Differential thermal analysis on the crystallization kinetics of K2O-B2O3-MgO-Al2O3-SiO2-TiO2-F glass

The crystallization kinetics of a glass based on one type of mica, NaMg3AlSi3O10F2, with the addition of a nucleating agent, TiO2, has been studied using differential thermal analysis (DTA) under both isothermal and nonisothermal conditions. Two distinct crystallization exotherms in the DTA curve are observed and resolved that correspond to the initial formation of magnesium titanate (MgTi2O5) and the later formation of mica, The activation energy for precipitation of each crystalline phase has been evaluated, and the crystallization mechanism has been studied. The results indicate that the growth of mica is a two-dimensional process, controlled by the crystal-glass interface reaction. The average calculated values of activation energies are 256 +/- 11 kJ/mol and 275 +/- 6 kJ/mol for the precipitation of MgTi2O5 and mica from the glass matrix, respectively.