Change in the surface OH group on soda lime silicate glass and silica glass after heat treatment in nitrogen atmosphere

Abstract The contact angle of water is measured to estimate the wettability of soda lime silicate and silica glass surfaces. The contact angle of the silica glass is increased to 33° with the heat treatment at 850 °C under an N2 atmosphere, which gradually decreases with elapsed time finally reaching the similar value of 5° before the heat-treatment. This indicates that the surface OH content is reduced by the heat treatment and recovers with time to the initial value, which is qualitatively confirmed by D-SIMS measurements. On the other hand, the contact angle for the soda lime silicate glass surface is almost the same before and after the heat treatment under an N2 atmosphere. It is considered that hydration of the soda lime silicate glass surface proceeds faster than the silica glass through exchange with alkali and/or alkali-earth cations.