Effect of Gas-phase Fluorination on Trap Level of Nano-Alumina / Epoxy Resin Nanocomposites

Abstract

In this work, nano-alumina / epoxy resin nanocomposites with nano-alumina fraction of 1, 3 and 5 wt.% were prepared and subsequently fluorinated at 40°C in F2/N2 gas mixture (20/80 v/v) with pressure of 0.05 MPa. The nano-alumina was treated by the saline coupling agent of $\gamma$-aminopropyltriethoxysilane (KH550) to restrict the aggregation. The chemical bonding was examined by Fourier transform infrared spectroscopy (FTIR) which has indicated the molecular-chain scission during the gas-phase fluorination. The trap density and trap level distribution in the nanocomposites before and after fluorination were investigated by thermally stimulated current (TSC). The results shown that fluorination introduces shallow traps on the surface which increases the surface conductivity. Hence depth of charge traps are considerably reduced after fluorination. The results shown that nanocomposites with 1 wt.% nano-alumina appeared with deeper traps and higher trap energy level comparing with the other samples. However with increased nano-alumina mass fraction, e.g. 3 and 5 wt.%, considerable over-lapping interaction zones appear, that results in the reduced trap energy level.