Anisotropic thermal diffusivity of aligned multiwall carbon nanotube arrays

TLDR

A photothermoelectric technique and a self‑heating 3ω method were used to determine the anisotropic thermal diffusivity of thick arrays of multi‑walled carbon nanotubes grown by CVD. The two measurement techniques agree within 2–13 %; diffusivity along the alignment direction is roughly two orders of magnitude lower than that of graphite planes, decreases slightly with temperature (80–300 K), and is about 25 × smaller across the alignment direction, which is 50 %–5× lower than graphite planes.

Abstract

A photothermoelectric technique was employed to determine the anisotropic thermal diffusivity of thick arrays of multiwalled carbon nanotubes grown by chemical-vapor deposition. The thermal diffusivity along the alignment direction was also determined using a self-heating 3ω method. The agreement between the measured thermal diffusivities with the two techniques is between 2% and 13% in the tested temperature range. The thermal diffusivity along the alignment direction decreases slightly with temperature in the 80–300-K temperature range and is ∼ two orders of magnitude smaller than the thermal diffusivity along the planes of graphite. The thermal diffusivity across the alignment direction is ∼25 times smaller than along the alignment direction and is between 50% and five times smaller than the thermal diffusivity across the planes of graphite in the measured temperature range.