Electrical properties of polymer nano-composites based on oxide and nitride fillers

Four polyethylene based nano-composites containing either silica or silicon nitride were prepared. After verifying their compositions and morphologies, their dielectric properties were followed as a function of conditioning (absorbed water content). The dielectric loss and DC breakdown strength were found to be strongly dependent on conditioning whilst the properties of a control sample (with no nano-filler) were found to be invariant. Under ambient conditions, silicon nitride provides a composite with reduced dielectric loss and increased breakdown strength compared to an analogous system employing silica. Silicon nitride based systems exhibit improved breakdown strength relative to the host polymer when dried and therefore hold significant potential for use in future HVDC cables.