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 liquidphase reduction method using hydrazine as reducing agent, the obtained powders have small particle size, large specific surface area and good dispersion.%以联氨为还原剂,在硫酸镍水溶液中控制液相还原反应条件制备了超细镍粉,并讨论了超细镍粉的还原生长机理.通过实验分析了工艺参数对还原反应的影响,采用X射线衍射(XRD),扫描电镜(SEM),比表面积测定等分析手段对超细镍粉进行表征,结果表明:超细镍粉的形核和生长独立进行;温度、Ni2+浓度和pH值调控着溶液中镍离子的释放并控制过饱和度,使形核过程非常短,形核率很高,晶核生长速度则相对较慢;表面活性剂可抑制粉末的团聚,易于获得单分散超细镍粉.采用该联氨液相还原法制备的超细镍粉纯度高、粒径小、呈类球形、比表面积大、分散性良好且镍粉转化率很高.
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