Effect of pH dependent gelation time and calcination temperature on silica network in SiO2-CaO and SiO2-MgO glasses

In this work we report a study on structural aspects of pure SiO2, and 0.7SiO2·0.3CaO and 0.7SiO2·0.3MgO binary systems prepared by sol-gel method under different pH conditions that influence the gelation time leading at low pH to a slow gelation and at higher pH to a rapid gelation. By means of DTA/TG, XRD, BET, SEM and FTIR analyses it was evidenced that the short range order of pure silica glass is maintained to a large extent in the quickly gelled binary systems incorporating a relative high amount of alkaline earth oxides.