Showing papers on "Cerium published in 1989"
TL;DR: The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable suppression of side reactions, particularly enolization.
Abstract: The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable suppression of side reactions, particularly enolization. Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.
526 citations
TL;DR: In this article, Fourier transform infrared spectroscopy (FT-IR) was used to detect peroxide adsorption on both surfaces of well-outgassed and partially reduced cerium oxide.
Abstract: {sup 16}O{sub 2} ({sup 18}O{sub 2}) adsorption on well-outgassed and partially reduced cerium oxide has been investigated by Fourier transform infrared spectroscopy (FT-IR) in the temperature range 200-373 K. Superoxide species (O{sub 2}{sup {minus}}{sub ads}) with a pair of characteristic bands at 1126 (1063) and 2237 (2112) cm{sup {minus}1} were detected from oxygen adsorption on both surfaces of well-outgassed and partially reduced cerium oxide. One additional band at 883 (835) cm{sup {minus}1} attributed to peroxide species (O{sub 2}{sup 2{minus}}{sub ads}) was observed together with the bands at 1129 and 2238 cm{sup {minus}1} after oxygen adsorption on partially reduced cerium oxide. The formation of these dioxygen species is strongly dependent on the pretreatment of cerium oxide. It is concluded that the superoxide species is mainly generated on a coordinatively unsaturated cerium ion while the peroxide species were formed on a pair of surface cerium ions with lower oxidation state created by reduction.
254 citations
TL;DR: In this article, the distribution of rare-earth elements between hydrochloric acid solutions and solutions of di-(2-ethylhexyl)-phosphoric acid (DEHPA) or 2-ethyl-hexyl 2-methylhexylphosphororic acid in kerosene have been investigated under different conditions.
184 citations
TL;DR: In this article, a sequence of 3D-XPS spectra is obtained for a ceria converted progressively (and partially) to Ce2O3 under increasing temperatures of reduction (up to 900°C).
137 citations
Patent•
31 May 1989TL;DR: In this paper, the authors proposed a catalytic composite for treating an exhaust gas to minimize the hydrogen sulfide content thereof and comprising a first support which is a refractory inorganic oxide having dispersed thereon at least one noble metal component and having dispersed immediately thereon an overlayer comprising at least an oxygen storage component and optionally a second support which are a refractive inorganic oxides, with alumina being preferred.
Abstract: This invention relates to a catalytic composite for treating an exhaust gas to minimize the hydrogen sulfide content thereof and comprising a first support which is a refractory inorganic oxide having dispersed thereon at least one noble metal component and having dispersed immediately thereon an overlayer comprising at least one oxygen storage component and optionally a second support which is a refractory inorganic oxide. The first support may be selected from the group consisting of alumina, silica, titania, zirconia and aluminosilicates with alumina being preferred. The noble metal component may be selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium. The oxygen storage component is an oxide of a metal which includes cerium, iron, nickel, cobalt lanthanium, neodymium, praseodymium, etc. and mixtures thereof. Cerium oxide is a preferred oxygen storage component. The second support may be selected from the group consisting of alumina, silica, titania, zirconia and aluminosilicates, with alumina preferred.
106 citations
TL;DR: In this article, the first salt-free mono-Cp⋆ yttrium complex with two carbyl ligands was obtained from Y(o-C6H4CH2NMe2)3 and Cp(H).
84 citations
TL;DR: In this paper, the thermal decomposition of OCH t Bu 3 ) 3 and [LiOC t Buy 3 ] n to the corresponding M(OCH t BU 2 ) n derivatives (M=Ce, Li) was studied.
Abstract: We report the preliminary results of our study of the thermal decomposition of Ce(OC t Bu 3 ) 3 and [LiOC t Bu 3 ] n to the corresponding M(OCH t Bu 2 ) n derivatives (M=Ce, Li)
65 citations
61 citations
Patent•
27 Sep 1989TL;DR: In this article, an improved catalytic composite for treating an exhaust gas comprising a first support which is a refractory inorganic oxide, having dispersed thereon at least one oxygen storage component and a noble metal component.
Abstract: This invention relates to an improved catalytic composite for treating an exhaust gas comprising a first support which is a refractory inorganic oxide, having dispersed thereon at least one oxygen storage component and at least one noble metal component and having dispersed immediately thereon an overlayer comprising lanthanum oxide and optionally a second support which is a refractory inorganic oxide. The first and second support may be selected from the group consisting of alumina, silica, titania, zirconia and aluminosilicates with alumina being preferred. Additionally, the noble metal component may be selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium. The oxygen storage component is an oxide of a metal which includes cerium, iron, nickel, cobalt lanthanum, neodymium, praesodymium, etc. and mixtures thereof. This invention also relates to a process for treating automotive exhaust comprising contacting the exhaust with the catalytic composite described above. The catalytic composite shows improved activity, especially for eliminating NOx, after extensive durability testing and also minimizes the formation of H2S.
60 citations
TL;DR: From X-ray Guinier powder data the crystal structures of the ternary germanides Ce(Rh or Ir)Ge and Ce(Pd or Pt)Ge were confirmed to be of the TiNiSi-type and the CeCu 2 -type.
55 citations
TL;DR: In this article, a rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00 −10.0 µg ml−1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution.
Abstract: A rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00–10.0 µg ml–1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing drugs. The results obtained for the assay of commercial pharmaceutical preparations compared well with those obtained by a reference method and demonstrated good accuracy and precision.
Patent•
22 Mar 1989TL;DR: An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel or cobalt (18), having sizes from 0.05 micrometer to 1.75micrometer and conductive oxide (19) selected from cerium
Abstract: An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.
TL;DR: From lattice volume, susceptibility, and resistivity measurements, it is concluded that cerium ions are in a mixed-valent state in CeRhIn.
Abstract: A new ternary equiatomic compound, CeRhIn, has been synthesized which is found to crystallize in the hexagonal ${\mathrm{Fe}}_{2}$P structure. The unit-cell volume of this compound deviates from that expected on the basis of lanthanide contraction, indicating the nontrivalent state of the Ce ions in this compound. The magnetic susceptibility of CeRhIn shows a broad maximum at about 150 K. Such a maximum is a characteristic feature of the mixed-valent cerium compounds. The resistivity of CeRhIn due to magnetic scattering also shows a broad maximum at about 140 K. Thus from lattice volume, susceptibility, and resistivity measurements, it is concluded that cerium ions are in a mixed-valent state in CeRhIn.
TL;DR: In this paper, it was suggested that molecules containing cerium ions with a formal valency +4 may form a ground state resembling a Kondo singlet, and the experimental consequences for these systems are discussed.
Abstract: It is suggested that molecules containing cerium ions with a formal valency +4 may form a ground state resembling a Kondo singlet. This is demonstrated explicitly by choosing cerocene as an example. Experimental consequences for these systems are discussed.
TL;DR: In this article, the formation of a gelatinous metal polyacrylate precipitate which can be easily removed from the mother liquor, and then calcined to form a high density ceramic oxide was studied using FTIR spectroscopy.
TL;DR: The use of cerium (111) chloride alters the chemoselectivity of the reaction of trimethylsilylmethyl magnesium chloride with ester-acetals and also greatly improves the efficiency of reaction with lactones as discussed by the authors.
Patent•
14 Jul 1989
TL;DR: In this paper, the erbium-doped phosphate glasses were used for an "eye-safe" wavelength and the ytterbium, chromium, and cerium ions were used as auxiliary dopants.
Abstract: Phosphate laser glass compositions which include erbium ions as the active laser ion material. In one aspect, ytterbium, chromium and cerium ions are present as auxiliary dopants. The ytterbium, chromium and cerium additives serve to sensitize the erbium-doped phosphate glasses of the present invention. The glasses are particularly useful in applications where an "eye-safe" wavelength is desirable.
TL;DR: In this article, the optical properties of calcium fluoride contaminated with cerium and europium ions have been analyzed and it was found that Ce3+ → Eu2+ energy transfer takes place in this crystal even for the very low concentration of the acceptor ions in the specimens analyzed.
Patent•
17 Nov 1989TL;DR: In this paper, a method for producing zirconia ceramics superior in mechanical strength, hardness and toughness was presented, which includes calcining a hydrate obtained by coprecipitation method from water-soluble salts of cerium and magnesium and a basic salt of Zirconium, and further grinding the calcined hydrate to obtain ZIRconia powders of 1 μm or less in average crystal grain size, then shaping the powders and sintering the resulting shaped product.
Abstract: Disclosed are zirconia ceramics superior in mechanical strength, hardness and toughness and a method for producing them. The zirconia ceramics contain ca. 7-12 mol % of cerium oxide and ca. 2-7 mol % of magnesium oxide and have an average crystal grain size of crystal grains thereof of 1 μm or less, at least ca. 80 mol % of the crystal grains being tetragonal grains and the balance being monoclinic grains, and have a bending strength of at least 100 kg/mm 2 , a fracture toughness of at least 10 MNm -1 .5 and a Vickers hardness of at least 1000 kg/mm 2 . The method comprises calcining a hydrate obtained by coprecipitation method from water-soluble salts of cerium and magnesium and a basic salt of zirconium or a hydrate obtained by adding water-soluble salts of cerium and magnesium to a zirconium hydrate and neutralizing the mixture of hydrates, further grinding the calcined hydrate to obtain zirconia powders of 1 μm or less in average crystal grain size, then shaping the powders and sintering the resulting shaped product.
TL;DR: Ce(DME)(OSiPh 3 ) 4 · C 6 H 5,CH 3, the crystal structure of which was determined by X-ray single-crystal techniques as mentioned in this paper.
TL;DR: In this paper, the growth of bulk Ta and Al-oxide follows logarithmic growth laws at room temperature and the absence of bulk oxide formation at liquid nitrogen temperature shows that the enhanced surface oxidation is limited by a thermally activated process and not by electron tunneling across the oxide barrier.
TL;DR: In this article, enthalpy increment measurements were carried out on BaZrO 3, BaMoO 4 and BaCeO 3 using a high temperature microcalorimeter.
Patent•
15 Feb 1989
TL;DR: A surface treatment bath for aluminum or its alloy comprising 10-1000 ppm of vanadium or cerium ion, 10-500 ppm of zirconium ion and 1-50 ppm of effective fluorine ion, and having pH of 2.0-4.0 as discussed by the authors.
Abstract: A surface treatment chemical for aluminum or its alloy comprising 10-1000 parts by weight of vanadium or cerium ion, 10-500 parts by weight of zirconium ion, 10-500 parts by weight of phosphate ion and 1-50 parts by weight of effective fluorine ion. A surface treatment bath for aluminum or its alloy comprising 10-1000 ppm of vanadium or cerium ion, 10-500 ppm of zirconium ion, 10-500 ppm of phosphate ion and 1-50 ppm of effective fluorine ion, and having pH of 2.0-4.0.
15 Nov 1989-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, it was found that yttrium was the most effective active element in combating the negative effect caused by the presence of sulphur in NiCrAl alloys and that an optimum amount of active element is required in order to get the best effect.
Abstract: The presence of trace amounts of sulphur causes an adverse effect on the oxidation behaviour of NiCrAl alloys. The deleterious effect can be checked by the addition of active elements such as yttrium, cerium or hafnium. It was found that yttrium was the most effective in combating the negative effect caused by the presence of sulphur. It was also found that an optimum amount of active element is required in order to get the best effect. This is in contrast to the sulphur-free samples where the oxidation behaviour is not critically dependent on the amount of active element. The main effect of active-element additions is a change in the composition of the scale in the initial stages of oxidation. The difference in the mechanism of active-element additions in a sulphur-containing alloy is compared with that of the sulphur-free alloy.
TL;DR: In this article, high active ammonia synthesis catalysts derived from cerium intermetallic alloy precursors were studied by in situ powder X-ray diffraction (XRD) with concurrent analysis of catalytic activity.
TL;DR: In this article, the reaction rate is very sensitive to the nature of the ring substituents (???= −5.4), which clearly suggests the operation of one electron transfer mechanism.
TL;DR: In this article, an irridium catalysts supported on alumina, magnesia, silica-alumina, cerium and niobium oxides were prepared by impregnation with iridium carbonyl and the metallic state was characterized by hydrogen and oxygen chemisorption as well as transmission electron microscopy.
TL;DR: In this paper, it is proposed that the cerium oxide/hydroxide creates a barrier to the reduction of oxygen stifling cathodic reaction with a corresponding reduction in corrosion rate and open circuit potential.
Abstract: The corrosion-resistance of aluminum-based alloys and metal-matrix composites can be increased by treatment with cerium compounds. Immersion in a 1000 ppm solution of CeCl/sub 3/ for periods of several days has been shown to increase the pitting potential and reduce the corrosion rate. Such treatment is considered as an alternative to the use of chromate conversion coatings. It is proposed that the cerium oxide/hydroxide creates a barrier to the reduction of oxygen stifling cathodic reaction with a corresponding reduction in corrosion rate and open circuit potential. The authors' study is described.