Steam strengthened glass

A novel glass strengthening method is achieved by exposing glass to water vapor under high temperature and pressure to create a surface compressive stress layer. The development of a surface compressive layer during steam strengthening requires consideration of two competing processes: 1.) generation of network strain by a diffusion and reaction mechanism, which is described by water diffusion into the glass, resulting in both molecular water stuffing and hydroxyl group formation reaction to generate swelling and 2.) a time-temperature dependent viscoelastic stress relaxation that is accelerated by reduction in local viscosity due to increased water content. A simulation was conducted to support the proposed strengthening and subsequent stress relaxation mechanisms. The data collected from Raman spectroscopy, 31P and 27Al MAS NMR on steam-treated glasses support the atomic structure changes presented by the diffusion and reaction mechanism.