Preparation silicon carbide

P. Tsui, K. E. Spear, in Emergent Process Methods for High-Technology Ceramics Morphological Study of Silicon Carbide Prepared by Chemical Vapor Deposition, (Eds. by R. F. Davis, H. Palmour, HI, and R. L. Porter), Materials Research 17, 1984, pp. 371-380. 

POROUS SILICON CARBIDE PREPARED BY PYROLYSIS OF THE ORGANOSILICON POLYMER... 

RT Yakimova, AA Kalnin. Study of the silicon carbide preparation in the silicon-scandium-caibon system. Phys Status SoUdi (a) 32 297, 1975. 

Carbon forms binary compounds with most elements those with metals are considered in this section whilst those with H, the halogens, O, and the chalcogens are discussed in subsequent sections. Alkali metal fullerides and encapsulated (endohedral) metallafullerenes have already been considered (pp. 285, 288 respectively) and met-allacarbohedrenes (metcars) will be dealt with later in this section (p. 300). Silicon carbide is discussed on p. 334. General methods of preparation of metal carbides are ... 

Soluble polydiorganosilane homo and copolymers have recently shown great potential in such areas as precursors for the preparation of silicon carbide fibers (1), as photoinitiators in alkene polymerization (2), as photoconductors (3), and as positive or negative self-developing photoresists for photolithographic applications (4). A number of copolydiorganosilane copolymers have been reported recently (5) in which the copolymer contained equal amounts of both monomers in the feed. 

Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (SijN ), and boron nitride (BN) offer a wide variety of unique physical properties such as high hardness and high structural stability under environmental extremes, as well as varied electronic and optical properties. These advantageous properties provide the driving force for intense research efforts directed toward developing new practical applications for these materials. These efforts occur despite the considerable expense often associated with their initial preparation and subsequent transformation into finished products. 

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. 

Other organosilicon polymer precursors for ceramics have either been prepared or improved by means of transition metal complex-catalyzed chemistry. For instance, the Nicalon silicon carbide-based ceramic fibers are fabricated from a polycarbosilane that is produced by thermal rearrangement of poly(dimethylsilylene) [18]. The CH3(H)SiCH2 group is the major constituent of this polycarbosilane. 

Summary A brief review of the preparation of silicon containing preceramic polymers to prepare silicon carbide and silicon carbonitride fibers is given. Methylchlorodisilanes are converted to polysilanes and polysilazanes which yield ceramic fibers after meltspinning, curing, and pyrolysis. 

The conventional production method for SiC - the reaction of coke and sand (Acheson process) -does not involve soluble or fusible intermediates. For many applications of silicon carbide this fact is not necessarily a disadvantage, but for the preparation of ceramic composites such intermediates are required. 

Silicon carbide, SiC or carborundum, has the diamond structure, and it is widely used as an abrasive in grinding wheels. These are made by crushing the SiC, adding clay, then heating the material in molds. Silicon carbide is prepared by the reaction... 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

PolyCy-benzyl L-glutamate) (PBLG), 15 109 Poly(y-ketosulfide)s, optically active, 23 711 Poly(P-alanine), 1 292 Poly-P-hydroxybutyrate (PHB), 12 482 Polybetaines, 20 479-482 applications of, 20 482 preparation of, 20 480-481 solution properties of, 20 481-482 synthesis of, 20 479-481 Polyborates, 4 256-258 Polyborosiloxanes, in silicon carbide manufacture and processing, 22 533 Polybrominated diphenyl ethers (PBDEs), 13 142-143 20 56... 

P. H. Cuong, B. Christophe, D. Thierry, E. Babrielle, E. Claude, and J. L. Marc, High surface area silicon carbide doped with zirconium for use as catalyst support preparation, characterization and catalytic application, Appl. Catal. A 180, 385—397 (1999). 

Silicon carbide is prepared by heating fine sdica with carbon (coke) and a little salt and sawdust in an electric furnace. 

Silica is reduced to silicon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous silicon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum halides, silica can be converted to silane in high yields by reaction with hydrogen (15). Silicon itself is not hydrogenated under these conditions. The formation of silicon by reduction of silica with carbon is important in the technical preparation of the element and its alloys and in the preparation of silicon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and silicate. At 800—900°C, silica is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce silica to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

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