Influence of annealing on thermal and electrical properties of carbon nanotube yarns

Abstract

The physical properties of dry-spun MWCNT yarns with diameters from 35 to 60 μm were systematically determined as a function of annealing up to 2700 °C. Raman spectroscopy showed a ~5 fold increase in relative CNT crystallinity after annealing. Electrical conductivity and magnetoresistance (in fields up to 9 T) were measured from 2 K to 390 K. Thermal conductivity from 50 K to 300 K was determined using the parallel thermal conductance method. The electrical and thermal conductivities of the yarns both increased by over 100 % after annealing to 2700 °C. The influence of adsorbed species on the electrical properties of the yarns was also studied.

High thermal conductivities of carbon nanotube films and micro-fibres and their dependence on morphology

“…It is generally accepted that the main resistance in CNT bulk materials is due to junctions between the CNTs or CNT bundles, and that the influence of crystallinity is only visible when near-perfect alignment and purity are achieved. The low-temperature resistivity decreases with increasing temperature (Figure 3), indicating that all films behave primarily as semiconductors [57] [23] [58] and only show a metallic upturn above the cross-over temperature T* ~220 -250 K. Similar temperature-dependent electrical conductivity hysteresis was reported previously [59].…”

“…As there is a trade-off between increasing the number of nanotubes and the resultant increase of junctions [30], a larger number of CNTs will increase the overall thermal conductivity, but the dominance of junctions will cause a decrease in conductivity of the bulk material. Improved bundle alignment would cause better contact and higher overlap area between the CNTs, increasing the thermal conductivity [53] [59] was measured here as 0.52 g cm  ³. )…”

Thermal conductivity of carbon nanotube networks: a review

“…The method is particularly useful for the samples which are not rigid enough to support the heaters and the thermometer, so it may be successfully applied mainly to measurements of certain CNT yarns [43,44], but also CNT sheets [45,46]. provides a schematic presentation of the measurement setup in the PTC method.…”

The influence of carbon source and catalyst nanoparticles on CVD synthesis of CNT aerogel

“…Alternatively, the CH 4 could be supplied so that the catalytic re-nucleation zone received only CH 4 , unaffected by the elevated temperatures of the hottest zone. When CH 4 was injected so that the jet was supplied only to the catalytic nanoparticle renucleation zone at a temperature profile position of ~900 °C, no aerogel was formed, indicating that CH 4 was not interacting with the catalytic nanoparticles to produce…”

“…Interest in producing macroscopic assemblies of CNTs, driven by their unique combination of properties continues to stimulate academic research around the world and to drive forward industrial development. At least two companies are currently working with research groups to commercialize FC-CVD technology [1,2], others are exploring the liquidcrystal spinning route[3] and dry-spinning techniques continue to develop [4][5][6]. The FC-CVD route, which facilitates the continuous collection of a CNT aerogel using techniques pioneered by Windle et al [7] is an attractive option for scale-up due to its relative simplicity and one-step production method.…”