Tetraethylorthosilicate TEOS Source

As with earlier work, it would be desirable to dope the films with P and/or B. This has been tried7 with liquid sources as well as phosphine and diborane. The liquid sources were  

Trimethylphosphate TMP-ate (CH30)3P0 Trimethylphosphite TMP-ite (CH30)3P Trimethylborate TMB (CH30)3B 

These have the major advantage of being safe, as contrasted to the very toxic phosphine and diborane. 

The films produced by these authors7 exhibited good chemical stability with doping levels of 5 wt % B and 5 wt % P. Since these doping levels are higher than typically achieved in the SiH4 process, reflow temperatures required can be lowered somewhat. 

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Two kinds of solution were prepared in advance. Solution A was a water solution containing an Si source, which was obtained by hydrolyzing metal alkoxide (tetraethylorthosilicate, TEOS) with a dilute tetrapropylammoniumhydroxide (TPA-OH)/water solution at room temperature. The molar ratio of Si to the template was 3. In peparation of ZSM-S zeolite nanoerystals, aluminium isopropoxide as an A1 source and sodium chloride were added into solution A. Solution B was an oi mic solution containing surfectant Nonionie surfactants, poljraxyethylene (15) cxslylether (C-15), polyoxyethylene (15) nonylphenylether (NP-15), and polyoxyethylene (15) oleylether (O-15), and ionic surfoctnnts, sodium bis(2-ethylhexyl) sulfosucdnate (AOT) and... 

Aerosol (97% Si02), tetraethylorthosilicate (TEOS), Na2Si03 and superfine Si02 as Si source have been studied, respectively. Using... 

Mixed alkoxide method. Hydrothermal synthesis using tetraethylorthosilicate (TEOS) as the source of Si, tetraethyltitanate (TEOT) as the source of Ti, tetrapropylammonium hydroxide (TPAOH) as structure directing agent (template), base and distilled water... 

The synthesis mixtures were prepared using tetraethylammonium hydroxide (40 % aqueous solution, Alfa or 35 % aqueous solution, Aldrich) with a very low alkali cations content (Na<2ppm, K<0.5ppm), deionized water, tetraethylorthotitanate (TEOT) or tetrabutylorthotitanate (TBOT) as a source of Ti and amorphous silica (Aerosil 200, Degussa) or tetraethylorthosilicate (TEOS, Aldrich) as the source of silica. Depending on the synthesis method a source of aluminium can be directly added to the synthesis mixture (metal Al, aluminium halide, etc.) or incorporated in the seeds of aluminosilicate zeolite Beta. Four synthetic procedures were developed and Table 1 summarizes the typical ranges of chemical composition of the initial mixture and the typical results of the syntheses. The methods are denoted according to the nature of the silica source and, in one case, the use of seeds. The preparation of the reaction mixtures was as follows ... 

Several BEA zeolites have been tested as catalysts for the liquid-phase acylation of toluene with AAN (Table 4.7). [S]-Named zeolites are hydro-thermally prepared using amorphous silica as the silicon source, whereas [T]-named zeolites are prepared by using tetraethylorthosilicate (TEOS) as the silicon source with different SAR. The acylation process represents a very selective route to 4-methylacetophenone 18 small amounts of ortho- and mete-methylacetophenone 19 and 20 are produced in less than 2% of the total yield of the acetylated products. For the [S]-type BEA zeolites, the acidity values are in good agreement with the catalytic activity, following the order [S]-BEA(32) > [S]-BEA(26) > [S]-BEA(54) [S]-BEA(76). In the [T]-BEA series, the catalytic activity decreases when the SAR increases, regardless of the increase of hydrophobicity. The conclusion is that low SAR lead to better yields in acetophenones (APs). However, the poisoning... 

A final example of the influence of microwave treatment on adsorption materials involves the synthesis of mesoporous silica materials known as FUD-1. Preparations of FUD-1 used microwave heating both with and without humic acid treatment. The materials were synthesized with a poly(ethylene oxide)-poly-(butylene oxide)-poly(ethylene oxide) triblock copolymer as a template and tetraethylorthosilicate (TEOS) as the source of silica. In addition to being well characterized, the resultant materials were also tested for their ability to adsorb Cd ions from solution at a fixed pH of 6. The incorporation of humic acid into FUD-1 led to significantly higher adsorption capacity of Cd + ions than materials without humic acid. As a result, these materials seem to be promising adsorbents for removal of cadmium and related heavy metal ions from aqueous waste streams. 

The gel compositions (in molar ratios) were as follows, using a mixture of TBA (tributyl-amine Huka) and DPTA (dipentylamine 99%, Janssen) as organic bases, and LUDOX AS-40 (Du Pont) or TEOS (tetraethylorthosilicate 98%, Janssen) as silicon sources ... 

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