In-Situ Electric Field-Assisted Preparation of SiC/Epoxy Composite Coatings with Oriented Filler Structure

The SiC/epoxy nonlinear conductive coating has shown great potential in DC GIS/GIL for its ability to suppress surface charge accumulation and homogenize the electric field. However, a high doping amount severely restricts its further application. In this paper, an in-situ electric field-assisted technology is introduced to fabricate epoxy-based composite coatings with aligned SiC fillers. In-situ microscopic observation and micro computed tomography (Micro-CT) characterizations reveal the 3D orientation of the coatings. A comparison with uniformly doped samples at a higher concentration shows that the oriented coatings at a lower concentration have more continuous conductive paths, facilitating carrier migration. As a result, compared with uniformly doped coatings, the oriented coatings exhibit significantly lower trap levels and higher shallow trap densities. Moreover, combining experimental and simulation results reveals that increasing the in-situ electric field amplitude can significantly enhance the permittivity and DC nonlinear conductivity in the orientation direction. This increase alleviates local electric field distortion and improves the DC flashover voltage of the samples. This technology is more effective than simply increasing the doping amount, showing great potential in the insulation design of high-voltage DC devices.