STRUCTURAL-CHANGES OF SILICA XEROGELS DURING LOW-TEMPERATURE DEHYDRATION

In this work, we investigated the temperature evolution of the structure of silica thin films by Fourier Transform Infrared (FTIR) Spectroscopy. The gels, prepared by hydrolysis and polycondensation in the presence of an excess of water to tetramethoxysilane, were thin enough to be studied in transmission. It was found that the removal of water from the pores and gel surface is easier when the gels are prepared in basic conditions. During the drying heat treatment, residual methanol oxidizes and produces formaldehyde, formic acid and formates. These species are still present in the gel at 300 degree C.