Synthesis And Characterization Of Core-shell Structure Ag Electric Contact Material

Electric contact materials played important roles in the process of transporting electriccurrent and converting electrical signal. They were important materials in circuit controller(e.g., protection switch, contactor, circuit breaker, automobile electronic instruments, etc,)they undertook the task of connecting circuit and loading current. The property of electriccontact materials played important roles on performance of the electric switch.At presentelectrical products had different requirements of electrical contact materials (such asheat-conducting property, oxidation resistance, resistance to fusion welding and arcerosion.) as electrical products increased widely,contributing to the type and preparationtechnology improving and developing. In this research, Ag-based electrical contactmaterials were synthesized by chemical plating. The sensitizer, silver nitrate concentration,reaction time， reaction temperature were studied on the effects of Ag-based electricalcontact material morphology and polymorphs. The contents and results mainly as follow:1. Ag/C electrical contact material were synthesized by chemical plating method，using stannous chloride as a sensitizer, formaldehyde as a reducing agent. Themorphology and polymorphs of the composite particles were characterized by X-raydiffraction, scanning electron microscopy. The effects of the sensitizer， silver nitrateconcentration, reaction time，reaction temperature on the surface and crystal morphologiesof Ag/C electrical contact material were investigated. And the effects of different reducingagents on quality of composite particles were studied. The results show that usingformaldehyde as a reducing agent， after sensitization, when the silver nitrateconcentration was0.4mol/L, reaction temperature was65°C，the synthesis of Ag/Celectrical contact material had good morphology. The effects of different reducing agent onphysical properties of Ag/C composite powders were investigated. Physical properties ofcomposite powders were studied by testing their vicker-hardness, compressive strength,density and resistivity. The results showed that Ag/C composite powder had good physical properties when reducing agent was formaldehyde.2. As silver-copper composite powders had good resistance to fusion welding，goodresistance to arc erosion and high heat-conducting property, they were widely used inelectric products, function packing and other fields.Silver-copper composite powders weresynthesized by chemical plating method in which the stannous chloride and formaldehydewere used as sensitizer and reducing agent, respectively. The morphology and polymorphsof the composite particles were characterized by X-ray diffraction, scanning electronmicroscopy. The effects of sensitizer stannous chloride, reaction temperature, reducingagent and pH value of solution on the surface and crystal morphologies of the compositeparticles were investigated. Results show that using formaldehyde as a reducing agentwith the post-treatment of sensitization, the silver-plated copper powders with wellmorphology can be obtained when the pH value of solution is10and the reactiontemperature is kept around50℃. The effects of different reducing agent on physicalproperties of Ag/Cu composite powders were investigated. Physical properties ofcomposite powders were studied by testing their vicker-hardness, compressive strength,density and resistivity. The results showed that Ag/Cu composite powder had goodphysical properties when reducing agent was formaldehyde.3. Ag/Al electrical contact materials which have excellent physical properties weresynthesized by chemical plating method by plating silver particles on the surface ofaluminum powder.The morphology and polymorphs of the composite particles werecharacterized by X-ray diffraction, scanning electron microscopy. The effects of sensitizerstannous chloride, silver nitrate concentration, reaction time, reaction temperature werestudied on the effects of Ag/Al electrical contact material morphology and polymorphs.Results show that using formaldehyde as a reducing agent with the post-treatment ofsensitization, the silver-plated aluminum powders with well morphology can be obtainedwhen the reaction time is60min and the reaction temperature is kept around45℃. Theeffects of different reducing agent on physical properties of Ag/Al composite powderswere investigated. Physical properties of composite powders were studied by testing their vicker-hardness, compressive strength, density and resistivity. The results showed thatAg/Al composite powder had good physical properties when reducing agent wasformaldehyde.