Broadband dielectric spectroscopy of silicone rubber nano-composites

In this paper, the impact of nano-fillers on the dielectric characteristics of nano-Al₂O₃/silicone rubber nano-composites is studied. Silicone rubber composites with the loading of 1%, 2%, 3% and 4% nano-Al₂O₃ are made by “bubble method”, and coupling agent is used in this preparation process to improve the dispersion further. The dispersion of nano-fillers in the matrix is observed by transmission electron microscope (TEM). The permittivity and tan delta of the composites at frequency 10⁶-10^-3Hz is measured by Novo-control impedance analyzer. The results show that, at the frequency from 10⁶ to 10¹ Hz, the permittivity of all the composites remains almost constant and tan delta increases gradually, and at 101 to 10^-3 Hz, real permittivity ε´ tends to increase, especially in the unfilled and 1% loading sample. With the increasing of filler loading from 1% to 3%, the permittivity and tan delta of the composites decrease and then increase when the loading reaches 4% in all the test frequency. Cole-Cole plot is used to analyze the change of the conductivity of the composites.