Preparation Of Monodispersed Ultra-fine Silver Powders By Chemical Reduction Process In Liquid Phase

Abstract:Silver powder is one of the most important functional materials in the electronics industry, and it is widely used. In recent years, with the rapid development and miniaturization of the electronics industry, the market demands for highly dispersive silver powders have been increased constantly. Therefore it is very meaningful to develop and prepare the high performance silver powder.The chemical reduction in liquid phase is the main method of preparing the silver powder in laboratory and in industry.In this paper, the ultrafine spherical silver powders and the polyhedron silver powders were prepared by chemical reduction in liquid phase. In this paper, the effects of temperature, concentration of silver nitrate, ascorbic acid and dispersing agent, the mixing speed and dispersant on particle size and the morphologies of the silver powders were investigated. The samples were characterized by Scanning electronic microscopy (SEM), Transmission electronic microscopy (TEM), X-ray diffraction (XRD) and Thermogravimetric analysis (TG-DTA), and some meaningful results were obtained.The optimized conditions for preparing the ultrafine spherical silver powders were as follows:the initial Ag+concentration0.1mol/L, the pH of9, the condition of temperature60℃, mixing speed of350r/min, ascorbic acid concentration0.06mol/L, and dispersant concentration0.4mol/L. Under this condition, the highly dispersive ultrafine spherical silver powders with mean size0.75μm were generated, and the spherical was good.The optimized conditions for preparing the polyhedron silver powders were as follows:adding A2as dispersant, Ag+concentration0.37mol/L, the condition of temperature40℃, ascorbic acid concentration0.48mol/L, dispersant concentration5wt%of the silver, charge time20min. The results show that the dispersant types have a great impact on the tap density of the silver powder. Under this condition, highly polyhedron silver powders of narrow sizes distributions were prepared with a mean particle size2～10μm.By varying the reaction conditions and the kinds of the dispersant, silver powders with the distribution of0.5～2μm were prepared in different morphology. The process has the following advantages:shorter flowsheet, higher efficiency.