Oxide precursors

In alkylation, phenols and amines are alkylated by sulfites in high yield and quaternary salts readily form (67). Ethylene sulfite reacts yielding hydroxyethyl derivatives and SO2 elimination, corresponding to its activity as an ethylene oxide precursor (68). 

Other methods for precipitation of tantalum and niobium oxide precursors... 

Other methods exist for the precipitation of tantalum and niobium hydroxides for subsequent use as oxide precursors. Application of ammonium carbonate, (NH4)2C03, instead of ammonia solution, also seems to have potential for the precipitation of tantalum and niobium hydroxides. Ammonium carbonate is relatively stable in aqueous media at room temperature and does not initiate the precipitation of hydroxides. Increasing the temperature of the solution causes hydrolysis and decomposition of ammonium carbonate yielding hydroxyl ions and an increase in pH, as follows ... 

Fig. 3. EXAFS analysis results for A) oxidic precursors before reduction, B) fresh samples after reduction, and C), D) bulk reference samples.

Zeolites are prepared by the linking of basic structural units around a template molecule. The structural units are typically based on oxides of silicon and aluminium, and the templates are usually individual small molecules. Under the right conditions, the silicon and aluminium oxide precursors will link up around the template to form a crystalline three-dimensional matrix containing the template molecules. The template... 

The performance of a supported metal or metal sulfide catalyst depends on the details of its preparation and pretreatraent. For petroleum refining applications, these catalysts are activated by reduction and/or sulfidation of an oxide precursor. The amount of the catalytic component converted to the active ase cind the dispersion of the active component are important factors in determining the catalytic performance of these materials. This investigation examines the process of reduction and sulfidation on unsupported 00 04 and silica-supported CO3O4 catalysts with different C03O4 dispersions. The C03O4 particle sizes were determined with electron microscopy. X-ray diffraction (XRD), emd... 

Nitridation of the oxide precursor was performed under pure ammonia flow. Different aluminophosphate oxynitrides AlPONs with variable nitrogen contents were obtained by modif3ring the time and/or the temperature of nitridation (Table 1). 

In this study butyl acetate (AcOBu) was hydrogenolysed to butanol over alumina supported Pt, Re, RePt and Re modified SnPt naphtha reforming catalysts both in a conventional autoclave and a high throughput (HT) slurry phase reactor system (AMTEC SPR 16). The oxide precursors of catalysts were characterized by Temperature-Programmed Reduction (TPR). The aim of this work was to study the role and efficiency of Sn and Re in the activation of the carbonyl group of esters. 

There are a number of ways to introduce dopants into an EC-ALE deposit. For instance, they can be introduced homogeneously throughout the deposit, or delta doped into the structure. For a relatively homogeneous distribution, low concentrations of oxidized precursors can be incorporated into the reactant solutions. By using very low concentrations, the amounts incorporated in each atomic layer will be limited. The dopant can also be incorporated in its own cycle step. Again, a low concentration would be used so that some fraction of an atomic layer is introduced each cycle. Alternatively, a delta doping scheme can be constructed where a fraction of an atomic layer of dopant is deposited every set number of cycles. All these scenarios involve only a simple modification of the EC-ALE program. 

Antimony telluride films have been grown from antimony(III) and tellurium(IV) oxides.167 Antimony telluride films were stoichimetric and consisted of nanoscale particles of the size 100 nm. The films had a good crystallinity.167 Indium selenide films were grown from indium sulphate and selenium oxide precursors.168 The films consisted of large particles, 70 to 200 nm in diameter. The band gap was 1.73 eV.168... 

Menzies, D. B. Dai, Q. Bourgeois, L. Caruso, R. A. Cheng, Y. B. Simon, G. P. Spiccia, L. 2007. Modification of mesoporous Ti02 electrodes by surface treatment with titanium(IV), indium(III) and zirconium(IV) oxide precursors Preparation, characterization and photovoltaic performance in dye-sensitized nanocrystalline solar cells. Nanotechnology 18 125608. 

Thermal dehydrochlorination of hydroximoyl chlorides affords nitrile oxides (50-52). O-Ethoxycarbonylbenzohydroximoyl chloride, generating benzonitrile oxide, was used as a stable nitrile oxide precursor, which was efficiently used in... 

Macrocycles containing isoxazoline or isoxazole ring systems, potential receptors in host—guest chemistry, have been prepared by multiple (double, triple or quadruple) 1,3-dipolar cycloadditions of nitrile oxides, (prepared in situ from hydroxamoyl chlorides) to bifunctional calixarenes, ethylene glycols, or silanes containing unsaturated ester or alkene moieties (453). This one-pot synthetic method has been readily extended to the preparation of different types of macrocycles such as cyclophanes, bis-calix[4]arenes and sila-macrocycles. The ring size of macrocycles can be controlled by appropriate choices of the nitrile oxide precursors and the bifunctional dipolarophiles. Multiple cycloadditive macrocy-clization is a potentially useful method for the synthesis of macrocycles. 

New isoxazoline derivatives of a-tocopherol, the main component of vitamin E, have been synthesized in a facile, two-step sequence consisting of nitration followed by 1,3-dipolar cycloaddition. 5-Nitromethyl-a-tocopheryl acetate, obtained from a-tocopheryl acetate by direct nitration in one step, act as the nitrile oxide precursor in the reaction with various alkenes. The facile conversion proceeds in the presence of equimolar amounts of PhNCO and catalytic amounts of triethylamine to give isoxazolines, 446 (489). 

Nitrile oxide precursors have been prepared by the reaction of an isocyanate and an alkyl nitroacetate. These precursors release alkanol and carbon dioxide when heated, to liberate the highly reactive nitrile oxide species. An improved synthetic procedure has been developed to afford novel cross-linking agents based on difunctional, trifunctional and aliphatic precursors. Application of these agents to polymer cross-linking has been demonstrated (527). 

The multiwall hollow WS2 nanotubes, which are obtained at the end of the process, are quite perfect in shape, which has a favorable effect on some of their physical and electronic properties. This strategy, that is, the preparation of nanowhiskers from an oxide precursor and their subsequent conversion into nanotubes, is likely to become a versatile vehicle for the synthesis of pure nanotube phases from other... 

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