Effect of AgNO_3 solution property on morphology and grain size of ultrafine silver powder

The dispersive ultrafine silver particles were prepared by the reduction of AgNO3 with ascorbic acid as reducer.The properties of the ultrafine silver powders were characterized by scanning electron microscope(SEM),ζ potential analyzer and ultraviolet-visible absorption spectrum analyzer(UV-VIS).The effects of concentration,the initial pH value and the addition of the surfactant on the morphology and size of the silver particles were investigated.The results show that,when c(AgNO3)0.30 mol/L,the prepared silver powders show rough surface,irregular morphology and worse dispersity.The particle size of silver powder decreases with increasing initial AgNO3 pH value,however,when the initial AgNO3 pH value is 7,the silver powder aggregate severely.The dispersive spherical silver particles with smooth surface can be prepared with the initial AgNO3 pH value of 5.0,concentration of less than 0.2 mol/L by the rapid addition of ascorbic acid without the addition of surfactant.It is deduced that the ascorbic acid plays the self-dispersive role in the reduction process.The size of silver particle can be decreased properly by adding dispersant PVP in AgNO3 solution,whereas,adding dispersant of butanediodic acid,polysorbate 80,PEG,PAA or isinglass has little improvement on the morphology of silver powder.