Influence of the drying technique on the structure of silica gels

In the present research the influence of drying technique on the structural properties of silica gels prepared by different routes was studied. The si lica aquagels were obtained by hydrolysis of tetraethylorthosilicate Si(OEt )(4) (TEOS) under base- or acid-catalyzed conditions or by the gelation of SiO2 sol prepared by the fast hydrolysis of Na2SiO3 aqueous solutions in th e presence of HCl. The drying techniques employed were freeze-drying as com pared to conventional thermal drying at 80 degrees C. Properties of resulti ng xerogels and cryogels were studied by N-2 adsorption at 77K, DTA and SEM . It was shown that the structural changes during both freeze-drying and co nventional drying are strongly influenced by the structure of initial aquag el.