Silicon carbide polycrystalline

T.J. McArdle, J.O. Chu, Y. Zhu, Z. Liu, M. Krishnan, C.M. Breslin, et al., Multilayer epitaxial graphene formed by pyrolysis of polycrystalline silicon-carbide grown on c-plane sapphire substrates, Applied Physics Letters, 98 (2011) 132108. 

The ceramic, polycrystalline silicon carbide [409-21 -2], SiC, is processed using p-silicon carbide and boron (9). The boron is a sintering aid used at... 

Among other topics, his research interests include the micro- and nanostructure of ceramic fibers derived from organosilicon precursors and polycrystalline silicon carbide fibers derived from organosilicon polymers. Dr. Lipowitz has nearly 20 U.S. patents and more than 50 publications to his credit. He is a member of several professional and honorary societies, including the American Ceramic Society, the Materials Research Society, Sigma Xi, and the New York Academy of Science. 

Polycrystalline silicon carbide obtained by the Acheson process exhibits a large number of different structures (polytypes), some of which dominate. These can be classified in the cubic, hexagonal, and rhombohedral crystal systems (Table 1). 

Polycrystalline silicon carbide obtained by the Acheson process exhibits a large number of different polytypes, some of which dominate. More than 200 different polytypes are currently known these can be classified into the cubic, hexagonal, and rhombohedral crystal system, and all have the same density of 3.21 gcm . Written polytype nomenclature [11] indicates the number of layers in the repeating layer pack by a numeral, while the crystal system is denoted by the letters C, H, or R. 

The properties of silicon carbide (4—6) depend on purity, polytype, and method of formation. The measurements made on commercial, polycrystalline products should not be interpreted as being representative of single-crystal silicon carbide. The pressureless-sintered silicon carbides, being essentially single-phase, fine-grained, and polycrystalline, have properties distinct from both single crystals and direct-bonded silicon carbide refractories. Table 1 lists the properties of the fully compacted, high purity material. 

Aside from experimental and developing processes, there are three competing commercial processes for further refining metallurgical silicon into semiconductor grade polycrystalline silicon (polysilicon) Siemens, Union Carbide Chemicals, and Ethyl Corporation methods. This industry exists primarily to support the electronics industry. 

In the United States, most of the consumption of silane is internal. Silane is consumed in a free-space polycrystalline silicon production facility (3000 t/yr) at Moses Lake, Washington. This facility was built by Union Carbide but as of 1996 was operated by Advanced Silicon Materials Inc., a joint venture controlled by Komatsu. Silane is also consumed in a fluidized-bed polycrystalline silicon production facility (1250 t/yr) in Pasadena, Texas, built by Ethyl Corporation and operated as of 1996 by MEMC, a publicly traded company 51% owned by Htls. The world merchant market for silane is about 250 t/yr. The bulk price for silane is 80— 120/kg much higher pricing is placed on small packages. The primary use of silane is in microelectronics. Minor applications exist in reprography, ie, in photocopiers, and in specialty glass technology. 

Polycrystalline diamond has been used for aluminum-matrix composites reinforced with particulate silicon carbide, boron carbide, or alumina. It also shows promise as a tool material for welding titanium, although this work is only in a preliminary stage. 

Lipowitz, J.. Structure and properties of Sylramic silicon carbide fiber a polycrystalline, stoichiometric p-SiC composition. Presentation to the Committee on Advanced Fibers for High-Temperature Ceramic Composites, National Materials Advisory Board, National Research Council, Cocoa Beach, Florida, January 16, 1997. 

Another important strategy is the adaptation of efficient PV semiconductor thin-films and nanostructures for effective use in PEC applications. Recent research in this area has focused on material classes with inherent bandgap tuning capabilities such as the amorphous silicon compounds (including silicon carbides and nitrides) [109, 112-114, 131, 132], and polycrystalline copper chalcopyrite compounds [133-137]. 

Yajima [76] was the first to study the preparation of silicon carbide fibers from carbosilanes. These and other SiC-containing polymers were used to produce SiC powders with a crystallite size as small as several nanometers [77, 78]. The advantage ofthe production route from liquid to solid to produce SiC has also attracted attention for SiC film production in microelectronics or as protection layers. In this way, amorphous, polycrystalline films of high purity produced by the dip-coating of substrates in PCS solutions and subsequent pyrolysis in an inert gas atmosphere, have been prepared [115]. 

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