Optical Characterization of Heat Transport in Vertically Aligned Carbon Nanotube Arrays

Abstract

Vertically aligned carbon nanotube (VACNT) arrays, absorbing virtually all incident light, are a novel material with unique applications including as sensors, solar energy converters, and as nearly ideal blackbody radiators. Their superior thermal and optical properties are attributed to their structure, which can vary with how they are grown. In applications where insulation between tubes is of high importance, measurement of transverse thermal diffusivity is critical. In contrast with methods that measure transverse thermal diffusivity by measuring the back surface, here, the distal ends of the nanotubes are flash-irradiated with a Gaussian laser pulse with 1µm wavelength and the infrared emission of the VACNT front surface is captured as a function of time. Analysis of the captured images provides measurement of the thermal diffusivity in the transverse direction of the VACNT array. This method has been used for other anisotropic materials, but has not yet been applied to VACNT arrays. The optical characterization method demonstrated here enables feedback for application-tailored optimization of VACNT synthesis processes.