Preparation of nano-crystalline Co powder from CoCO3

Abstract The nano-crystalline Co powder was prepared first by high-energy ball milling of CoCO 3 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 CoCO 3  + Co 3 O 4 to CoO within 60 h. The standard free energy changes for chemical reductions during high-energy ball milling confirm the probability for formation of Co 3 O 4 and CoO using the developed general computer program. The grain sizes of the Co powder reduced in H 2 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.