Aerogels sources

Because most of the adsorption occurs near P/Pq near 1, pore volumes and pore size distributions may be inaccurate for aerogels. Source. Reproduced with permission from reference 24. Copyright 1990. 

Solvents from pharmaceutical compounds and drugs from natural sources Extraction of volatile substances from substrates Drying and aerogel formation... 

The long-slit, i.e. one-dimensional, angular correlation (ACAR) apparatus used for these studies is similar to that shown in Figure 1.6. Silica aerogel (see subsection 1.5.2) was employed as a convenient source of positronium, emitted into the space between the pores. The chamber could be evacuated and the high purity gases under investigation then... 

Carbon aerogels and xerogels have been used as supports for Pt and Pt-based electrocatalysts for proton-exchange membrane fuel cells (PEMFCs), also known as polymer-electrolyte fuel cells [56,58,83-90], These fuel cells are convenient and environmentally acceptable power sources for portable and stationary devices and electric vehicle applications [91], These PEMFC systems can use H2 or methanol as fuel. This last type of fuel cell is sometimes called a DMFC (direct methanol fuel cell). 

Another application that benefits from the small pores and large inner surface of aerogels are photo-luminescent light sources [83]. Until now, in these devices a radioactive gas (e.g., tritium) was let into a glass tube coated with a phosphor at the inner surface. Integrating the phosphor in an aerogel of low density increases both the intensity and total output of the system. 

Ashley, C. S., Reed, S. T., Brinker, C. J., and Walko, R. J., Aerogel Composites for Radioluminescent Light Power Sources, 5th Int. Conf. Ultrastructure Processing, Orlando, Florida, February 1991. 

Entry Aerogel Metal source Metal wt.% Bulk density (gC" ) BET sur ce area (m g- ) Mean particle size (nm) XRD... 

In contrast to supercritical drying, operating parameters for subcritical drying including temperature and pressnre are below the critical point. Wei et al. [35] nsed E-40 (multi-polysiloxane) as silicon source and isobutyl alcohol as solvent to prepare Si02 gel. The prepared gel was placed in autoclave, adding an appropriate amonnt of isobutyl and surfactant, preserved sometime under pressure of 2.3-2.6 MPa, temperature of 240°C-260°C, and then deflated slowly and cooled naturally hydrophobic SiOj aerogel was finally obtained. 

Guilminot E, Fischer F, Chatenet M, Rigacci A, Berthon-Fabry S, Achard P, Chainet E (2007) Use of cellulose-based carbon aerogels as catalyst support for PEM fuel cell electrodes electrochemical characterization. J Power Sources 166 104-111... 

Other carbon sources have also been used as matrices such as multiwall carbon nanotubes (MWNTs), which led to narrower mesopore distributions than with carbon black pearls. In addition, the use of carbon fibers also allowed cylindrical mesopores to be obtained with low tortuosity. Carbon aerogel monoliths, obtained from resorcinol-formaldehyde gels after drying with COj under supercritical conditions and pyrolysis under nitrogen atmosphere at 1323 K, have also been used as templates for the generation of mesoporosity in zeolites [158]. This method presents the added advantage that the mesoporous zeolite can be synthesized as a monolith. 

W. Rupp, N. Huesing, and U. Schubert, Preparation of SUica-Titania Xerogels and Aerogels by Sol-Gel Processing of New Single-Source Precursors, J. Mater. Chem., 12, pp. 2594-96, 2002. 

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