Aerogel Fabrication Techniques

Gauthier BM, Bakrania SD, Anderson AM, Carroll MK (2004) A fast supercritical extraction technique for aerogel fabrication. J Non-Cryst Solids 350 238-243... 

In this chapter, we present a review of the s) thesis techniques for, properties of and applications of hydrophobic silica aerogels. In the following section, we review the techniques used to make silica aerogels. This is followed by sections devoted to the fabrication of hydrophobic aerogels, techniques for measuring hydrophobicity, a review of the literature on hydrophobic silica aerogels, and a summary of application areas for hydrophobic aerogels. 

Cellulose is one of the oldest materials used to produce fibers, filaments, and yams, from which fabrics of all kinds are manufacmred. Today s filament and yam production is a field for both natural and synthetic polymers [31]. All fibers used today have a compact microstracture and a very large aspect ratio. In contrast to these, Schmenk et al. [34] and Hacker et al. [35] produced an open porous, nanostmctured filament of cellulose aerogel for the first time using a sol-gel routine as described above for mmioliths and different spinning techniques. 

Yim T-J, Kim S Y, Yoo K-P (2002) Fabrication and thermophysical characterization of nano-porous siUca-polyurethane hybrid aerogels by sol-gel processing and supercritical solvent drying technique. Korean J Chem Eng 19 159-166... 

The techniques presented here allow to produce ultralight materials with anisotropic properties. Optical absorption and emission, hydrophobicity mechanical strength and index of refraction can be tuned within the same monolith. Conceivable applications of our technique include fabrication of photonic devices, membranes, radiation collimators, fuel cell electrodes as well as hierarchically structured materials that combine mechanical strength with the acoustic and thermal insulation properties of conventional aerogels. 

Figure 3.3 shows the flowchart of the possible routes of binder composite fabrication. The technique and the problems associated with resin binders have been discussed in Sect. 3.2. Figure 3.4 shows the cmshing of the silica aerogel when used with epoxy-acetone solution. 

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