Preparation of micro-sized and uniform spherical Ag powders by novel wet-chemical method

A novel wet-chemical method was presented for the preparation of the micro-sized and uniform spherical Ag powders on a mass-production scale. The well-defined particles were synthesized by mixing the iron(II) sulfate heptahydrate solution with silver nitrate solution directly by high-speed stirring at room temperature. It is found that a large number of micro-sized and uniform spherical particles with rough surfaces are obtained. The mass ratio of iron(II) sulfate heptahydrate to silver nitrate greatly affects the shape of particles, and when it is relatively low, spherical particles cannot be obtained. The reaction temperature has a great impact on the particle size. As the reaction temperature increases from 8 to 15 °C, the mean diameter of particles decreases from 3.5 to 1.6 (m. The additive n-methyl-2-pyrrolidone improves the surface smoothness and compactness of the particles while the particle size is kept unchanged. Scanning electron microscopy, X-ray diffractometry and energy dispersive X-ray analysis were used to characterize the particle products.