Space charge characteristics of graphene oxide/epoxy resin nanocomposites under polarity reversal voltage

In this paper, the grapheme oxide/epoxy resin (GO/EP) samples were prepared by adding monolayer grapheme into epoxy matrix with 0.5 wt% of nanofiller loading. For comparison purposes, the samples of pure epoxy resins (EP) were also prepared. Polarity reversal stresses of 20 kV/mm were applied on the samples at 80 C and 100 C, respectively, which reversal periods were set to 60 s. The space charge in the sample bulks during polarity reversal was simultaneously measured per 1 s in pulsed electro-acoustic (PEA) method. At 80 C, a small amount of space charge had been accumulated in the bulks of EP samples during first DC poling period, which had little effect on the electric field distortion. At 100 C, a large amount of space charge had been accumulated in the bulks of EP samples. Little space charge dissipated after the reversal, which seriously distorted the electric field distribution both before and after the reversal. By contrast, the accumulation of space charge in the bulks of GO samples was not obvious. No significant space charge accumulation was measured in the bulks of GO samples at 80 C. At 100 C, a small amount of space charge was observed in the bulks of GO samples, whose effect on the electric field distortion was also not obvious. The addition of graphene oxide mitigated space charge accumulation and uniformed the electric field distribution in the filled EP compared with the unfilled EP.