Carbon Fibers and Their Composites [1 ed.] 9780824709839, 0824709837

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CARBON FIBERS and their Composites

© 2005 by Taylor & Francis Group, LLC

CARBON FIBERS and their Composites Peter morgan

Boca Raton London New York Singapore

A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.

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Published in 2005 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2005 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-10: 0-8247-0983-7 (Hardcover) International Standard Book Number-13: 978-0-8247-0983-9 (Hardcover) This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Catalog record is available from the Library of Congress

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Introduction There is now a wealth of books covering the subject of carbon fibers, some of which are listed in the bibliography, and one may ask, why another book. The aim of this book is to give a practical approach to the subject, with an accent on manufacture and encourage the reader to investigate the references for further information on more theoretical aspects. The author looks back over the last thirty years and attempts to provide an insight into the problems and attempted solutions of some aspects of the production and testing of carbon fibres and their related products. Since PAN homopolymer is not used for the production of carbon fibres, the subject is not discussed. Similarly, stabilization in nitrogen is sparingly mentioned. The Internet has been useful in obtaining background information but, unfortunately, since items are unlikely to be permanent, they cannot be used as a reference. When searching, it must be remembered that there are the English and American ways of spelling (e.g. fibre and fiber), also the use of the word graphite in addition to carbon. An excellent source was an IBM site for US patents, now operated as http://www.delphion.com/.

1. RECOMMENDED TERMINOLOGY FOR THE DESCRIPTION OF CARBON AS A SOLID 1.1.

Introduction

In the early years of carbon fibers, there was an unfortunate tendency to specify carbon fibres made at about 2800K as graphite fibers which, in the majority of cases, is simply not true and should be avoided. The term graphite fibres is justified only if three-dimensional crystalline order is confirmed (e.g. by X-ray diffraction measurements). It is considered, at this stage, relevant to define the terminology for the various forms of solid carbon and associated products which are mentioned in this book and requisite information has been used from The International Union of Pure and Applied Chemistry (IUPAC) recommendations, (ß1995 IUPAC).

1.2.

Description of terms

1. ACTIVATED CARBON is a porous CARBON MATERIAL, a CHAR which has been subjected to reaction with gases, sometimes with the addition of chemicals (e.g. ZnCl2), before, during, or after CARBONIZATION. 2. AMORPHOUS CARBON is a CARBON MATERIAL without long range crystalline order. 3. BROOKS AND TAYLOR STRUCTURE IN THE CARBONACEOUS MESOPHASE refers to the structure of the anisotropic spheres which precipitate from isotropic PITCH during pyrolysis. The structure of the spheres consists of a lamellar arrangement of aromatic molecules in parallel layers, which are perpendicular to the polar axis of the sphere and which are perpendicular to the mesophase-isotropic phase interphase. 4. BULK MESOPHASE is a continuous anisotropic phase formed by the coalescence of mesophase spheres. BULK MESOPHASE retains fluidity and is deformable in the temperature range up to about 770K, and transforms into GREEN COKE by further loss of hydrogen or other low molecular weight species. 5. CARBON is the sixth element of the Periodic Table of Elements (electronic ground state 1s22s22p2).

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6.

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Note: For description of the various types of CARBON AS A SOLID, the term CARBON should be used only in combination with an additional noun or a clarifying adjective. CARBON BLACK is an industrially manufactured COLLOIDAL CARBON material, in the form of spheres as well as of their fused aggregates, with sizes below 1000 nm. Note: For historical reasons, CARBON BLACK is popularly, but incorrectly, regarded as a form of SOOT. CARBON-CARBON COMPOSITE is a carbon fiber reinforced carbon matrix material. The carbon matrix phase is typically formed by solid, liquid or gaseous pyrolysis of an organic precursor material. The matrix is either a GRAPHITIZABLE CARBON or NONGRAPHITIZABLE CARBON, and the carbonaceous reinforcement is fibrous. The composite may also contain other components in particulate or fibrous forms. CARBON FIBERS are fibers (filaments, tows, yarns, rovings) consisting of at least 92% (mass fraction) CARBON, usually in the NON-GRAPHITIC state. CARBON FIBERS HT are CARBON FIBERS with values of Young’s Modulus in the range 150–275 or 300 GPa. The term HT, referring to high tensile strength, was previously applied because fibers of this type display the highest tensile strengths. Note: The disposition of boundaries between the fiber types is somewhat arbitrary. The tensile strength of CARBON FIBERS is, however, flaw controlled and therefore, the measured values increase strongly as the diameter of the filaments is decreased. CARBON FIBERS TYPE HM (HIGH MODULUS) are CARBON FIBRES with a value of Young’s modulus (tensile modulus) larger than 300 GPa. Here again, tensile strength is influenced by flaws in the fiber. CARBON FIBERS TYPE IM (INTERMEDIATE MODULUS) are related to CARBON FIBERS TYPE HT because of the comparable values of tensile strength, but are characterized by greater stiffness. Note: The tensile modulus (Young’s modulus) varies ca. 275–350 GPa, but the disposition of the boundaries is somewhat arbitrary. The relatively high tensile strength required is achievable by a significant reduction of the single filament diameter down to about 5 mm. Such small filament diameters are typical of CARBON FIBRES TYPE IM. CARBON FIBERS TYPE LM (LOW MODULUS) are CARBON FIBRES with isotropic structure, tensile modulus values as low as 100 GPa and low strength values. CARBON FIBERS TYPE UHM (ULTRA HIGH MODULUS) designates a class of CARBON FIBERS having very high values of Young’s modulus, greater than 600 GPa. Note: Such high values of Young’s modulus can be achieved most readily in MESOPHASE PITCH BASED CARBON FIBERS (MPP based carbon fibers). CARBONACEOUS MESOPHASE is a liquid crystalline state of PITCH which shows the optical birefringence of disc-like (discotic) nematic crystals. It can be formed as an intermediate phase during thermolysis (pyrolysis) of an isotropic molten PITCH, or by precipitation from PITCH fractions prepared by selective extraction. With continuous heat treatment, the CARBONACEOUS MESOPHASE coalesces to a state of BULK MESOPHASE before solidification to GREEN COKE, with further loss of hydrogen or other low molecular weight compounds. CARBONIZATION is a process by which solid residues with increasing content of elemental carbon are formed from organic material, usually by pyrolysis in an inert atmosphere. As with all pyrolytic reactions, CARBONIZATION is a complex process in which many reactions take place concurrently, such as dehydrogenation, condensation, hydrogen transfer and isomerization. The final pyrolysis temperature applied controls the degree of CARBONIZATION and the residual content of foreign elements (e.g. at 1200K, the carbon content of the residue exceeds a mass fraction 90 wt%, whereas at 1600K, more than 99 wt.% carbon is found). CHAR is a solid decomposition product of a natural or synthetic organic material. CHARCOAL is a traditional term for a CHAR obtained from wood, peat, coal or other related natural organic materials. COAL TAR PITCH is a residue produced by distillation or heat treatment of coal tar. It is solid at room temperature, consists of a complex mixture of numerous, predominantly aromatic

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20. 21.

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hydrocarbons and heterocyclics, and exhibits a broad softening range, instead of a defined melting temperature. COKE is a solid, high in elemental carbon content and structurally in the NON-GRAPHITIC state. It is produced by pyrolysis of organic material which has passed, at least in part, through a liquid or liquid-crystalline state during the CARBONIZATION process. COKE can contain mineral matter. COLLOIDAL CARBON is a PARTICULATE CARBON with particle sizes below ca. 1000 nm in at least one direction. DIAMOND is an allotropic form of the element carbon, with cubic structure which is thermodynamically stable at pressures above 6 GPa at room temperature and metastable at atmospheric pressure. At low pressures and temperatures above 1900K in an inert atmosphere, DIAMOND converts rapidly to GRAPHITE. The chemical bonding between the carbon atoms is covalent, with sp3 hybridization. EXFOLIATED GRAPHITE is the product of very rapid heating of relatively large particle diameter (flakes) graphite intercalation compounds, such as graphite hydrogen sulphate. The vaporizing intercalated substances force the graphite layers apart. The EXFOLIATED GRAPHITE assumes an accordian-like shape, with an apparent volume often hundreds of times that of the original graphite flakes. FIBROUS ACTIVATED CARBON is an ACTIVATED CARBON in the form of fibers, filaments, yarns or rovings and fabrics or felts. Such fibers differ from CARBON FIBERS, used for reinforcement purposes in composites, in their high surface area, high porosity and low mechanical strength. FILAMENTOUS CARBON is a carbonaceous deposit from gaseous carbon compounds, consisting of filaments grown by the catalytic action of metal particles. Note: In general, such deposits are obtained at pressures of 5100 kPa in the temperature region 66–1300K on metals such as cobalt, iron and nickel. The filaments may be produced in different conformations, such as helical, twisted and straight. FULLERENES were discovered in 1985 [2] and can be considered as another major allotrope of carbon and differ from GRAPHITE and DIAMOND in that they form discrete molecular forms. FULLERENES are symmetrically closed convex GRAPHITE shells, consisting of twelve pentagons and various numbers of hexagons. Since they are arranged in the form of a geodesic spheroid, they were named buckminster fullerenes, after Buckminster Fuller, the architect associated with the geodesic dome, shortened to FULLERENES and known colloquially as bucky-balls. The FULLERENE structures are possible in many combinations but, as yet, the most important structures truly established are C60, C70, C76, C78 and C84. The first FULLERENE to be discovered was C60, comprising of twenty hexagons and twelve pentagons, with each carbon atom shared by one pentagon and two hexagons, assuming the well known spherical shape of a football. FURNACE BLACK is a type of CARBON that is produced industrially in a furnace by incomplete combustion. GAS PHASE GROWN CARBON FIBERS are CARBON FIBERS grown in an atmosphere of hydrocarbons with the aid of fine particulate solid catalysts such as iron or other transition metals and consisting of GRAPHITIZABLE CARBON. Note: GAS PHASE GROWN CARBON FIBERS transform during GRAPHITIZATION HEAT TREATMENT into GRAPHITE FIBERS. The term vapor grown carbon fibers is also acceptable but, CVD fibers is not acceptable, as it also describes fibers grown by a chemical vapor deposition (CVD) process on substrate fibers. GLASS-LIKE CARBON is an AGRANULAR, NON-GRAPHITIZABLE CARBON, with isotropy of its structural and physical properties and with a very low permeability for liquids and gases. Note: The terms Glassy Carbon and Vitreous Carbon are trademarks and should not be used and, moreover, as implied, there is no similarity in the structures of silicate glasses, other than the pseudo-glassy appearance of the surface. GRAPHENE is a single carbon layer of the graphite structure.

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30. GRAPHITE is an allotropic form of the element carbon, consisting of layers of hexagonally arranged carbon atoms in a planar condensed ring system (GRAPHENE LAYERS). The layers are stacked parallel to each other in a three-dimensional structure. The chemical bonds within the layers are covalent with sp2 hybridization. The weak bonds between the layers are metallic with a strength comparable to Van der Waals bonding. 31. GRAPHITE FIBERS are CARBON FIBERS consisting mostly of SYNTHETIC GRAPHITE, for which three-dimensional crystalline order is confirmed by X-ray diffraction. Note: GRAPHITE FIBERS can be obtained by GRAPHITIZATION HEAT TREATMENT of CARBON FIBERS, if these consist mostly of GRAPHITIZABLE CARBON. 32. GRAPHITE MATERIAL is a material consisting essentially of GRAPHITIC CARBON. 33. GRAPHITE WHISKERS consist of thin, approximately cylindrical filaments in which GRAPHENE LAYERS are arranged in a scroll-like manner. There is, at least in part, a regular stacking of the layers as in the GRAPHITE lattice. Along the cylinder axis, the physical properties of GRAPHITE WHISKERS approach those of GRAPHITE. Note: If there is no three-dimensional stacking order as in GRAPHITE, due to misalignment of the layers caused by their bending, the term CARBON WHISKERS should be used. GRAPHITE WHISKERS and CARBON WHISKERS should be distinguished from more disordered FILAMENTIOUS CARBON. 34. GRAPHITIC CARBONS are all varieties of substances consisting of the element carbon in the allotropic form of GRAPHITE, irrespective of the presence of structural defects. 35. GRAPHITIZABLE CARBON is a NON-GRAPHITIC CARBON which, upon GRAPHITIZATION HEAT TREATMENT, converts into GRAPHITIC CARBON. 36. GRAPHITIZATION is a solid state transformation of thermodynamically unstable NONGRAPHITIC CARBON into GRAPHITE by means of heat treatment. Note: The use of the term GRAPHITIZATION to indicate a process of thermal treatment of CARBON MATERIALS at 42500K, regardless of any crystallinity, is incorrect. 37. GRAPHITIZATION HEAT TREATMENT is a process of heat treatment of a NONGRAPHITIC CARBON, industrially performed at temperatures in the range 2500–3300K, to achieve transformation into GRAPHITIC CARBON. Note: The common use of the term GRAPHITIZATION for the heat treatment process only, regardless of the resultant crystallinity, is incorrect and should be avoided. 38. GRAPHITIZED CARBON is a GRAPHITIC CARBON with more or less perfect threedimensional hexagonal crystalline order, prepared from NON-GRAPHITIC CARBON by GRAPHITIZATION HEAT TREATMENT. Note: NON-GRAPHITIZABLE CARBONS do not transform into GRAPHITIC CARBON on heat treatment at temperatures above 2500K and therefore, are not GRAPHITIZED CARBONS. 39. GREEN COKE (RAW COKE) is the primary solid CARBONIZATION product from high boiling hydrocarbon fractions obtained at temperatures below 900K. It contains a fraction of matter that can be released as volatiles during subsequent heat treatment at temperatures up to approximately 1600K. This mass fraction, the so-called volatile matter, in the case of GREEN COKE is 4–15%, but it also depends on the heating rate. 40. HEXAGONAL GRAPHITE is the thermodynamically stable form of GRAPHITE, with an ABAB stacking sequence of the GRAPHENE LAYERS. Note: The use of the term GRAPHITE instead of the more exact term HEXAGONAL GRAPHITE may be tolerated in view of the minor importance of RHOMBOHEDRAL GRAPHITE, the other allotropic form. 41. ISOTROPIC CARBON is a monolithic CARBON MATERIAL without preferred crystallographic orientation of the microstructure. 42. ISOTROPIC PITCH BASED CARBON FIBERS are CARBON FIBERS obtained by CARBONIZATION of isotropic pitch fibers after these have been stabilized (i.e. made non-fusible). 43. LAMP BLACK is a special type of CARBON BLACK produced by incomplete combustion of a fuel rich in aromatics that is burned in flat pans. LAMP BLACK is characterized by a relatively broad particle size distribution.

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44. MESOPHASE PITCH is a PITCH with a complex mixture of numerous, essentially aromatic hydrocarbons containing anisotropic liquid crystalline particles (CARBONACEOUS MESOPHASE), detectable by optical microscopy and capable of coalescence into the BULK MESOPHASE. 45. MESOPHASE PITCH BASED CARBON FIBERS (MPP BASED CARBON FIBERS) are CARBON FIBERS obtained from MESOGENIC PITCH after it has been transformed into MESOPHASE PITCH (MPP) at least during the process of spinning, after the spun MESOPHASE PITCH fibers have been made non-fusible (stabilized) and carbonized. 46. NATURAL GRAPHITE is a mineral found in nature. It consists of GRAPHITIC CARBON, regardless of its crystalline perfection. 47. NON-GRAPHITIC CARBONS are all varieties of solids consisting mainly of the element carbon with two-dimensional long range order of the carbon atoms in planar hexagonal networks, but without any measurable crystallographic order in the third direction (c-direction) apart from more or less parallel stacking. 48. NON-GRAPHITIZABLE CARBON is a NON-GRAPHITIC CARBON which cannot be transformed into GRAPHITIC CARBON solely by high temperature treatment up to 3300K under atmospheric or lower pressure. 49. PAN BASED CARBON FIBERS are CARBON FIBERS obtained from polyacrylonitrile (PAN) precursor fibers by STABILIZATION TREATMENT, CARBONIZATION and final heat treatment. 50. PETROLEUM PITCH is a residue from heat treatment and distillation of petroleum fractions. It is a solid at room temperature, consists of a complex mixture of numerous, predominantly aromatic and alkyl substituted aromatic hydrocarbons, and exhibits a broad softening range instead of a defined melting temperature. 51. PITCH is a residue from the pyrolysis of organic material or tar distillation, which is solid at room temperature, consisting of a complex mixture of numerous, essentially aromatic hydrocarbons and heterocyclic compounds. It exhibits a broad softening range instead of a defined melting temperature. When cooled from the melt, pitches solidify without crystallization. 52. PITCH-BASED CARBON FIBERS are CARBON FIBERS obtained from PITCH precursor fibers after STABILIZATION TREATMENT, CARBONIZATION, and final heat treatment. 53. POLYCRYSTALLINE GRAPHITE is a GRAPHITE MATERIAL with coherent crystallographic domains of limited size regardless of the perfection and preferred orientation (texture) of their crystalline structure. 54. POLYGRANULAR CARBON is a CARBON MATERIAL composed of grains, which can be clearly distinguished by means of optical microscopy. 55. POLYGRANULAR GRAPHITE is a GRAPHITE MATERIAL composed of grains, which can be clearly distinguished by means of optical microscopy. 56. PYROLYTIC CARBON is a CARBON MATERIAL deposited from gaseous hydrocarbon compounds on suitable underlying substrates (CARBON MATERIALS, metals, ceramics) at temperatures ranging 1000–2500K (chemical vapor deposition). Note: Pyrocarbon is a trademark and should not be used as a term. 57. PYROLYTIC GRAPHITE is a GRAPHITE MATERIAL with a high degree of preferred crystallographic orientation of the c-axis perpendicular to the surface of the substrate, obtained by GRAPHITIZATION HEAT TREATMENT of PYROLYTIC CARBON or by chemical vapor deposition at temperatures above 2500K. Note: Pyrographite is a trademark and should not be used as a term. 58. RAYON-BASED CARBON FIBERS are CARBON FIBERS made from rayon (cellulose) precursor fibers. Note: RAYON-BASED CARBON FIBERS have a more isotropic structure than similarly heat treated polyacrylonitrile (PAN) or MESOPHASE PITCH (MPP) BASED CARBON FIBERS. Their Young’s modulus values are, therefore, drastically lower (5100 GPa). RAYON BASED CARBON FIBERS can be transformed into anisotropic CARBON FIBERS with high strength

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61.

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and Young’s modulus values by hot stretching treatment at temperatures of approximately 2800K. RHOMBOHEDRAL GRAPHITE is a thermodynamically unstable allotropic form of GRAPHITE with an ABCABC stacking sequence of the layers. SOOT is a randomly formed PARTICULATE CARBON material and may be coarse, fine, and/or colloidal in proportions, depending on its origin. SOOT consists of variable quantities of carbonaceous and inorganic solids, together with absorbed and occluded tars and resins. SYNTHETIC GRAPHITE is a material consisting of GRAPHITIC CARBON which has been obtained by graphitizing of NON-GRAPHITIC CARBON by chemical vapor deposition (CVD) from hydrocarbons at temperatures above 2500K, by decomposition of thermally unstable carbides, or by crystallising from metal melts supersaturated with carbon. THERMAL BLACK is a special type of CARBON BLACK produced by pyrolysis of gaseous hydrocarbons in a preheated chamber in the absence of air.

2. A BIBLIOGRAPHY OF BOOKS ON CARBON FIBERS AND THEIR COMPOSITES i) ii) iii) iv) v)

vi) vii) viii) ix) x) xi) xii) xiii) xiv) xv)

xvi) xvii)

xviii)

Smith EA ed, Carbon Fibres, Design Engineering Series, Morgan Grampian, West Wickham, 1970. Plastics Institute, Carbon fibres; their composites and applications, Proceedings of the International Conference organized by the Plastics Institute, London, Feb 2–4 1971. Gill RM, Carbon Fibres in Composite Materials, Iliffe Books, London, 1972. Jenkins GM, Kawamura K, Polymeric Carbons-carbon fibre, glass and char, Cambridge University Press, London, 1976. Institution of Mechanical Engineers, Designing with fibre reinforced materials, Conference sponsored by the Materials Technology Section of the Applied Mechanics Group of the Institution of Mechanical Engineers, Mechanical Engineering publications, London, 27–28 September, 1977. Sittig M ed., Carbon and Graphite Fibers: Manufacture and Applications, Vol. 162, Noyes Publications, Park Ridge, 1982. Donnet JB, Bansal RC, Carbon Fibers, Marcel Dekker, New York, 1984. Watt W, Perov BV eds., Handbook of Composites, Vol.1, Strong Fibres, Elsevier, Amsterdam, 1985. Fitzer E ed., Carbon Fibres and their Composites, Springer Verlag, Berlin, 1986. Plastics and Rubber Institute ed., Carbon Fibres: Technology, Uses and Prospects, Noyes Publications, 1986. Delmonte J, Technology of Carbon and Graphite Fiber Composites, Krieger Publishing Company, 1987. Dresselhaus MS, Dresselhaus G, Sugihara K, Spain IL, Goldberg HA, Graphite Fibers and Filaments, Series in Material Science, Vol. 5, Springer-Verlag, New York, 1988. Donnet JB, Bansal RC, Carbon Fibers, International Fiber Science and Technology, Vol. 10, 2nd ed., Marcel Dekker, New York, 1990. Ermolenko IN, Lyubliner LP, Gulko NV, Titovets EP, Chemically Modified Carbon Fibers and their Applications, Vch Pub, 1990. Figueiredo JL, Bernardo CA, Baker RTK, Hu¨ttinger KJ ed., Carbon Fibers Filaments and Composites (NATO Series E Applied Sciences, Vol. 177), Kluwer Academic Publishers, Dordrecht, 1990. Buckley JD, Edie DD ed., Carbon-Carbon Materials and Composites, Noyes Publications, 1992. Cogswell FN, Thermoplastic Aromatic Polymer Composites: A study of the Structure, Processing and Properties of Carbon Fibre Reinforced Polyetheretherketone and R, Combined Book Service Ltd., 1992. Savage GG, Carbon-Carbon Composites, Chapman and Hall, London, 1992.

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xix) xx) xxi) xxii)

xxiii) xxiv) xxv) xxvi) xxvii)

Pierson HO, Handbook of Carbon, Graphite, Diamond and Fullerenes: Properties, Processing and Applications, Noyes Publications, 1993. Thomas CR ed., Essentials of Carbon-Carbon Composites, The Royal Society of Chemistry, Books Britain, 1993. Chung DDL, Carbon Fiber Composites, Butterworth Heinemann, Newton, 1994. Lovell DR (completed by Starr T), Carbon and high performance fibres, Directory and Handbook, Edition 6, Chapman and Hall, London, 1994. Now published by Kluwer Academic Publishers. Peebles LH, Carbon fibers: Formation, Structure and properties, CRC Press, Florida, 1995. Lewin M, Handbook of Fiber Chemistry, 2nd ed. (International Fiber Science and Technology, Vol. 15), Marcel Dekker, 1998. Donnet JB, Wang TK, Peng JC, Rebouillat S, Carbon Fibers, Marcel Dekker, New York, 1998. Fitzer E, Manocha LM, Carbon Reinforcements and Carbon/Carbon Composites, Springer Verlag, Berlin, 1998. Kelly V. Carbon Fiber. Manufacture and Applications, Elsevier, Amsterdam, 2005.

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The Author Peter Ernest Morgan was born in 1931 and joined Courtaulds Ltd., Coventry from school in 1948. He became an Associate Member of The Royal Institute of Chemistry and worked on materials for chemical plants. Morgan undertook evaluation of carbon fibers produced in Courtauld’s research laboratories. He established procedures to coat carbon fibers with metals using electroless plating techniques and developed a surface treatment process to improve the bond of carbon fibers to epoxy resins. In 1968, Morgan joined a team at Courtaulds to manufacture carbon fibers and subsequently set up and managed a control laboratory to monitor production. He later became involved with production aspects relating to carbon fiber prepreg and pultrusion. Morgan took on the additional role of chief quality inspector in 1976 and gained approval for the production processes to Defence Standard 05-24, the forerunner of BS 5750. In 1980, he was appointed to Courtauld’s Carbon Fibres division board as director with technical responsibilities. Morgan joined RK Textiles Composite Fibres Ltd. in 1981 as Technical Director and became involved with the design, building, erection and transfer of technology for the sale of carbon fiber plants in Israel, South Korea and India, as well as plants for in-house use. From 1989 to 1993, Morgan was General Manager/Technical Director of the RK Carbon Fibres Ltd.’s production facility at Muir of Ord in Scotland. In 1993, as Technical Director/ Quality Manager, he obtained approval with BSI for BS 5750: Part 2, which later became ISO 9002. Morgan has written numerous articles on carbon fibers and is the author of ten patents.

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Acknowledgments Grateful thanks are due to my ex-colleagues at Courtaulds—David Carlton, James Darling, John Fagge, Geoff Gould, Tom Heath, John Ludlow and Ed Trewin; together with ex-colleagues at RK Carbon Fibres—Freda Cameron, Stuart Devine, Richard Glanville, Lance Hill, Hayley Robb and Philip Rose. John Johnson and Neil Turner, formerly of Rolls Royce, and Neil Hancox, previously with AERE Harwell, have been most supportive. Many universities in the UK have kindly supplied information and thanks are particularly due to Frank Matthews at Imperial College, Tim Mays at Bath, David Johnson at Leeds, and Frank Jones at Sheffield. Numerous references have been supplied by The British Library and acknowledgment is made to the many companies who have kindly supplied their trade literature and the publications ACM Monthly, Composites Market Reports, Nottingham University Composites Club Composite News and Reinforced Plastics Journal. Finally, I would like to express my gratitude to my wife Doris, for suffering a man with a mission and my daughter Deborah, for occasional proofreading and helpful advice. Peter E Morgan

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Contents Chapter 1 Structure of the Carbon Atom ......................................................................... 1 1.1. Introduction to the Element Carbon, its Isotopes and Allotropes ............................ 1 1.2. Structure of Carbon.................................................................................................... 2 1.2.1. Structure of the Atom .................................................................................... 2 1.2.2. Atomic Spectra and Quantum Theory ........................................................... 2 1.2.3. Directional Characteristics of Atomic Orbitals .............................................. 6 1.2.4. Hybridization of Atomic Orbitals .................................................................. 7 1.2.5. Covalence and Molecular Orbitals ................................................................. 9 References .......................................................................................................................... 13 Chapter 2 The Forms of Carbon..................................................................................... 2.1. The Allotropes of Carbon ........................................................................................ 2.2. The Carbon Phase Diagram ..................................................................................... 2.3. Diamond ................................................................................................................... 2.3.1. Occurrence, Production and Uses of Diamond ........................................... 2.3.1.1. Natural diamonds......................................................................... 2.3.1.2. High pressure synthetic diamonds................................................ 2.3.1.3. Polycrystalline diamond (PCD).................................................... 2.3.1.4. Chemical Vapor Deposition (CVD) diamond.............................. 2.3.1.5. Diamond-like carbon (DLC)........................................................ 2.3.2. Classification of Diamonds .......................................................................... 2.3.3. Identification of Diamond............................................................................ 2.3.4. The Crystal Structure of Diamond .............................................................. 2.3.5. The Properties of Diamond.......................................................................... 2.3.5.1. Density.......................................................................................... 2.3.5.2. Mechanical properties .................................................................. 2.3.5.2.1. Hardness ..................................................................... 2.3.5.2.2. Friction ....................................................................... 2.3.5.2.3. Elastic properties ........................................................ 2.3.5.2.4. Strength ...................................................................... 2.3.5.3. Thermal properties ....................................................................... 2.3.5.4. Optical properties ......................................................................... 2.3.5.5. Electrical properties...................................................................... 2.3.5.6. Graphitization .............................................................................. 2.3.5.7. Chemical resistance ...................................................................... 2.4. Graphite .................................................................................................................... 2.4.1. Introduction.................................................................................................. 2.4.2. Occurrence, Production and Uses of Graphite ............................................ 2.4.2.1. Natural graphite ........................................................................... 2.4.2.2. Kish graphite ................................................................................ 2.4.2.3. Synthetic graphite......................................................................... 2.4.3. Structure of Graphite ................................................................................... 2.4.4. The Properties of Graphite........................................................................... 2.4.4.1. Density.......................................................................................... 2.4.4.2. Mechanical properties .................................................................. 2.4.4.2.1. Elastic properties ........................................................

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15 15 16 17 17 17 17 18 18 18 19 19 19 20 20 22 22 22 22 23 23 23 23 23 23 24 24 24 24 24 25 27 31 31 32 33

2.4.4.3. Thermal properties ..................................................................... 2.4.4.4. Electrical properties .................................................................... 2.4.4.5. Chemical resistance..................................................................... 2.5. Pyrolytic Carbon and Pyrolytic Graphite............................................................... 2.6. Glass-like Carbon ................................................................................................... 2.7. Carbon Fibers ......................................................................................................... 2.8. Graphite Whiskers .................................................................................................. 2.9. Vapor-Grown Carbon Fibers (VGCF) and Catalytic Chemical Vapor-Deposited (CCVD) Filaments ..................................................... 2.10. Other Forms of Carbon.......................................................................................... 2.10.1. Carbon Black............................................................................................ 2.10.2. Charcoal ................................................................................................... 2.10.3. Coal .......................................................................................................... 2.10.4. Coke ......................................................................................................... 2.10.5. Soot .......................................................................................................... 2.11. New Forms of Carbon............................................................................................ 2.11.1. Fullerenes.................................................................................................. 2.11.1.1. Discovery and production of fullerenes ................................. 2.11.1.2. Properties and uses of fullerenes ............................................ 2.11.2. Carbon Nanotubes ................................................................................... 2.11.2.1. Discovery and production of carbon nanotubes ................... 2.11.3. Hyperfullerenes ......................................................................................... 2.12. Summary of Allotropic Forms of Carbon.............................................................. References ..........................................................................................................................

35 35 36 38 41 42 42

Chapter 3 History and Early Development of Carbon Fibers ........................................ 3.1. The Early Inventors .................................................................................................. 3.2. Work in the USA ..................................................................................................... 3.2.1. Black ‘Orlon’ ................................................................................................ 3.2.2. Some Early US Carbon Fibers..................................................................... 3.2.3. More Reent US Carbon Fibers.................................................................... 3.3. Work in Japan .......................................................................................................... 3.3.1. Early Work in Japan with PAN Precursor .................................................. 3.3.2. Work in Japan with Pitch Precursors .......................................................... 3.4. Work in the UK with PAN Precursors .................................................................... 3.4.1. Work at RAE, Farnborough........................................................................ 3.4.1.1. The RAE work with carbon fiber and cross-licencing of their patent............................................................................... 3.4.1.2. Surface treatment ......................................................................... 3.4.1.3. Testing and properties of single filaments and composites.......... 3.4.1.4. Composite fabrication .................................................................. 3.4.1.5. Friction and wear ......................................................................... 3.4.2. Work at the Atomic Energy Research Establishment, Harwell................... 3.4.2.1. Fiber production .......................................................................... 3.4.2.2. Surface treatment ......................................................................... 3.4.2.3. Testing and properties of single filaments and composites ............................................................................. 3.4.2.4. Carbon fiber reinforced ceramics, glass and cement....................

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3.4.2.5. 3.4.2.6. Work at 3.4.3.1. 3.4.3.2. 3.4.3.3. 3.4.3.4. Work at Work at 3.4.5.1. 3.4.5.2. 3.4.5.3. 3.4.5.4. 3.4.5.5. 3.4.5.6.

Carbon fiber reinforced metal composites. .................................. 87 Composite fabrication and design................................................ 89 3.4.3. Rolls Royce, Derby........................................................................ 89 Fiber production .......................................................................... 89 Factors affecting tensile strength of carbon fibers ....................... 91 Resin formulation and composite fabrication.............................. 92 Carbon fiber reinforced metal composites ................................... 97 3.4.4. Morganite Modmor, London ........................................................ 97 3.4.5. Courtaulds, Coventry..................................................................... 98 Carbon fiber production .............................................................. 98 Early work with X-ray diffraction to establish structure............ 100 Precursor technology ................................................................... 101 Oxidation stage............................................................................ 103 Surface treatment ........................................................................ 111 Testing and properties of virgin carbon fiber and composites ............................................................................ 112 3.4.5.7. Production procedures using carbon fiber .................................. 112 3.4.5.8. Use and design of carbon fiber in composite materials.............. 113 3.5. Early UK Prepreggers............................................................................................. 114 3.5.1. Ciba (ARL) Ltd., Duxford......................................................................... 114 3.5.2. Courtaulds Ltd., Coventry ......................................................................... 114 3.5.3. Fothergill and Harvey Ltd. (F&H), Littleborough .................................... 115 3.5.4. Rotorway Components Ltd., Clevedon...................................................... 115 References ........................................................................................................................ 115

Chapter 4 Precursors for Carbon Fiber Manufacture ................................................... 4.1. Introduction ............................................................................................................ 4.2. PAN Precursors ...................................................................................................... 4.2.1. History ........................................................................................................ 4.2.1.1. Commercially available PAN fiber ............................................. 4.2.2. Requirements for a PAN Precursor ........................................................... 4.2.3. Homopolymer PAN ................................................................................... 4.2.4. Comonomers............................................................................................... 4.2.5. Methods of Polymerization ........................................................................ 4.2.5.1. Solution polymerization .............................................................. 4.2.5.2. Aqueous dispersion polymerization ............................................ 4.2.6. Methods of Spinning .................................................................................. 4.2.6.1. Wet spinning................................................................................ 4.2.6.2. Dry spinning................................................................................ 4.2.6.3. Air gap spinning.......................................................................... 4.2.6.4. Melt spinning............................................................................... 4.2.7. Processing Stages ........................................................................................ 4.2.8. Modification of Spun Fiber........................................................................ 4.2.8.1. Stretching..................................................................................... 4.2.8.2. Chemical treatment ..................................................................... 4.2.9. Structure of PAN Fibers ............................................................................ 4.3. Cellulosic Precursors............................................................................................... 4.3.1. Historical Introduction ............................................................................... 4.3.2. Viscose Rayon Process ...............................................................................

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4.3.2.1. Introduction................................................................................. 4.3.2.2. Steeping stage .............................................................................. 4.3.2.3. Shredding and ageing stages ....................................................... 4.3.2.4. Xanthation stage ......................................................................... 4.3.2.5. Mixing and ripening stages ......................................................... 4.3.2.6. Spinning stage.............................................................................. 4.3.2.7. Final treatment stage................................................................... 4.3.3. Structure of Rayon Fibers.......................................................................... 4.4. Pitch Precursors ...................................................................................................... 4.4.1. Introduction................................................................................................ 4.4.1.1. Petroleum pitch ........................................................................... 4.4.1.2. Coal tar pitch .............................................................................. 4.4.2. Characterization of the Pitch ..................................................................... 4.4.3. Isotropic Pitches ......................................................................................... 4.4.4. Preparation of Mesophase Pitches ............................................................. 4.4.4.1. Introduction................................................................................. 4.4.4.2. Production of mesophase by pyrolysis ........................................ 4.4.4.3. Production of mesophase by solvent extraction.......................... 4.4.4.4. Production of mesophase by hydrogenation............................... 4.4.4.5. Production of mesophase by catalytic modification................................................................................. 4.4.5. Melt Spinning Mesophase Precursor Fibers............................................... 4.4.6. Structure of Pitch Precursor ....................................................................... 4.5. Other Precursors ..................................................................................................... References ........................................................................................................................

Chapter 5 Carbon Fiber Production using a PAN Precursor ....................................... 5.1. Introduction ............................................................................................................ 5.2. Carbon Fiber Manufacturers.................................................................................. 5.3. World Supply of PAN based Carbon Fiber........................................................... 5.4. Manufacturing Costs of PAN based Carbon Fiber ............................................... 5.5. Choice of Precursor ................................................................................................ 5.6. Desirable Attributes of a PAN based Precursor Polymer and its Subsequent Production ...................................................................................... 5.7. Types of PAN based Carbon Fiber........................................................................ 5.8. A Carbon Fiber Production Line ........................................................................... 5.8.1. Precursor Station...................................................................................... 5.8.2. Oxidation.................................................................................................. 5.8.3. Oxidation Plant ........................................................................................ 5.8.4. Removal of Effluent Gases Evolved in the Oxidation Process................ 5.8.5. Oxidized PAN Fiber................................................................................. 5.8.6. Low Temperature Carbonization ............................................................. 5.8.7. High Temperature Carbonization ............................................................ 5.8.8. High Modulus Fiber Production.............................................................. 5.8.9. Shrinkage during the Carbon Fiber Process ............................................ 5.8.10. Surface Treatment .................................................................................... 5.8.11. Sizing ........................................................................................................ 5.8.12. Collection ................................................................................................. 5.9. Fine Structure and Texture of PAN based Carbon Fibers ....................................

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5.10.

Aspects 5.10.1. 5.11. Aspects 5.11.1.

of Stabilization ........................................................................................ Structure of PAN Fibers Thermally Stabilized at 350
C........................ of Carbonization...................................................................................... Methods of Increasing Fiber Modulus and Effect on Strength.............. 5.11.1.1. Hot stretching ....................................................................... 5.11.1.2. Effects of neutron irradiation ............................................... 5.11.1.3. Annealing in the presence of boron ...................................... 5.11.2. Carbon Fiber Yield ................................................................................. 5.12. Relation of Carbon Fiber Tensile Properties to Process Conditions ................... 5.13. Developments........................................................................................................ 5.13.1. Improvements in Carbon Fiber Properties ............................................. 5.13.2. Alternative Polymer Formulations.......................................................... 5.13.3. A Family of Controlled Resistance Carbon Fibers ................................ 5.14. A Review of the Stabilization of PAN Precursors ............................................... 5.14.1. Stabilization Schemes of PAN and Associated Observations................. 5.15. Mechanisms for the Carbonization Stages of PAN Carbon Fibers ..................... References ........................................................................................................................

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Chapter 6 Carbon Fiber Production using a Cellulosic based Precursor...................... 6.1. Introduction ............................................................................................................ 6.2. Current Production................................................................................................. 6.2.1. Choice of a Suitable Precursor ................................................................... 6.2.2. Pyrolysis...................................................................................................... 6.2.3. Carbonization ............................................................................................. 6.2.4. Hot Stretching during Processing of Carbon Fiber ................................... 6.2.5. Sizing .......................................................................................................... 6.3. Mechanisms for the Pyrolysis and Carbonization Stages of Cellulosic based Precursors..................................................................................... References ........................................................................................................................

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Chapter 7 Carbon Fiber Production using a Pitch based Precursor ............................. 7.1. Introduction ............................................................................................................ 7.2. Choice of Melt Spun Precursor .............................................................................. 7.3. The Manufacturing Process .................................................................................... 7.3.1. Stabilization (thermosetting) of Spun Fiber ............................................... 7.3.2. Carbonization ..............................................