Damage by Hydroxyl Generation in Silica

When water diffuses into silica glass it reacts chemically forming nanometre sized pores that change the physical properties of the glass, for example, affect its strength. Here we discuss the effect of water on Young’s modulus, and show how it is reduced by the water reaction, whereby a proportional behaviour applies to small amounts of water involved in the reaction. The value of the elastic modulus will be not linear with the hydroxyl-quantity in the glass for very high concentrations. The relationship between hydroxyl concentration and Young’s modulus can be determined from measurements of sound wave velocity and will be represented by damage and pore models from literature.