Study On Preparation,Structure And Performance Of Ag/ZnO Electrical Contact Material

Ag/ZnO is a new type of nontoxic contactor,it has widely used in the field of low and medium voltage electrical appliances.Zinc and cadmium have similar physical and chemical properties because they belong to kin element.The performance of Ag/ZnO is close to Ag/CdO,and Ag/ZnO is most likely to replace the Ag/CdO contactor.However,the poor mechanical properties and arc erosion resistance limit the application of Ag/ZnO.Therefore,in order to improve Ag/ZnO contactor arc erosion resistance and other physical properties,we has improved the pulverizing process and added TiB2.Ag/ZnO composite powder was manufacture by improved mechanical blending and coprecipitation.In order to produce the most uniform distribution of Ag/ZnO powder,the paper studied the effect of the different parameters on the size of Ag particles and ZnO dispersion effect.In pressure and sintering process,experiments studied the effect of pressure,sintering time,sintering temperature,re-pressing and re-sinterong process on relative density and hardness of Ag/ZnO contactor.Finally,we studied that the influence of different synthesis method and the addition amount of TiB2 on the physical properties of Ag/ZnO electrical contact material.We got conclusions as follows.(1)When we applied the improved mechanical blending,using Na2CO3 as precipitating agent,and controlling dosage for the equivalent of 1.2 times,controlling the AgNO3 concentration was 0.25 mol/L and burning the precursor at 300? for 2h could get pure Ag/ZnO composite powders.The size of Ag particle was 1-4microns,and agglomeration was less,ZnO particles were dispersed well in composite powder.Using precipitation method,the size of Ag particle was 1-4 microns,reunion was not obvious,and ZnO particles were dispersed well in composite powders.(2)Increasing the pressure,sintering temperature and prolonging sintering time could improve the relative density of contactor.When the pressure and sintering temperature were particularly high,or the sintering time was too long,it would cause channels of pores were sealed.These had negative effect on improving density.When we controlled that the pressure of pressing was 320.9MPa,the sintering temperature was 750? for 2h,the pressure of re-pressing was 611.2MPa,the temperature of re-sintering is 700? for 2h,the pressure of three times pressing was 809.8MPa and the temperature of three times sintering was 700? for 2h,we would get the optimal performance of Ag/ZnO contactor.Relative density and hardness of the contract were 97.4%and 79.7.And the expansion of contactor did not appear in the process.(3)Using the improved mechanical blending method,the dispersion of ZnO,breakdown strength and elongation,tensile strength and electric conductivity of contactor were slightly better than the contactor of using coprecipitation.(4)When Ag/ZnO contactor was doped 0.5wt.%or lwt.%TiB2,its hardness,electrical conductivity and breakdown strength were higher than Ag-1?mZnO(8wt.%)contactor,but dispersion of ZnO and TiB2,relative density and elongation,tensile strength of the contact were reduced.It's proved that TiB2-doped can improve arc erosion resistance of Ag/ZnO contactor.When doping 0.5 wt.%TiB2,the contactor's arc erosion resistance and hardness were highest,they were respectively 3.96×107V/m and 83(HV).