Abstract
Electrical and thermal conductivity of materials are typically correlated, while some applications, including thermoelectrics, require these parameters to be controlled independently. Such independent control of thermal and electromagnetic properties can be achieved by using nanocomposites. In this study, nanocomposites were produced by mixing a small amount of carbon nanofibers (CNF), carbon coated cobalt (Co), and nickel nanowires (NiNW) with paraffin, which has low thermal and almost zero electrical conductivity. The fraction of nanoinclusions in the paraffin matrix was very low (below 1%). We showed that the thermal properties of nanocomposites are essentially the same as those of pure paraffin, while electromagnetic properties are significantly different. To determine the dependence of the heating rate on filler concentration, paraffin-based samples were heated in a microwave oven. We found that the heating rate of nanocomposites made of carbon nanofibers is much greater than that of any other nanocomposites. These findings suggest that at 2.45 GHz frequency, the heating rate is mostly controlled by the electrical losses in the fillers. The theoretical model predicts that the heating rate increases linearly with the particle concentration, which is in agreement with the experimental data.