Characterizing epoxy composites filled with carbonaceous nanoparticles from dc to microwave

We have used several methods to measure the effective complex permittivity of epoxy composites filled with carbonaceous (carbon black, single-walled carbon nanotube, and multi-walled carbon nanotube) over nine decades of frequency. The composite samples were fabricated by shear mixing. 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. The likely transport mechanisms responsible for the dielectric relaxation in these samples can be modelled by the dipolar relaxation and anomalous low-frequency dispersion below and above percolation, respectively. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4798296]