Effect of filler materials and pre-processing techniques on conduction processes in epoxy-based nanodielectrics

Research on nanodielectrics has grown considerably in the last few years, in a bid to tap their potential as a class of improved high voltage insulating materials with unique properties. In the authors´ group, improvement in dielectric properties of epoxy-resin samples (e.g. resistance to surface degradation) through the use of nano-sized alumina fillers was observed. Further, the improvement was even more pronounced when the nanometric fillers were pre-processed before use. The current work studies the effect of nano-fillers on polarisation and depolarisation currents of epoxy-based composites. Effect of filler materials and pre-processing techniques is also studied. The filler materials used in the composite are nanometer-sized spherical alumina (Al₂O₃), titania (TiO₂) and zinc oxide (ZnO) particles. It is believed that nano-fillers affect dielectric properties essentially due to the large interface area between bulk and filler materials. In an attempt to identify the polarisation mechanisms involved in the various samples, the absorption and desorption currents are studied by varying several parameters like electrification time, temperature, electrode material. It has been conclusively shown that addition of nanometric fillers considerably changes conduction behaviour. The zinc oxide (ZnO) filled composites draw lowest absorption current (steady value) followed by titania (TiO₂) and alumina (Al₂O₃) filled composites respectively. It is observed that preprocessing techniques like heating of particles and functionalization of heated particles before preparation of composites decrease conduction current as compared to composites with as-received fillers.