Silicon containing compounds silica

Even though silicon is extremely abundant, only one silicon-containing compound appears in the list of top 50 industrial chemicals. That is sodium silicate, Na2 Si03, used for the manufacture of silica gel and glass. Nevertheless, with the advent of the electronic age silicon has become an extremely important substance that is the primary ingredient of most semiconductors. Because these are microscale devices, the quantity of production of silicon remains small compared with that of fertilizers and construction materials. Although relatively small in quantity, the value of silicon products is quite high. 

Knowledge regarding renal injury and the development of anti-neutrophil cytoplasmic antibody (ANCA) positivity associated with silica exposure is rudimentary being hmited to epidemiological observations. Moreover, information about the health significance of the occupational exposure to other silicon containing compounds apart from silica and crystalline sihcates is lacking. 

A survey of the Hterature [28, 55-62, 66, 67, 69-74] indicates that the most frequent exposure to silicon involves exposure to silica and siUcates mainly in their crystalline forms. Health risks associated with the exposure to other silicon containing compounds were reported in the mortality study of 16.661 man-made mineral fiber workers employed during 1945 to 1963 at one of 17 U.S. manufacturing plants [70]. Fiber exposure... 

Nuyts et al. 1995 [74] 16 patients with Wegener s granulomatosis 32 age-matched general population Silica Silicon containing compounds 5.0 (1.4-11.6) 6.5 (1.3-13.5)... 

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

The fundamental silicon-oxygen compound is silica, which has the empirical formula Si02. Knowing the properties of the apparently similar compound carbon dioxide, one might expect silica to be a gas that contains discrete Si02 molecules. In fact, nothing could be further from the truth—... 

A tin hydride attached to fluorous ponytails is quite versatile in respect of easy separation of the desired products from organotin compounds. When an iodoalkene was treated with NaCNBHs in the presence of a catalytic amount of fluor-oalkyltin hydride, the desired tricyclic ketones were produced (Scheme 12.133) [240]. Application of the crude mixture to a small plug of fluorous reversed-phase silica gel enabled facile separation of the cyclic ketone obtained (fluorous solid-phase extraction, FSPE). In contrast, when tris(trimethylsilyl)silane (TTMSH) was employed as a hydride source chromatographic purification of the nonpolar and somewhat volatile products was impossible because of contamination by nonpolar silicon-containing byproducts. 

The supported chromium oxide catalysts can be prepared by impregnating a silica-alumina support with a solution of chromium ions or by coprecipitating the oxides. The preferred impregnating solutions contain dissolved Cr(N03)s.9H20 or CrOs in nitric acid because catalysts made from chromium chlorides or sulfates retain some of the anions after calcination. The solid mixture of chromium-silicon-aluminum compounds is calcined in dry air at 400-700° C or higher to obtain the desired oxide. This probably results in the reaction of surface hydroxy groups in the support material with CrOs to form chromate (IV) and dichromate (V) species ... 

The product also works in non-halogenated systems. It can be used with ATH, MgO, ammonium polyphosphate, silica, silicone polymers or melamine compounds in polyolefins, urethanes, polyamides and others. In the silicon containing systems, Firebrake ZB is understood to form a borosilicate glass at polymer combustion temperatures. 

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