COMPUTER MODELING OF NONISOTHERMAL CRYSTALLIZATION

A realistic computer model for simulating isothermal and non-isotherma l phase transformations proceeding by homogeneous and heterogeneous nu cleation and interface-limited growth is presented. A new treatment fo r particle size effects on the crystallization kinetics is developed a nd is incorporated into the numerical model. Time-dependent nucleation rates, size-dependent growth rates and surface crystallization are al so included. Model predictions are compared with experimental measurem ents of DSC/DTA peak parameters for the crystallization of lithium dis ilicate glass as a function of particle size, Pt doping levels, and wa ter content. The quantitative agreement that is demonstrated indicates that the numerical model can be used to extract key kinetic data from easily obtained calorimetric data. The model can also be used to prob e nucleation and growth behavior in regimes that are otherwise inacces sible. Based on a fit to data, an earlier prediction that the time-dep endent nucleation rare in a DSC/DTA scan can rise above the steady-sta te value at a temperature higher than the peak in the steady-state rat e is demonstrated.