Abstract: Organic synthesis using carbon centred radicals generated by one electron oxidants is of current interest. Although Mn(OAc)3 has received the most attention, it appears that cerium(IV) ammonium nitrate (CAN) would be a very useful reagent for the generation of radicals. The recent application of CAN in the construction of C–C bonds are highlighted in this review. CAN has been shown to mediate the facile oxidative addition of 1,3-dicarbonyl compounds to activated and unactivated alkenes leading to dihydrofurans and furanones. In most cases the reactions occur under milder conditions and the yields are superior when compared to Mn(OAc)3 mediated reactions. The results available thus far suggest that CAN offers cast potential in radical mediated organic synthesis.

Abstract: A chemical mechanical polishing composition comprising a soluble cerium compound at a pH above 3 and a method to selectively polish a silicon oxide overfill in preference to a silicon nitride film layer in a single step during the manufacture of integrated circuits and semiconductors.

Abstract: Absorption, reflection as well as luminescence emission, excitation, and decay curves for single crystals of and grown by the Bridgman technique have been measured at various temperatures. The fluorescence spectra photo-excited over a wide energy domain ranging from the UV to the x-ray region, and the kinetics are typical of the cerium and praseodymium ions. These experimental results show that the exciton transfer to the dopant occurs at around 8 eV, and the energy transfer via sequential hole and electron trapping is dominant at higher energy. This process must be considered as the main scintillation mechanism in this crystal. The high efficiency of this mechanism is explained by the small energy difference between the 4f level of the dopant and the top of the valence band, estimated from XPS measurements.

Abstract: The present invention relates to a zirconium, rare earth containing composition comprising zirconium, cerium, neodymium and praseodymium components and the use of this composition in a catalyst composition useful for the treatment of gases to reduce contaminants contained therein and method process to make the catalyst composition. The catalyst has the capability of substantially simultaneously catalyzing the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides.

Abstract: The production of cerium oxides, zirconium oxides, (Ce,Zr)O 2 mixed oxides and (Ce,Zr)O 2 solid solutions having improved particle size distribution, surface area, oxygen storage capacity and pore volume by the addition of an additive, such as anionic surfactants, nonionic surfactants, polyethylene glycols, carboxylic acids, and carboxylate salts, during the formation of the oxides or precursors thereof.

Abstract: An abrasive composition is provided comprising an oxidizing agent and abrasive particles which have a mean particle size of 2 μm or less, wherein each of the abrasive particles comprises (i) at least one oxide selected from aluminum oxide and silicon oxide and (ii) cerium oxide in an amount of 5% to 40% by weight in terms of cerium based on the oxide (i). A method for polishing and planarizing a metal layer formed on a semiconductor substrate using the abrasive composition is also provided.

Abstract: A composite zirconium-cerium oxide exhibiting excellent heat resistance and being capable of retaining its high specific surface area even when used under high-temperature conditions, which comprises zirconium and cerium at a weight ratio ranging from 51:49 to 95:5 in terms of zirconium oxide and ceric oxide, exhibits a specific surface area of 50 m /g or above, and can exhibit a specific surface area of 20 m /g or above even after 6-hour thermal treatment at 1100 DEG C; a process for the preparation thereof; and a cocatalyst for cleaning exhaust gas, prepared by the use of the composite oxide.

Abstract: The phases of cerium above 5GPa have been studied using angle-dispersive powder diffraction techniques. The phase obtained between 5 and 12GPa at room temperature with filings of Ce has a monoclinic, distorted-fcc structure with four atoms in a C-face-centered unit cell. Heating to 373K for many hours yields the known {alpha}-U phase. With a single cut piece as a sample, the {alpha}-U phase is obtained at room temperature. {copyright} {ital 1997} {ital The American Physical Society}

Abstract: The invention provides a catalyst for catalytic reduction of nitrogen oxides contained in exhaust gases wherein fuel is supplied and subjected to combustion under periodic rich/lean conditions and the resulting exhaust gases are brought into contact therewith, which catalyst comprises: (A) a catalyst component A comprising (c) ceria or (d) praseodymium oxide or (e) an oxide and/or a composite oxide of at least two elements selected from the group consisting of cerium, zirconium, praseodymium, neodymium, terbium, samarium, gadolinium and lanthanum; (B) a catalyst component B comprising (d) a noble metal catalyst component selected from the group consisting of platinum, rhodium, palladium and oxides thereof and (e) a carrier; and (C) a catalyst component C comprising (f) a solid acid, and (g) a solid acid supporting an oxide of at least one element selected from the group consisting of vanadium, tungsten, molybdenum, copper, iron, cobalt, nickel and manganese. The catalyst reduces NOx contained in exhaust gases wherein fuel is supplied and subjected to combustion with a periodic rich/lean excursions, whereby NOx is generated in the exhaust gases, with high durability in a wide temperature range even in the presence of oxygen, sulfur oxides or water.

Abstract: A new catalyst comprising cerium and silver ion-exchanged ZSM-5 zeolite is reported in this paper, for the reduction of nitric oxide by methane in the presence of excess oxygen. The bi-cation exchanged Ce—Ag-ZSM-5 catalyst was very active for this reaction, while either Ce-ZSM-5 or Ag-ZSM-5 alone showed low activity. The presence of oxygen in the feed gas mixture enhanced the activity of the catalyst and the NO conversion to N2 increased with the CH4/NO ratio and Ag loading of the zeolite. The presence of water vapor had a small adverse effect on the catalyst activity. The coexistence of Ce and Ag ions in the zeolite is crucial for achieving high NO conversion to N2. A small amount of cerium is adequate to promote the selective catalytic reduction of NO. The two main functions of Ce ions are (i) to provide the Ag ion sites with NO2 by catalyzing the oxidation of NO to NO2 and (ii) to suppress the direct CH4 oxidation to CO2. The Ag sites are the active centers where the reaction of NO2 with CH4 takes place.

Abstract: A composition based on cerium oxide and on zirconium oxide and, optionally, on a yttrium, scandium or rare-earth metal oxide. The cerium/zirconium atomic proportion is at least 1. The compound exhibits a specific surface, after calcination for 6 hours at 900° C. of at least 35 m2/g and an oxygen storage capacity at 400° C. of at least 1.5 ml of O2/g. The composition is prepared by mixing, in a liquid medium, a cerium compound, a zirconium compound and, if appropriate, a yttrium, scandium or rare-earth metal compound; heating and calcining the precipitate obtained; and using a zirconium solution having an amount of base necessary to reach the equivalent point during an acid/base titration of the solution having a molar ratio of OH−/Zr≦1.65. The composition thus obtained is used in the manufacture of multi-functional catalysts.

Abstract: An abrasive comprising an aqueous slurry of the following cerium oxide particles: (1) cerium oxide particles prepared by adding hydrogen peroxide to an aqueous dispersion of cerium carbonate, (2) cerium oxide particles prepared by adding ammonium hydrogencarbonate to an aqueous solution of cerium nitrate to form a precipitate and oxidizing this precipitate with hydrogen peroxide, and/or (3) cerium oxide particles prepared by neutralizing or alkalinizing an aqueous solution of ammonium cerium nitrate.

Abstract: The invention relates to an abrasive containing a slurry of the cerium oxide grains dispersed in water. The Cerium oxide grains are obtained by adding hydrogen peroxide to an aqueous dispersion of cerium carbonate. The Cerium oxide grains are obtained by oxidizing a precipitate, which is formed through addition of ammonium hydrogencarbonate to an aqueous solution of cerium nitrate, with hydrogen peroxide. The Cerium oxide grains are obtained by neutralizing or alkallfying an aqueous solution of cerium ammonium nitrate.

Abstract: Cerium dioxide is a rare earth oxide material that can be useful in various optical and electronic applications because of its high refractive index and its dielectric constant The purpose of this study was to conduct an x-ray photoelectron spectroscopy analysis of sputtered cerium dioxide thin films The thin films were deposited onto glass substrates using rf magnetron sputtering A cerium dioxide target was used and various oxygen–argon gas flow ratios under different sputtering power levels were used for deposition The results presented here characterize the properties of the rf sputtered cerium dioxide thin films under different deposition conditions

Abstract: The metal components inside jet engines which are exposed to hot combustion gases often must be thermally insulated with thermal barrier coatings. Most thermal barrier coatings consist of a porous zirconia layer deposited over a NiCoCrAlY layer. However, the zirconia layer can spall during thermal cycling unless it is stabilised to prevent the zirconia changing between its tetragonal and monoclinic phases. We have studied thermal barrier coatings in which the zirconia was stabilised by alloying with 2.5 wt.% yttria and 25 wt.% ceria. The spatial distributions of the cerium in the zirconia layer before and after heat treatment were studied using electron microscopy (back-scattered electron imaging and X-ray analysis). The different phases present were identified by X-ray diffraction. We found that the cerium distribution in the newly-formed zirconia layer was essentially uniform. However, heating at 1200 °C could cause the formation of ceriumrich zones provided the coating was not separated from the NiCoCrAlY layer and the substrate before heating. This implied an interaction between the zirconia and the underlying metal. Experiments in the presence of oxygen getters and experiments in vacuum both suggest that cerium migration in ceria-stabilised zirconia is enhanced at high temperatures (1100 °C) under reducing conditions.

Abstract: The physical properties and the microstructure of highly textured YBa2Cu3O7/Y2BaCuO5 ceramics, doped with platinum and/or cerium have been investigated by high resolution electron microscopy (HREM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The Ce, Pt and Ce + Pt doped samples show different Jc behaviours as function of the applied field and a systematic comparison of the microstructure at different scales has been performed. The combination of both dopants leads to a drastic improvement of the critical current density either under zero field or with an external magnetic field (fishtail effect). A critical current density up to 56 000 A/cm2 has been observed, which remains 43 000 A/cm2 under 1 T in a sample doped with 2 wt% cerium oxide and 0.5 wt% platinum oxide. We suggest that a slight introduction of Ce in the YBa2Cu3O7−δ matrix locally changes the superconducting properties, and enhances the flux pinning properties. Micron size BaCeO3 particles, which appear with a preferential orientation in the YBa2Cu3O7−δ matrix, are also potential candidates for strong pinning. Other secondary phases, formed during the growth and the presence of a nanocrystalline phase in the plate like gap of the Ce + Pt doped samples are other admixtures. Finally a high density of twins is observed in all samples with some differences between the cerium and the platinum doped samples. They most probably contribute to pinning under intermediate field.

Abstract: The invention is a method and apparatus using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. The method and apparatus further use an ultrasonic mixer to enhance the oxidation rate of the organic material in the electrochemical cell.

Abstract: A process for the manufacture of d,1-α-tocopherol by the catalyzed condensation of trimethylhydroquinone with isophytol comprises carrying out the condensation in the presence of bis-(trifluoromethylsulphonyl)amine [HN(SO2CF32] or a metal salt thereof of the formula Met [N(SO2CF3)2]n (I), wherein Met signifies a metal atom selected from the group of lithium, boron, magnesium, aluminium, silicon, scandium, titanium, vanadium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, rhodium, palladium, silver, tin, lanthanum, cerium, neodymium, praseodymium, europium, dysprosium, ytterbium, hafnium, platinum and gold and n signifies the corresponding valency (1, 2, 3 or 4) of the metal atom Met, as the catalyst or of a combination of a metal salt of formula (I) and a strong Bronsted acid as the catalyst system in an organic solvent. The product of the process is the most active member of the vitamin E group.

Abstract: A powder composition of ceric oxide and a stabilizing non-noble metal oxide, such as zirconium oxide, mixed at the atomic level in complete solid solution. The powder is used to form washcoats for catalytic converters. The composition has high oxygen storage capacity and maintains an ultrafine crystallite size at high temperatures. The powder is formed by a spray pyrolysis process that includes atomizing a clear solution of cerium ions and ions of the non-noble metal into a fine mist that is passed rapidly through a furnace to form powder particles.

Abstract: The direct α-iodination of various ketones using iodine-ammonium cerium(IV) nitrate in acetic acid or alcohol gave the corresponding α-iodo ketones in high yields The effect of cerium salt on the iodination of ketones, and the iodination of 5α-cholestan-3-one using several methods are also discussed In the reaction of 3,3,5-trimethylcyclohexanone and unsymmetrical ketones, such as 2-hexanone and 2-heptanone, using methanol, ethanol, 1-propanol, and 2-propanol, the regioselective iodination product was obtained In the case of bromination, the reaction of ketones with bromine and ammonium cerium(IV) nitrate also yielded the corresponding α-bromo ketones