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

Abstract

Thermal decomposition of cobalt oxalate (CoC 2O 4·2H 2O) 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 CoC 2O 4 to Co. Isothermal kinetic studies were conducted for the second stage of decomposition at six different temperatures between 295 and 370 °C in reducing (He + 15 vol% H 2) atmosphere. Kinetic equation was found to obey g( α) = [−ln(1 − α)] 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 °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.