| Ag-SnO2electrical contact material has been recognized as the most promising alternative to hazardous Ag/CdO in the use of low-voltage switches and power relays because of their remarkable resistance to welding and arc erosion. In the past years, many researches were developed around the preparation of SnO2powder with different sizes, compound technology of Ag-SnO2, application of additive to Ag-SnO2electrical contact materials, molding processing technology, effect of arc erosion on materials, etal. The result showed that size and shape of SnO2powder had a big effect on materials property, especially that sphere-like SnO2with finely size can strongly enhance the density, hardness, resistance to welding and arc erosion of Ag-SnO2electrical contact materials. Up to now, preparation of sphere-like SnO2powder has many problem to resolve to realize mass production. It is necessary to make research on the preparation of sphere-like SnO2and Ag-SnO2electrical contact material to promote the development of electrical contact material in theory or the reality.In this work, experiments were carried out according to simple preparation technology and mass production. SnCl2·2H2O, SnSO4and Na2SnO3were dissolved in solution as the tin source, the synthesis of SnO2powder were researched via adjust solution concentration, type of precipitant, mixing method and calcination temperature. The Ag-SnO2electrical contact materials were prepared with different SnO2powder via different synthesis method, and the materials property were tested. Through the experiment we finally got following conclusion:(1) When regarded SnCl2·2H2O as the tin source, H2C2O4as precipitant,0.1mol/L SnCl2solution was poured to0.2mol/L H2C2O4solution, then the precursor was got through washing and stoving the precipitation. Finally, the sphere-like SnO2powder with a diameter ranging from1μm to5μm was obtained through burning the precursor at1300℃for3h.(2) When regarded SnSO4as the tin source, H2C2O4as precipitant,0.1mol/L SnSO4solution was poured to0.2mol/L H2C2O4solution, then the precursor was got through washing and stoving the precipitation. Finally, the sphere-like SnO2powder with a diameter ranging from1μm to5u m was obtained through burning the precursor at1300℃for3h.(3) When regarded Na2SnO3as the tin source,0.1mol/L Na2SnO3solution was reacted with0.2mol/L H3PO4solution,0.2mol/L H2SO4solution and0.2mol/L HNO3solution with a controlling of PH in7, then the precursor was got through washing and stoving the precipitation. Finally, the SnO2powder was got through burning the precursor at1300℃for3h., but only Na2SnO3solution reacted with H3PO4solution can obtain the sphere-like SnO2powder with a diameter ranging from1u m to10u m.(4) The sphere-like SnO2powder with a diameter ranging from1μm to10u m can obtained through burning SnSO4at1300℃for3h directly.(5) The well coated and tightly coupled Ag-SnO2compound powder were obtained via chemical coating process. Because the volatile gases still inside the compound powder, the volume of the sample emerged a big expansion after sintering which result in the sample had a lower density. Through repressing and resintering, the density of the sample had a big enhancement.(6) The Ag-SnO2wire with a diameter of1.40mm can be obtained through hot extrusion and drawing combined with annealing during each pass, it proved that the material we prepared has excellent workability. Through this process, the material expressed severe plastic deformation witch leaded to re-dispersion of SnO2in the sample along the working direction, the cross-section expressed excellent hardness and the density of the material had a improvement.(7) The physical property and arc erosion test for the Ag-SnO2samples showed that the material which the SnO2powder prepared by burning SnSO4at1300℃for3h directly expressed excellent comprehensive property, the hardness was96.3HV, Electrical resistivity was2.096μΩ·cm, tensile strength was252.099MPa, Relative density was18.09%and the mass transfer value was lower. |
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