Preparation of Spherical Ultrafine Nickel Powder by Coordinated Precipitation-direct Reduction Process

The precursors,prepared by coordinated precipitation with NH_4HCO_3 as the precipitator,NiCl_2 as the raw material,and ammonia as the coordinator,were direct reduced by hydrogen to obtain a spherical nickel powder.The effects of parameters such as the concentration of reactants,pH value,additives,and reaction temperatures for precursor preparation and the reductive temperature,the composition of reductive atmosphere amid the reduction process were systematically investigated.The experimental study shows that,using 1(wt)% PVP as additive,well-dispersed precursors with a uniform spherical morphology can be obtained in a solution with Ni~(2+) concentration of 0.8mol/L and pH value of 7.5 at room temperature,while a pure and well-dispersed spherical nickel powder can be prepared by direct reduction of this precursor in a mixed atmosphere of nitrogen and hydrogen within the temperature range of(350～400 ℃).