Advanced Materials and Production Technologies 303640211X, 9783036402116

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Advanced Materials and Production Technologies

Edited by Prof. Iulian Antoniac Prof. Guillermo Requena Dr. Xinyu Hu Dr. Omar S. Dahham Dr. Nur Hidayati Othman

Advanced Materials and Production Technologies

Special topic volume with invited peer-reviewed papers only

Edited by

Prof. Iulian Antoniac, Prof. Guillermo Requena, Dr. Xinyu Hu, Dr. Omar S. Dahham and Dr. Nur Hidayati Othman

Copyright © 2022 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of the contents of this publication may be reproduced or transmitted in any form or by any means without the written permission of the publisher. Trans Tech Publications Ltd Seestrasse 24c CH-8806 Baech Switzerland https://www.scientific.net

Volume 1079 of Materials Science Forum ISSN print 0255-5476 ISSN web 1662-9752

Full text available online at https://www.scientific.net

Distributed worldwide by Trans Tech Publications Ltd Seestrasse 24c CH-8806 Baech Switzerland Phone: +41 (44) 922 10 22 e-mail: [email protected]

Preface The edition presents a series of research results in materials science and technologies of materials synthesis and processing. The first two chapters are devoted to the research of properties and technologies of processing structural materials: steel, alloys, polymeric and composite materials. Studying microstructure and mechanical properties of structural metals, analysis of technologies of deep drawing, spot welding and electrical discharge machining, researching biodegradable polymer synthesis and properties of the composites, etc., are described in these chapters. Results of preparation of ruthenium hollow spheres as catalysts for selective hydrogenation of benzene to cyclohexane, analysis of high-temperature physical and chemical properties of a molten salt system of aluminium electrolysis and reviewing some environmental remediation technologies are presented in the next two parts of the book. The last chapter presents research results on materials and technologies in construction. This edition will be helpful to engineers and researchers in materials processing, chemical synthesis, environmental engineering and construction.

Table of Contents Preface

Chapter 1: Properties and Treatment of Structural Metals Using Artificial Neural Networks to Predict Hardness and Impact Toughness of Aluminum Alloy 6061-T6 O. Bataineh and M. Smadi Effect of Co on Microstructure and Properties of Al-30%Si Alloys X.S. Li, W.Y. Zhong and R. Liao Comparative Study of the Mechanical Properties of Spot Welded Joints M.S. Fakhri, A.M. Al-Mukhtar and I.A. Mahmood Experimental Investigations of Surface Finish Generated by Wire Electrical Discharge Machining A.H. Hadi and A.A. Khleif Experimental Investigations of Hydrodynamic Deep Drawing of Galvanized Steel to Form a Hemispherical and Complex Cup A.R. Ahmed and A.A. Khleif Investigation of Fatigue Behavior for Al/Zn Functionally Graded Material Z.M.R. Al-Hadrayi, A.N. Al-Khazraji and A.A. Shandookh Alumina Nano Powder Impact on Electrical Discharge Machining of Titanium Alloy Wire F.N. Abed Strategies Regarding High-Temperature Strength and Toughness Applications for SUS304 Alloy M.R. Abdullah, L. Fang, H.N. Cai and Z. He

3 15 21 29 39 49 57 67

Chapter 2: Polymers and Composites Ring Opening Polymerization in Polylactic Acid Production Using Different Catalyst N.A. Binti Ghazali and N. Ibrahim Mechanical and Morphological Properties of PHB/Oil-Free Coffee Dregs (OFCD) Composites M.C.G. Rocha, N.I. Alvarez Acevedo and C.E.N. de Oliveira Conducting Behavior of Bischalcone Derivatives R. Aswini, D. Lakshmi Devi and S. Kothai Experimental Investigations on the Effect of Yarn Speed and Wrap Angle on Yarn-Solid and Yarn-Yarn Friction using Warp Knitting Machines M. Bruns, M. Krentzien, M. Beitelschmidt and C. Cherif

87 93 103 115

Chapter 3: Chemical Processes and Technologies Preparation of Ruthenium Hollow Spheres as Catalysts for Selective Hydrogenation of Benzene to Cyclohexene H.D. Rao, D.Y. Zhang, J.R. Li, L. Zhang and W. Cheng Molecular Dynamics Simulation of the Effect of Zr and b on Cryolite Molten Salt System 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 Z.H. Zhang, Y.S. Wang, J. Zeng and H.B. He

129 135

Chapter 4: Environmental Remediation Characterization of Heater-Cooler Blocks Fabricated from Aluminium Wastes for SteadyState Thermal Application B. Festus, T. Ewetumo, S. Oluyamo and P. Olubambi

147

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Adsorption of Cadmium(II) Ions from Aqueous Solutions Using Calcium Molybdate S.d.C. Pereira, A.d.G. Barbosa, A.T. de Figueiredo, C.M. Barrado, V.N. Alves and E. Longo

157

Chapter 5: Building Materials Effects of Basalt Fiber on Strength of Alkali-Activated Slag-Tailing Cement Bodies S. Tian, K. Li, X. Liu and Y. Li Effect of Ultraviolet Aging on Rheological Properties and Microstructure of Rubber Asphalt in High Altitude Area D.F. Guo, X.J. Ma, X.Y. Ma and J.H. Fang Experimental Study on Durable Asphalt Mixture for Bridge Deck Pavement C.Y. Zhang Experimental Study on Improving Frost Resistance of Ca Mortar L.K. Wang, L.H. Zhao and J.S. Zhang Experimental Study on Materials and Mechanical Properties of Steel Tube-Confined Coral Concrete Reinforcement Mechanism J. Huang, W.X. Shan and Y. Gao

171 179 187 193 199

CHAPTER 1: Properties and Treatment of Structural Metals

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 3-13 doi:10.4028/p-3l7vo5 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-15 Revised: 2022-08-04 Accepted: 2022-09-09 Online: 2022-12-26

Using Artificial Neural Networks to Predict Hardness and Impact Toughness of Aluminum Alloy 6061-T6 Omar Bataineh1, a*, Mohammad Alsmadi2,b Jordan University of Science and Technology, Irbid, Jordan

1,2 a*

[email protected], [email protected]

Keywords: Artificial neural network, Analysis of variance, Backpropagation, 6061.

Abstract. Predicting the material's mechanical properties is essential for reducing testing time, cost, and effort. In this study, the effect of temperature and holding time on the hardness and impact toughness of Al 6061 was investigated using the design of experiments (DOE) methodology. Analysis of variance (ANOVA) was used to analyze the results of DOE-factorial experiments. Two factors with five replicates were studied in the experiments: temperature with four levels (393.15, 423.15, 453.15, and 483.15 oK) and holding time with four levels (60, 120, 180, and 240 min). An artificial neural network (ANN) model was constructed to predict the hardness and impact toughness of precipitation-hardened 6061 aluminium alloy. The results revealed that the temperature, holding time, and interaction between them were significant factors on the hardness and impact toughness of Al 6061. ANN models' accuracy to predict the hardness and impact toughness of precipitation-hardened 6061 aluminium alloy was 99.1% and 97.6%, respectively. In this work, the ANN model accuracy was larger than ANOVA accuracy. Introduction Aluminum is the most used nonferrous metal in the local and global industries due to its excellent physical properties, and the wide range of mechanical properties that it attains through heat treatment and alloying [1]. Aluminum alloy 6061, in particular, can be heat-treated, quenched, and precipitation strengthened to give an ultimate tensile strength of more than 290 MPa. As aluminum alloy 6061 consists of added elements (mainly silicon and magnesium, in addition to other alloying elements); the final properties of this alloy may further be imparted by adjusting the percentages of these elements [2], [3]. Therefore, 6061 is widely used in important applications such as aircraft wings and fuselages, bicycle frames, auto chassis, rifle receivers, constant cross-section extrusions, and general hot forgings. Various heat treatment processes can be conducted to 6061 alloys. One of the most common ones is the T6 solutionizing and artificial aging treatment, which is used to give the maximum precipitation hardening. The T6 treatment is composed of three stages: solution treatment, quenching, and artificial ageing. In the solution-treatment stage, a homogenous solid solution is created by heating the alloy to a temperature between the solvus and solidus temperatures. In the quenching stage, the solutionized alloy is rapidly cooled, thus creating a supersaturated solid solution due to low or no diffusion in action [4]. Finally, artificial ageing is carried out where the supersaturated solution is heated below the recrystallization temperature to produce a finely dispersed precipitate [5]. Despite the well-defined steps in the T6 treatment, various factors affect the achieved values of mechanical properties such as hardness and impact toughness. Thus, many authors have addressed these influences in the literature. Mrówka-Nowotnik [6] investigated the influence of precipitation hardening on the microstructural and mechanical attributes of 6061, 6063 and 6082 Al alloys. The alloys were heated to 12 hours in a furnace at 565 °C before being water quenched. The heated and cooled samples were further exposed to artificial ageing for 98 hours at 175 °C. Their result showed that mechanical properties were not affected during artificial ageing by the prior precipitation process. Mansourinejad and Mirzakhani [7] studied the effect of different cold working and precipitation hardening schemes on the tensile strength of 6061 aluminum alloy. They noted that the application of a single artificial ageing process at 180 °C for 4 hours has increased the strength of the studied

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specimens whereas a double ageing process has no effect on the mechanical features of the specimens. Additionally, the pre-ageing process had a counteractive influence on the subsequent precipitation process on the material. These changes in the mechanical properties of the specimens were attributed to the microstructural changes caused by the effect of precipitation, softening, and strain hardening processes on these specimens. Kassner and Geantil [8] studied the quench sensitivity of 6061 and 6069 aluminum alloys by exploring the relationship between quench delay time and the mechanical properties at varying temperatures between 200 and 500 °C. Based on their findings, it was found that the quench sensitivity of 6069-T6 was higher than that of 6061, and this attributed to the differences in their composition. In addition, the study provided more insight on the quench sensitivity of the conventional 6061 alloys. Rajakumar et al. [9] prepared an action in friction stir welding for Al 6061 T6 and used response surface methodology (RSM) to predict the tensile strength value. Tan and Radzai [10] studied the effect of temperature and time during artificial ageing on the hardness of aluminum alloy 6061-T6. The results showed that the optimum hardness was achieved when the temperature was 175 to 195 °C and ageing time between 2 and 6 hours. Several modeling methods can be used to predict the mechanical attributes after heat treatment of aluminum alloy 6061, such as regression, adaptive neuro-fuzzy inference system, and artificial neural network [11], [12]. Kumar et al. [13] used neural programming to predict the loss of wear length for Al 6061 and Al2O3. The results showed that using neural programming can give new information related to metal corrosion without repeating the experiment in the laboratory. Zhang et al. [14] designed a back propagation (BP) model and active target particle swarm optimization (ATPSO) neural network to predict the mechanical properties of aluminum alloy 6061 and predict the optimal compression ratio. The results showed that the second model (ATPSO neural network) was highly accurate by predicting the results, which is higher than the first model ((BP) neural network,) and the standard error ratio was calculated for the first and second models where the error rate in the second model was much less from the first model. Merayo et al. [11] employed an artificial neural network to predict ultimate tensile stress and yield strength for Al 7010-T6 alloy, and the result showed that the artificial intelligence had the same performance in the empirical formula for the aluminum alloy material. Hassan et al. [15] used an artificial neural network to predict hardness and physical attributes. The total of specimens were 54 samples. The variables that were used included the weight percentage of copper and the volume fraction of reinforced particles. The results showed that the absolute relative error of output predicted values did not exceed 5.9%. Bagga et al. [16] created a matching between predicting data of tool wear and manual measurement data. The result presented that a large similar values between the artificial neural network model and manual measurement where the mean percentage difference was 3.4%. The accuracy achieved in the proposed model made it an effective method for condition monitoring of tool in turning process. In this study, a model will be designed to predict hardness and impact toughness of 6061-T6 aluminum alloy using artificial neural networks (ANNs). An ANN is a computing approach used to simulate what a human brain does for analyzing incoming information. It is the basis of artificial intelligence (AI) that can be used to solve problems that would be near impossible to solve by human or statistical standards. This model will be useful for reducing time, effort, and cost when using different conditions of T6 treatment. According to the previous studies, there is no study related to preparing a T6 precipitation heat treatment for 6061 aluminum alloy based on artificial intelligence to predict hardness and impact toughness. Experimental Work Specimens made of 6061 aluminum alloy were initially cut from a solid rectangular rod into smaller 20x20x55 mm pieces using a saw machine, as shown in Fig.1. A T6 precipitation heat treatment was then applied for the specimens. Subsequently, impact toughness (Charpy method) and Rockwell hardness (scale B) tests were carried out. The precipitation-hardening process involves three stages: solution treatment, quenching, and ageing. The solution treatment is the first stage in the precipitationhardening process where the alloy is heated above the recrystallization temperature (763.15 K) and

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soaked until a homogeneous solid solution (α) is produced. In the second stage, the iced water will be used in the quenching process, and all samples inserted into the fridge device. The last stage includes the heated specimens up to the required temperature and holds them at the required time. Experiments were carried out based on a two-factor factorial experiments with five replicates to study the effect of temperature and holding time. The temperature variable studied has four levels (393.15, 423.15, 453.15, and 483.15 oK), and the holding time that was studied also has four levels (60,120,180 and 240 min). Based on this design, 80 combinations of the two-factor levels were run randomly. This randomization is essential to eliminate the effect of nuisance factors [17], [18]. The methodology used to select the factor levels was based on the literature studies which indicated that reheating the samples to temperatures below 373.15 oK would not affect the deposition of impurities inside the atoms. Thus, the lowest value for the temperature used in the experiment was 393.15 oK.

Fig. 1: Saw machine for cutting Al 6061 solid rectangular rod. Artificial Neural Networks in WEKA Artificial neural networks are an essential tool increasingly used for modelling non-linear engineering problems by learning the relationships between inputs and outputs through a data-training process. An ANN consists of inputs (where data is received in the first neurons), hidden layers, and outputs according to a specific architecture. The data is processed in the hidden layer mathematically, then transferred to the output layer with final weight. The central equation used in this process is as follows: (1) Where Tj is the activity on the jth component of the target pattern, Oj is the activity on the jth output, Oi is the activity on the ith input, and N is the learning rate. ANN ∆𝑊𝑊𝑖𝑖𝑖𝑖 = 𝑁𝑁�𝑇𝑇𝑗𝑗 − 𝑂𝑂𝑗𝑗 � ∗ 𝑂𝑂𝑖𝑖 also requires architecture such as the multi-layer perceptron (MLP), which was used in this study for machine learning. The Back-Propagation (BP) technique was used in conjunction with MLP for the training process to perform learning on a feed-forward neural network. The basic formula of the BP algorithm is: (2) (3) Where W is the weight, N is the learning rate, E is the gradient of an error function, α is the step gradient factor and 𝛥𝛥 is the rate of change. To implement ANN, Weka (a type of data mining software written in java language) was used. Weka consists of tools for many applications such as data regression, classification, clustering, and visualization rule. The multi-layer perceptron (MLP) with backpropagation (BP) algorithm was used

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from the classification tool to construct ANN models for hardness, as shown in Fig. 2, and impact toughness.

Fig. 2: Multi-layer perceptron architecture for hardness. Weka also contains a preprocessor tab, classify tab, cluster tab, associate tab, attribute tab and visualize tab. This research focuses on classify tab; which provides several machine learning algorithms for the classification data. The classification process consists of model construction to describe a set of predetermined classes. Figure 7 shows the classification process.

Fig. 3: Classification steps in Weka. DOE Results and ANOVA The results of the experiments based on factorial design are presented in Tables 1 and 2. Table 1 shows the hardness as a function of the temperature and holding time with five replicates, and table 2 shows the impact toughness as a function of the temperature and holding time with 5 replicates. The hardness and impact toughness data shown were run randomly using Minitab statistical software, but they are shown in their standard order. The data of hardness are averaged for the same levels of the factors amd plotted against the various levels for each factor (temperature and holding time) to construct the main effect plots as shown in Fig. 4. From this figure, it can be seen that the hardness increases as holding time increases. This is because when the heating process begins at artificial ageing temperatures, GP (Guinier Preston) zones are formed at the micro level, and spreads in the form of cohesive clusters that resist the movement of dislocations and increase the amount of hardness. Then the hardness stops increasing with longer heating time, which is associated attributed to a lack of development and growth of GP zones. In the case of temperature, the hardness increases as temperature increases because at the start of the temperature increase, the GP zones begin to grow rapidly to a certain size which is typical for ageing temperature, and then the growth practically stops. However, the reduction in hardness is attributed

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to that GP zones are eventually replaced by GP-2 zones during the ageing process. The GP-2 region ("θ" phase) are larger and correspondingly fewer in their number because the amount of solvent in the regions does not change. As the ageing continues, the intermediate "θ" phase will begin to form causing recrystallization, softening, and a decrease in strength and hardness. This is known as excessive ageing. Sample Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Sample Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Temperature (Kelvin) 393.15 393.15 393.15 393.15 423.15 423.15 423.15 423.15 453.15 453.15 453.15 453.15 483.15 483.15 483.15 483.15

Temperature (Celsius) 393.15 393.15 393.15 393.15 423.15 423.15 423.15 423.15 453.15 453.15 453.15 453.15 483.15 483.15 483.15 483.15

Table 1: Rockwell hardness results. Holding Time (Min) 240 180 120 60 240 180 120 60 240 180 120 60 240 180 120 60

Hardness (HRB)

1 54.7 52 46.7 44.1 58.2 55.5 55.9 55.8 62 56.3 41 38 55 65 61 40

2 53.8 51.3 48 46.7 58 55.7 56.5 56 62.2 56.4 42.3 38.5 55.8 65.5 63 40.2

Replicates 3 53.6 50.7 47.7 43.8 58.3 56.3 56.9 56.2 62.7 56 41.7 37.9 56 66.2 64.7 41

4 54.5 50.8 47.3 45.5 58.6 57.1 56.6 56.3 63.5 56 42.1 37.8 51.3 66.1 63.7 42

5 54 51 47.1 44.5 58 57.3 56.7 55.9 64.7 56.2 42 38.1 52 66.7 62.8 43

Table 2: Results of impact toughness. Holding Time (Hour) 240 180 120 60 240 180 120 60 240 180 120 60 240 180 120 60

Impact Toughness (Joule)

1

2

4.1 3.5 2.9 2.8 2.5 2.4 2.2 2.1 5.4 4.8 4.10 4.1 5.5 6 5 4

3.5 3.3 2.9 2.5 2.5 2.3 2.3 2.0 5.5 4.9 4 3.9 5.6 6 5 3.5

Replicates 3 3.82 3.3 3 1.5 2.4 2.3 2.2 2.0 5.4 5 3.9 3.9 5.7 5.8 5 4

4

5

3.5 3.5 3.1 2.5 2.6 2.3 2.3 2.1 5.5 4.6 4.1 4.1 5.5 6 5 4

4 3.2 3.1 2.9 2.6 2.2 2.0 2.2 5.5 4.8 4 4.1 5.4 4.5 5 4.1

Similarly, the main effects plot for impact toughness is constructed and shown in Fig. 5. It can be seen from this figure that the impact toughness increases as holding time increases. This is attributed to the deposition of Mg and Si impurities in the form of clusters where they form a second phase (β) within the α-solution. As the holding time of the alloy increases, the formation of clusters increases, which forms a barrier that reduces the movement of dislocations within the crystal structure which leads to an increase in toughness. In the case of temperature at the same figure, the hardness increases as temperature increases and this is attributed to that the temperature of 423.15 K is considered a

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critical value because it means the beginning of a second stage (GP-2) of the evolution of the crystal structure, and the increasing in the temperature leads to an increase in the nucleation rate of Mg2Si precipitates. Thus, the distance between the precipitate particles becomes closer, leading to the formation of the GP-2 softer phase in the alloy. The reduction in impact toughness shown in the same figure was likely due to the amount of precipitation that occurred is not high which leads to fractures, shiny, and grains became more brittle.

Fig. 4: Main effect plots for holding time and temperature when hardness is the response variable.

Fig. 5: Main effect plots for holding time and temperature when impact toughness is the response variable. The ANOVA was applied using Minitab statistical software. The ANOVA results for the hardness values and impact toughness values in Tables 1 and 2 are shown in Fig. 6 and Fig. 7, respectively. Comparing the P-values in Fig. 6 to α, which is called the significance level (α = 0.05 in this study), factors with significant effect on the response will be determined [19]. Since the calculated P-values for the temperature, holding time, and their interaction in Fig. 6 and Fig. 7 are 0.000, 0.000, and 0.000, respectively, This indicates that the temperature, holding time, and their interaction have all significant effects with respect to both hardness and impact toughness.

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Fig. 6: Minitab output for the ANOVA calculations based on the hardness values from table 1.

Fig. 7: Minitab output for the ANOVA calculations based on the toughness values from table 2.

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ANN Results The error convergence was calculated for small to large number of epochs used to train the networks in Weka software while observing the root mean square error (RMSE). Different epoch numbers with ranges between 500 and 100000 data points were tested to investigate the error dependence on the number of epochs used. The result is shown in Fig. 8. It can be seen from this figure that at epoch number 40,000, RMSE reaches a steady state value at a minimum of less than 0.05. Hence all predictions considered in this study were reached after 40,000 epochs of training. Besides, a percentage split of 70% was used to divide data into two groups: 70% of data was used for training (56 samples) and 34% of data used for testing (24 samples). Each model's hidden layer's number was 5,3,1; training time equal 50,000, and other parameters were set to default. The ANN results using WEKA software for the MLP models of hardness and impact toughness are shown in Fig. 9 and Fig. 10, respectively. The mean absolute error (MAE) can be used among the result parameters to assess model accuracy. Therefore, the hardness model accuracy using ANN is very high (97.5%) since MAE equals 0.0251. The corresponding correlation coefficient is 99.12%, which is slightly higher than that using ANOVA (Equal to 98.97%). As for the impact toughness, model accuracy using ANN is 95.56% since MAE equals 0.0444. The corresponding correlation coefficient is 97.67%, which is higher than that using ANOVA (Equal to 96.80%). `

Fig. 8: Iteration number against Root mean square error.

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Fig. 9: ANN results using WEKA for the hardness model.

Fig. 10: ANN results using WEKA for the toughness model. Conclusions The effect of temperature and holding time on hardness and impact toughness of Al 6061 was investigated experimentally using DOE and ANN approaches. In the scope of the results and analysis revealed in this study, it can be concluded that both hardness and impact toughness of Al 6061 increase with temperature and holding time. However, this pattern changes in direction at some point

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due to the beginning of a second stage (GP-2) in the evolution of the crystal structure. The accuracy of ANN models for hardness and impact toughness were found to be very high, and slightly higher compared to that obtained from the ANOVA. The corresponding correlation coefficient for hardness and impact toughness using ANN models was 99.12% and 97.67%, respictively. These are slightly higher than their counterparts using ANOVA, which are 98.97% and 96.80%, respectively. References [1]

D. Kleiven and J. Akola, “Precipitate formation in aluminium alloys: Multi-scale modelling approach,” Acta Mater., vol. 195, pp. 123–131, 2020, doi: https://doi.org/10.1016/j.actamat.2020.05.050.

[2]

B. F. Jogi, P. K. Brahmankar, V. S. Nanda, and R. C. Prasad, “Some studies on fatigue crack growth rate of aluminum alloy 6061,” J. Mater. Process. Technol., vol. 201, no. 1, pp. 380– 384, 2008, doi: https://doi.org/10.1016/j.jmatprotec.2007.11.302.

[3]

O. Bataineh, “Effect of roller burnishing on the surface roughness and hardness of 6061-T6 aluminum alloy using ANOVA,” Int. J. Mech. Eng. Robot. Res., vol. 8, no. 4, pp. 565–569, 2019, doi: 10.18178/ijmerr.8.4.565-569.

[4]

A. M. Hassan, O. M. Bataineh, and K. M. Abed, “The effect of time and temperature on the precipitation behavior and hardness of Al-4 wt%Cu alloy using design of experiments,” J. Mater. Process. Technol., vol. 204, no. 1–3, pp. 343–349, 2008, doi: 10.1016/j.jmatprotec.2007.11.047.

[5]

S. J. Andersen, C. D. Marioara, J. Friis, S. Wenner, and R. Holmestad, “Precipitates in aluminium alloys,” Adv. Phys. X, vol. 3, no. 1, p. 1479984, Jan. 2018, doi: 10.1080/23746149.2018.1479984.

[6]

G. Mrówka-Nowotnik, “Influence of chemical composition variation and heat treatment on microstructure and mechanical properties of 6xxx alloys,” Arch. Mater. Sci. Eng., vol. 46, no. 2, pp. 98–107, 2010.

[7]

M. MANSOURINEJAD and B. MIRZAKHANI, “Influence of sequence of cold working and aging treatment on mechanical behaviour of 6061 aluminum alloy,” Trans. Nonferrous Met. Soc. China, vol. 22, no. 9, pp. 2072–2079, 2012, doi: https://doi.org/10.1016/S10036326(11)61430-1.

[8]

M. E. Kassner, P. Geantil, and X. Li, “A Study of the Quench Sensitivity of 6061-T6 and 6069T6 Aluminum Alloys,” J. Metall., vol. 2011, p. 747198, 2011, doi: 10.1155/2011/747198.

[9]

S. Rajakumar, C. Muralidharan, and V. Balasubramanian, “Predicting tensile strength, hardness and corrosion rate of friction stir welded AA6061-T6 aluminium alloy joints,” Mater. Des., vol. 32, no. 5, pp. 2878–2890, 2011, doi: 10.1016/j.matdes.2010.12.025.

[10]

C. F. Tan and M. R. Said, “Effect of hardness test on precipitation hardening aluminium alloy 6061-t6,” Chiang Mai J. Sci., vol. 36, no. 3, pp. 276–286, 2009.

[11]

D. Merayo, A. Rodríguez-Prieto, and A. M. Camacho, “Prediction of mechanical properties by artificial neural networks to characterize the plastic behavior of aluminum alloys,” Materials (Basel)., vol. 13, no. 22, pp. 1–22, 2020, doi: 10.3390/ma13225227.

[12]

O. Bataineh and D. Dalalah, “Strategy for optimising cutting parameters in the dry turning of 6061-T6 aluminium alloy based on design of experiments and the generalised pattern search algorithm,” Int. J. Mach. Mach. Mater., vol. 7, no. 1–2, pp. 39–57, 2010.

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[13]

G. B. Veeresh Kumar, R. Pramod, C. S. P. Rao, and P. S. S. Gouda, “Artificial Neural Network Prediction On Wear Of Al6061 Alloy Metal Matrix Composites Reinforced With -Al2o3,” Mater. Today Proc., vol. 5, no. 5, Part 2, pp. 11268–11276, 2018, doi: https://doi.org/10.1016/ j.matpr.2018.02.093.

[14]

J. Zhang, P. Gao, and F. Fang, “An ATPSO-BP neural network modeling and its application in mechanical property prediction,” Comput. Mater. Sci., vol. 163, pp. 262–266, 2019, doi: https://doi.org/10.1016/j.commatsci.2019.03.037.

[15]

A. M. Hassan, A. Alrashdan, M. T. Hayajneh, and A. T. Mayyas, “Prediction of density, porosity and hardness in aluminum–copper-based composite materials using artificial neural network,” J. Mater. Process. Tech., vol. 209, no. 2, pp. 894–899, 2009, doi: 10.1016/j.jmatprotec.2008.02.066.

[16]

P. J. Bagga, M. A. Makhesana, H. D. Patel, and K. M. Patel, “Indirect method of tool wear measurement and prediction using ANN network in machining process,” Mater. Today Proc., vol. 44, pp. 1549–1554, 2021, doi: 10.1016/j.matpr.2020.11.770.

[17]

O. M. Bataineh, M. A. Al-Shraideh, and A. T. Latifeh, “A quadratic regression model with interaction to optimize the turning conditions of Mild Carbon Steel,” Int. J. Mech. Eng. Robot. Res., vol. 7, no. 1, 2018, doi: 10.18178/ijmerr.7.1.78-82.

[18]

O. Bataineh and M. Almomani, “Applying ANOVA and DOE to study the effect of manganese on the hardness and wear rate of artificially aged Al-4.5wt%Cu alloys,” Int. J. Cast Met. Res., vol. 31, no. 1, 2018, doi: 10.1080/13640461.2017.1366128.

[19]

O. Bataineh, A. Al-shoubaki, and O. Barqawi, “Optimising process conditions in MIG welding of aluminum alloys through factorial design experiments,” in Latest Trends in Environmental and Manufacturing Engineering Optimising, 2012, pp. 21–26.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 15-20 doi:10.4028/p-ho07lr © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-22 Revised: 2022-07-27 Accepted: 2022-09-10 Online: 2022-12-26

Effect of Co on Microstructure and Properties of Al-30%Si Alloys Xiaosong Lia*, Wuyong Zhongb, Rui Liaoc School of Mechanical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, China, *[email protected], [email protected], [email protected]

a

Keywords: Co, Al-30%Si, microstructure, latent heat

Abstract. In this paper, the effects of different Co contents on the microstructure and properties of Al-30% Si alloy were studied by means of metallographic microscope, microhardness tester, XRD, conductivity tester and DSC thermal analyzer. The results show that cobalt can effectively improve the microstructure of the alloy, the long needle eutectic silicon becomes short rod, and the coarse irregular block primary silicon particles become smaller. When 0.3% cobalt is added into the alloy, the refining effect of eutectic silicon is the most obvious. When the amount of Co is 0.6%, the refinement effect of primary silicon is the best. The addition of Co can improve the hardness of the alloy. When 0.6 ~ 0.9% cobalt is added, the hardness is the highest. With the increase of Co content, the conductivity and transformation latent heat of the alloy show the same change law. When 0.6% cobalt is added, its value is the maximum. It can be seen that when the Co content is 0.6%, the microstructure and comprehensive properties of the alloy are the best. Introduction Hypereutectic Al-Si alloy is an important casting alloy. With the increase of silicon content, the wear resistance of hypereutectic Al-Si alloy is significantly improved, the coefficient of thermal expansion is greatly reduced, the energy storage density is high, the thermal stability is improved, and the high temperature performance is good, which makes it widely used in automotive, aerospace, electronic packaging, solar energy storage and other fields [1,2]. However, in the untreated cast hypereutectic Al-Si alloy, there are a large number of thick strips, five petal star shaped primary silicon and long needle shaped eutectic silicon. Under the action of external force, the primary silicon phase is easy to produce stress concentration, which reduces the mechanical properties of the alloy. In addition, the coarse silicon phase is thick, hard and brittle, and the machining performance is poor, which will make the surface cleanliness of parts low. The contradiction between excellent casting performance, friction performance, energy storage performance and poor mechanical and service properties greatly limits the application of hypereutectic Al-Si alloy [3]. In order to solve this problem, people have been studying effective methods to control the morphology of silicon phase, and put forward many effective solutions, such as refinement and modification [4-6], rapid solidification [7,8], melt treatment [9,10], semi-solid processing technology [11], spray deposition [12-14], etc [15]. These methods can greatly improve the morphology of silicon phase, but these methods or effects are not significant, or the process is complex and the cost is high, it is not suitable for industrial production and application. Therefore, it is of great practical significance for the application of hypereutectic AlSi alloy to explore a process method to refine the size of silicon phase, passivate and spheroidize eutectic silicon and primary silicon particles, with simple operation and low equipment requirements, which is suitable for industrial production. Alloying is an important way to optimize hypereutectic Al-Si alloys. Some studies believe that [16,17], Co can not only be used as a thermal strength element, but also neutralize the Fe rich phase in Al-Si alloy. However, there are few reports about the determination of Co content and the addition of Co on the microstructure and properties of Al-Si alloys. Therefore, in this work, Al-30%Si alloy was used as the matrix to study the effect of different content of Co on the morphology evolution and properties of Al-30%Si alloy silicon phase.

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Experimental Material preparation. The experimental alloy, Al-30%Si, is made from the smelting of 99.9wt% aluminum and 99.9wt% crystalline silicon. Put half of the 99.9wt% aluminum block into the graphite crucible, then place the 99.9wt% silicon over the aluminum block, and finally put in the remaining aluminum block. Put the graphite crucible into a 5.5KW well-type resistance furnace. Preheat the crucible to 200℃, and then heat it to 850℃ for 40 minutes. When the material is fully melted, add Al-10%Co intermediate alloy according to Table 1, and stir evenly. Then, after the temperature is reduced to 750℃, 0.5% hexachloroethane was added for refining, slag removal, and finally poured into the metal mold preheated to 200℃ to obtain the sample. Table 1 Table of quality scores of Co in different samples sample

1

2

3

4

5

Co(wt.%)

0

0.3

0.6

0.9

1.2

Material characterization. Sample separately in the middle of the pouring sample. After rough grinding, fine grinding, polished. Corrosion was performed with a hydrofluoric acid aqueous solution at a 0.5% concentration, and the metallographic tissue was visualized using a 4XC-type metallographic microscope. Vicker hardness of Al-30%Si alloy was measured using a microhardness meter with a load of F=1.19614N. Their phase structures are depicted with a DX-2700A XRD diffractometer. An eddy current conductivity tester was used to test the conductivity of the alloy before and after deterioration. A thermal analyzer was used to measure and analyze the latent heat of aluminum-silicon alloy after refining metamorphic agents of different contents. A small piece was taken in the middle of the sample and put into the alcohol solution for ultrasonic cleaning, with a mass of 5-10mg.The heating temperature range is heated from 30℃ to 660℃ with a heating rate of 20℃/min, adding nitrogen as a protective medium and with a nitrogen flow rate of 20 ml/min. Results and Discussion Effect of Different Co contents on Al-30%Si eutectic silicon. Fig.1 shows the microtissue morphology of Al-30%Si alloy with different Co content, and the Al-30%Si alloy eutectic silicon without Co addition in Fig.1a shows a thin needle and a long strip.Fig.1b shows the Microstructure of Al-30%Si alloy with 0.3% Co content, and Fig.1b compared to Fig.1a.In Fig.1c and Fig.1d, the eutectic silicon changes little, and the refinement effect is not obvious. As shown in Fig.1e, the long strip of eutectic silicon changed into short needles when the Co content was 1.2%.

Fig.1 Morphology of Al-30%Si alloy with different Co contents (a) 0; (b) 0.3%Co; (c) 0.6%Co; (d) 0.9%Co ; (e) 1.2%Co

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The results show that Co metamorphism is refined on the eutectic silicon organization of Al-30%Si alloy. When Co content is 0.3%, the microstructure refinement of eutectic silicon is the best. The refinement effect was poor when Co content of 0.6% and 0.9%. The refinement was better when the Co content was 1.2%. Effect of Different Co contents on Al-30Si% primary silicon. As shown in Fig.2, there are large amounts of irregular primary silicon in the al-30% Si alloy structure. Comparing with Fig.2a, the morphology of primary silicon in Fig.2b has little change, and there is less primary silicon in Fig.2c and 2e.Fig.2d primary silicon is obviously refined, with a large amount of primary silicon and relatively uniform distribution.

Fig.2 Morphology of Al-30%Si alloy with different Co contents (a) 0； (b) 0.3%Co； (c) 0.6%Co； (d) 0.9%Co； (e) 1.2%Co The results show that Co has fine effect on primary silicon in Al-30%Si alloy. The effect is not obvious when Co content is 0.3%. As it increases to 0.6%, primary silicon becomes small block, and the refinement effect of primary silicon is the best. When Co content is 0.9%, the size of primary silicon in Al-30%Si alloy tends to increase. When Co content is 1.2%, the amount of primary silicon is small, but the size is large. XRD analysis. Fig.3 shows the XRD pattern of Al-30%Si alloy with Co added. It can be seen that a new compound CoSi2 appeared in Al-30% Si alloy with Co added.

Fig.3 XRD pattern of Al-30%Si alloy with Co addition Hardness analysis. Figure 4 shows the microhardness of Al-30% Si alloy with different Co content. It can be seen from the figure that adding Co can significantly improve the microhardness of Al-30% Si alloy. With the increase of Co content, the microhardness of the alloy increases. Compared with the

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original alloy, when the Co content is 0.3% ~ 0.9%, the maximum increase is 33%. However, when the Co content increases to 1.2%, the microhardness of the alloy decreases. This is consistent with the previous analysis results of alloy microstructure.

Fig.4 Hardness of Al-30%Si alloy with different Co content Conductivity analysis. Figure 5 shows the conductivity of Al-30% Si alloy with different Co content. It can be seen from the figure that the addition of Co to Al-30% Si alloy has an effect on its conductivity. When the Co content is 0.3%, 0.9% and 1.2%, the conductivity of the alloy decreases compared with that without Co. When the content of Co is 0.3%, the conductivity decreases most significantly by 15.2%. This is mainly because the addition of Co in the alloy forms the main intermetallic compound CoSi2, and the co atoms are dispersed in the matrix and precipitates in the form of solute elements, resulting in lattice distortion, increasing grain defects, improving the scattering ability of electrons, and significantly reducing the conductivity of the alloy. The conductivity of Al-30%Si alloy with 0.6% Co content is 18.2% higher than that of Al-30%Si alloy without co addition.

Fig.5 Conductivity of Al-30%Si alloy with different Co content Compared with aluminum solid solution, the resistivity of silicon is very high, which is 3.0×1011μΩcm, about 3.4μΩcm at 20 ℃。Therefore, it is obvious that the conductivity (or resistivity) of binary Al-Si alloy will be greatly affected by the number of silicon phases in the microstructure. The different conductivity values of the original alloy and the alloy added with Co are the result of different eutectic silicon structures. As shown in Figure 1b, Co has a significant effect on refining

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eutectic silicon. The morphology of eutectic silicon has changed from long needle shape to short rod shape, and electrons are easier to pass through the eutectic region, thus improving the conductivity [18]. latent heat analysis. Figure 6 shows the latent heat change curve of Al-30%Si alloy with different Co content. It can be seen from the figure that adding Co to Al-30%Si alloy can effectively change its phase transformation latent heat. When the Co content is 0.3%, 0.9% and 1.2%, the latent heat of transformation decreases compared with the original alloy. When the Co content is 0.6%, the latent heat of phase transformation of the alloy is the highest, which is 9.5% higher than that of the alloy without Co. The effect of different Co content on the latent heat of phase transformation of Al-30%Si alloy is consistent with its effect on conductivity. The latent heat of phase transformation of Al-Si alloy is basically proportional to the content of Si phase. This is because the latent heat of phase transformation of Al-Si eutectic structure and primary Si during solid / liquid phase transformation is high. When the content of eutectic structure and primary Si decreases, the corresponding latent heat will also decrease. The change of silicon phase of the alloy in Figure 1 and Figure 2 just verifies this point.

Fig.6 Latent heat of Al-30%Si alloy with different Co content Conclusions (1) Co can refine the silicon phase of Al-30% Si alloy. When the Co content is 0.3%, the eutectic silicon refinement effect of Al-30% Si alloy is the best. When the Co content is 0.6%, the primary silicon refinement effect of al-30% Si alloy is the best. (2) Adding Co can significantly improve the microhardness of al-30% Si alloy. With the increase of CO content, the microhardness of the alloy increases. Compared with the original alloy, when the Co content is 0.3% - 0.9%, the maximum increase is 33%. (3) The addition of Co will affect the conductivity and phase transformation latent heat of Al-30% Si alloy. With the increase of Co content, the conductivity and phase transformation latent heat of the alloy show the same change law. When the Co content is 0.6%, the conductivity and transformation latent heat of Al-30% Si alloy are the largest. Adding an appropriate amount of Co can refine eutectic silicon and primary silicon, and make it easier for electrons to pass through the eutectic region. Therefore, the alloy has higher conductivity and heat storage capacity. Acknowledgement This work was supported by the Natural science foundation of Hunan Province (Grant no. 2021JJ30300).

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References [1]

Kobayashi K, Shingu P H, Ozaki R: Journal of Materials Science Vol. 10(1975), p. 290-299.

[2]

Min Z, Zhao D, Teng X, et al.: Materials & Design Vol. 47(2013), p. 857-864.

[3]

Xu C L, Jiang Q C, Yang Y F, et al.: Journal of Alloys and Compounds Vol. 422(2006), p. L1-L4.

[4]

Li, J. H., et al.: Acta Materialia Vol. 84(2015), p. 153-163.

[5]

Li C, Pan Y, Lu T, et al.: Metals and Materials International, Vol. 2018, 24(5).

[6]

Nogita K, Yasuda H, Yoshiya M, et al.: Journal of Alloys & Compounds Vol. 489(2010), p. 415-420.

[7]

Jun Shan, Zhuang De Xie, Yu Lai Gao: J Mater Sci Lett Vol. 20(2001), p. 1513.

[8]

Li Yuanyuan, Zhang Daton g, Zhang Weiwen: Trans Nonferrous Met Soc China Vol. 12(2002), p. 878.

[9]

Zoua Q, Ning H, Shenb Z, et al.: Separation and Purification Technology Vol. 207(2018).

[10] Jung J G, Ahn T Y, Cho Y H, et al.: Acta Materialia Vol. 2017, p. S1359645417308972. [11] Mirzadeh H, Niroumand B: Journal of Materials Processing Technology Vol. 209(2009), p. 4977-4982. [12] Srivastava V C, Mandal R K, Ojha S N: Materials Science & Engineering A Vol.383(2004), p. 14-20. [13] Srivastava V C, Mandal P K, Ojha S N: Mater Sci Eng A Vol. 304-306(2001), p. 555. [14] Kim W J, Yeon J H, Lee J E: J Alloys Comp. Vol. 308(2000), p. 237. [15] Zhao L Z, Zhao M J, Song L J, et al.: Materials & Design (1980-2015) Vol. 56(2014), p. 542-548. [16] Huang Huiyi, Liu Yiyuan, Tang Peng, et al.: Materials Reports Vol. 34(2020), p. 16087-16093. [17] Marcella G. C. Xavier, Thaisa M. G. Souza, Noé Cheung, et al.: Int. J. Adv. Manuf. Technol. Vol. 107 (2020), p. 717–730 . [18] Mulazimoglu M H, Drew R A L, Gruzleski J E.: Metallurgical Transactions A Vol., 20(1989), p. 383-389.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 21-28 doi:10.4028/p-488xsr © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-26 Revised: 2022-07-25 Accepted: 2022-09-11 Online: 2022-12-26

Comparative Study of the Mechanical Properties of Spot Welded Joints Marwah Sabah Fakhri1,a, Ahmed Al-Mukhtar2,b*,Ibtihal A. Mahmood3,c Ministry of Higher Education and Scientific Research-Baghdad, Iraq

1

College of Engineering, Al-Hussain University College, Iraq

2

Institute of Structural Mechanics, Bauhaus-Universität Weimar, Germany

2

University of Technology-Iraq, Baghdad, Iraq.

3

[email protected], [email protected], [email protected]

a

Keywords: Joint Strength; Spot weldability; Resistance spot welding; Shear strength; Fatigue strength

Abstract: This work presents a comparative study of the mechanical properties of resistance spot welded joints (RSW). RSW is widely used in sheet joining. Hence, the mechanical properties and their strength are presented. The main parameter is the welding current that has a big role on the heat generation and joint strength. The strength improvement due to the current increasing is regular and more effective than the weld time and the electrode pressure. Stainless steel has good weldability in sheet form. Galvanized steel, aluminum and carbon steel have been widely spotwelded. Moreover, dissimilar materials are also spot weldable where the two sheets of different metals can be joined. For the same sheet thickness at 1 mm, it was shown the shear strength of mild steel 3.8 KN, while for aluminum 1.4 KN this mean the shear strength of mild steel higher than aluminum. For the same metals, the increasing of the thickness will increase the strength. This is due to the weld area increasing. All the values were taken at the pull-out fracture condition. Hence, the suitable weld area at the welding condition was assumed. Fatigue strength for some metals has been presented. Fatigue strength of MS1300 is higher than those of steel DQSK, and steel DP800 at the for 1.6 mm thickness and stress ratio, R= 0.1. Because of the thickness, it has a minor effect on the fatigue properties of spot welded joints. Introduction In resistance spot welding (RSW), the two pieces of metal are welded together by passing an electric current through the interface surfaces. The ease of use, ability to use in the field, and adjustable according to the work-piece conditions, makes RSW one of the best processes for sheet metal fabrications [1][2][3][4][5]. Since decades, the parameters of RSW process effect on fracture strength, nugget formation, microstructure, and crack formation and metal weldability have been investigated extensively. Moreover, sheet thickness and surface conditions have also an effect [6][7]. By applying pressure, the local heating will form a local fused point that is called a nugget, see Fig. 1. Spot welding is commonly used in the automotive industry, where it is used to weld sheet metal that forms automobiles [8].

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Figure 1 Spot-welding parts and nugget formation The increasing of weld current for stainless steel will increase the nugget area, and the joint strength accordingly [9][10]. Several studies have investigated the spot welding of carbon steel, galvanized steel, and the aluminum alloys [11][12][13] due to their wide applications [14]. Carbon steels are the main typical materials for spot welding in thickness of (1-6 mm) because it have higher electrical resistance and lower thermal conductivity than electrodes made of copper [15][16]. Galvanized steel has a poor electrode problem and fracture defects which come from the alloying element high surface resistance [17][18]. The spot weld ability of high strength low alloys (HSLA) steels and SAE 1008 carbon steels was investigated in Refs. [19][20]. It was concluded that HSAL steels exhibited good spot weld ability. The welding current level of the HSLA steels (highest grades) was lower than that of the low carbon steel (unalloyed steel) due to the chemical compositions, physical and mechanical properties. Analysis of spot-weld strength according to welding parameters of aluminum alloys was performed in Refs. [21]–[23] . It is also possible to combine dissimilar materials such as aluminum with cold rolled and austenitic stainless steels [24]. This study focuses on the mechanical properties of spot welded joints, especially shear strength, and fatigue strength, which are the most important properties of spot welds. The shear strengths of similar and non-similar metals with different thicknesses were described and discussed. Fatigue strengths for different materials under the same conditions (plate metal thickness and load factor R) were presented. Mechanical Properties of Spot Welded Joints The standard tensile shear and transverse tensile tests described in American Welding Society AWS [25]. There are several other weld test methods described in the literature used to characterize spot welds according to the loading modes: tension and shear. Depending on the technical requirements, welded joints can be tested in tension, shear, or a combination of tension, and shear see Refs. [2]–[4], [26]–[29]. However, in specimens welded by spot welds, the term "stress" is meaningless to describe weld strength [29]. Hence, shear and tensile load can be used. The strength of a welded joint can be increased or decreased, it can be said that an appropriate combination of parameters is required to obtain the maximum strength of a spot welded joint [14] [30]. Shear Strength Shear stress is the traditional loading for sheets. The weld nugget will carry the load over the nugget area to produce the shear strength. The suitable weld area is achieved by determining of the effectiveness welding parameters on the weld strength, see Ref. [29]. The changing in current is also more effective in improving shear strength than the changes in the welding time or pressure. Traditionally, it has been shown that the nugget diameter will increase by increasing the weld current [31]. When the melting temperature is reached, the size and strength of the weld increases rapidly with a moderate increase in amps. A good correlation was obtained between

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strength and weld area [2]–[4], [26]–[29], [32]. If there is a defect in the nugget, a decrease in the welding area, a decrease in strength and deterioration of the electrode can be expected [24]. When the melting point is reached, the size and strength of the weld increases rapidly with a moderate increase in current.

Figure 2 Schematic illustrations of weld coupons for tensile shear specimen [28] Tables 1 and 2 show the relationship between the material thickness and tensile shear load for materials in two cases, similar, and dissimilar, respectively. These values for tensile shear load are shown in Figs. 3, and 4. Accordingly, a significance difference was obtained for different materials. Table 1 Tensile shear load for different similar materials in RSW Materials 1 Mild steel [14] 2 Mild steel [14] 3 Galvanized steels [33] 4 Aluminum AA1050 [34] 5 Aluminum AA1050 [34] 6 Aluminum AA1050 [34] 7 Aluminum 5182 [11] 8 Aluminum 5754 [11] 9 Carbon steel number 1.8902 [28] 10 Q&P980 Steel [35] 11 Galvanized sheet steel [36] 12 Martensitic (M190) steel [37]

Thickness (mm) 0.8 1 1.22 0.6 1 1.5 2 2 0.8 1.6 1.6 1.2

Tensile Shear Load (KN) 2.8 3.8 8 0.85 1.4 2.6 5 4 7 24 12 20

Table 2 Tensile shear load for different dissimilar materials in RSW Materials

1 2 3 4 5 6 7 8

low carbon steels / SPH 440 steel [12] Galvanized steel / Aluminum alloy 6008 [13] Aluminum alloy A5052 / Steel [13] Aluminum alloy A6061 / Stainless steel [13] Aluminum alloy / Steel [13] Aluminum alloy A6061 / Steel [13] Aluminum alloy A6061 / Copper [13] Aluminum alloy A6061 / Steel [13]

Thickness (mm) 9/2.9 1/1.5 1/1 2/2 1/0.8 1/1 1/1 2 /1.8

Tensile Shear Load (KN) 9.56 5.4 6.2 8.4 3.6 3.85 4.6 7

Figures 3 and 4, is showing the tensile shear load for different similar and dissimilar materials in RSW.

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30

Tensile Shear Load (KN)

25 20 15 10 5 0

12

11

10

9

8

7

6

5

4

3

2

1

Materials

Figure 3 General welding strength behavior for similar materials

Tensile Shear Load (KN)

10 8 6 4 2 0

8

7

6

5

4

3

2

1

Materials

Figure 4 General welding strength behavior for dissimilar materials Figures 3, and 4 show the relationship between thickness and tensile strength. From this, it can be seen that the shear resistance of spot welds increases significantly in various combinations with similar or different alloys for the same mild steel material as the thickness of the sample increases. For example, it can be seen that the tensile strength values increase from 2.8 to 3.8 k N with thicknesses of 0.8 and 1 mm. The same behavior for aluminum 1050 where the increasing of thickness from 0.6 to 1.5 mm will increase the tensile shear strength from 0.85 kN to 2.6 kN, respectively. This is due to the fact that increasing the thickness of the sample increases the cross-sectional area of the weld area, and the shear force acts parallel to the nugget cross-sectional area [34] [38]. The metals with high tensile strength will produce a higher spot weld shear strength, as shown for Aluminum 5182 and aluminum 5754, galvanized steel, and Q&P980 steel, see Table 1 and Fig. 3. Fatigue Strength The effect of cyclic loads on the sheet structures is important. Therefore, fatigue strength is investigated in Refs. [39] [40] [41]. Table 3 include the fatigue lives for three metals mild steel DQSK, AHSS steel DP800, and martensitic MS1300 in spot welds with thickness 1.6 mm and load ratio R= 0.1 [41].

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Table 3 Fatigue lives for three metals (mild steel DQSK, and AHSS steel DP800) DP800 1.6 mm [42] load Range Number of (N) cycle 48700 490000 48700 5250000 48700 5790000 48700 6340000 48700 6740000 48700 7810000

MS1300 1.6 mm [42] load Range Number of (N) cycle 78000 2460000 71800 4060000 71300 4620000 69800 4990000 69800 5160000 67300 5590000

DQSK 1.6 mm [42] load Range Number of (N) cycle 66400 5160000 66400 5640000 65100 6290000 62400 6630000 62200 7010000 60600 7420000

The fatigue performance of spot welding depends primarily on the stress ratio, base metals strength, and weld nugget area. 90000 Linear (DP800 1.6 mm thick)

80000

Linear (MS1300 1.6 mm thick) Linear (DQSK 1.6 mm thick)

Load Range (N)

70000 60000 50000 40000 30000 0E+00

1E+06

2E+06

3E+06

4E+06

5E+06

6E+06

7E+06

8E+06

9E+06

1E+07

Number of Cycle

Figure 5 Fatigue behavior for materials (DP800, MS1300 and DQSK) Fatigue Strength MS1300 has a higher fatigue strength value than mild steel DQSK and AHSS steel DP800 due to its high strength as shown in the Fig. 5. Conclusions In this work, an overview of the properties of welded joints and the features of spot welds has been presented. Tensile shear testing is most widely used to evaluate spot weldability by determining the mechanical properties. The fatigue strength was also investigated. The following conclusions can be concluded: 1. The parameters of RSW (welding time, welding current, electrode force) have a clear influence on the shear strength and fatigue strength. 2. Since the plate and plate thickness affect the welding current value and other parameters, the type and thickness of the material affect the shear resistance and fatigue strength. 3. Because the diameter of the fusion zone affects the weld strength, there is a good correlation between the shear strength and the weld zone area. 4. For the same material with different thickness, the shear strength increases with the increasing of the materials thickness.

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5. Fatigue strength has different values for different materials and depends on the chemical composition and type of metal microstructure. 6. The material has a great influence on the fatigue life of the structure. Increasing the spot weld diameter within a reasonable range of the spot weld diameter may increase the fatigue life of the spot weld. References [1]

D. Özyürek, “An effect of weld current and weld atmosphere on the resistance spot weldability of 304L austenitic stainless steel,” Mater. Des., vol. 29, no. 3, pp. 597–603, Jan. 2008, doi: 10.1016/j.matdes.2007.03.008.

[2]

A. M. Al-Mukhtar, Spot Weldabaility Principles and Considerations. Südwestdeutscher Verlag Für Hochschulschriften Ag Co. Kg, 2015.

[3]

K. M. Daws, A.-K. A. Al-Douri, and A. M. Al-Mukhtar, “Investigation of Some Welding Parameters in Resistance Spot Welding of Austenitic Stainleass Steel,” Coll. Eng. Journal, Baghdad Univ. Iraq, 2003.

[4]

A. M. Al-Mukhtar, “Spot Welding Efficiency and It ’ S Effect on Structural Strength of Gas Generator and Its Performance,” Baghdad University, 2002.

[5]

A. M. Al-Mukhtar, “Aircraft Fuselage Cracking and Simulation,” Procedia Struct. Integr., vol. 28, pp. 124–131, 2020, doi: 10.1016/j.prostr.2020.10.016.

[6]

K. Chan, “Weldability and degradation study of coated electrodes for resistance spot welding,” A thesis Present. to Univ. Waterloo fulfillment thesis Requir. degree Master Appl. Sci. Mech. Eng. Waterloo, Ontario, Canada© Kevin Randall Chan, 2005.

[7]

Z. Lei, H. Kang, and Y. Liu, “Finite Element Analysis for Transient Thermal Characteristics of Resistance Spot Welding Process with Three Sheets Assemblies,” Procedia Eng., vol. 16, pp. 622–631, Jan. 2011, doi: 10.1016/j.proeng.2011.08.1133.

[8]

and J. W. M. J.M. Sawhill, JR.H. Watanable, “Spot Weldability of Mn Mo Cb, V-N and SAE 1008 Steels,” 1977.

[9]

J. W. Elmer, J. Wong, and T. Ressler, “In-situ observations of phase transformations during solidification and cooling of austenitic stainless steel welds using time-resolved X-ray diffraction,” Scr. Mater., vol. 43, no. 8, pp. 751–757, 2000.

[10]

J. B. Shamsul and M. M. Hisyam, “Study of spot welding of austenitic stainless steel type 304,” J. Appl. Sci. Res., vol. 3, no. 11, pp. 1494–1499, 2007.

[11]

S. B. Behravesh, H. Jahed, and S. Lambert, “Characterization of magnesium spot welds under tensile and cyclic loadings,” Mater. Des., vol. 32, no. 10, pp. 4890–4900, 2011, doi: 10.1016/j.matdes.2011.06.001.

[12]

T. P. Kasih, A. Kharisma, and A. Suryanto, “Optimization of spot welding process parameters on dissimilar and unequal thickness of metal sheets by using Taguchi technique,” IOP Conf. Ser. Earth Environ. Sci., vol. 195, no. 1, 2018, doi: 10.1088/17551315/195/1/012036.

[13]

S. M. Manladan, F. Yusof, S. Ramesh, M. Fadzil, Z. Luo, and S. Ao, “A review on resistance spot welding of aluminum alloys,” Int. J. Adv. Manuf. Technol., vol. 90, no. 1–4, pp. 605– 634, 2017, doi: 10.1007/s00170-016-9225-9.

[14]

M. Raut and V. Achwal, “Optimization of spot welding process parameters for maximum tensile shear strength,” Int. J. Mech. Eng. Robot. Res., vol. 3, no. 4, pp. 506–517, 2014.

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[15]

N. Kahraman, “The influence of welding parameters on the joint strength of resistance spotwelded titanium sheets,” Mater. Des., vol. 28, no. 2, pp. 420–427, Jan. 2007, doi: 10.1016/ j.matdes.2005.09.010.

[16]

M. V. Nogin, “Spot Welding Hot Rolled Steel Without Prior Cleaning,” Weld. Prouduction, vol. 12, no. 3, p. 1965, 1965.

[17]

H. and G. K. Nies, “Formation of cracks in galvanized steel structures,” Leonardo, 2007.

[18]

S. and yoshitake Watanabe, Toichi, Sofue, Tadashi, “Spot welding of hot rolled-dipped galvanized steel sheet,” J. Japan Weld. Socity, vol. 6, no. 40, p. 1988, 1988.

[19]

J. M. Sawhill and J. C. Baker, “Spot weldability of high-strength sheet steels,” Weld. J., vol. 59, no. 1, pp. 19S-30S, 1980.

[20]

D. and Bargrad, “Resistance spot welding of high strength low alloy steel (HSLA) sheet, a survey,” Weld. world, vol. 23, no. 5/6, p. 1985, 1985.

[21]

L. Han, M. Thornton, D. Boomer, and M. Shergold, “Effect of aluminium sheet surface conditions on feasibility and quality of resistance spot welding,” J. Mater. Process. Technol., vol. 210, no. 8, pp. 1076–1082, Jun. 2010, doi: 10.1016/j.jmatprotec.2010.02.019.

[22]

R. S. Florea, D. J. Bammann, a. Yeldell, K. N. Solanki, and Y. Hammi, “Welding parameters influence on fatigue life and microstructure in resistance spot welding of 6061-T6 aluminum alloy,” Mater. Des., vol. 45, pp. 456–465, Mar. 2013, doi: 10.1016/j.matdes.2012.08.053.

[23]

D. K. Aidun and R. W. Bennett, “Effect of resistance welding variables on the strength of spot welded 6061-T6 aluminum alloy,” 1985.

[24]

R. Qiu, C. Iwamoto, and S. Satonaka, “Interfacial microstructure and strength of steel/aluminum alloy joints welded by resistance spot welding with cover plate,” J. Mater. Process. Technol., vol. 209, no. 8, pp. 4186–4193, Apr. 2009, doi: http://dx.doi.org/10.1016/ j.jmatprotec.2008.11.003.

[25]

A. W. S. R. W. Committee and E. A. Fenton, Recommended Practices for Resistance Welding. American Welding Society, 1966.

[26]

A. M. Al-Mukhtar, T. Rahman, and Q. M. Doos, “Spot Welding Joint’s Fracture Behavior and Fundamental,” in Fracture, Fatigue and Wear, Springer, 2019, pp. 18–27. doi: 10.1007/978-981-13-0411-8_2.

[27]

A. Al-Mukhtar and Q. Doos, “Cracking Phenomenon in Spot Welded Joints of Austenitic Stainless Steel,” Mater. Sci. Appl., vol. 4, no. October, pp. 656–662, 2013.

[28]

A. M. Al-Mukhtar and Q. Doos, “The Spot Weldability of Carbon Steel Sheet,” Adv. Mater. Sci. Eng., vol. 2013, pp. 1–6, 2013, doi: 10.1155/2013/146896.

[29]

A. M. Al-Mukhtar, “Review of Resistance Spot Welding Sheets: Processes and Failure Mode,” Adv. Eng. Forum, vol. 17, pp. 31–57, Jun. 2016, doi: 10.4028/www.scientific.net/ AEF.17.31.

[30]

C. Rajarajan, P. Sivaraj, T. Sonar, S. Raja, and N. Mathiazhagan, “Resistance spot welding of advanced high strength steel for fabrication of thin-walled automotive structural frames,” Forces Mech., vol. 7, no. February, p. 100084, 2022, doi: 10.1016/j.finmec.2022.100084.

[31]

X. Yuan, C. Li, J. Chen, X. Li, X. Liang, and X. Pan, “Resistance spot welding of dissimilar DP600 and DC54D steels,” J. Mater. Process. Technol., vol. 239, pp. 31–41, Jan. 2017, doi: http://dx.doi.org/10.1016/j.jmatprotec.2016.08.012.

[32]

A. M. Al-Mukhtar, S. A. K. Al-Jumaili, and A. H. F. Al-Jlehawy, “Effect of Heat Treatments on 302 Austenitic Stainless Steel Spot Weld,” Adv. Eng. Forum, vol. 29, pp. 19–25, Aug. 2018, doi: 10.4028/www.scientific.net/AEF.29.19.

28

Advanced Materials and Production Technologies

[33]

S. K. N. Sinhgad, “Shear Strength Prediction of Multi-Spot Welded Lap Shear Specimen through Experimentation and Validation by FEM Prasad P Kulkarni,” vol. 4, no. 4, pp. 80– 87, 2014.

[34]

I. K. Al Naimi, M. H. Al Saadi, K. M. Daws, and N. Bay, “Influence of surface pretreatment in resistance spot welding of aluminum AA1050,” Prod. Manuf. Res., vol. 3, no. 1, pp. 185– 200, 2015, doi: 10.1080/21693277.2015.1030795.

[35]

B. Wang et al., “Investigation on fatigue fracture behaviors of spot welded Q&P980 steel,” Int. J. Fatigue, vol. 66, pp. 20–28, 2014.

[36]

G. Wang and M. E. Barkey, “Investigating the spot weld fatigue crack growth process using X-ray imaging,” Weld. J., vol. 85, no. 4, pp. 84–90, 2006.

[37]

T. K. Pal and K. Chattopadhyay, “Resistance spot weldability and high cycle fatigue behaviour of martensitic (M190) steel sheet,” Fatigue Fract. Eng. Mater. Struct., vol. 34, no. 1, pp. 46–52, 2011.

[38]

L. Chen et al., “Investigation on shearing strength of resistance spot-welded joints of dissimilar steel plates with varying welding current and time,” J. Mater. Res. Technol., vol. 16, pp. 1021–1028, 2022, doi: 10.1016/j.jmrt.2021.12.079.

[39]

S. H. Lin, J. Pan, P. Wung, and J. Chiang, “A fatigue crack growth model for spot welds under cyclic loading conditions,” Int. J. Fatigue, vol. 28, no. 7, pp. 792–803, 2006, doi: 10.1016/j.ijfatigue.2005.08.003.

[40]

K. Vadivel, “Investigation of Fatigue Loading on Galvanized Iron AISI 4340 Sheet Metal using Spot Welded Joint in Finite Element Analysis,” Int. J. Res. Appl. Sci. Eng. Technol., vol. 7, no. 11, pp. 811–815, 2019, doi: 10.22214/ijraset.2019.11136.

[41]

M. K. Wahid, M. N. Muhammed Sufian, and M. S. Firdaus Hussin, “Effect of fatigue test on spot welded structural joint,” J. Teknol., vol. 79, no. 5–2, pp. 95–99, 2017, doi: 10.11113/jt.v79.11290.

[42]

H. T. Kang, A. Khosrovaneh, H. Hu, and U. De Souza, “A fatigue prediction method for spot welded joints,” SAE Technical Paper, 2013.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 29-38 doi:10.4028/p-0j3zgs © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-27 Revised: 2022-09-27 Accepted: 2022-09-27 Online: 2022-12-26

Experimental Investigations of Surface Finish Generated by Wire Electrical Discharge Machining Ali Hasan Hadia* and Ali Abbar Khleifb* Department of Production Engineering and Metallurgy, University of Technology-Iraq [email protected], [email protected]

a

Keywords: WEDM; Surface roughness; Geometrical accuracy;

Abstract. This study aims to investigate wire electrical discharge machining of copper alloys. Extensive research was done to design an optimum cutting method with adequate wire balance to achieve the requisite surface smoothness and geometrical dimensional correctness. Parameters were used in this work to simulate the process pulse-on time, pulse-off time, peak current, servo feed rate, servo-volt, wire-feed rate, wire tension, and water pressure. For each given treatment requirement, the primary impacting elements are highlighted. The results are the best standard settings that have been designed to satisfy the client’s varied developing needs. A low pulse achieves superior surface polish on time and a high pulse off time. According to the (ANOVA) findings, the most significant cutting parameter is the pulse on-time (Ton), which affects surface roughness by (42.922)%, followed by pulse off time (Toff), which affects surface roughness by (24.860)%, and servo feed (SF), which affects surface roughness by (6.850)%. The impact of the process variables was wire tension on response characteristics, dimensional deviation, cutting rate, and surface roughness. Introduction The Manufacturing requirements for alloy materials with high hardness, toughness, and impact resistance is growing in tandem with the expansion of the mechanical sector. Traditional machining technologies, however, find it challenging to machine such materials. The input parameters have a dynamic effect on output parameters such as material removal rate, surface quality, hardness, and wear resistance for optimal machining performance. As a result, non-traditional machining techniques such as electrochemical, ultrasonic, and electrical discharge machines (EDM) manufacture materials that are difficult to machine. The (WEDM) technique converts electrical energy into thermal energy for cutting materials using a thin wire as an electrode. This technology may manufacture alloy steel, conductive ceramics, and aerospace materials, independent of their hardness or toughness. (WEDM) can also provide a fine, accurate surface resistant to corrosion and wear. Wire-electrical discharge machine is a unique variation of the traditional-EDM method, which starts the sparking process using an electrode. WEDM on the other hand, it uses a constantly going wire electrode constructed of thin copper, brass, or tungsten with a diameter of (0.05-0.30) mm that may achieve very tiny corner radii. A mechanical tensioning mechanism keeps the wire taut, lowering the likelihood of making faulty components. During the (WEDM) process, the material is eroded ahead of the wire; thus, there is no direct contact between the workpiece and the wire, eliminating mechanical tensions during machining. Wire-cut EDM achieves great surface finishing quality and dimensional precision [1,2]. This research study aims to determine the parameters that mainly affect the surface finish of a product in terms of dimensional accuracy and surface roughness and to determine the parameters that control them. Inoor Zaman Khan et al. [3] Used Taguchi techniques based on an (L-18 hybrid) orthogonal array. The impacts of different (WEDM) cutting settings on wire crater depth, electrode wear rate, and surface roughness were investigated. Y. Fan et al. [4] developed aprecision pulse power generator based on a microcontroller unit. Double Complex programmable logic devices with a broad range of electric characteristics have been developed. Precision machining is possible because of the pulse duration and interval ranges of (0.08 s-20.4 s) (WEDM). In regulated resistance and capacitance precision pulse power mode, the effects of

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Advanced Materials and Production Technologies

capacitance on feasible processing thickness and surface roughness are investigated. It also uses the orthogonal experiment approach to investigate and modify the variables influencing surface roughness and processing speed. Basil et al.[5] determines how voltage, dielectric pressure, pulse on time, and pulse off time affect the spark gap of Ti6Al4V alloy. The spark gap of wire EDM was shown to be significantly influenced by the pulse on time, pulse off time, the interaction between dielectric pressure and pulse off time, and pulse on time and pulse off time. According to grey relational analysis, the ideal input variable combinations for the smallest spark gap are as follows: pulse on time of 20 s, high dielectric pressure of 15 kef/cm2, high pulse off time of 50 s, and voltage of 50 v. Incorrect pulse on and off time settings may cause wire breakage, which in turn lengthens the machining process. Less than 6% of the conformation data and the constructed model are in agreement. V. N. Najm et al.[6] The impacts of several WEDM factors on the heat-affected zone, white layer, and Surface Roughness (SR) of high-speed steel are being investigated. Analyzing the behavior of control parameters such as pulse on time (s), current, and wire tension using the ANOVA technique, the findings demonstrate that rising current and pulse on-time values impact the heataffected zone and the white layer more than rising wire tension values. That wire tension affects surface roughness more than current and pulse on time. Patil et al.[7] studied the most current wire EDM advancements. It provides information on wire EDM research pertaining to process parameter optimization and performance measure improvement. Various wire EDM industrial uses for a variety of materials have been documented. The future direction of wire EDM research is also discussed in the study. According to the literature, increasing the wire feed, pulse on time, gap voltage, and peak current will increase MRR or production. However, a key issue with raising peak current and gap voltage are that SR and kerf quality would drop. MRR decreases while SR rises when pulse off time is increased. Manikandan et al.[8] investigated wire- EDM optimized machining process parameters. In this study, the MRR, SR, and kerf width are used as the foundation for the performance characteristics of wire EDM. Pulse on time, pulse off time, discharge current, arc gap, flushing pressure, servo voltage, and wire tension were the wire EDM machining factors that impacted the performance metrics. By changing the servo voltage, pulse on time, and pulse off time parameters, experiments are conducted using the Taguchi design of experiments. The MRR, kerf width, and SR are used to gauge the process's efficiency. This study examined the effects of wire EDM on MRR, kerf width, surface quality, and manufacturing costs utilizing steel workpieces and copper wires with zinc coatings of 0.25 mm in diameter and EN-31 tools. The optimum value for maximum MRR, minimum SR, and Kerf width is provided as a pulse on time= 131 s, pulse off time= 36 s, wire tension= 6 kg, utilizing the multi-objective optimization approach grey relational theory. H. AlEthari et al. [9] Investigate the electrical discharge machining on fracture toughness, which is the most significant structural integrity indicator in the diverse range of applications for the composites under consideration. All samples in this study were made utilizing the stir casting process with a squeezing pressure applied during solidification. B4C particles having a diameter of 0.387m were used to reinforce samples at 0, 2, 4, and 6 weight percent. The stress intensity factor was measured experimentally using a compact tensile test and computationally using the finite element technique to calculate fracture toughness. The fracture toughness of the samples with 4wt% B4C improved. Keywords. B4C Particles, Aluminum base composite, Fracture toughness. R. M. Kirwin et al. [10] Modifying and applying the wire lag model based on surface feeding to increase accuracy in EDM wire for Ti-6Al-4V alloy. Wire lag may reduce the dimensional accuracy of (WEDM) products. The feasibility of modifying the operating G code to adjust for wire delays while cutting acute corners is investigated here. Automation experiments are used to build the software. The first step was to look at the impact of surface feeding on profile accuracy. Wire lag and profile accuracy were shown to be affected by feeding. A wire lag model is illustrated, as well as ways to design changes to decrease wiring lag by including surface feeding and eliminating the requirement for an off-site gauge. For each plasma discharge, a mechanism for connecting pulse length and voltage. The created application has been proven to forecast wire delay or angle error to 10% of the experimental value. The precision of the cutting process may be substantially improved by determining the amount of wire lag from the changed model and modifying the CNC. G codes using the built program to apply the cuts at the

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necessary angles, as this profile has been discovered. Mehmood S. et al. [11] studied wire electrical discharge machining to produce steel and form tools. The observed responses comprised time parameters, voltage, electrode tool geometry (clearance angle, included angle), surface roughness, and MRR (Material Removal Rate). The results showed that angle, MRR, and measured roughness were all significant determinants for clearance angle, with a pulse on time and pulse off time being the most important. A particular sort of dielectric environment was studied in a number of articles. Results from electrical discharge machining with kerosene or distilled water are often compared. Dariusz Poroś et al. [12] explored gaseous dielectric flushing in dry WEDM of cemented carbides. The experimental findings showed that gaseous dielectric successfully eradicated cobalt depletion, although increasing HAZ depth remained a drawback of this method. When residual stresses are created in the rim zone, fractures that extend deep into the basic material are produced. As a result, WEDM of cemented carbides needs to utilize the proper electrode, duration, and current parameters to prevent overheating the cut surface. Reduce the amount of time that WC-Co is immersed in water during WEDM. Additionally, it has been shown that the EDM conditions have little impact on the material's microstructures in the bulk of the workpiece. This indicates the depth at which EDM might cause harm to the treated surface. However, it is noted that the peak current and pulse duration are correlated with a rise in the depth of the damaged layer and the average length, breadth, and number of microcracks. When the peak current and pulse length are tuned to very low levels, the damaged layer and microcracks seem to vanish. Raj Kumar et al. [13] studied Energy Dispersive Spectroscopy (EDS), and a scanning electron microscope (SEM) were used to explore. The surface damage on the WEDM-machined sample is readily visible in the SEM micrograph, yet machining did not affect the entire FGCC microstructure. Additionally, it has been noted that the damaged layer's interior structure has fewer WC grains than the top machined surface. After polishing, the observed thickness of the damaged surface may be erased. Therefore, WEDM is a useful technique for machining FGCC and won't negatively impact the machined sample. 1. Methodology and Material used The workpiece material chosen in this study is an alloy of brass metal ASTM (C34500), with (250 x 70 x 20) mm in dimensions, as shown in figure 1, and the chemical composition and mechanical properties listed in tables (table 1, table 2). Samples were modeled using the design software Solidworks. In the wire-EDM machine, software and (NC) code are created for machining purposes. Figure 2 illustrates the dimensions of the required product. 250mm

70mm

20mm

Figure 1. The Workpiece used in this work

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Advanced Materials and Production Technologies

Table 1. Chemical composition of brass alloy chemical composition of workpiece material Brass (C34500) material

Zn %

Pb %

Sn %

P %

Mn %

Fe %

Ni %

Cr %

S %

Sb %

Cu%

Exp.

33.36

2.53

0.0015

0.006

0.0005

0.233

0.0052

0.0014

0.0074

0.003

63.8

ASTM

32.536.5

1.52.5

0.0

0.0

0.0

≥ 0.150

0.0

0.0

0.0

0.0

62-65

Material Brass (C34500)

Tensile Strength [Mpa] 325 372

Table 2. The mechanical properties of metal Elongation [%] 22 35

Yield strength [Mpa] 185 234

Hardness, Rockwell B 66

Thermal Conductivity [W/m.°C] 1220

ASTM Cu-Zn C34500

Figure 2. The required dimensions of the samples 2. Experimental Setup The processing activities are carried out on a Smart DEM 400 A wire-cut device. Deionized water is employed as an electrically insulating liquid using a brass wire diameter of (0.25) mm. The product surface roughness (Mahr Fed Company) with a precision of (0.05) µm. The probe sweeps the surface, comparing the signal (Ra) peaks and troughs in three places on the sample surface. For the precision of the geometric dimensions of the samples, we additionally employ the Geometrical Coordinate Measurement (3D) equipment. The procedure is explained using an analysis of variance (ANOVA) to identify the critical input factors that influence surface roughness. The Taguchi technique is used for optimization to find the best parameters for a low surface roughness ratio. A maximum of eight characteristics listed in table 3 can be accommodated by Taguchi's L20 hybrid orthogonal array. Conducting the wire electrical discharge machining operation for the 20 samples on the variable parameters. As shown in figures 3, and table 3.

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a

Cutting Wire-cut

33

wire cut reel

Upper guide

Workpiece

Holder

Lower guide

b Figure 3. (a) Machine parts, (b) Samples processed by WEDM

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Advanced Materials and Production Technologies

Table 3. Parameters and grades of wire EDM No 1 2 3 4 5 6 7 8

Parameters pulse-on time pulse-off time Peak-current servo feed rate servo-volt wire feed rate wire tension water pressure of the dielectric fluid

Symbol Units Ton µSec Toff µSec IP A SF mm/min SV Volt WF m/min WT gram WP Pascal

Level-1 100 40 12 500 10 5 5 5

Level-2 110 45 11 1000 15 8 8 8

Level-3 120 50 10 1800 20 10 10 11

3.1 Taguchi - ratio (S/N): The S/N ratio may be determined as a logarithmic shift of the loss function, with “lower is better” and “higher is better” being the specified attributes of (Ra). Table 4 lists the experimental values for (Ra) and the S/N ratios corresponding to them. (TON 120), (TOFF 50), (IP 10), (WP 11), (WF 10), (WT 10)), (SV 20), and (SF 1800) provide ideal (Ra); the optimal sum of the acquired parameters and values is (1.41). The S/N ratio and the optimal (Ra) value have been enhanced. A higher (S/N ratio) response (12.18) indicates that the machine has improved. The average (S/N ratio) values are presented in figure 4, the influence of control parameters on (Ra). In figure 5. Table 4. Surface roughness S/N ratios and experimental findings No

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ton [µSec]

100 100 100 100 100 100 100 100 100 110 110 110 110 110 110 110 110 110 120 120

Toff [µSec]

40 40 40 45 45 45 50 50 50 40 40 40 45 45 45 50 50 50 40 50

IP [A]

12 12 12 11 11 11 10 10 10 11 11 11 10 10 10 12 12 12 10 10

SF [mm/min]

500 500 500 1000 1000 1000 1800 1800 1800 1800 1800 1800 500 500 500 1000 1000 1000 1000 1800

SV [V]

10 15 20 10 15 20 10 15 20 10 15 20 10 15 20 10 15 20 10 20

WF [m/min]

5 8 10 5 8 10 5 8 10 8 10 5 8 10 5 8 10 5 10 10

WT [gram]

5 8 10 5 8 10 5 8 10 10 5 8 10 5 8 10 5 8 8 10

WP [pa]

5 8 11 8 11 5 11 5 8 5 8 11 8 11 5 11 5 8 5 11

Avg. Ra [µm]

1.908 1.893 1.792 1.91 1.786 1.918 1.942 1.896 1.863 1.799 2.02 1.99 1.823 2.061 1.99 1.86 1.891 1.941 1.883 1.41

S/N ratio

13.38 14.25 14.10 13.64 13.90 14.18 13.81 13.92 14.26 13.59 14.43 14.38 13.94 14.64 13.96 14.22 13.72 14.14 13.87 12.18

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Main Effects Plot for SN ratios Data Means

A

C

B

14.0

Mean of SN ratios

13.5 13.0

1

2

3

1

2

D

1

3

E

2

3

F

14.0 13.5 13.0

1

2

3

1

2

G

3

1

2

3

H

14.0 13.5 13.0

1

2

3

1

2

3

S ignal-to-noise: Larger is better

Figure 4. Surface roughness and the effect of control parameters Main Effects Plot for Means Data Means

C

B

A 200 150

Mean of Means

100 1

2

3

1

2

1

3

2

3

F

E

D 200 150 100 1

2

3

1

2

1

3

2

3

H

G 200 150 100 1

2

3

1

2

3

Figure 5. Surface roughness and the effect of control parameters 3.2 ANOVA (analysis of variance) The findings of the analysis of variance for (Ra) are given in tables (5) and (6) correspondingly. (DF) stands for degrees of freedom, (SS) for sums of squares, (V) variance, (F) for F-ratio value, and percent (p) for contribution percentage. Three types of information are evaluated for determining the F-ratio of one sample variance. One is the required confidence level; (two and three are the degrees of freedom DF) in the numerator (vi) and denominator (v2), respectively, associated with the sample variance. Table 5. ANOVA for Surface roughness No

ANOVA for Surface Roughness: Ton; Toff; IP; SF; SV; WF; WT; WP

1 2 3 4

Source Factor Error Total

DF 7 152 159

SS 21386398 5643862 27030260

MS 3055200 37131

F 82.28

P 0.000

5

S

192.7

R-Sq

79.12%

R-Sq(adj)

78.16%

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Table 6. ANOVA for parameters No

Individual 95 % CIs For Mean Based on Pooled StDev

1 2 3 4 5 6 7 8 9

Level Ton Toff IP SF SV WF WT WP

N 20 20 20 20 20 20 20 20

Mean 106.5 45 10.9 1130 15 7.9 7.8 8 Pooled StDev = 192.7

St Dev 6.7 4.3 0.9 544.9 4.3 2.1 2.1 2.6

Surface imperfections are often increased when discharge energy rises owing to significantly greater melting and re-solidification of materials. This is why the minimal (Ra) is obtained for smaller (IP) and (Ton) values, such as (10A) and (120 sec), respectively. With an increase in (WT), the minimal (Ra). Minimizes vibration and enhances surface smoothness. If the gap is too small, the dielectric between the electrode and the workpiece is not sufficiently clean, causing the current to take the path of least resistance through the gap, resulting in a high current arc that damages the workpiece surface. Higher (SV) values show that the gap between the electrode and the workpiece is large enough for ionization and current flow. This might explain why a rough surface can be created at lower spark gap voltages, such as 8V, but not the other way around. The parameter (WF) had no effect in this experiment (Ra). To prevent wire breakage, proper dielectric cleaning conditions are necessary. Previous research, however, has shown no impact on (Ra), and this study also showed no effect. Pulse-off time or surface roughness has not affected surface roughness (SF). A contrast diagram is shown in Figure 6. a

Main Effects Plot for Ra Data Means

T on

T off

IP

1.9 1.8 1.7 100

110

120

40

Mean

SF

45

50

10

SV

11

12

WF

1.9 1.8 1.7 500

1000

1800

10

WT

15

20

WP

1.9 1.8 1.7

.

5

8

10

5

8

11

5

8

10

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37

Interaction Plot for Ra Data Means

40

45

50

10

11

12

500 1000 1800

10

15

20

5

8

10

5

8

10

5

8

11

2.00 1.75

Ton

1.50 2.00 1.75

Toff

1.50 2.00 1.75

IP

1.50 2.00 1.75

SF

1.50 2.00 1.75

SV

1.50 2.00 1.75

WF

1.50 2.00 1.75

WT

1.50

Ton 100 110 120 Ton 100 Toff 110 40 120 45

50 Ton 100 Toff 110 IP40 120 1045 1150 Ton

12 100 Toff 110 IP40 120 1045 SF 50 11 500 Ton 12 1000 100 Toff

1800 110 IP40 120 1045 SF 50 11 500 SV Ton 12 1000 10 100 Toff 1800 15 110 IP40 2045 120 10 SF

50 11 500 SV Ton 12 1000 10 WF 100 Toff 5 1800 15 110 IP40 8SF 2045 120 10 10 50 11 500 SV 12 1000 WF 10 1800 15 W5 T 208 5 10 8 10

WP

c

Line Plot of Ton; Toff; IP; SF; SV; WF; WT; WP 2500

Ra 1.908 1.893 1.792 1.910 1.786 1.918 1.942 1.896 1.863 1.799 2.020 1.990 1.823 2.061 1.860 1.891 1.941 1.883 1.410

2000

Data

1500

1000

500

0 Ton

Toff

IP

SF

SV

WF

WT

WP

Figure 6. ANOVA chart for parameters (a) main effects plot for Ra, (b) Interaction polt for Ra, (c) line plot for parameters. 4. Conclusions The main objective of the research is to get the optimum values of the cutting process inputs in WEDM to get a good surface finish. ‫س‬Procedure research on an alloy of brass. This experimental work focused on the basic factors and variables that mainly affect (Ra) and variables such as peak current, spark gap, and specific pulse time, which affect the surface quality (Ra). However, their ideal values vary greatly. Other influencing variables, servo feed rate, pulse time, and wire tension, affected (Ra). The presented mathematical models predicted with (Ra) a high regression coefficient value. If parameters affecting surface quality are observed, it increases when discharge energy rises owing to significantly greater melting and re-solidification of materials. This is why the minimal (Ra) is obtained for smaller (IP) and (Ton) values, such as (10A) and (120 sec), respectively. With an increase

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in (WT), the minimal (Ra). Minimizes vibration and enhances surface smoothness. . The results of genetic optimization showed that cutting efficiency must be sacrificed to create high-quality surfaces and vice versa. References [1] S. F. Miller, A. J. Shih, and J. Qu, “Investigation of the spark cycle on material removal rate in wire electrical discharge machining of advanced materials,” Int. J. Mach. Tools Manuf., vol. 44, no. 4, pp. 391–400, Mar. (2004) [2] S. Sarkar, S. Mitra, B. B, “Parametric analysis and optimization of wire electrical discharge machining of γ-titanium aluminide alloy,”-J. of materials processing., vol. 159, pp. 286–294, (2005) [3] N. Z. Khan, M. A. Wahid, S. Singh, A. N.Siddiquee, and Z.A. KHAN, “Study on micro hardness in wire electrical discharge machining based on taguchi method,” International Journal of Mechanical and Production Engineering., vol-1,Issue-1, (2013) [4] Y. Fan, J. Bai, C. Li, and W. Xu, “Research on Precision Pulse Power Technology of WEDM,” Procedia CIRP, vol. 6, pp. 267–273, Jan. (2013) [5] Kuriachen Basil, Josephkunju Paul, and Jeoju M.Issac, “Spark gap optimization of WEDM process on Ti6Al4V,” International Journal of Engineering Science and Innovative Technology., vol. 2, Issue 1, January (2013) [6] V. N. Najm, “Experimental investigation of wire EDM process parameters on heat affected zone,” Eng. Technol. J., vol. 36, no. 1, pp. 64–70, (2018) [7] M. Patil, G. Naik, P. N., “Analysis of process parameters in wire EDM with stainless steel 410 using topics method,” J. Emerg. Technol. Innov. Res, vol. 5, pp. 728–735, (2018) [8] Manikandan D., Gokul Raja S., Joel J., Karthick S., and Karthikeyan A. S., “Optimisation machining process parameters in wire cut EDM,” International Journal of Innovative Research in Science, Engineering and Technology, vol. 5, special Issue 8, May, (2016) [9] H. Al-Ethari and Z. Fadhil, “Investigation of the effect of wire electrical discharge machining on the fracture toughness of aluminum-boron carbide composite,” IOP Publishing, vol. 1094, no. 1. (2021) [10] R. M. Kirwin, J. C. Moller, and M. P. Jahan, “Modification and adaptation of wire lag model based on surface feed for improving accuracy in wire EDM of Ti-6Al-4V alloy,” Int. J. Adv. Manuf. Technol., vol. 117, no. 9, pp. 2909–2920, Aug.(2021) [11] Arshad R., Mehmood S., Shah M., Imran M., Qayyum F., “Effect of distilled water and kerosene as dielectrics on machining rate and surface morphology of Al-6061 during electric discharge machining,” Advances in Science and Technology Research Journal, vol. 13(3):162–169, (2019) [12] D. Poroś, S. Zaborski, and T. Stechnij, “Analysis of WEDM application to cutting tools manufacturing for manual shaping of flat surfaces,” in AIP Conference Proceedings, vol., no. 1, p. 20023, (2017) [13] R. S. Parihar, R. K. Sahu, and G. Srinivasu, “Effect of wire electrical discharge machining on the functionally graded cemented tungsten carbide surface integrity,” Mater. Today Proc., vol. 5, no. 14, pp. 28164–28169, (2018)

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 39-48 doi:10.4028/p-yl008d © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-29 Revised: 2022-09-25 Accepted: 2022-09-26 Online: 2022-12-26

Experimental Investigations of Hydrodynamic Deep Drawing of Galvanized Steel to Form a Hemispherical and Complex Cup Ali Raad Ahmeda and Ali Abbar Khleifb Department of Production Engineering and Metallurgy, University of Technology-Iraq [email protected]

a

[email protected]

b

Keywords: Hydromechanical deep-drawing; Thickness distribution; sheet metal forming.

Abstract. In this work, a blank of galvanized steel blank with 80 mm diameter and 0.7 mm thickness and the hydromechanical deep drawing process to make a hemispherical and complex cup. Hydraulic oil is used to apply different amounts of fluid pressure. The work of this study is done in the following three states: In the first state, the experimental work is done without fluid pressure, so the product has wrinkles. In the second state, flaws like wrinkles are fixed by adding 1n/mm2. At a pressure of 1.7 n/mm2, the third state is done. The results show that a product with a blank holder force (BHF) that is neither too high nor too low may be free of defects. When BHF is low, faults in the cylinder cup look like wrinkles, and when BHF is too high, the cylinder cup breaks. So, the BHF value should change depending on the material, thickness, and nature of the product. Introduction There are only a few applications for the traditional sheet metal forming method. HDD and other advanced sheet metal forming processes are frequently used. Although deep drawing is still used for high-quality components, HDDs are more suitable for single- and mass-production [1]. HDD has a better thickness distribution and workpiece quality. The thickness and quality of a part are determined through deep hydromechanical drilling. Hydraulic backpressure is used to force the blank against the punch surface. The use of punches and blanks increases friction. Because the blank sticks to the punch surface, it prevents cup wall expansion and thinning, resulting in a more uniform thickness distribution [2]. HDD requires additional equipment to manufacture crucial aircraft components due to hydraulic backpressure [3,4]. Complex objects are efficiently created using the hydrodynamic deep drawing method. The hemispherical component can be generated using the HDD method with just one pull. During normal deep drawing and HDD [4]. Hydro-mechanical deep drawing is a sheet metal forming technology that originated from hydroforming. It combines the benefits of deep drawing and hydroforming in one product. LDR values for typical deep drawing techniques are around 2.2; however, LDR values for hydro-mechanical deep drawing are around 2.8. Automobiles and aeroplanes, for example, are made using this technology. Since then, extremely specialized machinery and technologies have been developed and deployed. Hydro-mechanical deep drawing can replace forging processes because it increases product quality without lowering output [5]. A seal ring on the die face kept fluid from leaking between the die and the blank [6]. H. Khademizadeh and S. Jamshidifard, etal., [7]. Investigates The thickness distribution and hydrostatic pressure in fluid machinery deep drawings HDD are measured. AL6111-T4 is a hemispheric cup. Fracture instability is assessed using the FLD damage criterion. Uniaxial stretching's material behavior is also investigated. Over the typical deep drawing approach, the best maximum backpressure distribution for the HDD technique improves the ideal thickness distribution by 4.25 percent. MHDD and advanced finite element models are used by Fanghui Jia and Liang Luo et al [8] to investigate the impacts of fluid pressure, surface roughness, and material inhomogeneity. annealed foil experiments and sophisticated finite element modeling are used to investigate MHDD. When the hydraulic pressure is excessive, the foil may wrinkle. It has an impact on the size and amount of wrinkles. MHDD pulls force at 5 and 30 MPa. Hydraulic pressures are separated. Maximum tensile force

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dispersion is caused by the size effect. On the drawing force curve, there are no more peaks. At high pressure, the foil has two local peaks. 1. Methodology and Material Used A 0.7 mm thick, 80 mm diameter galvanized steel blank is used to make a hemispherical and Complex cup. Hydraulic oil applied pressure. 2. Experimental Work Hydromechanical deep drawing (HDD) is frequently used (hemispherical cup and complex cup). to obtain two geometries The investigation used blanks made of galvanized steel, each with a thickness of (0.7) and a different type of fluid pressure. The diameter of the blank utilized was (80) mm. The properties of the metal to be used have a significant impact on the hydromechanical deepdrawing operation. The metals utilized in this work are chosen for their formability and low cost, as well as their widespread use in the industry. Table 1 shows the chemical composition of galvanized steel. Table 1. Chemical composition of galvanized steel. Element

Chemical composition

C%

0.0637

Si %

0.0253

Mn %

0.164

P%

0.0165

S%

0.0113

Cr %

0.0242

Mo %

0.0022

Ni %

0.0158

Al %

0.026

Cu %

0.0207

Fe %

Bal.

2.1 The Entire Method can be Summarized as follows: 1. The compressor is filled with hydraulic oil. The hydraulic oil is injected into the cylinder, where a pressure gauge can be used to measure it. The cylindrical blank is placed within the cylinder between the blank holder (from the bottom) and subsequently the die (from the top). The liquid will be as illustrated in Figure 1 under the blank. 2. Insert the blank into the cylinder between the blank holder and the die, starting from the top. The liquid will be as illustrated in Figure 2 under the blank. 3. Using the hydraulic press's force, press the die. The force will be applied from above, while the liquid pressure will be applied from below. The sculpting process begins here. 4. To allow product escape easier, reduce the force of the hydraulic press device and pump fluid from the fluid compressor, as indicated in Figure 3.

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Figure1. Hydromechanical deep drawing rig.

Figure 2. Schematic representation of the base.

Figure 3. The Hydraulic Pressure device and the system (HDD) tool. 2.2 Measurement of Thickness Distribution As illustrated in Figure 4, the product is separated into two pieces by utilizing the Wire Electro Discharge Machine (WEDM) to compute the product thickness variation and the cup depth. Figures demonstrate how the micrometer is used to measure the product thickness fluctuation and the cup depth.

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Figure 4. A-Before cutting the product B- after cutting the product 2.3 Strain Measurement A grid pattern of (5, 10, 15, 20, 25, 30, 35, 40) mm radii circles was printed on the blank (along eight intersecting lines, 45 degrees apart), as shown in Figure 5. to analyze strain distribution within the product cup during the hydromechanical deep drawing process.

Figure 5. Printed mechanical grid on the blank. 2.4 Product Shape The final products as shown in Figure 6.

Figure 6. A- Hemispherical cup B- complex cup 3. Results From Experimental Works The sheet metal that is made by the HDD process is used to make the item that people buy (the product shape depends on the punch). Choosing the right parameters for the hydromechanical deep drawing process is very important if you want to be able to draw a lot and make a good product. During this research, galvanized steel sheets are all used with a thickness of (0.7) mm, and different fluid pressures are tried. The following experiment shows what is done.

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3.1 The Experiment I It has a diameter of about 80 mm and is made of galvanized steel sheets. The machine is used to make things with a thickness of 0.7 mm with no fluid pressure, and at a speed of 5 mm/min (slow speed). Table 3 shows. Table 2. Parameter of experiment I Metal Galvanized steel

Thickness (mm) 0.7

To compute the area of the blank, we have: A is equal to 5024 mm2. Compute the pressing force on the blank:

Fluid Pressure Press pressure (N/mm2) (N/mm2) 0 1.4

A= π Db2/4 A = (3.14*80^2)

(1)

Pp = F/A (2) When Pp is the press pressure, F is the press load, and A is the blank area, Pp = 1.4 N/mm F = 7033.6 N In this experiment, the product is shown in Figure 6. Figure 7, explains a product problem (several wrinkles in the flange cup). When working without fluid pressure, the fluid pressure presses on the blank holder, resulting in the blank holder having very little force, leading the product to wrinkle.

Figure 7. The product of experiment I. 3.2 The Experiment II In this situation, galvanized steel sheets blank holder diameter is (80) mm is used. A thickness of 0.7 mm and fluid pressure of 0.8 N/mm2 is used, together with a 5 mm/min speed press (the speed is very low) table 3. Table 3. Parameter of experiment II Metal galvanized steel

Thickness (mm) 0.7

Fluid Pressure Press pressure (N/mm2) (N/mm2) 1 2

By determining the fluid pressure, this state (state No 2) differs from the first. The blank area (A) is 5024 mm2. To compute the force applied to the blank, Pp =F/A Pp = 2 N/mm2 F = 10048 N

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In this situation, the product may also cause wrinkling, but the wrinkling in this state is less than in-state one because the fluid pressure is insufficient to press on the blank holder to obtain a good product, which means the blank holder force (BHF) is low. When the BHF is low applied on the blank, it results in pure drawing, in which the metal flows freely in the die cavity under the effect of radial tensile stresses, and these radial stresses cause an In addition, as seen in Figure 8, this stress causes wrinkling.

Figure 8. Wrinkling in experiment II 3.3 The Experiment III In this situation, galvanized steel sheets are done with a thickness of 0.7 mm and a fluid pressure of 1.7 N/mm2. Table 5, also shows the speed of the press at (5) mm/min (slow speed)). The value pressure appropriate is 2.4 N/mm2 when applying the truth and error principle in determining the value, of the pressure fluid (states 1, 2, and 3). In this example, look at the influence of the suitable pressure fluid to get a defect-free product (cup hemispherical and complex shape) as shown in Figure 9. Table 4. Parameter of experiment III Metal galvanized steel

Thickness (mm) 0.7

Fluid Pressure Press pressure (N/mm2) (N/mm2) 1.7 2.4

The blank area (A) is 5024 mm2. To compute the force applied to the blank.

P p =F/A F=2.4*5024= 12057.6 N

Figure 9.The Product cup in experiment III The pressure used to create the blank holder force value should be appropriate (not too low or too high) so that the blank holder force does not have to remain constant (due to fluid pressure) throughout the deformation process, and the counter-pressure induces compressive stress on the blank, which reduces thinning and improves formability, resulting in a good product (without defect). The value of fluid pressure changes as the pressure press is changed in each experiment (I, II, and III), as shown in Figure 10.

pressure press (N/mm2 )

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4 3 2 1 0

0

0.5

1

1.5

Pressure in the Fluid

2

(N/mm2

2.5

3

)

Figure 10. The fluid pressure and pressure press The blank holder force and fluid pressure are related (BHF = P*ABH) in such a way that each increase in the fluid pressure wall increases the blank holder force. To calculate the blank holder force, BHF = P*ABH (3) The blank holder area (ABH) is determined: ABH = (D2-de2). π/4 (4) de= d+2. C+2Rd (when de = effective diameter of blank holder (mm)) when C= clearance C= 0.77 & de= 51.54 mm ABH = 2938.75 mm2 BHF = 5015.1 N DR=2

(5)

4. Thickness Distribution As for the thickness, it has been found that the thickness will stay the same under the punch face (the bottom of the cup). This is because the punch face is in contact with the blank, the pulling force, and friction, which all work to keep the punch from being affected by any metal deformation at the site. It gets a little thinner when the punch corner is under tensile stress. This happens because the blank holder's force makes it stretch even more than it already is. After that, the wall thickness of the cup tends to get thicker because of the compressive stress only in this area. It has to be cut into sections to determine how wide the cup is. When the blank thickness is equal to 0.7, the thickness distribution is listed in table 5. Table 5. Distribution of thickness (mm) of galvanized steel (hemispherical shape). Distance from the center of the cup Distribution of thickness (mm) (mm) 0 0.7 5 0.7 10 0.69 15 0.77 20 0.72 25 0.75 30 0.71 35 0.77 40 0.86 Figure 11, illustrates the blank chart's thickness distribution of galvanized steel (hemispherical shape).

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DISTRIBUTION OF THICKNESS (MM)

1 0.8

0.7

0.7

0.69

0.77

0.75

0.72

0.77

0.71

0.86

0.6 0.4 0.2 0

0

5

10

15

20

25

30

35

40

DISTANCE FROM THE CENTER OF THE CUP (MM)

Figure 11. Distribution of thickness of blank for galvanized steel (hemispherical shape) When the blank thickness is equal to 0.7, the thickness distribution is listed in table 6. Table 6. Distribution of thickness of galvanized steel (complex shape). Distance from the center of the cup Distribution of thickness (mm) (mm) 0 0.7 5 0.66 10 0.64 15 0.68 20 0.72 25 0.73 30 0.7 35 0.75 40 0.85 Figure 12 , illustrates the blank chart's thickness distribution of galvanized steel (complex shape). Distribution of thickness (mm)

0.9

0.85

0.8 0.7

0.7

0.66

0.6

0.64

0.73

0.72

0.68

0.75

0.7

0.5 0.4 0.3 0.2 0.1 0

0

5

10

15

20

25

30

35

40

Distance from the center of the cup (mm)

Figure 12. Distribution of thickness of blank for galvanized steel (complex shape). 4.1 The Experiment IV In this situation, it is used with a thickness of 0.7 mm and with different fluid pressure, also speed press (5) mm/min (speed very slow) as shown in Table 7.

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Table 7. The experiment IV Metal galvanized steel

Thickness (mm) 0.7

Fluid Pressure Press pressure (N/mm2) (N/mm2) 2.4 3

In this state, we get a cup with a defect (Tearing defect) shown in Figure 13.

Figure 13. Tearing defect in experiment IV The blank holder force is exceptionally strong because of the high fluid pressure pulling on it, and the final result had a tearing problem. Tearing happens when the cup walls are fractured during the hydromechanical deep drawing process. Axial (longitudinal) tension causes it, which is aggravated by regional cup wall thinning. The blank holder force is vital to the operation and helps to ensure defect-free goods. When the fluid pressure increases, the blank holder force increases as well. To execute the hydromechanical deep-drawing process, it is discovered in all four trials that raising the sheet metal thickness demands a high fluid pressure. The rise in press pressure is accompanied by an increase in sheet thickness. 5. Conclusions 1- When the thickness of the sheet metal is increased, the sheet metal hydrodynamic shaping becomes more difficult to accomplish. The pressure necessary to prevent Wrinkling grows quite significant, and it is impossible to accomplish with the lab setup. 2- The blank holder force (BHF) should be selected with attention. A low number for the blank holder force will result in the development of wrinkling faults in the hemispherical cup or complex cup, while a large value would result in the rupture of the finished goods. 3- Fluid pressure must match the blank holder force to generate a defect-free result. It may also examine the impact of friction coefficient, die-to-punch clearance, pressure pre-bulging, die radius, punch radius, and punch speed on blanking operations. References [1]

L. M. Smith, Hydroforming: Hydropiercing, end-cutting, and welding. Woodhead Publishing Limited, 2008.

[2]

S. Thiruvarudchelvan and M. J. Tan, “Fluid-pressure-assisted deep drawing,” J. Mater. Process. Technol., vol. 192–193, pp. 8–12, Oct. (2007)

[3]

K.Nakamura, T.Nakagawa, and K.Suzuki, “Counter-pressure deep drawing and its application in the forming of automobile parts,” J. Mater. Process. Technol., vol. 23, no. 3, pp. 243–265, Nov. (1990)

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[4]

L. Lang, T. Li, D. An, C. Chi, K. B. Nielsen, and J. Danckert, “Investigation into a hydromechanical deep drawing of aluminum alloy—Complicated components in aircraft manufacturing,” Mater. Sci. Eng. A, vol. 499, no. 1–2, pp. 320–324, Jan. (2009)

[5]

S. H. Zhang and J. Danckert, “Q. Wang, Hydromechanical deep-drawing, New Technol. New Process. 5 (1994) 23–24 (in Chinese).,” J. Mater. Process. Technol., vol. 83, no. 1–3, pp. 14– 25, Nov. (1998)

[6]

K. Nakamura and T. Nakagawa, “Sheet Metal Forming with Hydraulic Counter Pressure in Japan,” CIRP Ann., vol. 36, no. 1, pp. 191–194, Jan. (1987)

[7]

Investigation of Hydrostatic Counter Pressure Effect on Thickness Distribution in Hydromechanical Deep Drawing Process with Hemispherical Punch.

[8]

F. Jia, J. Zhao, L. Luo, H. Xie, and Z. Jiang, “Experimental and numerical study on micro deep drawing with aluminum-copper composite material,” Procedia Eng., vol. 207, pp. 1051–1056. (2017)

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 49-56 doi:10.4028/p-8umjsp © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-30 Revised: 2022-08-01 Accepted: 2022-09-12 Online: 2022-12-26

Investigation of Fatigue Behavior for Al/Zn Functionally Graded Material Al-Hadrayi Ziadoon M.R1,a*, Ahmed Naif Al-Khazraji2,b and Ahmed A. Shandookh3,c Mechanical Engineering Department, University of Technology, Baghdad, Iraq and Materials Engineering Department, Faculty of Engineering, University of Kufa, Najaf, Iraq

1

Mechanical Engineering Department, University of Technology, Baghdad, Iraq

2

Mechanical Engineering Department, University of Technology, Baghdad, Iraq

3

[email protected]/[email protected], b [email protected], [email protected]

a

*Corresponding author. Keywords: Fatigue life, functionally graded materials, Ansys program and mixing ratio.

Abstract. This paper presented an experimental and numerical study of functionally graded materials made by the permanent casting method and in three models with different mixing ratios between aluminum and zinc alloys (FGM1, FGM2, and FGM3) as in figure 1. In the permanent casting process, three models of the functionally graded material were produced and mechanical tests were conducted on them such as tensile and hardness tests, and the behavior of tensile strength, yield strength, elastic modulus, and fatigue was analyzed on them. The fatigue test was conducted at six levels of load and at room temperature. Simulations were carried out for the three models and a simulated fatigue test for the functionally graded material into the Ansys program. The results of the fatigue test showed a clear effect of the different mixing ratios of the functional-grade material. As well as the numerical results were, close to the experimental results. There was an improvement in the fatigue life compared of FGM3, by 23% than FGM2. In addition, the fatigue life of the FGM3 of 11% higher than from the FGM1 model. In addition to that, which is important, the improvement in the fatigue life characteristics of the third type was 36% compared to the alloys from which the functionally graded materials were made. Introduction Most of the failures in service for parts that are made of metal, are due to fatigue. As a result of the fluctuating stresses that occur in a metal structure at a certain point or points and a structural change occurs, these fluctuating stresses reach a peak with a sufficient number in the crack and may cause fracture, this process is called fatigue [1-3]. In a fatigue failure, the material fails under repeated cyclic or alternating stresses that would not fail only once. The prevention of fatigue failure is a major concern for engineers in many industries, such as transportation and power generation. Fatigue of critical components can lead to economic losses as well as life-threatening situations. There is a constant change in loads and stresses. Functionally graded materials are among the most important newly discovered advanced engineering materials and are in the process of studies and research. This material has variable and gradual properties depending on the application and method of manufacture. It consists of two different materials in which the components are gradient in order to give the best mechanical properties, for example fatigue life The manufacturing methods of this advanced material are different, including centrifugal and permanent casting, physical and chemical evaporation, powder technology, and 3D printing [5-11]. The use of Extending the finite element method (XFEM) in estimating fatigue life of functionally graded materials. The XFEM was that to simulate fatigue cracks growing in alloy/ceramic functionally graded materials (FGMs)[12]. In this study, functionally graded Ti–6Al–4V mesh structures are studied under identical bulk stress conditions to determine their fatigue behavior. Fatigue cracks begin in the weakest constituent, then spread until they fail structurally [13]. Microstructural anisotropy was investigated on fatigue crack growth behavior of laser powder bed

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fusion-fabricated functionally graded Inconel 718. A variety of nongraded (NG) was produced using a variety of manufacturing parameters, including low and high laser powers [14]. A study of alternating stress fatigue characteristics of Inconel 718 samples additively manufactured was conducted using experimental and numerical methods [15]. A porous titanium biomaterial was investigated for fatigue properties based on stress ratios. Different stress ratios were employed in the study, smooth and notched samples were subjected to constant amplitudes. It has been founded that stress ratio when it was increasing, the S-N curve has been moved upward [16]. Therefore, in this paper, a functionally gradient material manufacturing process has been used in three innovative gradient models. The functionally graded materials are manufactured using a permanent casting method, using weight ratios to ensure the grade of aluminum with zinc. The samples have been subjected to variable dynamic loads, as well as numerically and experimentally variable parameters. An Experimental Procedure Preparation of materials and samples In this work, the functionally graded materials which were aluminum-zinc alloys were fabricated which was provided from the local market. The manufacturing method was by casting and using an iron mold with dimensions (21 cm) in length and (2 cm) in diameter. After the manufacturing process of three models with different weight ratios, in order to avoid the disadvantages of casting, the annealing process was carried out for all samples. Specimens are shaped by turning to standard dimensions and according to ASTM. Fig.1 presented the flowchart for sample preparation and fatigue examination. 100% Zn

100% Zn

100% Zn

50%Zn, %50%A

70%Zn, %30%Al

30%Zn, %70%Al

50%Zn, %50%A

30%Zn, %70%Al

70%Zn, %30%Al

100%Al FGM2

100%Al FGM3

100%Al FGM1

Casting process Molted Zn

Zn Zn/Al

Molted Al

Zn/Al Al

Tensile test

ASTM (FGM samples)

Lathe process

Fatigue test

Figure 1. Flowchart of Preparation of materials, samples and tests

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After the turning process that was carried out on the functionally graded materials, the tensile samples were formed on the basis of ASTM E8M [17], and the fatigue samples were formed on the basis of ASTM 606-80 [18]. Tensile test As shown in Fig. 2, tensile testing was performed on a computerized universal testing machine type (WDW - 100E). ASTM E8M standard was followed for the preparation of the samples, as shown in fig 3. All tests were carried out at a constant rate of 1 mm/min until failure occurred. In order to satisfy an additional accuracy requirement, three readings from each FGM type were averaged. Results were shown in Table 1.

Figure 2. Setup for the tensile test.

Figure 3. Tensile Samples manufactured by casting.

Table 1. Material tensile test results. Material FGM1 FGM2 FGM3

σu (MPa) 355 344 377

Property σy (MPa) 242 230 260

E (GPa) 77 74 79

Fatigue Test The specimens were tested using a cantilever bending fixture similar to that type WP 140 GUNT based on their critical (i.e. failure) locations. On one side, a rotating sample was clamped and loaded with a concentrated force which reach to a maximum capacity of (1 KN) at a constant frequency of (50Hz). Through the experiment, a sinusoidal cyclic load was applied at a stress ratio R = -1 (minimum load/maximum load). As a result of a given number of load cycles, alternate bending stress was formed in the cylindrical sample. Fatigue of the material will rupture the sample with the curve of S-N of fatigue behaviour of FGM. Diagrams of the FGM specimen and the reversed fatigue testing machine were shown in figures 4 and 5. As shown in equation (4), alternating bending stress was determined using bending moment values. In the case of constant amplitude loads, stress ratio (R) can be calculated as follows [1]: R=

(For reversed bending, R= -1)

(1)

Based on the load and the lever arm, the bending moment (Mb) was calculated as follows: Mb = F. a

(2)

(3) As a result of the section modulus Ib of the sample, the alternating stress amplitude can be calculated as follows:

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(4) Where, σa is an alternating maximum stress (MPa), F is that applied force, their uint (N), a is the arm of bending as shown in fig.6 , = 106 and d is the diameter of sample =7.9

Figure 4. ASTM-specific dimensions of test samples (all measurements in mm) [18].

Figure 5. Machine of fatigue test

Figure 6. Machine of fatigue test

A stress-life curve illustrates fatigue data graphically. An alternating stress amplitude and cycle to failure are represented by a fatigue life function. S-N curves are often expressed analytically by the Basquin relation, for finite life (low or high cycle fatigue). By using this technique, the Basquin curve can be applied (equ. 5) [19] to life predictions without much information about the material: (5) is the cycles number to failure , σa is an alternating stess, and A,B are constants which Where, depend on the type of material and the geometry. In this equation (5) , coefficient A is the intercept between the stress-life curve, while coefficient B is the fatigue strength exponent. To calculate the coefficients, take the power law and find its logarithm. It's also possible to calculate the fatigue limit value using the fatigue life formula at 106 cycles, even though it's often difficult to determine the value on the S-N curve at this point. FEM Model A finite element method (FEM) can be used to simulate various analysis and solve any mechanical problem, including fatigue, creep, and structural problems. The fatigue analysis for functionally gradient materials was conducted using ANSYS. The elements were composed of solid hexahedrals (solid187), with 20 nodes. Modeling was conducted using the mechanical properties of the selected material (Modulus of elasticity, Yield stress, Tensile strength, etc.) and stress life data obtained from reversed bending experiments. Based on the model geometry shown in Figure 7.a and Figure 7 .b, the element mesh was generated. Based on the maximum loading condition, the boundary conditions of each load type are shown in Figures 7c, 7.d.

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b

a

c

d

Figure 7. Geometry, Mesh, boundary condition, and type of loading for strees life model apporoach

Results and Discussion This study investigated the fatigue lives of circumferentially round specimens subjected to reversed bending (R= -1) loadings with various models and gradient indices. FEA has been utilized for fatigue analysis of cylindrical specimens subjected to completely reversed bending using the stress life approach. Fatigue life and behavior of functionally graded materials presented on S-N curved shape. S-N curve The experimental and numerical results were presented in Figure 8. The results were in the form of a curve representing the alternating applied stress computed from the above-mentioned equations and that cycles to failure. As mentioned, there are few research studies on the behavior of functionally graded materials in fatigue, especially metal ones. In this paper, the behavior of functionally graded materials in fatigue was studied. The S-N curve was for three models that were experimentally and numerically represented. Through these results, it was noted that the behavior of the third type of material has endured a number of cycles that reached more than one million and two hundred thousand cycles to fail. This effect and the difference in the number of cycles is due to the reason for the different mixing ratio on which the materials were manufactured. The applied alternating stress has started from 100 MPa and has six levels, which samples used were six until it reached 350 MPa. In Table 2, fatigue life equations using the least square method are presented for loading mode. The error rate between the numerical results did not exceed 9%. Where the endurance limit for fatigue of the third type numerically reached 164.8 MPa, while experimentally 149.67 MPa, and on the basis of statistical calculations, the error rate is 9%, which is the highest among the three models. It also behaves like a curve and points completely different from familiar materials such as metals. Through the results, there was also a clear improvement in the mechanical

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properties as well as variable, and this is what distinguishes the functionally graded materials. The different behavior of curves and points is due to the different mixing ratio.

Figure 8. An experimental and numerical S-N curve for three models of FGMs Table 2. Fatigue life equations (experimentally and numerically). Material Al alloys Zn alloys FGM1 FGM2 FGM3

Fatigue life equation (Exp.) 33257 X-0.409 35829 X-0.419 121343 X-0.493 28561 X-0.398 3*106 X-0.717

Fatigue life equation (Num.) 36089 X-0.408 38990 X-0.418 80792 X-0.458 30631 X-0.399 5*106 X-0.747

Fatigue limit (Exp.) (MPa) 116.9 109.7 133.66 116.89 149.68

Fatigue limit (Num.) (MPa) 128.63 121.04 144.34 123.64 164.8

Error % 9.1 9.36 7.4 5.45 9.1

Figure 9. Experimental and Numerical values of fatigue limit

Conclusions An experiment and FEA analysis were used to investigate the fatigue life of specimens that were manufactured by the casting method under constant amplitude load under stress life load and high cycle fatigue (HCF). To verify the accuracy of the experimental solution, a comprehensive comparative study was performed with numerical techniques. This paper can be summarized as follows:

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• Experimentally, samples of functionally graded materials were fabricated in three models by casting method (FGM1, FGM2, and FGM3). • Through Basquin’s equation, the fatigue life equation was calculated experimentally and numerically, and the fatigue limit value was known. • A numerical model was built and implemented by the Ansys program. • The experimental and numerical results were somewhat close, and the results showed that the effect of the mixture ratio and the change of properties of the functionally graded materials, the improvement in the value of the fatigue limit of the third model was 23% and a higher value for the fatigue limit, which amounted to 149.67 MPa experimentally, and 164.8 MPa numerically. • The third type of functionally graded material is the best, as the results show with the original alloys or the other two models Acknowledgement This work was by supporting the University of Technology/Mechanical Engineering Department and University of Kufa/Faculty of Engineering/Materials Engineering Department, Iraq, Baghdad and Najaf respectively. References [1]

Njim, Emad Kadum, Sadeq H. Bakhy, and Muhannad Al-Waily. "A Study on the Influence of Stress Ratio and Loading Mode on Fatigue Life Characteristics of Porous Functionally Graded Polymeric Materials." International Journal of Energy and Environment 12.2 (2021): 115-128.

[2]

Njim, Emad, Sadeq H. Bakhi, and Muhannad Al-Waily. "Experimental and Numerical Flexural Properties of Sandwich Structure with Functionally Graded Porous Materials." Engineering and Technology Journal 40.1 (2022): 137-147.

[3]

Shareef, Mahdi, Ahmed N. Al-Khazraji, and Samir A. Amin. "Flexural Properties of Functionally Graded Polymer Alumina Nanoparticles." Engineering and Technology Journal 39.5 (2021): 821-835.

[4]

Emmerich, Thomas, Robert Vaßen, and Jarir Aktaa. "Thermal fatigue behavior of functionally graded W/EUROFER-layer systems using a new test apparatus." Fusion engineering and design 154 (2020): 111550.

[5]

Atiyah, Alaa A., Saad BH Farid, and Dheya N. Abdulamer. "Fabrication of ceramic-metal functionally graded materials." Eng. Technol. J 31.3 (2013): 513-525.

[6]

Atiyah, Alaa Abdulhasan. "Fabrication, Characterization and Modeling of Al2o3/Ni Functionally Graded Materials." Materials Engineering Department, University of Technology/Baghdad. Eng & Tech. Journal 32 (2014).

[7]

Ataiwi, Ali H., Alaa A. Atiyah, and Marwan A. Madhloom. "Mechanical Characteristics of Prepared Functionally Graded Cylinder by Centrifugal Casting." Enggineering & Technical Journal 32 (2014).

[8]

Njim, Emad Kadum, Muhannad Al-Waily, and Sadeq H. Bakhy. "A review of the recent research on the experimental tests of functionally graded sandwich panels." Journal of Mechanical Engineering Research and Developments 44.3 (2021): 420-441.

[9]

Shareef, Mahdi MS, Ahmed Naif Al-Khazraji, and Samir Ali Amin. "Flexural Properties of Functionally Graded Silica Nanoparticles." IOP Conference Series: Materials Science and Engineering. Vol. 1094. No. 1. IOP Publishing, 2021.

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[10] Oleiwi, Jawad K., Rana A. Anaee, and Lec Sura A. Muhsin. "Fabrication, characterization and Physical Properties of Functionally Graded Ti/HAP bioimplants." Wulfenia J 22.7 (2015): 336-348. [11] Oleiwi, Jawad K., Rana A. Anaee, and Sura A. Muhsin. "Physical and Mechanical Properties Estimation of Ti/HAP Functionally Graded Material Using Artificial Neural Network." Engineering and Technology Journal 34.12 Part (A) Engineering (2016). [12] Bhattacharya, S., Indra Vir Singh, and B. K. Mishra. "Fatigue-life estimation of functionally graded materials using XFEM." Engineering with computers 29.4 (2013): 427-448. [13] Wang, Q.S., et al. "Mechanistic understanding of compression-compression fatigue behavior of functionally graded Ti–6Al–4V mesh structure fabricated by electron beam melting." Journal of the Mechanical Behavior of Biomedical Materials 103 (2020): 103590. [14] Ghorbanpour, Saeede, et al. "Effect of microstructure induced anisotropy on fatigue behaviour of functionally graded Inconel 718 fabricated by additive manufacturing." Materials Characterization 179 (2021): 111350. [15] Nezhadfar, P.D., Alexander S. Johnson, and Nima Shamsaei. "Fatigue behavior and microstructural evolution of additively manufactured Inconel 718 under cyclic loading at elevated temperature." International Journal of Fatigue 136 (2020): 105598. [16] de Krijger, Joep, et al. "Effects of applied stress ratio on the fatigue behavior of additively manufactured porous biomaterials under compressive loading." Journal of the mechanical behavior of biomedical materials 70 (2017): 7-16. [17] ASTM international. (2016). E8/E8M-16a: Standard Test Methods for Tension Testing of Metallic Materials. ASTM international. [18] ASTM, E. "606–80 Constant-Amplitude Low-Cycle Fatigue Testing Annual Book of ASTM Standards." Section 3 (1986): 656-673. [19] Qasim, Bader, and K. Njim Emad. "Experimental and Numerical study of influence the loading mode on Fatigue Life in Notched Steel Beam." International Journal of Scientific & Engineering Research 5 (2014).

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 57-65 doi:10.4028/p-50kx64 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-07-02 Revised: 2022-09-25 Accepted: 2022-09-26 Online: 2022-12-26

Alumina Nano Powder Impact on Electrical Discharge Machining of Titanium Alloy Wire Farook Nehad Abed1a Faculty of Mechanical, Manufacturing Engineering, Imamaladham University College, Baghdad Iraq

1

[email protected]

a

Keywords: Nano powder(AL2O3), Recast layer, MRR, ANOVA.

Abstract: WEDM is an unconventional method of thermal machining that produces products with irregular shapes. The results of milling titanium (TI-6242) under various machining conditions that affect the WEDM process are provided. Pulse on time (Ton), pulse off time (Toff), peak current (Ip), voltage (V), wire tension (Wt), and wire feed are all considered machining parameters (Wf). They are established using an experimental design and the Box–Behnken approach to optimize the machining factors. The optimization goal is to attain the highest Material Removal Rate (MRR) and the least amount of recast layer (RL). ANOVA determines the most important factor. Moreover, a regression analysis is used to predict MRR and RL based on defined machining parameters. Ton = 120s, Toff = 50s, Ip = 11 A, Wt = 1kg, and V = 50 volt are the optimal regulatory factors for obtaining the highest MRR, depending on the consequences. Ton = 130s, Toff = 60s, Ip = 12 A, Wt = 3 kilogram, and V= 30 volt are the best control variables for achieving the lowest RL. Ton = 120s, Toff = 50s, Ip=10 A, and Wt=1kg are thought to be the ideal control parameters for achieving minimum RL and greatest MRR. In ideal machining circumstances, the microstructure of the machined surface exhibits a recast layer on the machined surface. Introduction Non-Traditional Machining Processes (NTMPs) replace tools with direct forms of various energy. Traditional processes are inferior to MPs. Because there is no physical, they can manufacture metallic and nonmetallic materials with minimal workpiece-tool contact, regardless of their hardness or strength. Furthermore, NTMP can produce complicated, elaborate shapes with great precision [1]. Wedm is a type of non-traditional thermal machine work where the material is on the work piece is removed is a spark that occurs Throughout the existence of a thin dielectric fluid layer on the work piece and the wire. With intricate geometries, WEDM is frequently employed in the aerospace, automotive, and medical industries [2 ,3]. Ductile titanium is a kind of titanium that is characterized by spherical graphite nodules in its structure. Ductile titanium (TI-6242) is a nodular iron having a microstructure that is predominantly ferritic and low alloy steel-like mechanical characteristics[4]. It possesses excellent improved strength, machinability, and castability and toughness, improved low molding performance and resistance to abrasion. These characteristics enable it to be employed in various Pipes, automobile wheels, gearboxes, pump housings, wind power system frames, and several more components other industrial applications. [5] Optimization of the WEDM process has been the subject of several research. When milling AISI304, B. Mathew et al. used Box–Behnken. Using a gray relational analysis, you can determine the ideal machining parameters[6]. The material removal rate reduced as the pulse on-time rose, indicating that it was the essential characteristic. The roughness of the surface increased [7]. improved WEDM cutting conditions, and D2 tool steel was used for better surface roughness and material removal. The experimental approach made use of the Box-Benkhen technique, and desirability functions were used for multiple parameterizations. The most influential criteria in influencing the surface roughness found observed to be the pulse on-time and pulse off time. On the other hand, the material removal rate was strongly influenced by the pulse of time [8]. The Box–

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Behnken and ANOVA approaches were used to improve the process variables to improve Inconel 625's surface roughness. As the pulse on time grew, the surface roughness increased and dropped as the pulse on-time decreased, demonstrating that the pulse current is a non-essential property [9]. While “cutting steel 300, R. Sen et al. developed neural network models to estimate cutting speed, surface roughness, and wire consumption. The outcome revealed that the fuzzy logic methodology was a superior option to parametric” optimization [10]. Box–Behnken for machining AISI 1045 steel. Ton had the most significant impact, followed by Toff [11]. optimized the WEDM of AISI304 stainless steel using statistical approaches combined with artificial intelligence techniques and soft computing. Despite attaining a decreased material removal rate, reduce pulse current and pulse on time, and increase pulse on time to reduce surface roughness [7]. used Box–Behnken, and regression equations to investigate MRR and RL based on WEDM process characteristics. Ton was the most critical metric [12]. studied the texture production method and machinability performance of textured and regular Tungsten Carbide tool inserts. The cutting force and RL were optimized using Box–experimental Behnken's design. According to the findings, Textured inserts reduce cutting forces and RL. [13]. Despite its importance and applicability, no previous research has looked into the effects of various machining parameters when cutting ductile titanium. This research aims to optimize when cutting ductile materials. The essential machining parameters are Ton, Toff, Ip, V, and S into the titanium (TI-6242) to achieve the highest MRR and lowest RL. The Box–Behnken method is used with ANOVA and regression analysis in this study's optimization methodology. Furthermore, the response optimization is used to identify the optimal control factor combination that produces the desired result, the RL and MRR ideals. Minitab software is used to do the statistical analysis required for this project. Experimental Configuration To reduce experimental trials, the Box–Behnken technique is utilized to build the experimental design [14,15, 16]. Find the best combination of machining factors yields the lowest RL and highest MRR. Five key control aspects are taken into account. The control factors and their levels are listed in Table 1. Each factor level value is chosen based on pilot testing. As a result, the experimental work is conducted using missed levels. Table 3 shows the experimental design, which was done using Minitab software. Table 1. The control factors and their levels Factor Factor Unit Level 1 Level 2 name symbol Pulse on Ton µm 120 130 time Pulse off Toff πm 50 60 time Peak Ip Ampere 10 12 current Voltage V Volt 20 50 Wire Wt Kg 1 3 tension Wire feed Wf M 1 3

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Table 2. Control and response factor experimental design matrix Response factor Run no. Ton Toff Ip V Wt wf MORE 1 125 60 11 35 1 1 3.89 2 125 55 10 50 3 1 1.69 3 125 55 12 20 3 5 6.01 4 125 50 12 35 1 3 7.81 5 130 55 12 35 3 5 7.37 6 120 55 10 35 3 5 1.36 7 125 55 10 20 3 5 1.31 8 130 55 11 20 5 3 1.87 9 130 55 11 20 1 3 3.53 10 125 50 11 35 1 1 4.93 11 125 50 12 35 5 3 6.1 12 125 55 11 35 3 3 2.54 13 125 55 10 50 3 5 1.81 14 125 55 11 35 3 3 3.53 15 120 55 11 20 1 3 2.39 16 130 60 11 50 3 3 3.08 17 120 50 11 50 3 3 1.33 18 125 55 10 20 3 1 2.87 19 125 55 12 50 3 1 6.01 20 125 60 12 35 1 3 8.14 21 120 60 11 20 3 3 1.93 22 125 60 10 35 5 3 1.87 23 120 55 11 50 5 3 1.81 24 125 50 11 35 5 1 1.93 25 125 55 11 35 3 3 3.87 26 130 50 11 50 3 3 2.11 27 130 60 11 20 3 3 2.05 28 125 60 11 35 1 5 4.05 29 120 55 12 35 3 1 6.61 30 125 55 11 35 3 3 2.88 31 125 50 10 35 1 3 2.57 32 120 55 12 35 3 5 7.11 51 52 53 54

125 125 120 125

50 55 50 60

10 11 11 11

35 35 20 35

5 3 3 5

3 3 3 5

1.54 3.66 1.94 5.81

RL 42.33 33.84 49.89 52.78 51.21 33.87 32.12 34.22 43.89 37.93 50.23 48.32 33.67 46.89 40.68 48.95 44.54 35.67 49.95 60.34 45.23 35.87 43.89 36.87 44.12 45.93 46.75 39.38 53.43 45.65 31.85 52.45 37.43 43.87 44.53 42.75

JIANGSU SANXING electric spark wire cutting machine is used for experiments (Model DK7750AZ). The 100x100x10-mm workpiece is ductile titanium (TI-6242). Table 3 shows the material's chemical composition. The cutting profile is a 1010 x 11 mm cuboid. The tool is 0.25 mm cote brass wire. Deionized water is utilised between tool and work piece. Table 3. Chemical composition of Ti-6242 Element Al Max.Weight(%) 6

Sn 2

Zn 4

Mo 2

Si 0.13

O2 0.15

C 0.08

N2 0.05

H2 Ti 0.0125 85.3

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Fig. 1. Concurrent processing of the workspace and experimental work. The MRR and RL are the process outputs that are considered when determining the best process parameters. The MRR is a precise measure of process profitability and cutting effectiveness because it represents the amount of material removed per unit. Furthermore, high machining quality is associated with good surface roughness [17]. Discussion and Result A. Graphs of Response The response graphs are used to see how The response variables are affected by each control factor level [18]. The MRR and the RL's reaction graphs are shown in Figure 2. The MRR and the RL are influenced mainly by IP. The response graph for the MRR is shown in Figure 2 (a). When Ip and V go up, the MRR goes up, but when Toff goes up, the MRR goes down. When the Ton is increased, the MRR grows until it reaches 64 seconds, at which point it decreases because the discharge is unsteady compared to the thickness of the workpiece. The MRR increases as S until it reached 50 mm per minute. It falls dramatically. The response graph for the RL is shown in Figure 2 (b). The RL is increased by increasing V, Ton, Ip, and decreasing Toff. The RL reduces when S is reduced until it hits 30 mm/min, which increases due to the increase. The wire spends more time in contact with the workpiece, resulting in a rougher surface.

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Fig. 2. Response diagrams with nano for (a) MRR and (b) RL. B. Anova Individual parameters cannot be judged or calculated using the Box–Behnken method, but ANOVA can reliably quantify individual parameter contributions . It illustrates how the control factors affect the response factors in statistical analysis. The ANOVA for the MRR and the RL is shown in Table 5. Because the P-value is less than 0.05, The MRR is significantly affected by all control parameters. Furthermore, because it obtains the most significant proportion of contributions (49.7%), Ip is a major influencing factor, V, Toff, Ton, and S are then mentioned was evident to the RL that Ip is the most crucial influencing element, accounting for 32.3 percent of the total. Because their P-values are more than 0.05, Toff, Ton, S, and V are insignificant. The contribution % of ANOVA for the MRR and RL is shown in Figure 3. Table 4. This variable represents the ANOVA for the MRR and the RL. ANOVA for the MRR Source Model A-pom B-Poff C-IP D-SPV E-wf Ft Lack of Fit Pure Error Cor Total Source Model A-pom B-Poff

Sum of DF An adjusted squares sum of squares 210.10 14 15.01 1.65 1 1.65 1.61 1 1.61 149.25 1 149.25 1.23 1 1.23 3.86 1 3.86 0.92 1 0.92 8.26 34 0.24 1.86 5 0.37 220.22 53 ANOVA for the RL Sum of DF An adjusted squares sum of squares 2650.68 17 155.92 16.24 1 16.24 6.43 1 6.43

Fvalue 57.81 6.37 6.19 574.92 4.75 14.88 3.56 0.65

P-value

Fvalue 59.03 6.15 2.43

P-value

< 0.0001 0.0158 0.0172 < 0.0001 0.0354 0.0004 0.0666 0.7941

< 0.0001 0.0180 0.1275

significant

not significant

significant

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C-IP D-SPV E-wf Ft Lack of Fit Pure Error Cor Total

Advanced Materials and Production Technologies

2140.05 1.05 9.07 2.62 70.02 25.08 2745.77

1 1 1 1 31 5 53

2140.05 1.05 9.07 2.62 2.26 5.02

810.15 0.40 3.43 0.99 0.45

< 0.0001 0.5324 0.0722 0.3259 0.9227

not significant

C. Regression Analysis Regression equations can help forecast the process output parameters instead of concluding experiments at matrix levels. It estimates the control-response relationship predicting [22]. Regression equations (1) and (2) can forecast MRR and RL. 𝑀𝑀𝑀𝑀𝑀𝑀 = +166.55285 + 0.052500 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝 − 0.48321 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 − 28.19656 ∗ 𝑖𝑖𝑖𝑖 − 0.19023 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 − 2.34719 ∗ 𝑤𝑤𝑤𝑤 − 6.73573 ∗ 𝑤𝑤𝑤𝑤 + 6.61667𝐸𝐸 − 003 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 + 0.028000 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑤𝑤𝑤𝑤 + 0.073125 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑤𝑤𝑤𝑤 + 0.15250 ∗ 𝑖𝑖𝑖𝑖 ∗ 𝑤𝑤𝑤𝑤 + 0.015083 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 ∗ 𝑤𝑤𝑤𝑤 + 0.20219 ∗ 𝑤𝑤𝑤𝑤 ∗ 𝑤𝑤𝑤𝑤 + 1.37422 ∗ 𝑖𝑖𝑖𝑖2 − 2.91181𝐸𝐸 − 003 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠2. (1) 𝑅𝑅𝑅𝑅 𝑤𝑤𝑤𝑤𝑤𝑤ℎ𝑜𝑜𝑜𝑜𝑜𝑜 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 = +176.82758 − 2.81600 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝 − 5.69342 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑓𝑓 + 14.09854 ∗ 𝑖𝑖𝑖𝑖 − 2.37898 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 + 63.61146 ∗ 𝑤𝑤𝑤𝑤 + 2.52500 ∗ 𝑤𝑤𝑤𝑤 + 0.053300 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 + 0.027275 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 − 0.30187 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑤𝑤𝑤𝑤 − 0.013567 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 − 0.13025 ∗ 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ∗ 𝑤𝑤𝑤𝑤 − 1.55187 ∗ 𝑖𝑖𝑖𝑖 ∗ 𝑤𝑤𝑤𝑤 + 0.051042 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠 ∗ 𝑤𝑤𝑤𝑤 + 0.39656 ∗ 𝑤𝑤𝑤𝑤 ∗ 𝑤𝑤𝑤𝑤 − 6.04877𝐸𝐸 − 003 ∗ 𝑠𝑠𝑠𝑠𝑠𝑠2 − 0.82102 ∗ 𝑤𝑤𝑤𝑤2 − 0.64665 ∗ 𝑤𝑤𝑤𝑤2. (2)

The interaction MRR and RL values computed using the regression equations are shown in Table 4. For the MRR and the RL, Figure 3 compares experimental and expected findings. There was no substantial difference between the observed and projected values, which was obvious.

a

b

Fig. 3. A comparison of experimental and interactions values of (a) MRR and (b) RL with nano.

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A. MRR And RL Optimization. Minitab responsive optimizer shows how different parameters alter model replies [19]. As illustrated in Figure 4, it's used to find the best control variables for improving the MRR and the RL simultaneously. Ton = 120s, Toff = 50s, Ip = 10 A, Wt = 1kg, and V = 20 volt are the best control factor combinations for achieving improved RL and MRR. Based on regression equations (1) and (2), the anticipated MRR and RL are 12.4219 and 4.3672, respectively, as shown in Figure 4. A confirmation experiment is carried out using the best control parameters to improve RL and MRR. The experimental and anticipated MRR and RL values in the optimal machining setup are shown in Table 6. A drop in the MRR led to an improvement in RL. In ideal machining circumstances, The microstructure of a machined surface is shown in Figure 4. It's possible to see a thin recast layer on top of the machined surface. As a result, this research aids the industry in achieving higher MRR, which leads to a shorter machining duration and lowers the product's net cost. In addition, a lower RL usually means fewer finishing requirements following machining. Table 5. The measured and anticipated RL without nano values and RL with nano values under ideal conditions. Responses MORE RL with nano

Experimental 1.1mm 29.37 µm

Prediction 7.93mm 58.63 µm a). Low (pulse on time =125µm, pulse off time =50µm, peak current=10A, spark gap voltage= 35V)

RL= 29.37 µm

RL=58.63 µm RL=58.63µm

b). high (pulse on time =125µm, pulse off time =60µm, peak current=12A , spark gap voltage= 20V) Figure 4. The machined surface microstructure. Conclusions An optimization strategy was used to attain the largest MRR and minimal RL with WEDM of ductile titanium, combining the Box–Behnken technique with ANOVA and regression analysis (TI6242). The experimental design was carried out using the Box–Behnken technique, and selected

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control parameters Ton, Toff, Ip, V, and S are just a few examples. Each control factor's effect on the response parameters was revealed using the response graph. The ANOVA approach was used to identify the most important factor influencing machining performance. For prediction and forecasting, The link between the control and response was studied using regression analysis parameters. The response optimizer was used to find the best set of control parameters for optimizing both the RL and the MRR at the same time. The IP, it can be inferred, is an influential factor that directly affects both MRR and RL. The lower the Ip and V, the higher the Ip, the better Toff, and the higher the MRR and RL values. Ton=125s, Toff=60s, IP =12 A, Wt =1kg, and V=20 volt is the best control factor combinations for achieving the lowest RL. Ton=130s, Toff=50s, Ip=12 A, Wt= 2kg, and V= 35 volt are the ideal control parameters for achieving the greatest MRR. Ton = 125s, Toff = 60s, Ip = 12 A, Wt = 2kg, and V = 30 volt are the best control variables for achieving greater RL and MRR combined. In ideal machining circumstances, the microstructure of the machined surface exhibits a recast layer on the machined surface. This study boosts MRR, resulting in a shorter machining period, lowering the product's net cost. In addition, a lower RL usually means fewer finishing requirements following machining. Future research must develop a computer-aided process optimization system for WEDM using finite element modeling. References [1] A. Bin Sapit et al., “Enhancement of the performance surface roughness of wire cutting process by additives nano [AL2O3],” Period. Eng. Nat. Sci., vol. 8, no. 2, pp. 933–941, 2020. [2] S. Prabhu and B. K. Vinayagam, “Nano surface generation of grinding process using carbon nano tubes,” Sadhana - Acad. Proc. Eng. Sci., vol. 35, no. 6, pp. 747–760, 2010 [3] A. Pramanik et al., “Understanding the wire electrical discharge machining of Ti6Al4V alloy,” Heliyon, vol. 5, no. 4, p. e01473, 2019 [4] S. Rajamanickam and J. Prasanna, Analysis of recast layer, wear rate and taper angle in micro-electrical discharge machining over Ti–6Al–4V. Springer Singapore, 2019. [5] K. D. Chattopadhyay, S. Verma, P. S. Satsangi, and P. C. Sharma, “Development of empirical model for different process parameters during rotary electrical discharge machining of copper-steel (EN-8) system,” J. Mater. Process. Technol., vol. 209, no. 3, pp. 1454–1465, 2009. [6] M. ZHANG et al., “Surface characterization and tribological performance analysis of electric discharge machined duplex stainless steel,” Int. J. Adv. Manuf. Technol., vol. 11, no. 8, pp. 1–14, 2020. [7] B. Mathew, B. A. Benkim, and J. Babu, “Multiple Process Parameter Optimization of WEDM on AISI304 Using Utility Approach,” Procedia Mater. Sci., vol. 5, pp. 1863–1872, 2014. [8] A. Bin Sapit, S. Kariem Shather, and F. Nehad Abed, “Enhancement of the performance surface roughness of wire cutting process by additives Nano [AL2O3],” vol. 8, no. 2, pp. 933–941, 2020. [9] S. K. Shather, A. F. Ibrahim, and N. Jammal, “Influence of EDM Parameters on the Appearance of Recast Layer,” Eng. Technol. J., vol. 35, no. December, pp. 694–700, 2017. [10] M. Manjaiah, R. F. Laubscher, A. Kumar, and S. Basavarajappa, “Parametric optimization of MRR and surface roughness in wire electro discharge machining (WEDM) of D2 steel using Taguchi-based utility approach,” Int. J. Mech. Mater. Eng., vol. 11, no. 1, 2016. [11] M. P. Garg et al., “Dynamic Distribution of Discharge Products Influenced by Composition of Dielectric in WEDM Narrow Slit were Observed and Exploration of its Mechanism,” Int. J. Adv. Manuf. Technol., vol. 71, no. 1–4, pp. 591–595, 2018. [12] F. Nehadabed, A. Bin Sapit, and S. Kariemshather, “AN ANALYSIS OF WIRE-CUT PARAMETERS IN ELECTRIC-DISCHARGE OF TITANIUM ALLOYS,” 2019.

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[13] F. Nehad Abed, A. Abdullah Hamad, and A. Bin Sapit, “The effect analysis for the nano powder dielectric processing of ti-6242 alloy is performed on wire cut-electric discharge,” Mater. Today Proc., Oct. 2020. [14] S. N. Migunov et al., “Dielectric properties of nanometer-thick barium-strontium titanate films,” Tech. Phys., vol. 53, no. 11, pp. 1485–1489, 2008. [15] G. S. Rao, G. V. Kumari, and B. P. Rao, Network for Biomedical Applications, vol. 2, no. January. Springer Singapore, 2019. [16] C. S. Lee et al., “Design and Analysis of Experiments,” Int. J. Adv. Manuf. Technol., vol. 53, no. 5, pp. 737–742, 2018. [17] D. Dwaipayan, N. Titas, and B. Asish, “Parametric study for wire cut electrical discharge machining of sintered titanium,” Stroj. Cas., vol. 69, no. 1, pp. 17–38, 2019. [18] S. Tripathy and D. K. Tripathy, “Multi-attribute optimization of machining process parameters in powder mixed electro-discharge machining using TOPSIS and grey relational analysis,” Eng. Sci. Technol. an Int. J., vol. 19, no. 1, pp. 62–70, 2016. [19] M.M. Rahman, “Modeling of machining parameters of Ti-6Al-4V for electric discharge machining: A neural network approach,” Sci. Res. Essays, vol. 7, no. 8, pp. 881–890, 2012.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 67-84 doi:10.4028/p-8dhk2i © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-15 Revised: 2022-08-21 Accepted: 2022-09-09 Online: 2022-12-26

Strategies Regarding High-Temperature Strength and Toughness Applications for SUS304 Alloy Muhammad Raies Abdullah1,a, Fang Liang1,2,b*, Cai Hongneng1,c, He Zhang1,d State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China

1

School of Mechanical & Electrical Engineering, Xiamen University Tan Kah Kee College, Zhangzhou 363105, China

2

E-mail address: [email protected], b*[email protected], [email protected], d [email protected] Keywords: Computational thermodynamics, Thermo-Calc, CALPHAD, toughness, interfacial energy, coarsening rate, phase transformations.

Abstract. Steel alloys with high Mn and low C, low Cr wt.%, were designed based on the composition system for traditional high toughness, creep resistance, and longevity for high-temperature applications. In terms of energy resource utilization during production and refining, CALPHAD strategical optimization is preferable for all steel alloys. Thermo-Calc software calculates the phase diagrams α-BCC (Ferrite), and M23C6 (carbide) phases. The vital temperatures which are highlighted in this work are Ac3 (threshold temperature at which ferrite is fully transformed into austenite (α→γ)), and A4 (the threshold temperature at which austenite is fully transformed into Delta ferrite (γ→δ)) are essential for phase transformations. JMatPro software is used to predict the mechanical properties of steel alloys. The interfacial energies with regards to alloying elements for M23C6 are calculated to be between ~0.272 J/m-2 to ~0.328 J/m-2 for α-BCC matrix, while γ-FCC have interfacial energy ranges to be between ~0.132 J/m-2 to ~0.168 J/m-2. This paper focuses on investigating the effect of alloying elements on phase transformations, interfacial energy, coarsening rate of carbides, and many other mechanical properties such as toughness at high-temperature applications using CALPHAD strategies. Introduction 304-grade steel, also known as Cr-Ni steel, is resistant to environmental degradation, has high strength, excellent toughness, good machinability, and has a wide range of usages ranging from kitchenware to surgical instruments, rebuildable vaporizers, and critical parts of nuclear reactor machinery [1–4]. SUS304 grade steel is also used for high-pressure and high-temperature applications, i.e., pressure vessels, and pipes, according to ASTM standards [5]. In high-temperature applications until 700 K such that reactor pressure vessels (RPV), the toughness of steel alloys decreases because of the higher coarsening rate (k) of carbides [6] and the presence of intermetallic phases such as sigma and G-phases. There are two ways to improve toughness, i.e., mechanically and thermodynamically. Firstly, it can be improved by grain refinement, by eliminating hard particles which fracture easily, by introducing ductile barriers to the propagation of cracks, and by mechanisms that damp the motion of cracks [7]. Secondly, thermodynamics is the second cure for toughness-related properties of steel alloys, i.e., (a) reduce interfacial energy, (b) reduce diffusion coefficients (chemical potentials), (c) decrease the solubility of precipitates in the matrix or parent phase [8]. The attractive mechanical properties of 304-grade alloys result from brittle carbides and toughness enriched matrix in Chromium, causing a protective oxide layer on the surface. Some mechanical properties like wear resistance of alloys might be controlled by the volume fraction of eutectic carbides, microstructure, orientation, and matrix properties. This class of steel owns a higher density, strength along with high stiffness, fracture toughness, and excellent corrosion resistance in comparison to the light metals (Al, Mg, Ti) alloys. The important role of precipitation or phase fractions in the success of excellent creep properties has been understood for a long time and comprehensively studied [9]. High or low-

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temperature toughness applications of stainless steel decreased significantly when some intermetallic and brittle 𝜎𝜎 phase and M23C6 carbides formed at the ferrite phase boundaries or inside the ferrite and austenite phase [9, 10]. M23C6 is considered an advantageous phase at the start of microstructure growth due to its finer particle size. However, the percentage volume increased, and particle size coarsening of M23C6 is generally detected during or after heat treatment, changing M23C6 into the secondary phase that is detrimental for creep resistance [11, 12]. Researchers worked on the problem of toughness at high-temperature applications, along with creep rupture life in 304-grade steel, have involved kinetic, thermodynamic, and microstructural investigations. However, very few fundamental investigations have been carried out on detrimental phases through thermodynamical optimization. Recently, there have been several attempts to modify the alloying composition of 304 grade to enhance its toughness, strength, and hardness. S. Ghosh et al. [13] predicted that the synergistic effect of precipitations at the grain boundary and their impact on the initiation of localized stress concentrations significantly deterioration in toughness and ductility are because of sensitization. They assumed that a decrease in YS and hardness was due to the predominance of the depletion of solid solution strengtheners over the factors that caused ductility and fracture toughness to deteriorate. J. Baek et al. [14] studied 304 steel pipe LNG transmission for very low-temperature fracture toughness. They concluded that a decrease in fracture toughness was related to inclusions consisting of silicon compounds. Calcagnotto et al. [15] concluded that grain refinement leads to an increase in both yield and tensile strength, as well as improves impact toughness. Chen and Nilsson et al. [16] concluded that loss of toughness is related to the presence of the sigma phase. V.K. Euser et al. suggested that short-time tempering within tempered martensite region improves toughness at constant strength levels. The reduction in retained austenite decomposition to inter-lath cementite associated with short-time tempering resulted in improved total hardness and decreased tempered martensite area intensity [17]. Any new material must demonstrate improved resilience, hardness, and strength, as the RPV which is the essential life-limiting component. Conditions such as high temperatures, pressures, corrosive environments, and neutron irradiations are all necessary factors in order for RPVs to work. These requirements necessitate the use of structural materials with exceptional properties. Most pressurized water reactors (PWR) operate between 650-700 K at a significant pressure of 15-23 MPa under normal operating conditions. In the present work, six different alloy compositions were chosen, as shown in Table 1, based on the chemistry of 304 steel reported, keeping in mind the metallurgical aspects [5]. The goal of the study is to identify the minimum number of alloying elements (Ni, Cr, Mn, Si), which retain the highest fraction of austenite and has a perfect combination of hardness, strength, toughness, and creep-rupture life for high-temperature (650-700 K) applications. Computational Specifications The design pattern of alloy chemistry focuses on the behavioral study of phase fractions and their consequences on structural and mechanical properties. The CALPHAD [18,19] approach was utilized to predict the alloying effect of phases on SUS304 steel with different concentrations of Ni, Cr, Mn, and Si. The purpose of alloying using different concentrations of Ni, Cr, Mn, and Si is to increase hardenability, improve strength and toughness at high-low temperatures along with machine-ability, resist grain growth, improve wear, corrosion, and creep resistance [20]. Nickel (12-20 wt.%) with low Carbon possesses excellent corrosion, scaling resistance, and grain refiner in steel alloys [21]. Chromium (10-27 wt.%) with a combination of Ni used for corrosion resistance also improves hardenability, strength, and non-scaling properties. Manganese (>1 wt.%) acts as a deoxidizer in steel manufacturing, also improves strength, hardenability, wear-resistance, and combined with Sulfur (MnS) prevents brittleness [22]. Two CALPHAD-based software packages have been used to propose the alloying composition for different SUS304 steel samples. In combination with Thermo-Calc® using the TCFE9 database, calculations have been carried out to the individual phases (γ-FCC, αBCC, M23C6, and 𝜎𝜎). JMatPro is used to verdict the hardness, strength, and Young’s Modulus of alloy with different compositions of Ni, Cr, Mn, and Si by comparing their yield, tensile strengths, and creep-rupture life. It has been confirmed that this software can be utilized to understand the overall

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trend of mechanical properties such as hardness, rupture life, and phase diagrams of multicomponent alloys [23–26]. Mechanical calculations related to SUS304 analysis were performed at 700 K temperature, and the grain size of γ-FCC was assumed 10-15 µm. Thermo-Calc® was used to calculate the interfacial energy, coarsening rate, and phase transformations at different temperatures with the TCFE9 database package. TCFE9 is a thermodynamic database for different kinds of steel and Fe-based alloys, such as stainless steel, tool steels, corrosion-resistant steels, and low-density steels [27]. This database is valid for simulation of the solidification process, the stability of matrix phases (γ-FCC and α-BCC), and precipitation of secondary phases such as sulfides, carbides, and intermetallic phases like sigma and G-phase [28]. Table 1: Chemical composition from ASTM for SUS304 [29], Reference baseline sample, Modified samples w.r.t Ni, Cr, Mn, and Si (wt.%). Samples ASTM (SUS304)

C 0.08

Si 1

Mn 2

P 0.045

S 0.030

Cr 18-20

Ni 8-11

Fe Balance

Ref Sample Baseline (RSB)

0.08

0.4

0.81

0.025

0.019

17. 81

8

Balance

Modified Sample Cr (MSCr) Modified Sample Ni (MSNi) Modified Sample Mn(MSMn) Modified Sample Si (MSSi)

0.08 0.08 0.08 0.08

0.4 0.4 0.4 0.4-1.2

0.81 0.81 0.8-2 0.81

0.025 0.025 0.025 0.025

0.019 0.019 0.019 0.019

17-23 17. 81 17. 81 17. 81

8 8-16 8 8

Balance Balance Balance Balance

Table 1 contains the ASTM standard composition of SUS304 and different types of modified samples of the same alloy with different compositions with regard to Ni, Cr, Mn, and Si. The range of composition of chromium in MSCr samples is between 17–23 wt.%. In MSNi, Ni is about 8–16 wt.%, while S and P are minimal in concentration. The composition of Mn and Si in MSMn and MSSi alloys are (0.81-2 wt.%) and (0.47-1.2 wt.%), respectively, shown in Table 1. The observed effects of detrimental phases (Sigma, M23C6, G-phase) on SUS304 toughness and ductility Sigma(σ) precipitate is an essential phase in several stainless steels, one of the main factors for mechanical properties, corrosion resistance, weldability, and hardness [16]. Nevertheless, based on metallography, X-ray diffraction (XRD) and electron microscopy analysis have shown that the σ phase has very poor consistency with γ and high interfacial energy, leading to increased interface cracking. Precipitation of intermetallic phases from γ usually relates to detrimental consequences like matrix impoverishment in alloying elements such as Chromium, Molybdenum, and Niobium verdict decrease ductility and toughness, a phenomenon known as σ phase embrittlement [30]. While finely dispersed M23C6 carbide particles in the matrix are known to reinforce austenitic stainless steels, M23C6 carbide is also undesirable due to intergranular corrosion and a reduction in ductility and toughness [11]. Conversely, the presence of M23C6 on the grain boundaries can make sliding more difficult for grain boundaries, therefore improving creep ductility [31]. During the process of γ → δ transformation, δ-ferrite grains are continuously grown through elemental diffusion, so the volume fraction increased, and they become coarser, which makes its presence detrimental for ductility and toughness [32]. Since phosphorus has low solubility in austenite, it can quickly segregate at grain boundaries or dendrites in the form of M(Fe, Cr)3P inclusions. Phosphorus is isolated in solid solution at austenite grain boundaries where phosphorus concentration is deficient [33]. MnS inclusions have beneficial effects in improving machinability and retarding grain growth in steels. Meanwhile, the morphology of these sulfide inclusions has substantial effects on the numerous properties of steel. Manganese sulfide has also adversely influenced the steel alloys' mechanical properties and corrosion parameters [22]. G-phase, as an intermetallic phase (the chemical composition following the ratio Ni:Mn: Si=16:6:7 is denoted as Ni16Mn6Si7 ), has been observed along with spinodal decomposition positioned at the α /α interface. G-phase increases strength and brittleness through interaction with mobile dislocations; however, it also reduces toughness and ductility [34].

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Results and Discussions Phase transformations. Thermo-Calc® was used to calculate the phase fractions present in SUS304 steel grade, i.e., austenite γ-FCC(FCC_A1), Ferrite α-BCC(BCC_A2), carbides (M23C6, M7C3), MnS, Sigma(𝜎𝜎), M3P_DOE, and liquid by changing the composition of C wt.% in SUS304 steel as shown in Fig. 1(a). According to ASTM standards, low concentrations of C were found in SUS304, so this study mainly focused on γ-FCC, α-BCC, M23C6, 𝜎𝜎 , M3P_DOE, and MnS phases shown as highlighted in Fig. 1a. γ-FCC is known as gamma iron and unstable at less than 659 K; additional alloying elements can make it stable at room temperature [35]. In SUS304, some elements are γ formers, e.g., C, Ni, Mn [36], and some are γ stabilizers, e.g., Ni and Mn [37].

Fig. 1: (a)Stable Phase diagram of SUS304 w.r.t to changing Carbon composition at 400 K to 1800 K (b) Property diagram for different phases in the RSB sample.

α-BCC is stable at room temperature and capable of containing up to only 0.008 wt.% carbon. Some influential ferrite formers are (e.g., Cr, Si), while some are stabilizers, e.g., Si, Cr, and P in SUS304 composition. The Sigma(σ) phase occurs between 700-1100 K depending on elemental compositions of Cr, Ni, Si, and Mn, which enhance its stability [32] shown in Fig. 1a. The diffusion of chromium in α-BCC is an essential thermodynamic process in the formation of the σ phase. The 𝜎𝜎 phase composition in austenitic stainless steels can be written as (Fe, Ni)3(Cr, Mo)2 [32]. At A4 temperature, γ transforms into δ-iron due to high solubility of Phosphorus and Sulfur in the δ-phase than that in γ phase, prominent to the enhancement of ductility by stifling of grain boundary segregation. Alternatively, when the volume of δ -ferrite is between 7-10%, ductility deteriorates dramatically due to the strain concentration at the interface caused by the disparity in deformation resistance between the two phases, δ, and γ. Therefore, adjusting δ-ferrite is essential for decreasing hot-working flaws [38]. Fig. 1(b) shows all phases for the reference sample for SUS304 grade steel, including secondary precipitates, which have detrimental effects on toughness and ductility at high-temperature applications.

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Fig. 2: Effect of Cr Concentration to MSCr alloy for a) FCC, BCC phases and Ac3 points, b) M23C6, c) Sigma phase, d) G-phase

Fig. 2 illustrates the phase transformations of MSCr alloys that have Cr concentrations of 17-23 wt.%. Chromium raises the eutectoid temperature, thereby shrinking the γ-FCC phase-field shown in Fig. 2a. At high temperatures, the reduction of Cr tends to shrink the δ phase and increase A4 temperature. As shown in Fig. 2a, increasing the Cr concentration lowers the Ac3 temperature and the molar fraction of the α phase. Cr increases the stability and molar fraction between 700 to 1100 K for most deleterious hard and brittle 𝜎𝜎 phase regarding toughness for RPV applications [12]. Increasing Cr content increases the M23C6 carbide stability between 1080-1115 K, which match the previous literature [39]. An increase in M23C6 carbide has adverse effects on ductility and toughness because M23C6 has a higher coarsening rate at high temperatures, i.e., Ostwald ripening effect [40]. The intermetallic G phase has complex behavior in SUS304 alloy, i.e., stability shows at maximum until Cr 19 wt.%; after that it diminishes. Well, SUS304 is a class of austenitic steel in which the parent phase is austenite, but Cr tends to stabilize ferrite phase and increase both Ac3 and A4 points to a higher temperature. Therefore overall increase of Cr is not beneficial for high-temperature applications; minimizing the Cr content is necessary. There is always a high Cr concentration in the α phase, since Cr is the α-BCC stabilizer and facilitates σ phase precipitation significantly, ferritic matrix advantageous sites for the sigma phase precipitation. As discussed above, formation of σ could become a significant problem; even a small percentage of this phase originates a drastic deterioration of toughness and ductility, called σ phase embrittlement. As for increasing the Ac3 and A4 critical temperatures, the problem instigates from the prospect of growing the stability of undesirable phase transformations during heat-treatment such as α-BCC and hard, brittle 𝜎𝜎 phase, which could reduce its toughness for RPV applications. On the other hand, subsequently, Cr stimulates high oxidation, and corrosion resistance in SUS304, so proper application-wise optimization is required.

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Fig. 3: Effect of Ni Concentration to MSNi alloy for a) FCC, BCC phases and Ac3 points, b) M23C6, c) Sigma phase, d)G_phase

Fig. 3 shows the phase transformations of MSNi alloys have Nickel concentrations of 8-16 wt.%. Ni promotes an austenitic structure because of increasing intrinsic matrix toughness and ductility and facilitating cross slip at lower temperatures. It also decreases the corrosion rate, and is thus beneficial in acid environments, improves the oxide stability, has high capacity alloying for other materials, resistant to carbon, nitrogen, and halogens [41, 42]. As shown in Fig. 3a, increasing Ni tends to increase the γ phase stability and reduce the δ phase. It lowers the Ac3 temperature and decreases the molar fraction of the α-ferrite phase, suitable for toughness and ductility. Ni concentration decreases the molar fraction of 𝜎𝜎 phase stability shown in Fig. 3b ranging between 700 to 900 K. Ni increases the stability of M23C6 phase between 1080-1110 K along with reducing its molar fraction. Ni is also used to form the intermetallic compounds; used to increase the strength during precipitation hardening steels [41]. In MSNi alloys, G-phase still has complex behavior like MSCr alloys. Fig. 3f shows two peaks of G-phase w.r.t Ni (8wt.% and 14wt.%) concentrations at 550 K and 630 K, respectively. Nickel stabilizes γ by increasing Carbon activity as well as partitioning responsible for the decomposition of retained γ is delayed at high temperatures [9]. Generally, engineering the mechanical stability of austenite and purifying retained austenite increase impact toughness over its crack arresting ability [15]. However, increasing Ni has several disadvantages, like the fact that it lowers the eutectic temperature by mixing with Sulphur, resulting in NiS in high-temperature applications, and it is also costly, necessitating proper optimization.

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Fig. 4: Effect of Mn Concentration to MSMn alloy for a) FCC, BCC phases and Ac3 points, b) M23C6, c)Sigma phase, d)G_phase

In Fig. 4, the graph shows the phase transformations of MSMn alloys that have Mn concentration between 0.8-2 wt.%. Manganese is commonly used in steel alloys to increase hot ductility. Its effect on the α/γ balance varies with temperature, as shown in Fig. 4a. Mn is an austenite stabilizer at a minimum of 1000 K along with decreasing behavior of Ac3 temperature. Regarding M23C6 carbide changing the concentration of Mn decreases the stability between 840-950 K. As shown in Fig. 4c, the highest stability of σ phase occurs between 700-800 K, increasing Mn concentration increases the molar fraction of σ phase along with temperature ranging from 500 to 950 K. Manganese sulfide inclusions improve machinability and retarding grain growth in steels and not suitable for corrosion resistance [22]. G-phase still has a complex behavior like MSCr and MSNi alloys, whereas Mn increases the stability of G-phase. As shown in Fig. 4f, G-phase's highest stability is on Mn 2wt.% at 600 K. Mn has been introduced in austenitic stainless steels as a substitute for Ni during shortages in the international market. In Fig. 5, the graph shows the phase transformations of MSSi alloys that have Silicon concentrations of 0.47-1.2wt.%. Silicon is a strongly oxidizing agent at both high and low temperatures. It promotes a δ-ferritic structure at high temperatures like 1400-1500 K, but at low temperatures 600-1200 K, it increases the austenitic behavior of alloys, as shown in Fig. 5a. Regarding Ac3 and A4 temperatures, the addition of Si lowers the Ac3 point and increases the A4 temperature. Si increases the molar fraction of the intermetallic σ phase; the highest molar fraction is at 750 K, as shown in Fig. 5b. In SUS304 steel, G-phase is primarily dependent on Si content, a minimum of 1.3 wt.% Si is required for precipitation of G-Phase.

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Fig. 5: Effect of Si Concentration to MSSi alloy for a) FCC, BCC phases and Ac3 points, b) M23C6, c) Sigma phase, d) G_phase

Higher Si content increases G-phase stability at higher temperatures, i.e., 500-675 K, as shown in Fig. 5(f). Si is also used as a beneficial alloying element to reduce the density of steel [43] and hinders the cementite from γ causes the remaining γ to become enriched with Carbon, which is retained in the final precipitates [32]. Carbides are eliminated using Silicon in steel instead of precipitating as cementite, C is rejected into the residual austenite, stabilizing it down to ambient temperature. The resulting microstructures are carbon-enriched regions of the γ phase [44]. Fig. 6 shows solidification behavior results using the Thermo-Calc simulation (Scheil module). Scheil simulation is helpful for the understanding of binary and multicomponent alloy's solidification paths. The Scheil module works on some assumptions that solid phases are ‘‘stationary’’ such that zero diffusion in solidified material and infinitely fast diffusion in liquid, this kind of simulation revolves on an individual step, recently formed solid and liquid phases must have the mass equilibrium with the residual liquid in the preceding step. The main objective for using CALPHAD methodology in this study was to check the alloy's solidification behavior regarding alloying elements. Fig. 6(a) shows the solidification path for RSB sample with an equilibrium dotted line, which starts to diverge at 1723 K because of starting micro-segregation in the alloy. In Fig. 6(a), the results showed the BCC (α) phase form as a primary phase at 1735 K, followed by the formation of FCC(γ), MnS, and M23C6 phases at 1707 K, 1692 K, and 1542 K respectively. The solidification path in SUS304 is L+α→ L+α+γ → L+α+γ +MnS → L+α+γ +MnS+ M23C6 between 1523-1735 K, as shown in Fig. 6.

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Fig. 6: (a) Scheil solidification diagram for the RF samples of SUS304 alloy (b) liquidus and (c)solidus temperature for baseline sample of SUS304

The liquidus temperature of SUS304 is around 1650 K to 1750 K, and solidus temperature is in the range of 1500 K to 1600 K from Scheil calculations shown in Fig. 6(b), (c). On the other hand, Gphase, Sigma, and M3P phases are not shown in the Scheil calculations, so they are assumed to be metastable phases. (a)

(d)

(b)

(e)

(c)

(f)

Fig. 7: Calculated site fractions of phases at different temperatures using Thermo-Calc for Ref sample (a) γ phase(b) α&δ phases, (c) M23C6 phase (d) M3P_DOI phase (e) MnS phase, (f) G-phase

In Fig. 7(a), γ is stable at high temperatures; constituents of this phase are Fe, Cr, and Ni. Fe and Ni are in equal fractions at 600 K then Fe increases, and Ni decreases to 940 K as shown in Fig. 7 (a). The stability of the ferrite phase occurs in both high (δ), and low (α) temperatures are shown in Fig. 7 (b). In the ferrite phase, the fractions of Fe and Cr are opposite to each other until 945 K as α and

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δ-ferrite phases. M23C6 is usually composed of Fe and Cr; at low-temperature, Cr is an active constituent for this carbide, and at high-temperature Cr is substituted by Fe, as shown in Fig. 7(c). Ni, Mn, Cr, and Si are enriched in G-phase shown in Fig. 7 (f), but at high-temperature, Ni is substitute by Cr, Si, and Mn [45]. At low temperatures, Phosphide phase M3P has more Cr contribution, i.e., Cr3P, but for higher temperatures, Cr is likely to be replaced by Fe, Ni, and Mn [46]. Coarsening and interfacial energy. Interfacial energy and coarsening rate of carbides are essential factors to control toughness for steel alloys. The Thermo-Calc thermodynamic database was used to calculate the coarsening rate and interfacial energy of M23C6 carbide in equilibrium. The study is related to the effect of many alloying elements on the coarsening rate coefficient (k) [47, 48] and interfacial energy [49]. Interfacial energy is an essential parameter used in precipitation simulations to calculate the rates of nucleation, growth/dissolution, and coarsening. The value of interfacial energy can vary dramatically (usually between 0.01 to 2.0 J/m2). The extended Becker’s model functions to estimate coherent interfacial energy (Eq. 1) by using thermodynamic data from existing CALPHAD thermodynamic databases: 𝑛𝑛 𝑧𝑧

(1)

𝜎𝜎𝑐𝑐 = 𝑁𝑁𝑠𝑠 𝑧𝑧𝑠𝑠 ∆𝐸𝐸𝑠𝑠 𝐴𝐴 𝑙𝑙

where 𝜎𝜎𝑐𝑐 is the coherent interfacial energy, 𝑛𝑛𝑠𝑠 is the number of atoms per unit area at the interface, 𝑧𝑧𝑠𝑠 is the number of cross bonds per atom at the interface, 𝑧𝑧𝑙𝑙 is the coordination number of an atom within the bulk crystal lattice, and ∆𝐸𝐸𝑠𝑠 is the energy of solution in a multicomponent system involving the two phases being considered [49]. According to the phase calculations, M23C6 is mainly distributed in two matrix phases, i.e., BCC and FCC at 650 K and 1050 K, respectively. Both phases have different behaviors on the coarsening rate and interfacial energy of M23C6 regarding alloying elements. (a)

Effect of C/Ni

(b)

Effect of C/Mn

(c)

Effect of C/Cr)

BCC matrix

(d)

(e)

(f)

FCC matrix

Fig. 8: Elemental effect on coarsening behavior of M23C6 carbide in two matrix phases(a) Ni effect in α-BCC matrix, (b) Mn effect in α-BCC matrix, (c) Cr effect in α-BCC matrix, (d) Ni effect in the γ-FCC matrix, (e) Mn effect in γFCC matrix(f) Cr effect in the γ-FCC matrix

However, to evaluate the influence of Ni, Mn, and Cr, the coarsening rate coefficient and interfacial energy were calculated for (Cr, Fe)23C6 carbides. C/Ni has a value between 6E-33 to 4.4E-32 m3/s, Mn has 5E-33 m3/s to 1.75E-32 m3/s, and C/Cr have 5.5E-33 m3/s to 1.7E-32 m3/s in the γ-FCC matrix as shown in fig. 8. The coarsening rate is less influenced by low Ni weight percent, while Mn and Cr have a dominant effect on the coarsening coefficient rate. Coarsening is a Property Model

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available when using the Property Model Calculator in Thermo-Calc [2, 3]. The overall equation (Eq. 2) for the coarsening rate coefficient is given below: 𝐾𝐾 =

𝛽𝛽

8𝜎𝜎𝑉𝑉𝑖𝑖 9

𝛽𝛽

𝑇𝑇

−1

𝛽𝛽

𝑛𝑛𝑛𝑛 [�𝑢𝑢𝑖𝑖 − 𝑢𝑢𝑖𝑖𝑎𝑎 � �𝐿𝐿𝑗𝑗𝑗𝑗 � �𝑢𝑢𝑘𝑘 − 𝑢𝑢𝑘𝑘𝑎𝑎 �]−1

(2)

Where V is molar volume, 𝑎𝑎 and 𝛽𝛽 are phases in this binary system. The interfacial energy σ is calculated using the extended Becker’s model [49]. At a high composition of Mn and Cr, a higher coarsening coefficient rate observed as shown in Fig. 9. In the γ-FCC matrix phase effect of elements on the coarsening rate is almost the same, i.e., increasing with wt.% of Ni, Mn, and Cr. If the volume diffusion controls the process, it is assumed that Ni, Cr, and Mn atoms diffused through a substitutional mechanism. M23C6 carbides act as obstacles for migrating boundaries, proving more effective in strengthening mechanisms [16]. (a)

Effect of C/Ni

(b)

Effect of C/Mn

(c)

Effect of C/Cr)

BCC matrix

(d)

(e)

(f)

FCC matrix

Fig. 9: Elemental effect on Interfacial energy of M23C6 carbide in two matrix phases(a) Ni effect in α-BCC matrix, (b) Mn effect in α-BCC matrix(c) Cr effect in α-BCC matrix (d) Ni effect in γ-FCC matrix(e) Mn effect in γ-FCC matrix (f) Cr effect in γ-FCC matrix

The interfacial energy refers to an important factor for nucleation and growth rate. Low interfacial energy corresponds to the low coarsening rate of carbides, which are beneficial for steel toughness and ductility. Fig. 9 shows that the value range for interfacial energy is between 0.272- 0.328 J/m-2 for the α-BCC matrix, while for γ-FCC matrix has interfacial energy ranges between 0.140 J/m-2 to 0.160 J/m-2 for C/Ni and for C/Mn, and C/Cr are simulated by Thermo-Calc. In the ferrite matrix shown in Fig. 9(a), (b), and (c), interfacial energy is dependent on Carbon concentrations such that Carbon has high interfacial energy, which is not beneficial regarding optimization w.r.t toughness and ductility of alloys. Mechanical properties. Fig. 10 depicts the influence of Cr, Mn, Si, and Ni on SUS304 mechanical properties, such as Modulus, hardness, yield strength, and tensile strength, as well as phase volume fraction, using JMatPro (Version 7). The addition of Cr in MSCr alloys increases hardness, tensile, and yield strength until 21wt.% then reduces again, as shown in Fig 10 (a) and 10 (c). Young’s Modulus of modified alloy steels are bounded between 170-190 GPa, while Cr decreases Modulus from 180 GPa to 172 GPa, as shown in Fig. 10 (c). Nevertheless, the Cr content cannot be significantly increased because it coarsens at high-temperature applications, which reduces toughness. Furthermore, 𝜎𝜎 phase is Cr-rich and depletes Chromium from the alloy matrix, which locally decreases solid solution strengthening and increases susceptibility [50]. In the next step, the same

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calculation has been carried out for different Ni concentrations in MSNi alloy samples, as shown in Fig. 10 (d),(e),(f).

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

Fig. 10: Effect of Cr content (a)Tensile strength, Yield strength, (b) Volume fraction of phases (c)Young’s Modulus and Hardness of MSCr Alloys at room temperature, Effect of Ni content(d)Tensile strength, Yield strength, (e) Volume fraction of phases (f)Young’s modulus and Hardness of MSNi Alloys at room temperature. Effect of Si content(g)Tensile strength, Yield strength, (h) Volume fraction of phases (i)Young’s Modulus and Hardness of MSSi Alloys at room temperature, Effect of Mn content (j)Tensile strength, Yield strength, (k) Volume fraction of phases (l)Young’s modulus and Hardness of MSMn Alloys at room temperature

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The slope of strengths and hardness curves gradually decreases until 12 wt.% of Ni then increases again until 16 wt.% of Ni content. Ni increases the parent phase austenite stability and decreases the volume fraction of the ferrite phase shown in Fig. 10 (e). Ni increases Young’s Modulus from 180188 GPa (Fig. 10) verdict high creep rupture life. Meanwhile, the lattice constants are related to elastic Modulus, and austenitic steels are estimated to exhibit higher elastic moduli because of their highpacking density. As the next step, the same calculation has been carried out for different Si concentrations in MSSi alloy samples, as shown in Fig. 10 (g),(h),(i). Si content increases the hardness, tensile strength, and yield strength to higher values in MSSi samples, as shown in Fig. 10 (g),(i). In terms of Young's Modulus, Si increases until it reaches 0.6 wt.%, then decreases. At the last step, the same calculations have been carried out for different Mn contents in MSMn samples, as shown in Fig. 10 (j),(k),(l). Mn content increases the hardness, tensile strength, and yield strength to higher values in MSMn samples, as shown in Fig. 10 (j)-(l). Regarding Young’s Modulus, Mn increases its value until 1.2 wt.%, as shown in Fig. 10 (l). As shown in Fig. 10, increasing the silicon concentration in MSSi samples increases the G-phase's dominant molar fraction (h). G-phase is an essential part of hindering the growth of cementite particles or making it finer or less in size in SUS304 steel grade, which is estimated to enhance the hardness and strength of the steel [51]. However, extreme hardness is achievable by hard and stiff precipitations and the blockage of dislocations by strong point defects interaction, which is also responsible for increasing modulus [12]. Creep properties are also related to alloy modulus because the higher the Modulus, the stronger the creep resistance. Creep is reflected to be a temperature-dependent process and satisfies the powerlaw equation (Eq. 3) [12]. 𝜎𝜎

−𝑄𝑄

𝜀𝜀 = 𝐴𝐴(𝐸𝐸)exp ( 𝑅𝑅𝑅𝑅 )

(3)

T is temperature, σ is significant stress, E is Modulus, and A is a material-dependent constant; however, R and Q are constant. R, T, and A are known, or constants, so only Q, E, and σ are responsible parameters that change the material's steady-state creep rate. Ni increase the Young’s Modulus, so it is also better for creep resistance of SUS304 grade. Proposed composition regarding high toughness-strength Mechanical Properties Based on the discussions above, a new composition of SUS304 alloy was introduced, which had high toughness, optimized strength and hardness, and better creep rupture life for high-temperature applications. The reason for changing the composition of alloying elements like Cr, Si, Mn, and Ni to control the mechanical properties by phase transformations of alloy, i.e., M23C6, sigma, and Gphase, are our main focus to minimize or optimize according to the requirement of the application. The proposed compositions are tabulated in Table 1 along with ASTM standards and reference baseline for SUS304. According to Fig. 2, increasing Cr content also increases δ, M23C6, and σ phase, which are detrimental for toughness such that shown in Fig. 11 (a), so we use the least value of Cr, which is 17.18 wt.% just for better corrosion resistance. Although in mechanical properties, maximum hardness and strength are observed at 21 wt.% of Cr content. As shown in Fig. 11 (b), changing the content of Mn does not affect the toughness value, but as discussed above in Fig. 4, Mn is a good replacement for Ni because it also stabilizes the austenite phase, so higher Mn content is more fruitful at 2 wt.%. From a mechanical aspect, it increases hardness and strength so that higher concentration will be fruitful. Ni increases toughness as shown in Fig. 11 (c), also Ni decreases molar fraction of the sigma phase, stabilizes the austenite phase, so it could be better to use high content (16 wt.%) of Ni. Silicon content increases the hardness and strength of alloys, as shown in Fig. 10, and also increases the toughness until 1.2 wt.%, as shown in Fig. 11 (d). G-Phase is also detrimental to the toughness of alloy, so Si content must be less than 1.3 wt.% content of Si. According to simulation results and the discussion above, the proposed composition for high-temperature applications is shown in Table 2.

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Table 2: Proposed composition according to simulation results and discussions along with ASTM Standard [29]

SUS304 Modified Sample ASTM Standard

C 0.08 0.08

Si 1.2 0.15-1.2

Mn 2 2

P 0.045 0.040

S 0.030 0.030

Cr 17.18 18-20

Ni 16 8-11

Fe Balance Balance

JMatPro is used to calculate stress-strain calculations with a 1000 K annealed sample along with 0.1 strain rate. The stress-strain curves method is used for toughness calculation with 0.1 strain-rate; integrating the stress-strain curves gives the toughness of alloys with different concentrations shown in Fig. 11.

(a)

(b) Mn Cr

(d)

(c) Ni

Si

Fig. 11: The toughness of SUS304 alloy composition. (a) MSCr alloys, (b) MSMn alloys, (c) MSNi alloys, (d) MSSi alloys

Eliminating G-phase by decreasing Si content until 1.2 wt.% also affects the alloy toughness, as shown in Fig. 11(c). Further experiments need to be considered to minimize sigma, M23C6 phases, and reduce Ac temperatures for better toughness and strength at high-temperature applications. Conclusions This work proposed a computational method on the CALPHAD based method to optimize the 304 compositions according to their phase transformations and mechanical properties such as hardness, strength, and toughness for high-temperature applications. Cr, Ni, Si, and Mn are the essential elements chosen for alloy optimization for high-temperature toughness properties. These elements were used in simulations as controlling the stability of major secondary phases, including sigma, Gphase, and M23C6 carbide, detrimental for toughness at high-temperature applications. 1. The simulation results indicated that the increasing Cr content until 23 wt.%, the stability of sigma, M23C6 phases and increased the interfacial energy and coarsening rate, which was not good for toughness and creep rupture life for high-temperature applications; however, the least amount 17.18 wt.% of Cr was used, which was necessary for corrosion resistance of steel. 2. Increased Ni content (16 wt.%) resulted in high impact toughness properties. It increased austenite stability, creep rupture life, Young’s Modulus, decreased δ phase stability, the molar fraction of the sigma phase, and lowered Ac3 temperature, making it more suitable for impact toughness.

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3. Mn acted as an austenite stabilizer as well as a suitable replacement of Ni, so 2 wt.% of Mn was the optimal value for this alloy at high-temperature applications. 4. Si increased G-phase precipitation's stability, suitable for the hardness of alloys but adverse effects on toughness and ductility if higher than 1.2 wt.%, so 1.2 wt.% was the optimum value for silicon. 5. The interfacial energies w.r.t alloying elements For M23C6 were calculated between ~0.272 J/m-2 to ~0.328 J/m-2 for ferrite matrix, and austenite matrix had interfacial energy ranges between ~0.132 J/m-2 to ~0.168 J/m-2. Further optimization and experimentation are still needed; however, it is concluded that, an increase in Ni and decrease in Cr concentrations are necessary to decrease the stability of the sigma phase and M23C6 carbides to improve the impact toughness of steel. Acknowledgments. The authors would like to thank K. Sun and M.E. Li and at Xi’an Jiaotong University for helpful discussions and revision. The authors are grateful for the financial support of the National Natural Science Foundation of China [Grant numbers 51375364, 52075417]. Conflict of interest. The authors declare that they have no conflict of interest. References [1] S. He, D. Jiang, Effect of the degree of rolling reduction on the stress corrosion cracking behavior of SUS 304 stainless steel, Int. J. Electrochem. Sci. 13 (2018) 1614–1628. [2] M. Mehrzad, A. Sadeghi, M. Farahani, Microstructure and properties of transient liquid phase bonding of AM60 Mg alloy to 304 stainless steel with Zn interlayer, J. Mater. Process. Technol. 266 (2019) 558–568. [3] W.J. Mills, Fracture toughness of type 304 and 316 stainless steels and their welds, Int. Mater. Rev. 42 (1997) 45–82. [4] A. Kundu, D.P. Field, P. Chandra Chakraborti, Influence of strain amplitude on the development of dislocation structure during cyclic plastic deformation of 304 LN austenitic stainless steel, Mater. Sci. Eng. A. 762 (2019) 138090. [5] M. Yasuoka, P. Wang, K. Zhang, Z. Qiu, K. Kusaka, Y.S. Pyoun, R. ichi Murakami, Improvement of the fatigue strength of SUS304 austenite stainless steel using ultrasonic nanocrystal surface modification, Surf. Coatings Technol. 218 (2013) 93–98. [6] M. Godec, D.A.S. Balantič, Coarsening behaviour of M23C6 carbides in creep-resistant steel exposed to high temperatures, Sci. Rep. 6 (2016) 1–7. [7] H.K.D.H. Bhadeshia, Mathematical models in materials science, Mater. Sci. Technol. 24 (2008) 128–136. [8] G.M.A.M. El-Fallah, S.W. Ooi, H.K.D.H. Bhadeshia, Effect of nickel aluminide on the bainite transformation in a Fe-0.45C–13Ni–3Al–4Co steel, and associated properties, Mater. Sci. Eng. A. 767 (2019) 138362. [9] K.H. Lo, C.H. Shek, J.K.L. Lai, Recent developments in stainless steels, Mater. Sci. Eng. R Reports. 65 (2009) 39–104. [10] K. Guan, X. Xu, H. Xu, Z. Wang, Effect of aging at 700 °c on precipitation and toughness of AISI 321 and AISI 347 austenitic stainless steel welds, Nucl. Eng. Des. 235 (2005) 2485–2494.

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[11] J. Li, C. Zhang, B. Jiang, L. Zhou, Y. Liu, Effect of large-size M23C6-type carbides on the low-temperature toughness of martensitic heat-resistant steels, J. Alloys Compd. 685 (2016) 248–257. [12] W. Wang, R. Wang, A. Dong, G. Zhu, D. Wang, W. Zhou, W. Pan, D. Shu, B. Sun, Creep behaviors of MC carbide reinforced nickel based composite, Mater. Sci. Eng. A. 756 (2019) 11–17. [13] S. Ghosh, V. Kain, A. Ray, H. Roy, S. Sivaprasad, S. Tarafder, K.K. Ray, Deterioration in fracture toughness of 304LN austenitic stainless steel due to sensitization, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 40 (2009) 2938–2949. [14] J.H. Baek, C.M. Kim, W.S. Kim, Y.T. Kho, Fatigue crack growth and fracture toughness properties of 304 stainless steel pipe for LNG transmission, Met. Mater. Int. 7 (2001) 579–585. [15] M. Calcagnotto, D. Ponge, D. Raabe, Effect of grain refinement to 1μm on strength and toughness of dual-phase steels, Mater. Sci. Eng. A. 527 (2010) 7832–7840. [16] K.H. Lo, C.H. Shek, J.K.L. Lai, Recent developments in stainless steels, Mater. Sci. Eng. R Reports. 65 (2009) 39–104. [17] V.K. Euser, D.L. Williamson, K.D. Clarke, K.O. Findley, J.G. Speer, A.J. Clarke, Effects of Short-Time Tempering on Impact Toughness, Strength, and Phase Evolution of 4340 Steel Within the Tempered Martensite Embrittlement Regime, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 50 (2019) 3654–3662. [18] W. Xiong, CALPHAD-Based Integrated Computational Materials Engineering Research for Materials Genomic Design, Jom. 67 (2015) 1864–1865. [19] S.L. Shang, H. Zhang, S. Ganeshan, Z.K. Liu, The development and application of a thermodynamic database for magnesium alloys, Jom. 60 (2008) 45–47. [20] B. Hu, X. Tu, H. Luo, X. Mao, Effect of warm rolling process on microstructures and tensile properties of 10 Mn steel, J. Mater. Sci. Technol. 47 (2020) 131–141. [21] A. Phillion, H.S. Zurob, C.R. Hutchinson, H. Guo, D. V. Malakhov, J. Nakano, G.R. Purdy, Studies of the influence of alloying elements on the growth of ferrite from austenite under decarburization conditions: Fe-C-Ni alloys, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 35 A (2004) 1237–1242. [22] S. Lin, CALPHAD-assisted morphology control of manganese sulfide inclusions in freecutting steels, (2016) 94. [23] Z. Dudás, Comparison of measured phase volumes with calculated ones created by TTT-CCT diagram transformation, Mater. Sci. Forum. 537–538 (2007) 497–504. [24] M. Sarizam, Y. Komizo, Effects of holding temperature on bainite transformation in Cr-Mo steel, J. Mech. Eng. Sci. 7 (2014) 1103–1114. [25] T. Falkenreck, A. Kromm, T. Böllinghaus, Investigation of physically simulated weld HAZ and CCT diagram of HSLA armour steel, Weld. World. 62 (2018) 47–54. [26] J.P. Schillé, Z. Guo, N. Saunders, A.P. Miodownik, Modeling phase transformations and material properties critical to processing simulation of steels, Mater. Manuf. Process. 26 (2011) 137– 143. [27] H.L. Chen, H. Mao, Q. Chen, Database development and Calphad calculations for high entropy alloys: Challenges, strategies, and tips, Mater. Chem. Phys. 210 (2018) 279–290. [28] Y.X. Wu, W.W. Sun, X. Gao, M.J. Styles, A. Arlazarov, C.R. Hutchinson, The effect of alloying elements on cementite coarsening during martensite tempering, Acta Mater. (2020).

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[29] W. Stichel, Handbook of comparitative world steel standards; USA-United KingdomGermany-France-Russia-Japan-Canada-Australia-International. Hrsg.: Albert & Melilli, 552 Seiten. ASTM Data Series DS 67, American Society for Testing and Materials, PA, USA 1996, £ 195.00, 1997. [30] D.D.S. Silva, J.M.B. Sobrinho, C.R. Souto, R.M. Gomes, Application of electromechanical impedance technique in the monitoring of sigma phase embrittlement in duplex stainless steel, Mater. Sci. Eng. A. 788 (2020). [31] T. Sourmail, Precipitation in creep resistant austenitic stainless steels, Mater. Sci. Technol. 17 (2001) 1–14. [32] Y.Q. Wang, J. Han, H.C. Wu, B. Yang, X.T. Wang, Effect of sigma phase precipitation on the mechanical and wear properties of Z3CN20.09M cast duplex stainless steel, Nucl. Eng. Des. 259 (2013) 1–7. [33] B. Lv, F.C. Zhang, M. Li, R.J. Hou, L.H. Qian, T.S. Wang, Effects of phosphorus and sulfur on the thermoplasticity of high manganese austenitic steel, Mater. Sci. Eng. A. 527 (2010) 5648– 5653. [34] I. Shuro, H.H. Kuo, T. Sasaki, K. Hono, Y. Todaka, M. Umemoto, G-phase precipitation in austenitic stainless steel deformed by high pressure torsion, Mater. Sci. Eng. A. 552 (2012) 194–198. [35] H. Kotan, Thermal stability, phase transformation and hardness of mechanically alloyed nanocrystalline Fe-18Cr-8Ni stainless steel with Zr and Y2O3 additions, J. Alloys Compd. 749 (2018) 948–954. [36] U.E. Klotz, C. Solenthaler, P.J. Uggowitzer, Martensitic-austenitic 9-12% Cr steels-Alloy design, microstructural stability and mechanical properties, Mater. Sci. Eng. A. 476 (2008) 186–194. [37] K.H. Lee, J.Y. Suh, J.Y. Huh, D.B. Park, S.M. Hong, J.H. Shim, W.S. Jung, Effect of Nb and Cu on the high temperature creep properties of a high Mn-N austenitic stainless steel, Mater. Charact. 83 (2013) 49–57. [38] L. Schäfer, Influence of delta ferrite and dendritic carbides on the impact and tensile properties of a martensitic chromium steel, J. Nucl. Mater. 258–263 (1998) 1336–1339. [39] F. Niessen, Austenite reversion in low-carbon martensitic stainless steels–a CALPHADassisted review, Mater. Sci. Technol. (United Kingdom). 34 (2018) 1401–1414. [40] Å. Gustafson, J. Ågren, Possible effect of Co on coarsening of M23C6 carbide and Orowan stress in a 9% Cr steel, ISIJ Int. 41 (2001) 356–360. [41] W.J. Nam, H.C. Choi, Effects of silicon, nickel, and vanadium on impact toughness in spring steels, Mater. Sci. Technol. 13 (1997) 568–574. [42] Q.Y. Chen, J. Chen, J.K. Ren, Z.H. Wang, Z.Y. Liu, Effect of Si content on microstructure and cryogenic toughness of heat affected zone of low nickel steel, Mater. Sci. Eng. A. 771 (2020) 138621. [43]

D.W. Suh, N.J. Kim, Low-density steels, Scr. Mater. 68 (2013) 337–338.

[44] J. Xue, G. Tao, C. Tang, N. Xu, F. Li, C. Yin, Effect of siliconizing with molten salt on the wear resistance and corrosion resistance of AISI 302 stainless steel, Surf. Coatings Technol. 382 (2020) 125217. [45] I. Shuro, H.H. Kuo, T. Sasaki, K. Hono, Y. Todaka, M. Umemoto, G-phase precipitation in austenitic stainless steel deformed by high pressure torsion, Mater. Sci. Eng. A. 552 (2012) 194–198. [46] Y. Mandiang, G. Cizeron, Precipitation of M3P phosphide in titanium modified type 316 stainless steel, Mater. Sci. Technol. 12 (1996) 771–775.

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[47] J.E. Morral, G.R. Purdy, Particle coarsening in binary and multicomponent alloys, Scr. Metall. Mater. 30 (1994) 905–908. [48] J.O. Andersson, J. Ågren, Models for numerical treatment of multicomponent diffusion in simple phases, J. Appl. Phys. 72 (1992) 1350–1355. [49] V.R. Becker, The nucleation during precipitation in metallic mixed crystals, Ann. Phys. 421 (1938) 128–140. [50] C.E. Slone, E.P. George, M.J. Mills, Elevated temperature microstructure evolution of a medium-entropy CrCoNi superalloy containing Al,Ti, J. Alloys Compd. 817 (2020) 152777. [51] S.C. Cha, S.H. Hong, I. Kim, M.Y. Kim, J. Park, J.Y. Suh, J.H. Shim, W.S. Jung, CALPHADbased alloy design for advanced automotive steels - Part I: Development of bearing steels with enhanced strength and optimized microstructure, Calphad Comput. Coupling Phase Diagrams Thermochem. 54 (2016) 165–171.

CHAPTER 2: Polymers and Composites

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 87-92 doi:10.4028/p-4gioc4 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-04-21 Accepted: 2022-07-27 Online: 2022-12-26

Ring Opening Polymerization in Polylactic Acid Production Using Different Catalyst Nur Athirah Binti Ghazali1,a and Norliza Ibrahim1,b* School of Chemical Engineering, College of Engineering, Universiti Teknologi MARA, Selangor, Malaysia

1

[email protected], [email protected]

a

Keywords: Polylactic acid, polymer, ring-opening, polymerization, catalyst.

Abstract. Polylactic acid is a biodegradable polymer with wide range of applications in food packaging and medical industries. Polylactic acid is commonly derived from lactic acid which is made from sugar and starch via bacterial fermentation. Whereas the production of polylactic acid via ring opening polymerization uses lactide as its precursor. This method undergoes reaction with the presence of catalyst. In this research, polylactic acid is produced via ring opening polymerization using different catalyst. However, very few studies conducted on how the catalyst effects the molecular structure of the PLA produced. The main objective is to study the effect of using stannous octoate (SnOct2)and anhydrous lithium chloride (LiCl) as catalyst in producing PLA. Lactide is reacted with SnOct2 and LiCl at 130°C at different ratio of lactide to catalyst (Lac/Cat) of 25/1, 50/1 and 100/1 by weight. The resulting PLA is characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyse the molecular structure and UV-Visible Spectrometer (UV-VIS) to measure the concentration of the PLA obtained. The ratio of Lac/Cat shows significant difference on the PLA with SnOct2 as the catalyst but shows no significant difference on the PLA with LiCl as the catalyst. Nevertheless, LiCl can still be used as the catalyst in producing PLA which has been proved by the presence of certain peaks on the FTIR spectrum. However, further investigation needs to be carried out to understand the ROP mechanism when using LiCl as the catalyst. Introduction Polylactic acid (PLA) is a biodegradable and compostable polymers that belongs to the family of aliphatic polyesters generally derived from α-hydroxy acids [1]. It is made from 100% renewable resources, has thermoplastic, high-strength and high modulus properties which can be used either in the industrial packaging sector and market for biocompatible medical devices [2], [3]. It is easily processed on standard plastics equipment to produce moulded parts, film or fibres and the stereochemical structure can easily be modified to be used for food contact and are generally recognized a safe (GRAS) [4]. There are two methods in synthesizing PLA which are direct polycondensation and ring-opening polymerization. In the former method, solvent is used and longer reaction times are needed and the resulting product has low molecular weight and poor mechanical properties. [5]. While for the latter method, lactide requires catalyst and the resulting PLA has a controlled molecular weight, depending on the monomer and the condition of the reactions [6], [7]. In this study, the ring-opening polymerization is selected to produce PLA. The ring-opening polymerization of lactide is currently gaining attention from industries in the production of polylactide [8]. There are many catalysts can be used in polymerizing lactide which includes transition metals such as zin, tin, aluminium, and the lanthanides which have different degrees of conversion and high racemization. Stannous octoate, SnOct2 is the mostly used catalyst in the production of high molecular weight polylactide via ROP of lactide [9]. Nevertheless, the elimination of the catalyst from the polymer obtained is found to be a problem which limits its utilization and it has been found, the economic lithium chloride, an almost non-toxic catalyst, could catalyse efficiently the ring-opening polymerization of lactide [10].

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This research paper aims to investigate the ring-opening polymerization of PLA using different catalyst. Stannous octoate (SnOct2) and anhydrous lithium chloride (LiCl) are chosen as the catalysts to compare between those two catalysts. SnOct2 is chosen as it is the most used catalyst in the ring opening polymerization of lactide. LiCl is chosen as there is a very few studies conducted regarding this catalyst and it is said acts as an efficient and biocompatible catalyst [10]. Methodology Material Lactide with 99% w/w in crystal form, stannous octoate (SnOct2) in liquid form, anhydrous lithium chloride (LiCl) and ethylene glycol (EG) were used as the raw material. Methods. The lactide was first diluted in distilled water to 1M while heating up to 90°C. The diluted lactide was then poured into the system shown in Fig. 1 and heated up until the temperature reached 130°C. Then, the catalyst, SnOct2 was added dropwise. The reaction was left for 1 hour. The resultant mixture was then collected for further analyzation. The experiment was repeated with different ratio of Lac/Cat; 25/1, 50/1, 100/1 and different catalyst; LiCl. For LiCl catalyst, since it was in anhydrous form, the LiCl was first diluted with distilled water and EG, which acts as the co-catalyst. It was then added into the lactide mixture.

Fig. 1: Polymerization experimental system Characterization Fourier Transform Infrared Spectroscopy. The FTIR spectrum was performed to identify the functional group and chemical structure of the resultant PLAs by using Perkin Elmer TGA/SDTA851. The absorption peak between 4000 cm-1 and 500 cm-1 were studied. UV-Visible Spectrometer. The UV absorbance and transmission of the PLAs were studied using UV-VIS Perkin Elmer LAMBDA750 using 232 nm wavelength at ambient temperature. Results and Discussion PLA Formation. The resultant liquid PLA is stored in a vial and is left for a few days to observe any polymer formed at the bottom of the vial. Fig. 2 shows the resultant PLA using LiCl catalyst. However, there is no solid/particle observed at the bottom of the vial even after a few days. While from Fig. 3, there is a flake look-like solid formed at the bottom of the vial when using SnOct2 as the catalyst. The mixture is then filtered using filter paper and is dried in the vacuum oven at 60°C overnight.

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Fig. 2: Resultant PLA with LiCl as the catalyst

Fig. 3: Resultant PLA with SnOct2 as the catalyst Molecular Structure. Based on Fig. 4 and 5, it can be seen that there are few differences in the FTIR spectrum of lactide and the PLA obtained which is due to the difference of the structure. There are few ring structure of C-C linkages on lactide spectrum compared to PLA. It is expected to have a band shift related to the C=O stretching in the lactide from 1720 to 1750cm-1 [11], however the band did not shifted but there is a difference in the peak intensity as the Lac/Cat ratio is increased which demonstrates the changes from monomer to polymer in the arrangement of molecules in the polymer chain. The peak 1720 cm-1 on the PLA indicates the absorption peak ester for COO [12] while the peak 1750 cm-1 indicates the presence of carbonyl group in the ester linkage of PLA [13]. For the PLA with ratio of Lac/Cat of 25/1, 2990 to 2940 cm-1 is from the asymmetric valence vibrations of C-H from CH3 [5], which shifted to 1120 cm-1, the valence vibrations of C-O-C of the aliphatic chain. However, the absence of 2990 to 2940 cm-1 on the PLA with ratio of 50/1 and 100/1 using SnOct2 as the catalyst and all the PLA with LiCl as the catalyst is not yet ascertained. The weak peak of 1450 cm-1 and 1366 cm-1 that appeared indicate the asymmetric and symmetric bending vibration of C-H from CH3, respectively. The presence of 1630 cm-1 is associated with the stretching vibration C=C [14]. The absorption band at 1218 cm-1 is assigned to C-O-H vibration absorption peak [15]. The peak around 3400 cm-1 indicates the presence of OH at the end of the PLA that contain impurities of -OH and the rate of the polymerization of PLA is not high [16]. This is because all of the samples are in liquid form and not in solid form, hence explain the high intensity of band 3400 cm-1. Based on [12], the peak of lactide at 3250cm-1 is observed which expected to be almost disappeared due to the reaction of polyesterification that consumes OH groups when reacting the acid groups to form the ester bond which indicates that the number of COOH and -OH are reduced and sharper

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absorption peak of C=O stretching at 1720 cm-1 is observed. However, based on Fig. 4 and 5, the peak 3250 cm-1 cannot be detected on the FTIR spectrum of lactide, yet the presence of 1720 cm-1 on PLA samples are identified. The FTIR spectrum of lactide is expected to appear the absorption peak of 936 cm-1 for COO ring of lactide which could not be appeared on the PLA spectrum. This is because the peak indicates the characteristic of lactide monomer and has been used to differentiate between lactide and PLA [17]. Yet, peak 936 cm-1 could not be seen even on the lactide spectrum on both Fig. 4 and 5.

Fig. 4: FTIR spectrum of PLA with SnOct2 as catalyst

Fig. 5: FTIR spectrum of PLA with LiCl as catalyst Concentration UV-VIS of the standard are run and the absorbance measurements at 232 nm are used to prepare the calibration curve. Based on the linear equation of the standard curve, the concentration of the PLAs from the study can be obtained. Fig. 6 shows the graph of ratio of Lac/Cat against the concentration of PLA with SnOct2 as the catalyst. The concentration of PLA obtained at ratio of Lac/Cat 25/1, 50/1 and 100/1 is 58.99 mg/L, 61.25 mg/L and 62.63 mg/L, respectively. From the graph, it can be seen that as the ratio of Lac/Cat is increased, the concentration of the PLA obtained also increased. Fig. 7 shows the relation between the ratio of Lac/Cat and the concentration of PLA obtained with LiCl as the catalyst. The concentration of PLA obtained is 71.21 mg/L, 66.99 mg/L and 67.68 mg/L for the ratio of Lac/Cat of 25/1, 50/1 and 100/1. Based on the graph below, the ratio of Lac/Cat almost certainly does give any significant to the concentration of PLA obtained.

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Fig. 6: Concentration of PLA with SnOct2 as the catalyst at different ratio of Lac/Cat

Fig. 7: Concentration of PLA with LiCl as the catalyst at different ratio of Lac/Cat Summary In summary, this paper has discussed the difference in producing PLA using two different catalysts SnOct2 and LiCl with different ratio of Lac/Cat. The results indicate that the ratio of Lac/Cat has significant effect when using SnOct2 as the catalyst. This can be seen through the FTIR spectrum that shows intensity difference of peak between the samples and can be relate with the concentration of the PLAs obtained using SnOct2 as the catalyst. While for the PLAs with LiCl as the catalyst, the ratio of Lac/Cat has no significant effect since there is no intensity difference between the peaks on the FTIR spectrum and the UV-VIS result shows no correlation between the ratio of Lac/Cat and the concentration of PLAs obtained. However, the FTIR spectrum of PLA with LiCl as the catalyst shows that the catalyst has potential in being an alternative catalyst for SnOct2 in producing PLA. References [1] D. Garlotta, “A literature review of poly(lactic acid),” J. Polym. Environ., 2001. [2] R. E. Drumright, P. R. Gruber, and D. E. Henton, “Polylactic acid technology,” Adv. Mater., 2000. [3] M. H. Hartmann, “High Molecular Weight Polylactic Acid Polymers,” in Biopolymers from Renewable Resources, 1998. [4] R. E. Conn et al., “Safety assessment of polylactide (PLA) for use as a food-contact polymer,” Food Chem. Toxicol., 1995. [5] D. Pholharn, Y. Srithep, and J. Morris, “Effect of initiators on synthesis of poly(L-lactide) by ring opening polymerization,” in IOP Conference Series: Materials Science and Engineering, 2017.

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[6] M. S. Lopes, A. L. Jardini, and R. M. Filho, “Synthesis and characterizations of poly (lactic acid) by ring-opening polymerization for biomedical applications,” Chem. Eng. Trans., 2014. [7] A. J. Rincon Lasprilla, G. A. Rueda Martinez, B. H. Lunelli, J. E. Jaimes Figueroa, A. L. Jardini, and R. M. Filho, “Synthesis and characterization of poly (Lactic Acid) for use in biomedical field,” in Chemical Engineering Transactions, 2011. [8] L. T. Sin and B. S. Tueen, “Synthesis and Production of Poly(Lactic Acid),” in Polylactic Acid, 2019. [9] K. J. Jem, J. F. van der Pol, and S. de Vos, “Microbial Lactic Acid, Its Polymer Poly(lactic acid), and Their Industrial Applications,” 2010. [10] W. Xie, D. Chen, X-H. Fan, J. Li, P. Wang, H.N. Cheng, and R. Nickol, “Lithium chloride as catalyst for the ring-opening polymerization of lactide in the presence of hydroxyl-containing compounds,” J. Polym. Sci. Part A Polym. Chem., 1999. [11] G. Swift, “Directions for Environmentally Biodegradable Polymer Research,” Acc. Chem. Res., 1993. [12] N. Choksi and H. Desai, “Synthesis of Biodegradable Polylactic Acid Polymer By Using Lactic Acid Monomer,” 2017. [13] S. K. Singh, P. Anthony, and A. Chowdhury, “High molecular weight poly(lactic acid) synthesized with apposite catalytic combination and longer time,” Orient. J. Chem., vol. 34, no. 4, 2018. [14] A. K. Helmy, S. G. de Bussetti, and E. A. Ferreiro, “The surface energy of palygorskite,” Powder Technol., vol. 171, no. 2, 2007. [15] C. Moliner, E. Finocchio, E. Arato, G. Ramis, and A. Lagazzo, “Influence of the degradation medium on water uptake, morphology, and chemical structure of Poly(Lactic Acid)-Sisal biocomposites,” Materials (Basel)., vol. 13, no. 18, 2020. [16] X. F. Zhu, J. Zhang, and B. C. Chen, “Study on Synthesis and Thermal Properties of Polylactic Acid,” in Journal of Physics: Conference Series, 2019, vol. 1176, no. 4. [17] K. Boua-In, N. Chaiyut, and B. Ksapabutr, “Preparation of polylactide by ring-opening polymerisation of lactide,” Optoelectron. Adv. Mater. Rapid Commun., vol. 4, no. 9, 2010.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 93-102 doi:10.4028/p-k5hv1o © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-17 Revised: 2022-09-13 Accepted: 2022-09-23 Online: 2022-12-26

Mechanical and Morphological Properties of PHB/Oil-Free Coffee Dregs (OFCD) Composites Marisa Cristina Guimarães Rocha1,a *, Nancy Isabel Alvarez Acevedo1,b and Carlos Eduardo Nazareth de Oliveira1,c Polytechnic Institute, Rio de Janeiro State University - UERJ, Nova Friburgo, 28625570, RJ, Brazil

1

*[email protected], [email protected], [email protected]

a

Keywords: Biodegradable polymers, biocomposites, poly(3-hydroxybutyrate), coffee dregs, oil extraction.

Abstract Poly(3-hydroxybutyrate) (PHB) and coffee dregs (CDs) are both biodegradable materials. The latter are household wastes with no commercial value that are discarded in landfills mixed with other organic wastes. PHB has properties equivalent to polypropylene (PP), but its prohibitive cost restricts its field of application. The incorporation of this residue in a PHB matrix is a way to obtain materials with a high cost/benefit ratio. The aim of this work was to investigate the effect of adding oil-free coffee dregs (OFCDs) on the mechanical and morphological properties of PHB. Soxhlet extraction using ethanol as a solvent was used to obtain OFCDs. The PHB/OFCD composites were prepared in a twin-screw extruder. Standardized methods were used to evaluate the tensile and flexural properties. The test specimens were obtained by compression molding. Scanning electron microscopy (SEM) was applied to evaluate the morphology of the composites obtained. The data obtained showed that the incorporation of 15 wt.% of OFCD caused no significant differences in the tensile modulus, tensile strength and flexural modulus. The flexural strength decreased with the incorporation of OFCD in the PHB. However, the material obtained was interesting, since it was more attractive in terms of cost and environmental impact. SEM micrographs showed good dispersion of OFCD in PHB when the OFCD content was 5 wt.%. However, when higher levels of residues were incorporated in the PHB, the formation of agglomerates became evident. Poor interfacial adhesion between the filler and matrix was indicated by the cracks and voids revealed in the micrographs. The results obtained indicated that PHB/OFCD composites prepared with 15 wt.% of OFCD particles have potential to be used in the production of PHB materials that require high stiffness, adequate strength, and lower cost, such as sheets and thermoformed products for food, medical, personal care and laboratory applications Introduction Coffee is one of the most consumed beverages in the world. In the last yearly harvest (20202021), world coffee production was 167.5 million 60-kilogram bags, 1.9% higher than the previous harvest [1]. Different residues such as husks, pulp, silver skins, parchments, low-quality coffee beans, water and spent coffee grounds are generated from harvest to consumption (roasted ground coffee or soluble coffee) [2, 3]. Spent coffee grounds (SCGs) are generated during the industrial production of instant or soluble coffee, where the ground-roasted beans undergo treatment with pressurized hot water. These residues are commonly used as fuel in boilers in the soluble coffee industry or as a compost additive in organic agriculture [4, 5]. These SCGs, hereafter referred to as oil-free coffee dregs (OFCDs), can also be obtained during the commercial or domestic process of infusion and filtering of the coffee powder to obtain the beverage [2, 6]. OFCDs have no defined commercial value and are discarded as domestic or commercial waste. OFCDs mixed with other wastes end up in landfills, where they break down and emit methane [6, 7]. In the last decade, studies to obtain coffee-ground based products with competitive costs and low environment impact began to appear in the literature. Currently, OFCDs are used in several applications, such as household products [8, 9]; heavy metal adsorbents, dyes and pharmaceuticals

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products in aqueous media [6, 10-12]; biofuels in the form of wood logs, chips or pellets [7, 13]; additives in the food and cosmetic industries [7, 14, 15]; and manufacture of smart fabrics [16, 17], among others. Biodegradable polymers occupy a growing market segment, expected to reach over US$ 23.3 billion per year by 2026, with applications ranging from food packaging to medical devices [18, 19]. Among this type of polymers, poly(3-hydroxybutyrate) (PHB) stands out due to its high crystallinity (50-60%), high melting temperature (160 -180 ºC) and good gas barrier performance [20, 21]. These characteristics make it a potential substitute for conventional polymers, such as polypropylene (PP) and polyethylene (PE) [20]. However, the low thermal stability, high brittleness and high production cost limit its applications [20, 22]. One of the alternative solutions proposed to improve the properties of PHB and reduce the production costs of PHB-based products is the addition of organic residues to the polymer composition. Peçanha [23] developed a biodegradable composite of PHB filled with coffee dregs. These composites had reduced elastic modulus and tensile strength, resulting from the low interfacial adhesion between the hydrophilic filler particles and the hydrophobic matrix of PHB. The oil contained in coffee dregs can promote adhesion and the formation of aggregates, affecting their dispersion in the polymeric matrix, and consequently affecting the mechanical properties of the composites obtained [24]. Therefore, the extraction of the oil fraction from the coffee dregs can generate improvements in the mechanical behavior of the materials. Chang et al. [24] obtained 3D printer filaments from PLA composites filled with OFCDs, which showed improvements in impact toughness up to 400%. Tellers et al. [25] observed that the catalytic effect of coffee dregs on the curing process of bio-based epoxy resin was more intense when the oil was removed from the dregs. In addition, composites containing OFCDs presented greater stiffness than those composed of both pristine resin and composites containing dregs without oil removal (CDs). Leow et al. [26] reported a decrease in the mechanical properties of an epoxy resin, with the addition of both OFCDs and CDs. However, the composites filled with OFCDs showed better mechanical behavior. There are good prospects for the use of OFCDs in various applications due to the high quality and low cost of the materials produced. Among these applications are the production of biodiesel [27-29]; the formulation of cosmetics [30]; precursors in the PHB production process [31, 32]; and substitution of palm oil in various food and beverage products [33]. On the other hand, the solid residue obtained from the extraction coffee oil can be used as garden fertilizer, raw material to produce ethanol and pellet fuels [34, 35], among others. This work is relevant because there are no works published in scientific journals involving the incorporation of OFCDs or CDs in the PHB matrices. Materials and Methods Materials. The polymeric matrix used in this work was a commercial poly(3-hydroxybutyrate) (PHB), Biocycle® 189C-1, in the form of white powder, supplied by PHB Industrial Brazil S.A. (Brazil). The coffee dregs (Mury coffee brand) were obtained from household wastes. Oil extraction from coffee dregs. Upon receipt, the coffee dregs were washed and subjected to the drying process in an oven with air circulation for 24 h, at 70 °C. Oil extraction was performed by the Soxhlet extraction method using ethyl alcohol as solvent for 24 h. After this period, the oilfree coffee dregs (OFCDs) were removed from the extractor, washed, and dried at 70 °C for 24 hours. Then, the residue was ground in a ball mill for 8 hours and passed through a Tyler series sieve with 60 mesh. Only the material with diameter less than or equal to 0.25 mm was used in the experiments. Preparation of composites. Three PHB/OFCD composite formulations, with OFCD contents of 5, 10 and 15 wt.%, were prepared and named PHB/OFCD5, PHB/OFCD10 and PHB/OFCD15, respectively. First, all materials were dried at 70 ºC for 24 hours. The dry materials were weighed and mechanically mixed according to the predefined formulations. The mixtures were processed in a Leistritz ZSE 18 MAXX co-rotational twin-screw extruder (supplied by Leistritz Extrusion

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Technology, Germany) with a rotation speed of 100 rpm. The temperature profile adopted, from the feed zone to the die, was 155/ 165/ 160/ 160/ 160/ 160 /160/ 160/ 155/ 155 ºC. The extruded threads were cooled in water at room temperature and pelletized. Determination of mechanical properties. Tensile and flexural testing of the polymeric matrix and the composites were performed with an Autograph AG-X Plus 100 kN universal testing machine (supplied by Shimadzu do Brazil). A minimum of five specimens of each material processed were used to determine the properties. The compression molded samples were prepared in a Carver 3851-OC hydraulic press (supplied by KCEN Comércio e Representações SA, Brazil) at 180 °C, applying a compression force of 10 tons during 5 min, followed by cooling for 20 min. The test conditions are shown in Table 1. The specimens were cut from compression-molded plates, using a Roland MDX 40A milling machine. The individual value plot statistical method (Minitab 15TM® software) was used to visually represent and evaluate the mechanical property data. One-way analysis of variance (ANOVA) and the Tukey test were used to determine significant pairwise differences in the means of each two samples of data obtained. Table 1. Test conditions used in tensile and flexural tests. Test Tensile strength 3-point flexural strength

Load cell Rate of displacement [kN] [mm min-1]

Test specimen

Method

5

0.5

V–type

ASTM D638 [36]

100

0.3

Rectangular

ASTM D790 [37]

Evaluation of composites’ morphology. A Hitachi TM 3000 scanning electron microscope (supplied by DP Union Instrumentação Analítica e Científica, Brazil) with electron beam incidence of 15 kV was used to evaluate the morphology of the fracture surfaces of the materials. The composites were analyzed at 400X magnification. Results and Discussion Tensile properties of PHB/OFCD composites. Lignocellulosic materials, such as coffee dregs, promote increased rigidity of polymers. Ghazvini, et al. [38] observed an increasing in the elastic modulus when silver skins were added in PLA and PLA/PBS composites. A silver skin is a thin film that surrounds the coffee bean, and is a residue produced during the roasting of the coffee beans. This result was attributed to the increase in crystallinity promoted by the silver skin, which acted as a nucleating agent, and to the high content of cellulose, around 18%. Georgopoulos et al. [39] observed that composites containing fibers with low cellulose content had a low modulus of elasticity and also reported the effect of cellulose content on the properties of composites filled with lignocellulosic materials. Table 2 and Figure 1 present the average values of the tensile properties of the materials under study. Figure 1 was drawn with the Minitab software by adding 95% confidence interval bars to create an interval plot and compare intervals of the means of groups. The Tukey test was performed to find means that were significantly different from each other. The data obtained showed a tendency to obtain higher values of modulus of elasticity with the incorporation of OFCDs. However, there was no statistically significant difference between the data. Therefore, the incorporation of 15 wt.% of residue in the PHB had no significant effect on the tensile modulus of elasticity. However, the material obtained was more attractive in terms of cost and environmental impact.

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Table 2. Tensile properties of PHB and PHB/oil-free coffee dreg (OFCD) composites. Tensile Modulus [MPa]

Tensile Strength [MPa]

Elongation at Break [%]

PHB

2345.8 ± 216.7

30.9 ± 3.6

2.3 ± 0.5

PHB/OFCD5

2517.5 ± 218.9

28.5 ± 2.8

1.7 ± 0.2

PHB/OFCD10

2556.4 ± 137.2

26.4 ± 1.6

1.5 ± 0.2

PHB/OFCD15

2651.4 ± 167.09

24.2 ± 1.8

1.4 ± 0.2

Materials

OFCD’X’: oil-free coffee dregs - ‘X’: content (wt.%) = 5, 10 or 15:

Figure 1. (a) Tensile modulus, (b) tensile strength and (c) elongation at break of PHB and PHB/oilfree coffee dreg (OFCD) composites. Peçanha [23] obtained lower modulus values from the addition of coffee dregs to PHB. The crystallinity degree of the samples, measured by differential scanning calorimetry (DSC), decreased with the incorporation of coffee dregs in the polymer matrix. The agglomeration of CD particles prevented the filler from functioning as a nucleating agent and reduced the surface contact area between filler and matrix. According to Chang et al. [24], the presence of oil in coffee dregs can promote adhesion and aggregation of the particles, affecting their dispersion in the polymer, and consequently affecting the mechanical properties of the composites. Wu et al. [40] observed an increase in modulus of polypropylene with incorporation of OFCD particles. This result was attributed to a greater interlock between OFCD particles and PP. The data obtained in the present study showed that the extraction of oil contributed to a better dispersion of the coffee dregs in the PHB. However, considering the data dispersion, the values of the modulus of elasticity obtained with the incorporation of OFCDs were equivalent to the modulus

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of elasticity of the pure PHB. The results also showed that the incorporation of 15% residue was possible without reducing the material’s stiffness. Table 2 and Figure 1 also show a tendency to obtain lower values of tensile strength with the incorporation of OFCDs. There was no statistical difference between the means of the PHB, PHB/OFCD5 and PHB/OFCD10 samples. There was a decrease in tensile strength when 15 wt.% of residues was incorporated in the PHB. This result indicates a weak ability to transfer stress from the matrix to the filler [41]. Effects such as unsatisfactory filler dispersion, formation of agglomerates and the presence of voids at the filler-matrix interface contribute to decrease the tensile strength of composites [42]. Other researchers obtained comparable results. Angelini et al. [41], in a study of PHB composites filled with lignin-rich residues, verified that the heterogeneity of the filler and the low compatibility between filler and the PHB matrix were responsible for the reduction in tensile strength of the composites obtained. Reis et al. [43] observed no significant changes in the tensile strength with the addition of 10 wt.% coffee residue (husk or parchment). However, the addition of a high content of these residues promoted a decrease in the tensile strength. Wu et al. [40] attributed the reduction in the tensile strength of polypropylene (PP) composites filled with spent coffee grounds (SCGs) to the poor adhesion between filler particles and PP matrix. However, the tensile strength values of composites of PP filled with oil-free spent coffee grounds (OFSCGs) were higher than those of PP/SCG composites. The results were attributed to the oil extraction and the refinement of the filler, which increased the interlocking and interaction between filler and PP. In this work, the incorporation of 15 wt.% of OFCD particles promoted a decrease in tensile strength of 22%. These results and the elastic modulus data indicated that the incorporation of a low content of OFCD to the PHB matrix can give rise to inexpensive PHB materials without major changes in tensile modulus and tensile strength. The elongation at break results showed that the incorporation of 5 wt.% of OFCD in the PHB promoted a decrease of around 26% in the elongation at break of PHB and tended to stabilize with the incorporation of higher levels of OFCDs. Flexural properties of PHB/OFCD composites. Table 3 shows the flexural properties of the pure PHB and the PHB/oil-free coffee dreg (OFCD) composites. Table 3. Flexural properties of PHB and PHB/oil-free coffee dreg (OFCD) composites. Flexural Modulus [MPa]

Flexural Strength [MPa]

PHB

2789.8 ± 67.0

54.3 ± 3.1

PHB/OFCD5

2700.6 ±115.4

47.6 ± 2.9

PHB/OFCD10

2671.3 ±197.0

44.3 ± 1.6

PHB/OFCD15

2571.2 ± 134.6

42.6 ± 1.7

Material

OFCD’X’: oil-free coffee dregs - ‘X’: content (wt.%) = 5, 10 or 15.

Table 3 and Figure 2 show that the incorporation of OFCDs in PHB had no significant effect on the flexural modulus of the polymer.

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Figure 2. (a) Flexural modulus and (b) flexural strength of PHB and oil-free coffee dreg (OFCD) composites. There was no statistically significant difference between the mean values of the flexural modulus of the PHB and the mean flexural modulus values of the PHB/OFCD15 sample, indicating that a content of 15 wt.% of OFCD can be added to PHB without deterioration of the flexural modulus. The analysis of variance showed that the incorporation of OFCDs in the PHB matrix promoted a decrease in the flexural strength. The addition of 15 wt.% of OFCD caused a 21.5% reduction in flexural strength. The flexural strength is a function of the density of the material. The decrease in crystallinity caused by the introduction of defects in the crystal lattice promoted by the incorporation of the filler may explain this result. These results show that the incorporation of 15 wt.% of OFCD in the PHB caused no significant changes in the tensile modulus, tensile strength and flexural modulus. However, the addition of this content of PHB promoted the decrease in flexural strength. Morphology of PHB/OFCD composites. As mentioned before, SEM was used to evaluated the morphological properties of the materials obtained. The SEM micrograph of the PHB, Figure 3a, shows a homogenous continuous structure with roughness, which according to Nery et al. [44], corresponds to a brittle fracture surface.

Figure 3. SEM micrograph of fracture surface of: (a) PHB; (b) PHB/OFCD5 composite; (c) PHB/OFCD10 composite; and (d) PHB/OFCD15 composite.

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The SEM micrographs of PHB composites, Figure 3b-d, show rough fracture surfaces with indentations and voids (as seen in the areas surrounded by white ellipses). The micrographs show a good distribution and dispersion of filler particles in composites with low OFCD content. The formation of agglomerates increased with OFCD content. OFCD particles have a hydrophilic character, and therefore form agglomerates when incorporated in a hydrophobic matrix such as PHB. The cracks and voids observed in the micrographs show the poor adhesion between OFCD particles and the matrix and explain the tensile strength results. Mustafa et al. [45] obtained very similar morphology. Conclusions The use of coffee dregs as a sustainable natural filler for polymer composites is an alternative to add value to this residue. The extraction of oil from coffee dregs is a way to reduce the agglomeration of filler particles and to obtain better mechanical properties. In this work, PHB composites containing oil-free coffee dregs were prepared and the mechanical and morphological properties were evaluated. There were no significant changes in the tensile modulus, tensile strength and flexural modulus with the incorporation of 15 wt.% of OFCD particles. However, the flexural strength decreased with the incorporation of these residues. SEM micrographs showed good distribution and dispersion of OFCD particles with incorporation of 5 wt.% of OFCD particles. However, the increase of filler concentration promoted the formation of agglomerates, deteriorating the mechanical properties. The cracks and voids present in the micrographs show the low interfacial adhesion between the filler particles and the polymer matrix and explain the tensile and flexural strength data. The results of this work indicate that although superior properties were not obtained with the incorporation of OFCD in PHB, the materials obtained have potential use for the production of environmentally friendly PHB materials that require high stiffness, adequate tensile strength, and lower cost. References [1] International Coffee Organization, Coffee Market www.ico.org/documents/cy2021-22/cmr-1221-e.pdf.

Report

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December

2021,

[2] A.S. Franca, L.S. Oliveira. Coffee processing solid wastes: Current uses and future perspectives, in: G.S. Ashworth, P. Azevedo (Eds.), Agricultural Wastes, ISBN 156978-160741-305-9, Nova Science Publishers Inc., New York, 2009, pp 155-90. [3] C.A.A. Durán, A. Tsukui, F.K.F. Santos, et al. Café: Aspectos gerais e seu aproveitamento para além da bebida, Rev. Virtual Quím. 9 (2017) 107-134. DOI: 10.21577/1984-6835.20170010. [4] A. Kovalcik, S. Obruca, I. Marova, Valorization of spent coffee grounds: A review, Food and Bioproducts Processing 110 (2018) 104-119. DOI: 10.1016/j.fbp. 2018.05.002. [5] A. Cervera-Mata, G. Delgado, A. Fernández-Arteaga, et al. Spent coffee grounds by products and their influence on soil C-N dynamics, J. Environ. Manage. 302-Part B (2022) 114075. DOI: 10.1016/j.jenvman.2021.114075. [6] F.J. Cerino-Córdova, N.E. Dávila-Guzmán, A.M. García León, et al., Revalorization of coffee waste, in: D. Toledo Castanheira (Ed.), Coffee - Production and Research, IntechOpenLimited, London, 2020. DOI: 10.5772/intechopen.92303. [7] Bio-Bean (homepage), The significant value of spent coffee grounds, www.biobean.com/news-post/the-significant-value-of-spent-coffee-grounds/ (2021, accessed 10 January 2022) [8] Coffee Based (homepage), www.coffeebased.nl/en/products/ (2021, accessed 10 January 2022) [9] Kaffeeform GmbH (homepage), www.kaffeeform.com/en/ (2022, accessed 10 January 2022).

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[10] R.J. Torres-Cabán, Adsorption of polluants by spent-coffee-grounds composite beads. PhD Thesis, University of Puerto Rico, Mayaguez Campus, PR, 2020. [11] L. Liu, L. Yu, W. Zhang, et al. Adsorption performance of Pb(II) ions from aqueous solution onto a novel complex of coffee grounds and attapulgite clay, Desalin. Water Treat. 153 (2019) 208-15. DOI: 10.5004/dwt.2019.24080. [12] R.F. Lessa, M.L. Nunes, A. Fajardo, Chitosan/waste coffee-grounds composite: An efficient and eco-friendly adsorbent for removal of pharmaceutical contaminants from water, Carbohydr. Polym. 189 (2018) 257-266. DOI: 10.1016/j.carbpol.2018.02.018 [13] I. Yang, G.S. Han, S.W. Oh, Larch pellets fabricated with coffee waste and the commercializing potential of the pellets, J. Korean Wood Sci. Technol. 46: 1 (2018) 48-59, DOI: 10.5658/wood.2018.46.1.48. [14] G. Semaan, S. Shobana, S. Arvindnarayan, et al., Food waste biorefinery: A case study for spent coffee grounds (SCGs) into bioactive compounds across the European Union, in: T. Bhaskar, S. Varjani, A. Pandey, E.R. Rene (Eds), Waste Biorefinery, Elsevier. 2021, pp 45973. DOI: 10.1016/B978-0-12-821879-2.00017-X. [15] Kaffe Bueno ApS (homepage), www.kaffebueno.com (2019, accessed in: 28 Jun 2021). [16] S.-T. Hung, Y.-Y. Yeh, C.-K. Yen, et al., Process of making yarns with coffee residue. U.S. Patent 8834753 B2 (2014). [17] Singtex Industrial Co., Ltd (homepage). Fabric, www.singtex.com/fabric/ (2021, accessed in 28 June 2021). [18] Markets and Markets, Biodegradable plastic market - Report CH2736. 09/2021, www.marketsandmarkets.com/Market-Reports/biodegradable-plastics-93.html. [19] R. Shah, R. Chen, H. Wong, Present and future trends in biodegradable polymers, Plastics Today, www.plasticstoday.com (10/20/2020, accessed 28 June 2021). [20] A. J. de Santos, L.V.O.D. Valentina, A.A.H. Schulz, et al., From obtaining to degradation of PHB: Material properties. Part I. Ing Cienc. 13: 26 (2017) 269-98. DOI: 10.17230/ingciencia.13.26.10. [21] B. McAdam, M. B. Fournet, P. McDonald. Production of polyhydroxybutyrate (PHB) and factors impacting its chemical and mechanical characteristics, Polymers 12: 12 (2020) 2908. DOI:10.3390/polym12122908. [22] E.A. Soares, Poli(hidroxobutirato) (PHB) – Ficha técnica com as principais características, aplicações e propriedades do poli(hidroxibutirato) (PHB), Plástico Industrial, www.arandanet.com.br/revista/pi/noticia/3146-Poli(hidroxibutirato)-(PHB) (26/11/2021, accessed 10 January 2022). .. [23] P.C. Peçanha, Avaliação das propriedades térmicas, mecânicas e morfológicas de compósitos de poli(3-hidroxibutirato)(PHB) e borra de café (COFD), Undergraduate Thesis, Universidade do Estado do Rio de Janeiro, Instituto Politécnico. Nova Friburgo, RJ, BR, 2017. [24] Chang Y-Ch, Chen Y, Nig J, et al., No such thing as trash: A 3D-printable polymer composite composed of oil-extracted spent coffee grounds and polylactic acid with enhanced impact toughness, ACS Sustainable Chem. Eng. 7: 18 (2019) 15304-310. DOI: 10.1021/acssuschemeng.9b02527. [25] J. Tellers, P. Willems, B. Tjeerdsma, et al., Spent coffee grounds as propertly enhancing filler in a wholly bio-based epoxi resin, Macromol. Mater. Eng. 306: 11 (2021) 2100323, DOI: 10.1002/mame.202100323.

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[26] Y. Leow, P.Y.M. Yew, P.L. Chee, et al., Recicling of spent coffee ground for useful extracts and green composites, RSC Advs, 11 (2020) 2682. DOI: 10.1039/d0ra09379c. [27] L.F. Xavier, T.S. Lisboa, I. Lula, Reaproveitamento da borra de café na obtenção de biodiesel e de carvão ativado para tratamento de rejeitos industriais têxteis, Sci. Amazon 6: 2 (2017) 91108. [28] Z. Al-Hamamre, S. Foerster, F. Hartmann, et al., Oil extracted from spent coffee grounds as a renewable source for fatty acid methyl ester manufacturing, Fuel 96 (2012) 70-76, DOI: 10.1016/j.fuel.2012.01.023. [29] Blinová L, Bartošová A, Sirotiak M. Biodiesel Production from spent coffee grounds, Research Papers Faculty of Materials Science and Technology Slovak University of Technology – FMST/SUT 25:40 (2017) 113-121. DOI: 10.1515/rput-2017-0013. [30] G. Sousa, L. Leal, New oils for cosmetic O/W emulsions: In vitro/in vivo evaluation, Cosmetics 5:1 (2018) 6. DOI: 10.3390/cosmetics5010006 [31] A.S.C. Bonfim, D.M. Oliveira, H.J.C. Voorwald, et al., Valorization of spent coffee grounds as precursors for biopolymers and composite production, Polymers 14: 3 (2022) 437. DOI: 10.3390/polym14030437. [32] S. Obruca, S. Petrik, P. Benesova, et al. Utilization of oil extracted from spent coffee grounds for sustainable production of polyhydroxyalkanoates, Appl. Microbiol. Biotechno. 98: 13 (2014):5883-90. DOI: 10.1007/s00253-014-5653-3. [33] D. Brom, This start-up is making a palm oil alternative from used coffee grounds. World Economic Forum, (02/05/2019, accessed 15 January 2020). www.weforum.org/agenda/2019/05/this-start-up-is-making-a-palm-oil-alternative-from-usedcoffee-grounds/ [34] N. Kondamudi, S.K. Mohapatra and M. Misra, Spent coffee grounds as a versatile source of green energy, J. Agric. Food Chem. 56: 24 (2008) 11757–60. DOI: 10.1021/jf802487s. [35] A.E. Atabani, S.M. Mercimek, S. Arvindnarayan, et al., Valorization of spent coffee grounds recycling as a potential alternative fuel resource in Turkey: An experimental study, J. Air Waste Manag. Assoc. 68: 3 (2018) 196-214, DOI: 10.1080/1096224 7.2017.1367738. [36] ASTM D638 - 14. Standard test method for tensile properties of plastics. [37] ASTM D790 - 17. Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials [38] A.K.A. Ghazvini, G. Ormondroyd, S. Curling, et al., An investigation on the possible use of coffee silverskin in PLA/PBS composites, J. Appl. Polym. Sci. 139: 2 (2022) e52264. DOI: 10.1002/app.52264. [39] S.T. Georgopoulos, P.A. Tarantili, E. Avgerinos, et al., Thermoplastic polymers reinforced with fibrous agricultural residues, Polym Degrad. Stab. 90: 2 (2005) 303-12. DOI: 10.1016/j.polymdegradstab.2005.02.020. [40] H. Wu, W. Hu, Y. Zhang, et al. Effect of oil extraction on properties of spent coffee ground– plastic composites, J. Mater. Sci. 51: 22 (2016) 10205-214. DOI: 10.1007/s10853-016-0248-2. [41] S. Angelini, P. Cerruti P, B. Immizi, et al., Effect of a lignocellulosic filler on the properties of poly (3-hydroxybutyrate), Int. J. Bio Macromol. 71 (2014) 163-76. DOI: 10.1016/j.ijbiomac.2014.07.038. [42] A.S.C. Bomfim, H.J.C. Voorwald, K.C.C.C. Benini, et al., Sustainable application of recycled espresso coffee capsules: Natural composite development for a home composter product. J Clean Prod 2021; 297:126647. DOI: 10.1016/j.jclepro.2021.126647.

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Advanced Materials and Production Technologies

[43] K.C. Reis, L. Pereira, I.C.N. Melo, et al. Particles of coffee wastes as reinforcement in Polyhydroxybutyrate (PHB) based composites, Mater. Res. 18: 3 (2015) :546-552. DOI:10.1590/1516-1439.318114. [44] T.B.R. Nery, Z.I.G. Santos, N.M. José, Desenvolvimento e caracterização de biocompósitos de polihidroxibutirato e fibra de bananeira, Matéria (Rio J.) 23: 4 (2018) e-12257. DOI: 10.1590/S1517-707620180004.0591. [45] H. Moustafa, C. Guizani and A. Dufresne. Sustainable biodegradable coffee grounds filler and its effect on the hydrophobicity, mechanical and t\Aaa\\\\hermal properties of biodegradable PBAT composites, J. Appl. Polym. Sci. 134 (2016) 44498. DOI: 10.1002/app.44498.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 103-113 doi:10.4028/p-1993t4 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-08-16 Revised: 2022-11-03 Accepted: 2022-11-03 Online: 2022-12-26

Conducting Behavior of Bischalcone Derivatives Aswini.R1,a*, D.Lakshmi Devi2,b and S.Kothai3,c, Research Scholar (Ph.D), Department of Chemistry, Ethiraj College For Women, Chennai-8.

1

Assistant Professor, Department of Biochemistry, Ethiraj College For Women, Chennai-8.

2

Principal, Associate Professor & Head, Department of Chemistry, Ethiraj College for Women, Chennai-8.

3

[email protected], [email protected],

a

[email protected]

c

Keywords: Copolyesters, Polycondensation, Bandgap energy, Thermal and Conductivity behavior.

Abstract. With the scope of bischalcone-based copolyesters can be used as semiconductors; two copolyesters were synthesized by the solution polycondensation method. The Bischalcone diol was analyzed by UV-Visible, FTIR, NMR (1H, 13C NMR) spectroscopy. Using the UV-Visible data, the bandgap energy of the Bischalcone diol was calculated and found to be 2.82 eV. The Physicochemical properties like Inherent viscosity and refractive index of the copolyesters were determined. Spectral studies such as FTIR, 1H and 13C NMR spectroscopy. The thermal property of the copolyesters was analyzed by differential scanning calorimetry. The melting temperature of the PTMI is observed at 320oC, and PTMT exhibits 360oC. The PTMT shows higher stability than the PTMT copolyester. The highest ionic conductivity for PTMI is 3.50 x 10-4 (S cm-1). The PTMT copolyester shows -0.0035 KJ mol-1 whereas the PTMI copolyester shows 0.0005 KJ mol-1. The electrochemical impedance analysis and conductivity measurement were examined for the two copolyesters expecting semi-conducting behavior which can be a good candidate for the optoelectronics application. Introduction In recent decades, conducting polymers have made many advances in the optoelectronic field due to the conjugated double bonds. They have diverse applications like conductive coating, energy storage devices [1-3], etc.; supercapacitors are also known as ultracapacitors. It is a power delivery device that easily captures, releases increased energy, and reduce emission. Due to this, ultracapacitors are used as excellent energy-storing devices [4]. Bischalcones are the class of chromophores with the (D-π-A-π-D) molecular configuration and having a large π-conjugation electronic system [5, 6]. In addition to its wide range of biological activities [7-10] like antioxidant, antibacterial, antifungal, etc., It is also explored in the field of optoelectronics. Bischalcone derivatives provide an intramolecular charge transfer and enhance their optical nonlinearity in most organic systems [11, 12]. Owing to the multifunctional aspects, studies on optical and electrochromic properties are sparse [13-15]. Synthetic polymers are long-chain molecules with repeating units that can be processed into any form or shape. Polymers are much more efficient by modifying their chemical structure and can control their properties [16]. The polymers have shown antimicrobial activity, liquid crystalline property, Photocrosslinking property, and Non-linear optical property [17-19]. Due to the development of photonic materials significantly explored in the field of luminescent properties [20, 21]. Chudger et al. (1994) investigated the electrical conductance of polyesters comprising of 4-4՛ dihydroxy bischalcone moiety, which behaved like semiconductors and exhibited thermal stability [22]. The movement of delocalized electrons through a conjugated system is reported to have effective intramolecular charge transfer across the molecule and enhance their optical nonlinearity. Bischalcones belong to the flavonoid family and were studied as an antioxidant, antibacterial, antifungal activity, etc.,

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In this study, the ultimate aim is to predict the thermal and conductivity property of the copolyesters. Bischalcone diol, along with various acid chlorides, is used in this study to synthesize novel copolyesters with conducting properties. These copolyesters are synthesized by easy procedure, cost-effective, and they are versatile. These copolyesters, in addition to the property of a typical polyester, also have electrical and optical properties. Therefore these copolyesters are studied for their conductance behavior by conductivity measurement (Hall Effect and Electrochemical Impedance Analysis). Since the synthesized copolyesters are found to be highly stable and have good conducting properties, they can behave as semiconductors. They can also be further studied as supercapacitors, thereby, energy storage devices. Materials and Methods 1-(4-hydroxy-3-methoxyphenyl) ethan-1-one, benzene-1,4-dicarbaldehyde, Isophthaloyl chloride, Terephthaloyl chloride, Pyridine, Potassium Hydroxide, methanol, Hydrochloric acid, ethanol were purchased from Sigma Aldrich and SD fine chemicals (India made Chemicals). A. Synthesis of Monomer diol (THMA) THMA – Terephthaldicarboxaldehyde -- 1-(4-hydroxy-3-methoxyphenyl)ethan-1-one -decomposed with dil. HCl acid. The monomer diol was synthesized by the base-catalyzed Claisen-Schmidt condensation method [22]. Two moles of 1-(4-hydroxy-3-methoxyphenyl) ethan-1-one and one mole of Terephthaldicarboxaldehyde are dissolved in 20 mL of methanol. 40 % of the methanolic solution of Potassium Hydroxide was added to the above mixture and stirred continuously. The above mixture was undisturbed overnight. After that, the reaction mixture was decomposed with a 1:1 dilute Hydrochloric acid. It is then precipitated, filtered, dried, and crystallized using ethanol. The schematic representation of monomer diol is presented in Figure 1. O

H

CH3

O

+

O

CH3

+

OCH 3 OH

O

1-(4-hydroxy-3-methoxy phenyl)ethan-1-one

OH

H

benzene-1,4-di carbaldehyde

OCH 3

1-(4-hydroxy-3-methoxy phenyl)ethan-1-one O

HO

H3CO

OCH 3

O

OH

THMA

Figure 1. Structure of Monomer Diol (THMA) B.Synthesis of Copolyester (PTMI) PTMI – Polymer -- Terephthaldicarboxaldehyde -- 1-(4-hydroxy-3-methoxyphenyl)ethan1-one [TM- reactant used in the Monomer]-- Isophthaloyl chloride. Copolyesters are synthesized using a simple polycondensation method [22]. One mole of THMA (monomer diol) and two moles of Isophthaloyl chloride (aromatic acid chloride) are dissolved in 20 mL of dry pyridine kept in an ice bath, stirred continuously, and maintained at the temperature of 5ºC. It is then acidified with 20 mL of 1:1 di. HCl, filtered, dried, and reprecipitated with acetic acid. The schematic representation of the copolyester (PTMI) is presented in Figure 2.

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O

O HO

Cl

+ O

OH

H 3CO

OCH 3

O

Cl

THMA

Benzene-1,3-dicarbonyl dichloride

H3C

O

O

O

H 3CO

OCH 3

O

O

O

n

CH3

PTMI

Figure 2. Structure of Copolyester PTMI Results and Discussion A. Bichalcone diol / Monomer diol (THMA) Optical Spectroscopy The UV-Visible spectrum of the bischalcone diol is shown in Figure 3. The UV-Visible spectroscopy (Perkin Elmer, India) of bischalcone moiety exhibit two absorption bands, namely ππ* transition (220 to 270 nm) and n-π* transition (340 to 390 nm). The absorption spectrum of monomer diol (THMA) is observed at 257 nm and 349 nm. The absorption peak at 257 is attributed to the π-π* transition [23], and the peak at 349 nm can be assigned to the n-π* transition, which may be attributed to the excitation in the aromatic rings and C=O group [24-27].

Figure 3. The UV-Visible spectrum of THMA Tauc Bandgap Energy From the UV-Visible spectral data, a tauc plot (Figure 4) can be assigned to calculate the bandgap energy [28-29]. The (Eg) bandgap energy of monomer diol (THMA) is 2.82 eV, confirming that this material exhibits a semiconducting property.

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Figure 4. Tauc Plot of THMA FTIR Spectroscopy FTIR spectroscopy (Perkin Elmer, India) recognizes the chemical bonds produced in an infrared absorption spectrum [30]. The FTIR spectrum of bischalcone diol is shown in Figure 5. In the FTIR spectrum of bischalcone diol, the carbonyl stretching vibration for the enones at 1657 cm-1. The peak at 3315 cm-1 corresponds to the OH stretching frequency, and the peak at 3017 cm-1 was observed for C-H Stretching frequency [31-32].

Figure 5. FTIR spectrum of THMA Nuclear Magnetic Resonance Spectroscopy NMR Spectroscopy is a technique to observe a local magnetic field around atomic nuclei. It is unique, well-resolved, and often predictable for small molecules [33]. The aromatic protons were observed at 6.88 ppm. The Vinylic protons attached to the carbonyl group were observed at 7.51 ppm [34]. The hydroxyl proton at 10.03 ppm is due to the intramolecular interaction between the carbonyl group. The methoxy proton in the bischalcone moiety ranges from 3.39 to 3.82 ppm. In the 13 C NMR spectrum, the carbonyl carbon was observed at 196.57 ppm [35, 36]. B. Copolyesters (PTMT, PTMI) Physico-Chemical Properties The inherent Viscosity of the Copolyesters PTMT and PTMI were determined by Ubbleholde Viscometer and Abbe refractometer, respectively, and were analyzed using DMAc as a solvent at 30ºC [34]. The physicochemical properties of the synthesized copolyesters are tabulated in Table 1.

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Table 1 Colour, Inherent Viscosity, Refractive Index and % yield of Copolyesters S.No Copolyester Colour Inherent Refractive % Code Viscosity (Cp) Index (η) Yield 1. PTMT White Crystalline 0.84 1.435 90 2.

PTMI

Pale White

0.86

1.433

83

Fourier Transform Infrared Spectroscopy The copolyester PTMT of the FTIR spectrum is shown in Figure 6. The O-H stretching frequency was observed at 3448 cm-1, and the ester carbonyl stretching frequency was observed at 1725 cm-1,1791 cm-1, which confirms polyester formation. The peak at 1684 cm-1 and 730 cm-1 corresponds to the C=C stretching frequency and C=C bending frequency. The IR Spectrum of PTMI is shown in Figure 7. The peak at 1722 cm-1 and 1740 cm-1 is due to ester carbonyl stretching frequency. Similarly, PTMI also shows the characteristics of bands and confirms their formation of Copolyester [37, 38].

Figure 6. FTIR Spectrum of PTMT

Figure 7. FTIR Spectrum of PTMI

NMR Spectroscopy It’s primarily used as an analytical technique (Bruker Biospin, Switzerland) to find out the structural information of a sample. Table 2 and 3 shows the 1H NMR and 13C NMR chemical shift values for the copolyesters. Table 2 1H NMR chemical shift values of the copolyesters S.No 1.

Sample Code PTMT

2.

PTMI

1H

NMR Chemical Shift Values Functional Group σ (ppm) Aromatic protons 8.03 Methylene protons 2.507 Methoxy protons 3.85 Aromatic protons 8.44 Methylene protons 2.510 Methoxy protons 3.89

The methoxy proton was observed in the range of 3.38 to 3.47 ppm. The aromatic protons were observed from 8.05 to 8.45 ppm, and the methylene protons attached to the carbonyl group were observed from 2.51 to 2.55 ppm. In the 13C NMR spectrum, the carbonyl carbon was observed from 167.00 to 167.10 ppm, and the aromatic carbons were observed in the range of 144.71 ppm for

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PTMI, but PTMT doesn’t show an aromatic carbon peak. The methylene carbon was observed from 39.30 to 39.90 ppm [34-36]. Table 3 13C NMR chemical shift values for the copolyesters S.No 1.

Sample Code PTMT

2.

PTMI

13C

NMR Chemical Shift Values Functional Group σ (ppm) C=O 167.25 -CH321.55 -CH239.89 C=O 167.13 -C=C144.71 -CH239.31

Differential Scanning Calorimetry (DSC) DSC (Perkin Elmer, India) was used to analyze the heat flow and temperature depending on the thermal transition. The thermal property of Copolyester was investigated by Differential Scanning Calorimetry. The DSC curve for the copolyester PTMT is shown in Figure 8. The glass transition temperature(Tg) of PTMT is around 155ºC. The melting temperature(Tm) of Copolyester was observed in the range of 320ºC [37, 38]. The DSC curve for the copolyesters PTMI is shown in Figure 9. The glass transition temperature(Tg) of PTMI is around 100ºC. The melting temperature(Tm) of Copolyester was observed in the range of 360ºC [37, 38].

Figure 8. DSC Thermogram of PTMT

Figure 9. DSC Thermogram of PTMI

Impedance Spectroscopy (EIS) Electrochemical impedance spectroscopy (ValueTronics International, India) is based on the perturbation of an equilibrium state. It is a non-destructive technique to provide time-dependent information about the properties of the samples. The Nyquist plot is represented by a symbol (Z) and is composed of real and imaginary parts. If the imaginary part is plotted on the y-axis and the real part is plotted on the x-axis, then the graph is termed a Nyquist Plot [39-41]. It results from the RC circuit, and then the semicircle is a characteristic of a single ‘‘time constant’’. The Conductivity (σ) of a sample was calculated by the formula σ = t / A x R,

(1)

where t is – the thickness of the sample, A – is the contact area of the sample, and R is – the resistance of the sample.

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Figure 10. Impedance Plot of Copolyester PTMT

109

Figure 11. Impedance Plot of Copolyester PTMI

Table 4 Ionic Conductivity of a Copolyesters S.No

Sample Code

Ionic Conductivity σ (S cm )

1.

PTMT

2.

PTMI

1.27 x 10

-1

-3

-4

3.50 x10

The impedance plot of copolyesters PTMT, and PTMI are shown in Figures 10 and 11. The highest ionic conductivity value for PTMI is 3.50 x10-4 (S cm-1). Hence, synthesized copolyesters behave like semiconductors. Conductivity Study The Copolyesters are prepared on a thin film with the dimension of 1 cm x 1 cm to study the conductivity study by using Hall Effect measurement (Acal BFi Germany GmbH, Dietzenbach, Germany). Thin film Preparation Copolyesters are mixed with 15 mL of THF (Tetrahydrofuran) and stirred for 15 minutes. After that PVC (Polyvinylchloride) was added and stirred for 30 minutes. Finally, the above mixture is cast in a petri dish. After drying, it was peeled off like a film. The electrical conductivity or specific conductance is a reciprocal of electrical resistivity. The SI unit of electrical conductivity is siemens per meter (S/cm). It represents a material’s ability to conduct electricity. The effect of temperature on the conductivity is examined by varying temperatures using a thin film of a sample. The variation of conductivity with temperature is expressed by a formula: σ = σº exp [ -ΔE / KBT ],

(2)

where σ – electrical conductivity at temperature T, σº – electrical conductivity at temperature T∞, E – electrical conductivity, KB – Boltzmann constant, T – temperature.

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Figure 12. Arrhenius Plot of Copolyesters PTMT, PTMI The Conductivity measurement for the copolyesters PTMT and PTMI were analyzed at different temperature ranges from 100 to 350 K. The plot of Ln σ (S/cm) vs 1000/T (K-1) was graphically plotted (Arrhenius plot) for the copolyesters, as shown in Figure 12. To get the activation energy values from the slope and pre-exponential factor from the intercept. In the x-axis, the peak at 1.74 PTMT drifted down from a linear straight line, whereas the PTMI slightly drifted down from a straight line. This may be due to the mechanism of conduction of a material. From the Arrhenius plot, the energy of activation and frequency factor is calculated for the copolyesters PTMT, and PTMI is reported in Table 5. Table 5 Arrhenius plot values of the Copolyesters S.No

Sample Code

1. 2.

PTMT PTMI

Arrhenius Plot Values Activation Energy Frequency Factor -1 Ea (K J mol ) An (L mol-1s-1) -0.0035 9.4569 x 10 -4 0.0005 9.1526 x 10 -3

The above graphs are produced in the equation used by Arrhenius. The Arrhenius equation can be compared and determine the Activation energy (Ea) and frequency factor (or) Pre- exponential factor (A). The copolyester PTMT exhibit a negative activation energy value due to the reaction rate decreasing with an increase in temperature, whereas the PTMI shows a positive activation energy value, and this may be attributed to the reaction rate increases with a decrease in temperature. The conductivity measurement results reveal that the copolyesters PTMT and PTMI behave like semiconductors from the Arrhenius plot. Conclusion The Bischalcone diol was prepared by the base-catalyzed Claisen – Schmidt condensation method. The synthesized Bischalcone moiety (THMA) was characterized by UV-Visible, FTIR, NMR (1H, 13C) Spectroscopy. The structural elucidation of a Bischalcone moiety was confirmed from the UV-Visible, FTIR, and NMR (1H, 13C) spectroscopy. From the UV-Visible spectral data, band gap energy is calculated. The two copolyesters were synthesized by varying diacid chlorides incorporated in a bischalcone moiety by the solution polycondensation method. The Physicochemical properties of the copolyesters were analyzed by inherent viscosity and refractive index. The FTIR, NMR (1H, 13C) spectroscopy results confirm the structural information of the copolyesters. The thermal properties of the copolyesters were also determined. The glass transition temperature of PTMT at 155oC and PTMI at 100oC. Due to this, the two copolyesters exhibit good

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thermal stability. The electrochemical impedance analysis was also determined. The PTMI copolyester exhibits higher ionic conductivity (3.50 x 10-4 S cm-1) than the PTMT. The two copolyesters were examined by conductivity study by the Hall effect measurement. The conductivity analysis for the two copolyesters was determined. The conductivity measurement evaluated activation energy and frequency factor from the Arrhenius plot. The PTMT copolyesters show -0.0035 KJ mol-1 due to the reaction rate decreasing with an increase in temperature. Hence, the two copolyesters exhibit good thermal stability and behave like semiconductors. Future Scope In this study, the synthesized copolyesters have a low refractive index, high glass transition temperature, and excellent electrical conductivity. Hence these copolyesters can be used in optical film. These copolyesters will be extensively studied for charge carrier mobility and NLO activity in the future. Acknowledgment The authors are grateful to the Ethiraj College for Women for ECRIC minor project grant to carry out this work. Authors also thank the instrumentation centers like Avinashilingam College for Women and MNIT Jaipur. Conflict of Interest The authors declare there is no conflict of interest. References [1] Shaojun Guo, Shaojun Dong, Erkang Wang. Three-Dimensional Pt-on-Pd Bimetallic and Advanced Nanoelectrocatalyst for Nanosheet: Facile Synthesis and Used as Nanodendrites Supported on Graphene Methanol Oxidation.ACS Nano., 4(1), (2009), 547-555. [2] Shen Y, Wan M. In situ doping polymerization of pyrrole with sulfonic acid as a dopant. Synth Met. 96(2): ( 1998), 127–32. [3] Shinde SS, Gund GS, Kumbhar VS, Patil BH, Lokhande CD. Novel chemical synthesis of polypyrrole thin-film electrodes for supercapacitor application. Eur Polym J. 49(11): (2013) 3734– 3749. [4] Joshi M, Adak B. Advances in nanotechnology-based functional, smart, and intelligent textiles: A review -Comprehensive Nanoscience, and Nanotechnology. Elsevier. 1–5, (2019), 253–290 . [5] Shen L, Li Z, Wu X, Zhou W, Yang J, Song Y. Ultrafast broadband nonlinear optical properties and excited-state dynamics of two bis-chalcone derivatives. RSC Adv. 10(26): (2020),15199– 15205. [6] Nohut Maşlakcı, N., Biçer, A., Turgut Cin, G., Uygun Öksüz, A. Electrochromic properties of some bis-chalcone derivatives-based nanofibers. Journal of Applied Polymer Science., 135(12), (2018), 25–30. [7] Asiri, A. M., Khan, S. A. Synthesis, characterization and optical properties of mono- and bischalcone. Materials Letters., 65(12), (2011), 1749–1752. [8] Pandeya SN, Sriram D, Nath G, Declercq E. Synthesis, antibacterial, antifungal and anti-HIV activities of Schiff and Mannich bases derived from isatin derivatives and N-[4-(4’chlorophenyl)thiazol-2-yl] thiosemicarbazide. Eur J Pharm Sci., 9(1): (1999), 25–31.

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[9] Ducki S, Forrest R, Hadfield JA, Kendall A, Lawrence NJ, McGown AT, et al. Potent antimitotic and cell growth inhibitory properties of substituted chalcones. Bioorganic Med Chem Lett. 8(9): .(1998), 1051–1060 [10] Konieczny MT, Konieczny W, Sabisz M, Skladanowski A, Wakieć R, Augustynowicz-Kopeć E, et al. Acid-catalyzed synthesis of oxathiolone fused chalcones. Comparison of their activity toward various microorganisms and human cancer cells line. Eur J Med Chem. 42(5): (2007), 729– 733. [11] Christodoulides, D.N., Khoo, I.C., Salamo, G.J., Stegeman, G.I., Van Stryland, E.W., Nonlinear refraction and absorption: mechanisms and magnitudes, Adv. Opt. Photonics. 2 (1). (2010), 60–200. [12] Yang, Y., Wu, X., Jia, J., Shen, L., Zhou, W., Yang, J., Song, Y. Investigation of ultrafast optical nonlinearities in novel bis-chalcone derivatives. Optics and Laser Technology, 123(10), (2020), 105903. [13] Jin, H., Li, X., Tan, T., Wang, S., Xiao, Y. Dyes and Pigments Electrochromic properties of novel chalcones containing triphenylamine moiety. Dyes and Pigments, 106, (2014), 154–160. [14] Modzelewska, A., Pettit, C., Achanta, G., Davidson, N. E. Anticancer activities of novel chalcone and bis-chalcone derivatives. Bioorganic and Medicinal Chemistry. 14, (2006), 3491– 3495. [15] Zhao, B., Wu, Y., Zhou, Z., Lu, W., Chen, C. Theoretical study on the organic molecular second-order hyperpolarizability. Applied Physics B - Lasers and Optics. 70, (2000), 601–605. [16] Geoghegan, M., Hadziioannou, G. Polymer Electronics, (2013), 1–6. [17] Sakthivel, P., Kannan, P. Novel Thermotropic Liquid Crystalline-cum- Photocrosslinkable Polyvanillylidene Alkyl/aryl phosphate Esters.Wiley InterScience.42, (2004), 5215–5226. [18] Kannan, P., Kishore, K. Novel photo-cross-linkable flame retardant polyvanillylidene aryl phosphate esters.Polymers. 38(17), (1997), 4349–4355. [19] Vidhya, T., Sidharthan, J. A study on photoactive bischalcone based liquid crystalline polyesters. 2(12), (2017), 200–205. [20] Burroughes, J.H., Bradley, D.D.C., Brown, A.R., Marks, R. N., Mackay, K., Friend, R. H., Burns, P.L., Holmes, A.B., Light-emitting diodes based on conjugated polymers. Nature. (1990), 347. [21] Lukacs, S. J., Cohen, S. M., Long, F. H. Optical Properties of a Liquid-Crystalline Random Copolyester. Journal of Physical Chemistry B, 103(32), (1999), 6648–6652. [22] Chudger, N.K., Sharma, H., Kansara, S.S., Negai, R., Synthesis of polyester with chalcone linkage as conducting polymer, Macromolecular Reports, (1994), 231-235. [23] Devia AC, Ferretti FH, Ponce CA, Tomas F. Conformational equilibrium and intramolecular hydrogen bond of 4’X and 4X substituted 2’(OH) chalcones. J Mol Struct Theochem 493: (1999), 187-197. [24] Crasta V, Ravindrachary V, Bhajantri RF, Gonsalves R. Growth and characterization of an organic NLO crystal:1-(4-methyl phenyl)-3-(4-methoxyphenyl)-2-propen-1-one. J Cryst Growth 267: (2004), 129-133. [25] Sarojini BK, Narayana B, Ashalatha BV, Indira J, Lobo KG. Synthesis, crystal growth and studies on non-linear optical property of new chalcones. J Cryst Growth 295: (2006), 54-59. [26] Evranos B, Ertan R. Spectral Properties of Chalcones II, .(2012), 205–216.

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[27] Tze Pei Phana, Kien Yung Teoa, Zhi-Qiang Liub, Jenn-Kai Tsai c, Meng Guan Taya, Application of unsymmetrical bis-chalcone compounds in dye sensitized solar cell, Chemical Data Collections, 22 (2019), 100259 [28] Prabhash PG, Nair SS. (2016). Synthesis of copper quantum dots by chemical reduction method and tailoring of its band gap., (9). [29] J. Tauc, R. Grigorovici, and A. (1966).Vancu, physica status solidi (b) 15, 627. [30] Smith, D.R.; Morgan, R.L.; Loewenstein, E.V. "Comparison of the Radiance of Far-Infrared Sources". J. Opt. Soc. Am. 58 (3): (1968), 433–434. [31] K. R. Harshitha and B. K. Sarojini,"Donor-acceptor-donor (DAD) type pipyridinonyl bischalcone derivatives as promising UVA filters", AIP Conference Proceedings 2244, 040001 (2020) https://doi.org/10.1063/5.0009078 [32] Kiruba, B., Chidambaravinayagam, S. (2022). Photocrosslinking Property of Certain Synthesized Bis(arylidene)cycloalkanone based Random Copolyesters with Computational Support and their Anticancer Study. Journal of Scientific Research, 14(3), 901–915. https://doi.org/ 10.3329/jsr.v14i3.57161 [33] Hoult, D. I.; Bhakar, B. "NMR signal reception: Virtual photons and coherent spontaneous emission". Concepts in Magnetic Resonance. 9 (5): (1997), 277–297. [34] Devi DL, Aswini R and Kothai S. Synthesis and Characterisation of chalcone-based copolyesters and their anticancer activity. Int J Pharm Sci Res., 9(4): (2018), 1589-1593. [35] L. O. A. Ferreira, A. K. S. M. Valdo, J. A. Nascimento Neto, L. Ribeiro, J. R. D. da Silva, L. H. K. Queiroz Jr, C. N. Perez and F. T. Martins, ss-NMR and single-crystal X-ray diffraction in the elucidation of a new polymorph of bischalcone (1E,4E)-1,5-bis(4-fluorophenyl)penta-1,4dien-3one, Acta Cryst. (2019). C75, 694-701 https://doi.org/10.1107/S2053229619006156 [36] Serdar Burmaoglua, Seyda Ozcanb, Sevgi Balciogluc, Melis Genceld, Samir Abbas Ali Nomac, Sebnem Essizd, Burhan Atesc, Oztekin Algul, Synthesis, biological evaluation and molecular docking studies of bischalcone derivatives as xanthine oxidase inhibitors and anticancer agents, Bioorganic Chemistry, 19, 2019, 103149. [37] S. Priyarega, A. Muthusamy, K. Kaniappan, S. C. Murugavel Synthesis and characterization of photosensitive polyesters by phase-transfer catalyzed polycondensation, Designed Monomers, and Polymers, 6:2, (2003), 187-196. [38] Vandersypen, Lieven M. K.; Steffen, Matthias; Breyta, Gregory; Yannoni, Costantino S.; Sherwood, Mark H.; Chuang, Isaac L. "Experimental realization of Shor's quantum factoring algorithm using nuclear magnetic resonance". Nature. 414 (6866): (2001), 883–887. [39] Barsukov, E., and Macdonald, J. R. Impedance Spectroscopy, 2nd ed. Wiley-Interscience, New York. (2005), 2. [40] Conway, B. E. Electrochemical Supercapacitors, Kluwer Academic/Plenum, New York, (1999). [41] Orazem, M., and Tribollet, B. Electrochemical Impedance Spectroscopy (The ECS Series of Texts and Monographs) Wiley-Interscience, New York, (2008).

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 115-126 doi:10.4028/p-118y5f © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-17 Revised: 2022-09-27 Accepted: 2022-10-06 Online: 2022-12-26

Experimental Investigations on the Effect of Yarn Speed and Wrap Angle on Yarn-Solid and Yarn-Yarn Friction Using Warp Knitting Machines Mathis Bruns1,a*, Maximilian Krentzien2,b, Michael Beitelschmidt2,c and Chokri Cherif1,d Faculty of Mechanical Science and Engineering, Institute of Textile Machinery and High Performance Material Technology (ITM) at Technische Universitaet Dresden (TUD), Germany 1

Faculty of Mechanical Science and Engineering, Institute of Solid Mechanics (IFKM), at Technische Universitaet Dresden (TUD), Germany

2

[email protected], [email protected], [email protected], [email protected]

a c

Keywords: friction, yarn, solid, model, modeling, modelling, measuring, warp knitting machine

Abstract. Warp knitting is appointed as a manufacturing method for high-performance and highquality textiles due to its versatility and production speed. To ensure a continuous and error-free manufacturing process under highly dynamic production conditions, a high level of knowledge of the yarn and machine interaction is required. Mechanical stresses from the machine are transferred to the yarn via friction points, as well as during the stitching process from one yarn to another, where the yarn is subjected to high stresses. Therefore, the focus of this research is the investigation of the friction between the yarn and yarn guiding elements and the friction between the yarns themselves during the stitch formation. For this reason, all contact points between yarn and yarn guiding elements as well as between the yarns themselves are examined and classified. A test rig is set up to determine all occurring frictions as a function of various machine parameters. The knowledge gained and the derived analytical expressions between machine settings and occurring friction can thus become the basis for modeling the friction points of the warp knitting machine, which is also presented. Furthermore, based on the findings a design improvement of the machine can be achieved and the friction model can serve as part of a simulation model of the entire warp knitting machine, which will be the focus of further publications. Introduction Warp knitting is a textile manufacturing process with very high productivity due to the simultaneous interlacing of all threads of a knitting thread system. Furthermore, it is highly versatile in terms of layer construction, arrangement and orientation, which makes warp knitting a predestined textile technology for the production of both high-performance technical textiles and high-quality textiles in the clothing industry [1, 2]. Therefore, warp knitting is used in the manufacture of hightech applications such as wind turbine rotors, automotive and shoe manufacturing as well as in the production of conventional garment textiles or even in medical applications [3, 4]. The current digitalization trend towards Industry 4.0 is also becoming increasingly popular in the textile industry and in the production of warp knitting machines and warp knitted fabrics. Considering this trend in particular, precise knowledge and understanding of the mechanical behavior of the machine with different and rapidly changing operating parameters is highly important to ensure a high productivity and a low error rate. The yarn tension during warp knitting has been investigated very often in order to improve the warp knitting process. Many patents and technical possibilities are available for an active or passive regulation of the yarn tension [5 – 8]. Yarn friction, which contributes to yarn tension, is more difficult to characterize and is therefore only marginally considered in yarn tension related publications. Nevertheless, literature exists

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specifically to determine the coefficients of friction of yarns, but these do not specifically refer to the highly dynamic yarn loads during the knitting process. Mei et al. showed that the hairiness of the yarns increased during the warp knitting process, while the tensile strength of the yarns decreased [9]. Frictional influences were mentioned here as the reason for this observation. Yuksekkay has reviewed publications by various scientists on the measurement of friction coefficients of yarns and showed for example, that for some researchers an increasing wrap angle increased the friction force, while other researchers have found that an increasing wrap angle reduces the friction force. However, the yarn speed was not taken into account in these investigations [10]. Consequently, the coefficient of friction is not an easy and uniform value to determine and dependends on different parameters, which change dynamically during the warp knitting process. For this reason, both the friction between the yarn and the yarn guiding element and the friction between the yarns themselves during stitch formation, are less well known. Error detection and process optimization are therefore often based on practical knowledge. With regard to the simulation of yarn friction in textile machines, Beitelschmidt has succeeded in simulating the incidental yarn-solid twill friction of a weaving machine [11]. Materials and Methods Mathematical description of yarn friction The Capstan equation (also Eytelwein’s formula) is a common mathematical description of the friction between a yarn and a solid body in relative motion. It refers to the input and output tension as well as to the wrap angle of a yarn wound around a deflection element and is expressed as

eµ𝜃𝜃 =

𝐹𝐹OUT 𝐹𝐹IN

,

(1)

where µ is the coefficient of friction, 𝜃𝜃 is the wrap angle of the yarn around the deflection element and F is the yarn force before (FIN) and after (FOUT) the deflection element. This equation is also used in standard test method “Coefficient of Friction, Yarn to solid Material” that is provided by the ASTM International [12] and has often been used, for example in work concerning the simulation of thread friction in a weaving machine [11] or to determine influences of different manufacturing parameters on the coefficient of friction [13]. For the calculation of the friction between two yarns, ASTM also provides a standard method in the form of ASTM D3412, where two optional procedures are included [14]. One is similar to the Capstan Method. One difference lies in the yarn arrangement. Here, the deflection element is wrapped by the yarn, so that the moving yarn is pulled over a yarn sheet with almost the same orientation in the contact point and can also settle in the lanes of the wrapping yarn. The second method is the twisted strand method, in which the yarn is twisted helically with itself. Figure 1 shows the given schematic structure.

Figure 1: Twisted Strand Yarn-to-Yarn Friction Apparatus – Twisted Yarn Method [14]

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The equation given in the ASTM D3412 to calculate the coefficient of friction is

µ=

F ln OUT FIN

2πnα

(2)

,

where nα is defined as the number of wraps but is supposed to be n times α. This standard approach and other recently developed instruments for the measurement of a dynamic friction coefficient, do not allow variation of the opening angle α (see Fig. 1) thus there is only limited possibility to adapt these test setups to the geometrical conditions of the knitting machine when using this analysis [15]. Another method of determining yarn-yarn friction is the hanging fiber method. Here, a yarn with a weight is pulled over another yarn by means of a tensile testing machine. The friction properties of the yarns can be determined by the force ratio between the ascending and descending pull of the yarn, but the real geometric conditions of the thread in a warp knitting machine are difficult to reproduce. Moreover, the required speeds cannot be reproduced with most tensile testing machines [16]. Another mathematical description of yarn-yarn friction is presented by Hobbes and Ridge [17]. In this work, the oscillating opening angle of the yarn entering and leaving the friction point is considered so that the equilibrium of forces at the friction point is taken into account. The derived equation in this paper is

µ=

γ 2

(FOUT −FIN )tan ( )

π(Nc −1)(FOUT sin2 α+FIN sin2 β)

,

(3)

where γ is the opening angle (in Fig. 1, this angle is labeled α), Nc is the number of wraps, α is the angle part of γ, which is enclosed by the outgoing yarn and the axis of the yarn helix and is the β the part that is enclosed by the incoming yarn and the axis of the yarn helix. Experimental procedure For determining the friction coefficients occurring during highly dynamic warp knitting, all friction pairs must be classified. This includes the geometrical analysis of the friction elements, the deflection angle of the yarn over them as well as the yarn running speeds and yarn tension forces. These values are determined using a Copcentra 3K warp knitting machine from Karl Mayer Textilmaschinenfabrik GmbH, Germany (formerly LIBA Maschinenfabrik GmbH, Germany). The machine has a theoretical production speed of up to 4400 rpm, but is limited by the type of yarn being processed. In general, the technically relevant range of yarn speed for high performance warp knitting is 20 to 100 m/min. A CAD model of the entire machine was created to calculate the yarn path (Fig. 2) and in particular, all deflection angles with which the yarn is guided over the yarn guiding elements (Fig. 3).

Figure 2: (a) CAD Modell of the warp knitting machine, (b) the derived Yarn path

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Figure 3: Removed relevant yarn guide elements

The yarn guiding elements, which are in direct contact with the yarn between the warp beam and the draw-off device as well as the corresponding deflection angles, are listed in Table 1. Table 1: Wrap angles of the yarn derived from the CAD model for relevant yarn-yarn guiding element friction pairings

Deflection Role* Thread Comb Deflection Role II* Tension Compensation Rod Guide needle Needle

*The deflection rollers do not rotate during machine operation

Guide Bar 1 (°) 31° 158° 172° 180° Not classifiable

Guide Bar 2 (°) 142° 173° 180° Not classifiable

Guide Bar 3 (°) 42,19° 129° 181° 180° Not classifiable

To classify the friction between the yarns during stitch formation, the corresponding wrap angles were graphically evaluated using a CAD model of the produced tricot knitted fabric (Fig. 4). Table 2 shows the occurring wrap angles in the modeled knit.

Figure 4: CAD Model of the Tricot Binding, (a) closed stitch, (b) open stitch Table 2: Wrap angles derived from the CAD model of the tricot binding for yarn-yarn friction

Wrap angle (°)

Tricot open 115-155

Tricot closed 60-78

To determine the frictional forces that occur during dynamic warp knitting process, cotton, textured PES (PES-tex), high tenacity PES (HT-PES or PES HT in Fig. 11) and aramid (Aramid) was used. These yarns are characterized by low strain capacity (except PES-tex) and are partly difficult to process. The mechanical properties of the yarns were acquired using a Z100 tensile testing machine by ZwickRoell GmbH & Co KG, Germany. The diameters of the yarns were determined by using an AxioImager M1m microscope from Carl Zeiss Microscopy GmbH, Germany. Figure 5 shows microscopic images of the yarns, in which the yarn structures are clearly visible. Table 3 shows the measured mechanical properties of the used yarns.

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Figure 5: Microscopic Images of the tested yarns. (a) PES tex, (b) Cotton, (c) HT PES and (d) Aramid

In order to measure the coefficient of friction, a CTT yarn tester by Lawson-Hemphill, USA, was used. With this device it is possible to measure the friction between a yarn and a metal pin at a wrap angle of 180 degree as well as the yarn-yarn friction. However, it is not possible to classify the friction between the yarn and the actual yarn guiding elements of the machine and to evaluate different deflection angles. Table 3: Investigated yarn materials and their structural and mechanical properties

Material

Manufacturer

PES-tex Cotton HT-PES Aramid

TWD fibres, Ger Rütex GmbH, Ger php Fibers GmbH, Ger Teijin Aramid BV, Nld

Yarn count (dtex) 179 200 140 225

Yarn Diameter (µm) 185 183 232 438

E-Modulus (GPa) 1 6 13 74

For this reason, the machine has been extended in a modular way with a self-designed application that allows the classification of yarn-yarn guiding element friction according to ASTM D3108 [12] (Fig. 6, left) and an application that allows the characterization of yarn-yarn-friction according to the mathematical description by Hobbes and Ridge (Eq. 3; Fig 6, right). The setup based on ASTM 3105 for the classification of yarn-metal friction has a fixture in which the yarn guiding elements removed from the machine can be mounted. By means of the adjustable, low-friction deflection rollers, the entry and exit angles of the yarns from the friction point can be precisely set and read off a scale. The setup for determining the yarn friction coefficients according to Equation 3 includes a vertically adjustable deflection roller for yarn guidance. The yarn can be twisted with itself in 0.5 rotations respectively 180 degree increments. The opening angle is continuously adjustable by deflection rollers. This ensures a precise position and alignment of the friction partners in the test setup according to the model of the existing warp knitting machine, so that the reproducible measurements can be performed at varying yarn running speeds. Furthermore, the yarn tension before and after the friction point were recorded by two FSP200 USB yarn tension sensors (measuring station, accuracy 200 cN ± 1.5%) from Hans Schmidt & Co GmbH, Germany. Yarn running speed and yarn tension were adjusted using the modules of the Lawson-Hemphill CTT. To represent the operating parameters of the warp knitting machine in an efficient test procedure a design of experiments (DOE) was done to set up a variation of the test parameters, yarn velocity and wrap angle for all friction pairings.

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Figure 6: Designed application for varying the wrap angle of yarn-solid friction with a chuck for the integration of different deflection elements of the wrap knitting machine (left) and yarn-yarn friction (right). Red line: yarn path, blue arrow: upper two pulleys are adjustable for varying the wrap angle.

All tests are carried out at yarn speeds of 20 m/min, 46 m/min and 72 m/min. Similarly, wrap angles of 30, 105 and 180 degrees were used in the experiments for yarn-solid friction. For the characterization of yarn-yarn friction, the yarn was oriented with an opening angle γ (see Eq. 3) of 60, 120 and 180 degrees and entangled with itself at one time and one and a half times, respectively. Due to the expected stick-and-slip phenomena during the yarn-yarn friction tests and the resulting subdivision of the opening angle γ into the partial angles α and β (see Fig. 7), the friction point was recorded (with a VCXU-23M camera from Baumer Optronic GmbH, Germany). The dynamic partial angles α and β were determined by means of Digital Image Correlation (DIC) via the Matlab programming software. Figure 7 shows the different positions of the wrap point depending on the stick and slip friction as well as the angle measurement via DIC and the oscillating inlet and outlet angles.

Figure 7: (a) Different positions of the wrap point, (b) DIC to measure the input and output angle of the yarn and (c) the measured angles

In the preparation of this work, yarn tension tests were carried out directly on the machine in order to determine a pretension of the yarns for the friction experiments. Based on this previous work, a yarn pretension of about 13 cN was set for the friction experiments, the value being slightly variable depending on the friction generated during the test. Furthermore, a simulation of the yarn-solid friction point as a multibody system was performed in this work, using the simulation software Simpack 2021x from Dassault Systèmes, France. Figure 8 shows the model of a yarn wrapped around the deflection role D25. In the model, the yarn was represented by a nonlinear SIMBEAM, using the finite difference method. The yarn was wrapped around a fixed rigid body and a pretension force of the yarn represented the input force of the yarn. The result of the implemented model was the output force of the yarn. The primitives shown in red

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(explicitly not being physically relevant) in Figure 8 are used for indicating a body specific velocity optically. Prismatic joint guiding yarn by rheonomical position law respectively using velocity

𝐹𝐹OUT

Flexible body using nonlinear SIMBEAM

Deflection Element: Rigid Body

199

J 0 Force element defined between bodies using friction coefficient

Movement indicators

Constraint allowing yarn to move in yarn axis direction 𝐹𝐹IN

Joint (J) or Constraint (C) with degrees of freedom

Rigid body fixed to environment

Yarn: Flexible Body using nonlinear SIMBEAM 5 J 0 rheonomic

C 1

Force Element with Library element number

Figure 8: Multibody System Model in Simpack 2021x and its topology

The relations between input and output entities for both the experimental evaluation and the simulation are shown in Table 4. Table 4: Input and output entities for experimental evaluation and for simulation

Input entities Evaluation of experiment

Simulation

FIN

FOUT

each is function of vyarn and 𝜃𝜃

FIN Pretension force FE 5

vyarn

µS or µD

𝜃𝜃

Output entities

µS or µD 𝐹𝐹� OUT

𝐹𝐹� IN Force of FE 199

FE: Force element of Simpack

Results and Discussion The static and dynamic friction coefficients determined as a function of the yarn running speed at various wrap angles of different yarns and yarn guiding elements are shown in Figure 9 – Figure 12. The static friction coefficient, which is always significant higher than the dynamic friction coefficients, is plotted in all Figures at the speed 0 m/min. It is assumed that the friction coefficient drops rapidly during the transition from static to dynamic friction, so that the characteristic curve should swiftly declines between 0 m/min and 20 m/min. It can be seen that higher friction occurs with PES tex, see Figure 9, than with cotton (Fig. 10). For the yarn guiding elements, the highest friction coefficients can be identified for guiding needle, especially at lower wrap angles. Furthermore, the influence of speed is very low in the measurements except for the guiding needle, with lower friction occurring when processing cotton than with PES tex. However, it can be seen that when PES-tex yarns are wrapped with smaller wrap angles, the type of fixed friction partner and the speed have a greater influence on the coefficient of friction than with larger wrap angles.

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Figure 9: Measured static (plotted at 0 m/min) and dynamic (plotted at 20-72 m/min) yarn-solid friction coefficients of PES tex for (a) 30°, (b) 105°, (c) 180° and the deflection elements Thread comb (D1), Thread compensation rod (D10), Deflection role (D25), guiding needle (GN) and knitting needle (KN)

The coefficient of friction for PES tex with the D10 guiding rod at a wrap of 30 degrees and a speed of 72 m/min increases strongly, therefore it is regarded as outliner. The measurements of yarn-solid friction with cotton yarns also confirm a small influence of yarn speed and wrap angle on the friction coefficient. However, the coefficient of friction for the friction pairing of cotton yarn and guiding needle with a wrap angle of 105 ° increases with increasing speed. This might be related to increased filament abrasion of the yarn sticking to the guiding needle. Nevertheless, also with cotton yarns the highest occurring frictions can generally be assigned to the yarn-guiding needle friction pairing.

Figure 10: Measured static (plotted at 0 m/min) and dynamic (plotted at 20-72 m/min) yarn-solid friction coefficients of Cotton for (a) 30°,(b) 105° and (c ) 180° and the deflection elements Thread comb (D1), Thread compensation rod (D10), Deflection role (D25), guiding needle (GN) and knitting needle (KN)

For the yarns PES high tenacity and aramid (see Fig. 11 and Fig. 12), similar results were obtained as for PES tex and cotton. Here, the influence of the yarn running speed is also generally very low and the friction pairing with the guiding needle leads to the highest friction coefficients. Especially with small wrap angles (Fig. 10a and Fig. 11a) the recorded friction coefficients are significant. The reason for the significant friction values of the yarn guiding needle friction pairing could furthermore be that the yarn follows a parabolic deflection curve with the guide needle at high wrap angles, while the deflection curve is tangential or s-shaped at small wrap angles (see Fig. 13). This could lead to higher material stress in the yarn.

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Figure 11: Measured static (plotted at 0 m/min) and dynamic (plotted at 20-72 m/min) yarn-solid friction coefficients of PES HT for (a) 30°, (b) 105°, (c) 180 and the deflection elements Thread comb (D1), Thread compensation rod (D10), Deflection role (D25), guiding needle (GN) and knitting needle (KN)

In addition, with the use of a microscope, it was found that the highest abrasion values occurred at the friction point for this friction combination, regardless of the yarns tested. This may further lead to higher measured friction coefficients and could also increase the occurring friction forces during the warp knitting process.

Figure 12: Measured static (plotted at 0 m/min) and dynamic (plotted at 20-72 m/min) yarn-solid friction coefficients of Aramid for (a) 30°, (b) 105° and (c) 180° and the deflection elements Thread comb (D1), Thread compensation rod (D10), Deflection role (D25), guiding needle (GN) and knitting needle (KN)

Figure 13: Close view of yarn deflection curve around the guiding needle at a wrap angle of (left) 180 degrees and (right) 30 degrees (image from the perspective of the angle bisecting axis)

In the case of yarn-yarn friction, only the tests with an opening angle of 30 degree could be evaluated, since at higher opening angles the difference between incoming and outgoing yarn tension resulted in friction coefficients >2, which is not realistic. Due to the opposite pulling direction of the incoming

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and outgoing yarn, there was a form fit causing a slow down of the relative movement of the yarn sections and thus prevented the yarns from slipping. Nevertheless, no significant influence of the yarn running speed on the friction coefficients could be found for the yarn-yarn friction either (see Fig. 14). The friction coefficients at a higher wrap count are larger, which can be explained by the larger contact area of the yarns.

Figure 14: Measured static and dynamic yarn-yarn friction coefficients at 30 degree opening angle for (left) HT-PES and CO and (right) Aramid and PES-tex

The simulation model of the friction between the yarn and the yarn guide element, which is used in this article as an example of the friction for CO yarn passing over the D25 guide roller at a velocity of 20 m/min, shows high agreement with the experiments (exp.) as shown in Table 4. Table 5: Results of the simulation on the example of cotton wrapped around the D25 deflection role.

Category

°

Exp. results FIN cN

Dynamic friction

30 105 180

14.65 12.63 12.67

Static friction

30 105 180

14.65 12.63 12.67

CO; D25; 20 m/min Units

Wrap angle 𝜃𝜃

Modelresults 𝐹𝐹� IN cN

Exp. results FOUT cN

14.65 12.63 12.67

15.96 16.39 18.10

14.65 12.63 12.67

17.45 20.36 28.73

Modelresults 𝐹𝐹� OUT cN

Deviation of output force to experiment %

15.97 16.36 18.01

0.0 -0.2 -0.5

17.51 20.34 27.12

0.3 -0.1 -5.6

The deviations in the simulation of the dynamic coefficient of friction are in all cases less than 1 %, the deviations in the simulation of the static coefficient of friction are only over 5 % for the wrap angle of 180 degrees. Here, the model can still be adjusted in further development. Overall, the model reproduces the experiments and thus the yarn-solid friction occurring in the warp knitting machine very accurately and can thus act as part of the overall simulation of the dynamic processes of the warp knitting machine. Conclusion The present work investigates in the yarn-yarn and yarn-solid friction coefficients, occurring in a high dynamic warp knitting machine. For this purpose, a test rig was developed in order to integrate the friction bodies in a simple way and to reproduce the geometric relationships of the friction partners analogously to the conditions of the warp knitting machine. In this way, the friction coefficients could

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be determined, whereby the guiding needle can be identified as the component with the highest occurring friction. In order to achieve lower yarn tensions during the warp knitting process, this result can be used to improve the design of warp knitting machines. Furthermore, it was seen that the influence of the yarn speed as well as the wrap in yarn-solid friction pairings is very low. In addition, a model was developed to simulate yarn-solid friction with a high accuracy and can thus become part of an overall model of the dynamic yarn processing process. Acknowledgement The DFG research project CH 174/44-1 is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). The financial support is gratefully acknowledged.

References [1]

C. Cherif, Textile Werkstoffe für den Leichtbau, Springer Berlin Heidelberg, Berlin, Heidelberg, 2011.

[2]

A. P. Čuden: 2 – Recent developments in knitting technology. In: Advanced Knitting Technology (2022), 13-66

[3]

M. O. Weber, T. Mutschler, L. M. Bahr: ITMA 2019 - Trends und Neuheiten: Kettenwirkerei, Melliand Textilberichte 2019 4 (2019), 237-240

[4]

W. Renkens, Y. Kyosev, Geometry modelling of warp knitted fabrics with 3D form, Textile Research Journal 81.4 (2011), 443-443

[5]

V. Pohlen, A. Schnabel, F. Neumann, T. Gries, Optimisation of the warp yarn tension on a warp knitting machine, Autex Research Journal 12.2 (2012), 29–33

[6]

A. Ünal: Analyse und Simulation des Fadenlängenausgleichs an Kettenwirkmaschinen für die optimale Konstruktion von Fadenspanneinrichtungen. Dresden, Technische Universität Dresden, Fakultät Maschinenwesen. Dissertation, 2003

[7]

W. Lanarolle et al: Effects Of Tension variations of individual yarns on quality of warp knitted fabrics. In: International Journal of Engineering Sciences & Research Technology (2017), 4045

[8]

G. Jiang, H. Cong, F. Xia, Q. Zhang and J. Zhng, U.S. Patent US10392733B2 - Jacquard warp tension device for warp knitting machine, 2015

[9]

D. Mei et al., Mechanical properties and hairiness characterizations of compact-spinning cotton yarn in warp-knitting processing, The Journal of The Textile Institute (2021), 1-8.

[10] M. Yuksekkay: More about fibre friction and its measurements, Textile Progress 41.3 (2009), 141-193 [11] M. Beitelschmidt, Simulation verschiedener Reibungsphänomene in Textilmaschinen. VDIBerichte 1736, Reibung und Schwingungen in Fahrzeugen. Maschinen und Anlagen: Tagung Hannover 26-27-Nov-2002. Düsseldorf, VDI Verlag 2002 [12] ASTM D3108 Standard test method for coefficient of friction, yarn to solid material, 2013 [13] A. Shahzad et al., Statistical analysis of yarn to metal frictional coefficient of cotton spun yarn using Taguchi design of experiment, The Journal of Strain Analysis for Engineering Design 53.7 (2018) 485-493.

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[14] ASTM D3412 Standard test method for coefficient of friction, yarn to yarn. West Conshohocken, 2007 [15] T. Wang et al., Development of a new low-cost instrument for dynamic friction coefficient measurement of yarns based on the entanglement method, The journal of the textile Institute, 2021, 1-12 [16] A. Alirezazadeh et al., Fiber-on-fiber friction measurement using hanging fiber method, The Journal of The Textile Institute 109.5 (2018) 636-646. [17] R. E. Hobbes, I. M. L. Ridge: A new estimate of the yarn-yarn-friction coefficient. Journal of strain analysis, 53(4), (2018) 191-196.

CHAPTER 3: Chemical Processes and Technologies

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 129-134 doi:10.4028/p-hx1wkt © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-10-17 Accepted: 2022-11-15 Online: 2022-12-26

Preparation of Ruthenium Hollow Spheres as Catalysts for Selective Hydrogenation of Benzene to Cyclohexene Houdong Rao1,a* , Dongyang Zhang1,b, Jingrui Li1,c, Ling Zhang1,d, Wei Cheng1,e Luoyang Ship Material Research Institute, Luoyang, 471023, China

1

[email protected], [email protected], [email protected], [email protected], e [email protected]

a

Keywords: Silica; Modification; Corrosion; The hollow ball; Ru

Abstract. In this paper, a simple and effective method was used to synthesize monodisperse metal Ruthenium nanospheres (Ru-HNSs), and the silicon dioxide (SiO2) nanospheres synthesized by Stober method were used as hard templates. The surface of SiO2 was double modified by γ-aminopropyltriethoxysilane (KH550) and salicylaldehyde, so that Ru3+ grew uniformly on the surface of modified SiO2 and reduced to form a stable and durable layer of Ru metal. Then the hard template SiO2 was corroded by chemical etching to obtain Ru-HNSs hollow spheres. The results show that the diameter of SiO2 microspheres was about 300nm, the wall thickness of Ru-HNSs was about 3nm, and the diameter was about 100nm. Introduction Cyclohexene is an important chemical intermediate [1], which can be converted into high value-added chemical products such as cyclohexanol, caprolactam and adipic acid through typical olefin reaction. So far, the selective hydrogenation of benzene to cyclohexene is the best method for large-scale industrial production of cyclohexene with high efficiency and low cost. The core of the process of selective hydrogenation of benzene to cyclohexene is the catalyst preparation technology [2], and the development of catalysts and the study of the reaction system of this process have important industrial value and significance. In the system of selective hydrogenation of benzene to cyclohexene [3], the common Ru catalysts [4] can be divided into two categories: (1) Supported catalysts: Wang Jianqiang et al. used γ-Al2O3 and Zirconium dioxide (ZrO2) as a support to prepare Ru-supported catalysts by coprecipitation [5]; (2) Unsupported catalyst: Asahi Kasei Company of Japan has published a patent to prepare unsupported Ru catalyst by precipitation method [6].The above two catalysts have good effects, but metal Ru is expensive, and it is an inevitable trend to develop metal Ru catalyst structure with high efficiency and low cost. The nano-hollow sphere is a nanomaterial with only shell and hollow layer [7]. Its low density and large specific surface area have attracted more attention. The application scope of the nano-hollow sphere material is constantly expanding in the continuous exploration, and it also shows great application value in industry and materials [8]. Hollow spheres with different functions can be obtained by modifying the surface of nano-hollow spheres [9], which can be used as lightweight structural materials, heat insulation, sound insulation and electrical insulation materials, pigments and catalyst support [10]. In this paper, the hollow metal spheres were introduced into the Ru-based catalytic system of selective hydrogenation of benzene to cyclohexene [11], and the metal Ru catalyst was designed as a hollow Ru sphere catalyst to improve the atomic utilization rate and study its forming structure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the structure, morphology and composition of the modified and corroded Ru hollow spheres. Currently, metal Platinum (Pt)[12], Palladium (Pd)[13] and Nickel (Ni)[14] hollow spheres have been successfully prepared, but the reports on the

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preparation of metal Ru hollow spheres are few. To this end, the research in this paper fills the gap in the preparation of metal Ru hollow spheres, and has extensive industrial application value and profound theoretical significance. Experimental Part Experimental Materials and Equipment. RuC13• xH2O(Ru≧37%), Kunming Guiyan Platinum Co., LTD.; Absolute ethanol, ammonia, tetraethyl orthosilicate, Sinopharm Chemical Reagent Co., LTD.; Salicylic aldehyde, Bailingway Technology Co., LTD.; Trisodium citrate, γ-aminopropyltrethoxysilane (KH550), Sodium borohydride, Tianjin Kemeiou Chemical Reagent Co., LTD. Model AB204-E analytical balance, model S312-90 constant speed stirrer, Model KQ5200DE NC ultrasonic cleaner, AXTG16G table top general centrifuge. Preparation of SiO2 Microspheres. Solution A: Took 18mL 28% concentrated ammonia, 32mL ethanol and 50mL water, mixed them in a three-necked flask, and stirred well at 800rpm. Solution B: Took 9mL tetraethyl orthosilicate (TEOS), 91mL ethanol, mixed and stirred well with a glass rod. Solution B was quickly added to solution A with a glass rod and react in a constant temperature water bath at 25℃ for 20 h at a stirring rate of 260rpm. The sample was separated by centrifugation to obtain the solid. After adding ethanol, the sample was redispersed by ultrasound and washed 3 times. Surface Modification of SiO2 Microspheres. 200mg prepared SiO2 was weighed. Took 40mL of anhydrous toluene and added it into a 250ml three-mouth flask. Absorbed 2mLKH550 with a disposable eyedropper and added it into a flask, and then sealed the flask with a hollow stopper. The SiO2 modified with KH550 was obtained by centrifugation and washed with ethanol for 3 times, as well as vacuum drying at 60℃ for 24h. 200mg SiO2 microspheres modified with KH550 was weighed. 30ml absolute ethanol was added into 250ml three-mouth flask, and another 100mL beaker was taken. 1ml salicylaldehyde was dissolved in 30ml absolute ethanol, stirred evenly and heated to 90℃. Then SiO2 was added by drop with a disposable dropper in the absolute ethanol to stir 0.5h. The reflux device was set up in the oil bath with 90℃. The magnetic stirring rate was 500rpm, and the condensation reflux rate was 20h. Finally, the double modified SiO2 microspheres were obtained. Preparation of Ru Hollow Spheres. 100mg double modified SiO2 was weighed. Took 50ml ethanol to disperse well and evenly, and then took another 500mg RuCl3, 1000mg trisodium citrate into 500ml beaker to add 50mL water, shake evenly and pour the ethanol dispersed SiO2 into it to seal with plastic wrap, and cleaned with a ultrasonic cleaner for 30min. 1000mg sodium borohydride and water were weighed into 100ml solution, and the above ultrasonic solution was added drop by drop by mechanical stirring. After stirring for 3h, the solution was washed by centrifugation (washed twice with water and once with absolute ethanol), and the brown precipitate (Ru ion without reduction reaction) was removed for vacuum drying at 60℃, and the corresponding Ru-modified SiO2 microspheres were obtained. Ru modified SiO2 microspheres were put into a centrifuge tube, and a small amount of hydrofluoric acid solution was added. After corrosion for 1 h, the particles were washed by centrifugation with water and absolute ethanol for several times, and dried under vacuum at 60℃ to obtain Ru hollow spheres. Sample Characterization. The structure, morphology and composition of modified and corroded Ru hollow spheres were characterized by SEM, TEM and XRD. Results and Discussion SiO2 Microspheres. Stober method [15] was used to prepare SiO2 microspheres. Stober et al. established the synthesis of amorphous SiO2 by base catalysis using ethyl orthosilicate (TEOS as raw

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material and ammonia as catalyst. This method has the advantages of simple operation, controllable size of silica particles and good monodispersity. It is one of the most commonly used methods for the synthesis of spherical silica particles. The results of scanning electron microscopy (SEM) characterization are shown in Fig. 1. It can be seen that SiO2 nanoparticles was evenly dispersed with smooth surface, and the size was about 300nm.

Fig. 1 SEM image of SiO2 microspheres

Double Modification SiO2 Microspheres. Scanning electron microscopy (SEM) characterization results are shown in Fig. 2. The particle diameter of double modification SiO2 microspheres was still 300nm, marked by red dot circle as shown in Fig. 2. It can be clearly observed that the surface of SiO2 is well coated and modified, and the size is still uniform and the dispersion is good, which provides the morphology basis for the next step of Ru loading.

Fig. 2 SEM image of double modified SiO2 microspheres

Metal Ru Loading in the Surface of Double Modification SiO2 Microsphere. The results are shown in Fig. 3. The Ru loading was 500mg in Fig.3 (a), (b), (c) and (d), 300mg in Fig.3 (e), (f), (g) and (h). When Ru is loaded more, the loading effect is better, and the coating layer thickness increases. The coating layer is more tightly coated.

Fig. 3 SEM image of double modification SiO2 microsphere with different Ru loads

As shown in Fig. 4. A layer of black Ru nanoparticles was uniformly loaded on the surface of SiO2 microspheres, as shown by the green arrow.

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Fig. 4 TEM image of double modification SiO2 microspheres with Ru loads

A large number of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization results fully showed that the metal nano-Ru particles were successfully loaded on the surface of double modification SiO2 microspheres. Metal RuHollow Spheres. As shown in Fig. 5. After hydrofluoric acid corroded the SiO2 microspheres, the existence of hollow spheres of Ru metal is clearly observed, and the diameter of the hollow spheres is about 100 nm, the diameter of the previously uncorroded SiO2 microspheres is about 300nm. This indicates that after hydrofluoric acid corroded SiO2 microspheres, the metal Ru shell coating on the surface of SiO2 microspheres collapses and contracts, forming a hollow sphere structure.

Fig. 5 TEM image of Metal Ru Hollow Spheres

As shown in Fig.6, SiO2 diffraction peaks were found in Fig. 6(a), (b) and (c) at 23°,(c) and (d), the characteristic diffraction peaks of Ru appear at 44°. It can be seen that the diffraction peaks of Ru were very weak after the double modified SiO2 microspheres were loaded with Ru metal. Combining with the characterization figures of SEM and TEM, it could be concluded that Ru metal was uniformly loaded on the surface of SiO2 microspheres, and then a very thin metal Ru shell was formed. When hydrofluoric acid corroded the SiO2 microspheres, the diffraction peak of SiO2 basically disappeared, and the characteristic peak of Ru became stronger, indicating that hydrofluoric acid corrosion for 1h could basically remove SiO2. At the same time, Ru metal may partially collapse and agglomerate. These results show that our method is an effective way to generate monodisperse and uniform Runanohollow spheres.

Intensity

(d) (c) (b) (a) 10

20

30

40

50

60

70

80

2 θ( ) o

Fig. 6 XRD image of (a) SiO2 microspheres, (b) single-modified SiO2, (c) double-modified SiO2 with Ru loads, (d) hollow Ru ball

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As shown in Fig. 7, the surface of SiO2 microspheres contains hydroxyl group, which acts with the silicon in the silane coupling agent to form Si-O-Si bond. Because the silane coupling agent is easy to hydrolyze in in the presence of water, therefore this paper chooses to modify SiO2 with the silane coupling agent under anhydrous condition. Because silane coupling agent contains amino groups, the N of amino groups could have a certain coordination effect with metal Ru3+. Ru3+ loaded on the surface of SiO2 microspheres and reduced with sodium borohydride solution. The Nano-Ru metal particle shell on the surface of the SiO2 microspheres was thus obtained, and then used the hydrofluoric acid to corrode the SiO2 microspheres. The metal Ru hollow spheres were obtained.

Fig. 7 Preparation mechanism diagram of metal Ru hollow spheres

Conclusion In this paper, SiO2 microspheres were prepared by Stober method. KH550 and salicylaldehyde were used to modify the surface of SiO2 microsphere. Then, Ru3+ adsorbed or complexed on the surface of the double-modified SiO2 microspheres, and Ru3+ were reduced to metal Ru that loaded on the surface of SiO2 microspheres through the hydrofluoric acid solution corrosion SiO2. Finally, the metal Ru hollow spheres were successfully prepared. The results showed that the metal Ru nanoparticles grow uniformly and densely coated on the surface of SiO2 microspheres, and the thickness of the coated metal Ru shell was about 3 nm. The diameter of metal Ru hollow spheres was about 100 nanometers. The core of selective hydrogenation of benzene to cyclohexene is the preparation technology of catalyst. This work has an important guiding role for the preparation of Ru catalyst and the reaction system. References [1] Cao, H. E., Zhu, B. R., Yang, Y. F., Xu, L., Yu, L., Xu, Q. Recent advances on controllable and selective catalytic oxidation of cyclohexene. Chinese Journal of Catalysis, 39(5)899-907, 2018. [2] Huang, Z. X., Liu, Z. Y., Wu, Y. M., Liu, S. C. Selective Hydrogenation of Benzene to Cyclohexene by a Novel Ru-Zn Catalyst. Journal of Molecular Catalysis, 20(3), 2006. [3] Dong, S., Fang, C. X., Wang, Y. T. Research progress on catalysts for selective hydrogenation of benzene to cyclohexene. Chemical Industry and Engineering Progress, 30(7), 2011. [4] Yang, X. L., Guo, Y. Q., Zhang, Z. J., Liu, S. C. Study on Ru-Co-B/ZrO2 catalyst for selective hydrogenation of benzene to cyclohexene. Chemical Research and Application, 15(5)664-665, 672, 2003. [5] Wang, J. Q., Xie, S. H., Chen, H. Y., Hu, J. G., Fan, K. N. The Preparation and Catalytic Behavior ofRu/ZrO2·xH2O in Benzene Selective Hydrogenation. Journal of Fudan University (Natural Science Edition), 41(4):429-432, 438, 2002. [6] Sun, H. J., Huang, Z. X., Chen, J. J., Dou, X. Y., Li, Y. Y., Liu, S. C., Liu, Z. Y. Comparison Between the Unsupported Ru-Zn Catalyst and the Supported Ru-Zn Catalyst for Selective Hydrogenation of Benzene to Cyclohexene. Acta Petrolei Sinica (Petroleum Processing), 33(4) 646-654, 2017.

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[7] Yan, C. M., Luo, Y. J., Zhao, X. P. The preparation research of inorganic hollow nanospheres. Journal of Functional Materials, 37(3)345-350, 2006. [8] Dai, Y. H., Jiang, H., Hu, Y. J., Fu, Y., Li, C. Z. Controlled Synthesis of Ultrathin Hollow Mesoporous Carbon Nanospheres for Supercapacitor Applications.Industrial & Engineering Chemistry Research,53(8)3125-3130, 2014. [9] Wang, Z. M., Jiang, S. Y., Li, Y. H., Xu, P. F., Zhao, K., Zong, L. B., Wang, H., Yu, R. B. Highly active CeO2 hollow-shell spheres with Al doping. Science China Materials, 60(7)646-653, 2017. [10] Sakanishi, K., Hasuo, H., Kishino, M., Mochida, I., Okuma, O. Catalytic Activity of NiMo Sulfide Supported on a Particular Carbon Black of Hollow Microsphere in the Liquefaction of a Subbituminous Coal. Energy Fuels, 10(1)216-219, 1996. [11] Ji, Y. L., Wang, Z. W., Liu, S. C., etc. Ru-series catalysts for selective hydrogenation of benzene to cyclohexene. Noble Metals, 24(1):5, 2003. [12] Li, C. L., Jiang, B., Imura, M., Malgras, V., Yamauchi, Y. MesoporousPt hollow cubes with controlled shell thicknesses and investigation of their electrocatalytic performance. Chem. Commun., 50, 15337-15340, 2014. [13] Zhang, Z. Y., Xiao, F., Xi, J. B., Sun, T., Xiao, S., Wang, H. R., Wang, S., Liu, Y. Q. Encapsulating Pd Nanoparticles in Double-Shelled Graphene@Carbon Hollow Spheres for Excellent Chemical Catalytic Property. Scientific Reports, 4, 2014. [14] Zhang, S. H., Gai, S. L., He, F., Dai, Y. L., Gao, P., Li, L., Chen, Y. J., Yang, P. P. Uniform Ni/SiO2@Au magnetic hollow microspheres: rational design and excellent catalytic performance in 4-nitrophenol reduction. Nanoscale, 6(12), 7025-7032, 2014. [15] Bhakta, S., Dixit, C. K., Bist, I., Jalil, K. A., Suib, S. L., Rusling, J. F. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles. Materials Research Express, 3(7)075025, 2016.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 135-144 doi:10.4028/p-j89jnx © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-06-07 Accepted: 2022-11-15 Online: 2022-12-26

Molecular Dynamics Simulation of the Effect of Zr and B on Cryolite Molten Salt System 78%Na3AlF6-9.5%Alf3-5.0%Caf2-7.5%Al2O3 Zhihao Zhang1,a, Yusi Wang1,b, Jing Zeng1,c and Hanbing He1,d* School of Metallurgy and Environment, Central South University, Changsha 410083, China

1

[email protected], [email protected], [email protected], [email protected]

a

Keywords: Aluminum electrolysis; Molecular Dynamics; Viscosity

Abstract. The analysis of high temperature physical and chemical properties of molten salt system of aluminum electrolysis has guiding significance for practical production In this paper, the molecular dynamics calculation method was used to simulate the physical and chemical properties of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 molten salt electrolyte system with Zr and B as additives at 1200K and standard atmospheric pressure. The effects of Zr and B elements on the radial distribution function, coordination number, diffusion coefficient, viscosity, and conductivity of electrolyte system were discussed in detail. The simulation results showed that Zr4+ weakened the connection between Al3+, while the addition of B3+ enhanced the interaction between Al3+, Na+, and F-. In the electrolyte system without impurities, the order of self-diffusion coefficient is Na+ > O2- > F- > Ca2+ > Al3+. And the addition of Zr4+ is conducive to the diffusion of ions in the system, while the addition of B3+ is not conducive to the diffusion of ions in the system. What’s more, the addition of Zr improves the conductivity of the system, while the addition of B reduces the conductivity of the system. Introduction As an important industrial non-ferrous metal, aluminum is generally prepared by electrolytic melting of alumina. Cryolite can greatly reduce the melting point of alumina, so that electrolytic production can be carried out at about 1200K. Adding a small number of dopants to cryolite molten alumina system will change the physical and chemical properties of aluminum electrolyte. Selecting appropriate additives can effectively improve the current utilization efficiency in the electrolysis process and reduce energy consumption. At present, there have been some studies on the physical and chemical properties of additives in the molten salt system of aluminum electrolysis. Gao et al [1] determined the primary crystallization temperature of Na3AlF6 in Na3AlF6-AlF3-CaF2-NaCl-Al2O3 electrolyte system during aluminum electrolysis through thermal analysis. P. Felner et al [2] studied the conductivity of molten ternary mixture Na3AlF6-Li3AlF6- AlF3 with molar ratio of n (Li3AlF6): n (AlF3) = 1:2. A. Solheim et al [3] measured the liquidus temperature of cryolite primary crystallization in Na3AlF6-AlF3-LiF-CaF2-MgF2 system through thermal analysis. In the molten salt system of aluminum electrolysis, the influence of additives is mainly concentrated in the aspects of primary crystal temperature, conductivity, viscosity and density. The analysis of various physical and chemical properties of the molten salt system of aluminum electrolysis at high temperature is of great significance to analyze and optimize the molten salt system. However, due to the volatility and corrosivity of fluoride salt, ordinary optical measuring instruments are vulnerable to fluoride salt corrosion, and volatile fluoride cannot be analyzed by ordinary spectrum. People have been looking for new means to explore the physical and chemical properties of cryolite system. For the above high-temperature detection of fluorine-containing salts, many researchers have used the method of molecular simulation [4-10]. In recent years, with the development of computational simulation technology, molecular dynamics method is one of the most advanced and basic methods used by computer simulation workers. At present, molecular dynamics research method has been applied to the research of Li2BeF4 [11], LIF-NaF-KF [12], Y3Al5O12 [13] and other molten salt systems. The high agreement between these research results and experimental data also proves that molecular dynamics calculation method is effective.

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The introduction of other ions into cryolite molten salt system will affect not only the combination mode of ions in the system, but also the migration and diffusion of ions in the system. However, the mechanism of the effects of different additives on the physical and chemical properties of the system remains unclear. Because aluminum electrolysis is generally carried out at a high temperature above 1200K, it is very difficult to study the influence of additives on molten salt system through practical experiments. Therefore, the physicochemical properties of ions in cryolite molten salt system with different amounts of Zr and B at 1.01 MPa and 1200K were systematically studied by molecular dynamics method. The structure, interaction, migration and diffusion parameters, conductivity and viscosity of ions in the system under this condition were discussed in detail. Computational Methods This calculation used Material Studio software to set a given number of various ions in a periodic box. The number of atoms in the simulation system and the size of the system are shown in Table 1. The Foeite module (UFF force field, time step of 1 fs) in MS was used to simulate the dynamic process of molten salt. The coulomb effect of simulated ions used the Ewald summation algorithm processing system, and the buffer width and energy calculation accuracy were set to 0.5 Å and 0.5kcal/mol. The cut-off radius of the short-range interaction was set to half the side length of the simulation box. Under the NPT system, the simulated molten salt tank was heated to 4000K under the pressure of 1.01MPa, and the structural relaxation of 100ps was carried out. In the simulation process, the number of particles, pressure and temperature of the molten salt system were set to remain unchanged. Then, in the NVT ensemble, the superheated liquid was cooled to the target molten salt melting point of 1200K at the rate of 1K/ps, and the molten salt model continued to undergo structural relaxation of 100ps. Table 1. The number of atoms in the simulation system and the size of the system. Number of particles

Additive No addition 10.0wt% ZrO2 20.0wt% ZrO2 10.0wt% B2O3 20.0wt% B2O3

Al

Na

F

Ca

O

Zr

B

60 60 60 60 60

80 80 80 80 80

229 229 229 229 229

20 20 20 20 20

25 41 61 64 103

0 12 30 0 0

0 0 0 26 52

Box side length/nm 1.96 2.02 2.1 2.02 2.08

Results and Discussion Radial Distribution Function. The radial distribution function is the ratio of the probability density of other ions at the distance r from the particle to the probability density of random distribution, which describes how the particle density changes as a function of the distance from the reference atom. The calculation formula of radial distribution function is as follows formula [14, 15]. 1

g(r) = 𝜌𝜌𝜌𝜌 (∑𝑖𝑖𝑖𝑖 𝛿𝛿|𝑟𝑟 − 𝑟𝑟𝑖𝑖𝑖𝑖 |).

(1)

ρ represents the average number density of the system, and N represents the total number of ions in the system. Fig. 1 shows the radial distribution function between different ions in 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3. The first peak of Al-Al and Al-Na was sharper, indicating that the Na ions around Al ions were arranged more orderly. The first peak of Al-Al, F-F, Al-F and Al-Na were about 3.79 Å, 2.67 Å, 3.27 Å and 2.85 Å, respectively. The radius of the first

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peak of Al-Al was significantly larger than that of Al-F, which indicates that part of F was used as a connecting atom to connect two Al atoms in the form of Al-F-Al [16]. Fig. 2 and Fig. 3 show the radial distribution function between different ions of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 mixed with 10wt% and 20wt% ZrO2. When the addition amount of Zr was 10%, the first peak value of Al-Al, F-F, Al-F and Al-Na were 3.89 Å, 2.59 Å, 3.17 Å and 2.85 Å respectively, and when the addition amount of Zr was 20%, the first peak value of Al-Al, F-F, Al-F and Al-Na were 3.77 Å, 2.69 Å, 3.29 Å and 2.85 Å respectively as shown in Fig.3. Comparing Fig.2 and Fig.3, we can also find that with the increase of ZrO2 addition, the sharpness of the first peak of Al-Al, Al-F and Al-Na decreased, which shows that the addition of Zr ions made the distribution of fluorine and sodium ions around Al ions more uniform. Fig. 4 and Fig. 5 show the radial distribution function between different ions of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 mixed with 10wt% and 20wt% B2O3. As shown in Fig 4, the first peak value of Al-Al, F-F, Al-F and Al-Na were 3.85 Å, 2.55 Å, 3.07 Å, and 2.85 Å respectively when the addition amount of B was 10%.

Figure 1. The radial distribution function between different ions in the electrolyte 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3. (a.Al-Al; b.F-F; c.Al-F; d.Al-Na).

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Figure 2. The radial distribution function between different ions in the electrolyte 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 with 10wt% ZrO2. (a.Al-Al; b.F-F; c.Al-F; d.Al-Na).

Figure 3. The radial distribution function between different ions in the electrolyte 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 with 20wt% ZrO2. (a.Al-Al; b.F-F; c.Al-F; d.Al-Na).

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Figure 4. The radial distribution function between different ions in the electrolyte 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 with 10wt% B2O3. (a.Al-Al; b.F-F; c.Al-F; d.Al-Na).

Figure 5. The radial distribution function between different ions in the electrolyte 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 with 20wt% B2O3. (a.Al-Al; b.F-F; c.Al-F; d.Al-Na).

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And when the addition amount of B was 20%, the first peak value of Al-Al, F-F, Al-F and Al-Na were 3.75 Å, 2.47 Å, 3.05 Å and 2.79 Å respectively. From Fig. 4 (c-d) and Fig. 5 (c-d), it can be clearly observed that the first peak of Al-F and Al Na became larger, indicating that the effect of B3+ was different from that of Zr4+, which can strengthen the interaction between Al3+ and F- and Na+. It can be concluded from the above analysis that Zr4+ weakened the connection between Al3+, while the addition of B3+ enhanced the interaction between Al, Na and F ions and the interaction between Al ions may be indirectly completed by the interaction of F ions. Table 2. The average bond length of each ion pair in the molten salt system with different additives The first peak radius of RDF (average bond length/nm) Additive Al-Al F-F Al-F Al-Na No addition 0.379 0.267 0.327 0.285 10.0wt% ZrO2 0.389 0.259 0.317 0.285 20.0wt% ZrO2 0.377 0.269 0.329 0.285 10.0wt% B2O3 0.385 0.255 0.307 0.285 20.0wt% B2O3 0.375 0.247 0.305 0.279 The radius of the first peak of the radial distribution function represents the average bond length of an ion pair [17, 18]. The results of simulation calculation are shown in Table 2. The simulation results show that when 10wt% ZrO2 was added, the average bond length of Al-Al increased, and the average bond length of F-F and Al-F decreased slightly. The average bond length of Al-Al in all systems was less than twice the average bond length of Al-F and greater than the average bond length of Al-F, indicating that there was most aluminum in the melt and the ions were connected in the form of Al-F-Al fluoride ion bridges. Coordination Number. Coordination number refers to the number of target particles within a certain distance around the central particle, which can intuitively reflect the interaction between ions in the system. The coordination number can be obtained by further calculation of radial distribution function. The specific formula is as follows [19, 20]. 𝑟𝑟

N = 4 ∏ 𝜌𝜌0 ∫0 𝑔𝑔(𝑟𝑟) ∙ 𝑟𝑟 2 ∙ 𝑑𝑑𝑑𝑑.

(2)

ρ0 represents the average density of the target particle, g (r) is the radial distribution function, and r is the first trough position of the radial distribution function. The N value obtained by integrating it is the coordination number of the target particle in the first coordination layer. The coordination numbers between Al3+-F- are given in Table 3. When the coordination number of F- around Al3+ was greater than 7, there might be [AlF7] 4- ionic group in the molten system. It can be seen from Table 3 that after adding Zr into the system, the coordination number between Al3+-F- decreased, which indicates that the interaction between Al3+-F- and the number of fluorine bridges formed in the system gradually decreased with the addition of Zr. After adding 20wt% B2O3 into the melt system, the coordination number between Al3+-F- decreased significantly, which also showed that the interaction between Al3+-F- decreased. Table 3. Coordination number of Al3+-F- in molten salt system with different additives Additive Coordination number of Al3+-FNo addition 7.377 10.0wt% ZrO2 7.066 20.0wt% ZrO2 7.025 10.0wt% B2O3 7.499 20.0wt% B2O3 6.403 Diffusion Coefficient. Diffusion coefficient is one of the important parameters to describe the dynamic characteristics of melt. It reflects the diffusion and migration speed of specified components in the melt. The diffusion coefficient can be calculated by Ein-stein equation [21, 22]:

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𝑑𝑑

𝐷𝐷𝑖𝑖 = 6 lim 𝑑𝑑𝑑𝑑 < [𝑟𝑟𝑖𝑖 (𝑡𝑡) − 𝑟𝑟𝑖𝑖 (0)]2 > 𝑡𝑡→∞

141

(3)

[ri(t)-ri(0)]2 represents the root mean square displacement of particle i, represents the ensemble average value, and ri(t) represents the position of particle i at time t. Table 4. Self-diffusion coefficient of ions in the system with different additives (D×109/m2• s-1) Additive Al3+ Na+ FCa2+ O2Zr4+ B3+ No addition 0.53 1.31 1.01 0.88 1.05 10.0wt% ZrO2 0.68 1.66 1.38 1.10 1.17 1.41 20.0wt% ZrO2 0.89 1.80 1.60 1.38 1.43 1.59 10.0wt% B2O3 0.36 0.85 0.69 0.59 0.62 0.46 20.0wt% B2O3 0.22 0.57 0.49 0.40 0.45 0.47 Table 4 shows the self-diffusion coefficient of each ion in the melting system. In the electrolyte system without impurities, the order of self-diffusion coefficient is Na+ > O2- > F- > Ca2+ > Al3+. After adding Zr4+, the self-diffusion coefficient of each ion increased. With the increase of Zr4+, the self-diffusion coefficient of each ion also further increased. After adding B3+, the self-diffusion coefficient of each ion decreased. With the increase of B3+, the self-diffusion coefficient of each ion further decreased. The data show that the addition of Zr4+ was conducive to the diffusion of ions in the system, while the addition of B3+ was not conducive to the diffusion of ions in the system. Conductivity. In the process of electrolytic aluminum, the conductivity of electrolyte affects the power consumption of electrolytic aluminum process to a great extent. Enhancing the conductivity of the system can effectively reduce energy consumption and improve current efficiency. At the same time, the study of the conductivity of the system also helps us to further understand the conductive mechanism of molten electrolyte. As shown in formula (4), the conductivity of the system can be obtained by Nernst-Einstein equation [23]. 𝑁𝑁𝑞𝑞 2

κ = 𝑘𝑘

𝐵𝐵 𝑇𝑇

(𝐷𝐷− + 𝐷𝐷+ ).

(4)

In the formula, N is the total number of ions per unit volume, q is the electron charge, D- and D+ are the diffusion coefficients of anion and cation respectively, and kB is the Boltzmann’s constant. Fig. 6 shows the conductivity of electrolyte systems containing different additives. The addition of Zr can increase the conductivity of the system. The addition of Zr was conducive to reduce the power consumption in the process of aluminum electrolysis, so as to save the production cost. When B was added, the conductivity of the system decreased, which will increase the power consumption in the production process. The main reason is that the addition of Zr improved the mobility of each ion and the conductivity of each carrier, while the addition of B had an opposite effect.

Figure 6. Conductivity of the system with different additives

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Viscosity. Viscosity is one of the important physicochemical properties in the process of electrolytic aluminum production. Since the main carrier of the target molten salt system is Na+, the viscosity of the system can be obtained from the Stokes-Einstein relationship according to the Na+ diffusion coefficient. The Stokes-Einstein relationship is as formula (5). 𝑘𝑘 𝑇𝑇

η = 6𝜋𝜋𝐷𝐷𝐵𝐵 𝑅𝑅 .

(5)

+ +

Where D+ is the diffusion coefficient of the cation, kB is the Boltzmann constant, and R+ is the kinetic diameter of the cation.

Figure 7. Viscosity of systems with different additives In order to find the effect of additives on the viscosity of the system, we added experimental groups with different additive amounts. The calculation results are shown in Fig. 7. In the range of 30wt%, with the increase of zirconium addition, the viscosity of zirconium containing molten salt system gradually decreased. The ion migration ability in the molten salt was enhanced, which is of positive significance to the electrolytic production of the system. When the additive was B, the viscosity of molten salt increased with the increase of additive proportion. In this regard, the addition of B will reduce the current efficiency of the electrolytic system. Conclusion In order to reveal the effect of adding Zr and B to the high temperature electrolytic aluminum system on the physical and chemical properties of the system, we carried out simulation calculation by molecular dynamics method. The target system is a molten salt system of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 at 1200K and 1.01MPa. We draw the following conclusions: (1) Zr4+ weakened the connection between Al ions, while the addition of B ion enhanced the interaction between Al, Na and F ions. (2) Al and F in the molten system may exist in the form of [AlF7] 4- ionic group. The interaction between Al3+-F- decreased gradually with the addition of Zr. After adding 20wt% B2O3 into the melt system, the interaction between Al3+-F- decreased. (3) In the electrolyte system without impurities, the order of self-diffusion coefficient was + Na > O2- > F- > Ca2+ > Al3+. The addition of Zr4+ was conducive to the diffusion of ions in the system, while the addition of B3+ was not conducive to the diffusion of ions in the system. (4) The addition of Zr can improve the conductivity of the system while the addition of B can reduce it.

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(5) Within the addition amount of 30wt%, the viscosity of molten salt system added with Zr decreased with the increase of the addition amount, while the viscosity of molten salt system added with B increased with the increase of the proportion of additives. Acknowledgements The financial support of National Key R&D Program of China (Grant No. 2021YFB3701400), Postgraduate Innovative Project of Central South University and Postgraduate Innovative Project of Hunan province are greatly appreciated. References [1] Gao B, Wang S, Ji A, et al. Liquidus Temperatures of Na3AlF6− AlF3− CaF2− NaCl− Al2O3 Melts. Journal of Chemical & Engineering Data. 55 (2010), 5214-5215. https://doi.org/10.1021/je100741b [2] Fellner P, Midtlyng S, Sterten A, et al. Electrical conductivity of low melting baths for aluminium electrolysis: the system Na3AlF6-Li3AlF6-AlF3 and the influence of additions of Al2O3, CaF2, and MgF2. Journal of applied electrochemistry. 23 (1993), 78-81. https://doi.org/10.1007/BF00241580 [3] Solheim A , Rolseth S , Skybakmoen E , et al. Liquidus Temperature and Alumina Solubility in the System Na3AlF6-AlF3-LiF-CaF2-MgF2. Essential Readings in Light Metals, Aluminum Reduction Technology. 2 (2013), 73. DOI: 10.1007/978-3-319-48156-2_10 [4] Feng Y, Li M, Hou W, et al. First-Principles Molecular Dynamics Simulation on High Silica Content Na3AlF6–Al2O3–SiO2 Molten Salt. Acs Omega. 6 (2021), 3745-3751. https://doi.org/10.1021/acsomega.0c05339 [5] Guo H, Li J, Zhang H, et al. Study on micro-structure and transport properties of KF-NaF-AlF3-Al2O3 system by first-principles molecular dynamics simulation. Journal of Fluorine Chemistry. 235 (2020), 109546. https://doi.org/10.1016/j.jfluchem.2020.109546 [6] Hou H Y, Xie G, Chen S R, 10 (2000), 914-917. [7] Lv X, Xu Z, Li J, et al. Molecular dynamics investigation on structural and transport properties of Na3AlF6-Al2O3 molten salt. Journal of Molecular Liquids. 211 (2016), 26-32. https://doi.org/10.1016/j.molliq.2016.05.064 [8] Lv X, Xu Z, Li J, et al. First-principles molecular dynamics investigation on Na3AlF6 molten salt. Journal of Fluorine Chemistry. 185 (2016), 42-47. https://doi.org/10.1016/ j.jfluchem.2016.03.004 [9] Machado K, Zanghi D, Salanne M, et al. Structural, Dynamic, and Thermodynamic Study of KF–AlF3 Melts by Combining High-Temperature NMR and Molecular Dynamics Simulations. The Journal of Physical Chemistry C. 123 (2019), 2147-2156. https://doi.org/ 10.1021/acs.jpcc.8b11907 [10] Machado K, Zanghi D, Sarou-Kanian V, et al. Study of NaF–AlF3 Melts by Coupling Molecular Dynamics, Density Functional Theory, and NMR Measurements. The Journal of Physical Chemistry C. 121 (2017), 10289-10297. https://doi.org/10.1021/acs.jpcc.7b01530 [11] Klix A, Suzuki A, Terai T. Study of tritium migration in liquid Li2BeF4 with ab initio molecular dynamics. Fusion engineering and design. 81 (2006), 713-717. https://doi.org/10.1016/j.fusengdes.2005.09.034 [12] Nam H O, Bengtson A, Vörtler K, et al. First-principles molecular dynamics modeling of the molten fluoride salt with Cr solute. Journal of Nuclear Materials. 449 (2014), 148-157. https://doi.org/10.1016/j.jnucmat.2014.03.014

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[13] Cristiglio V, Hennet L, Cuello G J, et al. Ab-initio molecular dynamics simulations of the structure of liquid aluminates. Journal of non-crystalline solids. 353 (2007), 1789-1792. https://doi.org/10.1016/j.jnoncrysol.2007.01.075 [14] Lv X, Xu Z, Li J, et al. Theoretical investigation on local structure and transport properties of NaFAlF3 molten salts under electric field environment. Journal of Molecular Structure. 1117 (2016), 105-112. https://doi.org/10.1016/j.molstruc.2016.03.076 [15] CAR R. Unified Approach for Molecular Dynamics and Density-Functional Theory. Physical Review Letters. 55 (1985), 2471. https://doi.org/10.1103/PhysRevLett.55.2471 [16] Lv X, Xu Z, Li J, et al. First-principles molecular dynamics investigation on Na3AlF6 molten salt. Journal of Fluorine Chemistry. 185 (2016), 42-47. https://doi.org/10.1016/j.jfluchem. 2016.03.004 [17] Cristiglio V, Hennet L, Cuello G J, et al. Local structure of liquid CaAl2O4 from ab initio molecular dynamics simulations. Journal of Non-Crystalline Solids. 354 (2008), 5337. [18] Cikit S, Akdeniz Z, Madden P A. Structure and Raman spectra in cryolitic melts: simulations with an ab initio interaction potential. The Journal of Physical Chemistry B. 118 (2014),.1064-1070. https://doi.org/10.1021/jp4080459 [19] Nazmutdinov R R, Zinkicheva T T, Vassiliev S Y, et al. A spectroscopic and computational study of Al (III) complexes in cryolite melts: Effect of cation nature. Chemical physics. 412 (2013), 22-29. https://doi.org/10.1016/j.saa.2009.12.035 [20] Shannon R D T, Prewitt C T. Effective ionic radii in oxides and fluorides. Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 25 (1969), 925-946. https://doi.org/10.1107/S0567740869003220 [21] Zhang L, Van Orman J A, Lacks D J. Molecular dynamics investigation of MgO–CaO–SiO2 liquids: Influence of pressure and composition on density and transport properties. Chemical Geology. 275 (2010), 50-57. https://doi.org/10.1016/j.chemgeo.2010.04.012 [22] McKee R A. A generalization of the Nernst-Einstein equation for self-diffusion in high defect concentration solids. Solid State Ionics. 5 (1981), 133-136. https://doi.org/10.1016/0167-2738 (81) 90210-1 [23] Searles D J, Evans D J. The fluctuation theorem and Green–Kubo relations. The Journal of Chemical Physics. 112 (2000), 9727-9735. https://doi.org/10.1063/1.481610

CHAPTER 4: Environmental Remediation

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 147-155 doi:10.4028/p-s7wbe2 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-07-05 Revised: 2022-12-02 Accepted: 2022-12-02 Online: 2022-12-26

Characterization of Heater-Cooler Blocks Fabricated from Aluminium Wastes for Steady-State Thermal Application Ben Festus1,2,a*, Ewetumo T.3,b, Oluyamo S.S.3,c, Olubambi P.A.2, d Department of Physics with Electronics, Federal Polytechnic Ede, Osun State, Nigeria

1

Centre for Nanoengineering and Tribocorrosion (CNT), University of Johannesburg, Johannesburg, South Africa

2

Department of Physics, Federal University of Technology, Akure, Nigeria

3

[email protected], [email protected] c [email protected], [email protected]

a

Keywords: Characterization, aluminium cast, fabrication, aluminium scraps, heater-cooler blocks, thermal conductivity, steady state, recycling

Abstract. Recycling of aluminium (Al) from waste aluminium scraps for fabricating aluminium casts is a waste management technique suitable for reducing environmental pollution. The aluminium casts can be further processed into different materials of engineering interests such as heater-cooler (thermal) blocks. In this study, the microstructural characterization of aluminium cast fabricated from recycled aluminium waste and adapted for use via the (steady-state technique) as heater-cooler blocks required in the determination of the thermal conductivity of conducting solid composites was investigated. The characterization was investigated using the Scanning Electron Microscopy (SEM), Energy Displacer Spectroscopy (EDS), X-ray Diffractometer (XRD), and X-ray Fluorescence (XRF). The XRD result confirms the crystalline structure of aluminium on the fabricated aluminium cast. The elemental composition results confirmed that the fabricated cast contains 90% Al, with Silicon (Si) accounting for about 8% of the chemical composition while the remaining 2% was contributed by C, O, Fe, Zn, and Cu. The compositional change observed during characterization was attributed to the recycling process used in fabricating the aluminium cast. 1

Introduction

Aluminium is one of the world’s largest metal deposits with high versatility in the metal recycling industry [1,2]. Generally, metal recycling has been found beneficial to the environment as it reduces pollution, conserves natural resources and prevents the destruction of habitats [3]. There is however growing demand for composite materials that bring together different alloys to address emerging engineering and scientific challenges. Brazil tops the world aluminium recycling chart with 98.2% aluminium can recycling followed by Japan at 82.5% [4,5], however, China joined the league at a whopping 57% global aluminium production rate in 2020 [6]. Records revealed that the United States (US) produces approximately 36% aluminium from recycled scraps with used beverage containers accounting for the largest portion of this processed scraps [2,7,8]. Consequently, it has been observed that secondary aluminium produced from recycled aluminium scraps was found to use energy of less than 5% while emitting only 5% carbon dioxide during processing compared to primary production of aluminium [9]. The implication of this global aluminium scrap recycling trend may be positive or negative even as China remains the most preferred destination for gathering, sorting and recycling aluminium scraps for use in different applications, minimize production costs and saving the environment from pollution [10]. Hence, maximizing the use of secondary aluminium scraps for production of materials of engineering interest will be of immense benefit to scrap dealers while also increasing demand for local foundries by decreasing cost the of processing. This has however created a crucial need to

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investigate the microstructural characterisation of these secondary aluminium products with a view to ascertain their suitability in thermal related applications [3]. Several methods exist for measuring the thermal conductivity of an unknown solid composite such as radial flow method [11], pulse-power method [11,12], comparative method [2,12,13]. Of all these methods, the comparative cut bar technique remains the simplest and easiest of the methods owing to the reduced time to attain steady state. The comparative cut bar is based on the American Standard Test Method (ASTM) E-1225 [14]. The American Standard Testing Materials (ASTM) E-1225 comparative cut bar technique requires that the test sample be sandwiched between a heat source and a heat sink (otherwise known as heatercooler blocks), thereby giving rise to a temperature gradient along the test column [12,13,15]. To achieve accurate steady state results using this technique, the material used to fabricate the heatercooler block is very important [14]. Several metals have been used as heat source and heat sink under the ASTM E-1225 standard [14,15], but aluminium remains the most widely used owing to its unique properties such as good electrical and thermal conductivity, corrosion resistance, light weight, nonmagnetic, impermeable, amongst others [31,32]. The microstructural characterization of Heater-Cooler blocks fabricated from aluminium casts using recycled aluminium waste was thus investigated in this study. The characterization was carried out using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), Energy Dispersion Spectrometer (EDS), and X-ray Fluorescence (XRF) 2

Materials and Methods

2.1 Sample Preparation The aluminium cast utilized for this investigation was fabricated from recycled aluminium wastes in a process described by [3]. After fabrication of the aluminium cast, portions of the cast were machined to a dimension of 10 mm in diameter with a corresponding thickness of 3 mm. The aluminium cast was cold mounted and prepared metallographically by grinding the exposed surface using silicon carbide papers, and subsequently polished to a flat finished surface using colloidal silica suspension. 2.2 Microstructural Characterization X-ray diffraction (XRD) pattern diffractogram of the fabricated aluminium cast sample was obtained using PANalytical X’Pert Pro multipurpose diffractometer (manufactured by Rigaku located in Japan) and equipped with X’Celerator detector having radiation voltage and current of 40kV, 45mA respectively, CuKα (λ = 1.5406 Å). The measurements were performed in the 2θ range of 50 - 900 over a step size of 0.017 at a screening rate of about 30 seconds per step. The surface morphologies of the fabricated aluminium cast were investigated using TESCAN Vega 3xmu Scanning Electron Microscope manufactured by Tescan from Czech Republic (equipped with a OXFORD X-max EDS system) at a working distance of 15 mm and magnification values of 100x and 500x. Elemental composition of the fabricated aluminium cast sample was carried out using Energy Dispersive -ray (EDX) analysis, and X-ray fluorescence (XRF) spectroscopy instrumentation manufactured by Rigaku in Japan. 3

Results and Discussions

3.1 Crystallographic properties XRD diffractogram pattern data obtained from the fabricated aluminium cast sample were matched with the standard data of the Joint Committee on Powder Diffraction Standard (JCPDS) card no 96900-8461, which confirmed the crystalline structure of the aluminium. The diffractogram of the fabricated aluminium cast is illustrated in Figure 1 showing five distinctly matched peaks. A

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prominent intensity peak was observed at 38.70, with other small distinct peaks seen at 44.90, 65.20, 78.50, and 82.70. This shows a clear indication of structural phase transformation from single phase to polycrystalline phase. Using Braggs equation, the inter-atomic distance of 2.33 Å, 2.02 Å, 1.43 Å, 1.22 Å, and 1.17 Å corresponding to the five distinct phases matched by 96-900-8461 were calculated.

Figure 1:

X-ray diffractogram pattern of the fabricated aluminium cast indicating the matched peaks and the d-spacings (Å).

3.2 Microstructural Properties The microstructure showing the morphological properties of the fabricated aluminium cast is shown in Figure 2(a)-(b) under 100 x and 500 x magnification. The microstructure shown agrees with similar findings presented by [29], [33-35], with Al particles having cylindrical and dendritic shapes of irregular nature, and a disturbed layer showing different degrees of porosity at the surface which was visibly observed at 100 x magnification. Although the cause of the porosity is not clear, likely explanations could be from residual oxides and metals contaminations during the sand-casting process [19-24], [27], [30] or improper degassing [25-26], [29], [34].

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(a)

(b)

Figure 2: SEM micrographs showing (a) the surface structure (b) the aluminium distribution Detrimental effects of porosity in Al casts have been reported on mechanical [36] and thermal conductivity [37-38] properties. However, to the best of our knowledge, no studies have shown that porosity does influence the thermal transport behaviour of an Al cast adapted for thermal applications like the one proposed in this study. Industrial studies have further shown that porous Al is an ideal material for heat exchange with higher heat exchange capacity than conventionally fabricated Al [39]. When adopting a metal for use as a heater-cooler block, the thermal conductivity of the heater-cooler block must be experimentally determined in line with the ASTM E-1225 standard. The thermal conductivity of porous Al lies in the range of 30 – 50 W/mK, thus making them well suited for use as heat transfer elements and excellent for cooling purposes (which is an underlying novelty of this study). As air or water flows through porous Al, the large internal surface absorbs temperature and transmits the same to a solid body in contact with the thermal Al block which is a fundamental principle of the ASTM E-1225 standard. 3.3 Elemental Properties To determine the elemental properties, present in the fabricated aluminium cast and explain the probable cause of the light globular scripts observed at the intermetallic phases as well as the elements present in the porous regions identified in Figure 2(a), EDX and XRF analysis was performed. During the EDX analysis, different areas were focused, and the corresponding peaks are shown in Figure 3(a)-(d).

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(a)

(b)

(c)

(d)

Figure 3: EDX spectrum of (a) the aluminium cast (b) – (d) porous region observed in the cast Figure 3(a) further confirms the formation of Al in the fabricated casts with EDX spectrum showing a 79.49% weight fraction for Al. Figure 3(b)-(d) shows the EDX spectrums of the porous regions observed in Figure 2(a). The quantity of Al observed in the porous regions is 20.55%, 26.07%, and 25.23% respectively in the order they were labelled in Figure 2(a). It is interesting to note that the Carbon (C) atom dominated in the EDX spectrum of the porous regions at weight fraction values of 34.90%, 36.81%, and 39.95% respectively, which is relatively higher than the values observed for Al. The rather unusual high value of C in the porous region of the fabricated Al cast shows contamination of the cast by soot possibly from the materials used in the recycling process. XRF result analysis (Figure 4) also confirms the formation of Al at a value of 88.25%. The XRF value is 8.76% different from that obtained in the EDX spectrum. EDX spectrum of Figure 3(a) and XRF result of Figure 4 both puts the value of Si at 9.80% and 8.13% weight fraction respectively with a difference of 0.67% between both results. This unusually high value of Si obtained by the EDX spectrum and XRF gives further indication that the light globular elongations observed on the surface structure (Figure 2(b)) is caused by the presence of a Si phase. The non-uniformity of the surface structure is also a function of the presence of different intermetallic phases occurring at the surface (although in very small fractions).

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100 90 80 70

Unit Mass %

60 50 40 30 20 10 0

Mg

Al

Si

S

K

Cr Mn Fe

Ni

Cu

Zn

Ga

Pd

Sn

Pb

Series1 0.01 88.2 8.13 0.04 0.05 0.04 0.14 0.8 0.07 1.54 0.74 0.01 0.04 0.07 0.08

Elemental Composition

Figure 4: XRF Analysis of Fabricated Aluminium Cast 4. Conclusion Heater-Cooler blocks which is one of the fundamental instrumentation sections of the ASTM E-1225 comparative cut bar steady-state technique for the determination of thermal conductivity of composites can be fabricated from aluminium casts recycled from aluminium wastes. This study, therefore, presented a novel method of fabricating thermal blocks for thermal applications. The Al cast fabricated was successfully characterized using XRF, SEM, EDX and XRF analysis and the result shows that a good yield of Al can be obtained from waste Al scraps and adapted for thermal applications. The evaluations show that the fabricated porous aluminium cast has properties consistent with those required for heater-cooler blocks and other thermal-related applications. This novel method of fabricating heater-cooler blocks (from recycled aluminium waste) for steady-state thermal applications will ultimately help reduce the cost of thermal conductivity measurement apparatus developed in line with the ASTM E-1225 comparative cut bar method, and as well minimize land pollution caused by incessant disposal of waste aluminium scraps in landfills. Author Contributions: Ben F.: conceptualization, data curation, methodology, experimentation, and writing the original draft. Ewetumo T.: conceptualization, fabrication and testing, casting and machining, supervision, writing – review and editing. Oluyamo S.S.: data analysis and interpretation, methodology, writing – review and editing, supervision. Olubambi P.A.: methodology, supervision, writing – review and editing. All authors have read and agreed to the published version of the manuscript. Declaration of Competing Interest The authors declare that there are no known competing personal relationships or financial interests that could have appeared to influence the research findings presented herein. Funding This research was carried out with partial funding from the Tertiary Education Trust Fund (TETFUND).

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Acknowledgement The authors wish to acknowledge the Tertiary Education Trust Fund (TETFUND) for providing funding for this collaborative research work. The authors equally wish to appreciate the Metallurgy Department, at the University of Johannesburg for providing a platform for research collaboration. References [1]

Aalco (2005); Aluminium Specifications, Properties, Classifications and Classes. Supplier Data by Aalco

[2]

USGS (2018); Aluminium Statistics and Information. National Minerals Information Centre. Accessed on 28th September from http://minerals.usgs.gov/minerals/pubs/commodity/ aluminum/mcs-2018-alumi.pdf

[3]

Festus B, Ewetumo T., Adedayo KD, Oluyamo SS (2019); Development of a Low-Cost Thermal Heater-Cooler Blocks Using Locally Recycled Waste. J. Biosens Bioelectron 10: 271

[4]

Alu (2010); Brazil’s recycling rate for aluminium beverage cans hit a new record as the country recycled 98.4% of packaging consumed in 2014, keeping the country as world leader since 2001. Retrieved Sep 28 2021 from https://recycling.world-aluminium.org/regionalreports/brazil.html.

[5]

The Free Library (2014); Brazil's unemployed catadores keep recycling rates high while earning much-needed cash. Retrieved September 28, 2021 from https://www.thefreelibrary.com/Brazil%27s+unemployed+catadores+keep+recycling+ra tes+high+while+earning...-a0221274010

[6]

DeAnne Toto (2021); ISRI2021: The trends shaping aluminium markets. Accessed on 28th September 2021 from https://www.recyclingtoday.com/article/chinas-role-aluminumproduction-consumption/

[7]

Patricia A. Plunkert (2006); Aluminum Recycling in the United States in 2000. Accessed 28th September, 2021 from https://pubs.usgs.gov/circ/c1196w/

[8]

EPA (2012); Common Wastes and Materials. Accessed 28th September, 2021 from https://www.epa.gov/environmental-topics/land-waste-and-cleanup-topics#process

[9]

Leigh C. Duren (2007); X-Ray Fluorescene Measurements of Molten Aluminum Elemental Composition. An unpublished Master Thesis, Department of Materials Science and Engineering, Worcester Polytechnic Institute.

[10] Spencer D. B. (2007); The High Speed Identification and Sorting of Nonferrous Scrap. Journal of the Minerals, Metals and Materials Society, Vol. 57, pp. 46-51 [11] Tritt, Terry M (2004); Thermal Conductivity: Theory, Properties and Applications. Kuwer Academic / Plenum Publishers, New York. [12] Aaron Christopher Whaley (2008); Experimental Measurement of Thermal Conductivity of an Unknown Material. Unpublished Masters Thesis, University of Tennesseee, Knoxville [13] Ben Festus (2021); Development of a Device for Determination of the Thermophysical properties of Conducting Solid Composites. An Unpublished PhD Thesis, Federal University of Technology, Akure. [14] Annual Book of ASTM (2004); General Methods and Instrumentation: Section 14. Volume 14 (2), ASTM International, West Conshohocken, PA, 2004 [15] ASTM (2009); Standard test method for thermal conductivity of solids by means of the guarded-comparative-longitudinal heat flow technique. Active Standard ASTM E1225, USA.

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[16] James Cook (2021); FAQ – XRD/XRF. Advanced Analytical Centre. James Cook University, https://www.jcu.eu.au/advanced-analytical-centre/resources/faq-xrdxrf; accessed 25th September, 2021 [17] TWI (2021); What is X-ray Diffraction Analysis (XRD) and how does it Work? https://www.twi-global.com/technical-knowledge/faqs/x-ray-diffraction accessed 25th September, 2021 [18] JoVE Science Education Database (2021): Materials Engineering. X-ray Diffraction. JoVE, Cambridge, MA. [19] Cindy Sithole, Kasongo Nyembwe and Peter Olubambi (2019); Process knowledge for improving quality in sand casting foundries: A literature review. Procedia Manufacturing 35 (2019) 356–360 [20] Mpanza Z., Nyembwe D., and Nel H. (2013); Investigating the impact of poor utilization of quality management system in a South African foundry, SAIIE25Proceedings,9th-11th of July 2013, Stellenbosch, South Africa pp. 5661-5 [21] Beeley P. R. (2000); Foundry Technology.2nded. Butterworth: Heinemann. [22] Brown J. R. (2000); Foseco Ferrous Froundryman's Handbook. New Delhi: ButterworthHeinemann. [23] Liu X et al (2015) Study on hydrogen removal of AZ91 alloys using ultrasonic argon degassing process. Ultrason Sonochem 26:73–80 [24] Mancilla E et al (2017) Comparison of the hydrodynamic performance of rotor-injector devices in a water physical model of an aluminum degassing ladle. Chem Eng Res Des 118:158–169 [25] Bhaskar M. R. and Tamilselvam N. (2021); Degassing of Aluminum Metals and Its Alloys in Non-ferrous Foundry. Advances in Materials Research, Springer Proceedings in Materials 5, https://doi.org/10.1007/978-981-15-8319-3_63 [26] C´aceres, C.H., Selling, B.I. (1996); Casting defects and the tensile properties of an Al-Si-Mg alloy. Mater. Sci. Eng. A 220, 109116. https://doi.org/10.1016/S0921-5093(96) 10433-0. [27] Chaijaruwanich, A., Dashwood, R.J., Lee, P.D., Nagaumi, H. (2006); Pore evolution in a direct chill cast Al-6 wt.% Mg alloy during hot rolling. Acta Mater. 54 (19), 5185–5194. https://doi.org/10.1016/j.actamat.2006.06.029. [28] Ammar, H.R., Samuel, A.M., Samuel, F.H. (2008); Porosity and the fatigue behaviour of hypoeutectic and hypereutectic aluminum-silicon casting alloy. Int. J. Fatigue 30 (6), 1024– 1035. https://doi.org/10.1016/j.ijfatigue.2007.08.012. [29] Jaime Lazaro-Nebreda, Jayesh B. P., and Zhongyun Fan (2021); Improved degassing efficiency and mechanical properties of A356 aluminium alloy castings by high shear melt conditioning (HSMC) technology. Journal of Materials Processing Tech. 294 (2021) 117146. https://doi.org/10.1016/j.jmatprotec.2021.117146 [30] Campbell, J. (2003); ‘Castings’, 2nd ed. Butterworth-Heinemann, Oxford. [31] Azom (2019); Aluminium – Advantages and Properties of Aluminium. Accessed on 30th September, 2021 from https://www.azom.com/amp/article.aspx?ArticleID=1446 [32] Marta Danylenko (2021); Materials Choice in Heat Exchanger Design: Aluminium vs. Copper. Accessed 30th September 2021 from https://matmatch.com/blog/materials-heat-exchanger/ [33] Uludag M., Cetin R., Gemi L., and Dispinar D. (2018); Change in Porosity of A356 by Holding Time and Its Effect on Mechanical Properties. ASM International, JMEPEG (2018) 27:5141– 5151. https://doi.org/10.1007/s11665-018-3534-0

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[34] Mohd B. N. S, Sajjad A. and Siddiqui M. A. (2018); Fabrication and characterization of aluminium hybrid composites reinforced with fly ash and silicon carbide through powder metallurgy. Mater. Res. Express 5 (2018) 046506. https://doi.org/10.1088/ 2053-1591/aab829 [35] Abdullahi U., Maleque M. A., and Ali M. Y. (2018); Characterizationof Carbon Nanotube Reinforced Aluminium Nano-composite using Field Emission Scanning Electron Microscope. International Journal of Engineering Materials and Manufacture 3(1) 63-67. https://doi.org/10.26776/ijemm.03.01.2018.08 [36] Michaela B., Hartmut H., and Ewald W. (2010); Heat Treatment of Aluminum Castings Combined with Hot Isostatic Pressing. Proceedings of the 12th International Conference on Aluminium Alloys, Yokohama, Japan. [37] Vandersluis E., and Ravindran C. (2019); The Role of Porosity in Reducing the Thermal Conductivity of B319 Al Alloy with Decreasing Solidification Rate. JOM, Vol. 71, No. 6, The Minerals, Metals & Materials Society, https://doi.org/10.1007/ s11837 -019-03376-0 [38] Alejandro M. R., Espinoza-Beltran F. J., Limon J. Y., Vorobiev Y., Gonzalez-Hernandez J., Hallen J. M.(1999); Effects of porosity on the thermal properties of a 380-aluminum alloy. Journal of Materials Research 14(10):3901-3906. DOI: 10.1557/JMR.1999.0528 [39] Exxentis (2012); Porous Aluminium for Heat Exchange. As retrieved on 12th February 2022 from http://www.porous-aluminum.com/aluminium-heat-exchangers.html

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 157-168 doi:10.4028/p-xj3902 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-08-05 Revised: 2022-10-31 Accepted: 2022-11-04 Online: 2022-12-26

Adsorption of Cadmium(II) Ions from Aqueous Solutions Using Calcium Molybdate Sandra de Cássia Pereira1,a, Amanda das Graças Barbosa1,b, Alberthmeiry Teixeira de Figueiredo1,c*, Cristiano Morita Barrado1,d, Vanessa Nunes Alves1,e and Elson Longo2,f Institute of Chemistry, Federal University of Catalão, Catalão, Brazil

1

Institute of Chemistry, UNESP, Araraquara, Brazil

2

[email protected], [email protected], [email protected], d [email protected], [email protected], and [email protected]

a

Keywords: Calcium molybdate, hydrothermal-microwave, adsorption, scheelite.

Abstract. The presence of toxic metals in aquatic environments poses serious problems for ecosystems and especially for human health. Numerous types of metal oxides have been used to remove these metals and other toxic organic compounds, using adsorption systems. In this work, CaMoO4 was synthesized via coprecipitation and processed for different periods of time using a microwave-assisted hydrothermal system. It was possible to synthesize CaMoO4 at room temperature without any heat treatment. In addition, small processing times in HTMW were able to produce CM with different morphologies. The effect of the reaction time on the morphology of the product and particle size was examined in SEM images. A plausible CaMO4 formation mechanism was proposed based on time and temperature parameters. The potential application of CaMO4 as an adsorbent in water treatment was also investigated and this material exhibited a favorable adsorption performance in the fast removal of cadmium(ii) ions from aqueous solution of 1 mg L-1 concentration. So, CM showed a promising potential for use in environmental remediation. Introduction Calcium molybdate, CaMoO4, possesses a scheelite structure and is widely used in industrial applications, including optic fibers, humidity sensors, catalysts, scintillation detectors, solid-state lasers, photoluminescent products, microwave devices, etc.[1-4] The properties of CM are controlled by its uniform shape and narrow size distribution. Several methods have therefore been used to synthesize CaMoO4 nanostructures, resulting in particles with different morphologies. Zhu et al. [5] prepared CaMoO4:Eu nanosheets and a uniform dried persimmon shape by precipitation. Chen et al. [6] obtained CaMoO4 microcrystallites with various morphologies, including rods, peanuts, dumbbells, peaches, and spherules. Wang et al. [7] demonstrated a simple solution-phase processing route for the shape- and size-controlled synthesis of CaMoO4 hierarchical doughnut-shaped microstructures. You et al. [8] reported the synthesis of CaMoO4 microspheres with nanopits prepared by a hydrothermal method. Gong et al. [9] synthesized CaMoO4 mesocrystals via a simple microemulsion route. Marques et al. [10] evaluated the effect of different solvent ratios on the growth process of CaMoO4 crystals. Industrial wastewater containing hazardous and toxic materials is frequently discharged directly into the environment without sufficient treatment, posing potential threats to ecosystems and human being health.[11-13] In this context, metal contamination (lead, cadmium, chromium, etc.) represents a major problem around the world from industrial wastewater discharged into natural water bodies.[14] Several methods can be used to reduce or eliminate waterborne metals. However, adsorption is considered one of the most feasible techniques due to its reproducibility, economy, simplicity, effectiveness and sensitivity to toxic substances [15-19], plus the fact that it does not contribute to the formation of secondary aggregates [20, 21]. The key to the adsorption technique is to choose an adsorbent with excellent adsorption efficiency. Basically, adsorption mass transfer is a process

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whereby a substance/contaminant passes from the liquid phase to the surface of the solid phase, binding it to the physical and/or chemical interaction. Activated carbon is the adsorbent most commonly used because of its high surface area, porous structure and surface reactivity. However, its disadvantages are its high cost and in non-reusability [20]. Recent research has focused on the development of new low cost highly efficient inorganic synthetic adsorbents, especially nanomaterials of metal oxides [20]. Nanomaterials, which have numerous unique physical and chemical properties, are being used as nanoadsorbents. At the nanoscale, they have higher surface area-to-particle size ratios and their optical, electrical and magnetic properties differ from those of macroscopic particles. A large number of metal oxide nanomaterials, such as Fe3O4 [22], TiO2 [23], ZnO [24], CuFe2O3 [20], as well as their composites, have been used for the removal of toxic metal ions and organic pollutants from water and wastewater [25]. The literature contains many studies using CaMoO4 for water remediation to remove dyes by means of photocatalytic processes [26,27], but we found no work describing the use of this material as an adsorbent of toxic metals. In this study, CaMoO4 particles were synthesized using a microwave-assisted coprecipitation method. The main objective of this work is to evaluate the ability to remove cadmium ions from an aqueous medium, and two results can be highlighted here: (i) obtaining tetragonal phase of CaMoO4 at room temperature without any heat treatment, and (ii) fast removal of all toxic cadmium(ii) ions from aqueous solution of 1 mg L-1 concentration. The characteristics of CaMoO4 particles are discussed in detail based on the HTMW synthesis. The synthesized CaMoO4 particles were characterized by Xray diffraction (XRD) and scanning electron microscopy (SEM). The adsorption properties were analyzed to identify the removal of Cd2+ ions in aqueous media, and it was evaluated the effect of the adsorption pH of cadmium ions by CaMoO4 samples. Experimental Section CaMoO4 (CM) samples were synthesized using the following precursors: Na2MoO4 (Sigma-Aldrich, ≥ 98%), Ca(NO3)2.4H2O (Synth, 99%) and NH4OH (Synth, 27%). These reagents were used without further purification. In the experimental procedure, 15 mmol of molybdenum precursor and calcium precursor were dissolved separately in distilled water. The two solutions were then mixed and the pH was adjusted with ammonium hydroxide to pH 8 (Standard Suspension). Here, the CM-0’ was obtained by filtering, washing and drying the formed powder. To produce the remaining CM samples, the Standard Suspension was transferred to a Teflon vessel and inserted into a reactor, which was sealed and placed in a hydrothermal-microwave (HTMW) system, where it was kept at 120ºC for 0.5, 1, 2, 4, and 8 minutes. The processing times in HTMW were set to be double the preceding time (exponential increase). These samples are described in Table 1. The HTMW system was operated at a frequency of 60 Hz and with a maximum power of 1500 W, under pressure of approximately 3 bar. After processing, the reactor was cooled to room temperature and the resulting precipitate was washed repeatedly in distilled water and dried at 80ºC for 12 hours. One of the samples (CM-0') was not processed in the HTMW system. Table 1: CM samples obtained at different processing times in HTMW. PROCESSING TIME SAMPLE REPRESENTATION [minutes] CaMoO4 0 CM-0’ CaMoO4 0.5 CM-0.5’ CaMoO4 1 CM-1’ CaMoO4 2 CM-2’ CaMoO4 4 CM-4’ CaMoO4 8 CM-8’

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To determine their structural characteristics, the powders were characterized by X-ray powder diffraction (XRD) in a Shimadzu XRD 6100 diffractometer, using CuKα (k = 1.5406 Å) radiation. The data were collected in fixed-time mode, from 20o to 85o in the 2θ range, using a divergence slit of 0.5o and receiving slit of 0.3 mm and a step size of 0.02o. Microstructural and morphological analyses were performed by field emission scanning electron microscopy (FESEM, Zeiss Supra 35), using 2 to 4 kV under different levels of magnification. Cadmium working solutions were prepared daily by diluting a standard cadmium solution (Titrisol 1000 mg L-1 – Merck, Germany). The pH of the solutions was adjusted by adding HNO3 0.1 mol L-1 (Synth, 65%) or NaOH 0.1 mol L-1 (Synth, 97%), which was controlled with a digital pH meter (HANNA HI2002-02 Edge). To determine the pH at the zero charge point (pHzcp), distilled water samples were prepared with different pH values (2 to 11). Then, 2.0 mg of adsorbent was added to each solution, which was kept in equilibrium for 24 h at room temperature. After this period, the pH of all the solutions was measured (Figure 1a) and a pHfinal-pHinitial graph was plotted as a function of the initial pH level. In Figure 2, note that a line is drawn at the point where ΔpH is equal to zero, and the point of intersection with the curve resulting from the graph indicates pHzcp.

Figure 1.Scheme of determination of a) pHpcz and b) adsorption study to CaMoO4.

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Figure 2. pH level at the zero charge point (pHzcp) of CM. The adsorption potential of the CM samples obtained at different processing times was measured using the following procedure: 5 mL of cadmium solution (1 mg L-1) at pH 7 were placed in falcon tubes. Then, 2.0 mg of the CM samples were added to this solution. The system was kept under agitation for 5 minutes in a vortex mixer. The filtrate was then isolated and analyzed by flame atomic absorption spectroscopy (FAAS). The same procedure was used for Cd solution with pH adjusted to 1 and 9 (Figure 1b). All the experiments were performed in triplicate. Cadmium ions were quantified in a Varian SpectrAA 220 flame atomic absorption spectrometer (Victoria, Australia) equipped with a cadmium hollow cathode lamp and a deuterium lamp for background correction. The FAAS instrument was operated as recommended by the manufacturer: lamp current of 4 mA, wavelength of 228.8 nm, slit width of 0.1 nm, burner height of 17 mm, acetylene flow rate of 2.0 L min−1, and airflow rate of 13.5 L min−1. Results and Discussion Figure 3 depicts the XRD patterns of the CM samples. These patterns show only CaMoO4 diffraction peaks, i.e., no peaks of impurities were detected, indicating the formation of pure products. The main parameters analyzed in the CM diffractograms do not show great differences in values (2θ, intensity, and FWHM). The CM-0.5' is the only sample that shows a slight shift in 2θ diffractograms peaks (dotted gray vertical line in the Fig. 3), however all the diffraction peaks observed here correspond perfectly to those of the tetragonal phase of CaMoO4 (JCPDS: 85-1267).

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Figure 3. CM X-ray diffractograms synthesized in the HTMW system at 120°C for different times. What sets this work apart is the fact that CaMoO4 was obtained immediately after mixing the precursors in the proposed reaction conditions. This required no special conditions of temperature or pressure, or even the use of surfactants of any kind. The diffractogram of the CM-0’ sample clearly shows all the diffraction peaks expected for the CM phase. A comparison to previously reported routes to produce CaMoO4 materials indicates that our method involves mild reaction conditions (ambient pressure and room temperature) and that is highly reproducible. FEG-SEM (field emission gun scanning electron microscopy) imaging was of fundamental importance to shed light on the morphological evolution of CaMoO4 crystals in the HTMW system as a function of variations in processing time. Figure 4 presents a FEG-SEM image of the CM-0’ sample, showing microstructures with rod-shaped, dumbbell-shaped and spherical morphologies. The inset in Figure 4 illustrates the formation of microstructures, with several nanocrystals nucleating and growing into small seed particles, these nanocrystals have an average size of 88 nm.

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Figure 4. SEM-FEG image of CM-0’. In order to study the microwave-assisted growth of CaMoO4 microstructures, the CM produced for different lengths of time in microwave processing was subjected to an in-depth FEG-SEM analysis (Figure 5). In general, increasing the processing time led to a gradual shift from rod-shaped to spherical morphology, with the dumbbell-shaped morphology corresponding to the intermediate structure. The progressive growth of ellipsoidal rods (Fig. 5a and 5b) at both ends led to dumbbellshaped aggregates (Fig. 5c and 5d), whose shapes were completed by successive self-similar growth, resulting in well-defined spheres (Fig. 5e and 5f).

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Figure 5. FEG-SEM images of CaMoO4 samples (a) CM-0’, (b) CM-0,5’, (c) CM-1’, (d) CM-2’, (e) CM-4’, and (f) CM-8’. Many studies in the literature discuss the growth mechanism of CaMoO4. The conditions of synthesis, including the reagents used, govern the growth mechanism of inorganic oxides. The role of microwaves is to provide very rapid heating and raise the solution to a desired temperature in just a few minutes, it leads to the creation of abrupt super-saturation resulting in a very high nucleation density in a very short time. Thus, in this work, the growth of the CaMoO4 crystal structure was governed by the process of oriented attachment, as described by Chen et al. [6]. The process begins with the nucleation of CM nanoparticles, followed by the process of orientation and aggregation of the particles precipitated from the solution. Lastly, crystal growth occurs by the Ostwald ripening mechanism, changing the morphology. Figure 6 illustrates the correlation between the growth process and microwave processing time.

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Figure 6. Schematic illustration of the correlation between growth process and microwave processing time. In order to evaluate the CM adsorbent capacity for cadmium(II) ions, adsorption tests were conducted to remove the cadmium ion as a contaminant in aqueous solution. As can be seen in Figure 7, CM is able to remove 100% of cadmium ions in an aqueous solution. Removals are almost complete for all samples with the pH of the solution adjusted to 7 or 9 and the best result was achieved using samples CM-2’ and CM-4’.

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Figure 7. Potential for adsorption of Cd (II) ions by CM obtained at different processing times in HTMW. High cadmium adsorption occurs at pH 7.0 or 9.0. This behavior is probably due to the fact that, in aqueous media, groups responsible for the adsorption process can be protonated or deprotonate to generate surface loads, which vary according to pH levels below or above the pHPZC (pH of the point of zero charge (PZC)), respectively. The pHPZC of this material is 6.49, indicating that below this value, the CM surface will contain groups with mostly positive loads, although the coexistence of a small number of groups with negative loads is possible. At pH levels between 7.0 and 9.0, cadmium ions are positively charged (Cd2+). These species are electrostatically attracted by the surface loads of the coexisting CM species. This attraction causes a considerable increase in the adsorption of the cadmium species in these conditions. Figure 8 illustrates the behavior of CM surface as a function of pH of the solution.

Figure 8. Scheme for CM surface under different pH conditions. Lastly, the solution with pH adjusted to 1 showed low adsorption, which may be attributed to the formation of a double layer between the charged surface of the sorbent and the polar medium. The diagram in Figure 9 illustrates a typical adsorption process dependent on the pH of the solution. If the pH level of the solution is too high, the adsorbent is deprotonated, favoring the electrostatic

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attraction between adsorbent and adsorbate, i.e., the adsorption process. On the other hand, low pH levels increase the electrostatic repulsion between adsorbent and adsorbate [28].

Figure 9. Scheme of the interaction process between adsorbent-adsorbate as a function of the pH of the solution. Adapted from [28] A solution with pH adjusted to 1 was used in this work, and the results suggest that the low adsorption may be explained by the formation of a double layer between the charged surface of sorbent and the polar medium. Another important information is related to the adsorptive behavior of CM synthesized at different processing times. Figure 7 reveals that there were no significant differences in the adsorptive behavior of the different materials, indicating that the adsorption process is independent of the structural and morphological characteristics of the synthesized CM. Conclusions A series of CaMoO4 samples were synthesized by coprecipitation and processed in a HTMW system. XRD analysis showed that the processing time in HTMW did not change the crystal structure of CM, even for the untreated sample in HTMW. However, FEG-SEM micrographs revealed the role of microwave on the morphologies ranging from dumbbells to spheres, resulting from the formation of clusters of nanoparticles. All the samples showed an excellent potential for adsorption of Cd (II) ions. The pH of the solution plays an important role in the adsorption of cadmium(II) ions by the CM samples. At pH adjusted to 7 or 9 the CM-2' and CM-4’ samples removed 100% of the metal ions in solution. These results thus confirm the promising potential of calcium molybdate as an effective adsorbent for the removal of toxic cadmium(II) ions from aqueous media. Due to the characteristics of this material, it can be used for applications in Industrial wastewater. These materials present treatment flexibility, final efficiency and environmental safety, in addition to the low cost of synthesis when compared to other synthetic adsorbents. Acknowledgment The authors acknowledge the FAPEG funding institution and the Interdisciplinary Laboratory of Electrochemistry and Ceramics (LIEC) at the Federal University of São Carlos.

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References [1] X.F. Zhao, E. Namila, X.G. Wang, Preparation and luminescence properties of CaMoO4:Eu3+/Sm3+ phosphors. Lumin., 37 (2022) 1446. [2] M. Ghaed-Amini, M. Bazarganipour, M. Salavati-Niasari, Calcium molybdate octahedral nanostructures, hierarchical self-assemblies controllable synthesis by coprecipitation method: Characterization and optical properties. J. Ind. Eng. Chem., 21 (2015) 1089. [3] T. Thongtem, S. Kungwankunakorn, B. Kuntalue, A. Phuruangrat, S. Thongtem, Luminescence and absorbance of highly crystalline CaMoO4, SrMoO4, CaWO4 and SrWO4 nanoparticles synthesized by co-precipitation method at room temperature. J. Alloy. Compd., 506 (2010) 475. [4] R.C. Pullar, S. Farrah, N.M. Alford, MgWO4, ZnWO4, NiWO4 and CoWO4 microwave dielectric ceramics. J. Eur. Ceram. Soc., 27 (2007) 1059. [5] H.Y. Zhu, Y.M. Chen, J.F. Li, G.L. Cui, X.L. Wang, High-pressure x-ray diffraction study, optical properties, and applications of CaMoO4:Eu3+ nanosheets in white leds. J. Alloy. Compd., 846 (2020) 156473. [6] D. Chen, K.B. Tang, F.Q. Li, H.G. Zheng, A simple aqueous mineralization process to synthesize tetragonal molybdate microcrystallites. Cryst. Growth Des., 6 (2006) 247. [7] W.S. Wang, Y.X. Hu, J. Goebl, Z.D. Lu, L. Zhen, Y.D. Yin, Shape- and size-controlled synthesis of calcium molybdate doughnut-shaped microstructures. J. Phys. Chem. C, 113 (2009) 16414. [8] J.F. You, L. Xin, X. Yu, X. Zhou, Y. Liu, Synthesis of homogeneous CaMoO4 microspheres with nanopits for high-capacity anode material in li-ion battery. Appl. Phys. A-Mater. Sci. Process., 124 (2018) 271. [9] Q. Gong, X.F. Qian, X.D. Ma, Z.K. Zhu, Large-scale fabrication of novel hierarchical 3d CaMoO4 and SrMoO4 mesocrystals via a microemulsion-mediated route. Cryst. Growth Des., 6 (2006) 1821. [10] V.S. Marques, L.S. Cavalcante, J.C. Sczancoski, A.F.P. Alcantara, M.O. Orlandi, E. Moraes, E. Longo, J.A. Varela, M.S. Li, M. Santos, Effect of different solvent ratios (water/ethylene glycol) on the growth process of camoo4 crystals and their optical properties. Cryst. Growth Des., 10 (2010) 4752. [11] H.R. Xing, X.B. Min, C.J. Tang, M. Sillanpaa, F.P. Zhao, Recent advances in membrane filtration for heavy metal removal from wastewater: A mini review. J. Water Process. Eng., 49 (2022) 103023. [12] M.G. Motitswe, K.O. Badmus, L. Khotseng, Development of Adsorptive Materials for Selective Removal of Toxic Metals in Wastewater: A Review. Catalyst, 12 (2022) 1057. [13] F.Q. An, R.Y. Wu, M. Li, T.P. Hu, J.F. Gao, Z.G. Yuan, Adsorption of heavy metal ions by iminodiacetic acid functionalized d301 resin: Kinetics, isotherms and thermodynamics. React. Funct. Polym., 118 (2017) 42. [14] S. Rajendran, A.K. Priya, P.S. Kumar, T.K.A. Hoang, K. Sekar, K.Y. Chong, K.S. Khoo, H.S. Ng, P.L. Show, A critical and recent developments on adsorption technique for removal of heavy metals from wastewater-A review. Chemosphere, 303 (2022) 135146. [15] Q.Q. Ye, Q.H. Li, X. Li, Removal of heavy metals from wastewater using biochars: adsorption and mechanisms. Environ. Pollut. Bioavailab., 34 (2022) 385. [16] Z.B. Wang, W.B. Xu, F.H. Jie, Z.W. Zhao, K. Zhou, H. Liu, The selective adsorption performance and mechanism of multiwall magnetic carbon nanotubes for heavy metals in wastewater. Sci. Rep., 11 (2021) 16878.

168

Advanced Materials and Production Technologies

[17] S. Singh, D. Kapoor, S. Khasnabis, J. Singh, P.C. Ramamurthy, Mechanism and kinetics of adsorption and removal of heavy metals from wastewater using nanomaterials. Environ. Chem. Lett., 19 (2021) 2351. [18] W. Zhang, F.E.I. Yulong, Y. WANG, B. ZHANG, X. Ma, Research Progress on the Adsorption of Heavy Metals in Industrial Wastewater by Magnetic Polyaniline Composites. Mater. Rep., 34 (2020) 9012. [19] O.G.M. Sandoval, G.C.D. Trujillo, A.E.L. Orozco, Amorphous silica waste from a geothermal central as an adsorption agent of heavy metal ions for the regeneration of industrial pre-treated wastewater. Water Resour. Ind., 20 (2018) 15. [20] N. Masunga, O.K. Mmelesi, K.K. Kefeni, B.B. Mamba, Recent advances in copper ferrite nanoparticles and nanocomposites synthesis, magnetic properties and application in water treatment: Review. J. Environ. Chem. Eng., 7 (2019) 103179. [21] J.Q. Jiang, S.M. Ashekuzzaman, Development of novel inorganic adsorbent for water treatment. Curr. Opin. Chem. Eng., 1 (2012) 191. [22] C.A.S. Silva, R. Silva, A.T. de Figueiredo, V.N. Alves, Magnetic solid-phase microextraction for lead detection in aqueous samples using magnetite nanoparticles. J. Braz. Chem. Soc., 31 (2020) 109. [23] I. Mironyuk, I. Mykytyn, H. Vasylyeva, K. Savka, Sodium-modified mesoporous TiO2: Sol-gel synthesis, characterization and adsorption activity toward heavy metal cations. J. Mol. Liq., 316 (2020) 113840. [24] M. Sharma, J. Singh, S. Hazra, S. Basu, Adsorption of heavy metal ions by mesoporous ZnO and TiO2@ZnO monoliths: Adsorption and kinetic studies. Microchem. J., 145 (2019) 105. [25] A. Thakur, P. Punia, R. Dhar, R.K. Aggarwal, P. Thakur, Separation of cadmium and chromium heavy metals from industrial wastewater by using Ni-Zn nanoferrites. Adv. Nano Res., 12 (2022) 457. [26] H. S. Chawda, A.K. Rai, R. Rathore, S.C. Ameta, R. Ameta, Undoped and carbon-doped calcium molybdate as photocatalyst for degradation of methylene blue. J. Indian Chem. Soc., 97 (2020) 2397. [27] Y.B. Xiang, J.M. Song, G. Hu, Y. Liu, Synthesis of CaMoO4 hierarchical structures via a simple slow-release co-precipitation method. Appl. Surf. Sci., 349 (2015) 374. [28] L. Wang, C.X. Shi, L. Wang, L. Pan, X.W. Zhang, J.J. Zou, Rational design, synthesis, adsorption principles and applications of metal oxide adsorbents: A review. Nanoscale, 12 (2020) 4790.

CHAPTER 5: Building Materials

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 171-177 doi:10.4028/p-4880gw © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-05-18 Accepted: 2022-11-15 Online: 2022-12-26

Effects of Basalt Fiber on Strength of Alkali-Activated Slag-Tailing Cement Bodies Shuai TIAN1,2,a *, Kun LI1,b, Xin LIU1,c and Yong LI1,d Institute of Land Reclamation and Ecological Restoration, China University of Mining and Technology (Beijing), Beijing 100083, China

1

Hebei Hongyuan Runze Land Planning and Design Company Limited, Baoding 071000, China

2

[email protected], [email protected], [email protected], [email protected]

a

Keywords: Alkali-activated material; Basalt fiber; Cement body; Strength, tailings

Abstract. The influences of different quantity of basalt fiber and lead–zinc tailings on the strength of alkali-activated slag-tailings cement bodies were studied. After adding basalt fiber, the uniaxial compressive strength of the 50 and 60 g per unit tailing cement bodies increased before decreasing throughout a 7-day curing period. During a 28-day curing period, the uniaxial compressive strength of the 50 g per unit tailings cement decreased gradually, while the uniaxial compressive strength of the 60 g per unit tailings cement increased first and then decreased. Furthermore, after adding basalt fiber, the flexural strength of the 50 g per unit tailings cement body decreased gradually during a 7-day curing period, while the 60 g per unit tailings cement increased first and then decreased. Under a 28-day curing period, the flexural strength decreased first and then increased for both cement bodies. Finally, At the confining pressures of 2, 4 and 6 Mpa, the increase amplitude of the triaxial compressive strength of the cementation body was different with the addition of basalt fiber. The increase amplitude of the triaxial confining pressure from 2 to 4 Mpa was higher than that of the triaxial compression from 4 to 6 Mpa. Introduction Mineral resources are important to social development and progress, and with the rapid development of the world economy, the demand for mineral products has greatly increased, causing the scale of mining developments and the amount of tailings to increase. Additionally, many mined metal ores are low grade and, to increase the output, substantial large-scale beneficiation has also led to an increase in the amount of tailings. These tailings are the solid wastes discharged by mining activities, under certain technical and economic conditions, because of the low content of useful target components in the concentrator. Tailings have become a regional security issue since they occupy a significant amount of land, pollute the environment, and increase the costs associated with mining [1]. The sustainable development of mining has become inevitable as society continues to progress. Tailing exploitation and utilization can "turn trash into treasure" and effectively relieve the resource and environmental pressures. Therefore, numerous researchers have addressed the utilization of tailings; for example, tailings are used in building materials and filling materials for filling underground mined-out areas [2]. Cementitious material is an important basis to utilizing tailings, and the application of alkali-activated cementing materials (AACM) in tailings has recently attracted extensive attention. AACM has high early strength, a short setting time, and excellent erosion resistance and is expected to replace Portland cement. AACM has been applied to tailings to utilize its unique advantages; for example, Pan et al. applied a sodium silicate and sodium aluminate composite solid alkali activator to the slag-red mud-mixed system and developed a new alkali-red mud cementing material with high early and ultimate strength and excellent chemical erosion resistance [3]. Chen et al. took fine-grained lead–zinc mine tailings as test materials to improve the performance of pulverized blast furnace slag and sodium silicate activated slag with low alkali dosage, using sodium hydroxide and sodium silicate as alkali activators [4]. Singh et al. developed an AACM using copper slag (CS) as an

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aluminosilicate material, and studied the effects of mineral admixtures such as fly ash and metakaolin on the properties of the alkali-activated CS. The compressive strength was enough to meet the structural requirements of various construction projects [5]. Further research has shown that fiber strengthens AACM, which provides a way for further optimization and performance improvement of AACM. For example, Nguyen et al. used different polypropylene (PP) fiber-reinforced cementite matrices to improve the mechanical properties of the cementite material in view of the brittleness of alkali-activated ladle cementite material [6]. Studies have shown that appropriate fiber reinforcement can make the gelled material obtain high ductility; for instance, Lee developed a new strain hardening fiber reinforced cementing material using a polyvinyl alcohol fiber reinforced slag-based alkali-activated mortar [7]. Furthermore, Kwon et al. found that PE fiber composites show excellent tensile properties in tensile strain capacity and crack morphology, while polypara-benzothiazole fiber composites have higher tensile strength level and tighter crack width and spacing [8]. Basalt fiber has excellent performance and acid, alkali, and corrosion resistance, which have a good role to improve the performance of cementitious materials. Currently, studies on alkali activated materials and lead-zinc tailings are limited. Therefore, this study used lead–zinc tailings as the primary raw material and, through adding different basalt fibers, studied its effects on the uniaxial compressive, flexural, and triaxial compressive strength of alkali-excited cement bodies. This study aims to provide a reference for the performance improvement and further utilization of lead–zinc tailings in cement bodies. Materials and Experimental Methods Materials. Lead–zinc tailings were obtained from a lead–zinc tailings reservoir in Yunnan Province. The particle size distribution of the tailings was analyzed via a Malvern laser particle analyzer (Mastersizer 2000, Malvern Instruments Ltd, United Kingdom); the volume fraction is shown in Fig.1. The main chemical components of the obtained tailings were Fe2O3, CaO, and SiO2. Slag was obtained from the Gongyi Water Purification Material Ltd, in Henan Province. The chemical composition of the obtained lead–zinc tailings and slag are listed in Table 1. The water glass was obtained from Yousuo Chemical Technology Ltd, Shandong Province. The modulus of water glass used was 3.3, with 26.5% SiO2 and 8.3% Na2O. The sodium hydroxide was obtained from the Damao Chemical Reagent Factory in Tianjin. The basalt fibers were obtained from Changsha Ningxiang Building Materials Ltd, Hunan Province; the properties of the basalt fibers are shown in Table 2.

Fig. 1. Particle size distribution of tailings used.

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Table 1. Chemical composition of lead-zinc tailing and slag used in experiments (%) Material Lead-zinc Tailing Slag Diameter /μm 17

CaO 23.20 34.00

Length /mm 6

SiO2 16.97 34.50

Al2O3 4.51 17.70

SO3 4.53 1.64

Fe2O3 40.35 1.03

Table 2. Properties of basalt fiber

Tensile Strength /MPa 3800-4800

MgO 6.01

Modulus of Elasticity /GPa 100

MnO 3.35

Other 7.09 5.12

Density /g·cm-3 2.8-3.3

Sample Preparation and Testing Preparation of Uniaxial Compressive and Flexural Strength Test Samples. First, 1.4 g of sodium hydroxide, 11.1 g of water glass, and 16 g of water per unit of test sample were mixed and stirred evenly and then cooled to room temperature to obtain the composite solution for the experiment. The mass of the lead–zinc tailings per unit of test sample was 50 or 60 g, and the mass of slag per unit of test sample was 15 g. Further, 0, 0.5, 1.0, and 1.5 kg/m3 basalt fibers were added to the tailing and slag and well mixed. The composite solution was added to the slag, lead–zinc tailing, and basalt fiber mixture. After mixing for 3 min, based on the Chinese standard GB/T 17671, mortars were molded into 40 × 40 × 160 mm prismatic molds and then vibrated for 2 min to remove entrained air. Then mortars were cured in the experiment room at normal temperature. After 2 d of curing, the demolded mortars were cured in the standard curing box at 21±2 ℃ and 95±3 % relative humidity until testing at days 7 and 28. The strengths of mortars at days 7 and 28 were measured on an electronic universal testing machine (model WDW-10D, Jinan Hengsi Shengda Instrument, Ltd, China). Preparation of Triaxial Compression Strength Test Samples. The preparation of the mortar samples was consistent with the preparation and curing methods of the test samples for uniaxial compressive and flexural strength, using a 50 × 100 mm cylindrical mold, based on the Chinese standard GB/T 50266. The experiment designed three confining pressures: 2, 4, and 6 MPa. After 45 d of curing, the compression tests were conducted, and the pressure gradually increased until the sample was destroyed. The triaxial compression tests were performed via a Rock Mechanics Test System (model MTS 815, MTS company, USA). Results and Discussion Influence of Uniaxial Compressive Strength Performance. The influences of different basalt fiber additions on the uniaxial compressive properties of alkali-activated slag and lead–zinc tailing cement bodies are shown in Fig. 2.

Fig. 2. Effect of basalt fiber on uniaxial compressive strength of cement bodies.

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When the quantity of lead–zinc tailings per unit of cement body was 50 g and with the quantity of basalt fiber added at 0, 0.5, 1.0 and 1.5 kg/m3, the uniaxial compressive strength of the cement bodies at 7 d were 4.39, 4.51, 5.11 and 3.98 Mpa, respectively (Fig. 2a). With the addition of basalt fiber, the uniaxial compressive value of cement bodies increased first and then decreased. The maximum uniaxial compressive of basalt was 5.11 Mpa at 1 kg/m3. When the quantity of basalt fiber was increased to 1.5 kg/m3, the uniaxial compressive value decreased to 3.98 Mpa, which was lower than that of the cement body without basalt fiber. At 28 d, the uniaxial compressive strength of the cement bodies also increased first and then decreased, but the maximum value was at the basalt fiber content of 0.5 kg/m3, when the uniaxial compressive strength was 24.17 Mpa. The lowest value at 28 d was 19.32 Mpa at 1.5 kg/m3 of added basalt, which was lower than the uniaxial compressive strength of basalt fiber without any additions. Fig. 2b shows the uniaxial compressive changes of the cement bodies with 60 g of tailings per unit. The uniaxial compressive strength of the cement bodies without basalt fiber were 3.96 Mpa at 7 d of curing. With the addition of basalt fiber, the uniaxial compressive strength of the cement bodies increased first and then decreased, and the maximum uniaxial compressive value was 3.3 Mpa, when 1 kg/m3 of basalt fiber was added. Meanwhile, when the basalt fiber added was 0.5 and 1.5 kg/m3, the uniaxial compressive strength was 2.98 and 2.93 Mpa, respectively. The cement bodies with 28 d of curing showed the same trend as those with 7 d of curing. The uniaxial compressive of cement bodies without basalt fiber were 23.05 Mpa, which was the highest uniaxial compressive value. With the addition of 0.5, 1.0, and 1.5 kg/m3 of basalt fibers, the uniaxial compressive values of the cement bodies were 21.17, 22.01, and 20.91 Mpa, respectively, showing a similar trend of increasing first and then decreasing. According to the uniaxial comprehensive analysis (Fig. 2), different quantities of basalt fiber had different influences on alkali-activated slag-tailing cement bodies, and there was an optimal addition value. Within the scope of optimal addition value, there was a positive effect on increasing the uniaxial compressive property of the cement body, and the uniaxial compressive strength increased. Beyond the optimal addition value, the uniaxial compressive property of the cement body is reduced to a certain extent, resulting in the reduction of the uniaxial compressive strength. Furthermore, the addition of basalt fiber has limited improvements to the uniaxial compressive properties of the cement bodies, and even reduced the compressive value. When 50 g of tailings per unit were added, the difference of maximum uniaxial compressive value by adding fiber and not adding fiber was 0.72 and 0.99 Mpa after curing for 7 and 28 d, respectively. When adding 60 g of tailings per unit, these values were -0.66 and -1.04 Mpa, respectively. The reasons may be related to the quantity of tailings added, gelation time, and the role played by basalt fibers, which lead to a small or negative effect on the uniaxial compressive properties of the cement bodies [9]. Influence of Flexural Strength Performance. When the quantity of lead–zinc tailings added was 50 g per unit of cement body, the flexural strength of the cement bodies without basalt fiber were 1.93 Mpa with a curing period of 7 d (Fig. 3a). With the addition of basalt fiber of 0.5, 1.0, and 1.5 kg/m3, the flexural strength of the cement bodies were 1.84, 1.44, and 1.4 Mpa, respectively, which showed a trend of gradual decline. The cement body with a curing period of 28 d differed from that of 7 d. The flexural strength of the cement body without basalt fiber was 3.32 Mpa. With the addition of basalt fiber, the flexural strength of the cement bodies were 3.06, 2.67, and 3.47 Mpa respectively, which showed a decreasing and then an increasing trend. The maximum flexural strength of 3.47 Mpa was observed when 1.5 kg/m3 of basalt fiber was added. When the quantity of lead–zinc tailings added was 60 g per unit of cement body, with the addition of basalt fiber of 0.5, 1.0, and 1.5 kg/m3, the flexural strength of the cement body with a curing period of 7 d was 1.08, 1.36, and 1.21 Mpa, respectively, showing a trend of increased first and then decreased. Meanwhile, the flexural strength of the cement body reached the maximum value at 1.0 kg/m3 of basalt fiber added, and the flexural strength of basalt fiber without addition was 1.65 MPa (Fig. 3b). When the curing period was 28 d, the overall flexural strengths of the cement bodies were improved. Without basalt fiber added, the flexural strength of the cement was 2.39 MPa. With

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the addition of basalt fiber, the flexural strength of the cement body decreased first and then increased, and the maximum value reached 3.51 Mpa, when 1.5 kg/m3 basalt fiber added.

Fig. 3. Effect of basalt fiber on flexural strength of cement bodies The flexural strength of the cement body with different basalt fibers increased as the curing time increased (Fig. 3). With 7-d of curing time, due to insufficient internal cementation, basalt fiber did not benefit it, and rather led to the reduction of flexural strength after addition. In the 28-d curing time, after the addition of basalt fiber, both 50 and 60 g tailings per unit of cement bodies showed a similar trend of decreasing first and then increasing, and reached the maximum value at 1.5 kg/m3 basalt fibers added. However, under the 50 g tailings per unit of cement body, the compressive strength of the cement body with 0.5 and 1.0 kg/m3 basalt fiber addition was lower than that without basalt fiber addition. The reasons for this interaction should be further investigated. Influence of Triaxial Compressive Strength Performance. With the addition of basalt fibers of 0, 0.5, 1.0, and 1.5 kg/m3, the triaxial compressive strength of the cement bodies under the three different confining pressures significantly differed. When the triaxial confining pressure was 2 Mpa, the compressive strength of the cement body increased first and then decreased, with the maximum value of 31.78 Mpa when the basalt fiber added was 1.0 kg/m3. When the confining pressure was 4 Mpa, the triaxial compressive strength decreased first and then increased gradually. The maximum triaxial compressive strength of the cement body without basalt fiber was 35.02 Mpa. Under the confining pressure of 6 Mpa, the triaxial compressive strength of the cement body increased first and then decreased, but the overall change was not significant. The maximum value appeared when the basalt fiber added was 0.5 kg/m3, and the triaxial compressive strength value was 35.65 Mpa. This shows that the cement bodies with different quantity of basalt fiber do not show obvious regularity under the confining pressures of 2, 4, and 6 Mpa. This is likely due to the influence of confining pressure, when the confining pressure value is small (2, 4 Mpa), the compressive property of basalt fiber takes effect at a certain extent. When the confining pressure increases (6 Mpa), the addition of basalt fiber has trivial or negative effect. The variation of triaxial compressive strengths of the cement bodies with the same quantity of basalt fiber under different confining pressures was consistent; that is, the value of triaxial compressive strength increased with the increase of confining pressures. When the maximum confining pressure was 6 Mpa, the triaxial compressive strengths of the three basalt fibers added were 35.65, 35.42, and 35.24 Mpa, respectively. When the confining pressure increased from 2 to 4 Mpa, the triaxial compressive strength of the three levels basalt fibers added increased for 4.48, 2.79, and 3.69 Mpa, respectively. When the confining pressure increased from 4 to 6 Mpa, the triaxial compressive strength of the three levels basalt fibers added increased for 1.31, 0.85, and 0.34 Mpa. The increase amplitude of the triaxial compressive strength of the cementation body is different under

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the three confining pressures of 2, 4, and 6 Mpa. The increase amplitude of the triaxial compressive strength of the cement body from 2 to 4 Mpa is significantly higher than that from 4 to 6 Mpa. It indicates that the cement body with different quantity of basalt fiber added had different response to the confining pressure and with the increase of confining pressure, the response of compressive strength decreased [10].

Fig. 4. Effect of basalt fiber on triaxial compressive strength of cement bodies Conclusion (1) With the addition of basalt fiber, the uniaxial compressive strength of the cement body varied significantly under different curing periods and tailing quantities. After the addition of basalt fiber, during the 7-day curing period, the uniaxial compressive strength of cement bodies with tailings quantity of 50 and 60 g per unit increased first and then decreased. In the 28-day curing period, the uniaxial compressive strength of cementation body with tailings quantity of 50 g per unit shows a trend of gradual decrease, while the tailings with the quantity of 60 g per unit added showed a trend of increasing first and then decreasing. (2) After the addition of basalt fiber, during the 7-day curing period, the flexural strengths of the cement bodies with the tailings quantity of 50 g per unit added presented a trend of gradual decline, while the flexural strengths of the cement bodies with the tailings quantity of 60 g per unit added presented a trend of first increased and then decreased. In the 28-d curing period, the flexural strengths of cement bodies with tailings quantity of 50 and 60 g per unit added decreased first and then increased. (3) With the addition of basalt fiber, the triaxial compressive strength of the cement bodies did not show obvious regularity under the confining pressures of 2, 4, and 6 Mpa. After the addition of basalt fiber, the increase amplitude of the triaxial compressive strength of the cementation body under three confining pressures was different, and the increase amplitude of the triaxial compressive strength from 2 to 4 Mpa was significantly higher than that from 2 to 6 Mpa. Acknowledgements This work was supported by the National Key Research and Development Program of China (No. 2018YFC1801704 and No. 2018YFC1801703).

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References [1] Dong L, Tong X, Li X, Zhou J, Wang S, Liu B. Some developments and new insights of environmental problems and deep mining strategy for cleaner production in mines. Journal of Cleaner Production, 210, PP: 1562-1578, 2019. https://doi.org/10.1016/j.jclepro.2018.10.291 [2] Qaidi SMA, Tayeh BA, Zeyad AM, Azevedo ARG, Ahmed HU, Emad W. Recycling of mine tailings for the geopolymers production: A systematic review. Case Studies in Construction Materials, 16, e00933, 2009. https://doi.org/10.1016/j.cscm.2022.e00933 [3] Pan Z, Li D, Yu J, Yang N. Properties and microstructure of the hardened alkali-activated red mud-slag cementitious material. Cement and Concrete Research, 33(9), PP: 1437-1441, 2003. https://doi.org/10.1016/S0008-8846(03)00093-0 [4] Chen W, Peng R, Straub C, Yuan B. Promoting the performance of one-part alkali-activated slag using fine lead-zinc mine tailings. Construction and Building Materials, 236, 117745, 2020. https://doi.org/10.1016/j.conbuildmat.2019.117745 [5] Singh J, Singh SP. Development of Alkali-activated Cementitious Material using Copper Slag. Construction and Building Materials, 211, PP: 73-79, 2019. https://doi.org/10.1016/j. conbuildmat.2019.03.233 [6] Nguyen H, Carvelli V, Adesanya E, Kinnunen P, Illikainen M. High performance cementitious composite from alkali-activated ladle slag reinforced with polypropylene fibers. Cement and Concrete Composites, 90, PP: 150-160, 2018. https://doi.org/10.1016/j.cemconcomp. 2018.03.024 [7] Lee BY, Cho CG, Lim HJ, Song JK, Yang KH, Li VC. Strain hardening fiber reinforced alkali-activated mortar – A feasibility study. Construction and Building Materials, 37, PP: 15-20, 2012. https://doi.org/10.1016/j.conbuildmat.2012.06.007 [8] Kwon SJ, Choi JI, Nguyen HH, Lee BY. Tensile strain-hardening behaviors and crack patterns of slag-based fiber-reinforced composites. Computers and Concrete, 21(3), PP: 231-237, 2018. https://doi.org/10.12989/cac.2018.21.3.231 [9] Jiang C, Fan K, Wu F, Chen D. Experimental study on the mechanical properties and microstructure of chopped basalt fiber reinforced concrete. Materials and Design, 58, PP: 187-193, 2014. https://doi.org/10.1016/j.matdes.2014.01.056 [10] Zheng B, Zhang D, Liu W, Yang Y, Yang H. Use of basalt fiber-reinforced tailings for improving the stability of tailings dam. materials, 12(8), 1306, 2019. https://doi.org/10.3390/ma12081306

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 179-185 doi:10.4028/p-834hjr © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-05-23 Accepted: 2022-11-15 Online: 2022-12-26

Effect of Ultraviolet Aging on Rheological Properties and Microstructure of Rubber Asphalt in High Altitude Area GUO Dongfeng1,a, MA Xiaojun2,b, MA Xiaoyan2,c* and FANG Jianhong3,d Qinghai Transportation Construction Management Co., Ltd., Xining 810000, China

1

School of Materials Science and Engineering, Chang'an University, Xi'an 710061, China

2

Qinghai Research Institute of Transportation, Xining 810016, China

3

[email protected], [email protected], [email protected] d [email protected]

a

Keywords: road engineering, Rubber asphalt, Rheological properties, AFM

Abstract. High altitude and strong ultraviolet radiation in Qinghai Tibet Plateau induces the brittleness and hardening of asphalt, which leads to temperature cracks, pits and other diseases of asphalt pavement. In this paper, the accelerated UV aging test of rubber asphalt was carried out by simulating the UV radiation intensity in Xining, Qinghai Province, and the rheological properties and microstructure changes of rubber asphalt were analyzed. The results show that the complex modulus of rubber asphalt increases exponentially with the extension of UV aging time. The phase angle of rubber asphalt decreases linearly with UV aging, and the deformation recovery performance of rubber asphalt increases; UV radiation has the most significant effect on the micro morphology of rubber asphalt. With the further extension of UV aging time, micro cracks are formed in rubber asphalt, and the low-temperature crack resistance and fatigue failure resistance of rubber asphalt are gradually reduced. Introduction Wasted tire rubber powder can be used to modify asphalt binder. Application of it not only solves the environmental pollution caused by wasted tire, but also significantly improves the high- and low-temperature properties of asphalt. At present, the research on the properties of rubber asphalt mostly focuses on high and low temperature properties, thermal aging and UV aging. UV aging induces the change of chemical property and composition of organic materials such as asphalt and the rubber powder, which resulted a deterioration of asphalt pavement resistance to low-temperature cracking and fatigue cracking [1, 2]. Therefore, it is of great significance to research the influence of UV aging on the performance of rubber asphalt. UV aging induces oxidative condensation occurring in asphalt binders, in which the unsaturated double bond is condensed into carbonyl and hydroxyl. Compared with the base asphalt and SBS modified asphalt, rubber asphalt has the lowest ductility attenuation rate after aging. This makes the rubber asphalt has obvious advantages in the performance of anti-aging [3,5]. When the UV aging time lies between 16h to 96h and temperature lies between 40 ℃ ~ 100 ℃, the softening point and viscosity of rubber asphalt increase significantly with the extension of aging time and the increase of aging temperature, but its low-temperature performance and the ability to dissipate temperature stress gradually decrease [6], After 180 hours of UV aging, the temperature sensitivity is the least [7]. The aging effect of ultraviolet aging on rubber asphalt is further enhanced in the combined action of oxygen and water, because water dissolves part of the aging products of asphalt [8, 9]. Microstructure of rubber asphalt and base asphalt binder show that the effect of UV aging on the carbonyl index of rubber asphalt is much smaller than that of base asphalt binder [10]. Rubber asphalt has an obviously better anti-aging performance than that of base asphalt, as a large amount of carbon black is released during the deep degradation of rubber powder [11, 13]. A large number of studies have conducted the UV aging properties of rubber asphalt; however, there is relatively little research on the UV aging of rubber asphalt in high-altitude areas where a strong ultraviolet radiation has. Ultraviolet oxidation caused the brittle of asphalt binder, presented an

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increased low-temperature modulus and decreased stress relaxation rate, that resulted in the occurrence of temperature shrinkage cracks, pits and other diseases in cold areas. Therefore, UV aging has a significant impact on Asphalt Pavement in Qinghai, Tibet and other plateau areas with long winter. This paper discusses the performance of rubber asphalt in the accelerated ultraviolet aging on rubber asphalt to simulate the ultraviolet radiation in Xining, Qinghai Province, and analyzed its rheological properties and micro surface structure. The result can be of great important in application of rubber asphalt in the areas of cold, high altitude and strong ultraviolet radiation. Material and Test Material. In this paper, the SK90 asphalt, 40 mesh rubber powder and light oil are used to produce rubber asphalt, in which the content of rubber powder is 20% and the content of light oil is 1%. Fabrication of rubber asphalt was as follows: first, heat the SK90 asphalt to 185 ℃ and add rubber powder, then, stir the mixture for 60min with a high-speed mixer at the temperature of 185 ℃, and the rubber asphalt was prepared. The property of rubber asphalt was shown in table 1. Table 1. Property of rubber asphalt Specifications Unit Tested result Penetration (25℃, 100g)5s) 0.1mm 62.0 Ductility (5℃, 5cm/min) cm 13.5 Softening pointTR&B ℃ 62.5 Viscosity (185℃) Pa∙s 2.5 Flash point ℃ 270 Density g/cm3 1.030 Loss of mass % +0.4 TFOT Residual ductility(10℃) cm 16.5

Requirement 40～80 ≮8.0 ≮55.0 ≯4.0 ≮245 Measured vaue ±0.8 ≮8

Method T0604 T0605 T0606 T0625 T0611 T0603 T0610 T0605

Test Method Simulation of Ultraviolet Aging of Rubber Asphalt. The thin film oven test (TFOT) and ultraviolet aging test (UV) were adopted to simulate the thermal aging and UV aging. A thickness of 1mm was place in the UV oven for accelerated aging. In view of the great difference of ultraviolet radiation with altitude in the Qinghai Tibet Plateau, this paper selects Xining City, Qinghai Province for experimental research. Among them, the latitude of Xining city is 36º 37´, solar altitude angle can be calculated as follow: (1) = h π / 4(90 − ϕ ) According to the formula, the annual average solar altitude angle of Xining city is between 30 ° ~ 76 °, and the annual average solar radiation Q is between 6680 MJ / m2 ~ 8400 MJ / m2. Study on the seasonal variation of UV radiation in the Qinghai Tibet Plateau showed that UV radiation in the plateau accounts for 35.8% of the total solar radiation in summer and 17.0% in winter. The average value selected in this paper showed that the UV radiation in this area accounts for 26.4% of the total solar radiation, and the UV radiation Q is between 1136 MJ / m2 and 3007 MJ / m2. Simulation of the UV radiation is referring to the heating aging of asphalt, a film with a 1mm thick of rubber asphalt is made in a vessel. The sample was exposed to ultraviolet radiation for 16h every day at the temperature of 40 ℃. The complex modulus, phase angle and microstructure of the sample of different aging time and ultraviolet radiation are tested respectively. The time and total radiation of UV are shown in Table 2. Number Time /h Radiation /kJ/cm2

1 0 0

Table 2. Time and Total Radiation of UV 2 3 4 5 6 60 200 410 620 850 5.69 15.5 30.1 40.1 53.4

7 1050 65.8

8 1400 80.6

9 1700 96.4

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Temperature Sweep of Rubber Asphalt (1) The Linear Viscoelastic Region of rubber asphalt Dynamic shear rheometer is applied to measure the complex shear modulus and phase angle. It is of great important to determine the linear viscoelastic region (LVE), as the LVE is an important input parameter in temperature sweep. In this study, the LVE was defined as the point of shear strain where the corresponding complex modulus reduced to 95% of the initial value. Loading process of shear strain sweep and the stress-strain relation during loading are shown as Figure.1 and Figure.2. Generally, LVE is determined by rubber asphalt, loading temperature, frequency and other factors, higher the modulus, smaller the value of LVE. In this paper, LVE of rubber asphalt was analysis under the condition of 20 ℃ ~ 60 ℃ and the loading frequency is 1Hz. L

6 5 4 3 2 1

S φ

S h

Figure.1 Shear Strain Sweep

Figure.2 Stress=strain Relation of Stain Sweep

(2) Temperature sweep of rubber asphalt The shear loading frequency of rubber asphalt is 1Hz and temperatures of 52℃, 58℃, 64℃, 70℃, 76℃, 82℃ were selected. τ (2) G∗ = 0 γ0 (3) δ= 2π∆t Result and Discussion The Complex Modulus and Phase Angle of Rubber Asphalt. The temperature sweep was applied to the sample of rubber asphalt of different UV aging time, and the complex shear modulus, G*, and phase angle, δ, were obtained, and he results were shown in Table 3. As the temperature rise from 52℃ to 88℃, the complex shear modulus of rubber asphalt decreases rapidly and the phase angle increases gradually, indicating that the resistance to shear deteriorated and its deformation recovery ability decreases with the increase of test temperature. As a typical viscoelastic material, the internal molecular movement of rubber asphalt intensifies, its molecular chain segments slide relatively in the process of shear deformation, and its ability to resist deformation and recovery decreases with the increase of temperature.

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Table 3. Complex Shear Modulus and Phase Angle of Rubber Asphalt Temperature /℃ 52 58 64 70 76 δ /º 63.67 66.01 69.10 72.31 75.00 G* / Pa 15890 8981 5097 2891 1717 δ /º 63.90 64.31 65.05 66.14 67.54 G* / Pa 20660 11420 6538 3873 2358 δ /º 61.95 62.25 63.02 64.23 65.77 G* / Pa 23400 13180 7533 4506 2751 δ /º 60.88 61.24 62.26 63.85 65.78 * G / Pa 24090 13730 7963 4787 2951 δ /º 59.47 59.84 60.80 62.42 64.44 G* / Pa 24030 13770 8111 4929 3077 δ /º 60.58 60.88 61.73 63.09 64.62 G* / Pa 24960 14160 8175 4920 3080 δ /º 59.24 59.73 60.87 62.61 64.82 G* / Pa 25190 14490 8502 5147 3137 δ /º 57.46 57.82 59.39 60.90 62.30 G* / Pa 26752 17472 9863 6320 4013 δ /º 54.82 55.60 57.90 59.36 61.62 G* / Pa 27659 18084 11283 6829 4302

82 78.94 1017 69.35 1454 67.28 1727 67.91 1861 66.55 1970 66.89 1899 66.58 2023 64.35 2358 63.23 2605

For rubber asphalt of different UV aging time, the phase angle and complex shear modulus were found to be increased exponentially with the extension of UV aging time and radiation at the same temperature. When the UV aging time is less than 400h, the complex shear modulus of rubber asphalt increases rapidly. However, when the UV aging time is more than 400h, the growth of complex shear modulus slowed down. Similarly, the phase angle of rubber asphalt decreases linearly with UV aging, indicating that the deformation recovery of rubber asphalt increases after UV aging. In the process of UV aging, the molecular structure of asphalt is destroyed, and new functional groups are formed after asphalt aging, in which the unsaturated double bond is oxidized to form carbonyl and carboxyl groups. The molecular weight of asphalt phase increases due to the association of structure, and its ability to resist high-temperature shear deformation and deformation recovery are enhanced. For the rubber powder in asphalt, UV aging causes the natural rubber and synthetic rubber to produce free radical and oxygen absorption reaction under the action of UV radiation, the content of gel in the rubber powder is reduced, and the rubber powder is further degraded. The oxidative condensation reaction of asphalt and the degradation of rubber powder cause the changes of complex shear modulus and phase angle of rubber asphalt during UV aging. Microstructure of Rubber Asphalt. As its high spatial resolution, as well as the ability to test Nano Mechanics and physical properties of materials, Atomic Force Microscope (AFM) has been widely applied in physics, chemistry and other fields in recent years. It is simple to prepare samples and operate the equipment. Its advantage is that it can accurately obtain the micro morphology and surface features of the material surface in the three-dimensional. As the thickness of rubber asphalt sample has a great influence on the result of AFM test, the quality of each sample needs to be strictly controlled to ensure the consistency of its thickness. For asphalt samples that have undergone UV aging for a long time, they still have high viscosity after heating and melting, so dipping is not suitable. Therefore, in this paper, the rubber asphalt sample is scraped with a scalpel and 0.05g asphalt was placed on the glass. And then heated at 120 ℃ for 7min. At last, the sample was moved to a drying dish for 24 hours. The test results are shown in Figure 3.

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(b) Rubber asphalt with UV aging of 60h

(c) Rubber asphalt with UV aging of 200h (d) Rubber asphalt with UV aging of 400h

(e) Rubber asphalt with UV aging of 1050h (f) Rubber asphalt with UV aging of 1700h Figure.3 AFM of Rubber Asphalt with UV Aging of Different Time

AFM diagram of rubber asphalt with different UV aging time clearly showed that the micro surface morphology of rubber asphalt is significantly affected by the UV aging time. With the increase of UV aging and radiation, the number of peak structure clusters on the surface of rubber asphalt decreases continuously. Among them, in the early stage of UV aging (the first 60h), the number of peak structure clusters decreases the most, and UV has the most significant effect on the micro morphology of rubber asphalt; When the UV aging time is between 60h ~ 410h and its radiation is between 5.69 to 30.10 kJ/cm2, it has little effect on the micro morphology of rubber asphalt, and the number and color of peak structure clusters do not change significantly. With the further prolong of UV aging time, the peak structure cluster in the micro morphology of rubber asphalt gradually widens, the fluctuation degree becomes weaker, the area of flat area further increases, and the color of the area outside the structure cluster also changes significantly. When the UV aging time reaches 1700 hours, a large number of valley areas appear in the AFM microstructure of rubber asphalt, which shows that micro cracks are forming. The low-temperature crack resistance and fatigue failure resistance of rubber asphalt are gradually reduced.

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Conclusion In this paper, the rheological properties and microstructure of rubber asphalt of different UV aging time are studied, and the following main conclusions are obtained: (1) With the prolonging of UV aging and the increase of UV radiation, the complex shear modulus of rubber asphalt showed an exponential growth trend. When the UV irradiation time was less than 400h, the complex shear modulus of rubber asphalt increases rapidly; As the UV aging was more than 400h, the growth rate of complex shear modulus slowed down. (2) Phase angle of rubber asphalt decreased linearly with the extension of UV aging time, and its performance of deformation recovery increased. Under the ultraviolet radiation, natural rubber and synthetic rubber produce free radicals to react with oxygen to absorb oxygen. The content of gel in rubber powder decreases, which further degrades the rubber powder. The oxidative condensation reaction of asphalt and the degradation of rubber powder cause the changes of complex shear modulus and phase angle during UV aging. (3) The micro surface morphology of rubber asphalt is significantly affected by UV aging. With the prolonging of UV aging and UV radiation, the number of peak structural clusters on the surface of rubber asphalt decreases. In the early stage of UV aging, UV radiation has the most significant effect on the micro morphology of rubber asphalt; When the UV radiation time is between 60h ~ 410h, UV aging has little effect on the micro morphology of rubber asphalt; With the further extension of UV aging, the peak structure cluster in the micro morphology of rubber asphalt gradually widens, the fluctuation becomes weaker, the area of flat area further increases, the color of the area outside the structure cluster also changes significantly, and micro cracks are formed. References [1]

Garrett J L, Leite M S, Munday J N. Multiscale Functional Imaging of Interfaces through Atomic Force Microscopy Using Harmonic Mixing. ACS Applied Materials&Interfaces, 10(34):50-59, 2018. https://doi.org/10.1021/acsami.8b08097

[2]

Koumoulos E P, Tofail S A M, Silien C, et al. Metrology and nano-mechanical tests for nano-manufacturing and nano-bio interface: Challenges & future perspectives. Materials & Design, 137:446-462, 2018. https://doi.org/10.1016/j.matdes.2017.10.035

[3]

Zeng W., Wu S. ,Pang Li., Chen H, Hu J., Sun Y., Chen Z. Research on Ultra Violet (UV) aging depth of asphalts. Construction and Building Materials, 160(Jan.30):620-627, 2018. https://doi.org/10.1016/j.conbuildmat.2017.11.047

[4]

WANG Q. Evolution of the Structure and Properties of Crumb Rubber Modified Asphalt in Aging Process. Shanghai Institute of Technology, 2016.

[5]

WANG Q, YUAN Y, OUYANG C F, et al. Research on Aging of Waste Rubber Modified Asphalt. Polymer Bulletin, (06):19-28, 2015. https://doi.org/10.14028/j.cnki. 1003-3726.2015.06.003

[6]

Xiao P, Wu M F, Jiang D A. Study on Properties of Ultraviolet Aged Rubber Asphalt. Journal of Nanjing University of Aeronautics & Astronautics, 45(01):152-156, 2013. https://doi.org/10.16356/j.1005-2615.2013.01.025

[7]

Liu HB, Zhang ZQ, Xie J.Q., Gui ZJ, Li NQ, Xu YF, Analysis of OMMT strengthened UV aging-resistance of Sasobit/SBS modified asphalt: Its preparation, characterization and mechanism. Journal of Cleaner Production, 315(Sep.15):128-139, 2021. https://doi.org/10.1016/j.jclepro.2021.128139

[8]

Mull M A. Stuart K. Yehia A. Fracture Resistance Characterization of Chemically Modified Crumb Rubber Asphalt Pavement. Journal of materials Science, 37(3):557-566, 2002. https://doi.org/10.1023/A:1013721708572

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[9]

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Guo S, Zhang Y, Tang H. Investigation of relationship between accelerated ultraviolet radiation aging in laboratory and weathering aging for asphalt binder. International Journal of Pavement Research and Technology, 14, 466–472, 2020. https://doi.org/10.1007/s42947-020-0158-1

[10] XAIO M, FAN L. Ultraviolet aging mechanism of asphalt molecular based on microscopic simulation. Construction and Building Materials, 319(FEB.14):126-157, 2022. https://doi.org/10.1016/j.conbuildmat.2021.126157 [11] XU L, LI Z G, ZHANG Q CH, et al. On the Effect of the UV-Aging on the Performance of the CTOR Rubber Asphalt. Traffic Engineering and Technology for National Defence, 15(05):4-8, 2017. https://doi.org/10.13219/j.gjgyat.2017.05.002 [12] Li J, Chen Z, Xiao F, et al. Surface activation of scrap tire crumb rubber to improve compatibility of rubberized asphalt. Resources Conservation and Recycling, 169:105518, 2021. https://doi.org/10.1016/j.resconrec.2021.105518 [13] SONG C Z, MA Q., YANG C., et al. Research on Technical Properties of High Viscosity Rubberized Asphalt Modified with Compound. Road Machinery & Construction Mechanization,37(Z1):17-22+27, 2020. https://doi.org/10.1016/j.sna.2007.01.007

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 187-192 doi:10.4028/p-01g746 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-07-05 Accepted: 2022-11-15 Online: 2022-12-26

Experimental Study on Durable Asphalt Mixture for Bridge Deck Pavement Chunyu Zhang1,a* Yunnan Science & Technology Research Institute of Highway,Kunming, China

1

[email protected]

a

Keywords: Bridge deck pavement, Modified asphalt mixture, Performance evaluation

Abstract. The main disease manifestations of bridge deck pavement are fatigue cracks and rutting deformation. This paper compares and analyzes the performance of traditional asphalt mixture, styrene butadiene styrene (SBS) modified asphalt mixture, epoxy resin (EP) modified asphalt mixture and high durability asphalt mixture (HDAM) applied to bridge deck pavement through laboratory tests. The results show that the fatigue life of EP modified asphalt mixture and HDAM is about 2.3 times and 3.4 times that of matrix asphalt mixture. EP modified asphalt mixture has better high temperature stability, and HDAM has higher low temperature resistance and water damage resistance. It can be used for reference in different service areas. Introduction At present, the bridge deck pavement material is mainly asphalt concrete, which plays a role in waterproof the bridge deck, improving the skid resistance, and improving the driving comfort [1]. Under the repeated load of vehicles, although this pavement structure can ensure the overall strength, the asphalt pavement has ruts, cracks, pits and other diseases due to its viscoplastic flow and heat absorption characteristics. These damages not only reduce the service life of the bridge, but also greatly increase the maintenance cost. Among these failure modes, fatigue cracking is the main reason affecting the durability of bridge deck structure. Fatigue cracking leads to water seepage of asphalt pavement, which reduces the strength of asphalt mixture and the bonding force between asphalt pavement and bridge deck [2]. A lot of research work has been carried out on the fatigue cracking resistance of bridge deck pavement materials, in which the introduction of modified high-performance asphalt mixture is an effective method. At present, high-dose styrene butadiene styrene (SBS) modified stone mastic asphalt (SMA) has been widely used in long-span steel deck pavement [3-6]. For instance, Xu Jiahuan [7] measured the road performance of EP modified asphalt mixture and SBS modified asphalt mixture, obtained the conclusion that the road performance of EP modified asphalt mixture is significantly better than that of SBS modified asphalt mixture, and proposed a curing agent that can effectively enhance the viscosity and stability of EP asphalt internal structural materials. Liu Haicheng et al. [8] Tested the performance of EP modified asphalt mixture and determined the structural scheme of epoxy asphalt pavement and the gradation of mixture through finite element numerical simulation analysis. They also determined the removal construction procedure and technology of old epoxy asphalt pavement. Zhang h. et al. [9] Investigated and tested the service performance of epoxy asphalt binder pavement on cable-stayed bridges, analyzed the causes of damage in heavy haul lanes, and gave the most severely damaged areas. Although high-quality paving materials are used, the damage of many steel bridge decks has not been effectively improved. This paper mainly studies three types of modified asphalt: SBS modified asphalt in thermoplastic rubber modified asphalt, epoxy resin (EP) in thermosetting resin modified asphalt and high durability asphalt binder (HDAB) mixed with hydrocarbons on the basis of SBS modified asphalt. High performance modified asphalt mixtures are prepared respectively. Experimental studies are carried out on these materials to evaluate their characteristics; it is used to select appropriate materials in the project to improve the fatigue crack resistance and water damage resistance of bridge deck pavement materials.

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Preparation of High Durability Asphalt Binder High durability asphalt binder (HDAB) is obtained by adding a certain amount of hydrocarbon into SBS modified asphalt at high temperature, which can better resist permanent deformation and fatigue cracking. The base asphalt extracted from crude oil contains aromatics and asphaltene. Adding SBS modifier can significantly improve the viscosity of asphalt binder. Adding hydrocarbons can increase the coordination between elastic substances in binder and SBS modifier, and improve the fatigue cracking resistance of asphalt binder by enhancing the connection between base asphalt and SBS modifier. Due to the temperature sensitivity of hydrocarbons, the poor workability caused by the increased proportion of SBS modifier can be alleviated. The manufacturing process of high durability asphalt binder is shown in Fig. 1.

Fig.1. HDAB manufacturing process

Raw Material and Aggregate Gradation The base asphalt used in the experiment is 70# road petroleum asphalt. SBS modifier with mass fraction of 4%, EP modifier with mass fraction of 3%, SBS modifier with mass fraction of 4% and HDAB modifier with mass fraction of 2% are added to the base asphalt respectively. SBS modified asphalt, EP modified asphalt and HDAB modified asphalt used in the experiment are prepared by asphalt high-speed shear mechanism. Three major index tests of four asphalt products, G*/sinδtest at 70 ℃ and G*/sinδtest after pressure aging test were carried out through indoor experiments. The test results of technical indexes of asphalt are shown in Table 1. Table 1. Technical indexes of base asphalt and modified asphalt Property Type

Base asphalt

SBS modified asphalt

EP modified asphalt

HDAB modified asphalt

Softening point (℃)

47.1

75.6

70.1

67.3

25℃ Thixotropic Index (0.1mm)

83

58

42.9

64.6

5℃ Ductility (m) Viscosity (135℃) (Pa·s) G*/sinδ(70℃) (kPa) Minimum, 1.0 kPa After PAV, G*sinδ (22℃) (kPa) Minimum, 5000 kPa

9.1 0.453

57.1 1.721

8.1 0.947

76.9 1.538

0.67

2.34

2.17

1.96

2326

2408

1326

201

The results in Table 1 show that the softening point of SBS modified asphalt, EP modified asphalt and HDAB modified asphalt are higher than that of the base asphalt, the penetration is lower than that of the base asphalt, the kinematic viscosity is more than twice that of the base asphalt, the G*/sinδ value is more than three times that of the base asphalt, indicating that the viscosity and high temperature stability of the modified asphalt have been significantly improved; The low temperature ductility of SBS modified asphalt and HDAB modified asphalt increased significantly, indicating that their low temperature crack resistance was improved; The DSR test results after the pressurized

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aging vessel (PAV) show that The G*/sinδ value of HDAB modified asphalt decreased significantly, indicating that its fatigue resistance was significantly higher than that of other asphalt products. The maximum particle size of the asphalt mixture aggregate for the test is 13 mm. The aggregate grading range is shown in Table 2. The four asphalt mixtures are AC-13, SBS modified asphalt AC-13, EP modified asphalt AC-13 and HDAM-13 respectively. The optimum asphalt content of the four mixtures is determined by Marshall design method: when the porosity is 4%, the matrix asphalt mixture is 5.1%; 4.8% for SBS modified asphalt mixture; 5.0% for EP modified asphalt AC-13 and 5.5% for HDAM. Aperture size Pass rate

26.5 100

19 95

16 74

Table 2. Aggregate grading 13.2 9.5 4.75 2.36 63 47 26 13

1.18 9

0.6 6

0.3 5

0.15 4

0.075 2

Asphalt Mixture Performance Test Fatigue Test. Generally, the repeated stress value of asphalt mixture with fatigue failure is called fatigue strength, and the corresponding number of stress repeated actions is called fatigue life. The anti-fatigue performance of asphalt mixture refers to the ability of asphalt mixture to resist fatigue failure under repeated load. Under the same repeated load, the asphalt mixture with small reduction of fatigue strength or small change rate of fatigue strength has good fatigue resistance. The test method used in this paper is the quarter point bending fatigue test of small laboratory specimens. Mts-100 servo hydraulic closed-loop tester is used for fatigue test. The size of the test specimen is 350mm×50mm×60mm, the test temperature is controlled around 20℃, and the test strain level is maintained at 1000×10-6. The test results are shown in Table 3. Asphalt mixture type Fatigue life (Times)

AC-13 22537

Table 3. Fatigue test results SBS modified asphalt AC-13 EP modified asphalt AC-13 26468 52364

HDAM-13 77324

According to the test results, when the test temperature, applied stress, loading rate, specimen size and other influencing factors are certain, the fatigue life of modified asphalt mixture is significantly longer than that of traditional asphalt, and the fatigue life of EP modified asphalt mixture is about 2.3 times that of matrix asphalt mixture, and that of HDAM asphalt mixture is about 3.4 times that of matrix asphalt mixture. It shows that EP modified asphalt and HDA modified asphalt can be used for bridge deck pavement in heavy traffic load sections, and their good fatigue resistance can prolong the service life of bridge deck pavement structure. Rutting Test. At present, the standard method is adopted for rutting test in China, and the size of the asphalt mixture plate specimen is 300mm×300mm×50mm, under the temperature of 60 ℃, the test wheel with wheel pressure of 0.7MPa walks repeatedly along the same track on the surface of the test piece at the frequency of 42 times /min, tests the rut depth formed on the surface of the test piece under the repeated action of the test wheel, and evaluates the rutting resistance of the asphalt mixture through the rutting test results. The rutting test is usually carried out for 60min or until the maximum deformation reaches 25mm, and then the dynamic stability DS is calculated according to the 45min load action and the 60min permanent deformation, as shown in formula 1. In order to avoid the test error caused by the randomness of the test, three groups of experiments were carried out on four types of asphalt mixtures. Finally, the average value of the three groups of experiments was taken as the dynamic stability of different types of asphalt mixtures. The test results are shown in Fig. 2. 42 ×15 . d 60 − d 45 In Eq. (1): DS - dynamic stability (time/mm), d60 - the deformation of the test piece when the test time is 60min (mm) d45 - the deformation of the test piece when the test time is 45min (mm) DS =

(1)

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35000

32631

Dynamic stability(time/mm)

30000 25000 20000 15000 10000 5730

5000

4150

2404

0

AC-13

SBS AC-13

EP AC-13

Fig. 2. Rutting test results

HDAM-13

According to the rutting test results, the dynamic stability of the three modified asphalt mixtures is greater than 2800 times/mm, which meets the requirements specified in the Technical Specifications for Construction of Highway Asphalt Pavements (JTGF40-2019). Therefore, the three modified asphalt mixtures have good high temperature stability. Compared with the three modified asphalt mixtures, the average dynamic stability of EP AC-13 reached 32631 times/mm, far exceeding the average dynamic stability of SBS modified asphalt 5730 times/mm and HDAM 4150 times /mm. It can be seen that if only the rutting resistance of asphalt concrete is considered, EP modified asphalt has greater advantages than SBS modified asphalt and HDAB modified asphalt. Low Temperature Bending Test. Low temperature bending test is one of the common methods to evaluate the low temperature deformation capacity of asphalt mixture. China's Specifications for Design of Highway Asphalt Pavement (JTGD50-2017) stipulates that the failure strain of low-temperature bending test is used as the low-temperature crack resistance performance index of modified asphalt mixture. The greater the flexural strain of asphalt mixture at low temperature, the better the flexibility and crack resistance at low temperature. Specimen size is 300mm×300mm×50mm. Firstly; the test piece shall be stored in a -10 ℃ temperature box for more than 6h. After taking it out, the concentrated load at the midspan shall be applied at the loading rate of 50mm/min until it is damaged. The results are shown in Fig. 3. 6000

5000

4143

4000

4000

Stiffness modulus(MPa)

Failure strain(με)

5000 3686 3021

3000 2394 2000 1000 0

4598

5142

AC-13

SBS AC-13

EP AC-13

HDAM-13

3301 3000

2567

2000 1000 0

AC-13

SBS AC-13

EP AC-13

(a) Failure strain. (b) Flexural tensile strength Fig. 3. Low temperature bending test results

HDAM-13

The test results show that the low-temperature stability of the three modified asphalt mixtures meet the specification requirements, and the failure strain of the three modified asphalt mixtures increases significantly, indicating that their low-temperature ductility is improved; In addition, the low-temperature bending tensile strength of SBS modified asphalt mixture is about 1.5 times that of traditional asphalt, the low-temperature bending tensile strength of EP modified asphalt mixture is

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about 2 times that of traditional asphalt, and the low-temperature bending tensile strength of HDAM is about 2.5 times that of traditional asphalt. Although the low-temperature stability of the three modified asphalt is better than that of the traditional asphalt, the low-temperature stability of HDAM asphalt mixture has more advantages. Water Stability Test. Water stability evaluates the ability of asphalt mixture to resist the damage caused by water erosion, such as peeling, loosening and potholes of asphalt membrane. If the water stability of asphalt mixture is poor, when there is ponding on the pavement and the vehicle load acts at the same time, the spalling of asphalt and mineral aggregate will intensify, forming loose thin blocks, the pavement is missing, and gradually forming potholes. In this study, the water stability of asphalt mixture is evaluated by the splitting strength ratio obtained from freeze-thaw splitting test. According to the method in the Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering (JTG E20-2011), in the freeze-thaw splitting test, the four asphalt mixture specimens are divided into two groups: one group of specimens is used to measure the splitting strength under normal conditions (without freeze-thaw); The other group was first saturated with vacuum water, then frozen at -18℃ for 16h, then immersed in 60℃ water for 24h, and finally measured the splitting strength.The freeze-thaw splitting strength ratio was calculated according to formula 2 and the test results are shown in Table 4. R TSR = 2 ×100 R1 . (2) In Eq. (2): TSR - the freeze-thaw splitting strength ratio (%), R2 - the splitting strength of the specimen after freeze-thaw cycle (MPa), R1 - the splitting strength of the specimen without freeze-thaw cycle (MPa).

Table 4 .Water stability test results of asphalt mixture Freeze thaw splitting Normal splitting TSR (%) strength (MPa) strength (MPa) AC-13 0.61 0.92 66.30 SBS modified asphalt AC-13 0.92 1.14 80.70 EP modified asphalt AC-13 1.26 1.37 91.97 HDAM-13 0.87 0.89 97.75 Asphalt mixture type

Reduction ratio of splitting strength (%) 33.70 19.30 8.03 2.25

The test results show that the matrix asphalt mixture has the lowest freeze-thaw splitting strength ratio and the worst water stability; Compared with traditional asphalt, the freeze-thaw splitting strength ratio of the three modified asphalt mixtures increased by 14.4%, 25.67% and 31.45% respectively. At the same time, the cleavage strength of HDAM modified asphalt mixture decreased by only 2.25% before and after freeze-thaw, reflecting excellent water stability. Conclusion Based on the diseases caused by the use of traditional asphalt mixture for bridge deck pavement, this paper developed a high durability asphalt mixture HDAM, and compared and analyzed the performance of SBS modified asphalt mixture and epoxy asphalt mixture commonly used in engineering, hoping to avoid or slow down the occurrence of diseases by improving the performance of the materials used for bridge deck pavement. The research conclusions are as follows: (1) After adding modifier, the viscosity and high-temperature stability of SBS modified asphalt, EP modified asphalt and HDAB modified asphalt have been significantly improved, the low-temperature crack resistance of SBS modified asphalt and HDAB modified asphalt has been improved, and the fatigue resistance of HDAB modified asphalt is significantly higher than that of other asphalt products. (2) The high temperature stability, low temperature crack resistance and water stability of the three modified asphalt mixtures are better than those of the traditional asphalt mixtures, and the fatigue life has also been significantly extended. Compared with the road performance of the three modified

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asphalt mixtures, EP modified asphalt mixture has better rutting resistance and high temperature stability; HDAB modified asphalt mixture has more advantages in low temperature crack resistance, water stability and fatigue life. Therefore, during bridge deck pavement, EP modified asphalt mixture is recommended for high-temperature areas, and HDAB modified asphalt mixture is recommended for heavy rainfall or low-temperature areas. Acknowledgments

This work is appreciating the financial support from the scientific and technological innovation and demonstration project of Department of transport of Yunnan Province "Research on complete set of technology for vertical crack treatment of prefabricated prestressed concrete T-beam". References [1] Jia, X., Huang, B., Chen, S. et al. Comparative investigation into field performance of steel bridge deck asphalt overlay systems. KSCE J Civ Eng 20, 2755–2764, 2016. https://doi.org/10.1007/s12205-016-0259-1 [2] Jia X., B. Huang, B. F. Bowers, and T. E. Rutherford. An investigation into a tack coat failure case in orthotropic steel bridge deck overlay-survey, and evaluation. Transportation Research Record: Journal of the Transportation Research Board, 2444(1), 28-37, 2014. https://doi.org/10.3141/2444-04 [3] Geng, L., Q. Xu, R. Ren, et al. Performance research of high- viscosity asphalt mixture as deck-paving materials for steel bridges. Road Materials and Pavement Design, 18, 208-220, 2016. https://doi.org/10.1080/14680629.2016.1163279 [4] Luo, Y., K. Zhang, P. Li, et al. Performance evaluation of stone mastic asphalt mixture with different high viscosity modified asphalt based on laboratory tests. Construction and Building Materials, 225, 214-222, 2019. https://doi.org/10.1016/j.conbuildmat.2019.07.119 [5] Zhang, D., F. Ye, J. Yuan. Analysis on Steel Bridge Pavement Structure Performance. Procedia-Social and Behavioral Sciences, 96, 2462-2465, 2013. https://doi.org/10.1016/j.sbspro. 2013.08.275 [6] Ren, R., L. Geng, L. Wang, et al. Design and performance evaluation of a SMA-5 high viscosity asphalt mixture. Building Mater, 19 (4) (2016), p.762-766. DOI:10.3969/j.issn.1007-9629. 2016.04.027 [7] Xu, J. Experimental study on pavement performance of epoxy asphalt mixture for bridge deck pavement. Highway and automobile transportation, (03), 123-126, 2021. [8] Liu, H., Q. Tang, Y. Chen, et al. Research on overall overhaul scheme design and project implementation of epoxy asphalt steel deck pavement. Highway, (03), 159-162, 2020. [9] H.Zhang, Q.Mao, Z. Zhu, Z.et al. Experimental study on service performance of epoxy asphalt steel deck pavement of cable stayed bridge. Case Stud. Constr. Mater., 13, 2020. e00392. https://doi.org/10.1016/j.cscm.2020.e00392

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 193-198 doi:10.4028/p-hwk266 © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-08-07 Accepted: 2022-11-15 Online: 2022-12-26

Experimental Study on Improving Frost Resistance of CA Mortar Likun Wang1,a*, Lihua Zhao2,b, Jisong Zhang3,c School of Civil Engineering, Dalian Jiaotong University, Dalian, 116028,China

1,2,3

[email protected], [email protected], [email protected]

a

Keywords: Cement asphalt mortar; Orthogonal experimental design; Air-entraining agent; Mechanical properties; Frost resistance.

Abstract. Cement asphalt mortar (CA mortar) is one of the key materials of slab ballastless track structure, and its performance directly affects the overall quality of ballastless track. The design of CA mortar mix proportion is studied by orthogonal exerimental method, and the reasonable dosage of cement, emulsified asphalt, sand and other materials is determined. The change of gas content of CA mortar is analyzed by adding air entraining agent and adjusting stirring process. The working properties, mechanical properties and freezing resistance of CA mortar are tested. The results show that the reasonable dosage of cement, emulsified asphalt and sand in CA mortar are 280~325kg/m3, 420~555kg/m3 and 360~690kg/m3, respectively. The dosage of cement has the most obvious influence on the 28d compressive strength of CA mortar, followed by emulsified asphalt. With the increase of air entraining agent content, stirring speed and stirring time, the air content in mortar will increase. Through the test of mortar's working performance, mechanical properties and frost resistance, it is shown that the appropriate amount of air entraining agent and mixing process can improve the frost resistance of CA mortar. Introduction Cement asphalt mortar (CA mortar) is one of the key materials of CRTS Ⅰ slab ballastless track [1, 2]. CA mortar is a new type of organic-inorganic composite material, which is composed of cement, emulsified asphalt, fine aggregate (sand) and various additives. It is formed by the joint action of cement hydration and hardening and asphalt breaking latex knot. It is located between the track plate and base plate, and plays the roles of adjustment, load transmission, support, vibration isolation and vibration reduction [3, 4]. Therefore, the performance of mortar directly affects the serviceability and durability of slab ballastless track [5]. For CA mortar serving in severe cold areas, good frost resistance is one of the key engineering problems that need to be solved urgently. According to the basic mix proportion of CA mortar applied in CRTS Ⅰ slab ballastless track of a high-speed railway, the appropriate amount of raw materials is determined by orthogonal experiment. The influence of air entraining agent content on the mechanical strength and air content of CA mortar is studied, and the mixing process is tested and analyzed, and the working performance, mechanical property test to test the performance of mortar. Furthermore, the freeze-thaw cycle test of CA mortar is carried out to analyze the frost resistance of the mortar specimens prepared in this test. Experiments Experimental Materials and Dosage. The test materials mainly include cationic emulsified asphalt, P.O 42.5R Portland cement, Natural River sand, polymer emulsion, defoamer, expansion agent, aluminum powder, air entraining agent, etc. The raw materials all meet the technical requirements. Among them, cement, sand, aluminum powder and expansion agent are mixed into dry powder materials, hereinafter collectively referred to as dry materials. CA mortar of CRTS Ⅰ slab ballastless track of a high-speed railway is taken as the basic mixing proportion, and the dosage of three basic raw materials (cement, emulsified asphalt and sand）is studied by orthogonal exerimental design. The orthogonal exeriment is L9 (33) test with three factors (cement, emulsified asphalt and sand)

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and three levels [6], and the test factor levels are shown in Table 1. The 28d compressive strength of CA mortar is taken as the performance test index, and the orthogonal exerimental results are shown in Table 2. Factor Level

1 2 3

Table 1. Level of orthogonal test factors [kg/m3] Cement (A) Emulsified asphalt (B) 280 440 310 470 340 500

Sand (C) 580 610 640

Table 2. Orthogonal test results and extreme difference analysis NO. A B C 28d Compressive strength[MPa] 1 1 1 1 1.77 2 1 2 2 1.67 3 1 3 3 1.58 4 2 1 2 2.45 5 2 2 3 2.26 6 3 3 1 2.08 7 3 1 3 3.09 8 3 2 1 2.83 9 3 3 2 2.60 K1 5.01 7.29 6.66 K2 6.78 6.75 6.72 28d Compressive strength[MPa] K3 8.52 6.27 6.93 Range(R) 3.51 1.02 0.27

As can be seen from the extreme values in Table 2, the influences of the dosage of cement, emulsified asphalt and sand on the compressive strength of CA mortar is gradually weaken. Reasonable compressive strength is very important for the stability of slab track structure. The research shows that the reasonable range of 28d compressive strength of CA mortar is 1.8~2.5 MPa. According to the trend line of the dosage of each raw material and the compressive strength of mortar, the dosage range of the three raw materials to meet the requirements of 28d compressive strength is determined, as shown in Fig. 1. 28d compressive strength[MPa]

3.0

The dosage of cement The dosage of emulsified asphalt The dosage of sand

2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 250

300

350

400

450

500

550

600

650

700

Dosage[kg/m3]

Fig. 1 Trend line of the relationship between the amount of each material and the average strength

It can be seen from Fig. 1 that the dosage of cement and emulsified asphalt has a significant influence on the compressive strength of CA mortar. The 28d compressive strength of CA mortar increases linearly with the increase of cement dosage and the growth rate is fast, while the strength of mortar decreases with the increase of emulsified asphalt dosage. The increasing amount of sand also makes the strength of mortar increase, but the strength increase is not obvious. It can be concluded that the reasonable dosage of cement, emulsified asphalt and sand are 280~325kg/m3, 420~555kg/m3 and 360~690kg/m3. Therefore, in practical engineering, the dosage of cement,

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emulsified asphalt and sand can be adjusted according to the above dosage range, and the CA mortar meeting the requirements can be obtained. Influence of Air Entraining Agent Dosage. Uniform and small bubbles can increase the fluidity and frost resistance of cement-based materials in the fresh state. The effective method to introduce bubbles is to add appropriate air entraining agent. In this experiment, six kinds of air-entraining agents (0.4‰, 0.6‰, 0.8‰, 1.0‰, 1.2‰ and 1.4‰) are selected to analyze the influence of the mixing amount of air entraining agent on the 7d and 28d compressive strength of CA mortar. Meanwhile, the air content of freshly mixed CA mortar is measured to determine the reasonable mixing amount of air entraining agent. The test results are shown in Table 3. Table 3. Properties of CA mortar with different air entraining agent content NO. 1 2 3 4 Air entraining agent dosage[‰] 0.4 0.6 0.8 1.0 Fresh CA mortar air content[%] 6.7 8.3 8.9 10.2 Compressive strength[MPa] 7d 1.42 1.16 1.03 0.99 28d 2.54 2.33 2.21 2.10

5 1.2 11.7 0.85 1.95

6 1.4 13.5 0.78 1.84

It can be seen from Table 3 that the 7d and 28d compressive strength of CA mortar decreases with the increase of the amount of air entraining agent, and the amount of air entraining agent has an obvious influence on the compressive strength of mortar. The air content of fresh CA mortar should be 8%~12%. When the amount of air entraining agent is 0.6‰~1.2‰, the 28d compressive strength of CA mortar is between 1.8~ 2.5MPa, which meets the requirements of the index. The dosage of air entraining agent in this test is 0.98‰. According to the performance index of CA mortar, the type, specification and dosage of raw materials are adjusted, and the best mixture proportion of CA mortar is finally determined, as shown in Table 4.The coordination of dry powder is shown in Table 5. Table 4. Cement emulsified Asphalt mortar proportioning Material

Emulsified asphalt

Polymer emulsion

Defoaming agent

Water

Dry powder material

Air-entraining agent

The proportion 1m3 mortar dosage[kg]

1.25 457.4

0.15 54.9

0.0004 0.146

0.16 58.4

2.5 914.8

0.004 1.46

Material The proportion

Table 5. Ratio of dry powder material (weight ratio) Expansive agent Cement Sand 0.02 0.98 2

Aluminum powder 0.00007~0.00012

Adjustment of Stirring Process. In practical engineering, mixing speed and mixing time have different degrees of influence on the working and mechanical properties of CA mortar. In this study, the mixing time of mortar is set as 5min, and the gas content in freshly mixed CA mortar is taken as an indicator to analyze the influence of different mixing speeds on the gas content of mortar. The results are shown in Fig. 2. In order to studying the influence of different mixing time on the air content of fresh CA mortar, this study selects 120r/min as the mixing speed on the basis of the above research, and adjusts the mixing time between 1~8min. The curve of air content with mixing time is shown in Fig. 3. It can be seen from Fig. 2 that the air content of the mortar is significantly affected by the mixing speed. When the mixing time is the same, the increase of the mixing speed makes the air content of the mortar increase accordingly. Therefore, according to the requirements of the gas content index of mortar, the reasonable mixing speed of mortar can be obtained between 100~140r/min. According to Fig. 3, the air content of freshly mixed CA mortar increases with the extension of mixing time, and the reasonable mixing time of mortar can be obtained from 3~ 6min according to the requirements of the air content index of mortar.In the subsequent performance analysis, the mixing speed of mortar is set as 120r /min, and the mixing time is set as 5min.

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The mixing time 5min

18

Stirring velocity 120r/min

16

16

14

Air content[%]

Air content[%]

14 12 10 8

12

10

8

6

6

4 2 20

40

60

80

100

120

140

160

180

Stirring velocity[r/min]

200

4

220

Fig.2 The curve of gas content changing with stirring velocity

0

1

2

3

4

5

6

7

8

9

The mixing time[min]

Fig. 3 Variation curve of gas content with stirring time

Performance Test of CA Mortar The working performance of CA mortar is usually characterized by fluidity, working time, material separation and expansion rate. The fluidity of CA mortar means that freshly mixed CA mortar sample is evenly injected into a J-shaped funnel wetted with water (upper caliber 70mm, lower caliber 10mm, height 450mm), and the time that the mortar flows out of the funnel is measured with a stopwatch. The working time refers to the time (min) experienced by the mortar in the specified range of fluidity. The separation degree of materials can reflect the mean level of CA mortar, and the determination method is to inject the freshly mixed CA mortar into a ϕ 50mm × 50mm cylinder mold. After the mortar is hardened, the upper and lower parts of the mortar hardened body are equally divided, and their respective weights are weighed. The calculation formula is as follows: Degree of material separation =

Lower mass − Upper mass × 0.5 × 100% Lower and upper average mass

(1)

The measurement method of CA mortar expansion rate is: slowly inject the CA mortar into a measuring cylinder with a measuring range of 250mL, place a flat glass plate at the mouth of the measuring cylinder, measure the depth H0 of the CA mortar surface from the glass plate with a caliper, and let it stand for 24 hours after the measurement, then measure the depth H24 of the mortar surface from the glass plate with a caliper again. The expansion rate is calculated as follows: Expansion rate(%) = 0.000314 × (H0 − H24 ) × D2

(2)

Where:D--Inner diameter of measuring cylinder, mm;𝐻𝐻0 --Initial depth, mm;𝐻𝐻24 --24h depth, mm. The working performance test results of CA mortar are shown in Table 6. The mechanical properties of CA mortar mainly include the compressive strength of 1d, 7d and 28d, and the elastic modulus of 28d. See Table 6 for the test results. Table 6. CA Mortar performance test values Item Unit Index Fluidity s 18~26 Available working time min ≥30 Degree of material separation % 0.10 The compressive 7d MPa >0.70 strength 28d >1.80 Modulus of elasticity (28d) MPa 100~300

Results 25 900 0.8 1.7 10.8 0.38 1.20 2.15 167

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The results show that the mixing ratio, mixing process and the amount of air entraining agent determined make the properties of CA mortar meet the requirements of the specification. Frost Resistance Test of CA Mortar Soak the cured mortar specimen in water, and the water surface is 20mm higher than the top surface of the specimen, and the water temperature is kept at 20 ± 2 °C. After 4 days, the soaked mortar specimen is weighed, and the initial mass is recorded as G0, and the initial value of transverse fundamental frequency of the specimen f0 is measured by the dynamic modulus tester. The freeze-thaw cycle testing machine is used to test the freeze-thaw resistance of the mortar specimens, and 25 times are taken as a freeze-thaw cycle. After each freeze-thaw cycle, the specimens are weighed, and the mass after the freeze-thaw cycle is recorded as Gn. After the measurement, the specimen is immediately put back and the next freeze-thaw cycle test is carried out. Sufficient water should be ensured during each freeze-thaw cycle. The relative dynamic modulus of CA mortar specimen is calculated by the following formula (3), and the mass loss of CA mortar specimens after freezing and thawing is calculated by the following formula (4). 𝑓𝑓n2 P = 2 × 100% . 𝑓𝑓0

(3)

Where: P--Relative dynamic modulus of the specimen after n freeze-thaw cycles; 𝑓𝑓0 --Initial value of transverse fundamental frequency of specimen before freeze-thaw cycle test; 𝑓𝑓𝑛𝑛 --Value of transverse fundamental frequency of specimen after n freeze-thaw cycles. ∆Wn =

G0 − Gn × 100% G0

(4)

Where:∆Wn --Mass loss rate of specimen after n freeze-thaw cycles; G0 -- time quality before freeze-thaw cycle test; Gn -- Quality of specimen after N freeze-thaw cycles. In this test, 25 freeze-thaw cycles are taken as a group, and 200 freeze-thaw cycles are carried out on the specimens, and the changes of transverse fundamental frequency, relative dynamic modulus and quality loss rate are analyzed [7]. The test results are shown in Fig. 4, Fig.5, Fig.6. As can be seen from Fig. 4, Fig. 5 and Fig. 6. 140

2100 2000 1900 1800 1700

8

130

The quality loss[%]

2200

Relative dynamic modulus

Transverse fundamental frequency[Hz]

10

150

2300

120 110 100

50

100

150

Freezing and thawing times

200

Fig.4 Horizontal fundamental frequency and freeze-thaw cycles

80

4

2

0

90

0

6

25

50

75

100

125

150

175

Freezing and thawing times

200

225

Fig.5 Relative elastic modulus and freeze-thaw cycles

-2

0

50

100

150

200

250

300

350

400

450

500

Freezing and thawing times

Fig.6 The quality loss rate and freeze-thaw cycles

After the freeze-thaw cycle, the transverse fundamental frequency of CA mortar increases first and then decreases with the increase of freeze-thaw times. When the number of freeze-thaw cycles reaches 100 times, the value of the transverse fundamental frequency of mortar reaches the maximum, and then the number of freeze-thaw increases, and the transverse fundamental frequency of mortar presents a trend of rapid decline. Before 100 freeze-thaw cycles, the relative dynamic modulus of CA mortar increases with the increase of the number of freeze-thaw cycles. The main reason is that the freezing fills the gaps in the internal structure of the mortar, which leads to the increase of mortar strength. However, with

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the continuation of freeze-thaw cycle, the mortar structure is obviously damaged by freeze-thaw cycle, and the relative dynamic modulus of CA mortar decreases rapidly. When the number of freeze-thaw cycles is less than 200 times, due to the freeze-thaw cycle, some closed voids in the mortar are converted into open voids, which makes the quality of CA mortar slightly increased, and the CA mortar test block does not produce local damage. After 300 freeze-thaw cycles, a small amount of mortar spalling on the surface of CA mortar, the relative dynamic modulus decreases to 76.81%, and the quality loss rate is 3.45%. After 500 freeze-thaw cycles, the surface spalling of CA mortar is serious, and the quality loss rate reaches 9.89%. Through the frost resistance test of CA mortar, it can be seen that after 500 freeze-thaw cycles of CA mortar, the surface spalling phenomenon is more serious, and the mass loss is great. However, after 300 freeze-thaw cycles, the relative dynamic modulus and mass loss rate are within the specification indexes, so the mortar specimens prepared in this test have good frost resistance. Conclusion (1) The mix proportion of CA mortar is determined by orthogonal test design.The proper dosage range of cement, emulsified asphalt and sand are 280~315kg/m3, 435~550kg/m3 and 350~745kg/m3, respectively. Within this range, the 28d compressive strength requirements of CA mortar are met. The amount of cement has the greatest influence on the compressive strength of mortar, followed by the amount of emulsified asphalt and the sand content has little influence. The increase of the amount of air entraining agent reduces the compressive strength of mortar. The gas content of CA mortar can be increased by adjusting the stirring speed and stirring time of CA mortar. (2) Based on the mixing proportion by orthogonal experiment and stirring process designed, the CA mortar made by adding proper amount of air entraining agent has good frost resistance. After 300 freeze-thaw cycles, the relative dynamic modulus of CA mortar decreases to 76.81% and the mass loss rate is 3.45%, but they all meet the requirements of the standard indexes. Acknowledgments The work is supported by National natural science foundation of China [5210840] and Scientific Research Support Project of Liaoning Provincial Department of Education [JDL2019018]. References [1] Coenraad, E. Recent development in slab track. European Railway Review, 9(2), 81-85, 2003. [2] Murata, O. Overview of recent structure technology R&D at RTRI. Quarterly Report of RITI, 44 (4), 133-135, 2003. [3] Katsuohi, A., Makoto, S., Hifumi A., Osamu, H. Development of slab tracks for Hokuriku Shinkansen line. Quarterly Report of RITI, 42 (1), 35-41, 2001. [4] Shigeru M., Hideyuki T., Masao U., and Yasuto F. The mechanism of railway track. Japan Railway and Transportation Review, 15(3), 38-45, 1998. [5] Yang K. N., Jin S. S. Research status of properties of cement emulsified asphalt mortar. Materials review, 35(S2), 145-149+157, 2021. [6] Jiang, G.Y., Li, R., Zhou, J., Tan, X. R., Li Y. T., Bai, S. Preparation and properties of cationic emulsified asphalt CA mortar. Chemical world, 53(02), 65-68, 2012. [7] Hu, S. G., Wang, T., Wang, F. Z., Liu, Z. C., Gao, T., Chen, L. Study on influencing factors of frost resistance of CA mortar. Journal of Wuhan University of Technology, (08), 30-33, 2008.

Materials Science Forum ISSN: 1662-9752, Vol. 1079, pp 199-205 doi:10.4028/p-jkfwni © 2022 Trans Tech Publications Ltd, Switzerland

Submitted: 2022-07-18 Accepted: 2022-11-15 Online: 2022-12-26

Experimental Study on Materials and Mechanical Properties of Steel Tube-Confined Coral Concrete Reinforcement Mechanism Jing Huang1,a, Wenxuan Shan1,b and Yi Gao1,c* Naval Logistics Academy, Tianjin, China

1

[email protected], [email protected], c,*[email protected]

a

Keywords: Steel tube-confined coral concrete; Hoop reinforcement; Lateral pressure coefficient; Experimental study

Abstract. Filling steel tubes with coral concrete to form concrete filled steel tube composite structures for compression members can compensate for its low aggregate strength. In order to demonstrate the reinforcement mechanism of coral concrete hoop under steel tube restraint and to propose the strength theory under the hoop effect, it is necessary to obtain the theoretical analysis based on the theory of triaxial compressive bearing theory of normal concrete. Therefore, starting from the failure mechanism of coral concrete under triaxial compression, the hoop reinforcement mechanism of coral concrete under different lateral pressure conditions is studied analytically. By the axial compression bearing capacity comparative test between normal concrete and coral concrete under steel tube restraint, comparative relationship between lateral pressure and circumferential strain is calculated and the conditions for taking values are acquired, which lays the foundation for the calculation theory of the compressive bearing capacity of it. Introduction The failure of coral concrete depends on its fracture strength, but the fracture performance of coral concrete is different from the plastic deformation of metal materials, and its material fracture conditions have a great relationship with the stress state. The ultimate elongation that coral concrete can withstand varies greatly depending on its stress state [1, 2]. The research on the basic mechanical properties of coral aggregate concrete shows that in the process of strength loading, the origin tangent modulus and the loading deformation modulus of coral concrete specimens are significantly lower than those of normal concrete [3]. For the determined elastic modulus of coral concrete and normal concrete at the same C40 strength grade [4], the average value of coral concrete is 24.7GPa, while ordinary concrete is 30~35Gpa [5]. The above factors determine the extent to which the axial compressive strength of coral concrete will increase due to the hoop reinforcement under the triaxial force differs from that of normal concrete. As shown in Figure 1.

Fig. 1 Compression failure surface comparison of normal crushed stone concrete and coral concrete

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Expression for the Triaxial Compressive Bearing Capacity of Coral Concrete As shown in Figure 2, the relationship between axial compressive stress σ c,c and lateral pressure pc of coral concrete under equal triaxial compression can be referred to the conclusion of the triaxial compression test of normal concrete, using both linear and nonlinear relationship models.

Fig. 2 Force diagram of coral concrete under equal triaxial compression

Fig. 3 Linear fitting of concrete column axial compressive strength under equal lateral pressure

Axial compressive stress σ c,c and lateral pressure pc are linear. Referring to the Richart model theory and the available data, as shown in Figure 3 [6], it can be considered that the same linear relationship model exists between the strength of axial compressive stress σ c,c and lateral pressure pc . The expression of the relationship is:

σ= f c,c + K c pc c,c where: f c ,c

, (1) - coral concrete axial compressive strength without lateral pressure; K C - coral concrete

lateral pressure coefficient. Axial compressive stress σ c,c and lateral pressure pc are nonlinear. According to a large number of existing test results, especially under high lateral pressure conditions (when the steel tube hoop coefficient is large), the triaxial compressed concrete axial stress and lateral pressure does not fully satisfy the linear relationship. It is considered that coral concrete is similar to normal concrete in the triaxial compressive stress state, and the ratio of pc / f c,c is regarded as the relative lateral compressive stress parameter under equal triaxial compression of coral concrete, then there are:

σ c,c = f c,c + (2 +

1.5 ) pc . pc / f c,c

(2)

Then the lateral pressure coefficient of coral concrete under high lateral pressure condition is K C = 2 + 1.5 / p c / f c ,c . At this time, the lateral pressure coefficient K c is not a constant, but a nonlinear function of the relative lateral stress parameter p c / f c ,c . Strength Test of Steel Tube Hoop Constrained Coral Concrete Test Material. (1) Coral sand aggregate. The concrete aggregate used in the test is the coral reef sand of the offshore islands and reefs, the aggregate particle size is 5~20mm, which is sieved and weighed for

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5~10mm, 10~15mm, 15~20mm particle size, and the ratio of the three is 1:1.05:0.93 as the aggregate gradation used [7]. Configure according to the ratio shown in Table 1 [8]. Cement [kg·m-3] 450

Coarse Aggregate [kg·m-3] 756

Table.1 The core concrete mixture ratio Fine Aggregate [kg·m-3] 734

Volumetric Sand Rate [%] 49.26

Net Water Consumption [kg·m-3] 225

In order to conduct a comparative test of the difference of the hoop reinforcement performance of coral concrete and normal concrete under triaxial stress, coral crushed stone is replaced with ordinary crushed stone, coral sand is replaced with ordinary river sand. And ordinary crushed stone is screened with coral aggregate gradation and configured with the same mix ratio in Table 1.After the mechanical performance test, the basic strength performance indicators of coral concrete and ordinary concrete are shown in Table 2. Table.2 Core concrete performance indicators Test Category

Concrete Type

Hoop Constraints Strength Test

Coral Concrete Ordinary Crushed Stone

Cube Compressive Strength f cu [N/mm2] 35.4 43.5

Axial Compressive Strength f c [N/mm2] 33.01 37.73

Elastic Modulus E [×104N/mm2] 3.081 3.244

(2) Steel tube. Steel tubes are made of Q235 hot-rolled steel sheets of different thicknesses, after cold processing and welding, they are cut and formed according to the design size of the test pieces. A square steel plate pad with a side length of 200mm and a height of 20mm is welded at one end of the steel tube. The performance indicators are shown in Table 3. Table.3 The testing steel performance Ultimate Strength f u Elastic Modulus E

Steel Variety

Yield Strength f y

Hot Rolled Steel Sheets

252.35

[N/mm2]

[N/mm2]

[×104N/mm2]

319.14

21.963

Poisson’s Ratio

µ

0.27

Test Design (1) Specimen parameters. The hoop strength test of steel tube restrained core coral concrete is designed for two groups of short column specimens with similar cross-sectional dimensions, two in each group, in which one group of steel tube is poured with coral aggregate concrete, and the other group is poured with ordinary crushed concrete. The two groups are filled with the same concrete aggregate grade and mix ratio and the specimen parameters are shown in Table 4. Table.4 The Specimen parameters of hoop constraints strength test Specimen Number

Outer Diameter of Steel Tube D [mm]

SC1 SC2 C1 C2

165.08 165.00 165.56 165.32

Wall Thickness of Steel Tube t [mm] 2.1 2.1 2.1 2.1

Column Length L [mm]

Steel Tube Strength f y

442 440 447 445

252.35 252.35 252.35 252.35

[N/mm2]

Core Concrete Strength f cu [N/mm2]

Concrete Type

35.4 35.4 43.5 43.5

Coral Reef Sand Coral Reef Sand Ordinary Crushed Stone Ordinary Crushed Stone

(2) Test objectives. Considering the difference in aggregate properties between coral aggregate concrete and ordinary concrete, the lateral compressive stress of the two should be different under the

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same steel tube hoop restraint conditions. Therefore, a comparative test of lateral compressive stress between the steel tube core coral concrete and the steel tube core ordinary concrete under axial compression condition is required. During the test, by applying a round steel spacer with a diameter smaller than the inner diameter of the steel tube on the bearing surface of the concrete filled steel tube specimen to achieve only the axial load applied to the core concrete, and the steel pipe does not directly bear the longitudinal load. The loading situation is shown in Figure 4.

Fig. 4 Loading conditions of steel tube hoop constrained concrete

Fig. 5 Layout of measuring points on steel tube hoop constrained core concrete

(3) Data Testing. The test data are recorded by burying concrete stress gauges at the upper 5 cm and lower 5 cm of the cross section in the specimen column vertically and by applying circumferential strain gauges uniformly on the outer surface of the steel tube. The layout of the measurement points is shown in Figure 5. Analysis of Test Results (1) Relationship between Axial Compressive Load of Specimen and Transverse Stress (Lateral Compressive Stress) of Core Concrete. The morphology of the specimen after reaching the ultimate damage is shown in Figure 6. During cyclic loading, the concrete embedded strain gauge reading increases or decreases as the axial compression load is loaded or unloaded. Except for the first loading and unloading, in the other two cyclic loading processes, the strain gage readings at the load are essentially the same and cyclic in nature. Taking 10kN, 100kN, and 200kN as the load characteristic points, the average values of the core restrained concrete of the two groups of specimens (columns SC1/SC2 and C1/C2) during three loading and unloading, corresponding to the transverse strain data are shown in Table 5. Table.5 Core concrete transverse strain under elastic cyclic loading

Load

Coral Concrete Transverse Strain Mean Value

ε

N

[kN] 10 100 200

Ordinary Concrete Transverse Strain Mean Value

First Load 5.18 63.13 131.12

[ µε ] Second Load 4.21 61.47 127.43

ε

Third Load 4.23 61.46 127.40

First Load 3.68 26.53 56.52

[ µε ] Second Load 1.15 25.37 54.21

Third Load 1.15 25.37 54.31

As the internal concrete is in elastic phase, the stresses in the core concrete inside the steel tube can be calculated by the strain and elastic modulus of the concrete, and the relationship between the vertical stress of the section and the lateral stress of the concrete (lateral compressive stress) can be obtained in the elastic stage. Under the same axial compression load, the lateral deformation of coral concrete restrained by steel tube is significantly larger than that of ordinary concrete, and the lateral

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compressive stress is higher. Taking the data comparison of column SC1 and C1 as an example, the relationship between section vertical stress and lateral compressive stress is shown in Figure 7.

Fig. 6 Failure mode of specimens

Fig. 7 Relationship of core concrete section vertical stress and lateral stress

The curve relationship also shows that the ratio k p of the transverse stress (lateral compressive stress) of the coral concrete and the ordinary concrete under the constraint of the steel tube hoop varies little in the elastic stage with the change of the vertical stress of the load section (Table 6). Table.6 Relationship of core concrete lateral pressure and the section vertical stress Cross-sectional Vertical Stress σ [N/mm2] 1.828 00 3.593 33 5.358 67 7.123 56 9.456 44

Coral Concrete Lateral Compressive Stress pc [N/mm2] 0.819 85 1.690 85 2.711 59 3.433 16 4.047 82

Ordinary Concrete Lateral Compressive Stress p [N/mm2] 0.299 42 0.673 45 1.010 18 1.309 60 1.833 51

k p = pc / p 2.73 2.94 2.78 2.29 2.20

In the elastic stage, the lateral compressive stress of core coral concrete is greater than that of core ordinary concrete under the vertical stress state of the same section. When the load continues to be loaded until the specimen reaches the ultimate failure, the ultimate load of the steel tube coral concrete specimen and the steel tube ordinary concrete specimen is basically similar, that is, the ultimate load value of the steel tube coral concrete is 1045kN, and the ultimate load value of the steel tube ordinary concrete is 1150kN. The ultimate load-bearing strengths of the two core concretes do not differ significantly. It can be assumed that when the ultimate load is reached, the lateral compressive stress of coral concrete is greater than that of ordinary concrete under the hoop restraint condition. For the value of the lateral compressive coefficient K, which characterizes the hoop reinforcement index under the triaxial force condition, the value of coral concrete is smaller than that of ordinary concrete. (2) Relationship between the Vertical Stress of the Section and the Circumferential Strain of the Steel Tube. In the process of loading the specimen to failure, with the increase of vertical stress, in the initial stage, the transverse strain basically maintains a slow and uniform growth. When the vertical stress increases to about 85% of the ultimate strength of the specimen section, the steel tube transverse strain increases suddenly and the surface of the steel tube of the specimen appears buckling bulge phenomenon. Figure 8 and Figure 9 reflect the relationship between the vertical stresses in the core concrete section and the transverse strains in the steel tube during the whole process of loading and stressing for the coral concrete filled steel tube specimen (SC1) and the ordinary concrete filled steel tube specimen (C1). It can be seen from the curve change that the steel tube circumferential strain of the two specimens has the same trend with the change of vertical stress of the core concrete section under the same loading condition. However, when the vertical stress in the section reaches the peak stress, the circumferential strain of the coral concrete filled steel tube specimen (SC1) is close to 1000 με,

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which is significantly larger than the circumferential strain of 500 με of the ordinary concrete filled steel tube specimen (C1).

Fig. 8 Relationship of section vertical stress and circumferential strain of the coral concrete filled steel tube specimen (SC1)

Fig. 9 Relationship of section vertical stress and circumferential strain of the common concrete filled steel tube specimen (C1)

In order to study the relationship between axial compressive strength and lateral compressive stress in coral concrete under lateral compression conditions under the action of a triaxial force hoop, the corresponding annular strain values of the steel tube when the specimen section reaches ultimate strength are recorded (Table 7). In the next step, based on the above test data, the corresponding section stress of the steel tube can be calculated by combining the steel tube principal structure relationship model [9], thus providing a test basis for further calculation of the lateral pressure coefficient K c of coral concrete under the steel tube restraint conditions. Table.7 The axial compressive strength and steel circumferential strain values of specimens Specimen Number

Axial Compression Strength f c*,c

SC1 SC2 C1 C2

[N/mm2] 46.52 45.21 51.12 49.30

Longitudinal Strain of Steel Tube ε1 [ µε ]

Circumferential Strain of Steel Tube ε 2 [ µε ]

4 241 4 110 2 047 1 654

4 380 4 190 2 265 1 989

Core Concrete Type

Coral Reef Sand Ordinary Crushed Stone

Conclusion Aiming at the reinforcement mechanism of steel tube-confined coral concrete, a comparative test on the strength of core concrete restrained by steel tube hoop is designed and carried out, which is based on the theoretical model of the hoop strength of coral concrete under triaxial stress state, starting from the analysis of the triaxial compression failure mechanism. The force characteristics of two types of core concrete with coral reef and ordinary crushed stone as aggregates under hoop restraint are analyzed for comparison, so as to grasp the apparently different variation relationship between axial stress and lateral compressive stress in the elastic phase of the two types of hoop-constrained concrete. Based on the experimental results, combined with the steel tube principal structure model, the lateral pressure coefficient of the steel tube-confined coral concrete can be further calculated, providing test and theoretical basis for the bearing strength of steel tube hoop constrained coral concrete.

Materials Science Forum Vol. 1079

205

References [1]

Zhao H., Gao Y., Li H. Y. Research of the compressive testes and bearing capacities of coral concrete filled square steel tube short columns. China Concrete and Cement Products, 2019(3): 43-47. Doi: 10.19761/j.1000-4637.2019.03.043.05

[2]

Gao Y., Li H. Y., Zhao H. Experimental research on axial compression behavior of CFRP coral concrete filled square steel tube short columns. Concrete, 2019(11):54-57 ． Doi ： 10.3969/j.issn.1002-3550.2019.11.012

[3]

Y. Gao, Y. Lu. Study on raw materials and structural performance of coral concrete composite structure. Domenico Lombardo, Ke Wang. Advances in Materials Science and Engineering: Proceedings of the 7th annual international workshop on materials science and engineering, (iwmse 2021). CRC Press/Balkema, 2022: 177-185. https://doi.org/10.1201/9781003225850-27

[4]

GB/T 50081-2019. Standard for test method of mechanical properties on ordinary concrete [S].

[5]

Gao Y., Wei Z. B. Sun Xiao. Experimental research on basic mechanical properties of coral aggregate concrete. Journal of Naval University of Engineering, 2017, 29(1): 64-68. Doi：10. 7495/j. issn. 1009 - 3486. 2017. 01. 013

[6]

Yan Y. X., Li B., Ton g Y. Z., Li X. M., Liu J. J. Analysis of axial compressive bearing capacity for RPC filled steel stub columns based on the limit equilibrium theory. Building Structure, 2020, 50(5): 135-139. Doi: 10.19701/j.jzjg.2020.05.023

[7]

Pan B. Z., Wei Z. B. Experimental study on effects to coral sand concrete compressive strength of raw materials. Engineering Mechanics, 2015, 32(s1): 221-224. Doi: 10.6052/j.issn.1000-4750.2014.05.S020

[8]

Gao Y. Huang Jing. Experimental study on axial compression properties of coral concrete filled steel tubular short column. Journal of Logistical Engineering University, 2017, 33(3): 9-10. Doi：10. 3969/j. issn. 1672 - 7843. 2017. 03. 002

[9]

Zhong S. T. Unified theory of concrete filled steel tubular: Research and Application. Bei Jing: Tsinghua University Press, 2006:78.

Keyword Index A Adsorption AFM Air-Entraining Agent Al-30%Si Alkali-Activated Material Aluminium Cast Aluminium Scraps Aluminum Electrolysis Analysis of Variance ANOVA Ansys Program Artificial Neural Network

157 179 193 15 171 147 147 135 3 57 49 3

Fatigue Strength Friction Frost Resistance Functionally Graded Materials

21 115 193 49

G Geometrical Accuracy

29

H Heater-Cooler Blocks Hollow Ball Hoop Reinforcement Hydromechanical Deep-Drawing Hydrothermal-Microwave

147 129 199 39 157

B Backpropagation Bandgap Energy Basalt Fiber Biocomposites Biodegradable Polymers Bridge Deck Pavement

3 103 171 93 93 187

Interfacial Energy

67

J Joint Strength

21

L

C Calcium Molybdate CALPHAD Catalyst Cement Asphalt Mortar Cement Body Characterization Co Coarsening Rate Coffee Dregs Computational Thermodynamics Conductivity Behavior Copolyesters Corrosion

I

157 67 87 193 171 147 15 67 93 67 103 103 129

Latent Heat Lateral Pressure Coefficient

199

N

15 199

M Measuring Mechanical Properties Microstructure Mixing Ratio Model Modelling Modification Modified Asphalt Mixture Molecular Dynamics MRR

115 193 15 49 115 115 129 187 135 57

E Experimental Study

Nano Powder(Al2O3)

57

F Fabrication Fatigue Life

147 49

O Oil Extraction

93

208

Advanced Materials and Production Technologies

Orthogonal Experimental Design

193

P Performance Evaluation Phase Transformation Poly(3-Hydroxybutyrate) Polycondensation Polylactic Acid Polymer Polymerization

187 67 93 103 87 87 87

57 147 21 179 87 179 129 179

S Scheelite Shear Strength Sheet Metal Forming Silica Solid Spot Weldability Steady State Steel Tube-Confined Coral Concrete Strength Surface Roughness

157 21 39 129 115 21 147 199 171 29

T Tailings Thermal Behavior Thermal Conductivity Thermo-Calc Thickness Distribution Toughness

171 103 147 67 39 67

V Viscosity

135

W Warp Knitting Machine

29

Y

R Recast Layer Recycling Resistance Spot Welding Rheological Properties Ring-Opening Road Engineering Ru Rubber Asphalt

WEDM

115

Yarn

115

Author Index A Abdullah, M.R. Abed, F.N. Ahmed, A.R. Al-Hadrayi, Z.M.R. Al-Khazraji, A.N. Al-Mukhtar, A.M. Alvarez Acevedo, N.I. Alves, V.N. Aswini, R.

67 57 39 49 49 21 93 157 103

157 157 3 115 87 115

C Cai, H.N. Cheng, W. Cherif, C.

Hadi, A.H. He, H.B. He, Z. Huang, J.

29 135 67 199

I Ibrahim, N.

87

K

B Barbosa, A.d.G. Barrado, C.M. Bataineh, O. Beitelschmidt, M. Binti Ghazali, N.A. Bruns, M.

H

67 129 115

Khleif, A.A. Kothai, S. Krentzien, M.

29, 39 103 115

L Lakshmi Devi, D. Li, J.R. Li, K. Li, X.S. Li, Y. Liao, R. Liu, X. Longo, E.

103 129 171 15 171 15 171 157

D de Figueiredo, A.T. de Oliveira, C.E.N.

157 93

E Ewetumo, T.

M Ma, X.J. Ma, X.Y. Mahmood, I.A.

179 179 21

147

O F Fakhri, M.S. Fang, J.H. Fang, L. Festus, B.

21 179 67 147

G Gao, Y. Guo, D.F.

Olubambi, P. Oluyamo, S.

147 147

P Pereira, S.d.C.

157

R 199 179

Rao, H.D. Rocha, M.C.G.

129 93

210

Advanced Materials and Production Technologies

S Shan, W.X. Shandookh, A.A. Smadi, M.

199 49 3

T Tian, S.

171

W Wang, L.K. Wang, Y.S.

193 135

Z Zeng, J. Zhang, C.Y. Zhang, D.Y. Zhang, J.S. Zhang, L. Zhang, Z.H. Zhao, L.H. Zhong, W.Y.

135 187 129 193 129 135 193 15