Abstract
Silica aerogels were synthesised by subcritical drying technique which involves controlled solvent exchange and aging of the wet gel in silane solution followed by drying under controlled conditions. Effect of temperature of aging in silane solution on the porosity characteristics of silica aerogels and the thermal pore stability of the resultant gels were investigated. Aging in silane solution leads to an increased degree of condensation reactions, siloxane crosslinking and the dissolution and reprecipitation of silica monomers to the gel structure and enhances the total strength of the gel. Thermal aging of the wet gel have a pronounced effect on bulk density, linear drying shrinkage, surface area and pore volume. As the temperature of aging increases the bulk density decreases whereas the surface area and pore volume were found to increase. We could achieve a surface area of 1040 m2/g, pore volume 1.2 cc/g and an average pore size of 49 Å corresponding to an aging temperature of 70 °C. Thermal pore stability of the gel was found to be up to 700 °C above which densification of SiO2 gel starts. The novel findings will help in tailoring the process parameters to prepare mesoporous oxides from sol–gel precursors with specific pore features.
Similar content being viewed by others
References
S.J. Teichner, in Aerogels, Springer Proceedings in Physics, ed. by J. Fricke (Springer, Berlin Heidelberg New York, 1986), p. 22
P. Tsou, J. Non-Cryst. Solids 186, 415 (1995)
M.S. Ahmed, Y.A. Attia, J. Non-Cryst. Solids 186, 402 (1995)
J. Alkemper, T. Bucholz, K. Murakami, L. Ratke, J. Non-Cryst. Solids 186, 395 (1995)
R.W. Pekala, S.T. Mayer, J.L. Kaschmitter, F.M. Kong, in Sol–Gel Processing and Applications, ed. by Y.A. Attia (Plenum Press, New York, 1994), p. 369
H.D. Gesser, P.C. Goswami, Chem. Rev. 89, 765 (1989)
G. Hermann, R. Iden, M. Mielke, F. Teich, B. Ziegler, J.␣Non-Cryst. Solids 186, 380 (1995)
B.C. Dave, B. Dunn, J.S. Valentine, J.I. Zink, Mater. Res. Soc. Symp. Proc. 431, 285 (1996)
S.J. Teichner M. Khalfallah D. Bianchi J.L. Gass, in Sol–Gel Processing and Applications, ed. by Y.A. Attia (Plenum Press, New York, 1994), p. 323
J. Fricke, A. Emmerling, J. Am. Ceram. Soc. 75, 2027 (1992)
M.M. Girona, E. Martinez, A. Roig, J. Esteve, E. Molins, J.␣Non-Cryst. Solids. 285, 244 (2001)
M.A. Einarsrud, M.B. Kirkedelen, E. Nilsen, K. Mortensen, J. Samseth, J. Non-Cryst. Solids 231, 10 (1998)
C.J. Brinker, G.W. Scherer, Sol–Gel Science: The Physics and Chemistry of Sol–Gel Processing (Academic Press, New York, 1989)
R. Deshpande, D.M. Smith, C.J. Brinker, J. Non-Cryst. Solids 144, 32 (1992)
M.A. Einarsrud, E. Nilsen, J. Non-Cryst. Solids 226, 122 (1998)
S. Haereid, E. Nilsen, M.A. Einarsrud, J. Non-Cryst. Solids 204, 228 (1996)
S. Haereid, M. Dahle, S. Lima, M.A. Einarsrud, J. Non-Cryst. Solids 186, 96 (1995)
R. Takahashi, K. Nakanishi, N. Soga, J. Non-Cryst. Solids 189, 66 (1995)
V. Rao, A. Parvathy Rao, M.M. Kulkarni, J. Non-Cryst. Solids 350, 224 (2004)
S. Haereid, J. Anderson, M.A. Einarsrud, D.W. Hua, D.M. Smith, J. Non-Cryst. Solids 185, 221 (1995)
M.K. Titulaer, J.B.H. Jansen, J.W. Geus, J. Non-Cryst. Solids 170, 11 (1994)
H. Hdach, T. Woignier, J. Phalippou, G.W. Scherer, J. Non-Cryst. Solids 121, 202 (1990)
P.J. Davis, R. Deshpande, D.M. Smith, C.J. Brinker, R.A. Assink, J. Non-Cryst. Solids 167, 295 (1994)
E. Nilsen, V. Ranum, A. Einarsrud, J. Sol–Gel Sci. Technol. 8, 153 (1997)
S. Smitha, P. Shajesh, P.R. Aravind, S. Rajesh Kumar, P. Krishna Pillai, K.G.K. Warrier, Microporous Mesoporous Mater. 91, 286 (2006)
R.K. Iler, The Chemistry of Silica (Wiley, New York, 1979)
S. Rajesh Kumar, P. Krishnapillai, K.G.K. Warrier, Polyhedron 17, 1699 (1998)
S.J. Gregg, K.S.W. Sing, Adsorption, Surface Area and Porosity, 2nd edn. (Academic Press, London, 1995)
Acknowledgements
The authors gratefully acknowledge Defence Research and Development Organisation for funding the work. Authors S.S and P.S acknowledge DRDO and CSIR, respectively for their fellowship.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Smitha, S., Shajesh, P., Rajesh Kumar, S. et al. Effect of aging temperature on the porosity characteristics of subcritically dried silica aerogels. J Porous Mater 14, 1–6 (2007). https://doi.org/10.1007/s10934-006-9000-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10934-006-9000-7