Structural and textural study of the effects of metal ions on the densification kinetics of nanoporous silica xerogels

Doped and undoped 50 A porous silica xerogels were heated at 1050 °C for periods of 5 s to 4 h. Raman spectroscopy was used to follow the structural changes occurring at various stages of the gel-to-glass transformation as well as to investigate the effects of metal ions on the structure of nanoporous silica xerogels. Raman spectra and textural measurements using nitrogen-gas sorption showed that while the heat-treatment time required to obtain the final densified state is shortened by a factor of 80 for a material doped with Ag+ ions, in the case of Ce3+, the densification time is prolonged by 30%.