Silicon Carbide SiC

The conventional industrial method for the synthesis of a-silicon carbide is to heat silica (sand) with coke in an electric furnace at 2,000-2,500 °C. However, because of the high melting point of the product, it is difficult to fabricate by sintering or melt techniques. Thus, the discovery of a lower temperature fabrication and synthesis route to silicon carbide by Yajima and coworkers in 197526,27 proved to be an important technological breakthrough. This is a preceramic polymer pyrolysis route that has been developed commercially for the production of ceramic fibers. 

The carbosilane is a white, soluble, and meltable material that can be melt-spun into fibers at 190 °C. Exposure of the fibers to air at the same temperature generates a surface coating of silica which stabilizes the structure throughout the cross-linking step prior to pyrolysis. Subsequent heating at 1,200-1,500 °C in a nitrogen atmosphere drives off 

A considerable amount of subsequent research and process development has been carried out to produce silicon carbide with a reduced level of excess carbon via processes that allow more facile cross-linking.2 -32 Several hundred papers and patents on this topic exist in the literature, and only a few examples will be mentioned here. One process development involves the slurry spinning of fibers in place of melt spinning.33 In this process, silicon carbide powder, made by a conventional industrial process, is dispersed in a solution of carbosilanes in toluene. The syrupy paste is spun into fibers and then pyrolyzed to silicon carbide. These fibers are reported to be stable at 1,500 °C for 120 hours. 

An example of the enhanced cross-linking approach involves the pyrolysis of cyclic and linear oligosilane precursors that bear vinyl or acetylenic side groups.34 These are 

Interrante and coworkers38 developed a multi-stage process leading to silicon carbide that starts from the readily available MeSiCl3. The reaction sequence is summarized in reaction (9). 

Aluminum nitride AIN 3.30 Does not melt but dissociates above 2500  

Alumina has a high melting point and is a widely used ceramic, but it does have a high expansion coefficient. When deposited via the sol gel method, excessive shrinkage occurs on drying and firing, which has to be counteracted by the addition of AI2O3 [144]. 

Mullite has a slightly lower melting point than alumina, but the expansion coefficient is low and similar to SiC. 

Silicon carbide shows great promise as a matrix material, retaining strength up to 1400°C, but unfortunately, it does exhibit brittle behavior up to 2000°C. Carbon fiber has been used 

Ansorge [153] produced a carbon fiber reinforced SiC ceramic matrix composite by liquid phase infiltration of Si into a carbon-carbon composite. 

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The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

The covalent carbides These include boron carbide B4C and silicon carbide SiC the latter is made by heating a mixture of silica and coke in an electric furnace to about 2000 K ... 

Silica (Si02) glasses and silicates Silicon carbide (SiC)... 

Ceramics themselves are sometimes protected in this way. Silicon carbide, SiC, and silicon nitride, Si3N4 both have large negative energies of oxidation (meaning that they oxidise easily). But when they do, the silicon in them turns to Si02 which quickly forms a protective skin and prevents further attack. 

Using the periodic table as a guide, predict which of the following compounds form ionic solutions in water silicon carbide, SiC magnesium bromide, MgBr2 carbon tetrabromide, CBr chromic chloride, CrCl3. 

The covalent carbides include silicon carbide, SiC, which is sold as carborundum ... 

Silicon carbide (SiC) is a major industrial material with a considerable number of applications. CVD plays a significant role in its development and production, SiC is a covalent carbide with two phases a and [3. The phase of major interest here is pSiC, which has a cubic zinc blend structure. It is the one reported here. 

Silicon Carbide. SiC has low thermal expansion, high hardness, and good resistance to oxidation. It is used extensively in the coating of graphite and carbon to impart wear and oxidation resistance. 

Present oxidation-protection systems are based on silicon carbide (SiC), which is applied by pack cementation or by chemical-vapor infiltration (CVI) (see Ch. 4).d ] Boron, zirconium, and other... 

The literature proposes a relatively large number of HEX reactors that have been designed and built of different materials such as glass, stainless steel, polyether ether ketone (PEEK), and silicon carbide (SiC). A presentation can be found in Amdoimaz et al. [13]. 

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 carbide, SiC [1] and silicon nitride, Si3N4 [2], have been known for some time. Their properties, especially high thermal and chemical stability, hardness, high strength, and a variety of other properties have led to useful applications for both of these materials. 

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... 

The treatment assumes that the point defects do not interact with each other. This is not a very good assumption because point defect interactions are important, and it is possible to take such interactions into account in more general formulas. For example, high-purity silicon carbide, SiC, appears to have important populations of carbon and silicon vacancies, and Vsj, which are equivalent to Schottky defects, together with a large population of divacancy pairs. 

SAQ 2.2 By looking at the electronegativities in Table 2.1, suggest whether the bonds in the following molecules will be polar or non-polar (a) hydrogen bromide, HBr (b) silicon carbide, SiC (c) sulphurdioxide, 0=S=0 and (d) sodium iodide, Nal. 

Silicon carbide SiC is another network solid. Silicon carbide is used as an abrasive because of its hard structure. 

The SRNL hybrid microwave concept design is shown in Figure 1. Metal tritide powder is slightly susceptible to conventional microwave frequency, so to obtain the high temperature needed a Silicon Carbide (SiC) susceptor is used to generate the hot temperature. This susceptor is used for all metal hydride materials regardless of the individual susceptibility of the sample. 

The sample of desorbed tritide is placed inside a quartz tube that is connected to a gas-handling manifold by a TorrSeal . A quartz sleeve with Silicon Carbide (SiC) in the annular space is placed around the end of the quartz tube, surrounding the sample with microwave susceptor. The quartz tube and susceptor sleeve are thermally insulated from the rest of the microwave cavity. An internal thermocouple measures the temperature of the sample and provides the temperature signal for process control of the desired temperature. A shine block (alumina foam), attached to the thermocouple, blocks radiant heating of the TorrSeal and the upper area of the quartz tube and manifold. An IR pyrometer is used as a secondary measure of the temperature of the susceptor, and therefore of the sample. A stainless steel shield reflects microwaves from the quartz tube not in the susceptor sleeve, eliminating the production of a plasma at low pressure in the quartz tube. 

Silicon carbide (SiC), nearly as hard as diamonds, is used as an abrasive in grinding wheels and metal-cutting tools, for lining furnaces, and as a refractory in producing nonferrous metals. 

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