Thermal characterization and scaling of a nanodielectric composite for use in compact ultra-high voltage capacitors
The University of Missouri has been developing compact capacitors for use in high voltage, pulsed power and directed energy applications. The capacitors are made from a proprietary nanodielectric, MU100, which is a polymer-ceramic composite composed of nanoceramic barium titanate and a proprietary binding agent. MU100 exhibits several novel qualities including high dielectric strength along with facile machining and assembly characteristics. The material was successfully used to fabricate capacitor prototypes capable of repeatable performance at 500 kV with lifetimes greater than 104 shots. These initial prototypes were smaller than comparable commercial devices by a factor of 2.5. The dielectric constant, thermal expansion, and dielectric strength were measured for MU100 from -40ºC to 120ºC. The results demonstrate the nanodielectric has a strong stability both electrically and mechanically across the entire temperature test range. The maximum capacitance percent difference of MU100 relevant to standard temperature was 9.8% occurring at 130ºC. The maximum linear coefficient of thermal expansion found was 1.5 PPM/ºC. The dielectric strength was found to show virtually no change with temperature. The MU100 substrates were then scaled to a diameter of 6.35 cm to allow for further size reduction of the final capacitor. With a 6.35 cm diameter design, a volume reduction of over 4 times, relative to commercial capacitors, was achieved while maintaining the same electrical performance as the first-generation device. The theory, methodologies, and results for characterizing and producing these capacitors is discussed in this work.
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