Investigation of Space Charge Characteristics and Deep Charging Effects in T-ZnOw/Polyimide Composites

Nonlinear conductive materials demonstrate significant potential for suppressing deep charging in spacecraft dielectrics due to their adaptive conductivity. This study integrates tetrapod-shaped ZnO whiskers (T-ZnOw) (0-30 wt%) into polyimide (PI) to investigate the space charge transport mechanism and deep charging evolution patterns. Results indicate enhanced nonlinear conductivity and dielectric constant with increasing T-ZnOw content, where nonlinear threshold field strength decreases from 15.29 kV/mm (5 wt%) to 0.56 kV/mm (30 wt%). However, dielectric strength declines substantially from 38.1 kV/mm (pure PI) to 1.5 kV/mm (30 wt%). The incorporation of T-ZnOw reduces trap energy levels, synergistically combined with the nonlinear conductivity, significantly suppressing the accumulation of internal space charges. Electron irradiation tests reveal that higher T-ZnOw loadings accelerate charge equilibrium attainment and yield lower absolute values of surface potentials. Under more severe irradiation conditions, high-content samples maintain optimal charge dissipation through localized field-triggered conductivity surges. Considering both dielectric properties and charge regulation capability comprehensively, the 10 wt% T-ZnOw/PI composite presents a promising candidate for next-generation spacecraft insulating dielectrics.