Study On Preparation And Formation Mechanism Of Nano Silver-Copper Coated Powder

As a new kind of functional composite material,Ag-Cu coated powder has a wide application prospect in many fields,such as electricity,optics,electromagnetism,medicine and so on.This paper mainly uses the preparation of silver copper coated powder was investigated step by step reduction,reducing agent,dispersing agent,reduction temperature,reduction time and the effect of stirring speed on the preparation of silver-copper powder coating process,discussed the formation mechanism of nano silver coated copper powder,the optimum process conditions were determined.The morphology,size and composition of silver copper coated powders were characterized by scanning electron microscopy?SEM?and energy dispersive spectroscopy?EDS?,X diffraction analysis?XRD?and transmission electron microscopy?TEM?.Research shows that reducing agent with formaldehyde,polyvinylpyrrolidone?PVP?as a dispersant in copper sulfate and silver nitrate solution,It can be used to prepare nano-Silver-copper coated powders with spherical,good dispersion and good particle distribution.The coating process of silver includes the substitution reaction and the reduction of formaldehyde,but the reduction of formaldehyde is the main one.At the reaction temperature of 70 ?,AgNO₃/CuSO₄ concentration ratio of 1:1,PVP content of1g/L the best conditions,the preparation of the silver copper coated powder particle size is about 100 nm,the coating thickness is about 2-3nm.When the reaction temperature is lower?<50 ??,there is a by-product of Cu2 O in the silver copper coated powder.With the increase of reaction temperature,Cu2 O will be reduced to copper by formaldehyde.The particle size of Ag-Cu coated powder decreases with the increase of stirring speed,and the dispersion is better.The larger the content of PVP,the dispersionof silver copper coated powder becomes worse.The higher the concentration ratio of AgNO₃/CuSO₄,the higher the encapsulation efficiency of Ag-Cu coated powder.With the increase of the reaction temperature,the antioxidant properties of the prepared silver coated copper powder becomes stronger,the higher the concentration of PVP,the antioxidant properties of silver-copper coated powder become worse with the increase of Ag content,the antioxidant properties of silver-copper coated powder became stronger.The process of preparing nano silver copper coated powder by step reduction method is mainly divided into two stages: reduction and growth of copper powder,reduction and coating of silver.The copper ions form and grow into copper powder under the action of reducing agent,Then the silver ions were heterogeneous nucleation and growth on the surface of copper powder,The surface of copper powder was coated on the surface of copper powder to form silver copper powder particles.