Reduction in metallurgy

A substance added to react with the charge, or a product of its reduction, in metallurgy usually added to lower a melting point. 

Re OPe . The final step in the chemical processing of rare earths depends on the intended use of the product. Rare-earth chlorides, usually electrolytically reduced to the metallic form for use in metallurgy, are obtained by crystallisation of aqueous chloride solutions. Rare-earth fluorides, used for electrolytic or metaHothermic reduction, are obtained by precipitation with hydrofluoric acid. Rare-earth oxides are obtained by firing hydroxides, carbonates or oxalates, first precipitated from the aqueous solution, at 900°C. 

Niobium is also important in nonferrous metallurgy. Addition of niobium to tirconium reduces the corrosion resistance somewhat but increases the mechanical strength. Because niobium has a low thermal-neutron cross section, it can be alloyed with tirconium for use in the cladding of nuclear fuel rods. A Zr—l%Nb [11107-78-1] alloy has been used as primary cladding in the countries of the former USSR and in Canada. A Zr—2.5 wt % Nb alloy has been used to replace Zircaloy-2 as the cladding in Candu-PHW (pressurized hot water) reactors and has resulted in a 20% reduction in wall thickness of cladding (63) (see Nuclear reactors). 

Smelting Chemical reduction of a substance at high temperature in metallurgy. 

In metallurgy, according to Ramachandran et al., hydrogen is used in the reduction stage in the production of nickel in a process known as the Sheritt Gordon Process. In electronics, hydrogen is used in the epitaxial growth of polysilicon by wafer and circuit manufacturers. 

Bobylev, VM., Ivashov, A.A., Krutiansky, M.M. (1976), Operation Conditions of Electric Arc Plasma Installation for Reduction of Cobalt Oxide, in Plasma Processes in Metallurgy and Technology of Inorganic Materials, A. A. Baikov Institute of Metallurgy of USSR Academy of Sciences, Nauka (Science), Moscow. 

Two major techniques realized for reduction of CO2 level in the atmosphere are CO2 sequestration, in which CO2 has to be buried deep into the earth or ocean, and CO2 decomposition, in which it is decomposed into its components and then recycled. Indeed, CO2 decomposition will result in a reduction of atmospheric CO2 content. In addition, the reaction products in this process will also help in potential exploitation in metallurgy, organic catalysis, H2 production, and restoring the natural carbon resources (Mahesh and Akira, 2010). Therefore, in this section, different methods of CO2 decomposition will be summarized. 

Carbon monoxide is a colourless gas, formed when C bums in a restricted supply of O2. Small-scale preparations involve the dehydration of methanoic acid (eq. 14.61). CO is manufactured by reduction of CO2 using coke heated above 1070 K or by the water-gas shift reaction (see Section 10.4). Industrially, CO is very important and we consider some relevant catalytic processes in Chapter 25. The thermodynamics of the oxidation of carbon is of immense importance in metallurgy as discussed in Section 8.8. cone H2SO4... 

An important part of metallurgy is the production of metals from their ores. This involves three basic steps preliminary treatment, reduction, and refining. In preliminary treatment, the ore is concentrated in its metal-containing mineral. The concentrated ore may also require a process such as roasting, in which the metal compound is transformed to one that is more easily reduced. In reduction, the metal compound is reduced to the metal, by either electrolysis or chemical reduction. In refining, the metal is purified, or freed of contaminants. 

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