Study on thermodynamic equilibrium and character inheritance of cobalt carbonate decomposition

Abstract

Presently, the main cobalt powder production method is the reduction of cobalt carbonate, and the decomposition process significantly influences the properties of the ensuing cobalt powder. Thus, the objective of this study was to investigate CoCO3 decomposition using thermodynamic simulations and calculations, as well as experiments. The results obtained led to the conclusion that in the absence of oxygen, CoCO3 primarily decomposes into CoO and CO2. However, in the presence of oxygen, it preferentially undergoes oxidation decomposition, generating Co3O4 and CO2, while the unreacted CoCO3 subsequently decomposed forming more CoO when O2 was exhausted. Additionally, Co3O4 decomposed to CoO and O2 at high temperatures. TG-DSC-MS analyses showed that the temperature at which CoCO3 decomposed into CoO was 332 °C. The analysis of the CoCO3 decomposition process performed in an inert atmosphere showed that the decomposition product, CoO was generated at temperatures above 300 °C. Furthermore, SEM results showed that the morphology of the CoO obtained depends on that of the raw material (CoCO3), and a higher temperature induced agglomeration; thus, increasing CoO size. Lower decomposition temperatures, higher gas flow rates, and lower heating rates resulted in a decrease in CoO particle size.