Abstract
Low density aerogels have numerous unique properties which suggest a number of applications such as ultra high efficiency thermal insulation. However, the commercial viability of these materials has been limited by the high costs associated with drying at high pressures (supercritical), low stability to water vapor, and low mechanical strength. Normally, critical point drying is employed to eliminate the surface tension and hence, the capillary pressure, of the pore fluid to essentially zero. However, we show that by employing a series of aging and surface derivatization steps, the capillary pressure and gel matrix strength may be controlled such that gel shrinkage is minimal during rapid drying at ambient pressure. The properties (density, surface area, pore size, SAXS) of aerogel monoliths prepared from base catalyzed silica gels using this technique, supercritical CO2 drying, and supercritical ethanol drying are compared. An additional advantage of this approach is that the final gels are hydrophobic.
Similar content being viewed by others
References
L. W. Hrubesh, Chemistry and Industry, 24, 824 (1990).
J. Fricke and R. Caps in Ultrastructure Processing of Advanced Ceramics edited by J. D. Mackenzie and D. R. Ulrich (Wiley, New York, 1988), p. 613.
J. Fricke in Sol-Gel Technology for Thin Films. Fibers. Preforms. Electronics and Speciality Shapes edited by L. C. Klein (Noyse Publications, Park Ridge NJ, 1988), p. 226.
C. J. Brinker and G. W. Scherer, Sol-Gel Science (Academic Press, San Diego, 1990).
D. M. Smith, C. L. Glaves, P. J. Davis, and C. J. Brinker, In Situ NMR Study of Gel Pore Structure During Drying and Aging in Better Ceramics Through Chemistry III edited by C. J. Brinker, D. E. Clark, and D. R. Ulrich (Mater. Res. Soc. Proc. 121, Pittsburgh, PA 1988) pp.657–662.
P. J. Davis, C. J. Brinker and D. M. Smith, Journal of Non-Crystalline Solids, in press.
P. J. Davis, C. J. Brinker, D. M. Smith and R. A. Assink, Journal of Non-Crystalline Solids, in press.
R. Deshpande, D. W. Hua, C. J. Brinker and D. M. Smith, Journal of Non-Crystalline Solids, in press.
S. S. Kistler, Nature, 127, 741 (1931).
R. Deshpande, D. M. Smith, C. J. Brinker, U. S. Patent Application, 1992.
C. J. Brinker, K. D. Keefer, D. W. Schaefer, and C. S. Ashley, J. Non- Crystalline Solids, 48, 47 (1982).
G. W. Scherer, H. Hdach, and J. Phalippou, Journal of Non-Crystalline Solids, 130 (1991) 157.
Acknowledgements
This work was supported by the UNM/NSF Center for Micro-Engineered Ceramics which is a collaborative effort of the National Science Foundation (CDR-8803512), Los Alamos and Sandia National Laboratories, the New Mexico Research and Development Institute, and the ceramics industry. The authors would like to thank J. Anderson, W. Ackerman, and Dr. D.W. Hua of CMEC for sample preparation, nitrogen sorption, and SAXS analysis respectively and Dr. G.W. Scherer of Du Pont for loan of equipment and software for dimensional change measurements.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Smith, D.M., Deshpande, R. & Jeffrey Brinke, C. Preparation of Low-Density Aerogels at Ambient Pressure. MRS Online Proceedings Library 271, 567–572 (1992). https://doi.org/10.1557/PROC-271-567
Published:
Issue Date:
DOI: https://doi.org/10.1557/PROC-271-567