Temperature refractory metal compounds

Submerged-Arc Furnace. Furnaces used for smelting and for certain electrochemical operations are similar in general design to the open-arc furnace in that they are usually three-phase, have three vertical electrode columns and a shell to contain the charge, but dkect current may also be utilised They are used in the production of phosphoms, calcium carbide, ferroalloys, siUcon, other metals and compounds (17), and numerous types of high temperature refractories. 

At elevated temperatures, CaH2 reacts with halogens, sulfur, phosphoms, alcohols, and ammonia. At high temperatures, it reacts with refractory metal oxides and haUdes. Calcium hydride is substantially inert to organic compounds that do not contain acidic hydrogens. 

Chlorination. In some instances, the extraction of a pure metal is more easily achieved from the chloride than from the oxide. Oxide ores and concentrates react at high temperature with chlorine gas to produce volatile chlorides of the metal. This reaction can be used for common nonferrous metals, but it is particularly useful for refractory metals like titanium (see Titanium and titanium alloys) and 2irconium (see Zirconium and zirconium compounds), and for reactive metals like aluminum. 

A detailed drawing of a simple metal atom reactor, largely build from commercially available parts, is given in Fig. 2. The main reaction chamber consists of a 3000-mL reaction flask and a four-necked top section. This reactor is suitable for all the experiments described in this chapter, with the possible exception of the molybdenum compounds. For syntheses of a practical scale with refractory metals (vaporization temperature greater than 2000°, e.g. Re, Mo, and W) a larger diameter reactor (140-178 mm) with a standard wall thickness (about 3.5 mm) is recommended to improve heat dissipation. 

Evaporation is suitable for all metals (the most refractory metals cannot be thermally evaporated, but can be e-beam evaporated), a few sublimable organic and organometallic compounds such as the phthalocyanines, and a relatively small number of inorganic dielectric materials, such as Mgp2 and SnC>2. Nearly all polymers decompose in one manner or another before a high enough temperature is obtained for them to become mobile in the vapor phase. 

Samsonov, G. V., Refractory Transition Metal Compounds High Temperature Cermets. Academic Press, New York, 1964. 

Hydrogen reduction of chlorides in thermal plasma can be apphed not only to produce powder of individual metals but also to produce different intermetalhc compounds. The composition of the generated crystals copies the composition of the chloride mixture in the gas phase. This effect permits the production of the intermetallic compounds with the required composition. Refractory intermetallic compounds based on niobium and vanadium were synthesized from their chlorides (conversion close to 100%) in a hydrogen plasma jet generated by RF-ICP discharge (Bashkirov Medvedev, 1968). The reaction products were crystallized on a substrate sustained at a temperature of about 1000°C. The plasma-metallurgical technology is proven to be effective in the synthesis of vanadium-Hsilicon... 

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