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Abstract
In the present work, the kinetics of mullite (3Al2O3.2SiO2) formation from Algerian kaolin was investigated using differential thermal analysis (DTA). The raw kaolin was wet ball milled for 5 h followed by attrition milling for 1 h. Differential thermal and thermogravimetric (DTA/TG) experiments were carried out on samples between room temperature and 1350°C at heating rates of 5, 10, 20 and 40°C min−1. The temperature of mullite crystallisation was found to be ∼1005°C. The activation energies measured from isothermal and non-isothermal treatments were around 1290 and 1260 kJ mol−1 respectively. The growth morphology parameters n (Avrami parameter which indicates the crystallisation mode) and m (a numerical factor which depends on the dimensionality of crystal growth) were found to be almost equal to 1˙5. Analysis of the results showed that bulk nucleation was dominant in mullite crystallisation followed by three-dimensional growth of mullite crystals with polyhedron-like morphology controlled by diffusion from a constant number of nuclei.