melanos, black, owing to the common smooth surface of the concretions; from Romanèche, Saône-et-Loire, France] (ICSD 202692 and PDF 42-618)

Pyrargyrite (syn., dark red silver ore, ruby silver ore) [from the Greek, pyros, and argyros, fire-silver in allusion to color and silver content] (ICSD 38389 and PDF 21-1173)

Pyrite [12068-85-8] (syn., Fool’s gold) [from Greek, pyros, fire since it gives off sparks when struck] (ICSD 316 and PDF 42-1340)

Pyrochlore [from the Greek, pyros, fire, and chloros, green owing to the green color after pyrolysis] (ICSD 27815 and PDF 17-746)

Pyrolusite (syn., wad, polianite) [from the Greek, pyros, fire and louein, to wash, because it was used to remove the yellowish color imparted to glass by iron compounds] (ICSD 73716 and PDF 24-735)

Tetragonal a = 438.8 pm c = 286.5 pm C4, tP6 (Z = 2) P.G. 422 S.G. P42/mnm Rutile group

Cubic (sometimes metamict or amorphous) a = 1037 pm (Z = 8)

Cubic a = 541.75 pm C2, cP12 (Z = 4) S.G. Pa3 P.G. 23 Pyrite type

Uniaxial R = 30.0–41.5%

Isotropic nD = 1.90–2.14 R = 13.0–13.8%

Isotropic R = 54.5%

Uniaxial (–) ε = 2.881 ω = 3.084 δ = 0.203 R = 29.6%

Biaxial (n.a.) R = 24.1–28.8%

3950– 4710 (4740)

3800– 4010 (4820)

6–6.5 (HV 225– 405)

5–5.5 (HV 572– 665)

6–6.5 (HV 1027– 1240)

5234

3700– 6400

4950– 5030 (5012)

2–2.5 5850 (HV 50–97 and 98– 126 //)

5–6 (HV 503– 627)

5.5

Mohs hardness (/HM) (Vickers)

Uniaxial (?)

Optical properties

Density (ρ/kg.m–3) (calc.)

Trigonal (Rhombohedral) a = 1105.2 pm c = 871.77 pm (Z = 6) P.G. 3m S.G. R3c

Hexagonal a = 1437.5 pm c = 461.5 pm (Z = 6) P.G. 6/m2/m2/m S.G. P6322

Fe2Ti3O9 M = 399.33 35.97 wt.% Ti 27.97 wt.% Fe 36.06 wt.% O (Oxides and hydroxides)

Pseudorutile [1310-39-0] [syn., arizonite, leucoxene] (ICSD 4131 and PDF 47-1777)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: reniform, columnar, fibrous, dendritic, or earthy. Color: steel gray, iron gray, or bluish gray. Diaphaneity: opaque. Luster: metallic. Cleavage: [110] perfect. Fracture: uneven, brittle. Chemical: dissolved by HCl, give a green blue pearl with moltem KOH or NaOH. Other: dielectric constant above 81. Electrical resistivity 0.007 to 30 Ω.m. Antiferromagnetic. Occurrence: in the oxidation zone of manganese ores with rhodonite. In marine sedimentary rocks such as limestone, hydrothermal.

Habit: octahedron, granular, disseminated. Color: brown, yellowish brown, yellow, greenish brown, or reddish brown. Diaphaneity: translucent to opaque. Luster: resinous, greasy or glassy. Streak: yellowish brown. Cleavage: [111]. Fracture: uneven to conchoidal. Chemical: insoluble in mineral acids. Other: Radioactive according to U content. Dielectric constant 3.4 to 5.1. Occurrence: in nepheline-syenite igneous rocks.

Habit: faces striated, druse, stalactitic, pyritohedral cubic crystal. Color: pale brass yellow. Luster: metallic. Diaphaneity: opaque. Fracture: conchoidal. Cleavage: {100} poor, {110} poor. Twinning: {110} iron cross. Streak: greenish black. Pyroelectric. Occurrence: sedimentary, magmatic, metamorphic, and hydrothermal. Others: specific heat capacity 62.17 J.K–1mol–1; aL = 26 μm/m.K; bulk modulus K = 149 GPa.

Habit: massive, crystalline, prismatic. Color: ruby red. Luster: adamantine to submetallic. Diaphaneity: translucent to opaque. Streak: red purple. Fracture: subconchoidal, brittle. Cleavage: (101). Twinning: {101}, {104}. Chemical: readily dissolved by HNO3 with formation of free S and precipitation of Sb2O3. Occurrence: epithermal veins with other silver-bearing ores.

Habit: massive, reniform, botryoidal, earthy, fibrous, dendritic. Color: dark black to dark steel gray. Luster: submetallic to dull. Diaphaneity: opaque. Streak: brown to black. Cleavage: none. Fracture: uneven to conchoidal, brittle. Occurrence: associated with cryptomelane. Note: wad is a common name for a low hardness varieties, while manganomelane describes high density varieties (i.e., above 3000 kg.m–3).

Habit: thin irregular plates with fibrous texture, fine grained, massive. Color: black, brown, red, gray. Diaphaneity: opaque. Luster: submetallic. Streak: reddish brown. Fracture: subconchoidal. Other properties: ferromagnetic. Occurrence: intermediate product during the weathering of ilmenite, found in ilmenite rich beach mineral sands often called leucoxene.

Other relevant mineralogical, physical, and chemical properties with occurrence

850 Minerals, Ores and Gemstones

Pb5(PO4)3Cl M = 1356.36678 6.85 wt.% P 76.38 wt.% Pb 2.61 wt.% Cl 14.15 wt.% O Traces of Ca, Ba, Sr, V, and F Coordinence Pb(6), P(4) (Phosphates, arsenates, and vanadates)

Mg3Al2(SiO4)3 M = 403.12738 18.09 wt.% Mg 13.39 wt.% Al 20.90 wt.% Si 47.63 wt.% O Coordinence Mg(8), Al(6), Si(4) (Nesosilicates)

MnTiO3 M = 150.803 31.75 wt.% Ti 36.43 wt.% Mn 31.83 wt.% O (Oxides, and hydroxides) Coordinence Mn(6), Ti(6)

Al2Si4O10(OH)2 M = 360.31 14.98 wt.% Al 31.18 wt.% Si 0.56 wt.% H 53.28 wt.% O Coordinence Al(6), Si(4) (Phyllosilicates, layered)

Fe1–xS (x = 0–0.17) M = 85.12065 62.33 wt.% Fe 37.67 wt.% S (Sulfides and sulfosalts) Coordinence Fe(6)

Mg2TiO4 M = 160.474 49.77 wt.% TiO2 50.23 wt.% MgO (Oxides and hydroxides)

Pyromorphite (syn., green lead ore, campylite, phosphomimetite) [from the Greek, pyros, fire, and morfe, form because a molten drop has crystalline forms on solidifying] (ICSD 203075 and PDF 19-701)

Pyrope (syn., rhodolite) [from the Greek, pyropos, fiery-eyed, in allusion to the red hue] (ICSD 71887 and PDF 15-742)

Pyrophanite [12032-74-5] [from Greek pyros, fire and phanos, shinning] (ICSD 6006 and PDF 29-902)

Pyrophyllite (1Tc) [Named after the Greek, pyros, fire, and phyllos, leaf referring to the effect of heat separating the laminae in foliated varieties] (ICSD 26742 and PDF 12-203)

Pyrrhotite (syn., magnetic pyrite) [from the Greek, pyrrhotes, redness, in allusion to its color] (ICSD 8064 and PDF 24-220)

Qandilite [12032-52-9] [Named after Qandil rocks intrusion, Qala-Dizeh region, Iraq] (ICSD 65792 and PDF 25-1157)

Cubic a = 843.76 pm H11, cF56 (Z = 8) S.G. Fd3m P.G. 432 Spinel type

Hexagonal a = 345.2 pm c = 576.2 pm (Z = 2) S.G. P-62c P.G. -62m Defect Niccolite type

Triclinic a = 516 pm b = 896 pm c = 935 pm α = 90.03° β = 100.37° γ= 89.75° (Z = 2) P.G. 1 S.G. P1

Trigonal (Rhombohedral) a = 513.7 pm c = 1428.3 pm (Z = 6) S.G. R3m P.G. 3 Ilmenite type

Cubic a = 1145.9 pm (Z = 8) P.G. 432 S.G. Ia3d (Garnet group: Pyralspite series)

Hexagonal a = 997 pm c = 733 pm (Z = 2) P.G. 6/m S.G. P63/m Apatite type

Isotrope R = 12.9%

Uniaxial R = 41.6%

Biaxial (–) α = 1.534–1.556 β = 1.586–1.589 γ = 1.596–1.601 δ = 0.045–0.062 2V = 52–62° Dispersion weak

Uniaxal (–) ω = 2.481 ε = 2.210 δ = 0.2700 Dispersion strong

Isotropic nD = 1.714

Uniaxial (–) ε = 2.048 ω = 2.058 δ = 0.010

ca. 7

3.5–4.5 (HV 230– 318)

1.5–2

5

6–7.5

3.5–4

4030– 4080 (4040)

4600

2650– 2900

4537 (4596)

3582

6850– 7000

Habit: small euhedral crystals. Color: iron-black; light gray with a pinkish tint in reflected light. Diaphaneity: opaque. Luster: submetallic to metallic. Streak: black. Fracture: brittle. Cleavage: [111] perfect. Other: strongly ferromagnetic like magnetite. Soluble in hot concentrated HCl. Occurrence: contact metamorphism with Ti-rich ultramafic intrusion. Melting point: 1732°C.

Habit: tabular, platy, massive, granular. Color: bronze yellow or red. Diaphaneity: opaque. Luster: metallic. Cleavage: (0001) imperfect, (1120) poor. Fracture: uneven. Streak: gray black. Electrical resistivity 2 to 160 μΩ.cm. Occurrence: wide spread occurrences in igneous and metamorphic rocks. Magnetic.

Habit: platy, foliated. Color: white, greenish white, or yellowish white. Diaphaneity: translucent to opaque. Luster: pearly. Luminescence: fluorescent. Streak: white. Cleavage: [001] perfect. Fracture: flexible.

Habit: thin tabullar rhombohedral crystals, scaly. Color: deep blood red, green yellow, dark red. Diaphaneity: opaque. Luster: vitreous to submetallic. Streak: ocher yellow. Fracture: subconchoidal. Cleavage: [0221]. Other: melting point at 1360°C. Deposits: metamorphosed manganese deposits, accessory mineral in granite, amphibolite, and serpentinites.

Habit: dodecahedral, granular, crystalline, lamellar. Color: red or black. Luster: vitreous (i.e., glassy). Streak: white. Cleavage: none. Parting: {110}. Fracture: conchoidal. Diaphaneity: transparent to translucent. Chemical: soluble in HF. Occurrence: ultrabasic igneous rocks.

Habit: reniform, prismatic, globular. Color: green, yellow, brown, grayish white, or yellowish red. Diaphaneity: transparent to translucent. Luster: adamantine, resinous. Streak: white. Cleavage: (1000) perfect, (1011) imperfect. Fracture: subconchoidal, brittle. Chemical: dissolved by HNO3. Fluorescence: yellow. Occurrence: in the weathering zone of lead–zinc ores deposits with anglesite, cerussite, hemimorphite, smithonite, and malachite.

Mineral and Gemstone Properties Table 851

Minerals, Ores and Gemstones

12

Trigonal (Hexagonal) a = 499.9 pm c = 545.7 pm C8, hP9 (Z = 3) S.G. P6222 (Dextrogyre), and P6422 (Levogyre) P.G. 622

Trigonal (Rhombohedral) a = 491.3 pm c = 540.5 pm (Z = 3) S.G. R3121 (Dextrogyre), and R3221 (Levogyre) P.G. 32

β-SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

α-SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

NiAs2 M = 208.53 28.14 wt.% Ni 71.86 wt.% As (Sulfides and sulfosalts)

MnO2 M = 86.93685 63.19 wt.% Mn 36.81 wt.% O (Oxides, and hydroxides)

AsS (= As4S4) M = 106.9876 70.03 wt.% As 29.97 wt.% S (Sulfides and sulfosalts) Coordinence AsS molecules

MnCO3 M = 114.946949 47.79 wt.% Mn

Quartz (High-temperature) [14808-60-7] [from the German, quarz, of uncertain origin probably from Saxon word querkluftertz meaning cross-vein ore]

Quartz (Low-temperature) [14808-60-7] (syn., rock crystal, smoky quartz: brown to black, amethyst: purple, citrine: yellow) [from the German, quarz, of uncertain origin] (ICSD 174 and PDF 46-1045)

Rammelsbergite [Named after the German chemist and mineralogist, Karl F. Rammelsberg (1813–1899)] (ICSD 42571 and PDF 15-441)

Ramsdellite [Named after the American mineralogist, Lewis Stephen Ramsdell (1895–1975) who first described the mineral] (ICSD 78331 and PDF 44-142)

Realgar [Named from the Arabic, rahj al ghar, powder of the mine] (ICSD 15238 and PDF 41-1494)

Rhodochrosite (syn., ponite: rich Fe varieties) [from Greek, rhodos, pink]

Trigonal a = 477.1 pm c = 1566.4 pm (Z = 6)

Monoclinic a = 929 pm b = 1353 pm c = 657 pm β = 106.55° Bl, mP32 (Z = 16) S.G. P21/c P.G. 2/m Realgar type

Orthorhombic

Uniaxial (–) ε = 1.540–1.617 ω = 1.750–1.850

Biaxial (–) α = 2.538 β = 2.684 γ = 2.704 δ = 0.166 2V = 40° Dispersion strong R = 18.5%

Biaxial

Biaxial (?) R = 58.0–60.0%

Uniaxial (+) ε = 1.543–1.545 ω = 1.552–1.554 δ = 0.009

3.5–4

1.5–2 (HV 47–60)

3

5.5–6 (HV 687– 778)

7

7

Mohs hardness (/HM) (Vickers)

Uniaxial (+) ε = 1.53 ω = 1.54 δ = 0.007

Optical properties

3200– 4050

3560

4370

7000– 7200 (7090)

2650

2530

Density (ρ/kg.m–3) (calc.)

Orthorhombic a = 475.9 pm b = 579.7 pm c = 353.9 pm (Z = 2) P.G. 2/m2/m2/m S.G. Pnnm Marcassite group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: massive. Color: rose-pink, pink, red, brown or brownish yellow, colorless. Luster: pearly, vitreous. Diaphaneity: transparent to translucent. Cleavage: (1011) perfect. Twinning: (0112). Fracture: uneven. Chemical: dissolved with effervescence in warm

Habit: prismatic, massive, granular, druse, earthy. Color: aurora red, orange yellow, or dark red. Diaphaneity: translucent to opaque. Luster: resinous, glassy, adamantine. Streak: orange red. Cleavage: [010], [001], and [100]. Twinning: (100). Fracture: brittle, sectile. Chemical: dissolved by HNO3, evolved a garlic odor when calcinated and gives sublimated As2O3 deposit on cold wall. Electrical resistivity 1 to 150 mΩ.m. Occurrence: hydrothermal with orpiment. Marcasite, and stibine. Sedimentary rocks.

Habit: massive, fibrous, platy. Color: steel gray or black. Diaphaneity: opaque. Luster: metallic. Fracture: brittle. Streak: brownish black. Occurrence: manganese deposits with pyrolucite.

Habit: rare prismatic crystals. Color: tin white to reddish white. Luster: metallic. Diaphaneity: opaque. Cleavage: (101). Fracture: uneven. Streak: grayish black. Occurrence: in Ni-Co-Ag-bearing vein deposits.

Habit: prismatic, massive, crystalline, coarse, druse. Color: colorless, yellow, red, or brown. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Luminescence: triboluminescent. Streak: white. Cleavage: (0110) indistinct. Twinning: {001}. Fracture: conchoidal. Chemical: resistant to strong mineral acids, attacked by HF. Transition temperature 573°C. Occurrence: granitic igneous rocks, metamorphic rocks. Other: high-purity and dry synthetic quartz crystals are hard and brittle capable of withstanding high pressure up to 3GPa and 1600K while natural quartz is easily deformed by creep at temperature not exceeding 700K and pressure below 0.2GPa.

Habit: stubby bipyramidal. Color: colorless. Luster: vitreous (i.e., glassy). Luminescence: triboluminescent. Streak: white. Twinning: {102}, {302}, {201}, {112}. Fracture: conchoidal. Chemical: resistant to strong mineral acids, attacked by HF, transition temperature 867°C.

Other relevant mineralogical, physical, and chemical properties with occurrence

852 Minerals, Ores and Gemstones

52.21 wt.% CO2 Coordinence Mn(6), C(3) (Nitrates, carbonates, and borates)

Mn[SiO3] M = 131.0218 41.96 wt.% Mn 21.37 wt.% Si 36.67 wt.% O Coordinence Mn(6), Ca(6), Si(4) (Inosilicates, chain) Traces of Fe and Ca

Na2Fe3Fe2Si8O22(OH)2 M = 935.90 4.91 wt.% Na 29.84 wt.% Fe 24.01 wt.% Si 0.22 wt.% H 41.03 wt.% O Inosilicates (double chains)

Mg2SiO4 M = 140.69 34.55 wt.% Mg 19.96 wt.% Si 45.49 wt.% O (Nesosilicates)

(Ca,Na,Mn)3(Zr,Ti,Fe)[SiO4]2(F,OH) (Nesosilicates)

TiO2 M = 79.8788 59.94 wt.% Ti 40.06 wt.% O Coordinence Ti(6) (Oxides and hydroxides)

(K,Na)(Si,Al)4O8 Coordinence K(10), Si(4), Al(4) (Tectosilicates, framework)

(ICSD 100677 and PDF 44-1472)

Rhodonite [Named after the Greek, rhodos, pink alluding to its color] (ICSD 200452 and PDF 13-138)

Riebeckite (syn., glaucophane, crocidolite for the asbestos form) [Named after the German traveler, E. Riebeck while crocidolite is named after the Greek, krokidos, the nap on cloth and lithos, stone] (ICSD 38218 and PDF 19-1061)

Ringwoodite [Named after the Austalian petrologist Alfred Edward Ringwood (1930–1993)] (ICSD 27531 and PDF 21-1258)

Rosenbuschite [Named after the German mineralogist and geologist K.h.F. Rosenbuch (1836–1914)] (ICSD 22334 and PDF 14-447)

Rutile [13463-67-7] [Named from the Latin, rutilus, meaning reddish] (ICSD 62677 and PDF 16-934)

Sanidine (syn., anorthoclase) [from the Greek, sanis, little plate, and idos, to see in reference to its tabular habit] (ICSD 39747 and PDF 25-618)

Monoclinic a = 856. 2 pm b = 1303.6 pm c = 719.3 pm β = 116.58° (Z = 4) P.G. 2/m S.G. C2/m

Tetragonal a = 459.37 pm c = 296.18 pm C4, tP6 (Z = 2) P.G. 422 S.G. P4/mnm Rutile type Packing fraction = 70%

Triclinic a = 1012.6 pm b = 1137.7 pm c = 735.8 pm α = 91.3° β = 101.15° γ = 112.02 (Z = 4)

Cubic a = 812.2 pm (Z = 4) P.G. 432 S.G. Fd3m Spinel group

Monoclinic a = 953.1 pm b = 1775.9 pm c = 530.3 pm β = 103.59° S.G. C2/m (Z = 2)

Triclinic a = 768 pm b = 1182 pm c = 671 pm α = 92.35° β = 93.95° γ = 105.67°, (Z = 2) P.G. 1, S.G. P1 Pyroxenoid group

P.G. 32/m S.G. R3c Calcite type

Biaxial (–) α = 1.518–1.527 β = 1.522–1.532 γ = 1.525–1.534 δ = 0.006–0.007 2V = 80–85°

Uniaxial (+) ε = 2.605–2.613 ω = 2.899–2.901 δ = 0.286–0.296 Dispersion strong R = 20.2%

Biaxial (+) α = 1.678–1.680 β = 1.687–1.688 γ = 1.705–1.708 δ = 0.027–0.028 2V = 68–78°

Isotropic nD = 1.768

Biaxial (–) α = 1.68–1.698 β = 1.683–1.700 γ = 1.685–1.706 δ = 0.005–0.008 2V = 68–85° Dispersion strong

Biaxial (+) α = 1.717 β = 1.720 γ = 1.730 δ = 0.013 2V = 63–76° Dispersion weak

Dispersion strong

δ = 0.190–0.230

6

6–6.5 (HV 1074– 1210)

5–6

n.a.

4

4.5–5

2560

4230– 4250 (4245)

3310– 3380

3900 (3900)

3020– 3420 (3130)

3500– 3700

Habit: blocky, prismatic, massive, granular. Color: colorless, white, gray, yellowish white, or reddish white. Diaphaneity: transparent to translucent. Luster: vitreous, pearly. Cleavage: [001] perfect, [010] good. Twinning: Carlsbad [001]. Fracture: uneven. Streak: white. Occurrence: acid volcanic igneous rocks.

Habit: acicular, prismatic, massive. Color: reddish brown, yellowish brown, black or bluish violet, inclusion in quartz. Diaphaneity: transparent, translucent, opaque. Luster: adamantine. Streak: grayish black. Fracture: uneven. Cleavage: {111}. Twinning: {101}, {301}. Chemical: insoluble in water, slightly soluble in HCl, HNO3, sol. HF and in hot H2SO4 or KHSO4. Attacked by molten Na2CO3. Other properties: Melting point of 1847°C. Electrical resistivity ranging from 29 to 910 Ω.m. Cp = 50 J.K–1mol–1. Slightly paramagnetic with a specific magnetic susceptibility of +74 × 10–9 m3.kg–1. Dielectric constant of 110–117.

Habit: acicular to prismatic crystals. Color: pale yellow to orange. Luster: vitreous. Diaphaneity: translucent. Cleavage: (010). Fracture: brittle, uneven. Streak: white. Gelatinizes in HCl. Occurrence: nepheline syenite.

Habit: anhedral microscopic grains. Color: purple to bluish gray. Luster: vitreous. Diaphaneity: translucent. Cleavage: unknown. Fracture: brittle, uneven. Streak: white. Occurrence: chondrite meteorite.

Habit: gray to lavender blue crystals, striated, fibrous, massive. Color: blue, black, or dark green. Diaphaneity: translucent to opaque. Luster: vitreous, silky. Cleavage: (110) perfect. Streak: greenish brown. Occurrence: magmatic and metamorphic rocks.

Habit: tabular, massive. Color: pink, red. Luster: vitreous. Diaphaneity: transparent to translucent. Streak: white. Fracture: conchoidal. Cleavage: (110) perfect, (001) distinct. Twinning: {010}.

dilute acids. On exposure to air develop a brown or black surface alteration layer. Deposits: high-temperature metasomatic deposits.

Mineral and Gemstone Properties Table 853

Minerals, Ores and Gemstones

12

Orthorhombic a = 1043 pm b = 896 pm c = 1015 pm (Z = 8) P.G. mmm S.G. P21/cab Scorodite type

Orthorhombic a = 497.1 pm

CaWO4 M = 287.9256 13.92 wt.% Ca 63.85 wt.% W 22.23 wt.% O Coordinence Ca(4),W(4) (Sulfates, chromates, molybdates, and tungstates)

NaFe3Al6(OH)4B3O9[Si6O18] Coordinence Na(6), Fe(6), Al(6), B(3), Si(4) (Cyclosilicates, ring)

V2Ti3O9 M = 389.4786 26.16 wt.% V 36.87 wt.% Ti 36.97 wt.% O Coordinence Ti(6) (Oxides, and hydroxides)

Fe(AsO4).2H2O M = 230.795 20.92 wt.% Fe 28.08 wt.% As 47.97 wt.% O 3.03 wt.% H Coordinence Fe(6), As(4) (Phosphates, arsenates, and vanadates)

α-PbO2 M = 239.1988

Scheelite [7790-75-2] [Named after the Swedish chemist, K.W. Scheele] (ICSD 60547 and PDF 41-1431)

Schorl [Named from the German word Schörl for tourmaline] (ICSD 74180 and PDF 43-1464)

Schreyerite [60430-06-0] [Named after German mineralogist Werner Schreyer]

Scorodite [10102-49-5] [Named from the Greek, skorodon, garlic, alluding to the arsenic odor when heated] (ICSD 627 and PDF 37-468)

Scrutinyite [Named after the close examination

Monoclinic a = 706 pm b = 501 pm c = 1874 pm β = 119.4° (Z = 6)

Trigonal a = 1646 pm c = 715 pm (Z = 3) P.G. 3m S.G. R3m Tourmaline group

Tetragonal a = 524.2 pm c = 1137.20 pm (Z = 4) P.G. 4/m S.G. I41/a Scheelite type

Biaxial (?) R = 17.9–18.8%

Biaxial(+) α = 1.784 β = 1.796 γ = 1.814 δ = 0.030 2V = 54°

Biaxial (?) nD = 2.7

Uniaxial (–) ε = 1.668 ω = 1.639 δ = 0.029

Uniaxial (+) ε = 1.918–1.920 ω = 1.934–1.937 δ = 0.016–0.017 R = 10.0%

n.a.

3–4

HV 1150

7–7.5

4.5–5 (HV 285– 429)

7.5

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 1.701–1.725 β = 1.703–1.728 γ = 1.705–1.732 δ = 0.005–0.007 2V = 50–114° O.A.P. (010)

Optical properties

(9867)

3200

4480

3270

6060– 6110

3400– 3580

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 996 pm b = 2860 pm c = 985 pm 110.5° (Z = 8)

(Mg,Fe)2Al2O6[SiO4] M = 683.33 21.34 wt.% Mg 25.67 wt.% Al 6.17 wt.% Si 46.83 wt.% O (Nesosilicates)

Sapphirine [Named after its blue color] (ICSD 100297 and PDF 44-1430)

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Table 12.23. (continued)

Habit: platty crystals. Color: dark reddish brown. Luster: submetallic. Diaphaneity: translucent in thin flakes to opaque. Streak: dark brown.

Habit: prismatic, dipyramidal. Color: green, brown. Streak: white. Diaphaneity: transparent to translucent. Luster: resinous. Fracture: uneven. Cleavage: (120) good, (100) perfect, (010) poor.

Habit: tiny crystals with lamellar twinning embedded in rutile crystals. Color: black. Luster: vitreous to resinous. Insoluble in acids. Melting point: 1740°C. Occurrence: in vanadium-rich gneisses associated with kyanite and rutile.

Habit: prismatic. Color: white. Luster: resinous. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (101) poor, {110} poor. Twinning: {101}. Fracture: subconchoidal.

Habit: massive, granular, disseminated, tabular, columnar, bypiramidal or pseudooctaedrons. Color: colorless, white, pale yellow, greenish, brownish yellow, or reddish yellow. Luster: vitreous (i.e., glassy), greasy or subadamantine. Diaphaneity: transparent to translucent. Luminescence: fluorescent under short UV light, bright bluish white, sometimes pale yellow (traces of Mo). Streak: white. Cleavage: (101) distinct, (112) poor. Twinning: {110}. Fracture: uneven, brittle. Chemical: soluble in HCl or HNO3 giving a yellow solid residue of WO3 soluble in NH4OH. The soln. in HCl gives a deep blue color when a crystal of pure Sn, or Zn is added. Other: dielectric constant 3.5 to 5.75. Melting point: 1620°C. Occurrence: high-temperature quartz veins, in metamorphism contact halo of intrusive granitic ingneous rocks, in detritic sedimendary rocks near granites.

Habit: granular or tabular crystals. Color: light to medium blue. Luster: vitreous. Diaphaneity: transparent to translucent. Cleavage: (010). Fracture: brittle, uneven. Streak: pale blue. Insoluble in conentrated mineral acids but dissolves readily in molten sodium carbonate or KHSO4. Occurrence: magnesium- and aluminum-rich metamorphic rocks.

Other relevant mineralogical, physical, and chemical properties with occurrence

854 Minerals, Ores and Gemstones

86.62 wt.% Pb 13.38 wt.% O (Oxides and hydroxides)

Sb2O3 M = 275.4988 88.39 wt.% Sb 11.61 wt.% O (Oxides and hydroxides)

Na2Ca2(CO3)3 M = 306.16 15.02 wt.% Na 26.18 wt.% Ca 11.77 wt.% C 47.03 wt.% O (Nitrates, carbonates, and borates)

FeCO3 M = 115.8539 62.1 wt.% FeO 37.9 wt.% CO2 Coordinence Fe(6), C(3) (Nitrates, carbonates, and borates)

Al2O[SiO4] = Al2SiO5 M = 162.04558 33.30 wt.% Al 17.33 wt.% Si 49.37 wt.% O Coordinence Al(6), Si(4), Al(4) Traces of Fe, Mn (Nesosubsilicates)

Ag M = 107.8682 Coordinence Ag(12) (Native elements)

MgAlBO4 M = 126.095138 19.28 wt.% Mg 21.40 wt.% Al 8.57 wt.% B 50.75 wt.% O Coordinence Mg(6), Al(6), B(4) (Nitrates, carbonates and borates)

required clearly to indentify the mineral] (ICSD 20362 and PDF 45-1416)

Senarmontite [Named after the French mineralogist, H.H. de Senarmont (1808–1862)] (ICSD 1944 and PDF 43-1071)

Shortite [Named after the American mineralogist, Maxwell Naylor Short (1889–1952)] (ICSD 16495 and PDF 21-1348)

Siderite (Siderose) [Named from Greek, sideros, iron] (ICSD 100678 and PDF 29-696)

Sillimanite (syn., fibrolite, viridine: green, fibrolite: acicular) [Named after the American chemist and mineralogist, Benjamin Silliman (1779–1864)] (ICSD 100450 and PDF 38-471)

Silver [7440-22-4] (syn., argentum) (ICSD 64994 and PDF 4-783)

Sinhalite [Named after the Sanskrit, Sinhala, for Sri Lanka] (ICSD 75942 and PDF 25-1379)

Orthorhombic a = 432.8 pm b = 987.8 pm c = 567.5 pm (Z = 4) P.G. mmm S.G. P21/mcn Olivine type

Cubic a = 408.56 pm A1, cF4 (Z = 4) P.G. m3m S.G. Fm3m Copper type

Orthorhombic a = 748.43 pm b = 767.30 pm c = 577.11 pm (Z = 4) P.G. mmm S.G. Pbmn

Trigonal (Rhombohedral) a = 468.87 pm c = 1537.3 pm (Z = 6) P.G. 32/m S.G. R3c Calcite type

Orthorhombic a = 496.1 pm b = 1103 pm c = 712 pm (Z = 2) P.G.mm2 S.G.Amm2

Cubic a = 1114 pm (Z = 16) P.G. 432 S.G. Fd3m

b = 595.6 pm c = 543.8 pm oP12 (Z = 4) P.G. 222 S.G. Pbcn

Biaxial (+) α = 1.670 β = 1.700 γ = 1.710 δ = 0.04 2V = 55°

Isotropic nD = 0.181 R = 95%

Biaxial (+) α = 1.653–1.661 β = 1.658–1.662 γ = 1.673–1.684 δ = 0.020–0.023 2V = 21–30° O.A.P. (010) Dispersion strong

Uniaxial (–) ε = 1.575–1.637 ω = 1.782–1.875 δ = 0.207–0.242 Dispersion strong

Biaxial α = 1.531 β = 1.555 γ = 1.570 2V = 75°

Isotropic nD = 2.087

6.5–7

2.5–3 (HV 48–63)

6.5–7.5

4.5–5

3

2

3420

10,506

3240

3500– 3960

2600 (2610)

5200– 5300

Habit: prismatic. Color: white, yellow. Diaphaneity: transparent to translucent. Luster: vitreous. Streak: green blue. Cleavage: good (010). Fracture: conchoidal.

Habit: octahedral, dendritic. Color: silver white. Diaphaneity: opaque. Luster: metallic. Streak: gray. Cleavage: none. Twinning: {111}. Fracture: hackly, malleable, ductile. Chemical: readily dissloved in nitric acid, HNO3.

Habit: fibrous, prismatic, acicular. Color: colorless, white, yellowish or green. Fracture: splintery, brittle. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Cleavage: (010) perfect. Streak: white. Fluorescence: white-bluish. Cleavage: (010) perfect. Chemical: insoluble in strong mineral acids, decomposed by molten Na2CO3. When heated in an aqueous solution of Co(NO3)2 gives a blue color (Thénard blue). Other properties: Unfusible and the most stable of the three aluminum silicates but when heated above 1600°C transforms to a mixture of silica and mullite (Al6Si2O13). Dielectric constant of 9.29. Diamagnetic with a specific magnetic susceptibility of –10–10 m3.kg–1. Occurrence: Metamorphosed peri-aluminous sedimentary rocks. Gneiss and shales.

Habit: rhombohedral, crystalline, coarse, stalactitic, massive. Color: yellow brown. Luster: vitreous (i.e., glassy). Diaphaneity: transparent, translucent, to opaque. Streak: white. Cleavage: (1014) perfect. Twinning: {0118}. Fracture: brittle, subconchoidal. Chemical: readily dissolved in diluted acids with evolution of carbon dioxide; natural siderite when heated in air above 425°C is subject to thermal decomposition the final product is hematite while magnetite and maghemite form as intermediate decomposition products. Occurrence: sedimentary rocks.

Habit: wedge-shaped, equant, or short prismatic crystals. Color: colorless to pale yellow. Diaphaneity: transparent. Luster: vitreous. Streak: n.a. Cleavage: (010). Fracture: conchoidal. Decomposes in water releasing an insoluble residue of calcium carbonate. Fluorescent under UV radiation. Occurrence: with calcite and pyrite.

Habit: euhedral crystals, massive-granular, encrustations. Color: white, colorless, or gray. Luster: adamantine. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (111) imperfect. Fracture: uneven. Occurrence: oxidation of stibnite and other antimony minerals.

Cleavage: (100) perfect; (010) imperfect. Fracture: brittle. Chemical properties: easily fusible and decomposed at red-heat into minium (Mn3O4). Soluble in hot conc. HCl with chlorine evolution, and slightly soluble in sulfuric and nitric acids with oxygen evolution. Dimporphous with plattnerite.

Mineral and Gemstone Properties Table 855

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

(Co,Ni)As3 M = 246.18 17.95 wt.% Co 5.96 wt.% Ni 76.09 wt.% As (Sulfides and sulfosalts) Coordinence Co(6), Ni(6)

ZnCO3 M = 125.3992 52.15 wt.% Zn 9.58 wt.% C 38.28 wt.% O Coordinence Zn(6), C(3) (Nitrates, carbonates, and borates)

Na8[Al6Si6O24]Cl2 M = 933.75868 19.70 wt.% Na 17.34 wt.% Al 18.05 wt.% Si 3.80 wt.% Cl 41.12 wt.% O Coordinence Na(7), Si(4), Al(4) Traces of K and Ca (Tectosilicates, framework)

PtAs2 M = 344.92 43.44 wt.% As 56.56 wt.% Pt (Sulfides and sulfosalts)

Mn3Al2(SiO4)3 M = 495.02653 33.29 wt.% Mn 10.90 wt.% Al 17.02 wt.% Si 38.78 wt.% O Coordinence Mn(8), Al(6), Si(4) (Nesosilicates)

ZnS M = 97.456 67.10 wt.% Zn 32.90 wt.% S

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Skutterudite [Named after the Norvegian locality, Skutterud] (ICSD 9188 and PDF 10-328)

Smithsonite [3486-35-9] (syn., galmei, calamine, zinc spar) [Named after the English mineralogist, J. Smithson] (ICSD 100679 and PDF 8-449)

Sodalite [from its chemical composition, Latin solidus, solid since it was a solid used in glassmaking] (ICSD 36050 and PDF 37-476)

Sperylite [Named after the American chemist, Francis L. Sperry (1861–1906)] (ICSD 38428 and PDF 42-1341)

Spessartine (syn., spessartite) [Named after the locality, Spessart, northwestern Bavaria, Germany] (ICSD 27365 and PDF 47-1815)

Sphalerite [1314-98-3] (syn., zinc blende, mock, lead ore, black Jack, False Galena)

Table 12.23. (continued)

Cubic a = 540.93 pm B3, cF8 (Z = 4)

Cubic a = 1162 pm (Z = 8) P.G. 432 S.G. Ia3d Garnet group (Pyralspite series)

Cubic a = 597 pm (Z = 4) P.G. 432 S.G. Pa3 Pyrite group

Cubic a = 891 pm (Z = 1) P.G. 43m S.G. P43m (Sodalite type)

Trigonal (Rhombohedral) a = 465.28 pm c = 1502.8 pm (Z = 6) P.G. -32/m S.G. R-3c Calcite type

Isotropic nD = 2.369 R = 17.5%

Isotropic nD = 1.805

Isotropic R = 22.8%

Isotropic nD = 1.483–1.487

Uniaxial (–) ε = 1.625 ω = 1.848 δ = 0.225

3.5–4 (HV 186– 209)

6.5–7.5

6.5 (HV 960– 1277

5.5–6

4.5

5.5–6 (HV 589– 724)

Mohs hardness (/HM) (Vickers)

Isotropic R = 55.8%

Optical properties

Habit: massive, granular, disseminated. Color: azure blue, white, yellow, pale pink, colorless, gray, or green. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), greasy. Streak: white. Cleavage: (110) good. Twinning: {111}. Fracture: conchoidal. Occurrence: volcanic tuffs and volcano-clastic sediments.

Habit: massive, botryoidal, reniform, earthy. Color: grayish white, dark gray, green, blue, or yellow. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), pearly. Streak: white. Cleavage: (1011) perfect. Fracture: subconchoidal, brittle. Chemical: readily attacked by strong mineral acids with evolution of carbon dioxide.

Habit: skeletal, cubic crystals. Color: tin white. Luster: metallic. Diaphaneity: opaque. Streak: black. Fracture: uneven. Cleavage: {100}, {111}. Twinning: {112}. Electrical resistivity 5 to 400 μΩ.cm.

Other relevant mineralogical, physical, and chemical properties with occurrence

4089

4180

Habit: tetrahedral crystals, granular, colloform. Color: brown, yellow, orange, red, green, or black. Luster: resinous, metallic, greasy. Diaphaneity: transparent to opaque. Luminescence: fluorescent and triboluminescent. Streak: brownish white. Cleavage: {110}. Fracture: uneven, conchoidal. Twinning: {111}. Chemical: attacked by strong mineral

Habit: massive, crystalline, lamellar. Color: red or brownish red. Diaphaneity: transparent to translucent. Luster: vitreous, resinous. Streak: white. Parting: {110}. Fracture: Subconchoidal. Occurrence: magmatic, metamorphic, and pegmatitic rocks.

10,600 Habit: cubic to cuboctahedral crystals. Color: tin white. Luster: metallic. (10,780) Diaphaneity: opaque. Cleavage: (100) indistinct. Fracture: brittle, conchoidal. Streak: black. Occurrence: epithermal sulfide vein deposits.

2270– 2330

4450

6100– 6800

Density (ρ/kg.m–3) (calc.)

Cubic a = 820 pm D02, cI32 (Z = 8) S.G. Im-3 P.G. m-3 CoAs3 type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

856 Minerals, Ores and Gemstones

Traces Fe, (Sulfides and sulfosalts) Coordinence Zn(4)

MgAl2O4 M = 142.26568 17.08 wt.% Mg 37.93 wt.% Al 44.98 wt.% O Coordinence Mg(4), Al(6) (Oxides and hydroxides)

LiAl[Si2O6] M = 186.09 3.73 wt.% Li 14.50 wt.% Al 30.18 wt.% Si 51.59 wt.% O Coordinence Li(6), Al(6), and Si(4) (Inosilicates, chains)

2Ca2[SiO4].CaCO3 M = 444.57 45.08 wt.% Ca 12.64 wt.% Si 2.70 wt.% C 39.59 wt.% O

Cu2FeSnS4 M = 429.913 12.99 wt.% Fe 29.56 wt.% Cu 27.61 wt.% Sn 29.83 wt.% S (Sulfides and sulfosalts)

(Fe,Mg,Zn)2(Al,Fe)9(Si,Al)4O22(OH)2 27–29 wt.% SiO2 53–54 wt.% Al2O3 1–3 wt.% Fe2O3 11–12 wt.% FeO 2–3 wt.% MgO Coordinence Al(6), Si(4), Fe(4) (Nesosubsilicates)

Ag5SbS4 M = 789.355 68.33 wt.% Ag 15.42 wt.% Sb 16.25 wt.% S (Sulfides and sulfosalts)

[from the Greek, sphaleros, misleading since it was often mistaken for galena but yielded no lead] (ICSD 60378 and PDF 5-566)

Spinel (syn., ruby spinal, Balas ruby, red rubicelle) [from Latin, spina, thorn, in allusion to sharply-pointed crystals] (ICSD 79000 and PDF 21-1152)

Spodumene (syn., pink: kunzite, hiddenite) [Named from the Greek spodoun, to reduce to ashes refers either to its ash-gray color or the ash-colored mass formed when heated before the blowpipe] (ICSD 30521 and PDF 33-786)

Spurrite [Named after the American Geologist, Josiah Edward Spurr (1870–1950)] (ICSD 25830 and PDF 13-496)

Stannite (syn., tin pyrites, Bell metal ore) [Named from the Latin, stannum, tin] (ICSD 200420 and PDF 44-1476)

Staurolite (syn., staurotide) [from the Greek, stauros, cross, and lithos, stone, in allusion to the common cross shaped twins of the crystals] (ICSD 67446 and PDF 41-1484)

Stephanite (syn., Brittle Silver Ore) [Named after the Austrian engineer, A. Stephan] (ICSD 16987 and PDF 11-108)

Orthorhombic P.G. mm2

Monoclinic (pseudo-orthorhombic) a = 790 pm b = 1665 pm c = 563 pm 90.0° (Z = 2) P.G. 2/m S.G. C2/m

Tetragonal a = 546 pm c = 1072 pm H26, tI16 (Z = 2) S.G. I42m

Monoclinic a = 1049 pm b = 671 pm c = 1415 pm β = 101.317° (Z = 4) P.G. 2/m S.G. P21a

Monoclinic a = 952 pm b = 832 pm c = 525 pm 110.46° (Z = 4) P.G. 2/m S.G. C2/m

Cubic a = 808.0 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m Spinel type

S.G. F-43m P.G. -43m Blende type

Biaxial

Biaxial (+) α = 1.739–1.747 β = 1.745–1.753 γ = 1.752–1.761 δ = 0.012–0.014 2V = 82–90° O.A.P. (100) Dispersion weak

Uniaxial R = 28%

Biaxial (–) α = 1.637–1.641 β = 1.672–1.676 γ = 1.676–1.681 δ = 0.039–0.040 2V = 35–41°

Biaxial (+) α = 1.650 β = 1.660 γ = 1.670 δ = 0.02 2V = 60–80° Dispersion weak

Isotropic nD = 1.719

2–2.5

7–7.5

3.5–4 (HV 197– 221)

5

6.5–7

7.5–8

6250

3740– 3830

4400

3010

3150

3583

Habit: pseudo hexagonal, tabular, massive. Color: iron black. Diaphaneity: opaque. Luster: metallic. Streak: black. Fracture: subconchoidal. Cleavage: [010] imperfect, [021] poor.

Habit: tabular, prismatic. Color: reddish brown, brownish black, or yellowish brown. Diaphaneity: translucent to opaque. Luster: vitreous (i.e., glassy), dull. Streak: gray. Twinning: common in cross. Cleavage: (001) distinct. Twinning: {031}, and {231}. Fracture: Subconchoidal. Chemical: attacked by hot conc. H2SO4. Unfusible. Other properties: dielectric constant of 6.80. Diagnetic with a specific magnetic susceptibility of +10–6 m3.kg–1. Occurrence: metamorphosed aluminous sedimentary rocks.

Habit: massive, euhedral crystals. Color: steel gray or olive green. Diaphaneity: opaque. Luster: metallic. Cleavage: [110] poor. Fracture: uneven. Streak: black. Electrical resistivity 1.2 to 570 mΩ.m.

Habit: granular masses. Color: white, pale blue to yellow. Diaphaneity: translucent. Luster: vitreous. Streak: white. Cleavage: (001). Fracture: uneven. Effervesce with dilute HCl. Occurrence: high-temperature contact metamorphism.

Habit: euhedral prismatic or long tabular crystals. Color: colorless to pink. Luster: vitreous (i.e., glassy). Diaphaneity: transparent, translucent. Streak: white. Cleavage: {110} perfect. Twinning: {100}. Fracture: uneven. Chemical: insoluble in strong mineral acids. Nevertheless when alpha-spodumene is heated above 1082°C it transforms irreversibly into beta spodumene which is , accompanied by a 30% volume increase and subsequent decrease in the specific gravity from 3.2 to 2.4 in addition beta-spodumene has a very low coefficient of thermal expansion of about 1 × 10–6 K–1 for the range 25°C to 1000°C and is readily attacked by hot concentrated H2SO4. Others. Bond’s work index of 21 kWh/tonne and Pennsylvania abrasive index of 0.416. Occurrence: granitic pegmatites.

Habit: euhedral crystals, massive, granular. Color: colorless, red, blue, green, or brown. Luster: vitreous (i.e., glassy). Diaphaneity: transparent, translucent, opaque. Streak: grayish white. Cleavage: {111} poor. Twinning: {111}. Fracture: conchoidal or uneven.

acids, HCl, or HNO3 with evolution of H2S and yellow precipitate of sulfur. Infusible. Electrical resistivity 2.7 mΩ.m. Occurrence: veins in igneous, sedimentary and metamorphic rocks.

Mineral and Gemstone Properties Table 857

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Sb2S3 M = 339.698 71.68 wt.% Sb 28.32 wt.% S (Sulfides and sulfosalts) Coordinence Sb(7)

(Ca,Na)Si7Al2O18.7H2O Coordinence Ca(6), Na(6), Si(4), and Al(4). (Tectosilicates, framework)

SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

AgCuS M = 203.4802 31.23 wt.% Cu 53.01 wt.% Ag 15.76 wt.% S (Sulfides and sulfosalts)

SrCO3 M = 147.6292 59.35 wt.% Sr 8.14 wt.% C 32.51 wt.% O (Sulfates, chromates, molybdates, and tungstates)

S8 M = 256.528 Coordinence S(2) (Native elements)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Stibnite (syn., antimonite, antimony glance, gray antimony, Stibium) [from the Greek, stimmi or stibi, antimony, hence to the Latin, stibium] (ICSD 15236 and PDF 42-1393)

Stilbite (ICSD 63232 and PDF 44-1479)

Stishovite [Named after the Russian crystallographer M.S. Stishov (1937–) who first synthesized the mineral in 1961] (ICSD 68409 and PDF 45-1374)

Stromeyerite [Named after the German chemist, F. Stromeyer] (ICSD 66580 and PDF 44-1436)

Strontianite [1633-05-2] [Named after Strontian, a small town in Argyllshire, Scotland] (ICSD 202793 and PDF 5-418)

Sulfur or Sulphur [from Sanskrit, sulvere, and Latin, sulfurium] (ICSD 63082 and PDF 8-247)

Table 12.23. (continued)

Orthorhombic a = 1046.46 pm b = 1286.60 pm c = 2448.60 pm A16, oF128

Orthorhombic a = 602.9 pm b = 841.4 pm c = 510.7 pm (Z = 4) P.G. mmm S.G. Pmcn Aragonite type

Orthorhombic P.G. 222

Tetragonal a = 417.9 pm c = 266.49 pm C4, tP6 (Z = 2) P.G. 422 S.G. P4/mnm Rutile type

Monoclinic a = 1364 pm b = 1824 pm c = 1127 pm 129.16° (Z = 4) P.G.: 2/m S.G. C2/m

Biaxial (+) α = 1.958 β = 2.038 γ = 2.245 δ = 0.290

Biaxial (–) α = 1.516–1.520 β = 1.664–1.667 γ = 1.666–1.669 δ = 0.149–0.150 2V = 7–10° Dispersion weak

Biaxial R = 32.3%

Uniaxial (+) ε = 1.826 ω = 1.799 δ = 0.027

Biaxial (–) α = 1.490 β = 1.500 γ = 1.500 δ = 0.010 2V = 30–50°

1.5–2.5

3.5

2.5–3 (HV 38–44)

6

3.5–4

2068

3720

6000– 6300

4300

2150

2 4630 (HV 42–109)

Mohs hardness (/HM) (Vickers)

Biaxial (?) α = 3.194 β = 4.046 γ = 4.303 δ = 1.110 2V = 26° R = 30.2–40.0%

Optical properties

Density (ρ/kg.m–3) (calc.)

Orthorhombic a = 1122.9 pm b = 1131.0 pm c = 383.89 pm D511, oP20 (Z = 4) S.G. Pccn P.G. 222 Stibnite type

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: massive, reniform, stalactitic. Color: yellow, yellowish brown, or gray. Diaphaneity: transparent to translucent. Luster: resinous. Streak: white. Cleavage: (101), (110). Fracture: sectile. Chemical: highly soluble in carbon disulfide CS2. Occurrence: volcanic exhalations and bacterial reduction of sulfates in sediments.

Habit: pseudohexagonal, columnar, massive, granular, acicular, spadelike. Color: white, yellowish gray, greenish gray, or bluish white. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Cleavage: (110) good. Fracture: uneveven, conchoidal, brittle. Streak: white. Chemical: decomposed at 1494°C giving off SrO and CO2. Soluble in strong mineral acids with evolution of CO2.

Habit: granular, massive, pseudo hexagonal. Color: steel gray. Luster: metallic. Diaphaneity: opaque. Streak: steel gray. Fracture: conchoidal. Occurrence: copper–silver veins where silver replaces copper in bornite.

Habit: prismatic. Color: colorless. Luster: vitreous (i.e., glassy). Streak: white. Twinning: {011}. Fracture: conchoidal. Chemical: resistant to strong mineral acids, attacked by HF and molten alkali-metal hydroxides.

Habit: prismatic, striated, curved crystals. Color: gray. Diaphaneity: translucent to transparent. Luster: pearly. Streak: gray. Cleavage: (010) distinct, (0010 poor, (101) poor. Fracture: Subconchoidal.

Habit: prismatic, faces striated, granular. Color: lead gray, bluish lead gray, steel gray, or black. Diaphaneity: opaque. Luster: Metallic. Streak: blackish gray. Cleavage: [010] perfect. Fracture: subconchoidal.

Other relevant mineralogical, physical, and chemical properties with occurrence

858 Minerals, Ores and Gemstones

(Au,Ag)2Te4 (Sulfides and Sulfosalts)

KCl M = 74.551 52.45 wt.% K 47.55 wt.% Cl (Halides) Coordinence K(6)

Mg3Si4O10(OH)2 M = 379.26568 19.23 wt.% Mg 29.62 wt.% Si 0.53 wt.% H 50.62 wt.% O Coordinence Mg(6), Si(4) (Phyllosilicates, layered)

(Fe,Mn)(Ta,Nb)2O6 M = 513.7392 70.44 wt.% Ta 10.87 wt.% Fe 18.69 wt.% O (Oxides, and hydroxides)

Te M = 127.60 (Native elements)

CuO M = 79.5454 79.89 wt.% Cu 20.11 wt.% O

Mn2SiO4 M = 201.96 gm 54.41 wt.% Mn 13.91 wt.% Si 31.69 wt.% O (Nesosilicates)

Sylvanite [Named after Transylvania] (ICSD 30874 and PDF 9-477)

Sylvite (syn., sylvinite) [7447-40-7] [Named after the Dutch chemist and physician of Leyden, Sylvia de la Boe (1614–1672)] (ICSD 22156 and PDF 41-1476)

Talc (2M1) (syn., steatite: massive, soapstone, kerolite) [Named from the Arabic] (ICSD 26741 and PDF 29-1493)

Tapiolite (syn., tantalite) [Named after the god Tapio of Finnish mythology] (ICSD 79685 and PDF 23-1124)

Tellurium [Named from Latin, tellus, earth] (ICSD 23058 and PDF 36-1452)

Tenorite (syn., melaconite, melanochalcite) [Named after the Italian botanist, M. Tenor] (ICSD 67850 and PDF 45-937)

Tephroite [Named from the Greek, tephros, ash gray for its color] (ICSD 100433 and PDF 35-748)

Orthorhombic a = 476 pm b = 102 pm c = 598 pm (Z = 4) P.G. mmm Olivine group

Triclinic P.G. -1

Hexagonal a = 446 pm c = 593 pm (Z = 3) S.G. P63 /mmc

Tetragonal a = 475.4 c = 922.8 (Z = 2)

Monoclinic a = 528.7 pm b = 915.8 pm c = 1895 pm β = 99.50° (Z = 4) P.G. m S.G. Cc Type 2M1 mica

Cubic a = 629.31 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 4-32 Rock salt type

Monoclinic a = 896 pm b = 449 pm c = 1462 pm (Z = 4) P.G. 2/m

(Z = 128 S or 16 S8) Sulfur type P.G. 222 S.G. Fddd

Biaxial (+) α = 1.759 β = 1.797 γ = 1.86 δ = 0.101 2V = 78°

Biaxial R = 23.4%

Uniaxial R = 57–68%

Biaxial

Biaxial (–) α = 1.539–1.550 β = 1.589–1.594 γ = 1.589–1.600 δ = 0.037–0.050 2V = 6–30°

Isotropic nD = 1.490

Biaxial R = 48.0–60.0%

2V = 68.58° Dispersion weak R = 13%

6.5

3.5–4 (HV 209– 254)

2–2.5

6–6.5

1

2.0

1.5–2 (HV 102– 125)

4110– 4390

6500

6100– 6300 (6230)

8170

2580– 2830

1988

7900– 8300

Habit: massive-granular, granular, prismatic. Color: gray, olive gray, flesh pink, or reddish brown. Luster: vitreous-greasy. Diaphaneity: transparent to translucent. Streak: gray. Cleavage: [010] indistinct. Fracture: brittle-conchoidal. Occurrence: Contact metamorphism of manganese-bearing rocks.

Habit: scaly, earthy, massive. Color: black. Luster: earthy (dull). Diaphaneity: opaque. Streak: black. Cleavage: none. Fracture: conchoidal. Occurrence: secondary copper mineral.

Habit: prismatic, columnar and granular crystals. Color: tin white. Luster: metallic. Diaphaneity: opaque. Cleavage: (010) perfect. Fracture: conchoidal. Streak: gray. Occurrence: hydrothermal veins.

Habit: granular. Color: black. Diaphaneity: opaque. Luster: metallic. Streak: brown. Cleavage: (110) imperfect. Fracture: uneven. Occurrence: pegmatites and alluvial deposits.

Habit: foliated, scaly, massive. Color: pale green, white, gray white, yellowish white, or brownish white. Diaphaneity: translucent. Luster: vitreous (i.e., glassy), pearly. Streak: white. Cleavage: (001) perfect. Fracture: uneven. Occurrence: hydrothermal alteration of non-aluminous magnesian silicates.

Habit: massive, cubic euhedral crystals, fibrous. Color: white, yellowish white, reddish white, bluish white, or brownish white. Luster: vitreous, greasy. Diaphaneity: transparent to translucent. Streak: white. Cleavage: (100), (010), (001). Fracture: uneven, brittle, sectile. Soluble in water, the soln. color the flame of a bunsen in violet. Bitter taste. Fusible (m.p. 778°C).

Habit: prismatic, skeletal, platy. Color: yellowish silver white or white. Luster: metallic. Diaphaneity: opaque. Streak: steel gray. Cleavage: [010] perfect. Fracture: uneven.

Mineral and Gemstone Properties Table 859

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Hg2ClO M = 452.63 88.63 wt.% Hg 7.83 wt.% Cl 3.53 wt.% O (Halides)

Bi2Te2S M = 705.2268 59.27 wt.% Bi 36.19 wt.% Te 4.55 wt.% S (Sulfides and sulfosalts)

(Cu,Fe)12Sb4S13 M = 1643.31 10.20 wt.% Fe 34.80 wt.% Cu 29.64 wt.% Sb 25.37 wt.% S (Sulfides and sulfosalts) Coordinence Cu(3), Cu(4)

ThO2 M = 264.04 87.88 wt.% Th 12.12 wt.% O (Oxides and hydroxides)

ThSiO4 M = 324.1212 71.59 wt.% Th 8.67 wt.% Si 9.74 wt.% O (Nesosilicates)

(Th,U,Ca)Ti2(O,OH)6 M = 390.82 2.05 wt.% Ca 23.75 wt.% Th 24.36 wt.% U 24.50 wt.% Ti 0.77 wt.% H 24.56 wt.% O

Al2TiO5 M = 181.827

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Terlinguaite [Named after Terlingua, Texas, USA] (ICSD 65483 and PDF 25-559)

Tetradymite [Named from the Greek, tetradymos, fourfold] (ICSD 26720 and PDF 42-1447)

Tetrahedrite [Named in 1845 after its tetrahedral crystal form] (ICSD 62116 and PDF 42-561)

Thorianite [Named from the presence of thorium] (ICSD 28685 and PDF 42-1462)

Thorite (syn., orangite) [Named from the Scandinavian God, Thor] (ICSD 1615 and PDF 11-419)

Thorutite [Named after thorium and rutile] (ICSD 14341 and PDF 19-1351)

Tialite [12004-39-6]

Table 12.23. (continued)

Orthorhombic a = 942.9 pm

Monoclinic a = 982 pm b = 382 pm c = 704 pm β = 118.83° (Z = 2) P.G. 2/m S.G. C2/m

Tetragonal a = 711.7 pm c = 629.5 pm (Z = 4)

Cubic a = 559.5 pm (Z = 4) P.G. 432 S.G. Fm3m

Cubic a = 1027 pm (Z = 2) P.G. 43m S.G. I43m Tetraedrite type

Trigonal a = 424 pm b = 2959 pm (Z = 3) P.G. 32/m S.G. R3m

Mohs hardness (/HM) (Vickers)

Biaxial (?)

Biaxial (–) Usually metamict hence isotropic

Uniaxial (–) ε = 1.78–1.82 ω = 1.79–1.84 δ = 0.010–0.020

Isotropic R = 14.6%

Isotropic nD = 2.720 R = 30.7%

Uniaxial R = 56.9%

n.a.

4.5–5.5

5

6 (HV 988– 1115)

3.5–4 (HV 328– 367)

1.5–2

Biaxial (–) 2–3 α = 2.35 β = 2.64 γ = 2.66 δ = 0.310 2V = 26° Dispersion strong

Optical properties

3702

5610– 5820 (6080)

5350

10,000

4600– 5200 (5070)

7550

8700

Density (ρ/kg.m–3) (calc.)

Monoclinic a = 1201 pm b = 591 pm c = 949 pm β = 106° (Z = 8) P.G. 2/m S.G. C2/c

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Melts at 1860°C

Habit: short prismatic crystals. Color: dark brown to black. Luster: resinous. Diaphaneity: translucent. Cleavage: (010) perfect. Fracture: conchoidal. Streak: light brown. Radioactive. Occurrence: in nepheline syenite, paragenesis with thorite and zircon.

Habit: prismatic, granular, massive. Color: reddish brown, black, or orange. Diaphaneity: transparent to translucent. Luster: resinous. Cleavage: (110) poor. Fracture: conchoidal. Streak: light brown. Occurrence: augite-syenite rocks.

Habit: pseudo hexagonal, granular. Color: black or brown. Diaphaneity: Opaque. Luster: metallic. Cleavage: (100), (010), (001) poor. Fracture: conchoidal, brittle. Streak: black. Radioactive. Occurrence: pegmatites and alluvial deposits.

Habit: tetrahedral crystals, granular, massive. Color: steel gray or black. Diaphaneity: opaque. Luster: metallic. Streak: brown, black. Cleavage: None. Twinning: {111}. Fracture: uneven, subconchoidal. Electrical resistivity 0.3 to 30,000 Ω.m. Occurrence: hydrothermal veins and contact metaporphism.

Habit: lamellar, granular, pseudo hexagonal. Color: steel gray or yellow gray. Diaphaneity: opaque. Luster: metallic. Cleavage: (0001) perfect. Fracture: uneven. Streak: steel gray.

Habit: striated, prismatic. Color: yellow or green. Luster: adamantine. Diaphaneity: transparent to translucent. Cleavage: [101] perfect. Occurrence: Oxidized portions of mercury deposits.

Other relevant mineralogical, physical, and chemical properties with occurrence

860 Minerals, Ores and Gemstones

29.70 wt.% Al 26.30 wt.% Ti 44.00 wt.% O Coordinence Ti(6)

HgSe M = 279.55 71.75 wt.% Hg 28.25 wt.% Se (Sulfides and sulfosalts)

CaTi[SiO4|(O,OH,F)] 28.6 wt.% CaO 40.8 wt.% TiO2 30.6 wt.% SiO2 Coordinence Ca(7), Ti(6), Si(4) (Nesosilicates)

Al2[SiO4](F,OH)2 M = 182.25 29.61 wt.% A 15.41 wt.% Si 0.50 wt.% H 43.02 wt.% O 11.47 wt.% F Coordinence Al(6), Si(4) (Nesosubsilicates)

Cu(UO2)2(VO4)2.8H2O Coordinence Cu(6), U(2), P(4) (Phosphates, arsenates, and vanadates)

Ca2Mg5Si8O22(OH)2 M = 812.37 9.87 wt.% Ca 14.96 wt.% Mg 27.66 wt.% Si 0.25 wt.% H 47.27 wt.% O Coordinence Ca(8), Mg(6), Si(4) (Inosilicates, double chain)

NiFe2O3 M = 234.38 47.65 wt.% Fe 25.04 wt.% Ni 27.30 wt.% O (Oxides, and hydroxides)

(syn. tieilite) (ICSD 24133 and PDF 41-258)

Tiemannite [Named after C.W.F. Tiemann] (ICSD 24322 and PDF 8-469)

Titanite (syn., sphene) [Named after titanium or from the Greek, sphen, coin] (ICSD 39870 and PDF 31-295)

Topaz (syn., pycnite: yellowish white) [Named after the locality, Topasos Island, in the Red Sea] (ICSD 75825 and PDF 12-765) (ICSD 75824 and PDF 44-269)

Torbernite [Named after the Swedish chemist, Tornbern Bergmann (1735–1784)]

Tremolite (syn., abestos) [Named after the Val Tremola, south side of mount Saint-Gothardt in the Swiss Alps] (ICSD 30126 and PDF 44-1402)

Trevorite [12186-55-9] [Named after the South-African geologist T.G. Trevor(1865–1958)] (ICSD 67846 and PDF 10-325)

Cubic a = 843 pm H11, cF56 (Z = 8) S.G. Fd3m Spinel type

Monoclinic a = 984.00 pm b = 180.52 pm c = 527.5 pm β = 104.75° (Z = 2) P.G. 2/m S.G. C2/m Tremolite type

Tetragonal a = 70 pm c = 206.7 pm P.G. 4/mmm S.G. I4/mmm (Z = 4)

Orthorhombic a = 464.9 pm b = 879.2 pm c = 839.4 pm (Z = 4) P.G. mmm S.G. Pbnm

Monoclinic a = 656 pm b = 872 pm c = 744 pm β = 119.72° (Z = 4) P.G. 2/m S.G. C2/c

Cubic P.G. Diploidal

b = 963.6 pm c = 359.1 pm (Z = 4) P.G. 2/m 2/m 2/S.G. Bbmm Pseudobrookite type 2.5

Isotropic nD = 2.30

Biaxial (–) α = 1.613–1.625 β = 1.634–1.645 γ = 1.646–1.666 δ = 0.017–0.020 2V = 65–86° Dispersion weak

Uniaxial (–)

Biaxial (+) α = 1.606–1.629 β = 1.609–1.631 γ = 1.616–1.638 δ = 0.009–0.011 2V = 48–68° O.A.P. (010) Dispersion low

5.5

5–6

2–2.5

8

Biaxial (+) 5–5.5 α = 1.843–1.950 β = 1.870–2.034 γ = 1.943–2.110 δ = 0.100–0.192 2V = 17–40° Dispersion strong O.A.P. (010)

Isotropic R = 29.8%

5260

3010– 3490

3250

3490– 3570

3450– 3550 (3480)

8190– 8470

Habit: massive or octahedral crystals. Color: black. Diaphaneity: opaque. Luster: submetallic. Streak: brown. Cleavage: (001). Fracture: uneven. Ferromagnetic. Occurrence: peridotites.

Habit: silky acicular crystals forming fibrous masses (asbestos). Color: colorless to pale green (traces Fe) or pink (traces Mn). Luster: glassy or pearly. Diaphaneity: transparent to translucent. Cleavage: (110) perfect with 124°, (010) distinct. Twinning: {100}. Fracture: subconchoidal. Streak: white. Others: not attacked by acids. Melts with difficulties yielding a greenish glass. Dielectric permittivity of 7.03 to 7.60. Luminescence: fluorescent under short UV light: yellow, and long UV light: pink. Occurrence: regional metamorphism and contact metamorphism of Ca-rich rocks.

Habit: thin to thick tabullar crystals. Color: emerald to dark green. Diaphaneity: transparent to translucent. Luster: vitreous to adamantine. Streak: green. Cleavage: (001). Fracture: uneven. Soluble in acids. Occurrence: secondary uranium mineral.

Habit: crystalline, well formed prismatic crystal with pinacoidal termination on one end and a small pinacoid face surrounded by pyramid and horizontal prism face at the other, massive, granular. Color: colorless, pale blue, yellow, yellowish brown, or red. Luster: vitreous (i.e., glassy). Diaphaneity: transparent. Streak: white. Cleavage: (001) perfect. Fracture: uneven, brittle. Luminescence: fluorescent under Short UV light: golden yellow, and long UV light: cream. Chemical: slightly attacked by hot conc. H2SO4. Other: dielectric constant 6.09 to 7.4. Occurrence: pegmatites and high-temperature quartz veins. Cavities in granites and rhyolites.

Habit: wedge shaped crystals, tabular, prismatic. Color: yellow, brown, white, greenish, gray, or red. Luster: adamantine, resinous, greasy. Diaphaneity: transparent to opaque. Cleavage: (110) perfect, (100) poor. Fracture: uneven, conchoidal. Twinning: {100}, {221} lamellar. Streak: reddish white. Chemical: insoluble in HCl, but decomposed by hot concentrated H2SO4. Fusible. Occurrence: igneous rocks, granitic, pegmatites.

Habit: euhedral crystals, granular. Color: dark lead gray. Luster: metallic. Diaphaneity: opaque. Streak: grayish black. Cleavage: none. Fracture: brittle.

Mineral and Gemstone Properties Table 861

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

SiO2 M = 60.0843 46.74 wt.% Si 53.26 wt.% O (Tectosilicates, framework) Coordinence Si (4)

LiFePO4 M = 157.76 4.40 wt.% Li 35.40 wt.% Fe 19.63 wt.% P 40.57 wt.% O Coordinence Li(8), Fe(8), and P(4) (Phosphates, arsenates, and vanadates) Traces of Mn

FeS M = 87.911 63.52 wt.% Fe 36.48 wt.% S

Na3(CO3)(HCO3) 2H2O M = 226.0262 30.51 wt.% Na 2.23 wt.% H 10.63 wt.% C 56.63 wt.% O (Nitrates, carbonates, and borates)

CuAl6(PO4)4(OH)2·4H2O M = 813.44052 19.90 wt.% Al 7.81 wt.% Cu 15.23 wt.% P 1.98 wt.% H 55.07 wt.% O Coordinence Cu(6), Al(6), P(4) (Phosphates, arsenates, and vanadates)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Tridymite [15468-32-3] [Named from the Greek tridymos, threefold since the crystals are often trillings] (ICSD 29343 and PDF 18-1169)

Triphylite [Named from the Greek for threefold and family] (ICSD 72545 and PDF 40-1499)

Troilite 1317-37-9 [Named after Domenico Troili the Italian Jesuit who first observed the mineral in the Albareto meteorite in 1776] (ICSD 68845 and PDF 37-477)

Trona [Named from Arabic origins meaning, natron] (ICSD 62200 and PDF 29-1447)

Turquoise (syn., callaite) [Named after Turkey from where it was brought to Europe] (ICSD 21062 and PDF 6-214)

Table 12.23. (continued)

Triclinic a = 748 pm b = 995 pm c = 768 pm α = 111.65° β = 115.38° γ = 69.43° (Z = 1) P.G. 1 S.G. P1

Monoclinic P.G. 2/m

Hexagonal a = 596.8 pm c = 1174.0 pm (Z = 12) S.G. P62c P.G. 6/m 2/m 2/m

Orthorhombic a = 601 pm b = 468 pm c = 1036 pm (Z = 4) P.G. mmm S.G. P21/mcn

Biaxial (+) α = 1.610 β = 1.615 γ = 1.650 δ = 0.040 2V = 40–44° Dispersion strong

Biaxial (–) α = 1.412 β = 1.492 γ = 1.540 δ = 0.128 2V = 72° Dispersion strong

Uniaxial (?)

Biaxial(–) α = 1.680 β = 1.680 γ = 1.690 δ = 0.01 2V = 0–56°

5–6

2.5

3.5–4.5 (HV 250)

5–5.5

6–7

Mohs hardness (/HM) (Vickers)

Uniaxial (+) ε = 1.475 ω = 1.479

Optical properties

2700

2110– 2170

4670– 4790 (4840)

3500– 5500

2280

Density (ρ/kg.m–3) (calc.)

Hexagonal a = 504.63 pm c = 825.63 pm C10, hP12 (Z = 4) P.G. 6mmm S.G. P63/mmc

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: concretionary, reniform, massive, encrustations. Color: light blue, apple green, or greenish blue. Diaphaneity: translucent to opaque. Luster: resinous, waxy. Streak: pale bluish white. Cleavage: (001) perfect, (010) good. Fracture: subconchoidal, brittle.

Habit: fibrous, columnar, massive. Color: yellowish white, gray, or white. Luster: vitreous (glassy). Diaphaneity: translucent. Streak: white. Cleavage: [100] perfect, [111] indistinct, [001] indistinct. Fracture: subconchoidal.

Habit: in meteorites as rounded nodules in siderites or anhedral grains in litholites. Color: light grayish brown. Luster: metallic. Diaphaneity: opaque. Streak: dark grayish brown. Occurrence: rare terrestrial occurrence such as in the Cañon Diablo meteorite, Disco Island in Greenland.

Habit: coarse massive. Color: blue green. Streak: white gray. Diaphaneity: transparent to translucent. Luster: vitreous, resinous. Fracture: subconchoidal. Cleavage: (001) perfect, (010) good.

Habit: wedge shaped. Color: colorless. Streak: white. Diaphaneity: transparent to translucent. Luster: vitreous(i.e., glassy). Fracture: conchoidal. Twinning: (110). Transition temperature 1470°C.

Other relevant mineralogical, physical, and chemical properties with occurrence

862 Minerals, Ores and Gemstones

Monoclinic a = 1587 pm b = 705 pm c = 666pm β = 97.25° (Z = 3) P.G. 2 S.G. P21

Tetragonal

Fe2TiO4 M = 223.555 21.42 wt.% Ti 49.96 wt.% Fe 28.63 wt.% O Coordinence Ti(4), Fe(6) (Oxides and hydroxides)

UO2 M = 270.0277 88.15 wt.% U 11.85 wt.% O Coordinence U(2) (Oxides, and hydroxides)

Ca(UO2)2SiO3(OH)2·5H2O M = 586.36418 6.84 wt.% Ca 40.59 wt.% U 9.58 wt.% Si 2.06 wt.% H 40.93 wt.% O (Inosilicates, chain)

(Th,U)[SiO4]

Ca3Cr2(SiO4)3 M = 500.4755 24.02 wt.% Ca 20.78 wt.% Cr 16.84 wt.% Si 38.36 wt.% O Coordinence Ca(8), Cr(6), Si(4) (Nesosilicates)

Ulvospinel [12063-18-2] (syn., ulvöspinel, ulvite) [Named after the Sodra Ulvö island, Angermanland archipelago, Northern Sweden and the spinel group of minerals] (ICSD 75367 and PDF 34-177)

Uraninite [Named after its chemical composition] (ICSD 29085 and PDF 41-1422)

Uranophane (syn., uranotile) [Named from Greek, uran and phanos, to appear] (ICSD 63029 and PDF 39-1360)

Uranothorite

Uvarovite [Named after Count Sergei Semeonovich Uvarov (1786–1855), Russian statesman, member of the Imperial Academy of St. Petersburg and ardent amateur mineral collector] (ICSD 27368 and PDF 11-696)

Cubic a = 1200 pm (Z = 8) P.G. 432 S.G. Ia3d Garnet group (Ugrandite series)

Cubic a = 546.82 pm C1, cF12 (Z = 4) P.G. 432 S.G. Fm3m Fluorite type

Cubic a = 845.96 pm H11, cF56 (Z = 8) P.G. m3m S.G. Fd3m P.G. 432 Spinel type (Ferrite series)

Cubic a = 588 pm FO1, cP12 (Z = 4) S.G. P213 P.G. 23 Ullmanite type

NiSbS M = 212.506 27.62 wt.% Ni 57.29 wt.% Sb 15.09 wt.% S (Sulfides and sulfosalts)

Ullmannite [Named after the German chemist and mineralogist, J.Ch. Ullmann] (ICSD 100259 and PDF 41-1472)

Triclinic a = 882 pm b = 1287 pm c = 668 pm α = 90.4° β = 109.1° γ = 105.0° (Z = 2) P.G. 1 S.G. P1

NaCaB5O6(OH)6.5H2O M = 405.23 5.67 wt.% Na 9.89 wt.% Ca 13.34 wt.% B 3.98 wt.% H 67.12 wt.% O Coordinence Na(6), Ca(9), B(3, and 4) (Nitrates, carbonates, and borates)

Ulexite (syn., natroborocalcite) [Named after the German chemist, George Ludwig Ulex (1811–1883)] (ICSD 100565 and PDF 12-419)

Isotropic nD = 1.860

Uniaxial

Biaxial (–) α = 1.643 β = 1.666 γ = 1.669 δ = 0.026 2V = 38° Dispersion strong

Isotropic R = 16.8%

Isotropic nD = 2.16–2.28 R=%

Isotropic R = 47.5%

Biaxial (+) α = 1.493 β = 1.505 γ = 1.526 δ = 0.029 2V = 73–78°

6.5–7.5

2.5

5–6 (HV 782– 839)

5.5–6

5–5.5 (HV 498– 542)

2.5

3900

3900

10,970

4780 (4771)

6700

1950– 1960

Habit: dodecahedral crystals. Color: green. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy). Streak: white. Fracture: subconchoidal. Occurrence: metamorphosed chromite deposits.

Habit: radial, earthy, massive, fibrous. Color: yellow. Diaphaneity: translucent. Luster: vitreous (i.e., glassy). Cleavage: (100) perfect. Fracture: uneven. Streak: yellowish white. Occurrence: alteration product of gummite.

Habit: cubic, massive. Color: black. Diaphaneity: opaque. Luster: metallic. Streak: brown, black. Cleavage: (100). Other: electrical resistivity 1.5 to 200 Ω.m. Radioactive. Occurrence: granites and syenite pegmatites. Hydrothermal high-temperature tin veins; sandstones and uraniferous conglomerates.

Habit: massive or as very fine exsoution lamellae. Cleavage: none. Color: iron black. Diaphaneity: opaque. Luster: metallic. Occurrence: occurs in titanoferrous magnetites, as exsolution lamellae.

Habit: tetrahedral crystals, massive, granular, massive. Color: steel gray or silvery white. Luster: metallic. Diaphaneity: opaque. Cleavage: [100], [010], [001]. Fracture: brittle uneven. Streak: grayish black.

Habit: nodules, needle-like crystals, and fibrous masses like cotton-balls. Color: colorless to white. Luster: chatoyant. Diaphaneity: translucent. Cleavage: [010] and [110] perfect. Fracture: brittle. Streak: white. Soluble in hot water. Occurrence: secondary borate mineral derived from weathering of primary borates such as borax.

Mineral and Gemstone Properties Table 863

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Sb2O3 M = 291.4982 83.53 wt.% Sb 16.47 wt.% O (Oxides, and hydroxides)

Pb5(VO4) Cl M = 1186.3921 87.33 wt.% Pb 4.29 wt.% V 5.39 wt.% O 2.99 wt.% Cl Coordinence Pb(6), V(4) (Phosphates, arsenates, and vanadates)

Al(PO4).2H2O M = 157.983 17.08 wt.% Al 19.61 wt.% P 60.76 wt.% O 2.55 wt.% H Coordinence Al(6), P(4) (Phosphates, arsenates, and vanadates)

Ca10(Mg,Fe)2Al4[Si2O7]2[SiO4]5(OH,F)4 Coordinence Ca(8), Mg(6), Fe(6), Al(6), Si(4) (Nesosilicates and sorosilicates)

NaF M = 41.98817 54.75 wt.% Na 45.25 wt.% F (Halides)

FeNi2S4 M = 301.475 18.52 wt.% Fe 38.94 wt.% Ni

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Valentinite (syn., antimony bloom) [Named after the German alchemist Basilius Valentinus (pseudonym for Johannes Thölde), working on the properties of antimony in the late 17th and early 18th century] (ICSD 27595 and PDF 11-689)

Vanadinite [Named after its vanadium content] (ICSD 203074 and PDF 43-1461)

Variscite (syn., strengite: Fe) (ICSD 819 and PDF 33-33)

Vesuvianite (syn., idocrase, cyprine) [from Greek, eidos, appearence, krasis, mixture, owing to the resseamblance of its crystals to other species, from Mt. Vesuvius volcano, Italy] (ICSD 79151 and PDF 38-473)

Villiaumite [7681-49-4] [Named after the French traveller and explorer,Villiaume who brought the specimen from Guinea] (ICSD 24443 and PDF 36-1455)

Violarite [Named from the Latin, violaris, purple] (ICSD and PDF 42-1449)

Table 12.23. (continued)

Cubic a = 946.4 pm H11, cF56 (Z = 8)

Cubic a = 463.42 pm B1, cF8 (Z = 4) S.G. Fm3m Rock salt type

Tetragonal a = 1560 pm c = 1180 pm (Z = 4) P.G. 4/mmm S.G. Pnnc

Orthorhombic a = 987 pm b = 957 pm c = 852 pm (Z = 8) P.G. mmm S.G. P21/cab Scorodite type

Hexagonal a = 1033 pm c = 735 pm (Z = 2) P.G. 6/m S.G. P63/m Apatite type

Isotropic R = 45%

Isotropic nD = 1.327

Uniaxial (–) ε = 1.700–1.746 ω = 1.703–1.752 δ = 0.01–0.008 Dispersion strong

Biaxial(–) α = 1.55–1.56 β = 1.57–1.58 γ = 1.58–1.59 δ = 0.03 2V = 48–54°

Uniaxial (–) ε = 2.350 ω = 2.416 δ = 0.066

4.5–5.5

2.5

6–7

4

3

2.5–3

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 2.18 β = 2.35 γ = 2.35 δ = 0.170

Optical properties

4500– 4800

2785

3330– 3430

2500

6900

5600– 5800

Density (ρ/kg.m–3) (calc.)

Orthorhombic D58, oP20 (Z = 8) S.G. Pbnm P.G. 222

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: octahedral crystals. Color: violet gray. Diaphaneity: opaque. Luster: metallic. Streak: gray. Cleavage: perfect {111}. Twinning: {111}. Fracture: uneven, conchoidal.

Habit: massive, granular. Color: crimson red, dark cherry red, or colorless. Luster: vitreous (i.e., glassy). Diaphaneity: transparent. Luminescence: fluorescent. Streak: pinkish white. Cleavage: [100], [010], [001]. Fracture: brittle. Occurrence: nepheline–syenite rocks. Soluble in water. Fusible (m.p. 996°C).

Habit: prismatic. Color: reddish brown to green, emerald green (Cr-rich), reddish brown (Ti-rich), pale yellow (Cu-rich). Luster: vitreous (i.e., glassy), greasy. Diaphaneity: transparent to opaque. Cleavage: (110), (100), (001). Fracture: uneven. Chemical: attacked by strong mineral acids after calcination. Deposits: contact metamorphism.

Habit: prismatic. Color: green, yellow. Streak: white. Diaphaneity: transparent to translucent. Luster: resinous. Fracture: subconchoidal, splintery. Cleavage: (010) good.

Habit: prismatic, hollow prisms, encrustation. Color: red orange. Streak: white yellow. Diaphaneity: translucent. Luster: resinous. Fracture: subconchoidal.

Habit: euhedral crystals, divergent, striated. Color: white, gray, or yellowish gray. Luster: adamantine. Streak: white. Cleavage: [110] perfect, [010] distinct. Fracture: uneven. Occurrence: occurs as an oxidation product of various antimony minerals.

Other relevant mineralogical, physical, and chemical properties with occurrence

864 Minerals, Ores and Gemstones

Orthorhombic a = 567 pm b = 1151 pm c = 826 pm (Z = 8) P.G. 2/m2/m2/m S.G. Imma

β-(Mg,Fe2+)2SiO4 M = 156.46 23.30 wt.% Mg 17.85 wt.% Fe 17.95 wt.% Si 40.90 wt.% O (Nesosilicates)

Al3(PO4)3(OH)3.5H2O M = 506.957507 15.97 wt.% Al 18.33 wt.% P 63.12 wt.% O 2.58 wt.% H Coordinence Al(6), P(4) (Phosphates, arsenates, and vanadates)

Zn2SiO4 M = 222.8631 58.68 wt.% Zn 12.60 wt.% Si 28.72 wt.% O (Nesosilicates)

BaCO3 M = 197.336 77.54 wt.% Ba 4.49 wt.% C 17.96 wt.% O Coordinence Ba(6), C(3) (Nitrates, carbonates, and borates)

Fe0.5Mn0.5WO4 M = 303.2291 9.06 wt.% Mn 9.21 wt.% Fe 60.63 wt.% W 21.10 wt.% O Traces of V, Nb, Ta, Sc, Ti, Mo, Al, and In. (Sulfates, chromates, molybdates, and tungstates)

Wadsleyite [Named after crystallographer A.D. Wadsley] (ICSD 66490 and PDF 37-415)

Wavellite [Named after the English physician William Wavell (died 1829)] (ICSD 26816 and PDF 41-1360)

Willemite (syn., Troostite) [Named after Willem I, King of the Netherlands] (ICSD 2425 and PDF 46-1316)

Witherite [513-77-9] [Named after the English physician, botanist & mineralogist, William Withering (1741–1799)] (ICSD 15196 and PDF 45-1471)

Wolframite [13870-24-1] [Named from the German, wolfram, name for tungsten] (ICSD 15192 and PDF 12-727)

Monoclinic a = 478.2 pm b = 573.1 pm c = 498.2 pm 90.57° (Z = 2) Wolframite type (Ferberite-Hubnerite)

Orthorhombic a = 643.0 pm b = 890.4 pm c = 531.4 pm (Z = 4) S.G. Pmcn P.G. mmm Aragonite type

Trigonal (Rhombohedral) a = 1394 pm c = 931 pm (Z = 18) P.G. 3

Orthorhombic a = 962 pm b = 1736 pm c = 699 pm (Z = 4) P.G. mmm S.G. P21/cmn

Monoclinic a = 1008 pm b = 1343 pm c = 470 pm β = 104.5° (Z = 2) P.G. 2/m S.G. C2/m

Fe3(PO4)3.8H2O M = 596.57180 28.08 wt.% Fe 15.58 wt.% P 53.64 wt.% O 2.70 wt.% H Coordinence Fe(6), P(4) (Phosphates, arsenates, and vanadates)

S.G. Fd-3m P.G. 4-32 Spinel type

Vivianite [Named after the English mineralogist, J.G. Vivian] (ICSD 200703 and PDF 30-662)

42.54 wt.% S (Sulfides and sulfosalts) Coordinence Ni(6), Fe(4)

Biaxial (+) α = 2.20–2.26 β = 2.22–2.32 γ = 2.30–2.42 δ = 0.10–0.16 2V = 73–90° Dispersion none R = 17.3%

Biaxial (–) α = 1.529 β = 1.676 γ = 1.677 δ = 0.148 2V = 16° Dispersion weak

Uniaxial (+) ω = 1.691–1.72 ε = 1.719–1.73 δ = 0.010–0.028

Biaxial(+) α = 1.525 β = 1.534 γ = 1.552 δ = 0.027 2V = 72°

Biaxial (?)

Biaxial(+) α = 1.579 β = 1.603 γ = 1.633 δ = 0.054 2V = 83°

4–4.5 (HV 357– 394)

3.5

5.5

3–4

n.a.

2

7510

4290– 4300

3900– 4200

2360

3840 (3840)

2580

Habit: prismatic, lamellar, tabular, massive, granular. Color: reddish and brownish black to iron black. Luster: resinous to submetallic. Diaphaneity: transparent to opaque. Streak: reddish brown. Cleavage: [010] perfect. Fracture: uneven, brittle. Chemical: attacked by conc. and hot HCl and H2SO4. Other: dielectric constant 12.51. Magnetic. Occurrence: high-temperature quartz veins, in greisen, pegmaties and skarns.

Habit: pseudo hexagonal, columnar, globular, reniform, fibrous. Color: colorless, milky white, grayish white, pale yellowish white, or pale brownish white. Luster: vitreous (i.e., glassy). Diaphaneity: transparent to translucent. Streak: white. Fracture: subconchoidal. Cleavage: (010), (110) distinct. Twinning: {110}. Chemical: decomposed at 1555°C giving off CO2. Soluble in diluted HCl with evolution of CO2.

Habit: prismatic, massive-granular, massive. Color: white, yellow, green, reddish brown, or black. Luster: vitreous-resinous. Diaphaneity: transparent to translucent to opaque. Streak: white. Luminescence: fluorescent, green under short uv wavelength. Cleavage: [0001] poor, [1120] poor. Occurrence: main ore mineral at franklin, a metamorphosed zinc orebody. Fracture: uneven.

Habit: globular, radiating, spherolitic. Color: white, yellow, green. Streak: white. Diaphaneity: translucent. Luster: vitreous. Fracture: subconchoidal. Cleavage: (101) perfect, (010) perfect.

Habit: fine-grained aggregates. Color: light grayish brown. Luster: vitreous. Diaphaneity: translucent. Cleavage: unknown. Fracture: brittle, uneven. Streak: white. Occurrence: impact meteorite.

Habit: reniform, lamellar, fibrous. Color: colorless, green. Streak: white. Diaphaneity: transparent to translucent. Luster: pearly, vitreous. Fracture: sectile. Cleavage: (010) perfect, (100) perfect.

Mineral and Gemstone Properties Table 865

Minerals, Ores and Gemstones

12

Theoretical chemical formula, relative molecular mass (12C = 12), mass percentages, coordinence number, major impurities, Strunz’s mineral class

Ca[SiO3] Coordinence Ca(6), Si(4) (Inosilicates, chain)

PbMoO4 M = 367.1376 26.13 wt.% Mo 56.44 wt.% Pb 17.43 wt.% O Coordinence Pb(6), Mo(4) (Sulfates, chromates, molybdates, and tungstates)

ZnS M = 97.456 67.10 wt.% Zn 32.90 wt.% S Traces Fe (Sulfides and sulfosalts) Coordinence Zn(4)

FeO M = 71.8444 77.73 wt.% Fe 22.27 wt.% O (Oxides and hydroxides) Coordinence Fe(6)

YPO4 M = 183.87721 48.35 wt.% Y 16.84 wt.% P 34.80 wt.% O Traces of U, Th, Zr, Si, and rare earths Coordinence Y(6), P(4) (Phosphates, arsenates, and vanadates)

Mineral name (IMA) [CAS RN] (Synonyms) [Etymology] (ICSD and PDF diffraction files numbers)

Wollastonite [Named after the English chemist and mineralogist William Hyde Wollaston (1766–1828)] (ICSD 201537 and PDF 42-547)

Wulfenite [10190-55-3] (syn., yellow lead ore) [Named after the Austrian mineralogist, F.X. Wulfen] (ICSD 26784 and PDF 44-1486)

Wurtzite (syn., radial blende, HT ZnS) [Named after the French chemist, Ch.A. Wurtze] (ICSD 67453 and PDF 36-1450)

Wustite [1345-25-1] (syn. ferrous oxide) [Named after the German metallurgist Friedrich Wüst (1860–1938)] (ICSD 24695 and PDF 46-1312)

Xenotime [Named from the Greek, xenos, foreign, and time, honor, owing to the rarity and the small size of its crystals] (ICSD 79754 and PDF 11-254)

Table 12.23. (continued)

Tetragonal a = 688.5 pm c = 598.2 pm I41/amd (Z = 4) P.G. 4/mmm S.G. I41/amd Zircon type

Cubic a = 430.7 pm B1, cF8 (Z = 4) S.G. Fm3m P.G. 432 Rock salt type Periclase group

Hexagonal a = 382.30 pm c = 625.65 pm B4, hP4 (Z = 2) S.G. P63mc P.G. 6mm Wurtzite type

Tetragonal a = 543.5 pm c = 1211.0 pm (Z = 4) P.G. 4/m S.G. I41/a Scheelite type

Uniaxial (+) ε = 1.720–1.721 ω = 1.816–1.827 δ = 0.095–0.107

Isotropic

Uniaxial (+) ε = 2.356 ω = 2.378 δ = 0.022 R = 17.4%

Uniaxial (–) ε = 2.283 ω = 2.404 δ = 0.121

4.5–5

5

3.5–4

2.9

4.5–5

Mohs hardness (/HM) (Vickers)

Biaxial (–) α = 1.620 β = 1.632 γ = 1.634 δ = 0.014 2V = 39° Dispersion weak

Optical properties

4750

5740 (5973)

4030

6750– 7000

3100

Density (ρ/kg.m–3) (calc.)

Triclinic a = 794 pm b = 732 pm c = 707 pm α = 90.03° β = 95.37° γ = 103.43° P.G. 1 S.G. P1 (Z = 4) Pyroxenoid group

Crystal system, lattice parameters, Strukturbericht, Pearson symbol, (Z), point group, space group, structure type

Habit: radial, prismatic, massive, and granular. Color: yellowish brown, greenish brown, gray, reddish brown, or brown. Luster: vitreous (i.e., glassy), greasy or resinous. Diaphaneity: translucent to opaque. Streak: pale brown. Cleavage: (100) perfect. Fracture: uneven, splintery. Chemical: insoluble in strong mineral acids.

Habit: tiny octahedral crystals or microspherules. Color: black to brown, gray in reflected light. Luster: metallic. Diaphaneity: opaque. Cleavage: (unknown). Fracture: (unknown). Streak: (unknown). Other: antiferromagnetic, melts at 1380°C. Chemical: dissolves in HCl. Occurrence: in iron meteorites (siderites), in deep-sea ferromanganese nodules, in highly reduced iron-bearing basalts (Disco Island, Greenland) and in natural coke from fired coal fields (Bihar, India).

Habit: pyramidal, radial, tabular, colloform. Color: orange red, light brown or dark brown. Luster: resinous. Luster: adamantine, resinous. Streak: brown yellow. Cleavage: {1010}, {0001}. Fracture: uneven. Conchoidal. Chemical: attacked by strong mineral acids, such as HCl, or HNO3 with evolution of H2S and yellow precipitate of sulfur. Infusible.

Habit: tabular, massive, granular, bipyramidal pseudooctahedron. Luster: resinous, greasy, or adamantine. Diaphaneity: subtransparent to subtranslucent. Color: orange yellow, waxy yellow, yellowish gray, olive green, or brown. Streak: yellowish white. Cleavage: (101) imperfect. Twinning: {001}. Fracture: subconchoidal, brittle.

Habit: prismatic, needlelike. Color: white. Luster: silky. Diaphaneity: transparent to translucent. Streak: white. Fracture: uneven. Cleavage: (100) perfect, (001) distinct. Twinning: {010}.

Other relevant mineralogical, physical, and chemical properties with occurrence

866 Minerals, Ores and Gemstones

(Zn,Mn)O M = 81.3894 80.34 wt.% Zn 19.66 wt.% O (Oxides, and hydroxides) Coordinence Zn(4)

KLiFeAl[Si3AlO10](F,OH)2 8.94 wt.% K 1.59 wt.% Li 12.35 wt.% Al 12.78 wt.% Fe 19.28 wt.% Si 0.12 wt.% H 6.52 wt.% F 38.43 wt.% O Phyllosilicates

Zr[SiO4] M = 183.3071 49.77 wt.% Zr 15.32 wt.% Si 34.91 wt.% O Traces of Hf, U, Th and daughter radionuclides Coordinence Zr(4), Si(4) (Nesosilicates)

CaZrTi2O7 M = 341.032 11.75 wt.% Ca 26.75 wt.% Zr 28.66 wt.% Ti 32.84 wt.% O (Oxides and hydroxides)

Ca2Al2O(OH)[SiO4][Si2O7] M = 427.37572 18.76 wt.% Ca 12.63 wt.% Al 19.71 wt.% Si 0.24 wt.% H 48.67 wt.% O Coordinence Ca(6, 9), Fe(6), Si(4) (Sorosilicates and nesosilicates)

Zincite [1314-13-2] (syn., red zinc oxide) [Named from the German, zink] (ICSD 31052 and PDF 36-1451)

Zinnwaldite [Named after Zinnwald, Bohemia, itself named for the local tin (German zinn) veins] (ICSD 10401 and PDF 42-1399)

Zircon [10101-52-7] (syn., hyacinthe: orange, red, malacon: white] [Named from Arabic, zar, gold, and gum, color] (ICSD 71943 and PDF 6-266)

Zirconolite (syn., zirkelite, polymignite) [Named after its chemical composition containing zirconium] (ICSD 71943 and PDF 6-266)

Zoïsite (syn., tanzanite: blue, thulite: pink or red, anyolite: green) [Named after the Austrian natural scientist, Siegmund Zois, Baron von Edelstein (1747–1819)] (ICSD 200920 and PDF 25-1298)

Orthorhombic a = 1615.0 pm b = 558.1 pm c = 1006.0 pm (Z = 4) P.G. 2/m S.G. P21/m Epidote group

Hexagonal a = 728.7 pm c = 1688.6 pm Z=3 S.G. P312

Tetragonal a = 660.70 pm c = 598.35 pm c/a = 0.906 (Z = 4) P.G. 4/mmm S.G. I41amd Zircon type

Monoclinic a = 530 pm b = 914 pm c = 1010 pm β = 100.83° (Z = 2) S.G. C2/m Biotite group

Trigonal (Hexagonal) a = 660.4 pm c = 597.9 pm B4, hP4 (Z = 2) S.G. P63mc P.G. 6mm Wurtzite type

Biaxial (–) α = 1.685–1.705 β = 1.688–1.710 γ = 1.697–1.725 δ = 0.004–0.008 2V = 0–60° Dispersion strong

Uniaxial ()

Uniaxal (+) ε = 1.923–1.960 ω = 11.968–2.015 δ = 10.042–0.065 Dispersion very strong

Biaxial (–) α= 1.535–1.558 β = 1.570–1.589 γ = 1.572–1.590 2V = 0°–40°

Uniaxial (+) ε = 12.013 ω = 12.029 δ = 10.016 R = 11.2%

6–6.5 (HV 680)

5.5

7.5 (6–6.5 metamict)

2.5–4

4–4.5 (HV 150– 157 and 295– 318 //)

3150– 3270

4720 (4880)

4660 (3900– 4200 metamict)

2900– 3020

5560

Habit: prismatic, striated, columnar. Color: gray, apple green, brown, blue, or rose red. Diaphaneity: transparent to translucent. Luster: vitreous (i.e., glassy), pearly. Streak: white. Cleavage: (100), perfect, (001) imperfect. Twinning: {100}. Fracture: uneven. Chemical: insoluble in strong mineral acids, fusible giving a white globule. Occurrence: regional metamorphic and pegmatite rocks.

Habit: hexagonal platy crystal often metamict due to its U and Th content; small grains. Color: black, brownish black. Diaphaneity: opaque but transparent in thin sections. Luster: resinous to submetallic. Cleavage: {100}, {010}. Twinning: Polysynthetic. Streak: reddish brown. Fracture: splintery, brittle. Occurrence: in alkaline and ultramafic igneous rocks such as carbonatites, kimberlites or syenites associated to pyrochlore or as a detrital mineral.

Habit: prismatic, tabular, crystalline. Color: brown, reddish brown, colorless, gray, green. Diaphaneity: transparent, translucent, opaque. Luster: adamantine. Streak: white. Fracture: uneven. Cleavage: (110). Twinning: {111}. Chemical: insoluble in HCl and HNO3, slightly soluble in concentrated H2SO4, readily dissolved by 50 wt.% HF. Radioactive owing to the isomorphic substitution of Zr(IV) cations by U(IV) and Th(IV) can contain some Pb from decaying. Above 1690°C zircon dissociates into constituents oxides forming two immiscible phases of ZrO2 and SiO2. Other: zircon exhibits a low bulk coefficient of linear thermal expansion: 4.5 10–6 K–1. Its bulk modulus of compressibility is comprised between 227 GPa and 234 GPa. Zircon is diamagnetic with a specific magnetic susceptibility of –0.78 × 10–6 m3.kg–1 along a-axis and +3.37 × 10–6 m3.kg–1 along c-axis.

Habit: tabular or prismatic crystals. Color: grayish-brown to yellowish brown. Diaphaneity: transparent to translucent. Luster: vitreous to pearly. Fracture: conchoidal. Cleavage: (001) perfect yielding flexible lamellae. Occurrence: granite pegmatites and hydrothermal tin-bearing veins.

Habit: massive, fibrous, granular, disseminated. Color: deep red or yellowish orange. Diaphaneity: translucent to translucent. Luster: submetallic, subadamantine. Streak: yellowish orange. Cleavage: [0001]. Parting: [110]. Fracture: Subconchoidal. Occurrence: metamorphosed weathered ore deposit.

Mineral and Gemstone Properties Table 867

Minerals, Ores and Gemstones

12

868

Minerals, Ores and Gemstones

12.8 Mineral Synonyms Absite = Brannerite Acerdese = Manganite Achrematite = Mimetite + Wulfenite Achroite = Elbaite Acmite = Aegirine Adularia = Orthoclase Agalmatolite = Talc or Pyrophyllite or Pinite Agate = Layered Chalcedony (Quartz) Agricolite = Eulytite Alabaster = Gypsum Alexandrite = Chrysoberyl Allcharite = Goethite Allenite = Pentahydrite Allopalladium = Stibiopalladinite Altmarkite = Lead amalgam Alum = Hydrous alkali alumiunium sulfates Alurgite = Mg, Fe, Mn Muscovite Alvite = Hf-Zircon Amazonite = Microcline Amethyst = Purple Quartz Amianthus = Tremolite, Actinolite, Chrysotile Amosite = Grunerite, Cummingtonite Ampangabeite = Samarskite Amphigene = Leucite Anarakite = Paratacamite Andrewsite = Hentschelite + Rockbridgeite + Chalcosiderite Annivite = Bi-Tetrahedrite Antimonite = Stibnite Aplome = Andradite Applelite = Calcite Apyrite = Rubellite (Elbaite) Aquamarine = Beryl Arduinite = Mordenite Argentite = Acanthite Argyrose = Argentite-Acanthite Argyrythrose = Pyrargyrite Arizonite = Pseudorutile, leucoxene Arkansite = Brookite Asbestos = Tremolite, Actinolite, Chrysotile Ashtonite = Mordenite Asphaltum = Mineral Pitch Astrakhanite = Bloedite Aventurine = Quartz + Mica Badenite = Bismuth + Safflorite + Modderite Baikalite = Diopside Barkevikite = Fe-hornblende Barsanovite = Eudialyte Baryte = Barite Bastonite = Biotite Bauxite = Hydroxides and oxides of Al and Fe Bellite = Mimetite Belorussite = Byelorussite Bentonite = Montmorillonite

Mineral Synonyms Bertonite = Bournonite Binnite = Tennantite Bisbeeite = Plancheite-Chrysocolla Blackjack = Sphalerite Blanchardite = Brochantite Bleiglanz = Galena Blende = Sphalerite Blockite = Penroseite Bloodstone = Chalcedony Borickite = Delvauxite Boronatrocalcite = Ulexite Brandisite = Clintonite Braunbleierz = Pyromorphite Bravoite = Ni-Pyrite Breislakite = Vonsenite (Ludwigite, Fibrous Ilvaite) Breunnerite = Fe-Magnesite Brocenite = Ce-Fergusonite Broggerite = Th-Uraninite Bromlite = Alstonite Bromyrite = Bromargyrite Bronzite = Fe-Enstatite Buratite = Aurichalcite Byssolite = Actinolite-Tremolite Cabrerite = Mg-Annabergite Cairngorm = Smoky Quartz Calamine = Hemimorphite Calciumlarsenite = Esperite Californite = Vesuvianite Campylite = P-Mimetite Canbyite = Hisingerite Carbonado = Black Diamond Carbonytrine = Y-Tengerite Carborundum = Synthetic Moissanite Carnelian = Carneol (Cornaline, Agate, Quartz) Carneol (Carnelian, Cornaline) = Red Chalcedony (Quartz) Carpathite = Karpatite (Coronene) Carphosiderite = Hydrogeno-Jarosite Caryocerite = Th-Melanocerite Cathophorite = Brabantite Catoptrite = Katoptrite Cenosite = Kainosite Centrallasite = Gyrolite Cerargyrite = Chlorargyrite Chalcedony = Quartz Chalcolite = Torbernite Chalcosine = Chalcocite Chalcotrichite = Cuprite Challantite = Ferricopiapite Chalmersite = Cubanite Chalybite = Siderite Chathamite = Fe-Skutterudite Chavesite = Monetite Chengbolite = Moncheite Chessylite = Azurite Chiastolite = Andalusite Chile Saltpeter = Nitratine (Soda Niter, Nitronatrite) Chileloeweite = Humberstonite

869

12 Minerals, Ores and Gemstones

870

Minerals, Ores and Gemstones Chloanthite = Nickelskutterudite Chlorastrolite = Pumpellyite Chlormanasseite = Altered Koenenite Chloromelanite = Jadeite Chloropal = Nontronite Chlorotile = Agardite Christensenite = Tridymite Christianite = Anorthite or Phillipsite Chromrutile = Redledgeite Chrysolite = Olivine Chrysoprase = Green Chalcedony (Quartz) Cinnamon Stone = Hessonite (Grossular) Cirrolite = Attacolite (Bearthite, Lazulite, Cyanite) Citrine = Yellow Quartz Cleveite = Uraninite Cleavelandite = Albite Cliftonite = Graphite Clinobarrandite = Al-Phosphosiderite Clinoeulite = Mg-Clinoferrosilite Clinostrengite = Phosphosiderite Cobaltoadamite = Adamite Cobaltocalcite = Sphaerocobaltite Coccinite = Moschelite Coccolite = Diopside Cocinerite = Chalcocite + Silver Collophanite = Carbonated Apatite Colophonite = Andradite Columbite = Ferrocolumbite (Magnocol, Maganocol) Comptonite = Thomsonite Connarite = Garnierite Copperas = Melanterite Corindon = Corundum Cornaline = Agate (Quartz) Corundophilite = Clinochlore Corynite = Sb-Gersdorffite Coutinite = Nd-Lanthanite Crestmoreite = Tobermorite + Wilkeite Crocidolite = Riebeckite Csiklovaite = Tetradymite + Galenobismutite + Bismuthinite Cummingtonite = Amosite, Grunerite Cyanite = Kyanite Cyanose = Chalcanthite Cymatolite = Muscovite + Albite Cymophane = Chrysoberyl Cyrtolite = Zircon D’ansite = Dansite Dahllite = Carbonated Hydroxylapatite Dakeite = Schroeckingerite Damourite = Muscovite Danaite = Co-Arsenopyrite Daphnite = Mg-Chamosite Dashkesanite = K- Hastingsite Davisonite = Apatite + Crandallite Dehrnite = Carbonate-Fluorapatite Delatorreite = Todorokite Delessite = Mg-Chamosite Delorenzite = Tanteuxenite

Mineral Synonyms Deltaite = Crandallite + Hydroxy-apatite Deltamooreite = Torreyite Demantoide = Andradite Dennisonite = Davisonite (Apatite + Crandallite) Desmine = Stilbite Destinezite = Diadochite Dewalquite = Ardennite Deweylite = Clinochrysotile-Lizardite Diabantite = Fe-Clinochlore Diallage = Diopside Dialogite = Rhodochrosite Diatomite =Tripolite (Opaline silica) Dipyre = Scapolite Disthene = Kyanite Djalmaite = Uranmicrolite Donatite = Chromite + Magnetite Dornbergite (Doernbergite) = Bottinoite Doverite = Synchysite Droogmansite = Kasolite Dubuissonite = Montmorillonite Duporthite =Talc + Chlorite Durdenite = Emmonsite Dysanalyte = Nb-Perovskite Dysodile = Resin Eardleyite = Takovite Eastonite = Phlogopite + Serpentine Ekbergite = Wernerite Elaterite = Mineral Rubber Electrum = Au-Ag alloy Eleonorite = Beraunite Ellestadite = Fluorellestadite-Hydroxyellestadite Ellsworthite = Uranpyrochlore Embolite = Br-Chlorargyrite or Cl-Bromargyrite Emerald = Beryl Endellite (Hydrohalloysite) = Halloysite Endlichite = As-Vanadinite Enigmatite = Aenigmatite Epidesmine = Stilbite Epiianthinite = Schoepite Eschynite = Aeschynite Eucolite = Eudialyte Fahlore = Tetrahedrite-Tennantite Fassaite = Diopside or Augite Femolite = Fe-Molybdenite Fengluanite = Isomertieite Ferchevkinite = Fe-Chevkinite Fernandinite = Bariandite + Roscoelite + Gypsum Ferridravite = Povondraite Ferrifayalite = Laihunite Ferrithorite = Thorite + Fe Hydroxide Hematoide = Quartz + Goethite-Hematite Ferutite = Davidite Fibrolite = Sillimanite Flint (Silex) = Quartz Fluorichterite = Richterite Fluorspar = Fluorite Forbesite = Annabergite + Arsenolite

871

12 Minerals, Ores and Gemstones

872

Minerals, Ores and Gemstones Forcherite = Opal Fowlerite = Zn-Rhodonite Francolite = Carbonated fluoroapatite Freirinite = Lavendulan Fuchsite = Cr-Muscovite Fuggerite = Melilite Genevite = Vesuvianite (Idocrase) Genthite = Garnierite Geyserite = Opal Gilpinite = Johannite Ginzburgite = Roggianite Giobertite = Magnesite Girasol = Opaline Quartz Glagerite = Halloysite Glaserite = Aphthitalite Glauber’s Salt = Mirabilite Glaukolite (Glavcolite) = Scapolite Glockerite = Lepidocrocite Goongarrite = Heyrovskyite Gorgyite = Goergeyite Goshenite = Beryl Grammatite = Tremolite Grandite = Grossular-Andradite Griffithite = Fe-Saponite Grunerite = Cummingtonite, Amosite Grunlingite (Gruenlingite) = Joseite + Bismuthinite Gummite = Secondary uranium oxides Hackmanite = Sodalite Hatchettite = Hydrocarbons Mixture Hatchettolite = Uranpyrochlore Heliodor = Beryl Heliotrope = Chalcedony or Plasma = Quartz Hemafibrite = Synadelphite Hessonite = Grossular Heubachite = Ni-Heterogenite Hexagonite = Mn-Tremolite Hexastannite = Stannoidite Hiddenite = Spodumene Hjelmite = Tapiolite + Pyrochlore Hokutolite = Pb-Barite Hortonolite = Mg-Mn-Fayalite Hoshiite = Ni-Magnesite Huehnerkobelite = Alluaudite or Ferroalluaudite Humboldtilite = Melilite Hyacinth = Orange Zircon Hyacinthe de Compostelle = Amethyste (Quartz) Hyalite = Opal Hyaloallophane = Allophane + Hyalite Hyalosiderite = Fayalite Hydrargillite = Gibbsite Hydrated Halloysite = Endellite Hydrogrossular = Hibschite-Katoite Hydrohalloysite = Endellite Hydromica = Brammallite, Hydrobiotite, Illite Hydrophilite = Antarcticite or Sinjarite Hydrotroilite = Colloidal Hydrous Ferrous Sulfide Idocrase = Vesuvianite

Mineral Synonyms Iglesiasite = Cerussite + Smithsonite Indicolite = Indigolite = Elbaite Iodobromite = I-Bromargyrite Iodyrite = Iodargyrite Iolite = Cordierite Iozite = Wuestite Iridosmine = Iridium osmium alloy Fe-Cordierite = Sekaninaite Iserine (Nigrine) = Ilmenite + Rutile Isoplatinocopper = Hongshiite Isostannite = Kesterite-Ferrokesterite Jade = Jadeite (Nephrite) Jasper = Quartz Jefferisite = Vermiculite Jeffersonite = Mn Zn Acmite or Augite Jelletite = Andradite Jenkinsite = Fe-Antigorite Johnstrupite = Mosandrite Josephinite = Awaruite, Kamacite, Taenite, Tetrataenite Kalllilite = Ullmannite Kamarezite = Brochantite Kammererite (Kaemmererite) = Cr-Clinochlore Karafveite = Monazite Karpinskyite = Leifite + Clay Kasoite = Celsian Katayamalite = Baratovite Keeleyite = Zinkenite Keilhauite = Yttrian Titanite Kellerite = Cu-Pentahydrite Kennedyite = Armalcolite or Pseudobrookite Kerchenite = Metavivianite Kerolite = Talc Kertschenite = Oxidation Product of Vivianite Khlopinite = Ta-Samarskite Klaprothite = Lazulite Kleberite = Pseudorutile Klipsteinite = Altered Rhodonite Knebelite = Mn-Fayalite Knipovichite = Cr-Alumohydrocalcite Knopite = Perovskite Kolskite = Lizardite + Sepiolite Koppite = Pyrochlore Kotschubeite = Cr-Clinochlore Kramerite = Probertite Kularite = Ce-Monazite Kunzite = Spodumene Kurskite = Carbonated fluorapatite Lapis Lazuli = Lazurite Lapparentite = Khademite (Rostite) Laubmannite = Dufrenite + Kidwellite + Beraunite Lavrovite = Diopside Lazarevicite = As-sulvanite Lehiite = Apatite + Crandallite Leonhardtite = Starkeyite Lepidomelane = Fe-Biotite Lesserite = Inderite Lettsomite = Cyanotrichite

873

12 Minerals, Ores and Gemstones

874

Minerals, Ores and Gemstones Leuchtenbergite = Clinochlore Leucochalcite = Olivenite Leucoxene = Alteration of Ilmenite, pseudorutile, arizonite Leverrierite = Kaolinite + Illite Lewistonite = Carbonated fluorapatite Lievrite = Ilvaite Lingaitukuang = Brabantite Liujinyinite = Uytenbogaardtite Lotrite = Pumpellyite Lovchorrite = Mosandrite Lunijianlaite = Cookeite + Pyrophyllite Lunnite = Pseudomalachite Lusakite = Co-Staurolite Lusungite = Goyazite Lydian Stone (Basanite, Touchstone) = Quartz Macconnellite = Mcconnellite Mackintoshite = Thorogummite Magnophorite = Ti-K-Richterite Maitlandite = Thorogummite Malacon = Zircon Mangan Neptunite = Manganneptunite Manganocalcite = Calcite Manganomelane = Manganese oxides Manganophyllite = Mn-Biotite Mannacanite = Ilmenite Marignacite = Ce-pyrochlore Mariposite = Cr-Phengite Marmatite = Fe-Sphalerite Martite = Hematite Pseudomorph on Magnetite Maskelynite = Glass of Plagioclase composition Mauzeliite = Pb-Romeite Medmontite = Chrysocolla + Mica Melaconite = Tenorite Melanite = Ti-Andradite Melanochalcite = Tenorite (Chrysocolla, Malachite) Melinose = Wulfenite Melnikovite = Greigite Menilite = Opal Meroxene = Biotite Merrilite = Whitlockite Mesitite = Fe-Magnesite Mesotype = Natrolite (Mesolite, Scolecite) Metahalloysite = Halloysite Metastrengite = Phosphosiderite Metauranopilite = Meta-uranopilite Minette = Iron Hydroxides And Oxides Miomirite = Pb-Davidite Mispickel = Arsenopyrite Mizzonite = Marialite-Meionite Moganite = Fine Crystalline Quartz Mohsite = Pb-Crichtonite Monheimite = Smithsonite Monsmedite = Voltaite Montdorite = Biotite Montesite = Pb-Herzenbergite Morencite = Nontronite Morganite = Beryl

Mineral Synonyms Morion = Quartz Mossite = Tantalite-Tapiolite Muchuanite = Altered Molybdenite Mushketovite = Magnetite Pseudomorph on Hematite Nanekevite = Ba-orthojoaquinite Nasturan = Pitchblende Nemalite = Fe-Brucite Nenadkevite = Uraninite + Boltwoodite Neotype = Barytocalcite Nephrite = Actinolite Nevyanskite = Iridosmine Niccolite = Nickeline Nickeliron = Kamacite (Taenite, Tetrataenite) Nigrine (Iserine) = Ilmenite + Rutile Nimesite = Brindleyite Niobite = Ferrocolumbite Niobozirconolite = Nb-Zirkelite Nitroglauberite = Darapskite + Nitratine Nitrokalit = Niter (Salpeter, Nitre, Salpetre) Nitronatrite = Nitratine (Soda Niter) Nocerite = Fluoborite Nuevite = Samarskite Nuttalite = Wernerite O’danielite = Odanielite Obruchevite = Y-pyrochlore Yellow Ochre = Limonite Octahedrite = Anatase Oellacherite = Ba-Muscovite Oligiste = Hematite Oligonite = Mn-Siderite Olivine = Peridot Onofrite = Se-Metacinnabar Onyx = Layered Chalcedony (Quartz) Orthite = Allanite Orthose = Orthoclase Osmiridium = Iridium-osmium alloy Outremer = Ultramarine (Lazurite) Ozocerite = Hydrocarbons Mixture Pageite = Vonsenite Paigeite = Hulsite Panabase = Tetrahedrite Pandaite = Ba-pyrochlore Pandermite = Priceite Paranthine = Wernerite Partridgeite = Bixbyite Paternoite = Kaliborite Paulite = Hypersthene Pennine (Penninite) = Clinochlore Pericline = Albite Peridot = Forsterite Peristerite = Albite Perthite = Intergrowth Orthoclase + Plagioclase Phacolite = Chabazite Pharaonite = Microsommite Phengite = Muscovite Piazolite = Hydrogrossular Picotite = Cr-Spinel

875

12 Minerals, Ores and Gemstones

876

Minerals, Ores and Gemstones Picrochromite = Magnesiochromite Pinite = Altered Cordierite Pisanite = Cu-Melanterite Pisekite = Monazite Pistacite = Epidote Pitchblende = Uraninite Plasma = Green Quartz Platiniridium = Iridium-platinium alloy Pleonaste = Fe-Spinel Plessite = Kamacite-Taenite Plumbago = Graphite Plumosite = Boulangerite Polianite = Pyrolusite Polyadelphite = Andradite Porcelainite = Mullite Prase = Green Quartz Priorite = Aeschynite Pseudowavellite = Crandallite Psilomelane = Romanechite Ptilolite = Mordenite Pycnite = Topaz Pyralspite = Garnet Subgroup Pyrophyllite = Soapstone Quercyite = Carbonate Apatite Rashleighite = Fe-Turquoise Resinite = Opal Rhodusite = Mg-riebeckite Rijkeboerite = Ba-microlite Ripidolite = Fe-Clinochlore Risorite = Fergusonite Rock Salt = Halite Roepperite = Fayalite or Tephroite Rostite = Khademite Rozhkovite = Pd-Auricupride Rubellane = Altered Biotite Rubellite = Elbaite Ruby = Corundum Ruby Silver = Proustite, Pyrargyrite Ruthenosmiridium = Iridium-Osmium-Ruthenium alloy Sagenite = Rutile Sal Ammoniac = Salmiac Salite = Sahlite = Diopside Salmiac = Salammoniac (Sal Ammoniac) Salpeter = Niter (Nitre, Salpetre, Nitrokalit) Samiresite = Pb-Uranpyrochlore Sapphire = Corundum Sard = Brown Chalcedony Saukovite = Cd-Metacinnabar Saussurite = Zoisite (Scapolite) Schefferite = Mn-Aegirine Scheibeite = Phoenicochroite Schizolite = Mn-Pectolite Schoenite = Picromerite Schuchardtite = Clinochlore (Vermiculite) Schwatzite (Schwazite) = Hg-Tetrahedrite Schweizerite = Serpentine Rock salt = Halite

Mineral Synonyms Selenite = Gypsum Sericite = Muscovite Seybertite = Clintonite Sheridanite = Clinochlore Sideretine = Pitticite Siderochrome = Chromite Siserskite (Syserskite) = Iridosmine Smaltite = Skutterudite Smoky Quartz = Brown Quartz Soapstone = Pyrophyllite Sobotkite = Al-Saponite Soda Feldspar = Albite Soda Niter = Nitratine (Nitronatrite) Sophiite = Sofiite Spartalite = Zincite Specularite = Hematite Sphene = Titanite Staffelite = Carbonated fluorapatite Staringite = Cassiterite + Tapiolite Stassfurtite = Boracite Steatite = Talc Steinsalz = Halite Stibine = Stibnite (Antimonite) Strahlstein = Actinolite Succinite = Amber Sukulaite = Sn-microlite Sylvinite = Halite + Sylvite Syssertskite = Osmium Taaffeite = Musgravite Tagilite = Pseudomalachite Tanzanite = Zoisite Tarasovite = Mica-Smectite M Tarnowitzite (Tarnowskite) = Pb-Aragonite Tavistockite = Apatite Tellurbismuth = Te-bismuthite Ternovskite = Mg-riebeckite Teruelite = Dolomite Thulite = Zoisite Thuringite = Fe-Chamosite Tibiscumite = Allophane Tiger Eye = Quartz + Crocidolite Tincal = Borax Toddite = Columbite + Samarskite Topazolite = Andradite Treanorite = Allanite Triphane = Spodumene Troostite = Mn-Willemite Trudellite = Chloraluminite + Natroalunite Tsavolite = Tsavorite = Grossular Turgite = Turjite (Hematite) Turnerite = Monazite Ufertite = Davidite Ugrandite = Garnet subgroup Ultramarine = Lazurite Ulvite = Ulvospinel Uralite = Amphibole Uranite = Autunite

877

12 Minerals, Ores and Gemstones

878

Minerals, Ores and Gemstones Uranotile = Uranophane Uranotile Beta = Uranophane Beta Vegasite = Pb-jarosite Verdelite = Tourmaline Vernadskite = Antlerite Vibertite = Bassanite Viridine = Mn-Andalusite Voltzite = Wurtzite Vorobievite = Beryl Vredenburgite = Jacobsite + Hausmannite Vulpinite = Anhydrite Wad = Mangnese Oxides Walchowite = Resinoid Warrenite = Owyheeite (Jamesonite) Westgrenite = Bi-microlite Wiikite = Y-pyrochlore + Euxenite Wilkeite = Apatite (Fluorellestadite) Williamsite = Antigorite Withamite = Piemontite Wolframite = Huebnerite-Ferberite Wood Tin = Cassiterite Yttroorthite = Y-Allanite Zeiringite = Aragonite + Aurichalcite Zigueline = Chalcopyrite + Cuprite + Limonite + Cinnabar Zinconine = Hydrozincite Zinkblende = Sphalerite

12.9 Further Reading 12.9.1 Crystallography BAYLISS, P.; ERD, D.C.; MROSE, M.E.; SABINA, A.P.; SMITH, D.K. (1986) Mineral Powder Diffraction File, Data Book. International Centre for Diffraction Data. BARRETT, C.; MASSALSKI, T.B. (1987) Structure of Metals, 3rd ed.: Crystallographic Methods, Principles, and Data, International Series on Materials Science and Technology, Volume 35. Pergamon Press, Oxford, New York. BOISON, M.B.; GIBBS, G.V. (eds.) (1990) Mathematical Crystallography. Mineralogical Society of America (MSA), Washington DC. BHAGAVANTAM, S. (1966) Crystal Symmetry and Physical Properties. Academic Press, New York. BORCHARDT-OTT, W. (ed.) (1995) Crystallography, 2nd. ed. Springer, Heidelberg. BUERGER, M.J. (1956) Elementary Crystallography. Wiley, New York. BUERGER, M.J. (1971) Introduction to Crystal Geometry. McGraw-Hill, New York. COLLECTIVE Strukturbericht, the original crystallographic reports. From 1919–1939 (Volumes 1–8) they were published in Germany. EWALD, P.P.; HERMANN, C. (eds.) (1931) Vol. I: Strukturbericht 1913–1928. Akademische Verlagsgesellschaft M.B.H., Leipzig. HERMANN, C.; LOHRMANN, O.; PHILIPP, H. (eds.) (1937) Vol. II: Strukturbericht Band II 1928–1932. Akademische Verlagsgesellschaft M.B.H., Leipzig. GOTTFRIED, C.; SCHOSSBERGER, F. (eds.) (1937) Vol. III: Strukturbericht Band III 1933–1935. Akademische Verlagsgesellschaft M.B.H., Leipzig. COLLECTIVE International Tables for Crystallography. Volume A: Space-group symmetry, 5th. ed. (2002).; Volume A1: Symmetry Relations between Space Groups. (2004); Volume B: Reciprocal Space. (2001); Volume C: Mathematical, Physical and Chemical Tables. (2004); Volume D: Physical Properties of Crystals. (2003); Volume E: Subperiodic Groups. (2002); Volume F: Crystallography of Biological Macromolecules. (2001); Volume G: Definition and Exchange of Crystallographic Data. (2004). DE JONG, W.F. (1959) General Crystallography. A Brief Compendium. W.H. Freeman and Co., San Francisco. DONOHUE, J. (1974) The Structures of the Elements. John Wiley & Sons, New York. DONNAY, J.D.H.; ONDIK, H.M. (1973) Crystal Data Determinative Tables, 3rd ed., Volume 2, Inorganic Compounds. Joint Committee on Powder Diffraction Standards (JCPDS), Swarthmore, PA.

Further Reading

879

EVANS, R.C. (1964) An Introduction to Crystal Chemistry. Cambridge University Press, Cambridge. FEDOROV, E.S. (1892) Zusammenstellung der Kristallographischen Resultate Zs. Krist 20. GIACOVAZZO, C.; MONACO, H.L.; ARTIOLI, G; VITERBO, D.; FERRARIS, G.; GILLI, G.; ZANOTTI, G.; CATTI, M. (2002) Fundamentals of Crystallography, 2nd. ed. Oxford University Press(OUP)/International Union of Crystallography (IUCr). KITTEL, C. (1964) Introduction to Solid State Physics, 7th. ed. Wiley, New York. PAULING, K.L. (1960) The Nature of the Chemical Bond and the Structure of Molecules and Crystals, 3rd. ed. Cornell University Press, Ithaca, NY. PHILIPPS, F.C. (1971) An Introduction to Crystallography, 3rd. ed. Wiley, New York. ROUSSEAU, J.-J. (1999) Basic Crystallography. Wiley, New York. SANDS, D.E. (1975) Introduction to Crystallography. Wiley, New York. SCHOENFLIES, A. (1891) Kristallsysteme und Kristallstructur Leipzig (1891) VAINSHTEIN, B.K. (1996) Modern Crystallography 1: Fundamentals of Crystals. Symmetry, and Methods of Structural Crystallography. Springer, Heidelberg. VAINSHTEIN, B.K.; FRIDKIN, V.M.; INDENBOM, V.L. (2000) Modern Crystallography 2: Structure of Crystals, 3rd. ed. Springer, Heidelberg. VAN MEERSHE, M.; FENEAU-DUPONT, J. (1984) Introduction à la Cristallographie et à la Chimie Structurale Éditions Peeters, Louvain-la-Neuve, Belgium. VILLARS, P.; CALVERT, L.D. (1991) Pearson's Handbook of Crystallographic Data for Intermetallic Phases, 2nd ed. ASM International, Materials Park, Ohio. WESTBROOK, J.H.; FLEISCHER, R.L. (eds.)(1995) Intermetallic Compounds: Principles and Practice, Vol 1: Principles. John Wiley & Sons, London. WYCKOFF, R.W.G. (1963, 1964) Crystal Structures: Vol. 1 and 2. John Wiley & Sons, New York, London.

12.9.2 Optical Mineralogy BLOSS, F.D. (1967) An Introduction to the Methods of Optical Crystallography. Holt, Rinehart and Wintson, New York. BLOSS, F.D. (1999) Optical Crystallography. Mineralogical Society of America Monographs, vol. 5, Washington DC. BORDET, P. (1968) Précis d’optique cristalline appliqué à l’identification des minéraux. Masson & Cie, Paris. CAMERON, E.N. (1961) Ore Microscopy. John Wiley, New York. EHLERS, E.G. (1987) Optical Mineralogy, Vol. 1 & 2. Blackwell Scientific Publications, Palo Alto, CA. FREUND, H. (ed.) (1966) Applied Ore Microscopy; Theory and Techniques. Macmillan, New York. GAY, P. (1962) An Introduction to Crystal Optics. Longmans, London. GLEASON, S. (1960) Ultraviolet Guide to Minerals. D. Van Nostrand Company, Princeton N.J. GRIBBLE, C.D.; HALL, A.J. (1993) Optical Mineralogy: Principles and Practice. Chapman & Hall, New York. JONES, M.P; FLEMING, M.G. (1965) Identification of Mineral Grains. A Systematic Approach to the Determination of Minerals for Mineral Processing Engineers and Students. Elsevier Publishing Co., Amsterdam, New York. LARSEN, E.S.; BERMAN, H. (1964) The Microscopic Determination of the Nonopaque Minerals. U.S. Geological Survey Bulletin No. 848, U.S. Government Printing Office, Washington, DC. McCRONE, W.C; McCRONE, L.B.; DELLY, J.G. (1995) Polarized Light Microscopy. McCrone Research Institute, Chicago, IL. NESSE, W.D. (1991) Introduction to Optical Mineralogy, 2nd. ed. Oxford University Press, New York. PHILLIPS, R.M. (1971) Mineral Optics. Principles and Techniques. W.H. Freeman and Co., San Francisco. PHILLIPS, W.R., and GRIFFEN, D.T. (1981) Optical Mineralogy, the Nonopaque Minerals. Freeman, New York. REVELL, P.W.; GRIFFEN, P.D.T. (1981) Optical Mineralogy: The Nonopaque Minerals. W.H. Freeman, San Francisco. ROGERS, A.F.; KERR, P.F. (1977) Optical Mineralogy, 4th ed. McGraw-Hill Book Company, Inc., New York, London. ROUBAULT, M.; FABRIES; J., TOURET, J.; WEISBROD, A. (1963) Détermination des Minéraux des Roches au Microscope Polarisant. Editions Lamarre-Poinat, Paris. SCHOUTEN, C. (1962) Determination Tables for Ore Microscopy. Elsevier Publishing Co., Amsterdam-New York. SHELLEY, D. (1985) Optical Mineralogy, 2nd ed. Elsevier, New York. UYTENBOGAARDT, W. (1951) Tables for Microscopic Identification of Ore Minerals. Princeton University Press, Princeton. WAHLSTROM, E.E. (1979) Optical Crystallography, 5th. ed. Wiley and Sons, New York.

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880

Minerals, Ores and Gemstones WINCHELL, A.N.; WINCHELL, N.H. (1959) Elements of Optical Mineralogy: an introduction to microscopic petrography, 4th ed. John Wiley & Sons, Inc., New York, and Chapman & Hall, Ltd. London. WOOD, E.A. (1977) Crystals and Light. An Introduction to Optical Crystallography. Dover Publication Inc., New York.

12.9.3 Mineralogy ANTHONY, J.W.; BIDEAUX, R.A.; BLADH, K.W.; NICHOLS, M.C. (eds.) (1990–2003) Handbook of Mineralogy. Published by the Mineralogical Society of America (MSA), Mineral Data Publishing, Washington, DC. Volume I: Elements, Sulfides, Sulfosalts. (1990). Volume II: Silica, Silicates (Part 1 & 2). (1995). Volume III: Halides, Hydroxides, Oxides. (1997). Volume IV: Arsenates, Phosphates, Vanadates. (2000). Volume V: Borates, Carbonates, Sulfates. (2003). AUBERT, G.; GUILLEMIN, C.; PIERROT, R. (1978) Précis de minéralogie. Masson & Cie, Paris. BABUSHKIN, V.I.; MATVEYEV, G.M.; MCHEDLOV-PETROSSYAN, O.P. (1985) Thermodynamics of Silicates. SpringerVerlag, New York. BERRY, L.G. (ed.) (1983) Mineralogy: Concepts, Descriptions, Determinations, 2nd. ed. Freeman and Co., San Francisco. BRUSH, G. (1926) Manual of Determinative Mineralogy with an Introduction on Blowpipe Analysis, 16th. ed. John Wiley & Sons, New York. BLACKBURN, W.H.; DENNEN, W.H. (1997) Encyclopedia of Mineral Names Special Publication of the Canadian Mineralogist. Mineralogical Association of Canada, Ottawa, ON, Canada. CAILLÈRE, S.; HÉNIN, S.; RAUTUREAU, M. (1982) Minéralogie des Argiles, Tome 1: Structure et Propriétés Physicochimiques, 2nd. ed. Masson & Cie, Paris. CAILLÈRE, S.; HÉNIN, S.; RAUTUREAU, M. (1982) Minéralogie des Argiles, Tome 2: Classification et Nomenclature, 2nd. ed. Masson & Cie, Paris. CARMICHAEL, R.S. (1989) Practical Handbook of Physical Properties of Rocks and Minerals. CRC Press, Boca Raton, FL. CLARK, A.M. (1993) Hey’s Mineral Index: Mineral Species, Varieties and Synonyms, 3rd. ed. Chapman & Hall, New York. CRIDDLE, A.J.; STANLEY, C.J. (1993) Quantitative Data File for Ore Minerals, 3rd. ed. Chapman & Hall. DANA, E.S.; FORD, W.E. (1949) A Textbook of Mineralogy, 4th ed. John Wiley and Son’s, New York. DANA, J.D. (1944) Dana’s System of Mineralogy, 7th ed. John Wiley & Son’s, New York. DEER, W.A.; HOWIE, R.A.; ZUSSMAN, J. (1992) An Introduction to the Rock-Forming MineralsAn Introduction to the Rock-Forming Minerals, 2nd. ed. -Longman Scientific and Technical, Harlow, Essex. DEER, W.A.; HOWIE, R.A.; ZUSSMAN, J. (1962) Rock-Forming Minerals (5 volumes). Vol. 1: Ortho- and RingSilicates, Vol. 2: Chain Silicates, Vol. 3: Sheet Silicates, Vol. 4: Framework Silicates, Vol. 5: Non-Silicates. Longman, London. EMBREY, P.G.; FULLER, J.P. (1983) A Manual of New Mineral Names 1892–1978. British Museum, London. FEKLICHEV, V.G. (1992) Diagnostic Constants of Minerals. CRC Press, Bocca Raton, FL. FISCHESSER, R. (1955) Données des principales espèces minérales. Éditions Sennac, Paris. FLEISCHER, M.; MANDARINO, J. (1995) Glossary of Mineral Species 1995. The Mineralogical Record Inc., Tucson, AZ. GAINES, R.V.; SKINNER, H.C.W; FOORD, E.E.; MASON, B.; ROSENZWEIG, A. (1997) Dana’s New Mineralogy: The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana 8th. Ed. John Wiley and Sons, New York. GLEASON, S. (1960) Ultraviolet Guide to Minerals. Van Nostrand, New York. GRILL, E. (1963) Minerali Industriali e Minerali delle Rocce. Edizioni Enrico Hoepli, Milano. HEY, M.H. (1974) A Second Appendix to the Second Edition of an Index of Mineral Species and Varieties arranged Chemically, 2nd ed. Trustees of the British Museum, London. HEY, M.H. (1975) An Index of Mineral Species arranged Chemically, 2nd ed. – British Museum, London. HEY, M.H. (1963) First Appendix to the Second Edition of an Index of Mineral Species and Varieties arranged Chemically, 2nd ed. The British Museum, London. JONES, A.P.; WILLIAMS, C.T.; WALL, F. (1996) Rare Earth Minerals: Chemistry, Origin and Ore Deposits, Chapman & Hall, New York. KIPFER, A., (1974) Mineralindex Ott Verlag. KLEIN, C. (2002) Manual of Mineral Science, 22th. ed. Wiley, New York. LACROIX, A. (1964) Minéralogie de la France et de ses anciens territoires d'outre-mer. Librairie Blanchard, Paris.

Further Reading

881

LAPADU-HARGUES, P. (1954) Précis de minéralogie. Masson & Cie, Paris. LIEBAU, F. (1985) Structural Chemistry of Silicates. Springer-Verlag, Berlin. MANGE, M.; MAURER, H. (1992) Heavy Minerals in Color. Chapman & Hall, New York. MILOVSKY, A.V.; KONONOV, O.V. (1985) Mineralogy. Mir Editions, Moscow. NICKEL, E.H.; NICHOLS, M.C. (1991) Mineral Reference Manual. Van Nostrand Reinhold, New York. PARFENOFF, A.; POMEROL, C.; TOURENQ, J. (1970) Les minéraux en grains: méthodes d’étude et détermination. Masson & Cie., Paris. PICOT, P.; Johan, Z. (1982) Atlas of Ore Minerals. Éditions du Bureau de Recherches Géologiques et Minières (BRGM), Orléans. PUTNIS, A. (1992) Introduction to Mineral Sciences. Cambridge University Press. RAMDOHR, P.; STRUNZ, H. (1978) Klockmanns Lehrbuch der Mineralogie, 16. Aufl. Ferdinand Enke Verlag, Stuttgart. RAMDOHR, P. (1969) The Ore Minerals and their Intergrowths, 3rd ed. Pergamon Press, New York. RAMDOHR, P. (1960) Die Erzmineralien und ihre Verwachsungen. Akademie Verlag, Berlin. RAMDOHR, P.; STRUNZ, H. (1960) Handbuch der Mineralogie. Akademie Verlag, Berlin. ROBERTS, W.L.; RAPP, G.R.; CAMBELL, T.J. (1990) Encyclopedia of Minerals, 2nd. ed. Van Nostrand Reinhold, New York. ROBBINS, M. (1983) The Collector’s book of Fluorescent Minerals. Van Nostrand and Reinhold, New York. ROBBINS, M. (1994) Fluorescence. Gems and Minerals under Ultraviolet Light. Geoscience Press, Phoenix, AZ. SINKANKAS, J. (1964) Mineralogy for Amateurs, 2nd. ed. Van Nostrand Reinhold Company, New York. SINKANKAS, J. (1975) Mineralogy. Van Nostrand Reinhold Company, New York. STRUNZ, H. (1978) Mineralogische Tabellen, 7. Auflage. Akademische Verlagsgesellschaft, Leipzig. STRUNZ, H.; NICKEL, E. (2001) Strunz Mineralogical Tables: Chemical-Structural Mineral Classification System, 9th ed. – E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart. SULLIVAN, J.D. (1927) Heavy liquids for mineralogical analyses. Washington, Govt. Print. Off. WENK, H.-R.; BULAKH, A. (2004) Minerals. Their Constitution and Origin. Cambridge University Press, Cambridge. ZOLTAI, T.; STOUT, J. (1985) Mineralogy, Concepts and Principles. Burges Publishing Company, Minneapolis, MN.

12.9.4 Industrial Minerals BATES, R.L. (1960) Geology of the Industrial Rocks and Minerals. Harper and Brothers Publishers, New York. BATEMANN, A.M. (1950) Economic Mineral Deposits. New York. CARR, D.D. (ed.) (1994) Industrial Minerals and Rocks, 6th ed. Society for Mining Metallurgy & Exploration. CHANG, L.L.Y. (2002) Industrial Mineralogy. Prentice Hall, New York. EVANS, A.N. (1992) Ore Geology and Industrial Minerals: An Introduction. 3rd ed. Blackwell Science Inc. GARRETT, D.E. (1998) Borates: Handbook of Deposits, Processing, Properties, and Use. Academic Press, New York. HARBEN, P.W. (1998) Industrial Minerals Handybook. Metal Bulletin plc, London. LEFOND, S.J. (ed.) (1975) Industrial Minerals and Rocks, 4th. ed. American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. (AIME), New York. LINDGREN, W. (1940) Mineral Deposits. New York. MANNING, D.A.C. (1995) Introduction to Industrial Minerals. Chapman & Hall, New York. VOGELY, W.A.;RISSER, H.E. (eds.) (1976) Economics of the Mineral Industries, 3rd. American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. (AIME), New York.

12.9.5 Ores AHRENS, T.J. (1995) Mineral Physics and Crystallography. A Handbook of Physical Constants. American Geophysical Union, Washington DC. CAMERON, E.N. (1961) Ore Microscopy. John Wiley & Sons, Inc., New York. CRIDDLE, A.J.; STANLEY, C.J. (1993) The Quantitative Data File for Ore Minerals Chapman & Hall, New York. BATEMANN, A.M. (1950) Economic Mineral Deposits. New York. BURNS, P.C.; FINCH, R. (1999) Uranium: Mineralogy, Geochemistry, and the Environment. Mineralogical Society of America (MSA), Washington DC. DIXON Atlas of Economic Mineral Deposits Chapman & Hall, New York (1979).

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882

Minerals, Ores and Gemstones EMMONS, W.H. (1940) The Principles of Economic Geology, 2nd ed. Mc-Graw-Hill, New York. FOUET, R.; POMEROL, C. (1954) Minerais et terres rares. Collection “Que sais-je?”, Presses Universitaires de France (PUF), Paris. FREUND, H. (ed.) (1966) Applied Ore Microscopy; Theory and Techniques. Macmillan, New York. HARTMAN, H.L. (ed.) (1992) SME Mining Engineering Handbook, 2nd ed. Society of Metallurgical Engineers (SME), New York. JONES, A.P.; WILLIAMS, C.T.; WALL, F. (1996) Rare Earth Minerals: Chemistry, Origin and Ore Deposits Chapman & Hall, New York. LAFITTE, P. (1957) Introduction à l’Étude des Roches Métamorphiques et des Gîtes Métallifères Masson & Cie, Paris. LINDGREN, W. (1940) Mineral Deposits New York. MANNING, D.A.C. (1995) Introduction to Industrial Minerals Chapman & Hall, New York. PETRUK, W. (2000) Applied Mineralogy in the Mining Industry. Elsevier Science, Amsterdam. PARK, C.F.; MACDIARMID, R.A. (1975) Ore Deposits, 3rd. ed. W.H. Freeman and Company, San Francisco. PICOT, P.; JOHAN, Z. (1982) Atlas of Ore Minerals. Éditions du Bureau de Recherches Géologiques et Minières (BRGM), Orléans. RAGUIN, E. (1961) Géologie des gîtes minéraux, 2nd. ed. Masson & Cie, Paris. RAMDOHR, P. (1969) The Ore Minerals and their Intergrowths, 3rd ed. Pergamon Press, New York. ROUBAULT, M. (1958) Géologie de l’uranium. Masson & Cie, Paris. ROUBAULT, M. (1960) Les minerais uranifères français et leurs gisements. (3 vol.) Institut National des Sciences et Techniques Nucléaires (INSTN), Saclay, France. ROUTHIER, P. (1963) Les Gisements Métallifères (2 volumes) Masson & Cie, Paris. SCHOUTEN, C. (1962) Determination Tables for Ore Microscopy. Elsevier Publishing Co., Amsterdam-New York. WELLMER, F.-W. (1998) Statistical Evaluations in Exploration for Mineral Deposits. Hannover, Germany.

12.9.6 Gemstones ANDERSON, B.W. (1976) Gemstones for Everyman. Van Nostrand Reinhold, New York. ANDERSON, B.W. (1990) Gem Testing, 10th. ed. Butterworths-Heinemann, Stoneham, MA. AREM, J. (1975) Gems and Jewelry. Bantam Books, New York. AREM, J. (1987) Color Encyclopedia of Gemstones, 2nd ed. Van Nostrand Reinhold, New York. BANCROFT, P. (1984) Gem and Crystal Treasures. Mineralogical Record, Carson City, NV. BARDET, M. (1975) Le Diamant, 2 vol. Éditions du Bureau de Recherches Géologiques & Minières (BRGM), Orléans. CAVENAGO BIGNAMI, S. (1964) Gemmologia. Edizioni Enrico Hoepli, Milano. CIPRIANI, C.; BORELI, A. (1986) Gems and Precious Stones. Simon and Schuster, New York. COPELAND, L.L.; LIDDICOAT, Jr, R.T.; BENSON, L.B.; MARTIN, J.G.M.; CROWNINGSHIELD, G.R. (1960) The Diamond Dictionary. The Gemological Institute of America (GIA), San Vincente, CA. EPPLER, W.F. (1973) Praktishe Gemmologie. Rühle-Diebener-Verlag KG, Stuttgart. HARLOW, G.E. (ed.) (1998) The Nature of Diamonds. Cambridge University Press, Cambridge. HUGHES, R.W. (1997) Ruby and Sapphire. RWH Publishing, Boulder, CO. HURLBUT Jr. C.S.; SWITZER, G.S. (1979) Gemology. Wiley, New York. HURLBUT, C.S. Jr.; KAMMERLING, R.C. (1991) Gemology, 2nd ed. Wiley, New York. KELLER, P.C. (1990) Gemstones and Their Origins. Van Nostrand Reinhold, New York. KUNZ, G.F. (1892) Gems and Precious Stones of North America. Reprinted in 1968 by Dover Publishing, New York. KRAUS, E.H.; SLAWSON, C.B. (1947) Gems and Gem Materials. McGraw-Hill, New-York. LIDDICOAT Jr, R.T. (1989) Handbook of Gem Identification, 12th. ed. Gemological Institute of America (GIA), Santa Monica, CA. MANUTCHEHR-DANAI, M. (2005) Dictionary of Gems and Gemology, 2nd. Springer, Heidelberg. NASSAU, K. (1980) Gems Made by Man. Chilton Book Co., Radnor, PA. NASSAU, K. (1984) Gemstones Enhancement. Butterworths, London. READ, P.G. (1988) Dictionnary of Gemmology 2nd. ed. Butterworths, Oxford. SCHUMANN, W (1997) Gemstones of the World. Sterling, New York. SINKANKAS, J. (1959) Gemstones of North America. D. Van Nostrand Company, Inc., Princeton. SINKANKAS, J. (1962) Gem Cutting: A Lapidary's Manual, 2nd. ed. Van Nostrand Reinhold, New York.

Further Reading

883

SINKANKAS, J. (1970) Prospecting for Gemstones and Minerals, 2nd. ed. Van Nostrand Reinhold, New York. SINKANKAS, J. (1981) Emerald and other Beryls. Chilton Way, Radnor, PA. SINKANKAS, J. (1988) Field Collecting Gemstones and Minerals, 2nd. ed. Geoscience Press, Prescott, AZ. SOFIANDES, A.S.; HARLOW, G.E. (1990) Gems & Crystals from the American Museum of Natural History. Simon & Schuster, New York. VAN LANDGHAM, S.L. (1984) Geology of World Gem Deposits. Van Nostrand Reinhold Co., New York. WEBSTER, R.; READ, P.G. (1994) Gems: Their Sources, Descriptions, and Identification, 5th. ed. Butterworths, Oxford.

12.9.7 Heavy Liquids and Mineral Dressing GAUDIN (1939) Principles of Mineral Dressing. McGraw Hill, New York, 1939. Textbook of Ores Dressing, 3rd Ed., McGraw Hill, New York, 1940. TAGGART, Ed. (1945) Handbook of Mineral Dressing. Ores and Industrial Minerals. 2nd edition. John Wiley, New York. E.J. PRYOR (1965) Mineral Processing, 3rd. edition, Elsevier Publishing, London, 1965. A. PARFENOFF, C. POMEROL, J. TOURENQ, Les minéraux en grains: méthodes d’étude et de détermination, Masson & Cie, Paris, 1970. U.S. Bureau of Mines, Rept. Inv., #2897, 1928. WALKER, ALLEN, Benefication of Industrial Minerals by Heavy Media Separation, Trans. Am. Inst. Min. Metall. Pet. Eng. Min. Branch, 184, 17, 1949. OSS, ERICKSON, APLAN, SPLEDEN, Viscosity Control in Heavy-Media Suspension, Proc. 7th Int. Miner. Process. Congr., New York, Sept., 20, 1964. VOLIN, VALENTYIK, Control of Heavy Media Plant, Pit Quarry, 62(12), 111, 1969. DOYLE. The Sink-Float Process in Lead-Zinc Concentration, AIME Symp. Lead-Zinc, St. Louis, 1970.

12 Minerals, Ores and Gemstones

Rocks and Meteorites

13.1 Introduction Rocks represent the overall geological materials constituting the Earth’s crust (i.e., lithosphere), which are commonly made from an aggregate of crystals of one or more minerals and/or glass. From a wide geological point of view, rocks can be either solid (e.g., granite, limestone, rock salt, and ice), fluid (e.g. sand, and volcanic ashes), liquid (i.e., bitumen, and oil), or gaseous (i.e., natural gas, and hydrothermal fluids). The important discipline of earth sciences which studies rock formation processes, chemical composition and physical properties, is named petrology (from Latin, petrus, stone) sometimes called lithology in old textbooks (from Greek, lithos, stone), while petrography sensu stricto only classifies rocks and can be understood as a simple taxonomy. There are several reasons to study, identify, and measure properties of the different type of rocks present in the Earth’s crust. First of all, rock materials contain valuable mineral ore deposits and can also contain fossil fuels (e.g., oil, coal, and natural gas). Hence understanding of the different types of rocks is necessary in order to locate and recover these valuable economic resources. Secondly, from a civil engineering point of view, the knowledge of the physical properties of different rocks used in construction is important in order to select the most appropriate building materials. Actually, some rock types are more susceptible to slope failure (i.e., landslides) or structural failure (i.e., disintegration under pressure) than others. Consequently, it is necessary to know the characteristics of the underlying rocks when doing any major civil engineering construction. Thirdly, from an agricultural point of view, rocks are the basic geological material from which all soils are formed (see Chapter 14). Hence, the rock chemical composition strongly influences the nature of the soil and

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the types of vegetation which the soil can support. Finally, from an environmental point of view, rock type also influences the flow of water, a major necessity of life, both above and below the ground surface.

13.2 Structure of the Earth’s Interior The knowledge of the structure of the interior of the Earth is obviously important for understanding the origin of most igneous rocks and minerals but it is also fascinating from a fundamental point of view regarding the behavior of materials under ultrahigh pressures and temperatures and hence it is briefly described here. The geosphere denotes the mineral part of the Earth; it consists of successive concentric layers from the outer crust down to the inner core. (see Figure 13.1). The structure of the interior of the Earth can be zoned by either its physical properties (e.g., density, velocity of P and S seismic waves, and temperature) or its chemical and mineralogical composition. The classification of the geosphere according to its chemical composition identifies three main chemical entities: the crust, the mantle, and the core, while physical properties identify five homogeneous entities: the lithosphere, the asthenosphere, the mesosphere, the outer core and the inner core.

Figure 13.1. Structure of the Earth’s interior

Structure of the Earth’s Interior

The Earth’s crust constitutes the outermost thin and solid layer of the geosphere with a thickness ranging from 3 km under the mid-oceanic ridges to 80 km under the oldest continents. The Earth’s crust is mainly composed of oxygen, silicon, aluminum and, to a lesser extent, calcium, magnesium and iron, and for that reason it was first denoted SiAl –3 by the Austrian geologist Suess. Owing to its low density, usually between 2500 kg.m and –3 3500 kg.m , the Earth’s crust floats over the denser mantle. Two types of crust can be distinguished: (i)

(ii)

The continental crust is a geological structure more than 1.5 Ga old mainly composed of granitic igneous rocks and sediments. It is quite thick, averaging 30–40 km and even more beneath mountain ranges until reaching 80 km in the oldest part of the continents called Archeans cratons. The oceanic crust is a younger geological structure less than 200 Ma old. It consists of a thin layer of 5–10 km thickness composed primarily of tholeitic basalt and possibly underlain by gabbro. The velocity of seismic waves is greater in the oceanic than in the continental crust.

The sharp boundary existing between the bottom of the Earth’s crust and the upper mantle that was first identified in 1909 by the Croatian seismologist Andriaja Mohorovicic by a clear change in the velocity of P seismic waves is called the Mohorovicic discontinuity or simply Moho. The mantle is a broad silicon-magnesium rich layer in the form of silicate minerals and it is called SiMa. From a petrological point of view, it is composed of ultramafic rocks such as peridotite and eclogite. It extends to a depth of about 2900 km beneath the crust and accounts for around 82% of the Earth’s total volume. Analysis of seismic waves shows that the mantle consists of rigid and plastic zones. The density of the mantle ranges from 3500 to –3 5800 kg.m . The mantle has a complex structure and it is subdivided into upper mantle, transition zone, and lower mantle, based upon the different velocities with which seismic waves travel through these regions. The upper mantle (10–410 km) is made of a rigid layer and a flowing layer called the asthenosphere. The temperature at the top of the mantle is about 870°C. From a mineralogical point of view, the silicon in silicate minerals exhibits the common tetrahedral coordination and olivine (60%), ortho-pyroxenes (23%), clinopyroxene (2%), and garnet (15%) are the dominant phases. The upper mantle includes a zone characterized by low velocities of seismic waves, called the low-velocity zone (LVZ), at 72−250 km depth. This zone corresponds to the asthenosphere derived from the Greek, asthenos, devoid of force, upon which the Earth’s crust plates glide by means of strong convection current. Actually, as heat from the core and lower mantle escapes to the surface, it causes convection cells to form in this easily-deformed asthenosphere. These currents of partially-melted rock help quickly transfer this heat to the surface. It is this hot, moving material that keeps the Earth a dynamic planet. As hot mantle rock rises, it can fully melt into magma, which then forces its way through the lithosphere to form hot spots. These magma plumes may form volcanic chains as in the Hawaiian Islands, and more importantly, are thought to drive seafloor spreading. This in turn is one of the driving mechanisms behind the movement of tectonic plates. The lateral movement of mantle rock at the topmost section of a convection cell also exerts a force called mantle drag on the bottom of a lithospheric plate, literally dragging it along the Earth’s surface. The transition zone (TZ) formerly called the mesosphere is the layer between two discontinuities in seismic wave-velocities that lie at depths of approximately 410 km and 660 km. It is important to note that there is confusion in the literature about whether 660 km or 1000 km depth, i.e., the former Repetti discontinuity, is the boundary between the upper and lower mantles and whether there are chemical changes deeper than 1000 km depth. The transition zone thus holds the key to whether there is wholemantle or layered-mantle convection. These discontinuities are related to polymorphic phase

887

13 Rocks and Meteorites

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Rocks and Meteorites

changes, caused by pressure-induced changes of the crystal lattice in certain minerals. Actually, the greater pressure promotes a denser packing of oxygen anions and part of the silicon atoms adopts the octahedral coordination. The 410 km discontinuity results from the con2+ version of the fayalite-forsterite isomorphous series [(Mg,Fe )2SiO4] with the olivine struc2+ ture into the more stable wadsleyite [β-(Mg,Fe )2SiO4] having a spinel-like structure (AB2O4) with a density increase of 8%, while deeper at 520 km the transformation of wadsleyite into 2+ ringwoodite [γ-(Mg,Fe )2SiO4] still having the spinel type but 2% denser. Earthquakes occur all the way down to 660 km, but never below. Finally, in the lower mantle (660–2900 km) the high pressure imposed forces the silicon to adopt the octahedral coordination exclusively. Therefore perovskite-type structures (ABO3) such as in CaSiO3 and MgSiO3 predominate, along with ferroan periclase (Mg,Fe)O, corundum and stishovite (i.e., SiO2 with a rutile structure). Seismic velocities in the upper mantle are overall less than those in the transition zone, and those of the transition zone are in turn less than those of the lower mantle. Faster propagation of seismic waves in the lower mantle implies that the lower mantle is more dense than the upper mantle. At the base of the lower mantle is the D" layer (D-doubleprime) for lack of a better name, a poorly-understood layer marked by yet another discontinuity or core-mantle boundary (CMB).The core-mantle boundary is characterized by the Gutenberg discontinuity that separates the mantle from the core. It was discovered in 1914 by Beno Gutenberg based on the observation that P waves vanished at a plane angle of 105° from the earthquake and reappear at about 140°; this 35° angle span is named the P-wave shadow zone. This may be an Fe-rich zone of transition between the outer core and the lower mantle. The core formerly called the pyrosphere is mostly composed of iron and nickel and was first called NiFe and remains very hot with an estimated temperature of ca. 7000K even after –3 4.5 Ga of cooling. Its average density is 14,000 kg.m . The core is structurally divided into two layers: (i)

(ii)

The liquid outer core – the fact that S waves do not travel through the core provides evidence for the existence of a liquid or molten state. The outer core is an electrically conducting liquid, mainly iron and nickel. This conductive layer combined with Earth’s rotation creates a dynamo effect that maintains a system of electrical currents creating the Earth’s magnetic field. It is also responsible for the nutation of the Earth’s rotation. This layer is not as dense as pure molten iron, which indicates the presence of lighter elements. Scientists suspect that about 10 wt.% of the layer is composed of sulfur and oxygen because these elements are abundant in the cosmos and dissolve readily in molten iron. The solid inner core – despite the tremendous temperatures this is in the solid state. It is believed to have solidified as a result of the huge pressure exerted by overlying layers and this is confirmed by the increased velocity of P waves passing through it. The inner core is made of solid iron and nickel and is unattached to the mantle, suspended in the molten outer core. The inner core may have a temperature up to 7500 K, which is hotter than the surface of the Sun, and the heat released comes entirely from the decay of primordial radionuclides (U, Th).

The Lehmann discontinuity that was predicted by the Danish seismologist Inge Lehmann in 1936, separates the outer core from the inner core. Lithosphere – the lithosphere, named from the Greek, lithos, stone, is the rigid outermost layer of the geosphere including the Earth crust and the uppermost rigid layer of the mantle. It averages about 100 kilometers in thickness, but may be 250 kilometers or more thick beneath the older portions of the continents (i.e., cratons).

Different Type of Rocks

Table 13.1. Principal physical characteristics of Earth’s interior discontinuities

1

13

Discontinuity

Radius (/km)

Depth (/km)

Density –3 ( /kg.m )

Velocity of longitudinal waves –1 (VP/km.s )

Velocity of transversal waves –1 (VS/km.s )

Lithostatic pressure (GPa)

Typical mid-crust

6356

15

2900

5.80

3.20

0.33

Mohorovicic discontinuity

6346

25

3380

6.80

3.90

0.6

Lehmann discontinuity

6151

220

3430

7.98

4.41

7.11

Upper mantle-transition zone

5971

400

3720

8.90

4.76

13.35

Transition zone-Lower mantle

5701

670

4380

10.26

5.57

23.83

Lower mantle-Outer core

3480

2891

5560

13.71

7.26

135.75

Outer core-Inner core

1221

5150

12,160

10.35

0.0

328.85

Earth’s center

0

6371

13,080

11.26

3.66

363.85

13.3 Different Type of Rocks Rocks can be classified into one of the four categories on the basis of their formation process: (i)

Igneous rocks or magmatic rocks are formed by the cooling and solidification of a molten silicate bath (i.e., magma). (ii) Sedimentary rocks are produced by the weathering/erosion process (i.e., physical erosion and chemical alteration) of pre-existing rocks. After that, raw materials undergo three successive processes: (1) the transportation of degradation material by several media (i.e., water, wind or ice); (2) the deposition as sediment; 2 (3) diagenesis after which the sediment is cemented or not into a sedimentary rock. (iii) Metamorphic rocks are rocks whose original form has been modified chemically and physically as a result of high temperature, high pressure, and hot fluids or both. Metamorphic rocks may form from igneous, sedimentary, or previous metamorphic rocks. (iv) Meteorites are extraterrestrial materials coming from the Solar System which are continually falling on Earth. The processes which produce the four general rock types, and the relationships between them, are summarized in the rock cycle depicted in the Figure 13.2.

1 2

889

from Anderson, D.L. (1989) Theory of the Earth. Blackwell Scientific Publications, Boston Diagenesis or lithification is the set of physical (e.g., pressure, temperature), chemical (e.g., dissolution, precipitation), or biological (e.g., fermentation) parameters which transform the unconsolidated sediment into a final rock.

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Figure 13.2. The rock cycle

13.4 Igneous Rocks Igneous rocks (sometimes called magmatic rocks or endogeneous rocks) are rocks resulting from the solidification on cooling of a molten silicate material called magma and occur in a wide variety of forms of different shapes and sizes. The magma is characterized by: (i)

a chemical composition which is essentially a silicate melt generated by melting deep within the Earth’s crust; (ii) a high melting temperature usually ranging between 500°C and 1500°C; and (iii) a mobility, i.e., ability to flow. Magma forms at depths of about 15–25 km, where temperatures are in the range of 500–1500°C and lithostatic pressure around 1 GPa (10 kbar). The types of igneous rocks that form from this magma depend generally on three factors: (i) original chemical composition of the magma; (ii) the temperature at which the cooling begins; and finally (iii) the cooling rate. According to the cooling depth, igneous rocks can be classified into two major subdivisions:

(i) (ii)

the extrusive or volcanic rocks; and the intrusive or plutonic rocks.

Plutonic or intrusive rocks are igneous rocks formed when a magma cools slowly as it rises through the Earth’s crust forming very large crystalline bodies called batholiths. Hence, this means that the crystal size is medium or coarse, and the rock exhibits a so-called typical

Igneous Rocks

phaneritic texture (e.g., granite, syenite, or gabbro). Intrusive rocks occur in variety of deposit forms. Vertical sheets of igneous rock are called dykes. Horizontal sheets, parallel or near parallel to layering are known as sills. Fatter pods of crystalline rock are called laccoliths. Volcanic or extrusive rocks are igneous rocks obtained when a magma cools rapidly and are formed if it reaches the surface of the Earth. Extrusive rocks form from lava flows and pyroclastic ash or debris that are ejected into the air during eruptions and are entirely related to volcanoes. These kinds of rocks often occur in characteristic volcanic cones. Submarine lava flows form characteristic pods called pillows. Therefore the rock texture exhibits a partially crystallized or totally amorphous texture called aphanitic and hyaline respectively (i.e., basalt, obsidian glass, and pumice). The magma is a molten silicate medium which takes its origin inside the Earth’s crust probably due to the partial melting of the deep lithospheric material. Petrologists have identified two main classes of magmas from which igneous rocks are generally derived. Hypersiliceous or felsic magmas are silicate melts having a high silica content (i.e., above 65 wt.% SiO2) and a low melting temperature range, usually 500–900°C. Due to these two chief characteristics these silica-rich magmas are highly viscous and hence move slowly and solidify slowly before reaching the Earth’s surface. This type of magma leads principally to the formation of plutonic rocks (e.g., granite). By contrast, hyposiliceous or mafic magmas are silicate melts having low silica contents (i.e., 45 to 52 wt.% SiO2) and a high melting temperature range, usually 1100–1500°C. Due to these two chief characteristics these magmas are highly fluid and hence move quickly upward to the Earth’s surface (i.e., volcanoes) and they lead to the formation of lavas and pyroclastic products. As a general rule, owing to the chemical composition of the deep lithosphere, mother magmas are initially hyposiliceous melts, but the fractional crystallization of ferromagnesian minerals (e.g., olivine, pyroxenes) occurring during cooling modifies their composition so that they become hypersiliceous. Igneous rocks rich in calcium, iron, and magnesium and relatively silica-poor form from mafic magma. These rocks are generally dark in color and contain alkaline elements. Some common mafic igneous rocks include: basalt, gabbro, and andesite. Rocks that contain relatively high quantities of sodium, aluminum and potassium and contain more than 65% silica originate from felsic magmas. The rocks created from felsic magma include granite and rhyolite. These rocks are light in color and are acidic in nature. Moreover, a silica-poor magma which solidifies at or near the Earth’s surface would give the aphanitic rock basalt and would be composed of a very finely crystalline aggregate of the minerals peridot, pyroxenes, and plagioclase. If the same silica-poor magma were instead cooled more slowly at some depth within the crust, the overall chemical composition of the resulting rock would be the same as that of the basalt, but the rock’s coarsely crystalline texture would instead classify if as a gabbro. Basalts and gabbros, having the same silica-poor composition, are considered to be extrusive and intrusive equivalents in the same way as rhyolite has an extrusive texture and granite has an intrusive texture.

13.4.1 Classification of Igneous Rocks The petrographic classification of igneous rocks is essentially based on the following three main characteristics, their actual mineralogical composition, their texture and their chemical composition. The texture of an igneous rock is principally a function of the cooling rate of the mother magma, while mineralogical composition is both a function of the chemistry and of the cooling history of a magma. Several quantitative parameters or indices are commonly used in order to help in the classification of igneous rocks.

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13.4.1.1 Crystals Morphology and Dimensions Table 13.2. Crystal dimensions Order of magnitude of crystal size Obsolete designation

Modern designation

decimeter (dm)

megablastes

megacrystals

centimeter (cm)

porphyroblastes

porphyrocrystals

millimeter (mm)

phaneroblastes

phanerocrystals

inframillimeter

phenoblastes

phenocrystals

submillimeter

spherolites, microlites spherocrystals, microcrystals

micrometer (μm)

crystalites

cryptocrystals

nonvisible

mesostase

glass, hyaline, amorphous

Table 13.3. Crystal development Development

Obsolete designation

Regular geometrical shape

Automorphous

Modern designation

Formes moyennement développées

Subautomorphous Hypidiomorphous

Subhedral

No regular geometrical shape

Xenomorphous

Anhedral

Idiomorphous

Example

Euhedral

Allotriomorphous

Table 13.4. Crystal proportion Proportion des cristaux

Designation (Latin root)

Designation (Greek root)

Similar crystal dimensions

Equigranular

Isogranular

Different crystal dimensiond Inequigranular Heterogranular

Table 13.5. Crystal external shapes External shape

Designation Example

Grain

Massive

Quartz

Plate

Tabular

Pyroxenes

Flake

Lamellar

Micas

Prism

Columnar

Beryl, Sillimanite

Fibrous, needlelike Acicular

Rutile, Abestos

13.4.1.2 Mineralogy Igneous rocks are essentially composed of the six major rock forming silicate minerals (i.e., they constitute about 95% of all igneous rocks), which include: peridots, pyroxenes, amphiboles, feldspars, micas, and quartz. Other minerals may also be present, but they usually make up only a small fraction of the rock. These less abundant and less common minerals

Igneous Rocks

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Figure 13.3. Bowen’s crystallization series Table 13.6. Mineral composition Category

Example

Essential minerals

Quartz, feldspars (i.e., orthoclase, Na and Ca plagioclases), olivine, pyroxenes, and amphiboles

Accessory minerals

Micas (i.e., biotite, and muscovite)

Less common minerals Rutile, titanite, apatite, beryl, tourmaline, zircon

are often called accessory minerals (e.g., micas). The modal composition corresponds to the actual mineralogical composition measured statistically under the polarizing microscope 3 with a thin section of the rock, while the normal composition CIPW is the ideal mineralogical composition calculated from the quantitative chemical analysis of the rock. The former allows us to estimate the mineralogy of partially- or hyaline-crystallized rocks, i.e., if the mother magma was able to solidify slowly. Nicholas L. Bowen devised the following crystallization series to explain the origin of all igneous rock types from a single parent magma. He observed that minerals crystallized at different temperatures, and reasoned that all igneous rocks could form from the parent basaltic magma through reaction and removal of certain crystals during cooling. Hence he summarized the temperature sequence of mineral crystallization in what is called Bowen’s reaction series. Initial mafic molten silicate liquids tend to crystallize minerals at relatively high temperatures to form mafic or ferromagnesian minerals rich in iron, magnesium, and calcium. These minerals (i.e., olivine, pyroxene, and calcium-rich plagioclase feldspar) tend to react with the silica-enriched melt to form the next mineral in the sequence and then crystallize in a specific sequence according to their melting point. Intermediate and silicic liquids crystallize at lower temperatures to form minerals which are richer in silica, sodium, and potassium. These pale-colored minerals (i.e., quartz, sodium-rich plagioclase feldspar, potassium feldspar) also crystallize in a specific sequence (see Figure 13.3). 3

CIPW from Cross, W.; Iddings, J.P.; Pirsson, L.V.; and Washington, H.S. A Quantitative Chemico-Mineralogical Classification and Nomenclature of Igneous Rocks J. Geology 10 (1912) 555–690.

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Table 13.7. Crystallization sequence (Rosenbuch) Early minerals Apatite, Zircon, Titanite Pyroxenes, Amphiboles, Biotite Ca-Plagioclases Ca-Na-Plagioclases Na-Plagioclases Albite, Orthoclase Late minerals

Quartz

Table 13.8. Minerals according to density (E. Lacroix) –3

Density (d/kg.m )

Class

d = 2770

Coupholites

d > 2770

Barylites

13.4.1.3 Coloration The coloration of igneous rocks is a dimensionless quantity introduced by the French geologist Élie de Beaumont. It corresponds to the surface fraction of white minerals in a thin section of the rock which is accurately determined using statistical counting methods. From a practical point of view, the coloration is determined by observing a thin section of the igneous rock under the microscope under non-polarized light. However, although this technique gives good result with igneous rocks having coarse grain size, for igneous rocks having a fine crystal size, with individual crystals too small to identify a less exact method must be used. In this particular case, coloration is obtained from the calculated mineralogical composition of the rock (i.e., modal analysis) using the following formulae: Coloration = 100 – vol.%(Quartz + Feldspars)

(saturated rocks)

Coloration = 100 – vol.%(Feldspars + Feldspathoids) (subsaturated rocks) This method generally associates higher silica content with lighter rock color. Lighter colored rocks are felsic or silicic which means that they contain abundant feldspars and quartz. Darker colored, mafic rocks are richer in mafic minerals such as olivine, pyroxene, and amphibole. These mafic minerals are also called ferro-magnesian minerals because they contain relatively large amounts of iron and magnesium. Mafic igneous rocks like basalt and gabbro

Table 13.9. Coloration (E. Beaumont) Designation

Fraction of white minerals (/%) Examples

Hololeucocrates

95–100

Leucogranite

Leucocrates

65–95

Granite

Mesocrates

35–65

Diorite

Melanocrates

5–35

Gabbro

Holomelanocrates 0–5

Pyroxenite

Igneous Rocks

also contain significant amounts of plagioclase feldspars. Ultra-mafic rocks are composed entirely or almost entirely of mafic minerals. Rocks such as andesite with color and composition between mafic and felsic are considered intermediate. Glassy rocks can be an exception to this generalization about color.

13.4.2 Texture of Igneous Rocks Rock texture is the overall appearance of a rock based on the size and arrangement of its interlocking crystals. Crystal size is the most important aspect of igneous texture. Among the several texture varieties, three main classes can be identified: phaneritic, aphanitic, and glassy textures. Phaneritic igneous rocks. Igneous rocks are formed from a slow cooling rate of a mother magma (i.e., far from the Earth’s surface). The rock possesses a coarse grain size, with visible grains (1–20 mm), and it exhibits a so-called typical phaneritic texture (e.g., granite, syenite, or gabbro). In a few cases, intrusive igneous rocks can have a distinctly mixed crystal size with a so-called porphyroid texture. In this case scattered, prominent, extremely coarse crystals often called megacrystals are surrounded by a groundmass of medium or coarse crystals. Porphyritic textures indicate that the magma stopped at some depth where the larger crystals formed, before migrating to the surface where it erupted. The magma may also have been supersaturated with the coarse crystalline mineral phase and the phaneritic rocks exhibit a pegmatitic texture and are called pegmatites. This texture possesses large crystals greater than 2–5 cm and usually above 12 cm in diameter. Sometimes, exceptionally large crystals may be several meters in size. These usually form in the latest stage of cooling of water-rich magmas, and represent the accumulated volatiles from the magma. Aphanitic and porphyritic igneous rocks. Aphanitic igneous rocks are also crystalline. They form by rapid cooling of lava at or near the Earth’s surface. As a result all or most of the crystals are so small that individual crystals cannot be distinguished. These tiny crystals, called microlites have a fine crystal size. Most aphanitic igneous rocks are also called extrusive or volcanic rocks because they are formed at or near the surface of the earth and are often associated with volcanoes. Sometimes aphanitic or glassy rocks contain scattered coarse or medium crystals called phenocrystals which are surrounded by a groundmass composed of fine crystals and/or glass. A rock with such a mixed crystal size has a porphyritic texture. This texture is sometimes formed by a two-stage cooling history. Initially, a magma rising through the crust begins to cool slowly at depth forming the phenocrysts. Then the magma is erupted onto the surface where the remaining liquid cools rapidly forming the matrix. In other cases, the phenocrystals represent crystals which had a much faster growth rate during cooling than did the fine crystals (e.g., porphyritic rhyolite). Glassy and hyaline igneous rocks. These rocks are the result of a rapidly solidified magma, and because it is a molten liquid cooled with a high cooling rate the random microscopic organization of a magma is fixed and avoids the crystallization process. Therefore, by contrast with other igneous rocks which are crystalline, these rapidly quenched materials exhibit an amorphous or vitreous aspect (i.e., glassy). Nevertheless, owing to the thermodynamic instability of glasses, some devitrification processes occur and particular textures such as cracks (i.e., spherolitic) and bubbles (i.e., perlitic) are often present.

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Table 13.10. Chief textures of igneous rocks Texture main type

Cooling rate

Definition

Varieties and facies

Phaneritic

Slow

All the minerals have a medium or coarse crystal size

Malgachitic, pegmatitic, pegmatoidic, rapa-kiwic, porphyroidal, granular, isogranular, saccharoidal, homogeneous, Dent de Cheval, orbicular, aplitic, cataclastic, graphic, amygdalar

Microphaneritic

Slow/ All the minerals have a small crystal moderate size

Porphyritic, Aphanitic, Phaneritic, Graphic, Ophitic Poecilitic, Intersertal, intergranular, lamproporphyric, doleritic

Aphanitic or microlitic

Rapid

The crystals are so small (i.e., microlites) that individual crystals cannot be distinguished without magnification and are surrounded by a glassy matrix. Aphanitic textures form primarily when cooling rates are fast such as lava flows.

Porphyritic, trachytic

The glassy or vitreous texture with no crystals usually indicates that the magma cooled extremely quickly and/or that it was so viscous that ions could not migrate to form crystals seed. Most glasses are related to pyroclastic igneous rocks.

Vitreous, amorphous, spherolitic, perlitic, fluidal, breccia-type, vacuolar, vesicular

Hyaline, glassy or High vitreous

Table 13.11. Crystallinity Glass fraction (/%) Category

Example

0–5

Holocrystalline Granite

5–55

Hypocrystalline Basalt

55–95

Hypohyaline

Pumice

95–100

Holohyaline

Obsidian

13.4.3 Chemistry of Igneous Rocks The chemical composition of an igneous rock is also an important parameter of its classification. The chemical composition of a rock may be expressed by the types of minerals present and their relative abundances or in the rock color. Rocks may also be analyzed chemically using quantitative chemical analysis techniques to determine the relative proportions of chemical elements present. These chemical abundances can be used directly to classify igneous rocks. The chemical composition of the mother magma and to a lesser extent that of the country rock (i.e., host rock) largely controls the types of minerals which may be formed.

Igneous Rocks

Table 13.12. Abundance of chemical elements

13

Category

Examples

Major chemical elementss

O, Si, Al, Fe, Mg, K, Na, Ca

Minor chemical elements

H, F, Cl

Dispersed chemical elements Ti, P Rare chemical elements

U, Th, Zr, Hf

Table 13.13. Acidity (i.e., silica content) Silica content (% wt. SiO2) Category

Examples

66–100

Acid igneous rocks

Granite

52–66

Neutral igneous rocks

Syenite

45–52

Mafic igneous rocks

Gabbro

0–45

Ultramafic igneous rocks Péridotites

Table 13.14. Saturation Category

Example

Sursaturated Granite Saturated

Syenite

Subsaturated Peridotites

Table 13.15. Alkalinity Category

Criterion

Alkaline igneous rocks

n(Na2O)+n(K2O) > n(Al2O3) n(Na2O)+n(K2O) > 1/6(SiO2)

Non-alkaline igneous rocks n(Na2O)+n(K2O) < n(Al2O3) n(Na2O)+n(K2O) < 1/6(SiO2)

Table 13.16. Feldspar index Category

F-Index (/%)

Alkaline igneous rocks

80–100

Subalkaline igneous rocks

60–80

Monzonitic igneous rocks

40–60

Subplagioclasic igneous rocks

20–40

Holoplagioclasic igneous rocks 0–20

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Table 13.17. Average chemical composition of igneous common rocks (/ wt.%) Igneous rock

SiO2

Andesite

57.94 0.87 17.02 3.27

4.04 0.14

3.33

6.79

Anorthosite

50.28 0.64 25.86 0.96

2.07 0.05

2.12

Basalt

49.20 1.84 15.74 3.79

7.13 0.20

6.73

9.47

Basanite

44.30 2.51 14.70 3.94

7.50 0.16

Dacite

65.01 0.58 15.91 2.43

2.30 0.09

Diorite

57.48 0.95 16.67 2.50

Dolerite Dunite Earth’s crust

4 5

5

TiO2 Al2O3 Fe2O3 FeO MnO MgO CaO

+4

–

Na2O K2O H2O

H2O P2O5 CO2

3.48

1.62 0.83

0.34 0.21 0.05

12.48 3.15

0.65 1.17

0.14 0.09 0.14

2.91

1.10 0.95

0.43 0.35 0.11

8.54

10.19 3.55

1.96 1.20

0.42 0.74 0.18

1.78

4.32

3.79

2.17 0.91

0.28 0.15 0.06

4.92 0.12

3.71

6.58

3.54

1.76 1.15

0.21 0.29 0.10

50.18 1.14 15.26 2.86

8.05 0.19

6.78

9.41

2.56

1.04 1.46

0.43 0.27 0.18

38.29 0.09 1.82

3.59

9.38 0.71

37.94 1.01

0.20

0.08 4.59

0.25 0.20 0.43

60.18 1.06 15.61 3.14

3.88 n.a.

3.56

5.17

3.91

3.19 n.a.

n.a.

Gabbro

50.14 1.12 15.48 3.01

7.62 0.12

7.59

9.58

2.39

0.93 0.75

0.11 0.24 0.07

Granite

71.30 0.31 14.32 1.21

1.64 0.05

0.71

1.84

3.68

4.07 0.64

0.13 0.12 0.05

Granodiorite

66.09 0.54 15.73 1.38

2.73 0.08

1.74

3.83

3.75

2.73 0.85

0.19 0.18 0.08

Hawaiite

47.48 3.23 15.74 4.94

7.36 0.19

5.58

7.91

3.97

1.53 0.79

0.55 0.74 0.04

Latite

61.25 0.81 16.01 3.28

2.07 0.09

2.22

4.34

3.71

3.87 1.09

0.57 0.33 0.19

Monzonite

62.60 0.78 15.65 1.92

3.08 0.10

2.02

4.17

3.73

4.06 0.90

0.19 0.25 0.08

Mugearite

50.52 2.09 16.71 4.88

5.86 0.26

3.20

6.14

4.73

2.46 1.27

0.87 0.75 0.15

Nephelenite

40.60 2.66 14.33 5.48

6.17 0.26

6.39

11.89 4.79

3.46 1.65

0.54 1.07 0.60

Nepheline syenite

54.99 0.60 20.96 2.25

2.05 0.15

0.77

2.31

8.23

5.58 1.30

0.17 0.13 0.20

Norite

50.44 1.00 16.28 2.21

7.39 0.14

8.73

9.41

2.26

0.70 0.84

0.13 0.15 0.18

Obsidian

73.84 –

0.79 –

0.49

1.52

3.82

3.92 0.53

–

Peridotite

42.26 0.63 4.23

3.61

6.58 0.41

31.24 5.05

0.49

0.34 3.91

0.31 0.10 0.30

Phonolite

56.19 0.62 19.04 2.79

2.03 0.17

1.07

2.72

7.79

5.24 1.57

0.37 0.18 0.08

Pumice

70.38 –

1.50 –

0.48

1.56

3.70

4.10 –

3.62 –

Pyroxenite

46.27 1.47 7.16

4.27

7.18 0.16

16.04 14.08 0.92

0.64 0.99

0.14 0.38 0.13

Rhyodacite

65.55 0.60 15.04 2.13

2.03 0.09

2.09

3.62

3.67

3.00 1.09

0.42 0.25 0.21

Rhyolite

71.30 0.28 13.27 1.48

1.11 0.06

0.39

1.14

3.55

4.30 1.10

0.31 0.07 0.05

Syenite

58.58 0.84 16.64 3.04

3.13 0.13

1.87

3.53

5.24

4.95 0.99

0.23 0.29 0.28

Tephrite

47.80 1.76 17.00 4.12

5.22 0.15

4.70

9.18

3.69

4.49 1.03

0.22 0.63 0.02

Tonalite

61.52 0.73 16.48 1.83

3.82 0.08

2.80

5.42

3.63

2.07 1.04

0.20 0.25 0.14

Trachyandesite

58.15 1.08 16.70 3.26

3.21 0.16

2.57

4.96

4.35

3.21 1.25

0.58 0.41 0.08

Trachybasalt

49.21 2.40 16.63 3.69

6.18 0.16

5.10

7.90

3.96

2.55 0.98

0.49 0.59 0.10

Trachyte

61.21 0.70 16.96 2.99

2.29 0.15

0.93

2.34

5.47

4.98 1.15

0.47 0.21 0.09

13.00 1.82

15.82 1.42

0.30 n.a.

–

–

–

Losses on ignition at 120°C Clarke, F.W.; and Washington, H.S. The Composition of the Earth’s Crust U.S. Geol. Survey, Profess. Paper 127 117 p. (1924).

Igneous Rocks

Table 13.18. Deposits depth location

13

Depth location in the Earth’s crust

Rock familly

Texture

Surface (e.g., lava flows, volcanoes)

Volcanic igneous rocks (Vulcanites)

Hyaline, microlitic

Mid-depth (e.g., veins)

Hypovolcanic igneous rocks Periplutonic igneous rocks

Aphanitic, doleritic, porphyritic

Deep deposits (e.g., intrusives)

Plutonic igneous rocks (Plutonites)

Phaneritic, phorphyroid, pegmatitic

13.4.4 General Classification of Igneous Rocks The actual mineralogical composition of an igneous rock can be based on the microscopic surface area fraction estimation of mineral species present in a thin section of a rock sample. The easiest classification scheme for the igneous rocks uses first the coloration of the rock described previously (i.e., fraction of dark minerals), then the most abundant rock-forming minerals in the rock, and finally the texture as the basis for naming. There are eight common names to remember, four intrusive rocks and four extrusive rocks. From the most acid to the most alkaline, the intrusive rocks are: granite, diorite, syenite, and gabbro. The corresponding extrusive rock names with similar composition and mineralogy are: rhyolite, trachyte, andesite, and basalt. The remaining names are applied to ultrabasic rocks with a very low silica content: peridotite, pyroxenite, and anorthosite. A very simple classification of igneous rocks is reported in Table 13.19. For a more quantitative and rigorous identification of igneous rocks excluding ultramafic rocks, the reader is recommended to refer to the most comprehensive and accurate classification of igneous rocks created by the International Union of Geological Sciences (IUGS): Subcommission on the Systematics of Igneous Rocks led by the Swiss petrologist Albert L. 6,7,8,9 Streckeisen . Streckeisen’s diagrams are now accepted by geologists worldwide as a classification of igneous, especially plutonic rocks (phaneritic rocks). This classification is based on modal analysis. The rock mineralogical composition is located inside a double triangle or QAPF-diagram. The acronym, QAPF, stands for Quartz, Alkali feldspars, Plagioclases, and Feldspathoid or Foid. Therefore, the vertices represent quartz (Q), alkali feldspars (A), feldspathoids (F), and potassic feldspars (P) respectively. Where Q, A, P and F are mass percentages normalized, i.e., recalculated so that their sum is 100%. QAPF diagrams are mostly used to classify plutonic rocks (cf. Figures 13.4 and 13.5), but are also used to classify volcanic rocks (cf. Figure 13.6) if modal mineralogical compositions have been determined.

6

7

8

9

899

Streckeisen, A.L. Classification of the Common Igneous Rocks by Means of their Chemical Composition: A provisional Attempt Neues Jahrbuch fur Mineralogie, Monatshefte H1 (1976) H1–15. Streckeisen, A.L. Classification and Nomenclature of Plutonic Rocks. Recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks. Geologische Rundschau. Internationale Zeitschrift für Geologie, 63 (2) (1974) 773–785. Streckeisen, A.L. IUGS Subcommission on the Systematics of Igneous Rocks. Classification and Nomenclature of Volcanic Rocks, Lamprophyres, Carbonatites and Melilite Rocks. Recommendations and Suggestions. Neues Jahrbuch für Mineralogie, Abhandlungen, 141 (1978) 1–14. Streckeisen, A.L. Classification and nomenclature of volcanic rocks, lamprophyres, carbonatites and melilitic rocks IUGS Subcommission on the Systematics of Igneous Rocks. Recommendations and suggestions. International Journal of Earth Sciences, 69 (1) (1980) 194–207.

Rocks and Meteorites

Ca-Plagioclases (i.e., labrador, bytownite, anorthite) An50-100

In bold character: phaneritic rocks

Holomelanocrate Non present or rare (i.e., dark)

Melanocrate

Mesocrate

Na-Plagioclases (i.e., albite oligoclase, andesine) An0-50

Orthoclases (i.e., orthose, and microcline)

Hololeucocrate (i.e., white)

Leucocrate

Feldspars group

Coloration

3.5 to 4.3

Tholeite (n.a.)

2.80 to 3.25 Quartz gabbro (n.a.)

Dacite (65.01)

2.80 to 2.90 Tonalite (61.52)

Rhyolite (72.82)

Basalt (49.20)

Gabbro (50.14)

Andesite (57.94)

Diorite (57.48)

Trachyte (61.21)

Syenite (58.58)

Basanite (44.30)

Theralite (n.a.)

Tephrite (47.80)

Essexite (n.a.)

Phonolite (56.19)

Nepheline syenite (54.99)

n.a.

Melteigite (n.a.)

Nephelenite (40.60)

Missourite (n.a.)

Nephelenite (n.a.)

Ijolite (n.a.)

Peridotite Pyroxenite (42.26) (46.27) Kimberlite

Pyroxenes

Amphibolite

Amphiboles

Subsaturated Ultrabasic (mafic) (45 wt.%>SiO2)

Feldspathoids Peridots

Feldspars and Feldspathoids

Both quartz and feldspars

Feldspars

Unsaturated (alkaline) (45 wt.%Cc > 3

GP

Poorly graded gravel

Gravels with more than 12% fines

Fines classify as ML or MH

GM

Silty gravel

Fines classify as CL or CH

GC

Clayey gravel

Clean sands with less than 5% fines

Cu ≥ 6 and 1 ≤ Cc ≤ 3

SW

Well-graded sand

Cu Cc > 3

SP

Poorly graded sand

Fines classify as ML or MH

SM

Silty sand

Fines classify as CL or CH

SC

Clayey sand

PI > 7 and plots on or above A-line

CL

Lean clay

PI < 4 or plots below A-line

ML

Silt

Ratio of liquid limit oven dried over not dried below 0.75

OL

Organic clay

PI plots above A-line

CH

Fat clay

PI plots below A-line

MH

Elastic silt

Ratio of liquid limit oven dried over not dried below 0.75

OH

Organic clay

Sands with more than 50% of coarse fraction passes on No. 4

Sands with more than 12% fines

Silts and clays Inorganic with liquid limit less than 50 Organic Silts and clays Inorganic with liquid limit more than 50 Organic

Primary organic matter, dark in color, and organic odor

Organic silt

Organic silt PT

Peat

Notes: Coefficient of uniformity: Cu = D60/D10; Coefficient of curvature: Cc = (D30) /D10 × D60; Plasticity index: PI 2

14.7 Soil Identification In the field a soil can be easily described using the checklist presented in Table 14.22. Table 14.22. Description of soils for engineering purposes according to ASTM D2488 Properties

Description

Group name Percentage in volume of cobbles, boulders or both (vol.%) Percentage by weight of gravel, sand, silt (dry weight basis) Particle-size range

Gravel: fine, coarse Sand: fine, medium coarse

Particle angularity

angular, subangular, subrounded, rounded

Particle shape

flat (width/thickness > 3, elongated

14 Soils and Fertilizers

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Soils and Fertilizers

Table 14.22. (continued) Properties

Description

Maximum particle size Hardness of coarse sand and larger particles Plasticity of fines

nonplastic, low, medium and high

Dry strength

none, low, medium, high, very high

Dilatancy

none, slow, rapid

Toughness Color Odor Moisture Reaction with HCl

Effervescence

Consistency Structure Cementation Local name Geologic

Nature of the bedrock

Others

roots, gypsum

14.8 ISO and ASTM Standards Several international standards for the characterization of soils were developed by standardization bodies in several countries; among them the standards from the International Organization for Standardization (ISO) and the American Society for Testing and Materials (ASTM) are well known. These are briefly listed in Tables 14.23 and 14.24. (continued) Table 14.23. ISO standards for the characterization of soils ISO Standard

Title

ISO 11264

Soil quality – Determination of herbicides. Method using HPLC with UV-detection.

ISO/AWI 23909

Soil quality – Sub sampling of bulk samples.

ISO/CD 17512-1

Soil quality – Avoidance test for testing the quality of soils and effects of chemicals on behavior. Part 1: Test with earthworms (Eisenia fetida and Eisenia andrei).

ISO/CD 17924

Soil quality – Bioavailability of metals in contaminated soil. Physiologically based extraction method.

ISO/CD 18512

Soil quality – Guidance on long and short term storage of soil samples.

ISO/CD 19492

Soil quality – Guidance on leaching procedures for subsequent chemical and ecotoxilogical testing of soils and soil materials. Influence of pH on leaching with initial acid/base addition.

ISO/CD 19730

Soil quality – Extraction of trace elements using ammonium nitrate solution.

ISO and ASTM Standards

959

Table 14.23. (continued) ISO Standard

Title

ISO/CD 23161

Soil quality – Determination of selected organotin compounds. Gas-chromatographic method.

ISO/CD 23611-3

Soil quality – Sampling of soil invertebrates. Part 3: Sampling and soil extraction of enchytraeids.

ISO/CD 23611-4

Soil quality – Sampling of soil invertebrates. Part 4: Sampling, extraction and identification of free-living stages of terrestrial nematodes.

ISO/DIS 11269-2

Soil quality – Determination of the effects of pollutants on soil flora. Part 2: Effects of chemicals on the emergence and growth of higher plants.

ISO/DIS 11464

Soil quality – Pretreatment of samples for physico-chemical analyses.

ISO/DIS 15952

Soil quality – Effects of pollutants on juvenile land snails (Helicidae). Determination of the effects on growth by soil contamination.

ISO/DIS 18287

Soil quality – Determination of polycyclic aromatic hydrocarbons (PAH). Gas chromatographic method with mass spectrometric detection (GC-MS).

ISO/DIS 19258

Soil quality – Guidance on the determination of background values.

ISO/DIS 20280

Soil quality – Determination of arsenic, antimony and selenium in aqua regia soil extracts with electrothermal or hydride-generation atomic absorption spectrometry.

ISO/DIS 21268-1

Soil quality – Leaching procedures for subsequent chemical and ecotoxicological testing. Part 1: Batch test using a liquid to solid ratio of 2 l to 1 kg.

ISO/DIS 21268-2

Soil quality – Leaching procedures for subsequent chemical and ecotoxicological testing of soil and soil materials. Part 2: Batch test using a liquid to solid ratio of 10 l/kg dry matter.

ISO/DIS 21268-3

Soil quality – Leaching procedures for subsequent chemical and ecotoxological testing of soil and soil materials. Part 3: Up-flow percolation test.

ISO/DIS 22155

Soil quality – Gas chromatographic quantitative determination of volatile aromatic and halogenated hydrocarbons and selected ethers. Static headspace method.

ISO/DIS 22892

Soil quality – Guidelines for the identification of target compounds by gas chromatography/mass spectrometry.

ISO/DIS 23470

Soil quality – Determination of effective cation exchange capacity (CEC) and exchangeable cations using a hexamminecobalt trichloride solution.

ISO/DIS 23611-1

Soil quality – Sampling of soil invertebrates. Part 1: Hand-sorting and formalin extraction of earthworms.

ISO/DIS 23611-2

Soil quality – Sampling of soil invertebrates. Part 2: Sampling and extraction of microarthropods (Collembola and Acarina).

ISO/FDIS 10381-5 Soil quality – Sampling. Part 5: Guidance on the procedure for the investigation of urban and industrial sites with regard to soil contamination. ISO/FDIS 10381-7 Soil quality – Sampling. Part 7: Guidance on sampling of soil gas. ISO/FDIS 10381-8 Soil quality – Sampling. Part 8: Guidance on sampling of stockpiles. ISO/FDIS 11074

Soil quality – Vocabulary.

ISO/FDIS 20279

Soil quality – Extraction of thallium and determination by electrothermal atomic absorption spectrometry.

ISO/FDIS 23753-1 Soil quality – Determination of dehydrogenase activity in soil. Part 1: Method using triphenyltetrazolium chloride (TTC). ISO/FDIS 23753-2 Soil quality – Determination of dehydrogenase activity in soil. Part 2: Method using iodotetrazolium chloride (INT).

14 Soils and Fertilizers

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Soils and Fertilizers

Table 14.23. (continued) ISO Standard

Title

ISO/WD 17402

Soil quality – Guidance for the development and selection of methods for the assessment of bioavailability in soil and soil-like materials.

ISO/WD 17616

Soil quality – Guidance on the assessment of tests applied in the field of ecotoxicological characterization of soils and soil materials.

ISO/WD 18772

Soil quality – Guidance on leaching procedures for subsequent chemical and ecotoxicological testing of soils and soil materials.

ISO/WD 22036

Soil quality – Determination of trace elements in extracts of soil by inductively coupled plasma atomic emission spectrometry (ICP AES).

Table 14.24. ASTM standards for the characterization of soils ASTM Standard

Title

D1194-94

Standard Test Method for Bearing Capacity of Soil for Static Load and Spread Footings

D3385-94

Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer

D4083-89

Standard Practice for Description of Frozen Soils (Visual-Manual Procedure).

D4429-93

Standard Test Method for CBR (California Bearing Ratio) of SOILs in Place.

D4564-93

Standard Test Method for Density of Soil in Place by the Sleeve Method

D4943-95

Standard Test Method for Shrinkage Factors of Soils by the Wax Method

D4944-98

Standard Test Method for Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester Method

D5298-94

Standard Test Method for Measurement of Soil Potential (Suction) Using Filter Paper

D5520-94

Standard Test Method for Laboratory Determination of Creep Properties of Frozen Soil Samples by Uniaxial Compression

D5522-99a

Standard Specification for Minimum Requirements for Laboratories Engaged in Chemical Analysis of Soil, Rock, and Contained Fluid

D5780-95

Standard Test Method for Individual Piles in Permafrost Under Static Axial Compressive Load

D5918-96

Standard Test Methods for Frost Heave and Thaw Weakening Susceptibility of Soils.

D6035-02

Standard Test Method for Determining the Effect of Freeze-Thaw on Hydraulic Conductivity of Compacted or Undisturbed Soil Specimens Using a Flexible Wall Permeameter

D6519-00

Standard Practice for Sampling of Soil Using the Hydraulically Operated Stationary Piston Sampler

D7099-04

Standard Terminology Relating to Frozen Soil and Rock

E1676-97

Standard Guide for Conducting Laboratory Soil Toxicity or Bioaccumulation Tests With the Lumbricid earthworm Eisenia fetida

Fertilizers

961

14.9 Physical Properties of Common Soils Table 14.25. Physical properties of soils Soil type

Density Specific heat capacity Thermal conductivity –3 –1 –1 –1 –1 (ρ/kg.m ) (cP/J.kg .K ) (k/W.m .K )

quartz sand (dry)

1600

753

0.3347

quartz sand (wet) (4–23 wt.% water)

1700

753

1.6736

sand, northway (4–10 wt.% water)

1700

837

0.8368

sand, quartz (wet) (4–23 wt.% water) 1700

753

1.6736

soil (average)

1300

1046

0.8368

soil, clayey (wet)

1500

2929

1.5062

soil, fine quartz flour (dry)

880

745

0.1674

soil, fine quartz flour (21 wt.% water) 1820

1464

2.2175

soil, loam (dry)

1200

837

0.2511

soil, loam (4–27 wt.% water)

1600

1046

0.4184

soil, sandy (8 wt.% water)

1750

1004

0.5858

soil, sandy dry

1650

795

0.2636

14.10 Fertilizers Fertilizers are intentionally described in this chapter because each year huge tonnages are utilized in agriculture in order to enrich soils artificially for improving the growth of crops and without them soils could not sustain intensive food production. Fertilizers are natural or synthetic chemical compounds containing nutrients essential for the normal growth and development of plants. As a general rule, all the carbon (C) and oxygen (O) necessary to the plants are provided, via photosynthesis, from carbon dioxide and oxygen gases from the atmosphere while rain and ground waters supply all the hydrogen (H) required. All other nutrients must be transformed from minerals and organic matter, by heterotrophic and autotrophic microorganisms respectively, before becoming available for plants. Among them, the three primary nutrients are: nitrogen (N), phosphorus (P) and potassium (K). The secondary nutrients are the three chemical elements: calcium (Ca), magnesium (Mg), and sulfur (S), while the remaining trace elements also called oligoelements or simply micronutrients are for instance: boron (B), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo) and chlorine (Cl). In addition, cobalt (Co) is usually added artificially to fertilizers because it is essential to animal health. In practice, either industrial minerals or chemicals are currently used as feedstocks for manufacturing fertilizers and hence it is necessary to distinguish two groups: (i) (ii)

mineral fertilizers, that consist mainly of natural or manufactured industrial minerals such as saltpeter, potash, phosphate rock; chemical fertilizers that are chemical commodities, such as ammonia and urea, produced as products or by-products by the chemical industry.

Moreover, the above materials can be used individually as straight fertilizers but most of the time several feedstocks are mixed together to obtain a given grade; for that reason they are called mixed fertilizers. Commercial mixed fertilizers are usually categorized into grades

14 Soils and Fertilizers

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Soils and Fertilizers

Table 14.26. Most common NPK fertilizer grades used in agriculture NPK ratios

NPK grades

1÷1 ÷1

15-15-15 16-16-16 17-17-17

1÷2÷3 1÷ 1.5 ÷ 2

5-10-15 6-12-18 10-15-20

1÷ 1÷ 1.5

13-13-21 14-14-20 12-12-17

3÷1÷1 2÷1÷1

24-8-8 20-10-10

Others

15÷5÷20 15÷9÷15

International nomenclature of NPK grades: N = wt.% nitrogen as N (min. 3 wt.%), P = wt.% phosphorus as P2O5 (min. 5 wt.%), K = wt.% potash as K2O (min. 5 wt.%), (N + P + K) >20 wt.%

according to the nitrogen-phosphorus-potassium ratio usually denoted by the three capital letters designation N-P-K, where the three successive numbers denote the mass percentage of nitrogen in wt.% N, the mass percentage of phosphorus in wt.% P2O5, and the mass percentage of potassium in wt.% K2O. If additional numbers are used the fourth figure is the mass percentage of MgO, while the fifth figure is the percentage of CaO. According to international standardized guidelines, NPK fertilizers must contain at least 3 wt.% N, 5 wt.% P2O5, 5 wt.% K2O and at least a total of nutrients above 20 wt.%. The most commonly used NPK ratios and grades are listed in Table 14.26. Hereafter, a brief description of major minerals and chemicals used in fertilizers is given, and for simplicity they are grouped according to the major chemical element they contain.

14.10.1 Nitrogen Fertilizers Usually, in soils heterotrophic microorganisms fix and convert atmospheric nitrogen (N2) – into available mineral nitrogen either as a nitrate anion (NO3 ) or into an ammonium cation + (NH4 ). After plant intake nitrogen compounds are converted into proteins by complex biochemical reactions. Hence, for improving the nitrogen intake of crops, nitrogen-rich feedstocks must be added to soils artificially; these can contain either nitrate or ammonium compounds. Historically, animal manure and bird excreta also called guano were the first nitrogen-rich materials applied to soils. Today, the major industrial minerals used as nitrogen-rich feedstocks are the natural alkali-metal nitrates such as saltpeter (KNO3) and soda niter (NaNO3) both mined from natural brines fields or guano deposits mainly located in South America (Chile, Bolivia), although synthetic inorganic chemicals such as liquid anhydrous liquid ammonia (NH3), calcium nitrate (Ca(NO3)2), ammonium nitrate (NH4NO3) are also extensively used. Finally, organic chemicals such as urea (NH2CONH2) or urea formaldehyde (NH2CONHCH2OH) are also important nitrogen-rich sources. The properties of major nitrogen-rich feedstocks are presented in Table 14.27.

Fertilizers

963

Table 14.27. Nitrogen-rich industrial minerals and synthetic chemicals used in fertilizers (ordered by decreasing nitrogen content) Chemical name (usual name, acronym)

Chemical formula (IUPAC)

Apparent Bulk Nitrogen 3 density density content –3 –3 (ρa/kg.m ) (ρb/kg.m ) (wN/wt.%)

max. solubility in water (s/wt.%)

Market price 4 2005 (US$/tonne)

Anhydrous ammonia NH3 (liquid)

682 (–33°C)

w/o

82.24

47

305–315

Urea

NH2CONH2

1320

n.a.

46.65

50

190–206

Ammonium nitrate (AN)

NH4NO3

1720

720

35.00

79

186–193

Calcium cyanamide (nitrolime)

CaCN2

2290

n.a.

34.97

insoluble

n.a.

Ureaformaldehyde (UFA, ureaform)

NH2CONHCH2OH

n.a.

750

31.10

10–15

n.a.

Ammonium sufate and ammonium nitrate (ASN)

50 wt.% NH4NO3 50 wt.% (NH4)2SO4

1745

720–930

28.10

n.a.

168–181

Ammonium chloride NH4Cl (salmiac)

1523

720–835

26.19

26

n.a.

Calcium and ammonium nitrates (CAN)

50 wt.% Ca(NO3)2 50 wt.% NH4NO3

2040

n.a.

26.04

n.a.

n.a.

Calcium nitrate (nitrocalcite)

Ca(NO3)2

2504

n.a.

17.07

51

n.a.

Sodium nitrate (soda niter)

NaNO3

2260

1120–1280 16.48

42

n.a.

Potassium nitrate (salpeter)

KNO3

2110

1220

12

n.a.

13.85

14.10.2 Phosphorus Fertilizers Among the three major nutrients phosphorus is the least used. In soils phosphorus is ab– sorbed by plants mainly as the dihydrogen phosphate anion (H2PO4 ). After plant intake, the inorganic anion encounters several complex biochemical reactions prior to being finally converted into phospholipids and nucleic acids. The role of phosphorus in the cells of plants is to provide chemical energy which is stored within the strong phosphorus chemical bond. The behavior of phosphorus is unique in soils as it is usually bound to clay minerals and does not move downward with percolating ground waters and hence it accumulates in the top soil. The major phosphorus-rich materials are synthetic chemicals obtained from chemical treatment of phosphate rock, that is, mainly apatite, by concentrated sulfuric acid. The first commercial product is called the superphosphate that consists of a mixture of calcium hydrogen phosphate [Ca(H2PO4)2] and gypsum [CaSO4.2H2O]. A higher grade is concentrated superphosphate that consists of calcium hydrogen phosphate [Ca(H2PO4)2] only. Other chemicals 3 4

Theoretical Fertilizer grade, bagged.

14 Soils and Fertilizers

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Soils and Fertilizers

Table 14.28. Phosphorus-rich industrial minerals and synthetic chemicals used in fertilizers (ordered by decreasing phosphorus content) Commercial name (IUPAC chemical name)

Chemical formula (IUPAC)

Apparent density –3 (ρa/kg.m )

Bulk density –3 (ρb/kg.m )

Phosphorus content as P2O5 (wP2O5/wt.%)

Market 5 price 2005 (US$/tonne)

Ammonium hydrogen phosphate (AHP)

NH4H2PO4

1800

n.a.

66.35

254–265

Calcium phosphate monobasic (calcium dihydrogen phosphate)

Ca(H2PO4)2

2220

n.a.

60.68

n.a.

Concentrated superphosphate (calcium di hydrogen phosphate monohydrate)

Ca(H2PO4)2.H2O

2220

n.a.

56.34

1275–1320

Diammonium hydrogen phosphate (DAHP)

(NH4)2HPO4

1619

n.a.

53.78

225–230

Calcium phosphate dibasic anhydrous (calcium hydrogen phosphate)

CaHPO4

2310

960

48.97

250

Triple superphosphate (mixture of calcium dihydrogen phosphate, hydrogen phosphate and gypsum)

30 wt.% Ca(H2PO4)2.H2O 10 wt.% CaHPO4 45 wt.% CaSO4.2H2O 6 10 wt.% impurities 5 wt.% water

n.a.

800–890

43–50

n.a.

Calcium phosphate tribasic (calcium orthophosphate)

Ca3(PO4)2

3140

n.a.

45.81

860

Superphosphate (mixture of calcium di hydrogen phosphate and gypsum)

40 wt.% Ca(H2PO4)2.H2O 60 wt.% CaSO4.2H2O

n.a.

n.a.

33.9

n.a.

Notes: 1 wt.% BPL = 0.4581 wt.% P2O5

used as phosphorus feedstocks to a lesser extent are ammonium hydrogen phosphate [(NH4)H2PO4], diammonium hydrogen phosphate [(NH4)2(HPO4)2]. The concentration of phosphorus in the fertilizer is either expressed as the mass percentage of phosphorus pentoxide (wt.% P2O5) or for calcium phosphates as bone phosphate of lime (wt.% BPL), that is, the mass percentage of calcium phosphate [wt.% Ca3(PO4)2]. The properties of major nitrogen-rich feedstocks are presented in Table 14.28.

14.10.3 Potassium Fertilizers Potassium is indispensable as a nutrient and it is required in large quantities by most plants. The role of potassium in plants is regulatory and catalytic. Growing plants absorb potassium + as potassium cations K but the metabolic route is still unclear. The major industrial mineral used as potassium feedstock is sylvinite (KCl) also known commercially as muriate of potash. 5 6

Fertilizer grade, bagged. Mainly iron oxides, silica and alumina

Fertilizers

965

Table 14.29. Potassium-rich industrial minerals and synthetic chemicals used in fertilizers (ordered by decreasing potassium content) Chemical name (usual name, acronym)

Chemical formula (IUPAC)

Apparent density –3 (ρa/kg.m )

Bulk density –3 (ρb/kg.m )

K 2O Market price 7 8 content 2005 (/wt.%) (US$/tonne)

Potassium sufate

K2SO4

2660

640–720

66.2

200–210

Potassium chloride (sylvite, muriate of potash)

KCl

1980

1280–2400

52.38 (as K)

115–138

Potassium nitrate (salpeter)

KNO3

2110

1217–1280

46.5

n.a.

Potassium dihydrogen phosphate (potassium phosphate monobasic)

KH2PO4

2340

n.a.

34.5

n.a.

14.10.4 Role of Micronutrients in Soils Micronutrients or oligoelements are trace metals only needed by plants in small quantities usually in the range of 0.001–0.1 kg per hectare per year. The role of each micronutrient in soils is listed in Table 14.30. Table 14.30. Role of micronutrients in soils

7 8

Micronutrient (oligoelement)

Biological role

Boron (B)

Boron fertilization allows the production of seeds. Usually boron is added as boronbearing industrial minerals such as borax (Na2B4O7.10H2O)or colemanite (Ca2B6O11.5H2O) or synthetic chemicals such as boric acid (H3BO3) or disodium octaborate tetrahydrate (Na2B8O13.4H2O) and in a lesser extent spent ground borosilicated glass.

Cobalt (Co)

Cobalt is not established as an essential micronutrient for plant growth but it is intentionally added to improve the animal health.

Copper (Cu)

Copper stimulates crop and seed production. Copper is added as copper sulfate (CuSO4.5H2O) or as ground copper slag.

Iron (Fe)

Iron is required for the synthesis of chlorophyll essential for sustaining the photosynthetic process. Iron is added as natural melanterite or byproduced copperas (FeSO4.7H2O), and in a lesser extent as hematite (Fe2O3), limonite and even pyrite (FeS2).

Manganese (Mn)

Manganese improves the intake of iron and is also involved in biocatalytic processes. Manganese is supplied as natural pyrolusite (MnO2) or synthetic manganous sulfate monohydrate (MnSO4).

Molybdebum (Mo)

Molybdenum is used in plants as catalyst during biochemical processes involving the intake of nitrogen. Molybdenum is added as natural molybdenite (MoS2) or synthetic ammonium heptamolybdate [(NH4)6Mo7O244H2O].

Zinc (Zn)

Zinc is a biochemical catalysts without which improper plant growth occurs. Zinc is added as a mixture of zinc sulfate monohydrate (ZnSO4.H2O) or heptahydrate (ZnSO4.7H2O), zinc sulfide (ZnS) and zinc oxide (ZnO).

Theoretical Fertilizer grade, bagged.

14 Soils and Fertilizers

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Soils and Fertilizers

14.11 Further Reading AUBERT, G.; BOULAINE, J. (1980) La pédologie, 3rd. ed Collection Que sais-je? Presse Universitaire de France (PUF), Paris. BAIZE, D. (2000) Guide des analyses en pédologie, 2nd. ed INRA Éditions, Paris. BAIZE, D.; JABIOL, B. (1995) Guide pour la description des sols INRA Éditions, Paris. BOULAINE, J. (1967) Géographie des sols Coll. SUP-PUF, Paris. BOULAINE, J. (1970) Les sols de France Collection Que sais-je? Presse Universitaire de France (PUF), Paris. BOULAINE, J. (1971) L’agrologie Collection Que sais-je? Presse Universitaire de France (PUF), Paris. BOULAINE, J. (1980) Pédologie appliquée Masson, Paris. BOULAINE, J. (1989) Histoire des pédologues et de la Science du Sol INRA Éditions, Paris. BUOL, S.W.; HOLE, F.D.; McCRACKEN, R.J.; SOUTHARD, R.J. (1997) Soil Genesis and Classification Iowa State University Press. BREWER, R. (1976) Fabric and Mineral Analysis of Soils R.E. Krieger Publishing Company, New-York. CALVET, R. (2003) Le sol, propriétés et fonctions. Tomes 1 et 2 France Agricole, Paris. CHAMAYOU, H.; LEGROS, J.P. (1989) Les bases physiques, chimiques et minéralogiques de la Science du Sol Édition ACCT-CILF-PUF, Paris. CHATELIN, Y (1979) Une épistémologie des sciences du sol Mémoire ORSTOM, n°88, Paris. COLLECTIVE (1998) Keys to Soil Taxonomy, 8th ed United States Department of Agriculture (USDA), Natural Resources Conservation Service, Washington D.C. C.P.C.S (1967) Classification française des sols Doc multigrade, Grignon. DECKERS, J.A.; NACHTERGAELE, F.O.; SPAARGAREN, O.C. (eds.) (1998) World Reference Base for Soil Resources. Introduction Editions ACCO, Leuven/Amersfoort. DEMOLON, A. (1960) Dynamique du sol Dunod, Paris. DOKUCHAEV, V. (1900) Zones verticales des sols, zones agricoles, sols du Caucase Exposition Universelle de 1900 à Paris. Sect. Russe, Editions du Ministère des Finances, Saint-Pétersbourg. DUCHAUFOUR, Ph.; FAIVRE, P.; GUY, M. (1976) Atlas Écologique des Sols du Monde Masson, Paris. DUCHAUFOUR, Ph. (1970) Précis de Pédologie, 3rd ed Masson & Cie, Paris. DUCHAUFOUR, Ph. (1968) L’évolution des sols Masson & Cie, Paris. DUCHAUFOUR, Ph. (1983) Pédologie. Tome 1: Pédogenèse et classification Masson, Paris. DUCHAUFOUR, Ph. (1977) Pédologie. Tome 2: Constituants et propriétés Masson, Paris. DUCHAUFOUR, Ph. (1997) Pédologie: sol, végétation, environnement Collection Abrégés, Masson, Paris. FAO-UNESCO (1987) Soils of the World Food and Agriculture Organization (FAO) and United Nations Educational, Scientific and Cultural Organization (UNESCO), Elsevier Science Publishing, New York, NY. FAO-UNESCO (1988) Revised Legend, Soil Map of the World. World Soil Resources report n°60 Food and Agriculture Organization (FAO), Rome. FRIDLAND, V.M. (1976) Pattern of the Soil Cover Israel Program for Scientific Translation, Jerusalem. GLAZOVSKAYA, M.A. (1983) Soils of the World. Vol.1. Soil Families and Soil Types New Dehli, India. GLINKA, K.D. (1931) Treatise on Soil Science National Science Foundation (NSF), Whashington (Translated from Russian in 1963). HELMS, D.; EFFLAND, A.B.W.; DURANA, P.J. (2002) Profiles in the History of the U.S. Soil Survey Iowa State Press. HENIN, S. (1977) Cours de physique du Sol, tomes I et II ORSTOM, Paris. JENNY H. (1941) Factors of Soil Formation. A System of Quantitative Pedology McGraw-Hill, New York. LAVELLE, P. (2001) Soil Ecology Kluwer, Dordrecht. LOYER, J.Y.; GAUTHEYROU, J.; PANSU, M. (1997) L’analyse du sol. Echantillonnage, instrumentation et contrôle Masson, Paris. LOZET, J.; MATHIEU, C. (2002) Dictionnaire de Science du Sol Lavoisier Tec & Doc., Paris. MARGULIS, H. (1963) Pédologie Générale Gauthier-Villars, Paris. MARGULIS, H., and REVON, A. (1973) Pédologie descriptive Privat Editeur, Paris. MATHIEU, C.; PIELTAIN, F. (2003) Analyse chimique des sols Lavoisier Tec/Doc, Paris. MILLOT, G. (1964) La géologie des argiles Masson, Paris. MUSY, A.; SOUTER, M. (1991) Physique du Sol Collection Gérer l’Environnement. Presses Polytechniques et Universitaires Romandes, Lausanne. PANSU, M.; GAUTHEYROU, J. (2003) L’analyse du sol, minéralogique, organique et minérale Springer-Verlag, Heidelberg. PLAISANCE, G.; CAILLEUX, A. (1958) Dictionnaire des sols La Maison Rustique, Paris. SCHEFFER, F.; SCHACHTSCHABEL, P. (1989) Lehrbuch der Bodenkunde Enke-Verlag, Stuttgart. SEGALEN, P. (1977) Les classifications de sols Editions ORSTOM, Paris. TARDY, Y. (1993) Pétrologie des latérites et des sols tropicaux Masson, Paris. WILDING, L.P.; SMECK, N.E.; HALL, G.F. (1983) Pedogenesis and Soil Taxonomy I. Concepts and Interactions. II. The Soil Orders Elsevier, New York.

Cements, Concrete, Building Stones and Construction Materials

15.1 Introduction Building materials are important man-made structural materials in modern civilization. Today concrete is the most widely used structural material in the world. Actually, the world annual production capacity reaches ca. 1.56 billion tonnes of Portland cement which is converted into 11.5 billion tonnes of concrete, that is, concrete with reinforced steel bars or rebars. Despite that fact that concrete is considerably weaker than steel, it is preferred because: (i) (ii)

concrete exhibits excellent resistance to weathering; freshly prepared concrete can be poured into almost any shape and size and after few hours it solidifies into a hardened and strong mass that acquires its final properties after only 28 days; (iii) concrete is the cheapest building material with an average price of 20 US$/tonne. Concrete must be considered as the first man-made large-scale composite material. Actually, concrete consists of a matrix of cement combined with aggregates, that is, granular materials such as sand, gravel or crushed rock or industrial slags. There are two types of cements: (i) (ii)

hydraulic; nonhydraulic.

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15.1.1 Nonhydraulic Cements Nonhydraulic cements are the most ancient type of cement. Most of these cements derive from the simple calcination of gypsum or calcium carbonates such as limestones. They harden when the calcine obtained is mixed with a given amount of water but the hardened products then produced when put in direct contact with water again are subject to dissolution and hence they are not resistant to water. Gypsum cement is still widely used in modern countries as plaster of Paris for interior applications like insulation panels. The transformation of natural gypsum to the calcium sulfate hemihydrate is obtained by moderate heat treating at 130–150°C and it is described by the following chemical reaction: 2CaSO4.2H2O(s) —> CaSO4 0.5H2O(s) + CaSO4(s) + 3H2O(g)↑ During curing, this reaction is reversed by adding water to gypsum cement and obtaining a hard coherent gypsum aggregate. Unfortunately, it is very soluble in water. A better nonhydraulic cement type is quick lime or simply lime or calcia (CaO), which has been used extensively in Europe and the Middle East since Ancient Times, through the Middle Ages and well into the nineteenth century, and in Central America by the Mayas. Quicklime is obtained from the calcination of limestone in a vertical shaft kiln or rotary kiln by intense heating at 900–1000°C. The calcium carbonate (calcite) of the limestones gives off carbon dioxide leaving quicklime as follows: CaCO3(s) —> CaO(s) + CO2(g)↑ The quick lime reacts exothermically with water (1.14 MJ/kg), and when it is mixed with an excess of water it gives a white slurry consisting of a suspension of calcium hydroxide [Ca(OH)2] in a saturated solution of calcium hydroxide called milk of lime: CaO(s) + H2O(l) —> Ca(OH)2(s) The slurry exhibits a paste consistency and when allowed to cool and dehydrate, it quickly sets and hardens by forming pure hydrated lime or slaked lime [Ca(OH)2]. The mortar made with hydrated lime is not stable over long periods because calcium hydroxide is soluble in water. However, if the exposure to water is controlled, the calcium hydroxide is allowed to react slowly with the carbon dioxide from the air and it forms stable calcium carbonate (calcite): Ca(OH)2(s) + CO2(g) —> CaCO3(s) + H2O(l) For instance, lime mortars that were used in structures during ancient times by the Greeks 1 and Romans were rendered hydraulic by the addition of pozzolan , that is, a volcanic ash rich in reactive silica. Actually, when the pozzolan is added to the limestone before calcination, its silica reacts with calcia to produce a water-resistant cementitious product made of a calcium silicate hydrate referred to by the acronym CSH that is stable upon exposure to water: CaO(s) + SiO2(s) + H2O(l) —> CaSiO3.H2O (= CSH)

15.2 Portland Cement According to the standard ASTM C125 from the American Society for Testing and Materials and the Portland Cement Association (PCA) an hydraulic cement is an inorganic material or 1

Pozzuoli is an Italian town near Naples where volcanic ash was mined.

Portland Cement

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a mixture of inorganic materials that sets and develops mechanical strength by means of chemical reaction with water due to the formation of hydrates and which is capable of hardening even under water. Portland cement is a hydraulic cement composed primarily of hydraulic calcium silicates.

15.2.1 History In England, in the 1700s, it was noticed that certain particular types of limestones containing clay minerals and silica could be calcined and that the product, after grinding and mixing with clear water, would set to a hard cement. This new type of cement was stronger than the cements in previous use at that time, such as the pozzolanic cement. Another important advantage was also noticed by the first users, that, it sets under water and hence, can be used for piers, lighthouse foundations, and canal locks. In reference to this type of cement, the mother limestones were designated as hydraulic limes or water limes. Further investigations demonstrated that mixture of pure limestone with clay and silica sand also produced a natural cement having these valuable properties. Later, in 1824, an Englishman, Joseph Aspdin from Leeds, observed that calcinating at higher temperature a limestone, called Portland stone, extensively used at that time as dimension stone in Great Britain, it was possible to obtain a cement of superior quality, especially strength, in comparison with natural cement. It was the beginning of the well-known Portland cement. Since the nineteenth century, Portland cement has been indispensable for civil engineering applications. In these applications Portland cement is the main ingredient in a castable or moldable mixture of cement with water and aggregates. The reaction produces nodules 5–30 mm in diameter that are called clinker. About 5 wt.% gypsum is added to the clinker to control the early setting and hardening reactions of the cement. The composite is then ground to less than 75 μm in diameter. This process releases large quantities of carbon dioxide (CO2), through burning as well as decomposition of carbonates. The cement industry is responsible for 8% of the world’s industrial production of CO2, and immense efforts are dedicated to reducing this problem.

15.2.2 Raw Materials for Portland Cement Although several variations of commercially manufactured Portland cement exist, Portland cement is usually made from the same raw materials and chemical components. The basic raw materials used for the manufacture of Portland cement depend upon availability at the quarry near the cement plant location, and are commonly limestones, shales, marl, chalk, clays and sand; other materials include industrial by-products such as mill scale and blast furnace slags. However, the particular intimate mixture must have an overall composition with 80 wt.% of low magnesium calcium carbonate, CaCO3, (i.e., such as limestone, marl, or chalk), and about 20 wt.% of clay in form of clays, shale or slag. This chemical composition expressed as oxide in percentage by weight is roughly 75 wt.% CaO and 25 wt.% SiO2. However, another important requirement regarding limestones for the manufacture of Portland cement is that they should contain no more than 3 wt.% MgO (i.e., 5 wt.% MgCO3). Therefore, this obviously excludes dolomites and dolomitic limestones and imposes a narrow selection for carbonate sedimentary rocks.

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15.2.3 Processing of Portland Cement In making Portland cement, the raw materials such as limestone or shale are supplied in a cement factory by silos and intimately mixed with sand, creating a blend, and are transported to the ball mill by a belt conveyor in order to be crushed, proportioned under close chemical control and ground to a fine powder by either a wet or a dry process. Actually, they are four grinding processes which are commonly used to manufacture Portland cement. These range from the dry process, through the semi-dry, and semi-wet, to the wet process. The selection of the appropriate process is determined by the composition of raw material available at the plant location, especially its moisture content. For instance, wet or semi-wet process are used for chalk or clay owing to their higher levels of moisture, while the more modern dry process is achieved for dry materials (i.e., low moisture content) such as limestones. After grinding, the powdered material is then preheated at 260°C and precalcined at 900°C in order to initiate the chemical reactions. The material is then transported to a rotary kiln to be calcined, i.e., high temperature firing in air. Actually, powder is fed into the upper end of a slightly inclined long rotary kiln, rotating at 3.5 revolutions per minute, which is a cylindrical steel reactor vessel, 5 meters outside diameter and 90 meters long lined with refractory bricks or castables. In a typical cement factory the kiln is rated at 4650 tonnes per day. The charge moves gradually down the kiln under gravity from the feed end toward the lower end, where elevated heat is produced by the combustion of coal, oil or natural gas and even powdered scrap tires. During calcination, the maximum temperature can reach 1450–1550°C, and in some regions the charge is partially melted, and it emerges as a vitreous (i.e., glassy) material, i.e., the clinker, mainly composed of calcium silicates and aluminates is a nodular product. After rapid cooling, the clinker is mixed with 2–4 wt.% gypsum, [CaSO4 2H2O] in order to regulate the setting time, and the final mixture is ground in a finish ball mill to a fine powder. The resulting powder is known as Portland cement. The cement is then stored in large silos prior to being dispatched either in: (i) (ii)

bulk quantities by road or by rail; or in sealed bag packed onto pallets.

The average chemical composition of Portland cement is given in Table 15.1. A typical cement factory produces annually about 1,500,000 tonnes of cement type I and II and one tonne of clinker is used to make approximately 1.1 tonnes of Portland cement. Table 15.1. Chemical composition of Portland cement Formula

Average mass fraction (x/wt.%)

SiO2

21.8–21.9

Al2O3

4.9–6.9

Fe2O3

2.4–2.9

CaO

63.0–65.0

MgO

1.1–2.5 (max. 3.0)

SO3

1.7–2.6

Na2O

0.2

K 2O

0.4

H 2O

1.4–1.5

Portland Cement

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15.2.4 Portland Cement Chemistry In cement chemistry, it is common to write the chemical formula of compounds involved in the calcination and hydration reactions by capital letters corresponding to the abbreviation of oxides. These standard symbols are listed in Table 15.2. For instance, the dicalcium silicate or belite can be written C2S. Therefore, it is possible to represent cement composition in a ternary phase diagramm C-S-A (i.e., CaO-SiO2-Al2O3). But most commercial cement compositions are restricted to the subsystem C-C5A3-C2S. 15

Table 15.2. Common letter designation of cement oxide components Oxide (common name)

Formula

Symbol

Silicon dioxide (silica)

SiO2

S

Aluminum sesquioxide (alumina)

Al2O3

A

Iron sesquioxide (haematite)

Fe2O3

F

Iron oxide (wustite)

FeO

f

Calcium oxide (calcia, lime)

CaO

C

Magnesium oxide (magnesia)

MgO

M

Sulfur trioxide

SO3

S

Sodium oxide (soda)

Na2O

N

Potassium oxide (potash)

K 2O

K

Loss on ignition (water)

H 2O

H, W, LOI

Chemistry during clinker formation. During the processing of Portland cement, several chemical reactions can be clearly identified. During calcination, the calcium carbonate (calcite) from the limestone and sometimes from marl gives off carbon dioxide producing free calcium oxide or quicklime (CaO). CaCO3(s) —> CaO(s) + CO2(g)↑ At the same time, clay materials and sand release silica (SiO2), alumina (Al2O3), iron sesquioxide (Fe2O3) and lose their constitutive water (H2O). On melting, these oxides produce, according to the following chemical reactions listed below, four new definite stoichiometric synthetic minerals. 3CaO + SiO2 —> Ca3(SiO5) ≡ C3S 2CaO + SiO2 —> Ca2(SiO4) ≡ C2S 3CaO + Al2O3 —> Ca3Al2O6 ≡ C3A 4CaO + Al2O3 + Fe2O3 —> Ca4Al2Fe2O10 ≡ C4AF Therefore, almost all types of Portland cements contain the same five main synthetic minerals: • Tricalcium silicate named alite with the chemical formula [Ca3(SiO5) ≡ C3S] hydrates

rapidly and hence it is responsible for the initial set and early strength of the cement.

• Dicalcium silicate named belite or larnite with the chemical formula [Ca2(SiO4) ≡ C2S]

hydrates and hardens more slowly than alite and gives to the concrete its late strength beyond one week.

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Cements, Concrete, Building Stones and Construction Materials • Tricalcium aluminate with the chemical formula [Ca3Al2O6 ≡ C3A] hydrates and hardens

the quickest with a highly exothermic reaction that releases a large amount of heat almost immediately and hence it contributes to the early strength of the cement. Moreover, it is responsible for the workability of the mortar and acts as fluxing agent assisting the melting of the clinker during calcination. • Gypsum [CaSO4.2H2O ≡ CSH2] prevents a too rapid setting (i.e., flash setting). Actually, the hydration of C3A without gypsum would cause Portland cement to set almost immediately after adding water. • Tetracalcium aluminoferrite [Ca4Al2Fe2O10 ≡ C4AF] has no significant hydraulic properties and owing to its iron oxide content provide the gray color to cement.

Hence, in the language of ceramists, Portland cement exhibits the general mineralogical composition of 50–55 wt.% C3S; 25 wt.% C2S, 12 wt.% C3A, 8 wt.% C4AF and 3.5 wt.% gypsum. Nevertheless, along with the previous main components, several other compounds can be found in the cement in minute amounts. The impurities are for instance magnesium and alkali metal salts from the fuel ashes and sulfur chemicals from the fuel, incomplete reaction products, weathering products of precursor during storage. The common designations of the synthetic minerals occurring in Portland cement are listed in Table 15.3. Table 15.3. Common designation of synthetic minerals occurring in Portland cement and after hydration Chemical compound

Mineral name

Chemical formula

Symbol

Tricalcium silicate

Alite (monoclinic)

3CaO.SiO2 = Ca3SiO5

C3S

Dicalcium silicate

Belite (larnite) (monoclinic)

2CaO.SiO2 = Ca2SiO4

C2S

Tricalcium aluminate

unamed

3CaO.Al2O3 = Ca3Al2O6

C3A

Tetracalcium aluminoferrite

unamed

4CaO.Al2O3.Fe2O3 = Ca4Al2Fe2O10

C4AF

Tricalcium trialuminum sulfate

unamed

3CaO.3Al2O3.SO3 = Ca3Al3SO15

C3A3S

Calcium sulfate dihydrate

Gypsum (monoclinic)

CaO.SO3.2H2O = CaSO4.2H2O

CSH

Calcium hydroxide

Portlandite (hexagonal)

CaO.H2O = Ca(OH)2

CH

Calcium aluminum hydroxy-sulfate hydrate

Ettringite (hexagonal)

6CaO.Al2O3.3SO3.32H2O = Ca6Al2(SO4)3(OH)12.26H2O

C6AS3H32

Pentacalcium dihydroxisilicate pentahydrate

Tobermorite (orthorhombic)

5CaO.6SiO2.5H2O = Ca5Si6O16(OH)2.4H2O

C5Si6H5

Nonacalcium hydroxisilicate undecahydrate

Jennite (triclinic)

9CaO.6SiO2.11H2O = Ca9Si6O16(OH)8.7H2O

C9S6H11

Chemistry of the hardening of cement. When Portland cement is mixed with water, several chemical reactions occur within minutes and continue over days and weeks. These hydration reactions are mostly responsible of the setting or hardening process of the Portland cement. These reactions begin as the spaces between cement particles are filled with water and they are of the sol–gel type. The important microstructural and mineralogical changes during the hydration process can be summarized as follows. Firstly, most compounds dissolve partially and the solution becomes alkaline because it is rapidly saturated with calcium hydroxide. Within a few minutes, acicular crystals of ettringite (C6AS3H32) form. Also large

Portland Cement

prismatic or tabular crystals of portlandite, that is, calcium hydroxide (CH) appear. Portlandite is stoichiometric and forms large crystals constituting 20–25% of the volume. Then a thin gel layer develops on each cement particle. The gel consists mainly of hydrated calcium aluminates and precipitated calcium hydroxide in the lime-saturated water between the grains. The rate of the reaction is controlled by adding gypsum which acts as a retardant. At this stage, setting is not sufficient to ensure sufficient strength but, owing to the hydration of calcium silicates, after 5 hours hardening produces a little strength and the process continues until the network of microfibrils grows and interconnects. Of the silicates, only the two minerals, C3S and C2S, react with gypsum and added water during the hydration process giving the required strength properties of Portland cement. As a general rule, cement properties can be obtained after a curing of 28 days. The presence of gypsum has an adverse effect on strength and durability. Later, very small crystals of calcium silicate hydrates CSH begin to fill the empty space, formerly occupied by water. C-S-H is not a well defined compound and its composition can vary considerably with temperature, age of hydration and the water:cement ratio, therefore the notation CSH is used. On complete hydration, the approximate composition is C3S2H3. CSH comprises 50–60 vol.% of the paste. The morphology varies from minute fibers to a network The crystal structure is still not resolved but it has some similarities with the chain silicate minerals tobermorite (C5S6H5) and jennite (C9S6H11), both related to wollastonite (CS). CSH has an extremely high surface energy, providing strength through Van der Waals forces. After a few days of hydration, ettringite becomes unstable and decomposes to form monosulfate hydrate (C4ASH12), which has hexagonal plate morphology. Heterogeneity is present at various scales. Pores in CSH are around 5 nm, and capillary voids occur in all sizes and shapes, from a few nanometers to micrometers. In concrete, the introduction of the rock aggregate produces an additional heterogeneity for the matrix and the interfacial transition zone between the aggregate and the cement is the weak link of the paste, because it is composed largely of lowstrength portlandite and ettringite.

15.2.5 Portland Cement Nomenclature The standard ASTM C-150 recognizes eight basic types of Portland cement concrete but there are also many other types of blended and proprietary cements hat are not mentioned here. Among them, type I is made in the greatest quantity. Table 15.4. Portland cement types according to the ASTM C-150 ASTM Type

Description

Compressive Applications strength after 28 days (/MPa)

Type I

Normal or Ordinary Portland Cement (NPC)

42

Type IA

Normal-Air Entraining

Type II

Modified Portland Cement (MPC)

Type IIA

Moderate Sulfate Resistance-Air Entraining

General uses, and hence used where no special properties are required. An air-entraining modification of Type I.

47

Low heat generation during the hydration process. More resistant to sulfate attack than previous type. Used in structures with large cross sections and for drainage pipes where sulfates level are low. An air-entraining modification of Type II

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Table 15.4. (continued) ASTM Type

Description

Compressive Applications strength after 28 days (/MPa)

Type III

Rapid Hardening Portland Cement (RHPC)

52

Type IIIA High Early Strength-Air Entraining

It is used when high early strength is needed. It is has more C3S than Type I cement and has been ground finer to provide a higher surface-to-volume ratio, both of which accelerate hydration. Strength gain is double that of Type I cement in the first 24 hours. An air-entraining modification of Type III

Type IV

Low-heat Portland Cement (LHPC)

34

Because it generates less heat during hydration than type II it is used for massive concrete construction where large heat generation could create issues such as in gravity dams. It contains about half the C3S and C3A and double the C2S of Type I cement. The C3A content must be maintained below 7 wt.%.

Type V

Sulfate-resisting Portland Cement (SRPC)

41

It exhibits a high sulfate resistance, and hence special cement used when severe sulfate attack is possible principally in soils or groundwaters having a high sulfate content. It gains strength at a slower rate than Type I cement. High sulfate resistance is attributable to low C3A content.

15.3 Aggregates Aggregates are various irregularly shaped and inert granular materials with two or more size distributions which are mined from quarries such as sand, gravel, crushed stone, or recovered from industrial wastes such as blast furnace slag, that, along with water and Portland cement, are an essential ingredient in concrete by providing its necessary volume and strength. As a rule of thumb one cubic meter of concrete contains two tonnes of both gravel and sand. For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete. Common aggregate processing consists of crushing, screening, and washing the aggregate to obtain proper cleanliness and gradation. If necessary, a benefaction process such as jigging or heavy media separation can be used to upgrade the quality. Once processed, the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination. Aggregates strongly influence the concrete’s freshly mixed and hardened properties, mixture proportions, and economy. Consequently, the proper selection of aggregates is an important factor. Although some variation in aggregate properties is expected, characteristics that are considered when selecting aggregate are briefly described in Table 15.5. Aggregates, which account for 60–75 vol.% of the total volume of concrete, are divided into two distinct categories: fine aggregates and coarse aggregates described hereafter.

Aggregates

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Table 15.5. Important characteristics when selecting aggregates Parameter

Description

Grading

Grading refers to the determination of the particle-size distribution for aggregate. Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements, workability, pumpability, and durability of concrete. In general, if the water:cement ratio is chosen correctly, a wide range in grading can be used without a major effect on strength. When gap-graded aggregate are specified, certain particle sizes of aggregate are omitted from the size continuum. Gap-graded aggregate are used to obtain uniform textures in exposed aggregate concrete. Close control of mix proportions is necessary to avoid segregation.

Durability

Durability refers to the ability of the aggregate to withstand alkaline conditions existing during the preparation of concrete and resistance against weathering.

Particle shape and surface texture

The particle shape and its surface texture strongly influence the properties of freshly mixed concrete more than the properties of hardened concrete. Rough-textured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. Consequently, the cement content must also be increased to maintain the water:cement ratio. Generally, flat and elongated particles are avoided or are limited to about 15% by weight of the total aggregate.

Abrasion and Abrasion and skid resistance of an aggregate are essential when the aggregate is to be used skid resistance in concrete constantly subject to abrasion as in heavy-duty floors or pavements. Different minerals in the aggregate wear and polish at different rates. Harder aggregate can be selected in highly abrasive conditions to minimize wear. Specific gravity and porosity

The specific gravity measures the volume that graded aggregate and the voids between them will occupy in concrete. The void content between particles affects the amount of cement paste required for the mix. Angular aggregate increase the void content. Larger sizes of well-graded aggregate and improved grading decrease the void content.

Water absorption and surface moisture

Absorption and surface moisture of aggregate are measured when selecting aggregate because the internal structure of aggregate is made up of solid material and voids that may or may not contain water. The amount of water in the concrete mixture must be adjusted to include the moisture conditions of the aggregate.

15.3.1 Coarse Aggregates Coarse aggregates are any particles greater than 4.75 mm (0.19 in), but generally range between 9.5 mm to 37.5 mm (3/8 in and 1.5 in) in diameter. Gravels constitute the majority of coarse aggregates used in concrete with crushed stone such as limestone, basalt, diabase, granite, gravel, blast furnace slag or other hard inert material with similar characteristics making up most of the remainder. Natural gravels are usually dug or dredged from a pit, river, lake, or seabed. Crushed aggregate is produced by crushing quarry rock, boulders, cobbles, or large-size gravel. Recycled concrete is also a viable source of coarse aggregates and has been satisfactorily used in granular subbases, soil-cement, and in new concrete. In some particular applications requiring high density, such as counterweights, dry docks or nuclear radiation shields, the following materials can be used as heavyweight coarse aggregates: crushed cast-iron scrap, heavy minerals and iron ores such as hematite, ilmenite and also barite. By contrast, lightweight aggregates essentially use pumice, lava, slag, shales, cinders from coal, and coke. However, in all cases, aggregate grains must be clean, durable, and free from organic matter and alkali metals.

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15.3.2 Fine Aggregates Fine aggregate consists of natural or manufactured sand with most particles passing through a 3/8-inch (9.5-mm) sieve. The material commonly used in fine aggregates is silica sand. It should be clean, hard, and free from organic matter and alkali metal compounds in the same ways coarse aggregates. Sometimes ground stones, blast furnace slag or other hard materials can replace silica sand partially or totally. Grain sizes must be not less than 95 wt.% passing through sieve no. 4 not less than 10 wt.% passing through sieve no. 50 and finally no more than 5 wt.% passing through sieve no. 100.

15.4 Mineral Admixtures Mineral admixtures are materials that contribute to the properties of hardened concrete through hydraulic or pozzolanic activity. Typical examples are natural pozzolans, fly ash, ground granulated blast-furnace slag, and fumed silica, which can be used individually with Portland or blended cement or in different combinations. These materials react chemically with calcium hydroxide released from the hydration of Portland cement to form cement compounds. These materials are often added to concrete to make concrete mixtures more economical, reduce permeability, increase strength, or influence other concrete properties. Fly ash, the most commonly used pozzolan in concrete, is a finely divided residue that results from the combustion of pulverized coal and is carried from the combustion chamber of the furnace by exhaust gases. Commercially available fly ash is a by-product of thermal power generating stations. Blast-furnace slag, or iron blast-furnace slag, is a metallurgical slag consisting essentially of silicates, aluminosilicates of calcium, and other compounds that are developed in a molten condition simultaneously with the iron in the blast-furnace. Fumed silica fume, also called condensed silica fume and microsilica, is a finely divided residue resulting from the production of elemental silicon or ferro-silicon alloys that is carried from the furnace by the exhaust gases. Silica fume, with or without fly ash or slag, is often used to make high-strength concrete.

15.5 Mortars and Concrete 15.5.1 Definitions Concrete and mortars are composite materials which chiefly consist of two main components: (i) (ii)

a matrix made of a hardened cement, in which, irregularly shaped aggregates, with two or more size distributions (e.g., coarse and fine) are dispersed.

As a general rule, a mortar is a mixture containing fine aggregates, i.e., with a maximum size of 2 mm (e.g., sand), and having a cement:fine aggregate:water mass ratio of 1:3:0.5, while concrete is a mixture made with fine and coarse aggregates, i.e., exhibiting a minimum size of 5 mm (e.g., gravel, crushed stones), and having a cement:fine:coarse aggregate:water mass ratio of 1:2:3:0.5. When additional structural material such as steel reinforcing bars or rebars are added, the concrete is defined as steel reinforced concrete, while when prestressed cables are inserted, concrete is defined as prestressed concrete. As a general rule Portland cement should always

Mortars and Concrete

977

be used for reinforced concrete, for mass concrete and concretes servicing under water. Moreover, many concretes prepared with normal Portland cement show very little gain in compressive strength after 28 days. The concrete mixture can be proportioned in numerous ways: (i)

arbitrary selection based on experience and common practice, such as for instance 1 part of cement, 2 parts of fine aggregate and 4 parts of coarse aggregates (i.e., 1:2:4); (ii) proportioning on the basis of the water:cement ratio; (iii) combining materials on the basis of either the voids in the aggregates or mechanicalanalysis curves in order to obtain the concrete with a maximum density for a given cement content. A properly designed concrete mixture will possess the desired workability for the fresh concrete and the required durability and strength for the hardened concrete. Typically, a mix is about 10–15 wt.% cement, 60–75 wt.% aggregate and 15–20 wt.% water. Entrained air in many concrete mixes may also take up another 5–8 wt.%. The character of the concrete is determined by the quality of the paste. The strength of the paste, in turn, depends on the ratio of water to cement. The water:cement ratio is the weight of the mixing water divided by the weight of the cement. High-quality concrete is produced by lowering the water:cement ratio as much as possible without sacrificing the workability of fresh concrete. Generally, using less water produces a higher quality concrete provided the concrete is properly placed, consolidated, and cured. 2

Table 15.6. Typical concrete mixtures (in wt.%)

Mixture Portland cement Fine aggregate Coarse aggregate Water Air Applications Mix I

15

28

31

18

8

Sidewalk, pavements

Mix II

7

24

51

14

4

Large concrete mass

Mix III

15

30

31

21

3

Mix IV

7

25.5

51

16

0.5

Table 15.7. Maximum allowable water:cement ratios (ACI 613) Application

Severe applications (air-entrained) in air

in fresh water

in sea water

Thin sections

0.49

0.44

0.40

Moderate sections

0.53

0.44

0.40

Heavy sections

0.58

0.49

0.44

15.5.2 Degradation Processes Concrete, like other materials commonly submitted to weathering, such as natural rocks or man-made construction materials, shows degradation as a function of service life; the degradation strongly depends both on the cement type and environmental conditions. As a general 2

Data from Portland Cement Association (PCA)

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Cements, Concrete, Building Stones and Construction Materials

rule, the major degradation processes are: sulfate attack, freezing and thawing, corrosion of reinforcing bars, thermal stresses, acid attack, and phase change. 2– Sulfate attack. Sulfate anions (SO4 ) present in soil, groundwater, seawater, decaying organic matter, acid rain, products from the alteration of pyrite or other sulfidic minerals occurring in aggregates and industrial effluents are known to have an adverse effect on the long-term durability of concrete. Sulfate attack on the hardened cement paste in concrete manifests itself in the form of cracking, spalling, increased permeability, and loss of strength. Therefore, concrete structures exposed to sulfate water must be designed for sulfate resistance. Sulfate attack occurs when sulfate anions penetrate the concrete from the surrounding environment. As the sulfate anions permeate the concrete, they react with portlandite to form gypsum, which is accompanied by a large volume increase (127 vol.%) and causes expansion and cracking according to the reaction scheme: 2–

Ca(OH)2 + SO4 + 2H2O —> CaSO4.2H2O + 2OH

–

For industrial Portland cements, tetracalcium aluminum monosulfate hydrate (C4ASH18), which is a major component of fully hydrated hardened cement, reacts with gypsum to form secondary ettringite (C6AS3H32). This reaction also causes expansion of 57 vol.% of the solid components: Ca4Al2SO4.18H2O + 2CaSO4.2H2O + 12H2O —> Ca6Al2(SO4)3(OH)12.26H2O In the presence of portlandite (CH), the tetracalcium aluminum monosulfate hydrate (C4ASH18) is converted to ettringite when the hydrated cement paste comes into contact with free sulfuric acid from the wet oxidation of sulfides: Ca4Al2SO4.18H2O + 2Ca(OH)2 + H2SO4 + 12H2O —> Ca6Al2(SO4)3(OH)12.26H2O Note that all these reactions involve a large volume increase and hence the formation of gypsum and ettringite by sulfate attack causes internal stresses. Alkali-silica reaction. The second destructive problem is attributed to a reaction of the silica-rich aggregates (e.g., cherts, obsidian, opal, quartzite), and alkalis present in the cement paste. In theory, any aggregate containing silica has the potential to participate in the alkali-silica reaction.

15.6 Ceramics for Construction The ceramics used in standard construction projects are of two types: (i) (ii)

fired ceramics (e.g. brick usually called common brick or face brick); and cast or formed hydraulic cement structures (e.g. regular poured or placed concrete; or pre-cured cement block or cinder block, pre-cast concrete shapes, occasionally glass block or similar ceramic).

However, none of these materials is intended specifically for service under severe chemical exposure, and all are designed for institutional, residence, or similar construction, and other buildings not normally subject to chemical spills. But today, with the acid rain phenomenon and corrosives included in off-gases from various processes, and from the incineration of industrial wastes, they may be exposed to conditions well beyond those of past years.

Building Stones

979

15.7 Building Stones 15.7.1 Limestones and Dolomites Limestone is the general name for a wide variety of calcareous sedimentary rocks made mainly of calcium carbonate while dolomite refers to calcareous rocks with magnesium carbonate content above 45 wt.%. Compared with basalt and granite, limestones are hard rocks –3 of middling density (i.e., 2150–2500 kg.m ) with a low compressive strength of 28–50 MPa. –3 Dolomites have a density ranging between 2800 and 2900 kg.m and exhibit similar mechanical properties to those of limestones. Both rock types are extensively used as building stones, as fluxes in steelmaking, and for the manufacture of lime (CaO), magnesia and dolime (MgO+CaO) in the chemical industry.

15.7.2 Sandstones Sandstones refer to consolidated, siliceous detritic sedimentary rocks. Usually, the main component is quartz grains cemented by amorphous silica; other occasional minerals are –3 feldspars, mica, and clays. The densities of sandstones range from 2240 to 2650 kg.m depending on the porosity, and a higher compressive strength of 70–90 MPa which is superior to that of limestones and dolomites. Sandstones are mainly used as building stones, and silica-rich varieties (i.e., more than 99 wt.% SiO2) such as quartzite are used as source of silica in glass making, and in metallurgy for ferroalloy preparation.

15.7.3 Basalt Basalt is dark-brown phaneritic volcanic igneous rock (see the Rocks and Meteorites section for a precise petrological definition). Its main components are microcrystals of alkali feldspars, pyroxenes and olivine embedded in a volcanic glass matrix. The quantitative chemical analysis usually falls into the following ranges: 45–48 wt.% SiO2, 14–16 wt.% Al2O3, 12–14 wt.% (Fe3O4, Fe2O3, FeO), 10–12 wt.% CaO, 8 wt.% MgO, 6 wt.% (K2O + Na2O), and 2 wt.% TiO2, with –3 traces of Mn and S. Basalt is a dense (i.e., 2880–3210 kg.m ), hard (Mohs hardness 5.5–6) rock, not subject to absorption. Moreover, it exhibits a high compressive strength of 150 MPa, and possesses a modulus of elasticity of 10–12 GPa. Its coefficient of linear thermal expansion is 0.6–0.8 μm/m.K, and its thermal operating limit is 500°C. The material is stated to have excellent resistance to acids except hydrofluoric to which it has only limited resistance, and to a wide range of alkalis and salts. It also has excellent abrasion resistance and finds its greatest use in the lining of hoppers and chutes where both abrasion and chemical resistance are required. Brick are made from this by melting it at 1250°C and casting it in molds. It is made in Europe in the form of bricks, cylinders for lining pipes, and special sectional shapes for lining all kinds of equipment.

15.7.4 Granite Granite and to a lesser extent granodiorite are coarse grained plutonic igneous rocks (see Rocks and Meteorites for a precise petrological definition) primarily composed of silicate minerals such as quartz and feldspars often with small amount of accessory minerals such as

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Cements, Concrete, Building Stones and Construction Materials

micas. Therefore silica, and alumina are the major components of granite. Granite is a very hard and compact rock (e.g., crushing strength about 160–240 MPa) of middling density –3 (i.e., between 2630 and 2800 kg.m ), with a low absorption. It exhibits a very low thermal conductivity, and a coefficient of thermal expansion close to that of acid brick. It has been used in construction since prehistoric times, and where ancient structures have best survived the effects of time and weathering, they have often been made of granite. It is an important building stone. Because of its durability and corrosion resistance, a few decades ago a major steel mill experimented with it as the sole construction material for a continuous pickler, and owing to its fine polish it is used for mill rods in the pulp and paper industry. Table 15.8. Physical, mechanical and thermal properties of selected building stones and construction materials (continued) Construction materials

Density Young’s Compressive Modulus of Thermal Specific heat Linear –3 (ρ/kg.m ) modulus strength rupture conductivity capacity thermal –1 –1 –1 –1 (E/GPa) (σc/MPa) (MoR/MPa) (k/W.m .K ) (cP/J.kg .K ) expansion coeff. –6 –1 (αL/10 K )

Andesite

2420–2900 6–44

Basalt

2880–3210 35–109

196–490

Concrete (1–4 dry)

2300

21–30

21–35

Concrete (cinder)

1600

30

Concrete (lightweight)

950

30

Concrete (stone; 1-2-4 mix)

2300

30

Concrete (highstrength)

30

0.6–1.26 4.7–6

18

7

0.92–2.6

627,950

0.75

657

0.34

657

0.21

657

1.46

880

5.4

43–131

Concrete 4000–6500 30 (heavyweight) Conglomerate 2200–2700

118–127

2.09

Diabase

2800–3100 68–105

177–265

1.17

698–753

Dolomite

2760–2840 70–91

49–171

2.93–5.0

728–921

Gneiss

2500–2900 13–35

79–323

2.1–3.4

736–816

Granite

2640–2760 40–68

36–372

10–20

2.51–3.97

775–837

6–20

Gravel (dry)

1400–1700

Limestone (hard)

2100–2760 18–78

39–137

7.4–12

1.67–2.15

907–921

9–22

Limestone (soft)

1200–2200 8

2–52

0.84–3.38

630–907

2.5–9.0

Marble

2680–2850 23–74

30–255

2.51–3.72

794–879

5.4–27

0.43

1088

2.92–8.04

698–1105

0.27–0.34

753–799

Plaster 1250 (molded, dry) Quartzite

2640–2730 56–79

Sand (dry)

1600–1700

25–315

9.8–19.6

6–12

16–20

Further Reading

981

Table 15.8. (continued) Construction materials

Density Young’s Compressive Modulus of Thermal Specific heat Linear –3 (ρ/kg.m ) modulus strength rupture conductivity capacity thermal –1 –1 –1 –1 (E/GPa) (σc/MPa) (MoR/MPa) (k/W.m .K ) (cP/J.kg .K ) expansion coeff. –6 –1 (αL/10 K )

Sandstone (hard)

2140–2650 39

39–247

12

4.2–4.6

928–963

5–19

Sandstone (medium)

2000–2140 13–16

16–34

5

1.30–4.18

745

5–19

Sandstone (soft)

1600–2000 0.98

7.8–16

Schist

1500–3200 15–70

Slate

2700–2950 10–110

2.5

1.0–1.30

728

59–307

0.58–3.26

774

59–304

0.9–3.3

711

5–19

10–12

15.8 Further Reading BARON, J.; SAUTEREY, R.(eds.)(1982) Le béton hydraulique. Presses de l’École Nationale des Ponts et Chaussées (ENPC), Paris. BOYTON, R.S. Chemistry and Technology of limestone, 2nd. ed. Wiley Interscience, New York. CORMON, P. (1977) La fabrication du béton. Éditions Eyrolles, Paris, 200 p. DREUX, G. (1981) Nouveau guide du béton. Éditions Eyrolles, Paris, 311 p. HOIBERG, A.J. (eds.) (1964–1965) Bituminous materials: Asphalts, Tars and Pitches, Volume 1. and 2. Interscience Publishers, New Jersey, 432 p. and 698 p. MALIER, Y. (1992) Les bétons à hautes performances: caractérisation, durabilité, applications, 2nd. ed. Presses de l’École Nationale des Ponts et Chaussées (ENPC), Paris, 673 p. TAYLOR, H.F.W. (1992) Cement Chemistry, 2nd. ed. Academic Press, London, 475 p.

15 Cements, Concrete, Building Stones …

Timbers and Woods

16.1 General Description Timber could be considered as a typical natural composite material with a highly anisotropic structure. Indeed, this structure has two chief directions both radially and longitudinally corresponding to its botanical organization. Furthermore, superimposed on these two degrees of variability are local effects such as growing conditions. As classifications, the terms hardwood and softwood have no relation to the actual mechanical hardness of the wood. It is only a broad botanical distinction. Hardwoods are generally broad-leaved deciduous trees which carry their seeds in seedcases (i.e., Angiosperms), such as: ash, balsa, beech, greenheart, oak, obeche, and maple, while softwoods are generally coniferous trees (i.e., Gymnosperms) such as: Douglas-fir, yellow pine, larch, spruce, hemlock, red cedar and yew. From a structural-botanical point of view, wood contains many cells. These cells have different functions depending on their location in the tree. Inner cells, located in the heartwood, and in which the reserve materials, e.g., starch, have been removed or converted into resinous substances are mostly dead and provide mechanical support for the tree. Heartwood is generally darker than sapwood, although the two are not always clearly differentiated. Cells located in the sapwood store nutrients and act as conduits for water. Only the cambium, i.e., one-cell-thick layer, located just beneath the bark, contains new growing cells allowing the tree to grow and subdivides the new wood from bark cells. This creates the rings each year. A detailed wood structure with descriptions of both common and botanical subdivisions is presented in Figures 16.1 and 16.2 and in Table 16.1.

984

Timbers and Woods

Figure 16.1. Detailed wood structure: Cross section of white oak tree trunk: a. outer bark (dry dead tissue); b. inner bark (living tissue); c. cambium; d. sapwood; e. heartwood; f. pith; g. wood rays. From U.S. Department of Agriculture (1999) Wood Handbook: Wood as an Engineering Material. USDA Forest Products Society, Madison, WI and reproduced with permission.

Figure 16.2. Detailed wood structure: The principal components of the bole of a typical hardwood. From Mettem, C.J. Structural Timber Design and Technology. Copyright © Longman, Harlow (1986). Reproduced with permission.

Here, wood is considered from a strict mechanical point of view, as a complex fiberreinforced composite composed of long, unidirectionally aligned tubular cellulosic polymer cells in a polymer matrix made of lignin. Cellulose is a naturally occurring carbohydrate and a thermoplastic polymer; it is arranged in long chains to form a framework. A bundle of these long chains is enclosed by both hemicellulose, a short polymer, and lignin, an organic cement that bonds these bundles, or microfibrils, together. Many of these unidirectionally aligned microfibrils compose the inner cell structure. Wrapped around the core is the cell wall consisting of more microfibrils, except that they are randomly oriented. Hence, specification

Properties of Woods

985

Table 16.1. Wood structure Practical subdivision

Botanical subdivisions

Description and biological role

Outer Bark

Epidermis

Protect underlying tissues from mechanical injuries

Inner bark

Periderm Cortex

Periderm cells form when epidermis ruptures due to phloem cells division

Primary phloem Food conducting tissue made of prosenchyma cells that carries the carbohydrates produced by photosynthesis from the leaves to the roots. Secondary phloem Cambium

Cambium

Region where the growth in diameter of the tree takes place

Sapwood

Secondary xylem

Sapwood that contains prosenchyma cells carries water and dissolved mineral cations from roots to inner cells antd it yields new wood every year.

Heartwood

Primary xylem

Heartwood is made of remaining dead cells from ancient sapwood. It forms the strongest part of the tree providing strength and support. It yields lumber and pulp.

Pith

Pith

Original soft tissue around which the first wood growth takes place.

Wood rays

Rays

Band tissue that radiate from pith to phloem and ensure nutrient storage.

of timber is not a simple matter of identification of the species of tree from which the material has been cut. As a general rule, accurate determination of a timber species from small samples of wood is quite impossible by macroscopic examination alone and always requires an accurate microscopic identification by a botanical expert, in particular with tropical timber species.

16.2 Properties of Woods Wood is an orthotropic material, that is, its physical properties are unique and independent in three mutually perpendicular directions: longitudinal, radial, and tangential. Moreover, the physical properties of wood strongly depend on its moisture content (i.e., mass fraction of water). Owing to this strong dependence of properties on moisture content, it is advisable when using timber in some particular applications (e.g., marine, chemical process industry, or foodstuffs) to take figures at maximum moisture content when data are available.

16.2.1 Moisture Content The moisture content of the wood is a dimensionless quantity, denoted M or wM, that corresponds to the mass fraction of water contained in the wood. Hence, it is usually expressed as a mass percentage (i.e., wt.%) of the oven-dry wood. Weight, shrinkage, strength, and other physical properties of wood rely strongly upon its moisture content. In trees, moisture content ranges from 30 wt.% up to 200 wt.% of the mass of wood substance. In softwoods, the moisture content of sapwood is usually greater than that of heartwood, while in hardwoods, the difference in moisture content between heartwood and sapwood depends on the species. Although a live tree contains large amounts of water, when the tree is cut the

16 Timbers and Woods

986

Timbers and Woods

moisture content depends on the relative humidity of the surrounding. The higher the humidity, the more water will remain contained in the dead wood. Wood is commonly grouped into five classes according to the moisture content: (i)

Green – it corresponds to freshly sawn wood or wood that essentially has received no formal drying. (ii) Air-dried – wood having an average moisture content of 25 wt.% or less, with no material over 30 wt.%. (iii) Kiln-dried – wood dried inside a kiln or by some other refined method to an average moisture content specified or understood to be suitable for a certain use. Kiln-dried lumber can be specified to be free of drying stresses. (iv) Partly Air-dried – wood with an average moisture content between 25 and 45 wt.%, with no material over 50 wt.%. (v) Shipping dry – lumber partially dried to prevent stain or mold in brief periods of transit, preferably with the outer 3 mm dried.

16.2.2 Specific Gravity and Density Specific gravity and density are two physical quantities related to important wood attributes such as mechanical strength, shrinkage, paper-forming properties, and cutting forces required in machining. The specific gravity of wood at a given moisture content wM, denoted GM, usually denoted as oven-dry values in tables, is the dimensionless ratio of wood density to the density of water at a specified reference temperature, usually the temperature of its maximum density (i.e., 3.98°C). In practice, it is calculated from the weight (i.e., mass) of the oven-dry wood W0 to the mass of water displaced by the sample at the given moisture condition wM as follows: Gm = W0 /(Wwater · wM) = WM/Wwater This may range from less than 0.34 for balsam poplar (i.e., Populus balsamifera) up to about 0.88 for live oak (i.e., Quercus virginiana). If the specific gravity of wood is known, based on oven-dry weight and volume at a specified moisture content, the specific gravity at any other moisture content between 0 and 30 wt.% can be calculated using the equation: Gm = Gb /(1 – 0.265 a·Gb) where Gm is the specific gravity based on volume at a given moisture content wM in wt.%, Gb is the basic specific gravity based on green volume, and a = (30 – wM)/30, with the condition wM < 30 wt.%. Usually, specific gravities of woods are reported for a moisture content of 12 wt.%. The mass density or simply density of the wood at a given moisture content, wM (usually –3 12 wt.%), denoted by ρm and expressed in kg.m corresponds to the mass of oven-dry wood and its contained water divided by its volume at the same moisture content. It is important to note that density measurements performed on the dry wood substance of several species –3 with a helium pycnometer gave an average density of 1460 kg.m . Like specific gravity, two factors affect the density of wood: (i) (ii)

the species; and its moisture content.

Water content and the type of tree control the density which, in turn, controls the mechanical properties. Hardwoods such as oak, elm, and maple have higher densities than softwoods

Properties of Woods

987

such as pine, spruce, and cedar. In practice, the following formula can be used to find the den–3 sity of wood ρm in kg.m as a function of its moisture content wM expressed in wt.%. ρm(kg.m ) = 1000 · [Gm/(1 + Gm · 0.0009wM)](1 + wM/100) –3

The density of wood, exclusive of water, varies greatly both within and between species. –3 Although the density of most species ranges between 320 and 720 kg.m , the range of density –3 –3 actually extends from about 160 kg.m for balsa to more than 1100 kg.m for tropical wood such as ebony. In practice, comparisons of species or products and estimations of product weight and specific gravity are preferred as a standard reference basis, rather than density.

16.2.3 Drying and Shrinkage Wood is dimensionally stable when the moisture content is greater than the fiber saturation point. Hence, wood swells when it gains water while it shrinks when losing moisture below that point. This shrinking and swelling can result in warping, checking, splitting, and loosening. With respect to shrinkage characteristics, wood is an anisotropic material. It shrinks most in the direction of the annual growth rings (i.e., tangentially), about half as much across the rings (i.e., radially), and only slightly along the grain (i.e., longitudinally). The combined effects of radial and tangential shrinkage can distort the shape of wood pieces because of the difference in shrinkage and the curvature of annual rings. Shrinkage values denoted by the capital letter S with subscript letters v, r, t (i.e., volumetric, radial, tangential) and expressed in percentage from the green to oven-dry condition (0 wt.% moisture content) or green to various air-dry conditions (6, 12 or 20 wt.% moisture content) are the most common properties reported. Estimation of shrinkage from the green condition to any moisture content can be done using the equation: Sm = S0 · [(30 – wM)/30] where Sm is the shrinkage (vol.%) from the green condition to moisture content wM ( xCO2(g) + y/2H2O(l) + uSO2(g) + z/2N2(g) While in dry air, assuming that the theoretical chemical composition of dry air is: 78.08 vol.% N2, 20.95 vol.% O2 and 0.97 vol.% Ar (i.e., a nitrogen to oxygen ratio of 3.727) and that again nitrogen gas is the only nitrogen-containing species present in the combustion products, the overall scheme of the reaction of combustion can be written as follows: CxHyNzOtSu + (x + y/4 + u – t/2)[O2(g) + 3.727 N2(g)] —> xCO2(g) + y/2H2O(l) + uSO2(g) + [3.727(x + y/4 + u – t/2) + z/2]N2(g)

17

Sometimes, a simplified approach is used in engineering textbooks, that simply assumes dry air as a mixture made of 79 vol.% N2 and 21 vol.% O2, hence the simplified nitrogen-tooxygen ratio becomes 3.76. CxHyNzOtSu + (x + y/4 + u – t/2)[O2(g) + 3.76 N2(g)] —> xCO2(g) + y/2H2O(l) + uSO2(g) + [3.76(x + y/4 + u – t/2) + z/2]N2(g)

17.2.1.1 Stoichiometric Combustion Ratios In practice, it is useful to use the ratios of the mass or volume of oxygen or dry air per unit mass or unit volume of fuel. The theoretical equations for calculating the stoichiometric combustion ratios are listed in Table 17.2. Table 17.2. Stoichiometric combustion ratios for organic compounds in pure oxygen and dry air Oxidant Stoichiometric combustion ratios for a fuel CxHyNzOtSu Oxygen mO2/mfuel = 31.9988(x + y/4 + u – t/2)/(12.011x + 1.00794y + 14.00674z + 15.9994t + 32.066u) in kg of oxygen per kg of fuel 3

vO2/mfuel = (RT/P)(x + y/4 + u – t/2)/(12.011x + 1.00794y + 14.00674z + 15.9994t + 32.066u) in m of oxygen per kg of fuel 3

3

vO2/vfuel = (x + y/4 + u – t/2) (for gaseous fuels only) in m of oxygen per m of fuel Dry air

mair/mfuel = 136.40504(x + y/4 + u – t/2)/(12.011x + 1.00794y + 14.00674z + 15.9994t + 32.066u) in kg of air per kg of fuel vair/mfuel = 4.727(RT/P)(x + y/4 + u – t/2)/(12.011x + 1.00794y + 14.00674z + 15.9994t + 32.066u) 3 in m of air per kg of fuel 3

3

vair/vfuel = 4.727(x + y/4 + u – t/2) (for gaseous fuels only) in m of air per m of fuel Note: composition of dry air assumed to be equal to 78.08 vol.% N2, 20.95 vol.% O2 and 0.97 vol.% Ar

17.2.1.2 Low (Net) and High (Gross) Heating Values Therefore either in pure oxygen or dry air, it is possible to apply Hess’s law to the previous combustion equations. The standard molar enthalpy and the internal energy of combustion

Fuels, Propellants and Explosives

1002

Fuels, Propellants and Explosives –1

both expressed in J.mol can be calculated from the standard enthalpies and energies of formation of the products minus that of the reactants as follows:

ΔH°comb = ΔRH° = x Δf H°[CO2(g)] + y/2 Δf H°[H2O(l)] + u Δf H°[SO2(g)] – Δf H°[CxHyNzOtSu] ΔU°comb = ΔRU° = x ΔfU°[CO2(g)] + y/2 ΔfU°[H2O(l)] + u ΔfU°[SO2(g)] – ΔfU°[CxHyNzOtSu] Note that the standard molar enthalpy of combustion corresponds to the heat of combustion at constant pressure Qp, while the standard molar internal energy of combustion corresponds to the heat of combustion at constant volume Qv. The two quantities are related as follows:

ΔH °comb = ΔU °comb + RT ∑jvjΔnj

Since the difference between isochore and isobare heat of reactions is often small, in most –1 cases it can be neglected. Actually, both Qv,and Qp are about several kJ.mol while the addi–1 tional term is J.mol . Usually, it is common in combustion engineering to consider two distinct physical quantities called high and low heating values (i.e., formerly gross and net caloric values). They correspond to the standard specific enthalpy of combustion, that is, the enthalpy per unit mass of fuel. The gross heating value (GHV) or high heating value (HHV) of the fuel corresponds to the specific enthalpy when all water vapor is condensed to the liquid state at standard temperature and pressure conditions (298.15 K and 101.325 kPa) with release of its latent enthalpy of vaporization that must be added to the specific standard enthalpy of combustion, while the low heating value (LHV) or net heating value (NHV) considers that all combustion products remain gaseous and it corresponds to the standard specific enthalpy of combustion alone. The relationship between the two quantities is given below: HHV = LHV + mwater ΔHvaporization

17.2.1.3 Air Excess Usually, a fuel is properly burned with excess air or oxygen to ensure complete combustion and prevent the formation of soot. The excess of air is usually characterized by the air excess ratio defined as: e = (mass of dry air used)/(stoichiometric mass of air required) Therefore, the equation for the reaction of complete combustion of a fuel CxHyNzOtSu in an excess of dry air is given by: CxHyNzOtSu + (1 + e)·(x + y/4 + u – t/2)[O2(g) + 3.76 N2(g)] —> xCO2(g) + y/2H2O(l) + uSO2(g) + (1 + e)·[3.76(x + y/4 + u – t/2) + z/2]N2(g) + e·(x + y/4 + u – t/2)O2(g)

17.2.1.4 Dulong’s Equations and Other Practical Equations The relationship between the high and low heating values of a fuel having the empirical chemical formula CxHyOzSu is given by Dulong’s equations. Note that the negative sign indicates the exothermic character of the combustion according to the international thermodynamic convention, but for most engineering purposes, the enthalpies of combustion, especially HHV and LHV, are usually expressed in the table as positive values: HHV (MJ/kg) = –[32.762 wC + 141.789 (wH – wO/8) – 9.256 wS] LHV (MJ/kg) = –[32.762 wC + 119.961 (wH – wO/8) – 9.256 wS] or in US Customary units: HHV (Btu/lb) = –[14.085 wC + 60.958 (wH – wO/8) – 3.979 wS] LHV (Btu/lb) = –[14.085 wC + 51.574 (wH – wO/8) – 3.979 wS]

Combustion Characteristics

1003

with wC, wH, wS, and wO, the mass fractions of carbon, hydrogen, sulfur and oxygen in the fuel obtained from the ultimate chemical analysis of the fuel or that can be easily calculated from the empirical chemical formula as follows: wC = 12.011x/(12.011x + 1.00794y + 15.9994z + 32.066u) wH = 1.00794y/(12.011x + 1.00794y + 15.9994z + 32.066u) wO = 15.9994z/(12.011x + 1.00794y + 15.9994z + 32.066u) wS = 32.066u/(12.011x + 1.00794y + 15.9994z + 32.066u) For an industrial gaseous fuel (e.g., natural gas, syngas, producer gas and water gas) containing carbon monoxide, hydrogen, methane, ethane and acetylene, the high and low heating values can be calculated with the following two equations based on the volume or mole fraction of each gas: 3

HHV (MJ/m ) = –[12.75xH2 + 12.63xCO + 38.82xCH4 + 63.41xC2H4 + 58.57xC2H2] 3

LHV (MJ/m ) = –[10.78xH2 + 12.63xCO + 35.88xCH4 + 59.46xC2H4 + 59.49xC2H2] 17

17.2.1.5 Adiabatic Flame Temperature The adiabatic flame temperature is calculated for powdered solid fuel and liquid and gaseous fuel assuming that the standard enthalpy of the reaction is entirely absorbed adiabatically in the entire mass of combustion products (i.e., ashes, residues, and flue gases) exhibiting an –1 –1 average specific heat capacity cP in J.K .kg . ΔTflame = (ΔQ – δQ)/mfuelcP where δQ represents the fraction of heat of combustion absorbed or loss during phase changes of combustion products (i.e., crystallographic transitions, fusion, vaporization, and sublimation) and also ionization processes occurring in the temperature range (i.e., between room temperature and the flame temperature): δQ = ∑imiΔhtranisition + ∑jmjΔhfusion + ∑kmkΔhvaporization + ∑lmlΔhsublimation + ∑pmpΔhionization

17.2.1.6 Wobbe Index for Gaseous Fuels In the particular case of gaseous fuels when, for technical or economical reasons, it is necessary to replace one gas by another using the same burner piping and control, several parameters, such as the heat content, burner stability, and oxidant, must remain unchanged to –3 ensure safe interchangeability. The Wobbe index (WI) expressed in MJ.m is used especially to evaluate the interchangeability of two gaseous fuels with respect to mass and heat flow rate. It is defined as follows: 1/2

WI = H0/(d0) = HS/(dS) with H0 HS d0 dS

1/2

–3

high heating value of the original fuel in MJ.m , –3 high heating value of the substitute fuel in MJ.m , specific gravity of the original fuel versus air, specific gravity of the substitute fuel versus air.

When both the original and substitute fuels have the same Wobbe index no major change in gas handling equipment and piping is necessary. Finally, combustion calculations regarding common hydrocarbons and other organic fuels require accurate experimental data. Therefore, the usual data required for these computations are reported in Table 17.3.

Fuels, Propellants and Explosives

1004

Fuels, Propellants and Explosives

Table 17.3. Thermodynamic properties of combustion products required in fuel calculations Combustion product

ΔH0f,298K

Δh0f,298K1

S0f,298K

Tempera- Molar heat capacity (CP/J.K–1.mol–1) ture range Cp = A + BT + CT 2 + DT 3 + E/T 2

(/kJ.mol–1) (/kJ.kg–1) (/J.K–1.mol–1) (/K) carbon dioxide (g)

A

B

C

D

E

–393.5224 –32.7635

213.676

298–1200 24.99735

55.18696 –33.69137 7.948387

carbon monoxide (g) –110.5300 –3.94610

197.660

298–1200 25.56759

6.096130 4.054656

sulfur dioxide (g)

–296.810

–9.2562

248.114

298–1200 21.43049

74.35094 –57.75217 16.35534

0.086731

sulfur trioxide (g)

–395.70

–4.94228

256.77

298–1200 24.02503

119.4607 –94.38686 26.96237

–0.117517

water (l)

–285.8304 –141.7894 69.950

298–500

–203.6060 1523.290 –3196.413 2474.455

3.8855326

water vapor (g)

–241.826

500–1700 30.09200

–119.9605 188.726

6.832514 6.793435

–0.136638

–2.671301 0.131021

–2.534480 0.082139

References: Cox, J.D.; Wagman, D.D.; Medvedev, V.A. (1984) CODATA Key Values for Thermodynamics. Hemisphere Publishing Corp., New York, 1984; Chase, M.W., Jr. (1998) NIST-JANAF Themochemical Tables, 4th.ed. J. Phys. Chem. Ref. Data, Monograph 9, Springer, New York.

Having described the main physical quantities related to the combustion of fuels, the description of the most important groups of fuels is presented in the following paragraphs.

17.3 Solid Fuels: Coals and Cokes The major solid fuels consist of natural carbon-rich matter such as wood (see Chapter 16) and peat, synthetic carbonaceous materials such as coke, synthetic carbon-rich materials (e.g., plastics, paper, cardboard) and waste residues which are by-products of industrial processes and human activity (e.g., plastic scrap, municipal wastes, newspapers, sawdust, sewage sludge, sugar cane wastes), and finally fossil fuels mainly coals. Coals originate from the diagenesis in anaerobic conditions (i.e., in the absence of air) of partially decomposed remains of trees, ferns, mosses, vines, and other forms of plants, accumulated under shallow-water which flourished in huge swamps, marshlands, and bogs in the paleozoic era during prolonged periods of humid rain forest climate and abundant rainfall. The precursor of coal was peat, which was formed in the early stage of diagenesis by bacterial and chemical action on the plant debris. Subsequent action of heat and lithostatic pressure during diagenesis metamorphosed the peat into the various ranks of coals. The petrographical classification of coal was carried out historically by microscopical examination of either thin sections under transmitted light or polished sections under reflected light. The first classification was carried out in transmitted light by Thiessen who identified three components termed anthraxylon, attritus, and fusain. Anthraxylon consists of the relic of wood tissues (i.e., decomposed lignine and cellulose). It occurs as thin bands 20 μm thick retaining the original structure of the plant cells. Owing to the presence of decomposition products of lignine, anthraxylon color ranges from orange to dark red depending on the degree of maturation. The attritus consists of: (i) translucent plant debris like anthraxylon but with a smaller size; (ii) opaque granules or black amorphous material; (iii) translucent resins, spores, pollens and algae.

1

Specific enthalpy of combustion reported per unit mass of fuel (i.e., C, H, S)

Solid Fuels: Coals and Cokes

Fusain consists of opaque to translucent irregularly shaped masses. On the other hand, the microscopical examination of polished coal carried out under reflected light, a methodology first initiated in France, led to four different classes also called lithotypes (macerals): vitrain, clarain, durain, and fusain. Each group is characterized by a particular reflectivity and aspect. The major maceral groups are vitrinite, exinite and inertinite. The quantitative characterization of coals and cokes can be performed in several ways. Usually, a classical ultimate chemical analysis provides the elemental chemical composition usually expressed in mass percentages of the major elements such as carbon (C), hydrogen (H) and oxygen (O), minor elements like sulfur (S) and nitrogen (N) and finally metals such as alkali and alkaline-earth metals, aluminum, iron, and vanadium. For most practical uses, the chemical composition of coal and coke are reported using the following technical characteristics: The fixed carbon (FC) represents the mass percentage of free carbon contained in the coal or coke, as received, excluding the carbon contained in volatile matter (hydrocarbon). In theory, it corresponds to the solid residue other than ash obtained after a destructive distillation performed under inert atmosphere. In practice, it is a value calculated, according to standard ASTM D3172, by subtraction of the mass of the volatile matter, ash content and moisture, with the result being expressed as a percentage of the total mass. Volatile matter (VM) represents the mass percentage of compounds contained in the coal or coke given-off upon heating at 950°C but excluding moisture. In practice, it corresponds to the weight loss other than moisture determined on the sample as received according to standard ASTM D3175. Ash content (AC) consists of inorganic residue mostly composed of sodium and potassium carbonate, silica, iron and aluminum sesquioxides remaining after ignition and calcination of a sample of coal or coke according to standard ASTM D3174. Moisture content (MC) is the amount of moisture (i.e., water) contained in a coal or a coke. It is determined by weight loss of the material oven dried at 110°C. Because the terminology used to characterize the chemistry of coal and coke in technical specifications is sometimes confusing, it is useful to clarify the relationships existing between the various terms and these are presented in Table 17.4. Table 17.4. Relationships between the terms used to described the overall chemical composition of coals Total composition

Composition breakdown

Standardized composition

Total carbon (wC)

Free carbon

Fixed carbon (FC)

Volatile hydrocarbons

Volatile matter (VM)

Mineral matter (wM) Water content (wH2O)

Volatile inorganic compounds (H2, N2, H2S) Ashes [(Na, K)2CO3, SiO2, Al2O3]

Ash content (AC)

Hydratation water

Moisture content (MC)

Absorbed water Superficial moisture Relations: wC + wM + wH2O = 100 wt.% FC + VM + AC + MC = 100 wt.%

Moreover, FC, VM, AC and MC can all be calculated on the mineral-matter-free basis us2 ing Parr’s formulae below:

2

Parr, S.W. (1928) The Classification of Coals. Bulletin No. 180, Engineering Experiment Station, University of Illinois.

1005

17 Fuels, Propellants and Explosives

1006

Fuels, Propellants and Explosives

FC (dry, mineral matter free) = 100 × (wC – 1.15wS)/[100 – (wM + 1.08 wA + 0.55wS)] VM (dry, mineral matter free) = (100 – FC) Moisture (dry, mineral matter free) = 100 × (0.000429 HHV – 50wS)/ [100 – (1.08 wA + 0.55wS)] mass percentage of fixed carbon, with wC mass percentage of mineral matter, wM wA mass percentage of ashes, wS mass percentage of sulfur, HHV high heating value in MJ/kg. Finally, heating performances are determined by measuring the high (gross) and low (net) heating values, while properties related to storing and handling can be assessed by measuring apparent and bulk densities, etc. For most engineering purposes, coals are classified according to their overall chemical composition and combustion properties. In North America, the most common standard is that introduced by the American Society for Testing of Materials (ASTM) in the 1930s. This classification establishes four categories of coal (i.e., anthracites, bituminous, subbituminous and lignites) based on gradational properties that depend essentially on the degree of metamorphism to which the coal was subjected while buried. Table 17.5. Classification of coals by rank according to ASTM D388 Class

I Anthracite coals

Group

IV Lignite coals

3 4 5

3

Volatile 4 matter (VM/wt.%)

Mois5 ture

High heating value –1 (HHV/MJ.kg )

Designation

Acronym Dry basis

Moist Dry basis basis

Moist (/wt.%) Dry basis basis

Moist basis

Metaanthracite

ma

> 98

> 92

30

5

34.2

> 32.5

High-volatile B

hvBb

57

53

57

40

7

28.3–34.2 30.2–32.5

High-volatile C

hvCb

54

45

54

40

16

31.0–35.1 26.7–30.2

Subbituminous A subA

55

45

55

38

18

28.3–31.0 24.4–26.7

Subbituminous B subB

56

43

56

35

24

28.8–31.6 24.4–26.7

Subbituminous C subC

53

37

53

36

30

27.4–30.3 22.1–24.4

Lignite A

ligA

52

32

52

35

38

25.1–28.7 19.3–22.1

Lignite B

ligB

52

26

52

32

50

20.2–26.6 14.7–19.3

II Bituminous Low-volatile coals Medium-volatile

III Subbituminous coals

Fixed carbon (FC/wt.%)

According to ASTM D1756 Test method for carbon in coal According to ASTM D3175 Test method for volatile matter in the analysis sample of coal and coke According to ASTM D3173 Test method for moisture in the analysis sample of coal and coke

Solid Fuels: Coals and Cokes

1007

Table 17.6. Selected physical properties of coals and cokes Name

Apparent Bulk Specific heat Coefficient of linear density density capacity thermal expansion –3 –3 –1 –1 –6 –1 (ρa/kg.m ) (ρb/kg.m ) (cP/J.kg K ) (αL/10 K )

Anthracite

1400–1700 700–790

920–960

n.a.

Bituminous coal

1250–1450 600–670

1000–1090

33–45

Coke (Petroleum) 1700–2000 700–1100

1100

3.4–9.0

Graphite (natural) 1800–2200 640

709

1.3–3.8

Lignite

888–920

n.a.

1100–1400 720–880

Table 17.7. Selected properties of solid fuels and waste fuels other than coals Name

Density Ash content Moisture content High or gross heating –3 –1 (ρ/kg.m ) (/wt.%) (/wt.%) value (/MJ.kg )

Animal fats

800–960

0

0

39.5

Brown paper

112

1.0

6.0

16.9

Carboard

112

5

5

16.4

10

4

18.6–20.9

1.5

20

23.3

Charcoal Coffee grounds 400–481 Coke

1700–2000 8–11

Corn cobs

160–240

1.5–3

5–10

33.14 21.6

Cork

192–320

3

10

18

Newspapers

112

6.0

10

17.6

Peat (air-dried)

240–400

5

25–50

12.5–14.7

Peat (mulled)

650–870

5–10

50–55

8.6–12.3

Peat (briquettes)

650–961

10–20

10–12

18.6–20.9

Rags

160–240

2.5

10

17.8

Rice hulls

400–481

7

15

13.9

Rubber waste

990–2000

20–30

PVC scrap

375

4.6

0.6

22–24

Scrap tires (metal free)

920–1200

6

0.5

36.1–38.2

Wheat straw

100–200

10

4

10–14

Wood log

300–400

74–82

0.5–2.2

19.9–21.5

Wood bark

190–320

3

10

21.0

Wood chips

160–480

1

20

20.0

Wood sawdust

160–190

3

10

20.0

Wood wastes 160–192 (50% moisture)

1

50

9.89

23.3

17 Fuels, Propellants and Explosives

Fuels, Propellants and Explosives

17.4 Liquid Fuels The most important liquid fuel is crude oil or petrolatum, derived from the Latin, petrus, stone and oleum, oil, literally oil of stone. Petroleum, like natural gas, originated from degradation of microorganism debris by bacterial and chemical action in anaerobic conditions (i.e., in the absence of air) in sea or brackish water. Petroleum accumulates over geological times in complex underground geologic formations, called reservoirs, made of porous sedimentary rocks (e.g., sandstones) surrounded by overlying and underlying strata of impervious rocks (e.g., clays, rock salt). Petroleum is a brownish-green to black liquid with an extremely complex chemical composition. Actually, it is a mixture of hydrocarbons (mainly alkanes) as well as compounds containing nitrogen, oxygen and sulfur. Most petroleum contains traces of nickel and vanadium. The most important physical and chemical properties of petroleum and its derivatives are: the specific gravity, the kinematic viscosity, the flash point, the high and low heating value and the C, H, N, S, and O content. The specific gravity of petroleum is measured at 60°F for historical reasons and usually expressed as a dimensionless index of density called the degree API (°API) from the American Petroleum Institute and defined as follows: °API = 141.5/SG(60°F) – 131.5 Table 17.8. Selected properties of liquid fuels at 15.66°C (60 °F) Kinematic viscosity at 37.8°C (100°F) –6 –2 (v/10 m.s )

Saybolt second universal at 37.8°C (100°F) (SSU)

Flash point (fp/°C) (closed-cup)

Low or net heating value –3 (LHV/MJ.dm )

High or gross heating value –3 (HHV/MJ.dm )

Distillation temperature range (ΔT/°C)

Benzene (Benzol)

879

30

0.74

31

–11

40.6

42.3

80.09

Cooking oil (used)

840

37

42

200

+315

39.3–43.0

Crude oil (Petroleum)

813–975 43–13 9.7

56

+44

41.9–46.5

Diesel fuel No. 1

856

34

1.3–2.4

n.a.

+38

Ethanol

790

50

0.89

n.a.

+13

Fuel oil

890–955 17–27 2.7

35

+66

43.8–45.1

Gasoline

739

60

0.71

n.a.

–40

44.7

37–185

Kerosene

819

40

2.71

35

+43

46.1

160–285

Methanol

796

46

0.57

n.a.

+11

18.1

64

Naphtha

641

89

n.a.

n.a.

+55

45.5

n.a.

Oil ASTM No. 1

806–845 44–36 1.4–2.2

n.a.

+38

36.4

38.2–39.2 216–288

Oil ASTM No. 2

855–876 34–30 2.0–3.6

33–38

+38

36.9

39.4–39.9 150–400

Oil ASTM No. 4

887–910 28–24 5.8–26.4

45–125

+55

37.1–38.5 40.2–40.7 150–500

Oil ASTM No. 5 (light)

922–934 18

32–65

150–300

+55

38.8

41.0

300–500

Oil ASTM No. 5 (light)

945–950 17

75–162

350–750

+55

39.4

41.6

300–500

Oil ASTM No. 6

959–986 15

198–1980 900–1000 +65

39.8–40.4 41.8–42.5 300–500

Recycled oil

838

37

10–2000

n.a.

+220

+350

40.7

Toluene (Toluol)

866

32

0.40

190

+7

40.9

42.9

–3

API degree (°API)

Liquid fuel Density (/kg.m ) at 15.56°C (60°F)

1008

–6

2

–1

20.92

15.87

43.5

288

23.2

78.5

n.a. 110.8 3

Conversion factors: 1 cSt = 10 m .s (E); 1 Btu/lb = 2.326 kJ/kg; 1 Btu/gal(US) = 278.716 kJ/dm .

Gaseous Fuels

1009

The measurement of the specific gravity of a crude oil expressed in °API and the sulfur content in wt.% S allows the approximate calculation of the high heating value of the liquid fuel using the empirical equations: HHV (MJ/kg) = 24.008 + 18.916/°API – 0.2377wS(wt.%) 3

HHV (MJ/dm ) = (°API + 131.5)·[0.18257 + 0.133682/°API – 0.0016799·wS(wt.%)]/

17.5 Gaseous Fuels Natural gas (NG) is a fossil gaseous fuel composed almost entirely of methane (see Chapter 19), but it also contains small amounts of other gases, including the five alkanes: ethane (C2H6), propane (C3H8), iso- and n-butane (C4H10) and n-pentane (C5H12) along with nitrogen, carbon dioxide and deleterious hydrogen sulfide (H2S). Natural gas is usually found in deep underground reservoirs formed by porous rock such as sandstones and surrounded by impermeable layers of clays and limestones. Natural gas (like petroleum) was formed millions of years ago when plants and sea animals were buried by sand and rock and underwent diagenetic processes under geothermal gradient and lithostatic pressure. With ice, natural gas forms the so-called natural-gas hydrates or clathrates that have two important practical implications: (i)

(ii)

first, clathrates represent a serious issue for gas companies that must transport natural gas in high pressure gas lines over long distances in cold climates (e.g., Alaska, Rus6 sia) . In order to prevent the plugging of the gas line, natural gas must be dehydrated; secondly, methane hydrates have an important role in global warming and climate change. Actually, solid clathrates are stable on the ocean floor at depths below a few hundred meters and will be solid within sea-floor sediments. Masses of methane hydrate, “yellow ice”, have been photographed on the sea floor. Chunks occasionally break loose and float to the surface, where they are unstable and effervesce as they decompose.

The stability of methane hydrates on the sea floor has a whole raft of implications. First, they may constitute a huge energy resource. Second, natural disturbances (and man-made ones, if we exploit gas hydrates and aren’t careful) might suddenly destabilize sea floor methane hydrates, triggering submarine landslides and huge releases of methane. Natural gas is used extensively in residential, commercial and industrial applications. The use of natural gas is also rapidly increasing in electric power generation and cooling, and as a transportation fuel. Commercially natural gas is sold from the wellhead in the production field to customers according to its energy content, the most common units used for natural gas are: the gigajoule 9 6 [1 GJ = 10 J (E)], millions of British thermal units [1 MMBtu = 10 Btu (IT) (E) = 1.055056 GJ] 3 or the thousands of normal cubic feet [1 Mscf or 1 Mcf = 1000 ft (E) = 1.055056 GJ], while 5 consumer bills are usually measured in heat content or therms [1 therm (EEG) = 10 Btu (IT) (E) = 105.5056 MJ]. On such a basis natural gas was priced in 2005 at between 8 and 10 US$/ MMBtu.

6

Paull, C.K.; and Dillon, W.P. (eds.) (2000) Natural Gas Hydrates; Occurrence, Distribution, and Detection. Geophysical Monograph 124, American Geophysical Union. Washington, D.C.

17 Fuels, Propellants and Explosives

Fuels, Propellants and Explosives

Vair/Vfuel

Adiabatic flame temp. in O2 (Tad/°C)

VO2/Vfuel

Chemical composition

Adiabatic flame temp. in air (Tad/°C)

Flammability Flammability limits in air limits in O2 (/vol.%) (/vol.%)

Maximum flame velocity –1 in air (v/m.s )

Gaseous fuel

High or gross heating –3 value (HHV/MJ.m )

Table 17.9. Combustion related properties of gaseous fuels Low or net heating value –3 7 (LHV/MJ.m )

1010

Acetylene

C2H2

56.06

58.02

2632

3072

2.5

81.0

2.67

2.5

11.90

Ammonia

NH3

37.30

45.04

1700

Blast furnace gas

(see notes)

3.01

3.04

1454

n.a.

15.0

28

35

73.5

Butane

n-C4H10

112.4

121.8

1973

2577

1.86

Carbon monoxide

CO

12.64

12.64

1950

2925

Carbureted (see water gas notes)

17.3

18.92

2038

Coke oven gas

(see notes)

58.20

64.82

Ethane Ethylene

C2H4

63.75

C2H4

59.06

Hydrogen

H2

Methane

CH4

15.0

79

0.75 3.57

8.41

1.8

49

0.379

6.5

30.95

12.5

74.2

15.5

94

0.52

0.5

2.38

2788

6.4

37.7

1988

n.a.

4.4

34.0

69.64

1949

2227

3.0

12.5

3.0

66

0.401

3.5

16.67

62.99

1975

3.1

32

3.0

80

0.683

3.0

14.29

22.20

24.06

2105

2974

4.0

74.2

4

94

2.83

0.5

2.38

35.82

39.75

1949

5.1

61

0.338

2.0

9.52

0.33

2.0

9.52

0.66

2643

5.0

15.0

Natural gas (see notes)

30.96– 34.80– 1600– 39.16 1870

2643

4.3

15

Propane

C3H8

86.49

94.01

1967

2832

2.1

10.1

2.3

55

0.390

5.0

23.8

Propylene

C3H6

86.01

91.90

1935

2893

2.4

10.3

2.1

53

0.438

4.5

21.43

Sasol gas

(see notes)

17.23

19.01

1900

Smelter gas

(see notes)

1900

Synthesis gas

(see notes)

1654

17.0

73.7

Town gas

(see notes)

2045

4.8

31.0

Water gas

(see notes)

9.32

4.30

0.26

10.14

Notes: Blast furnace gas: 55–60 vol.% N2 + 23–27 vol.% CO + 1–2 vol.% H2; Coke oven gas: 56 vol.% H2 + 26 vol.% CH4 + 6 vol.% CO; Carbureted water gas: 33.9 vol.% CO + 35.2 vol.% H2 + 14.8 vol.% CH4 + 12.8 vol.%C2H4 + 1.5 vol.% CO + 1.8 vol.% N2; Sasol gas: 48 vol.% H2 + 28 vo.% CH4 + 22 vol.% CO + 1 vol.% N2; Smelter or producer gas: 88–85 vol.% CO + 12–15 vol.% H2; Natural gas: 72–97 vol.% CH4 + 1.7–8 vol.% C2H6 + 2–18 vol.% N2 + 0.1–0.4 vol.% He; Water gas: 50 vol.% CO + 50 vol.% H2.

7

At STP, i.e., 298.15 K and 101.325 kPa

Propellants

1011

17.6 Prices of Common Fuels Table 17.10. Average prices of most common fuel (2006) Fuel

Average value in commercial units

Price per unit mass Price per unit volume Price per unit energy –1 –3 –1 (Pm/US$.kg ) (Pv/US$.m ) (Pe/US$.kWh )

Anthracite coal

100 US$/tonne

0.10

58–71

0.010

Bituminous coal

40 US$/tonne

0.04

28–32

0.004

Crude oil

70 US$/bbl

0.51

440

0.041

Fuel oil No. 2

1.75 US$/gal(US)

0.54

462

0.042

Hydrogen

1.8 US$/100 ft (STP) 7.12

0.65

0.179

Natural gas

10 US$/MMBtu

0.56

0.35

0.034

Petroleum coke

30 US$/tonne

0.03

16

0.003

0.03–0.04

30–40

0.003–0.004

3

Tires (metal free) 30–40 US$/tonne

17 Fuels, Propellants and Explosives

17.7 Propellants Propellants also called propergols are intimate chemical mixtures of a fuel and an oxidizer. This particular type of energetic material acts both as the energy source and the propelling agent, hence, they are extensively used as rocket propellants. Propellants are classified according to their physical state as: (i) liquid propellants; (ii) solid propellants; (iii) hybrid propellants. The two most important properties of rocket propellants are the thrust they impart to the rocket and their specific impulse IS. The thrust T, expressed in newtons, is given by the prod–1 –1 uct of the mass flow rate of propellant in kg.s and the velocity v of exhaust gases in m.s according to the simple equation: T = v ∂m/∂t = m v

IS = m  v/m  gn = v/gn

The specific impulse IS corresponds to the thrust, that is, the force of thrust obtained per unit mass flow rate of propellant released. Specific impulse is characteristic of the type of propellant, however, its exact value will vary to some extent with the operating conditions and design of the rocket nozzle.

17.7.1 Liquid Propellants In a liquid propellant, the fuel and oxidizer are stored in separate tanks, and are fed upon request through a system of pipes, valves, and turbopumps to a combustion chamber where they react chemically to produce thrust. Liquid propellantss offer several advantages compared to their solid propellant counterparts. Actually, by controlling the flow rate of propellant to the combustion chamber, the engine can be throttled, stopped, or restarted. A good liquid propellant exhibits a high specific impulse, that is, with a combustion reaction producing exhaust

1012

Fuels, Propellants and Explosives

gas with high velocities. This implies a high combustion temperature and exhaust gases with small molecular masses. However, other important factors are a high density to reduce the volume of storage tanks and the storage temperature. A propellant with a low storage temperature, i.e. a cryogenic liquid, will require efficient thermal insulation to reduce losses. Other important characteristics are toxicity and corrosivity towards tanks materials. Liquid propellants used in commercial launch vehicles can be classified into three types: (i) petroleum; (ii) cryogenics; (iii) hypergolics.

17.7.1.1 Petroleum-based Propellants Petroleum-based propellants are usually made of high-purity refined kerosene, i.e., n-dodecane (n-C12H26) denoted by the acronym RP-1. The chemical purity of the petroleum is an important parameter as combustion residues (e.g., soot, coke and tar) must be kept at a minimum to prevent clogging. Petroleum fuels are usually used in combination with liquid oxygen as the oxidizer. Despite delivering a lower specific impulse than cryogenic fuels, kerosene performs better than hypergolic propellants.

17.7.1.2 Cryogenic Propellants Cryogenic propellants are liquefied gases stored at very low temperatures. Owing to the low boiling points of most cryogenic propellants, they are difficult to store over long periods of time and proper thermal insulation of the tanks is a critical parameter. Among cryogenic fuels, liquid hydrogen (LH2, b.p. –253°C) is widely used; however, owing to its very low den–3 sity (70 kg.m ), it requires large insulated tanks. The best thermal insulation consists of a multilayered composite material made by alternating aluminum thin films with evacuated foam layers. Moreover, the remaining gaps are filled with helium to prevent deleterious solidification of air. Storage capacity can be greatly increased by using a slush of solid and –3 liquid hydrogen which is denser (80 kg.m ) than liquid hydrogen. The most common cryogenic oxidizer is liquid oxygen (LO2 or LOX, b.p. –183°C) with –3 a density of 1270 kg.m it occupies less volume and this helps to reduce storage costs. Other cryogenic oxidizers are liquid fluorine (LF2, b.p. –188°C), and liquid ozone (LO3, b.p. –112°C). Despite being the most oxidizing substance, fluorine is less used because it is highly corrosive, hazardous and generates toxic byproducts (HF), while ozone can explode if too concentrated in the propellant mixture. Both elements are sometimes used in mixtures with LOX to increase reactivity without compromising safety.

17.7.1.3 Hypergolic Propellants Hypergolic propellants or simply hypergolics are fuels and oxidizers that ignite spontaneously upon intimate contact and hence they do not require any external ignition source. The easy ignition capability of hypergolics makes them ideal propellants for spacecraft maneuvering systems. Because hypergolics are liquids at room temperature, they do not pose the storage problems of cryogenic propellants but, owing to their chemical reactivity they are highly hazardous and pose safety issues during handling. Common hypergolic fuels used in spacecraft are hydrazine, monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH). Hydrazine (NH2-NH2), with a density close –3 to that of water (1004 kg.m ), gives the best performance as a rocket fuel, but its high melting point (m.p. 1.4°C) combined with a poor thermal stability prevent its use as an engine coolant. Methyl hydrazine also called commercially monomethyl hydrazine (CH3-NH-NH2) referred –3 to by the common acronym (MMH) is lighter (866 kg.m ) and more heat-resistant than

Propellants

hydrazine. Moreover, its low freezing point (m.p. –53°C) allows it to be pumped easily. Finally, 1,1-dimethyl hydrazine [(CH3)2N-NH2] also called unsymmetrical dimethyl hydrazine (UDMH) has the lowest freezing point (m.p. –58°C) and a large operating temperature range (b.p. 63.9°C). For these reasons, it is extensively used in large regeneratively cooled engines. A common blend of the above fuels is Aerozine 50, that is, a mixture of 50 wt.% UDMH and 50 wt.% hydrazine. Aerozine 50 is almost as stable as UDMH and provides better performance. It is important to note that hydrazine is also frequently used as a monopropellant (monoergol) in catalytic decomposition engines. In these engines, a liquid fuel decomposes into hot gas in the presence of a catalyst. The decomposition of hydrazine produces temperatures of about 925°C and a specific impulse of about 230–240 seconds. Other liquid propellants of historical interest are ethanol (C2H5OH) in combination with liquid oxygen sometimes diluted with water to reduce flame temperature. Common hypergolic oxidizers are nitrogen tetroxide, fuming nitric acid, and hydrogen peroxide. Nitrogen tetroxide (N2O4), denoted NTO, is less corrosive than nitric acid and provides better performance, but it has a higher freezing point (–9.3°C) and a low boiling point (+21.3°C). Consequently, nitrogen tetroxide is usually the oxidizer of choice when freezing point is not an issue. Concentrated nitric acid is used as fuming acid with a corrosion inhibitor, the mixture is called inhibited red-fuming nitric acid, and referred to by the common acronym IRFNA. It consists of a mixture of concentrated nitric acid (97.5– 98.5 wt.% HNO3) in which 14 wt.% of N2O4 is dissolved imparting the redness of the solution, the remaining 0.6 wt.% being hydrogen fluoride (HF) used as a corrosion inhibitor. Concentrated hydrogen peroxide (H2O2) with at least 85 wt.% H2O2 is called perhydrol or high-test –3 peroxide (HTP). It exhibits performances and density (1450 kg.m ) close to that of fuming nitric acid but it is less hazardous and less corrosive towards tank materials; moreover, it can be stored in high-purity aluminum tanks. However, its high freezing point (–1.0°C for 95 wt.% H2O2) and instability are an issue. Hydrogen peroxide was also used extensively as

Table 17.11. Selected liquid propellants Fuel

Oxidizer

Chemical reaction

Optimized Velocity Specific –1 fuel ratio (/km.s ) impulse (mO/mF) (I/s)

Liquid hydrogen

Liquid oxygen

2H2(l) + O2(l) —> 2H2O(g)

4.00

4.1

370

Petroleum RP-1

Liquid oxygen

2C12H26(l) + 37O2(l) —> 24CO2(g) + 26H2O(g)

2.60

2.9

281

Liquid hydrogen

Liquid fluorine

H2(l) + F2(l) —> 2HF(g)

7.70

4.2

329

Petroleum RP-1 (n-dodecane)

Red-fuming nitric acid (RFNA)

5C12H26(l) + 64HNO3(l) —> 60CO2(g) + 102H2O(g) + 37N2(g)

n.a.

2.4

291

Petroleum RP-1 (n-dodecane)

Hydrogen peroxide (Perhydrol)

C12H26(l) + 37H2O2(l) —> 12CO2(g) + 50H2O(g)

n.a.

2.7

251

Hydrogen peroxide (85 wt.% H2O2) (Monopropellant)

2H2O2(l) —> 2H2O(g) + O2(g) catalyst: KMnO4, NaMnO4 or Ca(MnO4)2

n.a.

1.5

n.a.

Hydrazine

Nitrogen tetroxide

NH2-NH2(l) + 2N2O4(l) —> 2H2O(g) + 6NO(g)

1.30

2.9

292

Hydrazine

Liquid oxygen

NH2-NH2(l) + 2O2(l) —> 2H2O(g) + 2NO(g)

0.91

3.2

312

Ethanol + 25 wt.% water

Liquid oxygen

C2H5OH(l) +3O2(l) —> 2CO2(g) + 3H2O(g)

n.a.

n.a.

261

1013

17 Fuels, Propellants and Explosives

1014

Fuels, Propellants and Explosives

monopropellant (monergol), because in the presence of a catalyst, such as alkali-metal permanganate (e.g., KMnO4 or NaMnO4), it decomposes into oxygen and superheated steam that produces a specific impulse of about 150 s.

17.7.2 Solid Propellants Solid propellant motors are the simplest of all rocket designs. They consist of a casing, usually steel, filled with a mixture of solid compounds (fuel and oxidizer) which burns at a rapid rate, expelling hot gases from a nozzle to produce thrust. When ignited, a solid propellant burns from the center out towards the sides of the casing. The shape of the center channel determines the rate and pattern of the burn, thus providing a means to control thrust. Unlike liquid propellant engines, solid propellant motors cannot be shut down. Once ignited, they will burn until all the propellant is exhausted. There are two families of solids propellants: homogeneous and composite. Both types are dense, stable at ordinary temperatures, and easily storable. Homogeneous propellants are either simple base or double base. A simple base propellant consists of a single compound, usually nitrocellulose, which has both an oxidation capacity and a reduction capacity. Double base propellants usually consist of nitrocellulose and nitroglycerine, to which a plasticizer is added. Homogeneous propellants do not usually have specific impulses greater than about 210 seconds under normal conditions. Their main asset is that they do not produce traceable fumes and are, therefore, commonly used in tactical weapons. Modern composite propellants are heterogeneous powders (mixtures) which use a crystallized or finely ground mineral salt as an oxidizer, often ammonium perchlorate, which constitutes between 60 and 90% of the mass of the propellant. The fuel itself is highly pyrophoric aluminum metal powder. The propellant is held together by a polymeric binder, usually polyurethane or polybutadienes. Additional compounds are sometimes included, such as a catalyst to help increase the burning rate, or other agents to make the powder easier to manufacture. The final product is a rubber-like substance with the consistency of a hard rubber eraser. Composite propellants are often identified by the type of polymeric binder used. The two most common binders are polybutadiene acrylic acid acrylonitrile (PBAN) and hydroxyterminator polybutadiene (HTPB). PBAN formulations give a slightly higher specific impulse, density, and burn rate than equivalent formulations using HTPB. However, PBAN propellant is the more difficult to mix and process and requires an elevated curing temperature. HTPB binder is stronger and more flexible than PBAN binder. Both PBAN and HTPB formulations result in propellants that deliver excellent performance, have good mechanical properties, and offer potentially long burn times. Table 17.12. Solid propellants Commercial Type name (Country)

Composition

Balistite (USA)

Double base homogeneous

Nitrocellulose (51.5%), nitroglycerine (43.0%), plasticiser (1.0%), other (4.5%)

Cordite (Soviet)

Double base homogeneous

Nitrocellulose (51.5%), nitroglycerine (43.0%), plasticiser (1.0%), other (4.5%)

SRB propellant

Composite

Ammonium perchlorate (69.6%) as oxidizer, aluminum metal powder (16%) as fuel, iron oxidizer powder (0.4%) as catalyst, polybutadiene acrylic acid acrylonitrile (12.04%) as rubber-based binder, epoxy curing agent (1.96%)

Explosives

1015

17.8 Explosives Low explosives. These are combustible substances that deflagrate, that is, they exhibit a low –1 detonation velocity ranging from 0.01 to 400 m.s , but do not explode under normal conditions unless they are mixed with high explosives. Low explosives are normally employed as propellants (see Section 17.7). Typical low explosives are smokeless powders and pyrotechnic mixtures. High explosives. High explosives exhibit a detonation velocity ranging from 1000 to –1 9000 m.s . High explosives are conventionally subdivided into three classes according to their sensitivity: (i)

Primary explosives (primers) are extremely sensitive to shock, friction, and heat (e.g., mercury fulminate, lead azide, lead styphnate, tetrazene, and diazodinitrophenol). (ii) Secondary explosives or base explosives, are relatively insensitive to shock, friction, and heat, hence they can burn when exposed to a heat or flame source in small and unconfined quantities (e.g., Dynamite, TNT, RDX, PETN, HMX). (iii) Tertiary explosives (blasting agents) are also insensitive to shock and cannot be reliably detonated by using a primary explosive, and they require a secondary explosive (e.g., liquid oxygen–carbon-black mixtures, and ammonium-nitrate–fuel-oil mixtures or ANFO). These are primarily used in large-scale mining and construction operations. Table 17.13. Common explosive mixture names and compositions Explosive name

Composition

Ammonal

Ammonium nitrate (NH4NO3) and aluminum powder (Al)

ANFO

Ammonium nitrate (NH4NO3) and diesel fuel oil No. 2

Armstrong’s mixture Potassium chlorate (KClO3) and red phosphorus (P4) Black powder

75 wt.% Potassium nitrate (KNO3), 15 wt.% charcoal (C) and 10 wt.% sulfur (S8)

Cheddites

Potassium or sodium chlorates (KClO3, NaClO3) or perchlorates (KClO4, NaClO4) and diesel oil No.2

Dynamite

75 wt.% nitroglycerin mixed with 24.5 wt.% Kieselguhr (i.e., diatomaceous earth) and 0.5 wt.% sodium carbonate (Na2CO3).

Flash powder

Ultrafine metal powder (e.g., Al, Mg) and a strong oxidizer (e.g. potassium chlorate or perchlorate)

Nitrocellulose

Nitrated cellulose that can be a high (guncotton wt.% N) or low explosive (collodion wt.% N) depending on nitration level and conditions.

Oxyliquits

Mixture of carbon black (C) and and liquid oxygen (O2)

Panclastites

Mixtures of organic materials and dinitrogen tetroxide (N2O4)

Plastics

Mixture of powerful explosives such as RDX, PETN, HMX with a plasticizer to yield a plastic and malleable material

Sprengel explosives

Mixtures of potassium chlorate (KClO3) and nitromethane (CH3NO2)

17 Fuels, Propellants and Explosives

Fuels, Propellants and Explosives

Empirical chemical formula

Melting point (mp/°C)

Self-igntition temperature (T/°C)

Specific energy –1 released (Q/MJ.kg )

Detonation –1 speed (Vd/m.s )

Choc sensitivity Julius Peter (/J)

Friction sensitivity Julius Peter (/N)

Diazodinitrophenol (Dehn, 1920)

C6H2O5N4 M = 210.347 [87-81-0]

1630

158

180

6.112

7000

2.0

20

Lead azide (95–97 wt.%) (Curtius, 1891)

Pb(N3)2 M = 291.2 [13424-46-9]

4710– 350 4930

300

1.527

6100

4.0

0.2

40–60

Lead trinitroresorcinate (Lead styphnate) (1920)

Pb(C6HO8N3)·H2O M = 468.0 [15245-44-0]

3100

expl. 265– 280

1.912

5200

2.5–5

8

25–40

Mercury fulminate (Howard, 1800)

Hg(OCN)2 M = 284.62 [628-86-4]

4420

160 185 expl.

1.788

5400

2.2

8

45–50

Tetrazene (1960)

CH5O8N9·H2O M = 188 [31330-63-9]

1700

140 150 expl.

2.753

3

10

50

Blasting power or brisance 7 –1 –2 (B/10 kg.m .s )

Ballistic mortar strength (TNT = 100)

–3

8

Explosive name (acronym, trade names) (discoverer, year)

Density (ρ/kg.m )

Table 17.14. Properties of selected primary explosives

Table 17.15. Properties of selected secondary explosives

1725 169.6

2.630 100 2700 50

Ammonium perchlorate

NH4ClO4 M = 117.490 [7790-98-9]

1950 expl. 225

7.975 150 4850

8

9

–2

Friction sensitivity Julius Peter (/N)

Ballistic mortar strength (TNT = 100)

Blasting power or brisance 7 –1 –2 (B/10 kg.m .s )

Choc sensitivity Julius Peter (/J)

–1

Critical diameter (mm)

Specific energy released –1 (Q/MJ.kg )

–3

–1

9

NH4NO3 M = 80.0 [6484-52-2]

Detonation speed (Vd/m.s )

Ammonium nitrate (AN)

Self-igntition temperature (T/°C)

Empirical chemical formula

Melting point (mp/°C)

Explosive name (acronym, trade names) (discoverer, year)

Density (ρ/kg.m )

1016

353

75–80

12,300

2800

–3

The blasting power or brisance in kg.m .s corresponds to the product of the charge density (ρ) in kg.m times the squared detonation speed (D) in m/s times the dimensionless filling ratio (K) of a borehole as 2 follows: brisance = K·ρ·D . –1 –2 –3 The blasting power or brisance in kg.m .s corresponds to the product of the charge density (ρ) in kg.m times the squared detonation speed (D) in m/s times the dimensionless filling ratio (K) of a borehole as 2 follows: brisance = K·ρ·D .

Explosives

1017

9

7200

Cyclotetramethylene C4H8O8N8 tetranitrate (HMX, M = 296.639 homocyclonite, [2691-41-0] octogene)

1910 286

330

5.674 8

100

150–155 15,237

Cyclotrimethylene trinitramine (RDX, hexogene, cyclonite) (Henning, 1899)

C3H6O6N6 M = 222.12 [121-82-4]

1830 204 260 dec.

5.439 8

8640 4.5

113

120–155 12,413

Hexanitrostilbene (HNS) (Shipp, 1964)

C14H6O12N6 M = 450.231

1740 316

330

5.940 0.4

7120 8

340

120

Nitrocellulose (C6H7O11N3)n 13.45%N (guncotton) [9046-47-3]

1422– 90 1590

100

4.393 20

7300 3

353

105–130 7500

Nitroglycerine (Trinitrine) (Sobrero, 1847)

C3H5O9N3 M = 227.09 [55-63-0]

1600 13.2 217

7.322 24

7700 0.3

360

150

9486

Nitroguanidine (picrite)

CH4O2N4 M = 104.07

1760 232

3.017

7650 50

360

n.a.

9071

Nitromethane (NM)

CH3O2N M = 61.101 [75-42-5]

1132 –28.4 101.2

Nitrotriazolone (NTO, ONTA)

C2H2O3N4 M = 136.35

1910

7700 22

360

Pentaerythritol tetranitrate (PETN, penthrite) (1894)

C5H8O12N4 M = 316.14 [78-11-5]

1773 141.3 220

5.795 2

8350 6.0

44

135–175 12,132

2,4,6-Tetranitroaniline (Tetryl) (Mertens, 1877)

C7H5O8N5 M = 287.45 [479-45-8]

1730 129.4 195

4.250

7560 11

360

115–130

2,4,6-Trinitrobenzene C6H3O6N3 (TNB) M = 213.11 [99-35-4]

1478 121.5 550

12.970

7300

2,4,6-Trinitrophenol C6H3O7N3 (picric acid, melinite) M = 229.11 (Turpin, 1885) [88-89-1]

1763 122.5

4.310 4–9 7645

320

–3

Choc sensitivity Julius Peter (/J)

n.a.

Critical diameter (mm)

w/o

Ammonium nitrate – NH4NO3 and 930 fuel oil (ANFO) 5.6 wt.% diesel (Favier, 1900) fuel oil No. 2

Specific energy released –1 (Q/MJ.kg )

3.760 150 4560 50

1720 180

Self-igntition temperature (T/°C) n.a.

Melting point (mp/°C) w/o

Density (ρ/kg.m )

Blasting power or brisance 7 –1 –2 (B/10 kg.m .s )

NH4C6H2N3O7 M = 246.137 [131-74-8]

Ballistic mortar strength (TNT = 100)

Ammonium picrate

Friction sensitivity Julius Peter (/N)

Empirical chemical formula

–1

Explosive name (acronym, trade names) (discoverer, year)

Detonation speed (Vd/m.s )

Table 17.15. (continued)

7150

9100 5.2

17

232

264

8330

10,324

100

105–110

Fuels, Propellants and Explosives

Fuels, Propellants and Explosives

9

Ballistic mortar strength (TNT = 100)

Blasting power or brisance 7 –1 –2 (B/10 kg.m .s )

100

7856

Trinitrotriaminobenzene (TATB)

1940 440 320 dec.

5.020

353

120

10,556

–3

C6H6O6N6 M = 258.51

Choc sensitivity Julius Peter (/J)

290

Critical diameter (mm)

3.870 5–15 6940 50

Specific energy released –1 (Q/MJ.kg )

1654 80.8 290

Self-igntition temperature (T/°C)

2,4,6-Trinitrotoluene C7H5O6N3 (TNT, tolite, trotyl) M = 227.13 (Haussermann, 1891) [118-96-7]

Melting point (mp/°C)

Friction sensitivity Julius Peter (/N)

Empirical chemical formula

–1

Explosive name (acronym, trade names) (discoverer, year)

Detonation speed (Vd/m.s )

Table 17.15. (continued)

Density (ρ/kg.m )

1018

7658 50

17.9 Further Reading 17.9.1 Fuels and Combustion BAUKAL, C.E.; SCHWARTZ, R.E. (2001) The John Zink Combustion Handbook. CRC Press, Boca Raton, FL. BORMAN, G.L.; RAGLAND, K.W. (1998) Combustion Engineering. McGraw-Hill, Boston. CHOMIAK, J. (1990) Combustion: a Study in Theory, Fact, and Application. Abacus Press, New York. COLLECTIVE (1932) Combustion: a Reference Book on Theory and Practice. 3d ed. The American Gas Association (AGA), New York. COX, G. (1995) Combustion fundamentals of fire. Academic Press, London, Toronto. GARDINER, W.C. (1984) Combustion Chemistry. Springer-Verlag, New York. GLASSMAN, I. (1996) Combustion, 3rd ed. Academic Press, San Diego, CA. GAYDON, A.G.; WOLFHARD, H.G. Flames. Their Structure, Radiation and Temperature. Chapman and Hall Ltd., London. HASLAM, R.T. (1926) Fuels and their Combustion. McGraw-Hill, New York. LEWIS, B.; von ELBE, G. (1961) Combustion, Flames, and Explosions of Gases, 2nd. ed. Academic Press, New York. MONNOT, G. (ed.) (1978) La Combustion dans les fours et les chaudières. Technip, Paris. NIESSEN, W.R. (2002) Combustion and Incineration Processes, 3rd. ed. Marcel Dekker, New York. REED, R.J. (1997) North American Combustion Handbook: a Basic Reference on the Art and Science of Industrial Heating with Gaseous and Liquid Fuels, 3rd ed. North American Mfg. Co., Cleveland, OH. STREHLOW, R.A. (1984) Combustion Fundamentals. McGraw-Hill, New York.

17.9.2 Propellants and Explosives DAVIS, T.L. The Chemistry of Powders and Explosives. Wiley, London. MATHIEU, J.; STUCKI, H. (2004) Military high explosives. Chimia, 58(6)(2004)383–389. MEYER, R.; KÖHLER, J.; HOMBURG, A. (2002) Explosives. Wiley-VCH Weinheim. QUINCHON, J. (1987) Les poudres, propergols et explosifs Tome 1: les explosifs, 2nd. ed. Éditions Lavoisier, TechDoc, Paris. QUINCHON, J. (1984) Les poudres, propergols et explosifs. Tome 2: les nitrocelluloses & autres matières de base des poudres & propergols. Éditions Lavoisier, Tech-Doc, Paris. QUINCHON, J. (1986) Les poudres, propergols et explosifs. Tome 3: les poudres pour armes. Éditions Lavoisier, Tech-Doc, Paris. QUINCHON, J. (1991) Les poudres, propergols et explosifs. Tome 4: les propergols. Éditions Lavoisier, Tech-Doc, Paris. TAYLOR, W. (1959) Modern Explosives. London Royal Institute of Chemistry, London.

Composite Materials

18.1 Definitions A composite material or simply a composite is a duplex and multifunctional material composed of at least two elements working together to produce a structural material with mechanical and physical properties that are greatly enhanced compared to the properties of the components taken separately. In practice, most composites consist of a bulk material called the matrix and a reinforcement material or filler, added primarily to increase the mechanical strength and stiffness of the matrix but also sometimes to modify its thermal conductivity and electrical resistivity. This reinforcement is usually made of fibers (e.g., monofilaments, whiskers) but can also be particulates (i.e., dispersion strengthened and particle reinforced) or even material having a more complex shape (e.g., mesh, ribbon, laminates, etc.). Composites are first classified according to their matrix phase into three major classes: (i)

(ii)

Polymer Matrix Composites (PMCs) are the most common composites and are also known as fiber reinforced polymers, (FRPs) or formerly as resin-based composites (RBCs). These composite materials use a polymer-based resin as the matrix, and a variety of fibers such as E-glass, carbon monofilaments and polyaramide as the reinforcement. Ceramic Matrix Composites (CMCs) are composite materials used when both high temperature service and corrosion resistance to harsh environments are required. These composite materials use a ceramic as the matrix and a reinforcement made of short fibers or whiskers such as those made from silicon carbide (SiC) and boron nitride (BN). Two important subclasses are Glass and Glass–Ceramic-Matrix Composites (GMCs) and Carbon–Carbon Composites (CCCs) respectively.

Composite Materials

(iii) Metal Matrix Composites (MMCs) are often considered as advanced materials because they combine the properties of high stiffness and high strength-to-density ratio, corrosion resistance, and in some cases special electrical and thermal properties. This combination of properties makes advanced composites very attractive for aircraft and aerospace structural parts. Increasingly found in the automotive industry, these materials use a metal matrix such as aluminum or magnesium and a reinforcement made of advanced ceramic fibers such as silicon carbide or boron nitride. However, following the previous general definition and basic classification of composite materials, it is also important to note that numerous other everyday materials surrounding us are also composites. For instance, natural materials produced by biological processes such as bones (i.e., collagen and calcium phosphate) and wood (i.e., lignin as matrix and cellulose fibers) or man-made materials such as concrete (i.e., hydraulic cement and aggregates), cardboard and paper are composites exhibiting excellent mechanical performances. A general classification of the three classes of composites is given in Table 18.1.

Matrix type

Reinforcement type

Thermoplastics (e.g., PPS, PES)

Filler (e.g., metal or ceramic powders, particulate, beads)

Metal matrix composites (MMCs)

Class Polymer matrix composites (PMCs) (fiber reinforced polymers, resin based composites)

Table 18.1. Structural classification of composite materials

Ceramic matrix composites (CMCs)

1020

Fibers (e.g., carbon monofilaments/cut wires) Laminates (e.g., glass sheets, aluminum foil)

Thermosets (e.g., epoxy, PI, PA)

Filler (e.g., metal or ceramic powders, particulate, beads) Fibers (e.g., glass fibers, carbon monofilaments/cut wires) Laminates (e.g., glass sheets, aluminum foil, honeycomb)

Elastomers (e.g., rubber)

Filler (e.g., graphite powders, particulate, beads) Fibers (e.g., carbon monofilaments/cut wires) Laminates (e.g., glass sheets)

Metals (e.g., Al, Mg, Ti, Cu)

Particulates, flakes (e.g., ceramics, hardmetal, diamond-like carbon) Fibers (e.g., SiC or B4C monofilaments, whiskers) Others (e.g., expanded metal, mesh, honeycomb)

Alloys

Particulates, flakes (e.g., ceramics, hardmetal, diamond-like carbon) Fibers (e.g., SiC or B4C monofilaments, whiskers) Others (e.g., expanded metal, mesh, honeycomb)

Ceramic

Particulates or flakes Carbon monofilaments and whiskers Metal fibers, cut wires, and whiskers Others (e.g., expanded metal, mesh, honeycomb)

Glass or Glass-ceramic

Particulate

Carbon–carbon

Monofilaments, whiskers, fabric honeycomb

Properties of Composites

1021

18.2 Properties of Composites In this paragraph the physical properties of composite materials are briefly discussed. As a general rule, the properties of the composite are determined by the properties of the reinforcement materials, the physical properties of the matrix, the ratio of reinforcement to matrix in the composite and finally the geometry and orientation of the reinforcement materials in the composite. Usually, for scalar physical quantities such as density and specific heat capacity, the straightforward rule of mixtures can be applied in the most simple cases although vectorial or higher-rank tensorial properties (e.g., tensile strength, Young’s modulus, thermal conductivity, and permittivity, etc.) must be assessed by using more sophisticated calculation methods such as those based on the theory of elasticity or heat transfer in anisotropic materials.

18.2.1 Density If we consider a composite material made of a matrix M and a reinforcement material R, the total mass of the composite can be written as follows: Mc = mM + m R while the total volume of the composite material, taking into account the volume occupied by voids denoted Vv, is given by the following equation: Vc = VM + VR + Vv Hence the density of the composite materials, denoted, ρc, and expressed in kg.m is given by: –3

ρc = Mc/Vc = (mM + mR)/(VM + VR + Vv) Introducing the dimensionless mass fractions (wM, wR) and the mass densities (ρM, ρR) of the matrix and the reinforcement material respectively: wM = mM/(mM + mR)

ρM = mM/VM

wR = mR/(mM + mR)

with wM + wR = 1

ρR = mR/VR

we obtain:

ρc = [wM/ρM + wR/ρR+ Vv/(mM + mR)]–1= [wM/ρM + wR/ρR+ Vv/ρcVc]–1 Introducing the dimensionless volume fraction of voids also called the voids fraction: vv = Vv/Vc we obtain the equation of the density of the composite material:

ρc = 1/[wM/ρM + wR/ρR+ vv/ρc] Hence the voids fraction can be determined experimentally from accurate density measurements rewriting the equation as follows: vv = [1 – ρc(wM/ρM + wR/ρR)] On the other hand, if we introduce the dimensionless volume fractions (vM, vR) of the matrix and the reinforcement material respectively: vM = VM/(VM + VR + Vv)

vR = VR/VM + VR + Vv)

with vM + vR = 1

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we obtain

ρc = Mc/Vc = (ρMVM + ρRVR)/(VM + VR + Vv) Hence simply:

ρc = ρMvM + ρRvR The density of a composite material corresponds to the weighted average of the densities of each component material using the volume fraction as coefficients.

18.2.2 Tensile Strength and Elastic Moduli If we consider, for instance, a composite material reinforced with continuous fibers, the directions parallel and perpendicular to the fibers are the major axes. Loading parallel to fibers. First, if we applied an overall load, F, in N on the composite along the direction of the fibers, this load is carried either by the fibers and the matrix. Moreover, assuming a good bond between matrix and fibers, both stretch similarly and if the loading is isostrain, i.e., all strains are equals, we have: εc = εf = εm Therefore, the total load that the composite must withstand corresponds to the sum of individual loads, i.e., the load carried by fibers and matrix respectively, as follows: F = Ff + Fm Introducing the compression or tension stresses (σf and σm) and the cross sectional areas (Af and Am) of each material, we can replace loads by the product, stress times cross section area, and hence we obtain the simple equation: σc · Ac = σf · Af + σm · Am Rearranging the above equation by dividing by the total cross sectional area of the composite, we obtain an equation giving the stress of the composite material as a function of the stress and surface area fractions of the matrix and the fibers, i.e., volume fractions, since in this case the length of matrix, fibers, and composite are the same: σc = σf · Vf + σm · Vm Because we have Vf + Vm = 1, then the above equation can be simplified as follows: σc = σf · Vf + σm · (1 – Vf) On the other hand, since loading is isostrain, by dividing the above equation by each corresponding strain, we obtain: (σc/εc) = (σf /εf) · Vf + (σm/εm) · (1 – Vf) If the stresses applied are in the elastic region of each material, Hooke’s law can be applied to each material, and it is then permissible to replace each ratio by the corresponding Young’s modulus. This yields the general equation of the Young’s or elastic modulus of a composite material reinforced by continuous fibers as a function of the elastic moduli of each component and the volume fraction of fibers: Ec = Ef · Vf + Em · (1 – Vf)

Properties of Composites

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In practice, it is usually easier to know or measure the mass fraction of the reinforcement material rather than its volume fraction. If we replace the volume fractions (Vf and Vm) by the mass fractions (wf and wm) of fibers and matrix introducing their respective densities, we obtain the general equation: Ec = Ef · {1/[1 + (wf.ρm/wm.ρf)]} + Em · {1/[1 + (wm.ρf/wf.ρm)]} In the particular case, where the densities of matrix and fibers are equal or very close (e.g., aluminum alloys reinforced by boron fibers, magnesium reinforced by carbon fibers), the above equation becomes: Ec ≈ Ef · wf + Em · wm Loading perpendicular to fibers. When a load is applied to a composite material perpendicular to the direction of fibers, the load is supported by a series of resistances of the fibers and the matrix. Therefore the stress encountered in the matrix, fibers and the composite are equal. This particular condition is called isostress and is characterized by: σc = σf = σm

and

εc = εf · Vf + εm · (1 – Vf)

Therefore, introducing Young’s modulus using Hooke’s law, we have: εc = (σf/Ef) · Vf + (σm/Em) · (1 –Vf) By rearranging these equations, it is possible to express the elastic modulus as follows: Ec = Ef · Em/(Vf · Ef + Vm · Em)

18

It is important to note that isostress and isostrain loading conditions represent theoretical limits for the design of a composite material reinforced by continuous fibers. In practice, most of the time, mechanical performances fall between these limits. On the other hand, in the isostrain loading situation, a lower volume fraction of fibers is required to obtain a similar stiffness of the composite.

18.2.3 Specific Heat Capacity –1

–1

The specific heat capacity of a composite material denoted cPc and expressed in J.kg K is only related to the mass fractions, wk, of each component k and hence it is given by the simple equation: cpC = ∑kwkcpk

18.2.4 Thermal Conductivity As a general rule, the thermal conductivity of a composite material is a complex function of the thermal conductivity of the matrix (km) and that of the reinforcement (kf). In the particular case of an orthotropic composite material, the thermal conductivity of each component (i.e., matrix, reinforcement) is a tensor quantity [kij] with only three components k11, k22 and k33 along major axes, that is, one in the axial direction (k11) and two in the transversal directions (k22 and k33). In the particular case of transversely isotropic materials such as fiber reinforced composites, the axial thermal conductivity of the material, kC,axial, expressed in –1 –1 W.m K can be approximated by the rule of mixtures: kC,axial = k11 = Vf · kC + (1 – Vf·) · kC

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1024

Composite Materials

while the transverse conductivity is given by the more complex equation: 1/2

1/2

1/2

kC,transverse = k22 = k33 = [1 – (Vf) ]·km + km(Vf) /[1 – (Vf) (1 – km/kf2)]

18.2.5 Thermal Expansion Coefficient In the same way as for thermal conductivity, the coefficient of linear thermal expansion of a composite material is a complex function of the thermal expansion coefficients of the matrix (αm) and that of the reinforcement (αf). In the particular case of orthotropic composite materials, the thermal expansion coefficient of each component (i.e., matrix, reinforcement) is a tensor quantity [αij] with only three components α11, α22 and α33 along the major axis, that is, one in the axial direction (α11) and two in the transversal directions (α22 and α33). In the particular case of transversely isotropic materials such as for instance fiber reinforced composites, the axial coefficient of thermal expansion of the material, αaxial, expressed in –1 –1 W.m K can be approximated by the rule-of-mixtures by means of the Young’s moduli of the matrix and of the fiber: αaxial = α11 = [Vf · Ef1 · αf1 + (1 – Vf·) · Em · αm]/[Vf · Ef1 + (1 – Vf·) · Em] while the transverse thermal expansion is given by the more complex equation: αtransverse = α22 = α33 = αf1 · Vf + αm (1 – Vf ) · {1 +{Vf · Ef1 · αm/[Vf · Ef1 + (1 – Vf·) · Em ]}} 1/2

1/2

18.3 Fabrication Processes for Monofilaments Several processes can be utilized for producing high-performance monofilaments, among which the most widely used are the technologies described hereafter: (i)

(ii)

Extrusion of polymer fibers. This technique consists of melting a bulk solid polymer in 3 order to obtain a low-viscosity melt (i.e., with dynamic viscosities up to 10 Pa.s) or to dissolve it into an appropriate organic solvent. The melt or the solution is then filtered through a plate of holes called a spinnerette, to form fibers. Then the fiber produced solidifies over a distance of centimeters to meters under conditions of controlled temperature, stress, and mass transfer. This process is based on two physical concepts: melt or dry jet wet spinning from a nematic liquid crystalline phase in which the already rod-like molecules are uniaxially ordered, and melt or gel spinning and drawing of conventional, random-coil polymers under conditions that permit extremely high elongational forces (i.e., high drawn ratios) to elongate and orientate the component molecules mechanically. Pyrolytic conversion of precursor fibers. The technique uses precursors that can be pyrolyzed to form continuous inorganic filaments. It has been extensively used to manufacture synthetic inorganic fibers of many different compositions. The precursor materials include polym, a concentrated salt solution that may behave like polymeric materials, polymer-modified solutions, slurries, and sol–gel systems. Polymeric precursors are used for the fabrication of continuous nonoxide monofilaments such as carbon, graphite, and silicon carbide (SiC).

Other processes are (iii) the chemical conversion of precursor fibers; (iv) fibers produced by chemical vapor deposition; (v) single crystal fibers or whiskers.

Reinforcement Materials

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18.4 Reinforcement Materials As mentioned previously, the four main types of reinforcements used in composites are (i) (ii) (iii) (iv)

continuous fibers; discontinuous fibers; whiskers (i.e., elongated single crystals); particles.

Continuous, aligned fibers are the most efficient reinforcement form and hence are widely used for high-performance applications. However, for ease of fabrication and to achieve specific properties, such as improved strength, continuous fibers are converted into a wide variety of reinforcement forms using textile technology. Key among them at this time are two-dimensional and three-dimensional fabrics and braids.

18.4.1 Glass Fibers Glass fibers, first introduced in the late 1930s, are the first and still the most used material for reinforcing polymers. The major grades of glass used to manufacture glass fibers having good mechanical strength are E-glass, high-strength glass (HS) and to a lesser extent the high silica S-glass. Of these, the E-glass fibers are the most widely used reinforcement glass fibers due to a low cost and well-known manufacturing process although they were originally developed for electrical applications due to their excellent dielectric properties. Glass fibers usually exhibit both a low density and Young’s modulus but have a high strength (see Table 18.2). Therefore glass fibers have a high strength-to-density ratio that, combined with their low cost, makes them the cheapest fiber reinforcement material. The preparation of glass fiber is a relatively straightforward process. First the raw materials (i.e., low-iron silica sand, kaolin, feldspars, boric acid and colemanite) are carefully mixed batchwise and introduced with a hopper into a glass melting furnace. Afterwards, the molten glass is fed into electrically heated and perforated platinum crucibles called bushings. After exiting the hundreds of holes, the drawn glass filaments are gathered together into a single strand and wound onto a cold metallic rotating mandrel. The final characteristics, especially diameter of the glass fiber, depend on the diameter of the holes, the dynamic viscosity of the molten glass, the pouring temperature, and the vitrostatic head in the furnace. Moreover, in order to protect glass fibers from deleterious surface damage, a thin coating, called size, is applied by a proper sizing treatment. Glass fibers are usually produced as multifilament bundles with filament diameters ranging from 3 to 20 μm.

18.4.2 Boron Fibers Boron fibers were first introduced in the late 1950s primarily to reinforce metals and alloys. Because pure boron is highly brittle, commercially boron fibers are produced as monofilaments (i.e., single filaments) by depositing amorphous boron onto a core made of either a thin tungsten wire or, less often, of a carbon monofilament both of which act as a structural fiberlike core. Therefore, strictly speaking, boron fibers can be seen as an elementary composite material. Commercially, the deposition of amorphous boron is performed by chemical vapor deposition (CVD). The fabrication process consists of reacting a boron-rich gas, for instance a mixture of excess boron trichloride (BCl3) with hydrogen (H2), onto a hot and fast-moving

18 Composite Materials

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tungsten wire usually having a diameter of 12.5 μm. The rapidly moving tungsten filament is first preheated in a pure hydrogen atmosphere before it enters the reaction chamber. In both furnaces, the heat is provided by resistance or Joule’s heating, i.e., by circulating a high electric current into the wire until the desired temperature (e.g., from 1000°C to 1200°C) is reached in the same way as like in lamp bulbs. Air-tightness is ensured by liquid mercury seals. At the hot W-wire surface, the following decomposition reaction takes place: 2BCl3(g) + 3H2(g) —> B(s) + 6HCl(g) As previously mentioned, the tungsten wire that acts as substrate, remains entrapped and ends in the fiber. Therefore due to the dense preexisting wire of tungsten, the boron fibers produced by CVD exhibit: (i) (ii)

a typical coaxial structure with an inner tungsten core; relatively large diameters, usually ranging from 100–140 and even 200 μm; these diameters are larger than those of most other reinforcement fibers; –3 (iii) boron fibers are denser than pure boron (2490 to 2570 kg.m ). Moreover, in order to avoid the formation of brittle intermetallic phases of tungsten borides (e.g., W2B, WB, W2B5, and WB4) at the interface between the outer boron layer and the tungsten core, tungsten wire is coated with a layer of silicon carbide or even boron carbide prior to deposition. Microscopic examination reveals a peculiar morphology of boron fibers that exhibit a typical “corn-cob” aspect. The high cost of boron fibers compared to other fiber reinforcements, which is mainly driven by its tungsten content, restricts their widespread utilization. For that reason, boron fibers are only used in MMCs for civilian and military aircraft and also aerospace applications (e.g., space shuttle) and to a lesser extent for high-tech sporting goods (e.g., golf club).

18.4.3 Carbon Fibers –3

Carbon fibers exhibit a low density (2270 kg.m ) combined with an extremely high Young’s modulus. Carbon fibers are usually obtained by pyrolysis at high temperature of organic fiber precursors, usually polymers, although less often whiskers of carbon have also been made by chemical vapor deposition (CVD) onto an existing hot carbon fiber by reacting a hydrocarbon vapor and hydrogen gas using a suitable catalyst. Four types of polymer precursors are used commercially to manufacture carbon fibers: (i) (ii) (iii) (iv)

rayon; polyacrylonitrile (PAN); cellulose; pitch.

Therefore, a common designation of carbon fibers consists of naming them after the nature of the polymer precursor with the prefix ex, e.g., ex-PAN, ex-Pitch, etc. Historically, rayon was the first raw material used to produce high-performance carbon fibers and it dominated the market in the 1960s and early 1970s. However, because of its low carbon yield ranging between 20 and 30 wt.% C, high processing cost, and limited physical properties, today the use of rayon precursor is practically abandoned. Since ex-PAN carbon fibers represent the major carbon monofilaments, its production will be described here in detail. These fibers are obtained from the pyrolysis of precursor fibers called polyacrylonitrile or acrylic copolymers. The first step called fiberization consists of wet or dry spinning of a solution of the polymer in a solvent into PAN precursor fibers that are ultimately converted

Reinforcement Materials

1027

into carbon fibers; melt-spinning can also be used. The precursor fibers obtained differ significantly from the acrylic fibers used for textile applications. Actually, they exhibit fewer filaments per tow stage, a higher purity, smaller filament diameter, and higher acrylonitrile content. Afterwards, during stabilization, the fiber is heated in an air-oven at temperatures ranging from 200 to 300°C for one hour. The stabilization treatment is followed by carbonization in an inert atmosphere at temperatures greater than 1200°C in order to remove foreign elements. Orientation of the graphite-like crystal structure, and thus the fiber modulus, can be further increased by heat treatment called graphitization at temperatures up to 3000°C. The continuous carbon or graphite fiber is then surface treated and coated with a sizing agent prior to winding the continuous filaments onto a metallic mandrel to yield bobbins. The surface treatment is an oxidation of the fiber surface to promote adhesion to the matrix resin in the composite, and the size promotes handling and wettability of the fiber with the matrix resin. The resulting carbon fibers exhibit tensile strength ranging from 3.5 GPa to 7 GPa and they are classified into three major commercial grades: (i) standard or aerospace grade (E = 32–35 GPa); (ii) intermediate modulus grade (E = 40–50 GPa); (iii) high modulus grade (E = 55–85 GPa). Carbon fibers like parent graphite are good electrical conductors (e.g., 1000–10,000 μΩ.cm) –1 –1 and exhibit thermal conductivities ranging from 50 W.m K for ex-PAN fibers to 1100 –1 –1 W.m K for ex-Pitch fibers. 18

18.4.4 Polyethylene Fibers Macromolecules of polyethylene like most raw polymers usually exhibit a typical random coil configuration because of weak Van der Waals bonds existing between adjacent monomers. Therefore, when the polymer is stressed these weak bonds are the first to break while the strong covalent bonds occurring between carbon atoms do not take part in the initial deformation. On the other hand, highly oriented polyethylene, especially ultrahigh-molecular weight polyethylene (UHMW), exhibits both a high stiffness (i.e, Young’s modulus) and tensile strength that makes it suitable to be used as reinforcement material because of its linear chain. These fibers can be made either by: (i) (ii)

die extrusion of melted polymer; or by gel spinning.

Due to the low density of the parent polymer, UHMW polyethylene fibers have a strengthto-weight ratio even greater than polyaramide fibers. Most common commercial trade names are Spectra®, Dyneema® or Tekmilon®.

18.4.5 Polyaramide Fibers Polyaramide fibers are well known thermosets (see Polymers) having both a high-strength and stiffness combined with an excellent thermal resistance. They are commercialized under the trade names Kevlar® and Nomex® (E.I. DuPont de Nemours) and Technora® and Twaron® (Teijin) respectively.

Composite Materials

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18.4.6 Ceramic Oxide Fibers Various ceramic oxides are used for making ceramic fibers, among them pure alumina fibers and alumina-silica fibers are the most common. The former were commercialized by ICI Ltd. under the trade name Saffil® extensively used in high temperature insulation to replace asbestos and glass fiber felts that pose occupational safety issues, while alumina-silica fibers were commercialized by 3M under the trade name Nextel®. Various processing routes can be used to manufacture ceramic oxide fibers, the most common being: (i) (ii) (iii) (iv)

sol–gel processes; modified Czochralski; floating zone; inviscid melt technique.

Continuous alumina fibers are available from several suppliers. Chemical compositions and properties of the various fibers are significantly different.

18.4.7 Silicon Carbide Fibers Silicon carbide (SiC) monofilaments are usually made by chemical vapor deposition (CVD) by decomposing a silane such as methyltrichlorosilane (CH3SiCl3) in a hydrogen atmosphere onto a hot and fast-moving tungsten wire or pyrolitic carbon monofilament at a temperature of 1300°C. The equipment and process is the same as that used for making boron fibers (see Section 18.4.2). The chemical reaction occurring at the surface of the hot substrate is: CH3SiCl3(g) —> SiC(s) + 3HCl(g) Like boron fibers, the final SiC monofilament is relatively thick and consists of a core of tungsten of 12.5 μm diameter with a coating of SiC with an outside diameter of 140 μm. To overcome this important drawback, the Japanese team of Professor Yajima introduced an alternative process based on the pyrolysis of an organic silicon-rich polymer (i.e., polycarbosilane). First the polysilane is synthesized by dechlorinating a halogenated silane with metallic sodium. The polysilane is then decomposed thermally under pressure to yield the polycarbosilane precursor. After melt spinning, the precursor fiber obtained yields the final SiC monofilament by pyrolysis in air at 1300°C.

Coefficient linear thermal expansion –6 –1 (a/10 K )

Thermal conductivity –1 –1 (k/W.m .K ) 6.7

Alumina fiber (Saffil®) (99Al2O3-3SiO2)

3300

3

300–370 1900

Boron fiber (Tungsten core)

2490–2570 100–200 379–400 3800–4600 4.5

n.a.

Carbon (ex-PAN) (Thornel® 300)

1740

50

–3

Young’s elastic modulus (E/GPa)

7.9

Fiber diameter (d/μm)

Fiber material

Ultimate tensile strength (σUTS/MPa)

Table 18.2. Selected physical and mechanical properties of several reinforcement fibers Density (ρ/kg.m )

1028

7–8

220–250 2500–3200 –0.5

Polymer Matrix Composites (PMCs)

1029

Young’s elastic modulus (E/GPa)

Ultimate tensile strength (σUTS/MPa)

1600

7

345

1400–2200 –0.5

Carbon (ex-Rayon) (Thornel® 50)

1660

7–8

340–390 2200–2400 –0.7

70

Ceramic Nextel® 312 (62Al2O3-24SiO2-14B2O3)

2700

8–12

152

1700

0.120

Ceramic Nextel® 440 (70Al2O3-28SiO2-2B2O3) 3050

8–12

186

2000

Ceramic Nextel® 550 (73Al2O3-27SiO2)

3030

8–12

193

2000

Ceramic Nextel® 610 (99Al2O3-0.5 Fe2O3-0.5SiO2)

3750

8–12

370

1900

Ceramic Nextel® 720 (85Al2O3-15SiO2)

3400

8–12

260

2130

Glass (E-glass) (55SiO2-19CaO-8Al2O3-7.3B2O3-4.6MgO)

2550

10–20

70

1750

4.7

0.90

Glass (HS-glass)

2500

10

83

4200

4.1

0.90

Glass (S-glass) (65SiO2-25Al2O3-10MgO)

2490

8–14

86

4580

5.6

0.90

Glass (E-glass) (53SiO2-15Al2O3-22CaO-9B2O3)

2600

9

72

4800

5.0

1.3

Polyaramide (Kevlar® 119)

1440

12

55

3000

–2.0

0.04

Polyaramide (Kevlar® 129)

1450

12

100

3400

–2.0

0.04

Polyaramide (Kevlar® 149)

1470

12

147

2400

–2.0

0.04

Polyaramide (Kevlar® 49)

1450

13–16

131

2800

–4.9

0.04

Polyaramide (Kevlar® 68)

1440

12

101

2800

n.a.

0.04

Polyaramide (Kevlar® K29)

1440

12

65

2800

–4.0

0.04

Polyaramide (Technora)

1390

12

71

3100

Polyethylene (UHMW grade) (Spectra®9000) 970

10–12

119–172 2600–3000

Silicon Carbide

3000

10–20

400

3100

4.9

80

Silicon Carbide (Nicalon®)

2600

10–20

180

2000

3.1

80

Coefficient linear thermal expansion –6 –1 (a/10 K )

Fiber diameter (d/μm)

Carbon (ex-Pitch)

–3

Density (ρ/kg.m )

Fiber material

Thermal conductivity –1 –1 (k/W.m .K )

Table 18.2. (continued)

100

8.0

0.04

Trademarks: Saffil® (ICI); Spectra® 9000 (Allied Corp.); Nicalon® (Nippon Carbon Co.); Kevlar® (E.I. Dupont de Nemours); Nextel® (3M Corp.); Thornel® (Union Carbide).

18.5 Polymer Matrix Composites (PMCs) Description and general properties. Polymer matrix composites (PMCs) consist of a polymer matrix or resin reinforced with glass fibers and to a lesser extent carbon, boron and polyaramide fibers. The resin systems used to manufacture advanced composites are of two basic types: thermosets and thermoplastics (see Chapter 11). Thermosetting resins predominate today, while thermoplastics have only a minor role in advanced-composite manufacture. Thermoset resins require the addition of a curing agent or hardener and impregnation onto

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Table 18.3. PMCs manufacturing processes Polymer matrix

Reinforcement type

Techniques

Thermosetting polymers (e.g., epoxy)

Fibers, laminate, felts

Han-laying-up spraying

Monofilaments

Filament winding

Fibers

Pultrusion

Laminates

Autoclaving

Reinforcement porous preform

Resin molding, impregantion

Laminate

Stacking

Thermoplastics

Diaphragm forming Ribbon

Tape laying

Fiber Cut fibers, particulates

Injection molding

a reinforcing material, followed by a curing step to produce a cured or finished part. Once cured, the part cannot be changed or reformed, except for finishing. Some of the more common thermosets include: epoxies, polyurethanes, phenolic and amino resins, polyimides and polyamides. However, among thermosets, epoxies are the most commonly used today. Processing. Numerous processes are used for manufacturing PMCs and they are briefly listed in Table 18.3. (i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

Resin formulation. This consists of mixing epoxy or other resins with other ingredients to achieve desired performance parameters. These ingredients may be curing agents, accelerators, reactive diluents, pigments, etc. Prepregging. This involves the application of formulated resin products, in solution or molten form, to a reinforcement such as carbon, fiberglass or aramid fiber or cloth. The reinforcement is saturated by dipping through the liquid resin or by being impregnated through heat and pressure. Wet filament winding. In this process, continuous fiber reinforcement materials are drawn through a container of resin mixture and formed onto a rotating mandrel to achieve the desired shape. After winding, the part is cured in an oven. Hand lay-up of prepreg. Prepreg product is laid down and formed to the desired shape. Several layers may be required. After forming, the lay-up assembly is moved to an autoclave for cure under heat, vacuum and pressure. Automated tape lay-up. In this process, the prepreg tape material is fed through an automated tape application machine. The tape is applied across the surface of a mold in multiple layers by the preprogrammed robot. Resin transfer molding. Resin transfer molding is used when parts with two smooth surfaces are required or when a low-pressure molding process is advantageous. Fiber reinforcement fabric or mat is laid by hand into a mold and resin mixture is poured or injected into the mold cavity. The part is then cured under heat and pressure. Pultrusion. In this process, continuous roving strands are pulled from a creel through a strand-tensioning device into a resin bath. The coated strands are then passed through a heated die where curing occurs. The continuous cured part, usually a rod or similar shape, is then cut to the desired length.

Metal Matrix Composites (MMCs)

1031

(viii) Injection molding. In this process, thermoplastic granules are fed via a hopper into a screw-like plasticating barrel where melting occurs. The melted plastic is injected into a heated mold where the part is formed. (ix) Vacuum bagging and autoclave curing. Most parts made by hand lay-up or automated tape lay-up must be cured by a combination of heat, pressure, vacuum, and inert atmosphere. To achieve proper cure, the part is placed into a plastic bag inside an autoclave. A vacuum is applied to the bag to remove air and volatile products. Heat and pressure are applied for curing. Usually an inert atmosphere is provided inside the autoclave through the introduction of nitrogen or carbon dioxide. Table 18.4. Properties of selected polymer matrix composites (PMCs) Polymer matrix composite materials

Density Young’s Ultimate Linear thermal –3 (ρ/kg.m ) modulus tensile expansion (E/GPa) strength coefficient –6 –1 (/MPa) (αL/10 K )

Epoxy resin reinforced with 50 vol.% boron fibers

2020

201

Epoxy resin reinforced with 60 vol.% kevlar 49

1450

65

1365

56

Epoxy resin reinforced with 60 vol.% carbon fibers

1580

131

1516

30

Epoxy resin reinforced with 60 vol.% zirconia glass fibers

2004

45

1426

Epoxy resin reinforced with 72 vol.% S-glass

2130

61

1688

17

Nylon 66 reinforced with 40 vol.% glass fibers

1460

11

1350

25

Polypropylene reinforced with 40 vol.% S-glass fibers

1230

9

1220

6.1–30

18.6 Metal Matrix Composites (MMCs) Description and General Properties. Metal matrix composites (MMCs) consist of a metal or an alloy matrix with a reinforcement material (e.g., particulates, monofilaments, or whiskers). The matrix alloy, the reinforcement material, the volume and shape of the reinforcement, the location of the reinforcement, and the fabrication method can all be varied to achieve required properties. Most of the metal-matrix composites are made of an aluminum matrix. But aluminum-matrix composites must not be considered as a single material but as a family of materials whose stiffness, strength, density, and thermal and electrical properties can be tailored. Moreover a growing number of applications require improved matrix properties and therefore, metal matrices of magnesium, titanium, superalloys, copper, or even iron are now available commercially. Compared to bulk metals and their alloys, MMCs offer a number of advantages such as: (i) (ii) (iii) (iv) (v) (vi)

higher strength-to-density and stiffness-to-density ratios; better fatigue and wear resistance; better elevated temperature properties; higher tensile strength; lower creep rate; lower coefficients of thermal expansion.

Moreover, MMCs also exhibit better performances compared with other composites, especially polymer matrix composites, because they possess a higher temperature capability along with fire resistance and low outgassing, a greater transverse stiffness and strength,

18 Composite Materials

1032

Composite Materials

combined with excellent electrical and thermal conductivities. However, MMCs have some drawbacks because they are expensive materials that still require costly and complex fabrication methods. MMCs are usually reinforced by either monofilaments, discontinuous fibers, whiskers, particulates, or wires. With the exception of wires, which are metals, reinforcements are generally made of advanced ceramics such as boron, carbon, alumina and silicon carbide. The metal wires used are made of tungsten, beryllium, titanium, and molybdenum. Currently, the most important wire reinforcements are tungsten wire in superalloys and superconducting materials incorporating niobium-titanium and niobium-tin in a copper matrix. The most important MMC systems are presented in Table 18.5. Table 18.5. Major commercial MMCs Metal matrix

Reinforcement

Applications

Aluminum

Particulates of SiC and B4C

Brake rotors, pistons, and other automotive components

Monofilaments of C, B, SiC or Al2O3 Golf clubs, bicycles Discontinuous fibers of Al2O2, SiO2

Machinery components

Whiskers of SiC

Golf clubs, bicycles

Magnesium Particulates of SiC, B4C Monofilaments of C or Al2O3 Whiskers of SiC Titanium

Copper

Particulates of TiC

Thermal shields

Monofilaments of SiC or coated Al2O3

High-temperature, corrosion-resistant components or skin material for the space craft

Particulates of SiC, B4C, TiC

Heat sinks and electronic packaging

Monofilaments of C or SiC Wires of Nb3Ti and Nb3Sn Superalloys Tungsten wires

Superconductors Jet turbine engines that operate at temperatures above 900°C

Processing. Relatively large-diameter monofilament fibers, such as boron and silicon carbide are incorporated into metal matrices by hot pressing a layer of parallel fibers between foils to create a monolayer tape. In this operation, the metal flows around the fibers and diffusion bonding occurs. The same procedure can be used to produce diffusion-bonded laminates with layers of fibers oriented in specified directions to meet stiffness and strength requirements for a particular design. In some instances, laminates are produced by hot pressing monolayer tapes. Monolayer tapes are also produced by spraying metal plasmas on collimated fibers, followed by hot pressing. Structural shapes can be fabricated by creep and superplastic forming of laminates in a die. An alternative process is to place fibers and unbonded foils in a die and hot press the assembly. MMCs can also be made by infiltrating liquid metal into a fabric or prearranged fibrous configuration called a preform. Frequently, ceramic or organic binder materials are used to hold the fibers in position. The latter are burned off before or during infiltration. Infiltration can be carried out under vacuum, pressure, or both. Pressure infiltration, which promotes wetting of the fibers by the matrix and reduces porosity, is often called squeeze casting.

Ceramic Matrix Composites (CMCs)

1033

Table 18.6. Properties of selected metal matrix composites (MMCs) Metal matrix composite materials

Density Young’s Ultimate Fracture –3 (ρ/kg.m ) modulus tensile toughness 1/2 (E/GPa) strength (K1c/MPa.m ) (/MPa)

Linear thermal expansion coefficient –6 –1 (αL/10 K )

Aluminum matrix 6061 T6 reinforced with 70 vol.% SiC particles

3000

265

225

6.2

Aluminum matrix 6061 T6 reinforced with 13 vol.% SiC particles

2960

140

460

Aluminum matrix reinforced with 50 vol.% carbon fibers

2450

450

690

–0.5

Aluminum matrix reinforced with 60 vol.% alumina fibers

3400

240

1700

7

Aluminum matrix reinforced by boron carbide (Boralyn® H-10)

2685

86

415

21

15

Aluminum matrix reinforced by boron carbide (Boralyn® H-15)

2685

98

462

23

19

Aluminum matrix reinforced by boron carbide (Boralyn® H-20)

2657

107

524

28

21

Duralcan F3S20S reinforced with 20 vol.% carbon fibers

2770

98

51

17.0

Duralcan F3N20S reinforced with 15 vol.% carbon fibers

2710

110

45

17.5

Titanium alloy Ti6Al-4V reinforced with 10 vol.% B4C particles

4500

205

1055

Titanium metal reinforced with SiC particles

3600

260

1700

18

16.0

18

18.7 Ceramic Matrix Composites (CMCs) Description and general properties. Ceramic matrix composites (CMCs) have been developed to overcome the intrinsic brittleness and lack of reliability of monolithic ceramics, and to introduce ceramic-based materials for structural parts used in harsh environments, such as rocket and jet engines, gas turbines for power plants, heat shields for space vehicles, fusion reactor first wall, aircraft brakes, heat treatment furnaces, etc. Actually, the fracture 1/2 toughness of monocrystalline ceramics or glasses is typically as low as one MPa.m and the use of CMCs allows an increase of the operating temperature at which the materials can be used without damage. Further, the use of light CMCs in place of heavy superalloys is expected to yield significant mass savings. Although CMCs are promising thermostructural materials, their applications are still limited by the lack of suitable reinforcements, processing difficulties, and cost. Processing. Most of the advanced ceramics used in CMCs are SiC, Si3N4, SiO2 and Al2O3 all exhibiting high melting points ranging from 1700 to 2500°C. Therefore, powder processing routes are preferred techniques to melting and casting for preparing CMCs. The powder is mixed with a binder, then pressed into shape as a “green compact”. This is followed by hightemperature sintering, in which the powder is consolidated and the binder is burnt off. Better quality is achieved when pressure is applied from all directions such as in hot isostatic

Composite Materials

1034

Composite Materials

pressing (HIP). CMCs may also be processed by slip casting by suspending the ceramic powder in a water-based liquid to form a slurry. This can be cast into a porous mold, dried and fired. On the other hand, glass-ceramics are processed by conventional glass-making techniques. Other processes currently in use or under development for CMCs include matrix transfer molding; sol–gel processing and chemical vapor deposition. In situ processes are also possible, in which the ceramic matrix is formed by direct reaction between a molten metal and a gas in the presence of a reinforcement preform.

18.8 Carbon–Carbon Composites (CCs) Description and general properties. Carbon–carbon composites (CCs) consist of highlyordered graphite fibers embedded in a carbon matrix. These composites are made by gradually building up a carbon matrix on a fiber preform through a series of impregnation and pyrolysis steps or chemical vapor deposition. They tend to be stiffer, stronger and lighter than steel or other structural metals. The most important properties of carbon–carbon composites is their excellent thermal properties. Actually, these composites exhibits extremely low thermal expansion coefficients, making them dimensionally stable at a wide range of temperatures, and they have high thermal conductivity. Moreover, carbon–carbon composites retain their good mechanical properties even at temperatures up to 3000°C in vacuum or inert atmospheres. The combination of a low thermal expansion coefficient together with a high Young’s modulus makes them highly resistant to thermal shock, or fracture caused by rapid and extreme changes in temperature. The major drawback of carbon–carbon composites is that they oxidize readily at temperatures between 600 and 700°C in air. Therefore, a protective coating or barrier usually made of silicon carbide must be applied to prevent high-temperature oxidation, adding an additional manufacturing step and additional cost to the production process. Processing. Carbon–carbon composites consists of building up of the carbon matrix around the graphite fibers. There are two common processes used to prepare carbon–carbon composites: (i) (ii)

chemical vapor deposition; resin impregnation.

Chemical vapor deposition (CVD) starts with a preform with the desired shape of the part, usually formed from several layers of woven-carbon fabric. The preform is heated in a furnace pressurized with an organic gas, such as methane, acetylene or benzene. Under high heat and pressure, the gas decomposes and deposits a layer of pure carbon onto the carbon fibers. The gas must diffuse through the entire preform to make a uniform matrix, so the process is very slow, often requiring several weeks and several processing steps to make a single part. In the second process a thermosetting resin such as epoxy or phenolic is applied to the preform under pressure and then pyrolized into carbon at high temperature. Alternatively, a preform can be built up from resin-impregnated carbon textiles (woven or non-woven) or yarns, then cured and pyrolized. Shrinkage in the resin during carbonization results in tiny cracks in the matrix and a reduction in density. The part must then be reinjected and pyrolized several times to fill in the small cracks and to achieve the desired density. Densification can also be accomplished using CVD.

Further Reading

1035

Table 18.7. Properties of selected ceramic matrix composites (CMCs) Composite materials

Density Young’s Flexural Fracture –3 (ρ/kg.m ) modulus strength toughness 1/2 (E/GPa) (/MPa) (K1c/MPa.m )

Linear thermal expansion coefficient –6 –1 (αL/10 K )

Alumina matrix reinforced with 25 vol.% SiC

3700

6

Hot pressed alumina matrix reinforced with 30 wt.% TiC

3900

Lithium aluminosilicate reinforced with 50% SiC

2600

140

620–830 17.0

Carbon bonded carbon fiber

170

120–150

600–700 1

Silicon carbide with 54 vol.% BN

3300

317

588

Hardmetal 5.5 wt.%Co + 94.5 wt.% WC

14,800

660

n.a.

390

900

8.0

638

4.5–5.0

12.0

3 5.0

18.9 Further Reading ALTENBACH, H.; ALTENBACH, J.; KISSING, W. (2004) Mechanics of Composite Structural Elements. Springer, Heidelberg. BARBERO, E.J. (1998) Introduction to Composite Materials Design. Taylor & Francis, 336 pages. BERTHELOT, J.-M. (1999) Composite Materials. Mechanical Behavior and Structural Analysis. Springer, Heidelberg. CHAWLA, K.K. (2001) Composite Materials. Science and Engineering, 2nd ed. Springer, New York. CHUNG, D.D.L. (2004) Composite Materials · Functional Materials for Modern Technologies. Springer, London. DANIEL, I.M.; ISHAI, O. Engineering Mechanics of Composite Materials. Oxford University Press. FITZER, E.; MANOCHA, L.M. (1998) Carbon Reinforcements and Carbon/Carbon Composites. Springer, Heidelberg. GRAYSON, M. (Ed.) (1983) Encyclopedia of Composite Materials and Components. John Wiley & Sons, London. GUTOWSKI, T.G.(Ed.) (1997) Advanced Composites Manufacturing. John Wiley & Sons, London. HYER, M.W. (1998) Stress Analysis of Fiber-Reinforced Composite Materials. McGraw-Hill, New York. HARPER, C.A. (2002) Handbook of Plastics, Elastomers & Composites. McGraw-Hill, New York. KELLY, A.; MILEIKO, S.T. (eds.)(1983) Fabrication of Composites. North-Holland, Amsterdam. LEE, S.M. (Ed.) (1992) Handbook of Composite Reinforcements. John Wiley. MAZUMDAR, S.K. (2001) Composites Manufacturing: Materials, Product and Process Engineering. CRC Press, Bocca Raton, FL, 348 pages. NIELSEN, L.F. (2005) Composite Materials. Properties as Influenced by Phase Geometry. Springer, Heidelberg. PETERS, S.T. (Ed.) (1997) Handbook of Composites, 2nd ed. Chapman & Hall, 1140 pages, ISBN 0-412-54020-7. PILATO, L.A.; MICHNO, M.J. (1994) Advanced Composite Materials, Heidelberg. VLOT, A.; GUNNINK, J.W. (Eds.) (2002) Fibre Metal Laminates. An Introduction. 444 pages ISBN 1-4020-0391-9. VINSON, J.R.; SIERAKOWSKI, R.L. The Behavior of Structures Composed of Composite Materials.

18 Composite Materials

Gases

19.1 Properties of Gases The state of a gas is defined by the values of its volume (V), its absolute thermodynamic temperature (T), its absolute pressure (P) and the amount of substance or number of moles (n). An equation of state is a mathematical relationship between these four physical quantities: f = (P,V,T,n). The equation is obtained from knowledge of the experimental behavior of a system. Ideal gases. The ideal gas assumption is an ideal state, where the size of the microscopic entities (i.e., atoms or molecules) constitutive of the gas is negligible and the interatomic or intermolecular forces existing between them are neglected in a first approximation. Therefore, the ideal gas assumption is suitable for assessing properties of common gases under low pressure or at high temperature. Real gases. In real gases, non-ideality arises from either atomic or molecular size or intermolecular interactions caused by electrostatic attraction or repulsion (i.e., Coulomb’s forces). The departure from ideal behavior of a gas is particularly noticeable under high pressure or at cryogenic temperatures. Under high pressure, the volume occupied by the atoms or molecules of gas is no longer negligible compared with the overall volume and electrostatic attractions are more important so the equation of state of the actual gas must take additional parameters into account.

19.1.1 Pressure The pressure of a fluid (e.g., liquid, gas) is a scalar physical quantity, denoted P, and is expressed in the SI in pascals (Pa), corresponding to the force F expressed in newtons (N), exerted uniformly onto

1038

Gases 2

a surface having cross-sectional area A expressed in square meters (m ) according to the following equation: P = F/A Important notes (i)

Pressure is an intensive quantity, that is, it does not depend on the size of the system (i.e., volume, mass, etc.). (ii) The pressure is a scalar quantity by contrast with the stress which is a tensor. (iii) For an ideal fluid, i.e., without viscosity and incompressible (i.e., a constant mass density), the forces exerted onto the wall of a container are normal (i.e., orthogonal) to the surface. Actually, if the forces were not normal, they could be decomposed into two vectors (1) a normal component; and (2) a tangential component. Under the tangential force, the liquid would move alone along the wall. As discussed previously the pressure is a scalar physical quantity with the following di–1 –2 mensional equation: [P] = [ML T ]. In the Système International d’unités (SI), the pressure 1 –2 unit is a derived unit having a special name pascal , with the symbol Pa, hence 1 Pa = 1N.m –1 –2 = 1 kg.m .s . However, there also exist several obsolete units of pressure relative to different systems or used in particular scientific, and technical fields. Although these obsolete units should be discontinued their remanence exists for practical uses and they are listed in Table 19.1. Table 19.1. Non-SI units of pressure listed by alphabetical order Pressure unit

System

SI conversion factor

atmosphere (standard)

–

1 atm =101,325 Pa (E)

atmosphere (technical)

metric

1 at = 10 Pa (E)

bar

metric technical system

1 bar =10 Pa (E)

barye

cgs

1 barye = 1 μbar (E) = 1 dyne/cm (E) = 10 Pa (E)

foot of water (39.2°F)

FPS

1 ftH2O (4°C) = 2.988983226 × 10 Pa

UK, US

1 in Hg (0°C) = 3.38638816 × 10 Pa

inch of mercury (32°F)

2

–1

3

3

1 kgf/cm = 9.80665 × 10 Pa (E)

meter of water (4°C)

metric

1 mH2O (4°C) = 9.8063754 × 10 Pa

millimeter of mercury (0°C) centimeter of mercury (0°C)

obsolete

1 mmHg (0°C) = 133.322368421 Pa 1 cmHg (0°C) = 1333.22368421 Pa

ounce-force per square inch (osi)

UK, US

1 ozf/in = 430.922330823 Pa

pièze (pz)

MTS

1 Pz = 1 sthène/m (E) = 10 Pa (E)

pound-force per square inch (psi)

US, UK technical 1 lbf/in = 1 psi (E) = 6.89475729317 × 10 Pa system

poundal per square foot (pdsf)

FPS

1 pdl/ft = 1 pdsf (E) = 1.4881639437 Pa

obsolete

1 Torr = 1 mmHg (0°C) (E) = 133.322368421 Pa

2

2

5

kilogram-force per square centimeter MKpS

torr (Torr)

1

5

2

4

3

2

2

3

2

3

2

Unit name after the French mathematician, physicist and scientist Blaise Pascal [Clermont-Ferrand (1623), Paris (1662)]. Named after the Italian scientist Evangelista Torricelli (1608–1647).

Properties of Gases

1039

Table 19.2. Pressure of the standard atmosphere in numerous practical units –1

–1

–2

–3

1 atm = 101,325 kg.m .s (E) = 101,325 Pa (E) = 101,325 N.m (E) = 101,325 J.m (E). = 1.01325 bar = 1013.25 mbar = 1.01325 × 10 μbar = 1.01325 × 10 barye 6

6

= 101.325 pz (E) = 1.01325 hpz (E) –2

= 1.033227453 kgf.cm

= 760 Torr (E) = 760 mmHg(0°C) (E) = 76 cmHg(0°C) (E) = 29.9212598425 in Hg (32°F) = 10.33256384 mH2O (4°C) = 33.89948766 ftH2O (39.2°F) = 406.793852 inH2O (32°F) = 14.69594878 psia = 235.135180 osia

However, the best way to remember all these numerous conversion factors is to remember the exact value of the standard atmosphere in all these units or the relationships between them, as listed in Table 19.2.

19.1.2 The Boyle–Mariotte Law For a fixed mass of gas under isothermal (i.e., constant temperature) conditions, the product of absolute pressure, p times the volume, V, occupied by the gas is a constant. The constant increases with increasing temperature. PV = P1V1 = P2V2= … = PkVk = … = PnVn = constant Therefore, in a PV diagram they form hyperbolic curves (see Figure 19.1) Example: A commercial gas cylinder supplied by a gas manufacturer contains a volume V = 10 liters of compressed gas at a pressure P = 200 bar. What is the total volume of gas that 5 can be delivered under atmospheric pressure? Since 1 bar = 10 Pa (E) and Patm = 101.325 kPa, 7 3 the volume delivered in cubic decimeters is then Vatm = PV/Patm = [(2 × 10 × 10)/101,325] m 3 = 1974 dm .

Figure 19.1. PV diagram

19 Gases

1040

Gases

19.1.3 Charles and Gay-Lussac’s Law For a given mass of gas under isobaric (i.e., constant pressure) conditions, the ratio of the volume occupied by the gas to the absolute thermodynamic temperature is a constant (see Figure 19.2). This constant changes with changing pressure V/T = V1/T1 = V2/T2= … = Vk/Tk = … = Vn/Tn = constant

Figure 19.2. VT diagram

19.1.4 The Avogadro–Ampere Law Under isothermal and isobaric conditions (i.e., at constant T and P), equal volumes of gases contain equal numbers of atoms or molecules. The proportionality constant is independent of the identity of the gas. Some examples of molar volumes of an ideal gas at various T and P conditions are presented in Table 19.3. One important practical consequence is that mole fraction and volume fraction are identical quantities for ideal gases. –3

3

–1

Table 19.3. Molar volumes of ideal gas vs. T and P (/10 m .mol ) P0 = 101.325 kPa

P0 = 1 bar

T = 273.15 K

22.4135

22.7105

T = 298.15 K

24.4649

24.7891

19.1.5 Normal and Standard Conditions Since the properties of gases strongly depend on both pressure and temperature, it is important to define standardized conditions of T and P. Unfortunately there is a great variety of adopted conventions, academic, industrial and even commercial. In both theory and practice, the conditions recommended by the International Union of Pure and Applied Chemistry

Properties of Gases

1041

Table 19.4. Normal and standard temperature and pressure conditions 3

–1

Standardized conditions name

Temperature

Pressure

Molar volume (vm/dm .mol )

Normal conditions (IUPAC/IUPAP)

273.15 K (0°C)

101.325 Pa

22.4135

Normal conditions (US gas industry)

70°F (21.1°C)

101.325 Pa

24.1458

Standard conditions (IUPAC/IUPAP)

298.15 K (25°C)

101.325 Pa

24.4649

Standard conditions (US gas industry)

32°F (0°C)

101.325 Pa

22.4135

must be used for clarity. However, the other conditions especially those used in the American gas industry are also presented in Table 19.4.

19.1.6 Equation of State of Ideal Gases The gases that obey the three preceding laws are called ideal gases. The mathematical combination of these laws provides the general equation of state for an ideal gas also called the Avogadro–Ampere equation: PV = nRT with P V n R T

absolute pressure in Pa 3 volume occupied by the ideal gas in m amount of substance in mole –1 –1 ideal gas constant in J.K .mol absolute thermodynamic temperature, in K.

19

The ideal gas constant R can also be expressed in units other than the above SI –1

–1

–1

–1

–1

R = 8.3143 J.K .mol = 0.0820578 L-atm.K .mol = 1.98722 caltherm.K .mol –1 –1 –1 –1 = 0.083145 L bar.K .mol = 62.364 L-torr.K .mol

–1

Replacing the volume by the molar volume of the gas, Vm = V/n, i.e., the volume per unit 3 –1 amount of substance expressed in m .mol , we obtain the condensed equation of state of ideal gases: PVm = RT

19.1.7 Dalton’s Law of Partial Pressure The total absolute pressure, P, exerted by a mixture of N ideal gases is the sum of the partial pressures, pk, of each gas. The partial pressure, pk, is the pressure of a gas it would exert if it occupied the container alone. P = ∑ k Pk = P1 + P2 + … + Pk + … + PN

From the ideal gas law: Pk = nkRT/V P = (∑k nk)RT/V = nRT/V

Gases

1042

Gases

where n = ∑k nk = n1 + n2 + … + nk + … + nN. Therefore we obtain Dalton’s law of partial pressure: Pk/P = nk/n = xk or Pk = xkP where, xk, is the dimensionless mole fraction.

19.1.8 Equations of State of Real Gases In the case of real gases, departure from the theoretical equation of state for ideal gases can be expressed in different ways that have led historically to various equations of state among which the Van der Waals and the virial equations are the most noticeable. Other more complex equations of state for real gases are also briefly mentioned.

19.1.8.1 Van der Waals Equation of State Early on, the Dutch chemist Van der Waals realized that the equation of state for real gases can be drawn from that of ideal gases by introducing two correction factors. The first correction factor takes into account the size of the atoms or molecules in the gas while the second correction factor considers the electrostatic attraction exerted between atoms or molecules by intermolecular forces. Actually, the ideal volume of a gas is equal to the difference between the real volume occupied by the gas less the excluded volume of the gas entities. The excluded volume corresponds to the excluded molar volume or covolume, denoted historically by the letter b, and 3 –1 expressed in m .mol times the amount of substance, n, in mole. Videal = V – nb Thus the impact of the covolume becomes important only at high pressures or at cryogenic temperatures when gas atoms or gas molecules are close to each other. On the other hand, the intermolecular forces existing between the gas microscopic entities decrease the pressure that the gas exerts on the wall of the container. If Pideal is the absolute pressure without intermolecular forces and P the absolute pressure of the real gas, the difference between the two pressures δP is given by: Pideal = P + δP Because this pressure correction is only related to intermolecular forces, it is of electrostatic type and it can be easily calculated from the atomic theory. Actually, intermolecular interactions can be of various type: (i) London forces or dipole/dipole interaction; (ii) Debye’s forces or dipole/induced dipole interaction; (iii) Keesom’s forces or dispersion forces or also induced dipole/induced dipole interaction. In all cases, the electrostatic potential energy follows the Lennard–Jones equation as follows: –6

U(r) = –Ar + Br

–12

Therefore, the attractive potential energy per atom is inversely proportional to the sixth 2 power of the interatomic distance and hence to the reciprocal of the volume squared (1/V ). Finally, the pressure difference is related to the square of the amount of substance n. δP = +a(n/V)

2

Properties of Gases

1043

Substituting these two main corrections into the ideal gas law, we obtain the well-known Van der Waals equation of state for actual gases: 2

2

(P + an /V ) (V– nb) = nRT It is possible to simplify the equation of state introducing the molar volume: 2

(P + a/Vm ) (Vm – b) = RT The two empirical constants a and b are the Van der Waals constants of the real gas.

19.1.8.2 Virial Equation of State A different approach consists of representing the real equation of state by MacLaurin’s power series. In practice, there are two virial equations, one describing the product PVm as a function of the reciprocal of the molar volume and the second using the variable P. Under isothermal conditions, the absolute gas pressure can be expressed as a function of the reciprocal of the molar volume: P = f(1/Vm) = RT/Vm, and the developed MacLaurin’s power series of this equation is as follows: 2

2

2

n

n

n

P = (1/Vm)[∂P/∂(1/Vm)] + (1/Vm) [∂ P/∂(1/Vm) ]/2! + … + (1/Vm) [∂ P/∂(1/Vm) ]/n! After calculating the partial derivatives, the resulting power series has the following form: 2

PVm = [Av + Bv(1/Vm) + Cv(1/Vm) + …] The virial coefficients Av, Bv, and Cv are temperature dependent and they can be calculated from the two Van der Waals constants (a and b). Rewriting the Van der Waals equation as follows: PVm = (RT + bP) – a/Vm – ab/Vm

2

comparison of the terms with the McLaurin’s power series now yields: Av = (RT + bP)

Bv = – a

and

19

Cv = – ab

The three isothermal virial coefficients can also be determined experimentally from P-V-T data and assuming that a real gas approaches ideality as (1/Vm) —> 0 and as P —> 0 then Av = RT. Actually, writing the virial equation of state as follows: 2

PVm – RT = Bv(1/Vm) + Cv(1/Vm) + … Multiplying the above equation by the molar volume gives: Vm(PVm – RT) = Bv + Cv/Vm+ … A plot of the left member against the reciprocal of the molar volume will give Bv as a vertical intercept and Cv by the slope of the linear plot. If isochoric (i.e., constant volume) conditions are assumed, the virial equation becomes: 2

PVm = RT[Ap + BpPm + CvPm + …] In addition to the Van der Waals and virial equation of state, other equations obtained from experiments are presented in Table 19.5.

Gases

1044

Gases Table 19.5. Equation of state of real gases Equation name

Mathematical equation

Beattie–Bridgman

P = [(1 – g)RT(Vm + b) – a]/Vm a = ao[1 + (a/Vm)] b = bo[1– (b/Vm)] 3 g = co/VmT

Parameters

Benedict, Webb and Rubin

P = RTd + d {RT[B + bd] – [A + ad – aαd ] –2 2 2 – T [C – cd (1 + γd )exp(– γd )]}

Berthelot

P = RT/(V – b) – a/TV

Berthelot modified

P = RT/V[1 + (9PTc/128PcT)(1 –6Tc /T )]

Clausius

{P + a /[T(Vm + c) ]} ( Vm – b ) = RT

a = Vc – RTc/4Pc b = 3RTc/8Pc – Vc 2 3 c = 27R Tc /64Pc

Dieterici

P = [RT/(Vm – b)] exp(–a/RTVm)

a, b

Ideal gases

PVm = RT

none

Peng–Robinson

P = RT/(Vm – b) – a·T/Vm(Vm + b) + b (Vm – b)

a, b

Percus–Yevick

P = RT/(Vm + bVm + b )/(Vm – b) – a/Vm

2

a, b

Redlich–Kwong

P = RT/(Vm – b) – a/[T Vm(Vm + b)]

a, b

Redlich–Kwong–Soave

P = RT/(Vm – b) – a(T)/[Vm(Vm + b)] 1/2 2 a(T) = {1 + m[1 – (T/Tc) }

a, b, m

Redlich–Kwong–Soave– Gibbons–Laughton

P = RT/(Vm – b) – a(T)/[Vm(Vm + b)] 1/2 2 a(T) = {1+ x[(T/Tc) – 1]+ y[(T/Tc) –1]}

a, b,x, and y

Van der Waals

(P + a/Vm )(Vm – b) = RT

Van der Waals (reduced variables)

pr = 8Tr/(3Vr – 1) – 3/Vr

Virial

PVm = [Av + Bv(1/Vm) + Cv(1/Vm) + …] 2 PVm = RT[Ap + BpPm + CvPm + …]

Wohl

{P + a/[TVm(Vm – b )] – c/T Vm }·( Vm – b ) = RT

2

a, b, and g

2

4

2

a, b 2

2

Pc, Tc

2

2

A, B, C, a, b, c, d, α, β, γ

3

2

1/2

2

a, b

2

Tr = T/Tc pr = p/pc Vr = Vm/Vm,c 2

2

3

Av, Bv,and Cv Ap, Bp,and Cp 2

a = 6 PcTcVc b = Vc /4 2 3 c = 4 PcTc Vc

Notes: P = absolute pressure in Pa, a, b, c = empirical constants in appropriate SI units, Vm = molar volume –3 –1 –1 in mol.m , R = ideal gas constant in J.K mol , T = absolute thermodynamic temperature in K.

19.1.9 Density and Specific Gravity of Gases Based on the equation of state for an ideal gas, it is possible to establish the theoretical equa–3 tion of the mass density of a gas denoted by the Greek letter ρ and expressed in kg.m having a molar mass M as a function of the absolute pressure P and temperature T. Actually, the density being the ratio of the mass of the gas divided by the volume it occupies: ρ = m/V with PV = nRT = (m/M)RT then we obtain the equation of the density of the gas: ρ = PM/RT The above equation indicates that the mass density of an ideal gas under isothermal and isobaric conditions is only related to its molar atomic or molecular mass.

Properties of Gases

1045

Usually, engineers utilize the specific gravity or relative density of gases, denoted d or S.G. This dimensionless physical quantity refers to the ratio of the mass density of the gas over that of a reference gas, usually dry air, measured under normal conditions of temperature and pressure (NTP). For ideal gases, the specific gravity relative to dry air at the same temperature and pressure can be written as the ratio of their molar masses: dgas = ρgas/ρair = Mgas/Mair Therefore at 273.15K and 101.325 kPa, the molar molecular mass for dry air with the standard–3 –1 ized chemical composition of 79 vol.% N2, 20 vol.% O2 and 1 vol.% Ar is 28.930 × 10 kg.mol , and the practical equation for the specific gravity of a gas is given as follows: dgas ≈ Mgas/28.930 Therefore, in practice, knowledge of the molar atomic or molecular mass of a gas allows us to estimate its specific gravity with respect to dry air quickly; conversely, the measurement of the specific gravity of a gas with respect to air under known T and P conditions allows the determination of its molar mass. In the case of real gases at low pressure that satisfy the simplified virial equation of state, i.e., PV = n[RT + BpPm], the mass density is given by the following equation: ρ = PM/[RT(1 + BpP/RT)]

19.1.10 Barometric Equation –1

For a tall column containing an ideal gas with a molar mass M, in kg.mol , it is important to take into account the volume compressibility of the gas, i.e., the variation of its mass density with absolute pressure. In the column, the pressure variation, dP, in Pa is given by: dP = –ρgndZ The negative sign indicates that the pressure increases from the top of the column to the bottom as molecules lower down are affected by the mass of those higher up. Replacing the density of the ideal gas using the equation obtained at the beginning of Section 19.1.9, we obtain the following: dP = –(PM/RT)gndZ After integration, the pressure in the gas column is expressed as a direct function of the elevation, absolute temperature, and molar mass: P = P0exp[–Mgn·(Z – Z0)/RT] = P0exp[–(Z – Z0)/H] This equation is called the barometric equation by geophysicists (i.e., aerologists and meteorologists) because it provides the absolute pressure in an air column for a given geometric elevation (i.e., altitude, Z), and in this particular case the reference elevation Z0 is taken equal to 0 meters (i.e., on Earth, the sea level is the datum plane). Usually, the factor denoted H = RT/Mgn is named the scale height and it is expressed in m. It corresponds to the elevation at which the absolute gas pressure is divided by the Naperian base e = 2.718281828… Example: If we assume, in a first approximation, air to be an ideal gas, having the average –3 –1 –3 molar mass M = 28.930 × 10 kg.mol , a mass density ρ = 1.293 kg.m , at T = 273.15 K, the scale height is equal to about 7.986 km. This means that for an altitude equal to that of Mount Everest (8.846 km), the absolute pressure is roughly a third of pressure exerted at sea level!

19 Gases

1046

Gases

As a general rule, the barometric equation is useful when dealing with a huge column of gas as in oil drilling or geothermy. However, for usual chemical engineering calculations, it is a common agreement to consider a constant pressure in the overall gas column.

19.1.11 Isobaric Coefficient of Cubic Expansion When heated at constant pressure a gas undergoes an isotropic volumic expansion, and the volume occupied by a gas at a given absolute temperature T is given by the equation: V(T) = V(T0)[1 + β (T – T0)] where β denotes the cubic expansion coefficient of the gas, expressed in K and defined as follows: –1

β = (1/V)(∂V/∂T)p For an ideal gas, the cubic expansion coefficient is equal to the reciprocal of the absolute thermodynamic temperature:

β = (1/T) (ideal gas)

19.1.12 Compressibility Factor The compression factor or the compressibility factor (Z) of an actual gas is a dimensionless quantity defined by the ratio of actual and ideal molar volumes according to the equation: Z = Vm/Vm,ideal = PVm/RT Obviously, Z = 1 for an ideal gas under all conditions. At very high pressure, Z > 1, that is, Vm > Vm,id, so real gases are more difficult to compress than an ideal gas, indicating that repulsive interaction is dominant. At intermediate pressure, most gases have Z < 1, i.e., attractive forces dominate and favor compression. Z also depends on temperature. There is a temperature at which Z = 1 over a wide range of pressures, and this temperature is known as the Boyle temperature. In other words, the initial slope of the graphic plot of Z vas a function of pressure P is zero at T = TB.

19.1.13 Isotherms of Real Gases and Critical Constants The graphical representation of the absolute pressure, P, of a gas as a function of its molar volume, Vm, at constant temperature is called an isotherm [P = f(Vm)] (see Figure 19.3). The isotherm of a real gas at a high temperature T3 resembles that of an ideal gas, that is, it exhibits a hyperbolic curve following the equation P = a/Vm with the empirical constant, a, being closed to the product RT. Hence at high temperature any increase of pressure decreases the molar volume but no phase change occurs even in the highest pressure region. On the contrary, at a sufficiently low temperature T1, compressing the gas causes its molar volume to decrease until a point A at which the gas begins to condense into liquid, i.e., at that point the pressure exerted equals the vapor pressure of the liquid at T1. Afterwards, the reduction of volume continues but does not produce any pressure change because the condensation proceeds. When all the gas has been liquefied (point B), the pressure rises steeply because liquid

Properties of Gases

1047

Figure 19.3. Isotherm of real gases

is more difficult to compress than a gas. Similar behavior is also observed at a higher temperature T2, but the length of the constant pressure line becomes shorter. This behavior occurs until a certain high temperature is reached denoted Tc, and called the critical temperature. At that temperature, the constant pressure plateau shrinks into a single point (point C) called the critical point. The molar volume at that point is called critical molar volume Vm,c and the pressure is the critical pressure Pc. A gas cannot be condensed to a liquid at temperatures above Tc and there is no clear distinction between the liquid and gaseous phases because the two states cannot coexist with a sharp boundary between them. Experimentally, if a certain amount of gas and liquid is placed inside a pressurized container with transparent quartz windows and kept below Tc, two layers will be observed, separated by a sharp boundary. As the tube is warmed, the boundary becomes less distinct because the densities, and therefore the refractive indices, of the liquid and gas approach a common value. When the Tc is reached, the boundary becomes invisible and the iridescent aspect exhibited by the fluid is called critical opalescence. Hence the following definitions can be drawn for the critical constants of a real gas. The critical temperature of a gas is the absolute temperature, denoted Tc, above which the liquid phase cannot be formed no matter how great a pressure is applied to the system. The critical pressure of a gas denoted Pc is the vapor pressure of the liquid at the critical point. Hence, below the critical temperature any substance at a pressure above its vapor pressure will be liquid. The critical density is the density of the fluid at the critical temperature and pressure.

19.1.14 Critical Parameters Critical constants can be calculated analytically from several equations of state. But the sim3 plest way is to calculate them from the Van der Waals equation of state . Actually, when the molar volume of the gas is large, that is, at high temperature and low pressure, the Van der Waals equation becomes the ideal gas equation.

3

Eberhart, J.G. The many faces of Van der Waals’ equation of state Journal of Chemical Education, 66(1989)906.

19 Gases

1048

Gases

Since there is a point of inflection on the P, Vm plot, the first and second derivatives of pressure are both zero at that point. (∂P/∂Vm)T = 0 2

(∂P/∂Vm)T = –RT/(Vm – b) + 2a/Vm 2

2

and 3

2

3

(∂ P/∂Vm )T = 2RT/(Vm – b) – 6a/Vm and Pc = RTc/(Vm,c – b) – a/Vm,c

2

(∂ P/∂Vm )T = 0

4

2

We then obtain the critical parameters as a function of Van der Waals constants: Vm,c = 3b

Pc = a/27b

2

and

Tc = 8a/27Rb

or conversely the Van der Waals constants as a function of critical parameters: b = Vm,c/3

a = 3PcVm.c

2

and

R = 8PcVm,c/3Tc

and Zc = PcVm,c/RTc = 3/8 = 0.375

19.1.15 The Principle of Corresponding States For a better comparison between the behavior of different gases, it is necessary to choose a proper reference state. Gases depart from ideality when the temperature approaches the critical temperature. It is therefore more logical to compare gases at a temperature which is relative to their Tc. A set of three dimensionless reduced variables was introduced for this purpose; this is the principle of corresponding states: Tr = T/Tc

Pr = P/Pc

and

Vr = Vm/Vc

The principle can be applied satisfactorily for nonpolar gases with symmetrical molecules. The Van der Waals equation can be rewritten in terms of reduced variables as follows: 2

2

PrPc = RTrTc /(VrVm,c – b) – a/(Vr Vm,c ) Replacing the Van der Waals parameters by critical parameters we obtain the reduced Van der Waals equation: Pr = 8Tr /(3Vr – 1) – 3/Vr

2

19.1.16 Microscopic Properties of Gas Molecules Most of the properties and equations described in this paragraph are obtained from the kinetic theory of gases applied to ideal gases and assuming that atoms or molecules interact like hard spheres. Mean square velocity of gas molecules. The mean velocity of a gas molecule is given by the following equation: 2

= 3kT/m = 3RT/M Mean velocity of gas molecules. The mean velocity of gas molecules is given by: 2

1/2

1/2

1/2

= [8/3π] = [8kT/πm] = [8RT/πM]

Mean free path. The mean free path denoted, l, is the average distance achieved by a gas molecule between two collisions and it is given by the equation. l = m/πρσ √2= m/πρσ √2 2

2

Properties of Gases

1049

19.1.17 Molar and Specific Heat Capacities –1

–

The molar heat capacity of a gas denoted by the capital letter C and expressed in J.mol K , represents the heat stored by a mole of the gas when heated from a temperature T1 to a temperature T2. At constant pressure (i.e., isobaric transformation), the heat change corresponds to the variation of the enthalpy of the gas as follows: ΔQP = ΔH = CP ΔT while at constant volume (i.e., isochoric transformation) the heat change corresponds to the variation of the internal energy of the gas as follows: ΔQV = ΔU = CV ΔT The respective isobaric and isochoric molar heat capacities for ideal gases can be calculated from the kinetic theory and are given in Table 19.6. Table 19.6. Theoretical molar heat capacities of ideal gases Type of gas molecule

Molar heat capacities

Isentropic exponent γ = Cp/Cv

Isobaric Cp/R

Isochoric Cv/R

Monoatomic (e.g., He, Ne, Ar)

5/2

3/2

5/3

Diatomic (e.g., H2, D2, N2, O2)

7/2

5/2

7/5

Polyatomic with N degrees of freedom (e.g., CO2, SF6)

(N+2)/2

N/2

1+2/N

The difference between the molar heat capacities at constant pressure and constant volume is given by the general Mayer’s relation: Cp – Cv = [P + (∂U/∂V)T] · (∂V/∂T)p For ideal gases, the above equation becomes the Mayer’s equation for ideal gases: Cp – Cv = R

19.1.18 Dynamic and Kinematic Viscosities The dynamic viscosity or absolute viscosity of gases is denoted μ or η and is expressed in Pa.s. The kinetic theory of gases allows accurate prediction of the viscosity of ideal gases, and states that viscosity is independent of pressure and increases as temperature increases because atomic or molecular collisions increase. η = 1/3 ρ · v · l with ρ the density of the gas in kg.m , v the mean velocity in m.s , and l the mean free path in m. Usually under NTP, most gases exhibit a dynamic viscosity ranging from 7 to 100 μPa.s. However in practice, more complex relationships such as Sutherland’s equation must be used: –3

–1

η = η0[T /(1 + C/T)] 1/2

where η0 and C are empirical constants determined by experiments.

19 Gases

1050

Gases

19.1.19 Solubility of Gases in Liquids The solubility of gases in a liquid can be expressed in three different manners described as follows: The dimensionless Bunsen absorption coefficient denoted α(T) is equal to the volume 0 of gas Vgas measured under normal conditions of temperature and pressure (i.e., p0 = 101.325 kPa and T0 = 273.15K) dissolved into a volume of solvent VS(T) (usually 3 water with a volume taken as 100 cm in tables) at a given absolute temperature T and when the pressure of the gas without that of water vapor is equal to 101.325 kPa (i.e., under a partial pressure of the gas of 760 mmHg):

(i)

α(T) = Vgas/VS(T) 0

The dimensionless A coefficient denoted Α is equal to the volume of gas measured under normal conditions of temperature and pressure (i.e., p0 = 101.325 kPa and 3 T0 = 273.15K) dissolved into a given volume of water (usually taken as 1 cm in tables) at a given temperature and when the pressure of the gas plus that of the water vapor is equal to 101.325 kPa. (iii) The dimensionless L coefficient denoted Λ is equal to the volume of gas expressed in mL measured under normal conditions of temperature and pressure (i.e., p0 = 101.325 kPa 3 and T0 = 273.15K) dissolved into a given volume of water (usually taken as 100 cm in tables) at a given temperature and when the pressure of the gas plus that of the water vapor is equal to 101.325 kPa. (iv) Henry’s law states that the partial pressure of a solute A dissolved into a liquid B develops a partial pressure over the solution given by Henry’s equation: (ii)

pA = HA xA where HA is Henry’s coefficient expressed in Pa per mole fraction of solute. For a dilute solution, the molarity of the gas into the liquid is used pA = H*A CA –1

–3

where H*A is Henry’s molar coefficient expressed in Pa.mol .m of solute. For quite a number of gases Henry’s law holds well when the partial pressure of the solute is less than the atmospheric pressure. The dissolution of a gas into a solvent, especially water, is an exothermic reaction: Gas(g) + solvent —> Gas(soln) + ΔHsoln with ΔHsolnthe enthalpy of dissolution of the gas in J.mol . Therefore, from Le Chatelier’s principle, any increase of the temperature of the system leads to a decrease of the solubility of the gas. For that reason, gases may be expelled from a solution by boiling (e.g., boil distilled water to remove dissolved oxygen). Although this is true in most cases, some sparingly soluble gases such as hydrogen and noble gases behave differently especially in nonaqueous solvents (e.g., hydrocarbons, alcohols, acetone) where solubilities shows slight increase with temperature. Because the equilibrium constant of the above reaction at a given gas pressure is equal to the Bunsen absorption coefficient α of the gas, it is possible to express the temperature dependence of the solubility of the gas using the Van’t Hoff equation as follows: –1

ln [α(T2)/α(T1)] = +(ΔHsoln/RT) · [1/T1 – 1/T2]

Properties of Gases

1051

Table 19.7. Solubility of selected common gases in water (by increasing solubilities) Gas

Solubility in water at 273.15 K and 101.3265 kPa 3

3

(cm /kg H2O)

(mmol/dm )

Helium (He)

9.7

0.433

Neon (Ne)

10.5

0.469

Hydrogen (H2)

21.48

0.958

Nitrogen (N2)

23.54

1.050

Argon (Ar)

33.6

1.499

Carbon monoxide (CO)

35.4

1.578

Oxygen (O2)

48.89

2.181

Methane (CH4)

55.63

2.482

Krypton (Kr)

59.4

2.650

Nitric oxide (NO)

73.81

3.293

Xenon (Xe)

108.1

4.823

Sulfur dioxide (SO2)

177

7.897

Radon (Rn)

230

10.261

Ozone (O3)

490

21.861

Carbonyl sulfide (COS)

540

24.092

Nitrous oxide (N2O)

600

26.769

Carbon dioxide (CO2)

1713

76.291

Acetylene (C2H2)

1730

77.184

Chlorine (Cl2)

2260

100.830

Hydrogen sulfide (H2S)

4670

208.35

Ammonia (NH3)

1.130 × 10

6

50,415

19.1.20 Gas Permeability of Polymers Before giving the permeability coefficients of polymers for several common gases, a theoretical reminder is required owing to the numerous definitions that the reader can find in the technical literature. For a given pressure difference, i.e., for a given pressure gradient expressed in Pa/m, across a permeable membrane having a thickness d, in m, the flux JX of the fluid which itself possesses a dynamic viscosity, μ, expressed in Pa.s passing through the membrane is given by Darcy’s equation: JX = (1/A)·∂X/∂t = – (KX/η)·ΔP/Δx The proportionality coefficient, KX, is called the permeability coefficient of the membrane expressed in a unit depending on the unit of the flux (i.e., mass, volume, or molar basis). Moreover, in certain textbooks, the permeability coefficient is also defined as the ratio KX/η, or more rarely KX/ηΔx. The various dimensions of permeability coefficients are reported in Table 19.8.

19 Gases

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Gases

Table 19.8. Dimensions of the permeability coefficients Physical quantity Mass basis X=m [Jx]

[M.L .T ]

–2

–1

[η]

–1

–1

[M.L .T ]

[ΔP/Δx]

[M.L .T ]

–2

–2

Volume basis Molar basis X=v X=n 3

–2

–1

–1

–1

[M.L .T ]

[M.L .T ]

–2

–2

[M.L .T ]

[L .L .T ] [M.L .T ] –1

2

[Kx]

[Km]=[M.L ] [Kv]=[L ]

[Kx/η]

[T]

[Kx/ηΔx]

–1

3

–1

2

[M .L .T] –1

[T.L ]

[M .L .T]

–2

–1

–1

–1

–2

–2

[N.L .T ]

–1

[Kn]=[N.L ] –1

[N.M .T] –1

–1

[NM .L .T]

Table 19.9. Gas permeability coefficients of most common polymers and quartz glass (in barrers) Polymer membrane

O2

N2

H2

He

CO2

H 2O

Cellophane

0.0021

0.0032

0.0065

0.005

0.005

1900

Cellulose acetate (CA)

0.78

0.28

3.5

13.6

23

5500

Chlorinated polyvinyl chloride (PVDC)

0.0053

0.00094

–

0.31

0.03

0.5

Ethyl cellulose (EC)

2.8

31

0.403

0.143

3.0

1.14

0.36

12.0

Low-density polyethylene (LDPE)

2.88

0.969

12.0

4.9

12.6

90

Polyacrylonitrile (PAN)

0.0002

–

–

–

0.0008

300

Polyamide (Nylon 6)

0.038

0.0095

–

0.53

0.10

177

4.7

67

Polydimethysiloxane (PDMS)

280

360

n.a. 11

High-density polyethylene (HDPE)

Polycarbonate (PC)

CH4

3.6 900

Polyethylene terephthalate (PETP)

0.035

0.0065

3.70

1.32

0.17

130

Polypropylene (PP)

2.3

0.44

41

38

9.2

51

Polystyrene (PS)

2.63

2.27

23.2

3.51

10.5

1200

2.27

Polytetrafluoroethylene (PTFE)

2.63

0.788

23.3

62

10.5

1200

1.5

Polyvinyl alchol (PVA)

0.0089

0.001

0.009

0.001

0.001

–

Polyvinyl chloride (PVC)

0.0453

0.0118

1.70

2.05

0.157

275

0.048

0.29

Polyvinyl fluoride (PVF)

0.099

Polyterfluoroethylene (TFE)

0.025

Quartz glass (400°C) –10

0.003 nil

3

1.87 0.94

6.8 0.60

0.0064 0.00002

2

Note: 1 barrers = 10 cm (STP).cm/cm .s.cmHg (E)

19.1.21 Dielectric Properties of Gases, Permittivity and Breakdown Voltage The definitions and physical quantities used to describe the dielectric properties of insulating materials are described in detail in the Chapter 8. In the following paragraph, only the dielectric properties related to the gaseous state are briefly described. Most gases exhibit a relative electrical permittivity (i.e., dielectric constant) close to that of vacuum, that is, close to unity. Values of relative permittivity of gases may also be obtained from the data on refractive indices measured for radio frequencies by using the relation: εrμr = n

2

Properties of Gases

1053

Figure 19.4. Paschen curves for air, nitrogen and sulfur hexafluoride from Husain, E.; and Nema, R.S. – Analysis of the Paschen curves for air, N2, SF6 using the Townsend breakdown equation IEEE Transactions EI-17 (4) 350–353. Copyright © 1982 IEEE and used with permission.

This simple equation applies to non-absorbing gases with the magnetic permeability, μr, equal to unity for all diamagnetic gases except oxygen which is paramagnetic (see Chapter 7). The breakdown voltage, also called the disruptive potential, denoted Ed, and expressed in –1 V.m , corresponds to the electric field strength that creates an electric discharge (i.e., spark) (see Chapter 8). Usually, for gases the order of magnitude is several MV/m or kV/mm, for instance, dry air at 25°C and 101.325 kPa exhibits a breakdown ac voltage of 3.18 kV/mm (crest) or 2.19 kV/mm (rms). In the gaseous state, the breakdown voltage at which an electric discharge occurs is related to the T and P conditions but also to the product Pd of the electrode gap, d, in m, times the absolute pressure, P, in Pa.m (kPa.mm). The graphical representation of the variation of the breakdown voltage versus the product Pd at a constant temperature is called the Paschen curve of the gas [Ed = f(Pd) at T = cst]. The Paschen plot (see Figure 19.5) always exhibits a minimum point of abscissa (Pd)min and ordinate (Ed)min called the minimum pressure-distance and spark voltage respectively. As a rule of the thumb, Paschen’s law states that the sparking potential of a gas is only a function of the product (Pd). It is also important to note that the dielectric breakdown of a gas is also dependent on the geometries of the electrode (i.e., balls, plates or pins) and the material of the electrodes. Some dielectric properties of selected common gases are reported in Table 19.10. Table 19.10. Dielectric properties of selected common gases at 293.15 K and 101.325 kPa Gas

Permittivity (εr/nil)(*)

Breakdown voltage –1 (Ed/kV.mm )

Paschen’s parameters Minimum spark voltage (U/V)

Pressure-distance (Pd/kPa.mm)

Air

1.000536

3.24 (**)

327

0.759

Argon

1.000517

213

0.800

15.8

Carbon dioxide

1.0009216

419

0.680

12.8

Helium

1.000065

261

3.600

24.6

3.82

Ionization potential (I/eV)

19 Gases

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Gases

Table 19.10. (continued) Gas

Permittivity (εr/nil)(*)

Breakdown voltage –1 (Ed/kV.mm )

Paschen’s parameters Minimum spark voltage (U/V)

Pressure-distance (Pd/kPa.mm)

273

1.530

Ionization potential (I/eV)

Deuterium

1.000269

Hydrogen

1.000254

2.77

278

1.920

13.6

Nitrogen

1.000547

3.69

251

0.893

14.5

Oxygen

1.0004943

3.02

455

0.933

13.6

Sulfur dioxide

1.008200

457

0.440

13.1

Sulfur hexafluoride

1.002026

507

0.035

15.3

Water vapor

1.00587

16–20

12.6

Notes: (*) Relative permittivity at other temperature and pressure can be obtained using the equation: (εr – 1)(t) = (εr – 1) · P/{101.325[1 + 0.003411(t – 20)]} with P in kPa and t in°C (originally devised by the National Bureau of Standard (NBS), circular No. 537); (**) For dry air the breakdown voltage can be calculated at any other thermodynamic temperature T and absolute pressure P for an electrode gap d using the general equation: Ed (kV/mm) = 9.37382 × P(kPa) · d(mm)/T(K).

19.1.22 Psychrometry and Hygrometry The scope of psychrometry is the detailed study of gas–vapor mixtures, where gas refers to a noncondensing gaseous compound for the temperature range considered, while vapor refers to a gaseous phase in thermodynamic equilibrium with its liquid state. In the particular case where the gas is dry air, and the vapor is water vapor (i.e., steam), it is called hygrometry, and the mixture is called moist air. As a general rule, the humidity is the amount of water vapor contained in the dry air. The total pressure of the water–air mixture is described by the summation of partial pressures of each individual gas such as in the following Dalton’s equation: P = pw + pa where P denotes the total pressure of the gas mixture, and pw, and pa are respectively the partial pressures of water vapor, and air, all three expressed in Pa. Important note: Usually, unless otherwise specified, the psychrometric calculations refer to the normal atmospheric pressure of 101.325 kPa (or 1 bar in the recent convention), but obviously calculations can also be achieved for other total pressures.

19.1.23 Vapor Pressure The vapor pressure of water, denoted πw, is the independent pressure exerted by the water vapor in the air, and it is expressed in Pa. The natural tendency for pressures to equalize will cause moisture to migrate from an area of high vapor pressure to an area of low vapor pressure. The saturation vapor pressure varies with temperature.

19.1.23.1 Absolute Humidity or Humidity Ratio The absolute humidity is a dimensionless physical quantity, denoted H, which corresponds to the ratio of the mass of water vapor, mw, in kg contained in the moist air to the mass of dry

Properties of Gases

1055

Table 19.11. Vapor pressure of water (T/°C)

(πw/Pa)

–28.9

43

–23.3

74

–17.8

128

–12.2

213

–6.7

348

0.0

610

4.4

839

15.6

1767

26.7

3495

37.8

6545

48.9

11,670

60.0

19,917

air, ma, in kg. This may also be called the moisture content or mixing ratio. Note that for practical calculations in psychrometric charts, absolute humidity is expressed in the SI as kg of water per kg of dry air, or lb of water vapor per lb of dry air in the US customary system. Older UK and US references used grains of water vapor per pound of dry air (gr/lb). Assuming that both air and water are ideal gases and they are governed by the Avogadro–Ampere law, i.e., PV = nRT, the absolute humidity can be described by the following equation: H = mw/ma = (Mw/Ma)·[pw/(P – pw)] where P is the overall pressure of the gas mixture, and pw, the partial pressures of water vapor both expressed in Pa. Mw and Ma are respectively the relative molar masses of water (i.e., 18.015), and air (i.e., 28.964). Because the absolute humidity only depends on the ratio of the masses of the constituents, it is not affected by temperature. Therefore, absolute humidity is a useful quantity in calculating the amount of moisture involved in a particular process, such as the amount of moisture removed by ventilating a room or the amount of water vapor introduced by evaporative cooling. At saturation, when the partial pressure of water vapor is equal to the vapor pressure of liquid water, i.e., pw = πw, the absolute humidity at saturation, denoted HS, corresponds to the maximum amount of water vapor that the air can carry at a given temperature: HS = mw/ma = (Mw/Ma)·[πw/(P – πw)] Important notes: The theoretical humidity capacity of air is a direct function of temperature. For instance, at 30°C, a mass of dry air can contain up to 4 wt.% water vapor, while, at –40°C, it holds no more than 0.2 wt.%. The engineer and the meteorologist require an index of humidity that does not change with pressure or temperature. A property of this sort will identify an air mass when it is cooled or when it rises to lower pressures without losing or gaining water vapor. Because all the ideal gases will expand volumetrically equally, the ratios of the mass of water to the mass of dry air, or the dry air plus vapor, will be conserved during such changes and will continue identifying the air mass.

19 Gases

1056

Gases

19.1.23.2 Mass Fraction of Water Vapor or Specific Humidity Another dimensionless physical quantity is the mass fraction of water vapor in moist air, sometimes called specific humidity denoted, ww or, less often q, i.e., the ratio of the mass of water vapor over the masses of both air and water vapor. The relationship between the absolute humidity and water mass fraction is described by the following equation: ww = mw /(ma + mw) = 1/(1 + 1/H)

19.1.23.3 Relative Humidity When a volume of air at a given temperature holds the maximum amount of water vapor, the air is said to be saturated. Hence, relative humidity, sometimes called humidity ratio or degree of saturation denoted RH, is a dimensionless quantity which corresponds to the water-vapor content of the air relative to its maximum content at saturation at the same drybulb temperature. Relative humidity can also be regarded as the ratio of the mole fraction of water vapor in moist air to the mole fraction in moist air at saturation at the same temperature, and pressure. By use of the ideal gas law, this can be expressed as the ratio of the partial pressure of water vapor to the water vapor pressure at the same temperature. Therefore, relative humidity is the ratio of absolute humidity to absolute humidity at saturation, or the ratio of partial water vapor pressure, and vapor pressure of water at a given temperature: RH (%) = 100 · (pw /πw) = 100 · (H/HS) For instance, saturated air, by definition, has a relative humidity of 100% RH, and near the Earth the relative humidity very rarely falls below 30% RH. Unsaturated air can become saturated in three ways: (i) (ii)

by evaporation of water into the air; by the mixing of two masses of air of different temperatures, both initially unsaturated but saturated as a mixture; (iii) most commonly, by cooling the air, which reduces its capacity to hold moisture as water vapor sometimes to the point that the water vapor it holds is sufficient for saturation. Important note: In meteorology, great care must be taken to distinguish between the relative humidity of the air and its absolute humidity. The air masses above the tropical deserts such as the Sahara (Africa) and Mexican (Central America) deserts contain vast quantities of moisture as invisible water vapor; because of the high temperatures, however, relative humidities are very low. Conversely, air in very high latitudes, because of low temperatures, is frequently saturated even though the absolute amount of moisture in the air is low.

19.1.23.4 Humid Heat –1

–1

The humid heat denoted, cS, is the specific heat capacity of moist air expressed in J.kg .K . Therefore, it is the weighted sum of the respective specific heat capacities of dry air and pure water vapor: cS = ww · cp(water) + wa · cp(air)= cp(air)+ ww · [cp(water) – cp(air)]

19.1.23.5 Humid or Specific Volume 3

–1

The humid volume or specific volume denoted, vH, and expressed in m .kg , corresponds to the volume occupied by the moist air (i.e., water vapor, and dry air) over the mass of the dry air: vH = (va + vw)/ma = RT · {1/[Ma · (P – pw)] + H/(Mw · pw)]

Properties of Gases

1057

19.1.23.6 Dry-Bulb Temperature The dry-bulb temperature, denoted Tdb, is what is usually meant by air temperature. It is measured with a normal thermometer.

19.1.23.7 Wet-Bulb Temperature The wet-bulb temperature, denoted w.b., or twb, is measured by placing a common mercury thermometer, with a water-moistened wick covered bulb, into a fast moving stream of ambient air (e.g., using a sling thermometer). Evaporation of water from the wick cools the bulb, and the amount of cooling is proportional to the evaporation rate, which in turn is inversely proportional to the amount of water in the air.

19.1.23.8 Wet-Bulb Depression The wet-bulb depression is the difference between the dry-bulb and wet-bulb temperatures. The temperature is depressed by evaporative cooling of the wet bulb. The greater the difference between the amount of water in the air and the saturation water capacity the more rapid the evaporation and thus the greater the temperature depression. The wet-bulb depression allows one to determine the absolute humidity of dry air by means of the appropriate psychrometric chart.

19.1.23.9 Dew Point Temperature The dew point, denoted, d.p., or td, is the temperature at which condensation occurs as air is cooled at a constant pressure and humidity ratio. The dew point has the virtue of being easily interpreted because it is the temperature at which a blade of polished steel will become wet with dew from the air. Ideally, it is also the temperature of fog or cloud formation in meteorology. 19 Gases

19.1.23.10 Specific Enthalpy The specific enthalpy, denoted h, corresponds to the energy content of an air-water mixture. It is expressed in J/kg of dry air. Measurement of enthalpy is relative, i.e., the actual heat content is dependent on the datum or zero point chosen. The usual datum for dry air is 0°F (–17.78°C) and for water 32°F (0°C). h = cp(a)Tdb + H.hw h = cp(a)Tdb + H[Lv(w) + cP(w)Tdb] with cp(a) cP(w) Tdb H hw Lv(w)

–1

–1

specific heat capacity of dry air in J.kg .K –1 –1 specific heat capacity of water vaporin J.kg .K dry bulb temperature in K absolute humidity kg of water/kg dry air –1 enthalpy of water in J.kg –1 latent heat of vaporization of water in J.kg .

19.1.23.11 Latent Heat of Fusion –1

The latent heat of fusion of a solid, denoted, Lf, and expressed in J.kg is the heat required per unit mass of solid to melt it. For instance, in order to melt ice or to freeze water, 340 kJ/kg (146 Btu/lb) must be supplied or removed.

1058

Gases

19.1.23.12 Latent Heat of Vaporization The latent heat of vaporization of water corresponds to the heat required per unit mass of –1 liquid to vaporize it. It is usually denoted Lv, and it is expressed in J.kg . The latent heat of vaporization is a function of temperature as shown in Table 19.12. At room temperature, –1 a common value used for designing systems is 2.256 MJ.kg (970 Btu/lb) of water. Table 19.12. Latent heat of vaporization of water vs. T Temperature Latent enthalpy of vaporization (T/°C)

(Btu/lb)

(kJ/kg)

0.0

1075

2500

4.4

1071

2491

15.6

1059

2463

30.6

1044

2428

37.8

1037

2412

60.0

1014

2359

82.2

990

2302

100.0

970

2256

19.1.23.13 Refractivity of Moist Air The refractivity (nD – 1) of moist air can be calculated from the following empirical equation: (nD – 1) × 10 = (776.239/T) · pdry air + (1330.609/T) · pCO2 + (647.003/T)·(1 + 5748/T) · pH2O 6

where T is the absolute thermodynamic temperature expressed in K, and pdry air, pCO2, and pH2O, are the partial pressures in kPa of dry air, carbon dioxide and water vapor respectively.

19.1.23.14 Psychrometric Charts The psychrometric charts are nomographs obtained from experimental data and which are very useful tools for determining the air-water vapor mixture properties at given pressure conditions (see Figure 19.5). Precise psychrometric charts can be found in the latest edition of the ASHRAE Handbook: Fundamentals edited by the American Society of Heating, Refrigeration and Air-Conditioning Engineers, ASHRAE, Atlanta GA, United States.

19.1.23.15 Psychrometric Equations The psychrometric charts are very useful for determining air-water vapor mixture properties; however, for pressure conditions outside the range, it is useful to calculate the properties directly using fully detailed equations found in ASAE Standard Psychrometric Data ASAE D271.

Properties of Gases

1059

19 Gases

Figure 19.5. Psychrometric chart in SI units. Copyright material reproduced by permission of the LINRIC Company, Bedford, NH USA (www.linric.com).

1060

Gases

Figure 19.6. Psychrometric chart in US Customary units. Copyright material reproduced by permission of the LINRIC Company, Bedford, NH USA (www.linric.com).

Properties of Gases

1061

Table 19.13. Psychrometric equations (SI units) Properties

Equation

Temperature or Experimental pressure range coefficients

Water vapor pressure at saturation (in Pa) (i.e., saturation line at T)

For solid ice: lnπws = a1 + b1/T – c1lnT

255.38 K to 273.16 K

a1 = 31.9602 b1 = 6270.3605 c1 = 0.4657

For liquid water: 2 lnπws = a2 – b2/T – c2lnT + d2T

273.16 K to 647.13 K

a2 = 73.649 b2 = 7258.2 c2 = 7.3037 –6 d2 = 4.1653 × 10

Latent heat of sublimation of water at saturation (J/kg)

hSS = a3 – b3 · (T – 255.38)

255.8 K to 273.15 K

a3 = 1.839683144 × 10 b3 = 7212.56384

620.52 Pa to 4.688396 MPa

A0 = 19.5322 A1 = 13.6626 A2 = 1.17678 A3 = –0.189693 A4 = 0.087453 A5 = –0.0174053 A6 = 0.00214768 –3 A7 = –0.138343 × 10 –5 A8 = 0.38 × 10

Saturation line, T as a function of πws

Latent heat of vaporization at saturation

(T – 255.38) = ∑kAk · ln(0.00145 · πws)

For ice hvs = 2502535.259 – 2385.76424 (T – 273.16)

273.16 K to 338.72 K 2 1/2

hfg = (7329155978000 – 15995964.08 T )

338.72 K to 533.16 K

Wet bulb line

Pswb – πv = B1(Twb – T) Substitute hig1 for hfg1 where Twb < 273.16

255.38 K to 533.16 K

Absolute humidity or humidity ratio

H = (0.6219 πw)/(Patm – πw) with πw < Patm

255.38 K to 533.16 K

Air specific volume va = RT/[M·(Patm – πw)] Enthalpy

Dewpoint temperature (°C)

6

h = 1006.9254 (T – 273.16) – H[333 432.1 + 2030.598 (273.16 – Tdp)] + hig2 H + 1875.6864 H (T – Tdp)

255.38 K < Tdp < 273.16 K

h = 1006.9254 (T – 273.16) – 4186.8 H (Tdp – 273.16)] + hig2 H + 1875.6864 H (T – Tdp)

273.16 K < Tdp < 373.16 K 2

tdp = –60.45 + 7.0322 lnπw + 0.3700 lnπw

2 w

tdp = –35.957 – 1.8726 lnπw + 1.1689lnπ

–60°C < t < 0°C 0°C < t < 70°C

19

B1 = {1006.9254(πws – Patm) (1 + 0.15577[πw/Patm])} /(0.62194 hfg1)

Gases

1062

Gases

19.1.24 Flammability of Gases and Vapors Before a fire or explosion can occur, three conditions must be met simultaneously. A fuel (i.e., combustible gas), a comburant (e.g., oxygen, air, chlorine) must exist in certain proportions, along with a source of ignition (e.g., chemical, thermal, electrical, or mechanical), such as a spark or flame. The most important factors to consider when assessing the flammability of gas mixtures are the following: (i) (ii) (iii) (iv) (v) (vi)

lower and upper flammability limits; lower and upper explosive limits; the autoignition temperature; the minimum ignition energy; the maximum explosion pressure; the maximum rate of pressure rise.

All these physical quantities are briefly described here.

19.1.24.1 Flammability Limits For a flammable gas or vapor, the flammability limits correspond to the highest and lowest concentrations of a flammable gas or vapor in air that will burn when an ignition source is present (e.g., flame, spark). These threshold concentrations are called the upper flammability limit (UFL) and the lower flammability limit (LFL) respectively and are usually expressed as a volume fraction of gas or vapor in air in vol.% under NTP conditions unless other temperature and pressure conditions are indicated. It is important to note that flammability limits can also be reported for other oxidants such as pure oxygen or even chlorine gas. In the technical literature, concentrations of flammable gases are often given in terms of percentage of lower flammability limit (%LFL). The flammability range corresponds to the interval between the two flammability limits, hence at concentrations in air below the LFL, the amount of fuel is too low to maintain combustion (lean mixture) while at concentrations above the UFL there is not enough oxygen to initiate combustion. For instance, the flammability range of hydrogen gas is between 4.1 and 74.8 vol.% (NTP). From a safety aspect, the most common method used to ensure that the concentration of a potentially flammable gas or vapor is outside flammability limits is to dilute the flammable gas by using a sweep of inert gas such as nitrogen or argon. The experimental determination of flammability limits of a given gas–oxidant mixture is conducted following standardized tests such as those of recommended in ASTM E918.

19.1.24.2 Explosive Limits For a combustible material (e.g., fuel, flammable gas, vapor, or solvent), the explosive limits or explosivity limits corresponds to the highest and lowest concentrations of a flammable gas or vapor in air that will ignite and explode (i.e., deflagrate or detonate) when an ignition source is present. These concentrations are called the upper explosive limit (UEL)and the lower explosive limit (LEL) respectively and are usually expressed as a volume percentage of gas or vapor in air under NTP conditions unless other temperature and pressure conditions are indicated. It is important to note that explosive limits can also be reported for other oxidants such as pure oxygen or even chlorine gas. In the technical literature, concentrations of explosive gases are often given in terms of percentage of lower explosive limit (%LEL). The explosive range corresponds to the interval between the two explosive limits. For instance, the explosive range of hydrogen is between 18 and 59 vol.%(NTP).

Properties of Gases

1063

19.1.24.3 Autoignition Temperature The autoignition temperature of flammable gases or vapors is the minimum temperature to which the fuel must be heated in order to initiate self-sustained combustion after an extended time of exposure without an external source of ignition such as a flame or spark. Usually, the autoignition temperature decreases with increasing pressure. Moreover, it is important to note that the autoignition temperature in pure oxygen can be decreased by 300°C below that measured in air. In large containers and for certain wall materials, the ignition temperature may be lower. Finally, the autoignition temperature of mists can be lower than the flash point of the liquid (e.g., caused by decomposition reactions). The autoignition temperature on convex or flat surfaces is often higher than the standard ignition temperatures. Standardized tests to determine the autoignition temperature are, for instance: ASTM E659, DIN 51794 and IEC 6007.

19.1.24.4 Ignition Energy The minimum ignition energy, denoted Eign, and expressed in J is the minimal energy required to initiate the combustion of a fuel by any means (e.g., thermal, electrical, mechanical). Usually ignition energy of most fuels are in the order of a millijoule (mJ).

19.1.24.5 Maximum Explosion Pressure The maximum explosion pressure, denoted Pmax, and expressed in Pa is the peak value of the time-dependent pressure measured in a closed container upon deflagration of an explosive mixture of defined composition. The maximum explosion pressure is the maximum value of the explosion pressure determined by varying the composition of the mixture. The explosion pressure of gases and vapors is determined in resting mixtures according EN 13673-1.

19.1.24.6 Maximum Rate of Pressure Rise

19 –1

The maximum rate of pressure rise denoted (∂P/∂t)max and expressed in Pa.s is the highest or maximum value of the rate of pressure rise during the explosion of a gas or vapor obtained by varying the amount of combustible in its mixture with air. The rate of pressure rise (∂P/∂t)exp is the steepest gradient of the pressure–time curve of an explosion of a defined mixture of combustible and air and sometimes inert gas in a closed vessel under defined measuring conditions. The maximum rate of pressure rise depends on the volume and the shape of the vessel and the state of turbulence of the mixture.

19.1.24.7 High and Low Heating Values –1

High heating value (HHV). The high heating value, denoted HHV, and expressed in J.kg and formerly called the gross caloric value is the specific enthalpy of the combustion reaction of a gaseous fuel with air per unit mass of fuel including the latent heat of vaporization of water. The temperature of the fuel before the combustion and that of the combustion products must be 298.15 K and 101.325 kPa; the water formed by the combustion has to be liquid and the nitrogen must not be oxidized. –1 Low heating value (LHV). The low heating value denoted LHV and expressed in J.kg and formerly called the net caloric value is the specific enthalpy of the combustion reaction of a liquid or solid fuel with air per unit mass of fuel excluding the latent heat of vaporization of liquid water. The temperature of the fuel before the combustion and that of the combustion products must be 298.15 K and 101.325 kPa, the water formed by the combustion must remain as vapor and the nitrogen must not be oxidized.

Gases

1064

Gases

Table 19.14. Adiabatic flame temperature of selected gaseous fuel-oxidant mixture Gaseous fuel

Oxidant

Acetylene (C2H2) Air

2297

350

0.160

2807

n.a.

0.090

Nitrous oxide (N2O) 2957

400

0.180

Oxygen (O2)

3057

335

1.130

Air

1662

510

0.082

Oxygen (O2)

2577

490

0.500

2057

n.a

0.020

Oxygen (O2)

4467

n.a.

0.140–0.176

Air

2047

530

0.320

Oxygen (O2)

2697

450

0.900

Air

1662

510

0.082

Oxygen (O2)

2577

490

0.500

Nitric oxide (NO)

Butane (C4H10)

Cyanogen (C2N2) Air Hydrogen (H2) Propane (C3H8)

Adiabatic flame temp. Ignition temp. Burning velocity –1 (TQ/°C) (Tin/°C) (V/m.s )

19.1.25 Toxicity of Gases and Threshold Limit Averages The Threshold Limit Value – Time Weighted Average (TLV-TWA) allows a time-weighted average concentration for a normal 8-hour working day and a 40-hour working week, to which nearly all workers may be repeatedly exposed day after day, without adverse effect. The Threshold Limit Value – Short Term Exposure Limit (TLV-STEL) is defined as a 15-minute, time-weighted average which should not be exceeded at any time during a working day, even if the 8-hour time-weighted average is within the TLV. It is designed to protect workers from chemicals which may cause irritancy, chronic or irreversible tissue damage, or narcosis which may increase the likelihood of accidental injury.

19.2 Physico–Chemical Properties of Major Gases The general designation (i.e., chemical name, CAS registry number, UN number), the relative atomic and molar mass, the physical properties (i.e., density, viscosity), thermal properties (i.e., molar heat capacities, latent enthalpies, and thermal conductivity), optical properties (e.g., refractive index), along with properties important for health and safety (i.e., flammability limits, ignition temperature, toxicity) of some important gases are reported in Tables 19.15–19.17.

CAS Reg. No. [CARN]

[74-86-2]

[132259-10-0]

[7664-41-7]

[7440-37-1]

[7784-42-1]

[10294-34-5]

[7637-07-2]

[106-99-0]

[106-97-8]

[106-98-9]

[124-38-9|

[124-38-9]

[463-58-1]

[7782-50-5]

[75-00-3]

[74-87-3]

[75-72-9]

[460-19-5]

[75-19-4]

[7782-39-0]

[19287-45-7]

Name (synonyms)

Acetylene (ethyne)

Air

Ammonia

Argon

Arsine

Boron trichloride

Boron trifluoride

Butadiene 1,3

Butane (n-)

Butene-1

Carbon dioxide

Carbon monoxide

Carbonyl sulfide

Chlorine

Chloroethane (R160)

Chloromethane (R40)

Chlorotrifluoromethane (R13)

Cyanogen

Cyclopropane

Deuterium

Diborane

Designation

Table 19.15. Properties of Gases 1

B2H6

D2

C3H6

C2N2

CClF3

CH3Cl

C2H5Cl

Cl2

COS

CO

CO2

C4H8

C4H10

C4H6

BF3

BCl3

AsH3

Ar

NH3

[see note (1)]

C2H2

IUPAC chemical formula

27.6696

2.0141018

42.08064

52.03548

199.4509

50.48752

64.5144

70.9054

60.0764

28.0104

44.0098

56.10752

58.1234

54.09164

67.80621

117.1691

77.94542

39.94800

17.03056

28.96415

26.03788

107.7

18.5

145.8

245.3

92.15

175.5

134.2

172.2

134.3

61.55

194.8

87.75

134.9

164.3

145.2

165.9

156.2

83.95

195.5

59.75

192.5

(T/K) 188.45 78.8 239.75 87.25 210.65 285.55 173.35 268.75 272.65 266.85 194.65 81.65 222.85 239.18 285.45 249.35 191.75 252 240.35 23.55 180.75

–80.70 –213.4 –77.7 –189.2 –116.95 –107.3 –128.0 –108.9 –138.3 –185.4 –78.4 –211.6 –138.81 –101.0 –139 –97.7 –181 –27.84 –127.4 –254.65 –165.5

(T/K)

(Mr)

–92.4

–249.6

–32.8

–21.15

–81.4

–23.8

12.3

–33.97

–50.3

–191.5

–78.5

–6.3

–0.5

–4.4

–99.8

12.4

–62.5

–185.9

–33.4

–194.35

–84.70

(bp/°C)

Boiling temperature

(mp/°C)

Melting temperature

Rel. molar mass 12 ( C = 12)

4.4731

0.19

5.443

8.1

n.a.

129.7

4.4518

6.406

7.73

0.835

7.95

3.8484

1.114

7.985

4.242

2.109

1.195

1.185

5.655

n.a.

2.510

kJ.mol

–1

Fusion (ΔHf)

6.987

1.220

20.100

23.300

15.800

21.580

24.700

20.410

18.480

6.040

25.230

21.910

21.066

22.590

18.870

23.800

16.686

15.580

13.329

5.750

20.870

kJ.mol

–1

Vaporization (ΔHv)

Latent molar heat

1.2345

0.0899

1.7510

2.3350

2.0640

2.2525

2.8784

3.1635

2.5400

1.2497

1.9635

2.7200

2.5932

2.4133

2.3800

5.3260

3.2430

1.7841

0.7067

1.2931

1.1747

–3

(/kg.m )

Density @273K

0.955

0.069

1.354

1.806

1.596

1.742

2.226

2.446

1.964

0.966

1.518

2.103

2.0054

1.866

1.841

4.119

2.508

1.380

0.547

1.000

0.908

S.G.

Specific gravity vs. air

7.85

12.6

8.74

14.4

14.425

9.89

9.722

12.45

11.32

16.57

15.01

7.00

7.5

7.54

17.10

11.35

14.58

22.50

9.82

18.53

10.40

(η/μPa.s)

Dynamic viscosity (300K)

Physico–Chemical Properties of Major Gases 1065

Gases

19

Boiling temperature

CHCl2F

[75-43-4]

[4109-96-0]

[124-40-3]

[115-10-6]

[74-84-0]

[74-85-1]

[7782-41-4]

[7440-59-7]

Dichlorofluoromethane (R21)

Dichlorosilane

Dimethylamine

Dimethylether

Ethane

Ethylene

Fluorine

Helium (natural)

He

4

H2

[1333-74-0]

[10035-10-6]

[7647-01-0]

[74-90-8]

[7664-39-3]

[10034-85-2]

[7783-06-4]

[75-28-5]

[115-11-7]

[7439-90-9]

[74-82-8]

[7440-01-9]

[10102-43-9]

Helium-4

Hydrogen

Hydrogen bromide

Hydrogen chloride

Hydrogen cyanide

Hydrogen fluoride

Hydrogen iodide

Hydrogen sulfide

2-Methylpropane (Isobutane)

2-Methylpropene (Isobutene)

Krypton

Methane

Neon

Nitric oxide

NO

Ne

CH4

Kr

C4H8

C4H10

H 2S

HI

HF

HCN

HCl

HBr

3.016029

He

3

Helium-3

30.00614

20.1797

16.04276

83.798

56.10752

58.1234

34.08188

127.9124

20.00634

27.02568

36.46064

80.91194

2.01588

4.002603

4.002602

37.996806

28.05376

30.06964

46.06904

45.08432

101.0068

102.9227

120.9132

He

F2

C2H4

C2H6

(CH3)2O

(CH3)2NH

SiH2Cl2

CCl2F2

Dichlorodifluoromethane (R12) [75-71-8]

109.6

24.15

90.65

116

133.2

135.2

187.7

222.4

189.8

260

159

186.3

14.1

0.775

0.320

0.95

53.55

104

89.85

131.7

252.2

151.2

138.2

115.2

–163.6

–249.0

–182.5

–157.2

–140

–138

–85.5

–50.8

–83.4

–13.2

–114.2

–86.9

–259.05

–272.38

–272.83

–272.2

–219.6

–169.2

–183.3

–141.5

–21

–122

–135

–158

(mp/°C)

(T/K)

(Mr)

121.35

27.05

111.55

119.75

265.95

261.45

212.85

237.55

292.65

298.85

188.15

206.45

20.3

4.224

3.1905

4.15

85.03

169.35

184.45

248.25

400.15

281.55

282.05

243.35

(T/K)

–151.8

–246.1

–161.6

–153.4

–7.2

–11.7

–60.3

–35.6

19.5

25.7

–85

–66.7

–252.85

–268.93

–269.96

–269

–188.12

–103.8

–88.7

–24.9

127

8.4

8.9

–29.8

(bp/°C)

2.30

0.335

0.94

1.370

5.93

4.66

23.8

2.87

4.58

8.406

1.992

2.406

0.117

0.0138

0.51

800

683

4.94

5.94

n.a.

n.a.

4.14

kJ.mol

–1

13.830

1.710

8.180

9.080

22.460

21.300

18.670

19.770

7.468

25.220

16.140

17.610

0.904

0.0837

0.0255

0.0829

6.620

13.558

14.715

21.500

26.400

25.200

25.200

20.180

kJ.mol

–1

Vaporization (ΔHv)

Fusion (ΔHf)

Melting temperature

Rel. molar mass 12 ( C = 12)

Latent molar heat

IUPAC chemical formula

Name (synonyms)

CAS Reg. No. [CARN]

Designation

Table 19.15. (continued)

1.2700

0.9003

0.7158

3.7387

2.5033

2.5932

1.4060

4.4600

0.8926

1.0992

1.5000

3.3300

0.0899

0.1786

0.1346

0.1786

1.6953

1.3416

2.0554

2.0115

4.5065

4.5920

5.3947

–3

(/kg.m )

Density @273K

0.9821

0.6963

0.5535

2.8913

1.9359

2.0054

1.0873

3.4491

0.6903

0.8501

1.1600

2.5752

0.0696

0.1381

0.1041

0.1381

1.311

1.0375

1.590

1.556

3.485

3.551

4.172

S.G.

Specific gravity vs. air

19.2

29.75

11.2

25.6

7.32

6.89

12.8

16.55

11.461

2.9

14.6

17.5

15.3

11.1

23.159

10.4

8.52

9.16

7.694

11.232

11.533

11.69

(η/μPa.s)

Dynamic viscosity (300K)

1066 Gases

[10102-44-0]

[7783-54-2]

[10024-97-2]

[7782-44-7]

[10028-15-6]

[76-19-7]

[75-44-5]

[7803-51-2]

[7647-19-0]

[463-49-0]

[74-98-6]

[115-07-1]

[10043-92-2]

[7803-62-5]

[10026-04-7]

[7783-61-1]

[7446-09-5]

[2551-62-4]

[7446-11-9]

[75-73-0]

[7550-45-0]

[75-69-4]

[7783-81-5]

[7732-18-5]

[7440-63-3]

Nitrogen dioxide

Nitrogen trifluoride

Nitrous oxide

Oxygen

Ozone

Octafluoro propane (R218)

Phosgene

Phosphine

Phosphorus pentafluoride

Propadiene 1,2 (Allene)

Propane

Propene (Propylene)

Radon

Silane

Silicon tetrachloride

Silicon tetrafluoride

Sulphur dioxide

Sulphur hexafluoride

Sulphur trioxide

Tetrafluoro methane (R14)

Titanium tetrachloride

Trichlorofluoro methane (R11)

Uranium hexafluoride

Water (vapor)

Xenon

Xe

H 2O

UF6

CCl3F

TiCl4

CF4

SO3

SF6

SO2

SiF4

SiCl4

SiH4

Rn

C3H6

C3H8

C3H4

PF5

PH3

COCl2

C3F8

O3

O2

N 2O

NF3

NO2

N2

131.293

18.01528

352.019

137.3675

189.6778

88.00461

80.0642

146.0564

64.0648

104.0791

169.8963

32.11726

222

42.08064

44.09652

40.06476

125.9658

33.99758

98.9158

188.0202

47.9982

31.9988

44.01288

71.00195

46.00554

28.01348

161.4

273.2

337.2

162.1

248.2

89.15

335.5

152.2

197.7

177.5

204.3

88.15

202

87.85

85.4

136.9

179.4

139.2

145.2

125.5

80.65

54.1

182.2

66.35

262

63.1

330.8 182.95 263.15 209.25

–68.85 –95.7 –75.47 –121

–108.04

100

56.5

23.8

136.4

–128

–63.9

–10

–90.2

57.65

–111.4

5.02

7.40

9.51

7.60

0.670

3.247

1.81

6.009

19.19

6.97

9.97

165.11

161.75

–185

–61.75

3.0

373.15

211.4

–71.2

–47.8

4.18

–111.76

225.35

–185.3

–42.05

n.a.

0

231.1

–187.75

–34.5

n.a.

1.13

329.65

238.65

–136.3

–84.4

–87.8

64

188.75

–93.8

5.74

0.477

296.95

185.35

–134

7.5

–36.7

–111.1

280.65

–128

409.55

236.45

–147.69

–111.9

0.445

–25

161.25

–192.5

–183.05

6.540

0.71

90.1

–219.05

–88.5

0.398

7.34

145.15

184.65

–91

–129

21.1

–184

144.15

–206.8

0.720

8.6

294.25

–11.2

–195.85

62.3

77.3

–210.05

Note: (1) based on an air composition (vol.%) 78.084 N2 + 20.946 O2 + 0.934 Ar + 0.033 CO2.

[7727-37-9]

Nitrogen

40.660

40.660

28.900

25.008

36.200

11.940

40.700

17.100

24.940

25.648

28.700

12.100

18.100

18.420

18.750

18.610

17.160

14.600

24.400

19.600

10.840

6.820

16.530

11.570

19.810

5.577

5.8578

6.1288

3.9264

6.5164

2.8583

4.3700

1.4329

9.0740

1.8775

1.9674

1.4150

5.6201

1.5168

4.4132

8.3887

2.1415

1.4277

1.9637

3.1678

2.0526

1.2498

4.53

4.7396

3.0364

5.0394

2.2104

3.3795

1.1081

7.0172

1.4519

1.5215

1.094

4.3462

1.173

3.4129

6.4873

1.6561

1.1041

1.5186

2.4498

1.5873

0.9666

23.2

8.968

17.892

11.408

13.067

16.1

12.91

14.2

11.58

15.321

10.203

10.8

24.451

7.84

8.3

7.60

n.a.

10.6

11.613

12.5

20.8

13.6

19.2

13.2

17.9

Physico–Chemical Properties of Major Gases 1067

Gases

19

53.890

38.522

62.800

50.242

82.132

23.970

83.000

37.564

29.204

42.752

33.949

65.730

42.057

67.655

58.338

57.559

29.196

74.638

Arsine

Boron trichloride

Boron trifluoride

Butadiene 1,3

Butane (n-)

Butene-1

Carbon dioxide

Carbon monoxide

Carbonyl sulfide

Chlorine

Chloroethane (R160)

Chloromethane (R40)

Chlorotrifluoromethane (R13)

Cyanogen

Cyclopropane

Deuterium

Diborane

Dichlorodifluoromethane (R12) 74.372

Dichlorofluoromethane (R21)

Dichlorosilane

65.302

20.940

Argon

61.965

63.262

36.953

Ammonia

20.878

50.024

59.342

32.767

25.234

34.438

20.794

28.541

74.000

21.990

73.803

42.271

54.850

12.480

28.280

20.800

29.130

35.915

44.308

–1

Cv/J.K mol

Air

–1

Acetylene (ethyne)

Cp/J.K mol

–1

Isobar molar heat capacity (300K)

Name (synonyms)

Isochor molar heat capacity (300K)

Thermal Properties

Designation

Table 19.16. Properties of Gases 2

–1

1.1498

1.1389

1.1798

1.3984

1.1662

1.1401

1.2835

1.3454

1.2414

1.4044

1.3161

1.1109

1.0900

1.1129

1.1886

1.1449

1.6779

1.3067

1.4005

1.2337

k=Cp/Cv

–1

0.009700

0.009460

0.130630

0.016670

0.088280

0.012230

0.010500

0.015000

0.007910

0.010600

0.023200

0.016600

0.013600

0.013600

0.015690

0.017280

0.008577

0.008912

0.017744

0.022180

0.027790

0.020060

–1

W.m K

Isentropic Thermal exponent conduct (300K) ivity (298K)

1.25900

1.07800

1.04500

0.60480

0.02583

0.82930

0.78030

0.68730

0.75660

1.16000

0.63430

0.69750

0.14720

0.36430

1.27600

1.38900

1.21700

0.39800

1.56000

0.63270

0.13550

0.42250

0.13580

0.45160

3

–2

–1

0.00009992

0.0000998

0.00009672

0.00007437

0.00002397

0.0000742

0.00006952

0.0000811

0.0000648

0.0000903

0.0000542

0.00006628

0.0000395

0.0000427

0.000108

0.0001164

0.0001020

0.00005443

0.0001222

0.0000605

0.0000320

0.0000371

0.0000364

0.0000522

3

Co-volume

4.670

5.180

4.136

4.004

1.665

5.490

6.300

3.946

6.679

5.272

7.700

5.877

3.499

7.381

4.020

3.796

4.327

4.985

3.871

6.600

4.864

11.277

3.774

6.191

449.15

451.58

385

289.85

38.3

397.85

399.85

301.9

416.25

460.15

417.1

374.95

132.92

304.19

419.55

425.1

425.15

260.90

451.95

373.05

150.72

405.55

132.42

308.35

443

522

558

166

66.9

248

360

579

353

324

573

440

301

468

234

228

245

549

790

588

530

235

328

230

0.271

0.271

0.280

0.278

0.314

0.274

0.350

0.283

0.268

0.275

0.275

0.272

0.295

0.274

0.276

0.274

0.270

0.284

0.153

0.274

0.292

0.242

0.274

dec.

2.066

0.052

0.020

0.308

450

0.020

3.17

n.a.

4.610

1.330

0.03537

1.7163

0.0850

0.0325

0.450

139

dec.

0.240

0.0537

1130

0.0292

1.73

(α/vol.%)

Critical Solubility compress. water factor (0°C)

–3 (ρc/kg.m ) (Zc)

Critical Critical Critical pressure tempera- density ture

Critical constants

(a/Jm mol ) (b/m .mol ) (Pc/MPa) (Tc/K)

Attraction constant

Van der Waals constants

126.5

834

772

1476

482

452

379

281

374

292.6

606

–6

(nD–1/10 )

Refractive index (589nm)

1068 Gases

29.791

29.576

39.024

80.751

30.497

34.218

95.031

89.200

20.680

35.900

21.188

29.227

29.000

36.997

53.550

38.115

29.000

Hydrogen bromide

Hydrogen chloride

Hydrogen cyanide

Hydrogen fluoride

Hydrogen iodide

Hydrogen sulfide

2-Methylpropane (Isobutane)

2-Methylpropene (Isobutene)

Krypton

Methane

Neon

Nitric oxide

Nitrogen

Nitrogen dioxide

Nitrogen trifluoride

Nitrous oxide

Oxygen

21.000

29.269

20.000

20.891

12.834

27.500

12.408

78.606

86.720

25.806

21.784

47.698

29.789

20.976

20.980

21.000

1.3810

1.3023

1.4500

1.3990

1.6509

1.3055

1.6667

1.1348

1.0958

1.3260

1.4000

1.6930

1.3100

1.4100

1.4200

1.3810

0.024240

0.014500

0.021980

0.167400

0.024000

0.023400

0.045800

0.032800

0.008800

0.014100

0.013900

0.014004

0.004810

0.025470

0.012970

0.013472

0.008640

0.168350

0.015920

0.008710

37.159

29.000

Hydrogen

0.143000

0.141900

0.142600

Phosphine

20.790

Helium-4

1.6640

0.024700

0.020640

0.012700

20.790

Helium-3

12.500

1.3525

57.693

20.800

Helium (natural)

23.178

8.340

0.020120

0.013440

149.460

31.348

Fluorine

1.1916

Phosgene

10.370

Ethylene

44.769

50.180

Octafluoro propane (R218)

53.346

Ethane

0.014940

n.a.

65.690

Dimethylether

62.698

Ozone

72.040

Dimethylamine

0.0000851 0.00007742 0.0000651 0.0000582 0.000029 0.0000234

0.0000265 0.0000442 0.0000406 0.0000881 0.0000739 0.000053 0.0000434 0.0001168 0.0001086 0.0000106 0.0000431 0.0000167 0.0000289 0.0000385 0.0000443 0.0000545 0.00004435 0.00003186 0.00004977 0.0001338 0.0000834 0.00005155

1.04400 0.86900 0.55800 0.46120 0.11710 0.00341

0.02452 0.45000 0.37000 1.12900 0.95650 0.63090 0.45440 1.33600 1.27300 0.51930 0.23030 0.02080 0.14600 0.13610 0.53600 0.35800 0.38520 0.13820 0.35700 1.29600 1.06500 0.46930

5.2014

0.228

6.535

5.670

2.690

5.043

7.245

4.528

10.133

3.400

6.485

2.757

4.604

5.502

4.001

3.648

8.937

8.310

6.485

5.390

8.258

8.552

324.7

455.1

345

154.4

309.5

234

431

126.2

180.1

44.3

190.5

209.4

417.8

408.1

373.2

423.9

461.1

456.65

324.5

363.1

33.2

3.3093

0.115 1.298

5.2

144.2

282.6

305.5

400.05

437.22

0.230

5.215

5.076

4.914

5.370

5.340

300

520

628

436.1

452.5

598

557

314

520

483.5

162

908.5

234.9

221.3

310

976

290

195

450

809

30.09

69.45

41.19

69.30

574

218

212

242

241

0.274

0.285

0.279

0.288

0.274

0.277

0.233

0.292

0.250

0.300

0.288

0.288

0.275

0.282

0.284

0.288

0.117

0.197

0.249

0.284

0.305

0.302

0.288

0.277

0.274

0.274

0.273

0.233

dec.

0.0489

1.14

0.021

0.0234

0.074

0.014

0.054

0.099

0.1659

0.0325

4.670

425

506

611.6

0.02148

0.0089

reacts

0.226

0.052

34.06

117.8

272

516

297

297

67

444

427

630

906

447

140

138

36

195

696

891

Physico–Chemical Properties of Major Gases 1069

Gases

19

20.786

42.844

0.005680

1.6600

Xenon

12.658

0.018980

Water (vapor)

21.012

0.006910

Uranium hexafluoride

0.007860

68.3210

0.008420

77.613

Trichlorofluoro methane (R11)

80.600

Titanium tetrachloride

0.015000

1.1786

Tetrafluoro methane (R14)

49.286

0.010940

0.012000

Sulphur trioxide

58.087

97.854

Sulphur hexafluoride

0.008500

39.845

Sulphur dioxide

1.2825

0.015570

Silicon tetrafluoride

31.069

0.008600

73.600

Silicon tetrachloride

0.019100

0.003430

0.013900

0.015198

Silane

1.1568

1.1364

Radon

54.096

62.580

66.000

75.000

Propene (Propylene)

–1

Propane

–1

W.m K 0.015690

k=Cp/Cv n.a.

–1

60.840

–1

Cv/J.K mol

Propadiene 1,2 (Allene)

–1

Isentropic Thermal exponent conduct (300K) ivity (298K)

Phosphorus pentafluoride

Cp/J.K mol

–1

Isobar molar heat capacity (300K)

Name (synonyms)

Isochor molar heat capacity (300K)

Thermal Properties

Designation

Table 19.16. (continued)

0.41920

0.55370

1.60100

1.46800

2.54700

0.40400

0.85700

0.78570

6.86500

0.52590

2.09600

0.43000

0.66010

0.84110

0.93900

0.82300

n.a.

3

–2

–1

3.750

4.840

6.280

4.620

4.250

5.239

3.350

0.0000516

0.0000305

0.0001128

0.0001111

0.0001423

0.0000633

0.0000622

0.0000879

0.0000568

5.840

22.040

4.610

4.410

4.660

3.743

8.200

3.759

7.884

289.733

647.35

505.85

471.25

638.15

227.65

491.05

318.75

430.85

259.15

507.15

269.65

377.15

364.2

369.8

393.15

292

1105

325

1408

554

558

629

633

734

524

631

521

242

1586

233

217

247

0.286

0.229

0.277

0.279

0.299

0.277

0.256

0.282

0.269

0.285

0.278

0.287

0.281

0.275

0.280

0.281

0.203

w/o

0.179

0.369

0.005

0.0054

79.87

0.230

0.434

0.039

hydrolized

(α/vol.%)

Critical Solubility compress. water factor (0°C)

–3 (ρc/kg.m ) (Zc)

Critical Critical Critical pressure tempera- density ture

Critical constants

0.000072361 3.720

0.000147

0.0000579

0.00006239

0.00008211

0.0000905

0.0000747

n.a.

3

Co-volume

(a/Jm mol ) (b/m .mol ) (Pc/MPa) (Tc/K)

Attraction constant

Van der Waals constants

642

254

737

783

686

–6

(nD–1/10 )

Refractive index (589nm)

1070 Gases

n.a.

–32.10

–50.30

–41.00

–21.00

1.000985

1.000700

Butadiene 1,3

Butane (n-)

Butene-1

Carbon dioxide

Carbon monoxide

–40.50

–69.90

1.013200

1.000940

Chlorine

Chloroethane (R160)

Chloromethane (R40)

non flam

560

495

850

38

n.a.

Deuterium

–52.20

–39.20

Cyclopropane

Dichlorodifluoromethane (R12) 1.000290

–21.60

Cyanogen

non flam.

632

519

non flam

n.a.

652

non flam

382

430

415

w/o

w/o

285

non flam

651

non flam

406–440

Diborane

–45.30

Chlorotrifluoromethane (R13)

–32.00

–32.40

Carbonyl sulfide

–11.80

–59.90

–19.32

Boron trifluoride

1.000545

Argon

–16.30

Boron trichloride

1.007200

Ammonia

–35.20

1.000590

Air

–20.80

Arsine

1.001340

Acetylene (ethyne)

–9 3 –1 (χM/10 m mol ) (T/°C)

(HFL/vol.%) 81 w/o 30 w/o 77.8 w/o w/o 11.5 8.5 10 w/o 74.2 28.5 w/o 14.8 19 w/o 36.6 10.4 79.6 98 w/o

(LFL/vol.%) 2.5 w/o 15 w/o 3.9 w/o w/o 2.0 1.5 1.6 w/o 12.5 12 w/o 3.6 7.6 w/o 3.9 2.4 6.6 0.9 w/o

Low heating value (Net) –1

w/o

w/o

w/o

w/o

48.4909

49.5627

48.0613

w/o

w/o

w/o

w/o

49.9517

w/o

w/o

w/o

10.103

w/o

45.3506

45.7735

45.6182

w/o

w/o

w/o

w/o

48.2601

Toxicity data (2)

UN1028

UN1957

UN1027

UN1026

UN1022

UN1063

UN1037

UN1017

UN2204

UN1016

UN1013

UN1012

UN1011

UN1010

UN1008

UN1741

UN2188

UN1006

UN1005

UN1002

UN1001

1000

0.1

asphyxiant

10

50

100

0.5

0.5

25

5000

800

2

0.05

asphyxiant

25

w/o

asphyxiant

100

1

1

30,000

C1

35

w/o

(ppm vol.) (ppm vol.)

United TLV-TWA TLV-STEL Nations Number ID

(HHV/MJ.kg ) (LHV/MJ.kg ) UN No.

–1

Autoignition Low High High heating temp. flammability flammability value (Gross) limit limit

(εr)

Flammability data

Name (synonyms)

Relative Molar magnetic dielectric susceptibility permittivity

Designation

Table 19.17. Properties of Gases 3

Physico–Chemical Properties of Major Gases 1071

Gases

19

1.001440

Ethylene

1.003130

1.004600

Hydrogen bromide

Hydrogen chloride

–8.60

–47.70

1.002340

1.003000

Hydrogen fluoride

Hydrogen iodide

Hydrogen sulfide

–29.00

–17.40

1.000944

1.000127

Krypton

Methane

Neon

+1461

–12.00

Nitric oxide

Nitrogen

1.000580

–40.80

2-Methylpropene (Isobutene)

–6.96

–50.50

2-Methylpropane (Isobutane)

–25.50

n.a.

Hydrogen cyanide

–22.60

w/o

w/o

w/o

595

non flam.

465

460

260

non flam.

non flam.

538

non flam.

non flam.

560

1.000264

Hydrogen

n.a.

non flam.

–3.99

non flam.

non flam.

non flam.

Helium-4

–2.02

Helium (natural)

490

472.2

350

402

100

non flam

Helium-3

–9.63

Fluorine

1.000684

–26.80

Ethane

–18.80

–26.30

1.001500

Dimethylether

n.a.

1.000400

Dimethylamine

n.a.

n.a.

1.000490

Dichlorosilane

Dichlorofluoromethane (R21)

–9 3 –1 (χM/10 m mol ) (T/°C)

w/o

w/o

w/o

5.0

w/o

1.6

1.8

4.3

w/o

w/o

6

w/o

w/o

4

w/o

w/o

w/o

w/o

2.7

3.0

3

2.8

4.1

w/o

(LFL/vol.%)

w/o

w/o

w/o

15.0

w/o

10

8.5

45.5

w/o

w/o

41

w/o

w/o

75

w/o

w/o

w/o

w/o

34

12.5

18.6

14.4

98.8

w/o

(HFL/vol.%)

w/o

w/o

w/o

55.5409

w/o

48.2204

49.4447

w/o

w/o

w/o

w/o

15.8913

w/o

w/o

w/o

w/o

50.3348

51.9154

w/o

–1

Low heating value (Net) –1

w/o

w/o

w/o

50.0497

w/o

45.0801

45.655

w/o

w/o

w/o

w/o

13.4440

w/o

w/o

w/o

w/o

47.1946

47.5207

w/o

Toxicity data (2)

UN1066

UN1660

UN1065

UN1062

UN1056

UN1055

UN1969

UN1053

UN2197

UN1052

UN1050

UN1048

UN1049

UN1046

UN1045

UN1962

UN1035

UN1033

UN1032

UN2189

UN1029

asphyxiant

25

asphyxiant

asphyxiant

10

C3

C4.7

C2

C3

asphyxiant

asphyxiant

asphyxiant

asphyxiant

1

asphyxiant

asphyxiant

5

10

15

2

15

(ppm vol.) (ppm vol.)

United TLV-TWA TLV-STEL Nations Number ID

(HHV/MJ.kg ) (LHV/MJ.kg ) UN No.

Autoignition Low High High heating temp. flammability flammability value (Gross) limit limit

(εr)

Flammability data

Name (synonyms)

Relative Molar magnetic dielectric susceptibility permittivity

Designation

Table 19.17. (continued)

1072 Gases

1.000523

Oxygen

1.001238

Xenon

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

non flam.

< 85

non flam.

460

470

n.a.

w/o

80

w/o

w/o

w/o

w/o

w/o

w/o

w/o

Note: (2) 2003 TLVs and BEIs. – ACGIH Worldwide, Cincinnati, OH.

–45.50

–13.10

1.012600

Water (vapor)

–18.20

Sulphur dioxide

+43

n.a.

Silicon tetrafluoride

–58.70

–87.50

Silicon tetrachloride

Uranium hexafluoride

–20.40

Silane

Trichlorofluoro methane (R11)

n.a.

Radon

–54.00

–30.70

Propene (Propylene)

Titanium tetrachloride

–38.60

Propane

n.a.

–25.30

Propadiene 1,2 (Allene)

–28.54

n.a.

Phosphorus pentafluoride

Tetrafluoro methane (R14)

–26.20

Phosphine

Sulphur trioxide

–48.00

Phosgene

–44.00

n.a.

Octafluoro propane (R218)

Sulphur hexafluoride

+6.7

Ozone

1.000750

–18.90

Nitrous oxide

+3449

n.a.

1.001130

Nitrogen trifluoride

+150

Nitrogen dioxide

50.3842 48.9556

w/o w/o w/o w/o w/o w/o 11.5 9.5 11 w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o

w/o w/o w/o w/o w/o w/o 2.16 2.2 2 w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

48.4008

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

w/o

45.8154

46.3886

46.2018

w/o

w/o

w/o

w/o

w/o

w/o

w/o

UN2036

UN1029

UN1982

UN1080

UN1079

UN1859

UN2203

UN1077

UN1978

UN2200

UN2198

UN2199

UN1076

UN2424

UN1072

UN1070

UN2451

UN1067

asphyxiant

2

2500

0.05

50

10

3

C1000

5

5

Physico–Chemical Properties of Major Gases 1073

Gases

19

1074

Gases

19.3 Monographies on Major Industrial Gases In the following paragraphs, the detailed description of the physical and chemical properties, along with the natural occurrence, laboratory and industrial preparation, industrial uses, transport and storage and health and safety of the major commercial gases is provided. The selected gases are classified as follows: (i) atmospheric gases: air, nitrogen, oxygen, and argon; (ii) process gases: hydrogen, methane, carbon dioxide and carbon monoxide; (iii) noble and rare gases: helium, neon, argon, krypton and xenon.

19.3.1 Air Air is a gas mixture with an average chemical composition given in Table 19.18 based on the US Standard Atmosphere, 1976 (USSA1976). This composition is that of two parts, the lower atmosphere below 86 km altitude and the upper atmosphere from 86 km to 1000 km altitude. The lower atmosphere is further separated into seven regions expressed as a function of the geopotential height H (m). The upper atmosphere is further separated into five regions in geometric height Z (m). The lower atmosphere is easily described with relatively simple equations for molecular temperature TM (K) and pressure P (Pa). The upper atmosphere is much more complicated, requiring numerical integration to determine the number densities –3 ni (m ) of the major gas constituents (i.e., N2, O, O2, Ar, He, and H). Table 19.18. Chemical composition of dry air

4

Gas (formula)

volume fraction (vol.%)

mass fraction (/wt.%)

Nitogen (N2)

78.0840

75.5215

Oxygen (O2)

20.9476

23.139

Argon (Ar)

0.934

1.288 5

Carbon dioxide (CO2)

0.0380

Neon (Ne)

0.001818

0.0590 0.001267

Helium (He)

0.0005239

0.000724

Hydrogen (H2)

0.0005

0.000035

Methane (CH4)

0.0002

0.000111

Krypton (Kr)

0.000114

0.00030

Xenon (Xe)

0.0000087

0.000039

Notes: (i) Average chemical composition measured at sea-level (latitude 45°N), at a temperature of 15°C and –3 a pressure of 101.325 kPa. (ii) The mass density is taken as 1.225 kg.m and the mean relative molar mass as 28.964.

4

5

United States Committee on Extension to the Standard Atmosphere (COESA) (1976) U.S. Standard Atmosphere, 1976 National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), United States Air Force (USAF), US Government Printing Office, Washington DC. 2004 value

Monographies on Major Industrial Gases

1075

19.3.2 Nitrogen Description and general properties. Nitrogen [7727-37-9], with the atomic number 7, is the first chemical element of group VA(15) in Mendeleev’s periodic chart. In its free state, nitrogen is an odorless, colorless diatomic gas with chemical formula N2, and relative molecular molar mass of 28.01348. Nitrogen was first discovered independently by Scheele and Priestley in 1770. Nitrogen was named from the Latin word, nitrum and Greek genes, meaning sodaforming, while the French name azote was first given by the French chemist Antoine-Laurent de Lavoisier from the privative a and the Greek, zoos, meaning that it prevents life. Solid nitrogen exhibits two allotropes with a phase transition occurring at 36.15 K (–237°C). α-N2 β-N2

with

Tt = –237°C –3

At 21.15 K (–252°C) alpha-nitrogen has a mass density of 1026 kg.m while beta-nitrogen is –3 lighter with a mass density of 948kg.m . Above the melting temperature of 63.15K (–210°C) liquid nitrogen, denoted sometimes by the commercial acronym LN2, is a colorless and light –3 liquid (808 kg.m ) that boils at 77.347 K (–195.803°C) under atmospheric pressure. Under normal conditions of temperature and pressure (i.e., 101.325 kPa and 273.15 K) nitrogen gas –3 exhibits a mass density of 1.2498 kg.m and hence it is slightly less dense than air with a specific gravity of 0.967. Nitrogen is diamagnetic at any temperature. 2 2 3 2 3 From a chemical point of view, nitrogen with an electron structure: 1s 2s 2p = [He]2s 2p possesses the following valencies: –3 in hydrogen azide (HN3) and alkali-metal azides (MN3), +1 in nitrous oxide (N2O), +2 in nitric oxide (NO), +3 in ammonia (NH3) and alkali-metal amides (MNH2), +4 in nitrogen dioxide (NO2), and +5 like in nitrogen pentoxide N2O5. The nitrogen molecule is diatomic containing two nitrogen atoms linked by two sigma (σ) and –1 one pi (π) bonds; this short (dN ≡ N = 109.4 nm) and strong chemical bond (941 kJ.mol ) explains the chemical inertness of nitrogen at ambient temperature and pressure. However, when hot, nitrogen reacts readily with lithium metal, and the two alkaline-earth metals magnesium and calcium forming the corresponding nitrides according to the chemical reactions: 6Li + N2 —> 2Li3N 3Mg + N2 —> Mg3N2 3Ca + N2 —> Ca3N2 Nitrogen combines with boron only at temperatures above 1000°C to give boron nitride (BN) and with silicon only above 1100°C to give silicon nitride Si3N4. Although nitrogen requires a high temperature for reacting with oxygen, when mixed with oxygen and submitted to electric discharges it forms nitric oxide (NO) and nitrogen dioxide (NO2), while when heated with hydrogen and an appropriate iron-catalyst under high pressures it forms ammonia (Haber–Bosch process). When an electric discharge is produced in a nitrogen atmosphere, atomic nitrogen is produced and it reacts even at room temperature with most elements (e.g., S, P, Hg, Zn, and Cd) to give corresponding nitrides. 14 15 Natural occurrence. Nitrogen has two stable isotopes N (99.634 at.%) and N (0.366 at.%). Nitrogen gas is the major component of the atmosphere that contains ca. 78 vol.% N2. Nitrogen with 15 wt.% in proteins is also an important chemical element in living matter and also a major component in soils under temperate climate as humus (see Chapter 14); however, with a scarce relative abundance of 19 mg/kg in the Earth’s crust it is a trace element in most geological materials (i.e., minerals and rocks). Actually, the major nitrogen-bearing minerals are salpeter (KNO3, orthorhombic) and soda niter (NaNO3, rhombohedral) the latter being formed recently by the nitrification process (i.e., conversion of ammonium cations into nitrate anions) occurring in the huge guano deposits located in the coastline Chilean desert and well preserved by its exceptional dryness.

19 Gases

1076

Gases

Laboratory preparation. Pure nitrogen gas can be prepared from the oxidation of ammonia by cuprous oxide or nitrates. Industrial preparation. About 90% of nitrogen produced worldwide is obtained by a cryogenic process based on the fractional distillation of liquid air performed by important specialty gas companies (e.g., Dow, Air Liquide, Air Products, Praxair, BOC). The resulting nitrogen gas exhibits a high purity of 99.999 vol.%, with less than 1 ppm. vol. of oxygen. For the production of small quantities of nitrogen, the separation of nitrogen from air is obtained by a gas diffusion process using polymer membranes installed in a hollow fiber. The nitrogen gas produced by diffusion is less pure especially regarding traces of oxygen but they can be removed by reacting it with excess hydrogen and removing unreacted hydrogen by gas diffusion across a palladium-silver membrane. Industrial applications and uses. Nitrogen is an important raw chemical for the production of ammonia by the Haber process and consequently for the production of nitric acid, ammonium nitrate and urea, chemicals used essentially for preparing fertilizers and explosives. On the other hand, nitrogen is extensively used as blanketing or inerting gas in electric transformers, in welding or as inert atmosphere in steelmaking, nonferrous metallurgy, and finally chemicals processes. Nitrogen is used to a lesser extent as a carrier gas in the semiconductor industry and as cryogenic liquid in applications requiring low temperature such as medicine and superconductors.

19.3.3 Oxygen Description and general properties. Oxygen [7782-44-7], with atomic number 8, is the first chemical element of group VIA(16). It is an odorless, tasteless, and colorless diatomic gas with chemical formula O2 with a relative molecular molar mass of 31.9988. It was discovered independently in 1772 by the Swedish chemist Scheele, by thermal decomposition of a mixture of potassium nitrate (KNO3) and mercuric oxide (HgO), and in 1774 by the English chemist Priestley heating mercuric oxide. However, it was only identified as a chemical element in 1777 by Antoine-Laurent de Lavoisier who named it from the Greek, oxys, acid, and genes, meaning acid forming. It was first produced industrially in France, by Georges Claude in 1905. Under atmospheric pressure oxygen gas condenses at 90.18 K (–182.97°C) into a pale –3 blue liquid with a density of 1141 kg.m while it solidifies at 54.18 K (–218.79°C). Oxygen has three allotropic forms: normal oxygen or dioxygen (O2), triatomic oxygen called ozone (O3) and the rare unstable tetroxygen (O4). In the ground state, the dioxygen molecule has two unpaired electrons located in antibonding orbitals that explain its strong paramagnetism which is extensively used for analytical purposes. Moreover, when liquid oxygen is submitted to a strong magnetic field gradient, the fluid exhibits a characteristic magneto-archi6 medes effect capable of levitating dense solids and by this method it is possible to –3 obtain a tunable heavy liquid with densities up to 22,000 kg.m . From a nuclear point of 16 17 18 view, oxygen has three stable nuclide isotopes: O (99.762 at.%), O (0.038 at.%), and O (0.200 at.%) that are used to measure paleotemperatures. Under normal temperature and –3 pressure conditions the mass density of the gas is 1.428 kg.m and hence it is denser than air –3 –1 (SG = 1.104). Oxygen with a Henry’s constant of 0.6958 mg.m .Pa is poorly soluble in water 3 with 15 mg/dm at NTP but it is more soluble in other solvents. It is especially soluble in molten silver but when the metal solidifies it gases out suddenly (i.e., rocking). 2 2 4 The electronic structure of the oxygen atom in its ground state is 1s 2s 2p or simply 2 4 [He]2s 2p and it exhibits the second highest Pauling electronegativity (3.44) after fluorine. 6

Catherall, A.T.; Eaves, L.; King, P.J.; Booth, S.R Floating gold in cryogenic oxygen Nature, 422(4) (2003)579.

Monographies on Major Industrial Gases

1077

The diatomic oxygen molecule is stable until 1200°C above which temperature the gas begins to dissociate into atomic oxygen according to the reaction: O2 2O

.

with

ΔH = 490 kJ.mol

–1

For instance, at 3500 K about 25% of oxygen is atomic. Other techniques for preparing atomic oxygen are: (i) (ii)

to produce electric discharges in rarefied oxygen gas; by photolysis using short-wavelength ultraviolet radiation (190 nm).

Atomic oxygen is more reactive than molecular oxygen and it combines with most compounds. Owing to its strong electronegativity most chemical elements, especially metals, react with oxygen gas to form oxides (i.e., oxidation); the exceptions are the halogens, gold, platinum and the noble gases. The oxidation reaction of hot metals and nonmetals in pure oxygen is most often highly exothermic accompanied by a dazzling light (e.g., Mg, P, S) and for that reason it was called vigorous combustion by Antoine Laurent de Lavoisier. However, the combustion does not necessarily produce the most oxidized compound (e.g., SO2, Na2O2, Ba). On the other hand, despite being less impressive, slow-rate combustion (smoldering) must also be considered with great care since it can evolve into vigorous combustion (in coal dust, for example). Natural occurrence. Oxygen is the most abundant chemical element in the Earth’s crust with 46.1 wt.% mostly combined as silicates (e.g., quartz and silica, feldspars and feldspathoids, zircon), carbonates (e.g., calcite, dolomite, siderite) and oxides (e.g., hematite, rutile, zincite, cuprite), while it forms 20.65 vol.% of the air and 89 wt.% of the ocean water. Laboratory preparation. In the laboratory high-purity oxygen can be obtained by various chemical reactions, obsolete today because high-purity gas is supplied in gas cylinders; however, for historical interest they are mentioned here. (i)

Oxygen can be obtained at the anode of an electrolyzer during the electrolysis of water either in acidic or alkaline electrolyte according to the anode reactions: +

–

2H2O(l) —> O2(g) + 4H + 4e (in acidic electrolyte, e.g., H2SO4) –

–

4OH —> O2(g) + 2H2O(l) + 4e (in alkaline electrolytes, e.g., KOH)

(ii)

The inescapable traces of hydrogen can be removed by passing the gas stream onto a hot palladium foam and removing the water formed by P2O5. The simplest chemical preparation consists of reacting an aqueous solution of potassium permanganate with a diluted solution of hydrogen peroxide (3 wt.% H2O2) in the presence of some drops of concentrated sulfuric acid (98 wt.% H2SO4) as follows: 2KMnO4 + 5H2O2 + 3H2SO4 —> K2SO4 + 2MnSO4 + 8H2O + 5O2(g)

(iii) Another old technique consisted of reacting a mixture of sodium and barium peroxides with traces of copper oxide acting as catalyst, the whole mixture also being known commercially as Oxylite®, according to the chemical reaction: Na2O2(s) + H2O(l) —> 2NaOH + 1/2O2(g) (iv) Finally, from an historical point of view several metallic oxides are decomposed by heat at a given temperature, for instance: Ag2O (250°C), HgO (650°C), Mn2O3 (800°C), PbO2 (800°C) and BaO2 (1000°C). Industrial preparation. 95% of commercial oxygen is obtained, along with liquid nitrogen, by the fractional distillation of liquified air, itself obtained by a cryogenic process. Usually, atmospheric air is filtered, compressed between 500 and 700 kPa and the residual water

19 Gases

1078

Gases

and carbon dioxide removed by selective absorption within molecular sieves and later cooled by the exiting liquified air. Industrially, fractional distillation is performed with two large insulated distillation columns 6 m in diameter and 25 m tall made of aluminum and containing hundred of plates. In the first column, pure nitrogen gas leaves the upper section while the remaining liquid that contains up to 40 wt.% oxygen is fed to the second column from which high-purity oxygen is obtained at the bottom (99.5 vol.% the major impurity –3 being argon). The specific energy consumption of the cryogenic process is ca. 0.4 kWh.m . To a lesser extent, oxygen is also produced by a noncryogenic process called vacuum pres3 sure swing absorption when small quantities, usually less than 70,000 Nm per day, are required. In this process, after being dried and filtered air is directly fed into a column packed with a zeolite absorbent. The zeolite absorbs nitrogen selectively oxygen. Once saturated, the excess air is sent to the next column while the first column desorbs under vacuum. The oxygen produced by this process exhibits a purity ranging between 90 vol.% and 95 vol.% the major impurity being argon which is absorbed. The specific energy consumption of the vac–3 uum process is 0.4–0.5 kWh.m . Industrial applications and uses. Steelmaking represents by far the major industrial utilization of oxygen. Oxygen gas is used either during the treatment of molten iron in converter or in blast furnaces. The second important use is as an oxidant to replace air and improve combustion with a significant decrease in the formation of nitrogen oxides (NOx). Glassmaking along with some mineral processes involving the roasting or the fluidized bed treatment of ores utilizes oxygen as oxidant instead of air. Oxygen is an important chemical in the industrial production of ethylene and propylene oxides, vinyl chloride and titanium dioxide from the chloride process. Other commercial uses include metal cutting by oxyacetylene flame, high-purity breathable gas in medicine, bleaching agent in pulp and paper and waste water treatment. Finally liquid oxygen is used as oxidant either for rocket propellants or mixed with carbon powder as clean explosive without residues in underground mines. Health and safety. Oxygen is necessary for sustaining the life of all vertebrates and the respirable range for a man is between 14 vol.% and 75 vol.% O2. Hemoglobin in the blood combines with oxygen to give oxyhemoglobin. Actually, below 7 vol.% O2 severe troubles appear and below 3 vol.% asphyxiation occurs, while above 75 vol.% hyperoxy and even death occurs. Regarding storage, handling and delivery of oxygen gas, great care must be used to select the proper materials and to avoid hazardous situations. As a rule of thumb, reactive metals such as berylium, magnesium, aluminum, titanium and zirconium and their alloys are forbidden, while nickel-based alloys (e.g., nickel 200, inconel) and copper-based alloys (e.g., Electrolytic copper, Monel) are the most suitable. However, for safe practice, it is highly recommended to use the standard guide for evaluating metals for oxygen service (ASTM G94-92) before selecting proper piping materials.

19.3.4 Hydrogen Description and general properties. Hydrogen (hydrogenium) [12385-13-6], with a relative atomic molar mass of 1.00794 is the first chemical element of Mendeleev’s periodic chart and 1 head of group IA(1) with the simplest electronic configuration 1s . In its free state it is an odorless, tasteless and colorless diatomic gas (i.e., dihydrogen) with the chemical formula H2 [1333-74-0] and a relative molecular molar mass of 2.01588. First prepared by Paracelsus by dissolving metallic iron into spirit of vitriol (i.e., sulfuric acid), it was later named by Antoine-Laurent de Lavoisier after the Greek words, hydros, and genes, to give birth of water because it produces water after combustion with air (oxygen).

Monographies on Major Industrial Gases

1079

Hydrogen solidifies at 13.81 K (–259.34°C), solid hydrogen exhibits two allotropes: (i) (ii)

α-H2 with a face-centered-cubic structure (fcc; a = 533 pm); and β-H2 with an hexagonal-close-packed structure (hcp; a = 377 pm and c = 616 pm). α-H2 (fcc) β-H2(hcp)

The above transition occurs at 1.25 K (–271.9°C). Under extremely high pressure (300 GPa), it is 7 even possible to prepare metallic hydrogen with a density close to that of water . Liquid hydro–3 gen has a density of 70.78 kg.m , and exhibits both a low dynamic viscosity of 0.0132 mPa.s –1 –1 and a low thermal conductivity of 98.92 mW.m K . Liquid hydrogen boils at 20.268 K (–252.882°C) under atmospheric pressure. Because of its low critical temperature (32.976 K), hydrogen must be cooled before being liquefied. Hydrogen gas follows the law of ideal gases up to 20 MPa but above 50 MPa an empirical equation of state must be used. Owing to the nuclear spin of each atomic nucleus (I = 1/2), the diatomic hydrogen molecule exhibits two molecular isomers: (i) (ii)

para-hydrogen (p-H2) with anti-parallel spins; and ortho-hydrogen (o-H2) with parallel spins, p-H2 being the more thermodynamically stable isomer.

Chemical equilibrium occurs at each temperature between the two isomers: o-H2 p-H2

with

ΔcH = 1.054 kJ.mol at T < 77 K –1

This effect, also observed in other homonuclear diatomic molecules (e.g., D2, T2, N2, F2 and Cl2), was first predicted at the beginning of the 20th century by Werner Karl Heisenberg 8 based on quantum mechanics . At room temperature, hydrogen contains about 25 at.% of p-H2 while at absolute zero all the hydrogen exists as p-H 2. However, the kinetics of the transformation of the two isomers is quite slow, but it is possible to accelerate the conversion by means of a strong magnetic field or a suitable catalyst (e.g., activated charcoal, hydroxides of 9 the aluminum-nickel group such as Fe(III), Co(III), Ni(II), Cr(III), Mn(IV), etc.) . Moreover during cooling the conversion of o-H2 into p-H2 is highly exothermic so it contributes significantly to the evaporation of liquid hydrogen unless all the liquid is previously converted to p-H2; once the conversion is complete, liquid hydrogen stored in a Dewar container is stable for long periods. The physical properties of the two isomers are also slightly different, especially their thermal conductivities, vapor pressures and boiling points. Due to the existence of these isomers, the following designations are used: (i) (ii)

equilibrium hydrogen (e-H2) denotes a mixture at equilibrium at a given temperature; normal hydrogen (n-H2) denotes a mixture of the equilibrium concentrations under normal temperature and pressure conditions (101.325 kPa and 273.15 K).

From a nuclear point of view, hydrogen has two stable isotopes: (i) (ii)

1

hydrogen or protium H (99.985 at.%); and 2 deuterium H (0.015 at.%) discovered by H.C. Urey in 1931, usually denoted by the capital letter D. Deuterium and protium form a chemical equilibrium in natural hydrogen as follows: H2 + D2 = 2HD

7

8 9

Burgess, T.J.; Hawke, R.S. (1978) Metallic Hydrogen Research Report UCID-17977, 29 pages. also in Phys. Rev. Lett., 41(1978)994. Heisenberg, W.K Quantum mechanics Naturwissenschaften, 14(1926)989–994. Newton, C.L Chem. Process Eng., 48(12)(1967)51–58.

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Gases

Hence it appears either as the diatomic molecule D2 [7782-39-0] or HD [13983-20-5]. On the other hand, pure deuterium gas gives heavy water (D2O) when burned with air (oxygen). 3 Tritium is the radioactive isotope of hydrogen H denoted by the capital letter T that gives the diatomic molecules T2 [100028-17-8], HT [14885-60-0] and DT [14885-61-1] when in chemical equilibrium with protium or deuterium respectively. Tritium is a beta(-) emitting radionuclide with a half-life of 12.33 years and a maximum energy of the electron of 14.950 keV. When burned with oxygen tritium gives superheavy water (T2O). Tritium is an extremely rare cosmogenic radionuclide resulting from the interaction of cosmic rays with nitrogen in the upper atmosphere according to the nuclear reaction: 14

1

3

12

N + n —> H + C

Since 1952, most of the tritium measured in the atmosphere originates from thermonuclear explosions. Like hydrogen, deuterium and tritium also exhibit molecular isomerism. Because of the important differences between the relative atomic masses of the three isotopes, their physical properties (e.g., density, enthalpy of vaporization) differ greatly. This allows an easier isotopic separation than for any other element. Several separation processes are used for the enrichment and separation of hydrogen isotopes. Most of these processes use isotopic exchange reactions (e.g., H2D-H2O or NH3-HD) and to a lesser extent fractional distillation and water electrolysis (e.g., Norway, Canada). Hydrogen gas exhibits several salient physical properties: –3

(i) (ii)

It is the lightest gas with a mass density of 0.0899 kg.m under NTP (S.G. = 0.070). –1 –1 Hydrogen exhibits the highest thermal conductivity of all gases (k = 0.1826 W.m K ). This thermal property is extensively used to measure the concentration of hydrogen in a gas stream quantitatively and with a high accuracy. Actually, the sensor called a catharometer or thermal conductivity device (TCD) consists of measuring the electrical resistance of a calibrated pure platinum wire immersed in the gas stream and heated by a constant current. Because the electrical resistance of Pt depends on the temperature, the excellent conductibility of the hydrogen gas decreases it proportionally. –1 –1 (iii) Hydrogen with an isobaric molar heat capacity (Cp = 28.59 J.K mol ) exhibits a high –1 specific heat capacity of 14.18 kJ.kg . (iv) Hydrogen, due to its small molecule, has the highest diffusion capacity of all gases. Actually, it diffuses quickly in gases, liquids and even solids. For instance, under NTP –3 2 –1 its self-diffusion coefficient is 12.85 × 10 m s while it exhibits the highest diffusion –3 2 –1 coefficient in metals especially palladium (5 × 10 m s ). This remarkable property is extensively used to separate the gas from other gaseous impurities passing it through a heated foil of palladium acting as a hydrogen permeable membrane. Hydrogen is also highly soluble in certain inner transition metals (e.g., V, Pd) where it dissolves readily as an atomic species and occupies interstitial sites in the crystal lattice. Usually, the atomic fraction approaches simple stoichiometric ratios but without loss of the metallic character and because the stability of the new M-H system is greater the reaction is always exothermic: H2(g) —> 2H(dissolved in metal) + ΔabsH (< 0) For instance, palladium can absorb 2800 times its volume forming the nonstoichiometric comound PdH0.8. Hydrogen is only poorly soluble in water with a solubility of 0.00175 mol.% at NTP but it is more soluble in ethanol (0.0180 mol.%) and other organic solvents.

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Chemically speaking, with an ionization energy of 13.595 eV, the hydrogen atom is difficult to ionize. Hydrogen, due to its electronic configuration and a Pauling electronegativity of 2.1, yields four distinct types of compounds: (i)

It can gain one electron from a more electropositive element (e.g., alkali or alkaline+ – 2+ – earth metals) to form saline metal hydrides (M H or M H 2) with strong ionic bonds – implying the anion H , and that yield hydrogen when reacted with water. (ii) With more electronegative elements (e.g., O2, halogens), it can lose its valency electron + to yield the hydrogen cation (hydronium) H . (iii) With an element having the same electronegativity it can share its electron to form covalent hydrides with an electron pair. With group IIIA(13) and IVA(14) it yields boranes, alanes, alcanes, silanes, germananes and stannanes while with group VA(15) it gives ammonia (NH3), phosphine (PH3) and arsine (AsH3). (iv) Hydrogen gives nonstoichiometric metal hydrides (MxHy) with most inner transition metals in which the hydrogen atom can occupy interstitial sites. The only metals that have no known hydrides are gold and copper. The covalent character of the chemical bond formed depends of the electronegativity difference Δχ(A-H) existing between hydrogen and the other atom. Halogens (X2) reacts with hydrogen to yield corresponding hydrogen halides (HX). The reactivity is in the decreasing order: F2 > Cl2 > Br2. The reaction with fluorine is highly explosive and it occurs even at –210°C or in the dark. With chlorine the reaction is also explosive but it is initiated by sunlight or heat while short wavelength ultraviolet radiation is required for bromine. With iodine a chemical equilibrium occurs. Hydrogen reacts with oxygen explosively even at room temperature in the presence of a spark, a catalyst (Pt-foam) or another ignition source. Natural occurrence. With a relative abundance of 70–80 wt.% hydrogen is the most abundant element in the universe. But hydrogen gas is only found in the atmosphere at trace levels while being the second major chemical element (110 g/kg) after oxygen combined as water in the hydrosphere (i.e., oceans, seas, rivers and ice shields). With an Earth’s crust abundance of 1520 mg/kg hydrogen is the tenth most abundant element in the lithosphere, and it is found mostly combined with oxygen as water in mineral hydrates (e.g., gypsum, goethite, zeolites) or as the hydroxyl anion in silicates (e.g., micas, clays). Hydrogen is also the major component of hydrocarbons in oil and natural gas. It is also found in its free state in volcanic gases. Laboratory preparation. Pure hydrogen gas can be produced in the laboratory either by: (i) (ii)

reacting turnings of zinc metal with sulfuric acid in a Kipp’s apparatus; dissolving aluminum, zinc or silicium powder into a hot concentrated aqueous solution of sodium hydroxide; or (iii) mixing calcium hydride (Hydrolite®) with water. The corresponding chemical reactions are as follows: 0

+

–

2+

–

Zn (s) + 2H + 2 Cl —> Zn + 2Cl + H2(g) 0

+

–

+

–

Al (s) + Na + OH + H2O(l) —> Na + AlO2 + 3/2H2(g) CaH2(s) + H2O(l) —> Ca(OH)2(s)+ H2(g) Industrial production. Hydrogen can be produced commercially by several processes. Historically, it was first produced from coke oven gas, and in Germany by the Fischer– Tropsch process and to a lesser extent by the Messerschmidtt process. The hydrogen was separated from the coke oven gas (i.e., 56 vol.% H2 , 26 vol.% CH4, 7 vol.% CO and others) by liquefaction and used afterwards in ammonia synthesis. The Fischer–Tropsch process

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Gases

was extensively used in Germany before and during World War II. It consisted of reacting coke or lignite coal with superheated steam at 1000°C to produce a synthetic gas called, in this particular case, water gas, i.e., an equimolar mixture of carbon monoxide and hydrogen according to the chemical reaction. C(s) + H2O(g) —> CO(g) + H2(g) Carbon monoxide was later removed from the water gas either by liquefaction or by conversion into carbon dioxide and absorption by sodium carbonate. On the other hand, the 10 11 Messerschmidtt process and later the Lanes process also called the steam-iron process consisted of decomposing water vapor (steam) passing it over a fixed bed containing turnings of iron or prereduced iron oxides at red heat (600–650°C) according to the following chemical reaction: 4H2O(g) + 3Fe(s) —> 4H2(g) + Fe3O4(s) The coke oven gas process was replaced by more modern technologies. The Fischer–Tropsch process is now only used by the South African company SASOL to produce synthetic gaso12 line, while the third process, despite attempts to utilize a fluidized bed , is now totally abandoned. Today most of the hydrogen gas produced industrially is obtained by four major processes: (i) (ii) (iii) (iv)

steam reforming of natural gas; partial oxidation of hydrocarbons; water electrolysis; and least importantly, the cracking of ammonia.

Steam reforming consists of reacting natural gas (i.e., methane) or, to a lesser extent, other light hydrocarbons (e.g., ethane or propane), depending on availability at the plant location, with superheated steam in the presence of a suitable catalyst. The overall chemical reactions for methane and for a general hydrocarbon are: CH4(g) + H2O(g) —> CO(g) + 3H2(g)

ΔRH° = +226 kJ.mol at 1100 K

CxHy(g) + xH2O(g) —> xCO(g) + (x + y/2)H2(g)

(ΔRH° > 0)

–1

Because the above chemical reaction is highly endothermic, the reaction is conducted in 10 meter-long fired tubular reactors at high temperature (800°C). The reactors are grouped in bundles of hundreds of tubes heated externally and containing the catalyst. Before reforming the main impurities of the natural gas especially those poisoning the catalyst such as sulfur are removed by the Clauss desulfurization process. The reforming is usually performed between 800°C and 900°C under a pressure of 1.5–3.0 MPa. The catalysts consist of nickel oxide (NiO) supported on ceramic rings made of alumina, cement or magnesia and activated (i.e., reduced) by hydrogen gas prior to initiating the reaction. In practice, the gaseous product, called a synthetic gas, contains 70 vol.% hydrogen, 20 vol.% carbon monoxide and small quantities of carbon dioxide and unreacted methane (6 vol.% CH4). After the burner, the gases are cooled down to 200–500°C and then reacted with steam in order to convert all the carbon monoxide into carbon dioxide and hydrogen using a copper oxide

10

11 12

Messerschmidtt, A. Schachtofen für die Herstellung von Wasserstoff aus Eisen und Wasserdampf. German Patent No. 291902, February 12, 1914. Lanes, H. Process for the production of hydrogen. US Patent 1,078,686; November 18, 1913. Gasior, S.J.; Forney, A.J.; Field, J.H.; Bienstock, D.; Benson, H.E. (1961) Production of synthesis gas and hydrogen by the steam-iron process: pilot plant study of fluidized and free-falling beds. US Bureau of Mines, Report on Investigations R.I. 5911, US Dept of the Interior, Washington DC.

Monographies on Major Industrial Gases

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catalyst promoted by zinc oxide. Usually, the residual CO is below 0.1 vol.%. The overal reaction is the following: CO(g) + H2O(g) —> CO2(g) + H2(g) After scrubbing the exiting acidic gases, that is, CO2 and traces of H2S, under pressure by an alkaline aqueous solution containing either diethanolamine or sodium carbonate, all the carbon dioxide and impurities are removed below acceptable levels for the final purification of the hydrogen gas. Usually, the final purification utilizes pressure swing absorption (PSA). Partial oxidation, which can be applied to a wide range of hydrocarbons but also to other carbonaceous materials such as oil, petroleum coke and coal, consists of burning the hydrocarbons or powdered coal with a preheated gas mixture of steam and oxygen using a burner inside a refractory-lined combustion chamber. The role of the steam is to moderate the combustion. The overall reaction scheme for the partial oxidation of a hydrocarbon having the empirical chemical formula CxHy Su is: CxHySu(g) + (x/2 + y/4)O2(g) = xCO(g) + (y/2 – u)H2(g) + uH2S(g) The reaction is performed with a burner in a brick-lined reactor at a temperature close to 1400°C. Afterwards, reaction products are cooled down and liquid condensates containing mostly tar and heavy oil are recovered while off-gases are scrubbed in order to remove the deleterious impurities (i.e., H2S, COS, and CO2). Hydrogen is later separated from CO and used as-is for the synthesis of ammonia or purified. Theoretically, all hydrocarbons can be used as feedstocks for partial oxidation but for economical reasons only low-sulfur heavy residues from the petrochemical industries are used. Water electrolysis sometimes called water splitting is used essentially where cheap electricity is abundantly available or when high-purity hydrogen is required. Hence major commercial plants existing worldwide are built near hydropower stations (e.g., Norway and Canada). The electrolysis of water involves the electrochemical decomposition of water into hydrogen and oxygen according to the half-electrochemical reactions occurring at each electrodes with their standard Nernst electrode potentials at 298.15K and 101.325 kPa: At the cathode (–): +

2H

–

aq

+

+ 2e —> H2(g)

with E°(2H /H2) = 0.00 V/SHE (acid electrolyte)

–

2H2O(l) + 2e —> H2(g) + 2OH- with E°(H2O/H2) = –0.828 V/SHE (alkaline electrolyte) At the anode (+): 2H2O(l) —> O2(g) + 4H

+

–

aq

+ 4e with E° = +1.229 V/SHE (acid electrolyte) –

4OH- —> O2(g) + 2H2O(l) + 4e with E° = +0.401 V/SHE (alkaline electrolyte) The overall electrochemical reaction, with its theoretical cell voltage at 298.15 K, is: 2H2O(l) —> 2H2(g) + O2(g)

with ΔUth = 1.229 V at any pH

In commercial electrolyzers, electrolysis is performed using an alkaline aqueous electrolyte, usually 25–30 wt.% KOH. Acid electrolytes such as H2SO4 can lead to severe corrosion of the anode material and so require expensive platinum anodes. The electrolyzer that operates at 85°C consists of a cathode (–) made of mild steel activated with a coating of Raney’s nickel and a nickel plated iron anode (+). Anode and cathode are separated by a porous diaphragm to prevent the explosive mixing of evolved gases. The diaphragm is made of a nickel mesh insulated electrically from the two electrodes by an asbestos felt. The theoretical cell voltage (ΔUth) to decompose water at 25°C and 101.325 kPa is 1.229 V which leads to a theoretical –3 specific energy consumption of 32.7 kWh per kg of H2 (i.e., 2.92 kWh.m at NTP) assuming a faradaic current efficiency of 100%. But in practice, because both hydrogen and oxygen overpotentials exist at the electrodes, the operating cell voltage (ΔUcell) at an average current

19 Gases

1084

Gases –2

density of 2–3 kA.m is usually between 1.85 and 2.20 V while the faradaic current efficiency ranges between 70 and 90%. Therefore, the actual specific energy consumption ranges be–1 –1 –3 tween 60 kWh.kg and 84 kWh.kg (5.45–7.50 kWh.m ). Two electrolyzer designs are used industrially: (i) (ii)

the unipolar design only used by Stuart Electrolyzers with cells connected in parallel; the bipolar design used by other manufacturers (e.g., De Nora, Lurgi, etc.) with cells connected in series.

Commercial electrolyzers can be operated either at ambient pressure or under pressure up to 3 MPa (e.g., Lurgi). It is also interesting to note that high-temperature electrolysis (HTE) was extensively investigated in Germany in the 1980s. Electrolysis was performed on steam between 700°C and 1000°C using electrolyzers equipped with a solid oxide membrane –3 (SOM) made of yttria-stabilized zirconia. The specific energy consumption of 3.1 kWh.m was smaller than conventional electrolysis but for economic reasons no commercial process 13 exists yet . To a lesser extent, when cheap on-site generation of hydrogen is required and when nitrogen gas is not deleterious (e.g., metal processing applications), the thermal cracking of ammonia gas, which involves the decomposition of ammonia into hydrogen and nitrogen, is used. The endothermic reaction of decomposition is favored at high temperature and low pressure: 2NH3(g) —> N2(g) + 3H2(g) Industrially, the above reaction is conducted at atmospheric pressure and at 800–900°C with nickel or iron catalysts. The hydrogen-rich gas mixture (i.e., 75 vol.% H2 and 25 vol.% N2) that contains only traces of unreacted ammonia can be used as-is or purified by pressure swing absorption, or gas permeation through Pd-Ag membrane. It is also interesting to mention alternative processes for the production of hydrogen from –1 water. The high energy required to split the water molecule in the liquid state (15.8 MJkg ) restricts the use of a pure thermal process to produce hydrogen from water. Actually, from a theoretical point of view, it could be possible to dissociate water by providing sufficient thermal energy, but the direct thermal decomposition of water vapor only occurs at temperature above 3000 K (called the temperature of direct decomposition) which is too high for any industrial process because of materials issues. It is, however, possible to decompose water at a lower temperature but the complementary energy source can be chemical or electrical. It is well known that nuclear power reactors release waste heat without greenhouse gases. The wasted heat released can be efficiently used to perform the high thermochemical decomposition of water (HTDW) for producing hydrogen gas well below the temperature of direct 14 decomposition . Among the numerous pure thermochemical cycles studied, only the iodinesulfur cycle (I-S cycle), first proposed by GENERAL ATOMICS in the late 1970s, will be discussed here because it was close to commercial development for the thermal splitting of water. In this thermochemical cycle, the waste heat lost from a nuclear reactor is supplied to concentrated sulfuric acid (96 wt.%) by means of a helium gas heat exchanger. The high temperature existing in the loop leads to decomposition of the acid that occurs in two consecutive steps: First, between 400 and 600°C, sulfuric acid decomposes yielding sulfur trioxide and water vapor as follows: H2SO4(g) —> SO3(g) + H2O(g) 13

14

(400–600°C)

Doenitz, W. Hydrogen production by high temperature electrolysis of water vapour. Int. J. Hydrogen Energy, 5(1)(1980)55−63. Estève, B.; Lecoanet, A.; Roncato, J.P. Thermodynamique des cycles thermochimiques de décomposition de l'eau Entropie, 61(1975)70–83.

Monographies on Major Industrial Gases

1085

Afterward in a second step occurring around 850°C, sulfur trioxide releases its oxygen as follows: SO3(g) —> SO2(g) + 1/2O2(g)

(800–900°C)

The second reaction, conducted under pressure at 7 kPa, requires less energy despite being conducted at higher temperature. Moreover, when the second reaction is completed the 15 energy required to end the cycle is minimum ca. 71 kJ/mole , the overall decomposition reaction being: H2SO4(g) —> H2O(g) + SO2(g) + 1/2O2(g) The sulfur dioxide gas is later contacted with water vapor (i.e., steam) and iodine gas at 120°C in order to perform the Bunsen reaction and yield hydrogen iodide and regenerate the sulfuric acid: SO2(g) + I2(g) + 2H2O(g) —> H2SO4(l) + 2HI(l)

(25–120°C)

Then hydroiodic acid is collected along with sulfuric acid and excess water in an aqueous phase and later separated from sulfuric acid by extractive distillation to yield hydrogen iodide (HI). Later HI is decomposed at 300°C to yield hydrogen gas and iodine according to the decomposition reaction: HI(g) —> H2(g) + I2(g)

(200–400°C)

Iodine is recovered and recycled into the Bunsen reactor with SO2 to end the loop. This route with a practical energy efficiency ranging between 40 and 60% combined with cogeneration is particularly envisaged for the future type of high-temperature nuclear reactor (HTGR) and 16 is under joint development between the U.S. Department of Energy (DOE) , Sandia National Laboratory, and General Atomics in the United States, and the Commissariat à l’Énergie Atomique (CEA) in France. Other development programs also exist in Germany (KFA), and 17 Japan (JAERI) . However, there remain several major challenges to overcome such as: selection of materials resistant to corrosion for conducting decomposition of sulfuric acid and for the Bunsen reaction and clean separation between hydroiodic acid and sulfuric acid. Hybrid 18 cycles combining thermochemical and electrochemical stages were also extensively studied . Health and safety. Hydrogen gas is a simple asphyxiant but it is highly flammable yielding hot flames in air (2040°C) nearly invisible in daylight. Hydrogen forms highly explosive mixtures with air and oxygen. The flammability limits in air under normal conditions are 4.0–74.2 vol.% or 4.65–93.9 vol.% in pure oxygen. Because hydrogen exhibits high burning velocities (1.5–2.5 km/s), it is more prone to deflagration and detonation than other flammable gases such as hydrocarbons. Its detonation range in air is 18.3–59 vol.%. Note that flammability range of hydrogen, by contrast with most fuel gases, expands as the temperature increases but that its flammability range becomes narrower as the pressure increases until roughly 5 MPa. Transport and storage. Hydrogen is currently stored in tanks as a compressed gas or cryogenic liquid. The tanks can be transported by truck or the compressed gas can be sent 15

16

17

18

O’Keefe, D.R.; Norman, J.H.; Williamson, D.G. Catalysis research in thermochemical water-splitting processes Catal. Rev.-Sci. Eng., 22(3)(1980)325–369. Brown, L.C.; Lentsch, R.D.; Besenbruch, G.E.; Schultz, K.R.; Funk, J.E. Alternative flowsheets for the sulfur iodine thermochemical cycle Proceedings AIChE 2003 Spring National Meeting, New Orleans, LA, USA, March 30–April 3, 2003. Onuki, K.; Inagaki, Y.; Hino, R.; Tachibana, Y. R&D on nuclear hydrogen production using HTGR at JAERI Proceedings of the COES-INES International Symposium, Tokyo November 1st, 2004. Bilgen, E. and Bilgen, C. A hybrid thermochemical hydrogen producing process based on the CristinaMark cycles International Journal of Hydrogen Energy, 11(4)(1986)241–256.

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Table 19.19. Comparison of specific storage capabilities for hydrogen of various compounds Hydrogen storage compound

Relative Density molar mass

mass mass H2 percentage per unit H2 volume of compound –3

–3

(NTP) volume H2 per unit mass of compound 3

–1

(Mr)

(ρ/kg.m ) (/wt.%)

(/kg.m )

(m .kg )

Hydrogen gas (293.15 K and 20 MPa)

2.016

16.5

100

17

11.12

Liquid hydrogen (boiling point)

2.016

69.5

100

70

11.12

Water (H2O) (293.15 K and 101.325 kPa)

18.015

1000

11.19

111

1.244

Liquid ammonia (NH3) (239.45 K and 101.325 kPa)

17.031

682.8

17.76

121

1.975

Metal hydride (H6LaNi5)(*)

438.42

8576

13.79

1183

1.533

(*) LaNi5(s)+ 3H2(g) = H6LaNi5(s)

across very long distances by pipeline usually less than 100 km but exceptionally up to 200 km as it is in Germany. Other alternative methods, technologies that store hydrogen in a solid state, are inherently safer and have the potential to be more efficient than gas or liquid storage. These are particularly important for vehicles with on-board storage of hydrogen. Technologies under investigation include: metal hydrides that involve chemically reacting the hydrogen with a metal. Carbon nanotubes take advantage of the gas-on-solids adsorption of hydrogen. Glass microspheres rely on changes in glass permeability with temperature to fill the microspheres with hydrogen and trap it there. The physical characteristics of the various media used for hydrogen storage are presented for comparison in Table 19.19. Industrial applications and uses. Hydrogen finds use in several industrial applications. (i)

In the chemical process industries, hydrogen gas is extensively used primarily in the manufacture of ammonia by the Haber–Bosch process, in the refining of petroleum and for the synthesis of methanol. (ii) Hydrogen is also used in the food industry to hydrogenate unsaturated liquid oils such as soybean, fish, cottonseed and corn, converting them to semisolid materials such as shortenings, margarine and peanut butter. (iii) Hydrogen is also used extensively in metallurgical processes in which it serves as a protective atmosphere in high-temperature operations like stainless-steel manufacturing commonly being mixed with argon for the welding of austenitic stainless steels. It is used to support plasma welding and cutting operations as well. (iv) Hydrogen is used as liquid fuel for propellants in spacecraft, but also to power lifesupport systems and computers, yielding drinkable water as a by-product.

19.3.5 Methane Description and general properties. Methane [74-82-8], also called marsh gas, with the –3 chemical formula CH4, the relative molar mass of 16.04276 and a low density of 0.7168 kg.m under normal temperature and pressure conditions (273.15 K and 101.325 kPa), is the first and lightests member of the alkanes (i.e., saturated hydrocarbons or olefins with chemical formula CnH2n+2). Methane is a colorless, odorless, non-poisonous and flammable gas that solidifies at –182.4°C (90.75 K) and boils under atmospheric pressure at –161.5°C (111.65 K). 3 Methane is poorly soluble in water (e.g., 35 cm per kg of water at 17°C) but soluble in

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concentrated sulfuric acid (98 wt.% H2SO4) and many organic solvents such as diethyl ether, acetone, etc. From a chemical point of view, methane like other alkanes is not very reactive because of its strong covalent sigma bonds and high molecular symmetry. Actually, its covalent bonds are only prone to homolytic rupture. Moreover, if methane is heated to a high temperature or subjected to far-UV radiation, free radicals are produced. Outside these harsh conditions, methane is not chemically reactive; this is the reason why alkanes in general were called paraffins, from the Latin, paraffinum, meaning, poor affinities. Methane is chemically inert towards the action of strong alkalis and caustics (e.g., NaOH and KOH) and towards strong mineral acids such as concentrated sulfuric acid, even when put in contact with Nordhausen’s acid, also called oleum (i.e., up to 60 wt.% SO3 dissolved in 100 wt.% 19 sulfuric acid) , methane seems not to be attacked even though oleum readily oxidizes other alkanes producing sulfonic acids. However, methane burns in oxygen and air with a pale faintly luminous and hot flame and its ignition temperature in air is 650°C. The low and high flammability limits of methane are 5.53 and 15.0 vol.% respectively (see Chapter 17). Methane reacts violently and even explodes, with anhydrous chlorine gas if the mixture is exposed to sunlight, yielding carbon soot and hydrogen chloride. CH4(g) + 2Cl2(g) —>C(s) + 4HCl(g) When heated with water vapor or steam, it produces carbon monoxide and hydrogen; this reaction is used in steam reforming: CH4(g) + H2O(g) —>CO(g) + 3H2(g) Under high pressures, methane and ice form gas hydrates called clathrates. Methane hydrates can be considered as modified ice structures enclosing methane, melting at temperatures well above the melting point of pure ice. For instance, above a pressure of 3 MPa, methane hydrate is stable at temperatures above 0°C and under a pressure of 10 MPa it is stable at 15°C. From an environmental point of view methane exhibits a global warming potential 21 times the greenhouse gas effect of carbon dioxide. Preparation. In the laboratory methane can be prepared by hydrolysis of aluminum carbide (Al4C3) or to a lesser extent beryllium carbide (Be2C) or by decomposing sodium acetate with sodium hydroxide. Carbon reacts with pure hydrogen to yield methane at temperatures above 1100°C but the reaction becomes noticeable only above 1500°C. In addition, a catalyst must be used to prevent the formation of acetylene. Commercially methane is only obtained from natural gas (see Section 17.5) or from fermentation of cellulose or sewage sludges.

19.3.6 Carbon Monoxide Description and general properties. Carbon monoxide [630-08-0], with the chemical formula CO and the relative molar mass of 28.0104 is a colorless, odorless gas slightly lighter than air (SG = 0.967) that melts at –205°C (68 K) and boils at –192°C (81 K). It is very slightly 3 3 soluble in water (2.603 cm /dm at 25°C and 101.325 kPa) but it is more soluble in organic solvents such as ethanol, methanol, ethyl acetate, methyl chloride, and acetic acid. Carbon monoxide is a flammable gas that burns in air with a characteristic bright-blue flame, producing carbon dioxide. 2CO(g) + O2(g) —> 2CO2(g)

19

with

ΔrH = –284.512 kJ/mol 0

Potolovskii, L.A. Action of sulfuric acid on gaseous analogs of methane. Zavodskaya Laboratoriya, 15(1949)1152–1157.

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Gases

Flammability limits in air range between 12 and 75 vol.% CO. From a chemical point of view, carbon monoxide is a reducing agent, removing oxygen from many compounds and hence it is used in the reduction of metals, e.g., iron, from their ores. It also reduces water according to the reaction: CO(g) + H2O(g) —> CO2(g) + H2(g)

with

ΔrH = –41.84 kJ/mol 0

This reaction is used industrially to produce hydrogen or to remove carbon monoxide from water gas. By contrast, carbon monoxide becomes an oxidant towards hydrogen; actually, at high pressures and elevated temperatures together with a nickel catalyst, it reacts with hydrogen to yield methane: CO(g) + 3H2(g) —> CH4(g) + H2O(g) Moreover, under high pressure and in the presence of zinc oxide (ZnO) as a catalyst, it reacts with hydrogen to produce methanol: CO(g) + 2H2(g) —> CH3OH(g) Finally, in the presence of a cobalt catalyst, it yields hydrocarbons according to the Fisher– Tropsch reaction: nCO(g) + (2n + 1)H2(g) —> CnH2n+2 + nH2O(g) Carbon monoxide reacts with chlorine to produce phosgene (COCl2) or with sulfur to yield carbonyl sulfide (COS). Carbon monoxide also combines with inner transition metals to yield volatile metal carbonyls. Nickel carbonyl Ni(CO)4 is obtained by the direct combination of carbon monoxide and nickel metal at 60°C. For this reason, pure nickel tubing and parts must not come into prolonged contact with hot carbon monoxide. Nickel carbonyl decomposes readily back to Ni and CO upon contact with hot surfaces, and this method was once used for the industrial purification of nickel in the Mond process. Carbon monoxide is dangerous and life-threatening to humans and animals. Inhaling even relatively small amounts of it can lead to hypoxic injury, neurological damage, and possibly death. When carbon monoxide is inhaled, it replaces oxyhemoglobin (HbO2) the red blood pigment that carries oxygen by forming carboxyhemoglobin (HbCO) which is several hundred times more stable. These effects are cumulative and long-lasting, causing oxygen starvation throughout the body. Prolonged exposure to fresh air or pure oxygen is required to destroy carboxyhemoglobin. At lower levels of exposure, CO causes mild effects that are often mistaken for the flu. These symptoms include headaches, dizziness, disorientation, nausea and fatigue. The effects of CO exposure can vary greatly from person to person depending on age, overall health and the concentration and length of exposure. A concentration of as little as 400 ppm vol. carbon monoxide in the air can be fatal. The gas is especially dangerous because it is not easily detected by human senses. Natural occurrence. Carbon monoxide is produced during the incomplete combustion of carbon and carbon-containing compounds, hence it occurs in the exhaust of internalcombustion engines, in coal stoves, furnaces, and gas appliances functioning with an oxygen deficiency. Carbon monoxide is also naturally present in the atmosphere, chiefly as a product of volcanic activity. It occurs dissolved in molten volcanic rock at high pressures in the Earth’s mantle. Carbon monoxide contents of volcanic gases vary from less than 1000 ppm vol. to as much as 2 vol.%. It also occurs naturally in bushfires. Laboratory preparation. Carbon monoxide is prepared in the laboratory either by dehydrating formic acid with concentrated sulfuric acid as follows: HCOOH —> H2O(l) + CO(g)

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or by passing carbon dioxide over heated carbon: CO2(g) + C(s) —> 2 CO(g) Industrial preparation. Carbon monoxide is the major component of producer gas and water gas (see Section 19.3.4), which are widely used synthetic gaseous fuels. Industrially, carbon monoxide is prepared by the oxidation of natural gas, which consists primarily of methane or by the water gas reaction. It is also formed with by product oxygen by decomposition of carbon dioxide at very high temperatures (above 2000°C). Applications and uses. Carbon monoxide is a major industrial gas that has many applications in bulk chemicals manufacturing, including the production of methanol by hydrogenation and aldehydes by the hydroformylation reaction. It is also used in the industrial production of phosgene. Carbon monoxide and methanol react in the presence of a homogeneous rhodium catalyst and HI to give acetic acid in the Monsanto process, which is responsible for most of the industrial production of acetic acid.

19.3.7 Carbon Dioxide Description and general properties. Carbon dioxide [124-38-9], with the chemical formula CO2 and the relative molar mass of 44.0098 is a colorless, tasteless gas that is denser than air (SG = 1.517). It melts at –55.6°C and boils at –78.5°C. Gaseous or liquid carbon dioxide will form dry ice through an auto-refrigeration process if rapidly depressured. The dry ice obtained is at –78.5°C with two times the mass cooling capacity of ordinary ice. Carbon dioxide 3 3 is highly soluble in water (145 cm per dm at 25°C and 1 atm), but also in ethanol and in acetone. Carbon dioxide will not burn or support combustion and is a simple asphyxiant; air with a carbon dioxide content of more than 10 vol.% extinguishes an open flame. Air containing more than 10 vol.% CO2, if breathed, can be life-threatening. Such high concentrations may build up in silos, digestion chambers, wells, and sewers. Carbon dioxide is commercially available in high-pressure gas cylinders, in low-pressure gas cylinders (20 bar), as a refrigerated liquid, or as dry ice. Natural occurrence. Carbon dioxide which is present in the atmosphere at roughly 380 ppm vol. is produced by respiration and by combustion and it is consumed by plants during photosynthesis. Exhaled air contains as much as 4 vol.% carbon dioxide. However, it has a short residence time in this phase. The oceans hold much of the Earth’s total inventory of carbon dioxide. Laboratory preparation. Carbon dioxide is prepared by treating calcium carbonate (e.g., limestone) with dilute hydrochloric acid: CaCO3(s) + 2 HCl(l) —> CaCl2(s) + H2O(l) + CO2(g) or by calcining magnesium carbonate at 900°C in air: MgCO3(s) —> MgO(s) + CO2(g) Industrial preparation. Despite the atmosphere and ocean having huge reserves of carbon dioxide, neither the air nor the oceans has a concentration great enough to make them economically viable sources of carbon dioxide. Therefore, commercial quantities of carbon dioxide are produced by separating and purifying carbon-dioxide-rich gases produced after combustion, during metallurgical processes (e.g., producer gas) or biological processes (e.g., fermentation) that would otherwise be released directly to the atmosphere. Common sources are smelters, hydrogen plants, ammonia plants and fermentation operations such as production of beer or manufacture of ethanol from corn. Carbon dioxide is also recovered from underground formations in the western United States and in Canada.

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Gases

Industrial applications and uses. Large quantities of solid carbon dioxide (i.e., in the form of dry ice) are used in processes requiring large-scale refrigeration. Carbon dioxide is also used in fire extinguishers as a desirable alternative to water for most fires. It is a constituent of medical gases as it promotes exhalation. It is also used in carbonated drinks. In metallurgy, carbon dioxide is used on a large scale as a shield or blanketing gas in welding. Large quantities of carbon dioxide are used as a raw material in the chemical process industry, especially for methanol and urea production. Carbon dioxide is used in oil wells for oil extraction and to maintain pressure within an oil-bearing rock formation after extraction (see Section 10.10). Carbon dioxide gas is used to carbonate soft drinks, beers and wine and to prevent fungal and bacterial growth.

19.3.8 Helium and Noble Gases Description and general properties of the noble gases. The chemical elements of group VIIIA(8) of Mendeleev’s periodic table exhibit a peculiar electronic structure: their valence shell of electrons is filled completely. Actually, except for the helium atom having two valence 2 6 electrons, the electronic structure of all other gases exhibits eight valence electrons [ns np ]. This stable electronic configuration with respect to loss or gain of electrons is characterized by a high ionization potential (e.g., 10.75 eV/atom for radon up to 24.6 eV/atom for helium) and negative electron affinities. Hence, they only interact weakly with other chemical elements even with highly electronegative elements such as fluorine, chlorine and oxygen. This explains their well-known chemical inertness and the etymology of the name noble gases or inert gases. However, these etymologies along with the name rare gases are no longer justified since the work of Bartlett, who in 1962 prepared the first compound XePtF6. Since then, numerous other compounds of Kr, Xe and Rn have been prepared demonstrating that heavier elements in this group are not so chemically inert. In addition, regarding their scarcity, argon with an abundance of 0.94 vol.% in air is not so rare. The interactions between noble gases are ensured only by weak Van der Waals forces whose magnitude is proportional of to polarizability of the spherical atom and inversely proportional to the ionization potential of the element. Only krypton, xenon and radon can combine with the most electronegative elements. Helium, neon, argon, krypton, xenon and to a lesser extent radon are all colorless, tasteless, and odorless. All are monatomic gases with an isentropic exponent (i.e., the dimensionless ratio of isobar and isochoric molar heat capacities) of exactly 5/3 (i.e., 1.6667) and their actual behavior is close to the theoretical behavior of ideal gases under moderate pressure and temperature. Under high pressure, usually in the range of several megapascals, all noble gases except helium for which the atom is too small, are trapped in the crystal lattice of ice (or heavy ice, D2O) forming nonstoichiometric intercallation compounds called gas hydrates (deuterohydrates) or clathrates (see also Section 19.5). Clathrates of nobles gases are nonstoichiometric but usually consist of 7 or 8 atoms of noble gases for 46 molecules of water (e.g., 7.99 Ar.46 H2O). Other substances, especially organic compounds such as hydroquinone and phenol, can form stable clathrates with noble gases. Upon heating, clathrates decompose releasing the gas, sometimes violently. Description and general properties of helium. Helium [7440-59-7] with the chemical symbol, He, atomic number 2, a relative atomic molar mass of 4.002602(2) and a density of –3 0.1785 kg.m (S.G. 0.138) is the second lightest gas after hydrogen and the first element of 4 group VIII (18). Helium has two stable isotopes mainly He (99.9999863 at.%) and the scarce 3 He (1.37 ppm at.). Helium solidifies at –272.2°C (0.95 K) having the lowest melting point of all the elements and boils at only –268.93°C (4.216 K). The behavior of helium-4 in the liquid state is unique among the elements. Actually, helium-4 exhibits two liquid phases: helium I and helium II with a sharp second-order transition point at 2.174 K and 510 Pa. The existence

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4

range of the two phases is separated by a lambda-line. He(I) that occurs above this line is 4 4 a normal liquid, while He(II) exhibits an anomalous behavior below that line. He(II) expands on cooling, has a huge thermal conductivity (i.e., 200 times that of copper at room temperature), is a frictionless fluid with no viscosity close to 0 K (i.e., superfluid) and it cannot be solidified even by lowering the temperature, thus remaining liquid down to absolute 4 zero at ordinary pressure; however, He(I) can be solidified by increasing the pressure. He–1 –1 lium gas exhibits the second highest thermal conductivity (0.152 W.m .K ) after hydrogen –1 –1 and the highest specific heat capacity (5193 J.kg .K ) of all gases. The solubility of helium in 3 water is 9.7 cm per kg of water at 0°C. History. Helium was discovered by spectroscopic studies conducted by Jansen on the solar protuberance observed during the solar eclipse of 1868 and it was named by Frankland and Lockwood from the Greek, helios, for Sun. Later, helium was identified by Kayser in the Earth’s atmosphere and by Sir William Ramsay by dissolving the uranium mineral cleveite today known as uraninite [UO2, tetragonal or metamict] into acids. Natural occurrence. Helium, which is the second most abundant element after hydrogen in the Universe, is relatively scarce in the Earth’s atmosphere being the third noble gas after argon and neon with 0.000524 vol.% (see Section 19.3.1). Terrestrial helium originates mainly from alpha-decaying radionuclides contained in the lithosphere and oceans, especially radionuclides related to the three natural radioactive series, that is, uranium-238 (4n + 2), 4 2+ uranium-235 (4n + 3) and thorium-232 (4n). Alpha particles which are helions ( He ) recover their two electrons to yield neutral helium atoms after slowing down and interacting with matter (i.e., straggling process). The helium atoms thus produced over geological times are later trapped into uranium- and thorium-rich minerals or eventually collect with other gases especially natural gas at the top of oil reservoirs. In certain locations, natural gas can contain up to 0.8 vol.% He. To a lesser extent, hot springs in regions having a current or former volcanic activity contain helium gas dissolved in water. Industrial production. Commercially helium is extracted from natural gas wells. The richest natural gas reservoirs are located mainly in the United States (i.e., Texas, Oklahoma, and Kansas) and to a lesser extent in Algeria, Russia, Canada, Poland Russia, China and India. Applications. Owing to its chemical inertness helium is extensively used as blanketing gas during the casting of reactive and refractory metals (e.g., Ti, Zr, Hf) or as a gas shield during arc welding. Owing to its low density, non flammability and lower permeability through most textiles, helium was used as replacement for hazardous hydrogen gas for filling balloons, military and commercial airships. On the other hand, because of its high thermal conductivity combined with a high specific heat capacity, helium is used as a heat transfer medium in many high-temperature industrial applications such as gas-cooled nuclear reactor, or high-temperature heat exchangers. Helium is also used as filling gas and for the detection of leaks in vacuum systems using a mass spectrometer. Cryogenic helium is also extensively used in nuclear magnetic resonance for medical imaging.

19.3.8.1 Neon Neon [7440-01-9], with the chemical symbol, Ne, atomic number 10, and the relative atomic molar mass of 20.1797(6) is the second most abundant noble gas in the air (0.0018 vol.%) after argon. Neon was named from the Greek, neos, for new, and was discovered by Morris W. –3 Travers and Sir William Ramsay in 1898. Neon has a low density of 0.900 kg.m (S.G. 0.696) and it solidifies at −248.58°C (24.57 K) and boils at –246.06°C (27.09 K) under atmospheric 20 21 22 pressure. Neon has three stable isotopes Ne (90.48 at.%), Ne (0.270 at.%) and Ne 3 (9.250 at.%). Neon is poorly soluble in water with a solubility of 10.5 cm per kg of water at 20°C. Neon is extensively used in lighting tubes because of the intense red line emitted during electric discharge.

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Gases

19.3.8.2 Argon Argon [7440-37-1], with the chemical symbol, Ar (formerly A), atomic number 18, and the relative atomic molar mass of 39.948(1) is the most abundant of the noble gases in the atmosphere (0.94 vol.% in air). Argon was named from the Greek, argos, meaning inactive, because of its chemical inertness. It was discovered by Lord Rayleigh and Sir William Ramsay in 1894 and first isolated from dry air by absorbing oxygen with hot copper turnings and later the remaining nitrogen with magnesium turnings. Argon is a dense gas with a den–3 sity of 1.782 kg.m (S.G. 1.378) that solidifies into a fcc crystal at –189.15°C (84.0 K) and boils 3 at –185.89°C (87.26 K). Argon is poorly soluble in water with a solubility of 33.6 cm per kg of 36 38 40 water at 20°C. Argon has three stable isotopes Ar (0.3365 at.%), Ar (0.0632 at.%) and Ar (99.6003 at.%), the last isotope being the most abundant because it is the stable daughter 40 from the decay of the pure beta emitter K. Argon is obtained commercially from the fractional distillation of liquified air. Argon is extensively used as a gas shield during arc welding, as inert atmosphere in nonferrous metal processing, in nuclear detectors and in the manufacture of semiconductors.

19.3.8.3 Krypton Krypton [7439-90-9], with the chemical symbol, Kr, atomic number 36, and the relative atomic molar mass of 83.798(2) is the fourth most abundant noble gas in air (0.000114 vol.%) just after argon, neon, and helium. Krypton was named from the Greek, kryptos, meaning hidden because it was difficult to find in air. It was discovered by Sir William Ramsay and Morris W. Travers in the residual liquid remaining after evaporation of liquified air. Krypton –3 is a dense gas 3.739 kg.m (S.G. 2.892) that solidifies into fcc crystals at –271.51°C (1.64 K) 3 and boils at –153.36°C (119.79 K). Krypton is slightly soluble in water (59.4 cm per kg of wa78 ter at 20°C) with formation of the hydrate Kr.5.75H2O. Krypton has six stable isotopes Kr 80 82 83 84 86 (0.354 at.%), Kr (2.28 at.%), Kr (11.58 at.%), Kr (11.52 at.%), Kr (56.896 at.%), and Kr (17.37 at.%). Krypton forms compounds such as KrF2 with the most electronegative elements (e.g., F, Cl, and O). Krypton, like neon and argon, is obtained commercially from the fractional distillation of liquified air.

19.3.8.4 Xenon Xenon [7440-63-3], with the chemical symbol, Xe, atomic number 54, and the relative atomic molar mass of 131.293(6) is the fifth most abundant noble gas in air (86 ppb vol.). Xenon was named from the Greek, xenos, stranger. It was discovered by Sir William Ramsay and Morris W. Travers in the residual liquid remaining after evaporation of liquified air. Xenon is –3 a dense gas 5.858 kg.m (S.G. 4.53) that solidifies into fcc crystals at –111.75°C (K) and boils at −108.0°C (119.79 K). Xenon is more soluble in water than previous members of group VIIIA 3 124 (108.1 cm per kg of water at 20°C). Xenon possesses nine stable isotopes Xe (0.096 at.%), 126 128 129 130 131 Xe (0.090 at.%), Xe (1.919 at.%), Xe (26.44 at.%), Xe (4.08 at.%), Xe (21.18 at.%), 132 134 136 Xe (26.89 at.%), Xe (10.44 at.%) and Xe (8.87 at.%). Xenon forms compounds with the most electronegative elements (e.g., F, Cl, and O). Xenon is obtained commercially from the fractional distillation of liquified air.

19.3.8.5 Radon Radon [10043-92-2], with the chemical symbol Rn and atomic number 86 is the only radioactive noble gas occurring naturally and it was discovered in the early nineteen century by Ernest Rutherford. Radon it produced from the decay of its parent radionuclide radium, itself produced during the decay of one of the three natural radioactive series, that is, uranium-238 (4n + 2), uranium-235 (4n + 3) and thorium-232 (4n). For that reason, radon was first named 222 according to the former name of the parent radionuclide in each series; radon-222 ( Rn)

Halocarbons 226

1093

219

which is produced by the alpha-decay of Ra was named radon or niton (Nt), while Rn from 223 220 the alpha-decay of Ra (called actinium X) was named actinon (An), finally Rn decaying 224 from Ra (called thorium X) was called thoron (Tn). Moreover, to add confusion, all these obsolete names were also grouped under the general name emanation. Radon is the mona–3 tomic gas that exhibits the highest density 9.73 kg.m and has the highest solubility in water of 3 the noble gases with 230 cm per kg of water at 20°C. Radium is extracted from uranium and thorium minerals after separating it from helium by condensation into liquid nitrogen.

19.4 Halocarbons The naming system for halogenated hydrocarbons or simply halocarbons, originally commercialized as refrigerants under the trade name Freons® by E.I. Du Pont de Nemours, was developed by T. Midgley, Jr. and A.L. Henne in 1929, and further refined by J.D. Park. The naming of the halocarbons was originally: R-(C-atoms –1) (H-atoms + 1) (F-atoms) (Cl-atoms replaced by Br-atoms) letter x In the modern designation, the letter R is replaced by a three letter code XXX standing for CFC, HFC, HFC: XXX-(C-atoms –1) (H-atoms + 1) (F-atoms) (Cl-atoms replaced by Br-atoms) letter x The lower case letter -a- is added to identify isomers, the normal isomer in any number has the smallest mass difference on each carbon, and a, b, or c are added as the masses diverge from normal. Originally, halogenated alkanes that contained chlorine and fluorine were all referred to as chlorofluorocarbons under the common acronym, CFCs. Today, the group is subdivided into: (i) (ii) (iii) (iv)

chlorofluorobons, sensu stricto (CFCs); hydrochlorofluorocarbons (HCFCs); hydrofluorocarbons (HFCs); fully halogenated hydrocarbons (Halons).

Example:

HCFC-22 HCFC-123a HFC-23 HFC-134a Halon 1211

stands for chlorodifluoromethane [CHClF2] stands for 1,2 dichloro-1,1,2-trifluoroethane [CHClF-CClF2] stands for trifluoromethane [CHF3] stands for CH2FCF3 1,2,2,2 tetrafluoroethane [811-97-2] stands for CBrClF2

The most important application of halocarbons by far is as refrigerants in refrigeration and air-conditioning equipment. CFC, HCFC and HFCs are used as refrigerants in domestic, commercial and industrial refrigeration applications. The second most important use of halocarbons is as inert gas for foam blowing for making polyurethane (PU), polyisocyanurate (PIR), polyethylene (PE), and extruded polystyrene (XPS) foams using HCFCs. Aerosols and metered-dose inhalers use HCFCs. In the primary aluminum industry, the majority of emissions of perfluorinated carbons are generated during electrolysis as carbon tetrafluoride, CF4, and carbon hexafluoride, C2F6. These two halons are formed during the anode effect occurring in the electrolytic cells. In semiconductor manufacture, fluorinated compounds are used for cleaning chemical vapor deposition (CVD) chambers and for plasma dry etching. In the primary, magnesium industry, the safe casting of highly reactive molten magnesium and its alloys is conducted a under protective gas blanket of SF6.

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Gases

19.5 Hydrates of Gases and Clathrates Under high pressure, usually in the range of several megapascals, and low temperatures, small gas molecules intercallate into the crystal lattice of ice or heavy ice to form nonstoichiometric intercallation compounds called gas hydrates (deuterohydrates) or clathrates. The formation of gas hydrates must meet the four following conditions: (i) (ii) (ii)

a low temperature usually below the melting point of ice (273.15 K); a high pressure above 3.8 MPa; a nonpolar gas made of small atoms or molecules having an outside diameter between 350 and 900 pm; (iv) water or heavy water (D2O). Clathrates are not restricted to ice and other host substances especially organic compounds such as hydroquinone and phenol can form stable clathrates especially with noble gases. For gas hydrates, the guest atoms or molecules that can fit into the ice host, i.e., the cage of water molecules, are the noble gases (i.e., Ne, Ar, Kr, Xe, Rn) except helium for which the diameter of the atom is too small, alkanes such as methane, ethane, propane, iso- and n-butane, nitrogen, carbon dioxide and hydrogen sulfide. Although clathrates look like ice and exhibit a similar density they can store enormous volume of gas, for instance, methane 3 hydrate can contain 163 m of CH4 per cubic meters of ice. Upon heating above a certain temperature, all clathrates decompose into water and release the entrapped gas(es) sometimes violently. 20 There exist three types of crystal structures for gas hydrates : structure I, II and H respectively (see Table 19.20), the basic building block of all the three structures being a cage of 12 water molecules with twelve pentagonal faces, and denoted 5 , but for filling the entire space 2 another building unit made with two hexagonal face and denoted 6 must be used. Table 19.20. Three crystal structures of gas hydrates Gas hydrate structure

Type I

Type II

Type H

Crystal lattice

Cubic

Cubic

Hexagonal

Lattice parameters

a = 1200 pm

a = 1730 pm

a = 1226 pm c = 1017 pm

Space group (Hermann–Mauguin)

Pm3n

Fd3m

P6/mmm

Cavity type, size and number per unit cell

5 , small (395 pm) Z=2

5 6 , large (433 pm) Z=6

5 , small (391 pm) Z = 16

Coordination number of oxygen atoms

20

24

20

Packing fraction (%)

17.39

17.64

17.64

Water molecules per unit cells

46

46

136

Guest gases

Noble gases, methane, ethane, CO2

Propane, isobutane

Methane with superior alkanes

20

12

12 2

12

Smelik, E.A.; King, H.E. Jr. Crystal-growth studies of natural gas clathrate hydrates using a pressurized optical cell American Mineralogist, 82(1–2)(1997)88–98.

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1095

Clathrates have important implications industrially because they represent serious issues during transportation of natural gas with gas-lines in cold climates (see Section 19.3.5). Moreover, huge deposits of clathrates in the Arctic and offshore on the deep seafloor represent an enormous resource of natural gas for the future. Finally, due to the high greenhouse potential of methane gas a great concern exists about its release from clathrates due to global warming.

19.6 Materials for Drying and Purifying Gases 19.6.1 Drying Agents and Dessicants See Table 19.21, pages 1096–1098.

19.6.2 Molecular Sieves Molecular sieves are synthetically produced zeolites characterized by pores and crystalline cavities of extremely uniform dimensions. Molecular sieves are available in four different grades. These grades are different from one another because of their chemical composition and pore size. Molecular sieves are ceramic-appearing pellets or balls in diameters of 0.159 mm (1/16 in.) or 3.175 mm (1/8 in.). Molecular sieves have the lowest dusting factor of any commercially available desiccant; moreover, the pellets or balls do not change size or shape upon reaching saturation. Type 3A (three angstroms). Molecular sieve is the potassium form of the zeolite. Type 3A adsorbs molecules which have a critical diameter of less than three angstroms (e.g., He, H2 and CO). A type 3A molecular sieve is recommended for drying unsaturated hydrocarbons and highly polar compounds such as methanol and ethanol. The 3A structure is particularly effective in dehydrating the inner space of insulating glass windows and refrigerant gases. Type 4A (four angstroms). Molecular sieve is the sodium form of the zeolite. Type 4A adsorbs molecules having a critical diameter of less than four angstroms (e.g., NH3). A type 4A molecular sieve is typically used in regenerable drying systems to remove water vapor or contaminants which have a smaller critical diameter than four angstroms. Type 5A (five angstroms). Molecular sieve is the calcium form of the zeolite. Type 5A adsorbs molecules having a critical diameter of less than five angstroms (e.g., methanol, ethane, propane). Type 5A sieves can be used to separate normal paraffins from branched-chain and/cyclic hydrocarbons through a selective adsorption process. Type 13X (ten angstroms). Type 13X is a modified form of the sodium zeolite with a pore diameter of ten angstroms. Molecules of chloroform, carbon tetrachloride and benzene can be adsorbed on type 13X molecular sieves. Type 13X is used commercially for general gas drying, air plant feed purification (i.e., simultaneous removal of H2O and CO2) and liquid hydrocarbon and natural gas sweetening (i.e., H2S and mercaptan removal). All molecules which can be adsorbed on molecular sieves 3A, 4A and 5A can be adsorbed on type 13X. In addition, type 13X can adsorb molecules of larger critical diameters, such as aromatics and branched-chain hydrocarbons.

19 Gases

–1

2 × 10

acid

basic

Calcium chloride CaCl2 (fused)

CaH2

CaO

CaSO4

CuSO4

Calcium hydride

Calcium oxide

Calcium sulfate anhydrous (Drierite)

Copper sulfate

neutral

neutral

basic

basic

CaC2

Calcium carbide

– (2.8)

– –4 (5 × 10 )

0.660 (0.003)

(0.00001)

0.14 (0.10–0.20)

–

slightly (0.18) acid

Calcium bromide CaBr2

0.0002 (0.6 to 0.8)

50 (0.31)

–3

–2

3 × 10

5 × 10

–

– (0.07)

– (0.85)

31 0.1(1w) 0.3(2w)

– (0.56)

1100 (0.17)

– (0.12)

260 (0.2)

–5

< 10

–

–4

5 × 10

Ba(ClO4)2 neutral

Barium perchlorate (Desichlora)

–4

(0.00065)

4 × 10

BaO

Barium oxide

basic

Al2O3

–3

–

100

100

–

29

–

100

100

Residual Relative Tmax 22, 23 water vapor capacity (/°C) pressure (cmHg)

neutral, 0.003 1 × 10 –3 acid (2 to 5 × 10 )

Chemical Acidity Efficiency 3 21 formula (mg/dm )

Activated alumina

IUPAC name (usual or trade name)

Table 19.21. Performances and selected properties of drying agents and dessicants

hydratation

hydratation

chemical reaction

chemical reaction

hydratation

chemical reaction

hydratation

hydratation

chemical reaction

physisorption

Cheap highly efficient and easy to regenerate at 230–250°C. Reacts with ammonia.

Difficult to regenerate at 1000°C. Efficient but low capacity when CO2 is present, absorbs all acid gases. Ideal for ammonia, alcohols, amines. Incompatible with phenols and acids.

Evolves H2. Impossible to regenerate. Suitable for hydrocarbons, ethers, amines, esters and alcohols.

Low cost and compatible with numerous gases but poor capacity and it must be cooled down to 0°C to reduce water vapor pressure. Not suitable for alcohols, phenols and amines. Regeneration difficult at 250°C. Can contain CaO that must be converted into CaCO3 prior to drying CO2.

Impossible to regenerate. Risk of explosion with the evolved acetylene.

Highly efficient with a high capacity 35 wt.% water, but difficult to regenerate (48 h at 240°C under vacuum), explosion hazards with organic compounds.

Low capacity but can be regenerated by calcination at 1000°C. Suitable for hydrocarbons, alcohols, aldehydes and alkaline gases.

More efficient than molecular sieves but with lower capacity. Regeneration by heating at 175°C under vacuum during 24 h. Incompatible with oxidable polar substances. Suitable for hydrocarbons.

Drying process Notes

1096 Gases

MgSO4

Zeolithes neutral

Magnesium sulfate anhydrous

Molecular sieves Linde 4X and 5X (4Å and 5Å)

acid

P2O5

K2CO3

KOH

SiO2

CaO and NaOH

NaOH

Na2SO4

Phosphorus pentoxide

Potassium carbonate

Potassium hydroxide

Silicagel

Sodalime

Sodium hydroxide (caustic soda)

Sodium sulfate

–

0.0004 –5 (2.5 × 10 )

–

0.004 (0.001)

1–12

0.0002

(0.008)

neutral

basic

basic

neutral

(12)

0.51 (0.16)

0.070 (0.002)

basique (0.002)

basic

acid

Orthophosphoric H3PO4 acid (solid)

neutral

neutral

MgClO4

Magnesium perchlorate (Anhydrone)

w.o.

basic

N2 (liq)

Magnesium MgO oxide (magnesia)

Liquid nitrogen trap

–4

–3

–3

~2 × 10

– (1.25)

180 (8)

– (1.5)

320 (0.2)

–

–3

2 × 10

570 (0.5)

–

220 (0.18)

– (0.16)

–5

–

hydratation

30

Easy to regenerate at 150°C. Good for ketones, acids, alkyl chlorurides. Incompatible with alcohols.

Low capacity especially when CO2 is present. Absorbs all acid gases.

hydratation

100

Impossible to regenerate. Low capacity especially when CO2 is present.

Low capacity especially when CO2 is present. Absorbs all acid gases.

hydratation

100

Easy to regenerate at 158°C. Reacts with phenols and acids.

hydratation

hydratation

140

High efficiency and capacity, but yields acid and is non recoverable, non regenerable. Incompatible with alcohols, esters, amines and ketones.

100

chemisorption

100

Same efficiency as molecular sieves. Absorbs organics, easy to regenerate under vacuum at 200–350°C during 12 hours. Good for amines.

hydratation

100

Sieves absorb only molecules with a diameter inferior to that of pores. Easy to regenerate under vacuum atà 320°C. 5Å sieve for H2O et CO2. Also absorbs organics. 3Å sieve for CO2 purification.

Non regenerable. Excellent for inorganic vapors. Incompatible with primary alcohols.

20–25 physisorption

physisorption

hydratation

Highly efficient with a high absorption capacity of 35 wt.% water. Difficult to regenerate (48 hours under vacuum at 250°C). Good for inert gases, risk of explosion with organic vapors.

Can be regenerated at 800°C.

chemical reaction hydratation

Condenses all vapors and gases with a boiling point below that of liquid nitrogen (77 K)

condensation

–

– 100 (0.15–0.75)

1100 (0.24)

–

2 × 10

–3

~3 × 10

~1 × 10

5 × 10

– (0.45)

–

Materials for Drying and Purifying Gases 1097

Gases

19

ZnBr2

ZnCl2

Zinc bromide

Zinc chloride

23

22

21

H2SO4

Sulfuric acid (concentrated)

(0.85)

(1.16)

(0.003) –

– (3)

~3 × 10 –3

– (0.08)

–

3

650

53

86

4.184

4.184

Expressed as mg H2O/dm for a volume flow rate of nitrogen passing through 3 drying columns (diameter 14 mm, length 150 mm) Relative capacity for a given volume of drying agent. Efficiency expressed in mass of water retained by mass of dessicant.

body-centered cubic 20

721

11.0

10.5

10.5

10.5

1.0

21.5

4.184

4.184

Type 13X

simple cubic

138

69

0.5

721

705–737

Type 5A

simple cubic

n.a.

21

0.4

Type 4A

simple cubic

0.3

Type 3A

Oxidizing agent incompatible with alkaline media.

Used for organics solvents such as hydrocarbons and ethers. Not reusable

Equilibrium Bulk Crushing strength Heat of absorption pH water capacity density for beads of water (5 wt.% slurry) –3 –1 (/wt.% H2O) (ρb/kg.m ) (σc/kPa) (/MJ.kg )

hydratation

hydratation

hydratation

chemical reaction

Drying process Notes

Molecular sieves type Nominal Crystal lattice pore size (d/nm)

100

Residual Relative Tmax 22, 23 water vapor capacity (/°C) pressure (cmHg)

Table 19.22. Selected properties of molecular sieves

acid

acid

acid

Pb-9.5Na basic

Sodium-lead alloy

–

Chemical Acidity Efficiency 3 21 formula (mg/dm )

IUPAC name (usual or trade name)

Table 19.21. (continued)

1098 Gases

Materials for Drying and Purifying Gases

1099

An important adsorption characteristic of a molecular sieve is its ability to continue the adsorption process at temperatures which would cause other desiccants to desorb trapped contaminants. In a gas drying system, water will continue to be adsorbed even though the process temperature may be in excess of 150°C. It must be understood, however, that the adsorption capacity of all desiccants is negatively affected by temperatures in excess of 30°C. Molecular sieves, though, retain their ability to adsorb water molecules over a much wider spectrum of temperatures than other desiccant materials. Molecular sieves also have a much higher equilibrium capacity for water vapor under very low humidity conditions. Molecular sieves are very effective in reducing the water vapor content of gases in the parts per million range.

19.6.3 Getters and Scavengers Getters and scavengers are a particular class of materials that includes compounds which can remove gaseous impurities by adsorption, absorption or occlusion because they have the chemical ability to react strongly and rapidly with these gases. Owing to the extremely low amount of the impurities they are often used in order to purify vacuum-tight enclosures. Historically, the first getter materials were thin barium and titanium coatings deposited on glass walls of electronic lamps in order to absorb nitrogen and oxygen traces. Most getter materials are represented by pure reactive (e.g., Na, Li) and refractory metals (e.g., Ti, Zr, Hf, Nb, Ta) but also by their alloys. It is important to distinguish getters according to the impurities they remove, nevertheless, some getters are efficient for several gaseous impurities such as oxygen, nitrogen and hydrogen (e.g., Ti, Zr). It is also important to know if the getter material is permanent or reversible depending on whether it can release (i.e., desorb) the impurities on heating or not. 19

Table 19.23. Selected properties of getters and scavengers

Gases

Gaseous impurities to remove

Typical getter material

Type

Capacity

Residual pressure

Reliability

Oxygen

Ba, Ti, Zr, Hf, V, Nb, Ta

Permanent

Nitrogen

Ti, Zr, Hf, V, Nb, Ta, Eu, Y, Th, U, Ce

Permanent

Hydrogen

Ti

Reversible

300 torr.L/g 4000. Note that the critical zone is avoided in design because the flow is unstable and friction factors are uncertain. Colebrook, C.F. J. Inst. Civil Eng. 11(1938–39)133–156. Moody Trans. ASME 66(1944)671.

20 Liquids

1108

Liquids

Table 20.3. Absolute surface roughness of selected pipe materials Pipe material (condition)

Absolute surface roughness (e/mm)

Steel (riveted)

1–10

Concrete

0.30–3.0

Cast Iron

0.26

Wood stave

0.18–0.90

Steel (galvanized)

0.15

Steel (welded pipe)

0.14

Cast iron (asphalted)

0.12

High Density Polyethylene (HDPE) 0.0070 Brass and Copper (drawn tube)

0.0015

Polyvinylchloride (PVC)

0.00002

Glass and plastic (smooth)

0.00001

accuracy of ±15% over the full range, it can be used for design calculations for both circular and noncircular pipe flows and also open-channel flows. However, in the critical transition region between laminar and turbulent flow (i.e., 2300 < Re < 4000) there are no reliable friction factors and engineers must avoid designing piping leading to these conditions. Method for calculation of major losses of liquids. First determine fluid properties such as the density, and dynamic viscosity at the operating temperature. Determine the inner diameter of the pipe, and evaluate its absolute roughness based on Table 20.3. Then calculate the Reynolds number for average velocity of the liquid. Afterwards, either use the Moody chart to evaluate the Fanning friction factor based on the Reynolds number and relative roughness, or compute the Colebrook equation by successive iterations. Finally, use the Darcy– Weisbach equation to determine the friction head loss. Flow in noncircular ducts. In the case of a noncircular duct, the calculation follows that of the circular pipe using the same equations but with the diameter of the circular duct of simply replaced by the hydraulic diameter, DH. The hydraulic diameter is simply defined as four times the cross-sectional area A divided by the wetted perimeter Pw. The factor 4 is used to obtain the diameter for a circular pipe. DH = 4A/Pw = 4 RH Table 20.4. Hydraulic diameter for various cross sections Section (Parameter)

Hydraulic diameter

Circular (diameter = d)

DH = d

Annulus (inner diameter = d, outer diameter = D) DH = (D – d) Square (side = a)

DH = a

Rectangular (sides = a, b)

DH = 2ab/(a + b)

Equilateral triangle (side = a)

DH = 2a/√3

Ellipse (major axis = 2a, minor axis = 2b)

DH = ab/[K(a + b)]

Properties of Liquids

1109

20.1.6 Sedimentation and Free settling Sedimentation or free settling refers to the sinking of solid particles in a volume of liquid which is large with respect to the total volume of particles, hence particle crowding is a negligible phenomena. Usually, free settling predominates when the mass fraction of solids is less than 15 wt.%. –3 Consider a spherical particle of outside diameter, d, in m and density ρS in kg.m falling –2 under the acceleration of gravity gn in m.s in a viscous fluid of density ρF under free settling conditions, i.e., ideally in a fluid of infinite extent. The particle is acted upon by three forces: (i) its own weight P = mS gn acting downwards; (ii) the drag force D acting upwards; (iii) buoyancy force b = ρFVS gn due to displaced fluid acting upwards. Hence, Newton’s second law can be written P + b + D = mS a so: –ρSVS gn + ρFVS gn + D = mSdu/dt When the terminal velocity of the particle, denoted u = umax, is reached, du/dt = 0, therefore: D = VS gn (ρS – ρF) D = [πd gn (ρS – ρF)]/6 3

According to Stokes (1891) the drag force on a spherical particle is entirely due to viscous resistance and is described by following the equation: DStokes = 3πηdu while for Newton drag force is due to turbulent resistance and is expressed by: DNewton = 0.055πd ρFu 2

2

Therefore the terminal settling velocity of the solid particles is given by the two relations depending on the flow conditions: umax = [d gn (ρF – ρS)]/18η

(Stokes)

umax = [3d gn (ρF – ρS)/ρF]

(Newton)

2

1/2

Stokes’ law is valid for particles below about 50 μm in diameter. The upper size limit is determined by the dimensionless Reynolds number, while Newton’s law holds for particles larger than about 0.5 cm in diameter. There is therefore an intermediate range of particle size in which neither law fits experimental data. Both laws show that the terminal velocity of a particle in a particular fluid is a function only of the particle size and density. It can be seen that: (i) (ii)

If two particles have the same density, then the particle with the larger diameter has the higher terminal velocity. If two particles have the same diameter the heavier particle has the higher terminal velocity.

Consider two solid particles of densities ρA and ρB and outside diameter dA and dB respectively, falling in a fluid of density ρF, at exactly the same settling rate u. Their terminal velocity must be the same, and hence from the Stokes and Newton laws the relations are respectively: dA/dB = [(ρB – ρF)/(ρA – ρF)]

1/2

dA/dB = [(ρB – ρF)/(ρA – ρF)]

20 Liquids

1110

Liquids

These two expressions are known as the free-settling ratios of the two solids, i.e., the ratio of particle size required for the two particles to fall at equal rates. The free-settling ratio is therefore larger for coarse particles obeying Newton’s law than for particles obeying Stokes’ law. This means that the density difference between the particles has a more pronounced effect on classification at coarser size ranges. The general equation for the free-settling ratio can be deduced from the two previous particular equations: dA/dB = [(ρB – ρF)/(ρA – ρF)]

n

where n = 0.5 for small particles obeying Stokes’ law and n = 1 for coarse particles. The value of the exponent n lies in the range 0.5–1 for particles in the intermediate size range of 50 μm to 0.5 cm.

20.1.7 Vapor Pressure The vapor pressure existing over a liquid at a given thermodynamic temperature T denoted πv and expressed in Pa usually follows Antoine’s law: log10πv = a – b/T

lnπv = A – B/T or

with A and B (resp. a and b) empirical constants determined by experiments. The temperature dependence is usually obtained by differentiating the above equation or from the Clausius–Clapeyron equation: ∂πv /∂T = –(B · πv)/T = –(ln10 · b · πv)/T 2

2

20.1.8 Surface Tension, Wetting and Capillarity Surface tension, wetting and capillarity are phenomena acting only at interfaces between fluids (i.e., liquid–gas, or liquid–liquid) while wetting occurs between solids and fluids (i.e., solid–gas, or solid–liquid). Actually, the system must be able to warp in order to minimize its surface energy. Hence capillarity concerns those systems exhibiting mobile interfaces. Usually capillarity is concerned with meniscus and liquid drop studies or soap films.

20.1.8.1 Surface Tension Inside a liquid, each molecule is completely surrounded by other neighboring molecules (i.e., coordination number) (see Figure 20.1). Because, on average, the cohesive or intermolecular forces act isotropically, i.e., in all directions, with the same magnitude, the system is stable. Conversely, for a molecule at the liquid surface, however, because the coordination number per unit volume of a single molecule is halved, half of the intermolecular bonds are lost and a resultant inwards attraction occurs. As a consequence of this inward attraction, the surface of the liquid always tends to contract to the smallest possible area per unit volume and the surface tension opposes a further increase in the surface area. This explains why drops of liquid become spherical. Mechanical approach. Consider a soap film supported on a metallic mesh on which a wire is sliding (see Figure 20.2). The surface tension, denoted with a Greek letter γ (or σ), is –1 –2 expressed in N.m or J.m and represents the mechanical work required to increase the film surface area. The mechanical work can be written as: dW = γ dA = F dx

with dA = Af – Ai = ldx

Properties of Liquids

1111

Figure 20.1. Liquid and solid surfaces

Figure 20.2. Soap film

Therefore surface tension can be regarded as a force per unit length or energy per unit area: γ = (∂W/∂A) = (∂F/∂x) It is important to note that in practice the wire diameter must be taken into account because it forms a slab of liquid composed of two soap films. Hence the work required is: dW = 2γ dA Thermodynamical approach. In order to extend the area of the surface it is obviously necessary to provide work to bring molecules from the bulk of the solution into the surface against the inward attractive force; the mechanical work required to increase the surface area is called free surface energy. The tendency of a liquid to contract as it approaches a state of equilibrium can be regarded as a direct consequence of a diminution of free energy. For instance, consider a bubble of soap without gravity force; the bubble adopts a perfect spherical shape having a radius r in m which corresponds to a minimal surface energy for a given volume. The variation of the Gibbs free enthalpy of the system is given by: dG = 8πγ r dr On the other hand, the decrease in surface energy is compensated by an increase in the volume energy due to pressure against the wall of the bubble. Therefore, the work variation due to the pressure differential is given by: 2

dW = –ΔP 4πr dr At equilibrium, both energy variations are equal, dG = dW, therefore we obtain the following relation: ΔP = 2γ /r

20 Liquids

1112

Liquids

From a thermodynamics point of view we can write dW = –PdV + γ dA dU = dW + dQ = –PdV + γ dA + TdS + µdn dF = –PdV + γ dA – SdT + µdn Finally, a thermodynamic system always tends to reach the state of lowest potential energy. Therefore, the surface of a liquid is always a minimum surface. For instance, the minimum surface for a given volume is a sphere so if no other forces are present, a drop of liquid adopt a spherical shape.

20.1.8.2 Temperature Dependence and Order of Magnitude of Surface Tension –1

Typical values for the surface tension of liquids are around 70 mN.m for polar solvents such as water and aqueous solutions, while for non-polar organic solvents such as hydrocarbons, –1 –1 they range between 20 and 30 mN.m and are extremely high, in the range 100–2800 mN.m , –1 for liquid or molten metals and to a lesser extent for molten salts, 100–300 mN.m (see Table 20.5). The addition of surfactants can decrease the surface tension of aqueous solutions. The surface tension decreases with a temperature increase, and its temperature variation can be described by the following simple equation:

γ(T) = γ(0)[1 – a(T – T0)] with

γ(T) γ(0)

–1

surface tension at a given temperature, in N.m –1 surface tension at T0, in N.m –1 –1 a temperature coefficient of surface tension, in N.m .K T, T0 absolute thermodynamic temperature in K. Table 20.5. Surface tension of various liquids Liquid

Surface tension (γ /mN.m )

water

72.75

acetic acid

27.60

acetone

23.70

carbon tetrachloride

26.8

cyclohexane

25.30

ethanol

22.30

methanol

22.60

toluene

28.43

iron (1539°C)

1872

magnesium (651°C)

559

mercury (20°C; air)

484

potassium (62°C; CO2)

111

silver (961°C)

903

sodium (98°C)

195

NaCl (1000°C)

97.82

–1

Na3AlF6 (1000°C)

134.06 –1

–1

–2

–2

Exact conversion factors: 1 mN.m = 1 dyn.cm = 1 mJ.m = 1 erg.cm

Properties of Liquids

1113

Moreover, for many liquids, knowing the temperature dependence of the density of the liquid, the Eötvös equation allows us to calculate the temperature coefficient of the surface tension as follows: ∂[γ(M/ρ) ]/∂T = 2.12 2/3

with γ the surface tension in mN.m , M the molar mass in kg.mol and the density of the –3 liquid in kg.m . –1

–1

20.1.8.3 Parachor and Walden’s Rule Numerous methods have been proposed to estimate the surface tension of pure liquids and 5 liquid mixtures. One of the simplest is the empirical formula proposed by MacLeod in 1923. It expresses the surface tension of a liquid in equilibrium with its own vapor as a function of the liquid- and vapor-phase densities as:

γ = K(ρL – ρV)4 where K is an empirical constant which is independent of temperature but is an intrinsic 6 property of the liquid. In 1924, Sugden modified this expression as follows:

γ = [P · (ρL – ρV)/M]4 1/4

where P = MK is a temperature-independent parameter called the parachor. Another empirical equation is Walden’s equation that allows us to estimate the surface tension of a liq–1 uid at room temperature from its latent enthalpy of vaporization, ΔHv, in J.kg and from its –3 density at the boiling point expressed in kg.m as follows:

γ (mN.m–1)= 6.5661 × 10–4 · [ΔHv/ρbp]

20.1.8.4 Wetting When a drop of liquid rests on a solid supporting surface without any chemical reaction taking place, the actions of the various intermolecular forces present result in the drop assuming a particular shape. The shape strongly depends on the ratio of cohesive and repulsive forces. By studying the physical parameters of such a sessile drop, much information regarding the magnitude of surface forces may be obtained. 20 Liquids

20.1.8.5 Contact Angle A sessile drop of liquid at rest on the surface of a solid in contact with a gas comes to equilibrium with the contact angle, that is, the plane angle measured in the liquid, and denoted by the Greek letter, θ, and expressed in radians (see Figure 20.3) as

θ = mes (γLG, γSL).

20.1.8.6 Young’s Equation 7

In 1805, the British scientist Thomas Young , considering the mechanical equilibrium in air of a sessile drop of liquid on a supporting solid, established a general and practical equation. Assuming that surface tensions in the direction of the surface existing at each interface (γLG, liquid-gas interface, γSL, solid-liquid interface, and γSG, solid-gas interface) are equivalent to forces and by equating their horizontal components in order to satisfy Newton’s first law, it follows that:

γSL = γSG + γLGcosθ 5 6 7

McLeod, D.B. Trans. Faraday Soc., 19(1923)38. Sugden, J. Chem. Soc. (1924)1177. Young, T. Phil. Trans. Roy. Soc. London, 95(1805)65.

1114

Liquids

Figure 20.3. Sessile drop onto a solid

This equation is well-known today and called Young’s equation. The contact angle depends on these three interfacial tensions, but whether it is greater or less than π/2 radians is governed by the relative magnitudes of γSG and γSL. If the solid-gas interfacial tension (γSG) is greater than that of the solid-liquid (γSL) then cosθ must be positive, andθ is less than π/2 but if the reverse is true then θ must lies between π/2 and π radians. As a general rule, nonwetting is said to occur when θ is greater than π/2 rad (90°) and it corresponds to the situation where the cohesive forces dominate. Since a contact angle of π rad (180°) is impossible to achieve practically, complete non-wetting is not physically realizable. When the contact angle ranges between 0° and 90° partial wetting occurs, the adhesive forces dominate and the liquid spreads over the supporting surface, while at the extreme for complete wetting the contact angle must be close to 0°. In this case the liquid spreads spontaneously over the entire surface of the solid (see Figure 20.4). Table 20.6. Contact angle and wetting conditions Conditions

Contact angle

non-wetting

π/2 Au> Pt.

Pure silver, gold, and platinum

Refractory Magnesia (MgO), beryllia and advanced (BeO) and zinc oxide ceramics (ZnO)

Inert atmosphere until 600°C

Vitreous carbon

Noble and precious metals

Molten titanates

Molten hydroxides

Molybdenum (Mo), tungsten (W) and zirconium (Zr)

Ceramics and Borosilicated glass (Pyrex) Up to 230°C glasses Vycor and fused silica Until 600°C

Molten Refractory chloroaluminates metals

Appendix F: Corrosion Resistance of Materials Towards Various Corrosive Media 1239

Appendix F

Cryolite melts with dissolved aluminum metal

Molten sulfates

Molten nitrates

Polytetrafluoroethylene (PTFE)

Polymers

Inert atmosphere until 1000°C.

Boron nitride (HBN)

Impervious carbon

Inert atmosphere until 1000°C . A layer of Al4C3 forms at the inner surface. Becomes fragile.

Inert atmosphere until 1000°C. A layer of Al4C3 forms at the inner surface. Becomes fragile.

(*)Only in contact with alumina saturated melts (12 wt.% of dissolved Al2O3). Inert or oxidizing atmospheres until 1000°C.

Suitable below 280°C with eutectic mixtures.

Below 400°C

Below 400°C avoid the presence of peroxide anions.

Alumina (Al2O3)(*)

Fused silica (SiO2)

Carbon-based Graphite materials SGL grade R8710

Advanced ceramics

Ceramics

Platinum (Pt)

Pure iron (Fe)

Electrofused alumina (Al2O3)

Metals

Platinum (Pt)

Oxidizing atmosphere until 450°C

Ceramics

Oxidizing atmosphere until 1000°C

Graphite

Oxidizing atmosphere until 700°C

Electrofused alumina

High-chromium alloys

Metals

Ceramics

Oxidizing atmosphere until 600°C

Nickel-based alloys

Remarks Oxidizing atmosphere until 680°C

Metals and alloys

Molten carbonates

Austenitic stainless steel 310

Material class Resistant materials

Molten salts

Table F.2. (continued)

1240 Appendix F: Corrosion Resistance of Materials Towards Various Corrosive Media

Appendix F: Corrosion Resistance of Materials Towards Various Corrosive Media

1241

Table F.3. Maximum operating temperature (°C) of ceramics for handling liquid metals under inert atmosphere (A = Attacked) Molten metal or alloy

Ceramic material Pyrex

Fused silica (SiO2)

Mullite (Al6Si2O13)

Alumina (Al2O3)

Magnesia (MgO)

Spinel (MgAl2O4)

Zirconia (ZrO2)

Beryllia (BeO)

Ag

Graphite (C) 1300

Al

1200

Au

1897

1300

Bi

850

Ca

900

Cd

540

Fe

1600

Ga

560

1100

In

530

820

K

335

1550

1550

1550

Mg

1300

Mn

1710

Na Ni

1470

Pb

520

Sb

1470

1100

1400

800

850

850

Si

1890

Sn

285

590

Ti Zn

510

1300

1830

A

A

1450 910 1660

A

A

A

1300

A (TiC) 800

Table F.4. Corrosion rates of materials in hydrochloric acid and hydrogen chloride (HCl)

1

1800

1

Material class

Materials

Conc. and temp. range

Metals and Alloys

Carbon and low alloy steels

readily corroded

Austenitic stainless steels (AISI 304, 316L)

readily corroded

Nickel grade 200 and Monel® 400

resistant to dil. HCl