Aligned Carbon Nanotube to Enhance Through Thickness Thermal Conductivity in Adhesive Joints (Preprint)

摘要

Currently out of plane thermal conductivity (Kz) in adhesive joints fails to meet the needed Kz at the overall system level. Carbon nanotubes theoretically have an extremely high thermal conductivity along the longitudinal axis and according to molecular dynamics simulations the value can be as high as 3500 W/mK at room temperature for multi-walled carbon nanotubes (MWCNT). The thermal conductivity along the radial axis for MWCNTs is between 10-15 W/sq mK. Studies to increase Kz for adhesive joints only had minimal enhancement in the thermal conductivity. In order to utilize the superior thermal conductivity of the MWCNTs along the axial direction; vertically aligned MWCNTs have been used in this study. Vertically aligned MWCNTs have been grown on silicon wafers. The aligned nanotube array has been partially infused with epoxy. Selective reactive ion etching (RIE) of the epoxy revealed the nanotube tips. In order to reduce the impedance mismatch and phonon scattering at the interface, gold is thermally evaporated on the nanotube tip. A MEMS based steady state thermal conductivity measurement technique has been designed to assess the thermal conductivity of the device with special attention to the interface/transition zone.