Electrical and thermal properties of polyimide/silica nanocomposite

The electrical and thermal properties of thin films of polyimide/silica nanocomposites prepared via sol-gel process were studied as a function of nanosilica particles content, temperature and applied field frequency. It was found that the dielectric constant and dielectric loss of the nanocomposites decrease with both the frequency and the nanosilica content, while increase with temperature. The AC-conductivity measured in frequency range 200 kHz-1.5MHz decreases with the filler concentration and increases with increasing temperature. For the (25 wt%) nanocomposite, it was found that the AC-conductivity increases with temperature, and the Cole-Cole plots showed that the calculated activation energy and relaxation time decrease with temperature. The observed thermal conductivity increases gently with temperature. The empirical universal law was used to fit the observed electrical data under the measuring conditions.