FINE NICKEL POWDER MADE BY HYDRO-METALLURGYPRESSED HYDROGEN REDUCTION

The present paper has discussed a hydrometallurgical pressurized hydrogen reducing technolgy. Fine nickel powder(0.2-1.0μm) was obtAlNed by direct reduction from slurry, using alkali lithium carbonate as raw materials and water as the medium of slurry.Reducing conditions are as follows:P_H2-25kg/cm², temperature-175℃ and quantity of alkali lithiun carbonate750g/L. A required quantity of sulphuric-acid was added into slurry allowing sufficient concentration of initiative nickel ion and eliminating the unstable factors arisen from the fluctuation of raw material composition and pH value.At the sametime, anthraquinone and other catalyst were added into shurry for increasing surface activity of solid, completely eliminating introductive period or shortening it from about 50 to 3-5 minutes with a result of great improvement of productivity. It was also shown that after the ascertainment of the concentration of initiative nickel ion the surface activity of solid can be controlled by odding different kinds and quantities of catalysts with the aim of controlling particle sizes of products. Besides,reaction mechanism has been discussed from the ellipsoidal shape of nickel powder.It is considered that the direct reduction of alkali nickel carbonate may be conducted by the reduction of nickel ion solved in liquid phase. Finally, nickel powder and aluminium powder (or other metal or ceramic powders) were compounded by spray drying process to obtain nickel-based composite powder suitable for hot spray coating.