Thermal Diffusivity of Compounds Loaded with Carbon Nanofibers

In this work, the thermal enhancement in silicone grease-based compounds as a function of carbon nanofiber (CNF) volume fraction was investigated. The thermal diffusivity of the samples was determined by a photopyroelectrical technique with a sample thickness scan. The results show that heat transport on these compounds strongly depends on the CNF volume fraction, due to the high thermal conductivity of CNF compared to the matrix; hence, a low loading percentage of the fibers produce a significant growth in the thermal diffusivity of the composite. The results show that the thermal diffusivity values of the CNF-silicone composite are comparable with commercial thermal compounds based on diamond and Ag microparticle fillers. The thermal conductivity of the samples was calculated, and its enhancement was analyzed using a modified Lewis-Nielsen model, taking into account the dependence of the maximum packing fraction and the form factor with the aspect ratio of the CNF. The influence of the Kapitza thermal resistance was discussed. These materials might find practical applications in systems in which the CNF improves the ebbing of heat away from semiconductor devices or in any other application in which heat dissipation is needed.