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 10(9) 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 NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of 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 of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

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It is found that propylene carbonate (PC)‐based nano‐fluids (NFs) exhibit substantially larger breakdown voltages and higher breakdown stabilities than that of pure PC when they contain various nano‐particles with different conductivity and permittivity. However, both the fast electron scavenging model and the potential well model fail to explain these experimental phenomena rationally. It is proposed that the interaction region between nano‐particles and PC will create myriad trap sites and capture electric charge carriers effectively. Therefore, the trapped and accumulated homo‐charges can weaken the electric field intensity, increase the charge injection barrier height and reduce further charge injection in the vicinity of electrodes. This is the main physical mechanism for the enhanced dielectric performances of PC‐based NFs.

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