Structural properties of silica gels prepared from oxalic-acid-catalyzed tetraethoxysilane sonohydrolysis

✍ Scribed by Donatti, D. A. ;Ruiz, A. Ibañez ;Vicelli, M. R. ;Vollet, D. R.

• Book ID: 105363908
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 358 KB
• Volume: 204
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200622394

✦ Synopsis

Abstract

About ∼2.1 × 10^−3^ mol SiO~2~ cm^−3^ and ∼88%‐volume liquid‐phase silica wet gels were prepared from oxalic‐acid‐catalyzed tetraethoxysilane (TEOS) sonohydrolysis. Aerogels were obtained by supercritical CO~2~ extraction. The samples were analyzed by thermogravimetry, small‐angle X‐ray scattering and nitrogen adsorption. Wet gels can be described as mass fractal structures with fractal dimension D ∼ 1.94 and structural characteristic length ξ changing between ∼3.3 to ∼3.0 nm in the studied range of the catalyst concentration. A fraction of the porosity is apparently eliminated in the supercritical process. The values of the BET specific surface S~BET~, the total pore volume V~P~ and the mean pore size l~P~ of the aerogels were found to change almost randomly around the mean values S~BET~ = 874 m^2^ g^−1^, V~P~ = 0.961 cm^3^ g^−1^ and l~P~ = 4.4 nm with catalyst concentration variation. These values were not substantially different from those from an equivalent HCl‐catalyzed aerogel. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)