Aerogels mechanisms

Pekala RW and F.M. Kong FM. A synthetic route to organic aerogels-mechanism, structure, and properties. Revue de physique appliquee. ColloqueC4, tome 24, avril 1989. 

LeMay JD, TiUotson TM, Hrubesh LW, Pekala RW (1990) Microstructural dependence of aerogel mechanical properties Mat Res Soc Sym Proc 180 321-324... 

Pekala R.W., Kong F.M. A synthetic route to organic aerogels. Mechanism, structure and properties. Rev. Phys. Appl. 1989 C4(4) 33-40... 

R.W. Pekala, F.M. Kong, S)mthetic route to organic aerogels— mechanism structure and properties, J. Phys. CoUoques 50 (1989) C4-33-C4-40. 

Silica aerogels, a newly developing type of material, also have been produced as thermal insulations with superinsulation characteristics. The nanometer-size cells limit the gas phase conduction that can take place. The aerogels are transparent to visible light, so they have potential as window insulation. The use of superinsulations at present is limited by cost and the need to have a design that protects the evacuated packets or aerogels from mechanical damage. 

The contribution by Rouzaud et al. teaches to apply a modified version of high resolution Transmission Electron Microscopy (TEM) as an efficient technique of quantitative investigation of the mechanism of irreversible capacity loss in various carbon candidates for application in lithium-ion batteries. The authors introduce the Corridor model , which is interesting and is likely to stimulate active discussion within the lithium-ion battery community. Besides carbon fibers coated with polycarbon (a candidate anode material for lithium-ion technology), authors study carbon aerogels, a known material for supercapacitor application. Besides the capability to form an efficient double electric layer in these aerogels, authors... 

Hybrid polymer-silica aerogels have exceptional insulating and mechanical properties and will soon be commercialized as high-performance, low-cost insulators.6 Inorganic-organic silica areogels are non-flammable... 

The brittle behaviour of the silica aerogel remains upon the introduction of TMS-modihed PNPs. However, even a low polymer content promotes a clear improvement of the mechanical properties of the material Young s modulus increases and the maximum compression strength and the corresponding strain become three to five times higher. Furthermore, the improvement in mechanical behaviour is noticeable... 

Nitric acid synthesis, platinum-group metal catalysts in, 19 621 Nitric acid wet spinning process, 11 189 Nitric oxide (NO), 13 791-792. See also Nitrogen oxides (NOJ affinity for ruthenium, 19 638—639 air pollutant, 1 789, 796 cardioprotection role, 5 188 catalyst poison, 5 257t chemistry of, 13 443—444 control of, 26 691—692 effect on ozone depletion, 17 785 mechanism of action in muscle cells, 5 109, 112-113 oxidation of, 17 181 in photochemical smog, 1 789, 790 reduction with catalytic aerogels, l 763t, 764... 

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. 

The synthesis of paratolunitrile (PTN) and terephtalonitrile (TPN) by reaction of paraxylene with nitrogen monoxide was studied over a series of aerogel chromium oxide alumina catalysts. The stabilization of the active phase was interpreted on the basis of Cr O support interactions. Kinetic studies show that the reaction follows a "redox" mechanism for the formation of PTN and a Langmuir Hinshelwood mechanism for the production of TPN. 

An even larger pore volume can be obtained if the liquid phase is removed under supercritical conditions to give an aerogel . This type of gel has an extremely high surface area and pore volume (see Table 10.7), but it tends to be mechanically weak and unstable when exposed to water vapour because the particle coordination number is low. The upper limiting area of a silica composed of discrete primary particles would be =2000 m2 g 1, but specific surface areas of this magnitude are unlikely to be attained. 

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