Influence of the Presence of Bubbles on the Parameters of Crystal Nucleation in the 26Li2O · 74SiO2 Glass

摘要

The crystal nucleation in the glass of composition (mol %) 26Li2O · 74SiO2 has been investigated in the cases of homogeneous and heterogeneous nucleation. Parameters of homogeneous nucleation, such as the stationary nucleation rate I_(st), the time of nonstationary nucleation x, and the crystal growth rate U, have been determined. The temperature dependences of these parameters have been constructed. The surface energy σ at the nucleus-glass melt interface has been determined, and its temperature dependence has been obtained. The surface energy σ has been evaluated using the graphical method for solving the transcendental equation derived by transforming the relationships for the stationary crystal nucleation rate and the time of nonstationary crystal nucleation. The critical nucleus sizes r* and the free energy of formation of the critical nucleus Φ* have been determined. The heterogeneous nucleation on bubbles specially produced in the glass has been studied. It has been demonstrated that the presence of bubbles in the initial glass does not affect the crystal growth rate and substantially changes the nonstationary nucleation rate. The largest contribution to the change in the nucleation rate is made by "active" bubbles (filled by water vapor) formed in the glasses synthesized with the use of hydrated silicon dioxide.