Hydroxyl Formation By Reaction Of Molecular Hydrogen With Germania-Doped Vitreous Silica

Hydroxyl species formation in 100 mol% SiO2 6 mol% GeO2-94 mol% SiO2 and 14.6 mol% GeO2-85.4 mol% SiO2 glasses was monitored by infrared spectroscopy as a function of time under a hydration atmosphere of 700 Torr (pH2=93kPa) at 500; 600; 700; and 800 deg C. The rate of hydrogen reaction with binary GeO2-SiO2 glasses increases with increasing temperature and germania content. Hydroxyl concentration is uniform throughout the thickness of the sample after completion of the reaction. Hydride species do not form during heat treatment in hydrogen at any of the temperatures in any of these glasses. These reactions can be described by the tarnishing model.