A paraffin-wax-based system filled with sub-micrometer alumina particles is developed for use as impregnation of superconducting magnets operating at cryogenic temperatures. The addition of alumina fillers significantly enhances the thermal and cryo-mechanical performance of the wax matrix. Compared with pure wax, the filled system exhibits significant increases in compressive strength, elastic modulus and fracture toughness from room temperature down to its cryogenic service temperature. The filled wax retains a low melt viscosity, ensuring effective impregnation of coils, while the improved match in thermal expansion coefficient with other magnet components reduces the accumulation of local thermal stresses after cooldown. 2D representative volume element (RVE) simulations containing rigid particles embedded in the wax matrix were used to elucidate the mechanisms of damage initiation and stress evolution during thermal contraction and subsequent mechanical loading. The simulation results show good agreement with microscopic fracture observations and provide valuable insights for the design of mechanically robust and thermally compatible next-generation wax-based impregnation systems for superconducting magnets. • Paraffin-wax system filled with alumina developed for superconducting magnets. • 45 vol% alumina halves thermal contraction versus unfilled wax. • Filled wax retains low melt viscosity suitable for coil impregnation. • Tripled stiffness and compressive strength from ambient to cryogenic temperatures. • RVE simulations reveal thermal-mismatch stresses and matrix-particle damage.
Kong et al. (Sun,) studied this question.
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