Abstract In high temperature annealing of carbon nanotube (CNTs) bundles for structure and thermal conductivity (κ) improvement, the statistical errors from sample-wide structure variation and sample transfer/preparation significantly overshadows the understanding of structure-κ correlation and change. In this work, the sequential process of current-induced thermal annealing (CITA) on improving the structure, electrical and thermal conductivities of chemical vapor deposition grown CNT bundles is studied for the first time. Our in-situ κ measurement using the transient electro-thermal technique uncovers the conjugated dynamic electrical, thermal, and structural properties. The electrical resistance and thermal diffusivity evolution of CNT bundles during CITA is studied. The thermal diffusivity and κ before and after CITA are measured from room temperature down to 10 K to uncover the reduction of defect density and enhancement of inter-tube connection strength after CITA. Our micro-Raman spectroscopy study from the most annealed region to the non-annealed region reveals significantly improved order in sp2 bonding carbon structure and reduced defects along the sample length. The resulting κ has 5–19 times increase at the most annealed region of CNT bundles. The intrinsic κ of CNT walls against the annealing temperature is also determined, which reaches a level as high as 754 W/m·K after CITA.

中文翻译：

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碳纳米管束向高端热设计应用的 19 倍热导率增加

摘要 在碳纳米管 (CNTs) 束的高温退火以改善结构和热导率 (κ) 时，来自样品范围结构变化和样品转移/制备的统计误差显着掩盖了对结构-κ 相关性和变化的理解。在这项工作中，首次研究了电流诱导热退火 (CITA) 的顺序过程，以改善化学气相沉积生长的 CNT 束的结构、电导率和热导率。我们使用瞬态电热技术进行的原位 κ 测量揭示了共轭动态电、热和结构特性。研究了 CITA 过程中 CNT 束的电阻和热扩散率演变。从室温到 10 K 测量 CITA 前后的热扩散率和 κ 以揭示 CITA 后缺陷密度的降低和管间连接强度的增强。我们从最退火区域到非退火区域的微拉曼光谱研究表明，sp2 键合碳结构的有序性显着提高，并且沿样品长度方向的缺陷减少。由此产生的 κ 在 CNT 束最退火的区域增加了 5-19 倍。还确定了 CNT 壁对退火温度的固有 κ，在 CITA 后达到了高达 754 W/m·K 的水平。我们从最退火区域到非退火区域的微拉曼光谱研究表明，sp2 键合碳结构的有序性显着提高，并且沿样品长度方向的缺陷减少。由此产生的 κ 在 CNT 束最退火的区域增加了 5-19 倍。还确定了 CNT 壁对退火温度的固有 κ，在 CITA 后达到了高达 754 W/m·K 的水平。我们从最退火区域到非退火区域的微拉曼光谱研究表明，sp2 键合碳结构的有序性显着提高，并且沿样品长度方向的缺陷减少。由此产生的 κ 在 CNT 束最退火的区域增加了 5-19 倍。还确定了 CNT 壁对退火温度的固有 κ，在 CITA 后达到了高达 754 W/m·K 的水平。