Preparation of ultra-fine silver powders by precipitation-transformation method using glycerol as reductant

The preparation of ultra-fine silver powders was investigated by precipitation-transformation method using Ag2O as precursor and glycerol as reductant in H2O-PVP system.The samples were characterized by XRD,SEM and laser size analyzer;the formation mechanism and the mechanism of controlling morphology and size of silver powders were studied experimentally.The results show that silver powders are formed by crystallization of Ag atom obtained from the reduction of Ag+ ions,which come from the dissolution of Ag2O.The molar ratios of Ag2O/glycerol should be obtained at less or equal to 3:1 in order to reduce Ag2O into silver completely in the preparation.Adding ammonia as pH modifier is beneficial to prepare silver powders with uniform morphology and size,and glycerol concentration affects the sizes of silver powders seriously.Adding ammonia as pH modifier,under the condition of temperature of 80 ℃,Ag2O/ glycerol molar ratio of 2:1,glycerol concentration of 2.4 mol/L,reductant feeding rate of 6 mL/min and adding PVP of 1% Ag2O mass,the silver powders with a mean particle size of 0.52 ?m and narrow size distribution can be obtained.