Preparation of nano-crystalline Co powder from CoCO3

Abstract

abstract The nano-crystalline Co powder was prepared first by high-energy ball milling of CoCO 3 and then reduc-tion of its product of CoO. The nano-crystalline powders were characterized by means of XRD (X-ray dif-fraction) 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 ofthe 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-energyball milling confirm the probability for formation of Co 3 O 4 and CoO using the developed general com-puter program. The grain sizes of the Co powder reduced in H 2 atmosphere from CoO are below about40 nm below. The Co powder particles with sizes of 100 nm exhibit mainly an fcc phase and floccularmorphology. 2008 Elsevier Ltd. All rights reserved. 1. IntroductionCobalt metal and its compounds have found a wide range ofapplications in superalloy, magnetic materials, chemical catalyst,battery, cemented carbide and diamond tools. Cobalt nanoparticlesare expected to possess exceptionally high-density magnetic prop-erty, sintering reactivity, hardness levels, excellent impact resis-tance properties, etc. Many physical and chemical methods havebeen applied in fabrication of cobalt nanosized powders [1–8].Dong Jin Kin et al. reported on the preparation of 400 nm cobaltpowder from Co(OH)