Bulk and surface crystallization of silicate glasses

Kinetic aspects of nucleation in the bulk and on the surface of silicate glasses are analyzed using earlier experimental data. The number of nucleating crystals and the rate of steady-state nucleation are evaluated as functions of time and temperature, respectively. It is shown that glass crystallization can be adequately described in the framework of classical nucleation theory if account is taken of the temperature and nucleus-size dependences of the Gibbs energy of the interface between the glass-forming melt and a critical nucleus. The temperature at which the steady-state nucleation rate reaches a maximum is higher than the glass-transition temperature T-g in the case of surface nucleation and close to T-g in the case of bulk nucleation.