Nickel-aluminium alloys

The transition from non-protective internal oxidation to the formation of a protective external alumina layer on nickel aluminium alloys at 1 000-1 300°C was studied by Hindam and Smeltzer . Addition of 2% A1 led to an increase in the oxidation rate compared with pure nickel, and the development of a duplex scale of aluminium-doped nickel oxide and the nickel aluminate spinel with rod-like internal oxide of alumina. During the early stages of oxidation of a 6% A1 alloy somewhat irreproducible behaviour was observed while the a-alumina layer developed by the coalescence of the rodlike internal precipitates and lateral diffusion of aluminium. At a lower temperature (800°C) Stott and Wood observed that the rate of oxidation was reduced by the addition of 0-5-4% A1 which they attributed to the blocking action of internal precipitates accumulating at the scale/alloy interface. At higher temperatures up to 1 200°C, however, an increase in the oxidation rate was observed due to aluminium doping of the nickel oxide and the inability to establish a healing layer of alumina. 

Couch, D. E. and Connor, J. H., Nickel-Aluminium Alloy Coatings Produced by Electrodeposition and Diffusion , J. Electrochem. Soc., 107, 272 (1960)... 

The most important example of this category is Raney nickel, which is extensively used in hydrogenation reactions in fine chemistry. The catalyst has been named after Murray Raney who invented this catalyst in 1924. It is prepared by the reaction of a powdered nickel-aluminium alloy with aqueous sodium hydroxide to selectively remove a large fraction of the aluminium component (.see Figure 3.12). The product consists of porous nickel with a high... 

As already stated it is a specially active form of nickel and is prepared from a nickel-aluminium alloy sodium hydroxide is added to dissolve the aluminium and nickel is left as a black pyrophoric powder. 

Raney nickel (often abbreviated to RaNi) is a finely divided form of nickel made from a nickel-aluminium alloy. The aluminium is dissolved away using concentrated aqueous sodium hydroxide, leaving the nickel as a fine powder. The process liberates H2 (check this for yourself— on paper ), and some of this hydrogen remains adsorbed on to the nickel catalyst. This means that some hydrogenations, particularly those of C-S bonds, which you will come across later in... 

The macrocycle in [MnCl2(198)] -H20 can be reduced using a nickel-aluminium alloy under basic conditions.545 Addition of cold concentrated nitric acid then leads to isolation of the reduced macrocycle (201) as its tetrahydrogennitrate salt. 

The most commonly used method for the cleavage of hydrazones is catalytic hydrogenation in the presence of acid. An example is provided by the synthesis of secondary and tertiary amines by reduction of benzophenone hydrazones (14), derived as shown in Scheme 10. Nickel-aluminium alloy can also be used to reduce hydrazones to amines. ... 

Raney Nickel (nickel-aluminium alloy) is an effective catalyst for the conversion of thioketals to alkanes. Ultimately, a ketone is converted to the alkane with this mild method through a thioketal. Review Pettit, G. R. van Tamelen, E. E. Org. React. 1962,12, 356-529. 

For all these reasons an increase in chromium concentration may be the best solution to increase the sulphidation resistance of iron-aluminium alloys. The present work has shown that chromium has a very beneficial effect on the sulphidation resistance in oxygen deficient gases. Such improvement of sulphidation resistance in H2S environments has also been found in nickel-aluminium alloys, where the corrosion rate decreased significantly, when 8 wt% chromium were added [22], Whether chromium increases the rate of alumina formation or contributes to the formation of protective spinell type oxides Fe(Cr,Al)203 cannot be decided from the available results. It is also possible that chromium catalyses the transition from a less to a more protective type of A1203. It was for example found that chromium enhances the transition from 0-Al2O3 to a-Al203 in Ni-Al at temperatures above 1000°C [30],... 

Phenol in 10% sodium deuteroxide in deuterium oxide upon treatment with Raney nickel-aluminium alloy and heating at100 C for 3 hours afforded a pentedeurated product in 86% yield (ref.63). 

A more universal method of SpAs preparation is based on reduction of IcP bases (e.g., 2, 327 and 330) instead of the IcP quaternary salts mentioned above. The reduction was performed with nickel aluminium alloy or, better still, with a mixture of formic acid and triethylamine. In the latter case, reaction results in the formation of isolable 5-formyl SpAs derivatives (e.g., 554 and 555) readily hydrolyzed in hot hydrochloric acid to SpAs in 85-95% yield, unsubstituted (493) or substituted (556 and 557) at the ring nitrogen atoms. By this method, the previously unknown 2-aza-SpA 558 were prepared from l,2,3-triazolo[4,5-c]pyridine (2002ZOR440). 

Tiimethylsilyl)ethanesulphonyl chloride, Me3SiCH2CH2S02Cl, is useful for the protection of primary and secondary amines as sulphonamides, which are smoothly cleaved by fluoride ion. Use of the triazene moiety as a protecting group for aromatic amines is illustrated in eqnation 110. The protected compounds react with s-butyllithium, followed by an electrophile E (carbon dioxide, acetophenone or trimethylsilyl chloride), to give, respectively, the corresponding carboxyhc acid, alcohol or trimethylsilyl daivative, which are converted into the free amines by the action of nickel -aluminium alloy in aqueous-methanolic potassium hydroxide-... 

Raney nickel A spongy form of nickel made by the action of sodium hydroxide on a nickel-aluminium alloy. The sodium hydroxide dissolves the aluminium leaving a highly active form of nickel with a large surface area. The material is a black pyrophoric powder saturated with hydrogen, it is an extremely efficient catalyst, especially for hy-... 

Destruction of A-nitrosamines in laboratory wastes using nickel-aluminium alloy in potassium hydroxide solution. 

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