A study on isothermal kinetics of thermal decomposition of cobalt oxalate to cobalt

Thermal decomposition of cobalt oxalate (CoC2O4 center dot 2H(2)O) was studied using TG, DTA and XRD techniques. Non-isothermal studies revealed that the decomposition occurred in two main stages: removal of water and next decomposition of CoC2O4 to Co. Isothermal kinetic studies were conducted for the second stage of decomposition at six different temperatures between 295 and 370 degrees C in reducing (He + 15 vol% H-2) atmosphere. Kinetic equation was found to obey g(alpha) = [-In(1 - alpha)](1/n) = kt relationship with varying values of n between 2 and 4. The variation of activation energy between 73.23 and 119 kJ mol(-1) from the lowest to the highest temperature of decomposition indicated the multi-step nature of the process. SEM analysis revealed the formation of nano-size powder in this temperature range. Thermal decomposition at 550 degrees C for 30 min was found to be optimum condition producing fine size, non-pyrophoric and spherical powder in larger scale of production. Both hcp and fcc phases were present in the cobalt powder at room temperature. (C) 2008 Elsevier B.V. All rights reserved.