Surface Reconstruction Of Alumina Ceramics And Its Effect On Vacuum Surface Flashover Performance

It needs to know that insulators play an insulating and supporting role in high-power equipment and high vacuum devices,and have become one of the indispensable of the device.However,in high vacuum environment,the surface of insulators is prone to surface discharge breakdown,i.e,surface flashover.The existence of surface flashover greatly reduces the compressive strength of the entire insulation system,making some vacuum high-voltage equipment supported by insulators unable to operate normally and safely.Therefore,it is of great importance to explore ways to improve the surface flashover performance of insulators for the stable operation of the equipment.In this paper,the methods to improve the surface flashover performance of insulators are explored from two aspects of changing the surface composition and the surface morphology of insulators.Alumina ceramic?Al₂O₃content is more than 95%?insulation materials are taken as the research object,octadecyltrichlorosilane?OTS?molecular self-assembly and ultraviolet laser micromachining are used to modify the surface of alumina ceramic insulators.Through experimental design,this work investigated the influence of surface coated OTS molecular self-assembly film,surface laser microgroove construction and surface composite structure prepared by the combination of the two methods on the surface flashover performance of alumina ceramic insulators.The main research results as follows:?1?The preparation and properties of self-assembled molecular films on the surface of alumina ceramic insulators were studied by molecular self-assembly technology.The research shows that OTS forms a molecular self-assembly film by chemical bonding with the surface of alumina ceramic.After modification,the static water contact angle of alumina ceramic insulator surface is obviously improved,and the average value of surface static water contact angle is increased to 127.9°from 57.8°before modification.The preparation of the self-assembly film can be completed on the surface of the sample in a low concentration and in a short time.The molecular self-assembly film formed when the reaction time is 1h and the solution concentration is 1m M has the best effect.The flashover performance test results show that the flashover voltage of alumina ceramic insulator after surface modification by octadecyltrichlorosilane?OTS?is nearly200%higher than that of the original,reaching the practical application level,and the molecular self-assembly technology has been successfully applied to the insulation field.?2?In this work,by adjusting the processing parameters of ultraviolet laser and combining with laser defocusing technology,the micro-scale construction of groove morphology on alumina ceramic surface has been realized.The flashover voltage of alumina ceramic insulator after surface grooving treatment is tested.The results show that the vacuum surface flashover voltage can be greatly increased by grooving treatment on the surface of alumina ceramic insulator.Compared with the original alumina ceramic insulator,the flashover voltage is increased by nearly 200%,reaching the practical application level.However,unlike polymer insulator,grooving period does not have obvious regular effect on the surface flashover voltage of alumina ceramic insulator.?3?Alumina ceramic insulators with composite structure on the surface were prepared by combining laser micromachining technology with octadecyltrichlorosilane?OTS?molecular self-assembly technology.The flashover voltage test results show that the flashover voltage of alumina ceramic insulators with composite structure is further improved.