Effect of micro-ceramic fillers in epoxy composites on thermal and electrical stabilities of GdBCO coils

This paper reports the effects of ceramic fillers for epoxy composites used as impregnation materials on the thermal and electrical stabilities of three GdBCO coils impregnated with epoxy alone, with an epoxy/AlN composite, and with an epoxy/BN composite. During cool-down to 77 K, due to the high thermal conductivity of the filler materials, the coils impregnated with the epoxy composites that included the AlN and BN fillers exhibited faster cooling times than the coil impregnated with epoxy resin alone. Moreover, the addition of the filler could facilitate quench heat dissipation as well as ameliorate the discrepancy of thermal contraction between the GdBCO CC tape and the epoxy. In particular, the coil impregnated with the epoxy/BN composite exhibited superior performance in cooling, over-current, and repetitive-cooling tests. Therefore, the epoxy/BN composite could be the most effective impregnating material for the development of highly-stable superconducting rotating machines, with considerably enhanced reliability.