Charge Transport Characteristics of Core-Shell SiC Filled Epoxy Nanocomposites

Core-shell structured filler is helpful for the improvement of the nonlinear conductivity characteristics of nonlinear resistive field grading materials, but the effect of its filler loading on the charge transport characteristics of these materials is rarely reported. To aim at this, the core-shell SiC@SiO2 nanoparticles were fabricated at first, and were filled into epoxy matrix to prepare nanocomposites with 0, 1, 3, 5, and 10 wt%. The nanoparticles’ microstructure were characterized, whereas the relative permittivity, thermally stimulated current (TSC), conductivity, and surface potential decay (SPD) characteristics of epoxy nanocomposites were measured, respectively. Experimental results show that the relative permittivity decreases at first and then increases with the increase in filler loading. New shallow traps were introduced by core-shell nanoparticles when the filler loading is larger than 1 wt%, and increases with the filler loading. Only when the filler loading is no less than 5 wt%, the nanocomposites show distinct nonlinear conductivity characteristics, which are attributed to the presence of large amount of new shallow traps. The enhanced nonlinear conductivity characteristics are responsible for the SPD.