Templated aerogels

Porous chalcogenide aerogels is another broad class of non-oxidic framework that prepared by template-free routes [71-73]. These materials possess a continuous nanostructured chalcogenide framework that is penetrated by a random network of nanopore channels. Because these high surface area structures are random and not exhibit long-range pore periodicity, such systems are outside of the scope of this review and will not be covered further. 

The recent developments in science and technology require a more exact control of structure/ nanotexture and properties of various materials, including carbon materials. In order to meet the requirements for carbon materials, various novel carbonization processes have been proposed. In relation to electrochemistry, the following processes have to be mentioned template method, polymer blend method, defluorination of fluorinated hydrocarbons, and carbonization of organic aerogels [99],... 

High surface areas are normally obtained by using porous materials, and the pore sizes may condition the accessibility of the reactants to the active sites, especially in the case of microporous materials such as activated carbons. Pore diffusion limitations become more important as the pore sizes decrease in addition, the smaller pores may be more easily blocked (e.g., by coke deposition). Therefore, deactivation and diffusion phenomena will in general affect more strongly the performance of microporous carbons. As a result, there has been a drive to develop mesoporous carbon catalysts (such as aerogels, xerogels, and templated carbons) for some applications, especially in the liquid phase. 

Mesopores of carbon aerogels have possibility for reaction field and thereby carbon aerogels can be applied as template for production of new materials. Thus, carbon aerogels were used as a template for the preparation of highly crystalline zeolites (ZSM-5 and Y) with uniform mesoporous channels [162,163]. 

Paakko, M., Vapaavuori, J., Silvennoinen, R., Kosonen, H., Ankerfors, M., Lindstrom, T., 2008. Long and entangled native cellulose I nanofibers allow flexible aerogels and bier-archically porous templates for functionalities. Soft Matter 4 (12), 2492—2499. 

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. 

Gu, W., and G. Yushin. 2014. Review of nanostructured carbon materials for electrochemical capacitor applications Advantages and limitations of activated carbon, carbide-derived carbon, zeolite-templated carbon, carbon aerogels, carbon nanotubes, onion-Uke carbon, and graphene. Wiley Interdisciplinary Reviews Energy and Environment 3 424-473. 

From a materials point of view an incredible development happened in the twentieth century with the preparation of porous metal oxides by the decomposition of metal salts and layered oxides [30, 31], the invention of aerogels [32], and sol-gel processing [33]. In addition, the preparation of zeolites by hydrothermal processing became important for the synthesis of very well-ordered, uniform pore structures in the micropore range. In 1990, the concept of biphasic micellar systems as a template for well-ordered mesoporous materials was successfully introduced... 

Templated carbons Xerogels Aerogels Glassy carbon... 

Many surfactants have been used as templates for creating inter/intrac-rystalline mesoporosity in zeolites. For example, Schuth et al. synthesized mesoporous silicalite-1 zeolite by using an organic aerogel as a soft template [33]. Similarly, Xiao et al. prepared structured zeolites templated by... 

Anderson MT, Sawyer PS, Rieker T (1998) Surfactant-templated silica aerogels. Microporous Mesoporous Mater 20 53 5... 

The specific surface area of the surfactant- and polymer-templated gels, that is, the ambient pressure aerogels, is nearly the same as that of the aerogels prepared by the supercritical extraction of CO2. Also, the pore size and the pore volume, that is, the porosity, are larger (twice or more) than those of the xerogels, but smaller than those of the super-critically extracted aerogels, estimated to be ca. 55%. The pore size and pore volume depended on the properties of surfactants and polymers, molecular size, and micelle- or aggregate shape. Also, the concentration of polymers in the immersion solutions, as well as the kind of template materials, affected the pore size and pore volume (Table 7.2). 

Mulik S, Sotiriou-Leventis C, Leventis N (2008) Macroporous Electrically Conducting Carbon Networks by Pyrolysis of Isocyanate-Cross-Linked Resorcinol-Formaldehyde Aerogels. Chem Mater 20 6985-6997. Tanaka S, Katayama Y, Tate M, Hillhouse H, Miyake Y (2007) Fabrication of continuous mesoporous carbon films with face-centered orthorhombic symmetry through a soft templating pathway. J Mater Chem 17 3639-3645. 

Baumann T, Satcher J (2004) Template-directed synthesis of periodic macroporous organic and carixm aerogels. J Non-Cryst Solids 350 120-125. 

Table 13.1. Comparison of selected mechanical properties under quasi-static compression of polyurea-crosslinked vanadia (X-VOx) and acid-catalyzed surfactant-templated sihca aerogels (X-MP4-T310-1) with other strong materials [81-83]...

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