Crystallization Mechanism and Kinetics of BaO-Li2O-ZrO2-SiO2 Glasses

Abstract

Differential thermal analysis and scanning electron microscopy were used to determine the influence of the addition of BaO on the crystallization mechanism of Li2O-ZrO2-SiO2 systems. As the concentration of BaO in the samples increased, a transition occurred in the predominant crystallization mechanism, which passed from superficial to volumetric. To determine the maximum nucleation rate, the crystallization kinetics of the sample containing 20 mole % BaO, which showed the most uniform crystallization, was studied by counting the nuclei with an image analyzer. The first nuclei appeared at the first endothermic inflection point (at the start of Tg, at 440 °C), while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 °C). These results are similar to those observed for other materials that crystallize in volume, and confirm scanning electron microscopy data

Numerical study of the stress response of two-dimensional dense granular packings

“…More-over, [13] shows that the elastic framework can be further extended to anisotropic system. However, other experiments [14,15,16,17,18,19,20] show evidence for the possible validity of alternative approaches: [14] discusses the lateral diffusion of vertical stress increments due to the local application of a force in a brick wall; [16] and [20] focus on relatively small scale response experiments and [20] on ordered lattices; The study on isostatic networks of [16] and [19] show deviations from elasticity. These groups argue that on approaching the isostatic point the elasticity theory would break down and new approaches need to be considered to describe the stress response.…”