KINETICS OF THE DECOMPOSITION OF CALCIUM-CARBONATE IN THE PRESENCE OFBI2O3

Former studies concerning the formation of the compounds in the pseudo binary systems of Bi2O3-MO type (M = Ca, Sr, Ca + Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the pres ence of Bi2O3 in comparison with the decomposition of pure CaCO3. The presence of Bi2O3 exerts a complex influence on the CaCO3 decompositio n acting on the nucleation as well as on the diffusion of CO2. The dec omposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nuc leation is recorded for higher amounts of Bi2O3.