| The operation of any modern integrated system depends on the current signal or current energy transfer through electricity.The switch is turned on and off,and this process is called "electrical contact".The material with electrical contact behavior is called electrical contact material.In the actual on-off process,complex physical wear and chemical reactions occur on the electrical contact material,which will have a great impact on the properties of the material.Among the known types of electrical contact materials,silver-based electrical contact materials are widely developed and used,which have low resistivity and contact resistance.However,high-purity silver metal has poor electrical corrosion resistance,low melting point,low hardness,etc.When working in an atmosphere containing sulfur or sulfide for a long time,the surface may undergo chemical reaction and form sulfide film.Under the action of high temperature caused by direct current,silver metal is easy to melt.From melting to solidification,microscopic spikes may be formed,which will increase the surface roughness of the contact surface,making it easy to form electric arc between the contact planes,and make them weld.Moreover,the working conditions of large and medium power contacts are rather bad,and they are often under the strong action of electric arc,resulting in serious electrical erosion.Therefore,the purpose of this paper is to improve the wear resistance,ablation resistance and other characteristics of electrical contacts,and to analyze their mechanism,so as to improve the life of electrical contacts.The experiment is that graphene with excellent electrical,thermal and mechanical properties can be used as reinforcement in metal matrix composites to enhance the properties of metal materials.The main contents of this paper are as follows:(1)Preparation and detection of silver-graphene composite electroplating solution.First of all,considering the green manufacturing,coating smoothness,service quality and manufacturing cost,nicotinic acid cyanide-free silver plating process is selected.Please refer to the specific description below for the contents and percentages of various components in the electroless plating solution and matters needing attention.The composite plating solution needs to be tested in some aspects of performance,and the contact angle of the composite plating solution on the glass is 19.05,which is obviously lower than that of the unmodified plating solution.The absolute value of Zeta potential is 30.05 m V,which is obviously higher than that of the unmodified bath,and the bath has good dispersion performance.(2)Preparation and detection of silver-graphene composite coating.Please refer to the following description for the specific process parameters of silver-graphene composite electrodeposition.Different process parameters have great influence on the coating quality,thickness,wear resistance and the uniformity of the second term distribution.SEM,EDS,XRD and AFM results show that the main components of the coating are silver and graphene.After comparison,the addition of graphene does not change the crystal structure of silver metal itself,even has a certain effect of grain refinement,and the out-of-plane wrinkle effect of graphene is also obviously inhibited.(3)Study on current-carrying friction performance and mechanism of composite coating.By adding the second phase of graphene,the average Vickers hardness of the composite coating is increased by about 25% compared with that of pure silver.The depth of dry friction marks is reduced by more than 30%;The average friction coefficient is reduced by more than 35%.After electrical contact,the surface oxidation degree is reduced,the ablation area is smaller,the roughness is reduced by 10%～20%,and the specified service life is increased by more than 60%.In the process of composite electrodeposition,pyridine ring of organic acid and graphene have π-π interaction,which flattens graphene,inhibits its out-of-plane wrinkle effect,makes it have larger specific surface area,and enhances the properties of composite materials. |
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