Platinum alloys using

Gold and gold-based alloys ate used for corrosion-resistant equipment. Gold—platinum alloys, 75 Au-25 Pt or 84 Au-15 Pt-1 Rh, ate used as cmcible material for many molten salts (98). Spinnerets for rayon manufacture ate based on the Au—Pt system which exhibits a broad miscibility gap in the soHd state so that the alloys can be age-hardened. Spinneret alloys contain 30—40% or mote platinum modified by small additions of usually rhodium (99). Either gold or gold—platinum alloys ate used in mpture disks for service with corrosive gases (100). 

Plating and Coatings. Thin surface coatings of platinum and platinum alloys are used as decorative finishes and in critical appHcations 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(Il) and Pt(IV) and include H2[PtCl3] and its salts, eg, Pt—P—Salt, [Pt(NH3)2(N02)2] H2[Pt(S04)(N02)2] ... 

Gold Casting and Wrought Alloys. Gold alloys useful ki dentistry may contaki gold, silver, platinum, palladium, iridium, kidium, copper, nickel, tin, kon, and zkic. Other metals occasionally are found ki minor amounts. The effect of each of the constituents is empirical, but some observations have been made. 

Iridium [7439-88-5] Ir, and rhodium [7440-16-6] Rh, iadividually iacrease corrosion resistance, hardness, and strength of platinum alloys. They can be used to reduce grain size (140). 

The resistance of rhodium-platinum alloys to corrosion is about the same as or slightly better than that of pure platinum, but they are much more stable at high temperatures. They have excellent resistance to creep above 1 000°C, a factor which largely determines their extensive use in the glass industry, where continuous temperatures sometimes exceeding 1 500°C are encountered. Rhodium additions to platinum reduce appreciably the volatilisation of pure platinum at high temperatures. 

The most usual forms of platinum or, more frequently, of the platinum alloys containing 5 or 10% of rhodium, are thin protective sheaths contoured to conform with the shape of the underlying refractory. Sheaths of this type, generally 0-25 mm to 0-65 mm thick, are widely employed to protect tank lips, skimmer blocks, stirrers, thermocouple pockets, etc. More substantial —thicknesses-up to 2-5 mm thick —are used to protect orifices whose dimensional accuracy must be maintained to a high degree. 

Rhodium-platinum alloys containing up to 40% Rh are used in the form of wire or ribbon in electrical resistance windings for furnaces to operate continuously at temperatures up to 1 750°C. Such windings are usually completely embedded in a layer of high-grade alumina cement or flame-sprayed alumina to prevent volatilisation losses from the metal due to the free circulation of air over its surface. Furnaces of this type are widely employed for steel analysis, ash fusions and other high-temperature analytical procedures. 

A typical anode for practical use would be in the order of 25 to 48 mm in diameter, with hard platinum alloy pins of 0-50 mm diameter by 10 mm length, spaced every 150 to 300 mm and progressively positioned around the circumferenceThe pins are a press fit into holes in the lead or lead alloy (approximately 01 mm diametric interference) and lie flush with the surface. The lead is peened around the pins to improve the mechanical and electrical contact. 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

The Industrial Revolution was made possible by iron in the form of steel, an alloy used for construction and transportation. Other d-block metals, both as the elements and in compounds, are transforming our present. Copper, for instance, is an essential component of some superconductors. Vanadium and platinum are used in the development of catalysts to reduce pollution and in the continuing effort to make hydrogen the fuel of our future. 

Silvery, shiny, and hard. Unique metal, gives off an odor as it forms volatile 0s04 on the surface (oxidation states 81). Osmium is the densest element (22.6 g cm3 record ). Was replaced in filaments (Osram) by the cheaper tungsten. Used in platinum alloys and as a catalyst. Haber s first catalyst in ammonia synthesis was osmium, which fortunately could be replaced by doped iron. The addition of as little as 1 to 2 % of this expensive metal increases the strength of steel (e.g. fountain-pen tips, early gramophone needles, syringe needles). 

Scott, D. A. and W. Bray (1992), Pre-Hispanic platinum alloys Their composition and use in Ecuador and Colombia, in Scott, D. A. and P. Meyers (eds.), Archaeometry of Pre-Columbian Sites and Artifacts, Getty Conservation Institute, Los Angeles. 

Rhodium compounds, 19 644-648 synthesis of, 19 646 uses for, 19 646-648 Rhodium oxide, 10 42 Rhodium plating, 9 822 19 648 Rhodium-platinum alloys, 19 602 Rhodochrosite, 15 540 Rhodochrosite ore, 15 589 Rhodococcus, as a host system for gene expression, 12 478 Rhodonite, 15 540 color, 7 331 Rhodopsin, 9 512 Rhoeadine, 2 90 Rhoedales... 

Iridium s most common use is as an alloy metal that, when added to platinum, makes it harder and more durable. It is also mixed with other metals to make electrical contacts, thermocouples (two dissimilar metals joined to form a special type of thermometer), and instruments that will withstand high temperatures without breaking down. It is also used to make special laboratory vessels because iridium will not react with most chemical substances. An alloy of iridium and platinum is used as the standard kilogram weight because it is noncorrosive and will not oxidize and, thus, change its weight over long periods of time. 

Rhenium is a rare metal with total world production in 2007 estimated at about 50 tonnes. The principal industrial applications of rhenium are in high-temperature alloys used in jet engines and in platinum-rhenium catalysts used in the petroleum industry. In recent years, the demand for rhenium has increased and prices have risen to more than US 10,000 per kg. In late 2008, rhenium was the sixth most expensive traded element (WWW. lipmann.co.u k/fa cts/expe ns i ve. htm I)... 

Uses. Electroplating manufacture of rhodium-platinum alloys manufacture of high-reflectivity mirrors... 

Estonian scientist Karl Karlovitch Klaus The by-product of platinum refining useful as a catalyst in many industrial processes as an alloy, used for fountain pen nibs and electrical contacts. 

British chemist Smithson Tennant Brittle metal found chiefly in ores also containing nickel and platinum its alloys used in manufacturing electrical contacts and fountain pen nibs. 

Researchers are looking at ways to reduce the amount of platinum yet retain the catalytic activity. Peter Strasser, a researcher at the University of Houston in Texas, and his colleagues are trying to develop a platinum alloy that will do the job. An alloy such as bronze is a combination of elements, which in the case of bronze are tin and copper. Engineers often use alloys because they offer properties that are superior to those of a single metal, as described in chapter 1. A platinum alloy that acts as an effective catalyst in fuel cell electrodes yet contains less platinum would save a substantial amount of money. 

A dilatometer is used to measure the intrusion and extrusion volumes and several methods are used to measure the change in mercury level within the dilatometer stem as intrusion and extrusion take place. One method involves the use of platinum or platinum-alloy resistance wire placed coaxially in the stem of dilatometer tube. As the mercury level decreases, the amount of resistance wire exposed increases, thereby providing a voltage which increases linearly with decreasing mercury level. Very small current is used to minimize resistive heating of the mercury. Platinum or platinum-iridium alloy may be employed as the resistance wire because they do not amalgamate with mercury. 

It is further important to note that all the current/voltage characteristics depicted in Fig. 6 are unchanged by the presence of liquid fuels such as methanol, formaldehyde, formic acid, or hydrazine. The phthalocyanine electrode remains completely inert toward such substances. For this reason, no mixed potential can be formed at a phthalocyanine electrode, as for example can occur at a platinum electrode, when it is used as cathode in a methanol cell containing sulfuric acid. This is shown by a comparison (see Fig. 7) of the stationary characteristics of the platinum alloy we found to be the most active in the presence of methanol, namely a Raney ruthenium—rhodium electrode, with an iron phthalocyanine electrode, both measured in 4.5 N H2SO4+2M CH3OH. 

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