Rhenium alloys

Molybdenum hexafluoride is used in the manufacture of thin films (qv) for large-scale integrated circuits (qv) commonly known as LSIC systems (3,4), in the manufacture of metallised ceramics (see MetaL-MATRIX COMPOSITES) (5), and chemical vapor deposition of molybdenum and molybdenum—tungsten alloys (see Molybdenumand molybdenum alloys) (6,7). The latter process involves the reduction of gaseous metal fluorides by hydrogen at elevated temperatures to produce metals or their alloys such as molybdenum—tungsten, molybdenum—tungsten—rhenium, or molybdenum—rhenium alloys. 

Rhenium hexafluoride is a cosdy (ca 3000/kg) material and is often used as a small percentage composite with tungsten or molybdenum. The addition of rhenium to tungsten metal improves the ductility and high temperature properties of metal films or parts (11). Tungsten—rhenium alloys produced by CVD processes exhibit higher superconducting transition temperatures than those alloys produced by arc-melt processes (12). 

Tungsten with the addition of as much as 5% thoria is used for thermionic emission cathode wires and as filaments for vibration-resistant incandescent lamps. Tungsten—rhenium alloys are employed as heating elements and thermocouples. Tantalum and niobium form continuous soHd solutions with tungsten. Iron and nickel are used as ahoy agents for specialized appHcations. 

Two alloys containing tungsten are commercially available. The first, containing about 3 wt % rhenium, is used for heating filaments. The rhenium contributes improved resistance to thermal and mechanical shock. The second alloy contains about 25 wt % rhenium. This latter alloy is sold as sheet, rod, and heavy wire and may be fabricated for various uses. An important use of these rhenium alloys is in the constmction of thermocouples. Various combinations, 3 wt % Re—97 wt % W, or 25 wt % Re—75 wt % W, are usehil for measurement of temperatures to 2500°C (see Temperaturemeasurement). 

Molybdenum metalworking, 17 10-11 Molybdenum mill products, 17 9-10 Molybdenum-nickel alloys, 17 102 Molybdenum ore, U.S. exports of, 17 3t Molybdenum oxidation states, 17 20 Molybdenum oxides, 17 38 Molybdenum pentachloride, 17 23 Molybdenum-rhenium alloys, 17 15 Molybdenum sulfide, poisons in representative reactions, 5 258t Molybdenum-sulfur complexes, molecular, 17 37... 

Fritzberg, A. R. In Rhenium, Rhenium Alloys Proceedings of the International Symposium 1997 Bryskiii, B. D., Ed. Minerals, Metals Materials Society, Warrendale, U.S.A., 1998. 

Nickel—rhenium alloys containing thoria or other additives have been developed for use as cathodes on electrovacuum devices. Rhenium is found to improve the strength properties substantially. At 1000°C the strength of a 90 wt % Ni—10% Re alloy exceeds the strength of a Ni—V cathode material by 90%. Rigidity is exceeded by a factor of 150 to 200%. 

Heating elements -rhenium and rhenium alloys as [RHENIUM AND RHENIUM COMPOUNDS] (Vol 21) -silicon carbide in [CARBIDES - SILICON CARBIDE] (Vol 4) -use of silicon carbide [CARBIDES - SILICON CARBIDE] (Vol 4)... 

Mcrowave -molybdenum-rhenium alloys for [MOLYBDENUM AND MOLYBDENUM ALLOYS] (Vol 16) -for plasma formation [PLASMA TECHNOLOGY] (Vol 19)... 

When rhenium is added to other refractory metals, such as molybdenum and tungsten, ductility and tensile strength are improved. These improvements persist even after heating above the rccrystallization temperature. An excellent example is the. complete, ductility shown by a molybdenum-rhenium fusion weld. Rhenium and rhenium alloys have gained some acceptance in semiconductor, thermocouple, and nuclear reactor applications. The alloys also axe used in gyroscopes, miniature rockets, electrical contacts, electronic-tube components, and thermionic converters. 

Tantalum-hafnium and tantalum-zirconium alloys are less suitable for aggressive acid environments. Compared with tantalum-tungsten alloys, tantalum rhenium alloys are superior in corrosion resistance and to hydrogen embrittlement, but the major disadvantage is the high cost of rhenium. 

Rhenium alkoxocomplexes are of interest as homogeneous catalysts of olefine metathesis [519], They have also been used for the preparation of fine powders ofrhenium and rhenium alloys for catalytical and powder metallurgical use [1452]. 

Some of the materials that have been examined as catalysts include Pure Platinum, Platinum-Iridium Alloys, Various Compositions of Platinum-Rhodium Alloys, Platinum-Palladium Alloys, Platinum-Ruthenium Alloys, Platinum-Rhenium Alloys, Platinum-Tungsten Alloys, FejOj-M CVI Oj (Braun Oxide), CoO-Bi20j, CoO with AI2O3, Thorium, Cerium, Zinc and Cadmium. 

The resistance wires, made of tungsten or a tungsten-rhenium alloy, are heated with a DC source to a temperature above the block temperature... 

The heating element found in some household electric stoves is made from rhenium alloys. 

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