Noncontact thermal characterization of multiwall carbon nanotubes

In this work, a photothermal experiment is designed and conducted to characterize the thermal transport in carbon nanotubes (CNTs) along the axial direction exclusively. We characterize the thermal contact resistance between CNTs and the substrate. The measured value demonstrates a sound thermal contact between them. Our experimental result reveals a low thermal conductivity of the CNTs along their axial direction. The unique structure of the CNTs characterized in our work indicates that the thermal transport in the axial direction is across the carbon atomic layers. This explains why the measured thermal conductivity is much lower than theoretical predictions, in which the thermal conductivity is along the atomic layer direction. In addition, our transmission electron microscope observation of the CNTs reveals poor structural qualities, which can strongly enhance phonon scattering and reduce the thermal conductivity. (C) 2005 American Institute of Physics.