Investigation on Relationship between Breakdown Strength Enhancement of Composites and Dielectric Characteristics of Nanoparticle

In this work, the relationship between dielectric characteristics of nanoparticle and its effects on dielectric breakdown strength of Epoxy was investigated. The dielectric characteristic was tailored through silica surface encapsulation on TiO2. It was found that in contrast to raw TiO2, addition of TiO2@ SiO2 core-shell nanoparticle obviously improved the dielectric breakdown strength of epoxy resin. Meanwhile, peculiar increase of resistivity was also observed. Based on the results, a mechanism through "barrier effect" by electric double layer was proposed to explain this enhancement, which was regarded closely associated with the highly polarizable and surface insulating features of TiO2 after silica encapsulation. Experimental validation was also conducted with permittivity and space charge distribution measurement of composites. It was concluded that the high polarizability and surface insulativity firstly favored formation of the double layer, synergistically from which the resulted space charge in homo-pattern then suppressed excessive charge injection through Coulomb repulsive interaction, and improved electrical strength by retarding exorbitant localized field occurrence which had been found to be direct cause of breakdown when it exceed a critical value.