Study On The Synthesis And Conductive Properties Of Silver Micro Nano Materials

Silver metal micro-nanomaterials have received extensive attention in many different fields,due to their unique structure and improved electronic,catalytic,optical and other related properties.Their performance mainly depends on their size,shape,composition,and crystallinity,and their properties can be tuned by changing the reaction parameters in the micro-nano particles.Silver micro-nano particle materials have also been rapidly developed and matured in applications such as sensors,medical sterilization,and catalysis.Due to the high cost of silver,silver coated copper powder is also a kind of metal material to be explored in this paper in order to reduce cost and increase efficiency.Chemical preparation of silver micro-nano particles is the main process in industry at present,in which parameters of reactant are important factors affecting the morphology and properties of micro-nano materials.In this paper,four kinds of metal micro and nano materials,including nano silver spheres,hollow silver powder,dendritic silver powder and silver coated copper powder,were synthesized by liquid phase chemical reduction method.Comparative experiments were conducted by changing various reaction parameters to study their specific effects.(1)Ultrafine silver powder was prepared by silver ammonia solution reduction method to obtain silver powder suitable for conductive silver paste in solar cells.The particle size and performance of ultrafine silver powder were controlled by adjusting various reaction parameters.At the same time,repeated tests were carried out to obtain monodisperse silver nanoparticles with average particle size of 500 nm,and the silver film was prepared by sintering process.The square resistance was measured as 2±0.15 mΩ/□.(2)Ascorbic acid(L-aa)was used as reducing agent,silver nitrate as precursor and gum acacia(GA)as dispersing agent.Silver powders with different morphology(hollow spherical silver powder and dendritic silver powder)were directly reduced,and characterized by SEM,HRTEM,XRD and UV-vis.By adjusting the reaction parameters,the micrometer silver powder with different morphologic morphology was synthesized,and the hollow and dendritic growth mechanism was further discussed.The silver powder obtained from the optimal amplification experiment was prepared by sintering process,and the square resistance values were measured respectively.When the proportion of silver powder in hollow spherical paste is 60 wt%,the square resistance is 2.97±1 mΩ/□,the surface is dense and the adhesion is good.Dendritic silver powder due to its large specific surface area,accounting for 54%of the silver paste,the square resistance is4.5±0.58 mΩ/□,and the surface of the silver film layer is smooth and has good adhesion.(3)To reduce the cost without reducing the performance,continue the experiment of hollow spherical silver powder,prepare a group of silver coated copper powder(copper as core,silver as shell),change the ratio of silver to copper experiment to explore the impact on it,but the effect is not satisfactory,so the electroless plating reaction of copper and silver ion(Ag~+)replacement was used to prepare silver coated copper powder.The effects of different mass fractions of silver and different concentrations of Ag~+on silver coated copper powder were studied.