Mechanical Characterization of Aerogels

Lu and H. Luo Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080, USA 

Leventis Department of Chemistry, Missouri University of Science and Technology, 

Aegerter et al. (eds.). Aerogels Handbook, Advances in Sol-Gel Derived Materials and Technologies, DOI 10.1007/978-l-4419-7589-8 22, 

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Zirconia is a very interesting material in ceramic industry, with exceptional electrical, thermal (Chap. 23), and mechanical properties (Chap. 22 Mechanical characterization of aerogels) allowing its use in fuel cells, thermal barrier coatings, oxygen sensors, and many other high-temperature applications. In all these applications, this material is doped with other oxides to stabilize the tetragonal or cubic phase at low temperatures. 

Katti A, Shimpi N, Roy S, Lu H, Fahrizio E F, Dass A, Capadona L A, Leventis N (2006) Chemical, physical and mechanical characterization of isocyanate-crosslinked amine-modified silica aerogels. Chem Mater 18 285-296... 

In between, additional methods have been developed or adjusted for the structural characterization of aerogels. Particularly interesting is here the beam bending that allows determining mechanical and structural characteristics already in the gel state. 

Katti, A., N. Shimpi, S. Roy, H. Lu, E.F. Fabrizio, A. Dass, L.A. Capadona, and N. Leventis. 2006. Chemical, physical, and mechanical characterization of isocyanate cross-Linked amine-modified silica aerogels. Chemistry of Materials 18(2) 285-296. 

Luo H, Churu G, Fabrizio EF, Scbnobrich J, Hobbs A, Dass A, Mulik S, Zhang Y, Grady BP, Capecelatro A, et al (2008) Synthesis and characterization of the physical, chemical and mechanical properties of isocyanate-crosslinked vanadia aerogels. J Sol-Gel Sci Technol 48 113-134... 

Figure 13.3. A. Mechanical characterization by a short beam 3-point bending (see inset) of polyurea-crosslinked silica aerogel monoliths and their noncrosslinked (native) counterparts a, 0.63 gcm b, 0.44 gcm c, 0.38 gcm , and d, 0.28 gcm . Native samples do not register in the load-force scale shown. B. Cumulative data. Dark blue triangles and the dark blue line concern two-step aerogels made by acid-catalyzed hydrolysis and base-catalyzed gelation. All other samples use one-step base-catalyzed silica with different isocyanates. Multiple lines for crosslinked samples correspond to different di- and tri-isocyanate crosslinkers.

This contribution describes the different steps of the gel-aerogel-glass transformations and the characterization of the durability and mechanical properties of such glass-ceramics trapping the nuclear waste. The interest of silica aerogel as host matrix for nuclear waste containment is emphasized. 

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