Platinum alloys, applications

Platinum and Platinum Alloys Applications. Platinum and platinum alloys are important constituents of catalysts (chemistry, automotive exhaust gas cleaning, fuel cells), sensor materials (thermocouples, resistance thermometers), strong permanent magnet alloys, magnetic and magnetooptical (memory) devices, high temperature and corrosion resistant stmctural parts, and electrical contacts and connecting elements. Classical applications are jewelry and dentistry alloys. 

Alloys with rhodium Rhodium alloys readily with platinum in all proportions, although the workability of the resulting alloy decreases rapidly with increasing rhodium content. Alloys containing up to about 40% rhodium, however, are workable and find numerous applications. The principal physical and mechanical properties of rhodium-platinum alloys are listed in Table 6.3. 

Platinum and rhodium-platinum and iridium-platinum alloys are frequently employed to line and sheath autoclaves, reactor vessels and tubes, and a wide range of equipment. Linings are generally 0-13 mm to 0- 38 mm thick, and for certain applications co-extruded platinum-lined Inconel or other metal reactor or cooling tubes are fabricated. In such cases the platinum is bonded to the base metal, but in all other instances platinum linings are of the loose type. 

Plating and Coatings. Thin surface coatings of platinum and platinum alloys are used as decorative finishes and in critical applications where it is necessary to provide finishes resistant to corrosion or high temperature, eg, coatings on jet-engine turbine components (258). Compounds used in the electro deposition of platinum are based on Pt(II) and Pt(TV) and include H2[PtCl6] and its salts, eg, Pt—P—Salt, [Pt(NH3)2(N02)2] H2[Pt(S04)(N02)2] ... 

Polymer electrolyte fuel cells, also sometimes called SPEFC (solid polymer electrolyte fuel cells) or PEMFC (polymer electrolyte membrane fuel cell) use a proton exchange membrane as the electrolyte. PEEC are low-temperature fuel cells, generally operating between 40 and 90 °C and therefore need noble metal electrocatalysts (platinum or platinum alloys on anode and cathode). Characteristics of PEEC are the high power density and fast dynamics. A prominent application area is therefore the power train of automobiles, where quick start-up is required. 

Another system, where catalytic active oxide particles might lead to a new development, is the polymer electrolyte membrane fuel cell (PEMFC). This t5rpe of fuel cell preferentially works with platinum and platinum alloy catalysts. The development of an effective oxide catalyst could solve some of the problems connected with the application of these systems. 

Costs must always be considered, but it does not follow that an inexpensive metal or alloy will prove to be the cheapest in the long term platinum and platinum alloys are used in certain applications and apart from their high corrosion resistance have been a wise investment for the purchaser. However, mild steel, which has good mechanical properties, is readily available in a variety of forms and easily fabricated, is frequently preferred to more corrosion-resistant alloys for large structures, and its poor resistance to corrosion is counteracted by means of protective coatings, cathodic protection, conditioning the environment, etc. 

Although platinum and platinum alloys are the state-of-the-art electrocatalysts for PEM fuel cell applications, the platinum loading required to reduce the effective overpotential of the oxygen reduction reaction at high current densities (1-2 A/cm )... 

P. A. Cox, The Elements on Earth, Oxford University Press, Oxford, 1995 32.10 Johnson Matthey, Platinum Today Applications, http //www.platinum.matthey. com /applications /properties.html P. Wang, Themwcoufde Material, in ASM Handbook, Volume 2, Properties and Selection Nonferrous Alloys and Special-Purpose Materials, p. 869 888. ASM International, Metals Handbook, Metals Park OH, 1998... 

Using the microemulsion technique, metallic cobalt cobalt/platinum alloys , and gold-coated cobalt/platinum nanoparticles have been synthesized. MFep (M Mn, Co, Ni, Cu, Mg, or Cd, etc.) are among the most important magnetic materials and have been widely used for electronic applications . 

Catalytic activity is closely dependent on the method of preparation, so considerable attention has been focused upon new preparation methods to improve the performance of carbon-supported platinum alloy catalysts in DMFC applications. The simultaneous reduction of metal salts [86-88], microwave-assisted reactions [89, 90], micro-emulsion-based synthesis [91-93], and the reduction of single-source molecular precursors [94-99] have been used to various extents. 

Strategies to improve the durability of the cathode catalyst are being considered. They are application of oxidation-resistant carbon support, and application of dissolution-resistant platinum alloy catalyst. 

Yu Y, Sun Q, Liu X, Wu H, Zhou T, Shi G (2011) Size-controllable gold-platinum alloy nanoparticles on nine functionalized ionic-liquid surfaces and their application as electrocatalysts for hydrogen peroxide reduction. Chem Eur J 17(40) 11314-11323. doi 10.1002/... 

Gold can be used only in very small portions or very thin coatings because of its cost. Most of the applications for wliich it was used in the past have now been accomplished with tantalum at a much lower cost. A gold/ platinum/rhodium alloy is used in the manufacture of rayon-spinning jets in the production of rayon fibers. This alloy presents the combination of strength, corrosion resistance and abrasion resistance necessary to prevent changes in hole dimensions. 

Barnard, K. N., Christie, G. L. and Gage, D. G. Service Experience with Lead Silver Alloy Anodes in Cathodic Protection of Ships , Corrosion, 15, 11, 581-586 (1959) Peplow, D. B. and Shreir, L. L. Lead/Platinum Electrodes for Marine Applications , Corr. Tech. Apr. (1984)... 

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