Equilibrium of molybdenum in selected extraction systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tkac, Peter; Paulenova, Alena

2007-07-01

The concentration of molybdenum(VI) in dissolved irradiated nuclear fuel is comparable with the concentrations of Tc, Am and Np. Therefore it is of big interest to understand its behavior under conditions related to the UREX/TRUEX process. The effect of the poly-speciation of molybdenum in aqueous solution on its extraction by neutral solvents TBP and CMPO/TBP was studied. Extraction yields of molybdenum decreased significantly when AHA was added to aqueous phase. Our investigation confirmed a strong ability of the aceto-hydroxamic acid to form complexes with Mo in high acidic solutions. Spectroscopic data (UV-Vis) confirmed that a fraction of the Mo(VI)-AHA complexmore » is present in the organic phase after extraction. (authors)« less

Molybdenum mineralization related to the Yangtze's lower crust and differentiation in the Dabie Orogen: Evidence from the geochemical features of the Yaochong porphyry Mo deposit

NASA Astrophysics Data System (ADS)

Liu, Qing-Quan; Li, Bin; Shao, Yong-Jun; Lu, An-Huai; Lai, Jian-Qing; Li, Yong-Feng; Luo, Zheng-Zhuan

2017-06-01

The Dabie Orogen is a world-class case for large amounts of Mo mineralization in that it contains at least 10 porphyry Mo deposits with Mo metal reserves over 3 Mt from the time period of 156-110 Ma. However, the principal mechanism for the Mo mineralization remains controversial due to the lack of a precise definition of its source and shallow ore-forming process, which is essential to understand these rare large Mo deposits. Detailed geochronology, geochemistry, and isotopic data for ore-related granites and minerals were analyzed in order to place constraints on the massive Mo mineralization in the Dabie Orogen in eastern China. The Yaochong molybdenum orebodies were hosted in the transition belt and alteration zone between the granitic stocks and the Dabie Complex and were characterized as numerous veinlets with potassic, phyllic and propylitic alterations. The buried Yaochong granitic intrusions and associated molybdenum mineralization yield Early Cretaceous ages of magmatic activities at ca. 138 Ma and extremely similar Re-Os isotope ages for the corresponding Mo metallogenic event at ca. 137 Ma. The Yaochong monzogranite and granite porphyry belong to the highly fractionated I-type granites, which are believed to be derived from the dominantly Yangtze's lower crust mixed with the Northern Dabie Complex due to their geochemical and isotope features. The elemental diversity and isotopic homogeneity suggest that the formation of the Yaochong monzogranite involved the fractionation of biotite, garnet and minor feldspar and accessory minerals combined with a weak crustal assimilation process. In contrast, the granite porphyry was possibly generated by the partial melting of the same mixed lower continental crust via the differentiation process involving the fractionation of feldspar, apatite, and/or titanite. Fractional crystallization processes can significantly elevate the molybdenum concentration in the residual melts. The biotite fractional crystallization results in removal of molybdenum from the vestigial magma since molybdenum is compatible with it, which may account for the barren monzogranite with a low-grade molybdenum mineralization. The ore-bearing granite porphyry has more source materials from the Yangtze's lower crust, which may have contributed most of the molybdenum for the porphyry-related molybdenum deposits in the Dabie metallogenic zone. This porphyry molybdenum aggregation may have been deposited in a post-collision or intracontinental extensional setting.

Catalytic reduction of dinitrogen to ammonia at a single molybdenum center

PubMed Central

Weare, Walter W.; Dai, Xuliang; Byrnes, Matthew J.; Chin, Jia Min; Schrock, Richard R.; Müller, Peter

2006-01-01

Since our discovery of the catalytic reduction of dinitrogen to ammonia at a single molybdenum center, we have embarked on a variety of studies designed to further understand this complex reaction cycle. These include studies of both individual reaction steps and of ligand variations. An important step in the reaction sequence is exchange of ammonia for dinitrogen in neutral molybdenum(III) compounds. We have found that this exchange reaction is first order in dinitrogen and relatively fast (complete in <1 h) at 1 atm of dinitrogen. Variations of the terphenyl substituents in the triamidoamine ligand demonstrate that the original ligand is not unique in its ability to yield successful catalysts. However, complexes that contain sterically less demanding ligands fail to catalyze formation of ammonia from dinitrogen; it is proposed as a consequence of a base-catalyzed decomposition of a diazenido (MoNNH) intermediate. PMID:17085586

Separation of Molybdenum from Acidic High-Phosphorus Tungsten Solution by Solvent Extraction

NASA Astrophysics Data System (ADS)

Li, Yongli; Zhao, Zhongwei

2017-10-01

A solvent-extraction process for deep separation of molybdenum from an acidic high-phosphate tungsten solution was developed using tributyl phosphate (TBP) as the extractant and hydrogen peroxide (H2O2) as a complexing agent. The common aqueous complexes of tungsten and molybdenum (PMoxW12-xO40 3-, x = 0-12) are depolymerized to {PO4[Mo(O)2(O-O)]4}3- and {PO4[W(O)2(O-O)]4}3- by H2O2. The former can be preferentially extracted by TBP. The extractant concentration, phase contact time, H2O2 dosage, and H2SO4 concentration were optimized. By employing 80% by volume TBP, O:A = 1:1, 1.0 mol/L H2SO4, 1.0 mol/L H3PO4, a contact time of 2 min, and a molar ratio of H2O2/(W + Mo) equal to 1.5, 60.2% molybdenum was extracted in a single stage, while limiting tungsten co-extraction to 3.2%. An extraction isotherm indicated that the raffinate could be reduced to <0.1 g/L Mo in six stages of continuous counter-current extraction.

Astrocyte dysfunction following molybdenum-associated purine loading could initiate Parkinson's disease with dementia.

PubMed

Bourke, Christopher A

2018-01-01

Sporadic or idiopathic Parkinson's disease is a movement disorder with a worldwide distribution, a long pre-clinical latent period and a frequent association with dementia. The combination of molybdenum deficiency and purine ingestion could explain the movement disorder, the distribution, the latent period and the dementia association. Recent studies in sheep have shown that molybdenum deficiency enables some dietary purines to accumulate in the central nervous system. This causes astrocyte dysfunction, altered neuromodulation and eventually irreversible central nervous system disease. Humans and sheep share the ability to salvage purines and this ability places humans at risk when they ingest xanthosine, inosine, adenosine and guanosine. Adenosine ingestion in molybdenum-deficient humans will lead to adenosine loading and potentially a disturbance to the A2a adenosine receptors in the nigro-striatum. This could result in Parkinson's disease. Guanosine ingestion in molybdenum-deficient humans will lead to guanosine loading and potentially a disturbance to the guanosine receptors in the hippocampus, amygdala and ventral striatum. This could result in dementia. The molybdenum content of the average daily diet in the United States is 0.07 ppm and in the United Kingdom 0.04 ppm. Central nervous system disease occurs in sheep at <0.04 ppm. Consistent with the role proposed for molybdenum deficiency in Parkinson's disease is the observation that affected individuals have elevated sulfur amino acid levels, depressed sulfate levels, and depressed uric acid levels. Likewise the geographical distribution of Parkinson's dementia complex on Guam corresponds with the distribution of molybdenum-deficient soils hence molybdenum-deficient food gardens on that island.

Bacterial molybdoenzymes: old enzymes for new purposes.

PubMed

Leimkühler, Silke; Iobbi-Nivol, Chantal

2016-01-01

Molybdoenzymes are widespread in eukaryotic and prokaryotic organisms where they play crucial functions in detoxification reactions in the metabolism of humans and bacteria, in nitrate assimilation in plants and in anaerobic respiration in bacteria. To be fully active, these enzymes require complex molybdenum-containing cofactors, which are inserted into the apoenzymes after folding. For almost all the bacterial molybdoenzymes, molybdenum cofactor insertion requires the involvement of specific chaperones. In this review, an overview on the molybdenum cofactor biosynthetic pathway is given together with the role of specific chaperones dedicated for molybdenum cofactor insertion and maturation. Many bacteria are involved in geochemical cycles on earth and therefore have an environmental impact. The roles of molybdoenzymes in bioremediation and for environmental applications are presented. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Rhenium, Molybdenum, Tungsten - Prospects for Production and Industrial Applications

DTIC Science & Technology

1998-06-18

concentrates from unique complex copper -containing porphyry deposit of the Almalyk region. The ore containing over 10 associated valuable constituents is...L.I.Ruzin, M .F.Sherem etyev ............................................... 71 Recovery of rhenium as by-product of treatment of molybdenite and copper ...for processing copper -molybdenum ores from "Erdenet- Ovoo" deposit S.Davaanyam, I.Sh.Sataev, Zh.Baatarkhuu, A.M.Desyatov, M.I.Khersonsky

Reactions of rhenium(V) and molybdenum(V) oxypentahalides with 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashurova, N.Kh.; Yakubov, K.G.

1993-11-01

The author studied complexation reactions of rhenium(V) and molybdenum(V) with a macrocyclic ligand 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet a). The authors found that in hydrohalic acid medium, the onium complexes [H{sub 2}(Tet a)][EOX{sub 5}] are formed, with E = Re, Mo; X = Cl, Br. Reactions of [EOX{sub 5}]{sup 2{minus}} with (Tet a) in nitrometane yield complexes of molecular and cation types [EO(Tet a)Cl{sub 3}] and [EO(Tet a)Br]Br{sub 2}. Composition and structure of the obtained compounds are established by elemental analysis, conductometry, and mid- and far-IR spectroscopy.

Chemical composition of donor-acceptor complexes of hydroxyoxo(5,10,15,20-tetraphenylporphinato)molybdenum(V) with 3,5-dimethylpyrazole and equilibrium constants for their formation

NASA Astrophysics Data System (ADS)

Motorina, E. V.; Lomova, T. N.

2017-11-01

The results from a quantitative study of reactions between hydroxyoxo(5,10,15,20-tetraphenylporphinato)molybdenum(V) (O=Mo(OH)TPP) and 3,5-dimethylpyrazole, a biologically active base, in toluene are presented. The chemical structure and key parameters of intermediates and reaction products are determined by spectral means. The equilibrium constant ( K = 51.3 L/mol) is calculated and a full kinetic description of simple reactions that occur in this system during complex transformation is obtained. The prospect of using a mixed porphyrin-containing complex as a receptor for 3,5-dimethylpyrazole, a building block for alkaloids and pharmaceutical preparations, is substantiated.

Molecular orbital study of some eight-coordinate sulfur chelate complexes of molybdenum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, P.G.; Schultz, F.A.

1983-03-30

A number of molybdenum complexes involving the formal oxidation states Mo(IV) and Mo(V) have been studied by a self-consistent-field molecular orbital technique. All the complexes were of dodecahedral geometry and had eight sulfurs chelated to the central metal atom. In all, a series of five tetrakis complexes was studied, including the ligands dithiocarbamate (dtc), thioxanthate (txn), 1,1-dicyano-2,2-ethylenedithiolate (i-mnt), 1-cyano-1-carbethoxy-2,2-ethylenedithiolate (ced), and 1,1-dicarbethoxy-2,2-ethylenedithiolate (ded). The 4d orbitals were included on molybdenum, and the empty 3d levels on all sulfur atoms. The results show that the highest occupied molecular orbital in each case has over 90% metal d/sub xy/ character. Further, themore » energy of this orbital is linearly related to the reversible half-wave potentials for Mo(IV) ..-->.. Mo(V) and Mo(V) ..-->.. Mo(VI) oxidations of the complexes. A further irreversible oxidation observed experimentally also is closely related to the calculated energy levels. Relationships between the calculated results and Mo 3d/sub 5///sub 2/ X-ray photoelectron binding energies, EPR parameters, and charge-transfer absorption energies are discussed. Electrochemical and spectroscopic properties of these MoS/sub 8/ complexes can be understood in terms of a manifold of orbital energies that retain approximately constant spacings between one another and that move up or down in absolute energy in response to the charge donated or withdrawn by the ligands.« less

The alkaline earth intercalates of molybdenum disulfide

NASA Technical Reports Server (NTRS)

Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

1975-01-01

Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

The crystal structure of xanthine oxidoreductase during catalysis: Implications for reaction mechanism and enzyme inhibition

PubMed Central

Okamoto, Ken; Matsumoto, Koji; Hille, Russ; Eger, Bryan T.; Pai, Emil F.; Nishino, Takeshi

2004-01-01

Molybdenum is widely distributed in biology and is usually found as a mononuclear metal center in the active sites of many enzymes catalyzing oxygen atom transfer. The molybdenum hydroxylases are distinct from other biological systems catalyzing hydroxylation reactions in that the oxygen atom incorporated into the product is derived from water rather than molecular oxygen. Here, we present the crystal structure of the key intermediate in the hydroxylation reaction of xanthine oxidoreductase with a slow substrate, in which the carbon–oxygen bond of the product is formed, yet the product remains complexed to the molybdenum. This intermediate displays a stable broad charge–transfer band at ≈640 nm. The crystal structure of the complex indicates that the catalytically labile Mo—OH oxygen has formed a bond with a carbon atom of the substrate. In addition, the Mo⋕S group of the oxidized enzyme has become protonated to afford Mo—SH on reduction of the molybdenum center. In contrast to previous assignments, we find this last ligand at an equatorial position in the square-pyramidal metal coordination sphere, not the apical position. A water molecule usually seen in the active site of the enzyme is absent in the present structure, which probably accounts for the stability of this intermediate toward ligand displacement by hydroxide. PMID:15148401

Interplay between Organic-Organometallic Electrophores within Bis(cyclopentadienyl)Molybdenum Dithiolene Tetrathiafulvalene Complexes.

PubMed

Bellec, Nathalie; Vacher, Antoine; Barrière, Frédéric; Xu, Zijun; Roisnel, Thierry; Lorcy, Dominique

2015-05-18

Tetrathiafulvalenes (TTF) and bis(cyclopentadienyl) molybdenum dithiolene complexes, Cp2Mo(dithiolene) complexes, are known separately to act as good electron donor molecules. For an investigation of the interaction between both electrophores, two types of complexes were synthesized and characterized. The first type has one Cp2Mo fragment coordinated to one TTF dithiolate ligand, and the second type has one TTF bis(dithiolate) bridging two Cp2Mo fragments. Comparisons of the electrochemical properties of these complexes with those of models of each separate electrophore provide evidence for their mutual influence. All of these complexes act as very good electron donors with a first oxidation potential 430 mV lower than the tetrakis(methylthio)TTF. DFT calculations suggest that the HOMO of the neutral complex and the SOMO of the cation are delocalized across the whole TTF dithiolate ligand. The X-ray crystal structure analyses of the neutral and the mono-oxidized Cp2Mo(dithiolene)(bismethylthio)TTF complexes are consistent with the delocalized assignment of the highest occupied frontier molecular orbitals. UV-vis-NIR spectroelectrochemical investigations confirm this electronic delocalization within the TTF dithiolate ligand.

Effect of molybdenum ion implantation of the pitting corrosion of depleted uranium - 0.75 titanium alloy. (Reannouncement with new availability information). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, K.S.; Chang, F.; Levy, M.

1993-07-01

Pitting corrosion of molybdenum-ion-implanted, depleted uranium -0 75 Ti (DU -0 75 Ti) has been studied electrochemically in acidic, neutral, and alkaline solutions containing sodium chloride, and the results have been compared to those of the unimplanted DU -0 75 Ti. The data show that Mo implantation shifts the pitting potential of DU -0 75 Ti in the noble direction in acidic and alkaline solutions. In neutral 50 ppm Cl- solution, however, there is no beneficial effect of Mo implantation. Auger analysis studies show that before exposure to the solutions, all the molybdenum is in the oxide, which is approximatelymore » l000 A thick. After electrochemical scans in the acidic and alkaline chloride solutions, most of the Mo disappears from the oxide. However, no decrease in Mo concentration is found after exposure in neutral chloride solution. It is proposed that the implanted molybdenum dissolves in the acidic and alkaline solutions and forms simple or complex molybdates that inhibit pitting corrosion. The implanted molybdenum does not dissolve in the neutral chloride solution and inhibition does not occur.« less

Standard Method for Analyzing Gases in Titanium and Titanium Alloys. Standard Method for the Chemical Analysis of Titanium Alloys.

DTIC Science & Technology

1982-10-28

form a non- soluble complex. After filtering and burning the non-pure molybdenum trioxide is weighed. Ammonia water is used to dissolve the molybdenum...niobium and tantalum should use the methyl alcohol distillation - curcumin absorption luminosity 66 method for determination. II. The Methyl Alcohol...Distillation - Curcumin Absorption Luminosity Method 1. Summary of Method In a phosphorus sulfate medium, boron and methyl alcohol produce methyl borate

High-resolution molybdenum K-edge X-ray absorption spectroscopy analyzed with time-dependent density functional theory.

PubMed

Lima, Frederico A; Bjornsson, Ragnar; Weyhermüller, Thomas; Chandrasekaran, Perumalreddy; Glatzel, Pieter; Neese, Frank; DeBeer, Serena

2013-12-28

X-ray absorption spectroscopy (XAS) is a widely used experimental technique capable of selectively probing the local structure around an absorbing atomic species in molecules and materials. When applied to heavy elements, however, the quantitative interpretation can be challenging due to the intrinsic spectral broadening arising from the decrease in the core-hole lifetime. In this work we have used high-energy resolution fluorescence detected XAS (HERFD-XAS) to investigate a series of molybdenum complexes. The sharper spectral features obtained by HERFD-XAS measurements enable a clear assignment of the features present in the pre-edge region. Time-dependent density functional theory (TDDFT) has been previously shown to predict K-pre-edge XAS spectra of first row transition metal compounds with a reasonable degree of accuracy. Here we extend this approach to molybdenum K-edge HERFD-XAS and present the necessary calibration. Modern pure and hybrid functionals are utilized and relativistic effects are accounted for using either the Zeroth Order Regular Approximation (ZORA) or the second order Douglas-Kroll-Hess (DKH2) scalar relativistic approximations. We have found that both the predicted energies and intensities are in excellent agreement with experiment, independent of the functional used. The model chosen to account for relativistic effects also has little impact on the calculated spectra. This study provides an important calibration set for future applications of molybdenum HERFD-XAS to complex catalytic systems.

Evidence for the dissolution of molybdenum during tribocorrosion of CoCrMo hip implants in the presence of serum protein.

PubMed

Simoes, Thiago A; Bryant, Michael G; Brown, Andy P; Milne, Steven J; Ryan, Mary; Neville, Anne; Brydson, Rik

2016-11-01

We have characterized CoCrMo, Metal-on-Metal (MoM) implant, wear debris particles and their dissolution following cycling in a hip simulator, and have related the results to the tribocorrosion of synthetic wear debris produced by milling CoCrMo powders in solutions representative of environments in the human body. Importantly, we have employed a modified ICP-MS sample preparation procedure to measure the release of ions from CoCrMo alloys during wear simulation in different media; this involved use of nano-porous ultrafilters which allowed complete separation of particles from free ions and complexes in solution. As a result, we present a new perspective on the release of metal ions and formation of metal complexes from CoCrMo implants. The new methodology enables the mass balance of ions relative to complexes and particles during tribocorrosion in hip simulators to be determined. A much higher release of molybdenum ions relative to cobalt and chromium has been measured. The molybdenum dissolution was enhanced by the presence of bovine serum albumin (BSA), possibly due to the formation of metal-protein complexes. Overall, we believe that the results could have significant implications for the analysis and interpretation of metal ion levels in fluids extracted from hip arthroplasty patients; we suggest that metal levels, including molybdenum, be analysed in these fluids using the protocol described here. We have developed an important new protocol for the analysis of metal ion levels in fluids extracted from hip implant patients and also hip simulators. Using this procedure, we present a new perspective on the release of metal ions from CoCrMo alloy implants, revealing significantly lower levels of metal ion release during tribocorrosion in hip simulators than previously thought, combined with the release of much higher percentages of molybdenum ions relative to cobalt and chromium. This work is of relevance, both from the perspective of the fundamental science and study of metal-protein interactions, enabling understanding of the ongoing problem associated with the biotribocorrosion and the link to inflammation associated with Metal-on-Metal (MoM) hip implants made from CoCrMo alloys. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A structure-based catalytic mechanism for the xanthine oxidase family of molybdenum enzymes.

PubMed Central

Huber, R; Hof, P; Duarte, R O; Moura, J J; Moura, I; Liu, M Y; LeGall, J; Hille, R; Archer, M; Romão, M J

1996-01-01

The crystal structure of the xanthine oxidase-related molybdenum-iron protein aldehyde oxido-reductase from the sulfate reducing anaerobic Gram-negative bacterium Desulfovibrio gigas (Mop) was analyzed in its desulfo-, sulfo-, oxidized, reduced, and alcohol-bound forms at 1.8-A resolution. In the sulfo-form the molybdenum molybdopterin cytosine dinucleotide cofactor has a dithiolene-bound fac-[Mo, = O, = S, ---(OH2)] substructure. Bound inhibitory isopropanol in the inner compartment of the substrate binding tunnel is a model for the Michaelis complex of the reaction with aldehydes (H-C = O,-R). The reaction is proposed to proceed by transfer of the molybdenum-bound water molecule as OH- after proton transfer to Glu-869 to the carbonyl carbon of the substrate in concert with hydride transfer to the sulfido group to generate [MoIV, = O, -SH, ---(O-C = O, -R)). Dissociation of the carboxylic acid product may be facilitated by transient binding of Glu-869 to the molybdenum. The metal-bound water is replenished from a chain of internal water molecules. A second alcohol binding site in the spacious outer compartment may cause the strong substrate inhibition observed. This compartment is the putative binding site of large inhibitors of xanthine oxidase. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:8799115

In vitro synthesis of the iron–molybdenum cofactor of nitrogenase from iron, sulfur, molybdenum, and homocitrate using purified proteins

PubMed Central

Curatti, Leonardo; Hernandez, Jose A.; Igarashi, Robert Y.; Soboh, Basem; Zhao, Dehua; Rubio, Luis M.

2007-01-01

Biological nitrogen fixation, the conversion of atmospheric N2 to NH3, is an essential process in the global biogeochemical cycle of nitrogen that supports life on Earth. Most of the biological nitrogen fixation is catalyzed by the molybdenum nitrogenase, which contains at its active site one of the most complex metal cofactors known to date, the iron–molybdenum cofactor (FeMo-co). FeMo-co is composed of 7Fe, 9S, Mo, R-homocitrate, and one unidentified light atom. Here we demonstrate the complete in vitro synthesis of FeMo-co from Fe2+, S2−, MoO42−, and R-homocitrate using only purified Nif proteins. This synthesis provides direct biochemical support to the current model of FeMo-co biosynthesis. A minimal in vitro system, containing NifB, NifEN, and NifH proteins, together with Fe2+, S2−, MoO42−, R-homocitrate, S-adenosyl methionine, and Mg-ATP, is sufficient for the synthesis of FeMo-co and the activation of apo-dinitrogenase under anaerobic-reducing conditions. This in vitro system also provides a biochemical approach to further study the function of accessory proteins involved in nitrogenase maturation (as shown here for NifX and NafY). The significance of these findings in the understanding of the complete FeMo-co biosynthetic pathway and in the study of other complex Fe-S cluster biosyntheses is discussed. PMID:17978192

Low-temperature neutron structure determinations of a series of scorpionate complexes of molybdenum containing B sbnd H sbnd Mo agostic bonds

NASA Astrophysics Data System (ADS)

Piccoli, Paula M. B.; Cowan, John A.; Schultz, Arthur J.; Koetzle, Thomas F.; Yap, Glenn P. A.; Trofimenko, Swiatoslaw

2008-11-01

The structures of four dihydrobis(pyrazol-1-yl)borate (Bp) complexes of molybdenum have been determined at low temperature by single crystal neutron diffraction in order to accurately characterize the three-center B sbnd H sbnd Mo agostic bonding. The B sbnd H1A (agostic) distance is found to be elongated by about 0.05-0.08 Å compared to the B sbnd H1B distance (not agostically bound to the metal center). This systematic study of a series of molecules with different substituents on the Bp ligand permits us to examine the effects of electronic and steric factors on the overall structure and bonding, and particularly on the agostic bond. It is observed that a closer approach of H1A to Mo leads to a longer trans-Mo sbnd CO bond distance, analogous to the trans hydride structural effect in hydride complexes. In addition Fenske-Hall calculations were performed on these complexes, and the results are reported herein.

Recent advances in the development of alkyne metathesis catalysts

PubMed Central

Wu, Xian

2011-01-01

Summary The number of well-defined molybdenum and tungsten alkylidyne complexes that are able to catalyze alkyne metathesis reactions efficiently has been significantly expanded in recent years.The latest developments in this field featuring highly active imidazolin-2-iminato- and silanolate–alkylidyne complexes are outlined in this review. PMID:21286398

Structure of the molybdenum site in YedY, a sulfite oxidase homologue from Escherichia coli.

PubMed

Havelius, Kajsa G V; Reschke, Stefan; Horn, Sebastian; Döring, Alexander; Niks, Dimitri; Hille, Russ; Schulzke, Carola; Leimkühler, Silke; Haumann, Michael

2011-02-07

YedY from Escherichia coli is a new member of the sulfite oxidase family of molybdenum cofactor (Moco)-containing oxidoreductases. We investigated the atomic structure of the molybdenum site in YedY by X-ray absorption spectroscopy, in comparison to human sulfite oxidase (hSO) and to a Mo(IV) model complex. The K-edge energy was indicative of Mo(V) in YedY, in agreement with X- and Q-band electron paramagnetic resonance results, whereas the hSO protein contained Mo(VI). In YedY and hSO, molybdenum is coordinated by two sulfur ligands from the molybdopterin ligand of the Moco, one thiolate sulfur of a cysteine (average Mo-S bond length of ∼2.4 Å), and one (axial) oxo ligand (Mo═O, ∼1.7 Å). hSO contained a second oxo group at Mo as expected, but in YedY, two species in about a 1:1 ratio were found at the active site, corresponding to an equatorial Mo-OH bond (∼2.1 Å) or possibly to a shorter Mo-O(-) bond. Yet another oxygen (or nitrogen) at a ∼2.6 Å distance to Mo in YedY was identified, which could originate from a water molecule in the substrate binding cavity or from an amino acid residue close to the molybdenum site, i.e., Glu104, that is replaced by a glycine in hSO, or Asn45. The addition of the poor substrate dimethyl sulfoxide to YedY left the molybdenum coordination unchanged at high pH. In contrast, we found indications that the better substrate trimethylamine N-oxide and the substrate analogue acetone were bound at a ∼2.6 Å distance to the molybdenum, presumably replacing the equatorial oxygen ligand. These findings were used to interpret the recent crystal structure of YedY and bear implications for its catalytic mechanism.

Petrology, composition, and age of intrusive rocks associated with the Quartz Hill molybdenite deposit, southeastern Alaska.

USGS Publications Warehouse

Hudson, T.; Smith, James G.; Elliott, R.L.

1979-01-01

A large porphyry molybdenum deposit (Quartz Hill deposit) was recently discovered in the heart of the Coast Range batholithic complex about 70 km E of Ketchikan, SE Alaska. Intrusive rocks associated with the mineral deposit form two composite epizonal to hypabyssal stocks and many dikes in country rocks. All observed metallization and alteration is within the Quartz Hill stock. Molybdenite forms fracture coatings and occurs in veins with quartz. Alteration is widespread and includes development of secondary quartz, pyrite, K-feldspar, biotite, white mica, chlorite, and zeolite. Field relations indicate that the stocks were emplaced after regional uplift and erosion of the Coast Range batholithic complex, and K-Ar data show that intrusion and alteration took place in late Oligocene time, about 27 to 30 Ma ago. Data from the Ketchikan quadrangle indicate that porphyry molybdenum metallization in the Coast Range batholithic complex is associated with regionally extensive but spotty, middle Tertiary or younger, felsic magmatism. -from Authors

The use of XAFS to determine the nature of interaction of iron and molybdenum metal salts within PS-b-P2VP micelles.

PubMed

Riskin, Alexander; Beale, Andrew M; Boyen, Hans-Gerhard; Vantomme, André; Hardy, An; Van Bael, Marlies K

2013-02-07

The poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) micelle route is a well established method for the preparation of bimetallic nanoparticles used for the catalysis of carbon nanotubes and other applications like ultrahigh density storage devices, yet to date no information is available concerning the internal structure of the P2VP-metal salt complex. For the first time, XAFS measurements were performed on micelles loaded with either iron(III) chloride or molybdenum(V) chloride and a combination of both. Analysis of the data revealed that iron is tetrahedrally coordinated within the core, whereas molybdenum is octahedrally coordinated in the pure loaded micelles and trigonally coordinated in the mixed micelles. For the bimetallic samples, analysis of the Fe and Mo K-edge data revealed the existence of an interaction between iron and molybdenum. This approach to obtain detailed structural information during the preparation of these catalyst samples will allow for a deeper understanding of the effects of structure on the function of catalysts used for CNT growth i.e. to explain differences in yield as well as potentially providing a deeper understanding of the CNT growth mechanism itself.

Interaction of Tryptophane and Phenylalanine with Cadmium and Molybdenum Ferrocyanides and Its Implications in Chemical Evolution and Origins of Life.

NASA Astrophysics Data System (ADS)

Tewari, Brij

2016-07-01

Insoluble metal hexacyanoferrate(II) complexes could have concentrated biomonomers from dilute prebiotic soup during course of chemical evolution and origin of life or primitive earth. In the light of above hypothesis, adsorption of tryptophane and phenylalanine was studied on cadmium and molybdenum ferrocyanides at neutral pH (7.0 ± 0.01) and at a temperature of 30 ± 1º C. Interaction of amino acids with metal ferrocyanides are found to be maximum at neutral pH. Neutral pH is chosen for the adsorption studies because most of the reactions in biological systems taken place at neutral pH range. Adsorption trend follow Langmuir isotherm model. The Langmuir constants b and Qo were calculated at neutral pH, tryptophane was found to more adsorbed than phenylalanine on both metal ferrocyanides studied. Molybdenum ferrocyanides studied. Molybdenum ferrocyanides was found to have more uptake capacity for both adsorbates than cadmium ferrocyanides. The present study suggests that metal ferrocyanides might have played a role in the stabilization of biomolecules through their surface activity during course of chemical solution and origins of life on primitive earth.

Prospects of molybdenum and rhenium octahedral cluster complexes as X-ray contrast agents.

PubMed

Krasilnikova, Anna A; Shestopalov, Michael A; Brylev, Konstantin A; Kirilova, Irina A; Khripko, Olga P; Zubareva, Kristina E; Khripko, Yuri I; Podorognaya, Valentina T; Shestopalova, Lidiya V; Fedorov, Vladimir E; Mironov, Yuri V

2015-03-01

Investigation of new X-ray contrast media for radiography is an important field of science since discovering of X-rays in 1895. Despite the wide diversity of available X-ray contrast media the toxicity, especially nephrotoxicity, is still a big problem to be solved. The octahedral metal-cluster complexes of the general formula [{M6Q8}L6] can be considered as quite promising candidates for the role of new radiocontrast media due to the high local concentration of heavy elements, high tuning ability of ligand environment and low toxicity. To exemplify this, the X-ray computed tomography experiments for the first time were carried out on some octahedral cluster complexes of molybdenum and rhenium. Based on the obtained data it was proposed to investigate the toxicological proprieties of cluster complex Na2H8[{Re6Se8}(P(CH2CH2CONH2)(CH2CH2COO)2)6]. Observed low cytotoxic and acute toxic effects along with rapid renal excretion of the cluster complex evidence its perspective as an X-ray contrast media for radiography. Copyright © 2014 Elsevier Inc. All rights reserved.

Pulsed EPR investigations of systems modeling molybdenum enzymes: hyperfine and quadrupole parameters of oxo-17O in [Mo 17O(SPh)4]-.

PubMed

Astashkin, Andrei V; Neese, Frank; Raitsimring, Arnold M; Cooney, J Jon A; Bultman, Eric; Enemark, John H

2005-11-30

Ka band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole (nqi) interaction parameters for the oxo-17O ligand in [Mo 17O(SPh)4]-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-17O is much smaller than the values of approximately 20-40 MHz typical for the 17O nucleus of an equatorial OH(2) ligand in molybdenum enzymes. The 17O nqi parameter (e2qQ/h = 1.45 MHz, eta approximately = 0) is the first to be obtained for an oxo group in a metal complex. The parameters of the oxo-17O ligand, as well as other magnetic resonance parameters of [Mo 17O(SPh)4]- predicted by quasi-relativistic DFT calculations, were in good agreement with those obtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that the SOMO is almost entirely molybdenum d(xy) and sulfur p, while the spin density on the oxo-17O is negative, determined by spin polarization mechanisms. The results of this work will enable direct experimental identification of the oxo ligand in a variety of chemical and biological systems.

The Molybdenum Cofactor Biosynthesis Network: In vivo Protein-Protein Interactions of an Actin Associated Multi-Protein Complex.

PubMed

Kaufholdt, David; Baillie, Christin-Kirsty; Meinen, Rieke; Mendel, Ralf R; Hänsch, Robert

2017-01-01

Survival of plants and nearly all organisms depends on the pterin based molybdenum cofactor (Moco) as well as its effective biosynthesis and insertion into apo-enzymes. To this end, both the central Moco biosynthesis enzymes are characterized and the conserved four-step reaction pathway for Moco biosynthesis is well-understood. However, protection mechanisms to prevent degradation during biosynthesis as well as transfer of the highly oxygen sensitive Moco and its intermediates are not fully enlightened. The formation of protein complexes involving transient protein-protein interactions is an efficient strategy for protected metabolic channelling of sensitive molecules. In this review, Moco biosynthesis and allocation network is presented and discussed. This network was intensively studied based on two in vivo interaction methods: bimolecular fluorescence complementation (BiFC) and split-luciferase. Whereas BiFC allows localisation of interacting partners, split-luciferase assay determines interaction strengths in vivo . Results demonstrate (i) interaction of Cnx2 and Cnx3 within the mitochondria and (ii) assembly of a biosynthesis complex including the cytosolic enzymes Cnx5, Cnx6, Cnx7, and Cnx1, which enables a protected transfer of intermediates. The whole complex is associated with actin filaments via Cnx1 as anchor protein. After biosynthesis, Moco needs to be handed over to the specific apo-enzymes. A potential pathway was discovered. Molybdenum-containing enzymes of the sulphite oxidase family interact directly with Cnx1. In contrast, the xanthine oxidoreductase family acquires Moco indirectly via a Moco binding protein (MoBP2) and Moco sulphurase ABA3. In summary, the uncovered interaction matrix enables an efficient transfer for intermediate and product protection via micro-compartmentation.

Effects of copper sulfate supplement on growth, tissue concentration, and ruminal solubilities of molybdenum and copper in sheep fed low and high molybdenum diets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivan, M.; Veira, D.M.

1985-01-01

Each of four groups of six wethers were fed one of a low molybdenum, high molybdenum, high molybdenum plus copper sulfate, or high molybdenum plus copper sulfate corn silage-based diet for ad libitum intake for 221 days. Average daily gains and ratios of feed/gain were depressed for the high molybdenum diet as compared with the low molybdenum diet suggesting molybdenum toxicity in sheep fed the high molybdenum diet. This was alleviated partly by the copper sulfate supplement. The supplement also decreased solubility of both copper and molybdenum in the rumen but had no effect on copper concentration in blood plasma.more » Concentration of molybdenum was higher in both liver and kidney in sheep fed high-molybdenum diets as compared with low-molybdenum diets. Copper concentration was higher in kidneys of sheep fed high-molybdenum diets, but no difference was significant in liver copper between sheep fed diets high or low in molybdenum.« less

Cyanide-limited complexation of molybdenum(III): synthesis of octahedral [Mo(CN)(6)](3-) and cyano-bridged [Mo(2)(CN)(11)](5-).

PubMed

Beauvais, Laurance G; Long, Jeffrey R

2002-03-13

Octahedral coordination of molybdenum(III) is achieved by limiting the amount of cyanide available upon complex formation. Reaction of Mo(CF(3)SO(3))(3) with LiCN in DMF affords Li(3)[Mo(CN)(6)] x 6DMF (1), featuring the previously unknown octahedral complex [Mo(CN)(6)](3-). The complex exhibits a room-temperature moment of mu(eff) = 3.80 mu(B), and assignment of its absorption bands leads to the ligand field parameters Delta(o) = 24800 cm(-1) and B = 247 cm(-1). Further restricting the available cyanide in a reaction between Mo(CF(3)SO(3))(3) and (Et(4)N)CN in DMF, followed by recrystallization from DMF/MeOH, yields (Et(4)N)(5)[Mo(2)(CN)(11)] x 2DMF x 2MeOH (2). The dinuclear [Mo(2)(CN)(11)](5-) complex featured therein contains two octahedrally coordinated Mo(III) centers spanned by a bridging cyanide ligand. A fit to the magnetic susceptibility data for 2, gives J = -113 cm(-1) and g = 2.33, representing the strongest antiferromagnetic coupling yet observed through a cyanide bridge. Efforts to incorporate these new complexes in magnetic Prussian blue-type solids are ongoing.

Oxide strengthened molybdenum-rhenium alloy

DOEpatents

Bianco, Robert; Buckman, Jr., R. William

2000-01-01

Provided is a method of making an ODS molybdenum-rhenium alloy which includes the steps of: (a) forming a slurry containing molybdenum oxide and a metal salt dispersed in an aqueous medium, the metal salt being selected from nitrates or acetates of lanthanum, cerium or thorium; (b) heating the slurry in the presence of hydrogen to form a molybdenum powder comprising molybdenum and an oxide of the metal salt; (c) mixing rhenium powder with the molybdenum powder to form a molybdenum-rhenium powder; (d) pressing the molybdenum-rhenium powder to form a molybdenum-rhenium compact; (e) sintering the molybdenum-rhenium compact in hydrogen or under a vacuum to form a molybdenum-rhenium ingot; and (f) compacting the molybdenum-rhenium ingot to reduce the cross-sectional area of the molybdenum-rhenium ingot and form a molybdenum-rhenium alloy containing said metal oxide. The present invention also provides an ODS molybdenum-rhenium alloy made by the method. A preferred Mo--Re-ODS alloy contains 7-14 weight % rhenium and 2-4 volume % lanthanum oxide.

Viking Helmet Corroles: Activating Inert Oxidometal Corroles.

PubMed

Schweyen, Peter; Brandhorst, Kai; Hoffmann, Martin; Wolfram, Benedikt; Zaretzke, Marc-Kevin; Bröring, Martin

2017-10-09

Chemically inert oxidometal(V) corrols of molybdenum and rhenium undergo clean ligand-exchange reactions upon the action of SiCl 4 . The resulting dichlorido complexes show trigonal prismatic coordination of the metal ion with the chlorine atoms residing in a cis configuration, and were studied by optical and resonance spectroscopy as well as DFT calculations. In situ reactivity studies with carbon nucleophiles indicate high reactivity for chlorine replacement. Treatment with sodium cyclopentadienide paves the way to robust molybdenum corrolocene half-sandwich complexes. These organometallic compounds are the first corrole species that stabilize an air-stable and diamagnetic low spin d 2 -Mo IV center. Structural, spectroelectrochemical, and chemical investigations prove a reversible Mo IV /Mo V redox couple close to the Fc/Fc + potential for these systems. The high stability of the compounds in both redox states calls for future applications in catalysis and as redox switch. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional microporous materials of metal carboxylate: Gas-occlusion properties and catalytic activities

NASA Astrophysics Data System (ADS)

Mori, Wasuke; Sato, Tomohiko; Ohmura, Tesushi; Nozaki Kato, Chika; Takei, Tohru

2005-08-01

Copper(II) terephthalate is the first transition metal complex found capable of adsorbing gases. This complex has opened the new field of adsorbent complex chemistry. It is recognized as the lead complex in the construction of microporous complexes. This specific system has been expanded to a systematic series of derivatives of other isomorphous transition metals, molybdenum(II), ruthenium(II, III), and rhodium(II). These complexes with open frameworks are widely recognized as very useful materials for applications to catalysis, separation at molecular level, and gas storage.

The Myszkow porphyry copper-molybdenum deposit, Poland

USGS Publications Warehouse

Chaffee, M.A.; Eppinger, R.G.; Lason, K.; Slosarz, J.; Podemski, M.

1994-01-01

The porphyry copper-molybdenum deposit at Myszkow, south-central Poland, lies in the Cracow-Silesian orogenic belt, in the vicinity of a Paleozoic boundary between two tectonic plates. The deposit is hosted in a complex that includes early Paleozoic metasedimentary rocks intruded in the late Paleozoic by a predominantly granodioritic pluton. This deposit exhibits many features that are typical of porphyry copper deposits associated with calc-alkaline intrusive rocks, including ore- and alteration-mineral suites, zoning of ore and alteration minerals, fluid-inclusion chemistry, tectonic setting, and structural style of veining. Unusual features of the Myszkow deposit include high concentrations of tungsten and the late Paleozoic (Variscan) age. -Authors

Full-potential theoretical investigations of electron inelastic mean free paths and extended x-ray absorption fine structure in molybdenum.

PubMed

Chantler, C T; Bourke, J D

2014-04-09

X-ray absorption fine structure (XAFS) spectroscopy is one of the most robust, adaptable, and widely used structural analysis tools available for a range of material classes from bulk solids to aqueous solutions and active catalytic structures. Recent developments in XAFS theory have enabled high-accuracy calculations of spectra over an extended energy range using full-potential cluster modelling, and have demonstrated particular sensitivity in XAFS to a fundamental electron transport property-the electron inelastic mean free path (IMFP). We develop electron IMFP theory using a unique hybrid model that simultaneously incorporates second-order excitation losses, while precisely accounting for optical transitions dictated by the complex band structure of the solid. These advances are coupled with improved XAFS modelling to determine wide energy-range absorption spectra for molybdenum. This represents a critical test case of the theory, as measurements of molybdenum K-edge XAFS represent the most accurate determinations of XAFS spectra for any material. We find that we are able to reproduce an extended range of oscillatory structure in the absorption spectrum, and demonstrate a first-time theoretical determination of the absorption coefficient of molybdenum over the entire extended XAFS range utilizing a full-potential cluster model.

Sulphur shuttling across a chaperone during molybdenum cofactor maturation.

PubMed

Arnoux, Pascal; Ruppelt, Christian; Oudouhou, Flore; Lavergne, Jérôme; Siponen, Marina I; Toci, René; Mendel, Ralf R; Bittner, Florian; Pignol, David; Magalon, Axel; Walburger, Anne

2015-02-04

Formate dehydrogenases (FDHs) are of interest as they are natural catalysts that sequester atmospheric CO2, generating reduced carbon compounds with possible uses as fuel. FDHs activity in Escherichia coli strictly requires the sulphurtransferase EcFdhD, which likely transfers sulphur from IscS to the molybdenum cofactor (Mo-bisPGD) of FDHs. Here we show that EcFdhD binds Mo-bisPGD in vivo and has submicromolar affinity for GDP-used as a surrogate of the molybdenum cofactor's nucleotide moieties. The crystal structure of EcFdhD in complex with GDP shows two symmetrical binding sites located on the same face of the dimer. These binding sites are connected via a tunnel-like cavity to the opposite face of the dimer where two dynamic loops, each harbouring two functionally important cysteine residues, are present. On the basis of structure-guided mutagenesis, we propose a model for the sulphuration mechanism of Mo-bisPGD where the sulphur atom shuttles across the chaperone dimer.

Sulphur shuttling across a chaperone during molybdenum cofactor maturation

NASA Astrophysics Data System (ADS)

Arnoux, Pascal; Ruppelt, Christian; Oudouhou, Flore; Lavergne, Jérôme; Siponen, Marina I.; Toci, René; Mendel, Ralf R.; Bittner, Florian; Pignol, David; Magalon, Axel; Walburger, Anne

2015-02-01

Formate dehydrogenases (FDHs) are of interest as they are natural catalysts that sequester atmospheric CO2, generating reduced carbon compounds with possible uses as fuel. FDHs activity in Escherichia coli strictly requires the sulphurtransferase EcFdhD, which likely transfers sulphur from IscS to the molybdenum cofactor (Mo-bisPGD) of FDHs. Here we show that EcFdhD binds Mo-bisPGD in vivo and has submicromolar affinity for GDP—used as a surrogate of the molybdenum cofactor’s nucleotide moieties. The crystal structure of EcFdhD in complex with GDP shows two symmetrical binding sites located on the same face of the dimer. These binding sites are connected via a tunnel-like cavity to the opposite face of the dimer where two dynamic loops, each harbouring two functionally important cysteine residues, are present. On the basis of structure-guided mutagenesis, we propose a model for the sulphuration mechanism of Mo-bisPGD where the sulphur atom shuttles across the chaperone dimer.

Amorphous nickel-cobalt complexes hybridized with 1T-phase molybdenum disulfide via hydrazine-induced phase transformation for water splitting

NASA Astrophysics Data System (ADS)

Li, Haoyi; Chen, Shuangming; Jia, Xiaofan; Xu, Biao; Lin, Haifeng; Yang, Haozhou; Song, Li; Wang, Xun

2017-05-01

Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm-2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec-1. Moreover, we achieve 10 mA cm-2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2.

Evaluating molecular cobalt complexes for the conversion of N2 to NH3.

PubMed

Del Castillo, Trevor J; Thompson, Niklas B; Suess, Daniel L M; Ung, Gaël; Peters, Jonas C

2015-10-05

Well-defined molecular catalysts for the reduction of N2 to NH3 with protons and electrons remain very rare despite decades of interest and are currently limited to systems featuring molybdenum or iron. This report details the synthesis of a molecular cobalt complex that generates superstoichiometric yields of NH3 (>200% NH3 per Co-N2 precursor) via the direct reduction of N2 with protons and electrons. While the NH3 yields reported herein are modest by comparison to those of previously described iron and molybdenum systems, they intimate that other metals are likely to be viable as molecular N2 reduction catalysts. Additionally, a comparison of the featured tris(phosphine)borane Co-N2 complex with structurally related Co-N2 and Fe-N2 species shows how remarkably sensitive the N2 reduction performance of potential precatalysts is. These studies enable consideration of the structural and electronic effects that are likely relevant to N2 conversion activity, including the π basicity, charge state, and geometric flexibility.

Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys

NASA Technical Reports Server (NTRS)

Klopp, W. D.; Witzke, W. R.

1972-01-01

A study of molybdenum and three dilute molybdenum-rhenium alloys was undertaken to determine the effects of rhenium on the low temperature ductility and other mechanical properties of molybdenum. Alloys containing 3.9, 5.9, and 7.7 atomic percent rhenium exhibited lower ductile-brittle transition temperatures than did the unalloyed molybdenum. The maximum improvement in the annealed condition was observed for molybdenum - 7.7 rhenium, which had a ductile-brittle transition temperature approximately 200 C (360 F) lower than that for unalloyed molybdenum. Rhenium additions also increased the low and high temperature tensile strengths and the high temperature creep strength of molybdenum. The mechanical behavior of dilute molybdenum-rhenium alloys is similar to that observed for dilute tungsten-rhenium alloys.

Molybdenum in the environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jawell, W.M.; Page, A.L.; Elseewi, A.A.

1980-01-01

While molybdenum is an essential element for both plants and animals, it becomes toxic above certain critical levels. Reviewed are the natural supply of molybdenum in the environment. The molybdenum cycle, the importance of molybdenum in industry and agriculture, and potential hazards that may occur when excessive levels of molybdenum occur in the environment. Although the potential of molybdenum toxicity to humans and non-ruminant animals appears to be low, the enrichment of the environment with molybdenum from modern mining, agricultural, and industrial activities has potentially hazardous implications for ruminant animal health.

Molybdenum in the environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarrell, W.M.; Page, A.L.; Elseewi, A.A.

1980-01-01

While molybdenum is an essential element for both plants and animals, it becomes toxic above certain critical levels. Reviewed are the natural supply of molybdenum in the environment, the molybdenum cycle, the importance of molybdenum in industry and agriculture, and potential hazards that may occur when excessive levels of molybdenum occur in the environment. Although the potential of molybdenum toxicity to humans and non-ruminant animals appears to be low, the enrichment of the environment with molybdenum from modern mining, agricultural, and industrial activities has potentially hazardous implications for ruminant animal health. (3 graphs, numerous references, 16 tables)

Vapor deposition of molybdenum oxide using bis(ethylbenzene) molybdenum and water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drake, Tasha L.; Stair, Peter C., E-mail: pstair@u.northwestern.edu

2016-09-15

Three molybdenum precursors—bis(acetylacetonate) dioxomolybdenum, molybdenum isopropoxide, and bis(ethylbenzene) molybdenum—were tested for molybdenum oxide vapor deposition. Quartz crystal microbalance studies were performed to monitor growth. Molybdenum isopropoxide and bis(ethylbenzene) molybdenum achieved linear growth rates 0.01 and 0.08 Å/cycle, respectively, using atomic layer deposition techniques. Negligible MoO{sub x} growth was observed on alumina powder using molybdenum isopropoxide, as determined by inductively coupled plasma optical emission spectroscopy. Bis(ethylbenzene) molybdenum achieved loadings of 0.5, 1.1, and 1.9 Mo/nm{sup 2} on alumina powder after one, two, and five cycles, respectively, using atomic layer deposition techniques. The growth window for bis(ethylbenzene) molybdenum is 135–150 °C. An alternative pulsingmore » strategy was also developed for bis(ethylbenzene) molybdenum that results in higher growth rates in less time compared to atomic layer deposition techniques. The outlined process serves as a methodology for depositing molybdenum oxide for catalytic applications. All as-deposited materials undergo further calcination prior to characterization and testing.« less

Complex-formation between reduced xanthine oxidase and purine substrates demonstrated by electron paramagnetic resonance

PubMed Central

Pick, Frances M.; Bray, R. C.

1969-01-01

The origin of the Rapid molybdenum electron-paramagnetic-resonance signals, which are obtained on reducing xanthine oxidase with purine or with xanthine, and whose parameters were measured by Bray & Vänngård (1969), was studied. It is concluded that these signals represent complexes of reduced enzyme with substrate molecules. Xanthine forms one complex at high concentrations and a different one at low concentrations. Purine forms a complex indistinguishable from the low-concentration xanthine complex. There are indications that some other substrates also form complexes, but uric acid, a reaction product, does not appear to do so. The possible significance of the complexes in the catalytic cycle of the enzyme is discussed and it is suggested that they represent substrate molecules bound at the reduced active site, waiting their turn to react there, when the enzyme has been reoxidized. Support for this role for the complexes was deduced from experiments in which frozen samples of enzyme–xanthine mixtures, prepared by the rapid-freezing method, were warmed until the signals began to change. Under these conditions an increase in amplitude of the Very Rapid signal took place. Data bearing on the origin of the Slow molybdenum signal are also discussed. This signal disappears only slowly in the presence of oxygen, and its appearance rate is unaffected by change in the concentration of dithionite. It is concluded that, like other signals from the enzyme, it is due to Mov but that a slow change of ligand takes place before it is seen. The Slow species, like the Rapid, seems capable of forming complexes with purines. PMID:4310056

Determination of small amounts of molybdenum in tungsten and molybdenum ores

USGS Publications Warehouse

Grimaldi, F.S.; Wells, R.C.

1943-01-01

A rapid method has been developed for the determination of small amounts of molybdenum in tungsten and molybdenum ores. After removing iron and other major constituents the molybdenum thiocyanate color is developed in water-acetone solutions, using ammonium citrate to eliminate the interference of tungsten. Comparison is made by titrating a blank with a standard molybdenum solution. Aliquots are adjusted to deal with amounts of molybdenum ranging from 0.01 to 1.30 mg.

Thermoinduced laser-assisted deposition of molybdenum from aqueous solutions

NASA Astrophysics Data System (ADS)

Kochemirovsky, Vladimir V.; Logunov, Lev S.; Zhigley, Elvira S.; Baranauskaite, Valeriia

2015-05-01

Local molybdenum deposit obtainment is promising for micro thermocouples creation on dielectric surfaces. This paper is dedicated to development of method of laser-induced molybdenum deposition from water-based solution of inorganic salt on Sitall st-50 and glass dielectric substrates, as well as research of solution composition, pH and substrate optical properties influence on result of laser-induced molybdenum deposition from solution. It was shown that depending on dielectric substrate type, as a result of laser-induced deposition metallic molybdenum or molybdenum dioxide deposit forms: molybdenum dioxide deposits in case of optically clear substrate and metallic molybdenum deposits in case of opaque glass-ceramics. While modelling interim case via using clouded glass, mixture of molybdenum and its oxide was successfully obtained.

A Study of Energy Conversion Devices Using Photoactive Organometallic Electrocatalysts.

DTIC Science & Technology

1986-05-23

arylisocyanide complexes confined to polymeric thin films in solar energy conversion systems . The chemical systems of interest were chromium...The goals of the project then became threefold: 1) examine the thermo- dynamics an- ’ kinetics of charge transfer in the systems in which we had shown...complexes confined to polymeric thin films in solar energy conversion systems . The chemical systems of interest were chromium, molybdenum and

Amorphous nickel-cobalt complexes hybridized with 1T-phase molybdenum disulfide via hydrazine-induced phase transformation for water splitting

PubMed Central

Li, Haoyi; Chen, Shuangming; Jia, Xiaofan; Xu, Biao; Lin, Haifeng; Yang, Haozhou; Song, Li; Wang, Xun

2017-01-01

Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm−2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec−1. Moreover, we achieve 10 mA cm−2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2. PMID:28485395

Synthesis of hexavalent molybdenum formo- and aceto-hydroxamates and deferoxamine via liquid-liquid metal partitioning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breshears, Andrew T.; Brown, M. Alex; Bloom, Ira

We report a new method of crystal growth and synthesis based on liquid-liquid partitioning that allows for isolation and in-depth characterization of molybdenyl bis(formohydroxamate), Mo-FHA, molybdenyl bis(acetohydroxamate), Mo-AHA, and molybdenyl deferoxamine, Mo-DFO, for the first time. This novel approach affords shorter crystal growth time (hourly timeframe) without sacrificing crystal size or integrity when other methods of crystallization were unsuccessful. All three Mo complexes are characterized in solution via FTIR, NMR, UV-vis, and EXAFS spectroscopy. Mo-AHA and Mo-FHA structures are resolved by single crystal X-ray diffraction. Using the molybdenyl hydroxamate structural information, the speciation of Mo in a siderophore complex (Mo-DFO)more » is determined via complimentary spectroscopic methods and confirmed by DFT calculations. ESI-MS verifies that a complex of 1:1 molybdenum to deferoxamine is present in solution. Additionally, the Mo solution speciation in the precursor organic phase, MoO2(NO3)2HEH[EHP]2 (where HEH[EHP] is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), is characterized by FTIR and EXAFS spectroscopy as well as DFT calculations.« less

Monoanionic molybdenum and tungsten tris(dithiolene) complexes: a multifrequency EPR study.

PubMed

Sproules, Stephen; Banerjee, Priyabrata; Weyhermüller, Thomas; Yan, Yong; Donahue, James P; Wieghardt, Karl

2011-08-01

Numerous Mo and W tris(dithiolene) complexes in varying redox states have been prepared and representative examples characterized crystallographically: [M(S(2)C(2)R(2))(3)](z) [M = Mo, R = Ph, z = 0 (1) or 1- (2); M = W, R = Ph, z = 0 (4) or 1- (5); R = CN, z = 2-, M = Mo (3) or W (6)]. Changes in dithiolene C-S and C-C bond lengths for 1 versus 2 and 4 versus 5 are indicative of ligand reduction. Trigonal twist angles (Θ) and dithiolene fold angles (α) increase and decrease, respectively, for 2 versus 1, 5 versus 4. Cyclic voltammetry reveals generally two reversible couples corresponding to 0/1- and 1-/2- reductions. The electronic structures of monoanionic molybdenum tris(dithiolene) complexes have been analyzed by multifrequency (S-, X-, Q-band) EPR spectroscopy. Spin-Hamiltonian parameters afforded by spectral simulation for each complex demonstrate the existence of two distinctive electronic structure types. The first is [Mo(IV)((A)L(3)(5-•))](1-) ((A)L = olefinic dithiolene, type A), which has the unpaired electron restricted to the tris(dithiolene) unit and is characterized by isotropic g-values and small molybdenum superhyperfine coupling. The second is formulated as [Mo(V)((B)L(3)(6-))](1-) ((B)L = aromatic dithiolene, type B) with spectra distinguished by a prominent g-anisotropy and hyperfine coupling consistent with the (d(z(2)))(1) paramagnet. The electronic structure disparity is also manifested in their electronic absorption spectra. The compound [W(bdt)(3)](1-) exhibits spin-Hamiltonian parameters similar to those of [Mo(bdt)(3)](1-) and thus is formulated as [W(V)((B)L(3)(6-))](1-). The EPR spectra of [W((A)L(3))](1-) display spin-Hamiltonian parameters that suggest their electronic structure is best represented by two resonance forms {[W(IV)((A)L(3)(5-•))](1-) ↔ [W(V)((A)L(3)(6-))](1-)}. The contrast with the corresponding [Mo(IV)((A)L(3)(5-•))](1-) complexes highlights tungsten's preference for higher oxidation states. © 2011 American Chemical Society

Al Kushaymiyah as a target for a Colorado-type molybdenite deposit

USGS Publications Warehouse

Theobald, P.K.

1971-01-01

The granitic complex in the vicinity of Al Kushaymiyah was singled out by Whitlow (19,69, 1969a, 1971), as one of the most promising areas for exploration in the Southern Wajd quadrangle (Jackson and others, 1962). He noted in particular the intensity of shattering and silicification of these potassium-rich granites, and the presence of unusual concentrations of tungsten , molybdenum, and tin in samples from the area. In the light of shield-wide compilations, this area again stands out as the principal geochemical anomaly for the three metals. The similarity of these unusual geologic and geochemical features to those of Colorado-type molybdenite deposits is striking and suggests that the Al Kushaymiyah provides a favorableenvironment to explore for a stockwork molybdenum deposit.

A molecular molybdenum-oxo catalyst for generating hydrogen from water.

PubMed

Karunadasa, Hemamala I; Chang, Christopher J; Long, Jeffrey R

2010-04-29

A growing awareness of issues related to anthropogenic climate change and an increase in global energy demand have made the search for viable carbon-neutral sources of renewable energy one of the most important challenges in science today. The chemical community is therefore seeking efficient and inexpensive catalysts that can produce large quantities of hydrogen gas from water. Here we identify a molybdenum-oxo complex that can catalytically generate gaseous hydrogen either from water at neutral pH or from sea water. This work shows that high-valency metal-oxo species can be used to create reduction catalysts that are robust and functional in water, a concept that has broad implications for the design of 'green' and sustainable chemistry cycles.

Molybdenum, molybdenum oxides, and their electrochemistry.

PubMed

Saji, Viswanathan S; Lee, Chi-Woo

2012-07-01

The electrochemical behaviors of molybdenum and its oxides, both in bulk and thin film dimensions, are critical because of their widespread applications in steels, electrocatalysts, electrochromic materials, batteries, sensors, and solar cells. An important area of current interest is electrodeposited CIGS-based solar cells where a molybdenum/glass electrode forms the back contact. Surprisingly, the basic electrochemistry of molybdenum and its oxides has not been reviewed with due attention. In this Review, we assess the scattered information. The potential and pH dependent active, passive, and transpassive behaviors of molybdenum in aqueous media are explained. The major surface oxide species observed, reversible redox transitions of the surface oxides, pseudocapacitance and catalytic reduction are discussed along with carefully conducted experimental results on a typical molybdenum glass back contact employed in CIGS-based solar cells. The applications of molybdenum oxides and the electrodeposition of molybdenum are briefly reviewed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongfen, E-mail: wanghongfen11@163.com; Wang, Zhiqi; Chen, Shougang

Molybdenum carbides with surfactants as carbon sources were prepared using the carbothermal reduction of the appropriate precursors (molybdenum oxides deposited on surfactant micelles) at 1023 K under hydrogen gas. The carburized products were characterized using scanning electron microscopy (SEM), X-ray diffraction and BET surface area measurements. From the SEM images, hollow microspherical and rod-like molybdenum carbides were observed. X-ray diffraction patterns showed that the annealing time of carburization had a large effect on the conversion of molybdenum oxides to molybdenum carbides. And BET surface area measurements indicated that the difference of carbon sources brought a big difference in specific surfacemore » areas of molybdenum carbides. - Graphical abstract: Molybdenum carbides having hollow microspherical and hollow rod-like morphologies that are different from the conventional monodipersed platelet-like morphologies. Highlights: Black-Right-Pointing-Pointer Molybdenum carbides were prepared using surfactants as carbon sources. Black-Right-Pointing-Pointer The kinds of surfactants affected the morphologies of molybdenum carbides. Black-Right-Pointing-Pointer The time of heat preservation at 1023 K affected the carburization process. Black-Right-Pointing-Pointer Molybdenum carbides with hollow structures had larger specific surface areas.« less

The Development of Molybdenum Speciation as a Paleoredox Tool

NASA Astrophysics Data System (ADS)

Rodley, J.; Peacock, C.; Mosselmans, J. F. W.; Poulton, S.

2017-12-01

The redox state of the oceans has changed throughout geological time and an understanding of these changes is essential to elucidate links between ocean chemistry, climate and life. Due to its abundance in seawater and redox-sensitive nature, molybdenum has enormous potential as a paleoredox proxy. Although a significant amount of research has been done on molybdenum in ancient and modern sediments in terms of its concentrations and isotopic ratios there remains a limited understanding of the drawdown mechanisms of molybdenum under different redox conditions restricting its use in identifying a range of redox states. In order to address these uncertainties, we have developed a novel sequential extraction technique to examine molybdenum concentrations in six sediment fractions from modern samples that represent oxic, nitrogenous, ferruginous and euxinic environments. In addition we use µ-XRF and µ-XANES synchrotron spectroscopy to examine the molybdenum speciation within these fractions and environments. To interpret our µ-XANES data we have developed an extensive library of molybdenum XANES standards that represent molybdenum sequestration by the sediment fractions identified from the sequential extraction. To further verify our synchrotron results we developed a series of µ-XANES micro-column experiments to examine preferential uptake pathways of molybdenum to different sediment phases under a euxinic water column. The initial data from both the sequential extraction and µ-XANES methods indicate that molybdenum is not limited to a single burial pathway in any of the redox environments. We find that each of the redox environments can be characterised by a limited set of molybdenum phase associations, with molybdenum adsorption to pyrite likely the dominant burial pathway. These findings agree with existing research for molybdenum speciation in euxinic environments suggesting that both pyrite and sulphidised organic matter act as important molybdenum sinks. Our new research shows that pyrite is also an important sink for molybdenum in other redox environments.

Molybdenum Trafficking for Nitrogen Fixation†

PubMed Central

Hernandez, Jose A.; George, Simon J.; Rubio, Luis M.

2009-01-01

The molybdenum nitrogenase is responsible for most biological nitrogen fixation, a prokaryotic metabolic process that determines the global biogeochemical cycles of nitrogen and carbon. Here we describe the trafficking of molybdenum for nitrogen fixation in the model diazotrophic bacterium Azotobacter vinelandii. The genes and proteins involved in molybdenum uptake, homeostasis, storage, regulation, and nitrogenase cofactor biosynthesis are reviewed. Molybdenum biochemistry in A. vinelandii reveals unexpected mechanisms and a new role for iron-sulfur clusters in the sequestration and delivery of molybdenum. PMID:19772354

Mineral resource of the month: molybdenum

USGS Publications Warehouse

Polyak, Désire E.

2011-01-01

The article offers information about the mineral molybdenum. Sources includes byproduct or coproduct copper-molybdenum deposits in the Western Cordillera of North and South America. Among the uses of molybdenum are stainless steel applications, as an alloy material for manufacturing vessels and as lubricants, pigments or chemicals. Also noted is the role played by molybdenum in renewable energy technology.

Dimension and bridging ligand effects on Mo-mediated catalytic transformation of dinitrogen to ammonia: Chain-like extended models of Nishibayashi’s catalyst

DOE PAGES

Sheng, Xiao -Lan; Batista, Enrique Ricardo; Duan, Yi -Xiang; ...

2016-11-01

Previous studies suggested that in Nishibayashi’s homogenous catalytic systems based on molybdenum (Mo) complexes, the bimetallic structure facilitated dinitrogen to ammonia conversion in comparison to the corresponding monometallic complexes, likely due to the through-bond interactions between the two Mo centers. However, more detailed model systems are necessary to support this bimetallic hypothesis, and to elucidate the multi-metallic effects on the catalytic mechanism. In this work, we computationally examined the effects of dimension as well as the types of bridging ligands on the catalytic activities of molybdenum-dinitrogen complexes by using a set of extended model systems based on Nishibayashi’s bimetallic structure.more » The polynuclear chains containing four ([Mo] 4) or more Mo centers were found to drastically enhance the catalytic performance by comparing with both the monometallic and bimetallic complexes. Carbide ([:C≡C:] 2–) was found to be a more effective bridging ligand than N 2 in terms of electronic charges dispersion between metal centers thereby facilitating reactions in the catalytic cycle. Furthermore, the mechanistic modelling suggests that in principle, more efficient catalytic system for N 2 to NH 3 transformation might be obtained by extending the polynuclear chain to a proper size in combination with an effective bridging ligand for charge dispersion.« less

Dimension and bridging ligand effects on Mo-mediated catalytic transformation of dinitrogen to ammonia: Chain-like extended models of Nishibayashi’s catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Xiao -Lan; Batista, Enrique Ricardo; Duan, Yi -Xiang

Previous studies suggested that in Nishibayashi’s homogenous catalytic systems based on molybdenum (Mo) complexes, the bimetallic structure facilitated dinitrogen to ammonia conversion in comparison to the corresponding monometallic complexes, likely due to the through-bond interactions between the two Mo centers. However, more detailed model systems are necessary to support this bimetallic hypothesis, and to elucidate the multi-metallic effects on the catalytic mechanism. In this work, we computationally examined the effects of dimension as well as the types of bridging ligands on the catalytic activities of molybdenum-dinitrogen complexes by using a set of extended model systems based on Nishibayashi’s bimetallic structure.more » The polynuclear chains containing four ([Mo] 4) or more Mo centers were found to drastically enhance the catalytic performance by comparing with both the monometallic and bimetallic complexes. Carbide ([:C≡C:] 2–) was found to be a more effective bridging ligand than N 2 in terms of electronic charges dispersion between metal centers thereby facilitating reactions in the catalytic cycle. Furthermore, the mechanistic modelling suggests that in principle, more efficient catalytic system for N 2 to NH 3 transformation might be obtained by extending the polynuclear chain to a proper size in combination with an effective bridging ligand for charge dispersion.« less

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations.

PubMed

Hassan, Wafaa S; El-Henawee, Magda M; Gouda, Ayman A

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at lambda(max) 470nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70microgmL(-1) for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Hassan, Wafaa S.; El-Henawee, Magda M.; Gouda, Ayman A.

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at λmax 470 nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426 nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70 μg mL -1 for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Reactivity of cyclopentadienyl transition metal(ii) complexes with borate ligands: structural characterization of the toluene-activated molybdenum complex [Cp*Mo(CO)2(η3-CH2C6H5)].

PubMed

Ramalakshmi, Rongala; Maheswari, K; Sharmila, Dudekula; Paul, Anamika; Roisnel, Thierry; Halet, Jean-François; Ghosh, Sundargopal

2016-10-18

Reactions of cyclopentadienyl transition-metal halide complexes [Cp*Mo(CO) 3 Cl], 1, and [CpFe(CO) 2 I], 2, (Cp = C 5 H 5 ; Cp* = η 5 -C 5 Me 5 ) with borate ligands are reported. Treatment of 1 with [NaBt 2 ] (Bt 2 = dihydrobis(2-mercapto-benzothiazolyl)borate) in toluene yielded [Cp*Mo(CO) 2 (C 7 H 4 S 2 N)], 3, and [Cp*Mo(CO) 2 (η 3 -CH 2 C 6 H 5 )], 4, with a selective binding of toluene through C-H activation followed by orthometallation. Note that compound 4 is a structurally characterized toluene-activated molecule in which the metal is in η 3 -coordination mode. Under similar reaction conditions, [NaPy 2 ] (Py 2 = dihydrobis(2-mercaptopyridyl)borate) produced only the mercaptopyridyl molybdenum complex [Cp*Mo(CO) 2 (C 5 H 4 SN)], 5, in good yield. On the other hand, when compound 2 was treated individually with [NaBt] (Bt = trihydro(2-mercapto-benzothiazolyl)borate) and [NaPy 2 ] in THF, formation of the η 1 -coordinated complexes [CpFe(CO) 2 (C 7 H 4 S 2 N)], 6, and [CpFe(CO) 2 (C 5 H 4 SN)], 7, was observed. The solid-state molecular structures of compounds 3, 4, 6, and 7 have been established by single-crystal X-ray crystallographic analyses.

Genetics Home Reference: molybdenum cofactor deficiency

MedlinePlus

... called molybdenum cofactor. Molybdenum cofactor, which contains the element molybdenum, is essential to the function of several ... Citation on PubMed or Free article on PubMed Central Reiss J, Gross-Hardt S, Christensen E, Schmidt P, ...

Study of the effects of gaseous environmental on the hot corrosion of superalloy materials

NASA Technical Reports Server (NTRS)

Smeggil, J. G.

1981-01-01

Studies have been conducted to examine the effect of low concentrations of NaCl(g) on the high temperature oxidation behavior of complex superalloys and potential coating formulations modified by silicon and reactive element (i.e., yttrium and hafnium) additions. Depending on alloy composition, a variety of effects were thermogravimetrically produced. Aluminum free alloys such as MAR-M509 and Hastelloy X with molybdenum and tungsten in solid solution showed accelerated (or breakaway) kinetics similar to that observed for Ni-Cr alloys. For IN-792, an alloy high in chromium and low in aluminum, molybdenum and tungsten present in solid solution does not adversely affect oxidation kinetics in the presence of NaCl(g). On the other hand, nickel-base alloys high in aluminum and molybdenum are catastrophically attacked by NaCl-bearing atmospheres. Silicon additions were, in general, observed to slightly improve the oxidation resistance of Ni, Ni-40Cr and CoCrAlY compositions in NaCl(g)-bearing atmospheres. To the degree that processes responsible for Al2O3 whisker formation deleteriously affect protective scale adherence, the addition of yttrium or hafnium can inhibit such whisker growth.

Characterization by 27Al NMR, X-ray absorption spectroscopy, and density functional theory techniques of the species responsible for benzene hydrogenation in Y zeolite-supported carburized molybdenum catalysts.

PubMed

Rocha, Angela S; da Silva, Victor Teixeira; Eon, Jean G; de Menezes, Sônia M C; Faro, Arnaldo C; Rocha, Alexandre B

2006-08-17

Carburized molybdenum catalysts supported on a dealuminated NaH-Y zeolite were prepared by carburization under a 20% methane in hydrogen flow of two precursors obtained by adsorption of molybdenum hexacarbonyl, one containing 5 wt % and the other 10 wt % Mo, and a third one was prepared by impregnation with aqueous ammonium heptamolybdate, containing 5 wt % Mo. The three catalysts displayed very distinct behaviors in the benzene hydrogenation reaction at atmospheric pressure and 363 K. By using XANES spectroscopy at the molybdenum L edge, EXAFS and XANES spectroscopy at the molybdenum K edge, and 27Al solid-state NMR spectroscopy, it was shown that different carburized molybdenum species exist in each sample. In the catalyst containing 10 wt % Mo, formation of molybdenum carbide nanoparticles was observed, with an estimated diameter of 1.8 nm. In the catalyst containing 5 wt % Mo and prepared by carburization of adsorbed molybdenum hexacarbonyl, formation of molybdenum oxycarbide dimers is proposed. In the latter case, density functional theory calculations have led to a dimer structure which is compatible with EXAFS results. In the catalyst prepared by impregnation with ammonium heptamolybdate solution followed by carburization, the molybdenum seems to interact with extraframework alumina to produce highly disordered mixed molybdenum-aluminum oxycarbides.

Gel Fabrication of Molybdenum “Beads”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lowden, Richard Andrew; Armstrong, Beth L.; Cooley, Kevin M.

2016-11-01

Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of 99Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however,more » the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.« less

Spectrophotometric determination of some anti-tussive and anti-spasmodic drugs through ion-pair complex formation with thiocyanate and cobalt(II) or molybdenum(V)

NASA Astrophysics Data System (ADS)

El-Shiekh, Ragaa; Zahran, Faten; El-Fetouh Gouda, Ayman Abou

2007-04-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of anti-tussive drugs, e.g., dextromethorphan hydrobromide (DEX) and pipazethate hydrochloride (PiCl) and anti-spasmodic drugs, e.g., drotaverine hydrochloride (DvCl) and trimebutine maleate (TM) in bulk and in their pharmaceutical formulations. The proposed methods depend upon the reaction of cobalt(II)-thiocyanate (method A) and molybdenum(V)-thiocyanate ions (method B) with the cited drugs to form stable ion-pair complexes which extractable with an n-butnol-dichloromethane solvent mixture (3.5:6.5) and methylene chloride for methods A and B, respectively. The blue and orange red color complexes are determined either colorimetrically at λmax 625 nm (using method A) and 467 or 470 nm for (DEX and PiCl) or (DvCl and TM), respectively (using method B). The concentration range is 20-400 and 2.5-50 μg mL -1 for methods A and B, respectively. The proposed method was successfully applied for the determination of the studied drugs in pure and in pharmaceutical formulations applying the standard additions technique and the results obtained in good agreement well with those obtained by the official method.

Calculation of photoelectron spectra of molybdenum and tungsten complexes using Green's functions methods.

PubMed

Bayse, Craig A; Ortwine, Kristine N

2007-08-16

Green's functions calculations are presented for several complexes of molybdenum and tungsten, two metals that are similar structurally but display subtle, but significant, differences in electronic structure. Outer valence Green's functions IPs for M(CO)6, M(Me)6, MH6, [MCl4O](-), and [MO4](-) (M = Mo, W) are generally within +/-0.2 eV of available experimental photoelectron spectra. The calculations show that electrons in M-L bonding orbitals are ejected at lower energies for Mo while the detachment energy for electrons in d orbitals varies with metal and complex. For the metal carbonyls, the quasiparticle picture assumed in OVGF breaks down for the inner valence pi CO molecular orbitals due to the coupling of two-hole-one-particle charge transfer states to the one-hole states. Incorporation of the 2h1p states through a Tamm-Dancoff approximation calculation accurately represents the band due to detachment from these molecular orbitals. Though the ordering of IPs for Green's functions methods and DFT Koopmans' theorem IPs is similar for the highest IPs for most compounds considered, the breakdown of the quasiparticle picture for the metal carbonyls suggests that scaling of the latter values may result in a fortuitous or incorrect assignment of experimental VDEs.

Dehydrogenation, disproportionation and transfer hydrogenation reactions of formic acid catalyzed by molybdenum hydride compounds.

PubMed

Neary, Michelle C; Parkin, Gerard

2015-03-01

The cyclopentadienyl molybdenum hydride compounds, Cp R Mo(PMe 3 ) 3- x (CO) x H (Cp R = Cp, Cp*; x = 0, 1, 2 or 3), are catalysts for the dehydrogenation of formic acid, with the most active catalysts having the composition Cp R Mo(PMe 3 ) 2 (CO)H. The mechanism of the catalytic cycle is proposed to involve (i) protonation of the molybdenum hydride complex, (ii) elimination of H 2 and coordination of formate, and (iii) decarboxylation of the formate ligand to regenerate the hydride species. NMR spectroscopy indicates that the nature of the resting state depends on the composition of the catalyst. For example, (i) the resting states for the CpMo(CO) 3 H and CpMo(PMe 3 )(CO) 2 H systems are the hydride complexes themselves, (ii) the resting state for the CpMo(PMe 3 ) 3 H system is the protonated species [CpMo(PMe 3 ) 3 H 2 ] + , and (iii) the resting state for the CpMo(PMe 3 ) 2 (CO)H system is the formate complex, CpMo(PMe 3 ) 2 (CO)(κ 1 -O 2 CH), in the presence of a high concentration of formic acid, but CpMo(PMe 3 ) 2 (CO)H when the concentration of acid is low. While CO 2 and H 2 are the principal products of the catalytic reaction induced by Cp R Mo(PMe 3 ) 3- x (CO) x H, methanol and methyl formate are also observed. The generation of methanol is a consequence of disproportionation of formic acid, while methyl formate is a product of subsequent esterification. The disproportionation of formic acid is a manifestation of a transfer hydrogenation reaction, which may also be applied to the reduction of aldehydes and ketones. Thus, CpMo(CO) 3 H also catalyzes the reduction of a variety of ketones and aldehydes to alcohols by formic acid, via a mechanism that involves ionic hydrogenation.

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1972-01-01

An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

In situ optical diagnostic for monitoring or control of sodium diffusion in photovoltaics manufacturing

DOEpatents

Li, Jian; Levi, Dean; Contreras, Miguel; Glynn, Stephen

2015-09-15

A method of fabricating a photovoltaic device 100, includes the steps of providing a glass substrate 102, depositing a molybdenum layer 104 on a surface of the glass substrate, directing light through the glass substrate to the near-substrate region of the molybdenum layer 206, detecting an optical property of the near-substrate region of the molybdenum layer after interaction with the incident light 208 and determining a density of the near-substrate region of the molybdenum layer from the detected optical property 210. A molybdenum deposition parameter may be controlled based upon the determined density of the near-substrate region of the molybdenum layer 218. A non-contact method measures a density of the near-substrate region of a molybdenum layer and a deposition chamber 300.

Molybdenum disilicide composites

DOEpatents

Rodriguez, Robert P.; Petrovic, John J.

2001-01-01

Molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z, wherein z=a number from greater than 0 to about 5, composites are made by use of in situ reactions among .alpha.-silicon nitride, molybdenum disilicide, and aluminum. Molybdenum disilicide within a molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z eutectoid matrix is the resulting microstructure when the invention method is employed.

40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to...

40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to...

40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to...

40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to...

40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to...

Performance Evaluation of Titanium Ion Optics for the NASA 30 cm Ion Thruster

NASA Technical Reports Server (NTRS)

Soulas, George C.

2001-01-01

The results of performance tests with titanium ion optics were presented and compared to those of molybdenum ion optics. Both titanium and molybdenum ion optics were initially operated until ion optics performance parameters achieved steady state values. Afterwards, performance characterizations were conducted. This permitted proper performance comparisons of titanium and molybdenum ion optics. Ion optics' performance A,as characterized over a broad thruster input power range of 0.5 to 3.0 kW. All performance parameters for titanium ion optics of achieved steady state values after processing 1200 gm of propellant. Molybdenum ion optics exhibited no burn-in. Impingement-limited total voltages for titanium ion optics where up to 55 V greater than those for molybdenum ion optics. Comparisons of electron backstreaming limits as a function of peak beam current density for molybdenum and titanium ion optics demonstrated that titanium ion optics operated with a higher electron backstreaming limit than molybdenum ion optics for a given peak beam current density. Screen grid ion transparencies for titanium ion optics were as much as 3.8 percent lower than those for molybdenum ion optics. Beam divergence half-angles that enclosed 95 percent of the total beam current for titanium ion optics were within 1 to 3 deg. of those for molybdenum ion optics. All beam divergence thrust correction factors for titanium ion optics were within 1 percent of those with molybdenum ion optics.

Relativistic effects in metallocorroles: comparison of molybdenum and tungsten biscorroles

DOE PAGES

Alemayehu, Abraham B.; Vazquez-Lima, Hugo; McCormick, Laura J.; ...

2017-05-12

We present the homoleptic sandwich compounds-Mo and W biscorroles-have afforded a novel platform for experimental studies of relativistic effects. A 200 mV difference in reduction potential and a remarkable 130 nm shift of a near-IR spectral feature have been identified as manifestations of relativistic effects on the properties of these complexes.

Molecular molybdenum persulfide and related catalysts for generating hydrogen from water

DOEpatents

Long, Jeffrey R.; Chang, Christopher J.; Karunadasa, Hemamala I.; Majda, Marcin

2016-11-22

New metal persulfido compositions of matter are described. In one embodiment the metal is molybdenum and the metal persulfido complex mimics the structure and function of the triangular active edge site fragments of MoS.sub.2, a material that is the current industry standard for petroleum hydro desulfurization, as well as a promising low-cost alternative to platinum for electrocatalytic hydrogen production. This molecular [(PY5W.sub.2)MoS.sub.2].sup.x+ containing catalyst is capable of generating hydrogen from acidic-buffered water or even seawater at very low overpotentials at a turnover frequency rate in excess of 500 moles H.sub.2 per mole catalyst per second, with a turnover number (over a 20 hour period) of at least 19,000,000 moles H.sub.2 per mole of catalyst.

Molecular molybdenum persulfide and related catalysts for generating hydrogen from water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Jeffrey R.; Chang, Christopher J.; Karunadasa, Hemamala I.

New metal persulfido compositions of matter are described. In one embodiment the metal is molybdenum and the metal persulfido complex mimics the structure and function of the triangular active edge site fragments of MoS.sub.2, a material that is the current industry standard for petroleum hydro desulfurization, as well as a promising low-cost alternative to platinum for electrocatalytic hydrogen production. This molecular [(PY5W.sub.2)MoS.sub.2].sup.x+ containing catalyst is capable of generating hydrogen from acidic-buffered water or even seawater at very low overpotentials at a turnover frequency rate in excess of 500 moles H.sub.2 per mole catalyst per second, with a turnover number (overmore » a 20 hour period) of at least 19,000,000 moles H.sub.2 per mole of catalyst.« less

Spectrophotometric determination of molybdenum in rocks with thiocyanate

USGS Publications Warehouse

Lillie, E.G.; Greenland, L.P.

1974-01-01

A rapid procedure for the determination of microgram amounts of molybdenum in rocks is described. After acid decomposition, molybdenum is extracted from a hydrochloric acid solution into xylene with tributyl phosphate. After back-extraction with water, molybdenum is extracted as the ??-benzoinoximate into chloroform, stripped into hydrochloric acid extracted as the thiocyanate into amyl alcohol, and determined spectrophotometrically. The molybdenum thiocyanate color produced is stable, sensitive, and reproducible. Results of analyses of several of the U.S. Geological Survey standard rocks are given. ?? 1974.

Pre-treatment for molybdenum or molybdenum-rich alloy articles to be plated

DOEpatents

Wright, Ralph R.

1980-01-01

This invention is a method for etching a molybdenum or molybdenum-rich alloy surface to promote the formation of an adherent bond with a subsequently deposited metallic plating. In a typical application, the method is used as a pre-treatment for surfaces to be electrolessly plated with nickel. The pre-treatment comprises exposing the crystal boundaries of the surface by (a) anodizing the surface in acidic solution to form a continuous film of gray molybdenum oxide thereon and (b) removing the film.

METHOD FOR FORMING A COATING OF MOLYBDENUM CARBIDE ON A CARBON BODY

DOEpatents

Simnad, M.T.

1962-04-01

A method is described for coating a carbon bodywith molybdenum carbide in such a manner that the carbon body is rendered less permeable to the flow of gases and has increased resistance to corrosion and erosion. The method includes coating a carbon body with molybdenum trioxide by contacting it at a temperature below the condensation temperature with molybdenum trioxide vapors and thereafter carburizing the molybdenum trioxide in situ in an inert atmosphere on the carhon body. (AEC)

Calculated mammographic spectra confirmed with attenuation curves for molybdenum, rhodium, and tungsten targets.

PubMed

Blough, M M; Waggener, R G; Payne, W H; Terry, J A

1998-09-01

A model for calculating mammographic spectra independent of measured data and fitting parameters is presented. This model is based on first principles. Spectra were calculated using various target and filter combinations such as molybdenum/molybdenum, molybdenum/rhodium, rhodium/rhodium, and tungsten/aluminum. Once the spectra were calculated, attenuation curves were calculated and compared to measured attenuation curves. The attenuation curves were calculated and measured using aluminum alloy 1100 or high purity aluminum filtration. Percent differences were computed between the measured and calculated attenuation curves resulting in an average of 5.21% difference for tungsten/aluminum, 2.26% for molybdenum/molybdenum, 3.35% for rhodium/rhodium, and 3.18% for molybdenum/rhodium. Calculated spectra were also compared to measured spectra from the Food and Drug Administration [Fewell and Shuping, Handbook of Mammographic X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1979)] and a comparison will also be presented.

Improvement of wear resistance of plasma-sprayed molybdenum blend coatings

NASA Astrophysics Data System (ADS)

Ahn, Jeehoon; Hwang, Byoungchul; Lee, Sunghak

2005-06-01

The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl2 and Cu9Al4 formed inside the coating.

Spheroidization of molybdenum powder by radio frequency thermal plasma

NASA Astrophysics Data System (ADS)

Liu, Xiao-ping; Wang, Kuai-she; Hu, Ping; Chen, Qiang; Volinsky, Alex A.

2015-11-01

To control the morphology and particle size of dense spherical molybdenum powder prepared by radio frequency (RF) plasma from irregular molybdenum powder as a precursor, plasma process parameters were optimized in this paper. The effects of the carrier gas flow rate and molybdenum powder feeding rate on the shape and size of the final products were studied. The molybdenum powder morphology was examined using high-resolution scanning electron microscopy. The powder phases were analyzed by X-ray diffraction. The tap density and apparent density of the molybdenum powder were investigated using a Hall flow meter and a Scott volumeter. The optimal process parameters for the spherical molybdenum powder preparation are 50 g/min powder feeding rate and 0.6 m3/h carrier gas rate. In addition, pure spherical molybdenum powder can be obtained from irregular powder, and the tap density is enhanced after plasma processing. The average size is reduced from 72 to 62 µm, and the tap density is increased from 2.7 to 6.2 g/cm3. Therefore, RF plasma is a promising method for the preparation of high-density and high-purity spherical powders.

Determining the magnitude and direction of photoinduced ligand field switching in photochromic metal-organic complexes: molybdenum-tetracarbonyl spirooxazine complexes.

PubMed

Paquette, Michelle M; Patrick, Brian O; Frank, Natia L

2011-07-06

The ability to optically switch or tune the intrinsic properties of transition metals (e.g., redox potentials, emission/absorption energies, and spin states) with photochromic metal-ligand complexes is an important strategy for developing "smart" materials. We have described a methodology for using metal-carbonyl complexes as spectroscopic probes of ligand field changes associated with light-induced isomerization of photochromic ligands. Changes in ligand field between the ring-closed spirooxazine (SO) and ring-opened photomerocyanine (PMC) forms of photochromic azahomoadamantyl and indolyl phenanthroline-spirooxazine ligands are demonstrated through FT-IR, (13)C NMR, and computational studies of their molybdenum-tetracarbonyl complexes. The frontier molecular orbitals (MOs) of the SO and PMC forms differ considerably in both electron density distributions and energies. Of the multiple π* MOs in the SO and PMC forms of the ligands, the LUMO+1, a pseudo-b(1)-symmetry phenanthroline-based MO, mixes primarily with the Mo(CO)(4) fragment and provides the major pathway for Mo(d)→phen(π*) backbonding. The LUMO+1 is found to be 0.2-0.3 eV lower in energy in the SO form relative to the PMC form, suggesting that the SO form is a better π-acceptor. Light-induced isomerization of the photochromic ligands was therefore found to lead to changes in the energies of their frontier MOs, which in turn leads to changes in π-acceptor ability and ligand field strength. Ligand field changes associated with photoisomerizable ligands allow tuning of excited-state and ground-state energies that dictate energy/electron transfer, optical/electrical properties, and spin states of a metal center upon photoisomerization, positioning photochromic ligand-metal complexes as promising targets for smart materials.

Rolling Process Modeling Report. Finite-Element Model Validation and Parametric Study on various Rolling Process parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soulami, Ayoub; Lavender, Curt A.; Paxton, Dean M.

2015-06-15

Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum alloy plate-type fuel for high-performance research reactors in the United States. This work supports the U.S. Department of Energy National Nuclear Security Administration’s Office of Material Management and Minimization Reactor Conversion Program. This report documents modeling results of PNNL’s efforts to perform finite-element simulations to predict roll-separating forces for various rolling mill geometries for PNNL, Babcock & Wilcox Co., Y-12 National Security Complex, Los Alamos National Laboratory, and Idaho National Laboratory. The model developed and presented in a previous report has been subjected to further validationmore » study using new sets of experimental data generated from a rolling mill at PNNL. Simulation results of both hot rolling and cold rolling of uranium-10% molybdenum coupons have been compared with experimental results. The model was used to predict roll-separating forces at different temperatures and reductions for five rolling mills within the National Nuclear Security Administration Fuel Fabrication Capability project. This report also presents initial results of a finite-element model microstructure-based approach to study the surface roughness at the interface between zirconium and uranium-10% molybdenum.« less

Determination of iodine and molybdenum in milk by quadrupole ICP-MS.

PubMed

Reid, Helen J; Bashammakh, Abdul A; Goodall, Phillip S; Landon, Mark R; O'Connor, Ciaran; Sharp, Barry L

2008-03-15

A reliable method for the determination of iodine and molybdenum in milk samples, using alkaline digestion with tetramethylammonium hydroxide and hydrogen peroxide, followed by quadrupole ICP-MS analysis, has been developed and tested using certified reference materials. The use of He+O2 (1.0 ml min(-1) and 0.6 ml min(-1)) in the collision-reaction cell of the mass spectrometer to remove (129)Xe+-- initially to enable the determination of low levels of 129I--also resulted in the quantitative conversion of Mo(+) to MoO2+ which enabled the molybdenum in the milk to be determined at similar mass to the iodine with the use of Sb as a common internal standard. In order to separate and pre-concentrate iodine at sub microg l(-1) concentrations, a novel method was developed using a cation-exchange column loaded with Pd2+ and Ca2+ ions to selectively retain iodide followed by elution with a small volume of ammonium thiosulfate. This method showed excellent results for aqueous iodide solutions, although the complex milk digest matrix made the method unsuitable for such samples. An investigation of the iodine species formed during oxidation and extraction of milk sample digests was carried out with a view to controlling the iodine chemistry.

In vitro study of 6-mercaptopurine oxidation catalysed by aldehyde oxidase and xanthine oxidase.

PubMed

Rashidi, Mohammad-Reza; Beedham, Christine; Smith, John S; Davaran, Soodabeh

2007-08-01

In spite of over 40 years of clinical use of 6-mercaptopurine, many aspects of complex pharmacology and metabolism of this drug remain unclear. It is thought that 6-mercaptopurine is oxidized to 6-thiouric acid through 6-thioxanthine or 8-oxo-6-mercaptopurine by one of two molybdenum hydroxylases, xanthine oxidase (XO), however, the role of other molybdenum hydroxylase, aldehyde oxidase (AO), in the oxidation of 6-mercaptopurine and possible interactions of AO substrates and inhibitors has not been investigated in more details. In the present study, the role of AO and XO in the oxidation of 6- mercaptopurine has been investigated. 6-mercaptopurine was incubated with bovine milk xanthine oxidase or partially purified guinea pig liver molybdenum hydroxylase fractions in the absence and presence of XO and AO inhibitor/substrates, and the reactions were monitored by spectrophotometric and HPLC methods. According to the results obtained from the inhibition studies, it is more likely that 6- mercaptopurine is oxidized to 6-thiouric acid via 6-thioxanthine rather than 8-oxo-6-mercaptopurine. The first step which is the rate limiting step is catalyzed solely by XO, whereas both XO and AO are involved in the oxidation of 6-thioxanthine to 6-thiouric acid.

Reactions of Metal-Metal Multiple Bonds. 14. Synthesis and Characterization of Triangulo-W3 and Mo2W-oxo Capped Alkoxide Clusters. Comproportionation of M-M Triple Bonds, sigma(2)pi(4) and d(o) Metal-oxo Groups: M Triple Bond M + M Triple Bond O Yields M3(micron 3-O).

DTIC Science & Technology

1984-05-02

the syntheses of dinuclear and trinuclear complexes employing metal -alkylidyne or -alkylidene fragments.8 Reaction 1 also has a parallel with the...1 0 which was previously examined. The mixed metal complex is undoubtedly disordered with respect to the disposition of molybdenum and tungsten atoms...than for the analogous Mo3 complex suggests greater metal - metal overlap and possibly stronger bonding interactions in the W3 complex which would not

Method of producing molybdenum-99

DOEpatents

Pitcher, Eric John

2013-05-28

Method of producing molybdenum-99, comprising accelerating ions by means of an accelerator; directing the ions onto a metal target so as to generate neutrons having an energy of greater than 10 MeV; directing the neutrons through a converter material comprising techentium-99 to produce a mixture comprising molybdenum-99; and, chemically extracting the molybdenum-99 from the mixture.

Precipitation of molybdenum(V) as the hydroxide and its separation from rhenium.

PubMed

Yatirajam, V; Ahuja, U; Kakkar, L R

1975-03-01

A study of the conditions for precipitation of molybdenum(V) hydroxide shows that for Mo concentration 1 mg ml about 97.5% of the Mo can be precipitated between pH 5 and 5.8. Lower concentrations of molybdenum(V) or molybdenum(VI) can be precipitated quantitatively by using 20 times the amount of zirconium as collector, at the same pH. On this basis, a simple method is given for quantitative separation of rhenium from large amounts of molybdenum and is attested by analysis of synthetic and molybdenite samples.

Survey of Portions of the Chromium-Cobalt-Nickel-Molybdenum Quaternary System at 1,200 Degrees C

NASA Technical Reports Server (NTRS)

Rideout, Sheldon Paul; Beck, Paul A

1953-01-01

A survey was made of portions of the chromium-cobalt-nickel-molybdenum quaternary system at 1,200 degrees c by means of microscopic and x-ray diffraction studies. Since the face-centered cubic (alpha) solid solutions form the matrix of almost all practically useful high-temperature alloys, the solid solubility limits of the quaternary alpha phase were determined up to 20 percent molybdenum. The component cobalt-nickel-molybdenum, chromium-cobalt-molybdenum, and chromium-nickel-molybdenum ternary systems were also studied. The survey of these systems was confined to the determination of the boundaries of the face-centered cubic (alpha) solid solutions and of the phases coexisting with alpha at 1,200 degrees c.

Molybdenum Oxides - From Fundamentals to Functionality.

PubMed

de Castro, Isabela Alves; Datta, Robi Shankar; Ou, Jian Zhen; Castellanos-Gomez, Andres; Sriram, Sharath; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-10-01

The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancing the corrosion resistance of the 2205 duplex stainless steel bipolar plates in PEMFCs environment by surface enriched molybdenum

NASA Astrophysics Data System (ADS)

Jinlong, Lv; Zhuqing, Wang; Tongxiang, Liang; Ken, Suzuki; Hideo, Miura

Surface molybdenum enrichment on 2205 duplex stainless steel was obtained by the ball milling technique. The electrochemical results showed molybdenum enrichment on the surface of 2205 duplex stainless steel improved its corrosion resistance in a typical proton exchange membrane fuel cell environment. This was mainly attributed to higher molybdenum content in the passive film formed on 2205 duplex stainless steel after ball milling. The decreased donor and acceptor concentrations improved significantly the corrosion resistance of surface molybdenum-enriched 2205 duplex stainless steel bipolar plates in the simulated cathodic proton exchange membrane fuel cells environment. In addition, the interfacial contact resistance of the 2205 duplex stainless steel bipolar plates slightly decreased due to surface molybdenum enrichment.

An unexpected mechanism of hydrosilylation by a silyl hydride complex of molybdenum.

PubMed

Khalimon, Andrey Y; Ignatov, Stanislav K; Simionescu, Razvan; Kuzmina, Lyudmila G; Howard, Judith A K; Nikonov, Georgii I

2012-01-16

Carbonyl hydrosilylation catalyzed by (ArN)Mo(H)(SiH(2)Ph)(PMe(3))(3) (3) is unusual in that it does not involve the expected Si-O elimination from intermediate (ArN)Mo(SiH(2)Ph)(O(i)Pr)(PMe(3))(2) (7). Instead, 7 reversibly transfers β-CH hydrogen from the alkoxide ligand to metal.

Changes in concentrations of trace minerals in lambs fed sericea lespedeza leaf meal pellets with or without dietary sodium molybdate

USDA-ARS?s Scientific Manuscript database

Prolonged feeding of sericea lespedeza (SL; Lespedeza cuneata) previously led to reduced serum concentrations of molybdenum (Mo), a co-factor in an enzyme complex that may be involved in weight gain. The objective of this study was to determine the effect of Mo supplementation on changes in serum, f...

Environmental Benign Process for Production of Molybdenum Metal from Sulphide Based Minerals

NASA Astrophysics Data System (ADS)

Rajput, Priyanka; Janakiram, Vangada; Jayasankar, Kalidoss; Angadi, Shivakumar; Bhoi, Bhagyadhar; Mukherjee, Partha Sarathi

2017-10-01

Molybdenum is a strategic and high temperature refractory metal which is not found in nature in free state, it is predominantly found in earth's crust in the form of MoO3/MoS2. The main disadvantage of the industrial treatment of Mo concentrate is that the process contains many stages and requires very high temperature. Almost in every step many gaseous, liquid, solid chemical substances are formed which require further treatment. To overcome the above drawback, a new alternative one step novel process is developed for the treatment of sulphide and trioxide molybdenum concentrates. This paper presents the results of the investigations on molybdenite dissociation (MoS2) using microwave assisted plasma unit as well as transferred arc thermal plasma torch. It is a single step process for the preparation of pure molybdenum metal from MoS2 by hydrogen reduction in thermal plasma. Process variable such as H2 gas, Ar gas, input current, voltage and time have been examined to prepare molybdenum metal. Molybdenum recovery of the order of 95% was achieved. The XRD results confirm the phases of molybdenum metal and the chemical analysis of the end product indicate the formation of metallic molybdenum (Mo 98%).

Spectroscopic and Kinetic Properties of the Molybdenum-containing, NAD+-dependent Formate Dehydrogenase from Ralstonia eutropha*

PubMed Central

Niks, Dimitri; Duvvuru, Jayant; Escalona, Miguel; Hille, Russ

2016-01-01

We have examined the rapid reaction kinetics and spectroscopic properties of the molybdenum-containing, NAD+-dependent FdsABG formate dehydrogenase from Ralstonia eutropha. We confirm previous steady-state studies of the enzyme and extend its characterization to a rapid kinetic study of the reductive half-reaction (the reaction of formate with oxidized enzyme). We have also characterized the electron paramagnetic resonance signal of the molybdenum center in its MoV state and demonstrated the direct transfer of the substrate Cα hydrogen to the molybdenum center in the course of the reaction. Varying temperature, microwave power, and level of enzyme reduction, we are able to clearly identify the electron paramagnetic resonance signals for four of the iron/sulfur clusters of the enzyme and find suggestive evidence for two others; we observe a magnetic interaction between the molybdenum center and one of the iron/sulfur centers, permitting assignment of this signal to a specific iron/sulfur cluster in the enzyme. In light of recent advances in our understanding of the structure of the molybdenum center, we propose a reaction mechanism involving direct hydride transfer from formate to a molybdenum-sulfur group of the molybdenum center. PMID:26553877

Acidic ammonothermal growth of gallium nitride in a liner-free molybdenum alloy autoclave

NASA Astrophysics Data System (ADS)

Malkowski, Thomas F.; Pimputkar, Siddha; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji

2016-12-01

This paper discusses promising materials for use as internal, non-load bearing components as well as molybdenum-based alloys for autoclave structural components for an ammonothermal autoclave. An autoclave was constructed from the commercial titanium-zirconium-molybdenum (TZM) alloy and was found to be chemically inert and mechanically stable under acidic ammonothermal conditions. Preliminary seeded growth of GaN was demonstrated with negligible incorporation of transition metals (including molybdenum) into the grown material (<1017 cm-3). Molybdenum and TZM were exposed to a basic ammonothermal environment, leading to slight degradation through formation of molybdenum nitride powders on their surface at elevated temperatures (T>560 °C). The possibility of a 'universal', inexpensive, liner-free ammonothermal autoclave capable of exposure to basic and acidic chemistry is demonstrated.

High-temperature corrosion of metals in the salt and metallic melts containing rare earths

NASA Astrophysics Data System (ADS)

Karpov, V. V.; Abramov, A. V.; Zhilyakov, A. Yu.; Belikov, S. V.; Volkovich, V. A.; Polovov, I. B.; Rebrin, O. I.

2016-09-01

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl- KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of "low stability" materials.

X-ray emission spectroscopy evidences a central carbon in the nitrogenase iron-molybdenum cofactor.

PubMed

Lancaster, Kyle M; Roemelt, Michael; Ettenhuber, Patrick; Hu, Yilin; Ribbe, Markus W; Neese, Frank; Bergmann, Uwe; DeBeer, Serena

2011-11-18

Nitrogenase is a complex enzyme that catalyzes the reduction of dinitrogen to ammonia. Despite insight from structural and biochemical studies, its structure and mechanism await full characterization. An iron-molybdenum cofactor (FeMoco) is thought to be the site of dinitrogen reduction, but the identity of a central atom in this cofactor remains unknown. Fe Kβ x-ray emission spectroscopy (XES) of intact nitrogenase MoFe protein, isolated FeMoco, and the FeMoco-deficient nifB protein indicates that among the candidate atoms oxygen, nitrogen, and carbon, it is carbon that best fits the XES data. The experimental XES is supported by computational efforts, which show that oxidation and spin states do not affect the assignment of the central atom to C(4-). Identification of the central atom will drive further studies on its role in catalysis.

Reaction mechanism of molybdoenzyme formate dehydrogenase.

PubMed

Leopoldini, Monica; Chiodo, Sandro G; Toscano, Marirosa; Russo, Nino

2008-01-01

Formate dehydrogenase is a molybdoenzyme of the anaerobic formate hydrogen lyase complex of the Escherichia coli microorganism that catalyzes the oxidation of formate to carbon dioxide. The two proposed mechanisms of reaction, which differ in the occurrence of a direct coordination or not of a SeCys residue to the molybdenum metal during catalysis were analyzed at the density functional level in both vacuum and protein environments. Some DF functionals, in addition to the very popular B3LYP one, were employed to compute barrier heights. Results revealed the role played by the SeCys residue in performing the abstraction of the proton from the formate substrate. The computation of the energetic profiles for both mechanisms indicated that the reaction barriers are higher when the selenium is directly coordinated to the metal, whereas less energy is required when SeCys is not a ligand at the molybdenum site.

Brazing graphite to graphite

DOEpatents

Peterson, George R.

1976-01-01

Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of virtually graphite.

40 CFR 421.216 - Pretreatment standards for new sources.

Code of Federal Regulations, 2014 CFR

2014-07-01

... exceed the following values: (a) Molybdenum sulfide leachate. PSNS for the Primary Molybdenum and Rhenium...) Molybdic oxide leachate. PSNS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant...

40 CFR 421.216 - Pretreatment standards for new sources.

Code of Federal Regulations, 2013 CFR

2013-07-01

... exceed the following values: (a) Molybdenum sulfide leachate. PSNS for the Primary Molybdenum and Rhenium...) Molybdic oxide leachate. PSNS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant...

40 CFR 421.216 - Pretreatment standards for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... exceed the following values: (a) Molybdenum sulfide leachate. PSNS for the Primary Molybdenum and Rhenium...) Molybdic oxide leachate. PSNS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant...

40 CFR 421.216 - Pretreatment standards for new sources.

Code of Federal Regulations, 2012 CFR

2012-07-01

... exceed the following values: (a) Molybdenum sulfide leachate. PSNS for the Primary Molybdenum and Rhenium...) Molybdic oxide leachate. PSNS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant...

40 CFR 421.216 - Pretreatment standards for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... exceed the following values: (a) Molybdenum sulfide leachate. PSNS for the Primary Molybdenum and Rhenium...) Molybdic oxide leachate. PSNS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant...

40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS NONFERROUS METALS MANUFACTURING... to discharges resulting from the production of molybdenum or vanadium by secondary molybdenum and...

Silicon nitride reinforced with molybdenum disilicide

DOEpatents

Petrovic, John J.; Honnell, Richard E.

1991-01-01

Compositions of matter comprised of silicon nitride and molybdenum disilicide and methods of making the compositions, where the molybdenum disilicide is present in amounts ranging from about 5 to about 50 vol. %.

Biochemical abnormalities in workers exposed to molybdenum dust.

PubMed

Walravens, P A; Moure-Eraso, R; Solomons, C C; Chappell, W R; Bentley, G

1979-01-01

Exposure to molybdenum in dust was measured in a molybdenite roasting plant. This exposure was accompanied by large elevations of serum ceruloplasmin and smaller increases in mean serum uric acid levels in the workers. Absorption of molybdenum from the dust was demonstrated by increases in plasma and urinary molybdenum levels. It remains necessary to demonstrate whether such exposure results in long-term health effects.

Annealed CVD molybdenum thin film surface

DOEpatents

Carver, Gary E.; Seraphin, Bernhard O.

1984-01-01

Molybdenum thin films deposited by pyrolytic decomposition of Mo(CO).sub.6 attain, after anneal in a reducing atmosphere at temperatures greater than 700.degree. C., infrared reflectance values greater than reflectance of supersmooth bulk molybdenum. Black molybdenum films deposited under oxidizing conditions and annealed, when covered with an anti-reflecting coating, approach the ideal solar collector characteristic of visible light absorber and infrared energy reflector.

As-cast uranium-molybdenum based metallic fuel candidates and the effects of carbon addition

NASA Astrophysics Data System (ADS)

Blackwood, Van Stephen

The objective of this research was to develop and recommend a metallic nuclear fuel candidate that lowered the onset temperature of gamma phase formation comparable or better than the uranium-10 wt. pct. molybdenum alloy, offered a solidus temperature as high or higher than uranium-10 wt. pct. zirconium (1250°C), and stabilized the fuel phase against interaction with iron and steel at least as much as uranium-10 wt. pct. zirconium stabilized the fuel phase. Two new as-cast alloy compositions were characterized to assess thermal equilibrium boundaries of the gamma phase field and the effect of carbon addition up to 0.22 wt. pct. The first system investigated was uranium- x wt. pct. M where x ranged between 5-20 wt. pct. M was held at a constant ratio of 50 wt. pct. molybdenum, 43 wt. pct. titanium, and 7 wt. pct. zirconium. The second system investigated was the uranium-molybdenum-tungsten system in the range 90 wt. pct. uranium - 10 wt. pct. molybdenum - 0 wt. pct. tungsten to 80 wt. pct. uranium - 10 wt. pct. molybdenum - 10 wt. pct. tungsten. The results showed that the solidus temperature increased with increased addition of M up to 12.5 wt. pct. for the uranium-M system. Alloy additions of titanium and zirconium were removed from uranium-molybdenum solid solution by carbide formation and segregation. The uranium-molybdenum-tungsten system solidus temperature increased to 1218°C at 2.5 wt. pct. with no significant change in temperature up to 5 wt. pct. tungsten suggesting the solubility limit of tungsten had been reached. Carbides were observed with surrounding areas enriched in both molybdenum and tungsten. The peak solidus temperatures for the alloy systems were roughly the same at 1226°C for the uranium-M system and 1218°C for the uranium-molybdenum-tungsten system. The uranium-molybdenum-tungsten system required less alloy addition to achieve similar solidus temperatures as the uranium-M system.

Structural distortions upon oxidation in heteroleptic [Cp(2)W(dmit)] tungsten dithiolene complex: combined structural, spectroscopic, and magnetic studies.

PubMed

Reinheimer, Eric W; Olejniczak, Iwona; Łapiński, Andrzej; Swietlik, Roman; Jeannin, Olivier; Fourmigué, Marc

2010-11-01

Four different cation radical salts are obtained upon electrocrystallization of [Cp(2)W(dmit)] (dmit = 1,3-dithiole-2-thione-4,5-dithiolato) in the presence of the BF(4)(-), PF(6)(-), Br(-), and [Au(CN)(2)](-) anions. In these formally d(1) cations, the WS(2)C(2) metallacycle is folded along the S···S hinge to different extents in the four salts, an illustration of the noninnocent character of the dithiolate ligand. Structural characteristics and the charge distribution on atoms, for neutral and ionized complexes with various folding angles, were calculated using DFT methods, together with the normal vibrational modes and theoretical Raman spectra. Raman spectra of neutral complex [Cp(2)W(dmit)] and its salts formed with BF(4)(-), AsF(6)(-), PF(6)(-), Br(-), and [Au(CN)(2)](-) anions were measured using the red excitation (λ = 632.8 nm). A correlation between the folding angle of the metallacycle and the Raman spectroscopic properties is analyzed. The bands attributed to the C═C and C-S stretching modes shift toward higher and lower frequencies by about 0.3-0.4 cm(-1) deg(-1), respectively. The solid state structural and magnetic properties of the three salts are analyzed and compared with those of the corresponding molybdenum complexes. Temperature dependence of the magnetic susceptibility shows the presence of one-dimensional antiferromagnetic interactions in the BF(4)(-), PF(6)(-), and [Au(CN)(2)](-) salts, while an antiferromagnetic ground state is identified in the Br(-) salt below T(Néel) = 7 K. Interactions are systematically weaker in the tungsten salts than in the isostructural molybdenum analogs, a consequence of the decreased spin density on the dithiolene ligand in the tungsten complexes.

Modification of molybdenum disulfide in methanol solvent for hydrogen evolution reaction

NASA Astrophysics Data System (ADS)

Niyitanga, Theophile; Jeong, Hae Kyung

2018-05-01

Molybdenum disulfide is a promising catalyst to replace the expensive platinum as an electrocatalyst but needs to be modified to present excellent electrocatalytic properties. Herein, we successfully modify molybdenum disulfide in methanol solvent for hydrogen evolution reaction by using a simple hydrothermal method. Overpotential reduced to -0.6 V from -1.5 V, and energy band gap decreased from 1.73 eV to 1.58 eV after the modification. The modified molybdenum disulfide also demonstrated lower resistance (42 Ω) at high frequency (1000 kHz) compared with that (240 Ω) of the precursor, showing that conductivity of the modified molybdenum disulfide has improved.

Molybdenum-UO2 cermet irradiation at 1145 K.

NASA Technical Reports Server (NTRS)

Mcdonald, G.

1971-01-01

Two molybdenum-uranium dioxide cermet fuel pins with molybdenum clad were fission-heated in a forced-convection helium coolant for sufficient time to achieve 5.3% burnup. The cermet core contained 20 wt % of 93.2% enriched uranium dioxide. The results were as follows: there was no visible change in the appearance of the molybdenum clad during irradiation; the maximum increase in diameter of the fuel pins was 0.8%; there was no migration of uranium dioxide along grain boundaries and no evident interaction between molybdenum and uranium dioxide; and, finally, approximately 12% of the fission gas formed was released from the cermet core into the gas plenum.

Controlled Ring-Opening Metathesis Polymerization by Molybdenum and Tungsten Alkylidene Complexes

DTIC Science & Technology

1988-07-29

weights and low polydispersities (as low as 1.03) consistent with a living catalyst system employing 50, 100, 200, and 400 eq of monomer. The reactions are...secondary metathesis of polymer chains Bulky alkoxide ligands Wittig-like reaction Ring-opening metathesis polymerization (ROMP) Feast monomer Cyclic...olefins Retro Diels-Alder reaction Norbornene (NBE) Low temperature column chromatography Endo-,endo-5,6-dicarbomethoxynorbornene Discrete, soluble

Electrochemical way of molybdenum extraction from the Bimetallic systems of Mo-W

NASA Astrophysics Data System (ADS)

Kudreeva, L. K.; Nauryzbaev, M. K.; Kurbatov, A. P.; Kamysbaev, D. H.; Adilbekova, A. O.; Mukataeva, Z. S.

2015-12-01

Electrochemical dissolution of molybdenum and tungsten was investigated in water- dimethylsulfoxide (DMSO) media at different concentrations of lithium chloride and magnesium perchlorate. The terms of efficient extraction of molybdenum from bimetallic systems of Mo-W have been determined. The polarization curves of the electrooxidation of molybdenum in the solution of 0.25 M LiCl in the DMSO at the different rates of rotations and the scan rate equal to 50 mV/s were obtained. In the presence of the addition of water at the potential of 0.1-0.75 V the small area of polarizability occurs, then with increasing potentials above 1.5 V there is a sharp increase of the oxidation current. Comparison of the current values of anodic dissolution of molybdenum and tungsten showed that the rate of anodic dissolution of molybdenum significantly exceeds the rate of anodic dissolution of tungsten. In the case of molybdenum, the dissolution process is limited by diffusion, in the case of tungsten - by the passive film formation on the electrode surface.

Tensile Properties of Molybdenum and Tungsten from 2500 to 3700 F

NASA Technical Reports Server (NTRS)

Hall, Robert W.; Sikora, Paul F.

1959-01-01

Specimens of commercially pure sintered tungsten, arc-cast unalloyed molybdenum, and two arc-cast molybdenum-base alloys (one with 0.5 percent titanium, the other with 0.46 percent titanium and 0.07 percent zirconium) were fabricated from 1/2-inch-diameter rolled or swaged bars. All specimens were evaluated in short-time tensile tests in the as-received condition, and all except the molybdenum-titanium-zirconium alloy were tested after a 30-minute recrystallization anneal at 3800 F in a vacuum of approximately 0.1 micron. Results showed that the tungsten was considerably stronger than either the arc-cast unalloyed molybdenum or the molybdenum-base alloys over the 2500 to 3700 F temperature range. Recrystallization of swaged tungsten at 3800 F considerably reduced its tensile strength at 2500 F. However, above 3100 F, the as-swaged tungsten specimens recrystallized during testing, and had about the same strength as when recrystallized at 3800 F before evaluation. The ductility of molybdenum-base materials was very high at all test temperatures; the ductility of tungsten decreased sharply above about 3120 F.

Mineral resource of the month: molybdenum

USGS Publications Warehouse

Magyar, Michael J.

2004-01-01

Molybdenum is a metallic element that is most frequently used in alloy and stainless steels, which together represent the single largest market for molybdenum. Molybdenum has also proven invaluable in carbon steel, cast iron and superalloys. Its alloying versatility is unmatched because its addition enhances material performance under high-stress conditions in expanded temperature ranges and in highly corrosive environments. The metal is also used in catalysts, other chemicals, lubricants and many other applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stine, Andrew Martin; Pierce, Stanley W.; Moniz, Paul F.

The welding equipment used for welding iridium containers (clads) at Los Alamos National Laboratory is twenty five years old and is undergoing an upgrade. With the upgrade, there is a requirement for requalification of the welding process, and the opportunity for process improvement. Testing of the new system and requalification will require several welds on iridium test parts and clads, and any efforts to improve the process will add to the need for iridium parts. The extreme high cost of iridium imposes a severe limitation on the extent of test welding that can be done. The 2 inch diameter, 0.027more » inch thick, iridium blank disc that the clad cup is formed from, is useful for initial weld trials, but it costs $5000. The development clad sets needed for final tests and requalification cost $15,000 per set. A solution to iridium cost issue would be to do the majority of the weld development on a less expensive surrogate metal with similar weld characteristics. One such metal is molybdenum. Since its melting index (melting temperature x thermal conductivity) is closest to iridium, welds on molybdenum should be similar in size for a given weld power level. Molybdenum is inexpensive; a single 2 inch molybdenum disc costs only $9. In order to evaluate molybdenum as a surrogate for iridium, GTA welds were first developed to provide full penetration on 0.030 inch thick molybdenum discs at speeds of 20, 25, and 30 inches per minute (ipm). These weld parameters were then repeated on the standard 0.027 inch thick iridium blanks. The top surface and bottom surface (root) width and grain structure of the molybdenum and iridium welds were compared, and similarities were evident between the two metals. Due to material and thickness differences, the iridium welds were approximately 35% wider than the molybdenum welds. A reduction in iridium weld current of 35% produce welds slightly smaller than the molybdenum welds yet showed that current could be scaled according to molybdenum/iridium weld width ratio to achieve similar welds. Further weld trials using various thicknesses of molybdenum determined that 0.024 inch thick molybdenum material would best match the 0.027 inch thick iridium in achieving comparable welds when using the same welding parameters. Across the range of welding speeds, the characteristic weld pool shape and solidification grain structure in the two materials was also similar. With the similarity of welding characteristics confirmed, and the appropriate thickness of molybdenum determined, it has been concluded that the use of molybdenum discs and tube sections will greatly expand the weld testing opportunities prior to iridium weld qualification« less

Molybdenum-A Key Component of Metal Alloys

USGS Publications Warehouse

Kropschot, S.J.

2010-01-01

Molybdenum, whose chemical symbol is Mo, was first recognized as an element in 1778. Until that time, the mineral molybdenite-the most important source of molybdenum-was believed to be a lead mineral because of its metallic gray color, greasy feel, and softness. In the late 19th century, French metallurgists discovered that molybdenum, when alloyed (mixed) with steel in small quantities, creates a substance that is remarkably tougher than steel alone and is highly resistant to heat. The alloy was found to be ideal for making tools and armor plate. Today, the most common use of molybdenum is as an alloying agent in stainless steel, alloy steels, and superalloys to enhance hardness, strength, and resistance to corrosion.

The History of the Discovery of the Molybdenum Cofactor and Novel Aspects of its Biosynthesis in Bacteria

PubMed Central

Leimkühler, Silke; Wuebbens, Margot M.; Rajagopalan, K.V.

2010-01-01

Biosynthesis of the molybdenum cofactor in bacteria is described with a detailed analysis of each individual reaction leading to the formation of stable intermediates during the synthesis of molybdopterin from GTP. As a starting point, the discovery of molybdopterin and the elucidation of its structure through the study of stable degradation products are described. Subsequent to molybdopterin synthesis, the molybdenum atom is added to the molybdopterin dithiolene group to form the molybdenum cofactor. This cofactor is either inserted directly into specific molybdoenzymes or is further modified by the addition of nucleotides to the molybdopterin phosphate group or the replacement of ligands at the molybdenum center. PMID:21528011

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rabin, S.A.; Lotts, A.L.; Hammond, J.P.

Uranium --molybdenum alloy rods containing from 10 to 15 wt% Mo and 1/16- in. in diameter were successfully fabricated by hot rotary swaging, followed by machining to remove the protective sheathing (Inconel with molybdenum barrier). Structurally strong rods with densities greater than 95% of theoretical were produced from both calciumreduced uranium mixed with hydrogen-reduced molybdenum and acid-cleaned, prealloyed shot when reduced in area about 55% at 1050 or 1100 deg C. Alloy homogeneity was good with prealloyed powders; however, traces of molybdenum -rich, gamma phase persisted in the elemental uranium -molybdenum material after swaging at 1100 deg C. Swagings embodyingmore » hydride uranium or oxide- contaminated prealloyed shot were unsatisfactory because of insufficient consolidation or poor interparticle bonding. (auth)« less

Hexavalent Molybdenum Reduction to Mo-Blue by a Sodium-Dodecyl-Sulfate-Degrading Klebsiella oxytoca Strain DRY14

PubMed Central

Halmi, M. I. E.; Zuhainis, S. W.; Yusof, M. T.; Shaharuddin, N. A.; Helmi, W.; Shukor, Y.; Syed, M. A.; Ahmad, S. A.

2013-01-01

Bacteria with the ability to tolerate, remove, and/or degrade several xenobiotics simultaneously are urgently needed for remediation of polluted sites. A previously isolated bacterium with sodium dodecyl sulfate- (SDS-) degrading capacity was found to be able to reduce molybdenum to the nontoxic molybdenum blue. The optimal pH, carbon source, molybdate concentration, and temperature supporting molybdate reduction were pH 7.0, glucose at 1.5% (w/v), between 25 and 30 mM, and 25°C, respectively. The optimum phosphate concentration for molybdate reduction was 5 mM. The Mo-blue produced exhibits an absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. None of the respiratory inhibitors tested showed any inhibition to the molybdenum-reducing activity suggesting that the electron transport system of this bacterium is not the site of molybdenum reduction. Chromium, cadmium, silver, copper, mercury, and lead caused approximately 77, 65, 77, 89, 80, and 80% inhibition of the molybdenum-reducing activity, respectively. Ferrous and stannous ions markedly increased the activity of molybdenum-reducing activity in this bacterium. The maximum tolerable concentration of SDS as a cocontaminant was 3 g/L. The characteristics of this bacterium make it a suitable candidate for molybdenum bioremediation of sites cocontaminated with detergent pollutant. PMID:24383052

Molybdenum reduction to molybdenum blue in Serratia sp. Strain DRY5 is catalyzed by a novel molybdenum-reducing enzyme.

PubMed

Shukor, M Y; Halmi, M I E; Rahman, M F A; Shamaan, N A; Syed, M A

2014-01-01

The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a V max for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent K m for NADH was 0.79 mM. At 5 mM NADH, the apparent V max and apparent K m values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (k cat/K m ) of the Mo-reducing enzyme was 5.47 M(-1) s(-1). The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction.

Molybdenum Reduction to Molybdenum Blue in Serratia sp. Strain DRY5 Is Catalyzed by a Novel Molybdenum-Reducing Enzyme

PubMed Central

Shukor, M. Y.; Halmi, M. I. E.; Rahman, M. F. A.; Shamaan, N. A.; Syed, M. A.

2014-01-01

The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a V max for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent K m for NADH was 0.79 mM. At 5 mM NADH, the apparent V max and apparent K m values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (k cat/K m) of the Mo-reducing enzyme was 5.47 M−1 s−1. The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction. PMID:24724104

Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

NASA Technical Reports Server (NTRS)

Fieno, D.; Fox, T.; Mueller, R.

1972-01-01

Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

Transfer of molybdenum disulfide to various metals

NASA Technical Reports Server (NTRS)

Barton, G. C.; Pepper, S. V.

1977-01-01

Sliding friction experiments were conducted with molybdenum disulfide single crystals in contact with sputter cleaned surfaces of copper, nickel, gold, and 304 stainless steel. Transfer of the molybdenum disulfide to the metals was monitored with Auger electron spectroscopy. Results of the investigation indicate molybdenum disulfide transfers to all clean metal surfaces after a single pass over the metal surface with film thickness observed to increase with repeated passes over the same surfaces. Large particle transfer occurs when the orientation of the crystallites is other than basal. This is frequently accompanied by abrasion of the metal. Adhesion of molybdenum disulfide films occurred readily to copper and nickel, less readily to 304 stainless steel, and even less effectively to the gold, which indicates a chemical effect.

High-strength, creep-resistant molybdenum alloy and process for producing the same

DOEpatents

Bianco, R.; Buckman, R.W. Jr.; Geller, C.B.

1999-02-09

A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2--4% by volume (ca. 1--4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T{sub m} of molybdenum. 10 figs.

High-strength, creep-resistant molybdenum alloy and process for producing the same

DOEpatents

Bianco, Robert; Buckman, Jr., R. William; Geller, Clint B.

1999-01-01

A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2-4% by volume (.about.1-4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T.sub.m of molybdenum.

Molybdenum In Cathodes Of Sodium/Metal Chloride Cells

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

1992-01-01

Cyclic voltammetric curves of molybdenum wire in NaAlCl4 melt indicate molybdenum chloride useful as cathode material in rechargeable sodium/metal chloride electrochemical cells. Batteries used in electric vehicles, for electric-power load leveling, and other applications involving high energy and power densities.

Electrochemical synthesis of binary molybdenum-tungsten carbides (Mo,W)2C from tungstate-molybdate-carbonate melts

NASA Astrophysics Data System (ADS)

Kushkhov, Kh. B.; Kardanov, A. L.; Adamokova, M. N.

2013-02-01

Nanopowders of binary tungsten-molybdenum carbide are fabricated by high-temperature electrochemical synthesis. The optimum concentration relations between electrolyte components, the current density, and the quantity of electricity are determined to synthesize binary tungsten-molybdenum carbides.

Molybdenum Enzymes, Cofactors, and Model Systems.

ERIC Educational Resources Information Center

Burgmayer, S. J. N; Stiefel, E. I.

1985-01-01

Discusses: (l) molybdoenzymes (examining their distribution and metabolic role, composition and redox strategy, cofactors, substrate reactions, and mechanistic possibilities); (2) structural information on molybdenum (Mo) centers; (3) modeling studies (Mo-co models, nitrogenase models, and the MO-S duo); and (4) the copper-molybdenum antagonism.…

Edge-terminated molybdenum disulfide with a 9.4-Å interlayer spacing for electrochemical hydrogen production

DOE PAGES

Gao, Min -Rui; Chan, Maria K. Y.; Sun, Yugang

2015-07-03

In this study, layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of -103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10 -3more » mA cm -2, performing among the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance.« less

Edge-terminated molybdenum disulfide with a 9.4-Å interlayer spacing for electrochemical hydrogen production

PubMed Central

Gao, Min-Rui; Chan, Maria K.Y.; Sun, Yugang

2015-01-01

Layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of −103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10−3 mA cm−2, performing among the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance. PMID:26138031

Reduction of molybdate to molybdenum blue by Klebsiella sp. strain hkeem.

PubMed

Lim, H K; Syed, M A; Shukor, M Y

2012-06-01

A novel molybdate-reducing bacterium, tentatively identified as Klebsiella sp. strain hkeem and based on partial 16s rDNA gene sequencing and phylogenetic analysis, has been isolated. Strain hkeem produced 3 times more molybdenum blue than Serratia sp. strain Dr.Y8; the most potent Mo-reducing bacterium isolated to date. Molybdate was optimally reduced to molybdenum blue using 4.5 mM phosphate, 80 mM molybdate and using 1% (w/v) fructose as a carbon source. Molybdate reduction was optimum at 30 °C and at pH 7.3. The molybdenum blue produced from cellular reduction exhibited absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of electron transport system such as antimycin A, rotenone, sodium azide, and potassium cyanide did not inhibit the molybdenum-reducing enzyme. Mercury, silver, and copper at 1 ppm inhibited molybdenum blue formation in whole cells of strain hkeem. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deuterium retention and release from molybdenum exposed to a Penning discharge

NASA Astrophysics Data System (ADS)

Causey, R. A.; Kunz, C. L.; Cowgill, D. F.

2005-03-01

Both molybdenum and tungsten are candidate materials for plasma-facing applications in fusion reactors. While tungsten has a higher melting point and a higher threshold for sputtering, it is a brittle material that is difficult to machine into shapes required for fusion applications. For this reason, molybdenum is now receiving serious consideration as an alternative for tungsten. If molybdenum is to be used as a plasma-facing material, the hydrogen retention and recycling characteristics must be known. In this report, we present experimental results on deuterium retention in molybdenum after exposure to a Penning discharge at temperatures from 573 to 773 K. D2+ ions with energies of 1.2 keV were implanted into the 50 mm diameter molybdenum samples at fluxes of 10 20 D/m 2 s. Thermal desorption spectroscopy was used to determine both the amount of retained deuterium and the release kinetics. Low retention values similar to those measured previously for tungsten were observed.

Chemistry and Mechanism of Interaction Between Molybdenite Concentrate and Sodium Chloride When Heated in the Presence of Oxygen

NASA Astrophysics Data System (ADS)

Aleksandrov, P. V.; Medvedev, A. S.; Imideev, V. A.; Moskovskikh, D. O.

2017-04-01

Roasting of molybdenum concentrates with sodium chloride has high potential and can be an alternative to oxidizing roasting and autoclave leaching; however, the chemistry and mechanism are poorly known. The chemical mechanism of the roasting process between molybdenite concentrate and sodium chloride in the presence of atmospheric oxygen is proposed. It is demonstrated that the process occurs through molybdenite oxidation, up to molybdenum trioxide, with subsequent formation of sodium polymolybdates and molybdenum dioxydichloride from molybdenum trioxide. It is found that the formation of water-soluble sodium polymolybdates from molybdenum trioxide stops over time due to passivation of sodium chloride surface by polymolybdates. It is proved experimentally that preliminary grinding of the mixture in a furnace charge leads to an increase in the polymolybdate fraction of the roasting products, which constitutes approximately 65 pct of molybdenum initially in the roasted mixture against 20 to 22 pct in a nonground mixture (or 75 to 77 pct against 30 to 33 pct of molybdenum in calcine). For the first time, the presence of the Na2S2O7 phase in the calcine was confirmed experimentally. The suggested mechanism gives possible explanations for the sharp increase of MoO2Cl2 formation within the temperature range of 673 K to 723 K (400 °C to 450 °C) that is based on the catalytic reaction of molybdenum dioxydichloride from the Na2S2O7 liquid phase as it runs in a melt.

Mechanism of pyranopterin ring formation in molybdenum cofactor biosynthesis

DOE PAGES

Hover, Bradley M.; Tonthat, Nam K.; Schumacher, Maria A.; ...

2015-05-04

The molybdenum cofactor (Moco) is essential for all kingdoms of life, plays central roles in various biological processes, and must be biosynthesized de novo. During Moco biosynthesis, the characteristic pyranopterin ring is constructed by a complex rearrangement of guanosine 5'-triphosphate (GTP) into cyclic pyranopterin (cPMP) through the action of two enzymes, MoaA and MoaC (molybdenum cofactor biosynthesis protein A and C, respectively). Conventionally, MoaA was considered to catalyze the majority of this transformation, with MoaC playing little or no role in the pyranopterin formation. Recently, this view was challenged by the isolation of 3',8-cyclo-7,8-dihydro-guanosine 5'-triphosphate (3',8-cH 2GTP) as the productmore » of in vitro MoaA reactions. To elucidate the mechanism of formation of Moco pyranopterin backbone, in this paper we performed biochemical characterization of 3',8-cH 2GTP and functional and X-ray crystallographic characterizations of MoaC. These studies revealed that 3',8-cH 2GTP is the only product of MoaA that can be converted to cPMP by MoaC. Our structural studies captured the specific binding of 3',8-cH 2GTP in the active site of MoaC. These observations provided strong evidence that the physiological function of MoaA is the conversion of GTP to 3',8-cH 2GTP (GTP 3',8-cyclase), and that of MoaC is to catalyze the rearrangement of 3',8-cH 2GTP into cPMP (cPMP synthase). Furthermore, our structure-guided studies suggest that MoaC catalysis involves the dynamic motions of enzyme active-site loops as a way to control the timing of interaction between the reaction intermediates and catalytically essential amino acid residues. In conclusion, these results reveal the previously unidentified mechanism behind Moco biosynthesis and provide mechanistic and structural insights into how enzymes catalyze complex rearrangement reactions.« less

Molybdenum disilicide matrix composite

DOEpatents

Petrovic, John J.; Carter, David H.; Gac, Frank D.

1991-01-01

A composition consisting of an intermetallic compound, molybdenum disilicide, which is reinforced with VS silicon carbide whiskers dispersed throughout it and a method of making the reinforced composition. Use of the reinforcing material increases fracture toughness at low temperatures and strength at high temperatures, as compared to pure molybdenum disilicide.

Molybdenum disilicide matrix composite

DOEpatents

Petrovic, John J.; Carter, David H.; Gac, Frank D.

1990-01-01

A composition consisting of an intermetallic compound, molybdenum disilicide, which is reinforced with VS silicon carbide whiskers dispersed throughout it and a method of making the reinforced composition. Use of the reinforcing material increases fracture toughness at low temperatures and strength at high temperatures, as compared to pure molybdenum disilicide.

Development of a potentiometric EDTA method for determination of molybdenum. Use of the analysis for molybdenite concentrates

NASA Technical Reports Server (NTRS)

Khristova, R.; Vanmen, M.

1986-01-01

Based on considerations of principles and experimental data, the interference of sulfate ions in poteniometric titration of EDTA with FeCl3 was confirmed. The method of back complexometric titration of molybdenum of Nonova and Gasheva was improved by replacing hydrazine sulfate with hydrazine hydrochloride for reduction of Mo(VI) to Mo(V). The method can be used for one to tenths of mg of molybdenum with 0.04 mg standard deviation. The specific method of determination of molybdenum in molybdenite concentrates is presented.

Role of electron concentration in softening and hardening of ternary molybdenum alloys

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1975-01-01

Effects of various combinations of hafnium, tantalum, rhenium, osmium, iridium, and platinum in ternary molybdenum alloys on alloy softening and hardening were determined. Hardness tests were conducted at four test temperatures over the temperature range 77 to 411 K. Results showed that hardness data for ternary molybdenum alloys could be correlated with anticipated results from binary data based upon expressions involving the number of s and d electrons contributed by the solute elements. The correlation indicated that electron concentration plays a dominant role in controlling the hardness of ternary molybdenum alloys.

FY16 Status Report for the Uranium-Molybdenum Fuel Concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Wendy D.; Doherty, Ann L.; Henager, Charles H.

2016-09-22

The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. Uranium-Molybdenum fuel has the potential to provide superior performance based on its thermo-physical properties. With sufficient development, it may be able to provide the Light Water Reactor industry with a melt-resistant, accident-tolerant fuel with improved safety response. The Pacific Northwest National Laboratory has been tasked with extrusion development and performing ex-reactor corrosion testing to characterize the performance of Uranium-Molybdenum fuel in both these areas. This report documents the results of the fiscal yearmore » 2016 effort to develop the Uranium-Molybdenum metal fuel concept for light water reactors.« less

Structural and morphological properties of mesoporous carbon coated molybdenum oxide films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dayal, Saurabh, E-mail: saurabhdayal153@gmail.com; Kumar, C. Sasi, E-mail: csasimv@gmail.com

2016-05-06

In the present study, we report the structural and morphological properties of mesoporous carbon coated molybdenum oxide films. The deposition of films was carried out in a two-step process, the first step involves deposition of molybdenum and carbon bilayer thin films using DC magnetron sputtering. In the second step the sample was ex-situ annealed in a muffle furnace at different temperatures (400°C to 600°C) and air cooled in the ambient atmosphere. The formation of the meso-porous carbon clusters on molybdenum oxide during the cooling step was investigated using FESEM and AFM techniques. The structural details were explored using XRD. Themore » meso-porous carbon were found growing over molybdenum oxide layer as a result of segregation phenomena.« less

Infrared Multiple Photon Dissociation Spectroscopy of a Gas-Phase Oxo-Molybdenum Complex with 1,2-Dithiolene Ligands

PubMed Central

2015-01-01

Electrospray ionization (ESI) in the negative ion mode was used to create anionic, gas-phase oxo-molybdenum complexes with dithiolene ligands. By varying ESI and ion transfer conditions, both doubly and singly charged forms of the complex, with identical formulas, could be observed. Collision-induced dissociation (CID) of the dianion generated exclusively the monoanion, while fragmentation of the monoanion involved decomposition of the dithiolene ligands. The intrinsic structure of the monoanion and the dianion were determined by using wavelength-selective infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The IRMPD spectrum for the dianion exhibits absorptions that can be assigned to (ligand) C=C, C–S, C—C≡N, and Mo=O stretches. Comparison of the IRMPD spectrum to spectra predicted for various possible conformations allows assignment of a pseudo square pyramidal structure with C2v symmetry, equatorial coordination of MoO2+ by the S atoms of the dithiolene ligands, and a singlet spin state. A single absorption was observed for the oxidized complex. When the same scaling factor employed for the dianion is used for the oxidized version, theoretical spectra suggest that the absorption is the Mo=O stretch for a distorted square pyramidal structure and doublet spin state. A predicted change in conformation upon oxidation of the dianion is consistent with a proposed bonding scheme for the bent-metallocene dithiolene compounds [Lauher, J. W.; Hoffmann, R. J. Am. Chem. Soc.1976, 98, 1729−1742], where a large folding of the dithiolene moiety along the S···S vector is dependent on the occupancy of the in-plane metal d-orbital. PMID:24988369

Catalyst-free room-temperature iClick reaction of molybdenum(ii) and tungsten(ii) azide complexes with electron-poor alkynes: structural preferences and kinetic studies.

PubMed

Schmid, Paul; Maier, Matthias; Pfeiffer, Hendrik; Belz, Anja; Henry, Lucas; Friedrich, Alexandra; Schönfeld, Fabian; Edkins, Katharina; Schatzschneider, Ulrich

2017-10-10

Two isostructural and isoelectronic group VI azide complexes of the general formula [M(η 3 -allyl)(N 3 )(bpy)(CO) 2 ] with M = Mo, W and bpy = 2,2'-bipyridine were prepared and fully characterized, including X-ray structure analysis. Both reacted smoothly with electron-poor alkynes such as dimethyl acetylenedicarboxylate (DMAD) and 4,4,4-trifluoro-2-butynoic acid ethyl ester in a catalyst-free room-temperature iClick [3 + 2] cycloaddition reaction. Reaction with phenyl(trifluoromethyl)acetylene, on the other hand, did not lead to any product formation. X-ray structures of the four triazolate complexes isolated showed the monodentate ligand to be N2-coordinated in all cases, which requires a 1,2-shift of the nitrogen from the terminal azide to the triazolate cycloaddition product. On the other hand, a 19 F NMR spectroscopic study of the reaction of the fluorinated alkyne with the tungsten azide complex at 27 °C allowed detection of the N1-coordinated intermediate. With this method, the second-order rate constant was determined as (7.3 ± 0.1) × 10 -2 M -1 s -1 , which compares favorably with that of first-generation compounds such as difluorocyclooctyne (DIFO) used in the strain-promoted azide-alkyne cycloaddition (SPAAC). In contrast, the reaction of the molybdenum analogue was too fast to be studied with NMR methods. Alternatively, solution IR studies revealed pseudo-first order rate constants of 0.4 to 6.5 × 10 -3 s -1 , which increased in the order of Mo > W and F 3 C-C[triple bond, length as m-dash]C-COOEt > DMAD.

Synthesis and characterization of MoB{sub 2−x} thin films grown by nonreactive DC magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malinovskis, Paulius, E-mail: paulius.malinovskis@kemi.uu.se; Lewin, Erik; Jansson, Ulf

2016-05-15

DC magnetron sputtering was used to deposit molybdenum boride thin films for potential low-friction applications. The films exhibit a nanocomposite structure with ∼10 nm large MoB{sub 2−x} (x > 0.4) grains surrounded by a boron-rich tissue phase. The preferred formation of the metastable and substoichiometric hP3-MoB{sub 2} structure (AlB{sub 2}-type) is explained with kinetic constraints to form the thermodynamically stable hR18-MoB{sub 2} phase with a very complex crystal structure. Nanoindentation revealed a relatively high hardness of (29 ± 2) GPa, which is higher than bulk samples. The high hardness can be explained by a hardening effect associated with the nanocomposite microstructure where the surrounding tissuemore » phase restricts dislocation movement. A tribological study confirmed a significant formation of a tribofilm consisting of molybdenum oxide and boron oxide, however, without any lubricating effects at room temperature.« less

Light-Induced Activation of a Molybdenum Oxotransferase Model within a Ru(II)-Mo(VI) Dyad.

PubMed

Ducrot, Aurélien B; Coulson, Ben A; Perutz, Robin N; Duhme-Klair, Anne-Kathrin

2016-12-19

Nature uses molybdenum-containing enzymes to catalyze oxygen atom transfer (OAT) from water to organic substrates. In these enzymes, the two electrons that are released during the reaction are rapidly removed, one at a time, by spatially separated electron transfer units. Inspired by this design, a Ru(II)-Mo(VI) dyad was synthesized and characterized, with the aim of accelerating the rate-determining step in the cis-dioxo molybdenum-catalyzed OAT cycle, the transfer of an oxo ligand to triphenyl phosphine, via a photo-oxidation process. The dyad consists of a photoactive bis(bipyridyl)-phenanthroline ruthenium moiety that is covalently linked to a bioinspired cis-dioxo molybdenum thiosemicarbazone complex. The quantum yield and luminescence lifetimes of the dyad [Ru(bpy) 2 (L 2 )MoO 2 (solv)] 2+ were determined. The major component of the luminescence decay in MeCN solution (τ = 1149 ± 2 ns, 67%) corresponds closely to the lifetime of excited [Ru(bpy) 2 (phen-NH 2 )] 2+ , while the minor component (τ = 320 ± 1 ns, 31%) matches that of [Ru(bpy) 2 (H 2 -L 2 )] 2+ . In addition, the (spectro)electrochemical properties of the system were investigated. Catalytic tests showed that the dyad-catalyzed OAT from dimethyl sulfoxide to triphenyl phosphine proceeds significantly faster upon irradiation with visible light than in the dark. Methylviologen acts as a mediator in the photoredox cycle, but it is regenerated and hence only required in stoichiometric amounts with respect to the catalyst rather than sacrificial amounts. It is proposed that oxidative quenching of the photoexcited Ru unit, followed by intramolecular electron transfer, leads to the production of a reactive one-electron oxidized catalyst, which is not accessible by electrochemical methods. A significant, but less pronounced, rate enhancement was observed when an analogous bimolecular system was tested, indicating that intramolecular electron transfer between the photosensitizer and the catalytic center is more efficient than intermolecular electron transfer between the separate components.

Properties of Reactive Atomic Species Generated at High Temperatures and Their Low Temperature Reactions to Form Novel Substances

DTIC Science & Technology

1979-01-01

product is magnesium pinacolate, minor but important are the magnesium enolate of acetone and isopropoxide in 1:1 ratio. The double ketyl is a...tungsten, molybdenum and titanium were either unknown or had been made in very poor yield. Our vaporization techniques make these compounds readily...excess cyclooctatetraene. Mono and binuclear complexes of titanium have been isolated; the latter, triscyclooctatetraenedititanium was shown to be a

Molybdenum sealing glass-ceramic composition

DOEpatents

Eagan, Robert J.

1976-01-01

The invention relates to a glass-ceramic composition having low hydrogen and helium permeability properties, along with high fracture strength, a thermal coefficient of expansion similar to that of molybdenum, and adaptable for hermetically sealing to molybdenum at temperatures of between about 900.degree. and about 950.degree.C. to form a hermatically sealed insulator body.

Influence of Soil Solution Salinity on Molybdenum Adsorption by Soils

USDA-ARS?s Scientific Manuscript database

Molybdenum (Mo) adsorption on five arid-zone soils from California was investigated as a function of equilibrium solution Mo concentration (0-30 mg L-1), solution pH (4-8), and electrical conductivity (EC = 0.3 or 8 dS m-1). Molybdenum adsorption decreased with increasing pH. An adsorption maximum...

Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ringleb, F.; Eylers, K.; Teubner, Th.

2016-03-14

A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Basedmore » on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.« less

X-ray absorption fine structure analysis of molybdenum added to BaTiO3-based ceramics used for multilayer ceramic capacitors

NASA Astrophysics Data System (ADS)

Ogata, Yoichiro; Shimura, Tetsuo; Ryu, Minoru; Iwazaki, Yoshiki

2017-04-01

The effect of slight molybdenum doping of perovskite-type BaTiO3-based ceramics on the reliability of a multilayer ceramic capacitor (MLCC) and on the valence state of molybdenum in the BaTiO3-based ceramics has been investigated by highly accelerated lifetime tests and X-ray absorption fine structure analysis. The molybdenum added to the BaTiO3-based ceramics is located at Ti sites and improves the highly accelerated lifetime and lowers the initial dielectric resistivity in MLCCs. Through sintering in a reducing atmosphere, which is an important process in the fabrication of BaTiO3-based MLCCs, the oxidation state of the molybdenum added could be adjusted from +6 to a value close to +4.

Catalytic ionic hydrogenation of ketones using tungsten or molybdenum organometallic species

DOEpatents

Voges, Mark; Bullock, R. Morris

2000-01-01

The present invention is a process for the catalytic hydrogenation of ketones and aldehydes to alcohols at low temperatures and pressures using organometallic molybdenum and tungsten complexes. The functional group is selected from groups represented by the formulas R(C.dbd.O)R' and R(C.dbd.O)H, wherein R and R' are selected from hydrogen or any alkyl or aryl group. The active catalyst for the process has the form: [CpM(CO).sub.2 (PR*.sub.3) L].sup.+ A.sup.-, where Cp=.eta..sup.5 -R.sup..tangle-solidup..sub.m C.sub.5 H.sub.5-m and R.sup..tangle-solidup. represents an alkyl group or a halogen (F, Cl, Br, I) or R.sup..tangle-solidup. =OR' (where R'=H, an alkyl group or an aryl group) or R.sup..tangle-solidup. =CO.sub.2 R' (where R'=H, an alkyl group or an aryl group) and m=0 to 5; M represents a molybdenum atom or a tungsten atom; R*.sub.3 represents three hydrocarbon groups selected from a cyclohexyl group (C.sub.6 H.sub.11), a methyl group (CH.sub.3), and a phenyl group (C.sub.6 H.sub.5) and all three R* groups can be the same or different or two of the three groups can be the same; L represents a ligand; and A.sup.- represents an anion. In another embodiment, one, two or three of the R* groups can be an OR*.

High cell density media for Escherichia coli are generally designed for aerobic cultivations – consequences for large-scale bioprocesses and shake flask cultures

PubMed Central

Soini, Jaakko; Ukkonen, Kaisa; Neubauer, Peter

2008-01-01

Background For the cultivation of Escherichia coli in bioreactors trace element solutions are generally designed for optimal growth under aerobic conditions. They do normally not contain selenium and nickel. Molybdenum is only contained in few of them. These elements are part of the formate hydrogen lyase (FHL) complex which is induced under anaerobic conditions. As it is generally known that oxygen limitation appears in shake flask cultures and locally in large-scale bioreactors, function of the FHL complex may influence the process behaviour. Formate has been described to accumulate in large-scale cultures and may have toxic effects on E. coli. Although the anaerobic metabolism of E. coli is well studied, reference data which estimate the impact of the FHL complex on bioprocesses of E. coli with oxygen limitation have so far not been published, but are important for a better process understanding. Results Two sets of fed-batch cultures with conditions triggering oxygen limitation and formate accumulation were performed. Permanent oxygen limitation which is typical for shake flask cultures was caused in a bioreactor by reduction of the agitation rate. Transient oxygen limitation, which has been described to eventually occur in the feed-zone of large-scale bioreactors, was mimicked in a two-compartment scale-down bioreactor consisting of a stirred tank reactor and a plug flow reactor (PFR) with continuous glucose feeding into the PFR. In both models formate accumulated up to about 20 mM in the culture medium without addition of selenium, molybdenum and nickel. By addition of these trace elements the formate accumulation decreased below the level observed in well-mixed laboratory-scale cultures. Interestingly, addition of the extra trace elements caused accumulation of large amounts of lactate and reduced biomass yield in the simulator with permanent oxygen limitation, but not in the scale-down two-compartment bioreactor. Conclusion The accumulation of formate in oxygen limited cultivations of E. coli can be fully prevented by addition of the trace elements selenium, nickel and molybdenum, necessary for the function of FHL complex. For large-scale cultivations, if glucose gradients are likely, the results from the two-compartment scale-down bioreactor indicate that the addition of the extra trace elements is beneficial. No negative effects on the biomass yield or on any other bioprocess parameters could be observed in cultures with the extra trace elements if the cells were repeatedly exposed to transient oxygen limitation. PMID:18687130

Kinetics of molybdenum reduction to molybdenum blue by Bacillus sp. strain A.rzi.

PubMed

Othman, A R; Bakar, N A; Halmi, M I E; Johari, W L W; Ahmad, S A; Jirangon, H; Syed, M A; Shukor, M Y

2013-01-01

Molybdenum is very toxic to agricultural animals. Mo-reducing bacterium can be used to immobilize soluble molybdenum to insoluble forms, reducing its toxicity in the process. In this work the isolation of a novel molybdate-reducing Gram positive bacterium tentatively identified as Bacillus sp. strain A.rzi from a metal-contaminated soil is reported. The cellular reduction of molybdate to molybdenum blue occurred optimally at 4 mM phosphate, using 1% (w/v) glucose, 50 mM molybdate, between 28 and 30 °C and at pH 7.3. The spectrum of the Mo-blue product showed a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of bacterial electron transport system (ETS) such as rotenone, sodium azide, antimycin A, and potassium cyanide could not inhibit the molybdenum-reducing activity. At 0.1 mM, mercury, copper, cadmium, arsenic, lead, chromium, cobalt, and zinc showed strong inhibition on molybdate reduction by crude enzyme. The best model that fitted the experimental data well was Luong followed by Haldane and Monod. The calculated value for Luong's constants p max, K(s), S(m), and n was 5.88 μmole Mo-blue hr(-1), 70.36 mM, 108.22 mM, and 0.74, respectively. The characteristics of this bacterium make it an ideal tool for bioremediation of molybdenum pollution.

A Generator-Produced Gallium-68 Radiopharmaceutical for PET Imaging of Myocardial Perfusion

PubMed Central

Sharma, Vijay; Sivapackiam, Jothilingam; Harpstrite, Scott E.; Prior, Julie L.; Gu, Hannah; Rath, Nigam P.; Piwnica-Worms, David

2014-01-01

Lipophilic cationic technetium-99m-complexes are widely used for myocardial perfusion imaging (MPI). However, inherent uncertainties in the supply chain of molybdenum-99, the parent isotope required for manufacturing 99Mo/99mTc generators, intensifies the need for discovery of novel MPI agents incorporating alternative radionuclides. Recently, germanium/gallium (Ge/Ga) generators capable of producing high quality 68Ga, an isotope with excellent emission characteristics for clinical PET imaging, have emerged. Herein, we report a novel 68Ga-complex identified through mechanism-based cell screening that holds promise as a generator-produced radiopharmaceutical for PET MPI. PMID:25353349

40 CFR 421.223 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... molybdenum plus vanadium plus pure grade molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead...) Vanadium decomposition wet air pollution control. BAT Limitations for the Secondary Molybdenum and Vanadium... per million pounds) of vanadium produced by decomposition Arsenic 0.000 0.000 Chromium 0.000 0.000...

40 CFR 421.223 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... molybdenum plus vanadium plus pure grade molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead...) Vanadium decomposition wet air pollution control. BAT Limitations for the Secondary Molybdenum and Vanadium... per million pounds) of vanadium produced by decomposition Arsenic 0.000 0.000 Chromium 0.000 0.000...

40 CFR 421.226 - Pretreatment standards for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead 5.463 2.536 Nickel 10.731 7.219 Iron 23... technical grade molybdenum plus vanadium plus pure grade molybdenum produced Arsenic 80.952 36.108 Chromium...] [Reserved] Ammonia (as N) 24114.000 10600.000 (c) Vanadium decomposition wet air pollution control. PSNS for...

40 CFR 421.222 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... technical grade molybdenum plus vanadium plus pure grade molybdenum produced Arsenic 40.778 18.145 Chromium... vanadium plus pure grade molybdenum produced Arsenic 121.720 54.162 Chromium 25.625 10.483 Lead 24.460 11... times. (c) Vanadium decomposition wet air pollution control. BPT Limitations for the Secondary...

40 CFR 421.226 - Pretreatment standards for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead 5.463 2.536 Nickel 10.731 7.219 Iron 23... technical grade molybdenum plus vanadium plus pure grade molybdenum produced Arsenic 80.952 36.108 Chromium...] [Reserved] Ammonia (as N) 24114.000 10600.000 (c) Vanadium decomposition wet air pollution control. PSNS for...

Nickel-Catalyzed Molybdenum-Promoted Carbonylative Synthesis of Benzophenones.

PubMed

Peng, Jin-Bao; Wu, Fu-Peng; Li, Da; Qi, Xinxin; Ying, Jun; Wu, Xiao-Feng

2018-06-01

A nickel-catalyzed molybdenum-promoted carbonylative coupling reaction for the synthesis of benzophenones from aryl iodides has been developed. Various substituted diaryl ketones were synthesized in moderate to excellent yields under CO-gas-free conditions. A synergetic effect of both nickel and molybdenum has been observed, which is also responsible for the success of this transformation.

Interface confined hydrogen evolution reaction in zero valent metal nanoparticles-intercalated molybdenum disulfide

PubMed Central

Chen, Zhongxin; Leng, Kai; Zhao, Xiaoxu; Malkhandi, Souradip; Tang, Wei; Tian, Bingbing; Dong, Lei; Zheng, Lirong; Lin, Ming; Yeo, Boon Siang; Loh, Kian Ping

2017-01-01

Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T′-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications. PMID:28230105

Determination of molybenum in soils and rocks: A geochemical semimicro field method

USGS Publications Warehouse

Ward, F.N.

1951-01-01

Reconnaissance work in geochemical prospecting requires a simple, rapid, and moderately accurate method for the determination of small amounts of molybdenum in soils and rocks. The useful range of the suggested procedure is from 1 to 32 p.p.m. of molybdenum, but the upper limit can be extended. Duplicate determinations on eight soil samples containing less than 10 p.p.m. of molybdenum agree within 1 p.p.m., and a comparison of field results with those obtained by a conventional laboratory procedure shows that the method is sufficiently accurate for use in geochemical prospecting. The time required for analysis and the quantities of reagents needed have been decreased to provide essentially a "test tube" method for the determination of molybdenum in soils and rocks. With a minimum amount of skill, one analyst can make 30 molybdenum determinations in an 8-hour day.

Mapping the formation areas of giant molybdenum blue clusters: a spectroscopic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Botar, Bogdan; Ellern, Arkady; Kogerler, Paul

2012-05-18

The self-assembly of soluble molybdenum blue species from simple molybdate solutions has primarily been associated with giant mixed-valent wheel-shaped cluster anions, derived from the {MoV/VI154/176} archetypes, and a {MoV/VI368} lemon-shaped cluster. The combined use of Raman spectroscopy and kinetic precipitation as self-assembly monitoring techniques and single-crystal X-ray diffraction is key to mapping the realm of molybdenum blue species by establishing spherical {MoV/VI102}-type Keplerates as an important giant molybdenum blue-type species. We additionally rationalize the empirical effect of reducing agent concentration on the formation of all three relevant skeletal types: wheel, lemon and spheres. Whereas both wheels and the lemon-shaped {MoV/VI368}more » cluster are obtained from weakly reduced molybdenum blue solutions, considerably higher reduced solutions lead to {MoV/VI102}-type Keplerates.« less

Two temperature approach to femtosecond laser oxidation of molybdenum and morphological study

NASA Astrophysics Data System (ADS)

Kotsedi, L.; Kaviyarasu, K.; Fuku, X. G.; Eaton, S. M.; Amara, E. H.; Bireche, F.; Ramponi, R.; Maaza, M.

2017-11-01

The two-temperature model was used to gain insight into the thermal evolution of the hot electrons and the crystal lattice of the molybdenum thin coating during femtosecond laser treatment. The heat from the laser raised the bulk temperature of the sample through heat transfer from the hot electron to the crystal lattice of the material, which then led to the melting of the top layer of the film. This process resulted in the hot melt reacting ambient oxygen, which in turn oxidized the surface of molybdenum coating. The topological study and morphology of the oxidized film was conducted using high-resolution scanning electron microscope, with micrographs taken in both the cross-sectional geometry and normal incidence to the electron beam. The molybdenum oxide nanorods were clearly observed and the x-ray diffraction patterns showed the diffraction peaks due to molybdenum oxide.

Cytotoxicity of titanium and titanium alloying elements.

PubMed

Li, Y; Wong, C; Xiong, J; Hodgson, P; Wen, C

2010-05-01

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.

Determination of molybdenum in sea and estuarine water with BETA-naphthoin oxime and neutron activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuathilake, A.I.; Chatt, A.

1980-05-01

An analytical method has been developed for the determination of submicrogram quantities of molybdenum in sea and esturaine water. The method consists of preconcentration of molybdenum with BETA-naphthoin oxime followed by the determination of the element employing neutron activation analysis. Various factors that can influence yield and selectivity of the preconcentration process have been investigated in detail. A comparison study between ..cap alpha..-benzoin oxime and BETA-naphthoin oxime in preconcentrating molybdenum has been carried out using a standard steel sample. The method has been applied to determine molybdenum content of sea and estuarine water. A detection limit of 0.32 ..mu..g Momore » L/sup -1/ seawater has been acheived. The precision and accuracy of the method have been evaluated using an intercomparison fresh water and a biological standard reference material. 1 figure, 9 tables.« less

Development of aircraft brake materials. [evaluation of metal and ceramic materials in sliding tests simulation of aircraft braking

NASA Technical Reports Server (NTRS)

Ho, T. L.; Peterson, M. B.

1974-01-01

The requirements of brake materials were outlined and a survey made to select materials to meet the needs of high temperature brakes. A number of metals and ceramic materials were selected and evaluated in sliding tests which simulated aircraft braking. Nickel, molybdenum tungsten, Zr02, high temperature cements and carbons were tested. Additives were then incorporated into these materials to optimize their wear or strength behavior with particular emphasis on nickel and molybdenum base materials and a high temperature potassium silicate cement. Optimum materials were developed which improved wear behavior over conventional brake materials in the simulated test. The best materials are a nickel, aluminum oxide, lead tungstate composition containing graphite or molybdenum disulphite; a molybdenum base material containing LPA100 (an intermetallic compound of cobalt, molybdenum, and silicon); and a carbon material (P5).

Microwave-assisted synthesis and crystal structure of oxo(diperoxo)(4,4'-di-tert-butyl-2,2'-bipyridine)-molybdenum(VI).

PubMed

Amarante, Tatiana R; Almeida Paz, Filipe A; Gago, Sandra; Gonçalves, Isabel S; Pillinger, Martyn; Rodrigues, Alírio E; Abrantes, Marta

2009-09-16

The oxodiperoxo complex MoO(O2)(2)(tbbpy) (tbbpy = 4,4'-di-tert-butyl-2,2'- bipyridine) was isolated from the reaction of MoO2Cl(2)(tbbpy) in water under microwaveassisted heating at 120 masculineC for 4 h. The structure of the oxodiperoxo complex was determined by single crystal X-ray diffraction. The Mo(VI) centre is seven-coordinated with a geometry which strongly resembles a highly distorted bipyramid. Individual MoO(O2)(2)(tbbpy) complexes are interdigitated along the [010] direction to form a column. The crystal structure is formed by the close packing of the columnar-stacked complexes. Interactions between neighbouring columns are essentially of van der Waals type mediated by the need to effectively fill the available space.

Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N 2O 2 Schiff base

NASA Astrophysics Data System (ADS)

Abdel Aziz, Ayman A.

2010-08-01

Complexes of M(CO) 6 (M = Cr and Mo) with novel Schiff base N,N'-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H 2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO) 2(H 2L)] and [Mo(CO) 2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O) 2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.

Cathode material for lithium batteries

DOEpatents

Park, Sang-Ho; Amine, Khalil

2013-07-23

A method of manufacture an article of a cathode (positive electrode) material for lithium batteries. The cathode material is a lithium molybdenum composite transition metal oxide material and is prepared by mixing in a solid state an intermediate molybdenum composite transition metal oxide and a lithium source. The mixture is thermally treated to obtain the lithium molybdenum composite transition metal oxide cathode material.

Cathode material for lithium batteries

DOEpatents

Park, Sang-Ho; Amine, Khalil

2015-01-13

A method of manufacture an article of a cathode (positive electrode) material for lithium batteries. The cathode material is a lithium molybdenum composite transition metal oxide material and is prepared by mixing in a solid state an intermediate molybdenum composite transition metal oxide and a lithium source. The mixture is thermally treated to obtain the lithium molybdenum composite transition metal oxide cathode material.

Factors Influencing the Microstructural and Mechanical Properties of ULCB Steel Weldments

DTIC Science & Technology

1991-12-01

18 3. Molybdenum.................................... 19 4. Chromium ...................................... 19 5...WELDING METHODS UTILIZED IN ANALYSIS 1. Tungsten Inert Gas (TIG) Tungsten inert gas welding, also known as gas tungsten arc welding ( GTAW ), produces a weld...Abson, Pargeter, 1986, p.166). The role of molybdenum and chromium is not fully understood but the formation of molybdenum or chromium carbides may

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, Richard A.

1994-01-01

A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

Scalability of the LEU-Modified Cintichem Process: 3-MeV Van de Graaff and 35-MeV Electron Linear Accelerator Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rotsch, David A.; Brossard, Tom; Roussin, Ethan

Molybdenum-99, the mother of Tc-99m, can be produced from fission of U-235 in nuclear reactors and purified from fission products by the Cintichem process, later modified for low-enriched uranium (LEU) targets. The key step in this process is the precipitation of Mo with α-benzoin oxime (ABO). The stability of this complex to radiation has been examined. Molybdenum-ABO was irradiated with 3 MeV electrons produced by a Van de Graaff generator and 35 MeV electrons produced by a 50 MeV/25 kW electron linear accelerator. Dose equivalents of 1.7–31.2 kCi of Mo-99 were administered to freshly prepared Mo-ABO. Irradiated samples of Mo-ABOmore » were processed according to the LEU Modified-Cintichem process. The Van de Graaff data indicated good radiation stability of the Mo-ABO complex up to ~15 kCi dose equivalents of Mo-99 and nearly complete destruction at doses >24 kCi Mo-99. The linear accelerator data indicate that even at 6.2 kCi of Mo-99 equivalence of dose, the sample lost ~20% of Mo-99. The 20% loss of Mo-99 at this low dose may be attributed to thermal decomposition of the product from the heat deposited in the sample during irradiation.« less

Synthesis and characterization of two dehydroacetic acid derivatives and molybdenum(V) complexes: an NMR and crystallographic study

NASA Astrophysics Data System (ADS)

Cindrić, Marina; Vrdoljak, Višnja; Kajfež Novak, Tanja; Ćurić, Manda; Brbot-Šaranović, Ana; Kamenar, Boris

2004-09-01

Two enaminones ethyl 4-(4-hydroxy-6-methyl-2 H-pyran-2-on-3-yl)-2-(tryptamino)-4-oxo-2-butenoate ( HL1) and 3-(1-tryptaminoetylidene)-6-methyl-2 H-pyran-2,4(3H)-dione ( HL2) have been prepared by the reactions of tryptamine with 2-hydroxy-4-(4-hydroxy)-6-methyl)-2 Hbb-pyrane-2-on-3-yl)-4-oxo-2-butenoate (ehmpb) or with dehydroacetic acid (dha). The NMR spectroscopy confirmed that both tautomeric forms of HL1: endo-enol (tautomer A with hydroxyl group at position 4) and exo-enol form (tautomer B with hydroxyl group at position 7) are present in the DMSO- d6 solution. The molecular and crystal structure as well as the NMR data of HL2 showed that the condensation of dha and tryptamine occurs at acetyl-carbonyl and not at the pyrone-carbonyl group. Also new dinuclear [Mo 2O 4(L 1) 2(CH 3OH) 2] ( 1) and hexanuclear molybdenum(V) complexes (C 10H 12NH)[Mo 6O 12(OCH 3) 4(acac) 3] ( 2) have been prepared by the reactions of [Mo 2O 3(acac) 4] (acac=acetilacetonate ion) with HL1 or with tryptamine. All compounds have been characterized also by means of elemental analyses, IR spectroscopy as well as by thermal analyses.

First insights on the molybdenum-copper Bled M'Dena complex (Eglab massif, Algeria)

NASA Astrophysics Data System (ADS)

Lagraa, Karima; Salvi, Stefano; Béziat, Didier; Debat, Pierre; Kolli, Omar

2017-03-01

Molybdenum-Copper showings in the Eglab massif (eastern part of the Reguibat rise of Algeria), are found in quartz-monzodiorite and granodiorite of the Bled M'Dena complex, a Paleoproterozoic circular structure of ∼5 km in diameter, comprising volcanic and intrusive suites. The latter consist of quartz-diorite, quartz-monzodiorite and granodiorite with a metaluminous normative composition. They display an "adakitic character" with moderate light rare-earth element (LREE) enrichment, minor Eu anomalies, high Sr/Y ratio and low Yb concentration, suggestive of a hydrous, arc magma of volcanic-arc affinity. The mineralization occurs mostly in quartz + molybdenite + chalcopyrite stockwork veins marked by widespread propylitic alteration along the selvages. Molybdenite and chalcopyrite are commonly associated with calcite, which precipitated at relatively late stages of the hydrothermal alteration. Fluid inclusions related to the mineralization stage, range from aqueous to aqueous-carbonic to solid bearing. The latter inclusions have the highest homogenization temperature (up to ∼400 °C), are salt saturated, and commonly contain molybdenite and/or chalcopyrite crystals. The petrology and geochemistry of the host rocks, the style of the hydrothermal alteration, the ore mineral associations, and the characteristics of the fluid inclusions, are all coherent in indicating that the Bled M'Dena represents a Paleoproterozoic porphyry style Mo mineralization, which is far unreported in the African continent.

Microstructures and Hardness/Wear Performance of High-Carbon Stellite Alloys Containing Molybdenum

NASA Astrophysics Data System (ADS)

Liu, Rong; Yao, J. H.; Zhang, Q. L.; Yao, M. X.; Collier, Rachel

2015-12-01

Conventional high-carbon Stellite alloys contain a certain amount of tungsten which mainly serves to provide strengthening to the solid solution matrix. These alloys are designed for combating severe wear. High-carbon molybdenum-containing Stellite alloys are newly developed 700 series of Stellite family, with molybdenum replacing tungsten, which are particularly employed in severe wear condition with corrosion also involved. Three high-carbon Stellite alloys, designated as Stellite 706, Stellite 712, and Stellite 720, with different carbon and molybdenum contents, are studied experimentally in this research, focusing on microstructure and phases, hardness, and wear resistance, using SEM/EDX/XRD techniques, a Rockwell hardness tester, and a pin-on-disk tribometer. It is found that both carbon and molybdenum contents influence the microstructures of these alloys significantly. The former determines the volume fraction of carbides in the alloys, and the latter governs the amount of molybdenum-rich carbides precipitated in the alloys. The hardness and wear resistance of these alloys are increased with the carbide volume fraction. However, with the same or similar carbon content, high-carbon CoCrMo Stellite alloys exhibit worse wear resistance than high-carbon CoCrW Stellite alloys.

Molybdenum and vanadium do not replace tungsten in the catalytically active forms of the three tungstoenzymes in the hyperthermophilic archaeon Pyrococcus furiosus.

PubMed Central

Mukund, S; Adams, M W

1996-01-01

Three different types of tungsten-containing enzyme have been previously purified from Pyrococcus furiosus (optimum growth temperature, 100 degrees C): aldehyde ferredoxin oxidoreductase (AOR), formaldehyde ferredoxin oxidoreductase (FOR), and glyceraldehyde-3-phosphate oxidoreductase (GAPOR). In this study, the organism was grown in media containing added molybdenum (but not tungsten or vanadium) or added vanadium (but not molybdenum or tungsten). In both cell types, there were no dramatic changes compared with cells grown with tungsten, in the specific activities of hydrogenase, ferredoxin:NADP oxidoreductase, or the 2-keto acid ferredoxin oxidoreductases specific for pyruvate, indolepyruvate, 2-ketoglutarate, and 2-ketoisovalerate. Compared with tungsten-grown cells, the specific activities of AOR, FOR, and GAPOR were 40, 74, and 1%, respectively, in molybdenum-grown cells, and 7, 0, and 0%, respectively, in vanadium-grown cells. AOR purified from vanadium-grown cells lacked detectable vanadium, and its tungsten content and specific activity were both ca. 10% of the values for AOR purified from tungsten-grown cells. AOR and FOR purified from molybdenum-grown cells contained no detectable molybdenum, and their tungsten contents and specific activities were > 70% of the values for the enzymes purified from tungsten-grown cells. These results indicate that P. furiosus uses exclusively tungsten to synthesize the catalytically active forms of AOR, FOR, and GAPOR, and active molybdenum- or vanadium-containing isoenzymes are not expressed when the cells are grown in the presence of these other metals. PMID:8550411

Sodium modified molybdenum sulfide via molten salt electrolysis as an anode material for high performance sodium-ion batteries.

PubMed

Wang, Shuai; Tu, Jiguo; Yuan, Yan; Ma, Rui; Jiao, Shuqiang

2016-01-28

The paper reports a facile and cost effective method for fabricating sodium molybdenum sulfide nanoparticles through using MoS2 sheets as the precursor by sodium-modification. The electrochemical performances of sodium molybdenum sulfide nanoparticles are studied as anode materials for sodium-ion batteries. The galvanostatic charge-discharge measurements have been performed in a voltage range of 0.01-2.6 V vs. Na(+)/Na under different current densities, using the as-prepared sodium molybdenum sulfide nanoparticles as a working electrode. Typically, the initial discharge and charge capacities of sodium molybdenum sulfide nanoparticles are 475 and 380 mA h g(-1), respectively, at a current density of 20 mA g(-1). The sodium molybdenum sulfide nanoparticles exhibit high capacity with a reversible discharge capacity of about 190 mA h g(-1) after 100 cycles. It should be emphasized that the discharge reaction consists of two steps which correspond to voltage plateaus of 0.93 V and 0.85 V vs. Na(+)/Na in the first discharge curve of the Na/MoS2 battery, respectively. But there is only one apparent voltage plateau in the Na/Na-Mo-S battery, and it reduces to below 0.5 V vs. Na(+)/Na, which can enhance the power density. All of the findings demonstrate that sodium molybdenum sulfide nanoparticles have steady cycling performance and environmental and cost friendliness as next generation secondary batteries.

The Technological Mineralogical Research of Molybdenum in Skarn-type Ore of Huangshaping Polymetallic Mining Area, Hunan, China

NASA Astrophysics Data System (ADS)

Liu, W. H.; Pan, J. Y.

2017-10-01

Huangshaping is one of the most important polymetallic deposits in the south of Hunan Province. Through field investigation, chemical analysis, observation under the optical microscope, energy spectrum analysis of the SEM and X-ray diffraction, the author made a technological mineralogical research of molybdenum on skarn-type ore, and the result shows that the ore containing molybdenum is mainly on the contact of the granite porphyry and the impure limestone in the lower carboniferous Shidengzi group. Besides molybdenum, the ore minerals contain scheelite, native bismuth, bismuthinite, magnetite and so on; and the gangue minerals are mainly andradite, fluorite and wollastonite. Part of the molybdenum exists in the scheelite in form of isomorphism, and there is an obvious negative correlation between MoO3 and WO3. The molybdenite granularity is mainly located in the 0.04~ 0.08mm area, which accounts for 29.5% of the total and is the finely disseminated ore. For samples of 70%, 90%, and 100% with the particle size of more than 200 meshes, the maximum recovery of the molybdenite are 75.15%, 86.45% and 91.25% respectively. So there will be a better use of molybdenum if we properly improve the grinded particle size of the comprehensive samples. As part of the molybdenum is distributed in the scheelite lattice, the actual recovery rate in this area may decline compared with the ideal value.

Removing Molybdenum with the Microalgae Extracted from the Wastewater in Semiconductor Plants

NASA Astrophysics Data System (ADS)

Chiu, Yi-Chuan

2017-04-01

It has been well recognized that algae biomass can treat highly contaminated water in an effective way. Algae can grows in the natural environment without any care and can be efficiently cultivated. Both of living algae and dry algae biomass have been tested to absorb many kinds of toxic pollutants, because there are multiple functional groups on the algae surface capable of binding molybdenum. Therefore, algae become a good choice for the treatment of molybdenum in contaminated waters. In addition, in Taiwan, semiconductor industry is highly developed in the recent three decades. Subsequently, it is believed that some pollutants, such as molybdenum in this study, have become a threat to the surface water, groundwater and even the whole environment. In the previous studies, molybdenum is a well-known essential nutrient for the algae; therefore, the potential to remove molybdenum with algae from the wastewater is worth to be evaluated. The algae species, Chloroidium saccharophilum, was extracted from the wastewater in semiconductor plants for the study of removing molybdenum. A few sorption experiments have been conducted for evaluating the efficiency of removing molybdenum under different values of pH and molybdenum concentration. The absorption of Chloroidium saccharophilum can reach equilibrium in short times, which are 60 and 120 mins for molybdenum concentrations of 600 and 1200 ppb, respectively. The sorption experiments would accept the duration of 120 mins as the contact time and were performed at pH values of 6, 4 and 2 with different concentrations of molybdenum diluted by deionized water. The experiment data confirms that the isotherm has an excellent agreement on Langmuir adsorption model with the correlation coefficients (r2) of > 0.97. It demonstrates that the adsorption capacity (qmax) has an inverse relationship with pH value, which are 826, 2564 and 4761 mgkg-1 for pH 6, 4 and 2, respectively, while those of net enthalpy of adsorption (KL) are 3.98, 2.98 and 1.5 × 10-5 mgkg-1. In addition, a similar experiment was also conducted with domestic sewage instead of deionized water under pH=6 and obtained a much higher value of qmax (1923 mgkg-1) than that with deionized water. It is believed that the cations in the domestic sewage, such as Ca2+, Mg2+, Na+ and K+, are capable of replacing H+ from the algae surface, which can decrease the pH value of water and subsequently promote the absorption of MoO42- as the aforementioned. FTIR was utilized for determining the functional groups on algae surface in this study. There are five major absorption bands, which are corresponding to -O-H, -COO- , C-O-C, Mo-O and Mo-N. However, the responsible functional group to absorb MoO42- is still uncertain and the comparison of absorption behaviour of molybdenum among different algae species should be also evaluated. More researches will be studied in the future.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, R.A.

1994-04-05

A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

Electrothermal atomisation atomic absorption conditions and matrix modifications for determining antimony, arsenic, bismuth, cadmium, gallium, gold, indium, lead, molybdenum, palladium, platinum, selenium, silver, tellurium, thallium and tin following back-extraction of organic aminohalide extracts

USGS Publications Warehouse

Clark, J.R.

1986-01-01

A multi-element organic-extraction and back-extraction procedure, that had been developed previously to eliminate matrix interferences in the determination of a large number of trace elements in complex materials such as geological samples, produced organic and aqueous solutions that were complex. Electrothermal atomisation atomic absorption conditions and matrix modifications have been developed for 13 of the extracted elements (Ag, As, Au, Bi, Cd, Ga, In, Pb, Sb, Se, Sn, Te and Tl) that enhance sensitivity, alleviate problems resulting from the complex solutions and produce acceptable precision. Platinum, Pd and Mo can be determined without matrix modification directly on the original unstripped extracts.

Sulfur K-edge XAS of WV=O vs. MoV=O Bis(dithiolene) Complexes: Contributions of Relativistic Effects to Electronic Structure and Reactivity of Tungsten Enzymes†

PubMed Central

Tenderholt, Adam L.; Szilagyi, Robert K.; Holm, Richard H.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.

2009-01-01

Molybdenum- or tungsten-containing enzymes catalyze oxygen atom transfer reactions involved in carbon, sulfur, or nitrogen metabolism. It has been observed that reduction potentials and oxygen atom transfer rates are different for W relative to Mo enzymes and the isostructural Mo/W complexes. Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations on [MoVO(bdt)2]− and [WVO(bdt)2]−, where bdt = benzene-1,2-dithiolate(2−), have been used to determine that the energies of the half-filled redox-active orbital, and thus the reduction potentials and M=O bond strengths, are different for these complexes due to relativistic effects in the W sites. PMID:17720249

Unique behaviour of dinitrogen-bridged dimolybdenum complexes bearing pincer ligand towards catalytic formation of ammonia.

PubMed

Tanaka, Hiromasa; Arashiba, Kazuya; Kuriyama, Shogo; Sasada, Akira; Nakajima, Kazunari; Yoshizawa, Kazunari; Nishibayashi, Yoshiaki

2014-04-28

It is vital to design effective nitrogen fixation systems that operate under mild conditions, and to this end we recently reported an example of the catalytic formation of ammonia using a dinitrogen-bridged dimolybdenum complex bearing a pincer ligand, where up to twenty three equivalents of ammonia were produced based on the catalyst. Here we study the origin of the catalytic behaviour of the dinitrogen-bridged dimolybdenum complex bearing the pincer ligand with density functional theory calculations, based on stoichiometric and catalytic formation of ammonia from molecular dinitrogen under ambient conditions. Comparison of di- and mono-molybdenum systems shows that the dinitrogen-bridged dimolybdenum core structure plays a critical role in the protonation of the coordinated molecular dinitrogen in the catalytic cycle.

Molybdenum cofactor (chlorate-resistant) mutants of Klebsiella pneumoniae M5al can use hypoxanthine as the sole nitrogen source.

PubMed Central

Garzón, A; Li, J; Flores, A; Casadesus, J; Stewart, V

1992-01-01

Selection for chlorate resistance yields mol (formerly chl) mutants with defects in molybdenum cofactor synthesis. Complementation and genetic mapping analyses indicated that the Klebsiella pneumoniae mol genes are functionally homologous to those of Escherichia coli and occupy analogous genetic map positions. Hypoxanthine utilization in other organisms requires molybdenum cofactor as a component of xanthine dehydrogenase, and thus most chlorate-resistant mutants cannot use hypoxanthine as a sole source of nitrogen. Surprisingly, the K. pneumoniae mol mutants and the mol+ parent grew equally well with hypoxanthine as the sole nitrogen source, suggesting that K. pneumoniae has a molybdenum cofactor-independent pathway for hypoxanthine utilization. PMID:1400180

A molybdenum disulfide/carbon nanotube heterogeneous complementary inverter.

PubMed

Huang, Jun; Somu, Sivasubramanian; Busnaina, Ahmed

2012-08-24

We report a simple, bottom-up/top-down approach for integrating drastically different nanoscale building blocks to form a heterogeneous complementary inverter circuit based on layered molybdenum disulfide and carbon nanotube (CNT) bundles. The fabricated CNT/MoS(2) inverter is composed of n-type molybdenum disulfide (MOS(2)) and p-type CNT transistors, with a high voltage gain of 1.3. The CNT channels are fabricated using directed assembly while the layered molybdenum disulfide channels are fabricated by mechanical exfoliation. This bottom-up fabrication approach for integrating various nanoscale elements with unique characteristics provides an alternative cost-effective methodology to complementary metal-oxide-semiconductors, laying the foundation for the realization of high performance logic circuits.

An efficient molybdenum disulfide/cobalt diselenide hybrid catalyst for electrochemical hydrogen generation

PubMed Central

Gao, Min-Rui; Liang, Jin-Xia; Zheng, Ya-Rong; Xu, Yun-Fei; Jiang, Jun; Gao, Qiang; Li, Jun; Yu, Shu-Hong

2015-01-01

The electroreduction of water for sustainable hydrogen production is a critical component of several developing clean-energy technologies, such as water splitting and fuel cells. However, finding a cheap and efficient alternative catalyst to replace currently used platinum-based catalysts is still a prerequisite for the commercialization of these technologies. Here we report a robust and highly active catalyst for hydrogen evolution reaction that is constructed by in situ growth of molybdenum disulfide on the surface of cobalt diselenide. In acidic media, the molybdenum disulfide/cobalt diselenide catalyst exhibits fast hydrogen evolution kinetics with onset potential of −11 mV and Tafel slope of 36 mV per decade, which is the best among the non-noble metal hydrogen evolution catalysts and even approaches to the commercial platinum/carbon catalyst. The high hydrogen evolution activity of molybdenum disulfide/cobalt diselenide hybrid is likely due to the electrocatalytic synergistic effects between hydrogen evolution-active molybdenum disulfide and cobalt diselenide materials and the much increased catalytic sites. PMID:25585911

Investigating the Influence of MoS2 Nanosheets on E. coli from Metabolomics Level.

PubMed

Wu, Na; Yu, Yadong; Li, Tao; Ji, Xiaojun; Jiang, Ling; Zong, Jiajun; Huang, He

2016-01-01

Molybdenum disulfide, a type of two-dimensional layered material with unique properties, has been widely used in many fields. However, an exact understanding of its toxicity remains elusive, let alone its effects on the environmental microbial community. In this study, we utilized metabolomics technology to explore the effects of different concentrations of molybdenum disulfide nanosheets on Escherichia coli for the first time. The results showed that with increasing concentration of molybdenum disulfide nanosheets, the survival rate of Escherichia coli was decreased and the release of lactic dehydrogenase was increased. At the same time, intracellular concentrations of reactive oxygen species were dramatically increased. In addition, metabolomics analysis showed that high concentrations of molybdenum disulfide nanosheets (100, 1000 μg/mL) could significantly affect the metabolic profile of Escherichia coli, including glycine, serine and threonine metabolism, protein biosynthesis, urea cycle and pyruvate metabolism. These results will be beneficial for molybdenum disulfide toxicity assessment and further applications.

Erosion rate diagnostics in ion thrusters using laser-induced fluorescence

NASA Technical Reports Server (NTRS)

Gaeta, C. J.; Matossian, J. N.; Turley, R. S.; Beattie, J. R.; Williams, J. D.; Williamson, W. S.

1993-01-01

We have used laser-induced fluorescence (LIF) to monitor the charge-exchange ion erosion of the molybdenum accelerator electrode in ion thrusters. This real-time, nonintrusive method was implemented by operating a 30cm-diam ring-cusp thruster using xenon propellant. With the thruster operating at a total power of 5 kW, laser radiation at a wavelength of 390 nm (corresponding to a ground state atomic transition of molybdenum) was directed through the extracted ion beam adjacent to the downstream surface of the molybdenum accelerator electrode. Molybdenum atoms, sputtered from this surface as a result of charge-exchange ion erosion, were excited by the laser radiation. The intensity of the laser-induced fluorescence radiation, which is proportional to the sputter rate of the molybdenum atoms, was measured and correlated with variations in thruster operating conditions such as accelerator electrode voltage, accelerator electrode current, and test facility background pressure. We also demonstrated that the LIF technique has sufficient sensitivity and spatial resolution to evaluate accelerator electrode lifetime in ground-based test facilities.

Recovering and recycling uranium used for production of molybdenum-99

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reilly, Sean Douglas; May, Iain; Copping, Roy

A processes for recycling uranium that has been used for the production of molybdenum-99 involves irradiating a solution of uranium suitable for forming fission products including molybdenum-99, conditioning the irradiated solution to one suitable for inducing the formation of crystals of uranyl nitrate hydrates, then forming the crystals and a supernatant and then separating the crystals from the supernatant, thus using the crystals as a source of uranium for recycle. Molybdenum-99 is recovered from the supernatant using an adsorbent such as alumina. Another process involves irradiation of a solid target comprising uranium, forming an acidic solution from the irradiated targetmore » suitable for inducing the formation of crystals of uranyl nitrate hydrates, then forming the crystals and a supernatant and then separating the crystals from the supernatant, thus using the crystals as a source of uranium for recycle. Molybdenum-99 is recovered from the supernatant using an adsorbent such as alumina.« less

Recovery of Tungsten and Molybdenum from Low-Grade Scheelite

NASA Astrophysics Data System (ADS)

Li, Yongli; Yang, Jinhong; Zhao, Zhongwei

2017-10-01

With most high-quality tungsten ores being exhausted, the enhancement of low-grade scheelite concentrates processing has attracted a great deal of attention. The objective of this study is to develop a method to maximize the recovery tungsten and molybdenum from a low-grade scheelite via a new acid leaching process followed by solvent extraction. Under optimal conditions (350 g/L H2SO4, 95°C, and 2 h), approximately 99.8% of tungsten and 98% of molybdenum were leached out. In the subsequent solvent extraction process, more than 99% of the tungsten and molybdenum were extracted with a co-extraction system (50% TBP, 30% HDEHP, and 10% 2-octanol in kerosene) using a three-stage cross-flow extraction. The raffinate can be recycled for the next leaching process after replenishing the H2SO4 to the initial value (approximately 350 g/L). Based on these results, a conceptual flowsheet is presented to recover tungsten and molybdenum from the low-grade scheelite.

Flexible Molybdenum Electrodes towards Designing Affinity Based Protein Biosensors.

PubMed

Kamakoti, Vikramshankar; Panneer Selvam, Anjan; Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Prasad, Shalini

2016-07-18

Molybdenum electrode based flexible biosensor on porous polyamide substrates has been fabricated and tested for its functionality as a protein affinity based biosensor. The biosensor performance was evaluated using a key cardiac biomarker; cardiac Troponin-I (cTnI). Molybdenum is a transition metal and demonstrates electrochemical behavior upon interaction with an electrolyte. We have leveraged this property of molybdenum for designing an affinity based biosensor using electrochemical impedance spectroscopy. We have evaluated the feasibility of detection of cTnI in phosphate-buffered saline (PBS) and human serum (HS) by measuring impedance changes over a frequency window from 100 mHz to 1 MHz. Increasing changes to the measured impedance was correlated to the increased dose of cTnI molecules binding to the cTnI antibody functionalized molybdenum surface. We achieved cTnI detection limit of 10 pg/mL in PBS and 1 ng/mL in HS medium. The use of flexible substrates for designing the biosensor demonstrates promise for integration with a large-scale batch manufacturing process.

Electronic and steric influences of pendant amine groups on the protonation of molybdenum bis (dinitrogen) complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Labios, Liezel A.; Heiden, Zachariah M.; Mock, Michael T.

2015-05-04

The synthesis of a series of P EtP NRR' (P EtP NRR' = Et₂PCH₂CH₂P(CH₂NRR')₂, R = H, R' = Ph or 2,4-difluorophenyl; R = R' = Ph or iPr) diphosphine ligands containing mono- and disubstituted pendant amine groups, and the preparation of their corresponding molybdenum bis(dinitrogen) complexes trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') is described. In situ IR and multinuclear NMR spectroscopic studies monitoring the stepwise addition of (HOTf) to trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') complexes in THF at -40 °C show that the electronic and steric properties of the R and R' groups of the pendant amines influence whether the complexes are protonated atmore » Mo, a pendant amine, a coordinated N2 ligand, or a combination of these sites. For example, complexes containing mono-aryl substituted pendant amines are protonated at Mo and pendant amine to generate mono- and dicationic Mo–H species. Protonation of the complex containing less basic diphenyl-substituted pendant amines exclusively generates a monocationic hydrazido (Mo(NNH₂)) product, indicating preferential protonation of an N₂ ligand. Addition of HOTf to the complex featuring more basic diisopropyl amines primarily produces a monocationic product protonated at a pendant amine site, as well as a trace amount of dicationic Mo(NNH₂) product that contain protonated pendant amines. In addition, trans-Mo(N₂)₂(PMePh₂)₂(depe) (depe = Et₂PCH₂CH₂PEt₂) without a pendant amine was synthesized and treated with HOTf, generating a monocationic Mo(NNH₂) product. Protonolysis experiments conducted on select complexes in the series afforded trace amounts of NH₄⁺. Computational analysis of the series of trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') complexes provides further insight into the proton affinity values of the metal center, N₂ ligand, and pendant amine sites to rationalize the differing reactivity profiles. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Computational resources provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Characterization of molybdenum particles reinforced Al6082 aluminum matrix composites with improved ductility produced using friction stir processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selvakumar, S., E-mail: lathaselvam1963@gmail.com

Aluminum matrix composites (AMCs) reinforced with various ceramic particles suffer a loss in ductility. Hard metallic particles can be used as reinforcement to improve ductility. The present investigation focuses on using molybdenum (Mo) as potential reinforcement for Mo(0,6,12 and 18 vol.%)/6082Al AMCs produced using friction stir processing (FSP). Mo particles were successfully retained in the aluminum matrix in its elemental form without any interfacial reaction. A homogenous distribution of Mo particles in the composite was achieved. The distribution was independent upon the region within the stir zone. The grains in the composites were refined considerably due to dynamic recrystallization andmore » pinning effect. The tensile test results showed that Mo particles improved the strength of the composite without compromising on ductility. The fracture surfaces of the composites were characterized with deeply developed dimples confirming appreciable ductility. - Highlights: •Molybdenum particles used as reinforcement for aluminum composites to improve ductility. •Molybdenum particles were retained in elemental form without interfacial reaction. •Homogeneous dispersion of molybdenum particles were observed in the composite. •Molybdenum particles improved tensile strength without major loss in ductility. •Deeply developed dimples on the fracture surfaces confirmed improved ductility.« less

The role of oxygen in porous molybdenum electrodes for the alkali metal thermoelectric converter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, R.M.; Nagasubramanian, G.; Khanna, S.K.

1986-08-01

The alkali metal thermoelectric converter is a direct energy conversion device, utilizing a high alkali metal activity gradient to generate electrical power. Its operation is based on the unique ion conductive properties of beta''-alumina solid electrolyte. The major barrier to application of this device is identification of an electrode which can maintain optimum power densities for operation times of >10,000h. Thin, porous molybdenum electrodes have shown the best performance characteristics, but show a variety of time dependent phenomena, including eventual degradation to power densities 3-5 times lower than initial values. Several Na-Mo-O compounds, including Na/sub 2/MoO/sub 4/ and Na/sub 2/Mo/submore » 3/O/sub 6/, are formed during AMTEC operation. These compounds may be responsible for enhanced Na transport through Mo electrodes via sodium ion conduction, and eventual performance degradation due to their volatilization and decomposition. No decomposition of beta''-alumina has been observed under simulated AMTEC operating conditions up to 1373 K. In this paper, we present a model for chemical reactions occurring in porous molybdenum electrodes. The model is based on thermochemical and kinetic data, known sodium-molybdenum-oxygen chemistry, x-ray diffraction analysis of molybdenum and molybdenum oxide electrodes, and the electrochemical behavior of the cell.« less

Catalytic ionic hydrogenation of ketones using tungsten or molybdenum catalysts with increased lifetimes

DOEpatents

Bullock, R. Morris; Kimmich, Barbara F. M.; Fagan, Paul J.; Hauptman, Elisabeth

2003-09-02

The present invention is a process for the catalytic hydrogenation of ketones and aldehydes to alcohols at low temperatures and pressures using organometallic molybdenum and tungsten complexes and the catalyst used in the process. The reactants include a functional group which is selected from groups represented by the formulas R*(C.dbd.O)R' and R*(C.dbd.O)H, wherein R* and R' are selected from hydrogen or any alkyl or aryl group. The process includes reacting the organic compound in the presence of hydrogen and a catalyst to form a reaction mixture. The catalyst is prepared by reacting Ph.sub.3 C.sup.+ A.sup.- with a metal hydride. A.sup.- represents an anion and can be BF.sub.4.sup.-, PF.sub.6.sup.-, CF.sub.3 SO.sub.3.sup.- or Bar'.sub.4.sup.-, wherein Ar'=3,5-bis(trifluoromethyl)phenyl. The metal hydride is represented by the formula: HM(CO).sub.2 [.eta..sup.5 :.eta..sup.1 --C.sub.5 H.sub.4 (XH.sub.2).sub.n PR.sub.2 ] wherein M represents a molybdenum (Mo) atom or a tungsten (W) atom; X is a carbon atom, a silicon atom or a combination of carbon (C) and silicon (Si) atoms; n is any positive integer; R represents two hydrocarbon groups selected from H, an aryl group and an alkyl group, wherein both R groups can be the same or different. The metal hydride is reacted with Ph.sub.3 C.sup.+ A.sup.- either before reacting with the organic compound or in the reaction mixture.

Synthesis of New Inorganic and Organometallic Materials.

DTIC Science & Technology

1981-04-23

15. 16. & 17 . Distribution Statement Approved for public release; distribution unlimited. 18. Supplementary, Note’s’ 19. Key Words .. t rganometallic...CarbametallIaboranes 12 2. Activation of Acetylenes and Olefins by Metal Complexes 16 (a) Nickel 16 (b) Molybdenum 17 (c) Platinum 24 3. Fluorocarbon...Figure 9).3 - CO / Pt -. . . Pt 4Ph ’ / C-Fe C C C0 0 oc-( I C- Co FIGURE 9. Possible mode for conversion C’,p - h 3 of the anion into the metal

Cold cap subsidence for in situ vitrification and electrodes therefor

DOEpatents

Buelt, James L.; Carter, John G.; Eschbach, Eugene A.; FitzPatrick, Vincent F.; Koehmstedt, Paul L.; Morgan, William C.; Oma, Kenton H.; Timmerman, Craig L.

1992-01-01

An electrode for use in in situ vitrification of soil comprises a molybdenum rod received within a conductive sleeve or collar formed of graphite. Electrodes of this type are placed on either side of a region containing buried waste material and an electric current is passed therebetween for vitrifying the soil between the electrodes. The graphite collar enhances the thermal conductivity of the electrode, bringing heat to the surface, and preventing the formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is filled with a conductive ceramic powder of a type that sinters upon the molybdenum rod, protecting the same from oxidation as the graphite material is consumed, or a metal powder which liquifies at operating temperatures. The molybdenum rod in the former case may be coated with an oxidation protectant, e.g. of molybdenum disilicide. As insulative blanket is suitably placed on the surface of the soil during processing to promote subsidence by allowing off-gassing and reducing surface heat loss. In other embodiments, connection to vitrification electrodes is provided below ground level to avoid loss of connection due to electrodes deterioration, or a sacrificial electrode may be employed when operation is started. Outboard electrodes can be utilized to square up the vitrified area. Further, the center of the molybdenum rod can be made hollow and filled with a powdered metal, such as copper, which liquifies at operating temperatures. In one embodiment, the molybdenum rod and the graphite collar are physically joined at the bottom.

Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies

DOE PAGES

Cao, Bingfei; Neuefeind, Joerg C.; Adzic, Radoslav R.; ...

2015-02-09

Monometallic (δ-MoN, Mo 5N 6, and Mo 2N) and bimetallic molybdenum nitrides (Co 0.6Mo 1.4N 2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo 2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co 0.6Mo 1.4N 2), resulting in a modest onset potential of 0.713 V versusmore » reversible hydrogen electrode (RHE). Co 0.6Mo 1.4N 2 exhibits good stability in acidic environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co 0.6Mo 1.4N 2 structure, which has alternating layers of cations in octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).« less

Quantitative SIMS depth profiling of diffusion barrier gate-oxynitride structures in TFT-LCDs.

PubMed

Dreer, Sabine; Wilhartitz, Peter; Piplits, Kurt; Mayerhofer, Karl; Foisner, Johann; Hutter, Herbert

2004-06-01

Gate oxynitride structures of TFT-LCDs were investigated by SIMS, and successful solutions are demonstrated to overcome difficulties arising due to the charging effects of the multilayer systems, the matrix effect of the method, and the small pattern sizes of the samples. Because of the excellent reproducibility achieved by applying exponential relative sensitivity functions for quantitative analysis, minor differences in the barrier gate-oxynitride composition deposited on molybdenum capped aluminium-neodymium metallisation electrodes were determined between the centre and the edge of the TFT-LCD substrates. No differences were found for molybdenum-tungsten metallisations. Furthermore, at the edge of the glass substrates, aluminium, neodymium, and molybdenum SIMS depth profiles show an exponential trend. With TEM micrographs an inhomogeneous thickness of the molybdenum capping is revealed as the source of this effect, which influences the electrical behaviour of the device. The production process was improved after these results and the aging behaviour of TFT-LCDs was investigated in order to explain the change in control voltage occurring during the lifetime of the displays. SIMS and TEM show an enrichment of neodymium at the interface to the molybdenum layer, confirming good diffusion protection of the molybdenum barrier during accelerated aging. The reason for the shift of the control voltage was finally located by semi-quantitative depth profiling of the sodium diffusion originating from the glass substrate. Molybdenum-tungsten was a much better buffer for the highly-mobile charge carriers than aluminium-neodymium. Best results were achieved with PVD silicon oxynitride as diffusion barrier and gate insulator deposited on aluminium-neodymium metallisation layers.

Molybdenum cofactor in chlorate-resistant and nitrate reductase-deficient insertion mutants of Escherichia coli.

PubMed Central

Miller, J B; Amy, N K

1983-01-01

We examined molybdenum cofactor activity in chlorate-resistant (chl) and nitrate reductase-deficient (nar) insertion mutants and wild-type strains of Escherichia coli K-12. The bacterial molybdenum cofactor was assayed by its ability to restore activity to the cofactor-deficient nitrate reductase found in the nit-1 strain of Neurospora crassa. In the wild-type E. coli strains, molybdenum cofactor was synthesized constitutively and found in both cytoplasmic and membrane fractions. Cofactor was found in two forms: the demolybdo form required additional molybdate in the assay mix for detection, whereas the molybdenum-containing form was active without additional molybdate. The chlA and chlE mutants had no detectable cofactor. The chlB and the narG, narI, narK, and narL (previously designated chlC) strains had cofactor levels similar to those of the wild-type strains, except the chlB strains had two to threefold more membrane-bound cofactor. Cofactor levels in the chlD and chlG strains were sensitive to molybdate. When grown in 1 microM molybdate, the chlD strains had only 15 to 20% of the wild-type levels of the demolybdo and molybdenum-containing forms of the cofactor. In contrast, the chlG strains had near wild-type levels of demolybdo cofactor when grown in 1 microM molybdate, but none of the molybdenum-containing form of the cofactor. Near wild-type levels of both forms of the cofactor were restored to the chlD and chlG strains by growth in 1 mM molybdate. PMID:6307982

[Custom-made implant for complex facial reconstruction: A case of total replacement of temporo-mandibular joint, zygomatic arch and malar bone].

PubMed

Guillier, D; Moris, V; See, L-A; Girodon, M; Wajszczak, B-L; Zwetyenga, N

2017-02-01

Total prosthetic replacement of the temporo-mandibular joint (TMJ) has become a common procedure, but it is usually limited to the TMJ itself. We report about one case of complex prosthetic joint reconstruction extending to the neighbouring bony structures. A 57-year-old patient, operated several times for a cranio-facial fibrous dysplasia, presented with a recurring TMJ ankylosis and a complexe latero-facial bone loss on the right side. We performed a reconstruction procedure including the TMJ, the zygomatic arch and the malar bone by mean of custom made composite prosthesis (chrome-cobalt-molybdenum-titanium and polyethylene). Five years postoperatively, mouth opening, nutrition, pain and oral hygiene were significantly improved. Nowadays technical possibilities allow for complex facial alloplastic reconstructions with good medium term results. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Polymer-assisted deposition of films and preparation of carbon nanotube arrays using the films

DOEpatents

Luo, Hongmei; Li, Qingwen; Bauer, Eve; Burrell, Anthony Keiran; McCleskey, Thomas Mark; Jia, Quanxi

2013-07-16

Carbon nanotubes were prepared by coating a substrate with a coating solution including a suitable solvent, a soluble polymer, a metal precursor having a first metal selected from iron, nickel, cobalt, and molybdenum, and optionally a second metal selected from aluminum and magnesium, and also a binding agent that forms a complex with the first metal and a complex with the second metal. The coated substrate was exposed to a reducing atmosphere at elevated temperature, and then to a hydrocarbon in the reducing atmosphere. The result was decomposition of the polymer and formation of carbon nanotubes on the substrate. The carbon nanotubes were often in the form of an array on the substrate.

Mono- and binuclear molybdenum and tungsten complexes containing asymmetric bridging ligands: Effects of ligand conjugation and conformation on metal-metal interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, A.; Jeffery, J.C.; Maher, J.P.

The authors have prepared the new monodentate ligands 4-(4-methoxyphenyl)pyridine, 1-(4-pyridyl)-2-(4-methoxyphenyl)ethene, 1-(4-pyridyl)-2-(3-methoxyphenyl)ethene, and 1-(3-pyridyl)-2-(4-methoxyphenyl)ethene (L[sup 5]-L[sup 8]); demethylation of the methoxy group in each case afforded the new bridging bidentate ligands HL[sup 1]-HL[sup 4], which contain one pyridyl and one phenolate donor. Attachment of a MoL*(NO)Cl [L* = hydrotris(3,5-dimethylpyrazolyl)borate] moiety to the pyridyl groups of L[sup 5]-L[sup 8] gave the 17-electron complexes [Mo(NO)L*ClL[prime

Shared Sulfur Mobilization Routes for tRNA Thiolation and Molybdenum Cofactor Biosynthesis in Prokaryotes and Eukaryotes

PubMed Central

Leimkühler, Silke; Bühning, Martin; Beilschmidt, Lena

2017-01-01

Modifications of transfer RNA (tRNA) have been shown to play critical roles in the biogenesis, metabolism, structural stability and function of RNA molecules, and the specific modifications of nucleobases with sulfur atoms in tRNA are present in pro- and eukaryotes. Here, especially the thiomodifications xm5s2U at the wobble position 34 in tRNAs for Lys, Gln and Glu, were suggested to have an important role during the translation process by ensuring accurate deciphering of the genetic code and by stabilization of the tRNA structure. The trafficking and delivery of sulfur nucleosides is a complex process carried out by sulfur relay systems involving numerous proteins, which not only deliver sulfur to the specific tRNAs but also to other sulfur-containing molecules including iron–sulfur clusters, thiamin, biotin, lipoic acid and molybdopterin (MPT). Among the biosynthesis of these sulfur-containing molecules, the biosynthesis of the molybdenum cofactor (Moco) and the synthesis of thio-modified tRNAs in particular show a surprising link by sharing protein components for sulfur mobilization in pro- and eukaryotes. PMID:28098827

Dissecting the Re-Os molybdenite geochronometer.

PubMed

Barra, Fernando; Deditius, Artur; Reich, Martin; Kilburn, Matt R; Guagliardo, Paul; Roberts, Malcolm P

2017-11-22

Rhenium and osmium isotopes have been used for decades to date the formation of molybdenite (MoS 2 ), a common mineral in ore deposits and the world's main source of molybdenum and rhenium. Understanding the distribution of parent 187 Re and radiogenic daughter 187 Os isotopes in molybdenite is critical in interpreting isotopic measurements because it can compromise the accurate determination and interpretation of mineralization ages. In order to resolve the controls on the distribution of these elements, chemical and isotope mapping of MoS 2 grains from representative porphyry copper-molybdenum deposits were performed using electron microprobe and nano-scale secondary ion mass spectrometry. Our results show a heterogeneous distribution of 185,187 Re and 192 Os isotopes in MoS 2 , and that both 187 Re and 187 Os isotopes are not decoupled as previously thought. We conclude that Re and Os are structurally bound or present as nanoparticles in or next to molybdenite grains, recording a complex formation history and hindering the use of microbeam techniques for Re-Os molybdenite dating. Our study opens new avenues to explore the effects of isotope nuggeting in geochronometers.

Highly efficient molybdenum-based catalysts for enantioselective alkene metathesis

PubMed Central

Malcolmson, Steven J.; Meek, Simon J.; Sattely, Elizabeth S.; Schrock, Richard R.; Hoveyda, Amir H.

2009-01-01

Discovery of efficient catalysts is one of the most compelling objectives of modern chemistry. Chiral catalysts are in particularly high demand, as they facilitate synthesis of enantiomerically enriched small molecules that are critical to developments in medicine, biology and materials science1. Especially noteworthy are catalysts that promote—with otherwise inaccessible efficiency and selectivity levels—reactions demonstrated to be of great utility in chemical synthesis. Here we report a class of chiral catalysts that initiate alkene metathesis1 with very high efficiency and enantioselectivity. Such attributes arise from structural fluxionality of the chiral catalysts and the central role that enhanced electronic factors have in the catalytic cycle. The new catalysts have a stereogenic metal centre and carry only monodentate ligands; the molybdenum-based complexes are prepared stereoselectively by a ligand exchange process involving an enantiomerically pure aryloxide, a class of ligands scarcely used in enantioselective catalysis2,3. We demonstrate the application of the new catalysts in an enantioselective synthesis of the Aspidosperma alkaloid, quebrachamine, through an alkene metathesis reaction that cannot be promoted by any of the previously reported chiral catalysts. PMID:19011612

NifX and NifEN exchange NifB cofactor and the VK-cluster, a newly isolated intermediate of the iron-molybdenum cofactor biosynthetic pathway.

PubMed

Hernandez, Jose A; Igarashi, Robert Y; Soboh, Basem; Curatti, Leonardo; Dean, Dennis R; Ludden, Paul W; Rubio, Luis M

2007-01-01

The iron-molybdenum cofactor of nitrogenase (FeMo-co) is synthesized in a multistep process catalysed by several Nif proteins and is finally inserted into a pre-synthesized apo-dinitrogenase to generate mature dinitrogenase protein. The NifEN complex serves as scaffold for some steps of this synthesis, while NifX belongs to a family of small proteins that bind either FeMo-co precursors or FeMo-co during cofactor synthesis. In this work, the binding of FeMo-co precursors and their transfer between purified Azotobacter vinelandii NifX and NifEN proteins was studied to shed light on the role of NifX on FeMo-co synthesis. Purified NifX binds NifB cofactor (NifB-co), a precursor to FeMo-co, with high affinity and is able to transfer it to the NifEN complex. In addition, NifEN and NifX exchange another [Fe-S] cluster that serves as a FeMo-co precursor, and we have designated it as the VK-cluster. In contrast to NifB-co, the VK-cluster is electronic paramagnetic resonance (EPR)-active in the reduced and the oxidized states. The NifX/VK-cluster complex is unable to support in vitro FeMo-co synthesis in the absence of NifEN because further processing of the VK-cluster into FeMo-co requires the simultaneous activities of NifEN and NifH. Our in vitro studies suggest that the role of NifX in vivo is to serve as transient reservoir of FeMo-co precursors and thus help control their flux during FeMo-co synthesis.

A novel tridentate Schiff base dioxo-molybdenum(VI) complex: synthesis, experimental and theoretical studies on its crystal structure, FTIR, UV-visible, ¹H NMR and ¹³C NMR spectra.

PubMed

Saheb, Vahid; Sheikhshoaie, Iran; Stoeckli-Evans, Helen

2012-09-01

A new dioxo-molybdenum(VI) complex [MoO(2)(L)(H(2)O)] has been synthesized, using 5-methoxy 2-[(2-hydroxypropylimino)methyl]phenol as tridentate ONO donor Schiff base ligand (H(2)L) and MoO(2)(acac)(2). The yellow crystals of the compound are used for single-crystal X-ray analysis and measuring Fourier Transform Infrared (FTIR), UV-visible, (1)H NMR and (13)C NMR spectra. Electronic structure calculations at the B3LYP and PW91PW91 levels of theory are performed to optimize the molecular geometry and to calculate the UV-visible, FTIR, (1)H NMR and (13)C NMR spectra of the compound. Vibrational assignments and analysis of the fundamental modes of the compound are performed. Time-dependent density functional theory (TDDFT) method is used to calculate the electronic transitions of the complex. All theoretical methods can well reproduce the structure of the compound. The (1)H NMR shielding tensors computed at the B3LYP/DGDZVP level of theory is in agreement with experimental (1)H NMR spectra. However, the (13)C NMR shielding tensors computed at the B3LYP level, employing a combined basis set of DGDZVP for Mo and 6-31+G(2df,p) for other atoms, are in better agreement with experimental (13)C NMR spectra. The electronic transitions calculated at the B3LYP/DGDZVP level by using TD-DFT method is in accordance with the observed UV-visible spectrum of the compound. Copyright © 2012 Elsevier B.V. All rights reserved.

Preconcentration and determination of vanadium and molybdenum in milk, vegetables and foodstuffs by ultrasonic-thermostatic-assisted cloud point extraction coupled to flame atomic absorption spectrometry.

PubMed

Gürkan, Ramazan; Korkmaz, Sema; Altunay, Nail

2016-08-01

A new ultrasonic-thermostatic-assisted cloud point extraction procedure (UTA-CPE) was developed for preconcentration at the trace levels of vanadium (V) and molybdenum (Mo) in milk, vegetables and foodstuffs prior to determination via flame atomic absorption spectrometry (FAAS). The method is based on the ion-association of stable anionic oxalate complexes of V(V) and Mo(VI) with [9-(diethylamino)benzo[a]phenoxazin-5-ylidene]azanium; sulfate (Nile blue A) at pH 4.5, and then extraction of the formed ion-association complexes into micellar phase of polyoxyethylene(7.5)nonylphenyl ether (PONPE 7.5). The UTA-CPE is greatly simplified and accelerated compared to traditional cloud point extraction (CPE). The analytical parameters optimized are solution pH, the concentrations of complexing reagents (oxalate and Nile blue A), the PONPE 7.5 concentration, electrolyte concentration, sample volume, temperature and ultrasonic power. Under the optimum conditions, the calibration curves for Mo(VI) and V(V) are obtained in the concentration range of 3-340µgL(-1) and 5-250µgL(-1) with high sensitivity enhancement factors (EFs) of 145 and 115, respectively. The limits of detection (LODs) for Mo(VI) and V(V) are 0.86 and 1.55µgL(-1), respectively. The proposed method demonstrated good performances such as relative standard deviations (as RSD %) (≤3.5%) and spiked recoveries (95.7-102.3%). The accuracy of the method was assessed by analysis of two standard reference materials (SRMs) and recoveries of spiked solutions. The method was successfully applied into the determination of trace amounts of Mo(VI) and V(V) in milk, vegetables and foodstuffs with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

Molybdenum complexes of 1,2-bis(diphenylphosphino)benzene. Mononuclear molybdenum(II) species formed by facile metal-metal bond cleavage of the (Mo-/sup 4/Mo)/sup 4+/ core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakir, M.; Cotton, F.A.; Cudahy, M.M.

1988-07-27

The quadruply bonded dimolybdenum(II) complexes K/sub 4/Mo/sub 2/Cl/sub 8/, (NH/sub 4/)/sub 5/MoCl/sub 9/ /times/ H/sub 2/O, and (NH/sub 4/)/sub 4/Mo/sub 2/Br/sub 8/ react with 1,2-C/sub 6/H/sub 4/(PPh/sub 2/)/sub 2/(dppbe) in methanol at room temperature to afford /alpha/-Mo/sub 2/X/sub 4/(dppbe)/sub 2/ complexes (X = Cl, Br), which do not isomerize to the /beta/ isomers. Under more forcing reactions conditions (refluxing 1-propanol), these same reactions give mononuclear trans-MoX/sub 2/(dppbe)/sub 2/ in good yield (ca. 50%) together with some (MoOX(dppbe)/sub 2/)X /times/ nH/sub 2/O. An alternative synthetic strategy for the preparation of /alpha/-Mo/sub 2/X/sub 4/(dppbe)/sub 2/ involves the reaction of Mo/sub 2/(O/sub 2/CCH/submore » 3/)/sub 4/ with dppbe and Me/sub 3/SiX in THF. The compound MoCl/sub 2/(dppbe)/sub 2/ forms crystals in space group P2/sub 1//n, with the following unit cell parameters: a = 10.884 (2) /angstrom/, b = 12.753 (2) /angstrom/, c = 18.141 (4) /angstrom/, /beta/ = 91.43 (2)/degree/, V = 2517 (2) /angstrom//sup 3/, and Z = 2. The centrosymmetric trans molecule has Mo-Cl = 2.410 (1) /angstrom/, Mo-P = 2.481 (1), 2.511 (1) /angstrom/, and P-Mo-P(intra-ring) = 78.68 (4)/degree/. 25 refs., 1 fig., 4 tabs.« less

Note: Laser-cut molybdenum grids for a retarding field energy analyzer

NASA Astrophysics Data System (ADS)

Landheer, K.; Kobelev, A. A.; Smirnov, A. S.; Bosman, J.; Deelen, S.; Rossewij, M.; de Waal, A. C.; Poulios, I.; Benschop, A. F.; Schropp, R. E. I.; Rath, J. K.

2017-06-01

A retarding field energy analyzer (RFEA) with grids created by laser-cutting a honeycomb mesh in a 50 μm thick molybdenum foil is presented. The flat grids span an area of 1 cm2 and have high transmission (20 μm wide walls between 150 μm wide meshes). The molybdenum grids were tested in a 3-grid RFEA configuration with an analyzer depth of 0.87 mm.

THE CHEMICAL ANALYSIS OF TERNARY ALLOYS OF PLUTONIUM WITH MOLYBDENUM AND URANIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, G.; Woodhead, J.; Jenkins, E.N.

1958-09-01

It is shown that the absorptiometric determination of molybdenum as thiocyanate may be used in the presence of plutonium. Molybdenum interferes with previously published methods for determining uranium and plutonium but conditlons have been established for its complete removal by solvent extraction of the compound with alpha -benzoin oxime. The previous methods for uranium and plutonium are satisfactory when applied to the residual aqueous phase following this solvent extraction. (auth)

Impact resistance performance of diamond film on a curved molybdenum substrate

NASA Astrophysics Data System (ADS)

Chen, Yang; Gou, Li

2017-08-01

Diamond films with different thicknesses were deposited on flat and curved molybdenum substrate by the microwave plasma chemical vapour deposition (MPCVD) method. Scanning electronic microscopy, atomic force microscopy and Raman spectroscopy were employed to characterise the morphology, the surface roughness and the composition of the films, respectively. A NanoTest system was used for hardness, elastic modulus and nanoimpact tests. The curved surface and ductility of the molybdenum substrate allow large deformation for the thinner films. The substrate has less effect on impact for the thicker film, the deformation of which is mainly determined by the film composition. Under a load of 50 mN and 75 cycles, less deformation occurred for the 22 μm thick film on the curved molybdenum substrate.

Interpretation and modelling of fission product Ba and Mo releases from fuel

NASA Astrophysics Data System (ADS)

Brillant, G.

2010-02-01

The release mechanisms of two fission products (namely barium and molybdenum) in severe accident conditions are studied using the VERCORS experimental observations. Barium is observed to be mostly released under reducing conditions while molybdenum release is most observed under oxidizing conditions. As well, the volatility of some precipitates in fuel is evaluated by thermodynamic equilibrium calculations. The polymeric species (MoO 3) n are calculated to largely contribute to molybdenum partial pressure and barium volatility is greatly enhanced if the gas atmosphere is reducing. Analytical models of fission product release from fuel are proposed for barium and molybdenum. Finally, these models have been integrated in the ASTEC/ELSA code and validation calculations have been performed on several experimental tests.

Process development for the manufacture of an integrated dispenser cathode assembly using laser chemical vapor deposition

NASA Astrophysics Data System (ADS)

Johnson, Ryan William

2005-07-01

Laser Chemical Vapor Deposition (LCVD) has been shown to have great potential for the manufacture of small, complex, two or three dimensional metal and ceramic parts. One of the most promising applications of the technology is in the fabrication of an integrated dispenser cathode assembly. This application requires the deposition of a boron nitride-molybdenum composite structure. In order to realize this structure, work was done to improve the control and understanding of the LCVD process and to determine experimental conditions conducive to the growth of the required materials. A series of carbon fiber and line deposition studies were used to characterize process-shape relationships and study the kinetics of carbon LCVD. These studies provided a foundation for the fabrication of the first high aspect ratio multi-layered LCVD wall structures. The kinetics studies enabled the formulation of an advanced computational model in the FLUENT CFD package for studying energy transport, mass and momentum transport, and species transport within a forced flow LCVD environment. The model was applied to two different material systems and used to quantify deposition rates and identify rate-limiting regimes. A computational thermal-structural model was also developed using the ANSYS software package to study the thermal stress state within an LCVD deposit during growth. Georgia Tech's LCVD system was modified and used to characterize both boron nitride and molybdenum deposition independently. The focus was on understanding the relations among process parameters and deposit shape. Boron nitride was deposited using a B3 N3H6-N2 mixture and growth was characterized by sporadic nucleation followed by rapid bulk growth. Molybdenum was deposited from the MoCl5-H2 system and showed slow, but stable growth. Each material was used to grow both fibers and lines. The fabrication of a boron nitride-molybdenum composite was also demonstrated. In sum, this work served to both advance the general science of Laser Chemical Vapor Deposition and to elucidate the practicality of fabricating ceramic-metal composites using the process.

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orozco, C.; Melendez, A.; Manadhar, S.

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2O 4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–xMo xO 4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7more » g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+) for higher x while in a mixed chemical valence state (Mo 4+, Mo 5+, Mo 6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.« less

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

DOE PAGES

Orozco, C.; Melendez, A.; Manadhar, S.; ...

2017-09-26

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2O 4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–xMo xO 4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7more » g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+) for higher x while in a mixed chemical valence state (Mo 4+, Mo 5+, Mo 6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.« less

A STUDY OF DISLOCATION STRUCTURE OF SUBBOUNDARIES IN MOLYBDENUM SINGLE CRYSTALS,

DTIC Science & Technology

MOLYBDENUM, *DISLOCATIONS), GRAIN STRUCTURES(METALLURGY), SINGLE CRYSTALS, ZONE MELTING, ELECTRON BEAM MELTING, GRAIN BOUNDARIES, MATHEMATICAL ANALYSIS, ETCHED CRYSTALS, ETCHING, ELECTROEROSIVE MACHINING, CHINA

Applications of molybdenum-95 NMR spectroscopy. 7. Studies of metal-metal bonded systems including aqueous molybdenum(IV) and molybdenum(V). Crystal and molecular structure of Na/sub 2/(Mo/sub 3/O/sub 4/((O/sub 2/CCH/sub 2/)/sub 2/NCH/sub 3/)/sub 3/). 7H/sub 2/O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghellar, S.F.; Hambley, T.W.; Brownlee, R.T.

1983-03-23

Solution /sup 95/Mo NMR studies are reported on spin-coupled polynuclear systems of Mo(V), Mo(IV), and Mo(II). Resonances occur at low fields compared to mononuclear species. The chemical shifts of the Mo(IV)-aquo ion in 4 M p-toluenesulfonic and methanesulfonic acid media and those of the Mo(IV) complexes containing oxalate, EDTA, and methyliminodiacetate ligands (whose solid-state structures are based on the (Mo/sub 3/O/sub 4/)/sup 4 +/ cluster) fall in the narrow range of 172 ppm spanning 990-1162 ppm. As the known chemical shift scale for the /sup 95/Mo nucleus covers 7000 ppm, this observation indicates that the /sup 95/Mo nucleus is inmore » a similar chemical environment in each of the species examined and, taken with published evidence, confirms formulation of the Mo(IV)-aquo ion as (Mo/sub 3/O/sub 4/(H/sub 2/O)/sub 9/)/sup 4 +/. Two resonances are detected in the above range for Mo(IV)/sub aq/ in 4 M hydrochloric acid and for ((Mo/sub 3/O/sub 4/)/sub 2/(PDTA)/sub 3/)/sup 4 -/. Additional resonances appear at 539-608 ppm in the methanesulfonic acid, hydrochloric acid, and EDTA systems when stored in air. These are assigned to (Mo/sup v//sub 2/O/sub 4/)/sup 2 +/-based species by comparison with the observed resonances of the Mo(V)-aquo ion, (Mo/sup v//sub 2/O/sub 4/(H/sub 2/O)/sub 6/)/sup 2 +/, in the relevant acid media and with (Mo/sup v//sub 2/O/sub 4/(EDTA))/sup 2 -/ in H/sub 2/O. The (Mo/sup v//sub 2/O/sub 4/(PDTA))/sup 2 -/ anion exhibits two resonances associated with inequivalent molybdenum sites. Resonances for (Mo/sup II//sub 2/(O/sub 2/CR)/sub 4/) (R = CF/sub 3/, n-Pr), which contain formal quadruple bonds, have been observed for the first time and are the most deshielded /sup 95/Mo NMR signals detected to date. The methyliminodiacetate complex, Na/sub 2/(Mo/sub 3/O/sub 4/((O/sub 2/CCH/sub 2/)/sub 2/NCH/sub 3/)/sub 3/).7H/sub 2/O, was isolated. Its crystal structure contains a discrete trinuclear (Mo/sup IV//sub 3/O/sub 4/((O/sub 2/CCH/sub 2/)/sub 2/NCH/sub 3/)/sub 3/)/sup 2 -/ anion whose symmetry approaches C/sub 3v/.« less

The role of FeS clusters for molybdenum cofactor biosynthesis and molybdoenzymes in bacteria

PubMed Central

Yokoyama, Kenichi; Leimkühler, Silke

2016-01-01

Molybdenum is the only second row transition metal essential for biological systems, which is biologically available as molybdate ion. In eukarya, bacteria and archaea, molybdenum is bound to either to a tricyclic pyranopterin, thereby forming the molybdenum cofactor (Moco), or in some bacteria to the FeS cluster based iron-molybdenum cofactor (FeMoco), which forms the active site of nitrogenase. To date more than 50 Moco-containing enzymes have been purified and biochemically or structurally characterized. The physiological role of molybdenum in these enzymes is fundamental to organisms, since the reactions include the catalysis of key steps in carbon, nitrogen and sulfur metabolism. The catalyzed reactions are in most cases oxo-transfer reactions or the hydroxylation of carbon centers. The biosynthesis of Moco has been intensively studied, in addition to its insertion into molybdoenzymes. In particular, a link between the biosynthesis and maturation of molybdoenzymes and the biosynthesis and distribution of FeS clusters has been identified in the last years: 1) The synthesis of the first intermediate in Moco biosynthesis requires an FeS-cluster containing protein, 2) The sulfurtransferase for the dithiolene group in Moco is common also for the synthesis of FeS clusters, thiamin and thiolated tRNAs, 3) the modification of the active site with a sulfur atom additionally involves a sulfurtransferase, 4) most molybdoenzymes in bacteria require FeS clusters as additional redox active cofactors. In this review we will focus on the biosynthesis of the molybdenum cofactor in bacteria, its modification and insertion into molybdoenzymes, with an emphasis to its link to FeS cluster biosynthesis and sulfur transfer. PMID:25268953

Molybdenum-copper and tungsten-copper alloys and method of making

DOEpatents

Schmidt, Frederick A.; Verhoeven, John D.; Gibson, Edwin D.

1989-05-23

Molybdenum-copper and tungsten-copper alloys are prepared by a consumable electrode method in which the electrode consists of a copper matrix with embedded strips of refractory molybdenum or tungsten. The electrode is progressively melted at its lower end with a superatmospheric inert gas pressure maintained around the liquifying electrode. The inert gas pressure is sufficiently above the vapor pressure of copper at the liquidus temperature of the alloy being formed to suppress boiling of liquid copper.

Development of a Database of Thermochemical Parameters for Use with the SOLGASMIX Computer Program

DTIC Science & Technology

1988-07-01

TITANIUM CHLORIDE (TICL4) CL4Wl(CR) TUNGSTEN CHLORIDE (WCL4) CL4Wl(G) TUNGSTEN CHLORIDE (WCL4) CL4ZR1(CR) ZIRCONIUM CHLORIDE ( ZRCL4 ) CL4ZR1(G) ZIRCONIUM...CHLORIDE ( ZRCL4 ) % % % CL5MO1(CR) MOLYBDENUM CHLORIDE (MOCL5) CL5MO1(CR,L) MOLYBDENUM CHLORIDE (MOCL5) CL5MO1(G) MOLYBDENUM CHLORIDE (MOCL5) CL5MOI(L

Occurrence and distribution of molybdenum in the surface waters of Colorado geochemistry of water

USGS Publications Warehouse

Voegeli, Paul Thomas; King, Robert Ugstad

1969-01-01

Molybdenum was detected in 89 percent of the samples collected from all the principal Colorado streams and their chief tributaries and from a few reservoirs and lakes. Amounts detected ranged from 1 to 3,800 micrograms per liter. The greatest amounts of molybdenum detected were in samples from the Colorado River at and below Kremmling, the Dillon Reservoir, the Blue River below Dillon Dam, the Eagle River, and Tenmile Creek.

Hydrothermal preparation of blue molybdenum bronze nanoribbons: structural changes in mother crystals, related to solid-state conversion and crystallite splitting to nanomorphology

NASA Astrophysics Data System (ADS)

Nishida, Takamasa; Eda, Kazuo

2018-02-01

Hydrothermal syntheses of alkali-metal blue molybdenum bronze nanoribbons, which are expected to exhibit unique properties induced by a combined effect of extrinsic and intrinsic low-dimensionalities, from hydrated-alkali-metal molybdenum bronzes were investigated. Nanoribbons grown along the quasi-one-dimensional (1D) conductive direction of Cs0.3MoO3, which is difficult to prepare by the conventional methods, were first synthesized. The nanomorphology formation is achieved by a solid-state conversion (or crystallite splitting) and subsequent crystallite growth, and the structural changes of the starting material related to the conversion were first observed by powder X-ray diffraction and scanning transmission electron microscopy as a result of finely tuned reaction system and preparation conditions. The structural changes were analyzed by model simulations and were attributed to the structural modulations that were concerned with the intralayer packing disorder and with two-dimensional long-range ordered structure, formed in MoO3 sheets of the hydrated molybdenum bronze. Moreover, the modulations were related to displacement defects of the Mo-O framework units generated along the [100] direction in the hydrated molybdenum bronze. Then, it was suggested that the solid-state conversion into blue molybdenum bronze and the crystallite splitting to nanomorphology were initiated by the breaking of the Mo-O-Mo bonds at the defects. [Figure not available: see fulltext.

Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

PubMed

Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

2015-08-01

The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Low-temperature irradiation behavior of uranium-molybdenum alloy dispersion fuel

NASA Astrophysics Data System (ADS)

Meyer, M. K.; Hofman, G. L.; Hayes, S. L.; Clark, C. R.; Wiencek, T. C.; Snelgrove, J. L.; Strain, R. V.; Kim, K.-H.

2002-08-01

Irradiation tests have been conducted to evaluate the performance of a series of high-density uranium-molybdenum (U-Mo) alloy, aluminum matrix dispersion fuels. Fuel plates incorporating alloys with molybdenum content in the range of 4-10 wt% were tested. Two irradiation test vehicles were used to irradiate low-enrichment fuels to approximately 40 and 70 at.% 235U burnup in the advanced test reactor at fuel temperatures of approximately 65 °C. The fuel particles used to fabricate dispersion specimens for most of the test were produced by generating filings from a cast rod. In general, fuels with molybdenum contents of 6 wt% or more showed stable in-reactor fission gas behavior, exhibiting a distribution of small, stable gas bubbles. Fuel particle swelling was moderate and decreased with increasing alloy content. Fuel particles with a molybdenum content of 4 wt% performed poorly, exhibiting extensive fuel-matrix interaction and the growth of relatively large fission gas bubbles. Fuel particles with 4 or 6 wt% molybdenum reacted more rapidly with the aluminum matrix than those with higher-alloy content. Fuel particles produced by an atomization process were also included in the test to determine the effect of fuel particle morphology and microstructure on fuel performance for the U-10Mo composition. Both of the U-10Mo fuel particle types exhibited good irradiation performance, but showed visible differences in fission gas bubble nucleation and growth behavior.

[Mo2(CN)11]:5- A detailed description of ligand-field spectra and magnetic properties by first-principles calculations.

PubMed

Hendrickx, Marc F A; Clima, S; Chibotaru, L F; Ceulemans, A

2005-10-06

An ab initio multiconfigurational approach has been used to calculate the ligand-field spectrum and magnetic properties of the title cyano-bridged dinuclear molybdenum complex. The rather large magnetic coupling parameter J for a single cyano bridge, as derived experimentally for this complex by susceptibility measurements, is confirmed to a high degree of accuracy by our CASPT2 calculations. Its electronic structure is rationalized in terms of spin-spin coupling between the two constituent hexacyano-monomolybdate complexes. An in-depth analysis on the basis of Anderson's kinetic exchange theory provides a qualitative picture of the calculated CASSCF antiferromagnetic ground-state eigenvector in the Mo dimer. Dynamic electron correlations as incorporated into our first-principles calculations by means of the CASPT2 method are essential to obtain quantitative agreement between theory and experiment.

Flexible Molybdenum Electrodes towards Designing Affinity Based Protein Biosensors

PubMed Central

Kamakoti, Vikramshankar; Panneer Selvam, Anjan; Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Prasad, Shalini

2016-01-01

Molybdenum electrode based flexible biosensor on porous polyamide substrates has been fabricated and tested for its functionality as a protein affinity based biosensor. The biosensor performance was evaluated using a key cardiac biomarker; cardiac Troponin-I (cTnI). Molybdenum is a transition metal and demonstrates electrochemical behavior upon interaction with an electrolyte. We have leveraged this property of molybdenum for designing an affinity based biosensor using electrochemical impedance spectroscopy. We have evaluated the feasibility of detection of cTnI in phosphate-buffered saline (PBS) and human serum (HS) by measuring impedance changes over a frequency window from 100 mHz to 1 MHz. Increasing changes to the measured impedance was correlated to the increased dose of cTnI molecules binding to the cTnI antibody functionalized molybdenum surface. We achieved cTnI detection limit of 10 pg/mL in PBS and 1 ng/mL in HS medium. The use of flexible substrates for designing the biosensor demonstrates promise for integration with a large-scale batch manufacturing process. PMID:27438863

Electrode systems for in situ vitrification

DOEpatents

Buelt, James L.; Carter, John G.; Eschbach, Eugene A.; FitzPatrick, Vincent F.; Koehmstedt, Paul L.; Morgan, William C.; Oma, Kenton H.; Timmerman, Craig L.

1990-01-01

An electrode comprising a molybdenum rod is received within a conductive collar formed of graphite. The molybdenum rod and the graphite collar may be physically joined at the bottom. A pair of such electrodes are placed in soil containing buried waste material and an electric current is passed therebetween for vitrifying the soil. The graphite collar enhances the thermal conductivity of the combination, bringing heat to the surface, and preventing formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is suitably filled with a conductive ceramic powder that sinters upon the molybdenum rod, protecting the same from oxidation as graphite material is consumed, or a metal powder which liquefies at operating temperatures. The center of the molybdenum rod, used with a collar of separately, can be hollow and filled with a powdered metal, such as copper, which liquefies at operating temperatures. Connection to electrodes can be provided below ground level to avoid open circuit due to electrode deterioration, or sacrificial electrodes may be employed when operation is started. Outboard electrodes cna be utilized to square up a vitrified area.

Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide

PubMed Central

Tran, Phong D.; Tran, Thu V.; Orio, Maylis; Torelli, Stephane; Truong, Quang Duc; Nayuki, Keiichiro; Sasaki, Yoshikazu; Chiam, Sing Yang; Yi, Ren; Honma, Itaru; Barber, James; Artero, Vincent

2017-01-01

Molybdenum sulfides are very attractive noble-metal free electrocatalysts for the hydrogen evolution reaction (HER) from water. Atomic structure and identity of the catalytically active sites have been well established for crystalline molybdenum disulfide (c-MoS2) but not for amorphous molybdenum sulfide (a-MoSx) which displays significantly higher HER activity compared to its crystalline counterpart. Here we show that HER–active a-MoSx, prepared either as nanoparticles or as films, is a molecular–based coordination polymer consisting of discrete [Mo3S13]2– building blocks. Of the three terminal disulfide (S22–) ligands within these clusters, two are shared to form the polymer chain. The third one remains free and generates molybdenum hydride moieties as the active site under H2 evolution conditions. Such a molecular structure therefore provides a basis for revisiting the mechanism of a-MoSx catalytic activity, as well as explaining some of its special properties such as reductive activation and corrosion. Our findings open up new avenues for the rational optimisation of this HER electrocatalyst as an alternative to platinum. PMID:26974410

Understanding catalysis in a multiphasic two-dimensional transition metal dichalcogenide.

DOE PAGES

Chou, Stanley Shihyao; Sai, Na; Lu, Ping; ...

2015-10-07

Establishing processing–structure–property relationships for monolayer materials is crucial for a range of applications spanning optics, catalysis, electronics and energy. Presently, for molybdenum disulfide, a promising catalyst for artificial photosynthesis, considerable debate surrounds the structure/property relationships of its various allotropes. Here we unambiguously solve the structure of molybdenum disulfide monolayers using high-resolution transmission electron microscopy supported by density functional theory and show lithium intercalation to direct a preferential transformation of the basal plane from 2H (trigonal prismatic) to 1T' (clustered Mo). These changes alter the energetics of molybdenum disulfide interactions with hydrogen (ΔG H), and, with respect to catalysis, the 1T'more » transformation renders the normally inert basal plane amenable towards hydrogen adsorption and hydrogen evolution. Furthermore, we show basal plane activation of 1T' molybdenum disulfide and a lowering of ΔG H from +1.6 eV for 2H to +0.18 eV for 1T', comparable to 2H molybdenum disulfide edges on Au(111), one of the most active hydrogen evolution catalysts known.« less

Nuclear fuel alloys or mixtures and method of making thereof

DOEpatents

Mariani, Robert Dominick; Porter, Douglas Lloyd

2016-04-05

Nuclear fuel alloys or mixtures and methods of making nuclear fuel mixtures are provided. Pseudo-binary actinide-M fuel mixtures form alloys and exhibit: body-centered cubic solid phases at low temperatures; high solidus temperatures; and/or minimal or no reaction or inter-diffusion with steel and other cladding materials. Methods described herein through metallurgical and thermodynamics advancements guide the selection of amounts of fuel mixture components by use of phase diagrams. Weight percentages for components of a metallic additive to an actinide fuel are selected in a solid phase region of an isothermal phase diagram taken at a temperature below an upper temperature limit for the resulting fuel mixture in reactor use. Fuel mixtures include uranium-molybdenum-tungsten, uranium-molybdenum-tantalum, molybdenum-titanium-zirconium, and uranium-molybdenum-titanium systems.

Rate limiting mechanisms in lithium-molybdenum disulfide batteries

NASA Astrophysics Data System (ADS)

Laman, F. C.; Stiles, J. A. R.; Brandt, K.; Shank, R. J.

1985-03-01

One limitation of secondary lithium batteries using intercalation cathodes is generally related to relatively low power densities. Significant advances towards overcoming this limitation have been made in cells based on a utilization of lithium-molybdenum disulfide technology. Rate limiting mechanisms in cells of the lithium-molybdenum disulfide system have been studied with the aid of a frequency response analysis. It was found that diffusion-related contributions to cell impedance, and interfacial and resistive contributions to cell impedance, can be readily segregated by virtue of the fact that the diffusion-controlled mechanisms dominate the low frequency end of the impedance spectra, while the other mechanisms dominate the high frequency end. The present investigation is concerned with rate limitations at the high end of the frequency spectrum in lithium-molybdenum disulfide cathodes.

Mechanochemical processing of molybdenum and vanadium sulfides for metal recovery from spent catalysts wastes.

PubMed

Li, Zhao; Chen, Min; Zhang, Qiwu; Liu, Xinzhong; Saito, Fumio

2017-02-01

This work describes the mechanochemical transformations of molybdenum and vanadium sulfides into corresponding molybdate and vanadate, to serve as a new environment-friendly approach for processing hazardous spent hydrodesulphurization (HDS) catalysts solid waste to achieve an easy recovery of not only molybdenum and vanadium but also nickel and cobalt. Co-grinding the molybdenum and vanadium sulfides with oxidants and sodium carbonate stimulates solid-state reactions without any heating aid to form metal molybdates and vanadates. The reactions proceed with an increase in grinding time and were enhanced by using more sodium carbonate and stronger oxidant. The necessary conditions for the successful transformation can be explained on the basis of thermodynamic analyses, namely a negative change in Gibbs free energy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Molten Boron Phase-Change Thermal Energy Storage to Augment Solar Thermal Propulsion Systems

DTIC Science & Technology

2011-07-13

Thermodynamic Properties of Transition Metal Borides . I. The Molybdenum-boron system and Elemental Boron," Journal of Physical Chemistry, Vol. 81...February 1977, pp. 318-324. 38Itoh, H., Matsudaira, T., and Naka, S., "Formation Process of Tungsten Borides by Solid State Reaction Between Tungsten...Molybdenum-Boron and Some Properties of The Molybdenum- Borides ," Journal of Metals, September 1952, pp. 983-988. 40Stout, N. D., Mar, R. W., and Boo, W. O

Molybdenum sulfide/carbide catalysts

DOEpatents

Alonso, Gabriel [Chihuahua, MX; Chianelli, Russell R [El Paso, TX; Fuentes, Sergio [Ensenada, MX; Torres, Brenda [El Paso, TX

2007-05-29

The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

An Analysis of Changes in Threshold Limit Values Over Time

DTIC Science & Technology

1993-01-01

Metribuzin 21087-64-91 1984 1984 Mevinphos 7786-34-7 1982: 1982 _ _ Mica 12001-26-2 1 I987 1987 1 Mineral wool fiber _ 1987 1 1987 _ i t Molybdenum as Mo...1 _ _ i alpha-Methyl styrene _ __ 1968 6 Metribuzin Mevinphos t Mica _ _ _ Mineral wool fiber _ Molybdenum as Mo _ _ Soluble compounds I_...Metribuzin 0 0 i _ __ Mevinphos 0 0 Mica 0 10 ,0___ Mineral wool fiber 0 0 P _ _ Molybdenum as Mo _ ___ Soluble compounds 0 0 Insoluble compounds 1 j 00 _ i

Development of a low-permeability glass--ceramic to seal to molybdenum. [For long-life vacuum tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eagan, R. J.

1975-03-01

This report describes the development of low-permeability glass-ceramics which can be sealed directly to molybdenum for the purpose of producing long-life vacuum tubes. Low permeability to helium and thermal expansion match to molybdenum are the bases upon which particular glass-ceramic compositions were selected and developed. The fabrication of tube envelopes using glass-ceramics is simplified when compared to conventional ceramic/metal tubes and these melting and sealing techniques are presented.

Material and Energy Flows Associated with Select Metals in GREET 2. Molybdenum, Platinum, Zinc, Nickel, Silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benavides, Pahola T.; Dai, Qiang; Sullivan, John L.

2015-09-01

In this work, we analyzed the material and energy consumption from mining to production of molybdenum, platinum, zinc, and nickel. We also analyzed the production of solar- and semiconductor-grade silicon. We described new additions to and expansions of the data in GREET 2. In some cases, we used operating permits and sustainability reports to estimate the material and energy flows for molybdenum, platinum, and nickel, while for zinc and silicon we relied on information provided in the literature.

ON THE SEPARATION OF VANADIUM, MOLYBDENUM AND TUNGSTEN BY MEANS OF PAPER CHROMATOGRAPHY. PART I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tzou, S.; Liang, S.

1959-02-01

Molybdenum, tangsten, and vanadium are separated by chromatography as per-acids, and then detected with tannin solution. Of the seven solvents tested, n-butanolhydrogen peroxide-nitric acid mixtures offer the best separations. With the addition of dioxane, the R/sub F/ values of these elements increase, while vanadium and tungsten spots overlap. The formation of per-acids avoids the retainment of tungsten on the original spot and the tailings of vanadium and molybdenum spots. (B.O.G.)

Molybdenum-copper and tungsten-copper alloys and method of making

DOEpatents

Schmidt, F.A.; Verhoeven, J.D.; Gibson, E.D.

1989-05-23

Molybdenum-copper and tungsten-copper alloys are prepared by a consumable electrode method in which the electrode consists of a copper matrix with embedded strips of refractory molybdenum or tungsten. The electrode is progressively melted at its lower end with a superatmospheric inert gas pressure maintained around the liquefying electrode. The inert gas pressure is sufficiently above the vapor pressure of copper at the liquidus temperature of the alloy being formed to suppress boiling of liquid copper. 6 figs.

SOLVENT EXTRACTION PROCESS FOR URANIUM RECOVERY

DOEpatents

Clark, H.M.; Duffey, D.

1958-06-17

A process is described for extracting uranium from uranium ore, wherein the uranium is substantially free from molybdenum contamination. In a solvent extraction process for recovering uranium, uranium and molybdenum ions are extracted from the ore with ether under high acidity conditions. The ether phase is then stripped with water at a lower controiled acidity, resaturated with salting materials such as sodium nitrate, and reextracted with the separation of the molybdenum from the uranium without interference from other metals that have been previously extracted.

Electroplating and stripping copper on molybdenum and niobium

NASA Technical Reports Server (NTRS)

Power, J. L.

1978-01-01

Molybdenum and niobium are often electroplated and subsequently stripped of copper. Since general standard plating techniques produce poor quality coatings, general procedures have been optimized and specified to give good results.

Molybdenum and tungsten nanostructures and methods for making and using same

DOEpatents

Kotaro, Sasaki; Chen, Wei-Fu; Muckerman, James T; Adzic, Radoslav R

2015-01-06

The present invention provides molybdenum and tungsten nanostructures, for example, nanosheets and nanoparticles, and methods of making and using same, including using such nanostructures as catlysts for hydrogen evolution reactions.

Pure s-Process Molybdenum Found in PreSolar Silicon Carbide Grains

NASA Astrophysics Data System (ADS)

Stephan, T.; Trappitsch, R.; Boehnke, P.; Davis, A. M.; Pellin, M. J.; Pardo, O. S.

2017-07-01

Molybdenum isotopes analyzed with high precision in 18 presolar SiC grains using CHILI (Chicago Instrument for Laser Ionization) reflect variability of conditions in stellar environments during s-process nucleosynthesis.

Tribochemistry of contact interfaces of nanocrystalline molybdenum carbide films

NASA Astrophysics Data System (ADS)

Kumar, D. Dinesh; Kumar, N.; Panda, Kalpataru; Kamalan Kirubaharan, A. M.; Kuppusami, P.

2018-07-01

Transition metal carbides (TMC) are known for their improved tribological properties and are sensitive to the tribo-atmospheric environment. Nanocrystalline molybdenum carbide (MoC) thin films were deposited by DC magnetron sputtering technique using reactive CH4 gas. The friction and wear resistance properties of MoC thin films were significantly improved in humid-atmospheric condition as compared to high-vacuum tribo-condition. A comprehensive chemical analysis of deformed contact interfaces was carried out by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. XPS and Raman spectroscopy showed the formation of stable molybdenum-oxide (MoO), molybdenum carbide (MoC) and amorphous carbon (a-C) tribo-phases. Moreover, during the sliding in humid-atmospheric condition, these phases were extensively deposited on the sliding steel ball counter body which significantly protected against undesirable friction and wear.

Molybdenum electron impact width parameter measurement by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Sternberg, E. M. A.; Rodrigues, N. A. S.; Amorim, J.

2016-01-01

In this work, we suggest a method for electron impact width parameter calculation based on Stark broadening of emission lines of a laser-ablated plasma plume. First, electron density and temperature must be evaluated by means of the Saha-Boltzmann plot method for neutral and ionized species of the plasma. The method was applied for laser-ablated molybdenum plasma plume. For molybdenum plasma electron temperature, which varies around 10,000 K, and electron density, which reaches values around 1018 cm-3, and considering that total measured line broadening was due experimental and Stark broadening mainly, electron impact width parameter of molybdenum emission lines was determined as (0.01 ± 0.02) nm. Intending to validate the presented method, it was analyzed the laser-ablated aluminum plasma plume and the obtained results were in agreement with the predicted on the literature.

Structure and photochromic properties of molybdenum-containing silica gels obtained by molecular-lamination method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belotserkovskaya, N.G.; Dobychin, D.P.; Pak, V.N.

1992-05-10

The structure and physicochemical properties of molybdenum-containing silica gels obtained by molecular lamination have been studied quite extensively. Up to the present, however, no studies have been made of the influence of the pore structure of the original silica gel on the structure and properties of molybdenum-containing silica gels (MSG). The problem is quite important, since molybdenum silicas obtained by molecular lamination may find applications in catalysis and as sensors of UV radiation. In either case, the structure of the support is not a factor to be ignored. Here, the authors are reporting on an investigation of the structure ofmore » MSG materials with different pore structures and their susceptibility to reduction of the Mo(VI) oxide groupings when exposed to UV radiation. 16 refs., 2 figs., 2 tabs.« less

GEANT 4 simulation of (99)Mo photonuclear production in nanoparticles.

PubMed

Dikiy, N P; Dovbnya, A N; Fedorchenko, D V; Khazhmuradov, M A

2016-08-01

GEANT 4 Monte-Carlo simulation toolkit is used to study the kinematic recoil method of (99)Mo photonuclear production. Simulation for bremsstrahlung photon spectrum with maximum photon energy 30MeV showed that for MoO3 nanoparticle escape fraction decreases from 0.24 to 0.08 when nanoparticle size increases from 20nm to 80nm. For the natural molybdenum and pure (100)Mo we obtained the lower values: from 0.17 to 0.05. The generation of accompanying molybdenum nuclei is significantly lower for pure (100)Mo and is about 3.6 nuclei per single (99)Mo nucleus, while natural molybdenum nanoparticle produce about 48 accompanying nuclei. Also, we have shown that for high-energy photons escape fraction of (99)Mo decreases, while production of unwanted molybdenum isotopes is significantly higher. Copyright © 2016 Elsevier Ltd. All rights reserved.

Seasonal variations in the NO2 artifact from chemiluminescence measurements with a molybdenum converter at a suburban site in Korea (downwind of the Asian continental outflow) during 2015-2016

NASA Astrophysics Data System (ADS)

Jung, Jinsang; Lee, JaeYong; Kim, ByungMoon; Oh, SangHyub

2017-09-01

This paper investigates the NO2 artifact associated with the chemiluminescence measurement technique that uses a molybdenum converter by applying the same technique but with a photolytic converter at a site downwind of the Asian continental outflow (Daejeon, Korea). The NO2 to NO conversion efficiencies of the molybdenum and photolytic converters were found to be 100% and 95%, respectively, at an ambient level of NO2 (<100 ppbv). Two NO2 monitors equipped with molybdenum and photolytic converters were deployed for ambient NO2 measurements in Daejeon, Korea between the fall of 2015 and the summer of 2016. It was found that the monitor equipped with the molybdenum converter overestimated NO2 levels by 20.4 ± 14.7% when compared with the actual NO2 level in the Daejeon atmosphere over the entire measurement period. This NO2 artifact (ΔNO2), defined as the difference between molybdenum NO2 and photolytic NO2 values, correlated well with the PM2.5 mass concentration during the fall and winter seasons. Based on these findings, this study develops a simple correction model for ΔNO2 using the PM2.5 mass concentration during the fall and winter seasons. The model-corrected NO2 concentration correlated well with the actual NO2 values with a slope of approximately 1.0 and R2 value of 0.98 during the fall and winter seasons.

Complex, Precision Cast Columbium Alloy Gas Turbine Engine Nozzles Coated to Resist Oxidation.

DTIC Science & Technology

1980-04-01

Microstructures of Sprayed Specimens 64 Table 19 NS-4 Coated C129Y Alloy Specimens Weight Bisque Weight Sintered Weight Silicided Weight Pre-Oxidized...choice of another alloy , while perhaps assisting in the foundry process , would not have yielded a mechanical property data base with advantage over...Mo 250 ppm max; Fe 30 ppm max; Al , Ca, C, Si, Cr, Ni, Cu , Mn, Mg and Sn 10 ppm max each). Molybdenum វim powder (02 2000 ppm max; W 250 ppm max; Fe

Emission efficiency optimization of RE 2O 3 doped molybdenum thermionic cathode by application of pattern recognition method

NASA Astrophysics Data System (ADS)

Wang, Jinshu; Liu, Wei; Liu, Yanqin; Zhou, Meiling

2005-09-01

As an alternative for thoriated tungsten thermionic cathodes, molybdenum doped with either a single rare earth oxide such as La 2O 3, Y 2O 3 and Sc 2O 3 or a mixture thereof has been produced by powder metallurgy. It is shown that carbonization can greatly improve the emission properties (i.e. emission capability and stability) of RE 2O 3 doped molybdenum due to the formation of a (metallic) rare earth atomic layer on the surface of the cathode by the reduction reaction of molybdenum carbide and rare earth oxide. Among all the carbonized samples, La 2O 3 and Y 2O 3 co-doped molybdenum cathode showed the best performance in emission. In addition, computer pattern recognition technique has been used to optimize the composition of the material and of the cathode preparation technique. We derive the equation of the emission efficiency as a function of cathode composition and carbonization degree. Based on the projecting coordinates obtained from the equation, the optimum projection region was identified, which can serve as guide for the composition and carbonization degree design.

Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

DOE PAGES

Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; ...

2015-01-31

Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is moremore » than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.« less

Catalytic dehydrogenation of alcohol over solid-state molybdenum sulfide clusters with an octahedral metal framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamiguchi, Satoshi, E-mail: kamigu@riken.jp; Organometallic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako City, Saitama 351-0198; Okumura, Kazu

Graphical abstract: - Highlights: • Solid-state molybdenum sulfide clusters catalyzed the dehydrogenation of alcohol. • The dehydrogenation proceeded without the addition of any oxidants. • The catalytic activity developed when the cluster was activated at 300–500 °C in H{sub 2}. • The Lewis-acidic molybdenum atom and basic sulfur ligand were catalytically active. • The clusters function as bifunctional acid–base catalysts. - Abstract: Solid-state molybdenum sulfide clusters with an octahedral metal framework, the superconducting Chevrel phases, are applied to catalysis. A copper salt of a nonstoichiometric sulfur-deficient cluster, Cu{sub x}Mo{sub 6}S{sub 8–δ} (x = 2.94 and δ ≈ 0.3), is storedmore » in air for more than 90 days. When the oxygenated cluster is thermally activated in a hydrogen stream above 300 °C, catalytic activity for the dehydrogenation of primary alcohols to aldehydes and secondary alcohols to ketones develops. The addition of pyridine or benzoic acid decreases the dehydrogenation activity, indicating that both a Lewis-acidic coordinatively unsaturated molybdenum atom and a basic sulfur ligand synergistically act as the catalytic active sites.« less

Effect of cathodic current density on performance of tungsten coatings on molybdenum prepared by electrodeposition in molten salt

NASA Astrophysics Data System (ADS)

Jiang, Fan

2016-02-01

Smooth tungsten coatings were prepared at current density below 70 mA cm-2 by electrodeposition on molybdenum substrate from Na2WO4-WO3 -melt at 1173 K in air atmosphere. As the current density reached up to 90 mA cm-2, many significant nodules were observed on the surface of the coating. Surface characterization, microstructure and mechanical properties were performed on the tungsten coatings. As the increasing of current density, the preferred orientation of the coatings changed to (2 0 0). All coatings exhibited columnar-grained-crystalline. There was about a 2 μm thick diffusion layer between tungsten coating and molybdenum substrate. The bending test revealed the tungsten coating had -good bonding strength with the molybdenum substrate. There is a down trend of the grain size of the coating on molybdenum as the current density increased from 30 mA cm-2 to 50 mA cm-2. The coating obtained at 50 mA cm-2 had a minimum grain size of 4.57 μm, while the microhardness of this coating reached to a maximum value of 495 HV.

Control of C-H Bond Activation by Mo-Oxo Complexes: pKa or Bond Dissociation Free Energy (BDFE)?

PubMed

Nazemi, Azadeh; Cundari, Thomas R

2017-10-16

A density functional theory (DFT) study (BMK/6-31+G(d)) was initiated to investigate the activation of benzylic carbon-hydrogen bonds by a molybdenum-oxo complex with a potentially redox noninnocent supporting ligand-a simple mimic of the active species of the enzyme ethylbenzene dehydrogenase (EBDH)-through deprotonation (C-H bond heterolysis) or hydrogen atom abstraction (C-H bond homolysis) routes. Activation free-energy barriers for neutral and anionic Mo-oxo complexes were high, but lower for anionic complexes than neutral complexes. Interesting trends as a function of substituents were observed that indicated significant H δ+ character in the transition states (TS), which was further supported by the preference for [2 + 2] addition over HAA for most complexes. Hence, it was hypothesized that C-H activation by these EBDH mimics is controlled more by the pK a than by the bond dissociation free energy of the C-H bond being activated. Therefore, the results suggest promising pathways for designing more efficient and selective catalysts for hydrocarbon oxidation based on EBDH active-site mimics.

40 CFR 421.214 - Standards of performance for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... leachate. NSPS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant property Maximum....5 to 10.0 at all times. (c) Molybdic oxide leachate. NSPS for the Primary Molybdenum and Rhenium...

40 CFR 421.214 - Standards of performance for new sources.

Code of Federal Regulations, 2013 CFR

2013-07-01

... leachate. NSPS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant property Maximum....5 to 10.0 at all times. (c) Molybdic oxide leachate. NSPS for the Primary Molybdenum and Rhenium...

40 CFR 421.214 - Standards of performance for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... leachate. NSPS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant property Maximum....5 to 10.0 at all times. (c) Molybdic oxide leachate. NSPS for the Primary Molybdenum and Rhenium...

40 CFR 421.214 - Standards of performance for new sources.

Code of Federal Regulations, 2014 CFR

2014-07-01

... leachate. NSPS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant property Maximum....5 to 10.0 at all times. (c) Molybdic oxide leachate. NSPS for the Primary Molybdenum and Rhenium...

40 CFR 421.214 - Standards of performance for new sources.

Code of Federal Regulations, 2012 CFR

2012-07-01

... leachate. NSPS for the Primary Molybdenum and Rhenium Subcategory Pollutant or pollutant property Maximum....5 to 10.0 at all times. (c) Molybdic oxide leachate. NSPS for the Primary Molybdenum and Rhenium...

Pest resistant MoSi.sub.2 materials and method of making

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G. (Inventor)

1995-01-01

A pest resistant molybdenum disilicide composition is provided for use in high temperature structural applications. The composition includes molybdenum disilicide and silicon nitride and can be used to prepare improved reinforced composites.

Molybdenum nitride fibers or tubes via ammonolysis of polysulfide precursor

NASA Astrophysics Data System (ADS)

Wang, Shutao; Zhang, Zude; Zhang, Yange; Qian, Yitai

2004-08-01

Millimeter-sized molybdenum nitride (MoN), in the forms of fiber-like prisms or hollow tubes, has been successfully synthesized via thermal ammonolysis of molybdenum polysulfide precursor. The initial morphology of the precursor is well preserved in the final product. This method could be expanded to preparation of other fiber-like nonmetal ceramics without addition of template. The polysulfide precursor (abbreviated to PS), hydrothermally prepared at 30°C (PS1) or 150°C (PS2), was characterized by various methods for better comprehension of the sulfide-nitride topotactic conversion model.

Magnetoresistance measurements of superconducting molybdenum nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baskaran, R., E-mail: baskaran@igcar.gov.in; Arasu, A. V. Thanikai; Amaladass, E. P.

2016-05-23

Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

Structure Evolution and Distributions of Grain-Boundary Misorientainons in Submicrocrystalline Molybdenum Irradiated with a Pulsed Electron Beam

NASA Astrophysics Data System (ADS)

Stepanova, E. N.; Grabovetskaya, G. P.; Teresov, A. D.; Mishin, I. P.

2018-05-01

Using the methods of electron backscatter diffraction, electron microscopy and X-ray diffraction analysis, it is demonstrated that irradiation of the surface of a submicrocrystalline molybdenum specimen with a pulsed electron beam in a non-melt regime results in the formation of a gradient structure in its bulk. The irradiation temperature is shown to affect the density of defects, the value of stress, and the distributions of grain-boundary misorientations in the surface and bulk of the submicrocrystalline molybdenum specimens.

Use of spectroscopic technique to develop a reagent for Mo(VI) utilizing micellar effects on complex formation

NASA Astrophysics Data System (ADS)

Taşcioğlu, Sülin; Kaki, E.; Taşcioğlu, Senay

2012-09-01

Ultraviolet and visible spectral properties of aqueous solutions of molybdenum(VI) (Mo), gallic acid (GA), Lalanine (Ala), and L-Phenylalanine (Phe), and of their binary and ternary solutions were investigated in the absence and presence of anionic, cationic, and nonionic surfactant micelles. Evaluation of the spectra in a comparative way revealed that both Ala and Phe form ternary complexes with Mo and GA. The formation of a quaternary complex between Mo, GA, Phe, and cetyltrimethylammonium bromide at pH 4.5 provided a reagent system with a strikingly high sensitivity (1.2•106 l/(mol•cm)) for use in the spectrophotometric determination of Mo. A mechanism of micellar effects was discussed in terms of the substrate molecular charge and hydrophobicity, and rationalized on the basis of the spectral data obtained above and below the isoelectric pH of the amino acids.

Developing the Molybdenum Isotopic Proxy in Marine Barite

NASA Astrophysics Data System (ADS)

Erhardt, A. M.; Paytan, A.; Aggarwal, J.

2006-12-01

Molybdenum isotope ratios in seawater fluctuate in response to changing redox conditions and can provide clues into the degree of global ocean anoxia. The isotopic ratio of molybdenum has been shown to be sensitive to the relative proportion of oxic, suboxic, and euxinic environments. Deposition in oxic environments is isotopically light (~ -1.6‰ for δ^{97/95}Mo) relative to an average crustal source (0‰). Conversely, euxinic environments have been shown to be consistently heavier (~1.3‰) than the oxic sink through time, with suboxic sediments falling between these two signals. Shifts in the relative proportion of each sink, relative to a constant source, would alter the isotopic ratio of seawater over long time scales. Previously, this seawater value, and hence the degree of global anoxia, could only be inferred through mass balance calculations. We seek to quantify the isotopic signature of seawater though time using a phase that directly records this ratio. Marine barite precipitates inorganically in the water column directly from seawater, potentially providing a direct record of seawater characteristics. Molybdenum is a trace constituent of barite, with the molybdate ion substituting for sulfate at concentrations of about 1 ppm. To accurately determine the molybdenum isotopic ratio at these low concentrations (<15 ng per sample), modifications to existing measurement techniques are required. We will present the variations made to existing separation and mass-spectrometry techniques and the calibration of these new methods. The modifications were undertaken to reduce molybdenum blank to below 1 ng per analysis, to quantitatively remove interfering zirconium and to measure precise and reproducible isotope values. Preliminary data will be presented to illustrate potential applications for this new paleoredox proxy. This technique will allow for the measurement of molybdenum isotopic ratios at low concentrations, expanding the breath of compounds and signals that potentially record changes in planetary materials.

Molybdenum disulfide (MoS2) nanoflakes as inherently electroactive labels for DNA hybridization detection

NASA Astrophysics Data System (ADS)

Loo, Adeline Huiling; Bonanni, Alessandra; Ambrosi, Adriano; Pumera, Martin

2014-09-01

The detection of specific DNA sequences plays a critical role in the areas of medical diagnostics, environmental monitoring, drug discovery and food safety. This has therefore become a strong driving force behind the ever-increasing demand for simple, cost-effective, highly sensitive and selective DNA biosensors. In this study, we report for the first time, a novel approach for the utilization of molybdenum disulfide nanoflakes, a member of the transition metal dichalcogenides family, in the detection of DNA hybridization. Herein, molybdenum disulfide nanoflakes serve as inherently electroactive labels, with the inherent oxidation peak exploited as the analytical signal. The principle of detection is based on the differential affinity of molybdenum disulfide nanoflakes towards single-stranded DNA and double-stranded DNA. The employment of transition metal dichalcogenide nanomaterials for sensing and biosensing purposes represents an upcoming research area which holds great promise. Hence, our findings are anticipated to have significant contributions towards the fabrication of future DNA biosensors.The detection of specific DNA sequences plays a critical role in the areas of medical diagnostics, environmental monitoring, drug discovery and food safety. This has therefore become a strong driving force behind the ever-increasing demand for simple, cost-effective, highly sensitive and selective DNA biosensors. In this study, we report for the first time, a novel approach for the utilization of molybdenum disulfide nanoflakes, a member of the transition metal dichalcogenides family, in the detection of DNA hybridization. Herein, molybdenum disulfide nanoflakes serve as inherently electroactive labels, with the inherent oxidation peak exploited as the analytical signal. The principle of detection is based on the differential affinity of molybdenum disulfide nanoflakes towards single-stranded DNA and double-stranded DNA. The employment of transition metal dichalcogenide nanomaterials for sensing and biosensing purposes represents an upcoming research area which holds great promise. Hence, our findings are anticipated to have significant contributions towards the fabrication of future DNA biosensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03795b

Carbon nanotube synthesis via the catalytic chemical vapor deposition of methane in the presence of iron, molybdenum, and iron-molybdenum alloy thin layer catalysts

NASA Astrophysics Data System (ADS)

Yahyazadeh, Arash; Khoshandam, Behnam

In this study, we documented the catalytic chemical vapor deposition synthesis of carbon nanotubes (CNTs) using ferrocene and molybdenum hexacarbonyl as catalyst nanoparticle precursors and methane as a nontoxic and economical carbon source for the first time. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive X-ray spectrometry and transmission electron microscopy of the thin layer catalyst as a simple and cost effective catalyst preparation after methane decomposition reaction, along with Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the growth of CNTs, from bimetallic nanoparticles, which are converted into iron-molybdenum alloy nanoparticles at 700 °C for pretreatment by hydrogen after chemical vapor deposition of thin layers. An investigation of the weight percentages of the chemical elements present in the CNTs synthesized from iron-molybdenum catalyst using quartz sheet substrate at 750 °C, confirmed a significant carbon yield of 75.4% which represents high catalyst activity. Additionally, multi-walled carbon nanotubes (∼16-55 nm in diameter and 1.2 μm in length) were observed in the iron-molybdenum alloy sample after methane decomposition reaction at 750 °C for 35 min. To show the role of iron and molybdenum coated on silicon substrate as two thin layer catalysts, samples were considered for CNTs growth (diameter ∼47-69 nm) at 800 °C and 830 °C, respectively. Moreover, the effect of hydrogen pretreatment was evaluated in terms of active metal coating properly. The best graphitic structure due to Raman spectroscopy outcomes (ID/IG ratio) was obtained for iron coated on a quartz sheet, which was estimated at 0.8505. Thermogravimetric analysis proved the thermal stability of the synthesized CNTs using iron thin-layer catalyst up to 350 °C.

Structural evolution of molybdenum carbides in hot aqueous environments and impact on low-temperature hydroprocessing of acetic acid

DOE PAGES

Choi, Jae -Soon; Schwartz, Viviane; Santillan-Jimenez, Eduardo; ...

2015-03-13

In this paper, we investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating themore » possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. Finally, the results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils.« less

Molybdenum

Integrated Risk Information System (IRIS)

Molybdenum ; CASRN 7439 - 98 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

Investigation of hydrogen evolution activity for the nickel, nickel-molybdenum nickel-graphite composite and nickel-reduced graphene oxide composite coatings

NASA Astrophysics Data System (ADS)

Jinlong, Lv; Tongxiang, Liang; Chen, Wang

2016-03-01

The nickel, nickel-molybdenum alloy, nickel-graphite and nickel-reduced graphene oxide composite coatings were obtained by the electrodeposition technique from a nickel sulfate bath. Nanocrystalline molybdenum, graphite and reduced graphene oxide in nickel coatings promoted hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. However, the nickel-reduced graphene oxide composite coating exhibited the highest electrocatalytic activity for the hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. A large number of gaps between 'cauliflower' like grains could decrease effective area for hydrogen evolution reaction in slight amorphous nickel-molybdenum alloy. The synergistic effect between nickel and reduced graphene oxide promoted hydrogen evolution, moreover, refined grain in nickel-reduced graphene oxide composite coating and large specific surface of reduced graphene oxide also facilitated hydrogen evolution reaction.

Comparison of Tungsten and Molybdenum Based Emitters for Advanced Thermionic Space Nuclear Reactors

NASA Astrophysics Data System (ADS)

Lee, Hsing H.; Dickinson, Jeffrey W.; Klein, Andrew C.; Lamp, Thomas R.

1994-07-01

Variations to the Advanced Thermionic Initiative thermionic fuel element are analyzed. Analysis included neutronic modeling with MCNP for criticality determination and thermal power distribution, and thermionic performance modeling with TFEHX. Changes to the original ATI configuration include the addition of W-HfC wire to the emitter for high temperature creep resistance improvement and substitution of molybdenum for the tungsten base material. Results from MCNP showed that all the tungsten used in the coating and base material must be 100% W-184 to obtain criticality. The presence of molybdenum in the emitter base affects the neutronic performance of the TFE by increasing the emitter neutron absorption cross section. Due to the reduced thermal conductivity for the molybdenum based emitter, a higher temperature is obtained resulting in a greater electrical power production. The thermal conductivity and resistivity of the composite emitter region were derived for the W-Mo composite and used in TFEHX.

Molybdenum cell for x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures

NASA Astrophysics Data System (ADS)

Matsuda, Kazuhiro; Tamura, Kozaburo; Katoh, Masahiro; Inui, Masanori

2004-03-01

We have developed a sample cell for x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures. All parts of the cell are made of molybdenum which is resistant to the chemical corrosion of alkali metals. Single crystalline molybdenum disks electrolytically thinned down to 40 μm were used as the walls of the cell through which x rays pass. The crystal orientation of the disks was controlled in order to reduce the background from the cell. All parts of the cell were assembled and brazed together using a high-temperature Ru-Mo alloy. Energy dispersive x-ray diffraction measurements have been successfully carried out for fluid rubidium up to 1973 K and 16.2 MPa. The obtained S(Q) demonstrates the applicability of the molybdenum cell to x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures.

Microstructures define melting of molybdenum at high pressures

NASA Astrophysics Data System (ADS)

Hrubiak, Rostislav; Meng, Yue; Shen, Guoyin

2017-03-01

High-pressure melting anchors the phase diagram of a material, revealing the effect of pressure on the breakdown of the ordering of atoms in the solid. An important case is molybdenum, which has long been speculated to undergo an exceptionally steep increase in melting temperature when compressed. On the other hand, previous experiments showed nearly constant melting temperature as a function of pressure, in large discrepancy with theoretical expectations. Here we report a high-slope melting curve in molybdenum by synchrotron X-ray diffraction analysis of crystalline microstructures, generated by heating and subsequently rapidly quenching samples in a laser-heated diamond anvil cell. Distinct microstructural changes, observed at pressures up to 130 gigapascals, appear exclusively after melting, thus offering a reliable melting criterion. In addition, our study reveals a previously unsuspected transition in molybdenum at high pressure and high temperature, which yields highly textured body-centred cubic nanograins above a transition temperature.

Molybdenum Valence in Basaltic Silicate Melts: Effects of Temperature and Pressure

NASA Technical Reports Server (NTRS)

Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Choi, Y.; Pando, K.

2011-01-01

The metal-silicate partitioning behavior of molybdenum has been used as a test for equilibrium core formation hypotheses [for example, 1-6]. However, current models that apply experimental data to equilibrium core-mantle differentiation infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Molybdenum, a multi-valent element with a valence transition near the fO2 of interest for core formation (approx.IW-2) will be sensitive to changes in fO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo(6+) can be either octahedrally or tetrahedrally coordinated. Here we present X-ray absorption near edge structure (XANES) measurements of Mo valence in basaltic run products at a range of P, T, and fO2 and further quantify the valence transition of Mo.

Molybdenum Valence in Basaltic Silicate Melts

NASA Technical Reports Server (NTRS)

Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

2010-01-01

The moderately siderophile element molybdenum has been used as an indicator in planetary differentiation processes, and is particularly relevant to core formation [for example, 1-6]. However, models that apply experimental data to an equilibrium differentiation scenario infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Partitioning behavior of molybdenum, a multivalent element with a transition near the J02 of interest for core formation (IW-2) will be sensitive to changes in JO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo6+ can be either octahedrally or tetrahedrally coordinated. Here we present first XANES measurements of Mo valence in basaltic run products at a range of P, T, and JO2 and further quantify the valence transition of Mo.

Oven rack having integral lubricious, dry porcelain surface

DOEpatents

Ambrose, Jeffrey A; Mackiewicz-Ludtka, Gail; Sikka, Vinod K; Qu, Jun

2014-06-03

A lubricious glass-coated metal cooking article capable of withstanding repeated heating and cooling between room temperature and at least 500.degree. F. without chipping or cracking the glass coating, wherein the glass coating includes about 0.1 to about 20% by weight of a homogeneously distributed dry refractory lubricant material having a particle size less than about 200 .mu.m. The lubricant material is selected from the group consisting of carbon; graphite; boron nitride; cubic boron nitride; molybdenum (FV) sulfide; molybdenum sulfide; molybdenum (IV) selenide; molybdenum selenide, tungsten (IV) sulfide; tungsten disulfide; tungsten sulfide; silicon nitride (Si.sub.3N.sub.4); TiN; TiC; TiCN; TiO.sub.2; TiAlN; CrN; SiC; diamond-like carbon; tungsten carbide (WC); zirconium oxide (ZrO.sub.2); zirconium oxide and 0.1 to 40 weight % aluminum oxide; alumina-zirconia; antimony; antimony oxide; antimony trioxide; and mixtures thereof.

Molybdenum oxide nanocolloids prepared by an external field-assisted laser ablation in water

NASA Astrophysics Data System (ADS)

Spadaro, Salvatore; Bonsignore, Martina; Fazio, Enza; Cimino, Francesco; Speciale, Antonio; Trombetta, Domenico; Barreca, Francesco; Saija, Antonina; Neri, Fortunato

2018-01-01

he synthesis of extremely stable molybdenum oxide nanocolloids by pulsed laser ablation was studied. This green technique ensures the formation of contaminant-free nanostructures and the absence of by-products. A focused picosecond pulsed laser beam was used to ablate a solid molybdenum target immersed in deionized water. Molybdenum oxide nearly spherical nanoparticles with dimensions within few nanometers (20-100 nm) are synthesized when the ablation processes were carried out, in water, at room temperature and 80°C. The application of an external electric field during the ablation process induces a nanostructures reorganization, as indicated by Scanning-Transmission Electron Microscopy images analysis. The ablation products were also characterized by some spectroscopic techniques: conventional UV-vis optical absorption, atomic absorption, dynamic light scattering, micro-Raman and X-ray photoelectron spectroscopies. Finally, NIH/3T3 mouse fibroblasts were used to evaluate cell viability by the sulforhodamine B assay

Microstructures define melting of molybdenum at high pressures

PubMed Central

Hrubiak, Rostislav; Meng, Yue; Shen, Guoyin

2017-01-01

High-pressure melting anchors the phase diagram of a material, revealing the effect of pressure on the breakdown of the ordering of atoms in the solid. An important case is molybdenum, which has long been speculated to undergo an exceptionally steep increase in melting temperature when compressed. On the other hand, previous experiments showed nearly constant melting temperature as a function of pressure, in large discrepancy with theoretical expectations. Here we report a high-slope melting curve in molybdenum by synchrotron X-ray diffraction analysis of crystalline microstructures, generated by heating and subsequently rapidly quenching samples in a laser-heated diamond anvil cell. Distinct microstructural changes, observed at pressures up to 130 gigapascals, appear exclusively after melting, thus offering a reliable melting criterion. In addition, our study reveals a previously unsuspected transition in molybdenum at high pressure and high temperature, which yields highly textured body-centred cubic nanograins above a transition temperature. PMID:28248309

The Alternative complex III: properties and possible mechanisms for electron transfer and energy conservation.

PubMed

Refojo, Patrícia N; Teixeira, Miguel; Pereira, Manuela M

2012-10-01

Alternative complexes III (ACIII) are recently identified membrane-bound enzymes that replace functionally the cytochrome bc(1/)b(6)f complexes. In general, ACIII are composed of four transmembrane proteins and three peripheral subunits that contain iron-sulfur centers and C-type hemes. ACIII are built by a combination of modules present in different enzyme families, namely the complex iron-sulfur molybdenum containing enzymes. In this article a historical perspective on the investigation of ACIII is presented, followed by an overview of the present knowledge on these enzymes. Electron transfer pathways within the protein are discussed taking into account possible different locations (cytoplasmatic or periplasmatic) of the iron-sulfur containing protein and their contribution to energy conservation. In this way several hypotheses for energy conservation modes are raised including linear and bifurcating electron transfer pathways. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). Copyright © 2012 Elsevier B.V. All rights reserved.

Design of high-strength refractory complex solid-solution alloys

DOE PAGES

Singh, Prashant; Sharma, Aayush; Smirnov, A. V.; ...

2018-03-28

Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data. We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K)more » over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K). We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.« less

Design of high-strength refractory complex solid-solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Prashant; Sharma, Aayush; Smirnov, A. V.

Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data. We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K)more » over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K). We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.« less

Geologic reconnaissance and geochemical sampling survey of molybdenum mineralization near Schiestler Peak, Temple Peak Quadrangle, Sublette County, Wyoming

USGS Publications Warehouse

Lee, G.K.; Antweiler, J.C.; Love, J.D.; Benedict, J.F.

1982-01-01

A brief geologic reconnaissance and geochemical survey of molybdenum mineralization near Schiestler Peak, Sublette County, Wyo., indicates that molybdenite occurs in this area as disseminations and blebs in granitic or quartz monzonitic rocks intruded by felsic dikes of similar composition. Samples of stream sediments, panned concentrates from stream sediments, soils, rocks, and water were collected in the geochemical survey. Analytical results show that in reconnaissance, panned concentrates are the best of the sample types used in this study to detect molybdenum mineralization. More detailed analysis of the distribution of the molybdenum is best achieved through the collection of rock samples. Hydrothermal alteration is generally not conspicuous in the study area; however, rock samples that contain molybdenite are usually slightly enriched in silver, copper, lead, and in several instances, gold. Conversely, there appear to be negative associations between molybdenum and zinc and between molybdenum and several of the rare-earth elements. Mo concentrations in the rock samples with no visible molybdenite range from undetectable at a sensitivity of 5 parts per million (ppm) to 700 ppm. Mo content in rock samples containing visible molybdenite ranges from 10 ppm to greater than 2,000 ppm. Stream-sediment values range from undetected to 15 ppm; panned concentrates from undetected to 15 ppm; soils from undetected to 20 ppm. Analyses of the water samples indicate Mo concentrations from 0.8 parts per billion (ppb) to 4.8 ppb. As currently understood, this deposit is not extensive or continuous, but drilling to provide information on the vertical extent of mineralization may alter this opinion.

NTP Toxicology and Carcinogenesis Studies of Molybdenum Trioxide (CAS No. 1313-27-5) in F344 Rats and B6C3F1 Mice (Inhalation Studies).

PubMed

1997-04-01

Molybdenum is an essential element for the function of nitrogenase in plants and as a cofactor for enzymes including xanthine oxidoreductase, aldehyde oxidase, and sulfide oxidase in animals. Molybdenum trioxide is used primarily as an additive to steel and corrosion-resistant alloys. It is also used as a chemical intermediate for molybdenum products; an industrial catalyst; a pigment; a crop nutrient; components of glass, ceramics, and enamels; a flame retardant for polyester and polyvinyl chloride resins; and a reagent in chemical analyses. Molybdenum trioxide was nominated by the NCI for toxicity and carcinogenicity studies as a representative inorganic molybdenum compound. The production of molybdenum trioxide is the largest of all the molybdenum compounds examined. Male and female F344/N rats and B6C3F1 mice were exposed to molybdenum trioxide (approximately 99% pure) by inhalation for 14 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells. 14-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 3, 10, 30, 100, or 300 mg molybdenum trioxide/m(3). Rats were exposed for 6 hours per day, 5 days per week, for a total of 10 exposure days during a 14-day period. All rats survived to the end of the study. The final mean body weights of male rats exposed to 100 mg/m(3) and male and female rats exposed to 300 mg/m(3) were significantly lower than those of the control groups. Male rats exposed to 300 mg/m(3) lost weight during the study. There were no clinical findings related to exposure to molybdenum trioxide. No chemical-related lesions were observed. 14-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 3, 10, 30, 100, or 300 mg molybdenum trioxide/m(3). Mice were exposed 6 hours per day, 5 days per week, for a total of 10 exposure days during a 14-day period. All mice survived to the end of the study. Final mean body weights of male and female mice exposed to 300 mg/m(3) were significantly lower than those of the control groups. Male mice exposed to 300 mg/m(3) lost weight during the study. There were no clinical findings related to exposure to molybdenum trioxide. No chemical-related lesions were observed. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to molybdenum trioxide by inhalation at concentrations of 0, 1, 3, 10, 30, or 100 mg/m(3) for 6.5 hours per day, 5 days per week, for 13 weeks. All rats survived to the end of the study. The final mean body weights of exposed rats were similar to those of the control groups. No clinical findings related to molybdenum trioxide exposure were observed. There were no significant chemical-related differences in absolute or relative organ weights, hematology or clinical chemistry parameters, sperm counts or motility, or liver copper concentrations between control and exposed rats. No chemical-related lesions were observed. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to molybdenum trioxide by inhalation at concentrations of 0, 1, 3, 10, 30, or 100 mg/m(3) for 6.5 hours per day, 5 days per week, for 13 weeks. All mice survived to the end of the study. The final mean body weights of exposed mice were similar to those of the control groups. There were no chemical-related clinical findings. There were no significant differences in absolute or relative organ weights or sperm counts or motility between control and exposed mice. There were significant increases in liver copper concentrations in female mice exposed to 30 mg/m(3) and in male and female mice exposed to 100 mg/m(3) compared to those of the control groups. No chemical-related lesions were observed. 2-YEAR STUDIES IN RATS: Groups of 50 male and 50 female F344/N rats were exposed to molybdenum trioxide by inhalation at concentrations of 0, 10, 30, or 100 mg/m(3). Rats were exposed for 6 hours per day, 5 days per week, for 106 weeks. Survival, Body Weights, and Special Studies: Survival rates of exposed maleed male and female rats were similar to those of the control groups. Mean body weights of exposed groups of male and female rats were similar to those of the control groups throughout the study. There was a significant exposure-dependent increase in blood molybdenum concentration in exposed rats. Blood concentrations of molybdenum in exposed male rats were greater than those in exposed female rats. There were no toxicologically significant differences in bone density or curvature between control and exposed rats. Pathology Findings: The incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were increased in male rats with a marginally significant positive trend. No increase in the incidences of lung neoplasms occurred in female rats. Incidences of chronic alveolar inflammation in male and female rats exposed to 30 or 100 mg/m(3) were significantly greater than those in the control groups. No nasal or laryngeal neoplasms were attributed to exposure to molybdenum trioxide. Incidences of hyaline degeneration in the nasal respiratory epithelium in 30 and 100 mg/m(3) males and in all exposed groups of females were significantly greater than those in the control groups. The incidences of hyaline degeneration in the nasal olfactory epithelium of all exposed groups of females were significantly greater than that in the control group. In the larynx, incidences of squamous metaplasia of the epithelium lining the base of the epiglottis in all exposed groups of male and female rats were significantly greater than those in the control groups and increased with increasing exposure concentration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were exposed to molybdenum trioxide by inhalation at concentrations of 0, 10, 30, or 100 mg/m(3). Mice were exposed for 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Special Studies: The survival rate of male mice exposed to 30 mg/m(3) was marginally lower than that of the control group; survival rates of 10 and 100 mg/m(3) males and of all exposed groups of females were similar to those of the control groups. Mean body weights of exposed male mice were generally similar to those of the control group throughout the study. Mean body weights of exposed female mice were generally greater than those of the control group from week 11 until the end of the study. There was a significant exposure-dependent increase in blood molybdenum concentration in exposed mice. There were no toxicologically significant differences in bone density or curvature between control and exposed mice. Pathology Findings: The incidences of alveolar/bronchiolar carcinoma in all exposed groups of males were significantly greater than that in the control group. Incidences of alveolar/bronchiolar adenoma in females in the 30 and 100 mg/m(3) groups were significantly greater than that in the control group. Incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in 10 and 30 mg/m(3) males and in 100 mg/m(3) females were significantly greater than those in the control groups and exceeded the historical control ranges for 2-year NTP inhalation studies. Incidences of metaplasia of the alveolar epithelium of minimal severity in the centriacinar region of the lung were significantly increased in all exposed groups of mice. The incidences of histiocyte cellular infiltration in all exposed groups of males were significantly greater than that in the control group. Incidences of hyaline degeneration of the respiratory epithelium of the nasal cavity in 100 mg/m(3) males and females and hyaline degeneration of the olfactory epithelium of the nasal cavity in 100 mg/m(3) females were significantly greater than those in the control groups. The incidences of squamous metaplasia of the epithelium lining the base of the epiglottis were significantly increased in all exposed groups of males and females. In both male and female mice, the incidences of hyperplasia of the laryngeal epithelium in level II of the larynx increased with increasing exposure concentration. The increase was statistically significant only in mice exposed to 100 mg/m(3) with 82% of male and 70% of female mice affected. GENETIC TOXICOLOGY: Molybdenum trioxide was not mutagenic in any of five strains of Salmonella typhimurium, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells in vitro. All tests were conducted with and without S9 metabolic activation enzymes. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was equivocal evidence of carcinogenic activity of molybdenum trioxide in male F344/N rats based on a marginally significant positive trend of alveolar/bronchiolar adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of molybdenum trioxide in female F344/N rats exposed to 10, 30, or 100 mg/m(3). There was some evidence of carcinogenic activity of molybdenum trioxide in male B6C3F1 mice based on increased incidences of alveolar/bronchiolar carcinoma and adenoma or carcinoma (combined). There was some evidence of carcinogenic activity of molybdenum trioxide in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenoma and adenoma or carcinoma (combined). Exposure of male and female rats to molybdenum trioxide by inhalation resulted in increased incidences of chronic alveolar inflammation, hyaline degeneration of the respiratory epithelium, hyaline degeneration of the olfactory epithelium (females), and squamous metaplasia of the epiglottis. Exposure of male and female mice to molybdenum trioxide by inhalation resulted in increased incidences of metaplasia of the alveolar epithelium, histiocyte cellular infiltration (males), hyaline degeneration of the respiratory epithelium, hyaline degeneration of the olfactory epithelium (females), squamous metaplasia of the epiglottis, and hyperplasia of the larynx. Synonyms: Molybdic oxide; molybdic trioxide; molybdic anhydride; molybdenum (VI) oxide; molybdenum peroxide; molybdic acid anhydride; molybdenum anhydride; natural molybdite; molybdena

Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

USGS Publications Warehouse

Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

1998-01-01

Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in precipitation of uranium minerals. At the deepest exposed levels, wall-rocks were altered to sericite; and uraninite, coffinite, jordisite, fluorite, molybdenite, quartz, and pyrite were deposited in the veins. The fluids were progressively oxidized and cooled at higher levels in the system by boiling and degassing; iron-bearing minerals in wall rocks were oxidized to hematite, and quartz, fluorite, minor siderite, and uraninite were deposited in the veins. Near the ground surface, the fluids were acidified by condensation of volatiles and oxidation of hydrogen sulfide in near-surface, steam-heated, ground waters; wall rocks were altered to kaolinite, and quartz fluorite, and uraninite were deposited in veins. Secondary uranium minerals, hematite, and gypsum formed during supergene alteration later in the Cenozoic when the upper part of the mineralized system was exposed by erosion.

Cryogenically cooled detector pin mount

DOEpatents

Hunt, Jr., William E; Chrisp, Michael P

2014-06-03

A focal plane assembly facilitates a molybdenum base plate being mounted to another plate made from aluminum. The molybdenum pin is an interference fit (press fit) in the aluminum base plate. An annular cut out area in the base plate forms two annular flexures.

21 CFR 888.3390 - Hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis.

Code of Federal Regulations, 2014 CFR

2014-04-01

... includes prostheses that have a femoral component made of alloys, such as cobalt-chromium-molybdenum, and a snap-fit acetabular component made of an alloy, such as cobalt-chromium-molybdenum, and ultra-high...

21 CFR 888.3390 - Hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis.

Code of Federal Regulations, 2013 CFR

2013-04-01

... includes prostheses that have a femoral component made of alloys, such as cobalt-chromium-molybdenum, and a snap-fit acetabular component made of an alloy, such as cobalt-chromium-molybdenum, and ultra-high...

SURFACE TREATMENT OF MOLYBDENUM METAL

DOEpatents

Coffer, C.O.

1961-12-01

A process of descaling molybdenum articles comprises first immersing them in an aqueous sodium hydroxide-potassium permanganate solution of between 60 and 85 deg C, rinsing, and then immersing them in an aqueous solution containing a mixture of sulfuric, hydrochloric, and chromic acids.

Characterization of Diazotrophs Containing Mo-Independent Nitrogenases, Isolated from Diverse Natural Environments

USDA-ARS?s Scientific Manuscript database

Molybdenum-independent nitrogenases were first described in the nitrogen-fixing bacterium Azotobacter vinelandii and have since been described in other diazotrophic bacteria. Previously, we reported the isolation of seven diazotrophs with Molybdenum-independent nitrogenases from aquatic environments...

21 CFR 888.3390 - Hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis.

Code of Federal Regulations, 2011 CFR

2011-04-01

... includes prostheses that have a femoral component made of alloys, such as cobalt-chromium-molybdenum, and a snap-fit acetabular component made of an alloy, such as cobalt-chromium-molybdenum, and ultra-high...

Breaking America’s Dependence on Foreign…Molybdenum

PubMed Central

Einstein, Andrew J.

2009-01-01

Brief Unstructured Abstract Approximately 9 million nuclear cardiology studies performed each year in the United States employ technetium-99m, which is produced from the decay of molybdenum-99. The fragility of the worldwide technetium-99m supply chain has been underscored by current shortages caused by an unplanned shutdown of Europe’s largest reactor. The majority of the United States’ supply derives from a reactor in Canada nearing the end of its lifespan, whose planned replacements have been recently cancelled. In this article, the clinical importance of technetium-99m and our tenuous dependence on foreign supply of Molybdenum is addressed. PMID:19356583

A New Method of Metallization for Silicon Solar Cells

NASA Technical Reports Server (NTRS)

Macha, M.

1979-01-01

A low cost ohmic contact on silicon solar cells based on molybdenum-tin metal systems was developed. The approach is based on the formulation of a screenable ink composed from molybdenum oxide and tin mixture. The reduction of Mo03 into Mo and the establishment of Mo 03:Sn ratio is studied. Both tasks were done in an experimental station constructed for this purpose. The results show that molybdenum was formed from its oxide at 800 C. and improved in bonding to silicon at 900 C. A 20% Mo03-80%Sn mixture was converted into metallic coating within this temperature range.

Healing of voids in the aluminum metallization of integrated circuit chips

NASA Technical Reports Server (NTRS)

Cuddihy, Edward F.; Lawton, Russell A.; Gavin, Thomas R.

1990-01-01

The thermal stability of GaAs modulation-doped field effect transistors (MODFETs) is evaluated in order to identify failure mechanisms and validate the reliability of these devices. The transistors were exposed to thermal step-stress and characterized at ambient temperatures to indicate device reliability, especially that of the transistor ohmic contacts with and without molybdenum diffusion barriers. The devices without molybdenum exhibited important transconductance deterioration. MODFETs with molybdenum diffusion barriers were tolerant to temperatures above 300 C. This tolerance indicates that thermally activated failure mechanisms are slow at operational temperatures. Therefore, high-reliability MODFET-based circuits are possible.

Electron-Beam Deposition of Superconducting Molybdenum Thin Films for the Development of Mo/Au TES X-Ray Microcalorimeter

NASA Technical Reports Server (NTRS)

Finkbeiner, Fred Michael; Adams, Joseph S.; Bandler, Simon R.; Betancour-Martinez, Gabriele L.; Brown, Ari David; Chang, Meng-Ping; Chervenak, James A.; Chiao, Meng P.; Datesman, Aaron; Eckart, Megan E.;

Sorbent for use in hot gas desulfurization

DOEpatents

Gasper-Galvin, Lee D.; Atimtay, Aysel T.

1993-01-01

A multiple metal oxide sorbent supported on a zeolite of substantially silicon oxide is used for the desulfurization of process gas streams, such as from a coal gasifier, at temperatures in the range of about 1200.degree. to about 1600.degree. F. The sorbent is provided by a mixture of copper oxide and manganese oxide and preferably such a mixture with molybdenum oxide. The manganese oxide and the molybdenum are believed to function as promoters for the reaction of hydrogen sulfide with copper oxide. Also, the manganese oxide inhibits the volatilization of the molybdenum oxide at the higher temperatures.

40 CFR 471.51 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Molybdenum 7.87 4.07 Oil and grease 23.8 14.3 TSS 48.8 23.2 pH (1) (1) 1 Within the range of 7.5 to 10.0 at... Fluoride 7,200 3,200 Molybdenum 800 414 Oil and grease 2,420 1,450 TSS 4,960 2,360 pH (1) (1) 1 Within the... Molybdenum 2.21 1.14 Oil and grease 6.68 4.01 TSS 13.7 6.51 pH (1) (1) 1 Within the range of 7.5 to 10.0 at...

40 CFR 471.51 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Molybdenum 7.87 4.07 Oil and grease 23.8 14.3 TSS 48.8 23.2 pH (1) (1) 1 Within the range of 7.5 to 10.0 at... Fluoride 7,200 3,200 Molybdenum 800 414 Oil and grease 2,420 1,450 TSS 4,960 2,360 pH (1) (1) 1 Within the... Molybdenum 2.21 1.14 Oil and grease 6.68 4.01 TSS 13.7 6.51 pH (1) (1) 1 Within the range of 7.5 to 10.0 at...

Catalytic determination of molybdenum(VI) by means of an iodide ion-selective electrode and a landolt-type hydrogen peroxide-iodide reaction.

PubMed

Kataoka, M; Nishimura, K; Kambara, T

1983-12-01

A trace amount of molybdenum(VI) can be determined by using its catalytic effect on the oxidation of iodide to iodine by hydrogen peroxide in acidic medium. Addition of ascorbic acid added to the reaction mixture produces the Landolt effect, i.e., the iodine produced by the indicator reaction is reduced immediately by the ascorbic add. Hence the concentration of iodide begins to decrease once all the ascorbic acid has been consumed. The induction period is measured by monitoring the concentration of iodide ion with an iodide ion-selective electrode. The reciprocal of the induction period varies linearly with the concentration of molybdenum(VI). The most suitable pH and concentrations of hydrogen peroxide and potassium iodide are found to be 1.5, 5 and 10mM, respectively. An appropriate amount of ascorbic acid is added to the reaction mixture according to the concentration of molybdenum(VI) in the sample solution. A calibration graph with good proportionality is obtained for the molybdenum(VI) concentration range from 0.1 to 160 muM. Iron(III), vanadium(IV), zirconium(IV), tungsten(VI), copper(II) and chromium(VI) interfere, but iron(III) and copper(II) can be masked with EDTA.

Study of the strength of molybdenum under high pressure using electromagnetically applied compression-shear ramp loading

NASA Astrophysics Data System (ADS)

Ding, Jow; Alexander, C. Scott; Asay, James

2015-06-01

MAPS (Magnetically Applied Pressure Shear) is a new technique that has the potential to study material strength under mega-bar pressures. By applying a mixed-mode pressure-shear loading and measuring the resultant material responses, the technique provides explicit and direct information on material strength under high pressure. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. In this work, the mechanical behavior of molybdenum under MAPS loading was studied. To understand the experimental data, a viscoplasticity model with tension-compression asymmetry was also developed. Through a combination of experimental characterization, model development, and numerical simulation, many unique insights were gained on the inelastic behavior of molybdenum such as the effects of strength on the interplay between longitudinal and shear stresses, potential interaction between the magnetic field and molybdenum strength, and the possible tension-compression asymmetry of the inelastic material response. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Impedance spectroscopy and electric modulus behavior of Molybdenum doped Cobalt-Zinc ferrite

NASA Astrophysics Data System (ADS)

Pradhan, A. K.; Nath, T. K.; Saha, S.

2017-07-01

The complex impedance spectroscopy and the electric modulus of Mo doped Cobalt-Zinc inverse spinel ferrite has been investigated in detail. The conventional ceramic technique has been used to prepare the CZMO. The HRXRD technique has been used to study the structural analysis which confirms the inverse spinel structure of the material and also suggest the material have Fd3m space group. The complex impedance spectroscopic data and the electric modulus formalism have been used to understand the dielectric relaxation and conduction process. The contribution of grain and grain boundary in the electrical conduction process of CZMO has been confirmed from the Cole-Cole plot. The activation energy is calculated from both the IS (Impedance Spectroscopy) and electric modulus formalism and found to be nearly same for the materials.

40 CFR 421.212 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Molybdenum sulfide leachate. BPT Limitations for the Primary Molybdenum Rhenium Subcategory Pollutant or...) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Molybdic oxide leachate. BPT Limitations for...

40 CFR 421.212 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Molybdenum sulfide leachate. BPT Limitations for the Primary Molybdenum Rhenium Subcategory Pollutant or...) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Molybdic oxide leachate. BPT Limitations for...

40 CFR 421.212 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Molybdenum sulfide leachate. BPT Limitations for the Primary Molybdenum Rhenium Subcategory Pollutant or...) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Molybdic oxide leachate. BPT Limitations for...

40 CFR 421.212 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Molybdenum sulfide leachate. BPT Limitations for the Primary Molybdenum Rhenium Subcategory Pollutant or...) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Molybdic oxide leachate. BPT Limitations for...

40 CFR 421.212 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Molybdenum sulfide leachate. BPT Limitations for the Primary Molybdenum Rhenium Subcategory Pollutant or...) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Molybdic oxide leachate. BPT Limitations for...

Inert Reassessment Document for Sodium Molybdate - CAS No. 7631-95-0

EPA Pesticide Factsheets

Sodium molybdate is a soluble sodium salt form of molybdenum, a naturallyoccurringelement that is present in the earth's crust and in soils at background concentrations of1-2 mgkg. Molybdenum is an essential trace element for virtually all life forms.

Molybdenum disilicide composites reinforced with zirconia and silicon carbide

DOEpatents

Petrovic, John J.

1995-01-01

Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

Molybdenum oxide electrodes for thermoelectric generators

DOEpatents

Schmatz, Duane J.

1989-01-01

The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a thin film comprising molybdenum oxide as an electrode deposited by physical deposition techniques onto solid electrolyte. The invention is also directed to the method of making same.

Removal of Vanadium(III) and Molybdenum(V) from Wastewater Using Posidonia oceanica (Tracheophyta) Biomass

PubMed Central

Pennesi, Chiara; Totti, Cecilia; Beolchini, Francesca

2013-01-01

The use of dried and re-hydrated biomass of the seagrass Posidonia oceanica was investigated as an alternative and –low-cost biomaterial for removal of vanadium(III) and molybdenum(V) from wastewaters. Initial characterisation of this biomaterial identified carboxylic groups on the cuticle as potentially responsible for cation sorption, and confirmed the toxic-metal bioaccumulation. The combined effects on biosorption performance of equilibrium pH and metal concentrations were investigated in an ideal single-metal system and in more real-life multicomponent systems. There were either with one metal (vanadium or molybdenum) and sodium nitrate, as representative of high ionic strength systems, or with the two metals (vanadium and molybdenum). For the single-metal solutions, the optimum was at pH 3, where a significant proportion of vanadium was removed (ca. 70%) while there was ca. 40% adsorption of molybdenum. The data obtained from the more real-life multicomponent systems showed that biosorption of one metal was improved both by the presence of the other metal and by high ionic strength, suggesting a synergistic effect on biosorption rather than competition. There data ware used for the development of a simple multi-metal equilibrium model based on the non-competitive Langmuir approach, which was successfully fitted to experimental data and represents a useful support tool for the prediction of biosorption performance in such real-life systems. Overall, the results suggest that biomass of P. oceanica can be used as an efficient biosorbent for removal of vanadium(III) and molybdenum(V) from aqueous solutions. This process thus offers an eco-compatible solution for the reuse of the waste material of leaves that accumulate on the beach due to both human activities and to storms at sea. PMID:24204692

Molybdenum and copper in four varieties of common bean (Phaseolus vulgaris): new data of potential utility in designing healthy diet for diabetic patients.

PubMed

Ojeda, Armando Gómez; Wrobel, Kazimierz; Escobosa, Alma Rosa Corrales; Elguera, Julio César Torres; Garay-Sevilla, Ma Eugenia; Wrobel, Katarzyna

2015-02-01

Experimental evidence indicates that diabetic patients and individuals with impaired copper homeostasis could be at risk of molybdenum toxicity. A self-administered food frequency questionnaire revealed that in central Mexico, diabetic patients with severe complications tend to consume beans more often than individuals with less advanced disease. Four varieties of Phaseolus vulgaris were comparatively evaluated as the dietary sources of two elements; the results showed molybdenum concentration decreasing in the order peruvian > pinto > mayflower > black, whereas for copper, the order was peruvian > pinto ∼ black > mayflower. The two elements were determined in pre-soaking water, cooked legumes, and broth obtained in cooking procedure; an in vitro gut model was also applied to assess potentially bioavailable fraction of both elements in cooked beans. The results indicated that the black variety would be the healthiest bean choice for diabetic patients and individuals susceptible to Mo toxicity. Relatively low total molybdenum was found in this variety (2.9 ± 1.4 versus 4.3-10.9 μg g(-1) in other types), element availability was also low (15 % in supernatant from enzymolysis, 24.9 % in combined broth + supernatant fractions), and the molar ratio of Cu/Mo was the highest among four types (41, versus Cu/Mo <10 in peruvian, pinto, or mayflower). Considering peruvian and pinto beans, broth elimination would help to lower molybdenum intake with marginal effect on Cu/Mo molar ratio. This recommendation would be especially important for peruvian variety, which provided 1090, 803, and 197 μg day(-1) of molybdenum in raw grains, broth + supernatant, and supernatant, respectively (based on 100-g portion), exceeding the recommended daily allowance of 45 μg day(-1).

Microwave plasma torch mass spectrometry for the direct detection of copper and molybdenum ions in aqueous liquids.

PubMed

Xiong, Xiaohong; Jiang, Tao; Zhou, Runzhi; Wang, Shangxian; Zou, Wei; Zhu, Zhiqiang

2016-05-01

Microwave plasma torch (MPT) is a simple and low power-consumption ambient ion source. And the MPT Mass spectra of many metal elements usually exhibit some novel features different from their inductively coupled plasma (ICP) mass spectra, which may be helpful for metal element analysis. Here, we presented the results about the MPT mass spectra of copper and molybdenum elements by a linear ion trap mass spectrometer (LTQ). The generated copper or molybdenum contained ions in plasma were characterized further in collision-induced dissociated (CID) experiments. These researches built a novel, direct and sensitive method for the direct analysis of trace levels of copper and molybdenum in aqueous liquids. Quantitative results showed that the limit of detection (LOD) by using MS(2) procedure was estimated to be 0.265 µg/l (ppb) for copper and 0.497 µg/l for molybdenum. The linear dynamics ranges cover at least 2 orders of magnitude and the analysis of a single aqueous sample can be completed in 5-6 min with a reasonable semi-quantitative sense. Two practical aqueous samples, milk and urine, were also analyzed qualitatively with reasonable recovery rates and RSD. These experimental data demonstrated that the MPT MS is able to turn into a promising and hopeful tool in field analysis of copper and molybdenum ions in water and some aqueous media, and can be applied in many fields, such as environmental controlling, hydrogeology, and water quality inspection. Moreover, MPT MS could also be used as the supplement of ICP-MS for the rapid and in-situ analysis of metal ions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Molybdenum disilicide composites reinforced with zirconia and silicon carbide

DOEpatents

Petrovic, J.J.

1995-01-17

Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

Sialons as high temperature insulators

NASA Technical Reports Server (NTRS)

Phillips, W. M.; Kuo, Y. S.

1978-01-01

Sialons were evaluated for application as high temperature electrical insulators in contact with molybdenum and tungsten components in hard vacuum applications. Both D.C. and variable frequency A.C. resistivity data indicate the sialons to have electrical resistivity similar to common oxide in the 1000 C or higher range. Metallographic evaluations indicate good bonding of the type 15R ALN polytype to molybdenum and tungsten. The beta prime or modified silicon nitride phase was unacceptable in terms of vacuum stability. Additives effect on electrical resistivity. Similar resistivity decreases were produced by additions of molybdenum or tungsten to form cermets. The use of hot pressing at 1800 C with ALN, Al2 O3 and Si3N4 starting powders produced a better product than did a combination of SiO2 and AIN staring powders. It was indicated that sialons will be suitable insulators in the 1600K range in contact with molybdenum or tungsten if they are produced as a pure ceramic and subsequently bonded to the metal components at temperatures in the 1600K range.

Swift tuning from spherical molybdenum microspheres to hierarchical molybdenum disulfide nanostructures by switching from solvothermal to hydrothermal synthesis route

NASA Astrophysics Data System (ADS)

Qureshi, Nilam; Arbuj, Sudhir; Shinde, Manish; Rane, Sunit; Kulkarni, Milind; Amalnerkar, Dinesh; Lee, Haiwon

2017-09-01

Herein, we report the synthesis of metallic molybdenum microspheres and hierarchical MoS2 nanostructures by facile template-free solvothermal and hydrothermal approach, respectively. The morphological transition of the Mo microspheres to hierarchical MoS2 nanoflower architectures is observed to be accomplished with change in solvent from ethylenediamine to water. The resultant marigold flower-like MoS2 nanostructures are few layers thick with poor crystallinity while spherical ball-like molybdenum microspheres exhibit better crystalline nature. This is the first report pertaining to the synthesis of Mo microspheres and MoS2 nanoflowers without using any surfactant, template or substrate in hydro/solvothermal regime. It is opined that such nanoarchitectures of MoS2 are useful candidates for energy related applications such as hydrogen evolution reaction, Li ion battery and pseudocapacitors. Inquisitively, metallic Mo can potentially act as catalyst as well as fairly economical Surface Enhanced Raman Spectroscopy (SERS) substrate in biosensor applications.

Effect of thiomolybdate and ammonium molybdate in pregnant guinea pigs and their offspring.

PubMed

Howell, J M; Shunxiang, Y; Gawthorne, J M

1993-09-01

Groups of eight guinea pigs and their offspring were given drinking water containing molybdenum as ammonium molybdate (AM) or thiomolybdate (TM) throughout and subsequent to pregnancy. All adult females had oestrous cycles and conception rates were unaffected. Fetal death was common in groups given the high dose of TM. The concentration of copper in liver was reduced in all groups at all ages except for pups killed at birth from animals given AM. The concentration of molybdenum was elevated in liver and kidney of all groups and was statistically significant in the majority. The concentration in plasma of copper, molybdenum and copper insoluble in trichloroacetic acid was elevated in all groups. Superoxide dismutase activity was significantly reduced in dams and six-week-old pups in which TM administration commenced before mating. Histological damage occurred in the pancreas of animals given AM or TM. The effects on the fetus and pancreas were considered to result from copper deficiency rather than molybdenum toxicity.

Ion-Exchangeable Molybdenum Sulfide Porous Chalcogel: Gas Adsorption and Capture of Iodine and Mercury.

PubMed

Subrahmanyam, Kota S; Malliakas, Christos D; Sarma, Debajit; Armatas, Gerasimos S; Wu, Jinsong; Kanatzidis, Mercouri G

2015-11-04

We report the synthesis of ion-exchangeable molybdenum sulfide chalcogel through an oxidative coupling process, using (NH4)2MoS4 and iodine. After supercritical drying, the MoS(x) amorphous aerogel shows a large surface area up to 370 m(2)/g with a broad range of pore sizes. X-ray photoelectron spectroscopic and pair distribution function analyses reveal that Mo(6+) species undergo reduction during network assembly to produce Mo(4+)-containing species where the chalcogel network consists of [Mo3S13] building blocks comprising triangular Mo metal clusters and S2(2-) units. The optical band gap of the brown-black chalcogel is ∼1.36 eV. The ammonium sites present in the molybdenum sulfide chalcogel network are ion-exchangeable with K(+) and Cs(+) ions. The molybdenum sulfide aerogel exhibits high adsorption selectivities for CO2 and C2H6 over H2 and CH4. The aerogel also possesses high affinity for iodine and mercury.

Plasma-enhanced deposition and processing of transition metals and transition metal silicides for VLSI

NASA Astrophysics Data System (ADS)

Hess, D. W.

1986-05-01

Radiofrequency (rf) discharges have been used to deposit films of tungsten, molybdenum and titanium silicide. As-deposited tungsten films, from tungsten hexafluoride and hydrogen source gases, were metastable (beta W), with significant (>1 atomic percent) fluorine incorporation. Film resistivities were 40-55 micro ohm - cm due to the beta W, but dropped to about 8 micro ohm cm after a short heat treatment at 700 C which resulted in a phase transition to alpha W (bcc form). The high resistivity (>10,000 micro ohm) associated with molybdenum films deposited from molybdenum hexafluoride and hydrogen appeared to be a result of the formation of molybdenum trifluoride in the deposited material. Titanium silicide films formed from a discharge of titanium tetrachloride, silane, and hydrogen, displayed resistivities of about 150 micro ohm cm, due to small amounts of oxygen and chlorine incorporated during deposition. Plasma etching studies of tungsten films with fluorine containing gases suggest that the etchant species for tungsten in these discharges are fluorine atoms.

Recovery of uranium from an irradiated solid target after removal of molybdenum-99 produced from the irradiated target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reilly, Sean Douglas; May, Iain; Copping, Roy

A process for minimizing waste and maximizing utilization of uranium involves recovering uranium from an irradiated solid target after separating the medical isotope product, molybdenum-99, produced from the irradiated target. The process includes irradiating a solid target comprising uranium to produce fission products comprising molybdenum-99, and thereafter dissolving the target and conditioning the solution to prepare an aqueous nitric acid solution containing irradiated uranium. The acidic solution is then contacted with a solid sorbent whereby molybdenum-99 remains adsorbed to the sorbent for subsequent recovery. The uranium passes through the sorbent. The concentrations of acid and uranium are then adjusted tomore » concentrations suitable for crystallization of uranyl nitrate hydrates. After inducing the crystallization, the uranyl nitrate hydrates are separated from a supernatant. The process results in the purification of uranyl nitrate hydrates from fission products and other contaminants. The uranium is therefore available for reuse, storage, or disposal.« less

Molybdenum L-Edge XAS Spectra of MoFe Nitrogenase

PubMed Central

Bjornsson, Ragnar; Delgado-Jaime, Mario U; Lima, Frederico A; Sippel, Daniel; Schlesier, Julia; Weyhermüller, Thomas; Einsle, Oliver; Neese, Frank; DeBeer, Serena

2015-01-01

A molybdenum L-edge X-ray absorption spectroscopy (XAS) study is presented for native and oxidized MoFe protein of nitrogenase as well as Mo-Fe model compounds. Recently collected data on MoFe protein (in oxidized and reduced forms) is compared to previously published Mo XAS data on the isolated FeMo cofactor in NMF solution and put in context of the recent Mo K-edge XAS study, which showed a MoIII assignment for the molybdenum atom in FeMoco. The L3-edge data are interpreted within a simple ligand-field model, from which a time-dependent density functional theory (TDDFT) approach is proposed as a way to provide further insights into the analysis of the molybdenum L3-edges. The calculated results reproduce well the relative spectral trends that are observed experimentally. Ultimately, these results give further support for the MoIII assignment in protein-bound FeMoco, as well as isolated FeMoco. PMID:26213424

Watching adsorption and electron beam induced decomposition on the model system Mo(CO)6/Cu(1 1 1) by X-ray absorption and photoemission spectroscopies

NASA Astrophysics Data System (ADS)

Paufert, Pierre; Fonda, Emiliano; Li, Zheshen; Domenichini, Bruno; Bourgeois, Sylvie

2013-11-01

An in-depth study of the first steps of electron beam assisted growth of Mo from molybdenum hexacarbonyl on Cu(1 1 1) has been carried out exploiting the complementarity of X-ray photoemission and X-ray absorption spectroscopies. Frank van der Merwe (2D) growth mode has been observed for the completion of the two first monolayers of adsorbed molecules through a simple physisorption process. Irradiation of the Mo(CO)6 deposit by 1 keV electron beam induces a modification of molybdenum coordination, the average number of C-neighbors decreasing from 6 to 3. Decomposed molecules remain on the surface after annealing at 520 K and organize themselves, the molybdenum atoms moving in Cu(1 1 1) surface fcc hollow sites. After annealing at 670 K, metallic molybdenum growth begins, if the total amount of adsorbed Mo atoms exceeds 1.2 monolayers.

Effect of organic matter on nitrogenase metal cofactors homeostasis in Azotobacter vinelandii under diazotrophic conditions.

PubMed

Noumsi, Christelle Jouogo; Pourhassan, Nina; Darnajoux, Romain; Deicke, Michael; Wichard, Thomas; Burrus, Vincent; Bellenger, Jean-Philippe

2016-02-01

Biological nitrogen fixation can be catalysed by three isozymes of nitrogenase: molybdenum (Mo)-nitrogenase, vanadium (V)-nitrogenase and iron-only (Fe)-nitrogenase. The activity of these isozymes strongly depends on their metal cofactors, molybdenum, vanadium and iron, and their bioavailability in ecosystems. Here, we show how metal bioavailability can be affected by the presence of tannic acid (organic matter), and the subsequent consequences on diazotrophic growth of the soil bacterium Azotobacter vinelandii. In the presence of tannic acids, A. vinelandii produces a higher amount of metallophores, which coincides with an active, regulated and concomitant acquisition of molybdenum and vanadium under cellular conditions that are usually considered not molybdenum limiting. The associated nitrogenase genes exhibit decreased nifD expression and increased vnfD expression. Thus, in limiting bioavailable metal conditions, A. vinelandii takes advantage of its nitrogenase diversity to ensure optimal diazotrophic growth. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Bacterial formate hydrogenlyase complex.

PubMed

McDowall, Jennifer S; Murphy, Bonnie J; Haumann, Michael; Palmer, Tracy; Armstrong, Fraser A; Sargent, Frank

2014-09-23

Under anaerobic conditions, Escherichia coli can carry out a mixed-acid fermentation that ultimately produces molecular hydrogen. The enzyme directly responsible for hydrogen production is the membrane-bound formate hydrogenlyase (FHL) complex, which links formate oxidation to proton reduction and has evolutionary links to Complex I, the NADH:quinone oxidoreductase. Although the genetics, maturation, and some biochemistry of FHL are understood, the protein complex has never been isolated in an intact form to allow biochemical analysis. In this work, genetic tools are reported that allow the facile isolation of FHL in a single chromatographic step. The core complex is shown to comprise HycE (a [NiFe] hydrogenase component termed Hyd-3), FdhF (the molybdenum-dependent formate dehydrogenase-H), and three iron-sulfur proteins: HycB, HycF, and HycG. A proportion of this core complex remains associated with HycC and HycD, which are polytopic integral membrane proteins believed to anchor the core complex to the cytoplasmic side of the membrane. As isolated, the FHL complex retains formate hydrogenlyase activity in vitro. Protein film electrochemistry experiments on Hyd-3 demonstrate that it has a unique ability among [NiFe] hydrogenases to catalyze production of H2 even at high partial pressures of H2. Understanding and harnessing the activity of the FHL complex is critical to advancing future biohydrogen research efforts.

The measurement of the intrinsic impurities of molybdenum and carbon in the Alcator C-Mod tokamak plasma using low resolution spectroscopy

NASA Astrophysics Data System (ADS)

May, M. J.; Finkenthal, M.; Regan, S. P.; Moos, H. W.; Terry, J. L.; Goetz, J. A.; Graf, M. A.; Rice, J. E.; Marmar, E. S.; Fournier, K. B.; Goldstein, W. H.

1997-06-01

The intrinsic impurity content of molybdenum and carbon was measured in the Alcator C-Mod tokamak using low resolution, multilayer mirror (MLM) spectroscopy ( Delta lambda ~1-10 AA). Molybdenum was the dominant high-Z impurity and originated from the molybdenum armour tiles covering all of the plasma facing surfaces (including the inner column, the poloidal divertor plates and the ion cyclotron resonant frequency (ICRF) limiter) at Alcator C-Mod. Despite the all metal first wall, a carbon concentration of 1 to 2% existed in the plasma and was the major low-Z impurity in Alcator C-Mod. Thus, the behaviour of intrinsic molybdenum and carbon penetrating into the main plasma and the effect on the plasma must be measured and characterized during various modes of Alcator C-Mod operation. To this end, soft X-ray extreme ultraviolet (XUV) emission lines of charge states, ranging from hydrogen-like to helium-like lines of carbon (radius/minor radius, r/a~1) at the plasma edge to potassium to chlorine-like (0.4

The Role of Oxygen in the Evolution of Molybdenum Nitrogenase

NASA Astrophysics Data System (ADS)

Peters, J.; Boyd, E. S.; Hamilton, T. L.

2012-12-01

Since early in Earth's history, the supply of nitrogen (N) into the biosphere has been controlled by the activity of nitrogenase, an oxygen sensitive enzyme that catalyzes the reduction of dinitrogen gas (N2) to bioavailable ammonia. The most common form of nitrogenase harbors a complex molybdenum (Mo) cofactor at its active site [Mo-nitrogenase (Nif)], although other phylogenetically related (alternative) forms of nitrogenase that differ in their active-site metal composition also likely contribute NH3 in environments that are limiting in Mo. The solubility of Mo is significantly influenced by redox and this fact has been used to argue that that the iron (Fe)-dependent nitrogenase (Anf) was predominant prior to ~ 2.5 Ga because oceans were depleted in Mo and rich in Fe. This hypothesis, however, is inconsistent with recent phylogenetic data which strongly suggest that Anf is derived from Nif. Here, we examine the evolutionary history of the Nif enzyme complex in reference to the physiological, biochemical, and morphological strategies for reducing damage by molecular oxygen. A total of 189 nif operons were characterized and quantitatively mapped on a NifHDK concatenated phylogenetic tree. An overlay of the primary mode of metabolism, as defined as either anaerobic (AN) or aerobic/facultative aerobic (AFA), on the NifHDK tree indicates that Nif originated in an anoxic environment and was first acquired in an AFA lineage within the actinobacteria. The complexity of nif operons increased during the evolutionary history of Nif, with a pronounced increase observed during the transition from AN to AFA modes of metabolism. This increase in operon complexity is accompanied by a number of gene loss (nifI1 and nifI2) and gene acquisition (nifW, nifT, nifZ, nifQ) events, with variation in the overall composition of nif operons attributable to adaptations that mediated the toxicity of O2. Collectively, these results underscore the role of O2 in shaping the evolutionary history of Nif, presumably through selection to evolve regulatory and/or protective mechanisms to temporally or spatially decouple N2 fixation from aerobic metabolism.

22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geissbühler, Jonas, E-mail: jonas.geissbuehler@epfl.ch; Werner, Jérémie; Martin de Nicolas, Silvia

2015-08-24

Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. We circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

Onset of superconductivity in sodium and potassium intercalated molybdenum disulphide

NASA Technical Reports Server (NTRS)

Somoano, R. B.; Rembaum, A.

1971-01-01

Molybdenum disulfide in the form of natural crystals or powder has been intercalated at -65 to -70 C with sodium and potassium using the liquid ammonia technique. All intercalated samples were found to show a superconducting transition. A plot of the percent of diamagnetic throw versus temperature indicates the possible existence of two phases in the potassium intercalated molybdenum disulfide. The onset of superconductivity in potassium and sodium intercalated molybdenite powder was found to be approximately 6.2 and approximately 4.5 K, respectively. The observed superconductivity is believed to be due to an increase in electron density as a result of intercalation.

X-ray diffraction of molybdenum under shock compression to 450 GPa

DOE PAGES

Wang, Jue; Coppari, Federica; Smith, Raymond F.; ...

2015-11-20

Molybdenum (Mo) is a body-centered-cubic (bcc) transition metal that has widespread technological applications. Although the bcc transition elements are used as test cases for understanding the behavior of metals under extreme conditions, the melting curves and phase transitions of these elements have been the subject of stark disagreements in recent years. Here we use x-ray diffraction to examine the phase stability and melting behavior of Mo under shock loading to 450 GPa. The bcc phase of Mo remains stable along the Hugoniot until 380 GPa. Here, our results do not support previous claims of a shallow melting curve for molybdenum.

Investigation of welding and brazing of molybdenum and TZM alloy tubes

NASA Technical Reports Server (NTRS)

Lundblad, Wayne E.

1991-01-01

This effort involved investigating the welding and brazing techniques of molybdenum tubes to be used as cartridges in the crystal growth cartridge. Information is given in the form of charts and photomicrographs. It was found that the recrystallization temperature of molybdenum can be increased by alloying it with 0.5 percent titanium and 0.1 percent zirconium. Recrystallization temperatures for this alloy, known as TZM, become significant around 2500 F. A series of microhardness tests were run on samples of virgin and heat soaked TZM. The test results are given in tabular form. It was concluded that powder metallurgy TZM may be an acceptable cartridge material.

Electronic structure evolution in doping of fullerene (C{sub 60}) by ultra-thin layer molybdenum trioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chenggong; Wang, Congcong; Kauppi, John

2015-08-28

Ultra-thin layer molybdenum oxide doping of fullerene has been investigated using ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS). The highest occupied molecular orbital (HOMO) can be observed directly with UPS. It is observed that the Fermi level position in fullerene is modified by ultra-thin-layer molybdenum oxide doping, and the HOMO onset is shifted to less than 1.3 eV below the Fermi level. The XPS results indicate that charge transfer was observed from the C{sub 60} to MoO{sub x} and Mo{sup 6+} oxides is the basis as hole dopants.

22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

DOE PAGES

Geissbühler, Jonas; Werner, Jérémie; Nicolas, Silvia Martin de; ...

2015-08-24

Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. Furthermore, we circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

Estimation of 99Mo production rates from natural molybdenum in research reactors.

PubMed

Blaauw, M; Ridikas, D; Baytelesov, S; Salas, P S Bedregal; Chakrova, Y; Eun-Ha, Cho; Dahalan, R; Fortunato, A H; Jacimovic, R; Kling, A; Muñoz, L; Mohamed, N M A; Párkányi, D; Singh, T; Van Dong Duong

2017-01-01

Molybdenum-99 is one of the most important radionuclides for medical diagnostics. In 2015, the International Atomic Energy Agency organized a round-robin exercise where the participants measured and calculated specific saturation activities achievable for the 98 Mo(n,γ) 99 Mo reaction. This reaction is of interest as a means to locally, and on a small scale, produce 99 Mo from natural molybdenum. The current paper summarises a set of experimental results and reviews the methodology for calculating the corresponding saturation activities. Activation by epithermal neutrons and also epithermal neutron self-shielding are found to be of high importance in this case.

Selective emission multilayer coatings for a molybdenum thermophotovoltaic radiator

DOEpatents

Cockeram, Brian Vern

2004-01-27

Multilayer coating designs have been developed to provide selective emission for a molybdenum thermophotovoltaic (TPV) radiator surface. These coatings increase the surface emissivity of a molybdenum TPV radiator substrate in the wavelength range that matches the bandgap of the TPV cells to increase the power density of the TPV system. Radiator emission at wavelengths greater than the bandgap energy of the TPV cells is greatly reduced through the use of these coatings, which significantly increases the efficiency of the TPV system. The use of this coating greatly improves the performance of a TPV system, and the coating can be tailored to match the bandgap of any practical TPV system.

Molybdenum Accumulation in Marine Sediments as an Indicator of Hypoxic Water Conditions (NACAETAC)

EPA Science Inventory

Direct monitoring of hypoxic water column conditions over large spatial and temporal extents is difficult due to the substantial logistical and financial investment required. Recent studies have indicated that concentrations of molybdenum (Mo) in marine sediments may serve as a u...

Field Validation of Molybdenum Accumulation as an Indicator of Hypoxic Water Conditions

EPA Science Inventory

Laboratory experiments have shown that the accumulation rate of authigenic molybdenum (Mo) in marine sediments may serve as a quantitative surrogate for direct measurement of hypoxic conditions in overlying waters: Mo accumulation in the top 1 cm of sediment is linearly related t...

A Quantitative Model for the Exchange Current of Porous Molybdenum Electrodes on Sodium Beta-Alumina in Sodium Vapor

NASA Technical Reports Server (NTRS)

Williams, R. M.; Ryan, M. A.; LeDuc, H.; Cortez, R. H.; Saipetch, C.; Shields, V.; Manatt, K.; Homer, M. L.

1998-01-01

This paper presents a model of the exchange current developed for porous molybdenum electrodes on sodium beta-alumina ceramics in low pressure sodium vapor, but which has general applicability to gas/porous metal electrodes on solid electrolytes.

Molybdenum-platinum-oxide electrodes for thermoelectric generators

DOEpatents

Schmatz, Duane J.

1990-01-01

The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a solid electrolyte carrying a thin film comprising molybdenum-platinum-oxide as an electrode deposited by physical deposition techniques. The invention is also directed to the method of making same.

Laboratory Determination of Molybdenum Accumulation Rates as a Measure of Hypoxic Conditions

EPA Science Inventory

Redox sensitive metals, such as molybdenum (Mo), are enriched in reducing sediments due to authigenic fixation in anoxic interstitial waters of sediments. This study tested whether the process of fixation and accumulation of Mo in sediments could provide a geochemical indicator o...

Simultaneous material flow analysis of nickel, chromium, and molybdenum used in alloy steel by means of input-output analysis.

PubMed

Nakajima, Kenichi; Ohno, Hajime; Kondo, Yasushi; Matsubae, Kazuyo; Takeda, Osamu; Miki, Takahiro; Nakamura, Shinichiro; Nagasaka, Tetsuya

2013-05-07

Steel is not elemental iron but rather a group of iron-based alloys containing many elements, especially chromium, nickel, and molybdenum. Steel recycling is expected to promote efficient resource use. However, open-loop recycling of steel could result in quality loss of nickel and molybdenum and/or material loss of chromium. Knowledge about alloying element substance flow is needed to avoid such losses. Material flow analyses (MFAs) indicate the importance of steel recycling to recovery of alloying elements. Flows of nickel, chromium, and molybdenum are interconnected, but MFAs have paid little attention to the interconnected flow of materials/substances in supply chains. This study combined a waste input-output material flow model and physical unit input-output analysis to perform a simultaneous MFA for nickel, chromium, and molybdenum in the Japanese economy in 2000. Results indicated the importance of recovery of these elements in recycling policies for end-of-life (EoL) vehicles and constructions. Improvement in EoL sorting technologies and implementation of designs for recycling/disassembly at the manufacturing phase are needed. Possible solutions include development of sorting processes for steel scrap and introduction of easier methods for identifying the composition of secondary resources. Recovery of steel scrap with a high alloy content will reduce primary inputs of alloying elements and contribute to more efficient resource use.

Geochemical evidence for a brooks range mineral belt, Alaska

USGS Publications Warehouse

Marsh, S.P.; Cathrall, J.B.

1981-01-01

Geochemical studies in the central Brooks Range, Alaska, delineate a regional, structurally controlled mineral belt in east-west-trending metamorphic rocks and adjacent metasedimentary rocks. The mineral belt extends eastward from the Ambler River quadrangle to the Chandalar and Philip Smith quadrangles, Alaska, from 147?? to 156??W. longitude, a distance of more than 375 km, and spans a width from 67?? to 69??N. latitude, a distance of more than 222 km. Within this belt are several occurrences of copper and molybdenum mineralization associated with meta-igneous, metasedimentary, and metavolcanic rocks; the geochemical study delineates target areas for additional occurrences. A total of 4677 stream-sediment and 2286 panned-concentrate samples were collected in the central Brooks Range, Alaska, from 1975 to 1979. The -80 mesh ( 2.86) nonmagnetic fraction of the panned concentrates from stream sediment were analyzed by semiquantitative spectrographic methods. Two geochemical suites were recognized in this investigation; a base-metal suite of copper-lead-zinc and a molybdenum suite of molybdenum-tin-tungsten. These suites suggest several types of mineralization within the metamorphic belt. Anomalies in molybdenum with associated Cu and W suggest a potential porphyry molybdenum system associated with meta-igneous rocks. This regional study indicates that areas of metaigneous rocks in the central metamorphic belt are target areas for potential mineralized porphyry systems and that areas of metavolcanic rocks are target areas for potential massive sulfide mineralization. ?? 1981.

The Effect of Molybdenum Substrate Oxidation on Molybdenum Splat Formation

NASA Astrophysics Data System (ADS)

Wang, Jun; Li, Chang-Jiu

2018-01-01

Disk splats are usually observed when the deposition temperature exceeds the transition temperature, whereas thick oxide layer will reduce the adhesion resulting from high deposition temperature. In present study, single molybdenum splats were deposited onto polished molybdenum substrates with different preheating processes to clarify the effect of surface oxidation on the splat formation. Three substrate samples experienced three different preheating processes in an argon atmosphere. Two samples were preheated to 350 and 550 °C, and another sample was cooled to 350 °C after it was preheated to 550 °C. The chemistry and compositions of substrate surface were examined by XPS. The cross sections of splats were prepared by focus ion beam (FIB) and then characterized by SEM. Nearly disk-shaped splat with small fingers in the periphery was observed on the sample preheated to 350 °C. A perfect disk-shape splat was deposited at 550 °C. With the sample on the substrate preheated to 350 °C (cooling down from 550 °C), flower-shaped splat exhibited a central core and discrete periphery detached by some voids. The results of peeling off splats by carbon tape and the morphology of FIB sampled cross sections indicated that no effective bonding formed at the splat-substrate interface for the substrate ever heated to 550 °C, due to the increasing content of MoO3 on the preheated molybdenum surface.

Field Validation of Molybdenum Accumulation in Sediments as an Indication of Hypoxic Water Conditions

EPA Science Inventory

Accumulation of authigenic molybdenum (Mo) in marine sediments has often been used as qualitative indicator of periods of hypoxic bottom water, but rarely, if ever, used quantitatively. Laboratory experiments have shown that the accumulation rate of Mo may serve as a quantitative...

Method for welding chromium molybdenum steels

DOEpatents

Sikka, Vinod K.

1986-01-01

Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

Process for producing molybdenum foil and collapsible tubing

NASA Technical Reports Server (NTRS)

Bretts, G. R.; Gavert, R. B.; Groschke, G. F.

1971-01-01

Manufacturing process produces molybdenum foil 0.002 cm thick and 305 m long, and forms foil into high-strength, thin-walled tubing which can be flattened for storage on a spool. Desirable metal properties include high thermal conductivity stiffness, yield and tensile stress, and low thermal expansion coeffecient.

Effect of growth regulators, boron and molybdenum on sugarcane grown in the greenhouse

USDA-ARS?s Scientific Manuscript database

Tillering is an important characteristic in determining sugarcane yields. An experiment was conducted in the greenhouse using LCP 85-384 to determine the influence of the growth regulator Moddus, alone and in all possible combinations with boron and molybdenum, on the growth and development of young...

Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Final technical report, October 1990--December 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osseo-Asare, K.; Boakye, E.; Vittal, M.

1995-04-01

This report described the synthesis of Molybdenum Sulfides in microemulsions by acidification of ammonium tetrathiomolybdate. Molybdenum Sulfides have been shown to be potential coal liquefaction catalysts. The importance of particle size, temperature effects, and coal surface chemistry to impregnation are discussed.

Antioxidant capacity of chewing stick miswak Salvadora persica.

PubMed

Mohamed, Saleh A; Khan, Jalaluddin A

2013-02-21

Chewing stick (miswak Salvadora persica L.) is an effective tool for oral hygiene. It possessed various biological properties including significant antibacterial and anti-fungal effects. In the present study, we evaluated the antioxidant compounds in miswak. Miswak root was extracted with 80% methanol. Methanol extract as antioxidant was evaluated by using DPPH, ABTS and phosphomolybdenum complex assays and analysis by GC-MS. Peroxidase, catalase and polyphenoloxidase assays were performed for crude extract of miswak root. The methanol extract of miswak contained the highest amount of crude extract among the various solvent extracts. The methanol extract showed a concentration dependent scavenging of DPPH and ABTS radicals with IC50 values 4.8 and 1.6 μg crude extract, respectively. The total antioxidant activities, based on the reduction of molybdenum (VI) to molybdenum (V), increased with increasing crude extract content. The correlation coefficients (R2) between total crude extract and DPPH, ABTS scavenging activities and the formation of phosphomolybdenum complex were 0.97, 0.99 and 0.95, respectively. The GC-MS analysis showed that the methanol extract doesn't contain phenolic and flavonoid compounds or under detected limit. After silylation of methanol extract, three compounds namely 2-furancarboxaldehyde-5-(hydroxymethyl), furan-2-carboxylic acid-3-methyl- trimethylsilyl ester and D-erythro-pentofuranose-2-deoxy-1,3,5-tris-O-(trimethylsilyl) were identified by GC-MS analysis. These furan derivatives as they contain hydroxyl groups could be possessed antioxidant activities. The antioxidant enzymes were also detected in the miswak extract with high level of peroxidase and low level of catalase and polyphenoloxidase. The synergistic actions of antioxidant compounds and antioxidant enzymes make miswak is a good chewing stick for oral hygiene and food purposes.

Physiological and biochemical characterization of the soluble formate dehydrogenase, a molybdoenzyme from Alcaligenes eutrophus.

PubMed Central

Friedebold, J; Bowien, B

1993-01-01

Organoautotrophic growth of Alcaligenes eutrophus on formate was dependent on the presence of molybdate in the medium. Supplementation of the medium with tungstate lead to growth cessation. Corresponding effects of these anions were observed for the activity of the soluble, NAD(+)-linked formate dehydrogenase (S-FDH; EC 1.2.1.2) of the organism. Lack of molybdate or presence of tungstate resulted in an almost complete loss of S-FDH activity. S-FDH was purified to near homogeneity in the presence of nitrate as a stabilizing agent. The native enzyme exhibited an M(r) of 197,000 and a heterotetrameric quaternary structure with nonidentical subunits of M(r) 110,000 (alpha), 57,000 (beta), 19,400 (gamma), and 11,600 (delta). It contained 0.64 g-atom of molybdenum, 25 g-atom of nonheme iron, 20 g-atom of acid-labile sulfur, and 0.9 mol of flavin mononucleotide per mol. The fluorescence spectrum of iodine-oxidized S-FDH was nearly identical to the form A spectrum of milk xanthine oxidase, proving the presence of a pterin cofactor. The molybdenum-complexing cofactor was identified as molybdopterin guanine dinucleotide in an amount of 0.71 mol/mol of S-FDH. Apparent Km values of 3.3 mM for formate and 0.09 mM for NAD+ were determined. The enzyme coupled the oxidation of formate to a number of artificial electron acceptors and was strongly inactivated by formate in the absence of NAD+. It was inhibited by cyanide, azide, nitrate, and Hg2+ ions. Thus, the enzyme belongs to a new group of complex molybdo-flavo Fe-S FDH that so far has been detected in only one other aerobic bacterium. Images PMID:8335630

Development of explosively bonded TZM wire reinforced Columbian sheet composites

NASA Technical Reports Server (NTRS)

Otto, H. E.; Carpenter, S. H.

1972-01-01

Methods of producing TZM molybdenum wire reinforced C129Y columbium alloy composites by explosive welding were studied. Layers of TZM molybdenum wire were wound on frames with alternate layers of C129Y columbium alloy foil between the wire layers. The frames held both the wire and foils in place for the explosive bonding process. A goal of 33 volume percent molybdenum wire was achieved for some of the composites. Variables included wire diameter, foil thickness, wire separation, standoff distance between foils and types and amounts of explosive. The program was divided into two phases: (1) development of basic welding parameters using 5 x 10-inch composites, and (2) scaleup to 10 x 20-inch composites.

Effect of nature of oxygen interactions on friction of titanium, aluminum, and molybdenum

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1976-01-01

Friction studies were conducted with a gold pin contacting titanium, aluminum, and molybdenum surfaces after exposure to oxygen with various methods. Oxygen was adsorbed on the surface, it reacted with the surface, and the surface was ion bombarded with oxygen. The presence of oxygen was monitored with Auger spectroscopy. Titanium friction varied with the mode of the metal-oxygen interaction. It was highest with the adsorbed oxygen and least with ion bombardment using oxygen. Aluminum exhibited lower friction values for the reacted and the ion bombarded surfaces than for the surface having the adsorbed layer. With molybdenum the friction coefficients were generally the same despite the nature of the surface treatment with oxygen.

Effect of annealing on doping of graphene with molybdenum oxide

NASA Astrophysics Data System (ADS)

Ishikawa, Ryousuke; Watanabe, Sho; Nishida, Hiroki; Aoyama, Yuki; Oya, Tomoya; Nomoto, Takahiro; Tsuboi, Nozomu

2018-04-01

We investigated the effect of post-annealing on the doping of graphene with MoO3 in this study. The as-deposited molybdenum oxide thin film prepared using our method was not completely oxidized; in addition, it was in an amorphous state, due to which its doping effect was not significant. As the post-deposition annealing temperature was increased, the oxidation and crystallization of the molybdenum oxide progressed and the doping effect increased accordingly. After annealing at 350 °C, the holes were the most doped and the sheet resistance was the lowest. The doped graphene film obtained in this study shows higher doping effect and stability compared to other dopants.

Breaking America's dependence on imported molybdenum.

PubMed

Einstein, Andrew J

2009-03-01

Approximately 9 million nuclear cardiology studies performed each year in the U.S. use technetium-99m, which is produced from the decay of molybdenum-99. The fragility of the worldwide technetium-99m supply chain has been underscored by current shortages caused by an unplanned shutdown of Europe's largest reactor. The majority of the U.S. supply derives from a reactor in Canada that is nearing the end of its lifespan and whose planned replacements have been cancelled recently. In this article, the clinical importance of technetium-99m and our tenuous dependence on the foreign supply of molybdenum are addressed, along with potential measures that may be taken to ensure that America's supply chain remains unbroken.

Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli.

PubMed Central

Iuchi, S; Lin, E C

1987-01-01

In Escherichia coli the presence of nitrate prevents the utilization of fumarate as an anaerobic electron acceptor. The induction of the narC operon encoding the nitrate reductase is coupled to the repression of the frd operon encoding the fumarate reductase. This coupling is mediated by nitrate as an effector and the narL product as the regulatory protein (S. Iuchi and E. C. C. Lin, Proc. Natl. Acad. Sci. USA 84:3901-3905, 1987). The protein-ligand complex appears to control narC positively but frd negatively. In the present study we found that a molybdenum coeffector acted synergistically with nitrate in the regulation of frd and narC. In chlD mutants believed to be impaired in molybdate transport (or processing), full repression of phi(frd-lac) and full induction of phi(narC-lac) by nitrate did not occur unless the growth medium was directly supplemented with molybdate (1 microM). This requirement was not clearly manifested in wild-type cells, apparently because it was met by the trace quantities of molybdate present as a contaminant in the mineral medium. In chlB mutants, which are known to accumulate the Mo cofactor because of its failure to be inserted as a prosthetic group into proteins such as nitrate reductase, nitrate repression of frd and induction of narC were also intensified by molybdate supplementation. In this case a deficiency of the molybdenum coeffector might have resulted from enhanced feedback inhibition of molybdate transport (or processing) by the elevated level of the unutilized Mo cofactor. In addition, mutations in chlE, which are known to block the synthesis of the organic moiety of the Mo cofactor, lowered the threshold concentration of nitrate (< 1 micromole) necessary for frd repression and narC induction. These changes could be explained simply by the higher intracellular nitrate attainable in cells lacking the ability to destroy the effector. PMID:3301812

Calorimetric studies of the heats of protonation of the dangling phosphorus in [eta][sup 1]-Ph[sub 2]PCH[sub 2]PPh[sub 2] complexes of chromium, molybdenum, and tungsten

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rottink, M.K.; Angelici, R.J.

1993-05-26

Titration calorimetry has been used to determine the heats of protonation ([Delta]H[sub HP]) of M(CO)[sub 5]([eta][sup 1]-dppm) (M = Cr, Mo, W) and fac-M(CO)[sub 3](N-N)([eta][sup 1]-dppm) (M = Mo, N-N = bipy, phen; M = w, N-N = bipy) complexes with CF[sub 3]SO[sub 3]H in 1,2-dichloroethane solvent at 25.0 [degrees]C. Spectroscopic studies show that protonation occurs at the uncoordinated phosphorus atom of the [eta][sup 1]-coordinated dppm (Ph[sub 2]PCH[sub 2]PPh[sub 2]) ligand. For dppm, its monoprotonated form (dppmH[sup +]), and these complexes, the basicity ([Delta]H[sub HP]) of the dangling phosphorus increases from -14.9 kcal/mol to -23.1 kcal/mol in the order: dppmH[supmore » +]« less

Lewis Acid Assisted Nitrate Reduction with Biomimetic Molybdenum Oxotransferase Complex.

PubMed

Elrod, Lee Taylor; Kim, Eunsuk

2018-03-05

The reduction of nitrate (NO 3 - ) to nitrite (NO 2 - ) is of significant biological and environmental importance. While Mo IV (O) and Mo VI (O) 2 complexes that mimic the active site structure of nitrate reducing enzymes are prevalent, few of these model complexes can reduce nitrate to nitrite through oxygen atom transfer (OAT) chemistry. We present a novel strategy to induce nitrate reduction chemistry of a previously known catalyst Mo IV (O)(SN) 2 (2), where SN = bis(4- tert-butylphenyl)-2-pyridylmethanethiolate, that is otherwise incapable of achieving OAT with nitrate. Addition of nitrate with the Lewis acid Sc(OTf) 3 (OTf = trifluoromethanesulfonate) to 2 results in an immediate and clean conversion of 2 to Mo VI (O) 2 (SN) 2 (1). The Lewis acid additive further reacts with the OAT product, nitrite, to form N 2 O and O 2 . This work highlights the ability of Sc 3+ additives to expand the reactivity scope of an existing Mo IV (O) complex together with which Sc 3+ can convert nitrate to stable gaseous molecules.

Process for degrading hypochlorite and sodium hypochlorite

DOEpatents

Huxtable, William P.; Griffith, William L.; Compere, Alicia L.

1990-01-01

A process for degrading hypochlorite waste and lithium hypochlorite solutions uses a cobalt oxide/molybdenum oxide catalyst formed from about 1-10 w/w % cobalt oxide and 1-15 w/w % molybdenum oxide disposed on a suitable substrate. The major advantage of the catalyst lies in its high degree of effectiveness and its very low cost.

Preparation of isotopic molybdenum foils utilizing small quantities of material

NASA Astrophysics Data System (ADS)

Lipski, A. R.; Lee, L. L.; Liang, J. F.; Mahon, J. C.

1993-09-01

A simple method utilizing a small amount of isotopic material for production of molybdenum foils is discussed. An e-gun is used in the procedure. The Mo powder undergoes reduction-sintering and melting-solidifying steps leading to the creation of a metallic droplet suitable for further cold rolling or vacuum deposition.

Study of Wear-Preventive Properties of Macrocyclic Compounds for High Temperature Application

DTIC Science & Technology

1990-01-01

and hence its lubricating properties adversely affected. Another molybdenum based lubricant is molybdenum silicide . This has good resistance to...Porphyrins 21 Contract No. N62269-88-R-0234 Report No. NADC-91049-60 N N N N N\\ -/ N N .. 05 NICKEL PHTH-ALOCYANINE TETRASULFONIC ACID TETRA SODIUM SALT

Mo-Si-B-Based Coatings for Ceramic Base Substrates

NASA Technical Reports Server (NTRS)

Perepezko, John Harry (Inventor); Sakidja, Ridwan (Inventor); Ritt, Patrick (Inventor)

2015-01-01

Alumina-containing coatings based on molybdenum (Mo), silicon (Si), and boron (B) ("MoSiB coatings") that form protective, oxidation-resistant scales on ceramic substrate at high temperatures are provided. The protective scales comprise an aluminoborosilicate glass, and may additionally contain molybdenum. Two-stage deposition methods for forming the coatings are also provided.

Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

DTIC Science & Technology

2014-07-14

Lou, Sina Najmaei, Matin Amani, Matthew L. Chin, Zheng Se. TASK NUMBER Liu Sf. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8...Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide Sina Najmaei,t.§ Matin Ama ni,M Matthew L. Chin,* Zhe ng liu/ ·"·v: A. Gle n

Marine Exposure Tests on Stainless Steel Sheet

DTIC Science & Technology

1947-02-01

contained 17 to 20 percent of chromium, 7 to 10 percent of nickel, and, in seme Instances, sma.11 amounts of molybdenum, tita - nium, or columbium...3.5 percent, of molybdenum, exhibited much loss rust on weathering than those of the ordinary 18:8 type with or without additions of tita - nium or

Pseudo-Capacitors: SPPS Deposition and Electrochemical Analysis of α-MoO3 and Mo2N Coatings

NASA Astrophysics Data System (ADS)

Golozar, Mehdi; Chien, Ken; Lian, Keryn; Coyle, Thomas W.

2013-06-01

Solution precursor plasma spraying (SPPS) is a novel thermal spray process in which a solution precursor is injected into the high-temperature zone of a DC-arc plasma jet to allow solvent evaporation from the precursor droplets, solute precipitation, and precipitate pyrolysis prior to substrate impact. This investigation explored the potential of SPPS to fabricate α-MoO3 coatings with fine grain sizes, high porosity levels, and high surface area: characteristics needed for application as pseudo-capacitor electrodes. Since molybdenum nitride has shown a larger electrochemical stability window and higher specific area capacitance, the α-MoO3 deposits were subsequently converted into molybdenum nitride. A multistep heat-treatment procedure resulted in a topotactic phase-transformation mechanism, which retained the high surface area lath-shaped features of the original α-MoO3. The electrochemical behaviors of molybdenum oxide and molybdenum nitride deposits formed under different deposition conditions were studied using cyclic voltammetry to assess the influence of the resulting microstructure on the charge storage behavior and potential for use in pseudo-capacitors.

Deformation-induced structural transition in body-centred cubic molybdenum

PubMed Central

Wang, S. J.; Wang, H.; Du, K.; Zhang, W.; Sui, M. L.; Mao, S. X.

2014-01-01

Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original <001>-oriented body-centred cubic structure to a <110>-oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into <111>-oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama–Wassermann and Kurdjumov–Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions. PMID:24603655

Synthesis and Characterization of Molybdenum Based Colloidal Particles.

PubMed

Moreno; Vidoni; Ovalles; Chaudret; Urbina; Krentzein

1998-11-15

The synthesis and characterization of molybdenum colloidal particles were evaluated using thermal and sonochemical methods and starting from different metal precursors, Mo(CO)6 and (NH4)2MoS4. The products were characterized by elemental analysis, spectroscopic (UV, FTIR), and surface analysis (XPS) techniques, as well as by transmission electron microscopy (TEM) for determining the particle sizes. Using Mo(CO)6 as metal source, particle sizes with an average diameter of 1.5 nm can be obtained using tert-amyl alcohol as solvent and tetrahydrothiophene as sulfurating ligand. The characterization of these particles showed that they are composed of molybdenum oxide MoO3. Using (NH4)2MoS4 as metal precursor, particles with average diameters of 4.7 and 2.5 nm were synthesized using thermal and sonochemical methods, respectively. The characterization of these particles showed them to be composed of molybdenum sulfide, MoS2. The sonochemical method proved to be the fastest and most convenient synthetic pathway of obtaining small colloidal particles at low temperatures and with control of the average size. Copyright 1998 Academic Press.

Performance and Vibration of 30 cm Pyrolytic Ion Thruster Optics

NASA Technical Reports Server (NTRS)

Haag, Thomas; Soulas, George C.

2004-01-01

Carbon has a sputter erosion rate about an order of magnitude less than that of molybdenum, over the voltages typically used in ion thruster applications. To explore its design potential, 30 cm pyrolytic carbon ion thruster optics have been fabricated geometrically similar to the molybdenum ion optics used on NSTAR. They were then installed on an NSTAR Engineering Model thruster, and experimentally evaluated over much of the original operating envelope. Ion beam currents ranged from 0.51 to 1.76 Angstroms, at total voltages up to 1280 V. The perveance, electron back-streaming limit, and screen-grid transparency were plotted for these operating points, and compared with previous data obtained with molybdenum. While thruster performance with pyrolytic carbon was quite similar to that with molybdenum, behavior variations can reasonably be explained by slight geometric differences. Following all performance measurements, the pyrolytic carbon ion optics assembly was subjected to an abbreviated vibration test. The thruster endured 9.2 g(sub rms) of random vibration along the thrust axis, similar to DS 1 acceptance levels. Despite significant grid clashing, there was no observable damage to the ion optics assembly.

An Evaluation of Molybdenum Toxicity to the Oligochaete, Tubifex tubifex, and Early-Life Stages of Brown Trout, Salmo trutta.

PubMed

Lucas, Brett T; Quinteros, Claudio; Burnett-Seidel, Charlene; Elphick, James R

2017-06-01

Limited data are available describing the aquatic toxicity of molybdenum in freshwater environments, making it difficult to assess the aquatic risk to freshwater organisms. In order to increase available information on the aquatic toxicity of molybdenum, a 96-h LC50 test with the oligochaete Tubifex tubifex and an 85-day development test using brown trout, Salmo trutta, were conducted. The T. tubifex test resulted in an LC50 value of 2782 mg/L. No adverse effects were observed on brown trout survival or length in the concentrations tested, however an IC10 value for growth (wet weight) was determined to be 202 mg/L. Whole body fish tissue concentrations for molybdenum increased in all treatment concentrations tested, although bioconcentration factors decreased at greater exposure concentrations, and ranged from 0.13 at an exposure concentration of 20 mg/L to 0.04 at an exposure of 1247 mg/L. A body burden of 26.0 mg/kg was associated with reduced wet weight.

Density functional study of the structural, electronic, and magnetic properties of Mo n and Mo n S ( n = 1 - 10) clusters

NASA Astrophysics Data System (ADS)

Ziane, M.; Amitouche, F.; Bouarab, S.; Vega, A.

2017-12-01

Structural and electronic properties of pure molybdenum Mo n and molybdenum-sulfide Mo n S ( n = 1 - 10) clusters were investigated in the framework of the density functional theory within the generalized gradient approximation to exchange and correlation with the aim of addressing how doping with a single S atom affects the geometries, magnetic properties, and reactivity of pure molybdenum clusters. These clusters exhibit a less marked tendency to dimerization than their isoelectronic Cr counterparts despite sharing their half-filled valence shell configuration. Doping with a single S impurity is enough to change the structure of the host molybdenum cluster to a large extent, as well as to modify the bonding pattern, the magnetic state and the magnetic moment distribution in the Mo host. Vertical ionization potentials and electron affinities are calculated to determine global reactivity indicators like the electronegativity and the chemical hardness. The results are discussed in terms of the thermodynamical and relative stabilities, charge transfer effects, and spin-polarized densities of electronic states.

NASA Astrophysics Data System (ADS)

Sampath, S.; Wayne, S. F.

1994-09-01

Thermally sprayed molybdenum coatings are used in a variety of industrial applications, such as auto-motive piston rings, aeroturbine engines, and paper and plastics processing machinery. Molybdenum ex-hibits excellent scuffing resistance under sliding contact conditions. However, plasma-sprayed molybde-num coatings are relatively soft and require dispersion strengthening (e.g., Mo2C) or addition of a second phase (e.g., NiCrBSi) to improve hardness, wear resistance, and thus coating performance. In this study, Mo-Mo2C composite powders were plasma sprayed onto mild steel substrates. Considerable decarburi-zation was observed during air plasma spraying—a beneficial condition because carbon acts as a sacrifi-cial getter for the oxygen, thereby reducing the oxide content in the coating. Finer powders showed a greater degree of decarburization due to the increased surface area; however, the starting carbide con-tent in the powder exerted very little influence on the extent of decarburization. The friction properties of Mo-Mo2C coatings were significantly improved compared to those of pure molybdenum under con-tinuous sliding contact conditions. It also was found that the abrasion resistance of the coatings improved with increasing carbide addition.

Electrical and optical properties of molybdenum doped zinc oxide films prepared by reactive RF magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, R. Subba; Sreedhar, A.; Uthanna, S., E-mail: uthanna@rediffmail.com

Molybdenum doped zinc oxide (MZO) films were deposited on to glass substrates held at temperatures in the range from 303 to 673 K by reactive RF magnetron sputtering method. The chemical composition, crystallographic structure and surface morphology, electrical and optical properties of the films were determined. The films contained the molybdenum of 2.7 at. % in ZnO. The films deposited at 303 K were of X-ray amorphous. The films formed at 473 K were of nanocrystalline in nature with wurtzite structure. The crystallite size of the films was increased with the increase of substrate temperature. The optical transmittance of the films was inmore » the visible range was 80–85%. The molybdenum (2.7 at %) doped zinc oxide films deposited at substrate temperature of 573 K were of nanocrystalline with electrical resistivity of 7.2×10{sup −3} Ωcm, optical transmittance of 85 %, optical band gap of 3.35 eV and figure of merit 30.6 Ω{sup −1}cm{sup −1}.« less

Effect of metal chloride solutions on coloration and biaxial flexural strength of yttria-stabilized zirconia

NASA Astrophysics Data System (ADS)

Oh, Gye-Jeong; Lee, Kwangmin; Lee, Doh-Jae; Lim, Hyun-Pil; Yun, Kwi-Dug; Ban, Jae-Sam; Lee, Kyung-Ku; Fisher, John G.; Park, Sang-Won

2012-10-01

The effect of three kinds of transition metal dopants on the color and biaxial flexural strength of zirconia ceramics for dental applications was evaluated. Presintered zirconia discs were colored through immersion in aqueous chromium, molybdenum and vanadium chloride solutions and then sintered at 1450 °C. The color of the doped specimens was measured using a digital spectrophotometer. For biaxial flexural strength measurements, specimens infiltrated with 0.3 wt% of each aqueous chloride solution were used. Uncolored discs were used as a control. Zirconia specimens infiltrated with chromium, molybdenum and vanadium chloride solutions were dark brown, light yellow and dark yellow, respectively. CIE L*, a*, and b* values of all the chromium-doped specimens and the specimens infiltrated with 0.1 wt% molybdenum chloride solution were in the range of values for natural teeth. The biaxial flexural strengths of the three kinds of metal chloride groups were similar to the uncolored group. These results suggest that chromium and molybdenum dopants can be used as colorants to fabricate tooth colored zirconia ceramic restorations.

Molybdenum oxide and molybdenum oxide-nitride back contacts for CdTe solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drayton, Jennifer A., E-mail: drjadrayton@yahoo.com; Geisthardt, Russell M., E-mail: Russell.Geisthardt@gmail.com; Sites, James R., E-mail: james.sites@colostate.edu

2015-07-15

Molybdenum oxide (MoO{sub x}) and molybdenum oxynitride (MoON) thin film back contacts were formed by a unique ion-beam sputtering and ion-beam-assisted deposition process onto CdTe solar cells and compared to back contacts made using carbon–nickel (C/Ni) paint. Glancing-incidence x-ray diffraction and x-ray photoelectron spectroscopy measurements show that partially crystalline MoO{sub x} films are created with a mixture of Mo, MoO{sub 2}, and MoO{sub 3} components. Lower crystallinity content is observed in the MoON films, with an additional component of molybdenum nitride present. Three different film thicknesses of MoO{sub x} and MoON were investigated that were capped in situ in Ni.more » Small area devices were delineated and characterized using current–voltage (J-V), capacitance–frequency, capacitance–voltage, electroluminescence, and light beam-induced current techniques. In addition, J-V data measured as a function of temperature (JVT) were used to estimate back barrier heights for each thickness of MoO{sub x} and MoON and for the C/Ni paint. Characterization prior to stressing indicated the devices were similar in performance. Characterization after stress testing indicated little change to cells with 120 and 180-nm thick MoO{sub x} and MoON films. However, moderate-to-large cell degradation was observed for 60-nm thick MoO{sub x} and MoON films and for C/Ni painted back contacts.« less

GEMAS: Molybdenum Spatial Distribution Patterns in European Soil

NASA Astrophysics Data System (ADS)

Cicchella, Domenico; Zuzolo, Daniela; Demetriades, Alecos; De Vivo, Benedetto; Eklund, Mikael; Ladenberger, Anna; Negrel, Philippe; O'Connor, Patrick

2017-04-01

Molybdenum is an essential trace element for both plants and animals as well as for human being. It is one such trace element for which potential health concerns have been raised but for which few data exist and little investigation or interpretation of distributions in soils has been made. The main goal of this study was to fill this gap. Molybdenum (Mo) concentrations are reported for the <2 mm fraction of soil samples from agricultural (Ap horizon, 0-20 cm; N=2218) and grazing land (Gr, 0-10 cm; N=2127). The survey covers 33 European countries and 5.6 million km2 at a sample density of 1 site/2500 km2. All samples were analysed by ICP-MS following an aqua regia extraction. The European median Mo concentration is 0.416 mg/kg in agricultural soil and 0.424 mg/kg in grazing land soil. Molybdenum geochemical maps for both land use types (Ap and Gr) show overall similar spatial distribution patterns mainly governed by geology (parent material and mineralisation), as well as weathering, soil formation and climate since the last glaciations period. The dominant feature is represented by low Mo concentrations over the coarse-grained sandy deposits of the last glaciations in central northern Europe while the most extensive anomalies occur in Scandinavian soils. The highest Mo concentration value occurs to the North of Oslo close to one of the largest porphyry Mo deposit of the World. Some interesting anomalous patterns occur also in Italy in correspondence with alkaline volcanics, in Spain and Greece associated with sulfides mineralizations and in Slovenia and Croatia where are probably related to the long weathering history of karstic residual soils. Anomalous concentrations in some areas of Ireland represent a clear example of how an excess of molybdenum has produced potentially toxic pastures. In fact, these give rise to problems particularly in young cattle when excess molybdenum in the herbage acts as an antagonist, which militates against efficient copper absorption by the animal.

Experimental characterization and constitutive modeling of the mechanical behavior of molybdenum under electromagnetically applied compression-shear ramp loading

DOE PAGES

Alexander, C. Scott; Ding, Jow -Lian; Asay, James Russell

2016-03-09

Magnetically applied pressure-shear (MAPS) is a new experimental technique that provides a platform for direct measurement of material strength at extreme pressures. The technique employs an imposed quasi-static magnetic field and a pulsed power generator that produces an intense current on a planar driver panel, which in turn generates high amplitude magnetically induced longitudinal compression and transverse shear waves into a planar sample mounted on the drive panel. In order to apply sufficiently high shear traction to the test sample, a high strength material must be used for the drive panel. Molybdenum is a potential driver material for the MAPSmore » experiment because of its high yield strength and sufficient electrical conductivity. To properly interpret the results and gain useful information from the experiments, it is critical to have a good understanding and a predictive capability of the mechanical response of the driver. In this work, the inelastic behavior of molybdenum under uniaxial compression and biaxial compression-shear ramp loading conditions is experimentally characterized. It is observed that an imposed uniaxial magnetic field ramped to approximately 10 T through a period of approximately 2500 μs and held near the peak for about 250 μs before being tested appears to anneal the molybdenum panel. In order to provide a physical basis for model development, a general theoretical framework that incorporates electromagnetic loading and the coupling between the imposed field and the inelasticity of molybdenum was developed. Based on this framework, a multi-axial continuum model for molybdenum under electromagnetic loading is presented. The model reasonably captures all of the material characteristics displayed by the experimental data obtained from various experimental configurations. Additionally, data generated from shear loading provide invaluable information not only for validating but also for guiding the development of the material model for multiaxial loadings.« less

Atom probe study of grain boundary segregation in technically pure molybdenum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babinsky, K., E-mail: katharina.babinsky@stud.unileoben.ac.at; Weidow, J., E-mail: jonathan.weidow@chalmers.se; Knabl, W., E-mail: wolfram.knabl@plansee.com

2014-01-15

Molybdenum, a metal with excellent physical, chemical and high-temperature properties, is an interesting material for applications in lighting-technology, high performance electronics, high temperature furnace construction and coating technology. However, its applicability as a structural material is limited because of the poor oxidation resistance at high temperatures and a brittle-to-ductile transition around room temperature, which is influenced by the grain size and the content of interstitial impurities at the grain boundaries. Due to the progress of the powder metallurgical production during the last decades, the amount of impurities in the current quality of molybdenum has become so small that surface sensitivemore » techniques are not applicable anymore. Therefore, the atom probe, which allows the detection of small amounts of impurities as well as their location, seems to be a more suitable technique. However, a site-specific specimen preparation procedure for grain boundaries in refractory metals with a dual focused ion beam/scanning electron microscope is still required. The present investigation describes the development and successful application of such a site-specific preparation technique for grain boundaries in molybdenum, which is significantly improved by a combination with transmission electron microscopy. This complimentary technique helps to improve the visibility of grain boundaries during the last preparation steps and to evidence the presence of grain and subgrain boundaries without segregants in atom probe specimens. Furthermore, in industrially processed and recrystallized molybdenum sheets grain boundary segregation of oxygen, nitrogen and potassium is successfully detected close to segregated regions which are believed to be former sinter pores. - Highlights: • First study of grain boundary segregation in molybdenum by atom probe • Site-specific preparation technique by FIB and TEM successfully developed • Grain boundary segregation of oxygen, nitrogen and potassium found • Segregation in former sinter-pores detected • Presence of grain boundaries without segregation evidenced.« less

Cp[prime]M(NO)R[sub 2]: 16-electron piano-stool molecules of molybdenum and tungsten

DOE Office of Scientific and Technical Information (OSTI.GOV)

Legzdins, P.; Veltheer, J.E.

1993-02-01

A long-term goal of this research program is the development of organometallic nitrosyl complexes as specific reactants or selective catalysts for organic or organometallic transformations of practical significance. To attain this goal specifically with Cp[prime]M(NO)R[sub 2] system the authors developed new methods for their synthesis, established their characteristic physical and chemical properties, and are currently endeavoring to exploit those properties which are unique to the complexes. During our investigations, the authors have discovered that the Cp[prime]M(NO)R[sub 2] complexes react with a variety of small molecules, often in an unprecedented manner. The authors have also established several unique transformations that aremore » not exhibited by all members of this group of complexes. Indeed, the authors found that the chemical properties of these systems are often dependent on the metal, the nature of the R groups, and the type of Cp[prime] ligand. In this Account the authors summarize the synthesis, characterization, comparative reactivity, and distinctive chemical properties of the 16-electron Cp[prime]M(NO)R[sub 2] complexes known to date. 35 refs., 7 figs.« less

Formation of novel transition metal hydride complexes with ninefold hydrogen coordination

PubMed Central

Takagi, Shigeyuki; Iijima, Yuki; Sato, Toyoto; Saitoh, Hiroyuki; Ikeda, Kazutaka; Otomo, Toshiya; Miwa, Kazutoshi; Ikeshoji, Tamio; Orimo, Shin-ichi

2017-01-01

Ninefold coordination of hydrogen is very rare, and has been observed in two different hydride complexes comprising rhenium and technetium. Herein, based on a theoretical/experimental approach, we present evidence for the formation of ninefold H- coordination hydride complexes of molybdenum ([MoH9]3−), tungsten ([WH9]3−), niobium ([NbH9]4−) and tantalum ([TaH9]4−) in novel complex transition-metal hydrides, Li5MoH11, Li5WH11, Li6NbH11 and Li6TaH11, respectively. All of the synthesized materials are insulated with band gaps of approximately 4 eV, but contain a sufficient amount of hydrogen to cause the H 1s-derived states to reach the Fermi level. Such hydrogen-rich materials might be of interest for high-critical-temperature superconductivity if the gaps close under compression. Furthermore, the hydride complexes exhibit significant rotational motions associated with anharmonic librations at room temperature, which are often discussed in relation to the translational diffusion of cations in alkali-metal dodecahydro-closo-dodecaborates and strongly point to the emergence of a fast lithium conduction even at room temperature. PMID:28287143

Vaporisation of candidate nuclear fuels and targets for transmutation of minor actinides

NASA Astrophysics Data System (ADS)

Gotcu-Freis, P.; Hiernaut, J.-P.; Colle, J.-Y.; Nästrén, C.; Carretero, A. Fernandez; Konings, R. J. M.

2011-04-01

The thermal stability and high temperature behaviour of candidate fuels and targets for transmutation of minor actinides has been investigated. Zirconia-based solid solution, MgO-based CERCER and molybdenum-based CERMET fuels containing Am and/or Pu in various concentrations were heated up to 2700 K in a Knudsen cell coupled with a quadrupole mass spectrometer, to measure their vapour pressure and vapour composition. The results reveal that the vaporisation of the actinides from the samples is not only determined by the thermodynamics of the system but is also related to the dynamic evolution of multi-component mixtures with complex composition or microstructure.

MULTIPLE EPISODES OF IGNEOUS ACTIVITY, MINERALIZATION, AND ALTERATION IN THE WESTERN TUSHAR MOUNTAINS, UTAH.

USGS Publications Warehouse

Cunningham, Charles G.; Steven, Thomas A.; Campbell, David L.; Naeser, Charles W.; Pitkin, James A.; Duval, Joseph S.

1984-01-01

The report outlines the complex history of igneous activity and associated alteration and mineralization in the western Tushar Mountains, Utah and pointss out implciations for minerals exploration. The area has been subjected to recurrent episodes of igneous intrusion, hydrothermal alteration, and mineralization, and the mineral-resource potential of the different mineralized areas is directly related to local geologic history. The mineral commodities to be expected vary from one hydrothermal system to another, and from one depth to another within any given system. Uranium and molybdenum seem likely to have the greatest economic potential, although significant concentrations of gold may also exist.

Resource potential for commodities in addition to Uranium in sandstone-hosted deposits: Chapter 13

USGS Publications Warehouse

Breit, George N.

2016-01-01

Sandstone-hosted deposits mined primarily for their uranium content also have been a source of vanadium and modest amounts of copper. Processing of these ores has also recovered small amounts of molybdenum, rhenium, rare earth elements, scandium, and selenium. These deposits share a generally common origin, but variations in the source of metals, composition of ore-forming solutions, and geologic history result in complex variability in deposit composition. This heterogeneity is evident regionally within the same host rock, as well as within districts. Future recovery of elements associated with uranium in these deposits will be strongly dependent on mining and ore-processing methods.

Recognition of the geologic framework of porphyry deposits on ERTS-1 imagery. [copper/molybdenum porphyrys

NASA Technical Reports Server (NTRS)

Wilson, J. C. (Principal Investigator)

1974-01-01

The author has identified the following significant results. Three major tectonic provinces have been mapped by geologic photointerpretation of ERTS-1 imagery over the Ok Tedi test site. These areas can be characterized as follows: (1) A broad area of low relief and mature topography suggesting a history of relative tectonic stability. (2) A narrow belt of moderate to high relief, broad open folds and prominent linear features. The Mount Fubilan-type porphyry copper deposits and recent volcanic effusive centers occur in this province. (3) A heterogeneous zone of high relief and high drainage density suggestive of relative structural complexity.

Synthesis and application of a new fluorous-tagged ammonia equivalent.

PubMed

Nielsen, Simon D; Smith, Garrick; Begtrup, Mikael; Kristensen, Jesper L

2010-04-19

A novel fluorous-tagged ammonia equivalent has been developed. It is based on a nitrogen-oxygen bond, which can be cleaved in a traceless manner by a molybdenum complex or samarium diiodide. The application in the synthesis of ureas, amides, sulfonamides, and carbamates is described. The scope of the fluorous N-O linker is exemplified by the synthesis of itopride, a drug used for the treatment of functional dyspepsia. Itopride was synthesized with the aid of fluorous purification methods and the product was isolated in good overall yield, with high purity. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1993-08-31

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1,800 C and 30 PSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1993-01-01

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1994-01-01

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2200.degree. C. and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1994-08-09

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2,200 C and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made. 1 fig.

Genesis and evolution of the Baid al Jimalah tungsten deposit, Kingdom of Saudi Arabia

USGS Publications Warehouse

Kamilli, Robert J.

1986-01-01

Baid al Jimalah is similar in character and origin to other tungsten-tin greisen deposits in the world, especially the Hemerdon deposit in Devon, England. It is also analogous to Climax-type molybdenum deposits, which contain virtually identical mineral assemblages, but with the relative intensities of the molybdenum and tungsten mineralization reversed.

USSR Report, Earth Sciences.

DTIC Science & Technology

1985-04-19

Specifics of Geology of Saryshagan Molybdenum- Copper - Porphyry Deposit (Northwestern Balkash Area) (Yu. K. Kudryavtsev, V. V. Izotov, et al...SPECIFICS’OF GEOLOGY OF SARYSHAGAN MOLYBDENUM- COPPER - PORPHYRY DEPOSIT (NORTHWESTERN BALKASH AREA) Moscow IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY... Copper , Lead and Cadmium in Ooze Water of Central Pacific (A. Ye. Kosov, T. P. Demidova; GEOKHIMIYA, No 10, Oct 84) 37 Nickel Minerals in

Development of the copper and molybdenum industries and the Armenian economy

USGS Publications Warehouse

Bond, A.R.; Levine, R.M.

1997-01-01

Production of copper and molybdenum in Armenia is examined, with special emphasis on the location of major deposits, former and proposed future centers of processing, and contribution of metals exports to the country's foreign trade revenues. Particular emphasis is placed on the impacts on these industries of the disruption of economic ties resulting from the dissolution of the USSR and an economic crisis precipitated by a major earthquake, Armenia's tension with Azerbaijan over armed conflict in Nagorno-Karabakh and surrounding areas in Azerbaijan, an economic blockade imposed by Turkey and Azerbaijan, and a consequent severe energy crisis. The paper highlights developments in the mid-1990s in copper and molybdenum and in the recent expansion of trade relations with Iran.

Development and tests of molybdenum armored copper components for MITICA ion source

NASA Astrophysics Data System (ADS)

Pavei, Mauro; Böswirth, Bernd; Greuner, Henri; Marcuzzi, Diego; Rizzolo, Andrea; Valente, Matteo

2016-02-01

In order to prevent detrimental material erosion of components impinged by back-streaming positive D or H ions in the megavolt ITER injector and concept advancement beam source, a solution based on explosion bonding technique has been identified for producing a 1 mm thick molybdenum armour layer on copper substrate, compatible with ITER requirements. Prototypes have been recently manufactured and tested in the high heat flux test facility Garching Large Divertor Sample Test Facility (GLADIS) to check the capability of the molybdenum-copper interface to withstand several thermal shock cycles at high power density. This paper presents both the numerical fluid-dynamic analyses of the prototypes simulating the test conditions in GLADIS as well as the experimental results.

Evaluation of chromium oxide and molybdenum disulfide coatings in self-acting stops of an air-lubricated Rayleigh step thrust bearing

NASA Technical Reports Server (NTRS)

Nemeth, Z. N.

1974-01-01

Two coatings for a Rayleigh step thrust bearing were tested when coasting down and stopping under self-acting operation in air. The thrust bearing had an outside diameter of 8.9 cm (3.5 in.), an inside diameter of 5.4 cm (2.1 in.), and nine sectors. The load was 73 N (16.4 lbf). The load pressure was 19.1 kN/per square meter (2.77 lbf/per square inch) on the total thrust bearing area. The chromium oxide coating was good to 150 stops without bearing deterioration, and the molybdenum disulfide coating was good for only four stops before bearing deterioration. The molybdenum disulfide coated bearing failed after nine stops.

Composition for use in high-temperature hydrogen-fluorine environments and method for making the composition

DOEpatents

Kovach, L.; Holcombe, C.E.

1980-08-22

The present invention relates to a composition particularly suitable for use as structural components subject to high-temperature environments containing gaseous hydrogen and fluorine. The composition of the present invention consists essentially of lanthanum hexaboride-molybdenum diboride with dispersed silicon. The composition is formed by hot pressing a powder mixture of lanthanum hexaboride as the major constituent and molybdenum disilicide. This composition exhibits substantial resistance to thermal shock and corrosion in environments containing hydrogen and fluorine gases at material surface temperatures up to about 1850/sup 0/K. Upon exposure of the hot-pressed composition to high-temperature environments containing fluorine gases, a highly protective layer of lanthanum trifluoride containing dispersed molybdenum is formed on exposed surfaces of the composition.

Development and tests of molybdenum armored copper components for MITICA ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavei, Mauro, E-mail: mauro.pavei@igi.cnr.it; Marcuzzi, Diego; Rizzolo, Andrea

2016-02-15

In order to prevent detrimental material erosion of components impinged by back-streaming positive D or H ions in the megavolt ITER injector and concept advancement beam source, a solution based on explosion bonding technique has been identified for producing a 1 mm thick molybdenum armour layer on copper substrate, compatible with ITER requirements. Prototypes have been recently manufactured and tested in the high heat flux test facility Garching Large Divertor Sample Test Facility (GLADIS) to check the capability of the molybdenum-copper interface to withstand several thermal shock cycles at high power density. This paper presents both the numerical fluid-dynamic analysesmore » of the prototypes simulating the test conditions in GLADIS as well as the experimental results.« less

Development and tests of molybdenum armored copper components for MITICA ion source.

PubMed

Pavei, Mauro; Böswirth, Bernd; Greuner, Henri; Marcuzzi, Diego; Rizzolo, Andrea; Valente, Matteo

2016-02-01

In order to prevent detrimental material erosion of components impinged by back-streaming positive D or H ions in the megavolt ITER injector and concept advancement beam source, a solution based on explosion bonding technique has been identified for producing a 1 mm thick molybdenum armour layer on copper substrate, compatible with ITER requirements. Prototypes have been recently manufactured and tested in the high heat flux test facility Garching Large Divertor Sample Test Facility (GLADIS) to check the capability of the molybdenum-copper interface to withstand several thermal shock cycles at high power density. This paper presents both the numerical fluid-dynamic analyses of the prototypes simulating the test conditions in GLADIS as well as the experimental results.

Composition for use in high-temperature hydrogen-fluorine environments and method for making the composition

DOEpatents

Kovach, Louis; Holcombe, Cressie E.

1982-01-01

The present invention relates to a composition particularly suitable for as structural components subject to high-temperature environments containing gaseous hydrogen and fluorine. The composition of the present invention consists essentially of lanthanum hexaboride-molybdenum diboride with dispersed silicon. The composition is formed by hot pressing a powder mixture of lanthanum hexaboride as the major constituent and molybdenum disilicide. This composition exhibits substantial resistance to thermal shock and corrosion in environments containing hydrogen and fluorine gases at material surface temperatures up to about 1850.degree. K. Upon exposure of the hot-pressed composition to high-temperature environments containing fluorine gases, a highly protective layer of lanthanum trifluoride containing dispersed molybdenum is formed on exposed surfaces of the composition.

Fabrication of inorganic molybdenum disulfide fullerenes by arc in water

NASA Astrophysics Data System (ADS)

Sano, Noriaki; Wang, Haolan; Chhowalla, Manish; Alexandrou, Ioannis; Amaratunga, Gehan A. J.; Naito, Masakazu; Kanki, Tatsuo

2003-01-01

Closed caged fullerene-like molybdenum disulfide (MoS 2) nano-particles were obtained via an arc discharge between a graphite cathode and a molybdenum anode filled with microscopic MoS 2 powder submerged in de-ionized water. A statistical study of over 150 polyhedral fullerene-like MoS 2 nano-particles in plan view transmission electron microscopy revealed that the majority consisted of 2-3 layers with diameters of 5-15 nm. We show that the nano-particles are formed by seamless folding of MoS 2 sheets. A model based on the agglomeration of MoS 2 fragments over an extreme temperature gradient around a plasma ball in water is proposed to explain the formation of nano-particles.

Electrotransport and diffusivity of molybdenum, rhenium, tungsten, and zirconium in beta-thorium

NASA Technical Reports Server (NTRS)

Schmidt, F. A.; Beck, M. S.; Rehbein, D. K.; Conzemius, R. J.; Carlson, O. N.

1984-01-01

The electric mobilities, diffusivities, and effective valences were determined for molybdenum, rhenium, tungsten, and zirconium in beta-thorium. All four solutes migrated in the same direction as the electron flow. Rhenium and molybdenum were found to be very mobile, with tungsten somewhat slower. Zirconium was found to move at a rate near that of the self-diffusion of beta-thorium, viz., about 10 to the -11th sq m/s at 1500 C. The electromigration velocities showed a similar trend. A comparison was made between experimental data obtained by scanning laser mass spectrometry and theoretical transport equations for two purification experiments. Good agreement was obtained with both the concentration profile predicted by DeGroot and the purification ratio predicted by Verhoeven.

Materials Development for Auxiliary Components for Large Compact Mo/Au TES Arrays

NASA Technical Reports Server (NTRS)

Finkbeiner, F. m.; Chervenak, J. A.; Bandler, S. R.; Brekosky, R.; Brown, A. D.; Figueroa-Feliciano, E.; Iyomoto, N.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.;

The H-bond network surrounding the pyranopterins modulates redox cooperativity in the molybdenum-bisPGD cofactor in arsenite oxidase.

PubMed

Duval, Simon; Santini, Joanne M; Lemaire, David; Chaspoul, Florence; Russell, Michael J; Grimaldi, Stephane; Nitschke, Wolfgang; Schoepp-Cothenet, Barbara

2016-09-01

While the molybdenum cofactor in the majority of bisPGD enzymes goes through two consecutive 1-electron redox transitions, previous protein-film voltammetric results indicated the possibility of cooperative (n=2) redox behavior in the bioenergetic enzyme arsenite oxidase (Aio). Combining equilibrium redox titrations, optical and EPR spectroscopies on concentrated samples obtained via heterologous expression, we unambiguously confirm this claim and quantify Aio's redox cooperativity. The stability constant, Ks, of the Mo(V) semi-reduced intermediate is found to be lower than 10(-3). Site-directed mutagenesis of residues in the vicinity of the Mo-cofactor demonstrates that the degree of redox cooperativity is sensitive to H-bonding interactions between the pyranopterin moieties and amino acid residues. Remarkably, in particular replacing the Gln-726 residue by Gly results in stabilization of (low-temperature) EPR-observable Mo(V) with KS=4. As evidenced by comparison of room temperature optical and low temperature EPR titrations, the degree of stabilization is temperature-dependent. This highlights the importance of room-temperature redox characterizations for correctly interpreting catalytic properties in this group of enzymes. Geochemical and phylogenetic data strongly indicate that molybdenum played an essential biocatalytic roles in early life. Molybdenum's redox versatility and in particular the ability to show cooperative (n=2) redox behavior provide a rationale for its paramount catalytic importance throughout the evolutionary history of life. Implications of the H-bonding network modulating Molybdenum's redox properties on details of a putative inorganic metabolism at life's origin are discussed. Copyright © 2016. Published by Elsevier B.V.

40 CFR 421.224 - Standards of performance for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... plus vanadium plus pure grade molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead 5.463... produced Arsenic 80.952 36.108 Chromium 21.548 8.736 Lead 16.306 7.571 Nickel 32.031 21.548 Iron 69.887 35... pollution control. NSPS for the Secondary Molybdenum and Vanadium Subcategory Pollutant or pollutant...

40 CFR 421.224 - Standards of performance for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... plus vanadium plus pure grade molybdenum produced Arsenic 27.120 12.097 Chromium 7.219 2.927 Lead 5.463... produced Arsenic 80.952 36.108 Chromium 21.548 8.736 Lead 16.306 7.571 Nickel 32.031 21.548 Iron 69.887 35... pollution control. NSPS for the Secondary Molybdenum and Vanadium Subcategory Pollutant or pollutant...

Low activation ferritic alloys

DOEpatents

Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

1986-01-01

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Marine Corrosion.

DTIC Science & Technology

1985-04-24

cor- rosion resistant alloys such as molybdenum -containing stainless steels. For the latter the high degree of aeration in the splashing water...imposed by marine technology, such as elevated temperatures , tensile stresses, cyclic stresses, severe (tight) crevices, galvanic coupling and high ...corrosion in seawater in tight metal-to-non-metal crevices are titanium alloys 4, the high molybdenum nickel base alloys Hastelloy alloy C-276 and

Low activation ferritic alloys

DOEpatents

Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

1985-02-07

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

40 CFR 471.54 - Pretreatment standards for existing sources (PSES).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 12.1 Nickel 23.3 15.4 Fluoride 720 320 Molybdenum 80.0 41.4 (n) Alkaline cleaning spent baths... (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.635 0.334 Nickel 0.642 0.424 Fluoride 19.9 8.82 Molybdenum 2.21 1.14 (o) Alkaline cleaning rinse. Subpart E—PSES Pollutant or...

40 CFR 471.54 - Pretreatment standards for existing sources (PSES).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 12.1 Nickel 23.3 15.4 Fluoride 720 320 Molybdenum 80.0 41.4 (n) Alkaline cleaning spent baths... (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.635 0.334 Nickel 0.642 0.424 Fluoride 19.9 8.82 Molybdenum 2.21 1.14 (o) Alkaline cleaning rinse. Subpart E—PSES Pollutant or...

40 CFR 471.54 - Pretreatment standards for existing sources (PSES).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 12.1 Nickel 23.3 15.4 Fluoride 720 320 Molybdenum 80.0 41.4 (n) Alkaline cleaning spent baths... (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.635 0.334 Nickel 0.642 0.424 Fluoride 19.9 8.82 Molybdenum 2.21 1.14 (o) Alkaline cleaning rinse. Subpart E—PSES Pollutant or...

40 CFR 471.55 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2014 CFR

2014-07-01

... surface treated Copper 15.5 7.38 Nickel 6.66 4.48 Fluoride 720 320 Molybdenum 60.9 27.0 (n) Alkaline... monthly average mg/off-kg (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse...

40 CFR 471.55 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2011 CFR

2011-07-01

... surface treated Copper 15.5 7.38 Nickel 6.66 4.48 Fluoride 720 320 Molybdenum 60.9 27.0 (n) Alkaline... monthly average mg/off-kg (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse...

40 CFR 471.55 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... surface treated Copper 15.5 7.38 Nickel 6.66 4.48 Fluoride 720 320 Molybdenum 60.9 27.0 (n) Alkaline... monthly average mg/off-kg (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse...

40 CFR 471.54 - Pretreatment standards for existing sources (PSES).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 12.1 Nickel 23.3 15.4 Fluoride 720 320 Molybdenum 80.0 41.4 (n) Alkaline cleaning spent baths... (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.635 0.334 Nickel 0.642 0.424 Fluoride 19.9 8.82 Molybdenum 2.21 1.14 (o) Alkaline cleaning rinse. Subpart E—PSES Pollutant or...

40 CFR 471.55 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2012 CFR

2012-07-01

... surface treated Copper 15.5 7.38 Nickel 6.66 4.48 Fluoride 720 320 Molybdenum 60.9 27.0 (n) Alkaline... monthly average mg/off-kg (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse...

40 CFR 471.55 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2013 CFR

2013-07-01

... surface treated Copper 15.5 7.38 Nickel 6.66 4.48 Fluoride 720 320 Molybdenum 60.9 27.0 (n) Alkaline... monthly average mg/off-kg (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse...

40 CFR 471.54 - Pretreatment standards for existing sources (PSES).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 12.1 Nickel 23.3 15.4 Fluoride 720 320 Molybdenum 80.0 41.4 (n) Alkaline cleaning spent baths... (pounds per million off-pounds) of refractory metals alkaline cleaned Copper 0.635 0.334 Nickel 0.642 0.424 Fluoride 19.9 8.82 Molybdenum 2.21 1.14 (o) Alkaline cleaning rinse. Subpart E—PSES Pollutant or...

Advances in Low Carbon, High Strength Ferrous Alloys

DTIC Science & Technology

1993-04-01

35 TABLES 1. Specified chemical compositions and mechanical properties for GMAW/SAW/ GTAW wire electrodes, MIL-XXXS type, for welding...minimum service temperature of +300 F. The chromium and molybdenum additions improved hardenability and promoted the formation of mar- tensite in thick...alloying ele- ments ( chromium , nickel and molybdenum) are required, especially for thick sections. Production of high strength steel plate for military

Associating root morphology and physiology with molybdenum uptake of three rice varieties grown in three pH regimes

USDA-ARS?s Scientific Manuscript database

Molybdenum (Mo) is an essential micronutrient required in very low amounts (0.1-1 µg g-1 dry weight) in plants. It acts as a co-factor of certain enzymes carrying out redox reactions and is required for various physiological, biochemical and metabolic processes. However, its accumulation in excess l...

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

1990-01-01

Compositions of matter consisting of matrix matrials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

1991-01-01

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... process alone or in conjunction with other processes, for the beneficiation of copper, lead, zinc, gold, silver, or molybdenum ores, or any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach processes to extract copper from ores or ore waste materials; and (4) Mills...

40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach... operations other than placer deposits; (2) Mills that use the froth-flotation process alone or in conjunction... not apply to discharges from the Quartz Hill Molybdenum Project in the Tongass National Forest, Alaska...

40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach... operations other than placer deposits; (2) Mills that use the froth-flotation process alone or in conjunction... not apply to discharges from the Quartz Hill Molybdenum Project in the Tongass National Forest, Alaska...

40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... process alone or in conjunction with other processes, for the beneficiation of copper, lead, zinc, gold, silver, or molybdenum ores, or any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach processes to extract copper from ores or ore waste materials; and (4) Mills...

40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... process alone or in conjunction with other processes, for the beneficiation of copper, lead, zinc, gold, silver, or molybdenum ores, or any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach processes to extract copper from ores or ore waste materials; and (4) Mills...

Zirconia-molybdenum disilicide composites

DOEpatents

Petrovic, John J.; Honnell, Richard E.

1991-01-01

Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

[Study on the determination of trace gallium in molybdenum-coated pyrolytic graphite tube by electrothermal absorption spectrometry].

PubMed

Huang, Yu-an; Zhou, Fang-qin; Long, Si-hua; Yang, Liu

2004-02-01

The effects on gallium atomization in the pyrolytic graphite tube imposed by different matrix modifiers and different coatings were discussed detailedly in this paper. In the presence of matrix modifier of Ni(NO3)2 the matrix interference was eliminated efficiently. The pyrolytic graphite tubes were coated differently with lanthanum, zirconium, and molybdenum to avoid producing gallium carbide. Results showed that the tube with molybdenum coating was the best. On this basis, the mechanism of gallium atomization in the molybdenum-coated pyrolytic graphite tube using Ni(NO3)2 as a matrix modifier was studied furthermore; in addition, the parameters of the operation were optimized. As a result, a new method improved in many aspects was developed to detect trace gallium in complicated sample of gangue. The outcomes of practical applications indicated that the method could satisfy the requests of analysis and that the manipulations were simple to achieve. The characteristic content, the detection limit, and the adding recoveries were 2.12 x 10(-11) g, 1.4 x 10(-10) g and 97.4%-102.7% respectively, and the relative standard deviation was less than or equal to 3.6% (n = 11).

Selective recovery of molybdenum from spent HDS catalyst using oxidative soda ash leach/carbon adsorption method.

PubMed

Park, Kyung Ho; Mohapatra, D; Reddy, B Ramachandra

2006-11-16

The petroleum refining industry makes extensive use of hydroprocessing catalysts. These catalysts contain environmentally critical and economically valuable metals such as Mo, V, Ni and Co. In the present study, a simple hydrometallurgical processing of spent hydrodesulphurization (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixture was investigated. Recovery of molybdenum was largely dependent on the concentrations of Na2CO3 and H2O2 in the reaction medium, which in turn controls the pH of leach liquor and the presence of Al and Ni as impurities. Under the optimum leaching conditions (40 g L(-1) Na2CO3, 6 vol.% H2O2, room temperature, 1h) about 85% recovery of Mo was achieved. The leach liquor was processed by the carbon adsorption method, which selectively adsorbs Mo at pH around 0.75. Desorption of Mo was selective at 15 vol.% NH4OH. With a single stage contact, it was found possible to achieve >99%, adsorption and desorption efficiency. Using this method, recovery of molybdenum as MoO3 product of 99.4% purity was achieved.

Molybdenum Oxide Nitrides of the Mo2(O,N,□)5 Type: On the Way to Mo2O5.

PubMed

Weber, Dominik; Huber, Manop; Gorelik, Tatiana E; Abakumov, Artem M; Becker, Nils; Niehaus, Oliver; Schwickert, Christian; Culver, Sean P; Boysen, Hans; Senyshyn, Anatoliy; Pöttgen, Rainer; Dronskowski, Richard; Ressler, Thorsten; Kolb, Ute; Lerch, Martin

2017-08-07

Blue-colored molybdenum oxide nitrides of the Mo 2 (O,N,□) 5 type were synthesized by direct nitridation of commercially available molybdenum trioxide with a mixture of gaseous ammonia and oxygen. Chemical composition, crystal structure, and stability of the obtained and hitherto unknown compounds are studied extensively. The average oxidation state of +5 for molybdenum is proven by Mo K near-edge X-ray absorption spectroscopy; the magnetic behavior is in agreement with compounds exhibiting Mo V O 6 units. The new materials are stable up to ∼773 K in an inert gas atmosphere. At higher temperatures, decomposition is observed. X-ray and neutron powder diffraction, electron diffraction, and high-resolution transmission electron microscopy reveal the structure to be related to VNb 9 O 24.9 -type phases, however, with severe disorder hampering full structure determination. Still, the results demonstrate the possibility of a future synthesis of the potential binary oxide Mo 2 O 5 . On the basis of these findings, a tentative suggestion on the crystal structure of the potential compound Mo 2 O 5 , backed by electronic-structure and phonon calculations from first principles, is given.

Effect of molybdenum, vanadium, boron on mechanical properties of high chromium white cast iron in as-cast condition

NASA Astrophysics Data System (ADS)

Nurjaman, F.; Sumardi, S.; Shofi, A.; Aryati, M.; Suharno, B.

2016-02-01

In this experiment, the effect of the addition carbide forming elements on high chromium white cast iron, such as molybdenum, vanadium and boron on its mechanical properties and microstructure was investigated. The high chromium white cast iron was produced by casting process and formed in 50 mm size of grinding balls with several compositions. Characterization of these grinding balls was conducted by using some testing methods, such as: chemical and microstructure analysis, hardness, and impact test. From the results, the addition of molybdenum, vanadium, and boron on high chromium white cast iron provided a significant improvement on its hardness, but reduced its toughness. Molybdenum induced fully austenitic matrix and Mo2C formation among eutectic M7C3 carbide. Vanadium was dissolved in the matrix and carbide. While boron was played a role to form fine eutectic carbide. Grinding balls with 1.89 C-13.1 Cr-1.32 Mo-1.36 V-0.00051 B in as-cast condition had the highest hardness, which was caused by finer structure of eutectic carbide, needle like structure (upper bainite) matrix, and martensite on its carbide boundary.

The wire material and cross-section effect on double delta closing loops regarding load and spring rate magnitude: an in vitro study.

PubMed

Ferreira, M do A

1999-03-01

The mechanical behavior of orthodontics closing loops, with three different wire materials (stainless steel, cobalt-chromium and titanium-molybdenum) and with different cross-sections and a double delta design, was studied in tension tests. The springs were stress-relieved, except the titanium-molybdenum wires. There were 72 sample springs, divided into 33 stainless steel, 26 cobalt-chromium and 13 titanium-molybdenum, activated at 0.5 mm intervals, from neutral position to 3.0 mm. It was hypothesized that loads, after spring activation, and spring rate, are dependent on cross-section, wire material, and activation. The analysis of variance and the Tukey-Kramer test were applied to verify the differences between all coupled averages of the loads. Regression analysis was also used to verify if closing loops behavior was in accordance with Hooke's law and to obtain the spring rate. The results show that the loads are dependent on activation, cross-section, and wire material. Titanium-molybdenum 0.017 x 0.025 inch (Ormco) springs showed the smallest loads and the best spring rate. (beta = 84.9 g/mm)

Investigation of molybdenum-crosslinker interfaces for affinity based electrochemical biosensing applications

NASA Astrophysics Data System (ADS)

Kamakoti, Vikramshankar; Shanmugam, Nandhinee Radha; Tanak, Ambalika Sanjeev; Jagannath, Badrinath; Prasad, Shalini

2018-04-01

Molybdenum (Mo) has been investigated for implementation as an electrode material for affinity based biosensing towards devloping flexibe electronic biosensors. Treatment of the native oxide of molybdenum was investigated through two surface treatment strategies namely thiol and carbodiimide crosslinking methods. The binding interaction between cross-linker molecules and Mo electrode surface has been characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and optical microscopy. The efficacy of treatment of Mo with its native oxide using carbodiimide cross linking methodology was established. The carbodiimide cross-linking chemistry was found to possess better surface coverage and binding affinity with Molybdenum electrode surface when compared to thiol cross-linking chemistry.Electrochemical characterization of Mo electrode using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltametry (CV) techniques was performed to evaluate the effect of ionic properties of solution buffer on the Mo electrode's performance. Affinity based biosensing of C-Reactive Protein (CRP) has been demonstrated on a flexible nanoporous polymeric substrate with detection threshold of 100 pg/ml in synthetic urine buffer medium. The biosensor has been evaluated to be developed as a dipstick based point of care device for detection of biomarkers in urine.

Friction and wear of radiofrequency-sputtered borides, silicides, and carbides

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1978-01-01

The friction and wear properties of several refractory compound coatings were examined. These compounds were applied to 440 C bearing steel surfaces by radiofrequency (RF) sputtering. The refractory compounds were the titanium and molybdenum borides, the titanium and molybdenum silicides, and the titanium, molybdenum, and boron carbides. Friction testing was done with a pin-on-disk wear apparatus at loads from 0.1 to 5.0 newtons. Generally, the best wear properties were obtained when the coatings were bias sputtered onto 440 C disks that had been preoxidized. Adherence was improved because of the better bonding of the coatings to the iron oxide formed during preoxidation. As a class the carbides provided wear protection to the highest loads. Titanium boride coatings provided low friction and good wear properties to moderate loads.

Manufacturing of calcium, lithium and molybdenum targets for use in nuclear physics experiments

NASA Astrophysics Data System (ADS)

Kheswa, N. Y.; Papka, P.; Buthelezi, E. Z.; Lieder, R. M.; Neveling, R.; Newman, R. T.

2010-02-01

This paper describes methods used in the manufacturing of chemically reactive targets such as calcium ( natCa), lithium-6 ( 6Li) and molybdenum-97 ( 97Mo) for nuclear physics experiments at the iThemba LABS cyclotron facility (Faure, South Africa). Due to the chemical properties of these materials a suitable and controlled environment was established in order to minimize oxygen contamination of targets. Calcium was prepared by means of vacuum evaporation while lithium was cold rolled to a desired thickness. In the case of molybdenum, the metallic powder was melted under vacuum using an e-gun followed by cold rolling of the metal bead to a desired thickness. In addition, latest developments toward the establishment of a dedicated nuclear physics target laboratory are discussed.

Static strength of molybdenum to 92 GPa under radial X-ray diffraction

NASA Astrophysics Data System (ADS)

Xiong, L.; Tu, P.; Li, B.; Wu, S. Y.; Hao, J. B.; Bai, L. G.; Li, X. D.; Liu, J.

2018-06-01

The high-pressure strength of molybdenum (Mo) to 92 GPa has been studied by radial X-ray diffraction (RXRD) technique. The ratio of t/G is found to decrease above ˜24 GPa, showing the yield of Mo which is caused by plastic deformation at this pressure. Combined with high-pressure shear modulus, it was found that the differential stress corresponding to the yield of Mo at 24 GPa due to plastic deformation is 1.73 GPa. The second increase of t values occurs after ˜66 GPa, suggesting the strength of Mo with a differential stress of ˜1.93 GPa. In addition, the maximum difference stress of molybdenum at 87 GPa is 3.01 GPa.

Tunable Chiroptical Properties from the Plasmonic Band to Metal-Ligand Charge Transfer Band of the Cysteine Capped Molybdenum Oxide Nanoparticles.

PubMed

Li, Yiwen; Cheng, Jiaji; Li, Jiagen; Zhu, Xi; He, TingChao; Chen, Rui; Tang, Zikang

2018-06-25

Understanding the interactions between a semiconducting nanocrystal surface and chiral anchoring molecules could resolve the mechanism of chirality induction in nanoscale and facilitate the rational design of chiral semiconducting materials for chiroptics. Herein, we present chiral molybdenum oxide nanoparticles in which chirality is transferred via a bio-to-nano approach. With facile controlling on the amount of chiral cysteine molecules under redox treatment, circular dichroism (CD) signals are generated in plasmon region and metal-ligand charge transfer band. The obtained enhanced CD signals with tunable line-shapes illustrate the possibility of using chiral molybdenum oxide nanoparticles as potentials for chiral semiconductor nanosensors, optoelectronics and photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation and determination of molybdenum by inductively coupled plasma optical emission spectrometry using quercetin immobilization on silica gel

NASA Astrophysics Data System (ADS)

Azeredo, Laerte C.; Azeredo, Maria Aparecida A.; Castro, Rosane N.; Saldanha, Marcelo Francisco C.; Perez, Daniel V.

2002-12-01

A new method is described for the separation of molybdenum based on its chelation in a column packed with quercetin, immobilized on silica gel in a slightly acidic medium (pH 5.0). Recovery ranged from 95% (NIST 1515 apple leaves) to 99% (deionized, distilled water; DDW) with an absolute blank of 27.5±1.6 pg obtained for the analysis of DDW. Detection limits, absolute and relative, based on a 5.0-ml sample volume were 4.8 pg and 1 ng l -1, respectively. Results are presented for molybdenum determination in two standard reference materials, NIST 1515 and NIST 1547 peach leaves, using simple calibration curves for quantification. α-Benzoinoxime was used as the eluent.

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

NASA Astrophysics Data System (ADS)

Wagner, Meghan; Chappaz, Anthony; Lyons, Timothy W.

2017-06-01

Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth's history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes-many containing organic ligands-we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H2S(aq)] < 11 μM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO3, MoOxS4-x2- (intermediate thiomolybdates), and [MoOx(cat)4-x]2- (cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS42- (tetrathiomolybdate).

Shallow ground-water flow, water levels, and quality of water, 1980-84, Cowles Unit, Indiana Dunes National Lakeshore

USGS Publications Warehouse

Cohen, D.A.; Shedlock, R.J.

1986-01-01

Since the settling ponds were sealed, the concentration of boron has decreased while concentrations of cadmium, arsenic, zinc, and molybdenum in shallow ground water downgradient of the ponds show no definite trends in time. Arsenic, boron and molybdenum have remained at concentrations above those of shallow ground water in areas unaffected by settling-pond seepage.

Performance and Safety Characteristics of Lithium-molybdenum Disulfide Cells

NASA Technical Reports Server (NTRS)

Stiles, J. A.

1984-01-01

The lithium-molybdenum disulfide system offers attractive characteristics including high rate capability, successful operation up to 75 C, a very low self-discharge rate, a good cycle life and safety characteristics which compare favorably to those of other lithium cells. Moreover, the materials and manufacturing costs for the system is effectively controlled, so the cells should ultimately be competitive with currently marketed rechargeable cells.

Determination of rhenium in molybdenite by X-ray fluorescence: A combined chemical-spectrometric technique.

PubMed

Solt, M W; Wahlberg, J S; Myers, A T

1969-01-01

Rhenium in molybdenite is separated from molybdenum by distillation of rhenium heptoxide from a perchloric-sulphuric acid mixture. It is concentrated by precipitation of the sulphide and then determined by X-ray fluorescence. From 3 to 1000 microg of rhenium can be measured with a precision generally within 2%. The procedure tolerates larger amounts of molybdenum than the usual colorimetric methods.

40 CFR 471.52 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 320 Molybdenum 60.9 27.0 (n) Alkaline cleaning spent baths. Subpart E—BAT Pollutant or pollutant... refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse. Subpart E—BAT Pollutant or pollutant property Maximum for any 1 day...

40 CFR 471.52 - Effluent limitations representating the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 320 Molybdenum 60.9 27.0 (n) Alkaline cleaning spent baths. Subpart E—BAT Pollutant or pollutant... refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse. Subpart E—BAT Pollutant or pollutant property Maximum for any 1 day...

40 CFR 471.52 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 320 Molybdenum 60.9 27.0 (n) Alkaline cleaning spent baths. Subpart E—BAT Pollutant or pollutant... refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse. Subpart E—BAT Pollutant or pollutant property Maximum for any 1 day...

40 CFR 471.52 - Effluent limitations representating the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 320 Molybdenum 60.9 27.0 (n) Alkaline cleaning spent baths. Subpart E—BAT Pollutant or pollutant... refractory metals alkaline cleaned Copper 0.428 0.204 Nickel 0.184 0.124 Fluoride 19.9 8.82 Molybdenum 1.68 0.745 (o) Alkaline cleaning rinse. Subpart E—BAT Pollutant or pollutant property Maximum for any 1 day...

Molybdenum Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

USGS Publications Warehouse

Eisler, R.

1989-01-01

Ecological and toxicological aspects of molybdenum (Mo) in the environment are briefly reviewed, with emphasis on fish and wildlife. Subtopics include sources and uses, chemical properties, mode of action, background concentrations in biological and nonbiological samples, and lethal and sublethal effects on terrestrial plants and invertebrates, aquatic organisms, birds, and mammals. Current recommendations for Mo and the protection of sensitive living resources are presented.

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, J.J.; Honnell, R.E.; Gibbs, W.S.

1991-12-03

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions are disclosed. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms. 3 figures.

Mild and efficient molybdenum-mediated Pauson-Khand-type reaction.

PubMed

Adrio, Javier; Rivero, Marta Rodríguez; Carretero, Juan Carlos

2005-02-03

[reaction: see text] The molybdenum-mediated Pauson-Khand reaction promoted by Mo(CO)3(DMF)3 takes place under very mild conditions in the absence of any promoter. High yields in Pauson-Khand adducts are obtained in the cyclization of a wide variety of functionalized 1,6- and 1,7-enynes. Enynes bearing electron withdrawing groups at the alkene terminus are particularly good substrates.

Reduction of N-hydroxy-sulfonamides, including N-hydroxy-valdecoxib, by the molybdenum-containing enzyme mARC.

PubMed

Havemeyer, Antje; Grünewald, Sanja; Wahl, Bettina; Bittner, Florian; Mendel, Ralf; Erdélyi, Péter; Fischer, János; Clement, Bernd

2010-11-01

Purification of the mitochondrial enzyme responsible for reduction of N-hydroxylated amidine prodrugs led to the identification of two newly discovered mammalian molybdenum-containing proteins, the mitochondrial amidoxime reducing components mARC-1 and mARC-2 (Gruenewald et al., 2008). These 35-kDa proteins represent a novel group of molybdenum proteins in eukaryotes as they form a molybdenum cofactor-dependent enzyme system consisting of three separate proteins (Havemeyer et al., 2006). Each mARC protein reduces N-hydroxylated compounds after reconstitution with the electron transport proteins cytochrome b(5) and b(5) reductase. In continuation of our drug metabolism investigations (Havemeyer et al., 2006; Gruenewald et al., 2008), we present data from reconstituted enzyme systems with recombinant human and native porcine enzymes showing the reduction of N-hydroxy-sulfonamides (sulfohydroxamic acids) to sulfonamides: the N-hydroxy-sulfonamide N-hydroxy-valdecoxib (N-hydroxy-4-[5-methyl-3-phenyl-4-isoxazolyl]-benzenesulfonamide) represents a novel cyclooxygenase (COX)-2 inhibitor and is therefore a drug candidate in the treatment of diseases associated with rheumatic inflammation, pain, and fever. It was synthesized as an analog of the known COX-2 inhibitor valdecoxib (4-[5-methyl-3-phenyl-4-isoxazolyl]-benzenesulfonamide) (Talley et al., 2000). N-Hydroxy-valdecoxib had low in vitro COX-2 activity but showed significant analgesic activity in vivo and a prolonged therapeutic effect compared with valdecoxib (Erdélyi et al., 2008). In this report, we demonstrate that N-hydroxy-valdecoxib is enzymatically reduced to its pharmacologically active metabolite valdecoxib. Thus, N-hydroxy-valdecoxib acts as prodrug that is activated by the molybdenum-containing enzyme mARC.

Concentrations of boron, molybdenum, and selenium in chinook salmon

USGS Publications Warehouse

Hamilton, Steven J.; Wiedmeyer, Raymond H.

1990-01-01

The concentrations of boron, molybdenum, and selenium in young chinook salmon Oncorhynchus tshawytscha were determined in three partial life cycle chronic toxicity studies. In each study, fish were exposed to a mixture of boron, molybdenum, selenate, and selenite in the proportions found in subsurface agricultural drainage water in the basin of the San Joaquin Valley, California. Tests were conducted in well water and in site-specific fresh and brackish waters. No boron or molybdenum was detected in fish exposed to concentrations as high as 6,046 μg boron/L and 193 μg molybdenum/L for 90 d in well water or fresh water; however, whole-body concentrations of selenium increased with increasing exposure concentrations in well water and fresh water, but not in brackish water. Concentrations of selenium in chinook salmon were strongly correlated with reduced survival and growth of fish in well water and with reduced survival in a 15-d seawater challenge test of fish from fresh water. Concentrations of selenium in fish seemed to reach a steady state after 60 d of exposure in well water or fresh water. Fish in brackish water had only background concentrations of selenium after 60 d of exposure, and no effects on survival and growth in brackish water or on survival in a 10-d seawater challenge test were exhibited. This lack of effect in brackish water was attributed to initiation of the study with advanced fry, which were apparently better able to metabolize the trace element mixture than were the younger fish used in studies with well water and fresh water. In all three experimental waters, concentration factors (whole-body concentration/waterborne concentration) for selenium decreased with increasing exposure concentrations, suggesting decreased uptake or increased excretion, or both, of selenium at the higher concentrations.

Purification and properties of formate dehydrogenase from Pseudomonas aeruginosa. Electron-paramagnetic-resonance studies on the molybdenum centre.

PubMed Central

Gadsby, P M; Greenwood, C; Coddington, A; Thomson, A J; Godfrey, C

1987-01-01

Formate dehydrogenase from Pseudomonas aeruginosa contains molybdenum, a [4Fe-4S] cluster and cytochrome b. This paper reports the detection of molybdenum as Mo(V) by e.p.r. spectroscopy. In order to generate Mo(V) signals, addition of amounts of excess formate varying between 10- and 50-fold over enzyme, followed by 200-fold excess of sodium dithionite, were used. Two Mo(V) species were observed. One, the major component, has g1 = 2.012, g2 = 1.985 and g3 = 1.968, appeared at low concentrations of formate and increased linearly in intensity with increasing concentrations of formate up to 25-fold excess over the enzyme. At higher formate concentration this signal disappeared. The appearance and disappearance of this Mo(V) signal seems to parallel the state of reduction of the [4Fe-4S] clusters. A second, minor, Mo(V) species with g-values g1 = 1.996, g2 = 1.981 and g3 = 1.941 appears at a constant level during the formate-dithionite titration. No evidence has been obtained for nuclear hyperfine coupling to protons. The major Mo(V) species has unusual e.p.r. signals compared with other molybdenum-containing enzymes, except for that observed in the formate dehydrogenase from Methanobacterium formicicum [Barber, Siegel, Schauer, May & Ferry (1983) J. Biol. Chem. 258, 10839-10845]. The present work suggests that the enzyme is acting as a CO2 reductase, with dithionite as an electron donor to a [4Fe-4S] cluster, which in turn donates electrons to molybdenum, producing a Mo(V) species with CO2 bound to the metal. PMID:3038082

Retention of Sputtered Molybdenum on Ion Engine Discharge Chamber Surfaces

NASA Technical Reports Server (NTRS)

Sovey, James S.; Dever, Joyce A.; Power, John L.

2001-01-01

Grit-blasted anode surfaces are commonly used in ion engines to ensure adherence of sputtered coatings. Next generation ion engines will require higher power levels, longer operating times, and thus there will likely be thicker sputtered coatings on their anode surfaces than observed to date on 2.3 kW-class xenon ion engines. The thickness of coatings on the anode of a 10 kW, 40-centimeter diameter thruster, for example, may be 22 micrometers or more after extended operation. Grit-blasted wire mesh, titanium, and aluminum coupons were coated with molybdenum at accelerated rates to establish coating stability after the deposition process and after thermal cycling tests. These accelerated deposition rates are roughly three orders of magnitude more rapid than the rates at which the screen grid is sputtered in a 2.3 kW-class, 30-centimeter diameter ion engine. Using both RF and DC sputtering processes, the molybdenum coating thicknesses ranged from 8 to 130 micrometers, and deposition rates from 1.8 micrometers per hour to 5.1 micrometers per hour. In all cases, the molybdenum coatings were stable after the deposition process, and there was no evidence of spalling of the coatings after 20 cycles from about -60 to +320 C. The stable, 130 micrometer molybdenum coating on wire mesh is 26 times thicker than the thickest coating found on the anode of a 2.3 kW, xenon ion engine that was tested for 8200 hr. Additionally, this coating on wire mesh coupon is estimated to be a factor of greater than 4 thicker than one would expect to obtain on the anode of the next generation ion engine which may have xenon throughputs as high as 550 kg.

Ternary cobalt-molybdenum-zirconium coatings for alternative energies

NASA Astrophysics Data System (ADS)

Yar-Mukhamedova, Gulmira; Ved', Maryna; Sakhnenko, Nikolay; Koziar, Maryna

2017-11-01

Consistent patterns for electrodeposition of Co-Mo-Zr coatings from polyligand citrate-pyrophosphate bath were investigated. The effect of both current density amplitude and pulse on/off time on the quality, composition and surface morphology of the galvanic alloys were determined. It was established the coating Co-Mo-Zr enrichment by molybdenum with current density increasing up to 8 A dm-2 as well as the rising of pulse time and pause duration promotes the content of molybdenum because of subsequent chemical reduction of its intermediate oxides by hydrogen ad-atoms. It was found that the content of the alloying metals in the coating Co-Mo-Zr depends on the current density and on/off times extremely and maximum Mo and Zr content corresponds to the current density interval 4-6 A dm-2, on-/off-time 2-10 ms. Chemical resistance of binary and ternary coatings based on cobalt is caused by the increased tendency to passivity and high resistance to pitting corrosion in the presence of molybdenum and zirconium, as well as the acid nature of their oxides. Binary coating with molybdenum content not less than 20 at.% and ternary ones with zirconium content in terms of corrosion deep index are in a group ;very proof;. It was shown that Co-Mo-Zr alloys exhibits the greatest level of catalytic properties as cathode material for hydrogen electrolytic production from acidic media which is not inferior a platinum electrode. The deposits Co-Mo-Zr with zirconium content 2-4 at.% demonstrate high catalytic properties in the carbon(II) oxide conversion. This confirms the efficiency of materials as catalysts for the gaseous wastes purification and gives the reason to recommend them as catalysts for red-ox processes activating by oxygen as well as electrode materials for red-ox batteries.

Structural properties of molybdenum-lead-borate glasses.

PubMed

Rada, M; Rada, S; Pascuta, P; Culea, E

2010-11-01

Glasses and glass ceramics in the system xMoO₃·(100 - x)[3B₂O₃·PbO] with 0 ≤ x ≤ 30 mol% have been prepared from melt quenching method and characterized by means of X-ray diffraction, FTIR, UV-VIS and EPR spectroscopy. We have examined and analyzed the effects of systematic molybdenum ions intercalation on lead-borate glasses and glass ceramics with interesting results. 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. The pronounced affinity towards molybdate anions yields the formation of the PbMoO₄ crystalline phase. Then, the excess of oxygen can be supported into the glass network by the formation of [MoO₆] and [Mo₂O₇] structural units. Pb²(+) ions with 6s² configuration show strong absorption in the ultraviolet due to parity allowed s²-sp transition and yield an absorption band centered at about 310 nm. The changes in the features of the absorption bands centered at about 310 nm can be explained as a consequence of the appearance of additional absorption shoulder due to photoinduced color centers in the glass such as the formation of borate-molybdate and lead-molybdate paramagnetic defect centers in the glasses. The concentration of molybdenum ions influences the shape and width of the EPR signals located at g ∼ 1.86, 1.91 and 5.19. The microenvironment of molybdenum ions in glasses is expected to have mainly sixfold coordination. However, there is a possibility of reduction of a part of molybdenum ions from the Mo⁶(+) to the Mo⁵(+) and Mo⁴(+) to the Mo³(+) states. Copyright © 2010 Elsevier B.V. All rights reserved.

A test for interfacial effects and stress transfer in ceramic matrix composites

NASA Technical Reports Server (NTRS)

1988-01-01

A test specimen was devised for measuring stress transfer between a high modulus fiber and a ceramic matrix. Single filaments of SiC were embedded in chemically vapor deposited SiC on a thin plate of molybdenum. The CVD overcoating which encapsulated the fiber was continuous with a coating of SiC on the molybdenum. When placed in a microtensile test device and loaded in the fiber direction, the fiber fracture characteristics provide information on the fiber/matrix adhesion and stress transfer. Problems were encountered due to the formation of a weak boundary between the SiC and the molybdenum which obviated any meaningful tensile tests. Also, the high CVD temperature used in fabricating these specimens restrict the fiber, matrix (and substrate) to materials having similar thermal coefficients of expansion in order to minimize thermal stresses.

Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

NASA Technical Reports Server (NTRS)

Moore, D G; Bolz, L H; Pitts, J W; Harrison, W N

1951-01-01

The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation. The application of a protective coating is one method that might be used to achieve this goal. In the present work, a number of chromium-frit-type coatings were studied. These were bonded to molybdenum specimens by firing in controlled atmospheres to temperatures in the range of 2400 to 2700 F.

Controlled optical properties via chemical composition tuning in molybdenum-incorporated β-Ga2O3 nanocrystalline films

NASA Astrophysics Data System (ADS)

Battu, Anil K.; Manandhar, S.; Shutthanandan, V.; Ramana, C. V.

2017-09-01

An approach is presented to design refractory-metal incorporated Ga2O3-based materials with controlled structural and optical properties. The molybdenum (Mo)-content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo-content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo-content results in amorphization. Chemically-induced band gap variability (Eg ∼ 1 eV) coupled with structure-modification indicates the electronic-structure changes in Ga-Mo-O. The linear relationship between chemical-composition and optical properties suggests that tailoring the optical-quality and performance of Ga-Mo-O films is possible by tuning the Mo-content.

Controlled optical properties via chemical composition tuning in molybdenum-incorporated β-Ga 2 O 3 nanocrystalline films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Battu, Anil K.; Manandhar, S.; Shutthanandan, V.

An approach is presented to design refractory-metal incorporated Ga2O3-based materials with controlled structural and optical properties. The molybdenum (Mo)-content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo-content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo-content results in amorphization. Chemically-induced band gap variability (Eg~1 eV) coupled with structure-modification indicates the electronic-structure changes in Ga-Mo-O. The linear relationship between chemical-composition and optical properties suggests that tailoring the optical-quality and performance of Ga-Mo-O films is possible by tuning the Mo-content.

Methods for the Identification of Aircraft Tubing of Plain Carbon Steel and Chromium-Molybdenum Steel

NASA Technical Reports Server (NTRS)

Mutchler, W H; Buzzard, R W

1930-01-01

The survey of the possibilities for distinguishing between plain carbon and chromium-molybdenum steel tubing included the Herbert pendulum hardness, magnetic, sparks, and chemical tests. The Herbert pendulum test has the disadvantages of all hardness tests in being limited to factory use and being applicable only to scale-free, normalized material. The small difference in the range of hardness values between plain carbon and chromium-molybdenum steels is likewise a disadvantage. The Rockwell hardness test, at present used in the industry for this purpose, is much more reliable. It may be concluded on the basis of the experiments performed that of all methods surveyed, spark testing appears to be, at present, the most suitable for factory use from the standpoint of speed, accuracy, nondestructiveness and reliability. It is also applicable for field use.

Effect of Prestraining of Recrystallization Temperature and Mechanical Properties of Commercial, Sintered, Wrought Molybdenum

NASA Technical Reports Server (NTRS)

Dike, Kenneth C; Long, Roger A

1953-01-01

Given three presumably identical lots of commercial, sintered, wrought molybdenum, the 1-hour recrystallization temperature of one lot remained above 2900 F by limiting the amount of effective restraining to 35 percent or less. Different recrystallization temperatures were obtained in various atmospheres, the highest in argon and the lowest in hydrogen. Metal thus fabricated and then stress-relieved possessed an ultimate tensile strength at room temperature within 10 percent of metal swaged 99 percent and also possessed equivalent ductility. At 1800 F, equivalent strength and ductility was obtained irrespective of the amount of swaging over the range of 10 to 99 percent. The amount of swaging greatly influenced the recrystallized grain size but the difference in grain size is not the major controlling factor which determines whether recrystallized molybdenum is ductile or brittle at room temperature.

Methods for the separation of rhenium, osmium and molybdenum applicable to isotope geochemistry

USGS Publications Warehouse

Morgan, J.W.; Golightly, D.W.; Dorrzapf, A.F.

1991-01-01

Effective methods are described for the chemical separation of rhenium, osmium and molybdenum. The methods are based on distillation and anion-exchange chromatography, and have been the basis for rhenium-osmium isotope studies of ore deposits and meteorites. Successful anion-exchange separation of osmium requires both recognition and careful control of the osmium species in solution; thus, distillation of osmium tetroxide from a mixture of sulfuric acid and hydrogen peroxide is preferred to anion-exchange. Distribution coefficients measured for perrhenate in sulfuric acid media are sufficiently high (Kd > 500) for rhenium to be directly loaded onto an ion-exchange column from a distillation residue and subsequently eluted with nitric acid. Polymerization of molybdenum species during elution is prevented by use of a solution that is 1M in hydrochloric acid and 1M in sodium chloride. ?? 1991.

High density hexagonal boron nitride prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1992-01-01

Boron nitride powder with less than or equal to the oxygen content of starting powder (down to 0.5% or less) is hot isostatically pressed in a refractory metal container to produce hexagonal boron nitride with a bulk density greater than 2.0 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.21 g/cc. Complex shapes can be made.

Exploiting the locality of periodic subsystem density-functional theory: efficient sampling of the Brillouin zone.

PubMed

Genova, Alessandro; Pavanello, Michele

2015-12-16

In order to approximately satisfy the Bloch theorem, simulations of complex materials involving periodic systems are made n(k) times more complex by the need to sample the first Brillouin zone at n(k) points. By combining ideas from Kohn-Sham density-functional theory (DFT) and orbital-free DFT, for which no sampling is needed due to the absence of waves, subsystem DFT offers an interesting middle ground capable of sizable theoretical speedups against Kohn-Sham DFT. By splitting the supersystem into interacting subsystems, and mapping their quantum problem onto separate auxiliary Kohn-Sham systems, subsystem DFT allows an optimal topical sampling of the Brillouin zone. We elucidate this concept with two proof of principle simulations: a water bilayer on Pt[1 1 1]; and a complex system relevant to catalysis-a thiophene molecule physisorbed on a molybdenum sulfide monolayer deposited on top of an α-alumina support. For the latter system, a speedup of 300% is achieved against the subsystem DTF reference by using an optimized Brillouin zone sampling (600% against KS-DFT).

Phosphate determination in seawater: toward an autonomous electrochemical method.

PubMed

Jońca, Justyna; León Fernández, Violeta; Thouron, Danièle; Paulmier, Aurélien; Graco, Michelle; Garçon, Véronique

2011-12-15

Initial steps to create an autonomous in situ electrochemical sensor for orthophosphate determination in seawater are presented. First, the optimal conditions to form the molybdophosphate complex in artificial seawater medium were determined by addition of sulphuric acid and sodium molybdate to the solution containing orthophosphate. Secondly, the anodic oxidation of molybdenum to form molybdate ions and protons was used to create the molybdophosphate complex without addition of any liquid reagents. The molybdophosphate complex is detectable by amperometry with an average precision of 2.2% for the concentration range found in the open ocean and the detection limit is 0.12 μM. Three solutions are proposed to address the silicate interferences issue and one of these methods is used for the natural samples collected in the coastal waters offshore Peru during the Pelagico 1011-12-BIC OLAYA cruise in November-December 2010. Results showed a good precision with an average of 2.5% and a reasonable deviation of the amperometric analysis as compared with colorimetric measurements (4.9%). Copyright © 2011 Elsevier B.V. All rights reserved.

Anticancer activity of metal complexes: involvement of redox processes.

PubMed

Jungwirth, Ute; Kowol, Christian R; Keppler, Bernhard K; Hartinger, Christian G; Berger, Walter; Heffeter, Petra

2011-08-15

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.

Anticancer Activity of Metal Complexes: Involvement of Redox Processes

PubMed Central

Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

2012-01-01

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

Constructing the wonders of the bacterial world: biosynthesis of complex enzymes.

PubMed

Sargent, Frank

2007-03-01

The prokaryotic cytoplasmic membrane not only maintains cell integrity and forms a barrier between the cell and its outside environment, but is also the location for essential biochemical processes. Microbial model systems provide excellent bases for the study of fundamental problems in membrane biology including signal transduction, chemotaxis, solute transport and, as will be the topic of this review, energy metabolism. Bacterial respiration requires a diverse array of complex, multi-subunit, cofactor-containing redox enzymes, many of which are embedded within, or located on the extracellular side of, the membrane. The biosynthesis of these enzymes therefore requires carefully controlled expression, assembly, targeting and transport processes. Here, focusing on the molybdenum-containing respiratory enzymes central to anaerobic respiration in Escherichia coli, recent descriptions of a chaperone-mediated 'proofreading' system involved in coordinating assembly and export of complex extracellular enzymes will be discussed. The paradigm proofreading chaperones are members of a large group of proteins known as the TorD family, and recent research in this area highlights common principles that underpin biosynthesis of both exported and non-exported respiratory enzymes.

76 FR 2332 - Stainless Steel Sheet and Strip in Coils From Mexico; Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-13

... molybdenum, and between 0.20 and 0.80 percent manganese. This steel also contains, by weight, phosphorus of 0..., aluminum of no less than 5.0 percent, phosphorus of no more than 0.045 percent, sulfur of no more than 0.03... molybdenum each comprise, by weight, 0.05 percent or less, with phosphorus and sulfur each comprising, by...

State summaries: Idaho

USGS Publications Warehouse

Gillerman, V.S.; Weaver, M.J.; Bennett, E.H.

2006-01-01

According to the United States Geological Survey (USGS), Idaho's preliminary nonfuel mineral production value jumped to $893 million in 2005. Principal minerals by value included molybdenum concentrates, phosphate rock, sand and gravel, silver and portland cement. The state ranked second in phosphate and garnet production, third in silver and pumice, fourth in molybdenum concentrate production, and 21st overall. Majority of mining increases for the year were spurred by demand for metals by China's growing economy.

E-Gun Technology

DTIC Science & Technology

1981-07-01

at high temperature . This situation was alleviated by removing most of the molybdenum sur- face contact by milling the clips to two 1/8 in. wide strips...sides. Molybdenum is used because its high - temperature capability and compatibility with barium dispenser cathodes, and the tabs are made thin to reduce...and operating temperatures than normal were required to overcome the high arrival rate of contami- nants such as oxygen for the relatively high

Molybdenum emission from impurity-induced m= 1 snake-modes on the Alcator C-Mod tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delgado-Aparicio, L.; MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139; Bitter, M.

2012-10-15

A suite of novel high-resolution spectroscopic imaging diagnostics has facilitated the identification and localization of molybdenum impurities as the main species during the formation and lifetime of m= 1 impurity-induced snake-modes on Alcator C-Mod. Such measurements made it possible to infer, for the first time, the perturbed radiated power density profiles from which the impurity density can be deduced.

Determination of rhenium in molybdenite by X-ray fluorescence. A combined chemical-spectrometric technique

USGS Publications Warehouse

Solt, M.W.; Wahlberg, J.S.; Myers, A.T.

1969-01-01

Rhenium in molybdenite is separated from molybdenum by distillation of rhenium heptoxide from a perchloric-sulphuric acid mixture. It is concentrated by precipitation of the sulphide and then determined by X-ray fluorescence. From 3 to 1000 ??g of rhenium can be measured with a precision generally within 2%. The procedure tolerates larger amounts of molybdenum than the usual colorimetric methods. ?? 1969.