THE EFFECT OF PROCEDURAL VARIABLES AND MECHANICAL ACTIVATION ON THE THERMAL-DECOMPOSITION OF CALCITE - AN APPROACH BY EXPERIMENTAL-DESIGN

Second-order orthogonal experimental design has been used to examine t he effect of mechanical activation, mass sample, heating rate and mola r fraction of carbon dioxide in the environmental atmosphere on the th ermal decomposition of calcite. The mathematical model of the activati on energy (E(alpha)) for various mechanisms was examined by the Coats- Redfern equation using the best-fit procedure and the method of the sh ape of the TG/DTG curves. The best-fit procedure gave the second-order reaction mechanism (F2) as the predominant mechanism while the shape method gave the contacting area geometrical mechanism (R2) and the two -dimensional diffusion mechanism (D2) as the predominant mechanisms. T he mathematical models for the change of enthalpy (Delta H) and the te mperature of the maximum rate of decomposition (T-max) were found, but unfortunately only the T-max model was of significance.