Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

Abstract

Here we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈ 14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.The quantum confinement mediated landmark properties of one dimensional materials, such as nanowires, nanofibers, and nanotubes, makes them attractive to a number of high value applications. Recently, carbon nanotubes (CNTs) were extensively studied in scalable aligned architectures, commonly known as forests, which promise the design and facile manufacture of multifunctional material architectures with tunable properties.

Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology

“…2b demonstrates, R c plateaus at 0.1 ≤ w ≤ 0.3 and has a value of ∼1 nm for V f = 40% CNTs, a value that is on the same order of the curvature of ripples that are expected to form on the surface of ∼8 nm diameter (∼1.5 nm wall thickness) CNT during buckling, 30,31 indicating that the simulation results are physical for V f ≤ 40% CNTs. A note should be made that R c ∼ 1 nm is on the same order as the variations in the CNT inner and outer diameter that were reported previously, 32 and that such nanoscale surface features can arise through either Stone-Wales or inter-wall defects. [33][34][35][36] To ensure that R c is evaluated for an amount of waviness that is generalizable to other non-stochastic descriptions, e.g.…”

Recently emerging trends in thermal conductivity of polymer nanocomposites

“…Recent studies have confirmed the thermal conductivity of MWCNTs to be about 3000 W/m K, while that of SWCNTs is above 2000 W/m K (Pradhan et al 2009). Additionally, they exhibit thermal conductivity in longitudinal orientation within the range of 2800-6000 W/m K for single nanotube at ambient temperature (King et al 2010a,b, Lee et al 2015, which is similar to diamond but superior to graphite and CFs, in addition to an aspect ratio in the order of 103. Thus, enhancement in CNTs' thermal conductivity has been attributed to the formation of a percolation network comparable to the same mechanism observed for electrical conductivity Tai 2008, Wang et al 2014a,b).…”

“…The conductivity of phonons in CNTs is induced by several factors including the number of active modes in the phonon, the scattering at the boundary surface, phonons free path length, and the inelastic Umklapp scattering, which is an erratic electron-phonon or phononphonon scattering phenomenon ). Several researches have been conducted on polymer/ CNT thermal conductivity, in addition to other properties (Wang et al 2014a,b, Lee et al 2015. CNTs were reported to have induced enhancement of these properties (Pradhan et al 2009.…”

Void‐Free Layered Polymeric Architectures via Capillary‐Action of Nanoporous Films

“…VACNT synthesis (used here as the NPN) proceeded via a thermal catalytic chemical vapor deposition process with a quartz tube furnace of 44 mm inner diameter at atmospheric pressure, which was similar to a previously reported process . Ethylene was used as the carbon source, and water of 600 ppm was added to the helium gas.…”