Methods to Estimate the Number of Surface Nucleation Sites on Glass Particles

Abstract

Based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, we propose two new models to describe the crystallization kinetics of glass particles and use them to determinate the density of nucleation sites, Ns, on glass powders. We test these models with sintered compacts of diopside glass particles using sinter-crystallization treatments at 825 C (Tg~727 C), that covered from null to almost 100% crystallized volume fraction. We measured and compared the evolution of the crystallized volume fractions by optical microscopy and X-ray diffraction. Then we fit our expressions to experimental data using Ns and R (the average particle radius) as adjustable parameters. For comparison, we also fit to our data existing expressions that describe the crystallized volume fraction in glass powders. We demonstrate that all the methods allow one to estimate Ns with reasonable accuracy. For our ground and water-washed diopside glass powder, Ns is between 1010 - 10^11 sites.m^-2. The reasonable agreement between experimental and adjusted R confirms the consistency of all these methods. For one of our equations one does not need to deal with the change of crystallization mechanism from 3-dimension to 1-dimension model.