Cerium Metallurgy

An alternative commercial form of a metallic mixed lanthanide-containing material is rare-earth siUcide [68476-89-1/, produced in a submerged electric-arc furnace by the direct reduction of ore concentrate, bastnasite, iron ore, and quart2. The resulting alloy is approximately 1/3 mischmetal, 1/3 sihcon, and 1/3 iron. In addition there are some ferro-alloys, such as magnesium—ferrosilicons, derived from cerium concentrate, that contain a few percent of cerium. The consumption of metallic cerium is overwhelmingly in the mixed lanthanide form in ferrous metallurgy. 

The purity of the cerium-containing materials depends on the appHcation as indicated in Table 3, and purity can mean not only percentage of cerium content but also absence of unwanted components. For some uses, eg, gasoline production catalysts, the lanthanides are often used in the natural-ratio without separation and source Hterature for these appHcations often does not explicitly mention cerium. Conversely, particulady in ferrous metallurgy, cerium is often assumed to be synonymous with rare-earth or lanthanide and these terms are used somewhat interchangeably. 

The applications of ceria based materials are related to a potential redox chemistry involving Cerium(III) and Cerium(lV), high affinity of the element for oxygen and sulfur, and absorption / excitation energy bands associated with its electronic structure. Important areas for application of cerium based materials are catalysis and chemicals, glass and ceramics, phosphors and metallurgy. 

Metallurgy. — The metals of most of the cerium group elements have been prepared, three general methods having been used t (1) fusion of the anhydrous halides with sodium, potassium, calcium, or aluminium (2) electrolysis of the fused chlorides or of a solution of the oxide in the molten fluoride (3) heating the oxides with magnesium, calcium, or silicon. Reduction with aluminium has also been tried, but it is not satisfactory except possibly for cerium itself. Electrolysis has been the most successful, the other methods usually giving at best an alloy. 

VSE In metallurgy as deoxidizer for copper, beryllium, steel (together with silicon). To harden lead for bearings. Alloyed with cerium to make flints for cigarette and gas lighters. In manuf of electronic vacuum tubes as getter to fix residual gases as oxides, nitrides, hydrides of calcium. 

The rare earths did not play an important role in ancient metallurgy because of the difficulty of reducing their compounds, particularly their oxides. Even after the reduction of cerium by Mosander, in 1827, the metallurgy of rare earths advanced only sporadically during the next century or so. However, forty years ago with the more facile separation of rare earths, and hence their ready availability in pure form, the science has risen to impressive heights and now involves numerous laboratories around the world. Two of those most active in this area during its rapid ascension are the authors of chapter 78, K.A. Gschneidner, Jr. and A.H. Daane. 

Ahmann, D.H., 1950, Metallurgy of the Rare Earths with Particular Emphasis on Cerium, AECD-3205, U.S. Atomic Energy Commission Report. 

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