Ni-Al alloys

Protection of primary aryl amines as the triazene is accomplished by diazotiza-tion of the amine followed by reaction with pyrrolidine in aq. KOH. This group is stable to metalation of the aromatic ring by metal halogen exchange. The amine is recovered by reductive cleavage with Ni-Al alloy (aq. KOH, rt, 37-68% yield). ... 

The typical for Ni-Al alloys 7R and 3R (LIq) structures of martensite were formed in the investigated alloy. The thermally induced martensite in the homogenised sample was mainly of 7R type (Fig.2b). The LIq martensitic structure was mainly observed in samples after the hot deformation. 

Y.Zheng, W.M.Stobbs, The tweed microstructure in B2 Ni-rich Ni-Al alloys, in Electron Microscopy and Analysis 95, ed. D.Chems, Inst Phys.Conf Ser. No 147, Inst.of Physics (1995), p.353... 

Fig. 4.32 Anodic behaviour of Ni-Al alloys in 0-5 m H2SO4, de-aerated with H2, at 22°C the potential was increased by 0-01 or 0-02 V every 3 min in the active range and by 0-04 V in the passive range (after Crow, era/. )...

For the more complex alloys anodic polarisation offers a vital extra variable in the use of selective etchants and has been widely exploited for alloys for which simple chemical etchants have proved inadequate. Besides many types of alloys steelthis technique has been applied to copper and the Cu-Be-Ni-Zr alloys " , uranium-base alloys " , Ni-Al alloys , tin-bearing invar and many others. 

Figure 57.17. The top to bottom ranking of Ni2Als leachability in Ni/Al alloys containing 50 to 53 wt.% Ni.

The reduction of aryl ketones by Ni-Al alloy in water under reflux proceeded to give the methylene compounds within 2 h in 89.0-99.8% relative yields (Eq. 8.18).42... 

The first evidence for the electrodeposition of Ni-Al alloy from chloroaluminate melts was presented by Gale et al. [109], who attributed an unexpected oxidation... 

Fig. 20. Variation of the composition of Ni-Al alloy electrodeposits as a function of the applied potential in the 66.7 m/o AlCl3-EtMeImCl melt the Ni(n) concentrations were ( ) 10.0, (+) 25.0, ( ) 35.0, and (x) 50.0 mmol L 1. The dotted line represents the theoretical composition assuming an fee lattice at 40 °C, following the thermodynamic treatment of Moffat [80], Adapted from Pitner et al. [47] by permission of The Electrochemical Society.

Moffat [80] reported the electrodeposition of Ni-Al alloy from solutions of Ni(II) in the 66.7 m/o AlCl3-NaCl melt at 150 °C. The results obtained in this melt system are very similar to those found in the AlCh-EtMcImCI melt. For example, Ni deposits at the mass-transport-limited rate during the co-deposition of Al, and the co-deposition of Al commences several hundred millivolts positive of the thermodynamic potential for the A1(III)/A1 couple. A significant difference between the voltammetric-derived compositions from the AlCl3-NaCl melt and AlCl3-EtMeImCl melt is that alloy composition is independent of Ni(II) concentration at the elevated temperature. Similar to what has been observed for room-temperature Cu-Al, the rate of the aluminum partial reaction is first order in the Ni(II) concentration. Moffat s... 

Cr-Al, Mn-Al, and Ti-Al alloys can be obtained from acidic melt solutions containing Cr(II), Mn(II), or Ti(II), respectively, only if the deposition potential is held very close to or slightly negative of the thermodynamic potential for the electrodeposition of aluminum, i.e., 0 V. From these observations it can be concluded that the formal potentials of the Cr(II)/Cr, Mn(II)/Mn, and Ti(II)/Ti couples may be equal to or less than E0 for the A1(III)/A1 couple. Unlike the Ag-Al, Co-Al, Cu-Al, Fe-Al, and Ni-Al alloys discussed above, bulk electrodeposits of Cr-Al, Mn-Al, and Ti-Al that contain substantial amounts of A1 can often be prepared because problems associated with the thermodynamic instability of these alloys in the plating solution are absent. The details of each of the alloy systems are discussed below. 

To a stirred solution of 45g 3,5-dimethoxybenzoyl chloride and 17.4g thiophen in 300 ml benzene at 0° C, add dropwise 10.5g freshly distilled stannic chloride. Stir one hour at room temperature and add 200 ml 3% aqueous HC1. Separate the benzene layer and wash the aqueous layer with benzene. Dry and evaporate in vacuum the combined benzene layers and distill the red residue (250° C bath/4.5) to get 45g 2-(3,5-dimethoxybenzoyl) thiophen(I). Recrystallize from petroleum ether. Add a solution of 21 g AICI3 in 160 ml ether to a stirred suspension of 6.1 g lithium aluminum hydride in 140 ml ether. After 5 minutes add a solution of 39g(I) in 300 ml ether at a rate giving a gentle reflux. Reflux and stir 1 hour cool in an ice bath and treat dropwise with 50 ml water, then 50 ml 6N aqueous sulfuric acid. Separate the layers, extract the aqueous layer with 3X100 ml ether and dry, evaporate in vacuum the combined ether layers. Can distill the residue (230° C bath/5mm) to get 27g oily 2-(3,5-dimethoxybenzyl) thiophen (II). Recrystallize from petroleum ether. Reflux a solution of 5g (II) in 700 ml ethanol with W-7 Raney Nickel prepared from Ni-Al alloy (see Org. Synthesis Coll. Vol 111,176(1955)) for 6 hours. Filter, evaporate in vacuum and can distill (140/0.01) to get about 2.2g oily olivetol dimethyl ether which can be reduced to olivetol as described elsewhere here. -... 

Figure 6.13. Experimental arrangement of the hot-explosive compaction method for the preparation of consolidated Ni-Al alloys (after Kecskes etal. 2004). (a) Precursor powder sample inside a steel-tube container placed in, (b) an asbestos thermal insulation sheet (c) a concentric card-box filled with the powdered explosive (80% NH4NO3 + 20% TNT) (d) threaded steel plugs serving as contacts for the preliminary heating and to be lifted off just before detonating the explosive (e) detonating cords.

The hydrogenolysis of thiophene and its homologs has been investigated in the presence of Ni-Al alloy and aqueous alkali (65) and over vanadium oxide (47). It has been shown that / -(2-thenoyl)-propionic acid (II) on treatment with nickel aluminum alloy in aqueous alkali solution yielded... 

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]. 

Fig. 3.17 Squares of moment and of Tc and reciprocal of susceptibility plotted against composition in Ni-Al alloys. Reproduced from results of Wohlfarth (1971).

Examples which show that elastic interactions between particles can stabilize distributions of fine particles against coarsening include the observation by Miyazaki et al. that large particles in aged Ni-Si and Ni-Al alloys split into pairs and even octets of smaller particles as aging proceeds [18], In such cases, the reduction in... 

To promote the activity and selectivity of Raney nickel catalysts, alloying of the starting Ni-Al alloy with metal was often used. For instance, Montgomery (ref. 4) prepared catalysts by activating ternary alloy powders of Al (58 wt %)-Ni (37-42 wt %) - M (0.5 wt %) where M = Co, Cr, Cu, Fe and Mo. All promoted catalysts tested were more active than the reference catalyst, in hydrogenation of butyronitrile. Molybdenum was the most effective promoter. With Cr or Ti, hydrogenation of isophtalonitrile on Raney nickel occurred at lower optimum temperature than with non activated nickel (ref. 5). It was shown that addition of Ti or Co to Raney nickel suppressed the formation of secondary amine (ref. 6). 

The products distribution as a function of time is illustrated in Fig. 2 for the unpromoted catalyst derived from the Ni Al alloy. 

Introduction of molybdenum into the Ni Al alloy resulted in decreasing of the selectivity in primary amine to -v 76 %. The content of molybdenum had no appreciable effect on this selectivity, even in relatively large amounts (x = 0.4). In this late case, DPI accumulated in the reaction medium and reached 17 % of VN transformed into DPI at the maximum, compared to 8-9.5 % with the other Mo promoted catalysts. 

The modification of the Ni Al alloy by addition of molybdenum or chromium has a significant effect on the properties of the Raney nickel catalyst in the reaction of hydrogenation of valeronitrile. In the case of molybdenum, the catalytic properties may be correlated to the physico-chemical characteristics of the catalysts. Chromium is an effective promoter for initial activity and for selectivity. The mechanism for promotion of chromium in Raney nickel is not known exactly. 

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