Alloys of transitional metals

Shukla A, Neergat M, Parthasarathi B, Jayaram V, Hegde MS. 2001. An XPS study on binary and ternary alloys of transition metals with platinized carbon and its bearing upon oxygen electroreduction in direct methanol fuel cells. J Electroanal Chem 504 111-119. 

Figure 2.15. Relative extent of the mutual solid solubility in binary alloys of transition metals, ordered according to their group number in the Periodic Table. The group number is reported on the left and on the top of the figure.

Variation of average atomic moment with the number of 3d plus 4s electrons in binary alloys of transition metals. From R. Bozorth, Ferromagnetism (Piscataway, NJ IEEE Press, 1993). 

Consider a few examples of formation of intermetallic layers between a transition metal or an alloy of transition metals and molten aluminium. Let us begin with iron, a metal most widely used in practice. 

Solution enthalpies calculated by Miedema for alloys of transition metals... 

The numerous glass-forming binary alloys may be divided into two main categories metal-metal alloys and metal-metalloid alloys. The former category may again be subdivided into three subgroups comprising alloys of transition metals (3d, 4d, 5d), alloys of simple metals and alloys of transition metals with either rare earths... 

Studies of alloys of transition metals with silicon, particularly silicides containing the maximum amount of silicon, have been intensified since these materials are important in a number of metallurgical processes and also because of a number of recently discovered special Applications for materials of this type. In addition to this, such studies are of a definite theoretical interest. It Is known that there are, among the silicides, compounds with metallic and with semiconducting properties. The latter properties are technologically more important, although up till now the nature of their semiconductivity has not been thoroughly studied. 

Quantum mechanics show that the mean free path of the electrons in a metal cannot be smaller than the interatomic distance. For many concentrated alloys of transition metals this limit is approached. Near this hmit the resistivity becomes insensitive to a further increase of lattice disorder, and thus the TCR becomes low. It turns out that for these alloys the TCR is approximately zero when the resistivity is around 150 /U.S2 cm, positive when it is lower and negative when it is higher. Their low TCR makes these alloys useful for fixed resistors. 

Table 10.4. Effect of alloying on Pt catalyst grain size and ECSA. Weight percent of the metals is calculated from reagent concentrations. Pure metal lattice parameters flo(Pt) = 3.9231 A flo(Ni) = 3.5238 A ao(Co) = 3.5447 A [144]. (Reproduced from Journal of Electroanal54ical Chemistry, 504(1), Shukla AK, Neergat M, Bera P, Jayaram V, Hegde MS. An XPS study on hinary and ternary alloys of transition metals with platinized carhon and its hearing upon oxygen electroreduction in direct methanol fuel cells, 111-9, 2001, with permission from Elsevier.)...

Further thermochemical work on low-melting-temperature alloys need not be encouraged. Data for high-melting-temperature alloys, on the other hand, are still in short supply. Iron alloys, it is true, have attracted much attention from thermochemists, for obvious reasons, but in view of the large number of elements found in alloyed steels more results are still required. Thermochemists should make sure, however, that the ferrous system they intend to study has not already been adequately investigated. More thermochemical data are needed for alloys of transition metals of technical interest, such as titanium, zirconium, niobium, tantalum, chromium, molybdenum, and tungsten. 

Recent phase-diagram investigations have been performed in several transition metal based alloys. Concerning the alloys of transition metals with rare earths we may quote the studies performed by Bretschneider and Schaller (1990a) in the Ce-Pd alloy, by Sakamoto et al. (1990, 1991) in the Pd-(Ce, Ho, Er) systems, by Palenzona and Canepa (1989, 1990a,b) and Palenzona (1991) in the rare-earth-ruthenium systems, by Zhou et al. (1991)... 

The factor S was first obtained theoretically by Stoner (1938) in an attempt to rectify the poor agreement between the theoretical prediction of the Pauli susceptibility and the experimental values of the strongly paramagnetic alloys of transition metals. Attempts to clarify the microscopic origin of the enhancement factor came first from Izuyama et al. (1963) and Hubbard (1963). The dynamics of the electrons in the band is now completely described by the Hamiltonian ... 

---