Preparation And Properties Of Silver/Graphene Composite Coating For Electrical Contact

At present,China has used a large number of contacts made by Germany’s Siemens on super and ultra-high voltage transmission circuits.Heavy acid rain area,heavy industry pollution area and marine climate zone are mostly in China.The silver contacts in this environment are more easily discolored and the texture is softer.Addition,wear and corrosion resistance were bad,which further restricts the reliability and service life of silver contacts.In view of the disadvantages of hardness,wear resistance,and high temperature oxidation resistance of pure silver plating,silver-graphene composite coating was prepared by composite electrodeposition and electrophoresis-electrodeposition.Ultrasonic dispersion of graphene was performed using three different dispersants to compare wettability,sedimentation rate,and surface morphology of the coating.The amount of coating complexes was used as the standard to study the cathodic current density,stirring intensity,and graphene concentration in the plating solution for the composite electrodeposition process.From the viewpoint of plating performance,suitable electrophoretic-electrodeposition additives and electrophoretic process parameters were studied.The effect of graphene concentration in coating on hardness,friction resistance and electrical conductivity of coatings was studied.The electrophoresis-electrodeposition process of silver-graphene was studied.The main findings are as follows:Comparing sodium dodecyl sulfate,cetyl ammonium bromide,polyethylene glycol three dispersants can be found,SDS-dispersed graphene can easily enter the bath and its lower sedimentation rate is suitable for use as a dispersant for graphene in thiosulfate systems.Under the process conditions,surfactant C 0.2 g/L,grapheme 9 g/L in the hiosulfate silver system,current density 0.6 A/dm2,stirring speed 160 r/min,the silver-graphene composite coating with 5.4v% graphene was obtained.Thiosulfate system electrophoresis-electrodeposited silver-graphene process was studied,which was electrodeposition 5min-electrophoresis 5min-electrodeposition for 20 min.Electrophoresis was in isopropanol electrophoresis and magnesium nitrate hexahydrate provided charged particles for the electrophoretic solution.The silver-graphene composite coating was subsequently electrodeposited at electrophoresis voltage 100 V.The performance of the silver-graphene composite film has been found that the sheet resistance and the friction coefficient of the silver-graphene composite coating decrease with the increase of the amount of the graphene composite.Relative silver deposit,the friction coefficient of the silver graphene composite coating with graphene composite 5.4v% decreased by 80%.The wear rate decreased by 89%.Anti-high temperature discoloration performance of the coating were improved.Different composite coatings was obtained by electroless-electrodeposition.The square resistance of the silver-graphene composite coating was tested and an approximate calculation found that graphene conductivity was 6.7 times that of silver.During the silver-graphene composite membrane electrophoresis-electrodeposition process,the electrodeposition step caused a reduction of the matrix metal in the gap between the nanoparticles of the electrophoretic layer.Some of the nanoparticles would separate from the electrode surface.At the same time,during this process,the nanoparticles of the electrophoretic layer were also separated from each other by the reduction of the reduction reaction of the matrix metal or dued to the presence of the hydrogen evolution phenomenon.In a sense,nanoparticles were re-selected to refine the nanoparticles and reduce the occurrence of agglomeration.