The impedance characterization of hybrid cnt-silica epoxy nanocomposites

Carbon nanotubes grafted onto the surfaces of spherical silica gels were incorporated into epoxy polymer to yield nanocomposite. The efficiency of this approach in controlling the dispersion of carbon nanotubes within the epoxy matrices was observed from the scanning electron microscope images, where the nanotubes remained strongly attached to the surface of the gel. As the micron-sized silica introduced a large excluded volume within the polymer matrices, the nanotubes dispersion remained restricted to a region along the silica surface and bundle formation was prevented. This arrangement aided the formation of an electrically conductive network in an epoxy matrix, where the critical percolation threshold (pc) was calculated as pc = 0.5 wt., which is equivalent to 0.16 wt. % nanotubes, as previously determined from thermal gravimetric analysis. The equivalent circuit model to represent the electrical properties was proposed to analyse the interactions between the real impedance (Z’) and imaginary impedance (Z’’) components of the hybrid nanocomposites. The two parallel RC circuits were found to fit the data well, describing the interaction between epoxy and conductive silica– nanotubes hybrid.