HYDROXYL-FREE CLEAR SILICA GLASS BY SOL-GEL PROCESSING

Hydroxyl (OH)-free clear silica glass bodies (plates, discs, rods and small tubes) were prepared by the sol-gel process. The method involved preparation of silica gel shapes via a mixed sol obtained from tetraethyl orthosilicate, fumed silica and acidulated water. The gels were then heat treated in different atmospheres (oxygen, vacuum, carbon tetrachloride and helium) up to 1500-degrees-C for obtaining fully dense clear silica glass bodies. Infrared spectra of the glasses prepared at 1500-degrees-C showed complete absence of hydroxyl groups. The average surface hydroxyl coverage of the gels and the residual hydroxyl content of the glass bodies were determined.