EXPERIMENTAL STUDIES ON THE TRANSITION FROM XEROGELS TO GLASSES FOR THE SYSTEM SIO2-PBO-B2O3 WITH ADDED DMSO USING THE THERMAL-MASS SPECTROSCOPY COUPLING TECHNIQUE

The thermal-mass spectroscopy coupling technique (TG-DTA-MS) was used to study the thermal decomposition behaviour of the transition from xe rogels to glasses for the gradient refractive index materials SiO2-PbO -B2O3 with added dimethyl sulphoxide (DMSO). Compared with the TG-DTA- MS results for C2H5OH-system xerogels, the MS curves for DMSO-system x erogels show (in addition to CH3+ (m/z, 15)) the CH3O+ (mit, 31), C2H5 O+ (m/z, 45), [(CH3)(2)SO](+) (mz, 78), etc., positive-ion mass spectr um peaks. This indicates that adding DMSO enables many residual OR gro ups to remain in the forming xerogels. This was beneficial for the con densation of the incompletely hydrolysed product and for preventing cr acking of the xerogels. A preliminary study on the mechanism of therma l decomposition for DMSO-system xerogels is also given in this paper.