Abrasives silicon carbides

Table 6 shows the production of abrasive silicon carbide in the United States and Canada (131). In 1988, four firms were producing crude silicon carbide under various trade names at six plants in the United States and Canada, The Exolon-ESK Co. General Abrasive/Dresser Co. Norton Co. and Superior Graphite Co. Most plants are located in areas where electrical power is, or at one time, was available at relatively low rates. Other considerations are availability of labor, reasonable air and water pollution standards, future expansion potential, and proximity of raw materials and markets. 

Cutting wheels or wires with abrasives Aluminum oxide abrasives Silicon carbide abrasives i r Diamond abrasives... 

The first artificial abrasive, silicon carbide [409-21 -2], SiC, was produced by Edward Acheson in 1891 (19). This invention led to the formation of the Carborundum Company. The registered trademark, Carborundum, is essentially synonymous with silicon carbide. 

Aluminium contamination is seldom observed for low temperature vacuum sublimation. Aluminium has a low capture coefficient at low temperatures and it does not form refractory carbides with a low vapour pressure. Therefore, traces of aluminium can be easily removed by annealing the furnace in vacuum even if contamination occurs. However, if the material source is insufficiently pure, it can result in noticeable aluminium contamination, especially at elevated growth temperatures. For the bulk crystal growth, aluminium contamination is always observed when abrasive silicon carbide is used as source material [20,22]. The abrasive material usually is highly contaminated [1,22]. 

Although diamond is the abrasive that is used most frequently for ceramics, other abrasives are also used. The basic rule is that their hardness must be greater than the hardness of the material being processed. It is generally best to process aluminum oxide ceramics with diamond abrasives. Silicon carbide wet abrasive papers can be used for graphite, zinc oxide, and silicate ceramics. 

The remainder is used in the refractory and structural ceramic industries. As an abrasive, silicon carbide is best used on either very hard materials such as cemented carbide, granite and glass, or on soft materials such as wood, leather, plastics, rubber, etc. 

Silicon is important to plant and animal life. Diatoms in both fresh and salt water extract Silica from the water to build their cell walls. Silica is present in the ashes of plants and in the human skeleton. Silicon is an important ingredient in steel silicon carbide is one of the most important abrasives and has been used in lasers to produce coherent light of 4560 A. 

Silicon Carbide. Sihcon carbide is made by the electrofusion of siUca sand and carbon. SiUcon carbide is hard, abrasion resistant, and has a high thermal conductivity. It is relatively stable but has a tendency to oxidize above 1400°C. The siUca thus formed affords some protection against further oxidation (see Carbides). 

Seal Face Combinations The dynamic of seal faces is better understood today. Seal-face combinations have come a long way in the past 8-10 years. Stellite is being phased out of the petroleum and petrochemical applications. Better grades of ceramic are available, cost of tungsten has come down, and relapping of tungsten are available near most industrial areas. Silicon carbide is being used in abrasive service. 

Silicon carbide was made accidently by E. G. Acheson in 1891 he recognized its abrasive power and coined the name carborundum from carbo(n) and (co)rundum (AI2O3) to indicate that its hardness on the Mohs scale (9.5) was intermediate between that of diamond (10) and AI2O3 (9). Within months he had formed the Carborundum Co. for its manufacture, and current world production approaches 1 million tonnes annually. 

In 1885, Charles Martin Hall invented his aluminum process and Hamilton Young Castner in 1890 developed the mercury-type alkali-chlorine cell, which produced caustic (sodium hydroxide) in its purest form. Edward G. Acheson in 1891, while attempting to make diamonds in an electric furnace, produced silicon carbide, the first synthetic abrasive, second to diamond in hardness. Four years later, Jacobs melted aluminum oxide to make a superior emeiy cloth. Within two decades, these two abrasives had displaced most natural cutting materials, including naturally occurring mixtures of aluminum and iron oxides. 

Many ceramic applications are high value and small volume, so energy expenditure is high. Ferroelectric magnets, electronic substrates, electrooptics, abrasives such as silicon carbide and diamond, are examples. Diamond is found naturally, and made synthetically by the General Electric Company at high pressure and temperature. Synthetic diamonds for abrasives require less energy to make than the value in Table 4 nevertheless, the market is carefully divided between natural and synthetic diamonds. 

Pure silicon carbide is colorless, but iron impurities normally impart an almost black color to the crystals. Carborundum is an excellent abrasive because it is very hard, with a diamondlike structure that fractures into pieces with sharp edges (Fig. 14.43). 

FIGURE 26.4 Master curves on smooth, wavy glass, on a sihcon carbide track dusted with magnesium oxide and on a clean silicon carbide track of three acrylate-butadiene rubber (ABR) compounds as gum rubber, filled with 20 pphr carbon black and 50 pphr, respectively. (From Grosch, K.A., Sliding Friction and Abrasion of Rubbers, PhD thesis, University of London, London 1963.)... 

Silicon, like carbon, is relatively inactive at ordinary temperatures. But, when heated, it reacts vigorously with the halogens (fluorine, chlorine, bromine, cmd iodine) to form halides and with certain metals to form silicides. It is unaffected by all acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures of 2,000 to 2,600 °C (3,600 to 4700 °F), they form silicon carbide (Carborundum = SiC), which is an Importeint abrasive. When reacted with hydrogen, silicon forms a series of hydrides, the silanes. Silicon also forms a series of organic silicon compounds called silicones, when reacted with various organic compounds. 

Silicon carbide (carborundum) Talc Bluish-black, very hard crystals. Used as an abrasive and refractory material. A hydrous magnesium silicate used in ceramics, cosmetics, paint and pharmaceuticals. 

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... 

Abrasion-resistant white cast irons, molybdenum in, 17 17 Abrasive Grain Association (AGA), silicon carbide standards by, 22 537, 538 Abrasive materials, phenolic resins in,... 

Coated Abrasive Manufacturing Institute (CAMI), silicon carbide standards by, 22 537... 

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

Roughen the surface using silicon carbide abrasive paper 400. 

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. 

Hayashi H, Kajita A Silicon carbide in lung tissue of a worker in the abrasives industry. AmJlndMed 14 145-155, 1988... 

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