Study On The Preparation Of Ag Coated ZnO Powder And Properties Of Ag/ZnO Electrical Contact Material

Ag-ZnO electric contact materials are widely used in the field of low voltage electrical apparatus because of their unique properties,such as high current(3000-5000A)impact,good breaking performance,arc erosion resistance,non-toxic and other characteristics.Ag-ZnO electrical contact materials have the advantages of low contact resistance,stability,excellent resistance to welding and good arc erosion resistance.The dispersion of ZnO and the preparation methods of Ag-ZnO composite powders have great influence on the properties of Ag-ZnO electrical contact materials.Therefore,how to improve the dispersion of ZnO in composite powder and explore the new preparation methods of Ag-ZnO composite powder become an important way to improve the properties of Ag-ZnO electrical contact materials.Firstly,this paper attempted to adopt the technology of preparation of Ag coated ZnO composite powder,study the impact of the regulation method of pH parameters,reducing agent,dispersing agent,main salt concentration on the microstructure of the composite powder.It puts forward the optimized composite powder preparation technology on Ag-ZnO electrical contact materials preparation process and properties.The results show that:(1)This paper proposed to adopt the preparation method of Ag coated ZnO composite powder by chemical precipitation and pH control method.The main process:reduction preparation?preparation of reduced solution and mixed solution?synthesis of Ag coated ZnO composite powder.(2)The key of the composite powder preparation in the process of Ag coated ZnO is to accurately control the pH of the solution between 7-8.PH control method is adding sodium carbonate solution in the first step of the preparation of the reducing solution;adding VC solution in the second step of the preparation of the mixed solution of redox and Zinc Oxide;adding ammonia solution in the third step synthesis of Ag coated ZnO composite powder.Therefore,the pH value can be controlled in the whole preparation process.(3)The concentration of reducing agent,dispersant and main salt solution have great influence on the morphology and particle size of composite powder.The optimized process parameters used are the molar ratio of reducing agent(VC)to main salt is 1.5:1,reducing agent concentration is 2.78mol/L,the concentration of PVP is 0.32g/L,concentration of salt solution is 0.18mol/L.It prepared Ag coated ZnO composite powder that the spherical particle size is between 0.2-0.4pm and dispersion is good by the optimal process parameters.lt prepared the Ag-8%ZnO composite powder by increasing the initial amount of ZnO(13%).Therefore,it realized the controllable preparation of Ag coated ZnO composite powder.(4)Ag-8%ZnO electrical contact materials prepared by Ag coated ZnO composite powder have a good processing property.Ag-8%ZnO electrical contact materials obtained by the sintering and rolling processing have good mechanical and electrical properties which the hardness reaches 93.9HV,the conductivity is 73.10%IACS,the tensile strength is 282MPa,and the elongation is 9%.(5)Comparing with the uncoated Ag-ZnO electrical contact materials obtained by wet mixing of powders,the comprehensive performance of the electrical contact material prepared by coated composite powder has been improved.The conductivity has been increased by 11.58%,the tensile strength has been increased by 4.44%.The elongation has been increased by 12.5%,and the arc erosion performance has also been improved obviously(breakdown strength has been increased by 15.1%).This indicates that the coating method is an effective way to improve the properties of silver electrical contact materials.