KINETICS OF CRYSTALLIZATION IN THE SODA LIME SILICA SYSTEM .1. NA2O.CAO.2SIO2 AND NA2O.CAO.3SIO2 GLASSES BY DTA

DTA curves for the crystallization of the title glasses of various particle size fractions were analysed kinetically using the modified Kissinger method proposed by Matushita and Sakka. The kinetic results were compared with those obtained from microscopic measurements. For the Na2O.CaO.2SiO2 glass, it was observed that the kinetic obedience changes from a surface reaction model to a bulk crystallization model with increasing particle size. The values of the apparent activation energy E(app) corresponded excellently to that obtained microscopically, i.e. 343 kJ mol-1. However, the crystallization of Na2O.CaO.3SiO2 glass was regulated by the surface reaction mechanism irrespective of the particle size examined; the values of E(app) decreased with increasing particle size but no direct correspondence of these values to those determined by the microscopic measurements were found. The complicated behaviour of E(app) was explained with reference to the role and function of the nucleation at the reaction interface.