Chemical trichlorosilanes

The physical properties of siUcon tetrahaUdes are Hsted in Table 1 those of the halohydrides are Hsted in Table 2. A more complex review of the physical properties of these chemicals is available (2). Detailed Hsts of properties of the colorless fuming Hquids, siUcon tetrachloride and trichlorosilane, are given in Table 3. A review of the physical and thermodynamic properties of siUcon tetrachloride is given in Reference 3. 

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

Purification of Silicon. Chemical purity plays an equally important role in the bulk of materials as on the surface. To approach the goal of absolute stmctural perfection and chemical purity, semiconductor Si is purified by the distillation of trichlorosilane [10025-78-2] SiHCl, followed by chemical vapor deposition (CVD) of hulk polycrystalline siUcon. 

The submitters used trichlorosilane supplied by Union Carbide Corporation. The checkers obtained trichlorosilane from Tokyo Chemical Industries Company, Ltd., Japan. 

Most SiC deposition systems involve the Si-C-H-Cl chemical combination. Avery commonly used reaction is the decomposition of methyl trichlorosilane (MTS) P CP" ]... 

The reinforcing fibers are usually CVD SiC or modified aluminum oxide. A common matrix material is SiC deposited by chemical-vapor infiltration (CVI) (see Ch. 5). The CVD reaction is based on the decomposition of methyl-trichlorosilane at 1200°C. Densities approaching 90% are reported.b l Another common matrix material is Si3N4 which is deposited by isothermal CVI using the reaction of ammonia and silicon tetrachloride in hydrogen at 1100-1300°C and a total pressure of 5 torr.l" " ] The energy of fracture of such a composite is considerably higher than that of unreinforced hot-pressed silicon nitride. 

FIGURE 4.4 The production of polycrystalline silicon for the eleetronics industry involves several ehemieal steps aimed at the reduetion of impurities. These inelude (1) reaction of metallurgical grade silicon to produce a mixture of chlorosilanes, (2) distillation of trichlorosilane, and (3) reduction of trichlorosilane to polycrystalline silicon. Excerpted by special permission from Chemical Engineering, June 10, 1985. Copyright 1985 by McGraw-Hill, Inc., New York, NY 10020. 

Amongst the earliest measurements involving chemical functionality of the probe were those of Nakagawa et al. [69]. They investigated octadecyltrichlorosilane (OTS) chemically modified tips against chemically adsorbed monolayers of different alkyl-trichlorosilanes in ethanol, as shown schematically in Figure 14. When both tip and surface were modified by OTS, a large adhesive force was observed that was not present for the case of an unmodified silicon nitride tip on an OTS-modified surface. Additionally there... 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

Carboxylic acid-terminated organosilanes were used in the early studies on chemically bonded glycopeptides to immobilize vancomycin and thiostrepton via then-amino groups, leading to the formation of stable amide bonds between antibiotics and modified silica [7]. In a typical reaction, 4 g of dry silica gel is slurried on 50 mL of dry toluene. Two grams of [l-(carbomethoxy)ethyl]methyldichlorosilane or [2-(carbomethoxy)ethyl]trichlorosilane is dissolved in 15 mL of dry toluene contained in a dropping flask. The organosilane solution is added dropwise over 30 min... 

As with many polymers, the limits of strength are due to the presence of voids. For glass fibers, these voids generally occur on the surface, thus care is taken to protect these surfaces through surface treatments with methacrylatochromic chloride, vinyl trichlorosilanes, and other silanes. These surface agents chemically react with the fiber surface acting to repel and protect the surface from harmful agents such as moisture. 

Fig. 11 Wet thickness (H) of PAAm in water as a function of the PAAm graft density for samples prepared by surface-initiated ATRP on substrates with gradient of initiator density. The initiator was immobilized by the vapor-diffusion method using mixtures of l-trichlorosilyl-2-(fn/p-chloromethyl phenyl)ethan n-octyl trichlorosilane (w/w) 1 1 (squares), 1 2 (circles), and 1 5 (triangles). The inset shows a cartoon illustrating the polymer behavior. Reproduced with permission from [134] (Copyright 2003 American Chemical Society)...

Trichlorosilane derivatives of large dye molecules are difficult to purify and owing to moisture sensitivity are hard to handle. Their organic solutions tend to become turbid rather quickly owing to the formation of insoluble polymers. Thus, solutions must be replaced frequendy. An exception may be the combination of self-assembly and surface chemical reaction (186-189,202). On the other hand, co-substituted alkyltrichlorosilane derivatives are easy to synthesize the purify. These could be used for the engineering of surface free energy through the control of chemical functionalities in their SAMs, or as active layers for attachment of biomolecules in biosensors. 

The study of silicon halides began in the eady 1800s (1). Since then, essentially all of the monomeric silicon halides have been extensively studied and reported in the literature. These include mixed silicon halides and halohydrides. A large number of halogenated polysilanes have also been reported (1). Despite the extensive research in silicon halides, only two of these chemicals are produced on alaige industrial scale (excluding oiganohalosilanes). These are tetrachlorosilane [10026-04-7], SiCl and trichlorosilane [1025-78-2], HSiCl. ... 

Silicon is the most abundant solid element in the earth s crust and probably in the universe as a whole [19]. Silicon inorganic materials are all around us, sand, rocks, glasses, cements and mortars all have high silicon content and either occur naturally or are produced by well established processes which have often evolved through thousands of years. During the last few decades new classes of synthetic silicon inorganic materials have been discovered, developed and commercialized. All of the families are based on new chemical processes. The production of polycrystalline silicon with controlled purity by the chemical vapor deposition of trichlorosilane is probably one of the first examples of carefully synthesized silicon inorganic material. This silicon is the basis of the semiconductor industry. 

The chemical vapor deposition of trichlorosilane is significantly endothermic (AH = 964 kJ) and requires high reaction temperatures ( 1150°C). This reaction also yields considerable quantities of tetrachlorosilane as a byproduct ... 

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