High-temperature conduction behavior of carbon nanotube fiber from 25 °C to 1100 °C

The high-temperature conduction behaviors of pure CNT fibers and CNT/SiC and CNT/C composite-fibers from 25 °C to 1100 °C in a N2 atmosphere are reported. The results show a significant increase in the electrical conductivities of CNT fibers in the temperature regime, as the semi-conductive SiC and conductive C matrices were introduced. As the temperature increased, the conductivities of all fibers increase with temperature up to a critical temperature, Tc, beyond which the decrease in the conductivities was observed. The conduction behaviors of all fibers can be well explained by the three-dimensional variable range hopping mechanism at the temperature below Tc and followed a heterogeneous mechanism above Tc. Interestingly, Tc was reduced after the introductions of SiC and C matrices, and this is explained by the competing effect of the internal nanotube resistance and the contact resistance between nanotubes which decreases with the introduction of SiC and C matrices. We propose that the study of high-temperature conduction behaviors of the CNT fibers aids in improving their conductivities and applications at high temperatures, and the presented conduction mechanisms could be used for other kinds of CNT-structured fibers.