中国有色冶金

Aiming at the problems of particle size distribution control and anti-oxidation in the preparation of ultrafine nickel powder, this paper proposes a method for preparing ultrafine nickel powder by hydrazine hydrate-potassium borohydride reduction-hydrogen reduction system using nickel sulfate as raw material. The performance of nickel powder prepared under optimized conditions was analyzed by SEM, XRD and other characterization methods, and the following main conclusions were obtained. The optimized process conditions of hydrazine hydrate are as follows: reduction temperature 333.15K, reduction time 150min, solution pH 8.0~8.5, nickel ion molar concentration 1.25mol/L, mass ratio of hydrazine hydrate to nickel ion 1.35, mass concentration of sodium hexametaphosphate 1.5‰. Under these conditions, the nickel reduction rate can be stabilized at about 99%. The introduction of proper amount of potassium borohydride in the reduction and precipitation process of nickel powder can overcome the induction period of hydrazine hydrate reduction and improve the controllability of nickel powder particle size. Under the experimental conditions, the addition of 8.37×10^-3g/L potassium borohydride can make the particle size of nickel powder less than 1μm. The reduction of nickel powder by hydrogen can reduce the oxygen content of the product and control the length of the powder particles. Under the condition of reduction temperature of 673.15K and reduction time of 120min, the oxygen content of nickel powder is 0.56%, and the particle size is 0.51μm. The nickel powder prepared under the optimized process conditions has a purity of higher than 99.5%, a particle size of 0.5~1μm, a specific surface area of 3.6~4.24m²/g, and a loose specific gravity of 0.5~0.6g/cm³. This index has reached the level of similar foreign products due to similar domestic products. The innovation of this research lies in the introduction of potassium borohydride to control the particle size range during the preparation of nickel powder and the use of hydrogen reduction for anti-oxidation treatment. This method has short process flow, good working environment, no pollution, and has promotion value.