Preparation of submicrometer nickel powders by the reduction from nonaqueous media

Nickel powders in the submicrometer size range were prepared by a chemical reduction-precipitation method from nonaqueous solutions of nickel salts. Hydrazine was used as the reducing agent and paraffin oil, ethylene glycol, di- and tri-ethanolamine as the reaction media in order to carry out the reactions at higher temperatures, and, for the latter two media, to provide the appropriate basic environment for the reduction. The characteristics of the resulting endproducts, especially the particle size and size distribution, as well as the micromorphological characteristics, the yield of the reaction and the purity of the nickel powders, depend on the reaction conditions. The mean particle size of the nickel powders can be lowered also by changing the homogenous nucleation into a heterogeneous one by adding traces of palladium. Nickel powders with mean particle sizes ranging from 0.1 to several mu m and with up to 99.8% purity were obtained in this way. (C) 1999 Acta Metallurgica Inc.