Unraveling gas–solid interface charging mechanisms of insulator based on three-phase dominant charge behaviors

Abstract

In surface science, surface flashover is a plasma discharge phenomenon that occurs along the gas–solid interface of an insulator under a high electric field (E), threatening the operational reliability of power systems and advanced electronic devices. Owing to the complex charge transport across the gas–solid interface, the underlying physical mechanism of surface charging remains unclear, limiting the development of flashover theory and surface-modification technologies. Herein, surface gas ionization and surface charge-dissipation equations are proposed to establish a surface-charging model for insulators, and the effects of three-phase (gas, solid, and interface) transport parameters on surface charging are investigated. The results reveal an E-dependent competitive mechanism among the gas–solid–interface charge transport processes: Enhancing gas insulation strength and bulk conductivity effectively suppresses heteropolar charge accumulation and shifts the charge-polarity reversal point (Er) to higher E, with surface charging transitioning from gas-ionization-dominated to bulk-conductivity-dominated behavior. In contrast, increasing surface conductivity accelerates charge dissipation, causing surface charging to be governed by surface charge dissipation. Based on the dominant charging mechanisms, surface-modification strategies, including O3 treatment, surface polishing, and EP/SiC coating, are applied to insulators; all methods reduce surface-charging density and increase surface flashover voltage. This study establishes a systematic competitive framework for three-phase charge transport in surface charging, providing a theoretical foundation for dielectric surface charging/discharging theory and for surface modification in advanced electrical and electronic applications.