TiO2-MWCNTs Nanofillers Enhanced DC Surface Flashover Characteristics of Epoxy Nanocomposites in Vacuum

Surface flashover occurring along the gas-solid interface is one of the challenges inhibiting further development of electrical equipment and electronic devices. To improve the surface flashover voltage, various methods have been proposed, among which nanocomposites have attracted much attention. Nevertheless, the underlying mechanism is still unclear, especially in terms of microscopic properties. In the present study, with three different nanofillers, i.e., nonconductive (TiO
₂
), conductive (multiwall carbon nanotubes, MWCNTs) and nonconductive-conductive (TiO
₂
- MWCNTs), the vacuum DC flashover characteristics of those epoxy nanocomposites are investigated, which exhibit enhanced flashover voltages by about 14.15%, 23.07% and 36.04%, respectively at optimized nanofiller concentrations. The enhancement is attributed to the increased surface trap depth with nanofillers, which is characterized and analyzed by the surface potential decay measurement. It is proposed that deep traps not only inhibit the carrier transport but also vary the secondary electron emission, resulting in the improved flashover performance. With both TiO
₂
(2 wt%) and MWCNTs (0.1 wt%) nanofillers, the epoxy nanocomposite has the deepest trap level of 1.14 eV and highest flashover voltage of 44.97 kV. Results indicate the multiple nanofillers are a promising way to enhance the surface flashover voltage.