Abstract: The authors present the results of XPS (X-ray photoemission spectroscopy) and XRA (X-ray absorption) studies performed on several intermetallic cerium compounds (CeRh3, CeCo5, CeNi5, CeNi2, CeRu4B4, CePd3 and CeBe13). In CePd3 and CeBe13, the cerium is known to be in the so-called intermediate valence state; in CeRh3 and CeCo5, the cerium is thought to be in the tetravalent state: Ce4+ (4f05d2). Finally for CeNi5, CeNi2 and CeRu4B4 the situation is unclear. The main purpose of this paper is to show that the valence of cerium in these compounds cannot be deduced from XPS and XRA measurements in the same way as it is for other rare-earth compounds (Tm or Sm for instance). Indeed pure tetravalent compounds like CeRh3, CeCo5 or even insulating CeO2, present XPS and XRA spectra which are similar to those obtained for intermediate valence compounds like TmSe, SmB6, etc.... If one supposes that the final states starting from a Ce4+ initial state are essentially made of configurations which contain one more electron in the 4f shell, the authors show that the valencies of cerium at the surface and in the bulk, deduced from their XPS and XRA experiments, are in approximate agreement with those deduced from lattice parameter measurements. Then, the direct observation of replicates in the XPS or XRA spectra of these cerium intermetallic compounds cannot be considered as a proof of the existence of an intermediate valence state.

Abstract: Praseodymium metal undergoes a crystallographic phase transformation from a distorted fcc lattice to a distorted hcp structure at a pressure of ≃210 kbar. The phase change is accompanied by a large volume decrease of ≃19%. This decrease is analogous to the volume collapse at the γ‐α transition in cerium and thus provides strong evidence for a delocalization of the 4 f2 configuration into a 4f conduction band.

Abstract: Reports a study of crystal-field (CF) excitations by neutron spectroscopy and a study of magnetic susceptibility and electrical resistivity of some cubic cerium intermetallics having the CsCl or a related structure; namely the compounds CeZn, CeMg3 and CeInAg2, CeZn undergoes a first-order transition to antiferromagnetism with a strong magnetostriction at TN=30K, whereas for CeMg3 and CeInAg2 (TN=3.4 and 2.3K respectively) the transition is of second order. The magnetic resistivities of the cerium compounds obtained by subtracting the resistivities of homologous lanthanum compounds were found to decrease with increasing temperature over certain temperature ranges, indicating an incipient Kondo effect. CeMg3 has a CF splitting Delta of 195K, the ground state being the Gamma 7 doublet in contrast to the case of the CeMg compound with its Gamma 8 ground state. For CeZn and CeInAg2, the CF splitting is rather small ( Delta approximately 65 and 18K respectively).

Abstract: Aluminum alloy atomized powder containing 4 to 15% iron and 1 to 12% cerium or other rare earth metal, when properly compacted and shaped into a useful article, exhibits very high strength at relatively high temperatures. The iron content exceeds the cerium or rare earth metal content, and the powder may contain refractory elements such as W, Mo and others. The powder is produced by atomizing alloyed molten aluminum, preferably in a nonoxidizing atmosphere, and is compacted to a density approaching 100% under controlled conditions including controlled temperature conditions. The alloy may be subsequently shaped by conventional forging, extruding or rolling processes.

Abstract: Using high-performance liquid chromatography it has been possible to separate 14 lanthanide elements in less than 40 min by elution with an α-hydroxyisobutyric acid concentration gradient LiChrosorb KAT cation exchanger (10 µm) is used as the packing material and the eluted lanthanides are detected with an ultraviolet detector after complexation with Arsenazo III The detection limit is about 01 µgDeterminations of the rare-earth composition in monazite sand and rare-earth impurities in high-purity lanthanum(III), cerium(IV), samarium(III) and yttrium(III) oxides were carried out The proposed method is more convenient than others, and the separation of major components is not necessary in analyses of high-purity rare earths; the elution time is only about 1 h

Abstract: A process for regenerating a deteriorated antimony containing oxide catalyst comprising as essential components of (i) antimony and (ii) at least one metal element selected from the group consisting of iron, cobalt, nickel, manganese, uranium, cerium, tin and copper wherein the antimony containing oxide catalyst is impregnated or sprayed with an aqueous solution of nitric acid and/or a nitrate, and the impregnated catalyst is dried, and then calcined at a temperature in the range of from 400° to 1000° C.

Abstract: A number of tricarbonyliron–lactone complexes have been prepared from vinyl oxirans by treatment with pentacarbonyliron. In certain cases two η3-allyl complexes were isolated from a single vinyl oxiran. Oxidation of the complexes by cerium(IV) ammonium nitrate in acetonitrile leads predominantly to β-lactones. The stereochemical integrity of the initial complexes is reflected in the formation of the oxidation products. Reduction of these products with lithium aluminium hydride gave the expected diols.

Abstract: Short-term (<30 h) oxidation of CeO2-doped hot-pressed Si3N4, studied at 773 to 1623 K in flowing dry air, resulted in parabolic-weight gain curves and in oxidation-rate constants nearly independent of the amount of grain-boundary second phase. Exolution of CeO2 crystals occurs from the oxide layer; their morphology depends on oxidation temperature. Either a direct redox reaction between CeO2 and Si3N4 or solution of Si3N4 in the glassy silica-rich oxide layer, followed by its oxidation by dissolved oxygen, have been proposed as possible oxidation mechanisms, both appearing strongly dependent on the low solubility of cerium oxides hi silicate melts. The value of the activation energy for oxidation of 385 kj·mol−1 suggests additive and impurity migration from the bulk to the Si3N4/oxide reaction interface as the most probable rate-limiting step.

Abstract: An aqueous acidic solution and process for treating metal surfaces, particularly zinc and zinc alloy surfaces, for depositing a passivate film of improved clarity and hardness and to impart improved corrosion resistance thereto. The solution contains effective amounts of chromium ions substantially all of which are in the trivalent state, hydrogen ions to provide a pH of about 1.2 to about 2.5, an oxidizing agent, a bath soluble and compatible silicate compound present in an amount to provide improved corrosion protection to the substrate and increased hardness to the passivate film and at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanide mixtures as well as mixtures thereof. The treating solution may optionally further contain halide ions, a carboxylic acid or salt and a wetting agent.

Abstract: A gas containing oxygen, H 2 S and sulfur oxides is desulfurized by contacting same with cerium oxide at a temperature of from about 350°-600° C. This invention is particularly useful for desulfurizing tail gas from a Claus plant. In a preferred embodiment the cerium oxide is supported on alumina and oxygen is present in the gas in an amount more than that stoichiometrically required to convert the H 2 S and SO 2 to cerium oxysulfate.

Abstract: Three rare earth metals were zone refined under low contamination conditions. Where possible, effective distribution coefficients for the major impurities were determined, and these were used to estimate the ultimate potential for zone refining as a purification technique for the rare earth metals. It is concluded that zone refining will be of most value for refining with respect to certain common metallic impurities. The metallic impurity levels at one end of a zone-refined gadolinium rod are believed to be the lowest ever recorded for a rare earth metal.

Abstract: Cerium dioxide doped with Y/sup 3 +/ ions, which is of interest for its ionic conductivity, is here studied by anelastic methods. The internal friction peaks observed are analyzed into peaks A, B, C (with H/sub r/ = 0.64, 0.71 and 0.78 eV, respectively). Peak A, present at low Y/sup 3 +/ concentrations is established to be due to a YV pair (V = oxygen-ion vacancy), which is a charged defect compensated by an isolated Y. Peak B is believed to be due to a Y/sub 2/V complex with the Y-Y pair in the (1,0,0) configuration. For this defect, only relaxations involving the V motion are observable, giving an example of the frozen-free split phenomenon.

Abstract: The formation and the oxidation-reduction properties of mixed oxides in the Ce–U–O ternary system were examined by means of thermogravimetry and the X-ray diffraction technique. The mixed oxides were prepared by the reactions of CeO2 with U3O8 in air and in hydrogen. The composition of the products heated in air, followed by slow cooling to room temperature, was approximately expressed by this equation: yCeO2+(1–y)UO2.67. By X-ray diffraction, it was shown that the oxides formed at 1100 °C in air were mixtures of Ce0.6U0.4O2.3 and α-U3O8 in the y<0.6 range, while they were in single phases of solid solutions for y≥0.6. When the mixed oxides, MO2+X, where M indicates yCe+(1–y)U, were re-heated in air, weight loss due to oxygen liberation was observed above 500 °C, and it was enhanced with a rise in the temperature. The hydrogen reduction of the oxides proceeded in two steps; the first step was the reduction of MO2+X to MO2 below 600 °C, and the second one was the reduction of MO2 to MO2−X above 600 °C. The...

Abstract: A spherical cerium-activated catalyst for the NH 3 synthesis is prepared by: mixing magnetite with (by weight): 2-35% of aluminium oxide, 08-2% potassium hydroxide, 2-35% calcium oxide, 01-04% magnesium oxide and 02-05% silica; melting this mixture in a furnace at a temperature of at least 1600° C; air-cooling the molten mass, removing melted slag; crushing the deslagged mass in a crusher and pulverizing it in a rod-mill; adding in a mixer to the so obtained powder a cerium nitrate solution in quantities to obtain in the final catalyst a metallic cerium concentration of 05 to 25%; pelletising the so added powder in a tray pelletiser to obtain a sphere shaped catalyst; drying said catalytic spheres in a furnace at 100°-200° C, and sintering them in an argon atmosphere at a temperature of 1250°-1350° C

Abstract: XPS and LIII X-ray absorption edge studies regarding the valence state of cerium have been carried out on the intermetallic compounds CeCo2, which becomes superconducting at low temperatures. It is observed from XPS that the surface shows both Ce3+ and Ce4+ valence states, while the X-ray absorption edge studies reveal only Ce4+ in the bulk. Thus valence fluctuation and superconductivity do not coexist in the bulk of this compound.

Abstract: Process for applying a protective coating to a metal substrate which provides a thermal barrier and a barrier against oxidation of the substrate. The coating material is a mixture of two metals M1 and M2, e.g., cerium (M1) and cobalt (M2), one of which when exposed to an atmosphere containing a low partial pressure of oxygen and at a high temperature forms a stable oxide, the other of which does not form a stable oxide under such conditions. A coating consisting of such a metal alloy or mixture is subjected to such conditions to produce an outer oxide layer of metal M1 and an inner metal layer of M2 alloyed with one or more components of the substrate. The oxide layer provides thermal and oxidation protection and the inner layer bonds the coating to the substrate.

Abstract: Two 2-(alk-1-enyl)-3-(1-hydroxyalkyl)-1,4-dimethoxynaphthalenes are oxidised with silver(II) oxide to the corresponding naphthoquinones, while oxidation with cerium(IV) ammonium nitrate affords derivatives of the title compounds.

Abstract: OF THE DISCLOSURE A method for production of phenol or nucleus-substituted phenols from benzoic acid or nucleus-sub-stituted benzoic acids by gas-phase catalytic oxidation characterized by using an oxide catalyst of the formula, MoaWbXcYdZeOf wherein Mo is molybdenum, W is at least one of vanadium, niobium and tantalum, X is at least one of copper, silver, manganese, iron, cobalt, nickel, rhodium, palladium and platinum, Y is at least one of cerium, uranium, zirconium, chromium, tungsten, zinc, cadmium, tin, phosphorus, antimony, bismuth and tellurium, Z is at least one of thallium, alkali metals and alkaline earth metals, and when a is fixed to 12, b is 0.1 to 60, c is 0.1 to 60, d is 0 to 24, e is 0.1 to 120 and f is the number of oxygen atoms satisfying the valence of other elements.