Influence of hierarchy structure on electrical properties of gradient-distribution aluminum oxide/polyethylene nanocomposites

In the recent decades, the phenomena of space charge accumulation in the high voltage direct current (HVDC) insulation have attracted more and more attention. In this paper, the gradient-distribution multi-layered Al2O3/low density polyethylene (LDPE) nanocomposites were prepared via layer-by-layer melting blending and hot pressing method. Morphologies and electrical properties of these gradient-distribution structured composites were discussed. Results showed that this unique structure could largely enhance the breakdown strength of LDPE. The breakdown strength of the LDPE nanocomposites varied with nano-Al2O3 concentrations, and it could reach to 200 kV/mm for the LDPE nanocomposites. Besides, space charge of the LDPE nanocomposites was measured by pulsed electro-acoustic (PEA) method. The charge profiles indicated that space charge suppression of the gradient-distribution multi-layered composites was better than that of the monolayer ones with general mean-distribution structure. Their excellent insulating properties were attributed to the trap which exists in the surface, and that could well inhibit the charge injecting into the materials.