Enhanced surface flashover performance of oriented hexagonal boron nitride composites via anisotropic charge transportation

Surface flashover is a crucial issue for the miniaturisation of electronic facilities in military, industrial, and aerospace engineering. The oriented hexagonal boron nitride (hBN) composites, due to excellent thermal and electrical insulating properties, show a potential application in high-voltage power equipment, while the surface flashover performance of hBN composites dependent on oriented hBN texture is rarely reported. The effects of hBN orientation and contents on the surface flashover performances of oriented hBN composites are investigated. The isothermal surface potential decay of the oriented hBN composites was also studied. It is found that the charge transportation could be adjusted by the hBN orientation, thus regulating surface flashover strength. The DC flashover voltage of the in-plane oriented hBN composites with a thickness of 15 μm reached the maximum of 27.6 kV at the hBN loading of 20 wt%, 14.5% higher than that of the pure resin. The carrier mobility of out-of-plane oriented hBN composites is about three times greater than that of the in-plane oriented composites, indicating that the charges are easily transported along the hBN basal plane. The larger carrier mobility causes charge dissipation in composites near the electrode at the hBN basal plane parallel to the axis of electrodes and inhibits the distortion of the surface electric field on the composites, thus enhancing the surface flashover. Consequently, developing oriented insulators for high-voltage applications and enabling an optimum insulation design would be beneficial because of the compactness and high reliability of power apparatus for use in power grids.