Aerogel sheets

Another style of DLs using PAN fibers was presented by Glora et al. [20]. They developed carbon aerogel sheets, which were then used as diffusion layers in PEMFCs. In order to fabricate these DLs, resorcinol-formaldehyde (RF) aerogels... 

Figure 15.13. A. A 0.46 mm thick aerogel-nanofiber hybrid film bent almost 180° B. microscope image of 2 mm thick aerogel sheet after excessive repetitive bending and pulling apart by hand. Reprinted from [41], Copyright 2009 American Chemical Society.

Fig. 5.24 Highly insulating and light transmitting (HILIT) aerogel glazing aerogel sheet is placed between two glass panes and evacuated (taken from Jensen et al. (2004)).

Two more recent appHcations for amorphous siHcas are expected to grow to large volumes. Precipitated siHcas are used ia the manufacture of separator sheets placed between cells ia automotive batteries. Their function is to provide a controlled path for the migration of conductive ions as a result of the porosity of the siHca particles. Additionally, both precipitated siHcas and aerogels are being developed for use ia low temperature iasulation, where the low thermal conductivity of the dry siHca powders makes them useful ia consumer products such as refrigerators (83). 

Translucent sandwich panels for the side-facades were also made of glass-fiber-reinforced polyester composites (see Figure 1.8). The sandwich panels consisted of two layers separated by a composite fiber sheet with trapezoidal corrugations. The surface of the facade panels was finished with fleeces that also provide resistance to aging and U V radiation. As the main function of these facade elements was thermal insulation, the sandwich panels were filled with aerogels. They were therefore able to provide a K-value of 0.4 W m with a panel thickness of only 50 mm [18]. In terms of building fire considerations, a sprinkler system was installed as an active fire protection. 

Application of CNTs as reinforcement in composite materials is the most studied approach towards their macroscopic applications. However, in composites the resultant properties are governed by the individual properties of the matrix and the CNT-matrix interaction. Moreover, excellent properties of CNTs such as high thermal and electronic conductivities cannot be utilized effectively. To attain the intrinsic CNT properties at macroscale, CNT assemblies such as CNT films, fibers, sheets, mats, foams, etc., have been proposed. Such structures mainly rely on the van der Waals interaction between individual CNTs. Alternatively, at the cost of some of the CNT properties, a small amount of binder can be used to improve the binding. Low density and highly flexible CNT foams and aerogels, and viscoelastic rubbers are some such materials consisting of macroscopic CNT assembly. 

A simple experiment was carried out in-house to affirm this statement in the data sheet, as shown in Fig. 3.2, when the right beaker shows that siUca aerogels become whitish and settle down at the bottom after being subjected to heat in a furnace at... 

Cast the gelatin-silica aerogel in blocks of 75 mm by 50 mm and 25 mm on a metal plate laid with porous sheet. 

Another fabrication methodology is via the freeze drying (FD) method. The aqueous solution of gelatin is obtained via sonication as described in flie previous section. However, the solution in this case is not foamed by frothing as described in Fig. 3.12. Instead, the silica aerogel granules are mixed in the solution for about 10 min till a tacky mix is obtained. Thereafter, the mixture is casted onto a 100 mm diameter petri dish or in a metal mold of 75 mm x 50 mm by 25 mm laid witii a porous sheet. The composite mold is covered with transparent porous foil and... 

Figure 45.8 Cross-section of the granular aerogel-based glazing, consisting of two glass panels with a low-emissivity coating on the inside, two gaps, and an aerogel-filled PMMA double-skin sheet [25].

Spaceloft Safety Data Sheet (2009) http // www.aerogel.com/products/pdf/ Spaceloft MSDS.pdf (retrieved November 19,2009). 

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