Electrical and thermal conductivities of carbon nanotube-epoxy composites: Modeling and characterization

The motivation of this work is to develop adhesive layers from epoxy based nanocomposites using carbon nanotubes (CNTs) for use in thermal management applications in microelectronic devices. The focus of the experimental characterization is to measure the enhancement of electrical and thermal conductivities of polymeric nanocomposites consisting of XD grade CNTs as a function of a range of weight percentages. Comparison of the results obtained for these CNT-epoxy nanocomposites are made with other nanocomposite results from the literature and with initial micromechanics modeling efforts. The micromechanics model is centered on the use of the generalized self-consistent composite cylinders method in conjunction with multi-phase averaging methods, and is employed to predict the effective electrical and thermal properties of nanocomposites with randomly oriented CNTs, where the hollow nature of the CNTs and the possible presence of interphase regions precludes the direct use of the Eshelby solution. Interphase regions are identified to phenomenologically introduce nanoscale effects such as the thermal Kapitza resistance and electron hopping. It is observed that, as a result of the different character of the nanoscale effects associated with electrical and thermal properties, nanotube-polymer nanocomposites demonstrate a percolalion behavior in electrical conductivity not observed in thermal conductivity.