Silicides halogens

Silicon, like carbon, is relatively inactive at ordinary temperatures. But, when heated, it reacts vigorously with the halogens (fluorine, chlorine, bromine, cmd iodine) to form halides and with certain metals to form silicides. It is unaffected by all acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures of 2,000 to 2,600 °C (3,600 to 4700 °F), they form silicon carbide (Carborundum = SiC), which is an Importeint abrasive. When reacted with hydrogen, silicon forms a series of hydrides, the silanes. Silicon also forms a series of organic silicon compounds called silicones, when reacted with various organic compounds. 

Vanadium Subsilicide, V2Si, is obtained by fusing a mixture of vanadium trioxide, V2Os, and silicon, with the addition of either a large excess of vanadium or carbon or copper. The carbide or copper alloy produced is decomposed at the temperature employed.11 The silicide forms metallic prisms, of density 5-48 at 17° C., the m.pt. of which is higher than in the ease of the disilicide. It is attacked by the halogens, hydrogen chloride gas, and fused sodium or copper, but hydrochloric acid, nitric acid and sulphuric acid are without action. 

Silicon is a very hard but brittle element having a melting temperature of 1422°C and a density of 2.40. This element is fairly reactive toward the halogens and solutions of strong bases such as potassium hydroxide. Silicon reacts less readily with oxygen to form silicon dioxide and with other elements similarly to form a class of binary compounds known as silicides. 

There are countless examples of the interactions of various atoms and molecules with the clean Si(100) surface. In addition these adsorbate-surface interactions can differ with deposition conditions, such as the rate of deposition or temperature of the sample. For example, even the simplest adsorbate, hydrogen, can etch the surface at room temperature and also form a variety of ordered structures at elevated sample temperatures [57]. A number of adsorbates can form ordered structures commensurate with the surface (e.g. Ag [58], Ga [59], Bi [60]), most transition metals react with the surface to form silicides (e.g. Ni [61], Co [62], Er [63]), halogens can etch the surface at room temperature (e.g. F2 [64], CI2 [65], Br2 [66]), some molecules dissociate on the surface (e.g. PH3 [67], B2H6 [68], NH3 [37]) and other molecules can bond to the silicon in different adsorption configurations but remain intact (e.g. Benzene [69], Cu-phthalocyanine [70], C60 [71]). A detailed review of a number of adsorbate-Si(lOO) interactions can be found in [23,72] and a more specific review relating to organic adsorbates can be found in [22]. As an example of an adsorbate-silicon system we shall here consider the adsorption of a molecule that our group has extensive experience with phosphine. 

Another method34 involves fusion of the organosilicon with magnesium to produce magnesium silicide. This is then decomposed to produce gaseous silicon hydrides by addition of dil. sulphuric acid. The hydrides are absorbed in bromine water and thus hydrolysed to silicic acid. The latter is converted into molybdosilicic acid and determined colorimetrically as molybdenum blue. The error is 0.73 to 0.54% over the range 10.53 to 37.8% of silicon. After removal of silicon hydrides, the elementary carbon which separates is deactivated with ferric or aluminium salts and filtered off, when halogens can be determined in the filtrate by Volhard s method. 

TELLURIUM (13494-80-9) Finely divided powder or dust may be flammable and explosive. Violent reaction with strong oxidizers, bromine pentafluoride, halogens, interhalogens, iodine pentafluoride, hexalithium disilicide, lithium silicide, nitrosyl fluoride, oxygen difluoride, sodium peroxide, sulfur, zinc. Incompatible with cadmium, cesium, hafnium, strong bases, chemically active metals, iodic acid, iodine oxide, lead chlorite, lead oxide, mercury oxides, nitric acid, peroxyformic acid, platinum, silver bromate/iodate/ fluoride, nitryl fluoride, sodium nitrate. 

Pure iron is a white, lustrous metal, m.p. 1528°. It is not particularly hard, and it is quite reactive. In moist air it is rather rapidly oxidized to give a hydrous oxide which affords no protection since it flakes off, exposing fresh metal surfaces. In a very finely divided state, metallic iron is pyrophoric. It combines vigorously with chlorine on mild heating and also with a variety of other non-metals including the other halogens, sulfur, phosphorus, boron, carbon and silicon. The carbide and silicide phases play a major role in the technical metallurgy of iron. 

Direct synthesis is the preparative method that ultimately accounts for most of the commercial silicon hydride production. This is the synthesis of halosilanes by the direct reaction of a halogen or halide with silicon metal, silicon dioxide, silicon carbide, or metal silicide without an intervening chemical step or reagent. Trichlorosilane is produced by the reaction of hydrogen chloride and silicon, ferrosilicon, or calcium silicide with or without a copper catalyst (82,83). Standard purity is produced in a static bed at 400—900°C. 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium silicide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and telluride, respectively. In vapor phase, sodium forms halides with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

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