Effect of processing parameters on ultrafine silver particles prepared by spray-pyrolysis of AgNO₃ solution

The ultrafine silver powders were prepared by solution spray-pyrolysis with citric acid as additive in air atmosphere using AgNO₃ solution as raw materials. The properties of the ultrafine silver powders were characterized with scanning electron microscope (SEM), laser particle size analyzer, tap density tester and X-ray diffraction (XRD). The effects of reaction temperature, concentration and pH value of AgNO₃ solutions, compressed air flow and amount of citric acid on the morphology, tap density and average particle size of silver powders, were investigated systematically. The optimum conditions are determined as follows: temperature of 700 ℃, solution concentration of 2.0 mol/L, n(C₆H₆O₇)/n(AgNO₃) of 2.5 %, compressed air flow of 1.0 m³/h, solution pH value of 6.0. Under these conditions, the pure and dispersive spherical silver particles with smooth surface, average particle size of 3.16 μm and tap density of 4.24 g/cm³, can be prepared.