Anisotropic thermal diffusivity of aligned multiwall carbon nanotube arrays

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.