Platinum Group Metals and Alloys

All platinum metals are paramagnetic (x 0). The magnetic susceptibilities of palladium and platinum decrease with increasing temperature, the magnetic susceptibilities of rhodium, iridium, ruthenium, and osmium increase with increasing temperature (Fig. 3.1-272 [1.218]). 

The platinum group metals occur jointly as alloys and as mineral compounds in placer deposits of varying compositions. Ru and Os are separated from the PGM mix by distillation of their volatile oxides, whereas platinum, iridium, palladium, and rhodium are separated by repeated solution and precipitation as complex PGM chlorides, or by solvent extraction and thermal decomposition to sponge or powder. PGM scrap is recycled by melting with collector metals (lead, iron, or copper) followed by element-specific extraction. 

Palladium and Palladium Alloys Applications. Palladium and palladium alloys are important constituents of catalysts of chemical reactions and automobile exhaust gas cleaning, of electrical contacts, capacitors, permanent magnetic alloys, thermocouples, and for the production of high purity hydrogen. The low thermal neutron cross section permits their use in solders and brazes of nuclear structural parts. Classical applications are jewelry and dentistry alloys. 

Commercial grades of palladium are sponge and powder in purities of 99.9 wt% to 99.95-99.98 wt% (ASTM (B 589-82)). High purity electronic grade is 99.99 wt%. 

Prod uction. Palladium sponge or powder are compacted by pressing and sintering. Melting and alloying is performed in electrical heated furnaces, vacuum arc, or by electron beam melting. Crucible materials are AI2O3 and MgO. 

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Abnormal Infrared Effects of Nanometer-Scale Thin Film Material of Platinum Group Metals and Alloys at Electrode-Electrolyte Interfaces... 

In this chapter, the investigations of abnormal infrared effects (AIREs) of nanometer-scale thin him material of platinum group metals and alloys were reviewed. The AIREs describe the ensemble of abnormal IR features that have been discovered recently for CO and other molecules (CN SCN PoPD, etc.) adsorbed on nano structured hlms. It was observed on nanometer-scale thin him of... 

AIREs were observed with platinum group metals and alloys, which are of particular interest in wide applications, especially in electrocatalysis. 

Table 4.110. Platinum group metal and alloy suppliers ...

Lukaszewski M, Siwek H, Czerwinski A (2010) Analysis of the electrochemical quartz crystal microbai-ance response during oxidation of carbon oxides adsorption products on platinum group metals and alloys. J Solid State Electrochem 14(7) 1279-1292... 

Wynblatt, P. (1986). Platinum Group Metals and Alloys. In Encyclopedia of Materials Science and Engineering, Bever, M.B. Ed. Oxford, Cambridge Pergamon Press, pp. 3576-3579. 

Siwek, H., Lukaszewski, M., Czerwinski, A. Electrochemical study on the adsorption of carbon oxides and oxidation of their adsorption products on platinum group metals and alloys. Phys. Chem. Chem. Phys. 2008, 10, 3752-3765. 

Precious metal. This means gold, silver, or platinum group metals, and the principal alloys of those metals. 

Platinum family metals and alloys. The platinum family (platinum group) metals (Ru, Os, Rh, Ir, Pd, Pt) belong (together with Au and possibly Ag and Re) to the class of precious metals. This characteristic together with their inertness to the environment (with regard to corrosion and oxidation) is the basis for a number of uses such as in the following. 

Anodic passivation can be observed easily and clearly with iron group metals and alloys as shown in Fig. 11-10. In principal, anodic passivation occurs with most metals. For instance, even with noble metals such as platinum, which is resistant to anodic dissolution in sulfuric acid solutions, a bare metal surface is realized in the active state and a superficial thin oxide film is formed in the passive state. For less noble metals of which the affinity for the oxide formation is high, the active state is not observed because the metal surface is alwa covered with an oxide film. 

Magnetostriction of platinum-group metal and platinum-group metal alloys, expressed by the factor Si of proportionality according to M/l = SiH [1.217,... 

Rhodium is the whitest metal in the platinum group metals and it does not lose its luster under any atmospheres at ordinary temperatures. When rhodium is heated, the protective coating of rhodium oxide forms at 700°C. Further, at llOO C the oxide is dissociated to rhodium and oxygen. Rhodium dissolves in hot sulfuric acid or in aqua regia. Rhodium reacts with a halogen at high temperatures to afford a trihalide [1-6]. Rhodium has a high reflexibility and is used as a reflex mirror. The alloy with rhodium is used in thermocouples, crucibles, catalysts, electrical contact points, heat-resistant materials, corrosion resistant materials, etc. 

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

Electroplated Metals and Alloys. The metals electroplated on a commercial scale from specially formulated aqueous solutions iaclude cadmium, chromium, cobalt, copper, gold, iadium, iron, lead, nickel, platinum-group metals, silver, tin, and ziac. Although it is possible to electroplate some metals, such as aluminum, from nonaqueous solutions as well as some from molten salt baths, these processes appear to have achieved Httie commercial significance. 

JS/oble Metals. Noble or precious metals, ie, Pt, Pd, Ag, and Au, are ftequendy alloyed with the closely related metals, Ru, Rh, Os, and Ir (see Platinum-GROUP metals). These are usually supported on a metal oxide such as a-alumina, a-Al202, or siUca, Si02. The most frequently used precious metal components are platinum [7440-06-4J, Pt, palladium [7440-05-3] Pd, and rhodium [7440-16-6] Rh. The precious metals are more commonly used because of the abiUty to operate at lower temperatures. As a general rule, platinum is more active for the oxidation of paraffinic hydrocarbons palladium is more active for the oxidation of unsaturated hydrocarbons and CO (19). 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

Gold occurs as an alloy with copper, nickel and platinum group metals. Typically contains low amount of gold... 

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