Borosilicate glass alteration in vapor phase and aqueous medium

Abstract

A Na-alumino-borosilicate glass and its Ca-doped counterpart were altered in vapor phase (98% relative humidity) and aqueous medium at 90 °C. Both the alteration media were enriched in 17O. Characterization of the altered samples pointed out some differences between glass alteration in aqueous medium and vapor phase in terms of the alteration kinetics, the effect of Ca-doping on glass chemical durability, the behavior of elements in the gel layer, and the structure of the gel layer. Some of the key results are the recondensation of boron in the gel layer formed in the vapor phase and the utility of Rotation Echo DOuble Resonance Nuclear Magnetic Resonance spectroscopy to qualitatively distinguish between signals from the pristine glass and hydrated gel layer within a sample that was not altered to the core. The results gave rise to inferences about glass alteration mechanisms in both the alteration media and the differences between them.