Transport mechanisms and dielectric relaxation of epoxy nanocomposites in DC to microwave range

Using several methods we measure the effective complex permittivity of epoxy composites realized by shear mixing and filled with carbonaceous carbon black (CB), single wall CNT (SWCNT), and multiwalled carbon nanotube (MWCNT) over nine decades of frequency. The spectral analysis of permittivity of these nanocomposites is in good agreement with Jonscher´s modelling. We point out, taking these examples, that the experimental frequency dependence of the effective permittivity has a range of interesting properties. Likely transport mechanisms responsible for the dielectric relaxation in these samples can be modeled by the dipolar relaxation and anomalous low frequency dispersion (LFD) below and above percolation, respectively.