Preparation process and mechanism of ultra-fine spherical cobalt powders by hydrogen reduction of calcium cobaltite

Abstract

For the improvement of the properties of cemented carbides, ultra-fine spherical cobalt powders as binder were prepared using calcium cobaltite. The effects of the ratio of CaO to CoO, the calcination temperature and the reduction temperature on particle size and morphology of cobalt powders were studied. The results show that the average particle size of cobalt powders decreases with increasing the weight ratio of CaO to CoO, but increases with the calcination temperature and reduction temperature. The spherical cobalt powders with the mean particle size of 84 nm are obtained when the weight ratio of CaO to CoO is 7:4 and the calcination temperature and reduction temperature are 1000 °C and 700 °C, respectively. In addition, CaO regarded as the blocking agent can refine cobalt powders during the hydrogen reduction process.