Carbon aerogels mechanical properties

The third family of research grade materials is less well defined and encompasses aerogels of carbon [81,82] designed mesoscopic void structures in C3 with nanostruc-tured fillers [51,83], composites with nanocarbon fillers [24,82,84 88] and carbon-heterostructure [54,89-94] compounds. The references stated here are only examples for a wide range of activities stemming from the efforts to synthesize novel nanostruc-tured composites. These materials often exhibit unusual surface properties and are used in electrochemical and catalytic applications rather in the domain of traditional C3 compounds where mechanical properties dominate the application profile. 

On the other hand, the mechanical properties of monolithic carbon gels are of importance when they are to be used as adsorbents and catalyst supports in fixed-bed reactors, since they must resist the weight of the bed and the stress produced by its vibrations or movements. A few smdies have been published on the mechanical properties of resorcinol-formaldehyde carbon gels under compression [7,36,37]. The compressive stress-strain curves of carbon aerogels are typical of brittle materials. The elastic modulus and compressive strength depend largely on the network connectivity and therefore on the bulk density, which in turn depends on the porosity, mainly the meso- and macroporosity. These mechanical properties show a power-law density dependence with an exponent close to 2, which is typical of open-cell foams. 

Aerogels are quasi-stable, low-density, three-dimensional assemblies of nanoparticles, which have usually poor mechanical properties. A facile one-pot synthesis of Kevlar-like aerogels based on the reaction of multifunctional isocyanates and carboxylic acids has been reported [57]. The materials exhibit an ultimate compressive strength, a high specific energy absorption, and a thermal conductivity like foamed PS. By a pyrolysis process at 800 °C, the materials can be converted to a porous, electrically conducting carbon with a high surface area. 

Moner-Girona M, Martinez E, Roig A, Esteve J, Molins (2(X)1) Mechanical properties of silica aerogels measured by microindentation influence of sol-gel processing parameters and carbon addition. J Non-Cryst Solids 285 244-250... 

Mechanical Properties of Different Precursors and CNT/Polymer Nanocomposite Aerogels Fabricated by Deposition of Carbon Nanotubes onto Preformed Polymer Aerogels... 

Ma H.S., Roberts A.P, Prdvost J.H., Jullien R, Scherer G.W. Mechanical structure-propaly relationship of aerogels. J. Non-Cryst. Sohds 2000 277 127 Ma H.S., Pr6vost J.H., Jullien R., Scherer G.W. Computer simulation ofmechanical structure property relationship of aerogels. J. Non-Cryst. Sohds 2001 285 216 McEnaney B., Mays T.J. Characterization of macropores in carbons. In Porosity in Carbons, J.W. 

In this chapter, the recent advances in the field of carbon nanotube/polymer nanocomposite aerogels and related materials are described. An emphasis is paid to the relationship between the preparation method and the most characteristic properties of these materials such as density, surface area, electrical conductivity, mechanical strength, and so forth. 

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