Preparation And Properties Of The Ag-SnO₂ Electrical Contact Materials Prepared By Using Template Method

The Ag-SnO₂ electrical contact materials are widely used in the low-voltage apparatus and instruments attributed to its good comprehensive performance.At present,the main routes to manufacture Ag-SnO₂ electrical contact materials have some problems of the bad distribution and aggregation of SnO₂ in Ag matrix.In order to solver the problems,Ag-SnO₂ electrical contact materials were prepared by template method combining with dipping,calcination and sol-gel process.In this case,it is helpful to improve the SnO₂ particles dispersion in Ag matrix and the physical properties of Ag-SnO₂electric contact materials.The effect of the parameters of the processes on the performance and microstructure of these materials was investigated by using the X-ray diffraction?XRD?,the scanning electron microscope?SEM?,the energy dispersive spectrometer?EDS?,the electrical conductivity,the Vickers hardness,and the Archimedes method.And the parameters of the processes included the different preparation methods,SnO₂ mass fraction,calcination process,ethanol content and the concentration of AgNO₃.In order to further improve the dispersion of SnO₂ particles in the Ag matrix,the Ag-SnO₂ electrical contact materials were prepared by using the template method in combination with sol-gel process.Then its mechanism was studied.Finally,the effect of performance of the Ag-SnO₂ electric contact material were investigated according to different citric acid content.The main conclusions of this thesis are as follows.?1?The Ag-SnO₂ composite powder prepared by the high-energy ball milling technology have uniform size,compared with template method.However,it owns big powder particle size.Ag-SnO₂ electric contact materials prepared by powder metallurgy process have less holes on the surface.The physical properties of the Ag-SnO₂ electric contact material were investigated,the results show that the filter paper-template mathod and the high-energy ball milling technology are better than starch-template mathod.?2?The SnO₂ mass fraction has a great effect on the electrical conductivity,hardness and density of Ag-SnO₂ electrical contact materials.When the SnO₂ mass fraction is12wt.%,the Ag-SnO₂ electric contact materials prepared by starch template mothod have conductivity of 49.5%IACS,hardness of 69.7 HV,and density of 8.9475 g/cm³.The Ag-SnO₂ electric contact materials prepared by filter paper-template mothod have conductivity of 55.2%IACS,hardness of 89.4HV,and density of 9.1293g/cm³.From the factors of the cost of material and performance to consider,the SnO₂ content of 12 wt.%meets the requirements.?3?The calcination process of Ag-SnO₂ electric contact materials prepared by starch template mothod is heat-preservation 1h at 300?and improvement temperature to 650?heating preservation 4h.The physical properties of Ag-SnO₂ electric contact materials are the relatively best including conductivity of 47.6%IACS,hardness of 86.0 HV,and density of 9.3753 g/cm³.The calcination process of Ag-SnO₂ electric contact materials prepared by filter paper-template mothod is heat-preservation 1h at 300?and improvement temperature to 600?heating preservation 2h.The physical properties of Ag-SnO₂ electric contact materials are the relatively best including conductivity of 55.2%IACS,hardness of83.1 HV,and density of 9.2696 g/cm³.In this process,the dispersion of SnO₂ particles in Ag matrix is better.?4?It showed that the ethanol content has a little effect on the physical properties of the Ag-SnO₂ electrical contact material.However,the ethanol content is helpful to the dispersion of SnO₂ particles in Ag matrix.When the ethanol content is 30 vol.%,the dispersion of SnO₂ particles in Ag matrix is relatively the best.?5?The AgNO₃ concentration of 1mol/L,in the selected 0.5mol/L,1mol/L,1.5mol/L,was the best one.The Ag-SnO₂ electrical contact materials have uniform distribution phase and no holes on the surface of materials.When the AgNO₃ concentration of 0.5 mol/L,the dispersion of the SnO₂ in Ag matrix is poorer.When the AgNO₃ concentration of 1.5 mol/L,the surface of Ag-SnO₂ electrical contact materials is not flat and have more holes.?6?Ag-SnO₂ electrical contact materials were prepared by the template method and sol-gel process.Compared with no templates and starch template method,Ag-SnO₂composite powder prepared by filter paper template method has smaller size.The distribution of SnO₂ particles in Ag matrix is more homogeneous and hasn't obvious phenomenon of reunion.It was resulted that with the increase of the molar ratio of the citric acid and metal cations,the dispersion of SnO₂ in the Ag matrix is more uniform,and the electrical conductivity,hardness and density of Ag-SnO₂ electrical contact materials are also increased.During ratios of citric acid n?C₆H₈O₇?and metal cation n(Ag⁺+Sn⁴⁺)were 1:1,2:1,3:1,the ratio 3:1 is the best one.Dimensions and elements distribution of the Ag-SnO₂ composite powder were more uniform,and the physical properties of Ag-SnO₂ electrical contact materials?conductivity,hardness,density?is more excellent than others.The physical properties of Ag-SnO₂ electric contact materials using no templete are conductivity of 52.9%IACS,hardness of 120.6 HV,and density of 9.5085g/cm³.The physical properties of Ag-SnO₂ electric contact materials using starch templete are conductivity of 55.6%IACS,hardness of 117.9 HV,and density of 9.6099 g/cm³.The physical properties of Ag-SnO₂ electric contact materials using no templete are conductivity of 57.7%IACS,hardness of 119.2 HV,and density of 9.6213 g/cm³.