Thermal conductivity of multiwalled carbon nanotubes

Thermal conductivity of multiwalled carbon nanotubes (CNT's) prepared using a microwave plasma chemical vapor deposition system is investigated using a pulsed photothermal reflectance technique. We find that the average thermal conductivity of carbon nanotube films, with the film thickness from 10 to 50 \ensuremath{\mu}m, is around 15 W/m K at room temperature and independent of the tube length. Taking a small volume filling fraction of CNT's into account, the effective nanotube thermal conductivity could be $2\ifmmode\times\else\texttimes\fi{}{10}^{2}\mathrm{W}/\mathrm{m}\mathrm{}\mathrm{K},$ which is smaller than the thermal conductivity of diamond and in-plane graphite by a factor of 9 and 7.5, respectively.