Thermal decomposition kinetics of Algerian Tamazarte kaolinite by thermogravimetric analysis

The decomposition kinetics of Algerian Tamazarte kaolinite (TK) was investigated using thermogravimetric analysis (TG). Differential thermal analysis (DTA) and TG experiments were carried out between room temperature and 1400 degrees C, at different heating rates from 10 to 40 degrees C/min. The activation energies, measured by DTG from isothermal treatments using Johnson-Mehl-Avrami (JMA) and Ligero methods and by non-isothermal treatments using Ozawa, Boswell and Kissinger methods, were around 151 and 144 kJ/mol, respectively. The Avrami parameter of growth morphology (indicating the crystallization mode) was found to be around 1.57 using non-isothermal treatments; however, when using isothermal treatments it is found to be equal to 1.35. The numerical factor, which depends on the dimensionality of crystal growth, is found to be 1.53 using Matusita equation. The frequency factor calculated by the isothermal treatment is equal to 1.55x10(7) s(-1). The results show that the bulk nucleation is followed by three-dimensional growth of metakaolinite with polyhedron-like morphology controlled by diffusion from a constant number of nuclei.