Monolithic silica aerogels

Rigacci, A., Achard, R, Ehrburger-Dolle, F., and Rirard, R., Structural investigation in monolithic silica aerogels and thermal properties, J. Non-Crystl. Solids, 225, 260, 1998. 

K. Duer, S. Svendsen, Monolithic Silica Aerogel in Superinsulating Glazings, Solar Energy, 63, 259-267 (1998). 

Supercritical drying, on the other hand, permits to eliminate capillary stresses. Hence, this process produces monolithic silica aerogels of rather large dimensions (Figure 2.5), if required by a targeted application [59] (Figure 2.6). 

Figure 2.5. Monolithic silica aerogels obtained after supercritical CO2 extraction. Courtesy ofRigacci A.

Figure 2.6. Large monolithic silica aerogel monoliths integrated in demonstration glazing (left side) and window (right side) prototypes [60]. Courtesy ofKJ. Jensen and J.M. Schultz, DTU, Lyngby, Copenhagen.

Prassas M, Phalippou J, Zarzycki J (1986) Sintering of monolithic silica aerogels. In Hench LL and Ulrich DR (eds) Science of Ceramic Chemical Processing, WUey, New York... 

Wei, T, Chang, T, Lu, S, Chang, Y (2007) Preparation of monolithic silica aerogel of low thermal conductivity by ambient pressure drying. J Am Ceram Soc 90(7) 2003-2007. 

Prassas M, Woignier T, PhaUppou J (1990) Glasses from aerogels part 1 The synthesis of monolithic silica aerogel. J. Mater. Sci. 24 3111-3117... 

Lu, X., Wang, P., Buttner, D., Heinemaim, U., Nilsson, O., Kuhn, J. and Fricke, J., Thermal transport in opacified monolithic silica aerogels. High Temperatures - High Pressures, 1991. 23(4) p. 431-436. 

Figure 26.6. Evolution of the effective thermal conductivity X of some monolithic silica aerogels (as measured by the hot-disk method under ambient conditions) [28].

Figure 26.8. Hemispherical (black), direct (blue) and diffuse (red) normal transmission of a monolithic silica aerogel shown in Figure 26.7 presenting a transparency ratio %TR = (r — above 90% (as calculated...

Fig. 5.10 (a) Mercury porosimetry data for monolithic silica aerogel, irreversible shrinkage case,... 

It may be concluded that the supercritical route is most successful in preserving the gel during the drying step. Due to the absence of interfadal forces, both shrinkage and cracks can be successfiilly avoided. The standard technique uses carbon dioxide for its moderate critical values, and the necessary washing step is mostly done under supercritical conditions. In the frame of two recent European research projects (HILIT and HILIT +, 1998-2005), large monolithic silica aerogels for windows (55 X 55 X 1.5 cm, see Fig. 5.24) could be successfully produced by this route (Masmoudi, 2006). 

Finarsrud, M.-A., 1995. Preparation and properties of monolithic silica aerogels from TFOS-based alcogels aged in silane solutions. J. 

Rigacci A., Achard P., Ehrburger-Dolle F., Pirard R. Structural investigations in monolithic silica aerogels and thermal properties. J. Non-Cryst. Solids 1998 225 260 Rouquerol J., Avnir D., Fairbridge C.W., Everett D.H., Haynes J.H., Pernicone N., Ramsay J.D. F., Sing K.S.W., Unger K.K. Recommendations for the characterization of porous solids. Pure Appl. Chem. 1994 66 1739... 

TiUotson T.M., Hrubesh L.W. Transparent ultralow-density silica aerogels prepared by a two-step sol-gel process. J. Non-Gyst. Solids 1992 145 44-50 Wang J., Kuhn J., Lu X. Monolithic silica aerogel insulation doped with Ti02 powder and ceramic fibers. J. Non-Cryst. Solids 1995 186 285-290... 

Wong, J.C.H., Kaymak, H., Brunner, S. et al. (2014) Mechanical properties of monolithic silica aerogels made from polyethoxydisiloxanes. Microporous Mesoporous Mater., 183, 23-29. 

Haereid, S., Dahle, M., Lima, S., and Einarsrud, M.-A. (1995) Preparation and properties of monolithic silica aerogels from TEOS-based alcogels aged in silane solutions./. Non-Cryst Solids, 186, 96-103. 

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