Effect of Pressure on Glass Structure

Abstract

The anelastic response of a glass structure to pressure is examined in terms of the random‐network hypothesis. The analysis is based upon the premise that an asymmetrical distribution of bond lengths characterizes the randomness of the network. It is found that the effect of pressure is to change the amount of skewness and therefore the average bond length which determines the density. Two kinds of persisting density changes are found. One is reversible and is called densification, and the other is irreversible and is called compaction. Experimental results for Corning 7052 glass show that both densification and compaction exist for combinations of the p, T, τ conditions, 3800 to 6600 atmos, 100–300°C, 15 min—1 week. These experiments also show that the kinetics of the densification process agree qualitatively with that predicted by the theory.