EFFECT OF STRESS ON WATER DIFFUSION IN SILICA GLASS AT VARIOUS TEMPERATURES

Effects of stress on diffusion of water into silica glass were studied at several temperatures by hydrothermally treating the glass under applied stress. The surface hydrogen concentrations were determined using nuclear reaction analysis and the hydroxyl concentration profiles were analyzed with a Fourier transform infrared spectrophotometer. It was found that the effects of stress on water diffusion into silica glass strongly depend upon temperature; specifically the concentration of water in the glass surface is higher in glass under compression than in glass under tension at low temperatures (e.g., 250-degrees-C), while an opposite behavior was observed at high temperatures (e.g., 650-degrees-C). On the other hand, the effective diffusion coefficient of water was higher under tension than under compression at low temperatures, while the opposite behavior was observed at higher temperatures. The low temperature behavior was attributed to the effect of stress on the kinetics of water uptake, and the high temperature behavior was attributed to the effect of applied stress on the glass-water reaction equilibrium.