Carbon graphitization

Electrodes. Because of the numerous different processes, there are many different types of electrodes in use (9), eg, prefabricated graphite, prefabricated carbon, self-baking, and composite electrodes (see Carbon). Graphite electrodes are used primarily in smaller furnaces or in sealed furnaces. Prebaked carbon electrodes, made in diameters of <152 cm or 76 by 61 cm rectangular, are used primarily in smelting furnaces where the process requkes them. However, self-baking electrodes are preferred because of thek lower cost. 

Carbon-Graphite Group Calvert City, Ky. Chevron Cedar Bayou, Tex. calcium carbide 34 acetylenic chemicals... 

Among nonmetallic materials, glass, chemical stoneware, enameled steel, acid-proof brick, carbon, graphite, and wood are resistant to iodine and its solutions under suitable conditions, but carbon and graphite may be subject to attack. Polytetrafluoroethylene withstands Hquid iodine and its vapor up to 200°C although it discolors. Cloth fabrics made of Saran, a vinyHdene chloride polymer, have lasted for several years when used in the filtration of iodine recovered from oil-weU brines (64). 

Carbon, Carbides, and Nitrides. Carbon (graphite) is a good thermal and electrical conductor. It is not easily wetted by chemical action, which is an important consideration for corrosion resistance. As an important stmctural material at high temperature, pyrolytic graphite has shown a strength of 280 MPa (40,600 psi). It tends to oxidize at high temperatures, but can be used up to 2760°C for short periods in neutral or reducing conditions. The use of new composite materials made of carbon fibers is expected, especially in the field of aerospace stmcture. When heated under... 

By far the most common iadustrial refractories are those composed of single or mixed oxides of Al, Ca, Cr, Mg, Si, and Zr (see Tables 1, 4, and 6). These oxides exhibit relatively high degrees of stabiHty under both reduciag and oxidizing conditions. Carbon, graphite, and siHcon carbide have been used both alone and ia combination with the oxides. Refractories made from these materials are used ia toa-lot quantities, whereas siHcides are used ia relatively small quantities for specialty appHcation ia the auclear, electronic, and aerospace iadustries. 

Porous bron2e and iron, a variety of plastics, carbon—graphite, wood, and mbber are widely used in dry sliding or under conditions of sparse lubrication. These materials have commonly allowed design simplifications, freedom from regular maintenance, reduced sensitivity to contamination, and good performance at low speeds and with intermittent lubrication. Although these materials are often used dry or with sparse lubrication, performance normally improves the closer the approach to full-film lubrication. 

A hard, mst-resistant shaft of at least 0.25 micrometer finish is usually required. Common shaft surfaces are hardened tool steel, chrome plate, high strength bronze, and carbide and ceramic overlays. Test results over a broad speed range from 0.05 to 47 m/s (10 to 9200 fpm) iadicate that a coefficient of friction of 0.16—0.20 and a wear factor of 14 X 10 m /N(70x 10 ° in. min/ft-lb-h) are typical for dry operation of weU appHed grades of carbon—graphite (29). 

Organic clutch materials contain continuous-strand reinforcements in addition to fibrous reinforcements. These include cotton (primarily for processing), other organic yams, carbon—graphite yam, and asbestos yam, and brass wire or copper wire for high burst strength. 

Carbon—graphite materials employed for mechanical appHcations are prepared by mixing selected sizes and types of carbon and graphite with biader materials such as pitches and resias. The mixtures are formed iato compacts and baked to temperatures of ca 1000—3000°C. Specific raw materials and processiag techniques are employed to obtain desired properties for the finished carbon—graphite materials (24). 

Carbon—graphite materials do not gall or weld even when mbbed under excessive load and speed. Early carbon materials contained metal fillers to provide strength and high thermal conductivity, but these desirable properties can now be obtained ia tme carboa—graphite materials that completely eliminate the galling teadeacy and other disadvantages of metals. 

N. J. Fechter and P. S. Petmnich, Development of Seal Ring Carbon-Graphite Materials., NASA Contract Reports CR-72799, Jan. 1971 CR-72986, Aug. 1971 CR-120955, Aug. 1972 and CR-121092, Union Carbide Corp., Parma, Ohio, Jan. 1973. 

Carbon—graphite foam is a unique material that has yet to find a place among the various types of commercial specialty graphites. Its low thermal conductivity, mechanical stabiHty over a wide range of temperatures from room temperature to 3000°C, and light weight make it a prime candidate for thermal protection of new, emerging carbon—carbon aerospace reentry vehicles. 

J. E. Hove, Industrial Carbon Graphite, Papers Conf Eondon 1957, 1958, p. 509. 

More than 95% of current carbon fiber production for advanced composite appHcations is based on the thermal conversion of polyacrylonitrile (PAN) or pitch precursors to carbon or graphite fibers. Generally, the conversion of PAN or pitch precursor to carbon fiber involves similar process steps fiber formation, ie, spinning, stabilization to thermoset the fiber, carbonization—graphitization, surface treatment, and sizing. Schematic process flow diagrams are shown in Eigure 4. However, specific process details differ. 

Carbon-graphite 700 Good bearing and self-lubricating properties. Good resistance to chemicals, beat. 

Fig. 3.53. Ion fraction of He and He ions (open and full symbols, respectively) in LEIS from Cu (v,T) and different types of C (carbidic carbon , graphitic carbon O, 0,- -, ) as a function of the sum of the reciprocal velocities of the incoming and the scattered ion [3.139],...

Biomass phenolic and furan resins polyimides glassy carbons, binder and matrix carbons" graphite films and monoliths activated carbons ... 

Heintz, E.A., Influence of coke structure on the properties of the carbon-graphite artefact, FUEL, 1985, 64, 1192 1196. 

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