Study On Preparation Of Silver-coated Aluminum Powder By Substitution Method

Silver-coated aluminum powder is widely used in the electronics industry,communications industry,aerospace and other fields because of its high conductivity and corrosion resistance.However,since the aluminum powder has a relatively high specific surface area,agglomeration is likely to occur during the preparation process and the coated silver layer is not dense enough to ensure good conductivity and corrosion resistance of the silver-coated aluminum powder.Therefore,it is necessary to develop a process to obtain dense and uniform silvercoated aluminum powder.In this paper,through the discussion and exploration of the preparation method,the double replacement plating method is determined as the process of preparing silver-coated aluminum powder.The copper as the intermediate layer of silver-coated aluminum powder was determined by the research on copper powder replacement silver plating.And through the investigation of the dispersion of aluminum powder,it was determined that the addition of polyvinylpyrrolidone during the experiment can reduce the agglomeration of aluminum powder.Through orthogonal experiments on the composition and process of aluminum powder replacement copper plating,the composition and parameters of the copper plating process plating bath were determined: Cu SO₄·5H₂O: 4?5 g/L,EDTA·2Na: 9?10 g/L,C₄O₆H₄KNa: 7?8 g/L,2,2'-bipyridine: 12 mg/L,temperature: 30 ?,p H: 10?11.5.Scanning electron microscopy was used to characterize the appearance of the copper coating.The results showed that when the p H of the copper plating solution was 10.5?11.5,the temperature was lower than 45?,and the copper ion concentration was 0.6?0.7 g/L,the copper coating The coating is dense and uniform.The research on the reaction rate of copper plating shows that with the increasing p H,temperature and copper ion concentration of the plating solution,the faster the copper plating reaction speed.The particle size of the copper-coated aluminum powder was analyzed using a particle size analyzer.The results showed that when the copper ion concentration was 0.6-0.7 g/L,the particle size distribution of the copper-coated aluminum powder was relatively uniform.The physical properties of the copper-coated aluminum powder are judged to be relatively high in purity,and as the copper content in the coating layer continues to increase,the preferred orientation of the crystal plane?200?in the copper coating layer continues to increase..Four different silver complexing agents were selected,and it was determined that ammonia water was used as the silver complexing agent to prepare silvercoated aluminum powder.At the same time,on the basis of the copper-coated aluminum powder prepared above,the silver-coated aluminum powder is prepared again by the replacement method.The characterization of the macro color of the prepared silver-coated aluminum powder shows that as the n?Cu?/n?Ag?increases from 0.1 to 0.5,the macro color of the silver-coated aluminum powder changes from black to yellow and then White and finally yellow again.When the ratio of n?Cu?/n?Ag?is 0.4,the prepared silver-coated aluminum powder is white.The appearance of the silver-plated layer was characterized by scanning electron microscopy.The results showed that as the r atio of n?Cu?/n?Ag?increased from 0.1 to 0.5,the surface coating effect showed an inconsistent state.When the ratio of?Cu?/n?Ag?is 0.4,the intermediate layer of copper has just been consumed,and at the same time,silver is densely and evenly coated on the surface of the aluminum powder.