A study was performed to prepare spherical cobalt powder of about 400 nm from aqueous cobaltous hydroxide slurry under hydrogen reduction conditions using palladium chloride as a catalyst. The reduction kinetics showed good agreement with a surface reaction core model equation, and the activation energy of 35.6 kJ/mol was obtained from the Arrhenius plot at the temperature range of 145-195degreesC. Additionally, a relationship between the half-life of the reduction, the induction period, and the hydrogen gas pressure was found to be as t(1/2) - t(i) = aP(H2)(1-n). (C) 2002 Elsevier Science Ltd. All rights reserved.