Download Aerogels: Proceedings of the First International Symposium, by J. Fricke (auth.), Professor Dr. Jochen Fricke (eds.) PDF

By J. Fricke (auth.), Professor Dr. Jochen Fricke (eds.)

ISBN-10: 3540162569

ISBN-13: 9783540162568

This publication includes the papers provided on the "First foreign Sympo­ st sium on Aerogels (1 ISA)", held in September 1985 at. the collage of Wiirzburg, Fed. Rep. of Germany. It was once the 1st of this type, wit.h individuals from numerous ecu count.ries, the us of the United States, Canada, South the US, and Africa. The assembly was once interdisciplinary, with many of the members being physicists, chemists or fabric scientists ei­ ther from universities or from business examine institutes. allow me try and shed a few mild upon the category of drugs the symposium used to be approximately: Aerogels are super porous high-tech fabrics, consisting ei­ ther of silica, alumina, zirconia, stannic or tungsten oxide or combos of those oxides. as a result of their excessive porosity (up t.o 99%!) and t.heir huge internal floor, aerogels function specifically lively catalysts or as catalytic subst.rates, as adsorbents, fillers, reinforcement brokers, pigments and gellifying brokers. Silica aerogels as translucent or obvious superinsulating fillers in window structures might support to significantly decrease thermal losses in home windows and to enhance the power stability in passive sun structures. Aerogels even have fas­ cinating acoustic houses - the sound speed could be as little as a hundred m/s! The construction of aerogels starts off with the managed conversion of a sol right into a gel: the expansion of clusters or polymer chains from a chemical answer, the cross-linking of those basic entities and the formation of a coherent community - nonetheless embedded in a liquid.

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Additional resources for Aerogels: Proceedings of the First International Symposium, Würzburg, Fed. Rep. of Germany September 23–25, 1985

Example text

It is also observed that aerogels prepared with the concentration of aluminium sec-butoxide exceeding 10 % are no longer amorphous (Table II), despite the use of the stoichiometric amount of water for the formation of a trihydrate Al(OH)3 [eq. (4)]. This behaviour results from the fact that the precipitated alumina alcogels (before the treatment in the autoclave) are less and less hydrated (from trihydrate to monohydrate) when the concentration of aluminium sec-butoxide in sec-butanol increases from 10 % to 50 % (Table II).

For aerogels of mixed oxides (two or more), the principle is the same with two or more organic precursors (not necessary alcoholates) in an alcoholic solution. As an example, the preparation of the mixed Si02A1203 aerogels follows the reaction: x Si(OCH3)4 + 2yAl (OC3H7)3 + 10 (x + y) H20 .... x Si02, Y A1203, (2x + 3y) H20 4x CH 30H + 6y C3H70H (3) 23 Other examples are: A1 203-MgO, Ti0 2-MgO, Zr0 2-MgO [6, 8J. An important class of mixed oxides aerogels is that of heterogeneous catalysts, exhibiting catalytic properties (activity, selectivity, resistance to deactivation) which are not encountered in xerogel catalysts.

Table III. 9 a) metallic surface area of nickel determined by hydrogen chemisorption b) diameter of Ni particles determined by magnetic measurements. 27 c. Cu/A1 203 Aerogels This is another example of supported metal aerogel, with a surface area of 662 m2/g and copper metallic area of 30 m2/g Cu. It exhibits 100 % selectivity in the partial hydrogenations of acetylene into ethylene and of cyclopentadiene into cyclopentene [20, 21]. d. NiO/A1 203 Aerogels a) Partial oxidation of olefins and paraffins.

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