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Polymer nanocomposites are a promising substitute for energy-storage dielectric materials in pulsed power systems. A barium titanate/polyvinylidenefluoride (BT/PVDF) nanocomposite is one of the most widely studied composite systems due to its comprehensive excellent dielectric properties. As the dielectric response of nanocomposites depends strongly on the size of the fillers, in this study, BT/PVDF nanocomposites with 92.3 nm, 17.8 nm and 5.9 nm BT particle fillers are fabricated to reveal the particle size effect of the fillers on the energy storage performance of the polymer nanocomposites. Owing to the small particle size and good dispersibility of the nanofillers, the nanocomposites with smaller BT particles show more uniform and denser microstructures. Moreover, with the increase of the filler fraction, the dielectric results indicate a breakdown strength enhancement in the nanocomposites with sub-20 nm BT fillers, which is quite different from the nanocomposites with normal fillers, and therefore leads to superior energy storage performance. This study provides experimental evidence for the application of ultrafine nanofillers in the nanocomposite for future energy storage systems.

Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride-hexafluoropropylene [P(VDF-HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis loop, is employed as the polymer matrix. Highly dispersive Ba 0.6 Sr 0.4 TiO 3 (BST) nanoparticles with an average particle size of 12.1 nm are utilised to improve the polarisation of the blend film without sacrificing the dielectric strength. Uniform nanocomposite films with high flexibility and excellent energy-storage performance are obtained. Especially, due to the optimisation of both polymer matrix and fillers, the BST modified P(VDF-HFP)/PMMA blend films show improved breakdown strength and depressed energy loss, which leads to an enhanced energy density of 10.3 J/cm 3 at 378 kV/mm.

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Nanomaterials are playing more and more important roles in modern industry, while the large-scale fabrication and dispersibility still need to be addressed. This report explores the uniform fabrication and morphology control of ultrafine BaTiO 3 (BT) nanocrystals using a 'TEG-sol' method. By varying the reactant concentration, the obtained product sols, Ba/Ti ratios, structure and morphology of the nanocrystals are investigated. The results reveal that under low concentrations (0.4-0.8 mol/L), transparent sols with uniform BT nanocrystals are obtained. Increasing the concentration to higher than 1.0 mol/L, BT precipitates with abnormal large crystals are obtained. Moreover, the Ba/Ti ratio variation further reveals that the surface organics are critical to the control of crystal size and morphology. This investigation is potential to be extended to the synthesis of various perovskite nanocrystals.