Cerium oxide material

J. XAFS Studies of the Cerium Oxide Phase in Catalytic Materials 5.5.3.1. Structural and Electronic Details of the Cerium Oxide Materials... 

Chane, C. J. Y. Corma, A. Garcia, H. Multivalent metal cation-doped cerium oxide materials for photovoltaic cells and solar cells. Fr. Demande FR 2857783, 2005 Chem Abstr. 2005,142, 159487. 

Hydroxide. Freshly precipitated cerous hydroxide [15785-09-8] Ce(OH)2, is readily oxidized by air or oxygenated water, through poorly defined violet-tinged mixed valence intermediates, to the tetravalent buff colored ceric hydroxide [12014-56-17, Ce(OH)4. The precipitate, which can prove difficult to filter, is amorphous and on drying converts to hydrated ceric oxide, Ce02 2H20. This commercial material, cerium hydrate [23322-64-7] behaves essentially as a reactive cerium oxide. 

The cerium concentrate derived from bastnasite is an excellent polish base, and the oxide derived direcdy from the natural ratio rare-earth chloride, as long as the cerium oxide content is near or above 50 wt %, provides an adequate glass poHsh. The polishing activity of the latter is better than the Ce02 Ln0 ratio suggests. Materials prepared prior to any Ln purification steps are sources for the lowest cost poHshes available used to treat TV face plates, mirrors, and the like. For precision optical polishing the higher purity materials are preferred. 

Powder XR diffraction spectra confirm that all materials are single phase solid solutions with a cubic fluorite structure. Even when 10 mol% of the cations is substituted with dopant the original structure is retained. We used Kim s formula (28) and the corresponding ion radii (29) to estimate the concentration of dopant in the cerium oxide lattice. The calculated lattice parameters show that less dopant is present in the bulk than expected. As no other phases are present in the spectrum, we expect dopant-enriched crystal surfaces, and possibly some interstitial dopant cations. However, this kind of surface enrichment cannot be determined by XR diffraction owing to the lower ordering at the surface. 

Cerium oxides are outstanding oxide materials for catalytic purposes, and they are used in many catalytic applications, for example, for the oxidation of CO, the removal of SOx from fluid catalytic cracking flue gases, the water gas shift reaction, or in the oxidative coupling reaction of methane [155, 156]. Ceria is also widely used as an active component in the three-way catalyst for automotive exhaust pollution control,... 

Hatch well CE, Sammes NM, Tompsett GA, and Brown IWM. Chemical compatibility of chromium-based interconnect related materials with doped cerium oxide electrolyte. J. Eur. Ceram. Soc. 1999 19 1697-1703. 

Five types of commercial SOx catalysts were tested for comparative ranking. Three of these commercial-type additives were well defined materials high surface area gamma alumina 10% Ce, as cerium oxide, on gamma alumina and 100 ppm Ft on gamma alumina. 

The free world market for cerium-oxide based polishing compounds is not large—approximately 4400 metric tons per year—, and we do not see a substantial growth potential despite the 11% annual growth in sales of spectacle lenses. The reason is twofold first, faster more efficient polishing compounds are available which can be used in slurry concentrations one-half that of a few years ago second, fully half the market for ophthalmic glass lenses has been captured by plastic lenses of CR-39 polymer. Cerium oxide is ineffective in polishing this material specially treated alumina or stannic oxide are used. 

Lanthanide-containing porous materials have found many applications in various fields [20-22], They are known as active and selective catalysts for synthesis of higher hydrocarbons (mostly ethane and ethylene) from methane [23], which is of considerable importance for utilizing the reserves of natural gas around the World. Cerium oxide has been employed as a catalyst or as a structural promoter for supported metal oxide catalysts... 

CerOx [Cerium Oxidation] An electrochemical process for oxidizing organic materials such as pesticides in wastewater. Cerium ion is an intermediate. This is electrochemically oxidized to Ce4, which is the actual oxidant. 

Cerium(III) tris(/3-diketonate) complexes are readily oxidized to the cerium(IV) compounds. They are volatile with vapor pressures high enough for MOCVD use. A number of diketonates are now better characterised, prompted by the possibility of using them as CVD materials and petrol additives, as well as a source of cerium oxide as an oxygen store for catalytic converters. [Ce Me3CCOCHCOCMe2(OMe) 4], Ce(acac)4 (Figure 32), Ce(dbm)4, [Ce(pmhd)4], and Ce(tmhd)4 all have square-antiprismatic coordination of cerium (in the [Ce(catecholate)4]" ion the coordination is dodecahedral). 

Pale yellow cerium dioxide (ceria, ceric oxide) has the fluorite structure and is used in catalysis" ", solid oxide fuel cells (SOFC)", thin film optical waveguides" , reversible oxygen storage materials for automobile catalysts" and for doping copper oxide superconductors". The diverse cerium enolate precursors and deposition methods used in the formation of cerium oxide thin films are summarized in Table 6, whereby the most common precursor for ceria is Ce(thd)4. 

Cerium also has minor uses in other commercial catalysts [17]. The dominant catalyst for the production of styrene from ethylbenzene is an alkali-promoted iron-oxide based material. The addition of a few percent of cerium oxide to this system improves activity for styrene formation. The ammoxidation of propylene to produce acrylonitrile is carried out over catalytically active complex molybdates. Cerium, a component of several patented compositions [18], supports the chemical reaction. 

The addition of cerium oxide, for example, to zirconia produces a material with exceptional toughness and good strength [29], Cerium oxide-doped zirconia is used also in thermal barrier spray coatings on metal surfaces(30]. 

The use of mechanical milling is also a suitable method for powder preparation. The feature of this procedure is to obtain powders of small crystallite size of a few nanometers with a high concentration of lattice defects. There are many mechanochemical studies on the synthesis of alloys, solid solutions, nanophasc materials, and intermetallic compounds. Of course, the mechanical alloying also has been applied to prepare mixed oxides containing cerium oxide to enhance catalysis, such as CeOj-TbO, CeOj-HfOj, Ce02 Zr02-Mn0, and CeOt ... 

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