Turning carbon nanotubes from exceptional heat conductors into insulators.

Thermal conductivity (� ) of isolated carbon nanotubes (CNTs) is higher than theof diamond; however, in this Letter we show that theof a packed bed of three-dimensional random networks of single and multiwall CNTs is smaller than that of thermally insulating amorphous polymers. The thermoelectric power (� ) of the random network of CNTs was also measured. Theof a single wall nanotube network is very similar to that of isolated nanotubes and, in contrast with � , � shows a strong dependence on the tube diameter.