CNT-based Thermal Interface Materials for High-Temperature Applications

posted Jun 14, 2013, 8:42 AM by Timothy Fisher   [ updated Jun 16, 2013, 5:59 AM by Tim Fisher ]

Student: Menglong Hao

Faculty: Tim Fisher, Tim Sands

Sponsor: Department of Energy / General Motors

Summary: Thermoelectric Modules (TEM) are being designed to harvest heat at a higher temperature not only because of a higher conversion efficiency, but also because many thermal energy sources that are traditionally too hot to for conversion by other means may become accessible with high temperature TEMs. However, the harsh working environment also imposes serious challenges to all components of TEMs. A reliable Thermal Interface Material (TIM) is crucial to the successful implementation of TEMs. In addition to mechanical robustness, a good TIM should have low thermal resistance in order to maximize the electric power output of the module. At high working temperatures, differences in coefficients of thermal expansion on both sides of an interface are the most common cause of the failure. TIMs based on carbon nanotube (CNT) arrays developed in our group has achieved much success in terms of reducing thermal resistance. CNT-based TIMs are also ideal candidates for high temperature applications because their excellent mechanical compliance could substantially reduce thermal fatigue failures. BN (boron nitride) treatment is used to extend the thermal stability of CNTs.  CNTs in combination with brazing alloys are being studied to further optimize the thermomechanical properties of interfaces in TEMs as well as in other high temperature applications. A high temperature testing rig for TIMs is being developed with the schematic shown above (courtesy of Kim Saviers).