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Showing papers on "Molybdenum published in 2010"


Journal ArticleDOI
TL;DR: In this article, the electronic structure at the α-NPD/MoO 3 /Au interfaces has been investigated with ultraviolet photoemission spectroscopy (UPS), X-ray photoemiconductance spectrograph (XPS), and inverse photoemic emission spectrograms (IPES) and it was found that the MoO 3 layer contains some number of oxygen vacancies prior to any treatment and gap states are induced by the partial filling of the unoccupied 4d orbitals of molybdenum atoms neighboring oxygen vacancies.

212 citations


Journal ArticleDOI
Yuncang Li1, Cynthia S. Wong1, Jianyu Xiong1, Peter Hodgson1, Cuie Wen1 
TL;DR: In this paper, the cytotoxicity of titanium and titanium alloying elements in both forms of powder and bulk, using osteoblast-like SaOS(2) cells was assessed.
Abstract: It is commonly accepted that titanium and the titanium alloying elements of tantalum, niobium, zirconium, molybdenum, tin, and silicon are biocompatible. However, our research in the development of new titanium alloys for biomedical applications indicated that some titanium alloys containing molybdenum, niobium, and silicon produced by powder metallurgy show a certain degree of cytotoxicity. We hypothesized that the cytotoxicity is linked to the ion release from the metals. To prove this hypothesis, we assessed the cytotoxicity of titanium and titanium alloying elements in both forms of powder and bulk, using osteoblast-like SaOS(2) cells. Results indicated that the metal powders of titanium, niobium, molybdenum, and silicon are cytotoxic, and the bulk metals of silicon and molybdenum also showed cytotoxicity. Meanwhile, we established that the safe ion concentrations (below which the ion concentration is non-toxic) are 8.5, 15.5, 172.0, and 37,000.0 microg/L for molybdenum, titanium, niobium, and silicon, respectively.

211 citations


Journal ArticleDOI
TL;DR: To improve the catalytic activity and the sulfur-tolerance of the catalysts at lower temperatures, several metal elements were employed as dopants to modify the catalyst of Mn/alpha-Al2O3, and the best performance among the tested elements was achieved with molybdenum (Mo) as the dopant in the catalyst.
Abstract: In order to facilitate the removal of elemental mercury (Hg0) from coal-fired flue gas, catalytic oxidation of Hg0 with manganese oxides supported on inert alumina (α-Al2O3) was investigated at lower temperatures (373−473 K). To improve the catalytic activity and the sulfur-tolerance of the catalysts at lower temperatures, several metal elements were employed as dopants to modify the catalyst of Mn/α-Al2O3. The best performance among the tested elements was achieved with molybdenum (Mo) as the dopant in the catalysts. It can work even better than the noble metal catalyst Pd/α-Al2O3. Additionally, the Mo doped catalyst displayed excellent sulfur-tolerance performance at lower temperatures, and the catalytic oxidation efficiency for Mo(0.03)−Mn/α-Al2O3 was over 95% in the presence of 500 ppm SO2 versus only about 48% for the unmodified catalyst. The apparent catalytic reaction rate constant increased by approximately 5.5 times at 423 K. In addition, the possible mechanisms involved in Hg0 oxidation and the ...

208 citations


Journal ArticleDOI
TL;DR: In this article, the molybdenum nitride catalyst was found superior to vanadium and tungsten nitrides for catalytic hydrotreating of oleic acid in terms of fatty acid conversion, oxygen removal and production of normal alkanes.
Abstract: Nitrides of molybdenum, tungsten and vanadium supported on γ-Al 2 O 3 were prepared by temperature-programmed reaction with NH 3 and tested as catalysts for hydrodeoxygenation of oleic acid and canola oil at 380–410 °C and 7.15 MPa H 2 . The molybdenum nitride catalyst was found superior to the vanadium and tungsten nitrides for catalytic hydrotreating of oleic acid in terms of fatty acid conversion, oxygen removal and production of normal alkanes (diesel fuel cetane enhancers). The supported molybdenum nitride favoured the hydrodeoxygenation of oleic acid to n-C 18 H 38 three times out of four compared to decarbonylation and decarboxylation. A 450-h long hydrotreating test performed at 400 °C and 8.35 MPa H 2 with Mo 2 N/Al 2 O 3 and canola oil, indicated that oxygen removal exceeded 90% over the duration of the experiment and that the yield of middle distillate hydrocarbons (diesel fuel) ranged between 38 and 48 wt% (based on liquid feed).

150 citations


Patent
03 Sep 2010
TL;DR: A composition comprising at least 97% of an aluminium precursor of formula: Al(R 1 ) 2 (OR 2 ) with R 1 and R 2 independently selected in the group consisting of methyl, ethyl, propyl, isopropyl and t-butyl.
Abstract: A composition comprising, for 100% of its total mass, at least 97% of an aluminium precursor of formula: Al(R 1 ) 2 (OR 2 ) with R 1 and R 2 independently selected in the group consisting of methyl, ethyl, propyl, isopropyl and t-butyl; and : - From 200 ppb to 5 ppm of Mo (Molybdenum); - From 1000 ppb to 5 ppm of Fe (Iron); - From 200 ppb to 5 ppm of Cu (Copper); - From 200 ppb to 5 ppm of Ta (Tantalum).

146 citations


Journal ArticleDOI
TL;DR: The photocatalytic activity of doped titania samples was determined by the decomposition of Orange II dye during irradiation at 365 and 400 nm as mentioned in this paper, and the titania sample with 1.38% Mo has the highest catalytic activity.
Abstract: Molybdenum-doped anatase was prepared by thermal hydrolysis of peroxotitanium complex aqueous solutions containing a molybdenum peroxo-complex. The synthesized samples were characterized by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and surface area (BET) and porosity (BJH) determination. Molybdenum doping caused the increase of unit cell constants of anatase and changes in the morphology of particles from spindle-like shapes to the shapes with rectangular or square cross sections. The presence of Mo5+/Mo6+ ion doping in the TiO2 nanostructure has no significant effect on the transformation of anatase to rutile. In the visible region, the photocatalytic activity is substantially enhanced in the molybdenum concentration of about 1.38%. The photocatalytic activity of doped titania samples was determined by the decomposition of Orange II dye during irradiation at 365 and 400 nm. The titania sample with 1.38% Mo has the highest catalytic activity d...

135 citations



Journal ArticleDOI
TL;DR: In this paper, the optimum electrodeposition conditions with respect to HER overpotential were determined, e.g. Na2MoO4·2H2O concentration, current density and duty cycle.

113 citations


Journal ArticleDOI
TL;DR: In this paper, a commercially available extractant, LIX®63, was used to investigate the extraction of molybdenum(VI) and vanadium(V) from a synthetic sulphuric acid leach solution of spent hydrodesulphurisation catalysts.

113 citations


Journal ArticleDOI
TL;DR: In this article, focused ion beam (FIB) was used to anneal molybdenum pillars in a transmission electron microscope (TEM) to recover a mechanically pristine limited volume.

107 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of molybdenum addition on the structure of a simplified nuclear glass and to know how composition changes can affect molybdates crystallization tendency was studied by 29Si, 11B, 23Na MAS NMR and Raman spectroscopies.

Journal ArticleDOI
TL;DR: The mARC-1/MOSC-1 and hmARC-2 genes were found to be monomeric in their active forms, which is in contrast to all other eukaryotic molybdenum enzymes that act as homo- or heterodimers.

Journal ArticleDOI
TL;DR: The observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts, with Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones.

Journal ArticleDOI
02 Feb 2010-Langmuir
TL;DR: Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation and the effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed.
Abstract: Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides, namely nickel, chromium, molybdenum, manganese, iron, and titanium, were modified with long chain organic acids to better understand organic film formation The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid, and octadecylsulfonic acid on these substrates were examined in this study The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy, and matrix-assisted laser desorption ionization mass spectrometry The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation

Journal ArticleDOI
TL;DR: In this paper, it was shown that a MoO3 buffer layer can be reduced to form a metallic oxide buffer that exhibits more favorable energy-level alignment with N,N′-diphenyl-N,N, N′-bis-(1-naphthyl)-1-1′-biphensyl-4,4′-Diamine (α-NPD) than does MoO 3.
Abstract: Molybdenum trioxide (MoO3) is commonly used as a buffer layer in organic electronic devices to improve hole-injection. However, stoichiometric MoO3 is an insulator, and adds a series resistance. Here it is shown that a MoO3 buffer layer can be reduced to form a metallic oxide buffer that exhibits more favorable energy-level alignment with N,N′-diphenyl-N,N′-bis-(1-naphthyl)-1-1′-biphenyl-4,4′-diamine (α-NPD) than does MoO3. This buffer layer thus provides the conductivity of a metal with the favorable energy alignment of an oxide. Photoemission shows the reduced oxide contains Mo4+ and Mo5+, with a metallic valence band structure similar to MoO2.

Journal ArticleDOI
R. A. Sheldon1
TL;DR: In the homogeneous molybdenum-catalysed epoxidation of olefins by tert-alkyl hydroperoxides two competing processes have been delineated as discussed by the authors.
Abstract: In the homogeneous molybdenum-catalysed epoxidation of olefins by tert-alkyl hydroperoxides two competing processes, epoxidation and hydroperoxide decomposition, have been delineated. Hydroperoxide decomposition involves free-radical reactions initiated by electron-transfer reactions of Mo(V) and Mo(VI) complexes with the hydroperoxide. The rates and products of hydroperoxide decomposition are dependent on the solvent and the presence or absence of an olefin. The rate of epoxidation depends on the structure of the olefin and, after an initial period during which the rate changes, it becomes independent of the structure of the molybdenum compound originally added as the catalyst. The active catalyst in the epoxidation reaction is a molybdenum(VI) compound. The active epoxidizing agent is most likely a complex of molybdenum(VI) with the hydroperoxide, which transfers an oxygen atom to the olefin via a cyclic transition state analogous to that for the epoxidation of olefins with organic peracids.

Journal ArticleDOI
TL;DR: In this article, the effect of the cobalt or nickel content of molybdenum carbide DMR catalysts has been investigated and the results indicate that incorporating cobalt into the Mo2C structure at a Co/Mo ratio of 0.4, i.e. a Co0.4Mo1Cx catalyst, gives a DMR activity and stability that are markedly higher than those of Mo 2C catalysts.

01 Jan 2010
TL;DR: Recombinant expression of hmARC-1 and hm ARC-2 proteins in Escherichia coli reveals that both proteins are monomeric in their active forms, which is in contrast to all other eukaryotic molybdenum enzymes that act as homo- or heterodimers.
Abstract: The mitochondrial amidoxime reducing component mARC is a newly discovered molybdenum enzyme that is presumed to form the catalytical part of a three-component enzyme system, consisting of mARC, heme/cytochrome b5, and NADH/FADdependent cytochrome b5 reductase. mARC proteins share a significant degree of homology to the molybdenum cofactorbinding domain of eukaryotic molybdenum cofactor sulfurase proteins, the latter catalyzing the post-translational activation of aldehyde oxidase and xanthine oxidoreductase. The human genome harbors two mARC genes, referred to as hmARC-1/ MOSC-1 and hmARC-2/MOSC-2, which are organized in a tandem arrangement on chromosome 1. Recombinant expression of hmARC-1 and hmARC-2 proteins in Escherichia coli reveals that both proteins are monomeric in their active forms, which is in contrast to all other eukaryotic molybdenum enzymes that act as homo- or heterodimers. Both hmARC-1 and hmARC-2 catalyze the N-reduction of a variety of N-hydroxylated substrates such as N-hydroxy-cytosine, albeit with different specificities. Reconstitution of active molybdenum cofactor onto recombinant hmARC-1 and hmARC-2 proteins in the absence of sulfur indicates that mARC proteins do not belong to the xanthine oxidase family of molybdenum enzymes. Moreover, they also appear to be different from the sulfite oxidase family, because no cysteine residue could be identified as a putative ligand of the molybdenum atom. This suggests that the hmARC proteins and sulfurase represent members of a new family of molybdenum enzymes.

Journal ArticleDOI
TL;DR: In this paper, a p-dopant for hole injection at α-NPD/Au interfaces is investigated, which is achieved via doping-induced formation of a narrow depletion region in the organic semiconductor.
Abstract: Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd)3) is investigated as a p-dopant for organic semiconductors. With an electron affinity of 5.6 eV, Mo(tfd)3 is a strong oxidizing agent suitable for the oxidation of several hole transport materials (HTMs). Ultraviolet photoemission spectroscopy confirms p-doping of the standard HTM N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl-4,4′-diamine (α-NPD). Strong enhancement of hole injection at α-NPD/Au interfaces is achieved via doping-induced formation of a narrow depletion region in the organic semiconductor. Variable-temperature current−voltage measurements on α-NPD: Mo(tfd)3 (0−3.8 mol %) yield an activation energy for polaron transport that decreases with increasing doping concentration, which is consistent with the effect of the doping-induced filling of traps on hopping transport. Good stability of Mo(tfd)3 versus diffusion in the α-NPD host matrix is demonstrated by Rutherford backscattering for temperatures up to 110 °C. Densi...

Journal ArticleDOI
TL;DR: In this paper, powder neutron diffraction (PND) studies have confirmed unequivocally that the compound possesses the η-12 carbide structure, in which N atoms are exclusively located at 8a crystallographic sites, as opposed to the 16c sites exclusively occupied in the Co3Mo3N phase.
Abstract: The temperature-programmed reaction of Co3Mo3N under H2/Ar results in a new nitride with composition Co6Mo6N. Powder neutron diffraction (PND) studies have confirmed unequivocally that the compound possesses the η-12 carbide structure, in which N atoms are exclusively located at 8a crystallographic sites, as opposed to the 16c sites exclusively occupied in the Co3Mo3N phase. On this basis, it possible to rationalize the observation that 50% nitrogen loss occurs under the high-temperature reduction conditions employed. Reaction of the reduced η-12 phase under N2/H2 results in the regeneration of the η-6 Co3Mo3N nitride and return of nitrogen to the 16c sites (only). Although established for corresponding ternary carbide structures, the η-12 carbide structure is unprecedented in nitrides and a topotactic cycling between η-carbide structures is hitherto unknown. The ammonia synthesis activity of the η-6 nitride at ambient pressure and 400 °C is 167 μmol g−1 h−1, whereas the η-12 structure is unstable and rev...

Journal ArticleDOI
TL;DR: In this paper, pure molybdenum powder was sintered with SPS under various temperatures, external pressures and heating rates, and the relative density, the microhardness and the chord length distribution were measured.
Abstract: Pure molybdenum was sintered with SPS under various temperatures, external pressures and heating rates. The microstructure of the specimens representing the different sintering conditions was investigated by classical metallographic methods. The relative density, the microhardness and the chord length distribution were measured. Linear shrinkage, depending on time or temperature, was calculated from piston travel, which was recorded during sintering process. These results show that the main part of consolidation takes place during fast heating up. The densification behaviour is controlled mainly by sintering temperatures and applied pressure. The molybdenum powder was successfully consolidated by SPS in very short times. A relative density of 95% was reached by sintering temperatures of 1600 °C and external pressure of 67 MPa.

Journal ArticleDOI
TL;DR: In this paper, bimetallic ruthenium/molybdenum catalysts were used for the selective liquid phase hydrogenation of cyclohexylcarboxamide (CyCONH 2 ), with no secondary or tertiary amine byproduct formation.
Abstract: Recyclable, heterogeneous bimetallic ruthenium/molybdenum catalysts, formed in situ from triruthenium dodecacarbonyl [Ru 3 (CO) 12 ] and molybdenum hexacarbonyl [Mo(CO) 6 ], are effective for the selective liquid phase hydrogenation of cyclohexylcarboxamide (CyCONH 2 ) to cyclohexanemethylamine (CyCH 2 NH 2 ), with no secondary or tertiary amine by-product formation. Variation of Mo:Ru composition reveals both synergistic and poisoning effects, with the optimum combination of conversion and selectivity at ca. 0.5, and total inhibition of catalysis evident at ≥ 1. Good amide conversions are noted within the reaction condition regimes 20-100 bar hydrogen and 145-160 °C. The order of reactivity of these catalysts towards reduction of different amide functional groups is primary > tertiary ≽ secondary. In situ HP-FT-IR spectroscopy confirms that catalyst genesis occurs during an induction period associated with decomposition of the organometallic precursors. Ex situ characterisation, using XRD, XPS and EDX-STEM, for active Mo:Ru compositions, has provided evidence for intimately mixed ca. 2.5-4 nm particles that contain metallic ruthenium, and molybdenum (in several oxidation states, including zero).

Journal ArticleDOI
TL;DR: The characterisation of thiosemicarbazonato molybdenum(VI) complexes (1-4) in aqueous medium revealed that upon dissolving complexes in water, most likely to some extent dissociation took place, although experimental data didn't allow exact quantification of dissociation.

Journal ArticleDOI
TL;DR: The observations present in these mechanisms show the lead ions bonded ionic have a strong affinity towards [BO₃] units containing non-bridging oxygens and [MoO₄]²⁻ molybdate units, which yields the formation of the PbMoO ₄ crystalline phase.

Journal ArticleDOI
TL;DR: In this article, the effect of a number of dopants (lithium, silicon, ruthenium, molybdenum and tin) upon the transparency, crystallinity, porosity and conductivity of mesoporous WO3 films was investigated.

Journal ArticleDOI
TL;DR: In this paper, a static recrystallization diagram of molybdenum containing low concentrations of interstitial impurities is presented, which is based on the results of a detailed analysis of the current quality of technically pure moly bdenum.
Abstract: In the last decades the amount of interstitial impurities in the raw material used for powder metallurgical production of molybdenum has been reduced significantly. The quality of the production process has been adapted to the latest technological standards and, consequently, the properties of technically pure molybdenum have changed accordingly. For processing pure molybdenum and to predict the resulting mechanical properties, the recrystallization behavior, which strongly depends on the concentration of the prevailing impurities, e.g. carbon, nitrogen and oxygen, is decisive. A reliable recrystallization diagram of molybdenum was published in 1965, which does not accurately describe the recrystallization behavior of the current quality of technically pure molybdenum. Therefore, in the present investigation a diagram which reflects the static recrystallization behavior of molybdenum containing low concentrations of interstitial impurities was established. The recrystallization behavior has been monitored on differently deformed and subsequently heat-treated samples by means of hardness testing, light microscopy and scanning electron microscopy employing electron channeling contrast imaging (ECCI) and electron back scatter diffraction (EBSD). Especially ECCI and EBSD investigations offer the possibility to analyze the change of microstructure with regard to recovery and recrystallization effects, e.g. the evolution of subgrains. The quantity of the impurities was determined by standard chemical analysis methods. As a bcc metal, molybdenum exhibits a high stacking fault energy. Thus, the recrystallization behavior is strongly dominated by concurrent recovery processes, which deviate from that of fcc metals showing a comparably low stacking fault energy. A revised recrystallization diagram for technically pure powder metallurgically processed molybdenum is presented.

Journal ArticleDOI
TL;DR: In this paper, binary and ternary mixed oxide xerogels are formed in one step by nonhydrolytic condensation reactions of chloride precursors in non-aqueous medium.

Journal ArticleDOI
TL;DR: In this article, the surface films formed on type 316LN stainless steels with different nitrogen contents, during potentiodynamic polarization in acidified 1 M NaCl solution, were characterized by Laser Raman Spectroscopy (LRS).

Journal ArticleDOI
TL;DR: In this paper, the feasibility of development of silicide type of coating over molybdenum base TZM alloy shape (Mo < 99 ¼ %) using pack cementation coating technique was examined.

Journal ArticleDOI
TL;DR: In this paper, the influence of molybdenum on the surface morphology, structure, phase composition, corrosion and mechanical properties of the zinc-based alloys was investigated.
Abstract: Ternary Zn–Ni–Mo (1.2 wt.% Ni, 4.5 wt.% Mo) and Zn–Co–Mo (6 wt.% Co, 4 wt.% Mo) as well as reference binary Zn–Ni and Zn–Co alloy coatings were electrodeposited from citrate–sulphate baths. The influence of molybdenum on the surface morphology, structure, phase composition, corrosion and mechanical properties of the deposits was investigated. The XPS results revealed that the coatings with molybdenum contained appreciable amounts of Zn 2+ inclusions, which is probably due to the low hydrogen evolution overpotential on the ternary alloys. The increase in the interfacial pH, promoted by intensive hydrogen evolution, causes the formation of oxidized zinc species which incorporate into the coating. The presence of MoO 4 2− ions in the bath modified the morphology of the deposits — alloys with smoother surface were deposited. Polarization resistance measurements proved the beneficial influence of molybdenum on corrosion properties of examined alloy coatings. The presence of molybdenum improves the microhardness of the zinc-based alloys, but it has negative influence on the adhesion of the ternary coatings.