Thermal dissociation mechanism and morphological inheritance of basic cobalt carbonate

Rod-like basic cobalt carbonate (BCC) was prepared by reaction-precipitation method using CoCl2 &middot 6H2O and NH4HCO3 as starting materials. The thermal dissociation process of the prepared BCC was studied by TG-DTA-DSC thermal analysis technology. X-ray diffraction technology was used in the study of the phase composition of the thermal dissociation products of BCC calcined at different temperatures. Scanning electron microscopy was used in the observation of the morphologies of the BCC and its dissociation product at 700°C, i.e. Co3O4. It is shown that, after the calcining of the BCC at 450°C for 3 h, CoO still existed in the product with a mass fraction as high as 50.5%, indicating that the complete dissociation temperature of BCC to Co3O4 must higher than that of the predicted value of 359.5~421.1°C by thermal analysis. Pure Co3O4 can be prepared by calcining of the BCC at 700°C. Calcining of the BCC at 850°C which is lower than the predicted lowest temperature, i.e. 910~920°C by thermodynamics for the dissociation of Co3O4 to CoO, the mass faction of CoO dissociated from Co3O4 is as high as 47.93%. Therefore, for the preparation of pure Co3O4, the calcining condition must be controlled strictly. Based on the observed morphology inheritance of Co3O4 to its precursor BCC, it can be deduced that the morphology of Co3O4 can be controlled effectively through the controlling of its precursor.