Reactions of Glasses with Aqueous and Nonaqueous Environments

Abstract

ABSTRACTReactions of glasses with the environment occur directly on the glass surface and inside the glass after diffusion of molecules into it. Water, either vapor or liquid, is the most important reactant, but other gases can react with surface and internal silicon-hydroxyl and silicon-oxygen groups. Substantial amounts of water can be introduced into glasses at high temperatures and pressures; the resultant hydrosilicates have unusual properties.In multicomponent alkali silicate glasses water preferentially leaches components; the mobile alkali ions are leached over a wide pH range. Analysis of alkali profiles is straightforward, but measurement of hydrogen profiles requires special care because of outgassing of water. Hydration transforms the surface structure of less durable silicate glasses, leading to rapid outgassing and rapid ionic transport in the transformed layer.The rate of dissolution of the silicon-oxygen network depends on temperature, glass composition, and solution components, especially pH.Heavy metal fluoride glasses dissolve in water, and glass components precipitate on the glass surface. These glasses are quite durable in humid air, with a slow reaction with water to form HF vapor.