Laser-based and thermal studies of stress corrosion in vitreous silica

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Abstract
Crack-propagation rates in vitreous silica were monitored as specimens were heated thermally or irradiated by a laser beam. The laser was tuned to the OH bond vibration to determine the role of OH stretching in the dissociative chemisorption mechanism for stress corrosion of silica in moist environments. Laser radiation heated the silica near the crack tip but did not generate any bond-specific changes in crack velocity. For samples maintained in moist air, the propagation velocity decreases as temperature increases. The temperature dependence of crack velocity indicates that physisorption is an important step in stress corrosion, and a simple model of the process is proposed.