Kinetic Studies of Crystallization of Synthetic Mica Glass

The mechanism of crystallization of a synthetic mica glass was studied on the basis of microstructures and reaction kinetics. Uniform crystallization of this glass was found to occur by a two-stage process. The glass first transformed to an intermediate pseudocrystalline phase from which mica crystals subsequently were formed. The kinetics of the reaction leading to this intermediate pseudocrystalline phase were studied quantitatively by microscopic methods. The nucleation of this intermediate phase was found to be heterogeneous. The growth of the rim of the plate-shaped intermediate phase was an interface-controlled process having an activation energy of 84 kcal per mole. The rate of growth of the intermediate phase was found to be consistent with previous relations that describe the kinetics of growth of crystals from a glass. The final mica phase initially formed at the interfaces of the intermediate phase and parent glass phase; later it progressively formed within the intermediate phase.