Rare earth metal aluminium

For these and similar reactions recently a variety of Lewis acidic aluminium, rare earth metals, and titanium alkoxides have been applied. Alkoxides have the additional advantage that they can be made as enantiomers using asymmetric alcohols which opens the possibility of asymmetric catalysis. Examples of asymmetric alcohols are bis-naphtols, menthol, tartaric acid derivatives [28], Other reactions comprise activation of aldehydes towards a large number of nucleophiles, addition of nucleophiles to enones, ketones, etc. 

Nasonov and co-workers have investigated the phase equilibria of the aluminium-rare-earth-metal-carbon systems and given partial phase diagrams for the aluminium-(scandium, yttrium, lanthanum, gadolinium and erbium)-carbon systems (Nasonov 1981, Nasonov et al. 1988) in the Al-rich region at 572°C. However, we were unable to obtain their reports because of lack of international academic exchanges. 

Molten aluminium and gallium fluxes have shown themselves to be excellent routes to complex ternary and quaternary intermetallic phases such as R-T-Al and R-T-Al-Si, R-T-Al-Ge (when Al is used as solvent) or R-T-Ga, R-T-Si, R-T-Ga-Si, R-Ga-Ge (when Ga is used as solvent), where R = rare earth metal, T = transition metal. 

One method of preparation consists in a modification of the Goldschmidt process. Niobium pentoxide is mixed with an alloy of the rare earths, called mixed metal, obtained in the manufacture of thorium nitrate, and consisting roughly of 45 per cent, of cerium, 20 per cent, of lanthanum, 15 per cent, of didymium, and about 20 per cent, of other rare-earth metals. The reaction is carried out in a magnesia-lined crucible, and is started with a firing mixture of barium peroxide, potassium chlorate, and aluminium powder. Considerable evolution of heat takes place and the reduction is extremely rapid a button of niobium is obtained 4 which, however, is not pure. 

Aluminium and its Congeners, including the Rare Earth Metals (Group III, of the Periodic Table). By H F V. Little, B.So. (Lond.), A.RC.S, Chief Chemist to Thorium, Ltd. 

I Aluminium and its Congeners, including the Rare Earth Metals. 

In recent years, the use of rare earth metal salts as inhibitors has been gaining attention. Rare earth metal salts have been found to be effective inhibitors for the protection of aluminium alloys, mild steel and zinc. 

Rare earth metal oxide coating Coating on aluminium alloys [14]... 

Another interesting development using intermetallics has been described in the patent literature (ref. 20). Alloys of copper and oxidisable rare earth metals such as cerium and lanthanum were prepared by melting mixtures of the powders of the pure metals. Additives such as aluminium and palladium were investigated. The alloys were crushed and screened to obtain 0.6 to 0.85 mm particles that were suitable for laboratory testing under typical methanol synthesis conditions. Typical results obtained are presented in Table 2. 

The compounds R3MC and RM3C3 are the only known compositions that exist in the rare-earth-metal-(aluminium, gallium, indium and thallium)-carbon systems at the present time. A number of reports on the preparation of cubic perovskite-type carbides containing rare earth elements with the general formula RjMC 00 (Jeitschko et al. 1964, Rosen and Sprang 1965, Haschke et al. 1966a, b, Nowotny 1968) contain little information about their properties other than their lattice parameters. 

After the initial work on aluminium alkoxides, the metal-insertion ROP was extended to other metal ions including titanium [36-38], tin (11) [39-41], tin (IV) [42-44], zirconium [45, 46] and, more recently, rare-earth metals (Y, Er, Sm, Dy, Nd and La) [47-49]. 

Although an Ni/Mo alloy melt does not wet a-BN, slow interface reactions are observed [20]. On the other hand, mutual wettability of materials sometimes is a first indication for chemical affinity. Thus, the wettability of a-BN by aluminium and aluminium alloys increased with increasing temperature a content of rare earth metals in the aluminium melt leads to a decrease of the wettability [21]. Reaction-bonded a-BN is completely eroded by liquid steel at 1650°C in an Ar atmosphere [22]. The contact angles formed on graphite substrates by molten lead di-chloride/alkali metal chloride mixtures do not change when the Ar atmosphere is replaced by CI2. However, when air is introduced complete wetting is observed after about five minutes. This is not the case with a boron nitride substrate [23]. 

The major alloying elements are manganese, aluminium, zinc, zirconium, silicon, thorium, and rare earth metals (E). At present E elements are the most promising candidates for magnesium alloys, with high temperature stability as well as improved corrosion behavior. E metals are forming stable intermetallic compounds at high temperature and therefore they decrease casta-bility. Aluminium and zinc are introduced mainly to... 

The periodic table of elements is divided into horizontal rows and vertical colunuis. Elements in a particular column have similar chemical behaviom. Looking at the periodic table, the metals are in Row 2 (lithium, beryllium), Row 3 (sodimn, magnesium, aluminium), Row 4 (potassium, K through to gallium, Ga), Row 5 (rubidimn through to tin), Row 6 (caesium to bismuth) and Row 7 (francium to actinium). There are two special series of metals from atomic number 58-71 and 89-103. The first are the rare earth metals and the second the radioactive metals (those beyond 92 do not occur naturalfy). Nos 90 and 92 occur naturally and are used for atomic power. The rest of the elements in the table ate non-metals. Some have some metal-like properties and are called metalloids, e.g. nos 5, 14, 32, 33, 51, 52, 84 and 85. 

The reaction requires the use of a catalyst for the alkaline earth metals, rare earth metals and aluminium. The most common approaches are the use of (in the laboratory practice only) the salts of mercury(II) such as HgC or Hg(OAc)2. Very small portions of these salts cause amalgamation of the metal surface (and thus clean it from the oxide layer) and facilitate the reaction with alcohols. The larger scale synthesis (and thus the industrial one—in the scope of pollution danger) uses the initial addition of solid iodine (1 g or less per 1(X) g ofalkoxide to be prepared). Formation of metal iodide serves both for cleaning the surface and increases also slightly the acidity of alcohols via formation of solvate complexes. In the case of barium, the application of dry ammonia gas has been reported for this purpose (Caulton, 1990 Drake, 1992). The major factor facilitating the reaction ofmetals with alcohols is the solubility of the alkoxides formed. Insoluble alkoxides form a protective layer on the surface of the metal and it hinders the reaction. Even the reaction of sodium with BuOH in toluene may be almost stopped by the formation of poorly soluble NaO Bu. 

This kind of residue is almost inevitable for aluminium and rare earth metals, and can be singly removed by decantation at the end of the reaction. 

Synthesis ofheterometallic complexes by direct interaction ofhomometallic alkoxides has been reported in many cases also for the rare earth metals, but in this case it is necessary to keep in mind that the commercial Ln(OTr)3 usually contain the oxoalkoxide complex, Ln50(0 Pr)i3 as their major component. The reactivity of the latter toward other alkoxides is comparably low, and prolonged refluxing in toluene or the reaction in a melt is recommended to insure the completeness of transformation (Poncelet, 1989). The only reaction between the two high-valent metal alkoxides, not involving specific mechanisms with formation of oxoalkoxides, is the formation of the aluminium and hafnium isopropoxide (Turevskaya, 1997) ... 

The hemilabile nature of amine sidearm may play a role in the catalytic cycle since it could reversibly coordinate to the Ti center, thus stabilizing a highly reactive intermediate. Recently, several catalyst systems are reported to be able to effectively catalyze the hydroamination of carbodiimides and offer good yields, which includes alkaline metal catalysts,aluminium catalysts," and rare earth metal catalysts. The mechanisms are also proposed to undergo the similar insertion-protonation pathway. All of these mechanisms are significantly different from that is proposed for imido catalyst systems. The latter involves Ti=N species (Scheme 21.8). 

It can be seen from the large body of work in the literature dedicated to investigating rare earth metal compounds as corrosion inhibitors for a wide range of aluminium alloys that they show a great deal of promise as potential... 

Mansfield, F., Use of rare earth metal salt solutions for corrosion protection of aluminium alloys and mild steel. Russian Journal of Electrochemistry, 2000. 36(10) 1063-1071. 

Anodized anti-corrosion coatings for aluminium using rare earth metals... 

According to Kraft and Kahles (68), titanium, zirconium, rare earth metals, calcium, magnesium and silicon have a similar effect as aluminium. They are however unlikely to have any advantages over aluminium. Baths composed of nickel or nickel copper or nickel tin alloys, are not suitable for counteracting the formation of primary carbon dioxide to an acceptable degree of efficiency. 

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