Study on Preparation and Mechanism of Reduction and Growth of Ultrafine Nickel Powders

Ultrafine nickel powders were prepared in nickel sulfate aqueous solution by controlling reaction conditions of liquid-phase reduction method using hydrazine as reducing agent.Mechanism of reduction and growth of ultrafine nickel powder was also discussed.The effect of process parameters on reduction reaction was analyzed through the experiments.Ultrafine nickel powders were characterized by the X-ray diffraction(XRD),scanning electron microscopy(SEM) and specific surface area measurement.The results showed that the nucleation and growth of ultrafine nickel powder were independent.The release of nickel ions and the supersaturation,which can make it possible to achieve very short nucleation process,high nucleation rate and relative slow nuclei growth rate,were regulated by temperature,concentration of Ni2+ and pH value.In addition,the surfactant can inhibit the aggregation of powders and make it easy to prepare monodisperse ultrafine nickel powder.The ultrafine spherical nickel powders of high purity were synthesised in a high conversion rate by a liquid-phase reduction method using hydrazine as reducing agent,the obtained powders have small particle size,large specific surface area and good dispersion.