Silicate ortho

The prefix is also used in orthophosphates, orthocarbonates, orthoformates and ortho-silicates, which are derivatives of POCOH), the hypothetical C(OH)4, HC(OH)3 and Si(OH)4 respectively in these the word ortho is always written in full. 

Crisp, S., Merson, S., Wilson, A. D., Elliott, J. H. Hornsby, P. R. (1979). The formation and properties of mineral-polyacid cements. Part 1. Ortho- and pyro-silicates. Journal of Materials Science, 14, 2941-58. 

In earlier work, Bhaumik and Kumar (1995) have reported that the use of two liquid phases in the oxidation of hydrophobic organic substances with aqueous H2O2 using titanium silicate as the catalyst not only enhances the rate of oxidation but also improves selectivity for species like toluene, anisole, and benzyl alcohol. For a single liquid phase acetonitrile was u.sed a solvent. The solid-liquid system gives high ortho selectivity. Thus, in the case of anisole the ratios of o to p for. solid-liquid and solid-liquid-liquid system were 2.22 1 and 0.35 1, respectively. 

Sharma et al. [40] have used tetra-ethyl-ortho-silicate (TEOS) for the formation of Si02 matrix. The chemical structure of TEOS can be represented as shown in... 

Fig. 4 (a) Chemical structure of tetra-ethyl-ortho-silicate (TEOS). (b) Removal of two oxygen atoms from TEOS. (c) Mechanism depicting how TEOS chemisorbs onto silanol groups (Si-OH) on surface, (d) Formation of Si-O-Si bridges by elimination reactions with neighboring molecules. (Figure adapted from [40])... 

Silicone polymers which were developed in 1930s became commercially important during and after the World War II. The starting material for producing silicone polymers are alkyl chlorosilanes, arychlorosilanes or substituted esters of ortho-silicic acid. 

Ca (aq), Mg (aq), and HCOjCaq). Silicate weathering is an incongruent process. The most important of these reactions involves the weathering of the feldspar minerals, ortho-clase, albite, and anorthite. The dissolved products are K (aq), Na (aq), and Ca (aq), and the solid products are the clay minerals, illite, kaolinite, and montmorillonite. The weathering of kaolinite to gibbsite and the partial dissolution of quartz and chert also produces some DSi,... 

Also shown in Fig. 2 are the measured spectrum of a TEOS (tetra-ethyl-ortho-silicate)-TiN-Al stack, overlaid with the theoretical spectrum. The theoretical spectrum was based on such substrate modeling treatment. Given this empirical spectrum, both the TiN and TEOS thicknesses can be simulated and determined simultaneously. Alternatively, the TiN thickness can be fixed with only the TEOS needing to be measured. The latter method is better than the former because the more unknown film thicknesses there are, the more error is introduced. This can be demonstrated by the data in Table I, where the measurement results of the oxide thicknesses on TiN-Al substrates on the same wafer, for TiN thickness fixed and varying, are compared. 

Besides a variety of other methods, phenols can be prepared by metal-catalyzed oxidation of aromatic compounds with hydrogen peroxide. Often, however, the selectivity of this reaction is rather poor since phenol is more reactive toward oxidation than benzene itself, and substantial overoxidation occurs. In 1990/91 Kumar and coworkers reported on the hydroxylation of some aromatic compounds using titanium silicate TS-2 as catalyst and hydrogen peroxide as oxygen donor (equation 72) . Conversions ranged from 54% to 81% with substituted aromatic compounds being mainly transformed into the ortho-and para-products. With benzene as substrate, phenol as the monohydroxylated product... 

SILICIC. 1. Containing or pertaining to silicon. 2. Containing silicic acid (ortho) HrSiOa or silicic acid (meta) HiSiC or silicic acids of a higher degree of hydration (disilicic acids, trisilicic acids, etc.). 

Zinc forms a wide variety of other salts, many by reaction with the adds, though some can only be obtained by fusing the oxides together. The salts include arsenates (ortho, pyro, and meta), the borate, bromate, chlorate, chlorite, various chromates, cyanide, iodate. various periodates, permanganate, phosphates (ortho, pyro, meta, various double phosphates 1. die selenate, selenites, various silicates, fluosilicate. sulfate, sulfite, and duocyanate. 

In literature, numerous precursors for CVI of silica are proposed. Most common are silane [6,7,10], Tetra Ethyl Ortho Silicate (TEOS) [8,9,11,12] and silicon tetrachloride [13,14], As oxygen source mainly pure oxygen or water vapour in a helium or nitrogen flow is used. In... 

It follows that in this method of cocondensation one may employ even an unsubstituted silicon tetrahalide or orthoester in the mixture as a source of tetrafunctional groups. The unsubstituted SiX4 (where X is a halogen or ester group) hydrolyzes to the hypothetical ortho-silicic acid, Si(OH)4, and this cocondenses with the equally hypothetical organosilanediol to incorporate the silica unit within the polymeric structure ... 

Figure 4 Structures of (a) ortho (isolated) (b) single chain (c) double chain and (d) sheet silicates...

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