Dielectric properties of polyimide-based composites with boron nitride surface covering under high-energy electron beam radiation

When high-energy electron beam irradiation acts on space electrical equipment, the insulating materials undergo structural degradation and performance deterioration with increasing operation time, which compromises the operational safety of the space electrical equipment. In this work, a method of coating the surface of the insulating films with a higher barrier layer is proposed. A boron nitride (BN) layer with micro-nano thickness is in-situ deposited on the surface of the polyimide (PI) insulating film via plasma-enhanced chemical vapor deposition (PECVD), improving insulation performance and resistance to highenergy electron beam irradiation while ensuring strong interfacial bonding. The effects of different high-energy electron beam irradiation doses (1.0×10¹⁵-1.0×10¹⁶ e/cm²) on the microstructure and dielectric properties of pure PI films and PI-BN composites are investigated. Under high-energy electron beam irradiation, PI-BN composites exhibit no significant damage compared to pure PI films, including a surface roughness that is four times lower than that of pure PI films, and the breakdown strength decreases by only 3.6%. The BN deposition layer can scatter high-energy particles and alleviate insulation damage caused by highenergy electrons because of its higher barrier height and excellent insulation performance. This provides a novel insulating materials microstructure design approach for electrical equipment operating in space radiation environments.