Nucleation and crystallization kinetics of CaO-Al2O3-2SiO(2) in powdered anorthite glass

The nucleation and crystallization kinetics of CaO-Al2O3-2SiO(2) crystals in powdered anorthite glass with particle size < 44 mu m in which CaO-Al2O3-2SiO(2) crystals were found to crystallize in the heating process of the glass, were studied by nonisothermal measurements using differential thermal analysis (DTA). The temperature of maximum nucleation rate was determined from the DTA curves of samples heat treated at different temperatures. The activation energy and kinetic parameters were simultaneously calculated from the DTA data using previously reported kinetic models. The crystallization process of a sample heat treated at the temperature of the maximum nucleation rate was fitted to kinetic equations with an Avrami constant, n congruent to 2 and a dimensionality of crystal growth, m congruent to 2, indicating that the constant number of nuclei of CaO-Al2O3-2SiO(2) precipitated in a glass matrix grew two-dimensionally with an activation energy taken as an average of the values calculated by the Kissinger and also the Augis and Bennett method of 679 +/- 4 kJ mol(-1).