Improvement of Surface Insulating Performance for Ceramics used in Spark Plugs by APPJ with Two-Dimensional Dynamic Treatment

Cylindrical ceramics are commonly used as insulating materials in spark plugs for their high-temperature resistance and excellent insulating properties. However, the spark plug failures are always caused by carbon fouling due to the high polarity of the ceramic surfaces, which further decreases the surface insulation capability. Surface treatment is needed to restrain carbon fouling by decreasing the surface polarity of ceramics and enhancing surface insulation properties. In this paper, Ar/HDMSO APPJ excited by a nanosecond pulse power supply is employed for the two-dimensional dynamic treatment of cylindrical ceramic. The plasma source moves linearly with the ceramic rotating at constant velocity. The treatment effects are examined through the distribution of water contact angles (WCA) and polarity on the surfaces under different linear motion and rotary motion velocities. The insulating properties are analyzed through the variation of flashover voltage for different positions. Additionally, the surface morphology of ceramic materials at typical treatment positions is observed using SEM. The results indicate that the super-hydrophobic treatment is realized at ceramic surfaces and the surface polarity decreased by 67.8%, with the flashover voltage improvement of 29%, when the linear velocity is 1 mm/s and the rotary motion velocity is 4.2 r/min. SEM results reveal that a uniform thin film is deposited on the surface and a large number of white cluster-like structures are observed on the surface of ceramic. The results of this paper provide the experimental basis for the dynamic treatment of materials with irregular shapes by APPJ for applications in internal combustion engines.