CHARACTERIZATION OF B2O3-SIO2 GLASSES PREPARED VIA SOL-GEL

B2O3-SiO2 glasses were prepared by the sol-gel method from boron and silicon alkoxides. The gels were densified by several heat-treatments at temperatures above 800°C. The gel-glass transition was studied with the data obtained from differential thermal analysis, dilatometry and thermal evolution of density. The structural features of the glassy materials prepared were analyzed by means of infrared (IR) and near-infrared (NIR) spectroscopy. The IR spectra indicated the existence of mixed Si-O-B bonds, preferential located at the outside of the material particles. The NIR spectra, recorded from gels heat-treated at low temperatures, demonstrated the existence of a great number of OH- groups varying in nature, as well as their evolution and their positional changes on the silica particle surface as a function of the heat treatment.