Structural evolution of silica-gel in the late stages of the gelation process

Infrared spectroscopy has been used to analyze the structural changes in sa mples prepared-by the sol-gel method. Silica gels were prepared from alcoho lic solutions of tetraethylorthosilicate (TEOS) keeping the H2O/TEOS and Et -OH/TEOS molars ratios constant and equal to 11.66 and 4, respectively. The IR spectra was carried out in the wet state, before or after gelation whil e the gel was still impregnated by pore liquor. The IR spectra of these gel s, measured as a function of the gelation time, confirm that the final stru cture of the material is in relationship with the pattern in the late stage s of this gelation process. The preliminary results of IR allows some struc tural considerations to be advanced about the final SiO2 glasses obtained.