Research On Preparation Of Mono-dispersive Spherical Silver Powders With Glycerol As Reducing Agent

With the rapid development of microelectronic and photovoltaic industries, the market demand for highly dispersive spherical silver powders have been growing constantly, so the preparation techniques for silver powders of high performance becomes a research hotspot. There are many kinds of silver powders with different properties, while chemical reduction is the main method of preparing silver powders using silver chemicals in liquid or solid phases as precursors respectively. In this paper, mono-dispersive spherical silver powders were prepared by chemical reduction with glycerol as reducing agent and using Ag2O, Ag2CO3and AgNO3as precursors, separately. The influences of processing parameters on the particle sizes and morphologies of silver powders were studied by analyses of XRD, SEM and Laser size analyzer.In the study of preparing silver powders by chemical reduction of solid phase using Ag2O as precursor, the transform mechanism of solid phase, as well as the effect of molar ratio of Ag2O/glycerol, temperature, kinds of alkali, concentration of reducing agent, feeding rate of reducing agent, and dispersant on particle sizes and morphologies of silver powders were investigated experimentally. The results showed that formation mechanism of silver powders was through the dissolution of Ag2O, the reduction of Ag(I) ions to Ag atoms, as well as the crystallization of Ag atoms. The molar ratio of Ag2O/glycerol should be kept less than or equal to3:1in order to reduce Ag2O completely. Adding ammonia into the system was beneficial to preparing spherical-like silver powders of uniform morphology and size.In the research of preparation of silver powders by solid phase reduction method using Ag2CO3as precursor, the study found that the particle sizes of silver powders were increased with increasing temperature, and the optimum reaction temperature was70℃. The particle sizes of silver powders were decreased with decreasing molar ratio of Ag2CO3/glycerol. The particle sizes of silver powders and a number of large particles of silver powders were decreased with increasing concentration of glycerol, and feeding rate of glycerol. In the study of preparing silver powders by liquid phase reduction method using AgNO3as precursor, the effects of reaction systems, temperature, concentration of silver nitrate and reducing agent, kinds of alkali, concentration of ammonia, feeding rate of ammonia and dispersant on particle sizes and morphologies were investigated experimentally. The results showed that under the condition of temperature80℃, the volume ratio of water/ethanol1:1, silver nitrate concentration1.0mol/L, glycerol concentration1.2mol/L, adding ammonia as pH modifier, ammonia concentration5.4wt%, ammonia feeding rate6mL/min and adding PVP as dispersant, highly dispersive silver powders of narrow sizes distributions were prepared with a mean particle size0.52um. There are40figures,5tables,88references in this paper.