Crystallinity and CNT–CNT Interface Effects on Thermal and Electrical Conductivity in Ultralong CNT Bundles and Yarns
Haruto Kurono, Hiromu Hamasaki, Takayuki Nakano, Hiroya Ikeda, Hisashi Sugime, Y. Inoue
Abstract
We investigated the influence of crystal defects in carbon nanotubes (CNTs) and CNT–CNT interfaces on their thermal and electronic transport properties. Thermal and electrical conductivity measurements were performed on ultralong multiwalled CNT bundles (>10 cm) and CNT yarns fabricated via dry spinning of 600 μm-long multiwalled CNTs. The impact of enhanced crystallinity, achieved through annealing at temperatures up to 2800 °C, was systematically examined. The results show that defect repair and structural optimization of CNT–CNT interfaces significantly enhance transport properties. Phonon and electron scattering at crystal defects decreases with increasing crystallinity, resulting in higher respective conductivities. However, in CNT yarns, phonon scattering at CNT–CNT interfaces limits the thermal conductivity, leading to saturation even at high crystallinity. In contrast, electrical conductivity shows no such saturation, as defect scattering dominates over interfacial effects. These findings provide new insights into the transport phenomena in CNT assemblies and highlight their potential for advanced applications in electronic devices and thermal management systems.