Aerogels synthesis

H. Maleki, L. Duraes, and A. Portugal, An Overview on SUica Aerogels Synthesis and Different Mechanical Reinforcing Strategies, J. Non-Cryst. Solids, 385, 55-74 (2014). 

In this chapter, the aerogel synthesis method is detailed and recent catalytic examples, from 1999 up, will be presented and discussed. Because of their potentialities, ambigels, which do not require the use of an autoclave, are also briefly described. 

It seems that new opportunities exist in aerogel synthesis, taking advantage of both the ambigel method and the direct sol-gel chemistry under supercritical conditions. It is likely that these new methods could be of a great potential interest for scientists involved in the preparation of catalytic materials. 

Chervin CN, Clapsaddle BJ, Chiu HW, Gadi AE, Satcher JH Jr, Kauzlarich SM (2005) Aerogel Synthesis of Yttria-Stabilized Zirctmia by a Non-Alkoxide Sol-Gel Route Chem Mater 17 3345-3351 Gash AE, Pantoya M, Satcher JH, Simpson RL (2008) Nanostructured energetic materials aerogel thermite composites. Polymer Preprints (American Chemical Society, Division of Polymer Chemistry) 49 558-559... 

Soleimani DA, Abbasi MH (2008) Silica aerogel synthesis, properties and characterization. J Mater Proc Technol 199 10-26... 

Carraher CE Jr (2005) General topics silica aerogels-properties and uses. Polymer News, 30(12), 386-388 Carraher CE Jr (2005) Silica aerogels - synthesis and history. Polymer News, 30 62-64 Pajonk GM (2003) Some applications of silica aerogels. Colloid and Polymer Science, 281 637—651 Akimov YK (2003) Fields of Application of Aerogels (Review) Instruments and Experimental Techniques (Translation of Pribory i Tekhnika Eksperimenta), 46 287-299... 

Chervin CN, Clapsaddle BJ, Chiu HW, Gash AE, Sateher JH, Kauzlarich SM (2005) Aerogel synthesis of yttria-stabilized zirconia by a non-alkoxide sol-gel route. Chem Mater 17 3345 3351. 

The resorcinol-formaldehyde polymer is classified as a phenolic resin. In fact, phenol-formaldehyde condensates are the first synthetic polymers introduced commercially (Bakelite) in the beginning of the twentieth century. Thus, the phenolic resin chemistry, on which there is a vast amotmt of information, can be used to understand the chemistry of the RF aerogel synthesis. In the first step, resorcinol reacts with formaldehyde to form hydro-xymethylated resorcinol in the second step, the hydroxymethyl groups condense with each other to form nanometer-sized clusters, which then crosslink by the same chemistry to produce a gel. The formation of clusters is influenced by typical sol-gel parameters such as the temperature, pH, and concentration of reactants. Though the first RF aerogel is synthesized by the aqueous polycondensation of resorcinol with formaldehyde with the use of sodium carbonate as catalyst [6, 12, 13], now several literature reports exist for aerogels made from phenol and formaldehyde [14—16]. 

Scheme 11.1. Mechanism of the base-catalyzed RF aerogel synthesis.

An alternate approach to chalcogenide aerogel synthesis is to start with discrete nanoparticles of metal chalcogenides and condense them together to form a gel network. A method for doing just that was reported in 1997 by Gacoin and coworkers [21-25]. 

Abstract Carbon aerogels are nanostructure porous carbon materials with high specific surface areas and relative low electric resistance. In recent years, they have attracted much attention because of their extraordinary properties and potential uses in a wide variety of technological applications. Many studies have been carried out concerning carbon aerogel synthesis and characterization. This contribution summarizes recent developments in the synthesis, properties, and applications of carbon aerogels. 

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