Metal binary

In an attempt to find new active ORR catalysts, Liu et al. used a high-throughput method to screen both noble and non-noble metal binary catalysts for ORR in both acidic and methanol-containing media.223 Of the non-noble metal catalysts (CrCo, CrCu, CrFe, CrNi) none were found to be active in H2S04 or H2S04/methanol. 

Figure 4.40. Valence electron (s,p, d) concentration ranges for different types of phases as reported by Lee and Hoistad (1995). Experimental average values are compared with those computed. (For the conventional names of the phases, compare with Table 4.6.) On the left transition metal binary alloys, on the right the Hume-Rothery electron phases are shown.

Table 5.6. A selection of formulae and structure types of intermediate phases in the alkali metal binary alloys (CNE coordination number around the A alkali metal).

L. Kaufman, Coupled phase diagrams and thermochemical data for transition metal binary systems-VI, CALPHAD, 3 (1979) 45-76. 

Reasons for the Use of Metal Binary Carbonyl Compounds as Precursors in the Preparation of Tailored Supported Catalysts... 

Several reasons can be considered for using metal binary carbonyl precursors in the preparation of metal supported catalysts ... 

Many stable homo- and heteronuclear metal binary carbonyls are commercially available or easily prepared in the laboratory. 

The first two terms represent the Gibbs energy of f.c.c. Al Cr and Fe because the second sublattice consists entirely of unfilled interstitial sites. The next two terms represent the Gibbs energy of the CrC and FeC compounds which are formed when all of the interstitial sites of the f.c.c. Al lattice are filled with C. The second line is the ideal entropy term while the last four lines correspond to the excess term. It can be seen that, when j/ = 0, the model reduces to Eq. (5.21) for the simple substitutional mixing of Cr and Fe. This is particularly useful as thermodynamic assessments of metallic binary systems can be extended to include interstitial elements without the need for changing any of the existing parameters. 

Figure 5.20 Table of the binary hydrides and the Allred-Rochow electronegativity [26], Most elements react with hydrogen to form ionic, covalent or metallic binary hydrides.

The synthesis of M Cgo (M = Na, n = 2, 3 M = K, n = 3) has been achieved by the reaction of solid Cjq with solid MH or MBH4 [116]. The advantage of these reactions is the easier handling of small quantities of MH or MBH4 compared with alkali metals. As a source for alkali metals, binary alloys of the type CsM (M = Hg, Tl, Bi) can also be used [109]. However, the heavy metals partly co-intercalate into the Cgo lattice [115, 117]. 

The prediction of metal-to-metal bonding in transition metal binary and related compounds. Australian J. Chem. 17, 1191 (1964). 

Gloom for Oxide Superconductors Dismayed at the progress through the years, even with the most promising room-temperature metallic, binary oxides, many scientists abandoned the search for new high temperature oxide superconductors. Also, it should be mentioned that a deep-rooted prejudice had developed which claimed that the BCS theory had imposed a maximum transition temperature limit of 25 K for all superconducting materials, and that this temperature had already been achieved in certain alloys of niobium. Some scientists, however, were steadfast in their determination to break this barrier, optimistic in their outlook, and they continued their search for this unusual phenomenon in other metallic oxide systems. 

Compensation Behavior for Reactions on Metallic Binary Alloys 1... 

As a second example using the DoE assistant tool for designing libraries, the first library of 48 diverse Selox catalysts (Tab. 10.2, Section 10.2.4.2) was tested in both the presence and absence of hydrogen to evaluate the impact of operating conditions on Selox performance [18]. From the set of data giving the conversion of CO (not reported here), an analysis of the effect induced by the four selected factors (alkali addition, type of support, nature of the transition metals and of the noble metal binaries) was carried out following different models [18]. 

In the second example, the selective oxidation of propylene to propylene oxide (PO) was investigated with a huge library of y-alumina pellets impregnated with various single metals, binary metal combinations and catalyst loadings [40],... 

Solid solutions with complete solid solubility, i.e., solid solubility over the entire range of the composition, are possible to form, but always of the substitutional kind. For a metallic binary solution to exhibit a complete solid solubility, for instance, both metals must have the same type of crystal structure, because it must be possible to replace, progressively, all the atoms of the initial solvent with solute atoms without causing a change in crystal structure. 

A binary compound is an inorganic compound that contains two elements. Binary compounds may contain a metal and a non-metal or two non-metals. Binary compounds are often ionic compounds. To name a binary ionic compound, name the cation first and the anion second. For example, the compound that contains sodium and chlorine is called sodium chloride. 

In view of the very wide differences indeed between different substances it is pertinent to inquire whether all ionic, covalent, and metallic binary phases are variable in composition, and what factors determine the quantitative differences actually observed. 

As part of the early work to find alloys ofplatinum with higher reactivity for oxygen reduction than platinum alone, International Fuel Cells (now UTC Fuel Cells, LLC.) developed some platinum-refractory-metal binary-alloy electrocatalysts. The preferred alloy was a platinum-vanadium combination that had higher specific activity than platinum alone.25 The mechanism for this catalytic enhancement was not understood, and posttest analyses26 at Los Alamos National Laboratory showed that for this binary-alloy, the vanadium component was rapidly leached out, leaving behind only the platinum. The fuel- cell also manifested this catalyst degradation as a loss of performance with time. In this instance, as the vanadium was lost from the alloy, so the performance of the catalyst reverted to that of the platinum catalyst in the absence of vanadium. This process occurs fairly rapidly in terms of the fuel-cell lifetime, i.e., within 1-2000 hours. Such a performance loss means that this Pt-V alloy combination may not be important commercially but it does pose the question, why does the electrocatalytic enhancement for oxygen reduction occur ... 

Ross,33 and Beard and Ross34 had also been interested in electrocatalytic properties of Pt-3d transition metal binary-alloys, with a view that stable intermetallics could be formed. It was also their view that the catalytic enhancement shown by Pt-V, Pt-Cr, and latterly Pt-Co was due to the surface roughening of the platinum crystallites caused by leaching of the non-platinum elements from the surface. In the case of the Pt-Co alloy, they believed that a more stable alloy is formed that protects against further alloy degradation. 

Filippov, E. S., and A. M. Samarin Determination of the Structure of short Range Order in liquid metal binary alloys. Soviet Phys.-"Doklady (English Transl.) 10, 1101 (1966). 

For binary metal carbonyl compounds, the 18-electron mle is a very useful concept. Stable metal complexes will be formed when the metal has 18 electrons in its valence shell (metal valence electrons -H 2 electrons from each CO ligand). Since Tc(0) has 7 valence electrons, the neutral monomeric species Tc(CO) cannot be stable, but ions like [Tc(CO)6]" or [Tc(CO)5] attain a total of 18 electrons. In the neutral molecule, it will dimerize to Tc2(CO)io in order to obey the 18-electron rule. The formation of a Tc-Tc bond adds an electron on each Tc atom. This 18-electron mle is quite useful to predict the stmctures of the metal binary carbonyl compounds. 

Braga, D., Grepioni, F. and Sabatino, P. (1990). On the factors controlling the crystal packing of first row transition metal binary carbonyls. J. Chem. Soc., Dalton Trans., 3137 2. [153]... 

Structural information on transition-metal binary fluorides - shows that from group V through to the end of each transition series the transition-metal atom is coordinated by six fluorine ligands (F) on an octahedral framework. This is so for hexafluorides, pentafluorides, tetrafluorides, or trifluorides. 

Amidocarbonylation is a recently developed, organometallic-catalyzed route to amino acid generation - particularly A(-acyl a-amino acids - using either aldehydes or alkenes as starting materials and synthesis gas as an integral building block. The two principal classes of reaction are illustrated in eqs. (1) and (2). Both syntheses offer the opportunity to introduce two functionalities, amido and carboxylate, simultaneously where an amide is the co-reactant. Homogeneous amidocarbonylation catalysts are typically cobalt carbonyl-based, or utilize transition-metal binary systems, e. g. cobalt-rhodium, cobalt-palladium, and cobalt-iron. 

It is now widely accepted that the nuclearity of Group 11(IB) univalent metal binary pyrazolate complexes is strongly affected by the nature of the substituents on the heterocyclic ligand. In some cases, depending on the preparative method, complexes having different nuclearities have been selectively obtained. 

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