Study of dielectric relaxations in zinc oxide-epoxy resin nanocomposites

Broadband dielectric relaxation spectroscopy (DRS) (10(-3) to 10(6) Hz) and thermally stimulated depolarization currents (TSDC) techniques were used to investigate dielectric relaxations and molecular mobility in nanocomposites based on epoxy resin (ER) filled with nano-conductive particles. ZnO and Zn97%OAl3% nanoparticles were used as fillers and the dielectric measurements were performed at room temperature. The obtained data were first analysed in terms of the dielectric permittivity and then transformed to electric modulus to highlight conduction process. Interfacial relaxation is found to be strongly dependent on the presence of nano-filler particles. The overall molecular mobility is found to decrease in the glassy state in the nanocomposites as compared to the ER while it increases near the glassy-rubber transition. Heterogeneity introduced by the nano-filler particles has increased the space charge density in epoxy nanocomposites. AC conductivity of both ER-matrix and epoxy nanocomposites is frequency-dependent, follows the exponential law or sigma(ac) similar to omega(s) and shows a dc plateau in the low frequency range. An increase in dc conductivity was notified in nanocomposites. (C) 2008 Elsevier B.V. All rights reserved.