Effects of Carbon Nanotube Structure, Purity, and Alignment on the Heat Conduction Properties of Carbon Films and Fibers

Junjie Chen

doi:10.31586/materials.2022.248

Abstract

The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the parallel thermal conductance technique was employed to determine the thermal conductivity. The effects of carbon nanotube structure, purity, and alignment on the thermal conductivity of carbon films and fibers were investigated to understand the characteristics of thermal transport in the nanostructured material. The importance of bulk density and cross-sectional area was determined experimentally. The results indicated that the prepared carbon nanotube films and fibers are very efficient at conducting heat. The structure, purity, and alignment of carbon nanotubes play a fundamentally important role in determining the heat conduction properties of carbon films and fibers. Single-walled carbon nanotube films and fibers generally have high thermal conductivity. The presence of non-carbonaceous impurities degrades the thermal performance due to the low degree of bundle contact. The thermal conductivity may present power law dependence with temperature. The specific thermal conductivity decreases with increasing bulk density. At room temperature, a maximum specific thermal conductivity is obtained but Umklapp scattering occurs. The specific thermal conductivity of carbon nanotube fibers is significantly higher than that of carbon nanotube films due to the increased degree of bundle alignment.

Highlights

Carbon nanotubes can exhibit unique ability to conduct heat [1, 2], referred to as heat conduction properties
The specific thermal conductivity decreases with increasing bulk density
A maximum specific thermal conductivity is obtained at room temperature, which appears as a peak in the dependence of temperature in Figure 8, as determined previously [18, 32]

Summary

Introduction

Carbon nanotubes can exhibit unique ability to conduct heat [1, 2], referred to as heat conduction properties. Carbon nanotubes are a highly effective thermal conductor in the longitudinal direction. For an individual single-walled carbon nanotube, the thermal conductivity in the radial direction is around 1.52 W/(m·K) at room temperature [3]. Carbon nanotubes show superior heat conduction properties along the longitude directions. The thermal conductivity in the longitudinal direction is around 3500 W/(m·K) at room temperature [4]. Carbon nanotubes outperform diamond as the best thermal conductor. When macroscopic, ordered assemblies of single-walled carbon nanotubes are formed, the thermal conductivity of carbon nanotube films and fibers could reach up to around 1500 W/(m·K) at room temperature [5]. The heat conduction properties of carbon nanotube networks vary significantly, with a minimum of thermal conductivity less than 0.1 W/(m·K) [6].

Methods

Results

Conclusion