Investigation of temperature-dependent DC breakdown characteristics of nano-Al2O3/epoxy composites at low temperatures

Abstract

Epoxy resin is extensively utilized as an insulating material in low-temperature superconducting devices. Nevertheless, its breakdown behavior and mechanism at low temperatures have rarely been studied. This study aims to investigate the breakdown characteristics of bisphenol F epoxy resin and its nano-alumina composites under different temperatures. Additionally, a thermally stimulated current (TSC) platform was established to examine the molecular relaxation and trap charge parameters of epoxy from 4.2 K to 300 K. The epoxy resin matrix was modified by incorporating a series of nano-alumina particles (1%, 2%, 3%, 4%, 5%). In this paper, a breakdown transition temperature (Tb) between 77 K and 150 K was observed for epoxy resin, with a significant decline in insulation performance above and below Tb. This phenomenon can be attributed to the interplay between collisional ionization and thermal breakdown mechanisms. The inclusion of nano-alumina particles in the epoxy resin matrix demonstrates an improvement in insulation performance at low temperatures, with an optimal filler ratio of approximately 2%. However, an excessive amount of alumina nanoparticles may reduce the insulating capabilities of the epoxy resin. The experiments conducted on thermally stimulated currents revealed that trap charges within the resin are more readily excited at low temperatures.