Chemical Durability of Glass

Abstract

The term ‘chemical durability’ has been used conventionally to express the resistance offered by a glass towards attack by aqueous solutions and atmospheric agents. There is no absolute or explicit measure of chemical durability and glasses are usually graded relative to one another after subjecting them to similar experimental conditions; the nature of the experiment usually determines the relative order. Interferometry and weight loss measurements on the attacked glass as well as alkalimetric titration, pH and electrical conductivity measurements on the extracts have been in common use in the past. In recent years a complete analysis of the leached solutions for all the glass components and a detailed analysis of the leached glass surface have provided useful information about the various factors involved in the decomposition of glass. For example, changes in the near corroded surface of glass (1-20 A) can be monitored with Auger electron spectroscopy (AES) [1]. Electron spectroscopy for chemical analysis (ESCA) [2], ion-scattering spectroscopy (ISS) [3] or secondary-ion mass spectroscopy (SIMS) [4]. Coupling these methods with ion-beam milling yields highly detailed compositional profiles of the intermediate glass surface (20-2000 A) [5]. Measurement of the average composition of the deeper surface layers (l-l0 000A) can easily be made with electron-microprobe analysis (EMP), energy-dispersive X-ray analysis (EOX) in the scar:ning electron microscope (SEM), or infrared reflection spectroscopy (IRRS) [6].