Mechanical Stability of the Surface of Quartz Glass Subjected to Fine Annealing

Abstract

The results of studying the state of the surface of silica glass with a high content of OH groups obtained by high-temperature hydrolysis of SiCl4 and that it finely annealed are presented. A comparison of the IR reflection spectra before and after annealing showed the decomposition of silanol groups with the release of water from the material and the appearance of nonbridging Si–O– groups. Some of the nonbridging bonds are reduced to form three- and four-membered siloxane rings. To assess the change in the mechanical properties of the glass surface during annealing, the samples were subjected to point impact damage, in which the intensity of microcrack accumulation in the damaged layer were controlled by acoustic emission method. The marked attenuation of the mechanical strength of the annealed glass surface is attributed to the formation of small siloxane rings and a decrease in the connectivity of the silicate network due to the presence of residual nonbridging bonds.