Study on electrical properties of micro-nano structured epoxy composites

With the aim of reducing the insulation faults in GIS and achieving the purpose of GIS device miniaturization, it is very important to develop a new type insulation material. In this paper, the micro-nano Al₂O₃/Epoxy composites were proposed, and its dielectric breakdown strength was investigated. Nano-fillers and micro-fillers (α-Al₂O₃ with a purity of 99.9%, particle size range at 12~21 μm for micro fillers, and average particle size with 30 nm for nano fillers) were dispersed in the epoxy resin with shear force and ultrasonic vibration. The specimens were produced by a curing reaction with the hardener. Six kinds of material were prepared for this investigation, which were neat epoxy, nano-composite (loaded with 5 wt% nano-Al₂O₃ fillers), nano-composite (loaded with 5 wt% nano-TiO₂ fillers),micro-composite (loaded with 65 wt% micro-Al₂O₃ fillers), nano-micro-mixture-composites (loaded with 2 wt% nano-Al₂O₃ fillers and 63 wt% micro-Al₂O₃ fillers), nano-micro-mixture-composites (loaded with 2 wt% nano-TiO₂ fillers and 63 wt% micro-Al₂O₃ fillers). Dispersion of the micro and nano Al₂O₃ in the epoxy resin was observed through SEM, and thermal behavior was analyzed with Thermo-Gravimetric Analysis (TGA) and differential scanning calorimeter (DSC). The dielectric constant and dielectric loss were measured by broadband dielectric spectrum test facility. Dielectric breakdown experiments were carried out through the sphere-plate sample-sphere configuration under AC voltage.