High temperature resistant metal

Considerable interest in the sohd-state physics of sihcon carbide, that is, the relation between its semiconductor characteristics and crystal growth, has resulted from the expectation that SiC would be useflil as a high temperature-resistant semiconductor in devices such as point-contact diodes (148), rectifiers (149), and transistors (150,151) for use at temperatures above those where sihcon or germanium metals fail (see Semiconductors). 

Because of the HW temperatures involved, metal basket strainers tend to be popular, but in-line bag filters using high temperature-resistant bags are also widely used. The benefit of strainers and bags over cartridges and candle filters is that where iron oxide transport is the primary problem, the iron particles are trapped inside and cannot fall off or otherwise recontaminate the CR system. 

COBALT AND ITS COMPOUNDS Cobalt, Co, at wt 58.95, steel-gray metal, d 8.71 at 20°, mp 1495°, bp 2880° readily sol in nitric acid and less sol in dil hydrochloric or sulfuric acids. It is obtained from ore concentrates by roasting, followed by thermal reduction by A1 or other methods. The principal use of the metal is in alloys, especially Co steels for permanent supermagnets, Co-Cr high-speed tool steels, cemented carbides and high temperature-resisting alloys for jet engins, For a description of its alloys see Refs 1, 2, 3, 4, 5, 6 8. Cobalt Bomb is briefly discussed under Bombs in Vol 2,... 

At high temperatures the metal will react slowly with certain gases. With carbon monoxide it produces a surface film of carbide, with nitrogen it produces a nitride film, and with hydrogen sulphide it reacts to form molybdenum disulphide. All of these films presumably interfere with the flow of gas to the metal surface, and in each case only a thin film of the product arises. Molybdenum is also very resistant to corrosive attack by mineral acids except for those such as nitric acid or chromic... 

Applications Sodium sulfide is mainly used in tanning as a hair-removing agent (so-called asher). It is also utilized in ore flotation, dyeing with sulfur dyes in the textile industry and in the chemical industry e.g. for the precipitation of heavy metal ions. Anhydrous sodium sulfide is also utilized in the manufacture of polyphenylenesulfide (PPS), a high temperature-resistant plastic. The current production of sodium sulfide in Western Europe is estimated to be ca. 50 10- t/a. 

Monomeric vinylic metal n complexes undergo polymerisation reactions to form polymers that have limited applications because of their poor thermo-mechanical properties but they absorb UV without degrading in the process. Such polymers can be used as a UV-resistant coating and act as catalysts in other monomer reactions. Metallocene methylene polymers are high temperature resistant materials and have uses as ablative materials for space capsule heat shields. These materials use Fe and Ru in their metal polymers. 

In the case of an ac discharge, the thermal nature of the sample volatilization may decrease in favor of sputtering, as the thermal energy released is lower. Therefore, ablation of the anode begins to occur, which may be kept low by taking very hard and high-temperature resistant anode materials such as tungsten. This approach may be useful for the ablation of very weak and easily volatile metals such as lead alloys. 

Monoliths made out of metal were introduced to the market to some extent as an alternative to ceramic supports. As shown in Fig. 33, these supports consist of a metallic outer shell, in which a honeycomb-like metallic structure is fixed. The honeycomb is formed by alternate flat and corrugated thin metal foils (Fig. 34). These foils are made out of corrosion- and high-temperature-resistant steel, and are about 0.05 mm thick. 

Recently, economic factors as well as the favorable low temperature performance and high-temperature resistance of Pd have lead to an increased interest in palladium as main noble metal component for three-way catalysts. Several research groups have presented a new generation of palladium catalysts with and without addition of Rh [16-20],... 

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