Study on the Nonlinear Conductivity of SiC/ZnO/Epoxy Resin Micro- and Nanocomposite Materials

Abstract

To investigate the inhomogeneous distribution of electric fields in insulating equipment and components, five nonlinear-conductance composite materials based on epoxy resin (EP) (nano-SiC/EP, nano-ZnO/EP, micro-ZnO/EP, nano-SiC/ZnO/EP, and nano-micro-SiC/ZnO/EP), were prepared using nano-SiC, nano-ZnO, and micro-ZnO particles as fillers. The mass fractions of the inorganic fillers were 1, 3, and 5 wt%, respectively. The direct current (DC) voltage characteristics of the composites showed that the electrical conductivities and nonlinear coefficients of the composites utilizing single-filler types increased with increasing inorganic filler content. Under the same conditions, the conductivity and nonlinear coefficient of SiC/EP were both larger than those of the nano-ZnO/EP and micro-ZnO/EP. However, the nonlinear coefficient of the composites was significantly affected by the simultaneous addition of the two inorganic fillers, micro-ZnO and nano-SiC. When the content ratio of micro-ZnO to nano-SiC was 2:3, the nonlinear coefficient of the composite reached a maximum value of 3.506, significantly higher than those of the other samples. Compared with the nano-SiC/EP, micro-ZnO/EP and nano-ZnO/EP composites with 5 wt% inorganic filler, the nonlinear coefficient of the two-filler composite was greater by a factor of 0.82, 2.48, and 5.01, respectively.

Nonlinear Electrical Conduction in Polymer Composites for Field Grading in High-Voltage Applications: A Review

“…As described in the previous sections, the switching field intensity decreases and the conductivity increases with increasing the filler concentration [ 95 ]. The nonlinear coefficients of composite materials are significantly higher than that of undoped epoxy resin, and the nonlinear coefficients increase with increasing filler concentrations.…”

“…Therefore, the micro-ZnO inorganic filler had a greater influence on the nonlinear coefficients. Compared to the composites of 5 wt.% SiC/EP, micro-ZnO/EP, and nano-ZnO/EP, the nonlinear coefficient of 5 wt.% 3:2 micro-ZnO/SiC/EP composites was greater by a factor of 0.82, 2.48, and 5.01, respectively [ 95 ]. These results show that working with a combination of different fillers helps to tune the final electrical properties of composites and obtain different nonlinear conduction properties, depending on application specifications.…”

“…( a ) nano-SiC/EP composites, ( b ) nano-ZnO/EP composites, and ( c ) micro-ZnO/EP composites. Reprinted from [ 95 ].…”

“… Conductivity–electric field characteristic curves of epoxy-based composite materials with different fractions of inorganic fillers: ( a ) nano-ZnO/SiC/EP nanocomposites and ( b ) micro-ZnO/SiC/EP micro/nanocomposites. Reprinted from [ 95 ]. …”

“…CB grains may short-circuit certain SiC contacts, while a lower nonlinearity threshold field and nonlinearity exponent could be expected. Finally, Hu et al reported the characterization of composites fabricated with an epoxy resin and different fillers (nano-SiC, nano-ZnO, micro-ZnO) [95]. The mass fractions of inorganic fillers were 1, 3, and 5 wt.%.…”