Ceramic-Polymer Composite for High Energy Density Capacitors

The initial focus of the investigation was to look at various process variables to optimize the DC breakdown strength of the composite material. This processes included optimization of ceramic powder loading ratios, removal of agglomeration and particulate defects, various dispersion techniques, and polymer cure cycles. These studies produced materials that exceeded 1.9 J/cc material energy densities when cast as simple, single-layer 5.1cm disk capacitors. The secondary focus of the study was to take these quality materials and develop a design and manufacturing process that would allow for higher energy capacitor topologies. The goal of this portion of the study is to produce 100 kV capacitors with energy densities of approximately 1 J/cc that are capable of peak powers between 2-5 GW. A great deal of effort has been expended to overcome manufacturing issues which allow more complex multilayer capacitors to be cast. This portion of the investigation is ongoing, but to date, finished packaged capacitors that exceed 0.6 J/cc have been built with DC breakdown at mean fields as high as 1.25MV/cm. An example capacitor in this class is 6.35 cm x 7.62 cm x 0.71 cm. The capacitance was ~4.2 nF and failure occurred at >160 kV. At fields near DC breakdown, these capacitors have exhibited limited lifetime. Studies are currently underway to investigate the lifetime issue and determine whether it is an intrinsic property of the material or is a capacitor design issue. The peak power capability of these devices is also under investigation. Results from these portions of the study will be available. Although early in development, these capacitors show promise in advancing the state of the art in high energy density, high power capacitors.