Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and ch...Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and chemical properties,and wet flashover voltage is still unclear for inorganic ceramics.In this work,the surface insulation properties of ceramics under wet conditions are improved using nanosecond-pulsed dielectric barrier discharge with polydimethylsiloxane(PDMS)as the precursor.The relationships between PDMS concentration and the water contact angle,dry and wet flashover voltages are obtained to acquire the optimal concentration.The surface charge dissipation test and surface physio-chemical property measurement with SEM,AFM,XPS are carried out to further explore the mechanism of surface insulation enhancement.The results show that film deposition with micron thickness and superhydrophobicity occurs at the PDMS concentration of 1.5%.The dry flashover voltage is increased by 14.6%due to the induction of deep traps,while the wet flashover voltage is increased by 66.7%.The gap between dry-wet flashover voltage is decreased by 62.3%compared with the untreated one due to the self-cleaning effect.展开更多
Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays.In this paper,the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direc...Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays.In this paper,the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direct current(dc) 30 V/10 A circuit in the air.Molten pool simulation of the contacts is coupled with the gas dynamics to calculate the evaporation rate.A simplified arc model is constructed to obtain the contact voltage and current variations with time for the prediction of the current density and the heat flux distributions flowing from the arc into the contacts.The evaporation rate and mass variations with time during the breaking process are presented.Experiments are carried out to verify the simulation results.展开更多
Species composites of Ag-N_2,Ag-H_2 and Ag-He plasmas in the temperature range of 3,000-20,000 K and at 1 atmospheric pressure were calculated by using the minimization of Gibbs free energy.Thermodynamic properties an...Species composites of Ag-N_2,Ag-H_2 and Ag-He plasmas in the temperature range of 3,000-20,000 K and at 1 atmospheric pressure were calculated by using the minimization of Gibbs free energy.Thermodynamic properties and transport coefficients of nitrogen,hydrogen and helium plasmas mixed with a variety of silver vapor were then calculated based on the equilibrium composites and collision integral data.The calculation procedure was verified by comparing the results obtained in this paper with the published transport coefficients on the case of pure nitrogen plasma.The influences of the silver vapor concentration on composites,thermodynamic properties and transport coefficients were finally analyzed and summarized for all the three types of plasmas.Those physical properties were important for theoretical study and numerical calculation on arc plasma generated by silver-based electrodes in those gases in sealed electromagnetic relays and contacts.展开更多
基金partially supported by National Natural Science Foundation of China(Nos.51977104,52037004 and 52207160)the Natural Science Foundation of Jiangsu Province(No.BK20220341)。
文摘Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and chemical properties,and wet flashover voltage is still unclear for inorganic ceramics.In this work,the surface insulation properties of ceramics under wet conditions are improved using nanosecond-pulsed dielectric barrier discharge with polydimethylsiloxane(PDMS)as the precursor.The relationships between PDMS concentration and the water contact angle,dry and wet flashover voltages are obtained to acquire the optimal concentration.The surface charge dissipation test and surface physio-chemical property measurement with SEM,AFM,XPS are carried out to further explore the mechanism of surface insulation enhancement.The results show that film deposition with micron thickness and superhydrophobicity occurs at the PDMS concentration of 1.5%.The dry flashover voltage is increased by 14.6%due to the induction of deep traps,while the wet flashover voltage is increased by 66.7%.The gap between dry-wet flashover voltage is decreased by 62.3%compared with the untreated one due to the self-cleaning effect.
基金supported by National Natural Science Foundation of China(Nos.51377038,51307030)
文摘Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays.In this paper,the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direct current(dc) 30 V/10 A circuit in the air.Molten pool simulation of the contacts is coupled with the gas dynamics to calculate the evaporation rate.A simplified arc model is constructed to obtain the contact voltage and current variations with time for the prediction of the current density and the heat flux distributions flowing from the arc into the contacts.The evaporation rate and mass variations with time during the breaking process are presented.Experiments are carried out to verify the simulation results.
基金supported by National Natural Science Foundation of China(Nos.51277038 and 51307030)
文摘Species composites of Ag-N_2,Ag-H_2 and Ag-He plasmas in the temperature range of 3,000-20,000 K and at 1 atmospheric pressure were calculated by using the minimization of Gibbs free energy.Thermodynamic properties and transport coefficients of nitrogen,hydrogen and helium plasmas mixed with a variety of silver vapor were then calculated based on the equilibrium composites and collision integral data.The calculation procedure was verified by comparing the results obtained in this paper with the published transport coefficients on the case of pure nitrogen plasma.The influences of the silver vapor concentration on composites,thermodynamic properties and transport coefficients were finally analyzed and summarized for all the three types of plasmas.Those physical properties were important for theoretical study and numerical calculation on arc plasma generated by silver-based electrodes in those gases in sealed electromagnetic relays and contacts.
