Nickel alloys compounds

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

In atomization, a stream of molten metal is stmck with air or water jets. The particles formed are collected, sieved, and aimealed. This is the most common commercial method in use for all powders. Reduction of iron oxides or other compounds in soHd or gaseous media gives sponge iron or hydrogen-reduced mill scale. Decomposition of Hquid or gaseous metal carbonyls (qv) (iron or nickel) yields a fine powder (see Nickel and nickel alloys). Electrolytic deposition from molten salts or solutions either gives powder direcdy, or an adherent mass that has to be mechanically comminuted. 

Two different sets of experimental conditions have been used. Buu-Hoi et al. and Hansen have employed the method introduced by Papa et using Raney nickel alloy directly for the desulfurization in an alkaline medium. Under these conditions most functional groups are removed and this method is most convenient for the preparation of aliphatic acids. The other method uses Raney nickel catalysts of different reactivity in various solvents such as aqueous ammonia, alcohol, ether, or acetone. The solvent and activity of the catalyst can have an appreciable influence on yields and types of compounds formed, but have not yet been investigated in detail. In acetic anhydride, for instance, desulfurization of thiophenes does not occur and these reaction conditions have been employed for reductive acetylation of nitrothiophenes. Even under the mildest conditions, all double bonds are hydrogenated and all halogens removed. Nitro and oxime groups are reduced to amines. 

Fluorine is the most reactive of all elements, in part because of the weakness of the F—F bond (B.E. F—F = 153 kj/mol), but mostly because it is such a powerful oxidizing agent (E ed = +2.889 V). Fluorine combines with every element in the periodic table except He and Ne. With a few metals, it forms a surface film of metal fluoride, which adheres tightly enough to prevent further reaction. This is the case with nickel, where the product is NiF2. Fluorine gas is ordinarily stored in containers made of a nickel alloy, such as stainless steel (Fe, Cr, Ni) or Monel (Ni, Cu). Fluorine also reacts with many compounds including water, which is oxidized to a mixture of 02> 03> H202, and OF2. 

About 727,000 workers were potentially exposed to nickel metal, nickel alloys, or nickel compounds during the period 1980 to 1983 (USPHS 1993). Worker exposure differs from that of the general population in that the major route of exposure for nickel workers is inhalation and for the general population it is dermal contact (Sevin 1980). Nickel workers with lung cancer had elevated concentrations of 1.97 mg/kg DW in their lungs when compared to the general population (0.03 to 0.15 mg/kg DW USPHS 1977). Plasma concentrations of nickel quickly reflect current exposure history to nickel (USEPA 1980). Mean nickel concentrations in plasma of humans occupationally exposed to nickel have declined by about 50% since 1976, suggesting decreased exposure due to improved safety (Boysen et al. 1980). 

Nickel (Ni), 17 88-105. See also Chrome-nickel stainless steels Fe-Ni-Co alloys Ni entries Nickel alloys Nickel compounds Nickel metal chemical vapor deposition precursor, 5 805t... 

Nickel phosphorus (Ni-P) alloy deposition, 9 691-693. See also Ni-P entries Nickel phosphorus compounds, 17 124... 

Individually indexed alloys or intermetallic compounds are Aluminium amalgam, 0051 Aluminium-copper-zinc alloy, 0050 Aluminium-lanthanum-nickel alloy, 0080 Aluminium-lithium alloy, 0052 Aluminium-magnesium alloy, 0053 Aluminium-nickel alloys, 0055 Aluminium-titanium alloys, 0056 Copper-zinc alloys, 4268 Ferromanganese, 4389 Ferrotitanium, 4391 Lanthanum-nickel alloy, 4678 Lead-tin alloys, 4883 Lead-zirconium alloys, 4884 Lithium-magnesium alloy, 4681 Lithium-tin alloys, 4682 Plutonium bismuthide, 0231 Potassium antimonide, 4673 Potassium-sodium alloy, 4646 Silicon-zirconium alloys, 4910... 

Nickel is used mostly for the production of stainless steel and other nickel alloys with high corrosion and temperature resistance. Nickel alloys and nickel platings are used in vehicles, processing machinery, armaments, tools, electrical equipment, household appliances, and coins. Nickel compounds also are used as catalysts, pigments, and in batteries. 

Platinum-based catalysts are widely used in low-temperature fuel cells, so that up to 40% of the elementary fuel cell cost may come from platinum, making fuel cells expensive. The most electroreactive fuel is, of course, hydrogen, as in an acidic medium. Nickel-based compounds were used as catalysts in order to replace platinum for the electrochemical oxidation of hydrogen [66, 67]. Raney Ni catalysts appeared among the most active non-noble metals for the anode reaction in gas diffusion electrodes. However, the catalytic activity and stability of Raney Ni alone as a base metal for this reaction are limited. Indeed, Kiros and Schwartz [67] carried out durability tests with Ni and Pt-Pd gas diffusion electrodes in 6 M KOH medium and showed increased stability for the Pt-Pd-based catalysts compared with Raney Ni at a constant load of 100 mA cm and at temperatures close to 60 °C. Moreover, higher activity and stability could be achieved by doping Ni-Al alloys with a few percent of transition metals, such as Ti, Cr, Fe and Mo [68-70]. 

You may be exposed to higher levels of nickel if you work in industries that process or use nickel. You may be exposed to nickel by breathing dust or fumes (as from welding) or by skin contact with nickel-containing metal and dust or solutions containing dissolved nickel compounds. A national survey conducted from 1980 to 1983 estimated that 727,240 workers are potentially exposed to nickel metal, nickel alloys, or nickel compounds. 

Production, Import/Export, Use, and Release and Disposal. Information on the production, import, export, and use of nickel metal and nickel alloys is readily available (Chamberlain 1985 Kirk 1988a, 1988b NTD 1996 Tien and Howson 1981). However, information on the production, import, and use patterns of other nickel compounds is not generally available and is needed to assess human exposure to these compounds. Except for recycling of metal scrap, little information is available regarding the disposal of nickel and its compounds. 

Powder Formation. Metallic powders can be formed by any number of techniques, including the reduction of corresponding oxides and salts, the thermal dissociation of metal compounds, electrolysis, atomization, gas-phase synthesis or decomposition, or mechanical attrition. The atomization method is the one most commonly used, because it can produce powders from alloys as well as from pure metals. In the atomization process, a molten metal is forced through an orifice and the stream is broken up with a jet of water or gas. The molten metal forms droplets to minimize the surface area, which solidify very rapidly. Currently, iron-nickel-molybdenum alloys, stainless steels, tool steels, nickel alloys, titanium alloys, and aluminum alloys, as well as many pure metals, are manufactured by atomization processes. 

Beryllium hydroxide see Beryllium and beryllium compounds) Beryllium-nickel alloy see Beryllium and beryllium compounds) Beryllium oxide see Beryllium and beryllium compounds)... 

---