Effect of graphitization on mechanical properties of untwisted carbon nanotube yarn and its strength development mechanism
Effect of graphitization on mechanical properties of untwisted carbon nanotube yarn and its strength development mechanism
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DOI：
10.1299/transjsme.17-00585
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Tae Sung Kim;Anri Hayashi;Hidefumi Nikawa;K. Shirasu;G. Yamamoto;Toshiyuki Hashida;A. Hosoi;Hiroyuki Kawada
中科院分区：
文献类型：
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作者：
Tae Sung Kim;Anri Hayashi;Hidefumi Nikawa;K. Shirasu;G. Yamamoto;Toshiyuki Hashida;A. Hosoi;Hiroyuki Kawada
碳纳米管纱线是碳纳米管的聚集体，使碳纳米管能够在宏观范围内得到应用。然而，碳纳米管纱线的拉伸强度远低于碳纳米管本身，提高其力学性能对其实际应用是一个挑战。组成纱线的碳纳米管含有一些缺陷结构和杂质材料，它们的存在会导致纱线的拉伸强度下降。本研究采用干法纺丝法制备了无捻碳纳米管纱线，并在2800℃下进行了石墨化处理，以提高其力学性能。此外，还对组成纱线的碳纳米管的强度和碳纳米管之间的相互作用力进行了评估，以阐明石墨化碳纳米管纱线的强度发展机理。通过石墨化处理，碳纳米管的结晶度提高了十倍以上，缺陷结构和杂质被去除。单纤维拉伸试验表明，经石墨化处理后的纱线强力提高了20~35%。另一方面，组成纱线的碳纳米管的强度降低。石墨化使碳纳米管纱线的断裂形式由原来的拔出碳纳米管束变为折断碳纳米管束，表明碳纳米管束间的相互作用力增大。此外，分子动力学方法模拟的结果表明，范德华作用力的增加抑制了碳纳米管束的拔出。因此，未加捻碳纳米管纱线力学性能的改善不是由于纱线中碳纳米管强度的变化，而是碳纳米管之间相互作用力的增加。
Carbon nanotube yarn, which is an aggregation of Carbon nanotubes (CNTs), enables CNTs to be used on macro scale. However, tensile strength of the CNT yarn is much lower than CNT itself, and improvement of the mechanical properties is a challenge for practical application of the yarns. CNTs composing the yarns include some defect structures and impure materials, and their presence can cause a decrease in tensile strength of the yarn. In this study, untwisted CNT yarns were fabricated by dry spun method and graphitized at a temperature of 2800°C for the purpose of improving mechanical properties. Additionally, strength of a CNT composing the yarn and interactive force between the CNTs were evaluated to clarify strength development mechanism of the graphitized CNT yarn. Crystallinity of the CNT yarn was improved more than ten times, and defect structures and impure materials was removed by the graphitization treatment. As a result of single fiber tensile tests, strength of the yarn was increased by 20~35% after the graphitization. On the other hand, strength of the CNT composing the yarn was decreased. The breaking form of the CNT yarn was changed from pulling out of CNT bundles to rapture of the bundles by the graphitization, indicating an increase of interactive force between the bundles. In addition, as a result of pulling out simulations by molecular dynamics method, it was indicated that the pulling out of the CNT bundles were suppressed by increase in van der Waals force. Consequently, the improvement of mechanical properties of the untwisted CNT yarns was not due to the change in the strength of the CNT in the yarns but the main cause was the increase in the interactive force between the CNTs.