Effect of electrical modes on dielectric and insulation properties of plasma electrolytic oxidation ceramic films on Al

The preparation of insulating ceramic films on the surface of Al wires using plasma electrolytic oxidation technology can effectively achieve high temperature resistance and high thermal conductivity of ceramic insulated wires. The current study is not clear about the key factors and intrinsic influence mechanism which affect the dielectric and insulation properties of ceramic film. In this paper, the effects of different electrical modes and parameters on the microstructure, phase composition, dielectric and insulation properties of ceramic films are investigated. The results indicated that the effect of electrical modes on the dielectric property had no significant regularity. Among the three electrical modes, the effect of the current density mode is the most significant. When the current density increased from 8 A/dm2 to 20 A/dm2, the film thickness increased from 15.4 μm to 52.9 μm; the porosity increased from 2.74 % to 15.89 %; the breakdown voltage increased from 215 V to 345 V, and the breakdown strength decreased from 14 V/μm to 6.5 V/μm. Changing the electrical modes can change the microdischarge characteristics and realize the regulation of the microstructure, phase composition and content of the ceramic film, which in turn affects ceramic film's dielectric and insulation properties. The key factors to improve the dielectric and insulation properties of ceramic films are the increase of crystallinity and the reduction of defects and porosity. •Use three different electrical modes to control current pulse•Plasma discharge behavior during plasma electrolytic oxidation treatment•The effect of different electrical modes on dielectric and insulation properties of ceramic film•The influence of electrical modes on ceramic film microstructure and composition•Effect of microstructure and composition of ceramic film on dielectric and insulation properties