- Study of the effect of cerium nitrate on AA2024-T3 by means of electrochemical micro-cell technique
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This work evaluates the effect of cerium nitrate as corrosion inhibitor for AA2024-T3 in the view of its introduction in sol-gel coatings able to provide self-healing ability. Since it is well established that deposition of Ce species is activated by the local pH increase, the objective of this paper is to investigate the behavior of AA2024-T3 (open circuit potential and polarization curves) in the presence of Ce species in aggressive solutions by means of a local technique, the electrochemical micro-cell. This technique enables the investigation of small areas with resolution in the micrometer range by the use of glass capillaries to define the working electrode area. The micro-cell results clearly displayed that the entire AA2024-T3 area exposed to the cerium-containing electrolyte was involved in the cerium precipitation mechanism. The heterogeneous electrochemical behavior of the microstructure is minimized by the formation of a cerium-containing layer able to protect the metal substrate.
- Paussa,Andreatta,Rosero Navarro,Durán,Fedrizzi
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- Cerium deposition on aluminum alloy 2024-T3 in acidic NaCl solutions
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We analyzed the interaction of cerium ions with surface intermetallics on Al 2024-T3 in NaCl media under open circuit conditions at pH 3 using scanning electron microscopic, Auger-electron spectroscopic (AES), and energy dispersive X-ray techniques (EDX), as well as electrochemistry. The results indicate that cerium deposition in a pH 3.0 NaCl solution is strongly surface-site specific. The cerium deposition was the highest on the S-phase particles, lower on the (Cu, Fe, Mn)Al6 sites, and minimal on the bulk matrix. In addition to the formation of a cerium-rich film on the intermetallics, we found that cerium incorporated into the porous structure of the dealloyed S-phase particles (Cu-Mg-Al intermetallics). Our analyses show that cerium does not prevent the dealloying of the intermetallic particles; in fact, the dealloying is necessary for local cerium deposition. AES and EDX data also revealed significant chloride enrichment on the cerium-rich sites. From our electrochemical measurements we conclude that the cerium-rich layer formed in acidic solution at short exposure times does not inhibit cathodic reaction on the intermetallics.
- Kolics,Besing,Baradlai,Wieckowski
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- Mechanism of coke formation caused by catalytic nanochromium carbide particles from decomposition of CeCrO3
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Ce or CeO2 is often added to Fe-Cr-Ni base alloys to enhance protective Cr2O3 ceramic scale formation. In high-temperature carbonaceous reducing environments, however, it is still unsolved that Ce-containing alloys often exhibited increased carburization and coke formation. This research is aimed at understanding the mechanism of Ce-enhanced coke formation. It was found that CeO2 can cause catalytic activation of chromium carbide for carbon growth by first forming CeCrO3 and then decomposing CeCrO3 into CeO2 and active nanosize chromium carbide particles; the latter has proven to be conducive to coke formation. These findings can be helpful for the design of alloys with better ceramic coating resistant to carbonaceous degradation and for the growth of graphitic nanostructures using Cr-related catalysts.
- Li, Hao,Cui, Xinwei,Chen, Weixing
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- 8Beta-substituted-11-beta-pentyl-and 11-beta-hexyl-estra-1,3,5(10)-triene derivatives
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This invention describes the new 8β-substituted estratrienes of general formula (I),in which R2, R3, R6, R6′, R7, R7′, R14, R15, R15′, R16, R16′, R17, and R17′ have the meanings that are indicated in the description, R8 means a straight-chain or branched-chain, optionally partially or completely halogenated alkyl or alkenyl radical with up to 5 carbon atoms, an ethinyl or prop-1-inyl radical, and R11 means an n-pentyl or n-hexyl radical, as pharmaceutical active ingredients that have in vitro a higher affinity to estrogen receptor preparations from rat prostates than to estrogen receptor preparations from rat uteri and in vivo preferably exert a preferential contraceptive action on the ovary without stimulating the uterus, their production, their therapeutic use and pharmaceutical dispensing forms that contain the new compounds. The invention also describes the use of these compounds for contraception in men as well as the treatment of benign or malignant proliferative diseases of the ovary, such as, e.g., ovarian cancer, or granulosa cell tumors. 1
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- Preparation of lanthanum and cerium metals by hydrometallurgy
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Lanthanum and cerium metals were prepared by electrolytic synthesis of amalgams in aqueous solutions followed by the thermal decomposition. The amalgamation yields were almost quantitative. The preparation yield of lanthanide metals, however, deteriorated during thermal decomposition due to a density difference between lanthanide and mercury. The gaseous impurities in the prepared metals were found to be comparable with those in commercially available ones.
- Hasegawa,Sano,Aoshima,Shiokawa
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p. 246 - 249
(2008/10/08)
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- Process for producing pyromellitic acid
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A process for producing pyromellitic acid which comprises oxidizing 2,4,5-trimethylbenzealdehyde and/or its oxidized derivative in the presence of a catalyst containing iron, manganese and bromine, or additionally containing zirconium or cerium continuously or semi-continuously using aqueous acetic acid solvent and 0.05-2% by weight of bromide ion. The catalyst used in the present invention has high activity, and the catalyst solution has low corrosive because the reaction is performed at low bromide concentration by using a solvent of aqueous acetic acid. So pyromellitic acid is produced industrially advantageously in high yield continuously or semi-continuously which has been a major difficulty up to now.
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- Process for producing trimellitic anhydride
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A process for producing trimellitic anhydride which comprises performing liquid phase oxidation of pseudocumene containing 5% by weight or above of dimethyl bezaldehyde as a raw material for oxidation with air in aliphatic monocarboxylic acid having 1 to 5 carbon atoms as a solvent in the presence of a catalyst comprising both each metal of cobalt, manganese and zirconium and bromine to obtain trimellitic acid and then heat dehydrating trimellitic acid thus obtained or heat treating trimellitic acid thus obtained in the presence of a catalyst comprising 10 ppm or above of Ni thereby producing trimellitic anhydride.
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- Thermodynamics of formation of binary and ternary nitrides in the system Ce/Mn/N
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Drop solution calorimetry in high-temperature oxide melts has been shown to be very useful to study the energetics of nitride formation. This methodology was used to determine the enthalpies of formation from the elements of binary and ternary nitrides in
- Tessier, Franck,Ranade, Mandar R.,Navrotsky, Alexandra,Niewa, Rainer,DiSalvo, Francis J.,Leineweber, Andreas,Jacobs, Herbert
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p. 194 - 200
(2008/10/08)
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- Method and catalyst system for producing aromatic carbonates
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A method and catalyst system for producing aromatic carbonates from aromatic hydroxy compounds is disclosed. In one embodiment, the method includes the step of contacting at least one aromatic hydroxy compound with oxygen and carbon monoxide in the presence of a carbonylation catalyst system having an effective amount of an iron source as the primary catalyst component in the absence of a Group VIII B metal source. In various alternative embodiments, the carbonylation catalyst system can include at least one inorganic co-catalyst, as well as a halide composition and/or a base.
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- Method and catalyst system for producing aromatic carbonates
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A method and catalyst system for producing aromatic carbonates from aromatic hydroxy compounds. In one embodiment, the method includes the step of contacting at least one aromatic hydroxy compound with oxygen and carbon monoxide in the presence of a carbonylation catalyst system having an effective amount of a cobalt source in the absence of a Group VIII B metal source. In various alternative embodiments, the carbonylation catalyst system can include at least one inorganic co-catalyst, as well as a halide composition and/or a base.
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- Physiologically acceptable foamable formulation and foam
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There is described a foamable formulation comprising a foamable carrier and an active ingredient which may be admixed with the carrier or packaged separately and dispersed into the carrier during the foaming process. Alginate gel is a preferred foamable carrier. The foam produced from such a formulation, and a foam sheet produced by drying the foam, also form part of the invention. The formulation, foam and foam sheet are especially useful for medical applications, for example in treating burns. As apparatus to store the components of the formulation and to generate the foam is also described.
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- Temperature dependent rate constants for the reactions of gas phase lanthanides with N2O
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The reactivity of gas phase lanthanide (Ln) atoms (Ln=La-Yb with the exception of Pm) with N2O from 298 to 623 K is reported. Lanthanide atoms were produced by the photodissociation of Ln(TMHD)3 (TMHD=2,2,6,6-tetramethyl-3,5-heptanat
- Campbell, Mark L.
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p. 562 - 566
(2007/10/03)
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- Temperature-Dependent Rate Constants for the Reactions of Gas-Phase Lanthanides with O2
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The reactivity of the gas-phase lanthanide atoms Ln (Ln = La-Yb with the exception of Pm) with O2 is reported. Lanthanide atoms were produced by the photodissociation of [Ln(TMHD)3] and detected by laser-induced fluorescence. For all the lanthanides studied with the exception of Yb, the reaction mechanism is bimolecular abstraction of an oxygen atom. The bimolecular rate constants (in molecule-1 cm3 s-1) are described in Arrhenius form by k[Ce(1G4)] = (3.0 ± 0.4) × 10-10 exp(-3.4 ± 1.3 kJ mol-1/RT); Pr(4I9/2), (3.1 ± 0.7) × 10-10 exp(-5.3 ± 1.5 kJ mol-1/RT); Nd(5I4), (3.6 ± 0.3) × 10-10 exp(-6.2 ± 0.4 kJ mol-1/RT); Sm(7F0), (2.4 ± 0.4) × 10-10 exp(-6.2 ± 1.5 kJ mol-1/RT); Eu(8S7/2), (1.7 ± 0.3) × 10-10 exp(-9.6 ± 0.7 kJ mol-1/RT); Gd(9D2), (2.7 ± 0.3) × 10-10 exp(-5.2 ± 0.8 kJ mol-1/RT); Tb(6H15/2), (3.5 ± 0.6) × 10-10 exp(-7.2 ± 0.8 kJ mol-1/RT); Dy(5I8), (2.8 ± 0.6) × 10-10 exp(-9.1 ± 0.9 kJ mol-1/RT); Ho(4I15/2), (2.4 ± 0.4) × 10-10 exp(-9.4 ± 0.8 kJ mol-1/RT); Er(3H6), (3.0 ± 0.8) × 10-10 exp(-10.6 ± 1.1 kJ mol-1/RT); Tm(2F7/2), (2.9 ± 0.2) × 10-10 exp(-11.1 ± 0.4 kJ mol-1/RT), where the uncertainties represent ±2σ. The reaction barriers are found to correlate to the energy required to promote an electron out of the 6s subshell. The reaction of Yb(1S0) with O2 reacts through a termolecular mechanism. The limiting low-pressure third-order rate constants are described in Arrhenius form by k0[Yb(1S0)] = (2.0 ± 1.3) × 10-28 exp(-9.5 ± 2.8 kJ mol-1/RT) molecule-2 cm6 s-1.
- Campbell, Mark L.
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p. 7274 - 7279
(2007/10/03)
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- Metal exchanged zeolite catalysts for alcohol amination
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A process for the production of predominantly primary and secondary amines and little or no tertiary amines by the reductive amination of aliphatic alcohols using a metal exchanged crystalline aluminosilicate catalyst. The catalyst has a silica/alumina ratio ranging from about 10:1 to 40:1, contains about 1 to 10% by weight of cobalt or nickel and about 0.05 to 5% by weight of at least one other metal. High conversion rates are achieved at moderate temperatures and pressures.
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- Supported catalysts containing a platinum metal and process for preparing diaryl carbonates
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In the process for preparing an aromatic carbonate from an aromatic hydroxy compound, CO and O2 in the presence of a quaternary salt and a base, use is advantageously made of supported catalysts which, in the reaction-ready state, contain a platinum metal, a platinum metal compound or a complex containing a platinum metal compound on a support comprising a metal oxide whose metal can occur in a plurality of oxidation states.
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- Thermal Oxidation of Indium Phosphide in the Presence of Cerium Oxychloride Derivatives
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Thermal oxidation of indium phosphide in the presence of cerium(III) chloride was studied by ultrasoft x-ray and IR absorption spectroscopic measurements. The resultant oxide films are found to contain In2O3, InPO4, and phosphorus. The accelerated formation of indium phosphate is due to reaction of the InP substrate with the CeO2 forming during the preparation of the additive. The films contain small amounts of cerium and exhibit low dielectric strength.
- Mittova,Tomina,Antipko
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p. 201 - 202
(2008/10/08)
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- Desorption characteristics of rare earth (R) hydrides (R=Y, Ce, Pr, Nd, Sm, Gd and Tb) in relation to the HDDR behaviour of R-Fe-based-compounds
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Vacuum desorption characteristics of binary hydrides of rare earth metals (R=Ce, Pr, Nd, Y, Sm, Gd, Tb) were studied. A complete decomposition of hydrides, confirmed by X-ray diffraction, was achieved at temperatures up to 820°C. When heating the hydrogenated material in vacuum, two distinct hydrogen desorption events were observed for all the hydrides under investigation. The hydrogen desorption behaviour is different for the two groups of metals, namely group I (Ce, Pr and Nd) and group II (Y, Sm, Gd and Tb). The hydrogenation-disproportionation-desorption-recombination (HDDR) process was shown to take place for the Nd6Fe13Ge and Nd6Fe12.8Ga1.2 intermetallic compounds, both with the Nd6Fe13Si-type structure. The hydrogen absorption and desorption properties of these compounds were studied in relation to the desorption characteristics of neodymium hydride.
- Yartys,Gutfleisch,Panasyuk,Harris
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p. 128 - 133
(2008/10/08)
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- Thermochemical Characteristics of the Reaction between Calcium Metal and Cerium and Neodymium Chlorides in the Melt
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We have measured the enthalpies ΔH1133 for the reaction between calcium metal and neodymium and cerium chlorides in the melt and in solutions with KCl (-43.5, -39.6, -39.4, and -38.2 kcal mole-1 of chloride respectively).As the temperature increases ΔH decreases, with temperature coefficients of 0.01, 0.02, 0.03, and 0.03 respectively.The ΔH1133 values for the stepwise reduction of neodymium chloride in the melt have also been determined.Secondary phenomena which accompany the main reactions are discussed.
- Savin, V. D.,Mikhailova, N. P.
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p. 1282 - 1284
(2007/10/02)
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- Kinetics of the Reduction of Cerium and Neodymium from Their Chlorides by Calcium
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The kinetics of the calcio-thermic reduction of CeCl3 and NdCl3 in the melt and in KCl solutions have been studied.The features of the process are determined by the composition of the medium and by the nature of the reactants.The reduction of CeCl3 in the melt occurs in the activation-controlled region with an effective activation energy of 19.8 kcal mole-1, whereas in a solution containing KCl the reduction begins to take place in steps (Ea = 14.8 kcal mole-1), especially at high temperatures.The reduction of NdCl3 in the melt takes place in steps with activation energies for the various steps of 22.1, 29.9, and 21.9 kcal mole-1, whereas in solution with KCl the reaction is activation controlled (25.7 kcal mole-1).The medium has opposite effects on the reaction for the two chlorides: CaCl2 promotes the stepwise reduction of NdCl3, and KCl that of CeCl3.
- Savin, V. D.,Mikhailova, N. P.
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p. 1279 - 1281
(2007/10/02)
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