Silicate composites

Partial oxidation reactions are usually carried out over transition metal oxides capable of changing their valent state during their interaction with reacting molecules. Naturally, zeolites with their alumina-silicate composition did not prove themselves as good oxidation catalysts. They failed also to serve as efScient catalyst supporters, since transition metals being introduced into the zeolite matrix lose their ability to activate dioxygen [3,4],... 

S. Bharathi and O. Lev, Sol-gel-derived nanocrystalline gold-silicate composite biosensor. Anal. Commun. 35, 29-31 (1998). 

X. Yang, L. Huaa, H. Gonga, and S.N. Tan, Covalent immobilization of an enzyme (glucose oxidase) onto a carbon sol-gel silicate composite surface as a biosensing platform. Anal. Chim. Acta 478, 67-75 (2003). 

Li, J.Z., Euruno, T. and Katoh, S. (2001b). Preparation and properties of acetylated and propionylated wood-silicate composites. Holzforschung, 55(1), 93-96. 

The term alumen plumosum has had a long association with asbestos. Alumen (= alum) is a general term for naturally occurring hydrous alkali aluminum sulfates. These are efflorescent mineral materials of fibrous, feathery appearance. Confusion with the more durable silicate composition asbestos was not settled until 1741, by Tourneforte following a visit to asbestos deposits in Asia Minor. 

Fig. 6 Latex blending of NBR-layered silicate composites (reprinted from [10], with the permission from Elsevier)...

The pure siliceous MCM-41 sample (reference) synthesized earlier by the same procedure [4, 5] showed the typical high surface area, well resolved [100], [110], [200] and [210] diffraction peaks in the XRD pattern and an N2 adsorption isotherm (IUPAC type IV) revealing a sharp inflection in the curve at ca. p/po=0.33 due to pore condensation typical for a narrow pore size distribution around a value of 28 A. The siliceous composite samples obtained, using combinations of the C6 and C 4 templates and different synthesis... 

Previous characterisation (SEM, HREM) of the purely siliceous composite materials [4] revealed the formation of fairly complex aggregates of MFI and MCM-41 type material. The data were not sufficient to assess a more intimate integration of the two structures, although the enhanced hydrothermal stability obtained [5] would indicate the presence of a closer interaction between the two phases than just a physical mixture. The actual structure of the present samples has not been studied in further detail so far. Taking into account the considerable potential within catalytic applications for structures which may possess unique integrations of acidity and structural properties, the synthesis, modification, catalytic activity and structure of these materials should be studied closer. 

The Island of Pantelleria shows many characteristics that are commonly found in volcanoes from continental rift settings, such as the abundance of acid peralkaline rocks, the compositional gap between mafic and silicic compositions and the smooth inter-element trends. Therefore, its petro-genesis shares the same problems as magmatism from continental rifts (see Peccerillo et al. 2003 for discussion). The similar isotopic compositions of... 

Figure 17. TL sensitivity against silicate heterogeneity (a measure of metamorphic intensity since metamorphism homogenizes silicate compositions) expressed as percent mean deviation from the mean for the CO chondrite class.

Table I. Silicate Composition of a Slllcallte-Formlng Solution at 9S °C and Product Properties Obtained... 

Corrosion stability of SPC in high-concentration acid media permits its use widely in anticorrosive techniques. However, the corrosion resistance of SPC in alkalis and in weak water solutions of acids is not enough. The effect of corrosion in such environments is shown in deposits of salts in pores, cracks, and other voids. Crystallization of these salt deposits, introduced by the corrosion environment or formed by chemical reaction of the material and environment, leads to destruction of a silicate composition. 

Highly diffusive penetration of SPC can be drastically lowered by active additives that are capable of raising SPC density, and, therefore, its corrosion resistance. As indicated previously, the most effective results were obtained by introduction of FA or TFS additives. Addition of monomeric additives to silicate composition improves the physical-mechanical characteristics and chemical resistance of silicate compositions due to improvement in the quality of silicate bonds and better adhesion between the binder and coarse filler [1], In other words, the influence of the monomeric additives is conditioned by consolidation of liquid glass gel during hardening and modifications of alkaline components due to inoculation of furan radicals. 

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