Dielectric properties and AC conductivity of epoxy/hybrid nanocarbon filler composites

The electrical properties of epoxy composites filled with hybrid filler graphite nanoplatelets/carbon nanotubes (GNP/CNT) at different concentrations (0–5wt.%) were measured using AC impedance spectroscopy with frequencies ranging from 1kHz to 2MHz. The complex impedance and real and imaginary parts of permittivity and electrical conductivity were determined. It was found that dielectric permittivity and electrical conductivity increase with increasing content of hybrid carbon filler and are characterized by percolative behavior. It was found that substitution of graphite nanoplatelets by carbon nanotubes promotes the shift of percolation threshold into lower filler content and enhances the electrical conductivity, permittivity, and dielectric loss (tanδ) of composites compared with composites filled only with graphite nanoplatelets. The increase of carbon nanotube content in composites increases the electrical conductivity and weakens its dependence on frequency (related to electron tunneling transport process in composites) due to more effective formation of a continuous carbon network.