Abstract
Surface flashover seriously restricts the electrical performance of insulating system in vacuum. Surface properties of the insulating materials are the key factors affecting the electrical property along the surface. In this paper, Atmospheric-Pressure Plasma Enhanced Chemical Vapor Deposition (AP-PECVD) is used to deposit chromium oxide film on alumina ceramics to improve its flashover voltage in vacuum. Chromium acetylacetonate and argon are used as the precursor and working gas, respectively. A homemade ultrasonic atomizer and gas distribution system are used to ensure the uniformity during the AP-PECVD. For comparison, deposition experiments are both carried out at atmospheric and sub-atmospheric pressures. The experimental results show that the surface flashover voltages in 10−4 Pa are increased by 20% and 26% after the PECVD at atmospheric and sub-atmospheric pressures, respectively. The physicochemical and electrical property indicates that more shallow traps are introduced into the surface of alumina ceramics. The initial potential of the deposited sample decreases by 36% after the AP-PEVCD. Therefore, the deposition of chromium oxide films on alumina ceramics by AP-PECVD can effectively inhibit the surface charge accumulation and improve the surface flashover voltage in vacuum by reducing the trap energy level and its density. Based on the SEEA (secondary electron avalanche) theory and the distribution of the surface traps, the effects of chromium oxide films deposited on alumina ceramics are summarized for the application of vacuum insulation. The feasibility of depositing chromium oxide films to improve the vacuum surface flashover voltage of alumina ceramics by PECVD is proved. The process of the PECVD at atmospheric pressure is flexible, which provides a promising technical support for enhancing surface flashover for other insulating materials.
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