Palladium intermetallic compounds

Selenium occurs in the slimes as intermetallic compounds such as copper silver selenide [12040-91 -4], CuAgSe disilver selenide [1302-09-6], Ag2Se and Cu2 Se [20405-64-5], where x < 1. The primary purpose of slimes treatment is the recovery of the precious metals gold, silver, platinum, palladium, and rhodium. The recovery of selenium is a secondary concern. Because of the complexity and variabiUty of slimes composition throughout the world, a number of processes have been developed to recover both the precious metals and selenium. More recently, the emphasis has switched to the development of processes which result in early recovery of the higher value precious metals. Selenium and tellurium are released in the later stages. Processes in use at the primary copper refineries are described in detail elsewhere (25—44). 

At the m.p. of aluminium (600°C) an aluminium-sheathed palladium thermocouple formed an alloy with a flash and an exotherm to 2800°C [1]. The use of thin layers of palladium or platinum on aluminium foil or wire as igniters derives from the intense heat of alloy formation, which is sufficient to melt the intermetallic compounds [2],... 

Indium combines with several metals, such as sodium, potassium, magnesium, iron, palladium, platinum, lanthanium and cerium, forming semiconductor-type intermetallic compounds. 

Strictly speaking, we know only two real sensations the discovery (by Graham in 1863) of the hydrogen uptake by palladium with PdH0.6 formation and the practically occasional discovery of the reversible absorption of hydrogen at moderate conditions by some alloys and intermetallic compounds (IMCs) (Neumann Zijlsta Westendorp Wiswall Reilly). 

For metals promoting other metals, an interesting case was studied by Hurst and Rideal.2 In the combustion of mixtures of hydrogen and carbon monoxide, using copper as the basic catalyst the ratio of the gases burnt depends on the temperature, and also on the amount of small additions of palladium made to the copper. The proportion of carbon monoxide burnt is increased by addition of palladium, a maximum proportion of carbon monoxide being burnt when 0-2 per cent, of palladium is. present. With further amounts of palladium, the ratio CO H2 burnt falls off slowly until, with 5 per cent, palladium, it is nearly the same as with pure copper. This effect of palladium is ascribed to the introduction of a new type of surface, the line of contact between palladium and copper, though the proof that this is the cause of promotion is perhaps not complete. Mit-tasch and others,3 in elaborate studies of the promotion of various metal catalysts, particularly molybdenum, for the synthesis or decomposition of ammonia, concluded that the formation of intermetallic compounds... 

XPS The XPS data collected on the pure intermetallics before use in the catalytic tests are are listed in table 2. As indicated by this table, palladium is again partially covered by bismuth (Pd/Bi exp- > Pd/Bi theor) and is mainly in the metallic form, while bismuth is present on the surface of these intermetallic compounds in the oxidized form. 

Both silver and gold form ideal solid solutions with palladium. However, stoichiometric compositions with unique properties, such as in Hunter s preferred membrane composition of PdsAg, [31], might suggest the possibility of intermetallic compounds or ordered structures differing from that of the ideal solutions [35]. Palladium and copper also form ideal solid solutions, but in this system phase diagrams clearly show additional phases with crystal structures differing from the parent fee phase of the solid solutions. 

There have been several studies in which intermetallic compounds have been used as catalysts, but care is necessary because in some cases structural changes can occur during pre-treatment. Palladium-rare earth intermetallics MPdg (M = La,... 

A supported palladium-lead intermetallic compound, represented as PdsPb/CaCOs, was better than the Lindlar catalyst for the semi-hydrogenation... 

When equilibrium is established between ions in solution and the gas phase, we have gaseous electrodes the intermediates of this equilibrium are usually adatoms Pt, H2IH+..., or Pt, Cl2 Cl ... Palladium, hydrogen-sorbing alloys, and intermetallic compounds pertain to gaseous electrodes. However, at the same time, these systems are example of intercalation processes operating under equilibrium conditions, which brings them close to electrodes of the first kind. 

An alloy contains atoms of more than one element and has the properties of a metal. In a solution alloy the components are randomly dispersed. In a heterogeneous alloy the components are not evenly di rsed and can be distinguished at a macroscopic level In an intermetallic compound the components have interacted to form a compound substance, as in CU3AS 12.39 Statement (b) is false. 12.41 (a) True (b) false (c) false 12.43 (a) Nickel or palladium, substitutional alloy (b) copper, substitutional alloy (c) silver, substitutional alloy 12.45 (a) True (b) false (c) false (d) false... 

New Pd-Pb catalysts comprising of the intermetallic compound PdsPb has been reported with improved properties over commercially available Lindlar s catalysts for the selective reduction of 2-butyne and phenylacety-lene, in which overreduction and isomerisation are diminished. While commercially sourced Lindlar catalyst (Pd-Pb-CaCOs) was found to be comprised of palladium with highly dispersed lead covering its ciystallites, the intermetallic compound PdsPb catalyst appears to contain much more homogeneously dispersed alloy crystallites, although with lead enriched in the surface layer. ... 

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