Alloys, lanthanide-based

Broker GA, Klingshim MA, Rogers RD (2002) Green chemistry and lanthanide-based crystal engineering. J Alloys Compd 344 123-127... 

The prices of lanthanide elements are somewhat reasonable and are less than gold per kilogram. (Gold is about 1,800 per kg.) Cesium (Ce), which is relatively common, is often alloyed with La, Nd, and Pr and iron to form misch metal. This alloy has several uses based on its unique ability to spark when scratched. The most common use is as flints for cigarette lighters. 

In the case of the Pt/Ceo.8TbojjQ2-x catalyst, the formation of particles of a LnPts (Ln = Ce, Tb) phase, isostructural with CePts, has been confirmed (155). Figure 4.26(c) shows a HREM in which a particle of this intermetallic is present. The details of the DDP, Figure 4.26(d), can be interpreted as due to a [011] orientation of the alloy phase. HREM thus provides evidence about the incorporation of the lanthanides present in the support to the metal particles but, in the case of the catalysts based on the mixed Ce/Tb oxide, it fails to reveal the extent to which each of them come into the alloyed state. From the analysis of the contrasts in the HREM images of the intermetallic particles it is not possible to precise this point. 

The French transplutonium elements production program (essentially 21+3Am and 2l+,+ Cm) is based on the treatment of plutonium-aluminum alloy targets irradiated in the Celestin reactors at Mar-coule. At the time of chemical treatment, these targets (which initially contained approximately 400 g of 239Pu) contain 44 g of 21+2Pu, 8.5 g of 2l+3Am, 7.5 g of 2l+,+Cm, and about 340 g of fission products, including - 240 g of lanthanides, chiefly the elements La, Ce and Nd (J). 

Namy has recently described an alternative method for effecting Sml2-catalyzed pinacol couplings (Eq. 3.31) [54]. Using mischmetall, an inexpensive alloy of the light lanthanides ( 12/kg from Fluka), acetophenone can be reductively dimerized in 70% yield in contrast to the Endo system, no Me SiCl is necessary. Carbon-carbon bond formation is presumed to involve coupling of samarium ketyls, based on identical diastereoselectivity in the presence of catalytic and stoichiometric SmU. In the absence of Sml2, there is no reaction. 

First works on synthesis of porphyrin lanthanide complexes, both hydrophobic tetraaiylporphyrins [2, 3] and water-soluble [4], appeared at the end of the XX century. Classical techniques are based on boihng of porphyrin with lanthanide metal acetylacetonate in 1,2,4-trichlorobenzene in the inert atmosphere throughout 2.5 3 h. In case of hydrophilic derivatives a short alloying in an imidazole was applied, then the imidazole subhmation was carried out and metallocomplexes were isolated by various chromatography methods. 

Fig. 11.12. Reduced specific heat jump ACIACq vs reduced transition temperature TJT for (LaPr)Sn, alloys (solid circles and solid squares McCallum et al., 197Sa) and (LaSmjSn alloys (open circles DeLong et al., 1976). The solid line is derived from numerical calculations based on the theory of Keller and Fulde (1973) for crystal field-split lanthanide impurities in a superconductor. The BCS law of corresponding states behavior (dashed curve) and the AG behavior (dot-dashed curve) are shown for comparison. The negative deviations of the ACIACn vs TJT data from the AG curve are consistent with Kondo behavior (see fig. 11.10) for (I Sm)Sn3 alloys.

By comparison with natural samples, lanthanide-bearing species from manufactured sources are typically much simpler analytical targets. The samples are often more readily dissolved and, because many of them are rare-earth-based materials, preconcentration steps can sometimes be eliminated. Recent reports have apphed analytical separation methods to determine lanthanide concentrations in metals (Kobayashi et al. 1992), alloys (Al-Shawi and Dahl 1996), and magnets (Saraswati 1993), in high-purity rare-earth oxides (Stijfhoom et al. 1993, Yin et al. 1998, W. Li et al. 1997, 1998, Wu et al. 1997, Peng et al. 1997), and in optical materials (Bruzzoniti et al. 1996). 

One of the methods to protect metals or alloys against corrosion is addition of sp>ecies to the solution in contact with the surface in order to inhibit the corrosion reaction and reduce the corrosion rate (Trabenelli et al, 2005) known as corrosion inhibitor. A number of corrosion inhibitors for aluminium alloys have been developed for this purpose such as lanthanide chloride, tolytriazole, bitter leaf, Schiff base compounds and polyacrylic acid (Benthencourt et al, 1997 Onal and Aksut, 2000 Avwiri and Igho, 2003 Yurt et al, 2006 Amin et al, 2009). 

The approach to saturation in a-RX alloys when R5 Gd (fig. 103) is mainly governed by single-ion anisotropy. The dashed lines in fig. 103 are fits based on eq. 102 in the mean-field approximation (Ferrer et al. 1978). The analysis allows one to estimate the values for the random-anisotropy constant D and for the exchange interaction Jq, as summarized in table 4. For the light lanthanides (Pr, Nd fig. 103) this simple model is inapplicable, influences of fourth- and sixth-order electrostatic fields obviously have to be invoked. 

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