Controllable preparation and regulation mechanism of ultrafine spherical cobalt powders

The CoCO₃ precursors with fine, uniform, and controllable particle size were prepared by liquid-phase precipitation method, using CoCl₂·6H₂O and NH₄HCO₃ as raw materials, and then the ultrafine spherical cobalt powders were prepared by calcination-hydrogen reduction. The influence of stirring time and reaction temperature on the particle size and morphology of CoCO₃ precursors in the liquid-phase precipitation method was analyzed, and the effect of reduction temperature and reduction time on the phase, particle size, and microstructure of the reduction products was investigated. The results show that the nucleation rate of CoCO₃ precursors increases with the increase of stirring time and reaction temperature, and then the average particle size of CoCO₃ decreases. The CoCO₃ precursors with uniform particle size, high sphericity, and average particle size of 0.96 μm are prepared, when the stirring time is 45 min and the reaction temperature is 25 ℃. In the hydrogen reduction, the particle size of cobalt powders increases with the increase of hydrogen reduction time and temperature. When the hydrogen reduction temperature is 400 ℃ for 45 min, the cobalt powders show the good dispersion and uniform particle size with the average particle size of 0.4 μm