Increased Dielectric Strength of Polyimide/Silicon Dioxide Nanocomposites at Cryogenic Temperatures

Polyimide/silicon dioxide nanocomposites were synthesized and tested dielectrically at both room and cryogenic temperatures. The dielectric strength of the nanocomposites showed significant increase from about 150 kV/mm at room temperature to roughly 300 kV/mm at the cryogenic temperature. This increase in dielectric strength is a result of the contraction of the host polymer around the embedded nanoparticles, which shortens the mean free path of electrons as well as the distance needed for electrons to accelerate to induce avalanche breakdown. The contraction of the host polymer also reduces the overlapping of the transition region, the outermost layer of the multi-core model, between individual nanoparticles. The findings from our experimental results and multi-core model can potentially advance the field of cryogenic dielectrics.