Preparation of nano-crystalline Co powder from CoCO3

The nano-crystalline Co powder was prepared first by high-energy ball milling of CoCO3 and then reduction of its product of CoO. The nano-crystalline powders were characterized by means of XRD (X-ray diffraction) and SEM (scanning electron microscope). The XRD patterns data were analyzed by MDI Jade 5.0. The results show that the nano-crystalline grain sizes of the powders are decreased with the increase of the ball milling time, and the phase transformations during high-energy ball milling are from CoCO3 + Co3O4 to CoO within 60 h. The standard free energy changes for chemical reductions during high-energy ball milling confirm the probability for formation of Co3O4 and CoO using the developed general computer program. The grain sizes of the Co powder reduced in H2 atmosphere from CoO are below about 40 nm below. The Co powder particles with sizes of 100 nm exhibit mainly an fcc phase and floccular morphology.