Microhardness of SiO ₂ Glass in Various Environments

Abstract

It was shown in earlier studies that the crack initiation stress of SiO 2 glass was stressing‐time dependent only in water while it was time independent in nonaqueous liquids. In order to clarify the roles that various liquids play in the crack initiation of SiO 2 glass, Knoop microhardness measurements were made on SiO 2 glass in various liquids and FTIR spectroanalysis was performed on the indented SiO 2 glass. The microhardness measurements showed a similar loading‐time dependence to the crack initiation stress. The microhardness was separated into two parts: the surface contribution and the volume contribution. The results showed that the volume (or bulk) component was a nearly constant value for glass measured in nonaqueous liquids and that it was lower for glass measured in water. Consistent with these results, FTIR analysis showed that water entered the glass during indentation while nonaqueous liquids did not. The surface component showed a good correlation with the crack initiation stress.