Experimental study on breakdown characteristics of propylene carbonate-based nano-fluids under microsecond pulses

As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 10⁹ Ω·m and low freezing temperature (-49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NFs is composed of PC mixed with 0.5-1.4 vol% BaTiO₃ (BT) nano-particles at mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol% BT nano-particles at mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage is 33% higher than that of PC as the volume concentration of nano-particles with 100 nm average diameter is 0.9%, and the breakdown voltage is 40% higher as the volume concentration of nano-particles with 30 nm average diameter is 0.6%. The possible reason of these phenomena is the interfaces between nano-fillers and PC matrices providing myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.