Dichlorosilane gases

Dichlorosilane C E T Nickel and nickel steels and Stainless steel for moist gas... 

Three permethylated cyclosilanes of the formula [(CH3)2Si]B with n=5-7 are prepared by allowing dimethyldichlorosilane to react with sodium-potassium alloy in tetrahydrofuran. From this reaction, an insoluble polymeric mass and a crystalline solid are produced (21, 177). The latter consists, for the most part, of dodecamethylcyclohexasilane but it also contains decamethylcyclopentasilane and tetradecamethylcycloheptasilane in small quantities. The amounts of both five- and seven-membered cyclosilanes are much increased if the reaction is worked up immediately after the addition of the dichlorosilane is completed with little or no refluxing. The three cyclosilanes can be separated by preparative gas chromatography 21). 

Preparation of Preceramic Polysilazanes. At MIT (Massachusetts Institute of Technology), our initial research on silicon-based preceramic polymers was aimed at developing a precursor for silicon nitride. To this end, we studied the ammonolysis of dichlorosilane, H2SiCl2 (ii). This reaction had already been carried out on a millimolar scale in the gas phase and in benzene solution by Stock and Somieski in 1921 (12). We found that this reaction gave a much better yield of soluble ammonolysis product when it was carried out in more polar solvents such as dichloromethane or diethyl ether (ii). 

CH4CI2SI methyl dichlorosilane 75-54-7 in benzene 1.910 1 rTi6 C2H4CI20 bis(chloromethyl) ether 542-88-1 gas 0.989 1... 

Precursors that release stoichiometric silicon ifitride in an inert gas atmosphere and which therefore avoid segregation of silicon metal can be obtained by coammonolysis of dichlorosilane and trichlorosilane. - Such polymers exhibit nitrogen silicon ratios greater than 4 3. Compared to [SiH2NH] copolymers [SiH2NH] ,[SiH(NH)i 5] are more highly cross-linked, but in contrast to [Si(NH)2l , they are processable. 

The manufacture of cubic p-SiC, which is favored at temperatures below 2000°C, or mixtures of a- and p-SiC is carried out by deposition from the gas phase (Chemical Vapor Deposition). p-SiC powder with good sintering properties and small crystallite size is e.g. obtained by the thermal decomposition of alkyl silanes or alkyl dichlorosilanes in plasmas or flow reactors at temperatures above 1000°C ... 

Silicon epitaxy involves different types of chemical reactions according to the considered precursors. The gas precursors are SiED (silane), or chlorinated compounds like SiC L (silicon tetrachloride), Si 11C I a, (trichlorosilane), or SiE CD (dichlorosilane). The choice of precursor inevitably directs the epitaxy technique and the working temperature [8] ... 

Pyrolysis of dichlorosilane provides a good quality crystal with a growth rate relatively high. The dichlorosilane is more expensive than the previous one but stays in a gas state at atmospheric pressure. Moreover, the deposition temperature is around 1,100°C. 

Fig. 10.6. Temperature dependence of growth rates of silicon (from, precursor 1% of dichlorosilane in H2). Filled diamond no gas doping, filled square B2H6, filled circle PH3, filled triangle ASH3 [16]...

The F3 cyclic species is obtained through hydrolysis of the corresponding silane, methyl(3,3,3-trifluoropropyl)dichlorosilane. This silane is the hydrosilylation adduct of 3,3,3-trifluoropropene and methyldichlorosilane, CH3HSiCl2, a minor product of the Rochow-Muller direct process for manufacturing methylchlorosilanes. The hydrosilylation reaction is catalyzed with transition metal complexes of platinum or rhodium such as Speier s catalyst and hexachloroplatinic acid in isopropanol. The reaction conditions are very similar to those employed with unfluorinated reagents, complicated only by the fact that 3,3,3-trifluoropropene is a gas. 

Dichlorosilane is a highly flammable, corrosive, and toxic gas at room temperature and atmospheric pressure. It causes severe bums on contact with eyes, skin, and mucous membranes. With water or moisture, it hydrolyzes rapidly to yield silica and silicon oxyhydride along with hydrochloric acid. It is shipped as a liquefied gas in low pressure cylinders at its vapor pressure of 9.1 psig (62.7 kPa) at 70°F (21.1°C). It can form flammable mixtures with air and oxidizing agents. 

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