Preparation And Properties Of Silver-coated Aluminum Powder

Aluminum is the most abundant metal in the earth’s crust and has good electrical conductivity.The price of aluminum is relatively cheaper than metal materials such as gold,silver and copper.And its lighter weight and color have its own unique advantages in practical applications.However,the chemical properties of aluminum are very active.Pure aluminum is extremely easy to interact with oxygen when it is exposed in air,forming a thin and dense aluminum oxide film on the surface.On the one hand,this layer of oxide film can isolate the outside air from contacting the pure aluminum inside,thereby protecting the pure aluminum inside from being oxidized;on the other hand,Alumina itself is non-conductive,and the formation of aluminum oxide film will cause the micro-nano aluminum powder to lose its electrical conductivity.Silver is a stable precious metal material with excellent electrical and thermal conductivity.It is used in many fields,but its price is relatively expensive.The silver coating method is usually used to make the material have the properties of silver and reduce the cost.At present,the main researches are silver-plated copper powder,silver-plated nickel powder,silver-plated glass beads,silver-plated graphite,etc.In this paper,the method of electroless plating is used to prepare silver-plated aluminum powder,and further processed to obtain silver powder with hollow shell structure.Research indicates:1.Four methods were used to pre-treat aluminum powder: acid,alkali corrosion,copper plating intermediate layer method and fluoride complex method.After verification of silver plating,it is found that the silver deposition effect on the aluminum powder surface is better after the fluoride complexation method was used to pre-treat the aluminum powder.2.The process conditions for preparing silver-plated aluminum powder : the particle size of the aluminum powder is 1-20 μm,the pre-treatment uses NH4 F solution with a concentration of 1.8 g/L,the p H is 6-8,and the dispersant is PVP,using glucose as the reducing agent,the reaction is carried out by mechanical stirring at room temperature.The silver layer obtained by this process is a silver-plated aluminum powder with a network structure,which has excellent oxidation resistance and good electrical conductivity.3.The reaction mechanism of the silver-plated aluminum powder preparation process is analyzed: during the silver-plating process,due to the silver-aluminum micro galvanic-couple cell effect,electrons are obtained in the positive region of the micro battery,and silver ions are deposited as a framework of the network structure;the negative electrode region Silver ions cannot be deposited without electrons,so the silver layer eventually forms a network structure.Comparing the effects of ascorbic acid,glucose,potassium sodium tartrate and sodium citrate on the silver plating effect,It is found that adding appropriate reducing agent can improve the deposition morphology of silver particles and increase the compactness of the silver-plated layer,thereby reducing the sheet resistance of silver-plated aluminum powder,which provides a basis for further research and application of silver-plated aluminum powder.4.The silver-plated aluminum powder is further processed to obtain a hollow-shell structured silver powder with a small bulk density and a large specific surface area,which has potential application value in silver catalysis,sterilization and filling materials.