The effect of particle size on the kinetics of thermal decomposition of Co(C2O4)·2H2O nanopowders under non-isothermal conditions

Abstract

Cobalt oxalate dihydrate nanopowders have been prepared by precipitation method. The crystal size of Co(C2O4)·2H2O obtained in the absence and presence of CTAB surfactant was 30 and 60 nm, respectively. The effect of particle size on the thermal decomposition of Co(C2O4)·2H2O powders in air was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). Non-isothermal studies revealed that the decomposition occurred in two main stages: removal of water and next decomposition of CoC2O4 to Co3O4. Both oxalate and the final decomposition residue were characterized by means of XRD, FT-IR and TEM techniques. The kinetic parameters of the two decomposition steps were evaluated from TG to DTG data by several integral and differential calculation methods. Based on the iterative isoconversional calculation procedure, the activation energy values Eit associated with the decomposition steps were evaluated. Kinetic parameters are given, and the most probable mechanism functions are suggested. The results show that the decomposition increases with decreasing the particle size.