Carbon Nanotube Arrays for Enhanced Thermal Interfaces to Thermoelectric Modules

Abstract

Thermoelectric materials exploit the Seebeck effect in which an electric potential is generated from a supplied temperature gradient. High thermal conductance through the interfaces between the thermoelectric module and its heat source and sink is crucial for generating maximum power. Primarily due to increased surface contact area and inherently low diffusive thermal resistance, carbon nanotube arrays can provide low thermal interface resistance. Vertically aligned carbon nanotube arrays are synthesized on one or both sides of copper foil by microwave plasma chemical vapor deposition. Growth of similar structures on graphitic foil resulted in carbon nanofiber arrays. The products become insertable thermal interface materials. The thermal interface materials are evaluated by measuring the efficiency of a standard bismuth-telluride thermoelectric module with the thermal interface materials applied. Experiments indicate that a copper foil coated on both sides with carbon nanotubes increases thermoelectric power generation by 60% relative to the absence of thermal interface materials and by 25% relative to a bare copper foil. Photoacoustic results indicate that the thermal interface resistance decreases due to the presence of a carbon nanotube, reaching a minimum of for a double-sided carbon nanotube film on copper foil. However, carbon nanofiber arrays on graphitic foil showed no improvement in thermoelectric performance or decrease in thermal interface resistance.