Ternary alloys preparation

Honda metal, a ternary alloy prepared by Professor Honda of Japan, has a lower thermal coefficient of expansion even than silica. Its composition is given in the table on p. 297. 

Oranges, citric acid in, 6 632t ORBIT PRINT SELECT software, 18 243 Orbitrap, 15 662-663 Orb web, structure of, 22 630 Ordered intermetallic alloys, 13 530 Order, in amorphous semiconductor structure, 22 128-129 Ordering, in ternary semiconductor alloy preparation, 22 158-159 Order of addition, in large-scale... 

Many ternary alloys MeT2X2 (Me = Th, U, alkaline earth, rare earth metal, etc., T = Mn, Cr, Pt family metal, X = element of the 15th, 14th and occasionally 13th group) have been systematically prepared and investigated (Rossi cl al., 1979, Parthe and Chabot 1984). A few hundreds of them resulted in the ThCr2Si2 (or... 

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). 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

A solution of appropriate salts can also be reduced in the liquid phase by the addition of an appropriate reducing agent. Sodium borohydride has been used but care must be taken to remove the boron from the catalyst, particularly for the mixed noble metals. This has been accomplished by adding a dilute borohydride solution to the mixed metal salt solution under rapid agitation followed by a thorough washing of the precipitated metal black with warm water.The use of hydrazine, formaldehyde or formic acid is preferred to borohydride since the byproducts of the reduction do not contaminate the catalyst. Another procedure is to use a ternary alloy and to leach out one component as in the preparation of Raney nickel and similar catalysts. 

Ternary alloys and intermetallic compounds are obtained similarly e.g., MgNaPb and Mg4Na4,Pb3are prepared by fusing mixtures of Mg, Pb and NaPb or Na4Pb alloy in Nj or He in sealed Fe bombs at 650° and 725°C, respectively, with intermittent shaking. The alloy is allowed to cool slowly. 

Since classical Cu/ZnO catalysts exhibited a poor stability while the addition of alumina resulted in much better systems, it was tempting to add alumina to Cu-Ce intermetallic compounds. Jennings et al. (1992a), prepared ternary Cu-Ce-Al alloys of various compositions and also tried a variety of other metals (Ca, Cr, Mn, Pd, Zn). Among these ternary alloys aluminum-containing catalysts were the best. In spite of lower initial activities as compared to binary alloys, they exhibited a much better long-term stability. It is believed that the role of aluminum is to stabilize the disperse copper-ceria phases responsible for methanol synthesis activity, although the mechanism for such a process remains unclear. 

From an economic viewpoint, the classical determination of alloy phase diagrams is a laborious process, involving alloy preparation and heat treatment, compositional, structural, and microstructural analysis (and, even then, not yielding reliable phase boundary information at low temperatures due to kinetic limitations). While this investment is justified for alloys of major technical importance, the need for better economics has driven an effort to use alternative methods of phase discovery such as multiple source, gradient vapor deposition or sputter deposition followed by automated analysis alternatively, multicomponent diffusion couples are used to map binary or ternary alloy systems structurally and by properties (see Section 6). These techniques have been known for decades, but they have been reintroduced more recently as high-efficiency methodologies to create compositional libraries by a combinatorial approach, inspired perhaps by the recent, general introduction of combinatorial methods in chemistry. 

Therefore, as for GdFe, and for the GdCoMo, GdCoCu and GdCoAu alloys, the origin of Ku is always unknown. The reader is referred to the results reported in each of the sections relative to these alloys in order to have a better idea of the complexity of the problem. Moreover the large discussion about as-deposited and annealed binary and ternary alloys given by Heiman et al. (1978) shows that a clear conclusion is not possible. Muller et al. (1979) notice that the temperature dependence of Ku is widely sensitive to the preparation conditions. They conclude, as Heiman et al. (1978), that more than one mechanism is responsible for the anisotropy. 

Urner-Wille et al. (1980) have also studied ternary (Gdo.26Feo.74)i-jtSnx (0alloys prepared by the same method as the GdFeBi alloys. Such samples also have a perpendicular uniaxial anisotropy. The magnetic and the magnetooptic properties of tin alloys are similar to the ones of bismuth alloys Tcomp... 

Koel, 1955Koe2] also studied solid state equilibria in the ternary system. Alloys, prepared in a similar manner to those for investigation of the liquidus surface were firstly homogenized for 2 d at 1200°C. Optical... 

Rip] Ripley, R.L., The Preparation and Properties of Some Transition Phosphides , J. Less-Common Met., 4(6), 496-503 (1962) (Phase Relations, Experimental, Phys. Prop., 21) [1965Kanl] Kaneko, H., Nishizawa, T, Tamaki, K., Phosphide-Phases in Ternary Alloys of Iron, Phosphorus and Oflier Elements (in Japanese), Nippon Kinzoku Gakkai-shi, 29... 

The catalytic activity of Cu-Fe-Pt ternary alloy was investigated using an electrochemical mediod in a polymer electrolyte fuel cell by [2000Shi]. It was established that the electrode prepared using a Cu-Fe-Pt alloy catalyst showed higher cell performance dian unalloyed Pt. 

Binary and ternary alloy powders are also possible to produce using this technique. Table 4 summarizes experimental conditions and the different alloys prepared using pulsed electrochemistry and sonication in Refs. [59-61]. 

The phase equilibria in the ternary system Ce-Gd-Si have been established by Mokra (1979) by means of X-ray and metallographic analysis of 105 alloys prepared by arc melting and subsequent annealing in evacuated silica capsules for 800 h at 600 °C. The samples were finally quenched in water. Starting materials were Ce 99.56%, Gd 99.85% and Si 99.99%. 

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