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 3 omega 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 similar to two orders of magnitude smaller than the thermal diffusivity along the planes of graphite. The thermal diffusivity across the alignment direction is similar to 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. (c) 2005 American Institute of Physics.