| The electrical contact material is the interface material of the contact of the conductor.Its performance has a very important effect on the quality and service life of electrical apparatus.Ag-Ni electrical contact material has many advantages,such as good thermal conductivity,electrical conductivity,low loss under DC load,low contact resistance and outstanding technology.It is widely used in medium low voltage load electric.However,the hardness of the Ag-Ni electrical contact material is low and the corrosion resistance of the electric arc is poor.Therefore,Ag-Ni composite material is selected as the research object in this paper.Ag50-Ni50 nano electrical contact material was prepared by sol-gel and hot pressing method to improve the hardness and arc corrosion resistance of the material The main results and research content of this work are as follows:AgC2O4 and NiC2O4 precursors were synthesized by a chemical precipitation method.AgC2O4 was precipitated first while co precipitation reaction carrying out,which is easy to cause inhomogeneous composition.It will cause further growth when hot pressing is carrying out.But its resistance to arc erosion is better.It can be used to prepare micrometer Ag-Ni electrical contact materialAg50-Ni50 nanoscale powders were prepared by sol-gel method.When the molar ratio of citric acid to metal ion is 2:1,the powder has the best dispersity,the smallest particle size,and the average particle size is 120 nm.Zeta potential of silver and nickel particles is lower when the pH value is low,and is easy to reunite during Zeta potential analysis,.With the pH value increase,the particle potential improve and not easy to reunite.When the pH value is too large,the concentration of OH-ions in the solution improve,and the metal ions tend to form a hydrogen oxidation insoluble substance with OH-ions,and the aggregation will occur.When the pH value is 2,the particle dispersion is the best and the particle size is 50 nm.Through the exploration of the powder forming process and testing the performance,it is concluded that the best hot pressing temperature and time of the powder are 750℃ and 2 h.The microstructure and properties of Ag50-Ni50 nanoscale electrical contact materials change with the change of the molar ratio of citric acid to metal ions.Component aggregation and inhomogeneity occurred when the citric acid is lower or higher.When the citric acid mole ratio was 2:1,the two phase distribution is relatively uniform.And it has relatively large hardness value(212 HV)and high yield strength(971 MPa).With the pH value change,the microstructure and properties of Ag50-Ni50 nanomaterials changed.With the pH value increase,the dispersion of particles has been greatly improved.However,when the pH value is too large,the particle size became bigger.When the pH value is 2,the distribution of the sample is the most uniform and has the smallest size(400 nm),maximum hardness values(236 HV)and large voltage resistance(3.13×106 V·m-1).Because the Ni phase was dispersed in the Ag matrix,the load was transferred to the dispersed phase Ni particles when the Ag was subjected to pressure deformation.So the yield strength is raised.The samples with pH value of 0 and 2 showed higher fracture strength and yield strength,but the gap between yield strength(971 MPa)and fracture strength(972 MPa)samples with pH=0 was too small.The toughness of the sample with pH=2 is better(the yield strength is 793 MPa,the breaking strength is 861 MPa).And Its pressure resistance is higher,and the surface after test was more smooth and the resistance to arc was better.The Ag50-Ni50 contact material has higher hardness,lower resistivity and better conductivity while compared with the Ag-Ni40 electrical contact material of Advanced company in the United States,... |
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