Carbon in nickel

Nickel is a non-ferrous metal with a rather high carbon solubility at the melting point it is about 10 Sit.% (20 mg/g) and at 700°C about 0.5 at.% (1 mg/g). Carbon contents even below 1 at.% (2 mg/g) increase the electrical resistivity of the metal in a significant way. The same applies for the tensile strength, the yield point and the torsion-modulus. Elongation however is decreased (1). 

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A large number of intermediate pathways arc possible when catalytic reactions interfere with the polymerization-dehydrogenation steps. A common scenario is the catalytic dehydrogenation of hydrocarbons on nickel surfaces followed by dissolution of the activated carbon atoms and exsolution of graphene layers after exceeding the solubility limit of carbon in nickel. Such processes have been observed experimentally [40] and used to explain the shapes of carbon filaments. In the most recent synthetic routes to nanotubes [41] the catalytic action of in situ-prepared iron metal particles was applied to create a catalyst for the dehydrogenation of cither ethylene or benzene. 

Previous results from studies on the deposition from benzene (12) and other hydrocarbons (13) in the absence of hydrogen indicate that the reaction terminates after a fixed amount of carbon has been incorporated into the metal foil. Not surprisingly, the amount of carbon uptake by nickel foils corresponds to the solubility of carbon in nickel. 

Diamond S, Wert C. Diffusion of carbon in nickel above and below Curie temperature. Trans MetaU Soc Aime 1967 239 705-9. 

Lander JJ, Kem HE, Beach AL. Solubility and diffusion coefficient of carbon in nickel reactionrates of nickel-carbon alloys with barium oxide. Appl Phys Lett 1952 23 1305-9. 

Nat] Natesan, K., Kassner, T.F., Thermodynamics of Carbon in Nickel, Iron-Nickel and Iron-Chromium-Nickel Alloys , Metall. Trans., 4, 2557-2566 (1973) (Experimental, Phase Diagram, Thermodyn., 39)... 

Iron. Iron is typically used in nickel-base alloys to reduce cost, not to promote corrosion resistance. However, iron does provide nickel with improved resistance to H2SO4 in concentrations above 50%. Iron also increases the solubility of carbon in nickel, thereby improving the resistance to high-temperature carburizing environments. ... 

Cobalt. Cobalt is not generally used as a primary alloying element in materials designed for aqueous corrosion resistance. However, cobalt imparts unique strengthening characteristics to alloys designed for high-temperature service. Cobalt, like iron, increases the solubility of carbon in nickel-base alloys, therefore increasing the resistance to carburization. 

Strijckmans et al. (52) describe the determination of carbon in nickel. After irradiation with 7 MeV deuterons (degraded to 4.1 - 5.0 MeV) the sample is chemically etched in 3 volumes 40 % hydrofluoric acid and 2 volumes 14 M nitric acid and partly dissolved in 25 ml of a solution of 140 mg/1 ammonium hexachloroplatinate in 6 M hydrochloric acid. The ammonium hexachloroplatinate is added to speed up the dissolution. 30 min. is sufficient to dissolve 0.14 - 0.30 g/cm. The volume is adjusted to 50 ml... 

The diffusion coefficients for carbon in nickel are given at two temperatures, as follows ... 

Nickel tetrafluoroborate [14708-14-6] Ni(BE 2 prepared by dissolving nickel carbonate in tetrafluoroboric acid [16872-11-0] HBE. Nickel... 

Metals can be precipitated from the Hquid or gas phase. For example, nickel ammonium carbonate gives nickel powder when subjected to hydrogen in an autoclave. Copper, cobalt, molybdenum, and titanium powders can also be formed by precipitation. 

Nickel [7440-02-0] Ni, recognized as an element as early as 1754 (1), was not isolated until 1820 (2). It was mined from arsenic sulfide mineral deposits (3) and first used in an alloy called German Silver (4). Soon after, nickel was used as an anode in solutions of nickel sulfate [7786-81 A] NiSO, and nickel chloride [7718-54-9] NiCl, to electroplate jewelry. Nickel carbonyl [13463-39-3] Ni(C02)4, was discovered in 1890 (see Carbonyls). This material, distilled as a hquid, decomposes into carbon monoxide and pure nickel powder, a method used in nickel refining (5) (see Nickel and nickel alloys). 

Ma.nufa.cture. Several nickel oxides are manufactured commercially. A sintered form of green nickel oxide is made by smelting a purified nickel matte at 1000°C (30) a powder form is made by the desulfurization of nickel matte. Black nickel oxide is made by the calcination of nickel carbonate at 600°C (31). The carbonate results from an extraction process whereby pure nickel metal powder is oxidized with air in the presence of ammonia (qv) and carbon dioxide (qv) to hexaamminenickel(TT) carbonate [67806-76-2], [Ni(NH3)3]C03 (32). Nickel oxides also ate made by the calcination of nickel carbonate or nickel nitrate that were made from a pure form of nickel. A high purity, green nickel oxide is made by firing a mixture of nickel powder and water in air (25). 

Nickel carbonate is used in the manufacture of catalysts, in the preparation of colored glass (qv), in the manufacture of certain nickel pigments, and as a neutralizing compound in nickel electroplating solutions. It also is used in the preparation of many specialty nickel compounds. 

Nickel Salts and Chelates. Nickel salts of simple organic acids can be prepared by reaction of the organic acid and nickel carbonate of nickel hydroxide reaction of the acid and a water solution of a simple nickel salt and, in some cases, reaction of the acid and fine nickel powder or black nickel oxide. 

Cobalt(II) nitrate hexahydrate [10026-22-9], Co(N02)2 6H20, is a dark reddish to reddish brown, monoclinic crystalline material containing about 20% cobalt. It has a high solubiUty in water and solutions containing 14 or 15% cobalt are commonly used in commerce. Cobalt nitrate can be prepared by dissolution of the simple oxide or carbonate in nitric acid, but more often it is produced by direct oxidation of the metal with nitric acid. Dissolution of cobalt(III) and mixed valence oxides in nitric acid occurs in the presence of formic acid (5). The ttihydrate forms at 55°C from a melt of the hexahydrate. The nitrate is used in electronics as an additive in nickel—ca dmium batteries (qv), in ceramics (qv), and in the production of vitamin B 2 [68-19-9] (see Vitamins, VITAMIN B22)-... 

Catalytic reduction of quinazolines unsubstituted in position 4 using palladium-charcoal, palladium on calcium carbonate, Raney nickel, or Adam s platinum has been used for preparing 3,4-dihydro-... 

Valves must be made of fatigue-resistant carbon or alloy steel or 18-8 stainless steel, depending upon the service. The 18-8 stainless and 12-14 chrome steel is often used for corrosive and/or high temperature service. Any springs, as in the plate-type valves, are either carbon or nickel steel. Valve passages must be smooth, streamlined, and as large as possi-... 

For special applications special silicon-bearing austenitic steels are produced by a few manufacturers. Silicon contents are 4-5-3% and there is a corresponding increase in nickel and very low (<0-015%) carbon. In the welded state these are giving good service in nitric acid of over 90% strength up to 75°C. 

While carburisation itself is not a normal corrosion process, in that there is no metal wastage, absorption and diffusion of carbon can lead to significant changes in the mechanical properties of the affected material and in particular to marked embrittlement. Furthermore, initial carburisation can produce an acceleration of the normal oxidation process, a phenomenon that is notable in nickel-chromium alloys. 

The second stage in the carburisation process, that of carbon ingress through the protective oxide layer, is suppressed by the development of alumina or silica layers as already discussed and in some cases protective chromia scales can also form. Diffusion and solubility of carbon in the matrix has been shown by Schnaas et to be a minimum for binary Fe-Ni alloys with a nickel content of about 80<7o, and Hall has shown that increasing the nickel content for the nickel-iron-2S<7o-chromium system resulted in lower rates of carburisation (Fig. 7.54). 

The steel will be considered to be an ideal ternary solution, and therefore at all temperatures a, = 0-18, Ani = 0-08 and flpc = 0-74. Owing to the Y-phase stabilisation of iron by the nickel addition it will be assumed that the steel, at equilibrium, is austenitic at all temperatures, and the thermodynamics of dilute solutions of carbon in y iron only are considered. 

The discussion so far has been limited to the structure of pure metals, and to the defects which exist in crysteds comprised of atoms of one element only. In fact, of course, pure metals are comparatively rare and all commercial materials contain impurities and, in many cases also, deliberate alloying additions. In the production of commercially pure metals and of alloys, impurities are inevitably introduced into the metal, e.g. manganese, silicon and phosphorus in mild steel, and iron and silicon in aluminium alloys. However, most commercial materials are not even nominally pure metals but are alloys in which deliberate additions of one or more elements have been made, usually to improve some property of the metal examples are the addition of carbon or nickel and chromium to iron to give, respectively, carbon and stainless steels and the addition of copper to aluminium to give a high-strength age-hardenable alloy. 

Austenite the y-modification of iron, having an f.c.c. lattice, which is stable above about 700°C the term is also applicable to solid solutions of carbon, chromium, nickel, etc. in y-iron. 

The metal surface area at the inlet end of the catalyst bed in experiment HGR-12 was smaller than that at the outlet end this indicates that a decrease in nickel metal sites is part of the deactivation process. Sintering of the nickel is one possible mechanism, but carbon and carbide formation are suspected major causes. Loss of active Raney nickel sites could also conceivably result from diffusion of residual free aluminum from unleached catalyst and subsequent alloying with the free nickel to form an inactive material. 

Catalysts in an oxidized state showed high activity in the oxidation of carbon monoxide [nickel catalysts (146) ] and hydrogen [molybdenum catalysts (146a)]. 

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