| abstract |
A method for producing powdered metallic cobalt, comprising ultrafine metallic cobalt powder, by reducing cobalt sulfate ammonia (2+) in solution. A soluble silver salt, preferably silver sulfate or silver nitrate, is added in an amount providing a mass ratio of soluble silver to cobalt of 0.3-10 g of silver: 1 kg of cobalt, an organic dispersant, for example bone glue or polyacrylic acid or a mixture thereof, is introduced in an amount 0.01 to 2.5% by weight of cobalt, establish a molar ratio of ammonia to cobalt equal to 1.5: 1 - 3.0: 1, preferably 2.0: 1, heat the solution to 150 - 250 ° C, preferably approximately 180 ° C, with stirring under a hydrogen pressure of 3000 - 4000 kPa in those the induction period and the recovery period sufficient to reduce cobalt sulfate (2+) to cobalt metal in powder form. The ultrafine cobalt powder has globular particles of submicron size with a specific surface area of more than 2.0 m / g. Particle size and specific surface are essential for sintering at lower temperatures and to achieve the desired density of the sintered product. |