Inter-Carbon Nanotube Contact and Thermal Resistances in Heat Transport of Three-Phase Composites

Single-walled carbon nanotubes (SWNTs) tend to aggregate into bundles due to van der Waals forces during the fabrication of the composite. A computational model using an off-lattice Monte Carlo method is developed to systematically investigate the effects of SWNT bundles, the number of SWNTs per bundle and the thermal boundary resistance (TBR) at the SWNT-SWNT interfaces on the effective thermal conductivity (K-eff) of three-phase composites. It is found that the aggregation of the SWNTs in bundles can reduce significantly the K-eff of the composites with SWNTs oriented parallel or randomly to the heat flux direction, but it enhances slightly the K-eff of those with SWNTs perpendicular to the heat flux direction. The K-eff of the composites also decreases when more individual SWNTs aggregate in each bundle and with larger SWNT-SWNT TBR values. The thermal transport mechanism within the composites is dominated by a critical SWNT-SWNT TBR of 0.155 x 10(-8) m(2)K/W.