Physical and Structural Characteristics of Gel-derived Glasses Prepared via Different Drying Procedures

In the present work, monolithic gels were prepared through different drying procedures including super critical, infrared wavelengths and traditional drying methods. Dense and transparent glasses were obtained after controlled heat treatment of the dried porous xerogels in air atmosphere. The chemical bonding as well as different properties of the prepared gels and the relevant glasses were examined by means of Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmitt- Teller (BET) and UV-Vis spectrometer. Based on the obtained results, different drying conditions affect the average pore size and the total pore volume of the studied gels. The mean pore size was found to be 8.7 nm, 2.4 nm and 3.2 nm for super critical, IR radiation and slow drying in air atmosphere, respectively. The glass network structure was significantly changed by heat treatment  temperature so that the B-O-Si bonds were formed only after 450 °C. It was found that the gel dried under super critical condition was unable to reach to its full density all over the selected sintering temperature interval.