Crystal Nucleation In Glasses Research Articles

Combined Homogeneous and Heterogeneous Crystal Nucleation in Glasses

The temperature dependence of combined homogeneous and heterogeneous crystal nucleation is examined within the framework of the classical theory. It is demonstrated that nucleation can have a local maximum rate at one or two temperatures. The physical parameters which cause large changes in the structure of the nucleation curve are elucidated. Also, the influence of saturation effects on the structure of nucleation curves is illustrated. The utilization of these results for the interpretation of experiments and for the production of controlled crystal nucleation in glass is considered.

Isothermal and adiabatic nucleation in glass

A summary of both classical (isothermal) and adiabatic theories of nucleation is presented. Using experimentally determined parameters, such as viscosity, specific heat, glass transition temperature (Tg), melting temperature (Tf) and heat of fusion, the temperatures of maximum crystal nucleation rates, Tmax, were calculated for several glass forming systems and compared with experimental data. It is shown that both theories give a good estimate for Tmax. For systems which do not show volume (homogeneous) nucleation, Tmax is lower than Tg. For systems which show volume nucleation, Tmax >Tg. It is concluded that both theories can be used to predict the occurrence of internal crystal nucleation in glasses and that, in general, a high value of Tg (Tg/Tf > 0.58) indicates the absence of internal nucleation.