Stochastic approach to heterogeneous crystal nucleation in silicate glasses

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The project aims at creating a deeper understanding of the heterogeneous nucleation in silicate glasses by studying the mean lag time, nucleation rates and site activities from the time average of single nucleation events under dynamic and isothermal conditions. In particular, calorimetric experiments of repeated cooling-heating cycles which start and end above liquidus temperature of an individual glass volume are proposed. To account for the stochastic nature of nucleation ca. 300 cycles will be conducted in each experiment. Different series of experiments are designed to explore the nature of the nucleation sites from changing their geometry and number of as well as the type of contact material. Numerical calculations and the comparison of their results with experimental data are intended to improve the theoretical description of underlying heterogeneous nucleation mechanisms which will help to make predictions on their crystallization kinetics more reliable. On the practical side the experimental data will provide statistical certainty in contrast to previous one-time cooling experiments and will allow to construct temperature-time-transformation (TTT) and continous-cooling-transformation (CCT) diagrams. These representations of the crystallization kinetics from which for example critical cooling rates can be deduced are most relevant to industrial practice since heterogeneous nucleation is the dominating mechanism to control crystallization in glass-ceramic manufacturing.