Sample records for iridium hydrides

  1. Activation of C-H bonds in nitrones leads to iridium hydrides with antitumor activity.

    PubMed

    Song, Xiaoda; Qian, Yong; Ben, Rong; Lu, Xiang; Zhu, Hai-Liang; Chao, Hui; Zhao, Jing

    2013-08-22

    We report the design and synthesis of a series of new cyclometalated iridium hydrides derived from the C-H bond activation of aromatic nitrones and the biological evaluation of these iridium hydrides as antitumor agents. The nitrone ligands are based on the structure of a popular antioxidant, ?-phenyl-N-tert-butylnitrone (PBN). Compared to cisplatin, the iridium hydrides exhibit excellent antitumor activity on HepG2 cells. The metal-coordinated compound with the most potent anticancer activity, 2f, was selected for further analysis because of its ability to induce apoptosis and interact with DNA. During in vitro studies and in vivo efficacy analysis with tumor xenograft models in Institute of Cancer Research (ICR) mice, complex 2f exhibited antitumor activity that was markedly superior to that of cisplatin. Our results suggest, for the first time, that metal hydrides could be a new type of metal-based antitumor agent. PMID:23844605

  2. Nanoalloying bulk-immiscible iridium and palladium inhibits hydride formation and promotes catalytic performances

    NASA Astrophysics Data System (ADS)

    Zlotea, C.; Morfin, F.; Nguyen, T. S.; Nguyen, N. T.; Nelayah, J.; Ricolleau, C.; Latroche, M.; Piccolo, L.

    2014-08-01

    The hydrogen sorption properties of oxide-supported Ir-Pd nanoalloys have been determined for the first time, and correlated with their catalytic behavior. The addition of Ir to Pd suppresses hydride formation and leads to improved catalytic performances with respect to pure metals in the preferential oxidation of CO in H2 excess (PROX).The hydrogen sorption properties of oxide-supported Ir-Pd nanoalloys have been determined for the first time, and correlated with their catalytic behavior. The addition of Ir to Pd suppresses hydride formation and leads to improved catalytic performances with respect to pure metals in the preferential oxidation of CO in H2 excess (PROX). Electronic supplementary information (ESI) available: Detailed catalyst preparation procedure, additional TEM-EDX results, XRD data, and additional sorption and catalysis results. See DOI: 10.1039/c4nr02836h

  3. Stability and dynamic processes in 16VE iridium(III) ethyl hydride and rhodium(I) ?-ethane complexes: experimental and computational studies.

    PubMed

    Walter, Marc D; White, Peter S; Schauer, Cynthia K; Brookhart, Maurice

    2013-10-23

    Iridium(I) and rhodium(I) ethyl complexes, (PONOP)M(C2H5) (M = Ir (1-Et), Rh (2-Et)) and the iridium(I) propyl complex (PONOP)Ir(C3H7) (1-Pr), where PONOP is 2,6-(tBu2PO)2C5H3N, have been prepared. Low-temperature protonation of the Ir complexes yields the alkyl hydrides, (PONOP)Ir(H)(R) (1-(H)(Et)(+) and 1-(H)(Pr)(+)), respectively. Dynamic (1)H NMR characterization of 1-(H)(Et)(+) establishes site exchange between the Ir-H and Ir-CH2 protons (?G(exH)(‡)(-110 °C) = 7.2(1) kcal/mol), pointing to a ?-ethane intermediate. By dynamic (13)C NMR spectroscopy, the exchange barrier between the ? and ? carbons ("chain-walking") was measured (?G(exC)(‡)(-110 °C) = 8.1(1) kcal/mol). The barrier for ethane loss is 17.4(1) kcal/mol (-40 °C), to be compared with the reported barrier to methane loss in 1-(H)(Me)(+) of 22.4 kcal/mol (22 °C). A rhodium ?-ethane complex, (PONOP)Rh(EtH) (2-(EtH)(+)), was prepared by protonation of 2-Et at -150 °C. The barrier for ethane loss (?G(dec)(‡)(-132 °C) = 10.9(2) kcal/mol) is lower than for the methane complex, 2-(MeH)(+), (?G(dec)(‡)(-87 °C) = 14.5(4) kcal/mol). Full spectroscopic characterization of 2-(EtH)(+) is reported, a key feature of which is the upfield signal at -31.2 ppm for the coordinated CH3 group in the (13)C NMR spectrum. The exchange barrier of the hydrogens of the coordinated methyl group is too low to be measured, but the chain-walking barrier of 7.2(1) kcal/mol (-132 °C) is observable by (13)C NMR. The coordination mode of the alkane ligand and the exchange pathways for the Rh and Ir complexes are evaluated by DFT studies. On the basis of the computational studies, it is proposed that chain-walking occurs by different mechanisms: for Rh, the lowest energy path involves a ?(2)-ethane transition state, while for Ir, the lowest energy exchange pathway proceeds through the symmetrical ethylene dihydride complex. PMID:24053635

  4. Sealed aerospace metal-hydride batteries

    Microsoft Academic Search

    Dwaine Coates

    1992-01-01

    Nickel metal hydride and silver metal hydride batteries are being developed for aerospace applications. There is a growing market for smaller, lower cost satellites which require higher energy density power sources than aerospace nickel-cadmium at a lower cost than space nickel-hydrogen. These include small LEO satellites, tactical military satellites and satellite constellation programs such as Iridium and Brilliant Pebbles. Small

  5. Iridium porphyrins in CD3OD: reduction of Ir(III), CD3-OD bond cleavage, Ir-D acid dissociation and alkene reactions.

    PubMed

    Bhagan, Salome; Imler, Gregory H; Wayland, Bradford B

    2013-04-15

    Methanol solutions of iridium(III) tetra(p-sulfonatophenyl)porphyrin [(TSPP)Ir(III)] form an equilibrium distribution of methanol and methoxide complexes ([(TSPP)Ir(III)(CD3OD)(2-n)(OCD3)n]((3+n)-)). Reaction of [(TSPP)Ir(III) with dihydrogen (D2) in methanol produces an iridium hydride [(TSPP)Ir(III)-D(CD3OD)](4-) in equilibrium with an iridium(I) complex ([(TSPP)Ir(I)(CD3OD)](5-)). The acid dissociation constant of the iridium hydride (Ir-D) in methanol at 298 K is 3.5 × 10(-12). The iridium(I) complex ([(TSPP)Ir(I)(CD3OD)](5-)) catalyzes reaction of [(TSPP)Ir(III)-D(CD3OD)](4-) with CD3-OD to produce an iridium methyl complex [(TSPP)Ir(III)-CD3(CD3OD)](4-) and D2O. Reactions of the iridium hydride with ethene and propene produce iridium alkyl complexes, but the Ir-D complex fails to give observable addition with acetaldehyde and carbon monoxide in methanol. Reaction of the iridium hydride with propene forms both the isopropyl and propyl complexes with free energy changes (?G° 298 K) of -1.3 and -0.4 kcal mol(-1) respectively. Equilibrium thermodynamics and reactivity studies are used in discussing relative Ir-D, Ir-OCD3 and Ir-CD2- bond energetics in methanol. PMID:23540797

  6. Processing of Iridium and Iridium Alloys

    SciTech Connect

    Ohriner, Evan Keith [ORNL

    2008-01-01

    Iridium and its alloys have been considered to be difficult to fabricate due to their high melting temperatures, limited ductility, sensitivity to impurity content, and chemical properties. The variety of processing methods used for iridium and its alloys are reviewed, including purification, melting, forming, joining, and powder metallurgy techniques. Also included are coating and forming by the methods of electroplating, chemical and physical vapor deposition, and melt particle deposition.

  7. Sealed aerospace metal-hydride batteries

    NASA Astrophysics Data System (ADS)

    Coates, Dwaine

    1992-02-01

    Nickel metal hydride and silver metal hydride batteries are being developed for aerospace applications. There is a growing market for smaller, lower cost satellites which require higher energy density power sources than aerospace nickel-cadmium at a lower cost than space nickel-hydrogen. These include small LEO satellites, tactical military satellites and satellite constellation programs such as Iridium and Brilliant Pebbles. Small satellites typically do not have the spacecraft volume or the budget required for nickel-hydrogen batteries. NiCd's do not have adequate energy density as well as other problems such as overcharge capability and memory effort. Metal hydride batteries provide the ideal solution for these applications. Metal hydride batteries offer a number of advantages over other aerospace battery systems.

  8. The IRIDIUM communications system

    Microsoft Academic Search

    R. J. Leopold; A. Miller

    1993-01-01

    A description is given of the IRIDIUM communication system, so-called because the system design originally consisted of 77 networked satellites, and the element iridium has the atomic number 77. The goal is to make instant global communications a reality. The system design now consists of 60 satellites, a system control facility, gateways, and subscriber units. Each of these components is

  9. Iridium Interfacial Stack (IRIS)

    NASA Technical Reports Server (NTRS)

    Spry, David James (Inventor)

    2015-01-01

    An iridium interfacial stack ("IrIS") and a method for producing the same are provided. The IrIS may include ordered layers of TaSi.sub.2, platinum, iridium, and platinum, and may be placed on top of a titanium layer and a silicon carbide layer. The IrIS may prevent, reduce, or mitigate against diffusion of elements such as oxygen, platinum, and gold through at least some of its layers.

  10. Hydride compositions

    DOEpatents

    Lee, Myung, W.

    1994-01-01

    Disclosed are a composition for use in storing hydrogen and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the H equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to H, and then heating below the softening temperature of any of the constituents. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P{sub H}{sub 2} and determining H/M from the isothermic function of the composition.

  11. Mononuclear iridium dinitrogen complexes bonded to zeolite HY.

    PubMed

    Yang, Dong; Chen, Mingyang; Martinez-Macias, Claudia; Dixon, David A; Gates, Bruce C

    2015-01-01

    The adsorption of N2 on structurally well-defined dealuminated HY zeolite-supported iridium diethylene complexes was investigated. Iridium dinitrogen complexes formed when the sample was exposed to N2 in H2 at 298?K, as shown by infrared spectra recorded with isotopically labeled N2 . Four supported species formed in various flowing gases: Ir(N2 ), Ir(N2 )(N2 ), Ir(C2 H5 )(N2 ), and Ir(H)(N2 ). Their interconversions are summarized in a reaction network, showing, for example, that, in the presence of N2 , Ir(N2 ) was the predominant dinitrogen species at temperatures of 273-373?K. Ir(CO)(N2 ) formed transiently in flowing CO, and in the presence of H2 , rather stable iridium hydride complexes formed. Four structural models of each iridium complex bonded at the acidic sites of the zeolite were employed in a computational investigation, showing that the calculated vibrational frequencies agree well with experiment when full calculations are done at the level of density functional theory, independent of the size of the model of the zeolite. PMID:25381885

  12. Distortion/Interaction analysis reveals the origins of selectivities in iridium-catalyzed C-H borylation of substituted arenes and 5-membered heterocycles.

    PubMed

    Green, Aaron G; Liu, Peng; Merlic, Craig A; Houk, K N

    2014-03-26

    The iridium-catalyzed borylation of mono- and disubstituted arenes and heteroarenes has been studied with density functional theory. The distortion/interaction model was employed to understand the origins of selectivities in these reactions. Computations revealed that the transition states for C-H oxidative addition are very late, resembling the aryl iridium hydride intermediate with a fully formed Ir-C bond. Consequently, the regioselectivity is mainly controlled by differences in the interaction energies between the iridium catalyst and arene carbon. PMID:24580415

  13. Method for refining contaminated iridium

    DOEpatents

    Heshmatpour, Bahman (Waltham, MA); Heestand, Richard L. (Oak Ridge, TN)

    1983-01-01

    Contaminated iridium is refined by alloying it with an alloying agent selected from the group consisting of manganese and an alloy of manganese and copper, and then dissolving the alloying agent from the formed alloy to provide a purified iridium powder.

  14. Method for refining contaminated iridium

    DOEpatents

    Heshmatpour, B.; Heestand, R.L.

    1982-08-31

    Contaminated iridium is refined by alloying it with an alloying agent selected from the group consisting of manganese and an alloy of manganese and copper, and then dissolving the alloying agent from the formed alloy to provide a purified iridium powder.

  15. IRIDIUM(R) aeronautical satellite communications

    Microsoft Academic Search

    P. W. Lemme; S. M. Glenister; A. W. Miller

    1998-01-01

    The ever-increasing demand to stay in touch, to be able to communicate anywhere and anytime, has created a market for Low Earth Orbit (LEG) satellite communications services such as the Iridium System. The Iridium satellite communications network is being developed to support the needs of the passenger, the cabin crew and the flight crew. Iridium Communications LLC owns a network

  16. Hydridomethyl iridium complex

    DOEpatents

    Bergman, Robert G. (P.O. Box 7141, San Francisco, CA 94120-7141); Buchanan, J. Michael (P.O. Box 7141, San Francisco, CA 94120-7141); Stryker, Jeffrey M. (P.O. Box 7141, San Francisco, CA 94120-7141); Wax, Michael J. (P.O. Box 7141, San Francisco, CA 94120-7141)

    1989-01-01

    A process for functionalizing methane comprising: (a) reacting methane with a hydridoalkyl metal complex of the formula: CpIr[P(R.sub.1).sub.3 ]H(R.sub.2) wherein Cp represents a cyclopentadienyl or alkylcyclopentadienyl radical having from 1 to 5 carbon atoms; Ir represents an iridium atom; P represents a phosphorus atom; R.sub.1 represents an alkyl group; R.sub.2 represents an alkyl group having at least two carbon atoms; and H represents a hydrogen atom, in the presence of a liquid alkane R.sub.3 H having at least three carbon atoms to form a hydridomethyl complex of the formula: CpIr[P(R.sub.1).sub.3 ]HMe where Me represents a methyl radical. (b) reacting said hydridomethyl complex with an organic halogenating agent such as a tetrahalomethane or a haloform of the formulas: CX'X"X'"X"" or CHX'X"X'"; wherein X', X", X"', and X"" represent halogens selected from bromine, iodine and chlorine, to halomethyl complex of step (a) having the formula: CpIr[P(R.sub.1).sub.3 ]MeX: (c) reacting said halomethyl complex with a mercuric halide of the formula HgX.sub.2 to form a methyl mercuric halide of the formula HgMeX; and (d) reacting said methyl mercuric halide with a molecular halogen of the formula X.sub.2 to form methyl halide.

  17. Iridium in sea-water.

    PubMed

    Fresco, J; Weiss, H V; Phillips, R B; Askeland, R A

    1985-08-01

    Iridium in sea-water has been measured (after isolation from the saline matrix by reduction with magnesium) by neutron bombardment, radiochemical purification and high-resolution gamma-ray spectroscopy. The concentration obtained in a Pacific coastal water was 1.02 +/- 0.26 x 10(-14) g per g of sea-water. At such extremely low concentrations, seawater is an extremely unlikely source for anomalously high iridium concentrations measured in the Cretaceous-Tertiary boundary layer of deep-sea sediments. PMID:18964014

  18. WORLD DATA SERVICES Iridium Satellite LLC Rev. 2; June 15, 2001

    E-print Network

    Ashley, Michael C. B.

    WORLD DATA SERVICES Overview Iridium Satellite LLC Rev. 2; June 15, 2001 #12;IRIDIUM WORLD DATA Introduction to Iridium World Data Services............................................................................................ 6 Iridium Satellite LLC 2 Rev. 2; June 15, 2001 #12;IRIDIUM WORLD DATA SERVICES

  19. Analytical Characterization of Microlithographically Fabricated Iridium-Based Ultramicroelectrode Arrays

    E-print Network

    Kounaves, Samuel P.

    Analytical Characterization of Microlithographically Fabricated Iridium-Based Ultramicroelectrode Final version: October 31, 1997 Abstract The analytical performance of several mercury-coated iridiumUMEA surfaces. Keywords: Mercury-coated iridium ultramicroelectrode arrays, Stripping voltammetry

  20. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

    This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

  1. Regenerative Hydride Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.

    1992-01-01

    Hydride heat pump features regenerative heating and single circulation loop. Counterflow heat exchangers accommodate different temperatures of FeTi and LaNi4.7Al0.3 subloops. Heating scheme increases efficiency.

  2. Iridium(R) aeronautical satellite communications

    Microsoft Academic Search

    P. W. Lemme; S. M. Glenister; A. W. Miller

    1999-01-01

    The ever-increasing demand to stay in touch, to be able to communicate anywhere and anytime, has created a market for low Earth orbit (LEO) satellite communications services such as the Iridium system. The Iridium satellite communications network is being developed to support the needs of the passenger, the cabin crew and the flight crew for: aeronautical public correspondence (APC); aeronautical

  3. Ammonia fuel cell with iridium catalyst

    Microsoft Academic Search

    D. W. McKee; A. J. Jr. Scarpellino

    1973-01-01

    The design of a hydrazine fuel cell using iridium or an iridium alloy as the anode catalyst is described. A heating means is provided whereby the ammonia vapor is dissociated into hydrogen and nitrogen. A wide variety of electrodes and electrolytes are suitable in the fuel cell.

  4. Iridium material for hydrothermal oxidation environments

    DOEpatents

    Hong, Glenn T. (Tewksbury, MA); Zilberstein, Vladimir A. (Brookline, MA)

    1996-01-01

    A process for hydrothermal oxidation of combustible materials in which, during at least a part of the oxidation, corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises iridium, iridium oxide, an iridium alloy, or a base metal overlaid with an iridium coating. Iridium has been found to be highly resistant to environments encountered in the process of hydrothermal oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 800.degree. C.

  5. TCP Performance Enhancement Over Iridium

    NASA Technical Reports Server (NTRS)

    Torgerson, Leigh; Hutcherson, Joseph; McKelvey, James

    2007-01-01

    In support of iNET maturation, NASA-JPL has collaborated with NASA-Dryden to develop, test and demonstrate an over-the-horizon vehicle-to-ground networking capability, using Iridium as the vehicle-to-ground communications link for relaying critical vehicle telemetry. To ensure reliability concerns are met, the Space Communications Protocol Standards (SCPS) transport protocol was investigated for its performance characteristics in this environment. In particular, the SCPS-TP software performance was compared to that of the standard Transmission Control Protocol (TCP) over the Internet Protocol (IP). This paper will report on the results of this work.

  6. On the dissolution of iridium by aluminum.

    SciTech Connect

    Hewson, John C.

    2009-08-01

    The potential for liquid aluminum to dissolve an iridium solid is examined. Substantial uncertainties exist in material properties, and the available data for the iridium solubility and iridium diffusivity are discussed. The dissolution rate is expressed in terms of the regression velocity of the solid iridium when exposed to the solvent (aluminum). The temperature has the strongest influence in the dissolution rate. This dependence comes primarily from the solubility of iridium in aluminum and secondarily from the temperature dependence of the diffusion coefficient. This dissolution mass flux is geometry dependent and results are provided for simplified geometries at constant temperatures. For situations where there is negligible convective flow, simple time-dependent diffusion solutions are provided. Correlations for mass transfer are also given for natural convection and forced convection. These estimates suggest that dissolution of iridium can be significant for temperatures well below the melting temperature of iridium, but the uncertainties in actual rates are large because of uncertainties in the physical parameters and in the details of the relevant geometries.

  7. Photochromism in yttrium hydride

    NASA Astrophysics Data System (ADS)

    Ohmura, Ayako; Machida, Akihiko; Watanuki, Tetsu; Aoki, Katsutoshi; Nakano, Satoshi; Takemura, K.

    2007-10-01

    Transparent orange yttrium hydride turns to black when illuminated by visible laser light at pressures of several gigapascals at room temperature. The marked reduction in optical transmittance extends over the infrared region, suggesting that illumination creates persistent free carriers. The opaque black sample returns to the transparent orange hydride during room-temperature annealing for a few hours. Photochromism is pronounced for the coexistent state of the metallic fcc-YH2 and the insulating hexagonal-YH3 state but is depressed for the single phase of hexagonal-YH3. The results indicate that light illumination can modify the optical and possibly electronic properties during a certain period of times.

  8. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  9. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K. (Pleasanton, CA); Bystroff, Roman I. (Livermore, CA); Miller, Dale E. (Livermore, CA)

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  10. Cyclometallated Iridium and Platinum Complexes with Noninnocent Bhavna Hirani,

    E-print Network

    Goddard III, William A.

    Cyclometallated Iridium and Platinum Complexes with Noninnocent Ligands Bhavna Hirani, Jian Li of the cyclometalated (CN) complexes of iridium and platinum metals with a catechol ligand have been studied

  11. Thermal properties of yttrium hydride

    NASA Astrophysics Data System (ADS)

    Ito, Masato; Matsunaga, Junji; Setoyama, Daigo; Muta, Hiroaki; Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke

    2005-09-01

    The thermal properties of ?-phase yttrium hydrides (YH x: x = 1.72-2.00) were studied in the temperature range from 300 to 773 K. The heat capacities of yttrium hydrides are larger than that of yttrium metal because of hydrogen optical vibration. The thermal conductivities of the yttrium hydrides are larger than that of metal and have strong dependence on temperature. They are not markedly influenced by the hydrogen content.

  12. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

    1980-01-21

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  13. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, Moshe (Haifa, IL); Gruen, Dieter M. (Downers Grove, IL); Mendelsohn, Marshall H. (Woodridge, IL); Sheft, Irving (Oak Park, IL)

    1981-01-01

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  14. Superstoichiometric hydride of zirconium

    SciTech Connect

    Kupryazhkin, A.Ya.; Shchepetkin, A.A.; Zabolotskaya, E.V.; Pletnev, R.N.; Alyamovskii, S.I.; Kitaev, G.A.

    1987-12-01

    Superstoichiometric hydrides of zirconium have been obtained all the way up to the composition ZrH/sub 2.4/ by additional hydrogenation of ZrH/sub 2/ as a result of redistribution of hydrogen atoms between t- and o-positions. In the preparation of the hydrides the authors used zirconium iodide with an impurity content no greater than 10/sup -2/ to 10/sup -2/ mole %; the hydrogen and helium used in this work had a minimum purity of 99.95%. The content of hydrogen in the specimens was determined by a volumetric method. The x-ray diffraction analysis was performed in a DRON-2.0 unit (CuK/sub ..cap alpha../ radiation). PMR spectra were recorded in a broad-line spectrometer in the temperature interval 150-450 K.

  15. IRIDIUM (R): A Lockheed transition to commercial space

    NASA Technical Reports Server (NTRS)

    Tadano, Thomas N.

    1995-01-01

    At Lockheed Missiles & Space Company, the IRIDIUM commercial space program is dramatically revolutionizing spacecraft development and manufacturing processes to reduce cost while maintaining quality and reliability. This report includes the following sections: an overview of the IRIDIUM system, the Lockheed IRIDIUM project and challenges; cycle-time reduction through production reorganization; and design for manufacturing and quality.

  16. Compact Helical Ring Antenna for Iridium Communication C. Morlaas1

    E-print Network

    Paris-Sud XI, Université de

    Compact Helical Ring Antenna for Iridium Communication on UAV C. Morlaas1 , A. Chabory1 , B. Souny1 (Fly2Corsica project), the ENAC UAV team plans to use the Iridium satellite service. To render circular polarization antenna, Iridium antenna, helical ring antenna. 1. Introduction The ENAC UAV team

  17. Iridium Model 9500 and 9505 AT Command Compliance

    E-print Network

    Ashley, Michael C. B.

    Iridium Model 9500 and 9505 AT Command Compliance 1 TABLE OF CONTENTS 1 PURPOSE.............................................................................................................................8 #12;Iridium Model 9500 and 9505 AT Command Compliance 2 1 Purpose This document serves to identify AT Command comp liance of the Iridium Model 9500 and 9505 handsets. 2 Applicability The AT Command compliance

  18. Electrodeposited iridium oxide for neural stimulation and recording electrodes

    Microsoft Academic Search

    Ross D. Meyer; Stuart F. Cogan; Trung H. Nguyen; R. David Rauh

    2001-01-01

    Iridium oxide films formed by electrodeposition onto noniridium metal substrates are compared with activated iridium oxide films (AIROFs) as a low impedance, high charge capacity coating for neural stimulation and recording electrodes. The electrodeposited iridium oxide films (EIROFs) were deposited on Au, Pt, PtIr, and 316 LVM stainless steel substrates from a solution of IrCl 4, oxalic acid, and K

  19. PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium)

    E-print Network

    122 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data platinum-iridium alloys in prosthetic and biomedical devices. Salient Statistics--United States: 1996 1997,400 16,600 Iridium 1,810 1,860 1,950 2,270 2,640 Osmium NA 54 71 23 46 Exports: Platinum 12,700 23,000 14

  20. "Globalstar, Iridium and other Satellite-Based Mobile Phone

    E-print Network

    1 "Globalstar, Iridium and other Satellite-Based Mobile Phone Systems: How Do they Work and Where formed in the early 90's ­ Iridium [LEO, intersatellite links] ­ Globalstar [LEO, satellite diversity in their Flying Machines Iridium LEO Polar TDMA Globalstar LEO Inclined CDMA ICO MEO Inclined Custom Constellation

  1. Iridium Anomaly Approximately Synchronous with Terminal Eocene Extinctions

    Microsoft Academic Search

    Walter Alvarez; Frank Asaro; Helen V. Michel; Luis W. Alvarez

    1982-01-01

    An iridium anomaly has been found in coincidence with the known microtektite level in cores from Deep Sea Drilling Project site 149 in the Caribbean Sea. The iridium was probably not in the microtektites but deposited simultaneously with them; this could occur if the iridium was deposited from a dust cloud resulting from a bolide impact, as suggested for the

  2. 17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING SYSTEM WAS PART OF THE FAST ENRICHED URANIUM RECOVERY PROCESS. (11/11/59) - Rocky Flats Plant, General Manufacturing, Support, Records-Central Computing, Southern portion of Plant, Golden, Jefferson County, CO

  3. Hydrogenation using hydrides and acid

    DOEpatents

    Bullock, R. Morris (Wading River, NY)

    1990-10-30

    A process for the non-catalytic hydrogenation of organic compounds, which contain at least one reducible functional group, which comprises reacting the organic compound, a hydride complex, preferably a transition metal hydride complex or an organosilane, and a strong acid in a liquid phase.

  4. Xantphos-type complexes of group 9: rhodium versus iridium.

    PubMed

    Esteruelas, Miguel A; Oliván, Montserrat; Vélez, Andrea

    2013-05-01

    Treatment of the dimer [Rh(?-Cl)(C8H14)2]2 (1a) with 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene [xant(P(i)Pr2)2] leads to the d(8) square-planar complex RhCl{xant(P(i)Pr2)2} (2), whereas reaction of the iridium counterpart [Ir(?-Cl)(C8H14)2]2 (1b) gives the d(6) octahedral compound IrHCl{xant(P(i)Pr2)[(i)PrPCH(Me)CH2]} (3) as a result of the intramolecular C-H bond activation of one of the isopropyl substituents of the phosphine. Stirring 2 and 3 in 0.5 N KOH solutions of 2-propanol gives rise to the formation of hydrides RhH{xant(P(i)Pr2)2} (4) and IrH3{xant(P(i)Pr2)2} (5), respectively. In n-octane at 60 °C, complex 2 is stable. However, compound 3 activates the alkane to give the cis-dihydride IrH2Cl{xant(P(i)Pr2)2} (6) and a mixture of 3- and 4-octene. Complex 6 can be also obtained by the reaction of 3 with H2. Under the same conditions, 2 affords the rhodium analogue RhH2Cl{xant(P(i)Pr2)2} (7). Compounds 2-4 react with triflic acid (HOTf) to give RhHCl(OTf){xant(P(i)Pr2)2} (8), IrHCl(OTf){xant(P(i)Pr2)2} (9), and RhH2(OTf){xant(P(i)Pr2)2} (10), respectively. The related iridium derivative IrH2(OTf){xant(P(i)Pr2)2} (11) has also been prepared by the reaction of 6 with Tl(OTf). Complexes 2, 6, and 9 have been characterized by X-ray diffraction analysis. The {xant(P(i)Pr2)2}M skeleton is T-shaped with the metal center situated in the common vertex. PMID:23560531

  5. Dimensionally stable metallic hydride composition

    DOEpatents

    Heung, Leung K. (Aiken, SC)

    1994-01-01

    A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

  6. Thermodynamics and transport of gaseous iridium oxides in multi-hundred-watt thermoelectric generators

    Microsoft Academic Search

    D. E. Peterson

    1976-01-01

    Thermodynamic properties of the iridium oxide system were determined by using a mass spectrometer and target collection apparatus with a gas inlet system. Iridium dioxide and trioxide were identified as the predominant gaseous oxides in equilibrium with iridium metal in an oxygen atmosphere of .0001 to .01 atm at 1600-1800 C. The analyses indicated that iridium transport due to iridium

  7. Iridium-Catalyzed Arylative Cyclization of Alkynones by 1,4-Iridium Migration**

    PubMed Central

    Partridge, Benjamin M; Solana?González, Jorge; Lam, Hon Wai

    2014-01-01

    1,4-Metal migrations enable the remote functionalization of C—H bonds, and have been utilized in a wide variety of valuable synthetic methods. The vast majority of existing examples involve the 1,4-migration of palladium or rhodium. Herein, the stereoselective synthesis of complex polycycles by the iridium-catalyzed arylative cyclization of alkynones with arylboronic acids is described. To our knowledge, these reactions involve the first reported examples of 1,4-iridium migration. PMID:24842318

  8. Hydrogen storage and evolution catalysed by metal hydride complexes.

    PubMed

    Fukuzumi, Shunichi; Suenobu, Tomoyoshi

    2013-01-01

    The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-?N(2))benzoic acid-?C(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of ?-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (? > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes. PMID:23080061

  9. Iridium emissions from Hawaiian volcanoes

    NASA Technical Reports Server (NTRS)

    Finnegan, D. L.; Zoller, W. H.; Miller, T. M.

    1988-01-01

    Particle and gas samples were collected at Mauna Loa volcano during and after its eruption in March and April, 1984 and at Kilauea volcano in 1983, 1984, and 1985 during various phases of its ongoing activity. In the last two Kilauea sampling missions, samples were collected during eruptive activity. The samples were collected using a filterpack system consisting of a Teflon particle filter followed by a series of 4 base-treated Whatman filters. The samples were analyzed by INAA for over 40 elements. As previously reported in the literature, Ir was first detected on particle filters at the Mauna Loa Observatory and later from non-erupting high temperature vents at Kilauea. Since that time Ir was found in samples collected at Kilauea and Mauna Loa during fountaining activity as well as after eruptive activity. Enrichment factors for Ir in the volcanic fumes range from 10,000 to 100,000 relative to BHVO. Charcoal impregnated filters following a particle filter were collected to see if a significant amount of the Ir was in the gas phase during sample collection. Iridium was found on charcoal filters collected close to the vent, no Ir was found on the charcoal filters. This indicates that all of the Ir is in particulate form very soon after its release. Ratios of Ir to F and Cl were calculated for the samples from Mauna Loa and Kilauea collected during fountaining activity. The implications for the KT Ir anomaly are still unclear though as Ir was not found at volcanoes other than those at Hawaii. Further investigations are needed at other volcanoes to ascertain if basaltic volcanoes other than hot spots have Ir enrichments in their fumes.

  10. Iridium-Coated Rhenium Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

    1994-01-01

    Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

  11. Determining the Altitude of Iridium Flares

    NSDL National Science Digital Library

    2012-08-03

    This series of example calculations applies basic trigonometry to to calculate the altitude of satellites and Iridium satellite flares. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

  12. Osmium-191/iridium-191m radionuclide

    DOEpatents

    Knapp, Jr., Furn F. (Oak Ridge, TN); Butler, Thomas A. (Oak Ridge, TN); Brihaye, Claude (Liege, BE)

    1987-01-01

    A generator system to provide iridium-191m for clinical imaging applications comprises an activated carbon adsorbent loaded with a compound containing the parent nuclide, osmium-191. The generator, which has a shelf-life in excess of two weeks and does not require a scavenger column, can be eluted with physiologically compatible saline.

  13. Iridium-192 Production for Cancer Treatment

    SciTech Connect

    Rostelato, M.E.C.M.; Silva, C.P.G.; Rela, P.R.; Zeituni, C.A.; Lepki, V.; Feher, A.

    2004-10-05

    The purpose of this work is to settle a laboratory for Iridium -192 sources production, that is, to determine a wire activation method and to build a hot cell for the wires manipulation, quality control and packaging. The paper relates, mainly, the wire activation method and its quality control. The wire activation is carried out in our nuclear reactor, IEA- R1m.

  14. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium...Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium,...

  15. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium...Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium,...

  16. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium...Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium,...

  17. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium...Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium,...

  18. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium...Platinum Group Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium,...

  19. Application of the Iridium Satellite System to Aeronautical Communications

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Meza, Mike; Gupta, Om

    2008-01-01

    The next generation air transportation system will require greater air-ground communications capacity to accommodate more air traffic with increased safety and efficiency. Communications will remain primarily terrestrially based, but satellite communications will have an increased role. Inmarsat s aeronautical services have been approved and are in use for aeronautical safety communications provided by geostationary satellites. More recently the approval process for the Iridium low earth orbit constellation is nearing completion. The current Iridium system will be able to provide basic air traffic services communications suitable for oceanic, remote and polar regions. The planned second generation of the Iridium system, called Iridium NEXT, will provide enhanced capabilities and enable a greater role in the future of aeronautical communications. This paper will review the potential role of satellite communications in the future of air transportation, the Iridium approval process and relevant system testing, and the potential role of Iridium NEXT.

  20. PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium)

    E-print Network

    124 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,750 7,210 7,820 9,000 Ruthenium 2,590 2,740 4,490 9,880 6,000 Iridium 520 207 896 926 1,000 Osmium 46 57,300 -- -- -- Iridium 920 -- -- -- In addition to these quantities, the Stockpile contains 406 kilograms of nonstockpile

  1. PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium)

    E-print Network

    126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data use of PGM is in cancer chemotherapy. Other medical uses include platinum-iridium alloys in prosthetic,600 9,650 14,400 13,400 14,500 Ruthenium 7,520 15,600 11,500 9,230 9,500 Iridium 1,450 1,810 1,860 2

  2. THE RADIOCHEMISTRY OF IRIDIUM--NAS-NS 3045

    E-print Network

    ------..--------- !546.8 L472ra .c.8 THE RADIOCHEMISTRY OF IRIDIUM-- NAS-NS 3045 +- -:, G. W The Rctdiochemistry of Iridium #12;COMNll~EE ON. NUCLEAR SCIENCE L.F. CURTffS, CM~ " ROBLEY D.EVAiil%Vk8 Ckzi;c-TRY The Radiochemistry of Iridium G. W. LEDDI~ W Ridge Ndioml Lduwulwy Ckz&Ridge, T-&?See Chb3ber

  3. PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium)

    E-print Network

    126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data 7,750 7,210 7,820 9,600 10,000 Ruthenium 2,740 4,490 9,880 7,520 20,000 Iridium 207 896 926 1,450 2 for disposal Jan.-Sept. 96 Platinum 14,100 -- 311 -- Palladium 39,300 -- 467 -- Iridium 920

  4. Hydrogen recovery with metal hydrides

    SciTech Connect

    Santangelo, J.G.; Chen, G.T.

    1982-03-01

    Air Products pursued hydride technology because hydrides first came to our attention as a unique technology which could safely store hydrogen. The preliminary economics for using available hydrides to store hydrogen in motor vehicles were not encouraging at that time. However, the possibilities for using hydrides to selectively separate hydrogen from other components occurred to us. The authors obtained a DOE contract to study metal alloys which could be used to effectively store hydrogen fuel in motor vehicles, an interest of DOE at that time. They concurrently continued independent studies on the use of hydrides for hydrogen separation. It became obvious during initial stages, that to develop hydride technology would require a partner with metallurgical background and facilities. They teamed up with MPD Technology, a wholly owned subsidiary of International Nickel. This joint R and D program has been in progress for the past three years. During this time it has taken this technology from a laboratory curiosity to a successful pilot unit currently operating at Air Products' New Orleans ammonia plant where it is selectively removing hydrogen from the ammonia purge gas stream.

  5. Weldability of general purpose heat source iridium capsules

    SciTech Connect

    Kanne, W.R. Jr.

    1988-01-01

    Two weldability tests developed by ORNL for plate material have been demonstrated on iridium (Goodwin 1987 and David 1987), but neither test is applicable to underbead cracking in a capsule configuration. As a result of underbead cracking of welded iridium capsules at SRP, a weldability test was designed and demonstrated on capsules to measure the susceptibility of different batches of iridium to underbead cracking. The capsule weldability test and its use to determine the relative weldability of the ORNL new-process iridium is presented in this paper. 6 refs., 1 fig., 1 tab.

  6. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, John T.; Kazaroff, John M.; Appel, Marshall A.

    1988-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the meltimg temperature of iridium, 2400 C (4350 F).

  7. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, J. T.; Kazaroff, J. M.; Appel, M. A.

    1989-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the melting temperature of iridium, 2400 C (4350 F).

  8. Raman scattering study in iridium pyrochlore oxides

    Microsoft Academic Search

    T. Hasegawa; N. Ogita; K. Matsuhira; S. Takagi; M. Wakeshima; Y. Hinatsu; M. Udagawa

    2010-01-01

    Raman scattering spectra of iridium pyrochlore oxides R2Ir2O7 (R=Nd, Sm, and Eu) have been measured. These three compounds undergo metal-insulator transition. Below the transition temperature TMI, new peaks appear for R = Sm and Eu, but no remarkable change for R = Nd. Therefore, Sm2Ir2O7 and Eu2Ir2O7 accompany structural change with the transition, but not the case for Nd. Even

  9. A molecular dynamics study on iridium

    NASA Astrophysics Data System (ADS)

    Ferah, Gülen; Colakoglu, Kemal; Ciftci, Yasemin; Ozgen, Soner; Kazanc, Sefa

    2007-06-01

    In this study, molecular dynamics simulations are performed by using a modified form of Morse potential function in the framework of the Embedded Atom Method (EAM). Temperature-and pressure-dependent behaviours of bulk modulus, second-order elastic constants (SOEC), and the linear-thermal expansion coefficient is calculated and compared with the available experimental data. The melting temperature is estimated from 3 different plots. The obtained results are in agreement with the available experimental findings for iridium.

  10. Hydride reorientation in Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Chu, H. C.; Wu, S. K.; Kuo, R. C.

    2008-02-01

    The formation of radial hydrides in stress-relief annealed Zircaloy-4 cladding was studied. Specimens were firstly hydrided to different target hydrogen levels from 100 to 600 wt ppm and then thermally cycled in an autoclave under a constant hoop stress to form radial hydrides by a hydride reorientation process. The effect of thermal cycling on the hydride reorientation was more significant than that of isothermal treatment. Based on the experimental data, a thermodynamic model was proposed to elucidate the stress reorientation behavior of hydrides in Zircaloy cladding. According to the model, the bounds of stress and temperature to stress reorientation of hydride precipitates were developed. The threshold stress for hydrides to reorientation was a function of solution temperature and specimen hydrogen concentration.

  11. Gas-phase acidities of binary hydrides.

    NASA Technical Reports Server (NTRS)

    Brauman, J. I.; Eyler, J. R.; Blair, L. K.; White, M. J.; Comisarow, M. B.; Smyth, K. C.

    1971-01-01

    The preferred direction of proton transfer in a reaction between a hydride molecule and a hydride ion was studied in order to determine the relative acidities of some binary hydrides. Sufficient data are presented to make clear the periodic trends in acidities and the underlying trends in other fundamental thermochemical quantities which influence acidity. The bond dissociation energies and electron affinities of the hydrides considered are listed in a table.

  12. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, Leslie D. (Livermore, CA)

    1982-01-01

    A pressure controlled vanadium hydride gas generator to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  13. Weldability of general purpose heat source new-process iridium

    SciTech Connect

    Kanne, W.R.

    1987-01-01

    Weldability tests on General Purpose Heat Source (GPHS) iridium capsules showed that a new iridium fabrication process reduced susceptibility to underbead cracking. Seventeen capsules were welded (a total of 255 welds) in four categories and the number of cracks in each weld was measured.

  14. Variation of iridium in a differentiated tholeiitic dolerite

    USGS Publications Warehouse

    Greenland, L.P.

    1971-01-01

    Iridium has been determined in a drill core from the Great Lake (Tasmania) dolerite sheet. Iridium decreases systematically from the mafic dolerites (0.25 ppb) to the granophyres (0.006 ppb). The trend with differentiation closely parallels that of chromium. ?? 1971.

  15. Probing the oxidation chemistry of half-sandwich iridium complexes with oxygen atom transfer reagents.

    PubMed

    Turlington, Christopher R; Harrison, Daniel P; White, Peter S; Brookhart, Maurice; Templeton, Joseph L

    2013-10-01

    The new complexes [Ir(Cp*)(phpy)3,5-bis(trifluoromethyl)benzonitrile](+) (1-NCAr(+)) and [Ir(Cp*)(phpy)(styrene)](+) (1-Sty(+), Cp* = ?(5)-pentamethylcyclopentadienyl, phpy = 2-phenylene-?C(1')-pyridine-?N) were prepared as analogues of reported iridium water oxidation catalysts, to study their reactions with oxygen atom transfer (OAT) reagents at low temperatures. In no case was the desired product, an Ir(V)oxo complex, observed by spectroscopy. Instead, ligand oxidation was implicated. Oxidation of 1-NCAr(+) with the OAT reagent dimethyldioxirane (DMDO) yielded dioxygen when analyzed by GC, but formation of a heterogeneous or paramagnetic species was simultaneously observed. This amplifies uncertainty over the actual identity of iridium catalysts in the harsh oxidizing conditions required for water oxidation. Catalyst stability was then assessed for a reported styrene epoxidation mediated by [Ir(Cp*)(phpy)(OH2)](+) (1-OH2(+)). It was found that the OAT reagent iodosobenzene (PhIO) extensively oxidized the organic ligands of 1-OH2(+). Acetic acid was detected as a decomposition product. In addition, both the molecular structure and the aqueous electrochemistry of 1-OH2(+) are described for the first time. Oxidative scans revealed rapid decomposition of the complex. All of the above experiments indicate that degradation of the organic ligands in catalysts built with the Ir(Cp*)(phpy) framework are facile under oxidizing conditions. In separate experiments designed to promote ligand substitution, an unexpected silver-bridged, dinuclear Ir(III) species with terminal hydrides, [{Ir(Cp*)(phpy)H}2Ag](+) (2), was discovered. The source of Ag(+) for complex 2 was identified as AgCl. PMID:24063760

  16. Iridium/Rhenium Parts For Rocket Engines

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Harding, John T.; Wooten, John R.

    1991-01-01

    Oxidation/corrosion of metals at high temperatures primary life-limiting mechanism of parts in rocket engines. Combination of metals greatly increases operating temperature and longevity of these parts. Consists of two transition-element metals - iridium and rhenium - that melt at extremely high temperatures. Maximum operating temperature increased to 2,200 degrees C from 1,400 degrees C. Increases operating lifetimes of small rocket engines by more than factor of 10. Possible to make hotter-operating, longer-lasting components for turbines and other heat engines.

  17. HYDRIDE BED\\/FUELCELL PROJECT

    Microsoft Academic Search

    G. Cook Story

    2000-01-01

    The Hydride Bed\\/Fuelcell Project will result in the development and production of a prototype Fuelcell Powerplant for Mining\\/Tunneling Locomotives. This powerplant will replace and outperform batteries, currently utilized for mining and tunneling. The Mine Locomotive Project is a project of the Fuelcell Propulsion Institute (FCPI) consortium.

  18. Cheaper Hydride-Forming Cathodes

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Blue, Gary

    1990-01-01

    Hydride-forming cathodes for electrochemical experiments made of materials or combinations of materials cheaper and more abundant than pure palladium, according to proposal. Concept prompted by needs of experimenters in now-discredited concept of electrochemical nuclear fusion, cathodes useful in other electrochemical applications involving generation or storage of hydrogen, deuterium, or tritium.

  19. Properties of nanoscale metal hydrides.

    PubMed

    Fichtner, Maximilian

    2009-05-20

    Nanoscale hydride particles may exhibit chemical stabilities which differ from those of a macroscopic system. The stabilities are mainly influenced by a surface energy term which contains size-dependent values of the surface tension, the molar volume and an additional term which takes into account a potential reduction of the excess surface energy. Thus, the equilibrium of a nanoparticular hydride system may be shifted to the hydrogenated or to the dehydrogenated side, depending on the size and on the prefix of the surface energy term of the hydrogenated and dehydrogenated material. Additional complexity appears when solid-state reactions of complex hydrides are considered and phase segregation has to be taken into account. In such a case the reversibility of complex hydrides may be reduced if the nanoparticles are free standing on a surface. However, it may be enhanced if the system is enclosed by a nanoscale void which prevents the reaction partners on the dehydrogenated side from diffusing away from each other. Moreover, the generally enhanced diffusivity in nanocrystalline systems may lower the kinetic barriers for the material's transformation and, thus, facilitate hydrogen absorption and desorption. PMID:19420657

  20. Iridium wire grid polarizer fabricated using atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Weber, Thomas; Käsebier, Thomas; Szeghalmi, Adriana; Knez, Mato; Kley, Ernst-Bernhard; Tünnermann, Andreas

    2011-10-01

    In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved.

  1. PH sensors based on iridium oxide

    SciTech Connect

    Tarlov, M.J.; Huang, P.H.; Kreider, K.G. (Center for Chemical Technology, National Institute of Standards and Technology, Gaithersburg, MD (US))

    1988-01-01

    Iridium oxide shows considerable promise as a high temperature pH sensing material. It is being currently considered for measurement of hot geological brines in connection with nuclear waste disposal. The use of a sputtered thin film of iridium oxide may also lead to much smaller and less costly ionic sensor than those based on the glass electrode. The authors report on recent research which has concentrated on evaluating the long time stability and repeatability of the sputtered electrodes and developing an understanding of the hydroxylation of the oxide. The interaction of IrO/sub 2/ with water apparently affects its formal potential as an electrode. The understanding of this interaction may also help develop a determination of the mechanism for its Nernstian behavior. The electrochemical behavior and surface analysis of IrO/sub 2/ is, however, limited by the cleanliness of the surface and particular effort has been focussed on this problem. They investigate methods for producing both clear, hydroxyl-free and model, hydroxylated IrO/sub 2/ surfaces.

  2. The dual role of borohydride depending on reaction temperature: synthesis of iridium and iridium oxide.

    PubMed

    Chakrapani, Kalapu; Sampath, S

    2015-05-28

    Temperature dependent reaction products are observed when borohydride is present in aqueous solutions containing Ir(3+). At temperatures of 40 °C and above, metallic iridium is formed while under ambient conditions of 25 °C, borohydride results in an alkaline environment that helps in hydrolyzing the precursor to form IrO2. The Ir foams and IrO2 are subsequently used to study their catalytic properties. PMID:25978128

  3. Phase control of iridium and iridium oxide thin films in atomic layer deposition

    SciTech Connect

    Kim, Sung-Wook; Kwon, Se-Hun; Kwak, Dong-Kee; Kang, Sang-Won [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2008-01-15

    The atomic layer deposition of iridium (Ir) and iridium oxide (IrO{sub 2}) films was investigated using an alternating supply of (ethylcyclopentadienyl)(1,5-cyclooctadiene) iridium and oxygen gas at temperatures between 230 and 290 deg. C. The phase transition between Ir and IrO{sub 2} occurred at the critical oxygen partial pressure during the oxygen injection pulse. The oxygen partial pressure was controlled by the O{sub 2}/(Ar+O{sub 2}) ratio or deposition pressures. The resistivity of the deposited Ir and IrO{sub 2} films was about 9 and 120 {mu}{omega} cm, respectively. In addition, the critical oxygen partial pressure for the phase transition between Ir and IrO{sub 2} was increased with increasing the deposition temperature. Thus, the phase of the deposited film, either Ir or IrO{sub 2}, was controlled by the oxygen partial pressure and the deposition temperature. However, the formation of a thin Ir layer was detected between the IrO{sub 2} and SiO{sub 2} substrate. To remove this interfacial layer, the oxygen partial pressure is increased to a severe condition. And the impurity contents were below the detection limit of Auger electron spectroscopy in both Ir and IrO{sub 2} films.

  4. Iridium abundances across the ordovician-silurian stratotype.

    PubMed

    Wilde, P; Berry, W B; Quinby-Hunt, M S; Orth, C J; Quintana, L R; Gilmore, J S

    1986-07-18

    Chemostratigraphic analyses in the Ordovician-Silurian boundary stratotype section, bracketing a major extinction event in the graptolitic shale section at Dob's Linn, Scotland, show persistently high iridium concentrations of 0.050 to 0.250 parts per billion. There is no iridiumn concentration spike in the boundary interval or elsewhere in the 13 graptolite zones examined encompassing about 20 million years. Iridium correlated with chromium, both elements showing a gradual decrease with time into the middle part of the Lower Silurian. The chromium-iridium ratio averages about 10(6). Paleogeographic and geologic reconstructions coupled with the occurrence of ophiolites and other deep crustal rocks in the source area suggest that the high iridium and chromium concentrations observed in the shales result from terrestrial erosion of exposed upper mantle ultramafic rocks rather than from a cataclysmic extraterrestrial event. PMID:17737622

  5. GPS/GNSS Interference from Iridium Data Transmitters

    NASA Astrophysics Data System (ADS)

    Berglund, H. T.; Blume, F.; Estey, L.; White, S.

    2011-12-01

    The Iridium satellite communication system broadcasts in the 1610 to 1626.5 MHz band. The L1 frequencies broadcast by GPS, Galileo and GLONASS satellites are 1575.42 MHz, 1575.42 MHz and 1602 MHz + n × 0.5625 MHz, respectively (each GLONASS satellite uses a unique frequency). The proximity of the Iridium frequency band with the L1 frequencies of the GPS, Galileo and GLONASS systems leaves GNSS receivers susceptible to interference from Iridium data transmissions. Interference from Iridium transmissions can cause cycle slips and loss of lock on the carrier and code phases, thereby degrading the quality of GNSS observations and position estimates. In 2008, UNAVCO staff members observed that the percent of slips vs. the number of observations increased as the distance between a GPS choke ring antenna (TRM29659.00) and an Iridium antenna decreased. From those observations they suggested that Iridium antennas and GPS antennas should be separated by >30 m to minimize cycle slips caused by the interference from Iridium data transmissions. A second test conducted in 2009 using a newer Trimble GNSS choke ring antenna (TRM59800.00) showed similar results to the previous test despite the wider frequency range of the newer antenna. More recent testing conducted to investigate the response of new receiver models to iridium transmissions has shown that many GNSS enabled models, when combined with GNSS enabled antennas, have increased sensitivity to interference when compared to older GPS-only models. The broader frequency spectrum of the Low Noise Amplifiers (LNA) installed in many newer GNSS antennas can increase the impact of near-band RF interference on tracking performance. Our testing has shown that the quality of data collected at sites collocated with iridium communications is highly degraded for antenna separations exceeding 100m. Using older GPS antenna models (e.g. TRM29659.00) with newer GNSS enabled receivers can reduce this effect. To mitigate the effects that iridium data transmissions have on receiver tracking performance, we tested a custom cavity-type notch filter designed to attenuate the Iridium RF band. The filter has a >20dB rejection at 1616-1626.5 MHz. Test results when using the filter have shown excellent GPS data quality at antenna separations of ~30 m. Determining what impact the filter has on GLONASS and Galileo observations will require further testing. Future investigations will also include alternative RF mitigation methods, including RF shielding.

  6. Development of Hydride Absorber for Fast Reactor—Evaluation of Design Method for Hydride Absorber Rod—

    Microsoft Academic Search

    Yoshihisa Tahra; Tomohiko IWASKI; Kenji KONASKI

    2010-01-01

    A hydride control rod is being developed to improve the economy of fast reactor plants because it has a longer lifetime than the currently used B4C control rod. A hydride burnable poison rod is also under development to reduce the number of control rods by decreasing core excess reactivity. Hydrogen in the hydride control rod causes neutron spectrum interference between

  7. Hydrogen /Hydride/-air secondary battery

    NASA Technical Reports Server (NTRS)

    Sarradin, J.; Bronoel, G.; Percheron-Guegan, A.; Achard, J. C.

    1979-01-01

    The use of metal hydrides as negative electrodes in a hydrogen-air secondary battery seems promising. However, in an unpressurized cell, more stable hydrides that LaNi5H6 must be selected. Partial substitutions of nickel by aluminium or manganese increase the stability of hydrides. Combined with an air reversible electrode, a specific energy close to 100 Wh/kg can be expected.

  8. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, L.D.

    1980-03-13

    A pressure controlled vanadium hydride gas generator was designed to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  9. ?-Oxido-bis­[hydridotris(tri­methyl­phosphane-?P)iridium(III)](Ir—Ir) bis­(tetra­fluorido­borate) dihydrate

    PubMed Central

    Merola, Joseph; Husebo, Trang Le

    2014-01-01

    The title compound, [Ir2H2O(C3H9P)6](BF4)2·2H2O, was isolated from the reaction between [Ir(COD)(PMe3)3]BF4 and H2 in water (COD is cyclo­octa-1,5-diene). The asymmetric unit consists of one IrIII atom bonded to three PMe3 groups, one hydride ligand and half an oxide ligand, in addition to a BF4 ? counter-ion and one water molecule of hydration. The single oxide ligand bridging two IrIII atoms is disordered across an inversion center with each O atom having a 50% site occupancy. Each IrIII atom has three PMe3 groups occupying facial positions, with the half-occupancy O atoms, a hydride ligand and an Ir—Ir bond completing the coordination sphere. The Ir—Ir distance is 2.8614?(12)?Å, comparable to other iridium(III) metal–metal bonds. Two water mol­ecules hydrogen bond to two BF4 ? anions in the unit cell. PMID:24826089

  10. pH sensor properties of electrochemically grown iridium oxide

    Microsoft Academic Search

    W. Olthuis; M. A. M. Robben; P. Bergveld; M. Bos; Linden van der W. E

    1990-01-01

    The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between ?60 and ?80 mV\\/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high valence state), the sensitivity is also higher. This

  11. CCMR: New Iridium Complexes for the Dehydrogenation of Alkanes

    NSDL National Science Digital Library

    Wang, David

    2004-08-17

    To introduce small variations on the previously investigated iridium P-C-P pincer complexes. The variations include substitution of cyclohexyl groups for the tert-butyl and the iso-propyl groups found on the phosphines.Thus, synthesis of these new iridium P-C-P pincer complexes was performed with the aim of improved catalytic dehydrogenation activity as well as a better understand of the influence that ligand sterics and electronics have on the active species.

  12. Synthesis and characterization of nitrides of iridium and palladiums

    SciTech Connect

    Crowhurst, Jonathan C.; Goncharov, Alexander F.; Sadigh, B.; Zaug, J.M.; Aberg, D.; Meng, Yue; Prakapenka, Vitali B. (LLNL); (CIW); (UC)

    2008-08-14

    We describe the synthesis of nitrides of iridium and palladium using the laser-heated diamond anvil cell. We have used the in situ techniques of x-ray powder diffraction and Raman scattering to characterize these compounds and have compared our experimental findings where possible to the results of first-principles theoretical calculations. We suggest that palladium nitride is isostructural with pyrite, while iridium nitride has a monoclinic symmetry and is isostructural with baddeleyite.

  13. Iridium{reg_sign} worldwide personal communication system

    SciTech Connect

    Helm, J. [Senior Systems Engineer Motorola Mobile Satellite Systems Division 1600 W. Chandler Blvd., Suite 150 Chandler, Arizona85224 (United States)

    1997-01-01

    The IRIDIUM system is a personal worldwide communication system designed to support portable, low power subscriber units through the use of a constellation of satellites in low earth polar orbit. The satellites are networked together to form a system which provides continuous line-of-sight communications between the IRIDIUM system and any point within 30 km of the earth{close_quote}s surface. The system architecture and operation are described. {copyright} {ital 1997 American Institute of Physics.}

  14. Complex hydrides for hydrogen storage

    DOEpatents

    Zidan, Ragaiy

    2006-08-22

    A hydrogen storage material and process of forming the material is provided in which complex hydrides are combined under conditions of elevated temperatures and/or elevated temperature and pressure with a titanium metal such as titanium butoxide. The resulting fused product exhibits hydrogen desorption kinetics having a first hydrogen release point which occurs at normal atmospheres and at a temperature between 50.degree. C. and 90.degree. C.

  15. CO adsorption on neutral iridium clusters

    E-print Network

    Kerpal, Christian; Meijer, Gerard; Fielicke, André

    2010-01-01

    The adsorption of carbon monoxide on neutral iridium clusters in the size range of n = 3 to 21 atoms is investigated with infrared multiple photon dissociation spectroscopy. For each cluster size only a single v(CO) band is present with frequencies in the range between 1962 cm-1 (n = 8) and 1985 cm-1 (n = 18) which can be attributed to an atop binding geometry. This behaviour is compared to the CO binding geometries on clusters of other group 9 and 10 transition metals as well as to that on extended surfaces. The preference of Ir for atop binding is rationalized by relativistic effects on the electronic structure of the later 5d metals.

  16. Raman scattering study in iridium pyrochlore oxides

    NASA Astrophysics Data System (ADS)

    Hasegawa, T.; Ogita, N.; Matsuhira, K.; Takagi, S.; Wakeshima, M.; Hinatsu, Y.; Udagawa, M.

    2010-01-01

    Raman scattering spectra of iridium pyrochlore oxides R2Ir2O7 (R=Nd, Sm, and Eu) have been measured. These three compounds undergo metal-insulator transition. Below the transition temperature TMI, new peaks appear for R = Sm and Eu, but no remarkable change for R = Nd. Therefore, Sm2Ir2O7 and Eu2Ir2O7 accompany structural change with the transition, but not the case for Nd. Even if Nd2Ir2O7 deforms, the distortion is different from that of Sm2Ir2O7 and Eu2Ir2O7, because the spectra of Nd are clearly different from those of Sm and Eu below TMI.

  17. PURIFICATION OF IRIDIUM BY ELECTRON BEAM MELTING

    SciTech Connect

    Ohriner, Evan Keith [ORNL

    2008-01-01

    The purification of iridium metal by electron beam melting has been characterized for 48 impurity elements. Chemical analysis was performed by glow discharge mass spectrographic (GDMS) analysis for all elements except carbon, which was analyzed by combustion. The average levels of individual elemental impurities in the starting powder varied from 37 g/g to 0.02 g/g. The impurity elements Li, Na, Mg, P, S, Cl, K, Ca, Mn, Co, Ni, Cu, Zn, As, Pd, Ag, Cd, Sn, Sb, Te, Ba, Ce, Tl, Pb, and Bi were not detectable following the purification. No significant change in concentration of the elements Ti, V, Zr, Nb, Mo, and Re was found. The elements B, C, Al, Si, Cr, Fe, Ru, Rh, and Pt were partially removed by vaporization during electron beam melting. Langmuir's equation for ideal vaporization into a vacuum was used to calculate for each impurity element the expected ratio of impurity content after melting to that before melting. Equilibrium vapor pressures were calculated using Henry's law, with activity coefficients obtained from published data for the elements Fe, Ti, and Pt. Activity coefficients were estimated from enthalpy data for Al, Si, V, Cr, Mn, Co, Ni, Zr, Nb, Mo, and Hf and an ideal solution model was used for the remaining elements. The melt temperature was determined from measured iridium weight loss. Excellent agreement was found between measured and calculated impurity ratios for all impurity elements. The results are consistent with some localized heating of the melt pool due to rastering of the electron beam, with an average vaporization temperature of 3100 K as compared to a temperature of 2965 K calculated for uniform heating of the melt pool. The results are also consistent with ideal mixing in the melt pool.

  18. Kinetics of hydride front in Zircaloy-2 and H release from a fractional hydrided surface

    SciTech Connect

    Diaz, M.; Gonzalez-Gonzalez, A.; Moya, J. S.; Remartinez, B.; Perez, S.; Sacedon, J. L. [Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz 3, Cantoblanco, 28049 Madrid (Spain); Iberdrola, Tomas Redondo 3, 28033 Madrid (Spain); Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz 3, Cantoblanco, 28049 Madrid (Spain)

    2009-07-15

    The authors study the hydriding process on commercial nuclear fuel claddings from their inner surface using an ultrahigh vacuum method. The method allows determining the incubation and failure times of the fuel claddings, as well as the dissipated energy and the partial pressure of the desorbed H{sub 2} from the outer surface of fuel claddings during the hydriding process. The correlation between the hydriding dissipated energy and the amount of zirconium hydride (formed at different stages of the hydriding process) leads to a near t{sup 1/2} potential law corresponding to the time scaling of the reaction for the majority of the tested samples. The calibrated relation between energy and hydride thickness allows one to calculate the enthalpy of the {delta}-ZrH{sub 1.5} phase. The measured H{sub 2} desorption from the external surface is in agreement with a proposed kinetic desorption model from the hydrides precipitated at the surface.

  19. DETERMINATION OF HETEROGENEOUS ELECTRON TRANSFER RATE CONSTANTS AT MICROFABRICATED IRIDIUM ELECTRODES. (R825511C022)

    EPA Science Inventory

    There has been an increasing use of both solid metal and microfabricated iridium electrodes as substrates for various types of electroanalysis. However, investigations to determine heterogeneous electron transfer rate constants on iridium, especially at an electron beam evapor...

  20. DOI: 10.1002/adsc.200700546 Iridium-Catalyzed Asymmetric Hydrogenation of Vinyl Ethers

    E-print Network

    Burgess, Kevin

    DOI: 10.1002/adsc.200700546 Iridium-Catalyzed Asymmetric Hydrogenation of Vinyl Ethers Ye Zhua,P-ligated iridium complexes in asymmetric hydrogenations of the silyl and methyl enol ethers D and E, but complex

  1. Hydrodesulfurization of Thiophene and Benzothiophene to Butane and Ethylbenzene by a Homogeneous Iridium

    E-print Network

    Jones, William D.

    Iridium Complex David A. Vicic and William D. Jones* Department of Chemistry, University of Rochester such as benzothiophene. This led us to explore the reactivity of the bis(µ-hydrido)- bis[chloro(pentamethylcyclopentadienyl)]iridium

  2. Integrated electrolyser—metal hydride compression system

    Microsoft Academic Search

    F. Laurencelle; Z. Dehouche; J. Goyette; T. K. Bose

    2006-01-01

    Metal hydride thermal compression is a reliable process to compress hydrogen without contamination. We report on the development of a three-stage metal hydride hydrogen compressor. It will compress a part of the hydrogen produced by an electrolyser and will recycle the heat released by the electrolytic cells as its principal energy supply. This compressor will raise the hydrogen pressure from

  3. Direct synthesis of catalyzed hydride compounds

    DOEpatents

    Gross, Karl J.; Majzoub, Eric

    2004-09-21

    A method is disclosed for directly preparing alkali metal aluminum hydrides such as NaAlH.sub.4 and Na.sub.3 AlH.sub.6 from either the alkali metal or its hydride, and aluminum. The hydride thus prepared is doped with a small portion of a transition metal catalyst compound, such as TiCl.sub.3, TiF.sub.3, or a mixture of these materials, in order to render them reversibly hydridable. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen while heating the mixture to about 125.degree. C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

  4. Electrodeposition of highly ordered macroporous iridium oxide through self-assembled colloidal templates

    E-print Network

    Steiner, Ullrich

    Electrodeposition of highly ordered macroporous iridium oxide through self-assembled colloidal as an Advance Article on the web 24th April 2009 DOI: 10.1039/b900279k Iridium oxide electrodeposited through devices. Introduction Iridium oxide (IrOx) films are well known for their applications in electrochromism

  5. Synthesis and characterization of a series of rhodium, iridium, and ruthenium isocyanide complexes

    E-print Network

    Jones, William D.

    Synthesis and characterization of a series of rhodium, iridium, and ruthenium isocyanide complexes in revised form 16 July 2013 Accepted 18 July 2013 Available online 8 August 2013 Keywords: Rhodium Iridium with novel electrophilic rhodium and iridium complexes possessing a fac-chelating bis-pyrazolylacetate ligand

  6. Copyright c 2008 IEEE. Reprinted from Ujjwal Deep Dahal, Brent R. Petersen and Julian Meng, "Iridium

    E-print Network

    Petersen, Brent

    , "Iridium communication system for data telemetry of renewable distributed generation system," in 2008 24th, you agree to all provisions of the copyright laws protecting it. #12;Iridium Communication System for the required telemetry. The Iridium satellite system is able to provide global communications at a reasonable

  7. Epitaxial graphene prepared by chemical vapor deposition on single crystal thin iridium films on sapphire

    E-print Network

    Boyer, Edmond

    Epitaxial graphene prepared by chemical vapor deposition on single crystal thin iridium films- gle layer graphene on top. Iridium is one of the low C solubility metals onto which pure single layer(0001)] wafers (Roditi Ltd.), cut in 6.5×8.5 mm2 pieces, were used as substrates. Iridium was grown by pulsed

  8. REVIEW OF SCIENTIFIC INSTRUMENTS 82, 116105 (2011) Note: Electrochemical etching of sharp iridium tips

    E-print Network

    Grütter, Peter

    2011-01-01

    REVIEW OF SCIENTIFIC INSTRUMENTS 82, 116105 (2011) Note: Electrochemical etching of sharp iridium iridium tips with apex radii of 15­70 nm, as determined by scanning electron microscopy, field ion American Institute of Physics. [doi:10.1063/1.3662473] Iridium (Ir) has a very high Young's modulus (528

  9. Deposition and Stripping Properties of Mercury on Iridium S. P. Kounaves*'1 and J. Buffle

    E-print Network

    Kounaves, Samuel P.

    Deposition and Stripping Properties of Mercury on Iridium Electrodes S. P. Kounaves*'1 and J ABSTRACT The reduction of mercury on a fresh iridium surface is reversible with a half-wave potential documented in the literature, the same cannot be said for iridium. During the past 30 years, only a few

  10. Abstract. --The 193 Ir IVtossbauer isomer shifts of a set of closely related iridium carbonyl

    E-print Network

    Paris-Sud XI, Université de

    Abstract. -- The 193 Ir IVtossbauer isomer shifts of a set of closely related iridium carbonyl.228+0.024 1.888+0.042 (°) Vs. iridium metal. (*) Publication : Chem. Phys. Letters, 38 (1976), 310. DEPENDENCE OF IRIDIUM MOSSBAUER ISOMER SHIFTS ON OXIDATION STATE : AN INVERSION FOR LOW VALENT CARBONYL COMPLEXES (*) R

  11. Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition Fengyan ZHANG

    E-print Network

    Wang, Deli

    Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition Fengyan, U.S.A. (Received December 9, 2004; accepted February 3, 2005; published March 4, 2005) Iridium oxide) iridium (I) as the precursor on Si or SiO2 substrate with and without metal nanoparticles as catalysts

  12. Adsorptive Stripping Analysis of Trace Nickel at Iridium-Based Ultramicroelectrode Arrays

    E-print Network

    Kounaves, Samuel P.

    Adsorptive Stripping Analysis of Trace Nickel at Iridium-Based Ultramicroelectrode Arrays Joseph: July 27, 1999 Abstract Lithographically fabricated iridium-based mercury microelectrode arrays the iridium-based microelectrode array very attractive for on-site measurements of trace metals that cannot

  13. IRIDIUM SATELLITE SIGNALS: A CASE STUDY IN INTERFERENCE CHARACTERIZATION AND MITIGATION FOR

    E-print Network

    Lewis, Brian Murray

    IRIDIUM SATELLITE SIGNALS: A CASE STUDY IN INTERFERENCE CHARACTERIZATION AND MITIGATION FOR RADIO of the Iridium System. So astronomers are now studying a variety of diverse approaches to mitigating the effects-detection approaches to the identification and mitigation of RFI originating from the Iridium System. OBSERVATIONS

  14. Heterolytic CH Activation and Catalysis by an O-Donor Iridium-Hydroxo Complex

    E-print Network

    Goddard III, William A.

    Notes Heterolytic CH Activation and Catalysis by an O-Donor Iridium-Hydroxo Complex William J. Tenn, Pasadena, California 91125 ReceiVed July 21, 2006 Summary: A well-defined, O-donor ligated iridium-R and H2O. Specifically, we report the preparation of the O-donor iridium- (III) hydroxide complex (acac

  15. Chemical bath method to grow precipitated nanorods of iridium oxide on alumina membranes

    E-print Network

    Chiao, Jung-Chih

    Chemical bath method to grow precipitated nanorods of iridium oxide on alumina membranes C; Received on 23rd September 2012; Revised on 14th November 2012 High aspect ratio iridium (IV) oxide and densely packed iridium oxide (IrO2) nanostructures. Nanorods with an aspect ratio of 22 can be synthesised

  16. Catalytic Arene H/D Exchange with Novel Rhodium and Iridium Complexes

    E-print Network

    Jones, William D.

    Catalytic Arene H/D Exchange with Novel Rhodium and Iridium Complexes Jennifer L. Rhinehart to improve the efficiency of the system. Periana has reported using iridium26,27 with a wide variety an acetate is intricately involved in the C-H activation.30,31 Herein we report new rhodium and iridium

  17. Sensors and Actuators B 50 (1998) 117124 Failure analysis of microfabricated iridium ultramicroelectrodes in

    E-print Network

    Kounaves, Samuel P.

    1998-01-01

    Sensors and Actuators B 50 (1998) 117­124 Failure analysis of microfabricated iridium consisting of an array of microlithographically fabricated iridium ultramicroelectrodes (UME) on a silicon such as gold, platinum, iridium and carbon have been utilized as the electrode substrate. Most of these sensors

  18. Chiral Proline-Based Ligands for Iridium-Catalyzed Asymmetric Hydrogenation

    E-print Network

    Amrhein, Valentin

    Chiral Proline-Based Ligands for Iridium-Catalyzed Asymmetric Hydrogenation Inauguraldissertation. Parts of this work have been previously published: ,,Proline-Based P,O Ligands/Iridium Complexes in Iridium-Catalyzed Asymmetric Hydrogenation: New Catalysts, Substrates and Applications in Total Synthesis

  19. An ephemeral Frenkel pair in iridium (*) M.-H. Gly, A. Dunlop and Y. Qur

    E-print Network

    Paris-Sud XI, Université de

    L-219 An ephemeral Frenkel pair in iridium (*) M.-H. Gély, A. Dunlop and Y. Quéré Section d, accepte le 28 janvier 1983) Résumé. 2014 Après activation sous flux de neutrons, de l'iridium est maintenu activation, iridium samples have been kept at low temperature (22 K). The electrical resistivity decreases

  20. Goals: Reduction of IridiumGoals: Reduction of Iridium--usage; ASV Collaboration under Constraints; Online Datausage; ASV Collaboration under Constraints; Online Data--streamingstreaming CoastalCoastal FreewaveFreewave network; Hierarchical Control Scheme

    E-print Network

    Smith, Ryan N.

    Goals: Reduction of IridiumGoals: Reduction of Iridium--usage; ASV Collaboration under Constraints endurance (~4 wks) + Collaborative robotic sensing - Slow moving (Iridium is expensive (>$2500 instead of Iridium whenever in range. o Network should support multiple gliders simultaneously to enable

  1. Activated aluminum hydride hydrogen storage compositions and uses thereof

    DOEpatents

    Sandrock, Gary (Ringwood, NJ); Reilly, James (Bellport, NY); Graetz, Jason (Mastic, NY); Wegrzyn, James E. (Brookhaven, NY)

    2010-11-23

    In one aspect, the invention relates to activated aluminum hydride hydrogen storage compositions containing aluminum hydride in the presence of, or absence of, hydrogen desorption stimulants. The invention particularly relates to such compositions having one or more hydrogen desorption stimulants selected from metal hydrides and metal aluminum hydrides. In another aspect, the invention relates to methods for generating hydrogen from such hydrogen storage compositions.

  2. THE ROLE OF HYDRIDE SIZE, MATRIX STRENGTH.AND STRESS STATE ON FRACTURE INITIATION AT HYDRIDE PRECIPITATES IN ZIRCONIUM ALLOYS

    E-print Network

    Paris-Sud XI, Université de

    718 THE ROLE OF HYDRIDE SIZE, MATRIX STRENGTH.AND STRESS STATE ON FRACTURE INITIATION AT HYDRIDE to develop a theoretical understanding of KIH, a criterion for the initiation of fracture at hydride in the material tested (3). The conditions for fracture initiation at hydrides are, therefore, complex, requiring

  3. Hydrogen-storing hydride complexes

    DOEpatents

    Srinivasan, Sesha S. (Tampa, FL); Niemann, Michael U. (Venice, FL); Goswami, D. Yogi (Tampa, FL); Stefanakos, Elias K. (Tampa, FL)

    2012-04-10

    A ternary hydrogen storage system having a constant stoichiometric molar ratio of LiNH.sub.2:MgH.sub.2:LiBH.sub.4 of 2:1:1. It was found that the incorporation of MgH.sub.2 particles of approximately 10 nm to 20 nm exhibit a lower initial hydrogen release temperature of 150.degree. C. Furthermore, it is observed that the particle size of LiBNH quaternary hydride has a significant effect on the hydrogen sorption concentration with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160.degree. C. and the other around 300.degree. C., with the main hydrogen release temperature reduced from 310.degree. C. to 270.degree. C., while hydrogen is first reversibly released at temperatures as low as 150.degree. C. with a total hydrogen capacity of 6 wt. % to 8 wt. %. Detailed thermal, capacity, structural and microstructural properties have been demonstrated and correlated with the activation energies of these materials.

  4. Regeneration of lithium aluminum hydride.

    PubMed

    Graetz, Jason; Wegrzyn, James; Reilly, James J

    2008-12-31

    Lithium aluminum hydride (LiAlH(4)) is a promising compound for hydrogen storage, with a high gravimetric and volumetric hydrogen density and a low decomposition temperature. Similar to other metastable hydrides, LiAlH(4) does not form by direct hydrogenation at reasonable hydrogen pressures; therefore, there is considerable interest in developing new routes to regenerate the material from the dehydrogenated products LiH and Al. Here we demonstrate a low-energy route to regenerate LiAlH(4) from LiH and Ti-catalyzed Al. The initial hydrogenation occurs in a tetrahydrofuran slurry and forms the adduct LiAlH(4).4THF. The thermodynamics of this reversible reaction were investigated by measuring pressure-composition isotherms, and the free energy was found to be small and slightly negative (DeltaG = -1.1 kJ/mol H(2)), suggesting an equilibrium hydrogen pressure of just under 1 bar at 300 K. We also demonstrate that the adduct LiAlH(4).4THF can be desolvated at low temperature to yield crystalline LiAlH(4). PMID:19053465

  5. Liquid suspensions of reversible metal hydrides

    DOEpatents

    Reilly, J.J.; Grohse, E.W.; Winsche, W.E.

    1983-12-08

    The reversibility of the process M + x/2 H/sub 2/ ..-->.. MH/sub x/, where M is a metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under a liquid, thereby to reduce contamination, provide better temperature control and provide in situ mobility of the reactants. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen (at high pressures) and to release (at low pressures) previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the former is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the H/sub 2/ pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  6. Experimental determination of the solubility of iridium in silicate melts: Preliminary results

    NASA Technical Reports Server (NTRS)

    Borisov, Alexander; Dingwell, Donald B.; Oneill, Hugh ST.C.; Palme, Herbert

    1992-01-01

    Little is known of the geochemical behavior of iridium. Normally this element is taken to be chalcophile and/or siderophile so that during planetary differentiation processes, e.g., core formation, iridium is extracted from silicate phases into metallic phases. Experimental determination of the metal/silicate partition coefficient of iridium is difficult simply because it is so large. Also there are no data on the solubility behavior of iridium in silicate melts. With information on the solubility of iridium in silicate melts it is possible, in combination with experimental data for Fe-Ir alloys, to calculate the partition coefficient between a metallic phase and a silicate melt.

  7. pH sensors based on iridium oxide

    SciTech Connect

    Tarlov, M.J.; Kreider, K.G.; Semancik, S.; Huang, P. (National Inst. of Standards and Technology, Gaithersburg, MD (USA). Chemical Process Metrology Div.)

    1990-03-01

    Results are presented on the pH-potential response of dc magnetron reactively sputtered iridium oxide films. The films exhibit a nearly Nernstian response to pH, no hysteresis effects, and minimal response to ionic interferences. Sensitivity to certain redox species is observed, however. In addition, methods are discussed for preparing model iridium oxide sensor surfaces for ultrahigh vacuum surface analytical studies. Stoichiometric IrO{sub 2}-like surfaces are shown to be relatively inert to gas phase water. However, hydroxylation of IrO{sub 2}-like surfaces can be induced by rf water plasma treatment. 17 refs., 5 figs.

  8. Iridium anomaly from the Acraman impact ejecta horizon - Impacts can produce sedimentary iridium peaks

    NASA Astrophysics Data System (ADS)

    Gostin, V. A.; Keays, R. R.; Wallace, M. W.

    1989-08-01

    Data from the Acraman impact ejecta horizon, South Australia, are presented which conclusively links high sedimentary iridium concentrations to a major meteoroid-impact structure and its widely dispersed ejecta. An Ir anomaly is present within the ejecta from the Acraman impact event preserved in late Precambrian shales within the Adelaide Geosyncline. The highest Ir concentrations within the ejecta are associated with the coarser-grained clasts of acid volcanics, suggesting that most of the Ir is carried by these fragments. The target rocks at the impact site are comparable acid volcanics that have very low Ir, Au, Pt, Pd, Ru, and Cr concentrations, indicating a meteoritic origin for the anomalous Ir levels within the ejecta.

  9. Potential-modulated reflectance study of the oxidation state of iridium in anodic iridium oxide films

    SciTech Connect

    Gutierrez, C.; Sanchez, M.; Pena, J.I.; Martinez, C.; Martinez, M.A.

    1987-09-01

    In an attempt to identify the changes of oxidation state involved in the electrochromic effect of anodic iridium oxide films (AIROF's) the authors obtained potential-modulated reflectance (PMR) spectra of AIROF's at three pH values: 0.9, 6.7, and 13.0, in the wavelength range 200-650 nm and at an angle of incidence of 45/sup 0/. Depending on pH, the voltammograms show up to four peaks (I-IV) in the anodic scan, the coloration-bleaching process corresponding to the main voltammetric peak II. The PMR spectra measured at a given voltammetric feature were nearly independent of pH, which shows that (i) the chemical composition of the AIROF is largely independent of the pH of the solution in which it was grown; (ii) the reflectance signal is originated by changes of the oxidation state of iridium in the AIROF. The PMR spectra were independent of the thickness of the AIROF, and therefore were not a trivial interference effect. The PMR maximum at 580-610 nm at voltammetric peak II has been tentatively assigned to an Ir(IV) oxide or oxyhydroxide, as have the PMR maximum at 330-360 nm at the minimum between voltammetric peaks II and III and the PMR maximum at 220-260 nm at potentials at or above voltammetric peak III. Apparently an Ir(IV) oxide or oxyhydroxide predominates in the potential range between voltammetric peaks II and IV, and different transitions become possible in this oxide at increasingly positive potentials.

  10. Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes

    E-print Network

    Robinson, R

    2011-01-01

    Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  11. A comparison of the IRIDIUM and AMPS systems

    Microsoft Academic Search

    Yvette C. Hubbel

    1997-01-01

    A brief history of progress made in the mobile telecommunications industry is presented. This article compares the IRIDIUM system (which uses satellite operating in the 22.55 to 23.55 GHz range) to the existing Advanced Phone System (AMPS) cellular system. It is concluded that although the two systems' architectures, services provided, and subscriber number formats vary enormously, the methods used for

  12. Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes

    E-print Network

    R. Robinson; M. Thoennessen

    2011-09-02

    Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  13. Discovery of tantalum, rhenium, osmium, and iridium isotopes

    SciTech Connect

    Robinson, R.; Thoennessen, M., E-mail: thoennessen@nscl.msu.edu

    2012-09-15

    Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  14. METALLIC HYDRIDES. Magnetic properties of laves-phase rare earth hydrides

    E-print Network

    Boyer, Edmond

    METALLIC HYDRIDES. Magnetic properties of laves-phase rare earth hydrides J. J. Rhyne and G. E on the rare earth site. The rare earth spins disorder at a temperature lower than the bulk Tc in ErFe2 H3 5 per formula unit assuming complete occupation of 3 tetrahedral sites. The heavy rare earth (RFe2

  15. EXPERIMENTAL INVESTIGATION OF STRAIN, DAMAGE AND FAILURE OF HYDRIDED ZIRCONIUM ALLOYS WITH VARIOUS HYDRIDE ORIENTATIONS

    Microsoft Academic Search

    A. Racine; M. Bornert; C. Cappelaere; D. Caldemaison

    This experimental investigation is devoted to the hydride embrittlement of fuel cladding tubes and especially to the influence of the orientation of hydrides with respect to the applied stress on strain, damage and failure mechanisms. Ring tensile tests are performed on cladding tube material (unirradiated cold worked stress-relieved Zircaloy-4). The average hydrogen content of the material is about 200ppm, and

  16. Optimal hydride fueled BWR assembly designs

    SciTech Connect

    Fratoni, M.; Greenspan, E. [Nuclear Engineering Dept., Univ. of California at Berkeley, Berkeley, CA 94720-1730 (United States)

    2006-07-01

    The feasibility of improving the performance of BWR's by using hydride fuel instead of oxide fuel is assessed. Performance improvements looked for including enhanced power density, simplified fuel bundle and core design and less negative void coefficient of reactivity. A 3-D neutronic analysis is performed to determine attainable discharge burn-up, pin-by-pin power distribution, axial power distribution, reactivity coefficients, reactivity worth of control elements and burnable absorber effects. It is found that hydride fuel bundle design can be greatly simplified by eliminating water rods and partial length fuel rods and by shrinking the water gaps surrounding the bundle box. As a result the hydride fuel bundle contains 96 full length fuel rods of a uniform composition versus 71 effective full length fuel rods of 8 different compositions of the reference oxide fuel bundle. The cruciform control elements are replaced by a cluster of control rods without increasing the number of control drive mechanisms. IFBA is identified as the preferred burnable poison. A companion study of the thermal-hydraulic and vibration characteristics of BWR cores predicts that the increase in the number of fuel rods per given core volume combined with the low peak-to-average pin-wise power distribution of hydride fuel designs enables increasing the BWR power density by up to 40% relative to the oxide fuel design. The net outcome is expected to be improved BWR economics even though hydride fuel requires higher uranium enrichment. Use of hydride fuel may also improve the stability of BWR's against power oscillations as the void coefficient of reactivity of hydride fuelled designs is less negative than that of oxide fuelled designs. (authors)

  17. Optimization of hydride fueled pressurized water reactor cores

    E-print Network

    Shuffler, Carter Alexander

    2004-01-01

    This thesis contributes to the Hydride Fuels Project, a collaborative effort between UC Berkeley and MIT aimed at investigating the potential benefits of hydride fuel use in light water reactors (LWRs). This pursuit involves ...

  18. Simulation of dose distribution for iridium-192 brachytherapy source type-H01 using MCNPX

    SciTech Connect

    Purwaningsih, Anik [Center for development of nuclear informatics, National Nuclear Energy Agency, PUSPIPTEK, Serpong, Banten 15310 (Indonesia)

    2014-09-30

    Dosimetric data for a brachytherapy source should be known before it used for clinical treatment. Iridium-192 source type H01 was manufactured by PRR-BATAN aimed to brachytherapy is not yet known its dosimetric data. Radial dose function and anisotropic dose distribution are some primary keys in brachytherapy source. Dose distribution for Iridium-192 source type H01 was obtained from the dose calculation formalism recommended in the AAPM TG-43U1 report using MCNPX 2.6.0 Monte Carlo simulation code. To know the effect of cavity on Iridium-192 type H01 caused by manufacturing process, also calculated on Iridium-192 type H01 if without cavity. The result of calculation of radial dose function and anisotropic dose distribution for Iridium-192 source type H01 were compared with another model of Iridium-192 source.

  19. Thin-film metal hydrides.

    PubMed

    Remhof, Arndt; Borgschulte, Andreas

    2008-12-01

    The goal of the medieval alchemist, the chemical transformation of common metals into nobel metals, will forever be a dream. However, key characteristics of metals, such as their electronic band structure and, consequently, their electric, magnetic and optical properties, can be tailored by controlled hydrogen doping. Due to their morphology and well-defined geometry with flat, coplanar surfaces/interfaces, novel phenomena may be observed in thin films. Prominent examples are the eye-catching hydrogen switchable mirror effect, the visualization of solid-state diffusion and the formation of complex surface morphologies. Thin films do not suffer as much from embrittlement and/or decrepitation as bulk materials, allowing the study of cyclic absorption and desorption. Therefore, thin-metal hydride films are used as model systems to study metal-insulator transitions, for high throughput combinatorial research or they may be used as indicator layers to study hydrogen diffusion. They can be found in technological applications as hydrogen sensors, in electrochromic and thermochromic devices. In this review, we discuss the effect of hydrogen loading of thin niobium and yttrium films as archetypical examples of a transition metal and a rare earth metal, respectively. Our focus thereby lies on the hydrogen induced changes of the electronic structure and the morphology of the thin films, their optical properties, the visualization and the control of hydrogen diffusion and on the study of surface phenomena and catalysis. PMID:18980236

  20. High H? ionic conductivity in barium hydride.

    PubMed

    Verbraeken, Maarten C; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T S

    2015-01-01

    With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H(-)) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm(-1) at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on. PMID:25485988

  1. Reactivity of yttrium carboxylates toward alkylaluminum hydrides.

    PubMed

    Schädle, Christoph; Fischbach, Andreas; Herdtweck, Eberhardt; Törnroos, Karl W; Anwander, Reiner

    2013-11-25

    Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(?-OOCAr(Me))(?-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(?-H)AlMe2(?-H)AlMe2(?-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(?-OOCAr(Me))(?-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of ?=-88.1 ppm (R=CH2SiMe3) and ?=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments. PMID:24151216

  2. Electrooxidation of methanol on iridium in acidic solutions: electrocatalysis and surface characterization by infrared spectroscopy

    Microsoft Academic Search

    Akiko. Aramata; Tadayoshi. Yamazaki; Keiji. Kunimatsu; Michio. Enyo

    1987-01-01

    Electrooxidation of methanol was studied on iridium in HâSOâ and CHlOâ solutions in connection with catalytic activities of the electrode in various oxidation states and of the adsorbed CO observed by infrared spectrometry. Iridium was found to show higher catalytic activity than platinum at low positive potential regions. The catalytic activity of iridium decreased with time at a constant-potential polarization

  3. Stratigraphic occurrences of iridium anomalies at four Cretaceous\\/Tertiary boundary sites in New Zealand

    Microsoft Academic Search

    Robert R. Brooks; C. Percy Strong; Julian Lee; Charles J. Orth; James S. Gilmore; Douglas E. Ryan; Jiri Holzbecher

    1986-01-01

    Three new iridium anomaly sites have been discovered in Cretaceous\\/Tertiary boundary sequences in New Zealand. These are at Needles Point, Chancet Rocks, and Waipara, where integrated iridium deposition values were 165, 211, and 7 ng\\/cm2, respectively. In contrast to the previously reported Woodside Creek stratigraphic sequence that had an iridium anomaly of 187 ng\\/cm2, a ferruginous boundary clay is absent

  4. Meteoric smoke fallout over the Holocene epoch revealed by iridium and platinum in Greenland ice

    Microsoft Academic Search

    Paolo Gabrielli; Carlo Barbante; John M. C. Plane; Anita Varga; Sungmin Hong; Giulio Cozzi; Vania Gaspari; Frédéric A. M. Planchon; Warren Cairns; Christophe Ferrari; Paul Crutzen; Paolo Cescon; Claude F. Boutron

    2004-01-01

    An iridium anomaly at the Cretaceous\\/Tertiary boundary layer has been attributed to an extraterrestrial body that struck the Earth some 65million years ago. It has been suggested that, during this event, the carrier of iridium was probably a micrometre-sized silicate-enclosed aggregate or the nanophase material of the vaporized impactor. But the fate of platinum-group elements (such as iridium) that regularly

  5. Thermal property measurements of high pressure metal hydrides

    Microsoft Academic Search

    Scott Michael Flueckiger

    2009-01-01

    Metal hydrides are potential materials for onboard hydrogen storage. Thermal property measurements are needed to optimize the thermal management design of metal hydride storage systems which require a measurement technique developed with considerations of the thermodynamics of the hydriding process and the pyrophoric nature of the material. In the present work, a transient plane source (TPS) apparatus was integrated with

  6. Accurate simplified dynamic model of a metal hydride tank

    Microsoft Academic Search

    Tim M. Brown; Jacob Brouwer; G. Scott Samuelsen; Franklin H. Holcomb; Joel King

    2008-01-01

    As proton exchange membrane fuel cell technology advances, the need for hydrogen storage intensifies. Metal hydride alloys offer one potential solution. However, for metal hydride tanks to become a viable hydrogen storage option, the dynamic performance of practical tank geometries and configurations must be understood and incorporated into fuel cell system analyses. A dynamic, axially-symmetric, multi-nodal metal hydride tank model

  7. Potassium Hydride in Paraffin: A Useful Base for Organic Synthesis

    E-print Network

    Taber, Douglass

    Potassium Hydride in Paraffin: A Useful Base for Organic Synthesis Douglass F. Taber taberdf@udel.edu ReceiVed July 7, 2006 The preparation of potassium hydride as a 1:1 homogenate be a generally useful base for organic synthesis. Sodium hydride (NaH), potassium tert-butoxide, and n-BuLi have

  8. Synthesis, characterization, and reactivity studies of iridium complexes bearing the ligand diphenylphosphidoboratabenzene

    E-print Network

    Arizpe, Luis (Luis Alfredo)

    2011-01-01

    The synthesis, structure, and reactivity properties of three iridium square planar complexes bearing the anionic phosphine ligand diphenylphosphidoboratabenzene (DPB) are described. Reactivity studies show a rate enhancement ...

  9. Delayed hydride cracking of zirconium alloys

    SciTech Connect

    Yau, T.L. [Teledyne Wah Chang, Albany, OR (United States); Webster, R.T. [Webster (R.T.), Scio, OR (United States)

    1995-10-01

    High-strength zirconium alloys are susceptible to a mechanism for crack initiation and propagation termed delayed hydride cracking (DHC). In these alloys, it is possible to generate a large enough stress gradient so that hydrogen moves to the highly stressed areas. Therefore, hydrides precipitate and grow in these areas. When the tensile stress is sufficiently great, crack initiation starts at some of these hydrides. Crack propagation occurs by repeating the same process at the crack tip. Of concern for the chemical process industries is the DHC of Zr-2.5Nb welds. Results of long-term tests and case histories indicate that stress relieving is one of the major measures for preventing DHC, provided that ASME mechanical requirements are met.

  10. Iridium-catalyzed C-H borylation of pyridines.

    PubMed

    Sadler, Scott A; Tajuddin, Hazmi; Mkhalid, Ibraheem A I; Batsanov, Andrei S; Albesa-Jove, David; Cheung, Man Sing; Maxwell, Aoife C; Shukla, Lena; Roberts, Bryan; Blakemore, David C; Lin, Zhenyang; Marder, Todd B; Steel, Patrick G

    2014-10-01

    The iridium-catalysed C-H borylation is a valuable and attractive method for the preparation of aryl and heteroaryl boronates. However, application of this methodology for the preparation of pyridyl and related azinyl boronates can be challenged by low reactivity and propensity for rapid protodeborylation, particularly for a boronate ester ortho to the azinyl nitrogen. Competition experiments have revealed that the low reactivity is due to inhibition of the active catalyst through coordination of the azinyl nitrogen lone pair at the vacant site on the iridium. This effect can be overcome through the incorporation of a substituent at C-2. Moreover, when this is sufficiently electron-withdrawing protodeborylation is sufficiently slowed to permit isolation and purification of the C-6 boronate ester. Following functionalization, reduction of the directing C-2 substituent provides the product arising from formal ortho borylation of an unhindered pyridine ring. PMID:25116330

  11. Received 21 Jul 2013 | Accepted 7 Jan 2014 | Published 3 Feb 2014 Iridium oxide nanotube electrodes for

    E-print Network

    Cui, Yi

    ARTICLE Received 21 Jul 2013 | Accepted 7 Jan 2014 | Published 3 Feb 2014 Iridium oxide nanotube- rodes of a new geometry, namely nanotubes of iridium oxide. When cardiomyocytes are cultured upon those

  12. Mechanistic Investigation of Iridium-Catalyzed Hydrovinylation of Jonas Oxgaard, Gaurav Bhalla, Roy A. Periana, and William A. Goddard, III*,

    E-print Network

    Goddard III, William A.

    Mechanistic Investigation of Iridium-Catalyzed Hydrovinylation of Olefins Jonas Oxgaard, Gaurav metallacyclopentane intermediates have also been postulated.8 Only a related iridium complex, Tp*Ir(C2H4)2, has been

  13. Decomposition of lithium magnesium aluminum hydride

    Microsoft Academic Search

    Hilde Grove; Ole Martin Løvvik; Weiming Huang; Susanne M. Opalka; Richard H. Heyn; Bjørn C. Hauback

    2011-01-01

    The quaternary aluminum hydride LiMg(AlH4)3 contains 9.7 wt% hydrogen, of which 7.2 wt% can be released in a two-step decomposition reaction via first formation of LiMgAlH6 and then the binary hydrides MgH2 and LiH. In-situ synchrotron radiation powder X–ray diffraction and thermal desorption spectroscopy measurements were performed to analyze the product distributions formed during the thermal decomposition of LiMg(AlD4)3. The first decomposition

  14. Iridium NEXT: A Global access for your sensor needs

    Microsoft Academic Search

    O. P. Gupta; C. S. Fish

    2010-01-01

    The operational Iridium constellation is comprised of 66 satellites, used to primarily provide worldwide voice and data coverage to satellite phones, pagers and integrated transceivers. The satellites are in low Earth orbit at 781 km and inclination of 86.4 deg, resulting in unprecedented 24\\/7 coverage and real-time visibility of the entire globe. Recently, through funding from the National Science Foundation

  15. Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution

    NASA Technical Reports Server (NTRS)

    Valdez, Thomas I.; Narayan, Sri R.; Billings, Keith J.

    2011-01-01

    NASA requires a durable and efficient catalyst for the electrolysis of water in a polymer-electrolyte-membrane (PEM) cell. Ruthenium oxide in a slightly reduced form is known to be a very efficient catalyst for the anodic oxidation of water to oxygen, but it degrades rapidly, reducing efficiency. To combat this tendency of ruthenium oxide to change oxidation states, it is combined with iridium, which has a tendency to stabilize ruthenium oxide at oxygen evolution potentials. The novel oxygen evolution catalyst was fabricated under flowing argon in order to allow the iridium to preferentially react with oxygen from the ruthenium oxide, and not oxygen from the environment. Nanoparticulate iridium black and anhydrous ruthenium oxide are weighed out and mixed to 5 18 atomic percent. They are then heat treated at 300 C under flowing argon (in order to create an inert environment) for a minimum of 14 hours. This temperature was chosen because it is approximately the creep temperature of ruthenium oxide, and is below the sintering temperature of both materials. In general, the temperature should always be below the sintering temperature of both materials. The iridium- doped ruthenium oxide catalyst is then fabricated into a PEM-based membrane- electrode assembly (MEA), and then mounted into test cells. The result is an electrolyzer system that can sustain electrolysis at twice the current density, and at the same efficiency as commercial catalysts in the range of 100-200 mA/sq cm. At 200 mA/sq cm, this new system operates at an efficiency of 85 percent, which is 2 percent greater than commercially available catalysts. Testing has shown that this material is as stable as commercially available oxygen evolution catalysts. This means that this new catalyst can be used to regenerate fuel cell systems in space, and as a hydrogen generator on Earth.

  16. STRUCTURAL AND OPTICAL PROPERTIES OF IRIDIUM FILMS ANNEALED IN AIR

    Microsoft Academic Search

    Sandeep Kohli; David Niles; Christopher D. Rithner; Peter K. Dorhout

    The present paper describes the changes in the structural and optical properties of the sputter deposited iridium films annealed in air and slow cooled from 673K-1073K. Glancing Angle X- ray Diffraction (GAXRD) and X-ray Reflectivity (XRR) measurements were used for the structural investigations of the films. GAXRD and X-ray reflectivity measurements showed growth of ~4nm IrO2 over-layer by annealing at

  17. Chronic neural stimulation with thin-film, iridium oxide electrodes

    Microsoft Academic Search

    James D. Weiland; David J. Anderson

    2000-01-01

    Experiments were conducted to assess the effect of chronic stimulation on the electrical properties of the elec- trode-tissue system, as measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Silicon, mi- cromachined probes with multiple iridium oxide stimulating electrodes (400-1600 m ) were implanted in guinea pig cortex. A 10-17 day post-operative recovery period was followed by five days

  18. 1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. OPERATIONS IN THE GLOVE BOX IN THE BACKGROUND OF THE PHOTOGRAPH INCLUDED HYDRIDING OF PLUTONIUM AND HYDRIDE SEPARATION. IN THE FOREGROUND, THE VACUUM MONITOR CONTROL PANEL MEASURED TEMPERATURES WITHIN THE GLOVEBOX. THE CENTER CONTROL PANEL REGULATED THE FURNACE INSIDE THE GLOVE BOX USED IN THE HYDRIDING PROCESSES. THIS EQUIPMENT WAS ESSENTIAL TO THE HYDRIDING PROCESS, AS WELL AS OTHER GLOVE BOX OPERATIONS. - Rocky Flats Plant, Plutonium Laboratory, North-central section of industrial area at 79 Drive, Golden, Jefferson County, CO

  19. Mono- and bis-tolylterpyridine iridium(III) complexes

    SciTech Connect

    Hinkle, Lindsay M.; Young, Jr., Victor G.; Mann, Kent R. (UMM)

    2012-01-20

    The first structure report of trichlorido[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) dimethyl sulfoxide solvate, [IrCl{sub 3}(C{sub 22}H{sub 17}N{sub 3})] {center_dot} C{sub 2}H{sub 6}OS, (I), is presented, along with a higher-symmetry setting of previously reported bis[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) tris(hexafluoridophosphate) acetonitrile disolvate, [Ir(C{sub 22}H{sub 17}N{sub 3})2](PF{sub 6}){sub 3} {center_dot} 2C{sub 2}H{sub 3}N, (II) [Yoshikawa, Yamabe, Kanehisa, Kai, Takashima & Tsukahara (2007). Eur. J. Inorg. Chem. pp. 1911-1919]. For (I), the data were collected with synchrotron radiation and the dimethyl sulfoxide solvent molecule is disordered over three positions, one of which is an inversion center. The previously reported structure of (II) is presented in the more appropriate C2/c space group. The iridium complex and one PF{sub 6}{sup -} anion lie on twofold axes in this structure, making half of the molecule unique.

  20. Spin-orbit coupling in phosphorescent iridium(III) complexes.

    PubMed

    Smith, Arthur R G; Burn, Paul L; Powell, Ben J

    2011-09-12

    We study the excited states of two iridium(III) complexes with potential applications in organic light-emitting diodes: fac-tris(2-phenylpyridyl)iridium(III) [Ir(ppy)(3)] and fac-tris(1-methyl-5-phenyl-3-n-propyl-[1,2,4]triazolyl)iridium(III) [Ir(ptz)(3)]. Herein we report calculations of the excited states of these complexes from time-dependent density functional theory (TDDFT) with the zeroth-order regular approximation (ZORA). We show that results from the one-component formulation of ZORA, with spin-orbit coupling included perturbatively, accurately reproduce both the results of the two-component calculations and previously published experimental absorption spectra of the complexes. We are able to trace the effects of both scalar relativistic correction and spin-orbit coupling on the low-energy excitations and radiative lifetimes of these complexes. In particular, we show that there is an indirect relativistic stabilisation of the metal-to-ligand charge transfer (MLCT) states. This is important because it means that indirect relativistic effects increase the degree to which SOC can hybridise singlet and triplet states and hence plays an important role in determining the optical properties of these complexes. We find that these two compounds are remarkably similar in these respects, despite Ir(ppy)(3) and Ir(ptz)(3) emitting green and blue light respectively. However, we predict that these two complexes will show marked differences in their magnetic circular dichroism (MCD) spectra. PMID:21786381

  1. Hydridable material for the negative electrode in a nickel-metal hydride storage battery

    DOEpatents

    Knosp, Bernard (Neuilly-sur-Seine, FR); Bouet, Jacques (Paris, FR); Jordy, Christian (Dourdan, FR); Mimoun, Michel (Neuilly-sur-Marne, FR); Gicquel, Daniel (Lanorville, FR)

    1997-01-01

    A monophase hydridable material for the negative electrode of a nickel-metal hydride storage battery with a "Lave's phase" structure of hexagonal C14 type (MgZn.sub.2) has the general formula: Zr.sub.1-x Ti.sub.x Ni.sub.a Mn.sub.b Al.sub.c Co.sub.d V.sub.e where ##EQU1##

  2. An experimental study of the solubility and partitioning of iridium, osmium and gold between olivine and silicate melt

    E-print Network

    Mcdonough, William F.

    = An experimental study of the solubility and partitioning of iridium, osmium and gold between­melt partitioning experiments to understand the behaviour of iridium, osmium and gold during crust; osmium; iridium; gold; partitioning; olivine 1. Introduction Owing to their refractory nature, and unique

  3. Effects of Electrodeposition Conditions and Protocol on the Properties of Iridium Oxide pH Sensor Electrodes

    E-print Network

    Majda, Marcin

    Effects of Electrodeposition Conditions and Protocol on the Properties of Iridium Oxide pH Sensor of California, Berkeley, Berkeley, California 94720-1460, USA The properties of iridium oxide pH sensors substrates with iridium oxide. Increasing the film thickness beyond the full coverage did not further

  4. A Combined Ab Initio and Bond-Order Potentials Study of Cohesion in Iridium Marc J. Cawkwell1

    E-print Network

    Vitek, Vaclav

    A Combined Ab Initio and Bond-Order Potentials Study of Cohesion in Iridium Marc J. Cawkwell1 , Duc and excellent resistance to oxidation and corrosion offered by iridium suggest numerous applications since highlighted iridium as worthy of significant industrial interest and academic study. Owing to its

  5. A Cost-effective Microcontroller-based Iridium Satellite Communication Architecture for a Remote Renewable Energy Source

    E-print Network

    Petersen, Brent

    A Cost-effective Microcontroller-based Iridium Satellite Communication Architecture for a Remote, 2008 #12;ii DEDICATION This thesis is dedicated to my parents. #12;iii ABSTRACT The Iridium Satellite (SBD) transceiver for data communications. A cost-effective microcontroller-based Iridium SBD satellite

  6. Effects of ?-hydride precipitation at a crack tip on crack propagation in delayed hydride cracking of Zircaloy-2

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Kobayashi, Y.

    2013-08-01

    Delayed hydride cracking (DHC) of Zircaloy-2 is one possible mechanism for the failure of boiling water reactor fuel rods in ramp tests at high burnup. Analyses were made for hydrogen diffusion around a crack tip to estimate the crack velocity of DHC in zirconium alloys, placing importance on effects of precipitation of ?-hydride. The stress distribution around the crack tip is significantly altered by precipitation of hydride, which was strictly analyzed using a finite element computer code. Then, stress-driven hydrogen diffusion under the altered stress distribution was analyzed by a differential method. Overlapping of external stress and hydride precipitation at a crack tip induces two stress peaks; one at a crack tip and the other at the front end of the hydride precipitate. Since the latter is larger than the former, more hydrogen diffuses to the front end of the hydride precipitate, thereby accelerating hydride growth compared with that in the absence of the hydride. These results indicated that, after hydride was formed in front of the crack tip, it grew almost steadily accompanying the interaction of hydrogen diffusion, hydride growth and the stress alteration by hydride precipitation. Finally, crack velocity was estimated from the calculated hydrogen flux into the crack tip as a function of temperature, stress intensity factor and material strength. There was qualitatively good agreement between calculation results and experimental data. The stress distribution around the crack tip is significantly altered by precipitation of hydride. Overlapping of external stress and hydride precipitation at a crack tip induces two stress peaks; one at a crack tip and the other at the front end of the hydride precipitate. Since the latter is larger than the former, more hydrogen diffuses to the front end of the hydride precipitate, thereby accelerating hydride growth compared with that in the absence of the hydride. These results indicated that, after hydride was formed in front of the crack tip, it grew almost steadily accompanying the interaction of hydrogen diffusion, hydride growth and the stress alteration by hydride precipitation. Crack velocity was estimated from the calculated hydrogen flux into the crack tip as a function of temperature, stress intensity factor and material strength. There was qualitatively good agreement between calculation results and experimental data. Macroscopic stress, ?c in a fiber reinforced composite with fibers aligned in a loading direction can be expressed as follows: ?c = ?fVf + ?m (1 - Vf), where suffices f, m and c refer to fiber, matrix and composite, respectively, and Vf is volume fraction of fibers.

  7. Ionic hydrogenations of hindered olefins at low temperature. Hydride transfer reactions of transition metal hydrides

    SciTech Connect

    Bullock, R.M.; Song, J.S. (Brookhaven National Lab., Upton, NY (United States))

    1994-09-21

    Sterically hindered olefins can be hydrogenated at -50[degree]C in dichloromethane using triflic acid (CF[sub 3]SO[sub 3]H) and a hydride donor. Mechanistic studies indicate that these reactions proceed by hydride transfer to the carbenium ion that is formed by protonation of the olefin. Olefins that form tertiary carbenium ions upon protonation are hydrogenated in high yields (90-100%). Styrenes generally produce lower yields of hydrogenated products (50-60%). Suitable hydride donors include HSiE[sub 3] and several transition metal carbonyl hydrides HW(CO)[sub 3]Cp, HW(CO)[sub 3]Cp[sup +], HMo-(CO)[sub 3]Cp, HMn(CO)[sub 5], HRe(CO)[sub 3], and HO[sub 3](CO)[sub 1]Cp*; Cp = [eta][sup 5]-C[sub 3]H[sub 5+], Cp* = [eta][sup 5]-C[sub 5]Me[sub 5]. A characteristic that is required for transition metal hydrides to be effective is that the cationic dihydrides (or dihydrogen complexes) that result from their protonation must have sufficient acidity to transfer a proton to the olefin, as well as sufficient thermal stability to avoid significant decomposition on the time scale of the hydrogenation reaction. Metal hydrides that fall due to insufficient stability of their protonated forms include HMo(CO)[sub 2](PPH[sub 3])Cp, HMo(CO)[sub 3]Cp*, and HFe(CO)[sub 2]Cp*. 62 refs., 2 tabs.

  8. Hydrides for Processing and Storing Tritium

    Microsoft Academic Search

    Theodore Motyka

    The Savannah River Site (SRS) has 50 years of experience in handling and processing tritium for defense and other special applications. During the past 20 years, a new technology, metal hy- dride technology, was introduced to the tritium facilities. This technology dramatically changed the way tritium and the other hydrogen isotopes were handled and processed at SRS. Metal hydrides allowed

  9. Hydride embrittlement in ZIRCALOY-4 plate: Part II. interaction between the tensile stress and the hydride morphology

    NASA Astrophysics Data System (ADS)

    Bai, J. B.; Ji, N.; Gilbon, D.; Prioul, C.; François, D.

    1994-06-01

    The effect of an applied tensile stress on the hydrides morphology in ZIRCALOY-4 was studied. To this end, the residual stresses around the hydride caused by the hydride precipitation was first evaluated. Considering the disability to predict hydride transformation stresses by ordinary macroscopical mechanical calculation in previous studies, X-ray diffraction (XRD) profile analysis and transmission electron microscopy (TEM) observations were carried out to quantify the microstructural evolution in hydrided ZIRCALOY-4. The residual microstrains and microstresses in the matrix and around the hydride were thus estimated. The big discrepancy between our results and the existing studies were explained by the major self-accomodation of phase transformation deformation remaining inside the hydrides and the local plastic accommodation of ZIRCALOY-4. In order to study the stress effect on hydride orientation and to estimate the hydride orientation threshold stresses, hydrogen was introduced into the specimens under tensile stress. A quantitative technique was used to evaluate the susceptibility to perpendicular hydride formation under the influence of texture, residual stresses, and externally applied tensile stresses, following an improved approach that had been first developed by Sauthoff and then applied to Zr-H system by Puls. Both analytical and experimental results indicate that the threshold stress for producing perpendicular hydrides varies with the microstructural features, the yield strength, and the residual stresses.

  10. Migratory insertion reactions of indenyliridium dialkyls and alkyl and aryl hydrides

    SciTech Connect

    Foo, T.; Bergman, R.G. [Lawrence Berkeley National Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States)

    1992-05-01

    This paper reports the migratory insertion chemistry of indenyliridium complexes described in the companion paper. Complexes of general formula ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(R)(R{prime}), where R = alkyl or aryl and R{prime} = alkyl, aryl, or hydride (4-6) react with dative ligands L such as tert-butylisocyanide and CO. These transformations lead to {eta}{sup 5} to {eta}{sup 1} isomerization of the indenyl ligand, giving octahedral iridium complexes of general formula ({eta}{sup 1}-Ind)(PMe{sub 3})(L){sub 2}Ir(R)(R{prime}) (8, 9, 11). Treatment of the methyl aryl and dimethyl {eta}{sup 1}-indenyl complexes 9a, 9d, and 9e with trimethylamine oxide removes CO, allowing the indenyl ligand to reestablish {eta}{sup 5}-coordination by inducing CO migratory insertion to give acyl complexes 10. Reaction of {eta}{sup 1}-indenyl aryl and methyl hydrides 6 (as well as the dihydride ({eta}{sup 5}-Ind)(PMe{sub 3})IrH{sub 2} (7)) with CO leads to reductive elimination of arene, methane, or H{sub 2} rather than migratory insertion, forming ({eta}{sup 1}-Ind)-(CO){sub 3}(PMe{sub 3})Ir (12) as the organometallic product. In contrast, treatment of methyl and aryl hydrides 6 with alkynes leads to the methyl vinyl complexes ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(Me)(CR{double_prime}C(R{prime})(H)) (13) and reaction of 6a with ethylene gives the methyl ethyl complex ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(Me)(Et) (14). Isotope labeling, stereochemical, and kinetic studies have been carried out on the insertion reaction of 6a with 3,3-dimethyl-1-butyne. The results of these experiments are most consistent with a mechanism involving initial reversible coordination of alkyne to the metal center (probably with concurrent {eta}{sup 5}-{eta}{sup 3} isomerization of the indenyl ligand) followed by irreversible migration of the metal-bound hydrogen to the tert-butyl-substituted carbon of the alkyne and then rapid recoordination of the indenyl group. 22 refs., 3 figs., 2 tabs.

  11. Phosphorescent Imaging of Living Cells Using a Cyclometalated Iridium(III) Complex

    PubMed Central

    Ma, Dik-Lung; Zhong, Hai-Jing; Fu, Wai-Chung; Chan, Daniel Shiu-Hin; Kwan, Hiu-Yee; Fong, Wang-Fun; Chung, Lai-Hon; Wong, Chun-Yuen; Leung, Chung-Hang

    2013-01-01

    A cell permeable cyclometalated iridium(III) complex has been developed as a phosphorescent probe for cell imaging. The iridium(III) solvato complex [Ir(phq)2(H2O]2)] preferentially stains the cytoplasm of both live and dead cells with a bright luminescence. PMID:23457478

  12. Inadequacy of iridium implant as sole radiation treatment for operable breast cancer

    Microsoft Academic Search

    I. S. Fentiman; C. Poole; D. Tong; P. J. Winter; W. M. Gregory; H. M. O. Mayles; P. Turner; M. A. Chaudary; R. D. Rubens

    1996-01-01

    In order to avoid a prolonged course of external irradiation as part of breast conservation therapy, 27 patients received an iridium implant to the primary tumour bed as sole radiation treatment. Surgery was standardised comprising tumourectomy and axillary clearance. Using a rigid implant afterloading with iridium192 wires, 55 Gy was delivered on a continuous basis over 5 days. After 6

  13. An overview of the IRIDIUM (R) low Earth orbit (LEO) satellite system

    Microsoft Academic Search

    Carl E. Fossa; Richard A. Raines; Gregg H. Gunsch; Michael A. Temple

    1998-01-01

    This paper provides a tutorial overview of the IRIDIUM(R) low earth orbit (LEO) satellite system. Section I contains an introduction to the IRIDIUM(R) network as well as the system specifications. Section II discusses the satellite constellation design, orbital parameters, and horizontal pointing angles between satellites. Section III introduces the idea of time dependent connectivity in a mobile network, and analyzes

  14. Anodically Electrodeposited Iridium Oxide Films (AEIROF) from Alkaline Solutions for Electrochromic Display Devices

    Microsoft Academic Search

    Kazusuke Yamanaka

    1989-01-01

    Anodically electrodeposited iridium oxide films from alkaline solutions were investigated for application to electrochromic devices. Micro-crystalline (diameter: 15Å) films obtained by the electrolysis of aqueous alkaline solutions containing iridium chloride, oxalic acid and potassium carbonate showed good electrochromic reaction reversibility. The coloration efficiency of the films was about one third that of typical evaporated tungsten oxide films, and the response

  15. Arsenic in marine tissues — The challenging problems to electrothermal and hydride generation atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Karadjova, Irina B.; Petrov, Panayot K.; Serafimovski, Ivan; Stafilov, Traj?e; Tsalev, Dimiter L.

    2007-03-01

    Analytical problems in determination of arsenic in marine tissues are addressed. Procedures for the determination of total As in solubilized or extracted tissues with tetramethylammonium hydroxide and methanol have been elaborated. Several typical lyophilized tissues were used: NIST SRM 1566a 'Oyster Tissue', BCR-60 CRM 'Trace Elements in an Aquatic Plant ( Lagarosiphon major)', BCR-627 'Forms of As in Tuna Fish Tissue', IAEA-140/TM 'Sea Plant Homogenate', NRCC DOLT-1 'Dogfish Liver' and two representatives of the Black Sea biota, Mediterranean mussel ( Mytilus galloprovincialis) and Brown algae ( Cystoseira barbata). Tissues (nominal 0.3 g) were extracted in tetramethylammonium hydroxide (TMAH) 1 ml of 25% m/v TMAH and 2 ml of water) or 5 ml of aqueous 80% v/v methanol (MeOH) in closed vessels in a microwave oven at 50 °C for 30 min. Arsenic in solubilized or extracted tissues was determined by electrothermal atomic absorption spectrometry (ETAAS) after appropriate dilution (nominally to 25 ml, with further dilution as required) under optimal instrumental parameters (pyrolysis temperature 900 °C and atomization temperature 2100 °C) with 1.5 ?g Pd as modifier on Zr-Ir treated platform. Platforms have been pre-treated with 2.7 ?mol of zirconium and then with 0.10 ?mol of iridium which served as a permanent chemical modifier in direct ETAAS measurements and as an efficient hydride sequestration medium in flow injection hydride generation (FI-HG)-ETAAS. TMAH and methanol extract 96-108% and 51-100% of As from CRMs. Various calibration approaches have been considered and critically evaluated. The effect of species-dependent slope of calibration graph or standard additions plot for total As determination in a sample comprising of several individual As species with different ETAAS behavior has been considered as a kind of 'intrinsic element speciation interference' that cannot be completely overcome by standard additions technique. Calibration by means of CRMs has given only semi-quantitative results. The limits of detection (3 ?) were in the range 0.5-1.2 mg kg - 1 As dry weight (wt.) for direct ETAAS analysis of extracts in both TMAH and MeOH. Within-run precision (RSD%) was 5-15% and 7-20% for TMAH and MeOH extracts at As levels 4-50 mg kg - 1 dry wt., respectively. The hydride active fraction of As species in extracts, i.e. the sum of toxicologically-relevant arsenic species (inorganic As(III), inorganic As(V), monomethylarsonate (MMA) and dimethylarsinate (DMA)) was determined by FI-HG-ETAAS in diluted tissue extracts. Arsine, monomethylarsine and dimethylarsine were generated from diluted TMAH and MeOH extracts in the presence of 0.06-0.09 mol l - 1 hydrochloric acid and 0.075 mol l - 1 L-cysteine. Collection, pyrolysis and atomization temperatures were 450, 500, 2100 and 2150 °C, respectively. The LODs for the determination of hydride forming fraction (arsenite + arsenate + MMA + DMA) in TMAH and MeOH extracts were in the range 0.003-0.02 mg kg - 1 As dry wt. Within-run precision (RSD%) was 3-12% and 3-7% for TMAH and methanol extracts at As levels 0.15-2.4 mg kg - 1 dry wt., respectively. Results for the hydride forming fraction of As in TMAH and MeOH extract as % from the certified value for total As (for CRMs) or vs. the total As in TMAH extract (for real marine samples) are generally in agreement.

  16. Iridium: Global OTH data communications for high altitude scientific ballooning

    NASA Astrophysics Data System (ADS)

    Denney, A.

    While the scientific community is no stranger to embracing commercially available technologies, the growth and availability of truly affordable cutting edge technologies is opening the door to an entirely new means of global communications. For many years high altitude ballooning has provided science an alternative to costly satellite based experimental platforms. As with any project, evolution becomes an integral part of development. Specifically in the NSBF ballooning program, where flight durations have evolved from the earlier days of hours to several weeks and plans are underway to provide missions up to 100 days. Addressing increased flight durations, the harsh operational environment, along with cumbersome and outdated systems used on existing systems, such as the balloon vehicles Support Instrumentation Package (SIP) and ground-based systems, a new Over-The-Horizon (OTH) communications medium is sought. Current OTH equipment planning to be phased-out include: HF commanding systems, ARGOS PTT telemetry downlinks and INMARSAT data terminals. Other aspects up for review in addition to the SIP to utilize this communications medium include pathfinder balloon platforms - thereby, adding commanding abilities and increased data rates, plus providing a package for ultra-small experiments to ride aloft. Existing communication systems employed by the National Scientific Balloon Facility ballooning program have been limited not only by increased cost, slow data rates and "special government use only" services such as TDRSS (Tracking and Data Relay Satellite System), but have had to make special provisions to geographical flight location. Development of the Support Instrumentation Packages whether LDB (Long Duration Balloon), ULDB (Ultra Long Duration Balloon) or conventional ballooning have been plagued by non-standard systems configurations requiring additional support equipment for different regions and missions along with a myriad of backup for redundancy. Several beneficial points provided by the Iridium platform include pure global accessibility (as well as polar), cost effectiveness because it is available as a COTS (Commercially Off The Shelf) technology, reliability in that the equipment must operate in extreme conditions (near space), integration and development time into current systems must be minimized. As a bonus Motorola and NAL Research Corporation are developing SBD (Short Burst Data) into the Iridium network. This may lead the way to a global IP (Internet Protocol) node based ballooning platform. The Iridium satellite data modems employ the Iridium Low-Earth Orbit (LEO) satellite network. The scope of this paper is to introduce an OTH communications alternative, albeit not necessarily a primary one, to existing ballooning platforms using COTS based emerging technologies. Design aspects, characteristics, actual flight testing statistics, principles of the Iridium modems and communication paths are described including payload and support instrumentation interfacing. Not limited to high altitude ballooning, the Iridium communications platform opens a new era in remote commanding and data retrieval.

  17. Iridium in marine organisms from the Gulf of Mexico

    E-print Network

    Wells, Mona Cara

    1987-01-01

    . (3) (4) This Study (Figure 3) 23 24 25 26 27 28 29 30 31 32 33 34 35 36 38 39 40 41 42 Phytoplankton Squid Mantle Squid Mantle Oyster, depurated Oyster, depu rated Oyster, non-d cpu rated Oyster, non-depu rated Oyster, non... at the K-T geologic boundary. The samples came from the Gulf of Mexico and included phytoplankton, zooplankton, fish, squid and oysters. Iridium in organisms ranges from less than the detection limit of 4 pg/g (pptr) to approximately 100 pptr...

  18. SURFACE STUDIES OF SIMPLE HYDROCARBONS ON IRIDIUM BY FLASH DESORPTION.

    SciTech Connect

    Burns, Robert Arthur

    1970-01-01

    Flash desorption of hydrogen and fourteen simple hydrocarbons on iridium was studied with decomposition products analyzed mass spectrometrically. Saturated hydrocarbons were found to absorb more slowly and to a smaller extent than the unsaturated hydrocarbons, and their decomposition was shown to occur below 400 degreesK. The decompositions of the unsaturated hydrocarbons were all similar in their hydrogen decomposition spectra and were not complete until 700 degreesK. Mechanisms are given for adsorption and decomposition which are consistent with the results. A model is proposed of the bonding to the surface to account for the adsorbed species observed. (author)

  19. Intercalation of graphene on iridium with sodium atoms

    NASA Astrophysics Data System (ADS)

    Rut'kov, E. V.; Gall', N. R.

    2015-06-01

    It has been shown that sodium atoms deposited on the surface of graphene atop iridium at T ? 850 K diffuse under the graphene layer into an intercalated state and accumulate there in significant concentrations ˜(2-3) × 1014 atoms cm-2. The release of the atoms from under the graphene "carpet" takes place upon destruction of the layer at T ? 1800 K. The physical nature of the differences in the processes of release of atoms of different alkali metals from under graphene has been discussed.

  20. Levitation of iridium and liquid mercury by ultrasound.

    PubMed

    Xie, W J; Cao, C D; Lü, Y J; Wei, B

    2002-09-01

    Single-axis acoustic levitation of the heaviest solid (iridium, rho=22.6 g cm(-3)) and liquid (mercury, rho=13.6 g cm(-3) on the Earth is achieved by greatly enhancing both the levitation force and stability through optimizing the geometric parameters of the levitator. The acoustically levitated Pb-Sn eutectic alloy melt (rho=8.5 g cm(-3)) is highly undercooled by up to 38 K, which results in a microstructural transition of "lamellae-broken lamellae-dendrites." The drastic enhancement of levitation capability indicates a broader application range of single-axis acoustic levitation. PMID:12225198

  1. Olefin oxygenation by water on an iridium center.

    PubMed

    Ghatak, Tapas; Sarkar, Mithun; Dinda, Shrabani; Dutta, Indranil; Rahaman, S M Wahidur; Bera, Jitendra K

    2015-05-20

    Oxygenation of 1,5-cyclooctadiene (COD) is achieved on an iridium center using water as a reagent. A hydrogen-bonding interaction with an unbound nitrogen atom of the naphthyridine-based ligand architecture promotes nucleophilic attack of water to the metal-bound COD. Irida-oxetane and oxo-irida-allyl compounds are isolated, products which are normally accessed from reactions with H2O2 or O2. DFT studies support a ligand-assisted water activation mechanism. PMID:25951226

  2. Determination of iridium in mafic rocks by atomic absorption

    USGS Publications Warehouse

    Grimaldi, F.S.; Schnepfe, M.M.

    1970-01-01

    Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Interelement interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively. ?? 1970.

  3. Measurements of the hard-x-ray reflectivity of iridium

    SciTech Connect

    Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

    2007-01-10

    In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

  4. Methanol dehydrogenation by iridium N-heterocyclic carbene complexes.

    PubMed

    Campos, Jesús; Sharninghausen, Liam S; Manas, Michael G; Crabtree, Robert H

    2015-06-01

    A series of homogeneous iridium bis(N-heterocyclic carbene) catalysts are active for three transformations involving dehydrogenative methanol activation: acceptorless dehydrogenation, transfer hydrogenation, and amine monoalkylation. The acceptorless dehydrogenation reaction requires base, yielding formate and carbonate, as well as 2-3 equivalents of H2. Of the few homogeneous systems known for this reaction, our catalysts tolerate air and employ simple ligands. Transfer hydrogenation of ketones and imines from methanol is also possible. Finally, N-monomethylation of anilines occurs through a "borrowing hydrogen" reaction. Notably, this reaction is highly selective for the monomethylated product. PMID:25615426

  5. A theoretical and experimental study of hydrides in zirconium alloys

    Microsoft Academic Search

    A. A. Shmakov; D. Yan; R. L. Eadie

    2006-01-01

    A method developed for computing the critical length and thickness of hydride plates formed in delayed hydride cracking (DHC)\\u000a in zirconium alloys is considered. The model is based on analyzing the distribution of tensile stresses in the plane of a\\u000a sharp normal tensile crack. The characteristics of hydrides formed due to DHC in reactor tubes produced from alloy Zr-2.5%\\u000a Nb

  6. HYDRIDE-INDUCED EMBRITTLEMENT IN METALS - STRESS AND TEMPERATURE EFFECTS

    Microsoft Academic Search

    A. G. Varias; A. R. Massih

    A robust mathematical model for the hydrogen embrittlement of hydride forming metals has been developed. The model takes into account the coupling of the operating physical processes, namely: (i) hydrogen diffusion, (ii) hydride precipitation, (iii) non-mechanical energy flow, and (iv) hydride\\/solid-solution deformation. Crack growth is simulated by using a new version of de-cohesion model with time-dependent energy of de-cohesion due

  7. Growth and decomposition of lithium and lithium hydride on nickel

    Microsoft Academic Search

    Jakob Engbæk; Gunver Nielsen; Jane H. Nielsen; Ib Chorkendorff

    2006-01-01

    In this paper we have investigated the deposition, structure and decomposition of lithium and lithium-hydride films on a nickel substrate. Using surface sensitive techniques it was possible to quantify the deposited Li amount, and to optimize the deposition procedure for synthesizing lithium-hydride films.By only making thin films of LiH it is possible to study the stability of these hydride layers

  8. Synthesis and properties of platinum hydride

    NASA Astrophysics Data System (ADS)

    Scheler, Thomas; Degtyareva, Olga; Marqués, Miriam; Guillaume, Christophe L.; Proctor, John E.; Evans, Shaun; Gregoryanz, Eugene

    2011-06-01

    Synchrotron x-ray diffraction experiments on compressed platinum-hydrogen mixtures reveal the formation of platinum hydride at a pressure of 27(1) GPa at room temperature. This compound exhibits two phases, PtH-I and PtH-II, coexisting up to the pressure of 42 GPa, above which the single phase of PtH-II is observed. Pt atoms in the PtH-II phase are shown to form a hexagonal closed-packed structure. This phase exhibits a high bulk modulus of 310 (10) GPa and is stable up to at least 53 GPa. Ab initio calculations show that PtH-II is superconducting with Tc = 12 K at 90 GPa, the highest temperature of superconducting transition among any known metal hydride.

  9. Unoccupied electronic states in cerium hydrides

    NASA Astrophysics Data System (ADS)

    Osterwalder, J.; Schlapbach, L.

    1985-05-01

    We present UV isochromat spectra of polycrystalline CeH 2.1 and CeH 2.9. The intensity at EF is small in CeH 2.1 and vanishes in CeH 2.9 as it is expected from XPS, UPS and conductivity data. In both hydrides broad features (?2 eV FWHM) appear between 4 and 5 eV above EF. This is in qualitative agreement with bandstructure calculations.

  10. Lightweight hydrides for automotive storage of hydrogen

    SciTech Connect

    Rohy, D.A.; Nachman, J.F.; Argabright, T.A.

    1981-01-01

    Hydrogen is a potential automotive fuel in mid- and far-term projections. The use of hydrogen as an energy carrier is dependent on the solution of two primary technical problems: inexpensive production of hydrogen and lightweight storage of hydrogen. This paper addresses the storage problem. Development of the magnesium hydride alloys is described and related to the requirements of the automotive SI (spark ignition) engine. 3 refs.

  11. The Thermal Decomposition of Lithium Aluminium Hydride

    Microsoft Academic Search

    W. E. Garner; E. W. Haycock

    1952-01-01

    Lithium aluminium hydride on heating decomposes in three stages: (a) an initial surface reaction during the induction period, followed by (b) an interface reaction giving an S-shaped pressure against time curve, corresponding to LiAlH4rightharpoonup LiAlH2 + H2, and (c) a slow process during which a third hydrogen atom is liberated. The initial reaction is rapid at first and then slows

  12. The IEA/DOE/SNL on-line hydride databases

    NASA Astrophysics Data System (ADS)

    Sandrock, G.; Thomas, G.

    2001-04-01

    A series of comprehensive hydride databases have been constructed and made freely available on the Internet (URL http://hydpark.ca.sandia.gov). They include extensive listings of alloys reported to hydride, detailed engineering properties on selected hydrogen-storage elements and alloys and a hydride-applications database. These databases and an associated reference database are described, along with other hydride information available on the web site. The databases were created under the auspices of the International Energy Agency (IEA) with financial support from the U.S. Department of Energy (DOE) and Internet service support from the Sandia National Laboratories (SNL).

  13. Investigation of yttrium and yttrium hydride by AES and REELS

    NASA Astrophysics Data System (ADS)

    Bracconi, P.; Pörschke, E.; Lässer, R.

    1988-08-01

    The results of combined investigations by Auger electron spectroscopy (AES) and reflection electron energy loss spectroscopy (REELS) of thin films of yttrium and yttrium hydride are presented. The hydride phase was prepared by exposing evaporated metal films to hydrogen in a high pressure reaction chamber connected to the main UHV vessel. Special attention was paid to the effects of surface contamination by oxygen. The specific spectroscopic characteristics of the metal and the hydride phase are compared and analysed in terms of the known electronic structures of yttrium and yttrium hydrides.

  14. AC impedance studies on metal hydride electrodes

    SciTech Connect

    Zhang, W.; Sridhar Kumar, M.P.; Srinivasan, S.; Ploehn, H.J. [Texas A and M Univ., College Station, TX (United States)

    1995-09-01

    The metal hydride (MH{sub x}) electrode is the negative electrode in one of the most advanced secondary batteries (i.e., nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydriding reaction in the battery by using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MH{sub x} electrode reaction is proposed. The rate capability of charge and discharge of the MH{sub x} electrode is determined by the kinetics of the charge-transfer reaction at the allow surface, which is mainly represented by the EIS responses in the low frequency region. Transient and pseudo-steady-state analyses (cyclic voltammetry and potential vs. current density behavior) qualitatively and quantitatively support the EIS results. EIS studies on electrodes with (1) three types of binding additives, (2) varying amounts of active materials, and (3) two types of alloys as active materials demonstrate the usefulness of this technique for developing electrodes with the optimum composition and structure.

  15. Plasmonic hydrogen sensing with nanostructured metal hydrides.

    PubMed

    Wadell, Carl; Syrenova, Svetlana; Langhammer, Christoph

    2014-12-23

    In this review, we discuss the evolution of localized surface plasmon resonance and surface plasmon resonance hydrogen sensors based on nanostructured metal hydrides, which has accelerated significantly during the past 5 years. We put particular focus on how, conceptually, plasmonic resonances can be used to study metal-hydrogen interactions at the nanoscale, both at the ensemble and at the single-nanoparticle level. Such efforts are motivated by a fundamental interest in understanding the role of nanosizing on metal hydride formation processes in the quest to develop efficient solid-state hydrogen storage materials with fast response times, reasonable thermodynamics, and acceptable long-term stability. Therefore, a brief introduction to the thermodynamics of metal hydride formation is also given. However, plasmonic hydrogen sensors not only are of academic interest as research tool in materials science but also are predicted to find more practical use as all-optical gas detectors in industrial and medical applications, as well as in a future hydrogen economy, where hydrogen is used as a carbon free energy carrier. Therefore, the wide range of different plasmonic hydrogen sensor designs already available is reviewed together with theoretical efforts to understand their fundamentals and optimize their performance in terms of sensitivity. In this context, we also highlight important challenges to be addressed in the future to take plasmonic hydrogen sensors from the laboratory to real applications in devices, including poisoning/deactivation of the active materials, sensor lifetime, and cross-sensitivity toward other gas species. PMID:25427244

  16. Formylated chloro-bridged iridium(iii) dimers as OLED materials: opening up new possibilities.

    PubMed

    Wong, Michael Y; Xie, Guohua; Tourbillon, Clarisse; Sandroni, Martina; Cordes, David B; Slawin, Alexandra M Z; Samuel, Ifor D W; Zysman-Colman, Eli

    2015-04-29

    In this study, a series of four formyl-substituted chloro-bridged iridium(iii) dimers were prepared. Their absorption, photophysical and electrochemical properties were studied in dichloromethane solution. It was found that as the formyl content increased on the cyclometalating ligands, emission unexpectedly became brighter. Organic light-emitting diodes (OLEDs) were fabricated using each of these iridium dimers as the emitter. The OLED fabricated using the brightest of the series, , as the dopant afforded a decent external quantum efficiency (EQE) of 2.6%. This suggests that chloro-bridged iridium dimers are potential candidates as solid-state emitters. PMID:25609226

  17. Analysis of Abrasive Blasting of DOP-26 Iridium Alloy

    SciTech Connect

    Ohriner, Evan Keith [ORNL; Zhang, Wei [ORNL; Ulrich, George B [ORNL

    2012-01-01

    The effects of abrasive blasting on the surface geometry and microstructure of DOP-26 iridium alloy (Ir-0.3% W-0.006% Th 0.005% Al) have been investigated. Abrasive blasting has been used to control emissivity of components operating at elevated temperature. The effects of abrasive blasting conditions on surface morphology were investigated both experimentally and by numerical modeling. The simplified model, based on finite element analysis of a single angular particle impacting on Ir alloy disk, calculates the surface deformation and residual strain distribution. The experimental results and modeling results both indicate that the surface geometry is not sensitive to the abrasive blast process conditions of nozzle pressure and standoff distance considered in this study. On the other hand, the modeling results suggest that the angularity of the abrasive particle has an important role in determining surface geometry, which in turn, affects the emissivity. Abrasive blasting causes localized surface strains and localized recrystallization, but it does not affect grain size following extended exposure at elevated temperature. The dependence of emissivity of the DOP-26 alloy on mean surface slope follows a similar trend to that reported for pure iridium.

  18. Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision

    NASA Technical Reports Server (NTRS)

    Anz-Meador, P. D.; Liou, Jer-Chi

    2010-01-01

    The collision of Iridium 33 and Cosmos 2251, on 10 February 2009, was the first known unintentional hypervelocity collision in space of intact satellites. Iridium 33 was an active commercial telecommunications satellite, while Cosmos 2251 was a derelict communication satellite of the Strela-2M class. The collision occurred at a relative velocity of 11.6 km/s at an altitude of approximately 790 km over the Great Siberian Plain and near the northern apex of Cosmos 2251 s orbit. This paper describes the physical and orbital characteristics of the relevant spacecraft classes and reports upon our analysis of the resulting debris clouds size, mass, area-to-mass ratio, and relative velocity/directionality distributions. We compare these distributions to those predicted by the NASA breakup model and notable recent fragmentation events; in particular, we compare the area-to-mass ratio distribution for each spacecraft to that exhibited by the FY-1C debris cloud for the purpose of assessing the relative contribution of modern aerospace materials to debris clouds resulting from energetic collisions. In addition, we examine the long-term consequences of this event for the low Earth orbit (LEO) environment. Finally, we discuss "lessons learned", which may be incorporated into NASA s environmental models.

  19. Performance and cost analysis of a hydride air conditioning system

    Microsoft Academic Search

    1977-01-01

    Results are presented of a performance and cost analysis of a metal hydride air conditioning (heat pump) system as compared to conventional absorption heat pumps. The system analyzed represents one of several possible implementations of the Hydride Conversion and Storage System (HYCSOS) concept developed by the Argonne National Laboratory. Due to the preliminary state of development of the HYCSOS concept,

  20. Method of making crack-free zirconium hydride

    DOEpatents

    Sullivan, Richard W. (Denver, CO)

    1980-01-01

    Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.

  1. A nickel metal hydride battery for electric vehicles

    Microsoft Academic Search

    S. R. Ovshinsky; M. A. Fetcenko; J. Ross

    1993-01-01

    Widespread use of electric vehicles can have significant impact on urban air quality, national energy independence, and international balance of trade. An efficient battery is the key technological element to the development of practical electric vehicles. The science and technology of a nickel metal hydride battery, which stores hydrogen in the solid hydride phase and has high energy density, high

  2. Solubility of hydrogen isotopes in stressed hydride-forming metals

    Microsoft Academic Search

    C. E. Coleman; J. F. R. Ambler

    1983-01-01

    Components made from hydride-forming metals can be brittle when particles of hydride are present. The solid solubility limit of hydrogen in these metals needs to be known so that fracture resistance can be properly assessed. Stress affects the solubility of hydrogen in metals. As hydrogen dissolves the metal volume increases, an applied hydrostatic tensile stress supplies work to increase the

  3. Ab initio treatment of electron correlations in polymers: Lithium hydride chain and beryllium hydride polymer

    E-print Network

    Birkenheuer, Uwe

    H and beryllium hydride Be2H4 . First, employing a Wannier-function-based approach, the systems are studied Hartree­Fock Wannier functions of the infinite chain into the complementary space of localized unoccupied for the treatment of large molecules.3 Simi- larly, in infinite systems localized Wannier functions provide a better

  4. Binuclear cyclopentadienylrhenium hydride chemistry: terminal versus bridging hydride and cyclopentadienyl ligands.

    PubMed

    Gao, Xiaozhen; Li, Nan; King, R Bruce; Schaefer, Henry F

    2015-01-01

    Theoretical studies predict the lowest energy structures of the binuclear cyclopentadienylrhenium hydrides Cp2Re2H n (Cp = ?(5)-C5H5; n?=?4, 6, 8) to have a central doubly bridged Re2(?-H)2 unit with terminal ?(5)-Cp rings and the remaining hydrides as terminal ligands. However, the lowest energy Cp2Re2H2 structure by more than 12 kcal mol(-1) has one terminal ?(5)-Cp ring, a bridging ?(3),?(2)-Cp ring, and two terminal hydride ligands bonded to the same Re atom. The lowest energy hydride-free Cp2Re2 structure is a perpendicular structure with two bridging ?(3),?(2)-Cp rings. The previously predicted bent singlet Cp2Re2 structure with terminal ?(5)-Cp rings and a formal Re-Re sextuple bond lies ?37 kcal mol(-1) above this lowest energy (?(3),?(2)-Cp)2Re2 structure. The thermochemistry of the CpReH n and Cp2Re2H n systems is consistent with the reported synthesis of the permethylated derivatives Cp*ReH6 and Cp*2Re2H6 (Cp* = ?(5)-Me5C5) as very stable compounds. Additionally, natural bond orbital analysis, atoms-in-molecules and overlap population density-of-state in AOMIX were applied to present the existence of rhenium-rhenium multiple bonds. PMID:25605597

  5. Stratigraphic occurrences of iridium anomalies at four Cretaceous/Tertiary boundary sites in New Zealand

    SciTech Connect

    Brooks, R.R.; Strong, C.P.; Lee, J.; Orth, C.J.; Gilmore, J.S.; Ryan, D.E.; Holzbecher, J.

    1986-09-01

    Three new iridium anomaly sites have been discovered in Cretaceous/Tertiary boundary sequences in New Zealand. These are at Needles Point, Chancet Rocks, and Waipara, where integrated iridium deposition values were 165, 211, and 7 ng/cm/sup 2/, respectively. In contrast to the previously reported Woodside Creek stratigraphic sequence that had an iridium anomaly of 187 ng/cm/sup 2/, a ferruginous boundary clay is absent in the three new sites, though the base of the Tertiary is marked by limonite staining. The relatively weak anomaly at the Waipara section is probably due to extensive bioturbation coupled with a high sedimentation rate at the time of deposition. The discovery of these additional boundary rock sequences in New Zealand negates suggestions that the Woodside Creek iridium.

  6. Iridium-Catalyzed Branch-Selective Hydroarylation of Vinyl Ethers via C-H Bond Activation.

    PubMed

    Ebe, Yusuke; Nishimura, Takahiro

    2015-05-13

    Iridium-catalyzed hydroarylation of vinyl ethers via a directed C-H bond activation of aromatic compounds gave high yields of the corresponding addition products with high branch selectivity. PMID:25928127

  7. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, William A. (Los Alamos, NM); Olsen, Clayton E. (Los Alamos, NM)

    1982-01-01

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  8. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, W.A.; Olsen, C.E.

    1980-03-12

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  9. Recent advances in metal hydrides for clean energy applications

    SciTech Connect

    Ronnebro, Ewa; Majzoub, Eric H.

    2013-06-01

    Metal hydrides are a fascinating class of materials that can be utilized for a surprising variety of clean energy applications, including smart solar collectors, smart windows, sensors, thermal energy storage, and batteries, in addition to their traditional application for hydrogen storage. Over the past decade, research on metal hydrides for hydrogen storage increased due to global governmental incentives and an increased focus on hydrogen storage research for polymer electrolyte membrane fuel cell operation. Tremendous progress has been made in so-called complex metal hydrides for hydrogen storage applications with the discovery of many new hydrides containing covalently bound complex anions. Many of these materials have applications beyond hydrogen storage and are being investigated for lithium-ion battery separator and anode materials. In this issue of MRS Bulletin , we present the state of the art of key evolving metal-hydride-based clean energy technologies with an outlook toward future needs.

  10. Growth and decomposition of lithium and lithium hydride on nickel

    NASA Astrophysics Data System (ADS)

    Engbæk, Jakob; Nielsen, Gunver; Nielsen, Jane H.; Chorkendorff, Ib

    2006-04-01

    In this paper we have investigated the deposition, structure and decomposition of lithium and lithium-hydride films on a nickel substrate. Using surface sensitive techniques it was possible to quantify the deposited Li amount, and to optimize the deposition procedure for synthesizing lithium-hydride films. By only making thin films of LiH it is possible to study the stability of these hydride layers and compare it directly with the stability of pure Li without having any transport phenomena or adsorbed oxygen to obscure the results. The desorption of metallic lithium takes place at a lower temperature than the decomposition of the lithium-hydride, confirming the high stability and sintering problems of lithium-hydride making the storage potential a challenge.

  11. Preparation of platinum/iridium scanning probe microscopy tips

    NASA Astrophysics Data System (ADS)

    Sørensen, A. H.; Hvid, U.; Mortensen, M. W.; Mørch, K. A.

    1999-07-01

    We report on the development of an etching setup for use in the preparation of platinum/iridium tips for atomic force microscopy and scanning electrostatic force microscopy as well as scanning tunneling microscopy. The etching process is based on a two step electrochemical procedure. The first step is a coarse alternating current (ac) etching in which the etching is continuous and stops automatically when the lower part of the wire drops off, while the second step is a fine etching made by a number of ac pulses, each of a certain duration and separated by a certain interval of time. When the tip material being etched is platinum/iridium (10%) the influence of the stop phase of the ac current terminating each pulse in the second etching is found to be negligible, while in the case of second etching of tungsten wires it is important to break the pulse in a certain phase to avoid formation of a thick oxide layer. In order to explain the relatively high etching rates observed for the otherwise noble metal platinum we suggest that besides anodic corrosion of the platinum by the electrolyte containing chloride ions, a different etching mechanism causes a substantial increase of the etching rate. This mechanism is based on the formation of oxygen and hydrogen at the platinum/iridium electrode when the potential is above the dissociation potential of water (˜1.23 V) and storage of these products interstitially in the outer layers of the platinum wire. This leads to "microexplosions" that detach fragments of platinum from the wire surface and hereby give rise to "etching" of the wire. In the second etching blunt tips become sharp while tips which are already sharp apparently stay sharp. Therefore, the second etching scheme with pulses separated by pauses is found to be a very important factor for the production of sharp tips. After being etched the tips are ready for use in scanning tunneling microscopes, or they may be bent to form integrated tip/cantilever systems in ordinary commercial atomic force microscopes, being applicable as tapping mode tips and as electrostatic force microscopy tips.

  12. Measurements of iridium and the hypothesis of meteoritic impact as the end of the Cretaceous period

    Microsoft Academic Search

    Francisco Sircillineto

    1986-01-01

    Analysis methods applied for neutron activation and radiochemistry for determination of trace elements, iridium and gold, were utilized in cosmochemistry. The concentrations analyzed were in the parts per billion band. The analysis by neutron activation determined the concentration of 1.5 gram irradiated iridium sample during 32 hours in thermal flux as 10 to the 13th power neutrons\\/sq cm\\/sec. Gamma spectrometry

  13. Multidirectional Synthesis of Substituted Indazoles via Iridium-Catalyzed C-H Borylation.

    PubMed

    Sadler, Scott A; Hones, Andrew C; Roberts, Bryan; Blakemore, David; Marder, Todd B; Steel, Patrick G

    2015-05-15

    In the absence of a steric directing group, iridium-catalyzed C-H borylation of N-protected indazoles occurs rapidly and selectively at C-3 and the resulting boronate esters can be utilized in a range of downstream conversions. The functional group tolerance of the iridium-catalyzed C-H borylation reaction enables simple and efficient multidirectional syntheses of substituted indazoles to be realized. PMID:25894824

  14. Modular hydride beds for mobile applications

    SciTech Connect

    Malinowski, M.E.; Stewart, K.D.

    1997-08-01

    Design, construction, initial testing and simple thermal modeling of modular, metal hydride beds have been completed. Originally designed for supplying hydrogen to a fuel cell on a mobile vehicle, the complete bed design consists of 8 modules and is intended for use on the Palm Desert Vehicle (PDV) under development at the Schatz Energy Center, Humbolt State University. Each module contains approximately 2 kg of a commercially available, low temperature, hydride-forming metal alloy. Waste heat from the fuel cell in the form of heated water is used to desorb hydrogen from the alloy for supplying feed hydrogen to the fuel cell. In order to help determine the performance of such a modular bed system, six modules were constructed and tested. The design and construction of the modules is described in detail. Initial testing of the modules both individually and as a group showed that each module can store {approximately} 30 g of hydrogen (at 165 PSIA fill pressure, 17 C), could be filled with hydrogen in 6 minutes at a nominal, 75 standard liters/min (slm) fueling rate, and could supply hydrogen during desorption at rates of 25 slm, the maximum anticipated hydrogen fuel cell input requirement. Tests made of 5 modules as a group indicated that the behavior of the group run in parallel both in fueling and gas delivery could be directly predicted from the corresponding, single module characteristics by using an appropriate scaling factor. Simple thermal modeling of a module as an array of cylindrical, hydride-filled tubes was performed. The predictions of the model are in good agreement with experimental data.

  15. Development of a Potential Surface for Simulation of Proton and Hydride Transfer Reactions in Solution: Application to NADH Hydride Transfer

    E-print Network

    Hammes-Schiffer, Sharon

    Development of a Potential Surface for Simulation of Proton and Hydride Transfer Reactions surface that describes these reactions must incorporate quantum mechanical effects such as the formation that incorporates significant quantum mechanical effects for proton and hydride transfer reactions in solution

  16. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D. (Martinez, CA); Jankowski, Alan F. (Livermore, CA); Yu, Conrad (Antioch, CA)

    2010-08-10

    An apparatus having a first substrate having (1) a cavity, (2) one or more resistive heaters, and (3) one or more coatings forming a diffusion barrier to hydrogen; a second substrate having (1) an outlet valve comprising a pressure relief structure and (2) one or more coatings forming a diffusion barrier to hydrogen, wherein said second substrate is coupled to said first substrate forming a sealed volume in said cavity; a metal hydride material contained within said cavity; and a gas distribution system formed by coupling a microfluidic interconnect to said pressure relief structure. Additional apparatuses and methods are also disclosed.

  17. IMC hydrides with high hydrogen dissociation pressure

    Microsoft Academic Search

    T. A. Zotov; R. B. Sivov; E. A. Movlaev; S. V. Mitrokhin; V. N. Verbetsky

    2011-01-01

    Hydrogen sorption properties of a large variety of solid solutions on the base of ZrCr2 and TiFe2 intermetallic compounds are studied at pressures up to 300MPa. Partial substitution of Cr by small amounts of Me=Al, Mn, Mo, Ni and B does not significantly change the H\\/M ratio of hydrides of the Ti(Cr1?xMex)2?a alloys with 0

  18. Iridium Clusters in KLTL Zeolite: Synthesis, Structural Characterization, and Catalysis of Toluene Hydrogenation and n-Hexane Dehydrocyclization

    Microsoft Academic Search

    Ailian Zhao; R. E. Jentoft; B. C. Gates

    1997-01-01

    Iridium clusters incorporating about six atoms each, on average, were prepared in KLTL zeolite by decarbonylation (in H2at 400°C) of iridium carbonyl clusters formed by treatment of adsorbed [Ir(CO)2(acac)] in CO at 1 atm and 175°C. The supported species were characterized by infrared and extended X-ray absorption fine structure (EXAFS) spectroscopies. The iridium carbonyls formed from [Ir(CO)2(acac)] were predominantly [HIr4(CO)11]?with

  19. Stress-reorientation of hydrides and hydride embrittlement of Zr-2.5 wt% Nb pressure tube alloy

    NASA Astrophysics Data System (ADS)

    Singh, R. N.; Kishore, R.; Singh, S. S.; Sinha, T. K.; Kashyap, B. P.

    2004-02-01

    Hydrogen in excess of the terminal solid solubility precipitates out as a brittle hydride phase in zirconium alloys. The hydrides acquire platelet shaped morphology due to their accommodation in the matrix and can cause severe embrittlement, especially when these are oriented normal to the tensile stress axis. The precipitation of hydride platelets normal to the tensile stress when cooled under stress from a solution-annealing temperature is commonly referred to as 'stress-reorientation'. The stress-reorientation is associated with a threshold stress below which no reorientation is observed. In this work, stress-reorientation of hydrides was investigated for unirradiated, cold worked and stress-relieved Zr-2.5 wt% Nb pressure tube material for a reorientation temperature of 423-723 K. The effect of the reoriented hydrides on the tensile properties of the Zr-2.5 wt% Nb pressure tube alloy was evaluated in the temperature range of 298-573 K.

  20. Comparative modelling of chemical ordering in palladium-iridium nanoalloys

    NASA Astrophysics Data System (ADS)

    Davis, Jack B. A.; Johnston, Roy L.; Rubinovich, Leonid; Polak, Micha

    2014-12-01

    Chemical ordering in "magic-number" palladium-iridium nanoalloys has been studied by means of density functional theory (DFT) computations, and compared to those obtained by the Free Energy Concentration Expansion Method (FCEM) using derived coordination dependent bond energy variations (CBEV), and by the Birmingham Cluster Genetic Algorithm using the Gupta potential. Several compositions have been studied for 38- and 79-atom particles as well as the site preference for a single Ir dopant atom in the 201-atom truncated octahedron (TO). The 79- and 38-atom nanoalloy homotops predicted for the TO by the FCEM/CBEV are shown to be, respectively, the global minima and competitive low energy minima. Significant reordering of minima predicted by the Gupta potential is seen after reoptimisation at the DFT level.

  1. Large Deformation Change in Iridium Isotopes from Laser Spectroscopy

    SciTech Connect

    D. Verney; L. Cabaret; J. Crawford; H.T. Duong; J. Genevey; G. Hubert; F. Ibrahim; M. Krieg; F. Le Blanc; J.K.P. Lee; G. Le Scornet; D. Lunney; J. Obert; J. Oms; J. Pinard; J.C. Putaux; B. Roussiere; J. Sauvage; V. Sebastian

    1999-12-31

    Laser spectroscopy measurements have been performed on neutron-deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2} {yields}5d{sup 7}6s6p {sup 6}F{sub 11/2} have been studied for the {sup 182-189}Ir, {sup 186}Ir{sup m} and {sup 191,193}Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the hyperfine splitting measurements and the changes of the mean square charge radii from the isotope shift measurements. A large deformation change between {sup 187}Ir and {sup 186}Ir and between {sup 186}Ir{sup m} and {sup 186}Ir{sup g} has been observed.

  2. Large deformation change in iridium isotopes from laser spectroscopy

    SciTech Connect

    Verney, D.; Le Blanc, F.; Obert, J.; Oms, J.; Putaux, J. C.; Roussiere, B.; Sauvage, J. [Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay Cedex (France); Cabaret, L.; Duong, H. T.; Pinard, J. [Laboratoire Aime Cotton, 91405 Orsay Cedex (France); Crawford, J.; Lee, J. K. P. [Physics Department, Mc Gill University, H3A2T8 Montreal (Canada); Genevey, J.; Ibrahim, F. [Institut des Sciences Nucleaires, IN2P3-CNRS, 38026 Grenoble Cedex (France); Hubert, G.; Krieg, M.; Sebastian, V. [Institut fuer Physik der Univeristaet Mainz (Germany); Le Scornet, G.; Lunney, D. [CSNSM, IN2P3-CNRS, 91405 Orsay Cedex (France)

    1999-11-16

    Laser spectroscopy measurements have been performed on neutron-deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2}{yields}5d{sup 7}6s6p {sup 6}F{sub 11/2} have been studied for the {sup 182-189}Ir, {sup 180}Ir{sup m} and {sup 191,193}Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the hyperfine splitting measurements and the changes of the mean square charge radii from the isotope shift measurements. A large deformation change between {sup 187}Ir and {sup 186}Ir and between {sup 186}Ir{sup m} and {sup 186}Ir{sup g} has been observed.

  3. A Porphyrin-Stabilized Iridium Oxide Water Oxidation Catalyst

    SciTech Connect

    Sherman, Ben; Pillai, Smitha; Kodis, Gerdenis; Bergkamp, Jesse; Mallouk, Thomas E.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.

    2011-01-01

    Colloidal solutions of iridium oxide hydrate (IrO{sub 2}·NH{sub 2}O) were formed using porphyrin stabilizers bearing malonate-like functional groups at each of the four meso positions of the porphyrin ring. Cyclic voltammetry and monitoring of solution oxygen concentrations under constant applied potential demonstrated the electrochemical catalytic activity of the porphyrin–IrO{sub 2}·NH{sub 2}O complexes for the oxidation of water to oxygen. Quenching of the porphyrin fluorescence in the complex implies strong interaction between the porphyrin and the IrO{sub 2}·NH{sub 2}O. These results mark a step toward developing a porphyrin-based photoanode for use in a photoelectrochemical water-splitting cell.

  4. Iridium-alloy processing experience in FY 1989

    SciTech Connect

    Ohriner, E.K.

    1990-11-01

    Iridium-alloy blanks and foil are produced at the Oak Ridge National Laboratory for use as fuel cladding material in radioisotope thermoelectric generators for space power sources. Until 1984, the material was produced from small 500-g drop castings. A new process has been developed in which consumable electrodes of about 10 kg are arc melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1989 included the arc melting of three electrodes and the extruding and rolling to sheet of three billets. Significant improvements have been made in the extruding and arc-melting processes. Preliminary results show that these improvements have had an important effect in increasing the rate of blank acceptance in nondestructive evaluations. 4 refs., 33 figs., 11 tabs.

  5. The regioselective hydroformylation of vinylsilanes. A remarkable difference in the selectivity and reactivity of cobalt, rhodium, and iridium catalysts

    SciTech Connect

    Crudden, C.M.; Alper, H. [Univ. of Ottawa, Ontario (Canada)

    1994-06-03

    Rhodium, iridium, and cobalt complexes were evaluated as catalysts for hydroformylation of vinylsilanes. Regioselectivities, product structures, and reaction yields were widely variable for these catalysts.

  6. Determination of iridium in industrial concentrates by controlled-potential coulometry with a glassy-carbon electrode

    SciTech Connect

    Stril'chenko, T.G.; Kabanova, O.L.; Danilova, F.I.

    1987-02-01

    The authors present a coulometric method for determining iridium without separating nonferrous and noble metals using a glassy-carbon (GC) crucible instead of the expensive platinum electrode. The crucible also serves as the electrochemical cell for the coulometric determination and as a vessel in which an aliquot weight of the analyzed solution is taken. The KP-3 concentrate contains several metals that accompany iridium. The main metals which interfere in the electrochemical determination of iridium with the use of a platinum electrode are iron and ruthenium. This paper describes the authors' proposed procedure for determining iridium in hydrochloric acid solutions with the GC crucible-electrode.

  7. Millimeter-Wave Spectroscopy of Ethylmercury Hydride

    NASA Astrophysics Data System (ADS)

    Goubet, M.; Motiyenko, R. A.; Margulès, L.; Guillemin, J.-C.

    2012-06-01

    The first millimeter-wave rotational spectrum of an organomercury compound, ethylmercury hydride (CH_3CH_2HgH), has been recorded using the Lille fast-scan spectrometer in the frequency range 120 -- 180 GHz. The spectroscopic study is complemented by quantum chemical calculations taking into account relativistic effects on the mercury atom. The very good agreement between theoretical and experimental molecular parameters validates the chosen ab initio method, in particular its capability to predict the accurate values of the quartic centrifugal distortion constants related to this type of compound. Estimations of the nuclear quadrupole coupling constants are not as predictive as the structural parameters but good enough to satisfy the spectroscopic needs. In addition, the orientation of the H--Hg--C bonds axis deduced from the experimental nuclear quadrupole coupling constants compares well with the corresponding ab initio value. From the good agreement between experimental and theoretical results, together with the observation of the six most abundant isotopes of mercury, ethylmercury hydride is unambiguously identified and its calculated equilibrium geometry is confirmed. Alekseev, E.A. et al. Radio Physics and Radio Astronomy 3 (2012) 78.

  8. Metal hydrides for lithium-ion batteries.

    PubMed

    Oumellal, Y; Rougier, A; Nazri, G A; Tarascon, J-M; Aymard, L

    2008-11-01

    Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries. PMID:18849978

  9. Metal hydrides for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Oumellal, Y.; Rougier, A.; Nazri, G. A.; Tarascon, J.-M.; Aymard, L.

    2008-11-01

    Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH2 with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH2 electrode shows a large, reversible capacity of 1,480mAhg-1 at an average voltage of 0.5V versus Li+/Li? which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH2. Furthermore, the reaction is not specific to MgH2, as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH2, which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.

  10. Molecular rare-earth-metal hydrides in non-cyclopentadienyl environments.

    PubMed

    Fegler, Waldemar; Venugopal, Ajay; Kramer, Mathias; Okuda, Jun

    2015-02-01

    Molecular hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial hydrides. Structurally well-characterized non-metallocene-type hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available. PMID:25413985

  11. Carbon-Fluorine Bond Cleavage by Zirconium Metal Hydride Complexes

    E-print Network

    Jones, William D.

    Carbon-Fluorine Bond Cleavage by Zirconium Metal Hydride Complexes Brian L. Edelbach, A. K. Fazlur, Rochester, New York 14627 Received April 8, 1999 The zirconium hydride dimer [Cp2ZrH2]2 reacts with C6F6. [Cp2ZrH2]2 reacts with C6F5H to give Cp2Zr(p-C6F4H)F, Cp2ZrF2, C6F4H2, and H2. The zirconium hydride

  12. Chemical Hydride Slurry for Hydrogen Production and Storage

    SciTech Connect

    McClaine, Andrew W.

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston University have demonstrated the technical viability of the process and have provided data for the cost analyses that have been performed. We also concluded that a carbothermic process could also produce magnesium at acceptable costs. The use of slurry as a medium to carry chemical hydrides has been shown during this project to offer significant advantages for storing, delivering, and distributing hydrogen: • Magnesium hydride slurry is stable for months and pumpable. • The oils of the slurry minimize the contact of oxygen and moisture in the air with the metal hydride in the slurry. Thus reactive chemicals, such as lithium hydride, can be handled safely in the air when encased in the oils of the slurry. • Though magnesium hydride offers an additional safety feature of not reacting readily with water at room temperatures, it does react readily with water at temperatures above the boiling point of water. Thus when hydrogen is needed, the slurry and water are heated until the reaction begins, then the reaction energy provides heat for more slurry and water to be heated. • The reaction system can be relatively small and light and the slurry can be stored in conventional liquid fuel tanks. When transported and stored, the conventional liquid fuel infrastructure can be used. • The particular metal hydride of interest in this project, magnesium hydride, forms benign byproducts, magnesium hydroxide (“Milk of Magnesia”) and magnesium oxide. • We have estimated that a magnesium hydride slurry system (including the mixer device and tanks) could meet the DOE 2010 energy density goals. ? During the investigation of hydriding techniques, we learned that magnesium hydride in a slurry can also be cycled in a rechargeable fashion. Thus, magnesium hydride slurry can act either as a chemical hydride storage medium or as a rechargeable hydride storage system. Hydrogen can be stored and delivered and then stored again thus significantly reducing the cost of storing and delivering hydrogen. Further evaluation and development of this concept will be performed as follow-on work under a

  13. Titanium Anodes with Active Coatings Based on Iridium Oxides: The Corrosion Resistance and Electrochemical Behavior of Anodes Coated by Mixed Iridium, Ruthenium, and Titanium Oxides

    Microsoft Academic Search

    V. V. Gorodetskii; V. A. Neburchilov

    2005-01-01

    A study of the corrosion resistance and electrochemical behavior of titanium anodes with active coatings prepared from mixed oxides iridium, ruthenium, and titanium (OIRTA) is continued. The dependence of the catalytic activity, selectivity, and corrosion resistance of these anodes with x mol % RuO2 + (30 ? x ) mol % IrO2 + 70 mol % TiO2 is studied in

  14. IEEE SENSORS JOURNAL, VOL. 13, NO. 10, OCTOBER 2013 3857 Sol-Gel Iridium Oxide-Based pH Sensor Array on

    E-print Network

    Chiao, Jung-Chih

    IEEE SENSORS JOURNAL, VOL. 13, NO. 10, OCTOBER 2013 3857 Sol-Gel Iridium Oxide-Based pH Sensor, Mu Chiao, and Jung-Chih Chiao Abstract--Iridium oxide pH sensing film is demonstrated with wide p and less labor-intensive method, to deposit iridium oxide thin films for pH sensing is reported previously

  15. Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand with Zn2+

    E-print Network

    Boyer, Edmond

    Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl as an Advance Article on the web 1st December 2009 DOI: 10.1039/b9nj00515c A novel iridium complex incorporating and emission, and a shorter luminescence lifetime. Cyclometallated iridium(III) complexes are well known

  16. Abstrac In this work, we introduced pH-sensing iridium oxide (IrOx) nanotubes grown on metal electrodes which were

    E-print Network

    Chiao, Jung-Chih

    Abstrac In this work, we introduced pH-sensing iridium oxide (IrOx) nanotubes grown on metal with a measured sensitivity of 74.3 mV/pH. Keywords: Iridium oxide, pH sensor, nanotubes, nanotemplate, aluminum oxide template, microfabrication. I. INTRODUCTION Iridium oxide nanostructures have recently attracted

  17. Evaluation of oxide-coated iridium-rhenium chambers

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1994-01-01

    Iridium-coated rhenium (Ir-Re) provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase Ir-Re rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated Ir-Re, 22-N rocket chambers were tested with gaseous hydrogen/gaseous oxygen (GHz/G02) propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia (HfO2) or zirconia (ZrO2). Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of ZrO2 infiltrated with sol gel HfO2. The other chamber had a coating composed of an Ir-oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. Testing the Ir-oxide composite-coated chamber included over 29 min at mixture ratio 16. The thicker walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner walled coatings did not experience the macrocracking and chipping of the chambers that was seen with the thick, monolithic coatings. However, burn-throughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stoichiometric. The burn-throughs were probably the result of oxygen diffusion through the oxide coating that allowed the underlying Ir and Re layers to be oxidized. The results of this test program indicated that the thin-walled oxide coatings are better suited for repeated thermal cycling than the thick-walled coating, while thicker coatings may be required for operation in aggressively oxidizing environments.

  18. Electrooxidation of methanol on iridium in acidic solutions: electrocatalysis and surface characterization by infrared spectroscopy

    SciTech Connect

    Aramata, A.; Yamazaki, T.; Kunimatsu, K.; Enyo, M.

    1987-04-23

    Electrooxidation of methanol was studied on iridium in H/sub 2/SO/sub 4/ and CHlO/sub 4/ solutions in connection with catalytic activities of the electrode in various oxidation states and of the adsorbed CO observed by infrared spectrometry. Iridium was found to show higher catalytic activity than platinum at low positive potential regions. The catalytic activity of iridium decreased with time at a constant-potential polarization and was inhibited by the introduction of CO gas. In situ infrared spectra were observed in the measurement conditions of electrode potential modulation and of constant electrode potential. The spectra for the above different conditions agreed in the wavenumber region of the spectra but not in absorbance intensity or in its relative values at different electrode potentials. The spectral maxima of the adsorbed CO, derived from methanol, were 2045 cm/sup -1/ at 0.2 V (vs. RHE) and 2054 cm/sup -1/ at 0.5 V. These maxima were shifted 20 cm/sup -1/ to higher wavenumber by the addition of CO gas. The catalytic activity of iridium was discussed in relation to redox coupling of iridium species in different oxidation states, the rate of their redox coupling, and the adsorbed CO observed by infrared spectroscopy.

  19. Solution-processable phosphorescence based on iridium-cored small molecules with the trifluoromethyl group

    NASA Astrophysics Data System (ADS)

    Zhang, Wenguan; He, Zhiqun; Wang, Yongsheng; Zhao, Shengmin

    2015-04-01

    A novel cyclometallated ligand 2-(4-(2?-ethylhexyloxy)phenyl)-5-trifluoromethyl-pyridine (EHO-5CF3-ppy) was synthesized, and two solution-processable iridium complexes bis[2-(4-(2?-ethylhexyloxy)phenyl)-5-trifluoromethylpyridinto-C3, N] iridium (acetylacetonate) (EHO-5CF3-ppy)2Ir(acac) (5) and bis[2-(4-(2?-ethylhexyl-oxy)phenyl)-5-trifluoromethylpyridinto-C3, N] iridium (2-picolinic acid) (EHO-5CF3-ppy)2Ir(pic) (6) were afforded. Trifluoromethyl and dendritic ethylhexyloxy group were incorporated into iridium ligands to tune luminescent color, to reduce luminescence quenching and to improve the solution-processable property. Photoluminescent spectra of 5 and 6 in tetrahydrofuran peaked at around 540 and 523 nm. Electrophosphorescent devices were fabricated using 5 and 6 as dopant emitters (2%), which exhibited electroluminescent (EL) peaks at 536 and 524 nm, and current efficiencies of 10.4 and 16.7 cd/A, respectively. With the concentration of iridium complexes increasing to 8%, the main EL peak showed a 4 nm of red shift and a distinct shoulder peak occurred at 583 nm for 5 or 560 nm for 6, respectively. Maximum external quantum efficiencies of the devices at the concentration of 2% and 8% were 2.8% and 4.2% for 5, 4.7% and 4.8% for 6. These indicated that 5 and 6 were efficient solution-processable emitters.

  20. Design, analysis, and fabrication of oxide-coated iridium/rhenium combustion chambers

    NASA Technical Reports Server (NTRS)

    Jang, Q.; Tuffias, R. H.; Laferla, R.; Ghoniem, N. M.

    1993-01-01

    Iridium-coated rhenium (Ir/Re) combustion chambers provide high temperature, oxidation-resistant operation for radiation-cooled liquid-fueled rocket engines. A 22-N (5-lb(sub f)) chamber has been operated for 15 hours at 2200 C (4000 F) using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) propellant, with negligible internal erosion. The oxidation resistance of these chambers could be further increased by the addition of refractory oxide coatings, providing longer life and/or operation in more oxidizing and higher temperature environments. The oxide coatings would serve as a thermal and diffusion barrier for the iridium coating, lowering the temperature of the iridium layer while also preventing the ingress of oxygen and egress of iridium oxides. This would serve to slow the failure mechanisms of Ir/Re chambers, namely the diffusion of rhenium to the inner surface and the oxidation of iridium. Such protection could extend chamber lifetimes by tens or perhaps hundreds of hours, and allow chamber operation on stoichiometric or higher mixture ratio oxygen/hydrogen (O2/H2) propellant. Extensive thermomechanical, thermochemical, and mass transport modeling was performed as a key material/structure design tool. Based on the results of these analyses, several 22-N oxide-coated Ir/Re chambers were fabricated and delivered to NASA Lewis Research Center for hot-fire testing.

  1. The Boreas concept for imaging polar winds from the Iridium-NEXT constellation

    NASA Astrophysics Data System (ADS)

    Chesters, Dennis; Riishojgaard, Lars Peter

    2008-08-01

    The Iridium communications satellite constellation is a swarm of 66 LEO satellites in 6 pole-crossing orbits. Iridium LLC plans a NEXT generation to be launched 2013-16, and has invited secondary "bolt and go" payloads from Earthobserving agencies. A swarm of infrared imagers on Iridium-NEXT could track water vapor and clouds to estimate the unobserved winds above the 55-60 degree latitude limit of geosynchronous satellite imagery. This kind of polar overpass data has been demonstrated to significantly improve medium-range weather forecasts by tracking water vapor features at 6.7 microns in successive images near the pole from NASA's MODIS instruments. A "Boreas" instrument design is proposed for a push-broom imager combining two miniature sensors: uncooled microbolometric cameras gathering 4- band infrared radiometry, and small star trackers providing attitude information. An autonomous instrument package has been designed with low mass, power, and data rate. The "Boreas" instrument would use the Iridium constellation itself to relay the raw imagery from 3 successive images to ground stations that would navigate the data and extract wind vectors. Wind vectors could be generated automatically for the polar caps every few hours, and delivered for assimilation into numerical weather models during Iridium-NEXT operations, during 2016-2030.

  2. Ab-Initio Study of the Group 2 Hydride Anions

    NASA Astrophysics Data System (ADS)

    Harris, Joe P.; Wright, Timothy G.; Manship, Daniel R.

    2013-06-01

    The beryllium hydride (BeH)- dimer has recently been shown to be surprisingly strongly bound, with an electronic structure which is highly dependent on internuclear separation. At the equilibrium distance, the negative charge is to be found on the beryllium atom, despite the higher electronegativity of the hydrogen. The current study expands this investigation to the other Group 2 hydrides, and attempts to explain these effects. M. Verdicchio, G. L. Bendazzoli, S. Evangelisti, T. Leininger J. Phys. Chem. A, 117, 192, (2013)

  3. Electronic structure, bonding and chemisorption in metallic hydrides

    SciTech Connect

    Ward, J.W.

    1980-01-01

    Problems that can arise during the cycling steps for a hydride storage system usually involve events at surfaces. Chemisorption and reaction processes can be affected by small amounts of contaminants that may act as catalytic poisons. The nature of the poisoning process can vary greatly for the different metals and alloys that form hydrides. A unifying concept is offered, which satisfactorily correlates many of the properties of transition-metal, rare-earth and actinide hydrides. The metallic hydrides can be differentiated on the basis of electronegativity, metallic radius (valence) and electronic structure. For those systems where there are d (transition metals) or f (early actinides) electrons near the Fermi level a broad range of chemical and catalytic behaviors are found, depending on bandwidth and energy. The more electropositive metals (rare-earths, actinides, transition metals with d < 5) tend to strongly chemisorb electrophilic molecules; this is a consequence of the manner in which new bonding states are introduced. More electronegative metals (d >> 5) dissolve hydrogen and form hydrides by an electronically somewhat different process, and as a class tend to adsorb electrophobic molecules. The net charge-transfer in either situation is subtle; however, the small differences are responsible for many of the observed structural, chemical, and catalytic properties in these hydride systems.

  4. Hydride-containing molten salts and their technology implications

    NASA Astrophysics Data System (ADS)

    Liaw, Bor Y.

    1993-03-01

    Hydride-conducting molten salts such as LiH in eutectic LiCl-KCl are attractive electrolyte systems for intermediate-temperature applications. The chemically reducing characteristics of these hydride melts provide a unique method to clean metal surfaces. The high conductivity of these hydride melts makes them the best electrolytes for hydrogen-based energy applications at intermediate temperatures. We will review some earlier work on hydride-conducting molten salts and their potential applications in energy technology. We will also describe some recent work on these hydride-containing molten salts for energy conversion and storage applications, including hydrogen sensing and hydrogen storage, electrochemical characterizations, and thermodynamic and kinetic investigations of metal-hydrogen reactions. More recently, lithium deuteride containing eutectic LiCl-KCl melts have been used for excess heat production by the process of electrolysis to charge deuterium into metal matrix such as Pd and Ti. From these studies we illustrate the prospects of this hydride molten salt technology and its implications for the use in intermediate-temperature electro-chemical energy conversion configurations. It will also reveal some interesting electrochemical aspects involved in the processes.

  5. Effect of niobium additions on initial hydriding kinetics of uranium

    NASA Astrophysics Data System (ADS)

    Li, Ruiwen; Wang, Xiaolin

    2014-06-01

    To study the behavior of hydrogen corrosion at the surface of U, U-2.5 wt%Nb alloy and U-5.7 wt%Nb, a gas-solid reaction system with an in situ microscope was designed. The nucleation and growth of the hydride of the alloy were continuously observed and recorded by a computer. The different characteristics of the hydrides on U metal and U-2.5 wt%Nb showed that the later alloy is more susceptible to hydrogen corrosion than the former. The growth rate of hydride of U-2.5 wt%Nb, calculated by measuring the perimeter of the hydride spots recorded by the in situ microscope, exhibited a reaction temperature dependency in the range of 40-160 °C, for pressure of 0.8 × 105 Pa. An Arrhenius plot for growth rate versus temperature yielded activation energy of 24.34 kJ/mol for the hydriding of U-2.5 wt%Nb alloy. The maximum hydriding rate was obtained at 125 °C, whose thermodynamics reason was discussed.

  6. Trialkylborane-Assisted CO2 Reduction by Late Transition Metal Hydrides

    PubMed Central

    Miller, Alexander J. M.; Labinger, Jay A.; Bercaw, John E.

    2011-01-01

    Trialkylborane additives promote reduction of CO2 to formate by bis(diphosphine) Ni(II) and Rh(III) hydride complexes. The late transition metal hydrides, which can be formed from dihydrogen, transfer hydride to CO2 to give a formate-borane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant hydride transfer enhancement, while stronger acids abstract hydride without CO2 reduction. The mechanism likely involves a pre-equilibrium hydride transfer followed by formation of a stabilizing formate-borane adduct. PMID:21909178

  7. High Strain Rate Tensile Testing of DOP-26 Iridium

    SciTech Connect

    Schneibel, Joachim H [ORNL; Carmichael Jr, Cecil Albert [ORNL; George, Easo P [ORNL

    2007-11-01

    The iridium alloy DOP-26 was developed through the Radioisotope Power Systems Program in the Office of Nuclear Energy of the Department of Energy. It is used for clad vent set cups containing radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for spacecraft. This report describes mechanical testing results for DOP-26. Specimens were given a vacuum recrystallization anneal of 1 hour at 1375 C and tested in tension in orientations parallel and perpendicular to the rolling direction of the sheet from which they were fabricated. The tests were performed at temperatures ranging from room temperature to 1090 C and strain rates ranging from 1 x 10{sup -3} to 50 s{sup -1}. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1 x 10{sup -4} Torr. The yield stress (YS) and the ultimate tensile stress (UTS) decreased with increasing temperature and increased with increasing strain rate. Between 600 and 1090 C, the ductility showed a slight increase with increasing temperature. Within the scatter of the data, the ductility did not depend on the strain rate. The reduction in area (RA), on the other hand, decreased with increasing strain rate. The YS and UTS values did not differ significantly for the longitudinal and transverse specimens. The ductility and RA values of the transverse specimens were marginally lower than those of the longitudinal specimens.

  8. Segregation of lutetium and yttrium to grain boundaries in iridium alloys

    SciTech Connect

    Gubbi, A.N.; George, E.P.; Ohriner, E.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.] [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Zee, R.H. [Auburn Univ., AL (United States). Materials Engineering Program] [Auburn Univ., AL (United States). Materials Engineering Program

    1998-01-23

    The equilibrium segregation of lutetium and yttrium to grain boundaries in iridium alloys containing 0.3 wt% tungsten was studied. The segregation level of Lu decreased with increasing annealing temperature whereas that of Y initially increased with increasing temperature but then decreased with further increases in temperature. At all temperatures, Y segregated more strongly than lutetium. The observed segregation behavior of the two dopants was explained on the basis of their free energies of segregation and solid solubilities, and the solvus lines for Lu and Y were obtained from the results. Energies of segregation and energies of solution for Lu and Y in the iridium alloy were also determined. Iridium alloys containing nominally 0.3 wt% W, 60 wppm Th and 50 wppm Al are used to clad the plutonia fuel pellets used in radioisotope thermoelectric generators for space power applications.

  9. High resolution transmission electron microscopy of dislocation core dissociations in gold and iridium

    NASA Astrophysics Data System (ADS)

    Balk, T. J.; Hemker, K. J.

    2001-06-01

    The occurrence of brittle fracture in iridium has attracted significant attention in recent years and is thought to be related to the energetics of the dislocation core, in particular the extremely high unstable stacking energy. Although it is not experimentally possible to measure the unstable stacking energy, first-principles calculations have been used to predict both this and the stacking-fault energy. These calculations suggest that, despite large differences in stacking-fault energy and elastic constants, gold and iridium exhibit similar dissociation behaviours, with screw dislocations in both metals dissociated by approximately 1 nm. In the current study, high-resolution transmission electron microscopy (HRTEM) has been utilized to observe experimentally the arrangement of atomic columns surrounding dislocation cores. Deviations from perfect lattice sites have been measured, and experimental observations quantified through comparisons with image simulations. In the case of screw dislocations, the displacement field of atomic columns relative to a perfect lattice was used to determine the extent of in-plane lattice distortion. Through comparison with simulated displacement maps, this allowed the screw dissociation width in both gold and iridium to be measured as 0.8 nm. Direct comparisons of simulated and experimentally obtained images were used to characterize the core structures of 60° dislocations, which were found to be dissociated by 3.25 nm (gold) and 1.25 nm (iridium). The stacking-fault energy for gold (33 m J m- 2), as calculated from the present high-resolution measurements, is in good agreement with previous weakbeam studies. Finally, weak-beam observations of dissociated dislocations in iridium agree well with HRTEM measurements and yield a stacking-fault energy of 420 m J m-2. For gold and iridium, both high-resolution and weakbeam measurements of dissociation distance agree with the orientation dependence of stacking-fault width as predicted by anisotropic elasticity.

  10. Designing metal hydride complexes for water splitting reactions: a molecular electrostatic potential approach.

    PubMed

    Sandhya, K S; Suresh, Cherumuttathu H

    2014-08-28

    The hydridic character of octahedral metal hydride complexes of groups VI, VII and VIII has been systematically studied using molecular electrostatic potential (MESP) topography. The absolute minimum of MESP at the hydride ligand (Vmin) and the MESP value at the hydride nucleus (VH) are found to be very good measures of the hydridic character of the hydride ligand. The increasing/decreasing electron donating feature of the ligand environment is clearly reflected in the increasing/decreasing negative character of Vmin and VH. The formation of an outer sphere metal hydride-water complex showing the HH dihydrogen interaction is supported by the location and the value of Vmin near the hydride ligand. A higher negative MESP suggested lower activation energy for H2 elimination. Thus, MESP features provided a way to fine-tune the ligand environment of a metal-hydride complex to achieve high hydridicity for the hydride ligand. The applicability of an MESP based hydridic descriptor in designing water splitting reactions is tested for group VI metal hydride model complexes of tungsten. PMID:24984110

  11. Why is iridium the best substrate for single crystal diamond growth?

    NASA Astrophysics Data System (ADS)

    Verstraete, Matthieu J.; Charlier, Jean-Christophe

    2005-05-01

    The synthesis of heteroepitaxial monocrystalline diamond films has been of technological and scientific interest for several decades. Using chemical vapor deposition techniques, polycrystalline diamond has been successfully grown on many substrates. However, iridium emerges in providing highly oriented films, significantly better than any other transition metals. In the present work we propose an ab initio density functional study of the interaction of diamond with different substrates used experimentally. The origin of iridium's specific behavior is investigated. The kinetics of carbon atoms in the substrate lattice is found to play a key role, determining the nucleation mechanisms and hence the quality of the final diamond film.

  12. Iridium on Biaxially Textured Oxide Templates: A Concept to Grow Single Crystals on Arbitrary Substrates

    NASA Astrophysics Data System (ADS)

    Gsell, Stefan; Schreck, Matthias; Brescia, Rosaria; Stritzker, Bernd; Arendt, Paul N.; Groves, James R.

    2008-12-01

    Ion beam assisted deposition (IBAD) allows a biaxial texturing of oxide layers on polycrystalline or amorphous substrates. Even the best layers still contain an in-plane angular spread of about 4°. We report here a method to grow Ir films on top of these oxide layers with a factor of 5 lower misorientation. It is shown that the huge texture improvement involves a massive realignment of the iridium islands and an orientation averaging process. Heteroepitaxial diamond was successfully deposited on the Ir/IBAD-MgO multilayer stacks. The described texture improvement by iridium layers provides a general concept towards single crystal growth on arbitrary substrates.

  13. Solubility of hydrogen isotopes in stressed hydride-forming metals

    SciTech Connect

    Coleman, C.E.; Ambler, J.F.R.

    1983-01-01

    Components made from hydride-forming metals can be brittle when particles of hydride are present. The solid solubility limit of hydrogen in these metals needs to be known so that fracture resistance can be properly assessed. Stress affects the solubility of hydrogen in metals. As hydrogen dissolves the metal volume increases, an applied hydrostatic tensile stress supplies work to increase the solubility. Precipitation of hydrides increases the volume further. A hydrostatic tensile stress promotes the formation of hydrides and tends to reduce the terminal solubility. For materials containing hydrogen in solution in equilibrium with hydrides, the effect of stress on the terminal solubility is given. Hydrogen migrates up tensile stress gradients because of the effect of stress on the solubility and solubility limit. Consequently, hydrogen concentrates at flaws. When hydrides are present in the metal matrix, those remote from the flaw tip will preferentially dissolve in favor of those precipitated at the flaw. If the stress is large enough, at some critical condition the hydrides at the flaw will crack. This is delayed hydrogen cracking. Notched and fatigue-cracked cantilever beam specimens (6) (38 x 4 x 3 mm) were machined from the circumferential direction of several cold-worked Zr-2.5 at. % Nb pressure tubes. The chemical compositions had the ranges (in atomic %) Nb - 2.5 to 2.7; O - 0.58 to 0.71; H - 0.018 to 0.18. The effect of test temperature is for a specimen containing 0.13 at. % protium and 0.29 at .% deuterium. Between 505 K and 530 K was less than 1 hr, between 530 K and 537 K it increased to 25.8 h, while at 538 K no cracking was observed up to the 54 h.

  14. Studies in Boron Hydrides Inorganic Chemistry, Vol. 12,No. 9, 1973 2091

    E-print Network

    Bodner, George M.

    Studies in Boron Hydrides Table Ia Inorganic Chemistry, Vol. 12,No. 9, 1973 2091 B , M logh, log, Illinois 61801 Studies in Boron Hydrides. X. SubstituentEffectsin the Decahydrodecaborate(2-) Ion ALLEN R

  15. The Use of Metal Hydrides for Hydrogen Recovery from Industrial Off-Gas Streams 

    E-print Network

    Rebello, W. J.; Guerrero, P. S.; Goodell, P. D.

    1987-01-01

    Black 242 Chlorine & Caustic 335 Coke Oven Gas 969 Cyclohexane 21 Ethylene (Olefins) 1117 Float Glass 1 Formaldehyde 160 Methanol 103 Petroleum Refining 107 Styrene 88 Total(15 industries) 3634 HYDRIDING ALLOY CHARACTERISTICS THE HYDRIDING...

  16. Inverse potassium hydride: a theoretical study.

    PubMed

    Sawicka, Agnieszka; Skurski, Piotr; Simons, Jack

    2005-02-10

    Results of an experimental study on the unusual "inverse" charge state (H(+)Na(-)) in salts where the H(+) ion is sequestered, combined with our earlier theoretical calculations on an unsequestered model compound (Me(3)N-H(+)...Na(-)), prompted us to further investigate such systems. In particular, we examined Et(3)N-H(+)...K(-) because considerations of the proton affinity of the amine and of the metal-hydride bond strength suggested that this ion-pair complex might be more stable to proton abstraction than was Me(3)N-H(+)...Na(-). In the present work, the ground-state potential energy surface of the Et(3)N-H(+)...K(-) ion pair was examined using second-order Møller-Plesset perturbation theory and 6-311++G basis sets. We found Et(3)N-H(+)...K(-) to be metastable to dissociation with a barrier of 8 kcal mol(-1) (computed at the CCSD(T) level of theory). This barrier indeed is substantially larger than that found earlier for (Me(3)N-H(+)...Na(-)) and suggests that unsequestered inverse-charged H(+)M(-) ion-pair salts may offer a reasonable route to creating high-energy materials if a means for synthesizing them in the laboratory can be designed. PMID:16838965

  17. The crystal structure and orientation of hydrides formed within ?-Zr (Zr-20 wt% Nb)

    NASA Astrophysics Data System (ADS)

    Khatamian, D.; Swainson, I. P.; Lucas, M. J. W.; Root, J. H.

    1998-04-01

    The structure and orientation of the hydrides formed within ?-Zr have been investigated by neutron diffraction. At room temperature, the hydrides appear to have an orthorhombic structure with Cccm or Pncm symmetry. This structure is stable up to the hydride dissolution temperature. It was also determined that the `close-packed' planes, the (1 1 0) in ?-Zr and the (1 1 1) in the hydride, exhibit similar texture.

  18. Comparison of the interactions in the rare gas hydride and Group 2 metal hydride anions

    NASA Astrophysics Data System (ADS)

    Harris, Joe P.; Manship, Daniel R.; Breckenridge, W. H.; Wright, Timothy G.

    2014-02-01

    We study both the rare gas hydride anions, RG-H- (RG = He-Rn) and Group 2 (Group IIa) metal hydride anions, MIIaH- (MIIa = Be-Ra), calculating potential energy curves at the CCSD(T) level with augmented quadruple and quintuple basis sets, and extrapolating the results to the basis set limit. We report spectroscopic parameters obtained from these curves; additionally, we study the Be-He complex. While the RG-H- and Be-He species are weakly bound, we show that, as with the previously studied BeH- and MgH- species, the other MIIaH- species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns2) and H-(1s2). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the MIIaH- species than for RG-H-. Our analyses lead us to conclude that the stronger interaction in the case of the MIIaH- species arises from sp and spd hybridization, which allows electron density on the MIIa atom to move away from the incoming H-.

  19. The influence of temperature and yield strength on delayed hydride cracking in hydrided Zircaloy-2

    SciTech Connect

    Efsing, P.; Pettersson, K. [Royal Inst. of Tech., Stockholm (Sweden)

    1996-12-31

    To determine if delayed hydride cracking (DHC) can be the cause of the long axial cracks occasionally found in BWR fuel cladding, a systematic study of DHC in Zircaloy cladding has begun. In the initial stage of the project, a test technique was developed and applied to unirradiated samples of Zircaloy. The present study includes an investigation of the influence of the yield strength and temperature on the crack growth rate and the threshold stress intensity that must be exceeded before cracking begins. Recrystallized (RXA) Zircaloy-2 has been compared to stress relief annealed (SRA) Zircaloy-2 with similar texture and composition. The results show that the crack propagation rate increases with increasing yield strength at similar stress intensity levels by as much as a decade when the yield strength is tripled. The maximum crack propagation rate measured in this study is {approximately}6 {times} 10{sup {minus}7} m/s. The threshold stress intensity, K{sub IH}, was found to decrease with increasing yield stress. The measured threshold values are in the range of 13.5 to 7.5 MPa. These figures are close to theoretically derived values using a critical fracture stress criterion of the hydrides as the limiting factor. The incubation period before cracking begins is found to be longer at 200 C than it is at 300 C.

  20. Comparison of the interactions in the rare gas hydride and Group 2 metal hydride anions.

    PubMed

    Harris, Joe P; Manship, Daniel R; Breckenridge, W H; Wright, Timothy G

    2014-02-28

    We study both the rare gas hydride anions, RG-H(-) (RG = He-Rn) and Group 2 (Group IIa) metal hydride anions, MIIaH(-) (MIIa = Be-Ra), calculating potential energy curves at the CCSD(T) level with augmented quadruple and quintuple basis sets, and extrapolating the results to the basis set limit. We report spectroscopic parameters obtained from these curves; additionally, we study the Be-He complex. While the RG-H(-) and Be-He species are weakly bound, we show that, as with the previously studied BeH(-) and MgH(-) species, the other MIIaH(-) species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns(2)) and H(-)(1s(2)). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the MIIaH(-) species than for RG-H(-). Our analyses lead us to conclude that the stronger interaction in the case of the MIIaH(-) species arises from sp and spd hybridization, which allows electron density on the MIIa atom to move away from the incoming H(-). PMID:24588166

  1. Metal hydrides: properties and practical applications. review of the works in cis-countries

    Microsoft Academic Search

    V. N Verbetsky; S. P Malyshenko; S. V Mitrokhin; V. V Solovei; Yu. F Shmal’ko

    1998-01-01

    A short review of RandD in the field of hydrogen hydride technologies in Russia and CIS countries is presented. As a result of basic research of physical and chemical features of intermetallic alloys and their hydrides, their structural peculiarities, absorption kinetics, thermal processes, etc., methods have been developed for creation high efficient alloys for different applications in metal hydride technology.

  2. Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part II—Analysis of Real Samples

    Microsoft Academic Search

    Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

    2012-01-01

    Abstract: As an extended discussion of Part I, this review provides a survey of the literature about the elemental and speciation analysis of hydride-forming and non-hydride-forming elements in real samples by using hydride generation–analytical atomic spectrometry based on the recently developed technique summarized in Part I, with emphasis on the sample pretreatment methods and interference elimination.

  3. Recent Advance of Hydride Generation-Analytical Atomic Spectrometry: Part II- Analysis of Real Samples

    Microsoft Academic Search

    Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

    2012-01-01

    As an extended discussion of Part I, this review provides a survey of the literature about the elemental and speciation analysis of hydride-forming and non-hydride forming elements in real samples by using hydride generation-analytical atomic spectrometry based on the recently developed technique summarized in Part I, with emphesis on the sample pretreatment methods and interference elimination.

  4. Iridium-Catalyzed, Regio- and Enantioselective Allylic Substitution with Aromatic and Aliphatic Sulfinates

    PubMed Central

    Ueda, Mitsuhiro; Hartwig, John F.

    2009-01-01

    The iridium-catalyzed allylation of sodium sulfinate to form branched allylic sulfones is reported. The reactions between various sodium sulfinates and achiral allylic carbonates occur in good yields, with high selectivity for the branched isomer, and high enantioselectivities (up to 98% ee). PMID:19954200

  5. Enantioselective synthesis of alcohols and amines by iridium-catalyzed hydrogenation, transfer hydrogenation, and related processes.

    PubMed

    Bartoszewicz, Agnieszka; Ahlsten, Nanna; Martín-Matute, Belén

    2013-06-01

    The preparation of chiral alcohols and amines by using iridium catalysis is reviewed. The methods presented include the reduction of ketones or imines by using hydrogen (hydrogenations), isopropanol, formic acid, or formate (transfer hydrogenations). Also dynamic and oxidative kinetic resolutions leading to chiral alcohols and amines are included. Selected literature reports from early contributions to December 2012 are discussed. PMID:23606577

  6. Improved Turn-on Times of Iridium Electroluminescent Devices by Use of Ionic Liquids

    E-print Network

    Bernhard, Stefan

    Improved Turn-on Times of Iridium Electroluminescent Devices by Use of Ionic Liquids Sara T. ParkerVised Manuscript ReceiVed April 13, 2005 We demonstrate an improvement in the turn-on time of electroluminescent Electroluminescent devices based on ionic transition metal complexes (iTMCs) are being extensively studied

  7. Efficient Yellow Electroluminescence from a Single Layer of a Cyclometalated Iridium Complex

    E-print Network

    Bernhard, Stefan

    Efficient Yellow Electroluminescence from a Single Layer of a Cyclometalated Iridium Complex Jason@ccmr.cornell.edu Abstract: We report on the spectroscopic, electrochemical, and electroluminescent properties of [Ir(ppy)2 as multifunctional chromophores for single-layer, solid-state electroluminescent devices.1-6 In these devices

  8. High resolution transmission electron microscopy of dislocation core dissociations in gold and iridium

    Microsoft Academic Search

    T. J. Balk; K. J. Hemker

    2001-01-01

    The occurrence of brittle fracture in iridium has attracted significant attention in recent years and is thought to be related to the energetics of the dislocation core, in particular the extremely high unstable stacking energy. Although it is not experimentally possible to measure the unstable stacking energy, first-principles calculations have been used to predict both this and the stacking-fault energy.

  9. An Operational and Performance Overview of the IRIDIUM Low Earth Orbit Satellite System

    Microsoft Academic Search

    Stephen R. Pratt; Richard A. Raines; Carl E. Fossa Jr.; Michael A. Temple

    1999-01-01

    Today, both the military and commercial sectors are placing an increased emphasis on global communications. This has prompted the development of several low earth orbit satellite systems that promise worldwide connectivity and real-time voice communications. This article provides a tutorial overview of the IRIDIUM low earth orbit satellite system and performance results obtained via simulation. First, it presents an overview

  10. Determination of platinum and iridium in marine waters, sediments, and organisms

    Microsoft Academic Search

    Vern. Hodge; Martha. Stallard; Minoru. Koide; Edward D. Goldberg

    1986-01-01

    The determination of platinum and iridium at picogram levels in marine samples is based upon an isolation of anionic forms of these elements upon appropriate resins with a subsequent purification by uptake on a single ion exchange bead. All steps are followed by radiotracers, and yields vary between 35 and 90%. Graphite furnace atomic absorption spectrometry is employed as the

  11. Salvage irradiation of oropharyngeal cancers using iridium 192 wire implants: 5-year results of 70 cases

    Microsoft Academic Search

    Jean-Jacques Mazeron; Denis Langlois; Daniel Glaubiger; Judith Huart; Michel Martin; Michel Raynal; Elie Calitchi; Gerard Ganem; Marl Faraldi; Franck Feuilhade

    1987-01-01

    Between May 1971 and November 1980, 70 patients with recurrent or new oropharyngeal cancers arising in previously irradiated tissues were treated using iridium 192 afterloading techniques. The actuarial local control was 72% at 2 years and 69% at 5 years. Although local control of the tumor was achieved in the majority of these patients, only 10 patients remained alive at

  12. Tetraphenylborate versus tetraimidazolylborate as counterions for cationic iridium(iii) complexes: enhanced electrochemical stabilities and electroluminescence.

    PubMed

    Ma, Dongxin; Duan, Lian; Qiu, Yong

    2015-04-29

    Tetraimidazolylborate is first used as the counterion of two novel ionic iridium complexes, instead of tetraphenylborate. Both the electrochemical stabilities and electroluminescence are sharply improved. Organic light-emitting diodes have been successfully fabricated with a high current efficiency of 9.48 cd A(-1) and a maximum brightness of 5163 cd m(-2). PMID:25437109

  13. A pH Sensor Based on a Stainless Steel Electrode Electrodeposited with Iridium Oxide

    ERIC Educational Resources Information Center

    Martinez, C. C. M.; Madrid, R. E.; Felice, C. J.

    2009-01-01

    A simple procedure to make an iridium oxide (IrO[subscript 2]) electrodeposited pH sensor, that can be used in a chemical, biomedical, or materials laboratory, is presented here. Some exercises, based on this sensor, that can be used to teach important concepts in the field of biomedical, biochemical, tissue, or materials engineering, are also…

  14. Elegant Approach to the Synthesis of a Unique Heteroleptic Cyclometalated Iridium(III)-Polyoxometalate Conjugate

    Microsoft Academic Search

    Benjamin Matt; Jamal Moussa; Lise-Marie Chamoreau; Carlos Afonso; Anna Proust; Hani Amouri; Guillaume Izzet

    2012-01-01

    A novel heteroleptic cyclometalated iridium(III) complex with one picolinic acid derivative bearing a pendant terminal alkynyl tether has been prepared following a new synthetic route. This pendant alkynyl tether can be further engaged in palladium C?C coupling reactions, allowing its grafting to a Keggin-type polyoxometalate and thus providing a unique iridio-POM conjugate.

  15. Testing and evaluation of oxide-coated iridium/rhenium chambers

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1993-01-01

    Iridium-coated rhenium provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase iridium/rhenium rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated iridium/rhenium, 22 N rocket chambers were tested on gaseous hydrogen/gaseous oxygen propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia or zirconia. Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of zirconia infiltrated with sol gel hafnia. The other chamber had a coating composed of an iridium/oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. The iridium/oxide composite coated chamber included testing for over 29 minutes at mixture ratio 16. The thicker-walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner-walled coatings did not experience the macrocracking and chipping of the chambers seen with the thick, monolithic coatings. However, burnthroughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stochiometric. The burn-throughs were probably the result of oxygen-diffusion through the oxide coating that allowed the underlying iridium and rhenium layers to be oxidized. The results of this test program indicated that the thin-walled oxide coatings are better suited for repeated thermal cycling than the thick-walled coating, while thicker coatings may be required for operation in aggressively oxidizing environments.

  16. AC-impedance studies on metal hydride electrodes

    SciTech Connect

    Zhang, W.; Kumar, M.P.S.; Visintin, A.; Srinivasan, S. [Texas A and M Univ., College Station, TX (United States)

    1994-12-31

    The metal hydride (MH{sub x}) electrode is the negative electrode in one of the most advanced rechargeable batteries (i.e. nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydriding reaction in the battery, using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MH{sub x} electrode reaction is proposed. The rate capabilities of charge/discharge reaction of MH{sub x} electrode are determined by the kinetics of charge transfer reaction at the alloy surface. Transient and pseudo steady-state analyses (cyclic voltammetry and potential vs. current density behavior) qualitatively and quantitatively support the EIS results. EIS studies on electrodes with (i) three types of binding additives, (ii) varying amounts of active material, and (iii) two types of alloys as active materials demonstrate the usefulness of this technique to develop electrodes with the optimum compositions and structures.

  17. Models for Metal Hydride Particle Shape, Packing, and Heat Transfer

    E-print Network

    Kyle C. Smith; Timothy S. Fisher

    2012-05-04

    A multiphysics modeling approach for heat conduction in metal hydride powders is presented, including particle shape distribution, size distribution, granular packing structure, and effective thermal conductivity. A statistical geometric model is presented that replicates features of particle size and shape distributions observed experimentally that result from cyclic hydride decreptitation. The quasi-static dense packing of a sample set of these particles is simulated via energy-based structural optimization methods. These particles jam (i.e., solidify) at a density (solid volume fraction) of 0.665+/-0.015 - higher than prior experimental estimates. Effective thermal conductivity of the jammed system is simulated and found to follow the behavior predicted by granular effective medium theory. Finally, a theory is presented that links the properties of bi-porous cohesive powders to the present systems based on recent experimental observations of jammed packings of fine powder. This theory produces quantitative experimental agreement with metal hydride powders of various compositions.

  18. Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

    SciTech Connect

    Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

    2012-02-01

    In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70 degC. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 degC lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This

  19. Hydrogen storage in fullerenes and in an organic hydride

    SciTech Connect

    Wang, J.C.; Murphy, R.W.; Chen, F.C. [Oak Ridge National Lab., TN (United States). Energy Div.; Loutfy, R.O.; Veksler, E.; Li, W. [Materials and Electrochemical Research Corp., Tucson, AZ (United States)

    1998-05-29

    While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the results of this effort as follows: (1) Liquid phase hydrogenation of fullerenes indicated that more than 6 wt% capacity can be obtained at 180 C, 350--400 psi; (2) Dehydrogenation of fullerenes hydrides below 225 C was demonstrated using an Ir-based P-C-P pincer complex catalyst; (3) Cyclic hydrogenation and dehydrogenation tests of an organic hydride at 7 wt% capacity were conducted at 180--260 C; and (4) Physical models developed for fullerenes were determined to be applicable to this organic hydride (with much smaller activation energies).

  20. Sub-millimeter Spectroscopy of Diatomic Hydrides of Astrophysical Interest

    NASA Astrophysics Data System (ADS)

    Halfen, D. T.; Savage, C. S.; Apponi, A. J.; Ziurys, L. M.

    2005-05-01

    One class of interstellar molecules that are unique to the millimeter/far-infrared region of the electromagnetic spectrum are diatomic hydrides. These species have low moments of inertia, and therefore their rotational spectrum lies exclusively at sub-millimeter wavelengths and shorter. They are therefore extremely good targets for space-borne and airborne platforms such as Herschel, SOFIA, and SAFIR. Diatomic hydrides, both neutral (MH) and ionic (MH+) forms, are also basic building blocks of interstellar chemistry. In ionic form, they may be the "hidden" carriers of refractory elements in dense gas. To date, there is very little high resolution data available for many hydride species, in particular the ionic form. In the Ziurys laboratory, we have been conducting studies of metal hydrides using sub-millimeter direct absorption and velocity modulation techniques. We have measured the pure rotational spectrum of AlH (J = 0 -> 1), CrH (N = 0 -> 1), and SH+ (N = 0 -> 1). The hydride neutrals were created in a DC discharge of H2 and metal vapor, generated in a Broida-type oven. In the case of AlH (X1}? {+), the quadrupole hyperfine splitting in the J = 0 -> 1 transition was significantly revised from past measurements. The strongest five hyperfine transitions were recorded for CrH (X6}? {+) in its N = 0 -> 1 transition, the first direct observation of these lines. Spectra of AlD and CrD were measured as well. Finally, the N = 0 -> 1 transition of the SH+ ion (X3}? {-) has been recorded. For this molecule, an AC discharge of H2S and argon or CH3SH and argon was used for the synthesis, and velocity modulation methods were employed to isolate ion signals. Currently, velocity modulation techniques are being developed to study other diatomic hydride ions. Results of these investigations will be reported. This work is supported by NASA Grant NAG5-12719.

  1. Inverse sodium hydride: a theoretical study.

    PubMed

    Sawicka, Agnieszka; Skurski, Piotr; Simons, Jack

    2003-04-01

    A recent experimental investigation in which a salt containing the unusual charge distribution H(+) and Na(-) was synthesized and characterized prompted us to undertake an ab initio theoretical investigation. In the salt synthesized, the H(+) is bound to the nitrogen center of an amine and the Na(-) alkalide is "blocked" from approaching the protonated amine site by steric constraints of a cage structure. Although one expects that the Na(-) would deprotonate an unprotected R(3)N-H(+) cation, we decided to further explore this issue. Using extended atomic orbital basis sets and Møller-Plesset and coupled-cluster treatments of electron correlation, we examined the relative stabilities of the prototype (Me)(3)N + NaH, (Me)(3)N + Na(+) + H(-), (Me)(3)N-H(+) + Na(-), and (Me)(3)N-Na(+) + H(-) as well as the ion pair complexes (Me)(3)N-H(+).Na(-) and (Me)(3)N-Na(+).H(-). The primary focus of this effort was to determine whether the high-energy (Me)(3)N-H(+).Na(-) ion pair, which is the analogue of what the earlier workers termed "inverse sodium hydride", might be stable with respect to proton abstraction under any reasonable solvation conditions (which we treated within the polarized continuum model). Indeed, we find that such ion pairs are metastable (i.e., locally geometrically stable with a barrier to dissociation) for solvents having dielectric constants below approximately 2 but spontaneously decompose into their constituent ions for solvents with higher dielectric constants. We suggest that amines with large proton affinities and/or metals with weaker MH bond strengths should be explored experimentally. PMID:12656631

  2. Cycle performance of a silver-metal hydride cell

    SciTech Connect

    Lipka, S.M.; Nechev, K.S. [Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Ocean Engineering

    1996-11-01

    Cycling experiments were conducted on a silver oxide-metal hydride cell Previous work on this system determined the influence of electrolyte concentration on rate capability, charge retention and cycle life. The emphasis of this work was placed on enhancing the cycle life of this system. Cells were assembled using sintered silver and AB{sub 5} metal hydride electrodes. Cycle data were collected on flooded cells containing 31 and 45% KOH. A major variable in the improvement of the cycle performance was the silver migration barrier material.

  3. Materials science of Mg-Ni-based new hydrides

    Microsoft Academic Search

    S. Orimo; H. Fujii

    2001-01-01

    .   One of the advantageous functional properties of Mg alloys (or compounds) is to exhibit the reversible hydriding reaction.\\u000a In this paper, we present our systematic studies regarding the relationship between nanometer- or atomistic-scale structures\\u000a and the specific hydriding properties of the Mg-Ni binary system, such as(1) nanostructured (n)-Mg2Ni, (2) a mixture of n-Mg2Ni and amorphous (a)-MgNi,(3) pure a-MgNi, and(4)

  4. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H., E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Xiang [Center for Space Science and Technology, University of Maryland–Baltimore County, Baltimore, Maryland 21250 (United States)] [Center for Space Science and Technology, University of Maryland–Baltimore County, Baltimore, Maryland 21250 (United States); Kiran, Boggavarapu, E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry and Physics, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry and Physics, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K. [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)] [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup ?}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  5. Ab-initio study of transition metal hydrides

    NASA Astrophysics Data System (ADS)

    Sharma, Ramesh; Shukla, Seema; Dwivedi, Shalini; Sharma, Yamini

    2014-04-01

    We have performed ab initio self consistent calculations based on Full potential linearized augmented plane wave (FP-LAPW) method to investigate the optical and thermal properties of yttrium hydrides. From the band structure and density of states, the optical absorption spectra and specific heats have been calculated. The band structure of Yttrium metal changes dramatically due to hybridization of Y sp orbitals with H s orbitals and there is a net charge transfer from metal to hydrogen site. The electrical resistivity and specific heats of yttrium hydrides are lowered but the thermal conductivity is slightly enhanced due to increase in scattering from hydrogen sites.

  6. Testing of electroformed deposited iridium/powder metallurgy rhenium rockets

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Dickerson, Robert

    1996-01-01

    High-temperature, oxidation-resistant chamber materials offer the thermal margin for high performance and extended lifetimes for radiation-cooled rockets. Rhenium (Re) coated with iridium (Ir) allow hours of operation at 2200 C on Earth-storable propellants. One process for manufacturing Ir/Re rocket chambers is the fabrication of Re substrates by powder metallurgy (PM) and the application of Ir coatings by using electroformed deposition (ED). ED Ir coatings, however, have been found to be porous and poorly adherent. The integrity of ED Ir coatings could be improved by densification after the electroforming process. This report summarizes the testing of two 22-N, ED Ir/PM Re rocket chambers that were subjected to post-deposition treatments in an effort to densify the Ir coating. One chamber was vacuum annealed, while the other chamber was subjected to hot isostatic pressure (HIP). The chambers were tested on gaseous oxygen/gaseous hydrogen propellants, at mixture ratios that simulated the oxidizing environments of Earth-storable propellants. ne annealed ED Ir/PM Re chamber was tested for a total of 24 firings and 4.58 hr at a mixture ratio of 4.2. After only 9 firings, the annealed ED Ir coating began to blister and spall upstream of the throat. The blistering and spalling were similar to what had been experienced with unannealed, as-deposited ED Ir coatings. The HIP ED Ir/PM Re chamber was tested for a total of 91 firings and 11.45 hr at mixture ratios of 3.2 and 4.2. The HIP ED Ir coating remained adherent to the Re substrate throughout testing; there were no visible signs of coating degradation. Metallography revealed, however, thinning of the HIP Ir coating and occasional pores in the Re layer upstream of the throat. Pinholes in the Ir coating may have provided a path for oxidation of the Re substrate at these locations. The HIP ED Ir coating proved to be more effective than vacuum annealed and as-deposited ED Ir. Further densification is still required to match the integrity of chemically vapor deposited Ir coatings. Despite this, the successful long duration testing of the HIP ED Ir chamber, in an oxidizing environment comparable to Earth-storable propellants, demonstrated the viability of this Ir/Re rocket fabrication process.

  7. Iridium and Spherules in Late Eocene Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, F. T.; Liu, S.

    2002-01-01

    We have been independently examining the Ir (FTK) and spherule (SL) contents of recently discovered late Eocene impact deposits from the south Atlantic and western Indian oceans. These include ODP Sites 1090 [14,15], 709 [lo], and 699 [Liu in prep.]. Iridium abundances at these sites are within the typical range reported for late Eocene deposits, with peak concentrations between 100 and 1000 pg/g. In Table 1 we present estimated net Ir fluences (in ng Ir/cm ) for these and nine other sites. Although there are fewer sites than the K/T boundary, the average of 9 ng Ir/cm2 is probably a good estimate of the late Eocene global flux. This is enough Ir for a 6 km comet (assuming 250 ng/g Ir, p=1.5), is sufficient to produce the Popigai or Chesapeake Bay structures, and is 16% of the flux estimated for the K/T boundary (55 ng/cm2 [ 161). Figure 1 shows the relative abundances of Ir, glassy microtektites and cpx-bearing spherules in sediments from Sites 699 and 1090, which are separated by only 3100 km. Although these two sites have similar Ir anomalies, the abundances of spherules are quite different. Site 1090 has well-defined peaks for both types of spherules, with a peak of 562 cpx spheruledg, while Site 699 contains only a few glassy microtektites and no cpx spherules. While the different abundances of spherules may reflect a heterogeneous distribution of spherules on the Earth s surface, an equally likely cause of this difference may be differential preservation of spherules in the sediment. recovered are only a trace residue of the initial impact deposit. Earlier work found 0.22 ng/g Ir in glassy microtektites from Site 689 [17], an insufficient concentration to support 0.16 ng/g in the bulk sediment at this site. We measured 15 ng/g Ir in a group of 95 cpx spherules from Site 1090 with sizes from 63 to -200 pm, a set typical of the size distribution at this site. Although this is a significant concentration it also cannot support the Ir peak. We presently lack quantitative data on the mass concentration of cpx spherules in Site 1090 sediments, but it is certainly <1 mg/g in The impact record in the late Eocene is very different from that at the Cretaceous-Tertiary In contrast, the late Eocene probably experienced multiple impact events.

  8. Development of a gamma-ray detector with iridium transition edge sensor coupled to a Pb absorber

    E-print Network

    Leman, Steven W.

    We have recently started to develop a high-resolution gamma-ray spectrometer for material defect analysis. Our gamma-ray detector is a microcalorimeter consisting of an iridium/gold bilayer transition edge sensor (TES) ...

  9. High performance Zr-based metal hydride alloys for nickel metal hydride batteries

    SciTech Connect

    Young, R.C.; Ovshinsky, S.R.; Huang, B.; Chao, B.S.; Li, Y.

    2000-07-01

    Based upon Ovonic's multi-element, atomic engineering approach, two families of alloys are being used in commercial Nickel Metal Hydride (NiMH) rechargeable batteries, i.e., the mischmetal (Mm) based AB{sub 5} and Zr based AB{sub 2} alloys. While Mm based alloys are faster to activate, they are limited by a discharge capacity of only 320--340 mAh/g. The Zr based alloy, although slightly slower to activate, provides a much higher discharge capacity. In this paper, the authors first discuss the use of Ovonic's multi-element approach to generate a spectrum of disordered local environments. They then present experimental data to illustrate that through these atomically engineered local environments, they are able to control the hydrogen site occupancy, discharge capacity, kinetics, and surface states. The Zr based alloy with a specific discharge capacity of 465 mAh/g and excellent rate capability has been demonstrated.

  10. Determination of Se in urine by flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping

    NASA Astrophysics Data System (ADS)

    Tyson, Julian F.; Sundin, Nils G.; Hanna, Christopher P.; McIntosh, Susan A.

    1997-10-01

    Following digestion of the sample in a mixture of bromate and hydrobromic acid, the inorganic selenium produced was quantified by trapping hydrogen selenide, formed when a 500 ?l sample volume injected into a hydrochloric acid carrier stream merged with a stream of sodium borohydride solution, on the iridium-pretreated interior of a graphite furnace atomizer. A number of parameters relating to the digestion, flow injection manifold and trapping in the atomizer were investigated, including a study of factors affecting the detection limit. It was found necessary to heat the digest under reflux at a temperature of 150°C for 2 h. Quantitative recoveries, from a human urine matrix, of selenite, selenate, trimethylselenium, selenocystine, selenopurine and selenomethionine spikes were obtained. The efficiency of hydride generation, transport and trapping was 75%. The major factors affecting the detection limit were the reagent purity and the volume injected. For high-purity hydrobromic acid and borohydride free of caking agent, the detection limit, based on three times the standard deviation of the blank, was 0.06 ?g l -1 for a 1000 ?l injection volume corresponding to a detection limit of 3 ?g l -1 for a urine sample. The method was validated by the accurate analyses of Standard Reference Material 2670 from the National Institute of Standards and Technology, and urine samples from an interlaboratory comparison program. The procedure avoids the need for perchloric acid and produces selenium in the +4 oxidation state and thus no reduction is needed prior to generation of the hydrogen selenide. The use of a graphite furnace atomizer avoids the need for frequent reconditioning of the atomizer surface and the need for the standard additions method, both of which are drawbacks of procedures which make use of the quartz tube atomizer. All sample handling procedures following the digestion were automated by the use of flow injection technology.

  11. Determination of fracture strength of ?-zirconium hydrides embedded in zirconium matrix at high temperatures

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Kobayashi, Y.; Uchikoshi, H.

    2013-04-01

    The fracture strength of ?-zirconium hydrides embedded in a zirconium matrix was determined at temperatures between 25 °C and 250 °C by ring tensile tests using Zircaloy-2 tubes. Essentially all of the present hydrides in the tubes were re-oriented in the radial direction by a temperature cycling treatment and then tensile stress was applied perpendicular to the hydrides to ensure that brittle fracture would occur at the hydrides. The hydrides failed in a brittle manner below 100 °C where-as the zirconium matrix itself underwent ductile fracture without hydride cracking at temperatures above 200 °C under plane stress condition. Brittle fracture of the hydrides continued to occur at temperatures up to 250 °C under plane strain condition, suggesting that the upper limit temperature for hydride fracture, Tupper, was raised by the triaxial stress state under the plane strain condition. The apparent fracture strength of the hydrides, ?hydridef, was determined at temperatures below Tupper from the measured fracture strength of the tubes, making a correction for the compressive transformation stress in the hydrides. ?hydridef was about 710 MPa at temperatures between 25 °C and 250 °C at both plane stress and plane strain conditions. The temperature dependency was very small in this temperature range. Tupper was almost equivalent to the cross-over temperature between ?hydridef and the ultimate tensile strength (UTS), which suggests that, at temperatures above Tupper, the zirconium matrix would undergo ductile fracture before the stress in the hydride is raised above ?hydridef, since UTS is smaller than ?hydridef.

  12. Effect of radial hydrides on the axial and hoop mechanical properties of Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Chu, H. C.; Wu, S. K.; Chien, K. F.; Kuo, R. C.

    2007-05-01

    The effect of radial hydrides on the mechanical properties of stress-relief annealed Zircaloy-4 cladding was studied. Specimens were firstly hydrided to different target hydrogen levels between 100 and 600 wt ppm and then thermally cycled in an autoclave under a constant hoop stress to form radial hydrides by a hydride reorientation process. The effect of radial hydrides on the axial properties of the cladding was insignificant. On the other hand, the cladding ductility measurements decreased as its radial hydride content increased when the specimen was tested in plane strain tension. A reference hydrogen concentration for radial hydrides in the cladding was defined for assessing the fuel cladding integrity based on a criterion of the tensile strength 600 MPa. The reference hydrogen concentration increased with the specimen (bulk) hydrogen concentration to a maximum of ˜90 wt ppm at the bulk concentration ˜300 wt ppm H and then decreased towards higher concentrations.

  13. Highly Active Iridium/Iridium Tin/Tin Oxide Heterogeneous Nanoparticles as Alternative Electrocatalysts for the Ethanol Oxidation Reaction

    SciTech Connect

    Du W.; Su D.; Wang Q.; Saxner D.; Deskins N.A.; Krzanowski J.E.; Frenkel A.I.; Teng X.

    2011-08-03

    Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass. However, the implementation of ethanol fuel cell technology has been hindered by the lack of low-cost, highly active anode catalysts. In this paper, we have studied Iridium (Ir)-based binary catalysts as low-cost alternative electrocatalysts replacing platinum (Pt)-based catalysts for the direct ethanol fuel cell (DEFC) reaction. We report the synthesis of carbon supported Ir{sub 71}Sn{sub 29} catalysts with an average diameter of 2.7 {+-} 0.6 nm through a 'surfactant-free' wet chemistry approach. The complementary characterization techniques, including aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, are used to identify the 'real' heterogeneous structure of Ir{sub 71}Sn{sub 29}/C particles as Ir/Ir-Sn/SnO{sub 2}, which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO{sub 2} present on the surface. The Ir{sub 71}Sn{sub 29}/C heterogeneous catalyst exhibited high electrochemical activity toward the ethanol oxidation reaction compared to the commercial Pt/C (ETEK), PtRu/C (Johnson Matthey) as well as PtSn/C catalysts. Electrochemical measurements and density functional theory calculations demonstrate that the superior electro-activity is directly related to the high degree of Ir-Sn alloy formation as well as the existence of nonalloyed SnO{sub 2} on surface. Our cross-disciplinary work, from novel 'surfactant-free' synthesis of Ir-Sn catalysts, theoretical simulations, and catalytic measurements to the characterizations of 'real' heterogeneous nanostructures, will not only highlight the intriguing structure-property correlations in nanosized catalysts but also have a transformative impact on the commercialization of DEFC technology by replacing Pt with low-cost, highly active Ir-based catalysts.

  14. JOURNAL DE PHYSIQUE Colloque C6,supplbment au no 8,Tome 39, aotit 1978,page C6-608 SUPERCONDUCTING PROPERTIES OF IRIDIUM THIN FiLMS

    E-print Network

    Paris-Sud XI, Université de

    PROPERTIES OF IRIDIUM THIN FiLMS ++L.B. Holdeman, R.J. Soulen, Jr.,T.F. ~inne~an'and P.N. Peters Center supraconducteurs de type Dayem et des jonctions tunnel A1-A1203-Ir 1 partir de couches minces d'iridium que nous avons mesurb la variation avec la tempb- rature du gap d'bnergie de ces couches minces d'iridium en

  15. Process of forming a sol-gel/metal hydride composite

    DOEpatents

    Congdon, James W. (Aiken, SC)

    2009-03-17

    An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

  16. Bipolar silver-metal hydride cell studies: Preliminary results

    SciTech Connect

    Reisner, D.E.; Plivelich, R.F.; Klein, M.G. [Electro Energy, Inc., Danbury, CT (United States)

    1995-12-31

    Electro Energy, Inc. (EEI) is developing a patented wafer cell based upon the use of a conductive plastic film as the cell face. Recent studies of silver-metal hydride cells have augmented its principal development of a bipolar Ni-MH battery. Initial wafer cell cycle life test data are reported.

  17. Titanium based Laves phase hydrides with high dissociation pressure

    Microsoft Academic Search

    S. V. Mitrokhin; V. N. Verbetsky

    1996-01-01

    A method for quantitative prediction of the hydrogen sorption properties of Laves phases is proposed. It is based on the empirical rules formulated earlier by Bernauer. The investigation showed that the chosen alloys possess rather high hydrogen dissociation pressure. The isotherms and thermodynamic properties of the hydride phases were determined. The correlation between the experimental and calculated values is discussed.

  18. The cobalt hydride that never was: revisiting Schrauzer's "hydridocobaloxime".

    PubMed

    Lacy, David C; Roberts, Gerri M; Peters, Jonas C

    2015-04-15

    Molecular cobalt-dmg (dmg = dimethylglyoxime) complexes are an important class of electrocatalysts used heavily in mechanistic model studies of the hydrogen evolution reaction (HER). Schrauzer's early isolation of a phosphine-stabilized "[H-Co(III)(dmgH)2P(nBu)3]" complex has long provided circumstantial support for the plausible intermediacy of Co(III)-H species in HER by cobaloximes in solution. Our investigation of this complex has led to a reassignment of its structure as [Co(II)(dmgH)2P(nBu)3], a complex that contains no hydride ligand and dimerizes to form an unsupported Co-Co bond in the solid state. A paramagnetic S = 3/2 impurity that forms during the synthesis of [Co(II)(dmgH)2P(nBu)3] when exposed to adventitious oxygen has also been characterized. This impurity features a (1)H NMR resonance at -5.06 ppm that was recently but erroneously attributed to the hydride resonance of "[H-Co(III)(dmgH)2P(nBu)3]". We draw attention to this reassignment because of its relevance to cobaloxime hydrides and HER catalysis and because Schrauzer's "hydridocobaloxime" is often cited as the primary example of a bona fide hydride that can be isolated and characterized on this widely studied HER platform. PMID:25798900

  19. Aluminium hydride: a reversible material for hydrogen storage.

    PubMed

    Zidan, Ragaiy; Garcia-Diaz, Brenda L; Fewox, Christopher S; Stowe, Ashley C; Gray, Joshua R; Harter, Andrew G

    2009-07-01

    Aluminium hydride has been synthesized electrochemically, providing a synthetic route which closes a reversible cycle for regeneration of the material and bypasses expensive thermodynamic costs which have precluded AlH(3) from being considered as a H(2) storage material. PMID:19557259

  20. Performance analysis of a compressor driven metal hydride cooling system

    Microsoft Academic Search

    S. S. Bedbak; M. Ram Gopal

    2005-01-01

    A compressor-driven metal hydride cooling system is analyzed in terms of its energetic and exergetic efficiencies. Applying the first and second laws of thermodynamics, the system COP, contribution of individual irreversibilities and the second law efficiency of the system are obtained. Effects of important design and operating parameters on system performance are presented. Performance comparison is made between systems working

  1. Sites and Diffusion of Muons in Fcc Metal Hydride Systems.

    NASA Astrophysics Data System (ADS)

    Kempton, James Russell

    1987-09-01

    A positive muon can be considered an isotope of hydrogen due to similarities in spin and charge. For metal hydride systems, the muon enters the sample "as the last hydrogen added," and competes for the same sites as the hydrogen atoms. To observe the site competition and diffusion of both particles (muon and proton), several FCC metal hydrides, TiH_{1.83}, TiH_{1.97}, TiH _{1.99}, YH_{1.77 }, YH_2, ZrH _{1.94}, and LaH_ {2.06}, were studied using transverse -, zero-, and low longitudinal-field muSR. The low temperature region results indicate that the muon predominately occupies octahedral sites for the FCC metal hydrides in this study. The probability for a muon to occupy a tetrahedral site in titanium and zirconium hydrides at these temperatures is proportional to the vacancy concentration. Whereas the probability for T site occupation in yttrium hydride is proportional to the number of protons not occupying these sites which increases with hydrogen concentration. Muon T site occupancy below room temperature for LaH _{2.06} was not observed and was not expected since these sites are occupied by protons. Around 300 K, the muon diffuses over interstitial O sites to vacancies in the H sublattice of TiH_{1.99}. The vibration of the hydrogen lattice is found to be the mechanism responsible for the activation of the muon out of the O site. Above room temperature, the muon occupies tetrahedral sites in yttrium and titanium hydrides. At high temperatures, the field-correlation time for a muon in titanium and yttrium hydrides is approximately one to two orders of magnitude greater than for a proton as measured by NMR. The results of a Monte Carlo simulation indicate that the presence of the muon inhibits the motion of the nearest-neighbor protons at high temperatures. The dynamics of the proton spins are observed by zero- and low longitudinal -field muSR through the oscillation of the muon polarization at long times for a static muon in a T or O site. This observation is not predicted by the Kubo-Toyabe treatment for a stationary muon.

  2. An Analysis of the FY-1C, Iridium 33, and Cosmos 2251 Fragments

    NASA Technical Reports Server (NTRS)

    Liou, J.-C.

    2014-01-01

    The beginning of the year 2013 marks the sixth anniversary of the destruction of the Fengyun-1C (FY-1C) weather satellite as the result of an anti-satellite test conducted by China in January 2007 and the fourth anniversary of the accidental collision between Cosmos 2251 and the operational Iridium 33 in February 2009. These two events represent the worst satellite breakups in history. A total of 5579 fragments have been cataloged by the U.S. Space Surveillance Network (SSN), and almost 5000 of them were still in orbit in January 2013. In addition to these cataloged objects, hundreds of thousands (or more) of fragments down to the millimeter size regime were also generated during the breakups. These fragments are too small to be tracked by the SSN, but are large enough to be a safety concern for human space activities and robotic missions in low Earth orbit (LEO, the region below 2000 km altitude). Like their cataloged siblings, many of them remain in orbit today. These two breakup events dramatically changed the landscape of the orbital debris environment in LEO. The spatial density of the cataloged population in January 2013 is shown as the top blue curve. The combined FY-1C, Iridium 33, and Cosmos 2251 fragments (black curve) account for about 50 percent of the cataloged population below an altitude of 1000 km. They are also responsible for the concentrations at 770 km and 850 km, altitudes at which the collisions occurred. The effects of the FY-1C, Iridium 33, and Cosmos 2251 fragments will continue to be felt for decades to come. For example, approximately half of the generated FY-1C fragments will remain in orbit 20 years from now. In general, the Iridium 33 and Cosmos 2251 fragments will decay faster than the FY-1C fragments because of their lower altitudes. Of the Iridium 33 and Cosmos 2251 fragments, the former have much shorter orbital lifetimes than the latter, because lightweight composite materials were heavily used in the construction of the Iridium vehicle, leading to the higher area-to-mass ratios of the fragments.

  3. High pressure hydriding of sponge-Zr in steam-hydrogen mixtures

    NASA Astrophysics Data System (ADS)

    Soo Kim, Yeon; Wang, Wei-E.; Olander, D. R.; Yagnik, S. K.

    1997-07-01

    Hydriding kinetics of thin sponge-Zr layers metallurgically bonded to a Zircaloy disk has been studied by thermogravimetry in the temperature range 350-400°C in 7 MPa hydrogen-steam mixtures. Some specimens were prefilmed with a thin oxide layer prior to exposure to the reactant gas; all were coated with a thin layer of gold to avoid premature reaction at edges. Two types of hydriding were observed in prefilmed specimens, viz., a slow hydrogen absorption process that precedes an accelerated (massive) hydriding. At 7 MPa total pressure, the critical ratio of H 2/H 2O above which massive hydriding occurs at 400°C is ˜ 200. The critical H 2/H 20 ratio is shifted to ˜2.5 × 103 at 350°C. The slow hydriding process occurs only when conditions for hydriding and oxidation are approximately equally favorable. Based on maximum weight gain, the specimen is completely converted to ?-ZrH 2 by massive hydriding in ˜5 h at a hydriding rate of ˜10 -6 mol H/cm 2 s. Incubation times of 10-20 h prior to the onset of massive hydriding increases with prefilm oxide thickness in the range of 0-10 ?m. By changing to a steam-enriched gas, massive hydriding that initially started in a steam-starved condition was arrested by re-formation of a protective oxide scale.

  4. Hydride structures in Ti-aluminides subjected to high temperature and hydrogen pressure charging conditions

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1991-01-01

    The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and X-ray diffraction techniques. The alloys were exposed at 650 C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride.

  5. Preliminary design studies for an iridium rod target at the BNL-AGS

    SciTech Connect

    Ludewig, H.; Hastings, J.; Montanez, P.; Todosow, M.

    1998-12-31

    The BNL-AGS is an intense source of 24 GeV protons. It is proposed to explore the potential to use these protons as the driver for a Pulsed Spallation Neutron Source target. The proposed target design is based on an edge cooled iridium rod concept--similar to the anti-proton production target which operated reliably at CERN under similar conditions. Lead, lead fluoride, and beryllium are investigated as possible reflector materials, and ambient temperature light water and 80 K light water ice are proposed as initial moderator materials. Both moderators are decoupled by cadmium containing moderator chamber walls. The small size of the target has the advantage that the moderators can be placed close to the target (resulting in a bright source), and since a large fraction of the radioactive inventory is contained in the iridium rod, removal and disposition of this inventory should be relatively simple and inexpensive.

  6. Theoretical studies on electronic and electron blocking properties of iridium complexes with phenylpyrazolato ligands

    Microsoft Academic Search

    Hongze Gao; Rigen Mo; Houyu Zhang; Yue Wang; Zhong-Min Su

    2010-01-01

    The tris(1-phenylpyrazolato,N,C2?)iridium(III) Ir(ppz)3, (fac-Ir(ppz)3, 1; mer-Ir(ppz)3, 2) and iridium(III)bis(1-phenylpyrazolato,N,C2?) (2,2,6,6-tetramethyl-3,5-heptane-dionato-O,O) ppz2Ir(dpm) (C-cis,N-trans-ppz2Ir(dpm), 3; C-cis,N-cis-ppz2Ir(dpm), 4) have been investigated theoretically to explore their electronic structures, spectroscopic and electron blocking properties. A detailed comparison of the electronic structure characteristics of the two isomers has been addressed for pointing out differences in absorption and emission properties. The geometries and electronic structures are investigated

  7. Research of remote control for Chinese Antarctica Telescope based on iridium satellite communication

    NASA Astrophysics Data System (ADS)

    Xu, Lingzhe; Yang, Shihai

    2010-07-01

    Astronomers are ever dreaming of sites with best seeing on the Earth surface for celestial observation, and the Antarctica is one of a few such sites only left owing to the global air pollution. However, Antarctica region is largely unaccessible for human being due to lacking of fundamental living conditions, travel facilities and effective ways of communication. Worst of all, the popular internet source as a general way of communication scarcely exists there. Facing such a dilemma and as a solution remote control and data transmission for telescopes through iridium satellite communication has been put forward for the Chinese network Antarctic Schmidt Telescopes 3 (AST3), which is currently under all round research and development. This paper presents iridium satellite-based remote control application adapted to telescope control. The pioneer work in China involves hardware and software configuration utilizing techniques for reliable and secure communication, which is outlined in the paper too.

  8. Strongly improved electrochemical cycling durability by adding iridium to electrochromic nickel oxide films.

    PubMed

    Wen, Rui-Tao; Niklasson, Gunnar A; Granqvist, Claes G

    2015-05-13

    Anodically colored nickel oxide (NiO) thin films are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. However, NiO films are prone to suffering severe charge density degradation upon prolonged electrochemical cycling, which can lead to insufficient device lifetime. Therefore, a means to improve the durability of NiO-based films is an important challenge at present. Here we report that the incorporation of a modest amount of iridium into NiO films [Ir/(Ir + Ni) = 7.6 atom %] leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting electrolyte, along with significantly improved optical modulation during extended cycling. Structure characterization showed that the face-centered-cubic-type NiO structure remained after iridium addition. Moreover, the crystallinity of these films was enhanced upon electrochemical cycling. PMID:25919917

  9. Merger of visible light induced oxidation and enantioselective alkylation with a chiral iridium catalyst.

    PubMed

    Wang, Chuanyong; Zheng, Yu; Huo, Haohua; Röse, Philipp; Zhang, Lilu; Harms, Klaus; Hilt, Gerhard; Meggers, Eric

    2015-05-11

    A single chiral octahedral iridium(III) complex is used for visible light activated asymmetric photoredox catalysis. In the presence of a conventional household lamp and under an atmosphere of air, the oxidative coupling of 2-acyl-1-phenylimidazoles with N,N-diaryl-N-(trimethylsilyl)methylamines provides aminoalkylated products in 61-93?% yields with high enantiomeric excess (90-98?% ee). Notably, the iridium center simultaneously serves three distinct functions: as the exclusive source of chirality, as the catalytically active Lewis acid, and as a central part of the photoredox sensitizer. This conceptionally simple reaction Scheme may provide new avenues for the green synthesis of non-racemic chiral molecules. PMID:25832794

  10. DEFORMATION MODELING OF IRIDIUM DOP-26 ALLOY TO DETERMINE POTENTIAL FOR SECONDARY RECRYSTALLIZATION

    SciTech Connect

    Ohriner, Evan Keith [ORNL; Sabau, Adrian S [ORNL; Ulrich, George B [ORNL; George, Easo P [ORNL

    2008-01-01

    The DOP-26 iridium alloy (Ir-0.3%W-0.006%Th-0.005% Al) contains a distribution of thorium-containing intermetallic particles, typically less than 1 micrometer in size, which serve to pin grain boundaries. The alloy is thus subject to secondary recrystallization during long-term exposure at elevated temperature if prior plastic strains are within a critical range. A finite element method was used to model the deformation and resulting local plastic strains introduced by sizing operations on recrystallized iridium alloy cups. The results of the analysis show that local strains introduced by the deformation of cups are in all cases maintained below 0.025, the lower critical level for secondary recrystallization at 1600 K. The effects of die clearance and applied load on local plastic strain values were also treated.

  11. Cationic, luminescent cyclometalated iridium(iii) complexes based on substituted 2-phenylthiazole ligands.

    PubMed

    Stokes, Emily C; Langdon-Jones, Emily E; Groves, Lara M; Platts, James A; Horton, Peter N; Fallis, Ian A; Coles, Simon J; Pope, Simon J A

    2015-04-29

    Ten cationic heteroleptic iridium(iii) complexes, [Ir(emptz)2(N^N)](PF6) were prepared from a cyclometalated iridium bridged-chloride dimer involving two ethyl-4-methylphenylthiazole-5-carboxylate (emptz) ligands. One X-ray crystallographic study was undertaken where the ancillary N^N ligand was 4,7-diphenyl-1,10-phenanthroline and revealed the anticipated structure, showing a distorted octahedral coordination geometry at Ir(iii). The complexes were visibly luminescent with modestly structured emission at 540-590 nm and lifetimes (60-340 ns) consistent with phosphorescence. TD-DFT calculations suggest that strong MLCT character contributes to the visible absorption characteristics, whilst the moderately structured emission profiles indicate a (3)MLCT/(3)IL admixture of states to the phosphorescence. PMID:25501466

  12. Iridium-catalyzed H/D exchange: ligand complexes with improved efficiency and scope.

    PubMed

    Parmentier, Michael; Hartung, Thomas; Pfaltz, Andreas; Muri, Dieter

    2014-09-01

    Hydrogen isotope exchange (HIE) is one of the most attractive tools for the introduction of deuterium or tritium to an organic compound. Herein, iridium complexes with N,P-ligands, highly active catalysts for asymmetric double bond reductions, have been tested for their HIE capabilities. Electron-rich ligands, containing dicyclohexylphosphines or phosphinites, have been identified as excellent ligands for efficient deuterium incorporation. Substrates with strong directing groups, that is, pyridines, ketones, and amides, as well as weak ligating units, such as, nitro, sulfones, and sulfonamides, could be labeled efficiently. With the addition of tris(pentafluorophenyl) borane to the reaction mixture, also highly deactivating nitrile substituents were well tolerated in the reaction. Based on the excellent results obtained with the chiral ThrePhox ligand, a structurally simpler, achiral ligand was developed. The iridium complex containing this ligand, proved to be a powerful catalyst for HIE reactions. PMID:25043104

  13. High-resolution x-ray spectrometry using iridium-gold phase transition thermometers

    Microsoft Academic Search

    J. Höhne; M. Altmann; G. Angloher; P. Hettl; J. Jochum; S. Pfnür; J. Schnagl; M. L. Sarsa; S. Wänninger; F. v. Feilitzsch

    1999-01-01

    We are developing cryogenic detectors based on iridium\\/gold phase transition thermometers for various applications in astroparticle physics aiming at high energy resolution, low energy threshold and moderate count rates. A microcalorimeter with an energy resolution of 15.5 eV (FWHM) for the 55Mn K?1 X-ray line for tentative use in an analytical X-ray system (e.g. SEM, TRFA) is presented.

  14. Sputtered thin-film pH electrodes of platinum, palladium, ruthenium, and iridium oxides

    Microsoft Academic Search

    Kenneth G. Kreider; Michael J. Tarlov; James P. Cline

    1995-01-01

    Thin-film metal oxides have been investigated for use as pH electrodes. These materials may have potential for measuring pH under conditions that are not favorable for glass electrodes. Reactive sputtering of platinum, palladium, ruthenium, and iridium metal targets in argon-oxygen atmospheres is used to produce 1 ?m thick electrodes on alumina and silicon substrates. The structure of the deposits is

  15. An iridium abundance anomaly at the palynological Cretaceous-Tertiary boundary in northern New Mexico

    USGS Publications Warehouse

    Orth, C.J.; Gilmore, J.S.; Knight, J.D.; Pillmore, C.L.; Tschudy, R.H.; Fassett, J.E.

    1981-01-01

    An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct. Copyright ?? 1981 AAAS.

  16. Accretion rate of cosmic matter from iridium and osmium contents of deep-sea sediments

    Microsoft Academic Search

    John L. Barker Jr.; Edward Anders

    1968-01-01

    Iridium and osmium concentrations were measured in dated deep-sea sediments by neutron activation analysis to attempt to set limits on the influx rate of cosmic matter. Twentyone measurements on five cores from the central Pacific gave Ir and Os contents from 0·06 to 0·4 ppb, with an observed precision of ±15 percent. The Ir and Os contents were correlated with

  17. A Site-Isolated Iridium Diethylene Complex Supported on Highly Dealuminated Y Zeolite: Synthesis and Characterization

    SciTech Connect

    Uzun,A.; Bhirud, V.; Kletnieks, P.; Haw, J.; Gates, B.

    2007-01-01

    Highly dealuminated Y zeolite-supported mononuclear iridium complexes with reactive ethylene ligands were synthesized by chemisorption of Ir(C2H4)2(C5H7O2). The resultant structure and its treatment in He, CO, ethylene, and H2 were investigated with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The IR spectra show that Ir(C2H4)2(C5H7O2) reacted readily with surface OH groups of the zeolite, leading to the removal of C5H7O2 ligands and the formation of supported mononuclear iridium complexes, confirmed by the lack of Ir-Ir contributions in the EXAFS spectra. The EXAFS data show that each Ir atom was bonded to four carbon atoms at an average distance of 2.10 Angstroms, consistent with the presence of two ethylene ligands per Ir atom and in agreement with the IR spectra indicating p-bonded ethylene ligands. The EXAFS data also indicate that each Ir atom was bonded to two oxygen atoms of the zeolite at a distance of 2.15 Angstroms . The supported iridium-ethylene complex reacted with H2 to give ethane, and it also catalyzed ethylene hydrogenation at atmospheric pressure and 294 K. Treatment of the sample in CO led to the formation of Ir(CO)2 complexes bonded to the zeolite. The sharpness of the ?CO bands indicates a high degree of uniformity of these complexes on the support. The iridium-ethylene complex on the crystalline zeolite support is inferred to be one of the most nearly uniform supported metal complex catalysts. The results indicate that it is isostructural with a previously reported rhodium complex on the same zeolite; thus, the results are a start to a family of analogous, structurally well-defined supported metal complex catalysts.

  18. Polymer phosphorescent light-emitting devices doped with tris(2-phenylpyridine) iridium as a triplet emitter

    Microsoft Academic Search

    Chang-Lyoul Lee; Kyung Bok Lee; Jang-Joo Kim

    2000-01-01

    We have fabricated phosphorescent polymer light-emitting devices with tris(2-phenylpyridine) iridium [Ir(ppy)3] as a triplet emissive dopant in poly(vinylcarbazole) (PVK) host. The device with 8% doping concentration of [Ir(ppy)3] in PVK showed the external quantum efficiency of 1.9% and the peak luminance of 2,500 cd\\/m2. The emission spectrum of the device exhibited no emission from PVK, indicating that the energy transfer

  19. Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary

    Microsoft Academic Search

    P. E. Olsen; D. V. Kent; H.-D. Sues; C. Koeberl; A. Montanari; E. C. Rainforth; S. J. Fowell; M. J. Szajna; B. W. Hartline

    2002-01-01

    Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per

  20. Copper(i) complexes as alternatives to iridium(iii) complexes for highly efficient oxygen sensing.

    PubMed

    Medina-Rodríguez, Santiago; Orriach-Fernández, Francisco J; Poole, Christopher; Kumar, Prashant; de la Torre-Vega, Ángel; Fernández-Sánchez, Jorge F; Baranoff, Etienne; Fernández-Gutiérrez, Alberto

    2015-07-01

    The complex [Cu(xantphos)(dmp)][PF6] (dmp = 2,9-dimethyl-1,10-phenanthroline) in a nanostructured metal oxyde matrix shows better sensitivity to oxygen (KSV = 9.74 ± 0.87 kPa(-1) between 0 and 1 kPa pO2 and 5.59 ± 0.15 kPa(-1) between 0 and 10 kPa pO2) than cyclometallated iridium complexes in the same conditions. PMID:26086848

  1. Solvent free selective dehydrogenation of indolic and carbazolic molecules with an iridium pincer catalyst.

    PubMed

    Brayton, Daniel F; Jensen, Craig M

    2014-06-01

    A previously known iridium POCOP pincer catalyst was found to selectively dehydrogenate the heterocyclic portion of several indolic and carbazolic molecules. These molecules were found to have an "activity window" (172-178 °C) upon which only the heterocyclic ring underwent dehydrogenation. All reactions were run solvent free, yields for selected substrates were excellent, and the products were isolated by either distillation or alumina plug filtration. PMID:24763968

  2. Consumable arc-melting, extruding, and rolling process for iridium sheet

    SciTech Connect

    Heestand, R.L.; Copeland, G.L.; Martin, M.M.

    1986-06-01

    An iridium alloy has been used as cladding for the /sup 238/PuO/sub 2/ fuel in radioisotope thermoelectric generators (RTGs) for recent interplanetary spacecraft such as Voyagers 1 and 2 and will be used for the Galileo and Ulysses spacecraft. The iridium alloy sheet for the fuel cladding used on these missions was fabricated by hot and cold rolling of arc-melted and drop-cast 0.5-kg ingots. Upon completion of production for these spacecraft, an opportunity was taken to conduct process improvement studies that would increase processing batch sizes, develop a more uniform product, decrease rejections due to internal delaminations and surface defects, and reduce costs. The studies to scale up and improve the fabrication process are described. In the new process, iridium is electron beam melted, alloyed by arc melting, and then consumable arc melted to form a cylindrical ingot of approximately 7 kg for extrusion. The ingot is extruded to sheet bar and hot and cold rooled into sheet. Sheet evaluated from the first two ingots showed 100% acceptance with no defects on inspection. An improved uniformity of microstructure was obtained, and chemistry was controlled within specification limits.

  3. Production of iridium-alloy clad vent sets for the Cassini mission to Saturn

    SciTech Connect

    Helle, K.J. [Martin Marietta Energy Systems, Inc., P.O. Box 2009, MS-8208, Oak Ridge, Tennessee 37831-8208 (United States); Moore, J.P. [Martin Marietta Energy Systems, Inc., P.O. Box 2008, MS-6079, Oak Ridge, Tennessee 37831-6079 (United States)

    1995-01-20

    Martin Marietta Energy Systems, Inc., has successfully produced the iridium-alloy clad vent sets required for encapsulation of plutonia for the National Aeronautics and Space Administration Cassini mission to Saturn. Numerous improvements were made to the manufacturing process in various areas including dye-penetrant examination of cups, foil part stamping, chemical analysis, tungsten fixturing for laser welding, and enhanced inspections at high magnification. In addition, systems were initiated to ensure process control, and a detailed quality and technical surveillance program was prepared and followed to detect any incipient production problem early in the process so that corrective action could be taken immediately. The quality of the resulting iridium components has been high, and production yields have been above 90%. During the course of the production campaign for the Cassini mission, worker efficiencies lowered production costs, and further cost reductions are possible if operations are consolidated into a single area and bare-forming of the iridium alloys cups can be qualified for flight-quality clad vent sets.

  4. Rhodium and iridium salts inhibit proliferation and induce DNA damage in rat fibroblasts in vitro.

    PubMed

    Iavicoli, Ivo; Cufino, Valerio; Corbi, Maddalena; Goracci, Martina; Caredda, Emanuele; Cittadini, Achille; Bergamaschi, Antonio; Sgambato, Alessandro

    2012-09-01

    Environmental concentration of the platinum group elements is increased in the last years due to their use in automobile catalytic converters. Limited data are available on the effects of such elements at a cellular level and on their toxicity, especially for rhodium and iridium which have been more recently introduced in use. The toxic effects of rhodium and iridium salts were analyzed on a normal diploid rat fibroblast cell line in vitro. Both salts halted cell growth in a dose- and time-dependent fashion by inhibiting cell cycle progression, inducing apoptosis and modulating the expression of cell cycle regulatory proteins. In fact, they both caused an accumulation of cells in the G2/M phase of the cell cycle and affected the expression levels of pRb, cyclins D1 and E, p21(Waf1) and p27(Kip1). DNA strand breaks, as assessed by comet test, and an increase in the intracellular levels of reactive oxygen species also occurred in exposed cell cultures. These findings suggest a potential toxicity of both iridium and rhodium salts and emphasize the need for further studies to understand their effects at a cellular level to enable a better assessment of their toxic effects and to identify ways for their modulation and/or prevention. PMID:22521858

  5. Green Phosphorescence and Electroluminescence of Sulfur Pentafluoride-Functionalized Cationic Iridium(III) Complexes.

    PubMed

    Shavaleev, Nail M; Xie, Guohua; Varghese, Shinto; Cordes, David B; Slawin, Alexandra M Z; Momblona, Cristina; Ortí, Enrique; Bolink, Henk J; Samuel, Ifor D W; Zysman-Colman, Eli

    2015-06-15

    We report on four cationic iridium(III) complexes [Ir(C^N)2(dtBubpy)](PF6) that have sulfur pentafluoride-modified 1-phenylpyrazole and 2-phenylpyridine cyclometalating (C^N) ligands (dtBubpy = 4,4'-di-tert-butyl-2,2'-bipyridyl). Three of the complexes were characterized by single-crystal X-ray structure analysis. In cyclic voltammetry, the complexes undergo reversible oxidation of iridium(III) and irreversible reduction of the SF5 group. They emit bright green phosphorescence in acetonitrile solution and in thin films at room temperature, with emission maxima in the range of 482-519 nm and photoluminescence quantum yields of up to 79%. The electron-withdrawing sulfur pentafluoride group on the cyclometalating ligands increases the oxidation potential and the redox gap and blue-shifts the phosphorescence of the iridium complexes more so than the commonly employed fluoro and trifluoromethyl groups. The irreversible reduction of the SF5 group may be a problem in organic electronics; for example, the complexes do not exhibit electroluminescence in light-emitting electrochemical cells (LEECs). Nevertheless, the complexes exhibit green to yellow-green electroluminescence in doped multilayer organic light-emitting diodes (OLEDs) with emission maxima ranging from 501 nm to 520 nm and with an external quantum efficiency (EQE) of up to 1.7% in solution-processed devices. PMID:26037410

  6. Neutron activation determination of iridium, gold, platinum, and silver in geologic samples

    USGS Publications Warehouse

    Millard, H.T., Jr.

    1987-01-01

    Low-level methods for the determination of iridium and other noble metals have become increasingly important in recent years due to interest in locating abundance anomalies associated with the Cretaceous and Tertiary (K-T) boundary. Typical iridium anomalies are in the range of 1 to 100 ??g/kg (ppb). Thus methods with detection limits near 0.1 ??g/kg should be adequate to detect K-T boundary anomalies. Radiochemical neutron activation analysis methods continue to be required although instrumental neutron activation analysis techniques employing elaborate gamma-counters are under development. In the procedure developed in this study samples irradiated in the epithermal neutron facility of the U. S. Geological Survey TRIGA Reactor (Denver, Colorado) are treated with a mini-fire assay technique. The iridium, gold, and silver are collected in a 1-gram metallic lead button. Primary contaminants at this stage are arsenic and antimony. These can be removed by heating the button with a mixture of sodium perioxide and sodium hydroxide. The resulting 0.2-gram lead bead is counted in a Compton suppression spectrometer. Carrier yields are determined by reirradiation of the lead beads. This procedure has been applied to the U.S.G.S. Standard Rock PCC-1 and samples from K-T boundary sites in the Western Interior of North America. ?? 1987 Akade??miai Kiado??.

  7. Results of the treatment of 165 lid carcinomas by iridium wire implant

    SciTech Connect

    Daly, N.J.; de Lafontan, B.; Combes, P.F.

    1984-04-01

    A group of 160 adult patients with epithelial tumors of the lid and/or canthi treated by iridium 192 wire implant are presented. There were l65 epithelial tumors, most of them were basocellular type (85%). In all cases, a nonradioactive procedure was used with disposable angiocatheters before introducing active wires. Respectively, 111/114 (97.4%) of ''new'' lesions and 48/51 (94%) of previously treated tumors were definitively cured by iridium wire implant. Among the 6 local recurrences, 4 were salvaged by a second iridium implant, and the two others by extensive surgery. Local side effects were present in 30 patients (18%): impairment of the eyelid aperture 9, stenosis of lacrymal ducts 7, eversion of the lid 7, lack of substance 7. These postherapeutic complications were significantly more frequent in treating recurrent lesions (15/48, 31.2%) than in previously untreated tumors (15/112, 13.4%). No visual complication was observed even in the early patients of this series.

  8. FEASIBILITY OF RECYCLING PLUTONIUM AND MINOR ACTINIDES IN LIGHT WATER REACTORS USING HYDRIDE FUEL

    SciTech Connect

    Greenspan, Ehud; Todreas, Neil; Taiwo, Temitope

    2009-03-10

    The objective of this DOE NERI program sponsored project was to assess the feasibility of improving the plutonium (Pu) and minor actinide (MA) recycling capabilities of pressurized water reactors (PWRs) by using hydride instead of oxide fuels. There are four general parts to this assessment: 1) Identifying promising hydride fuel assembly designs for recycling Pu and MAs in PWRs 2) Performing a comprehensive systems analysis that compares the fuel cycle characteristics of Pu and MA recycling in PWRs using the promising hydride fuel assembly designs identified in Part 1 versus using oxide fuel assembly designs 3) Conducting a safety analysis to assess the likelihood of licensing hydride fuel assembly designs 4) Assessing the compatibility of hydride fuel with cladding materials and water under typical PWR operating conditions Hydride fuel was found to offer promising transmutation characteristics and is recommended for further examination as a possible preferred option for recycling plutonium in PWRs.

  9. Grain Growth Behavior, Tensile Impact Ductility, and Weldability of Cerium-Doped Iridium Alloys

    SciTech Connect

    McKamey, C.G.

    2002-05-28

    An iridium alloy doped with small amounts of cerium and thorium is being developed as a potential replacement for the iridium-based DOP-26 alloy (doped with thorium only) that is currently used by the National Aeronautics and Space Administration (NASA) for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the iridium-based alloy (designated as DOP-40) containing both cerium and thorium. Included within this report are data on grain growth of sheet material in vacuum and low-pressure oxygen environments, grain growth in vacuum of the clad vent set cup material, weldability, and the effect of grain size and test temperature on tensile properties. Where applicable, data for the DOP-26 alloy are included for comparison. Both grain size and grain-boundary cohesion affect the ductility of iridium alloys. In this study it was found that cerium and thorium, when added together, refine grain size more effectively than when thorium is added by itself (especially at high temperatures). In addition, the effect of cerium additions on grain-boundary cohesion is similar to that of thorium. Mechanical testing at both low ({approx} 10{sup -3}s{sup -1}) and high ({approx} 10{sup -3}s{sup -1}) strain rates showed that the Ce/Th-doped alloys have tensile ductilities that are as good or better than the DOP-26 alloy. The general conclusion from these studies is that cerium can be used to replace some of the radioactive thorium currently used in DOP-26 while maintaining or improving its metallurgical properties. The current DOP-26 alloy meets all requirements for cladding the radioactive fuel in the RTG heat source, but the new DOP-40 alloy could serve as a back-up alloy to be used if the costs of refining, handling, and transporting DOP-26 become prohibitively high.

  10. Hydrosilylation of alkynes by Ni(CO)3-stabilized silicon(II) hydride.

    PubMed

    Stoelzel, Miriam; Präsang, Carsten; Inoue, Shigeyoshi; Enthaler, Stephan; Driess, Matthias

    2012-01-01

    Not copy and paste: Although ?-diketiminato ligands have been employed for the stabilization of Ge(II) and Sn(II) hydrides, the corresponding Si(II) hydride is not accessible. However, coordination of silicon(II) to a {Ni(CO)(3)} fragment allowed the isolation of the first Si(II) hydride metal complex 1. This complex was used for the first silicon(II)-based and Ni(0)-mediated, stereoselective hydrosilylation of alkynes. R = phenyl, tolyl. PMID:22105836

  11. Neutral binuclear rare-earth metal complexes with four ??-bridging hydrides.

    PubMed

    Rong, Weifeng; He, Dongliang; Wang, Meiyan; Mou, Zehuai; Cheng, Jianhua; Yao, Changguang; Li, Shihui; Trifonov, Alexander A; Lyubov, Dmitrii M; Cui, Dongmei

    2015-03-25

    The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH2]2 (2-Ln; Ln = Y, Lu; NPNPN: N[Ph2PNC6H3((i)Pr)2]2) bearing ?2-bridging hydride ligands have been synthesized. In the presence of THF, 2-Y undergoes intramolecular activation of the sp(2) C-H bond to form dinuclear aryl-hydride complex 3-Y containing three ?2-bridging hydride ligands. PMID:25713818

  12. Complications from dual roles of sodium hydride as a base and as a reducing agent.

    PubMed

    Hesek, Dusan; Lee, Mijoon; Noll, Bruce C; Fisher, Jed F; Mobashery, Shahriar

    2009-03-20

    Sodium hydride is a common reagent for substrate activation in nucleophilic substitution reactions. Sodium hydride can behave both as a base and as a source of hydride. This dual ability in the presence of an electrophile such as benzyl bromide results in the formation of byproducts when dimethylformamide or acetonitrile are used as solvents for these reactions. The structural nature of these byproducts is revealed in this report. PMID:19215116

  13. Development of a Passively Cooled, Electrically Heated Hydride (PACE) Bed

    SciTech Connect

    Klein, J.E.

    2001-07-26

    A nominal 1500 STP-L Passively Cooled, Electrically heated hydride (PACE) Bed has been developed and tested. Protium absorption rates were measured at pressures of 253, 413, and 680 kPa (1900, 3100, and 5100 torr, respectively) with forced convection cooling air flow rates ranging from 50 to 150 SLPM air. Desorption rates were measured at pressures ranging from 200 to 933 kPa (1500 to 7000 torr) using dual and single 400 watt electric heaters. Methods for estimating absorption rates using a hydride material different than the test material are presented along with a method of estimating tritium absorption rates using protium absorption data. In-Bed Accountability (IBA) tests were preformed using electric heaters to simulate tritium decay and gave a full bed inventory measurement error of 0.6 percent of a full bed.

  14. Synthesis of polyacetylene with titanocene-aluminum hydride catalysts

    SciTech Connect

    Rozova, E.A.; Erofeev, A.B.; Sizov, A.I.; Bulychev, B.M. [M. V. Lomonosov Moscow State Univ., Moscow (Russian Federation)

    1994-09-01

    Heterometallic hydride titanocene-aluminum complexes Cp{sub 2}Ti({mu}-H){sub 2}AlH(X) and (Cp{sub 2}Ti){sub 2}AlH{sub 4}X are highly efficient homogeneous catalysts for acetylene polymerization. The binuclear complex of the composition Cp{sub 2}Ti({mu}-H){sub 2}AlH{sub 2} at 2.2-3.2 M concentrations in ether-toluene solutions exhibits the maximum activity in this reaction. It is believed that the mechanisms of the isomerization of olefins and the polymerization of acetylene are similar and, correspondingly, the compositions and structures of the active sites in both processes are close to each other. The polyacetylene formed with hydride catalysts (mostly the cis-isomer) after doping with iodine has an electrical conductivity of 1.5-2.0{center_dot}10{sup 4} Ohm{sup -1}cm{sup -1}.

  15. Reversible metal–hydride phase transformation in epitaxial films

    NASA Astrophysics Data System (ADS)

    Roytburd, Alexander L.; Boyerinas, Brad M.; Bruck, Hugh A.

    2015-03-01

    Metal–hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal–hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film–substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

  16. Reversible metal-hydride phase transformation in epitaxial films.

    PubMed

    Roytburd, Alexander L; Boyerinas, Brad M; Bruck, Hugh A

    2015-03-11

    Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system. PMID:25671335

  17. Detecting low concentrations of plutonium hydride with magnetization measurements

    NASA Astrophysics Data System (ADS)

    Kim, Jae Wook; Mun, E. D.; Baiardo, J. P.; Smith, A. I.; Richmond, S.; Mitchell, J.; Schwartz, D.; Zapf, V. S.; Mielke, C. H.

    2015-02-01

    We report the formation of plutonium hydride in 2 at. % Ga-stabilized ?-Pu, with 1 at. % H charging. We show that magnetization measurements are a sensitive, quantitative measure of ferromagnetic plutonium hydride against the nonmagnetic background of plutonium. It was previously shown that at low hydrogen concentrations, hydrogen forms super-abundant vacancy complexes with plutonium, resulting in a bulk lattice contraction. Here, we use magnetization, X-ray, and neutron diffraction measurements to show that in addition to forming vacancy complexes, at least 30% of the H atoms bond with Pu to precipitate PuHx on the surface of the sample with x ˜ 1.9. We observe magnetic hysteresis loops below 40 K with magnetic remanence, consistent with ferromagnetic PuH1.9.

  18. Cataractogenic effects of a boron hydride disulfide compound.

    PubMed

    Fukui, H N; Iwata, S; Epstein, D L; Merola, L O

    1977-07-01

    The disulfide form but not the sulfhydryl form of a boron hydride compound was found to be cataractogenic. Apparently this compound attaches to the sulfhydryl group of Na-K ATPase in the lens epithelium inactivating this crucial enzyme. The consequence is that a defect in the cation pump activity arises, leading to a rapid influx of Na ions and loss of K ions and marked increase in hydration. These changes are thought to lead to opacification. PMID:141427

  19. Metal-Hydride Films with Switchable Optical Properties

    Microsoft Academic Search

    R. Griessen

    1997-01-01

    We have discovered^1,2 that yttrium-, lanthanum-, and rare-earth-hydride films exhibit spectacular changes in their optical properties when the hydrogen concentration is increased from 0 to 3. For example, a 500 nm thick YH2 film is metallic and shiny, while YH_3-delta is yellowish and transparent. The transition is reversible, fast, and can simply be induced by adding or removing hydrogen from

  20. Titanium-based Laves phase hydrides with high dissociation pressure

    Microsoft Academic Search

    S. V. Mitrokhin; V. N. Verbetsky

    1997-01-01

    The results of the investigation of the hydrogen interaction with Laves phases having general composition Ti1 ? xZrxMn2 ? y ? zCryFez are presented. The hydride phases are characterized by the rather high dissociation pressure of hydrogen at ambient temperature. The experiments were staged in standard Sieverts apparatus at pressures up to 100 atm and in a special apparatus which

  1. Synthesis and properties of multicomponent hydrides with high density

    Microsoft Academic Search

    V. N. Verbetsky; S. V. Mitrokhin; E. A. Movlaev

    1999-01-01

    The results of research of interaction of hydrogen with alloys of Ti–V–M (M=Fe, Co, Ni), Ti–Ta; Zr–Ta; Ti–W; Ti–Ta–W; Zr–Sc; Hf–Sc systems are presented. The study of these materials was carried out in two directions aimed at an increase of hydride density preserving a high content of hydrogen in them and a decrease of synthesis parameters preserving high thermal stability

  2. Reaction between magnesium ammine complex compound and lithium hydride

    Microsoft Academic Search

    Masami Tsubota; Satoshi Hino; Hironobu Fujii; Chie Oomatsu; Masashi Yamana; Takayuki Ichikawa; Yoshitsugu Kojima

    2010-01-01

    The possibility of using ammonia as a hydrogen carrier is examined for the reaction between magnesium ammine complex MgCl2(NH3)6 and lithium hydride LiH. Sample was milled at low temperature of ?40 °C to avoid decomposition of MgCl2(NH3)6 during the milling. The effects of milling time, milling speed (revolutions per minute), and catalysts on hydrogen storage properties were investigated by thermogravimetry, thermal

  3. leur spcifique de l'iridium jusqu' la temprature de fusion, teln-peratllre certainement trs peu in.frieure celle de la flamme du

    E-print Network

    Paris-Sud XI, Université de

    85 leur spécifique de l'iridium jusqu'à la température de fusion, teln- peratllre certainement très peu in.férieure à celle de la flamme du chalumeau, on en conclut que l'iridium fond à 1950°. Or. 2013

  4. Iridium-catalyzed enantioselective cycloisomerization of nitrogen-bridged 1,6-enynes to 3-azabicylo[4.1.0]heptenes

    Microsoft Academic Search

    Takanori Shibata; Yuka Kobayashi; Shunsuke Maekawa; Natsuko Toshida; Kentaro Takagi

    2005-01-01

    A cationic iridium complex catalyzes a cycloisomerization of nitrogen-bridged 1,6-enynes to give 3-azabicyclo[4.1.0]heptenes in good to high yield. When an iridium-chiral diphosphine complex is used, the reaction proceeds enantiomerically to give chiral cyclopropanes fused by a six-membered ring system.

  5. Measurement and modeling of strain fields in zirconium hydrides precipitated at a stress concentration

    SciTech Connect

    Allen, Gregory B.; Kerr, Matthew; Daymond, Mark R. (Queens)

    2012-10-23

    Hydrogen adsorption into zirconium, as a result of corrosion in aqueous environments, leads to the precipitation of a secondary brittle hydride phase. These hydrides tend to first form at stress concentrations such as fretting flaws or cracks in engineering components, potentially degrading the structural integrity of the component. One mechanism for component failure is a slow crack growth mechanism known as Delayed Hydride Cracking (DHC), where hydride fracture occurs followed by crack arrest in the ductile zirconium matrix. The current work employs both an experimental and a modeling approach to better characterize the effects and behavior of hydride precipitation at such stress concentrations. Strains around stress concentrations containing hydrides were mapped using High Energy X-ray Diffraction (HEXRD). These studies highlighted important differences in the behavior of the hydride phase and the surrounding zirconium matrix, as well as the strain associated with the precipitation of the hydride. A finite element model was also developed and compared to the X-ray strain mapping results. This model provided greater insight into details that could not be obtained directly from the experimental approaches, as well as providing a framework for future modeling to predict the effects of hydride precipitation under varied conditions.

  6. Strain evolution of zirconium hydride embedded in a Zircaloy-2 matrix.

    SciTech Connect

    Kerr, M.; Daymond, M. R.; Holt, R. A.; Almer, J. D.; Queen's Univ.

    2008-01-01

    In situ synchrotron X-ray diffraction has been used to determine strain evolution in a minority phase, zirconium hydride, embedded in Zircaloy-2 (<100 wt ppm average hydrogen content). The elastic modulus of the hydride is similar to that of Zircaloy-2. Three regimes are observed: I - elastic, II - post-yield load transfer from Zircaloy-2 to hydride, and III - strain saturation, possibly due to hydride fracture. The interpretation is supported by finite element calculations and scanning electron microscopy of the fracture surface.

  7. Phase changes in the niobium-hydrogen system I: accommodation effects during hydride precipitation

    SciTech Connect

    Makenas, B.J.; Birnbaum, H.K.

    1980-07-01

    The accommodation effects which accompany hydride precipitation were studied in the Nb-H system using T.E.M. Elastic accommodation and punching of prismatic dislocation loops in the solid solution matrix were observed on precipitation. The reversibility of the plastic accommodation processes was studied. Dislocation generation and motion in the hydride were observed during reversion. These observations were related to the volume changes due to hydride formation and to the thermodynamics of the phase change. Direct evidence for the inhibition of hydride precipitation due to trapping at O and N interstitials is presented.

  8. Some new techniques in tritium gas handling as applied to metal hydride synthesis

    SciTech Connect

    Nasise, J.E.

    1988-01-01

    A state-of-the-art tritium Hydriding Synthesis System (HSS) was designed and built to replace the existing system within the Tritium Salt Facility (TSF) at the Los Alamos National Laboratory. This new hydriding system utilizes unique fast-cycling 7.9 mole uranium beds (47.5g of T at 100% loading) and novel gas circulating hydriding furnaces. Tritium system components discussed include fast-cycling uranium beds, circulating gas hydriding furnaces, valves, storage volumes, manifolds, gas transfer pumps, and graphic display and control consoles. Many of the tritium handling and processing techniques incorporated into this system are directly applicable to today's fusion fuel loops. 12 refs., 7 figs.

  9. Structure and properties of complex hydride perovskite materials.

    PubMed

    Schouwink, Pascal; Ley, Morten B; Tissot, Antoine; Hagemann, Hans; Jensen, Torben R; Smr?ok, Lubomír; ?erný, Radovan

    2014-01-01

    Perovskite materials host an incredible variety of functionalities. Although the lightest element, hydrogen, is rarely encountered in oxide perovskite lattices, it was recently observed as the hydride anion H(-), substituting for the oxide anion in BaTiO3. Here we present a series of 30 new complex hydride perovskite-type materials, based on the non-spherical tetrahydroborate anion BH4(-) and new synthesis protocols involving rare-earth elements. Photophysical, electronic and hydrogen storage properties are discussed, along with counterintuitive trends in structural behaviour. The electronic structure is investigated theoretically with density functional theory solid-state calculations. BH4-specific anion dynamics are introduced to perovskites, mediating mechanisms that freeze lattice instabilities and generate supercells of up to 16 × the unit cell volume in AB(BH4)3. In this view, homopolar hydridic di-hydrogen contacts arise as a potential tool with which to tailor crystal symmetries, thus merging concepts of molecular chemistry with ceramic-like host lattices. Furthermore, anion mixing BH4(-)?X(-) (X(-)=Cl(-), Br(-), I(-)) provides a link to the known ABX3 halides. PMID:25490884

  10. Band gap closure in yttrium hydride under high pressure

    NASA Astrophysics Data System (ADS)

    Machida, Akihiko; Nakano, Satoshi

    2005-03-01

    Trivalent rare-earth metals demonstrate spectacular change in electronic properties by hydrogenation. With increase in hydrogen concentration beyond x ˜2.7, yttrium hydride, YHx, shows metal-insulator phase transition with structural change from the fcc to hcp of yttrium metal lattice. Band gap opening due to orbital hybridization between 1s (H) and 4d (Y) has theoretically been proposed for the metal- insulator transition. Theoretical studies have also predicted that the volume reduction by applying hydrostatic pressure would lead to metallization in association with band gap closure. We have investigated structural properties of yttrium hydrides by means of x-ray diffraction and infrared absorption beyond a predicted metallization pressure of ˜18 GPa. Hydride specimen was prepared by hydrogenation reaction of yttrium powder or foil with liquid hydrogen in a diamond anvil cell at room temperature. With increase in pressure beyond ˜10 GPa, the hcp lattice of YH3 transforms gradually to a fcc structure. Infrared spectra show peak position change in the hydrogen vibrational region of 450-1500 cm-1 above ˜11 GPa, corresponding to the x-ray diffraction results. The H-Y bonding state and expected metallization are discussed on the basis of the high pressure experimental results obtained x-ray diffraction and infrared absorption.

  11. Yttrium and lanthanum hydride films with switchable optical properties

    NASA Astrophysics Data System (ADS)

    Huiberts, J. N.; Griessen, R.; Rector, J. H.; Wijngaarden, R. J.; Dekker, J. P.; de Groot, D. G.; Koeman, N. J.

    1996-03-01

    IN many substances, changes in chemical composition, pressure or temperature can induce metal-to-insulator transitions1. Although dramatic changes in optical and electrical properties accompany such transitions, their interpretation is often complicated by attendant changes in crystallographic structure2. Yttrium, lanthanum and the trivalent rare-earth elements form hydrides that also exhibit metal-insulator transitions3-5, but the extreme reactivity and fragility of these materials hinder experimental studies5,6. To overcome these difficulties, we have coated thin films of yttrium and lanthanum with a layer of palladium through which hydrogen can diffuse. Real-time transitions from metallic (YH2 or LaH2) to semiconducting (YH3 or LaH3) behaviour occur in these films during continuous absorption of hydrogen, accompanied by pronounced changes in their optical properties. Although the timescale on which this transition occurs is at present rather slow (a few seconds), there appears to be considerable scope for improvement through the choice of rare-earth element and by adopting electrochemical means for driving the transition. In view of the spectacular changes in optical properties-yttrium hydride, for example, changes from a shiny mirror to a yellow, transparent window-metal hydrides might find important technological applications.

  12. New reactions of terminal hydrides on a diiron dithiolate.

    PubMed

    Wang, Wenguang; Rauchfuss, Thomas B; Zhu, Lingyang; Zampella, Giuseppe

    2014-04-16

    Mechanisms for biological and bioinspired dihydrogen activation and production often invoke the intermediacy of diiron dithiolato dihydrides. The first example of such a Fe2(SR)2H2 species is provided by the complex [(term-H)(?-H)Fe2(pdt)(CO)(dppv)2] ([H1H](0)). Spectroscopic and computational studies indicate that [H1H](0) contains both a bridging hydride and a terminal hydride, which, notably, occupies a basal site. The synthesis begins with [(?-H)Fe2(pdt)(CO)2(dppv)2](+) ([H1(CO)](+)), which undergoes substitution to afford [(?-H)Fe2(pdt)(CO)(NCMe)(dppv)2](+) ([H1(NCMe)](+)). Upon treatment of [H1(NCMe)](+) with borohydride salts, the MeCN ligand is displaced to afford [H1H](0). DNMR (EXSY, SST) experiments on this complex show that the terminal and bridging hydride ligands interchange intramolecularly at a rate of 1 s(-1) at -40 °C. The compound reacts with D2 to afford [D1D](0), but not mixed isotopomers such as [H1D](0). The dihydride undergoes oxidation with Fc(+) under CO to give [1(CO)](+) and H2. Protonation in MeCN solution gives [H1(NCMe)](+) and H2. Carbonylation converts [H1H](0) into [1(CO)](0). PMID:24661238

  13. Electronic structure of ternary rhodium hydrides with lithium and magnesium.

    PubMed

    Becker, Jonas Nils; Bauer, Jessica; Giehr, Andreas; Chu, Pui Ieng; Kunkel, Nathalie; Springborg, Michael; Kohlmann, Holger

    2014-01-21

    Chemical bonding in and electronic structure of lithium and magnesium rhodium hydrides are studied theoretically using DFT methods. For Li3RhH4 with planar complex RhH4 structural units, Crystal Orbital Hamilton Populations reveal significant Rh?Rh interactions within infinite one-dimensional ? 1 [RhH4] stacks in addition to strong rhodium?hydrogen bonding. These metal?metal interactions are considerably weaker in the hypothetical, heavier homologue Na3RhH4. Both compounds are small-band gap semiconductors. The electronic structures of Li3RhH6 and Na3RhH6 with rhodium surrounded octahedrally by hydrogen, on the other hand, are compatible with a classical complex hydride model according to the limiting ionic formula (M+)3[RhH6]3? without any metal?metal interaction between the 18-electron hydridorhodate complexes. In MgRhH, building blocks of the composition (RhH2)4 are formed with strong rhodium?hydrogen and significant rhodium?rhodium bonding (bond lengths of 298 pm within Rh4 squares). These units are linked together to infinite two-dimensional layers ? 2 [(RhH2/2)4] via common hydrogen atoms. Li3RhH4 and MgRhH are accordingly examples for border cases of chemical bonding where the classical picture of hydridometalate complexes in complex hydrides is not sufficient to properly describe the chemical bonding situation. PMID:24372174

  14. Superconductive sodalite-like clathrate calcium hydride at high pressures

    PubMed Central

    Wang, Hui; Tse, John S.; Tanaka, Kaori; Iitaka, Toshiaki; Ma, Yanming

    2012-01-01

    Hydrogen-rich compounds hold promise as high-temperature superconductors under high pressures. Recent theoretical hydride structures on achieving high-pressure superconductivity are composed mainly of H2 fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particle-swam optimization structural search, we show that in the stoichiometry CaH6 a body-centered cubic structure with hydrogen that forms unusual “sodalite” cages containing enclathrated Ca stabilizes above pressure 150 GPa. The stability of this structure is derived from the acceptance by two H2 of electrons donated by Ca forming an “H4” unit as the building block in the construction of the three-dimensional sodalite cage. This unique structure has a partial occupation of the degenerated orbitals at the zone center. The resultant dynamic Jahn–Teller effect helps to enhance electron–phonon coupling and leads to superconductivity of CaH6. A superconducting critical temperature (Tc) of 220–235 K at 150 GPa obtained from the solution of the Eliashberg equations is the highest among all hydrides studied thus far. PMID:22492976

  15. Computational design of an Iridium based catalyst for releasing H2 from hydrogenated BN nanotubes.

    PubMed

    Roy, Lisa; Paul, Ankan

    2015-06-16

    Through carefully calibrated density functional studies we predict that Ir pincer complexes, previously known to effectuate simultaneous proton and hydride transfer from ammonia-borane under ambient conditions, are equally efficient catalysts for the concerted dehydrogenation and subsequent release of H2 from hydrogenated boron nitride nanotubes overcoming free energy of activation accessible at room temperature. PMID:26038268

  16. High Aspect-Ratio Iridium-Coated Nanopillars for Highly Reproducible Surface-Enhanced Raman Scattering (SERS).

    PubMed

    Kang, Guoguo; Matikainen, Antti; Stenberg, Petri; Färm, Elina; Li, Peng; Ritala, Mikko; Vahimaa, Pasi; Honkanen, Seppo; Tan, Xiaodi

    2015-06-01

    A variety of different gold and silver nanostructures have been proposed over the years as high sensitivity surface-enhanced Raman scattering (SERS) sensors. However, efficient use of SERS has been hindered by the difficulty of realizing SERS substrates that provide reproducible SERS response over the whole active area. Here, we show that atomic layer deposition (ALD) grown iridium can be used to produce highly reliable SERS substrates. The substrates are based on a periodic array of high aspect-ratio iridium coated nanopillars that feature efficient and symmetrically distributed hot spots within the interpillar gaps (gap width < 10 nm). We show that the enhancement with the iridium based nanostructures is of significant magnitude and it equals the enhancement of silver based reference substrates. Most notably, we demonstrate that the ordered and well-defined plasmonic nanopillars offer a measurement-to-measurement variability of 5%, which paves the way for truly quantitative SERS measurements. PMID:25961706

  17. Development of U.S. Government General Technical Requirements for UAS Flight Safety Systems Utilizing the Iridium Satellite Constellation

    NASA Technical Reports Server (NTRS)

    Murray, Jennifer; Birr, Richard

    2010-01-01

    This slide presentation reviews the development of technical requirements for Unmanned Aircraft Systems (UAS) utilization of the Iridium Satellite Constellation to provide flight safety. The Federal Aviation Authority (FAA) required an over-the-horizon communication standard to guarantee flight safety before permitting widespread UAS flights in the National Air Space (NAS). This is important to ensure reliable control of UASs during loss-link and over-the-horizon scenarios. The core requirement was to utilize a satellite system to send GPS tracking data and other telemetry from a flight vehicle down to the ground. Iridium was chosen as the system because it is one of the only true satellite systems that has world wide coverage, and the service has a highly reliable link margin. The Iridium system, the flight modems, and the test flight are described.

  18. Combined on-board hydride slurry storage and reactor system and process for hydrogen-powered vehicles and devices

    DOEpatents

    Brooks, Kriston P; Holladay, Jamelyn D; Simmons, Kevin L; Herling, Darrell R

    2014-11-18

    An on-board hydride storage system and process are described. The system includes a slurry storage system that includes a slurry reactor and a variable concentration slurry. In one preferred configuration, the storage system stores a slurry containing a hydride storage material in a carrier fluid at a first concentration of hydride solids. The slurry reactor receives the slurry containing a second concentration of the hydride storage material and releases hydrogen as a fuel to hydrogen-power devices and vehicles.

  19. Spectroscopic characterization of alumina-supported bis(allyl)iridium complexes : site-isolation, reactivity, and decomposition studies

    Microsoft Academic Search

    Ryan J. Trovitch; Neng Guo; Michael T. Janicke; Hongbo Li; Christopher L. Marshall; Jeffrey T. Miller; Alfred P. Sattelberger; Kevin D. John; R. Thomas Baker

    2010-01-01

    The covalent attachment of tris(allyl)iridium to partially dehydroxylated ?-alumina is found to proceed via surface hydroxyl group protonation of one allyl ligand to form an immobilized bis(allyl)iridium moiety, (?AlO)Ir(allyl)2, as characterized by CP-MAS 13C NMR, inductively coupled plasma-mass spectrometry, and Ir L3 edge X-ray absorption spectroscopy. Extended X-ray absorption fine-structure (EXAFS) measurements taken on unsupported Ir(allyl)3 and several associated tertiary

  20. An investigation on structure, deformation and fracture of hydrides in titanium with a large range of hydrogen contents

    Microsoft Academic Search

    C. Q. Chen; S. X. Li; H. Zheng; L. B. Wang; K. Lu

    2004-01-01

    The deformation and fracture behaviors of ? hydrides in cyclic strained titanium containing 350, 720 and 930 ppm hydrogen were investigated and compared to that of ? hydrides in 77 ppm hydrogen specimens. It was found that the ? and ? hydrides, respectively, in 77 and 350 ppm hydrogen specimens could be plastically deformed readily along with the matrix without

  1. Optimization of dimethyltin chloride determination by hydride generation gas phase molecular absorption spectrometry using a central composite design

    Microsoft Academic Search

    Jesús Sanz; Margarita Pérez; Mar??a T. Mart??nez; Mar??a Plaza

    2000-01-01

    A factorial design is applied to the optimization of the determination of dimethyltin chloride by hydride generation gas phase molecular absorption spectrometry (HG-GPMAS). A method is described for the determination of dimethyltin chloride after conversion into gaseous dimethyltin hydride by adding a sodium tetrahydroborate (III) solution. The hydride generated is collected in a liquid nitrogen cryogenic trap. This is revolatilized,

  2. Evaluation of the delayed hydride cracking mechanism for transgranular stress corrosion cracking of magnesium alloys

    Microsoft Academic Search

    N. Winzer; A. Atrens; W. Dietzel; G. Song; K. U. Kainer

    2007-01-01

    This paper evaluates the important elements of delayed hydride cracking (DHC) for transgranular stress corrosion cracking (TGSCC) of Mg alloys. A DHC model was formulated with the following components: (i) transient H diffusion towards the crack tip driven by stress and H concentration gradients; (ii) hydride precipitation when the H solvus is exceeded; and (iii) crack propagation through the extent

  3. Hydrogen storage as a hydride. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    NONE

    1996-04-01

    The bibliography contains citations concerning the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron-titanium, lanthanum-nickel, magnesium-copper, and magnesium-nickel among others. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  4. Hydrogen storage as a hydride. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    NONE

    1997-06-01

    The bibliography contains citations concerning the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron-titanium, lanthanum-nickel, magnesium-copper, and magnesium-nickel among others. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  5. Insights into the origin of the separation selectivity with silica hydride adsorbents.

    PubMed

    Kulsing, Chadin; Nolvachai, Yada; Marriott, Philip J; Boysen, Reinhard I; Matyska, Maria T; Pesek, Joseph J; Hearn, Milton T W

    2015-02-19

    In this study, the surface properties of type-B silica have been compared with an unmodified silica hydride phase, a diamond hydride phase and silica hydride phases modified with bidentate anchored octyl (BDC8), bidentate anchored octadecyl (BDC18), phenyl and cholesteryl groups. Atomic distributions of the surface elemental composition of each type of stationary phase were determined using energy-dispersive X-ray spectroscopy. For the type-B silica, unmodified silica hydride, diamond hydride as well as BDC18 and cholesteryl silica hydride phases, the increase in carbon contents correlated with more negative surface ? potential values (R(2) = 0.92). The origin of these more negative ? potentials has been evaluated with mobile phases up to 100% (v/v) methanol content, with this property attributed to either an increase in the amount of adsorbed hydroxide ions or a decrease in the amount of adsorbed protons on the surfaces modified silica hydride phases of higher carbon content. This property of chemically modified silica hydride phases is in accordance with the unique propensity for hydroxide ions to be preferentially adsorbed onto hydrophobic surfaces of low permittivity and effects due to the specific accumulated water molecules associated with the electrical interfacial double layer of the adsorbent. PMID:25656442

  6. INFLUENCE OF HYDRIDE MICROSTRUCTURE ON THROUGH-THICKNESS CRACK GROWTH IN ZIRCALOY-4 SHEET

    E-print Network

    Motta, Arthur T.

    associated with waterside corrosion on the component surface. The resulting uptake of hydrogen has long been-induced loss of ductility occurs when a surface crack initiates within a hydride rim or blister to the orientation of the hydride platelets such that KQ decreases by roughly a factor of three when a significant

  7. PREPRINT submitted to Journal of Physics B Electronic structure of the Magnesium hydride

    E-print Network

    Recanati, Catherine

    PREPRINT submitted to Journal of Physics B Electronic structure of the Magnesium hydride molecular: 31.15.AR,31.15.Ct,31.50.Be,31.50.Df #12; Electronic structure of the Magnesium hydride molecular ion 2 1. Introduction The reactivity of molecular systems in the gas phase at low temperature (as low

  8. The Mechanochemical Self-Propagating Reaction between Hexachlorobenzene and Calcium Hydride

    Microsoft Academic Search

    G. Mulas; S. Loiselle; L. Schiffini; G. Cocco

    1997-01-01

    We report on studies of the solid state reaction between hexachlorobenzene and calcium hydride carried out by high-energy ball milling. The transformation behavior depends on the intensity of the mechanical energy transferred to the reactants at the impact. At lower energy regimes, chemical conversions increase gradually as a function of the milling time and a large excess of calcium hydride

  9. Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part I—Technique Development

    Microsoft Academic Search

    Zhou Long; Yamin Luo; Chengbin Zheng; Pengchi Deng; Xiandeng Hou

    2012-01-01

    Hydride generation is the most popular and widely used chemical vapor generation technique and is interesting to analytical chemists as an effective sample introduction method, especially for elemental determination and speciation analysis by analytical atomic spectrometry. The present review provides a literature survey on the hydride generation technique coupled to analytical atomic spectrometry during the past several years, covering the

  10. Recent Advance of Hydride Generation-Analytical Atomic Spectrometry: Part I-Technique Development

    Microsoft Academic Search

    Zhou Long; Yamin Luo; Chengbin Zheng; Pengchi Deng; Xiandeng Hou

    2012-01-01

    Hydride generation is the most popular and widely used chemical vapor generation, which is always interesting to analytical chemists as an effective sample introduction method, especially for elemental determination and speciation analysis by analytical atomic spectrometry. The present review provides a literature survey on the hydride generation technique coupled to analytical atomic spectrometry during the past several years, covering the

  11. Hydrogenation of CeNi: hydride formation, structure and magnetic J.-L. Bobet b*

    E-print Network

    Paris-Sud XI, Université de

    during hydriding. A survey of the crystal structures of RExT intermetallics where RE is a rare earthHydrogenation of CeNi: hydride formation, structure and magnetic properties J.-L. Bobet b* , E ______________________________________________________________________ Abstract The hydrogenation at different temperatures and hydrogen pressures of the binary intermetallic

  12. Reduction of carbon monoxide by a tetrakis(aryloxide)diniobium complex having four bridging hydrides.

    PubMed

    Kurogi, Takashi; Ishida, Yutaka; Hatanaka, Tsubasa; Kawaguchi, Hiroyuki

    2013-06-01

    The use of a sterically demanding aryloxide ligand allows us to isolate a tetrakis(aryloxide)diniobium complex bridged by four hydride ligands. This hydride aryloxide undergoes reduction of CO via hydrogenation and deoxygenation, resulting in formation of a methylidene species. Further carbonylation gives a vinylidene complex. PMID:23235738

  13. A microcalorimetric investigation of the thermodynamics and kinetics of hydriding-dehydriding reactions

    Microsoft Academic Search

    Wenlin Zhang; M. P. Sridhar Kumar; Arnaldo Visintin; Supramaniam Srinivasan; Harry J. Ploehn

    1996-01-01

    A microcalorimetric technique was used to study the thermodynamics and kinetics of the hydriding-dehydriding reactions of some AB5-type alloys. The effects of Ce, Co and Sn substitution were analyzed. Co and Sn substitution increase the stability of the hydride state, while Ce substitution has the opposite effect. These observations are rationalized on the basis of the rule of reversed stability

  14. Complex transition metal hydrides: linear correlation of countercation electronegativity versus T-D bond lengths.

    PubMed

    Humphries, T D; Sheppard, D A; Buckley, C E

    2015-06-30

    For homoleptic 18-electron complex hydrides, an inverse linear correlation has been established between the T-deuterium bond length (T = Fe, Co, Ni) and the average electronegativity of the metal countercations. This relationship can be further employed towards aiding structural solutions and predicting physical properties of novel complex transition metal hydrides. PMID:26077621

  15. Hydride-related degradation of spent-fuel cladding under repository conditions

    SciTech Connect

    Chung, H. M.

    2000-04-03

    This report summarizes results of an analysis of hydride-related degradation of commercial spent-nuclear-fuel cladding under repository conditions. Based on applicable laboratory data on critical stress intensity obtained under isothermal conditions, occurrence of delayed hydride cracking from the inner-diameter side of cladding is concluded to be extremely unlikely. The key process for potential initiation of delayed hydride cracking at the outer-diameter side is long-term microstructural evolution near the localized regions of concentrated hydrides, i.e., nucleation, growth, and cracking of hydride blisters. Such locally concentrated hydrides are, however, limited to some high-burnup cladding only, and the potential for crack initiation and propagation at the outer-diameter side is expected to be insignificant for most spent fuels. Some degree of hydride reorientation could occur in high-burnup spent-fuel cladding. However, even if hydride reorientation occurs, accompanying stress-rupture failure in spent-fuel cladding is unlikely to occur.

  16. An anisotropic Gurson type model to represent the ductile rupture of hydrided Zircaloy4 sheets

    Microsoft Academic Search

    M. Grange; J. Besson; E. Andrieu

    2000-01-01

    The aim of this work is to model the ductile fracture of Zircaloy-4 sheets containing various amount of embrittling hydride precipitates. The proposed model is based on the Gurson–Tvergaard–Needleman model which is extended to take into account plastic anisotropy and viscoplasticity. The mechanical behavior is identified by conducting tensile tests and the damage nucleation rate (hydride cracking) is measured using

  17. Performance improvement analysis of boiling water reactors by incorporation of hydride fuel

    Microsoft Academic Search

    Wang Kan; Greenspan Ehud

    2004-01-01

    The feasibility of improving the neutronic characteristics of boiling water reactors (BWR) by using U–Zr hydride fuel is studied. Several modified BWR fuel assembly designs are considered. These include designs in which hydride fuel rods replace water rods only, replace water rods and a fraction of the oxide fuel rods, replace oxide fuel in the upper half of all the

  18. The initiation of delayed hydride cracking in zirconium-2.5 niobium

    Microsoft Academic Search

    Derong Yan

    1999-01-01

    This thesis contains two parts of work that study the initiation of the delayed hydride cracking (DHC) in zirconium alloys in different aspects. The first part is a theoretical work in which the effect of stress on the hydride precipitation solvus in zirconium, is studied from the view point of thermodynamics. The material equilibrium of a closed thermodynamic system which

  19. Measurement of dosimetric parameters for the Alpha-Omega high-dose-rate Iridium-192 source

    SciTech Connect

    Muller-Runkel, R. [Department of Radiation Oncology, Saint Margaret Mercy Healthcare Centers, Hammond, IN (United States)]. E-mail: renate.muller@ssfhs.org

    2005-09-30

    Thermoluminescent (TLD) measurements of dose-rate constant, anisotropy function, and radial dose function are reported for the Alpha-Omega high dose rate (HDR) Iridium-192 ({sup 192}Ir) source, which has been available since 1998 for use in the MicroSelectron HDR afterloader manufactured by the Nucletron Corporation. Measurement results are compared with published or available Monte Carlo calculations for both sources. They are found in good agreement, and, within experimental accuracy, no difference is seen in the dosimetric parameters of both sources.

  20. The oxidative addition of simple selenium molecules to an unsaturated iridium (I) compound

    E-print Network

    Hsieh, Mel-Lin Mary

    1970-01-01

    in the activated comply. On the other hand, the reaction of Ir(I) with oxygen 20 exihibited an increase in the 0-0 bond length ( 1. 30 A) in the addition compound (0-0 bond distance: 1. 21 A for 02', 1. 28 A for 2- 02 , 1. 49 A for 02 ). The two oxygen atoms... are equidistant from the iridium atom as shown in Pig. 3(b) with an average Ir-0 ~ 7 distance of 2. 07 A. The reason for the weak v-interaction between Ir(I) and s-acids such as oxygen can be attributed to the following: (1) they are poor acceptor ligands...

  1. The effects of iridium on the renal function of female Wistar rats.

    PubMed

    Iavicoli, Ivo; Fontana, Luca; Marinaccio, Alessandro; Alimonti, Alessandro; Pino, Anna; Bergamaschi, Antonio; Calabrese, Edward J

    2011-10-01

    Despite the widespread use of iridium (Ir) in catalytic converters for improved capacity for reducing carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO(x)) emissions, there is a lack of studies that have assessed possible toxicological hazards of exposure to Ir. The present investigation indicates that female Wistar rats exposed to Ir in the drinking water for 90 days displayed renal toxicity based on the elevated urinary retinol binding protein (RBP) and albumin. The RBP was more sensitive to albumin, showing significant increases at 0.01 mg/L. PMID:21764451

  2. Intermolecular C?H Bond Activation by a Cationic Iridium(III) Dichloride Phenanthroline Complex.

    PubMed

    Swift, Christopher A; Gronert, Scott

    2015-05-26

    It is demonstrated that a cationic iridium(III) dichloride phenanthroline complex is capable of C?H activation and H/D exchange. It can cleave benzylic and unactivated secondary C?H bonds, but exhibits unique selectivity when compared to similar systems that have been studied in the condensed phase. Gas-phase rate constants and kinetic isotope effects are reported for a variety of substrates and the analysis is supported by DFT calculations at the M06/QZVP level. PMID:25865960

  3. Iridium 192 implantation of T1 and T2 carcinomas of the mobile tongue

    Microsoft Academic Search

    J. J. Mazeron; J. M. Crook; V. Benck; G. Marinello; M. Martin; M. Raynal; E. Haddad; R. Peynegre; J. P. Le Bourgeois; W. Walop

    1990-01-01

    Between 1970 and 1986, 166 patients with T1 or T2 epidermoid carcinomas of the mobile tongue were treated by iridium 192 implantation (70 T1N0, 83 T2N0, 13 T1-2 N1-3). Five-year actuarial survival was 52% for T1N0, 44% for T2aN0, and 8% for or T1-2 N1-3. Cause specific survivals were 90%, 71%, and 46%, respectively. Local control was 87% for both

  4. Relationship between mass extinction and iridium across the Cretaceous-Paleogene boundary in New Jersey

    USGS Publications Warehouse

    Miller, K.G.; Sherrell, R.M.; Browning, J.V.; Field, M.P.; Gallagher, W.; Olsson, R.K.; Sugarman, P.J.; Tuorto, S.; Wahyudi, H.

    2010-01-01

    We directly link iridium (Ir) anomalies in New Jersey to the mass extinction of marine plankton marking the Cretaceous-Paleogene (K-Pg) boundary. We confirm previous reports of an Ir anomaly 20 cm below the extinction of Cretaceous macrofauna (the "Pinna" bed) with new results from a muddy sand section from Tighe Park, Freehold, New Jersey (United States), but we also show that Ir anomalies correlate with marine mass extinctions at three other clay-rich New Jersey sections. Thus, we attribute the anomaly at Freehold to the downward movement of Ir and reaffirm the link between impact and mass extinction. ?? 2010 Geological Society of America.

  5. Evolution of odd A transitional iridium nuclei at the strong deformation limit levels of $\\^{185}$Ir

    E-print Network

    Sébille-Schück, C; Genevey-Rivier, J; Höglund, A; Huck, A; Knipper, A; Richard-Serre, Claude; Walter, G

    1976-01-01

    A level scheme is proposed for neutron deficient /sup 185/Ir obtained by the decay of /sup 185/Pt produced with the ISOLDE on-line separator (CERN). This level scheme is compared to those of heavier mass iridium nuclei where the negative parity levels had been interpreted in the asymmetric-rotor-plus-particle model. In /sup 185/Ir similar systems of levels appear with a stronger prolate deformation of the nucleus. They seem correctly described by coupling an odd-particle (or a hole) to a symmetric rotor.

  6. Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan

    USGS Publications Warehouse

    Nichols, D.J.; Jarzen, D.M.; Orth, C.J.; Oliver, P.Q.

    1986-01-01

    The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

  7. The Collision of Iridium 33 and Cosmos 2251: The Shape of Things to Come

    NASA Technical Reports Server (NTRS)

    Nicholas, Johnson

    2009-01-01

    The collision of Iridium 33 and Cosmos 2251 was the most severe accidental fragmentation on record. More than 1800 debris approx. 10 cm and larger were produced. If solar activity returns to normal, half of the tracked debris will reenter within five years. Less than 60 cataloged debris had reentered by 1 October 2009. Some debris from both satellites will remain in orbit through the end of the century. The collision rate of one every five years will increase without future removal of large derelict spacecraft and launch vehicle orbital stages.

  8. Theoretical study of absorption and emission properties of green and yellow emitting iridium(III) complexes.

    PubMed

    Kadari, Amel; Moncomble, Aurélien; Ciofini, Ilaria; Brahimi, Méziane; Adamo, Carlo

    2011-10-27

    Iridium(III) complexes are among the most used phosphorescent materials for the development of organic light emitting diodes (OLEDs). In this work, the photophysical properties of a family of complexes based on phenyldiazine ligands were studied. Their ground state geometric and electronic structures as well as their absorption and emission spectra were investigated by the means of density functional theory (DFT) and time-dependent DFT (TD-DFT). An extremely good agreement between the computed and experimental values is obtained, thus suggesting that the computational protocol here applied could be used for the in silico screening and design of new Ir-based emitting complexes. PMID:21888348

  9. Light-emitting materials from cyclometalated heteroleptic iridium(III) complexes—A physicochemical study

    NASA Astrophysics Data System (ADS)

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Venkatesh Perumal, Marimuthu

    2012-02-01

    Phosphorescent studies of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes with picolinic acid as the ancillary ligand were made. The observed experimental data reveal that these complexes possess dominantly 3MLCT and 3?-?* excited states and the solvent shift of these complexes is interpreted by Reichardt-Dimroth and Marcus solvent functions. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition ( kr) increases with increasing ?em.

  10. New iridium complexes with cyclometalated 2-arylimidazole ligands as highly efficient saturated green emitters

    NASA Astrophysics Data System (ADS)

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Saravanan, Kanagarathinam; Venkatesh Perumal, Marimuthu

    2012-06-01

    Phosphorescence studies of a series of heteroleptic cyclometalated iridium(III) complexes have been carried out. From the photoluminescent properties, it was found that these complexes possess dominantly 3MLCT and 3?-?* excited states. The solvent shifts are interpreted in terms of Reichardt-Dimroth solvent ET parameters and Marcus theory. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies reveal that kr increases with increasing ?em and linear correlation between ln(knr) and energy gap. The effect of Eg and ?Qe on knr is discussed in detail.

  11. Synthesis and physico-chemical studies of cyclometalated heteroleptic iridium(III) complexes

    NASA Astrophysics Data System (ADS)

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Jayamoorthy, Karunamoorthy

    Phosphorescent studies of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes with picolinic acid as the ancillary ligand were made. The observed experimental data reveals that these complexes possess dominantly 3MLCT and 3?-?* excited states and the solvent shift of these complexes are interpreted by Reichardt-Dimroth and Marcus solvent functions. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition (kr), increases with increasing ?emi.

  12. Light-emitting materials from cyclometalated heteroleptic iridium(III) complexes--A physicochemical study.

    PubMed

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Venkatesh Perumal, Marimuthu

    2012-02-15

    Phosphorescent studies of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes with picolinic acid as the ancillary ligand were made. The observed experimental data reveal that these complexes possess dominantly (3)MLCT and (3)?-?* excited states and the solvent shift of these complexes is interpreted by Reichardt-Dimroth and Marcus solvent functions. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition (k(r)) increases with increasing ?(em). PMID:22153595

  13. Synthesis and physico-chemical studies of cyclometalated heteroleptic iridium(III) complexes.

    PubMed

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Jayamoorthy, Karunamoorthy

    2012-07-01

    Phosphorescent studies of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes with picolinic acid as the ancillary ligand were made. The observed experimental data reveals that these complexes possess dominantly (3)MLCT and (3)?-?* excited states and the solvent shift of these complexes are interpreted by Reichardt-Dimroth and Marcus solvent functions. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition (k(r)), increases with increasing ?(emi). PMID:22484258

  14. Carcinoma of the female urethra: combined iridium Ir 192 interstitial and external beam radiotherapy

    SciTech Connect

    Klein, F.A.; Ali, M.M.; Kersh, R.

    1987-09-01

    Three female patients (mean age 55) with carcinoma of the urethra were treated with combined external beam irradiation (4,000 to 5,000 rads) and interstitial irradiation with iridium Ir 192 (2,700 to 3,000 rads) applied with a modified Syed-Neblett template. Two patients are alive with no evidence of disease at 27 and 37 months. One patient died of a second primary tumor at 30 months, without histologic evidence of the original urethral neoplasm. No patient had significant complications of therapy. This treatment regimen is effective for selected women with urethral carcinoma.

  15. Getting metal-hydrides to do what you want them to

    SciTech Connect

    Gruen, D.M.

    1981-01-01

    With the discovery of AB/sub 5/ compounds, intermetallic hydrides with unusual properties began to be developed (H dissociation pressures of one to several atmospheres, extremely rapid and reversible adsorption/desorption very large amounts of H adsorbed). This paper reviews the factors that must be controlled in order to modify these hydrides to make them useful. The system LaNi/sub 5/ + H/sub 2/ is used as example. Use of AB/sub 5/ hydrides to construct a chemical heat pumps is discussed. Results of a systematic study substituting Al for Ni are reported; the HYCSOS pump is described briefly. Use of hydrides as hydrogen getters (substituted ZrV/sub 2/) is also discussed. Finally, possible developments in intermetallic hydride research in the 1980's and the hydrogen economy are discussed. 10 figures. (DLC)

  16. Study on Hydride Reorientation in Zry-2 Fuel Claddings during Interim Dry Storage

    SciTech Connect

    Sakamoto, K. [Global Nuclear Fuel - Japan Co., Ltd. (GNF-J), 2163, Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki 311-1313 (Japan); Matsuoka, H. [Global Nuclear Fuel - Japan Co., Ltd. (GNF-J), 3-1, Uchikawa 2-chome, Yokosuka-shi, Kanagawa 239-0836 (Japan); Takagi, A. [Tokyo Electric Power Co., Ltd. (TEPCO), 1-3 Uchisaiwai-cho, 1-chome, Chiyoda-ku, Tokyo 100-8560 (Japan); Kashibe, S. [Nippon Nuclear Fuel Development Co., Ltd. (NFD), 2163, Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki 311-1313 (Japan)

    2007-07-01

    The hydride reorientation during the interim dry storage was examined by hydride reorientation test using unirradiated recrystallized Zry-2 fuel claddings (Zr-lined). In the case of high hydrogen concentration (above 200 ppm), no measurable hydride reorientation was observed under the condition examined. On the other hand, for low hydrogen concentration (30 - 80 ppm), a significant hydride reorientation was observed above 618 K. The effects of thermal cycling and cooling rate were also examined. The mechanical property of the hydride-reoriented specimens was evaluated at room temperature by the ring-tensile test, which showed no degradation of hoop strength and ductility when temperature and hoop stress were not greater than 573 K and 70 MPa, even if the effects of cooling rate and thermal cycling were taken into account. (authors)

  17. A mechanical-force-driven physical vapour deposition approach to fabricating complex hydride nanostructures.

    PubMed

    Pang, Yuepeng; Liu, Yongfeng; Gao, Mingxia; Ouyang, Liuzhang; Liu, Jiangwen; Wang, Hui; Zhu, Min; Pan, Hongge

    2014-01-01

    Nanoscale hydrides desorb and absorb hydrogen at faster rates and lower temperatures than bulk hydrides because of their high surface areas, abundant grain boundaries and short diffusion distances. No current methods exist for the direct fabrication of nanoscale complex hydrides (for example, alanates, borohydrides) with unique morphologies because of their extremely high reducibility, relatively low thermodynamic stability and complicated elemental composition. Here, we demonstrate a mechanical-force-driven physical vapour deposition procedure for preparing nanoscale complex hydrides without scaffolds or supports. Magnesium alanate nanorods measuring 20-40?nm in diameter and lithium borohydride nanobelts measuring 10-40?nm in width are successfully synthesised on the basis of the one-dimensional structure of the corresponding organic coordination polymers. The dehydrogenation kinetics of the magnesium alanate nanorods are improved, and the nanorod morphology persists through the dehydrogenation-hydrogenation process. Our findings may facilitate the fabrication of such hydrides with improved hydrogen storage properties for practical applications. PMID:24663074

  18. Hydride-phase formation and its influence on fatigue crack propagationbehavior in a Zircaloy-4 alloy

    SciTech Connect

    Garlea, Elena [University of Tennessee, Knoxville (UTK); Choo, H. [University of Tennessee, Knoxville (UTK); Wang, G Y [University of Tennessee, Knoxville (UTK); Liaw, Peter K [University of Tennessee, Knoxville (UTK); Clausen, B [Los Alamos National Laboratory (LANL); Brown, D. W. [Los Alamos National Laboratory (LANL); Park, Jae-Sung [University of Tennessee, Knoxville (UTK); Rack, P. D. [University of Tennessee, Knoxville (UTK); Kenik, Edward A [ORNL

    2010-01-01

    The hydride-phase formation and its influence on the fatigue behavior of a Zircaloy-4 alloy charged with hydrogen gas are investigated. First, the microstructure and fatigue crack propagation rate of the alloy in the as-received condition are studied. Second, the formation and homogeneous distribution of delta zirconium hydride ( -ZrH2) in the bulk, and its effect on the fatigue crack propagation rate are presented. The results show that in the presence of hydrides the zirconium alloy exhibits reduced toughness and enhanced crack growth rates. Finally, the influence of a pre-existing fatigue crack in the specimen and the subsequent hydride formation were investigated. The residual lattice strain profile around the fatigue crack tip was measured using neutron diffraction. The combined effects of residual strains and hydride precipitation on the fatigue behavior are discussed.

  19. Strategies for the improvement of the hydrogen storage properties of metal hydride materials.

    PubMed

    Wu, Hui

    2008-10-24

    Metal hydrides are an important family of materials that can potentially be used for safe, efficient and reversible on-board hydrogen storage. Light-weight metal hydrides in particular have attracted intense interest due to their high hydrogen density. However, most of these hydrides have rather slow absorption kinetics, relatively high thermal stability, and/or problems with the reversibility of hydrogen absorption/desorption cycling. This paper discusses a number of different approaches for the improvement of the hydrogen storage properties of these materials, with emphasis on recent research on tuning the ionic mobility in mixed hydrides. This concept opens a promising pathway to accelerate hydrogenation kinetics, reduce the activation energy for hydrogen release, and minimize deleterious possible by-products often associated with complex hydride systems. PMID:18821548

  20. Materials for Hydrogen Storage: From Complex Hydrides to Functionalized Nanostructures

    NASA Astrophysics Data System (ADS)

    Das, G. P.

    2011-07-01

    The world wide effort for a transition to renewable and clean (i.e. carbon-free) form of energy has resulted in an upsurge of interest in harnessing and utilizing Hydrogen. Apart from being the most abundant element in the universe, hydrogen offers many advantages over other fuels: it is non-toxic, clean to use, and packs more energy per mass than any other fuel. Hydrogen energy production, storage and distribution constitute a multi-disciplinary area of research. Coming to the material issues for solid state storage of hydrogen, the most desirable criteria are high storage capacity, satisfactory kinetics, and optimal thermodynamics. Complex hydrides involving light metals, such as Alanates, Imides, Borates, Amidoboranes etc. show impressive gravimetric efficiencies, although the hydrogen desorption temperatures turn out to be rather high. Apart from complex hydrides, there are other kinds of novel materials that have been investigated, e.g. carbon based materials activated with nano-catalysts, clathrate hydrates, metal-organic complexes, and more recently nanostructured cages viz. fullerenes and nanotubes decorated with simple or transition metals that serve to attract hydrogen in molecular form. In this talk, after giving a broad overview on hydrogen economy, I shall focus on first-principles design of materials for hydrogen storage, from complex hydrides to various kinds of functinalized nanostructures, and discuss the recent results obtained in our laboratory [1-6]. Some outstanding issues and challenges, like how to circumvent the problem of metal clustering on surface, or how to bring down the hydrogen desorption temperature etc. will be discussed.

  1. Mathematical modeling of the nickel/metal hydride battery system

    SciTech Connect

    Paxton, B K [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

    1995-09-01

    A group of compounds referred to as metal hydrides, when used as electrode materials, is a less toxic alternative to the cadmium hydroxide electrode found in nickel/cadmium secondary battery systems. For this and other reasons, the nickel/metal hydride battery system is becoming a popular rechargeable battery for electric vehicle and consumer electronics applications. A model of this battery system is presented. Specifically the metal hydride material, LaNi{sub 5}H{sub 6}, is chosen for investigation due to the wealth of information available in the literature on this compound. The model results are compared to experiments found in the literature. Fundamental analyses as well as engineering optimizations are performed from the results of the battery model. In order to examine diffusion limitations in the nickel oxide electrode, a ``pseudo 2-D model`` is developed. This model allows for the theoretical examination of the effects of a diffusion coefficient that is a function of the state of charge of the active material. It is found using present data from the literature that diffusion in the solid phase is usually not an important limitation in the nickel oxide electrode. This finding is contrary to the conclusions reached by other authors. Although diffusion in the nickel oxide active material is treated rigorously with the pseudo 2-D model, a general methodology is presented for determining the best constant diffusion coefficient to use in a standard one-dimensional battery model. The diffusion coefficients determined by this method are shown to be able to partially capture the behavior that results from a diffusion coefficient that varies with the state of charge of the active material.

  2. Magnesium hydrides and the dearomatisation of pyridine and quinoline derivatives.

    PubMed

    Hill, Michael S; Kociok-Köhn, Gabriele; MacDougall, Dugald J; Mahon, Mary F; Weetman, Catherine

    2011-12-14

    Reactions of the ?-diketiminato n-butyl magnesium complex, [HC{(Me)CN(2,6-(i)Pr(2)C(6)H(3))}(2)Mg(n)Bu], with a range of substituted pyridines and fused-ring quinolines in the presence of PhSiH(3) has been found to result in dearomatisation of the N-heterocyclic compounds. This reaction is proposed to occur through the formation of an unobserved N-heterocycle-coordinated magnesium hydride and subsequent hydride transfer via the C2-position of the heterocycle prior to hydride transfer to the C4-position and formation of thermodynamically-favoured magnesium 1,4-dihydropyridides. This reaction is kinetically suppressed for 2,6-dimethylpyridine while the kinetic product, the 1,2-dihydropyridide derivative, was isolated through reaction with 4-methylpyridine (4-methylpyridine), in which case the formation of the 1,4-dihyropyridide is prevented by the presence of the 4-methyl substituent. X-ray structures of the products of these reactions with 4-methylpyridine, 3,5-dimethylpyridine and iso-quinoline comprise a pseudo-tetrahedral magnesium centre while the regiochemistry of the particular dearomatisation reaction is determined by the substitution pattern of the N-heterocycle under observation. The compounds are all air-sensitive and exposure of the magnesium derivatives of dearomatised pyridine and 4-dimethylaminopyridine (DMAP) to air resulted in ligand rearomatisation and the formation of dimeric ?(2)-?(2)-?(2)-peroxomagnesium compounds which have also been subject to analysis by single crystal X-ray diffraction analysis. An unsuccessful extension of this chemistry to N-heterocycle hydrosilylation is suggested to be a consequence of the low basicity of the silane reagent in comparison to the pyridine substrates which effectively impedes any further interaction with the magnesium centres. PMID:21986998

  3. Optical properties of metal-hydride switchable films

    NASA Astrophysics Data System (ADS)

    Griessen, Ronald

    2001-03-01

    In 1996 we discovered that yttrium-, lanthanum-, and rare-earth-hydride (REHx) films [1] protected by a thin palladium layer, exhibit spectacular changes in their optical properties when the hydrogen concentration x is increased from 2 to 3. For example, a 500 nm thick YH2 film is metallic and shiny while YH3 is yellowish and transparent. The transition is reversible, fast [2, 3], and can simply be induced by adding or removing hydrogen from the gas phase, an electrolyte or from an H containing liquid. The optical switching that occurs near the metal-insulator transition of these hydrides is remarkably robust as it is not affected by structural or compositional disorder. It occurs in polycrystalline and epitaxial films, in alloys with cubic or hexagonal crystal structures,and deuterides [4] switch as well as hydrides. At small length scales epitaxial YHx films exhibit surprising structural properties which open the way to pixel-by-pixel optical switching [5]. Colour-neutral switchable mirrors based on RE-Mg alloys [6] can be used in all-solid-state switchable devices. Newest results for Rare-Earth free switchable mirrors will be presented. [1] J. N. Huiberts, R. Griessen, J. H. Rector, R. J. Wijngaarden, J. P. Dekker, D. G. de Groot and N. J. Koeman, Nature 380 (1996) 231; [2] S. J. van der Molen, J. W. J. Kerssemakers, J. H. Rector, N. J. Koeman, B. Dam, R. Griessen, J. Appl. Phys. 86 (1999) 6107; [3] F. J. A. den Broeder, S. J. van der Molen, et al., Nature 394 (1998)656; [4] A. T. M. van Gogh, E. S. Kooij, R. Griessen, Phys. Rev. Lett. 83 (1999) 4614; [5] J. W. J. Kerssemakers, S. J. van der Molen and R. Griessen, Nature 406 (2000) 489; [6] P. van der Sluis, M. Ouwerkerk and P. A. Duine, Appl. Phys. Lett. 70 (1997) 3356.

  4. Structure of hydrides based on V-Cr alloys

    NASA Astrophysics Data System (ADS)

    Lushnikov, S. A.; Verbetskii, V. N.; Somenkov, V. A.; Glazkov, V. P.

    2014-11-01

    The structure of deuterides based on V0.9Cr0.1 and V0.5Cr0.5 alloys has been investigated by neutron diffraction at room and low (77 K) temperatures. It is found that V0.9Cr0.1D2.0 deuteride has a CaF2 ( Fm3 m) crystal structure, which corresponds to vanadium dihydride. V0.5Cr0.5D0.7 deuteride has a NiAs ( P6/3 mmc) structure type, similar to chromium hydride.

  5. Electrophilicity of quinones and its relationship with hydride affinity

    NASA Astrophysics Data System (ADS)

    Campodónico, Paola R.; Aizman, Arie; Contreras, Renato

    2009-03-01

    In this Letter we show that the electrophilicity index assesses well the hydride affinity (HA) order of quinones established for a limited number of cases experimentally observed. Further comparisons with predicted HA values for a larger data base suggest that both the electrophilicity index and HA are tightly related quantities. Furthermore, electrophilic activation/deactivation patterns induced by electron-withdrawing and electron-donating groups may be consistently accounted for by the model. These results open the possibility of predicting HA for quinones not evaluated experimentally up to date.

  6. Bipolar Nickel-Metal Hydride Battery Development Project

    NASA Technical Reports Server (NTRS)

    Cole, John H.

    1999-01-01

    This paper reviews the development of the Electro Energy, Inc.'s bipolar nickel metal hydride battery. The advantages of the design are that each cell is individually sealed, and that there are no external cell terminals, no electrode current collectors, it is compatible with plastic bonded electrodes, adaptable to heat transfer fins, scalable to large area, capacity and high voltage. The design will allow for automated flexible manufacturing, improved energy and power density and lower cost. The development and testing of the battery's component are described. Graphic presentation of the results of many of the tests are included.

  7. Stress analysis of hydride bed vessels used for tritium storage

    SciTech Connect

    McKillip, S.T.; Bannister, C.E.; Clark, E.A.

    1991-12-31

    A prototype hydride storage bed, using LaNi{sub 4.25}Al{sub 0.75} as the storage material, was fitted with strain gages to measure strains occurring in the stainless steel bed vessel caused by expansion of the storage powder upon uptake of hydrogen. The strain remained low in the bed as hydrogen was added, up to a bed loading of about 0.5 hydrogen to metal atom ratio (H/M). The strain then increased with increasing hydrogen loading ({approximately} 0.8 H/M). Different locations exhibited greatly different levels of maximum strain. In no case was the design stress of the vessel exceeded.

  8. Stress analysis of hydride bed vessels used for tritium storage

    SciTech Connect

    McKillip, S.T.; Bannister, C.E.; Clark, E.A.

    1991-01-01

    A prototype hydride storage bed, using LaNi{sub 4.25}Al{sub 0.75} as the storage material, was fitted with strain gages to measure strains occurring in the stainless steel bed vessel caused by expansion of the storage powder upon uptake of hydrogen. The strain remained low in the bed as hydrogen was added, up to a bed loading of about 0.5 hydrogen to metal atom ratio (H/M). The strain then increased with increasing hydrogen loading ({approximately} 0.8 H/M). Different locations exhibited greatly different levels of maximum strain. In no case was the design stress of the vessel exceeded.

  9. Electrochemical process and production of novel complex hydrides

    DOEpatents

    Zidan, Ragaiy

    2013-06-25

    A process of using an electrochemical cell to generate aluminum hydride (AlH.sub.3) is provided. The electrolytic cell uses a polar solvent to solubilize NaAlH.sub.4. The resulting electrochemical process results in the formation of AlH.sub.3. The AlH.sub.3 can be recovered and used as a source of hydrogen for the automotive industry. The resulting spent aluminum can be regenerated into NaAlH.sub.4 as part of a closed loop process of AlH.sub.3 generation.

  10. Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

  11. Chemical Hydrides for Hydrogen Storage in Fuel Cell Applications

    SciTech Connect

    Devarakonda, Maruthi N.; Brooks, Kriston P.; Ronnebro, Ewa; Rassat, Scot D.; Holladay, Jamelyn D.

    2012-04-16

    Due to its high hydrogen storage capacity (up to 19.6% by weight for the release of 2.5 molar equivalents of hydrogen gas) and its stability under typical ambient conditions, ammonia borane (AB) is a promising material for chemical hydrogen storage for fuel cell applications in transportation sector. Several systems models for chemical hydride materials such as solid AB, liquid AB and alane were developed and evaluated at PNNL to determine an optimal configuration that would meet the 2010 and future DOE targets for hydrogen storage. This paper presents an overview of those systems models and discusses the simulation results for various transient drive cycle scenarios.

  12. Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications

    NASA Astrophysics Data System (ADS)

    Thanawala, Sachin

    Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

  13. Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications

    SciTech Connect

    Huxford, T.J.; Ohriner, E.K.

    1992-12-31

    Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

  14. Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications

    SciTech Connect

    Huxford, T.J.; Ohriner, E.K.

    1992-01-01

    Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

  15. In vitro comparison of sputtered iridium oxide and platinum-coated neural implantable microelectrode arrays.

    PubMed

    Negi, S; Bhandari, R; Rieth, L; Solzbacher, F

    2010-02-01

    Neural interfaces connect signal processing electronics to the nervous system via implanted microelectrode arrays such as the Utah electrode array (UEA). The active sites of the UEA are coated with thin films of either platinum (Pt) or iridium oxide (IrOx). Pt and IrOx have attracted attention as a stimulating or recording material due to their ability to transfer between ionic and electronic current and to resist corrosion. The physical, mechanical, chemical, electrical and optical properties of thin films depend on the method and deposition parameters used to deposit the films. In this work, surface morphology, impedance and charge capacity of Pt and sputtered iridium oxide film (SIROF) were investigated and compared with each other. UEAs with similar electrode area and shape were employed in this study. DC sputtering was used to deposit Pt films and pulsed-dc reactive sputtering was used to deposit SIROF. The electrodes coated with SIROF and Pt were characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and potential transient measurements to measure charge injection capacity (CIC). SIROF and Pt selectively deposited on the electrode tip had dendrite and granular microstructure, respectively. The CIC of unbiased SIROF and Pt was 2 and 0.3 mC cm(-2), respectively. The average impedance at 1 kHz, of SIROF and Pt electrodes, was 6 kOmega and 125 kOmega, respectively. Low impedance and high CIC make SIROF promising stimulation/recording material for neural prosthetic applications. PMID:20124668

  16. Measurement of K-shell fluorescent yield in iridium: testing internal-conversion theory

    NASA Astrophysics Data System (ADS)

    Montague, J. R.; Nica, N.; Iacob, V. E.; Hardy, J. C.

    2004-10-01

    Internal conversion coefficients (ICC) play an essential role in nuclear decay schemes. Even so, calculated ICCs agree with experiment only to within a few percent and, for transitions with high multipolarity and energies close to the electron binding energies, they depend strongly on whether the final state is taken to include the atomic vacancy created by the conversion process. Recently, we measured the ratio of K X-rays to ? -rays for the 80.2-keV M4 transition in ^193mIr, determined the product ? _K? K and extracted ? K using the value ? _K=0.958(4) taken from a global fit to a set of elements not including iridium. The result strongly supported the calculation that includes the vacancy. To solidify this result, we now report a new experiment to determine directly the ? K for iridium. We selected the 129.4-keV M1+E2 transition in ^191Ir for which the ? K calculation is nearly independent of the vacancy treatment. We again used the X-to-? decay-rate ratio but this time divided the result by the calculated ? K to obtain ? _K. Our preliminary result is ? _K=0.948(8), in good agreement with the value taken from the global fit.

  17. Phase diagram and electrical behavior of silicon-rich iridium silicide compounds

    NASA Technical Reports Server (NTRS)

    Allevato, C. E.; Vining, Cronin B.

    1992-01-01

    The iridium-silicon phase diagram on the silicon-rich side was investigated by means of X-ray powder diffraction, density, differential thermal analysis, metalography, microprobe analysis, and electrical resistivity. Attempts were made to prepare eight previously reported silicon-rich iridium silicide compounds by arc melting and Bridgman-like growth. However, microprobe analysis identified only four distinct compositions: IrSi, Ir3Si4, Ir3Si5 and IrSi sub about 3. The existence of Ir4Si5 could not be confirmed in this study, even though the crystal structure has been previously reported. Differential thermal analysis (DTA) in conjunction with X-ray powder diffraction confirm polymorphism in IrSi sub about 3, determined to have orthorhombic and monoclinic unit cells in the high and low temperature forms. A eutectic composition alloy of 83 +/- 1 atomic percent silicon was observed between IrSi sub about 3 and silicon. Ir3Si4 exhibits distinct metallic behavior while Ir3Si5 is semiconducting. Both and IrSi and IrSi sub about 3 exhibit nearly temperature independent electrical resistivities on the order of 5-10 x 10 exp -6 ohms-m.

  18. High-Performance Computer Modeling of the Cosmos-Iridium Collision

    SciTech Connect

    Olivier, S; Cook, K; Fasenfest, B; Jefferson, D; Jiang, M; Leek, J; Levatin, J; Nikolaev, S; Pertica, A; Phillion, D; Springer, K; De Vries, W

    2009-08-28

    This paper describes the application of a new, integrated modeling and simulation framework, encompassing the space situational awareness (SSA) enterprise, to the recent Cosmos-Iridium collision. This framework is based on a flexible, scalable architecture to enable efficient simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel, high-performance computer systems available, for example, at Lawrence Livermore National Laboratory. We will describe the application of this framework to the recent collision of the Cosmos and Iridium satellites, including (1) detailed hydrodynamic modeling of the satellite collision and resulting debris generation, (2) orbital propagation of the simulated debris and analysis of the increased risk to other satellites (3) calculation of the radar and optical signatures of the simulated debris and modeling of debris detection with space surveillance radar and optical systems (4) determination of simulated debris orbits from modeled space surveillance observations and analysis of the resulting orbital accuracy, (5) comparison of these modeling and simulation results with Space Surveillance Network observations. We will also discuss the use of this integrated modeling and simulation framework to analyze the risks and consequences of future satellite collisions and to assess strategies for mitigating or avoiding future incidents, including the addition of new sensor systems, used in conjunction with the Space Surveillance Network, for improving space situational awareness.

  19. para-C-H Borylation of Benzene Derivatives by a Bulky Iridium Catalyst.

    PubMed

    Saito, Yutaro; Segawa, Yasutomo; Itami, Kenichiro

    2015-04-22

    A highly para-selective aromatic C-H borylation has been accomplished. By a new iridium catalyst bearing a bulky diphosphine ligand, Xyl-MeO-BIPHEP, the C-H borylation of monosubstituted benzenes can be affected with para-selectivity up to 91%. This catalytic system is quite different from the usual iridium catalysts that cannot distinguish meta- and para-C-H bonds of monosubstituted benzene derivatives, resulting in the preferred formation of meta-products. The para-selectivity increases with increasing bulkiness of the substituent on the arene, indicating that the regioselectivity of the present reaction is primarily controlled by steric repulsion between substrate and catalyst. Caramiphen, an anticholinergic drug used in the treatment of Parkinson's disease, was converted into five derivatives via our para-selective borylation. The present [Ir(cod)OH]2/Xyl-MeO-BIPHEP catalyst represents a unique, sterically controlled, para-selective, aromatic C-H borylation system that should find use in streamlined, predictable chemical synthesis and in the rapid discovery and optimization of pharmaceuticals and materials. PMID:25860511

  20. Iridium- and Osmium-decorated Reduced Graphenes as Promising Catalysts for Hydrogen Evolution.

    PubMed

    Lim, Chee Shan; Sofer, Zden?k; Toh, Rou Jun; Eng, Alex Yong Sheng; Luxa, Jan; Pumera, Martin

    2015-06-22

    Renewable energy sources are highly sought after as a result of numerous worldwide problems concerning the environment and the shortage of energy. Currently, the focus in the field is on the development of catalysts that are able to provide water splitting catalysis and energy storage for the hydrogen evolution reaction (HER). While platinum is an excellent material for HER catalysis, it is costly and rare. In this work, we investigated the electrocatalytic abilities of various graphene-metal hybrids to replace platinum for the HER. The graphene materials were doped with 4f metals, namely, iridium, osmium, platinum and rhenium, as well as 3d metals, namely, cobalt, iron and manganese. We discovered that a few hybrids, in particular iridium- and osmium-doped graphenes, have the potential to become competent electrocatalysts owing to their low costs and-more importantly-to their promising electrochemical performances towards the HER. One of the more noteworthy observations of this work is the superiority of these two hybrids over MoS2 , a well-known electrocatalyst for the HER. PMID:25908556

  1. Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction

    SciTech Connect

    Karan, Hiroko I.; Sasaki, Kotaro; Kuttiyiel, Kurian; Farberow, Carrie A.; Mavrikakis, Manos; Adzic, Radoslav R.

    2012-05-04

    A new type of electrocatalyst with a core?shell structure that consists of a platinum monolayer shell placed on an iridium? rhenium nanoparticle core or platinum and palladium bilayer shell deposited on that core has been prepared and tested for electrocatalytic activity for the oxygen reduction reaction. Carbon-supported iridium? rhenium alloy nanoparticles with several different molar ratios of Ir to Re were prepared by reducing metal chlorides dispersed on Vulcan carbon with hydrogen gas at 400 °C for 1 h. These catalysts showed specific electrocatalytic activity for oxygen reduction reaction comparable to that of platinum. The activities of PtML/PdML/Ir2Re1, PtML/Pd2layers/Ir2Re1, and PtML/Pd2layers/Ir7Re3 catalysts were, in fact, better than that of conventional platinum electrocatalysts, and their mass activities exceeded the 2015 DOE target. Our density functional theory calculations revealed that the molar ratio of Ir to Re affects the binding strength of adsorbed OH and, thereby, the O2 reduction activity of the catalysts. The maximum specific activity was found for an intermediate OH binding energy with the corresponding catalyst on the top of the volcano plot. The monolayer concept facilitates the use of much less platinum than in other approaches. The results with the PtML/PdML/Ir2Re electrocatalyst indicate that it is a promising alternative to conventional Pt electrocatalysts in low-temperature fuel cells.

  2. Dynamic Structural Changes in a Molecular Zeolite-Supported Iridium Catalyst for Ethene Hydrogenation

    SciTech Connect

    Uzun, Alper; Gates, Bruce C.; (UCD)

    2009-11-16

    The structure of a catalyst often changes as a result of changes in the reactive environment during operation. Examples include changes in bulk phases, extended surface structures, and nanoparticle morphologies; now we report real-time characterization of changes in the structure of a working supported catalyst at the molecular level. Time-resolved extended X-ray absorption fine structure (EXAFS) data demonstrate the reversible interconversion of mononuclear iridium complexes and tetrairidium clusters inside zeolite Y cages, with the structure controlled by the C{sub 2}H{sub 4}/H{sub 2} ratio during ethene hydrogenation at 353 K. The data demonstrate break-up of tetrairidium clusters into mononuclear complexes indicated by a decrease in the Ir-Ir coordination number in ethene-rich feed. When the feed composition was switched to first equimolar and then to a H{sub 2}-rich (C{sub 2}H{sub 4}/H{sub 2} = 0.3) feed, the EXAFS spectra show the reformation of tetrairidium clusters as the Ir-Ir coordination number increased again. When the feed composition was cycled from ethene-rich to H{sub 2}-rich, the predominant species in the catalyst cycled accordingly. Evidence confirming the structural change is provided by IR spectra of iridium carbonyls formed by probing of the catalyst with CO. The data are the first showing how to tune the structure of a solid catalyst at the molecular scale by choice of the reactant composition.

  3. Emissive iridium(III) diimine complexes formed by double cyclometalation of coordinated triphenylphosphite.

    PubMed

    Chang, Yao-Yuan; Hung, Jui-Yi; Chi, Yun; Chyn, Jong-Pyng; Chung, Min-Wen; Lin, Chia-Li; Chou, Pi-Tai; Lee, Gene-Hsiang; Chang, Chih-Hao; Lin, Wei-Chieh

    2011-06-01

    We report on the synthesis of a new series of iridium(III) complexes functionalized with various diimine chromophores, together with a facially coordinated dicyclometalated phosphite chelate and a monodentate anionic ancillary. This conceptual design presents a novel strategy in obtaining a new class of iridium(III) diimine complexes without employment of traditional nitrogen-containing polyaromatic cyclometalates. Additionally, we discuss the basic charactersistics of the ground and lower-lying excited states involved, as documented by crystal structural, photophysical studies, and density functional theory calculations. Fabrication of the green-emitting organic light-emitting diodes with one such dopant, [Ir(dbbpy)(tpit)NCS] (2b), where dbbpy and tpit represent di-tert-butyl-2,2'-bipyridine and dicyclometalated triphenylphosphite, respectively, was successfully made, attaining a peak external quantum efficiency (?(ext)), a luminance efficiency (?(l)), and a power efficiency (?(p)) of 14.1%, 46.6 cd A(-1), and 39.9 lm W(-1), respectively. PMID:21542620

  4. Picosecond laser micromachining of nitinol and platinum-iridium alloy for coronary stent applications

    NASA Astrophysics Data System (ADS)

    Muhammad, N.; Whitehead, D.; Boor, A.; Oppenlander, W.; Liu, Z.; Li, L.

    2012-03-01

    The demand for micromachining of coronary stents by means of industrial lasers rises quickly for treating coronary artery diseases, which cause more than one million deaths each year. The most widely used types of laser for stent manufacturing are Nd:YAG laser systems with a wavelength of 1064 nm with pulse lengths of 10-3-10-2 seconds. Considerable post-processing is required to remove heat-affected zones (HAZ), and to improve surface finishes and geometry. Using a third harmonic laser radiation of picosecond laser (6×10-12 s pulse duration) in UV range, the capability of the picosecond laser micromachining of nitinol and platinum-iridium alloy for coronary stent applications are presented. In this study dross-free cut of nitinol and platinum-iridium alloy tubes are demonstrated and topography analysis of the cut surface is carried out. The HAZ characteristics have been investigated by means of microscopic examinations and measurement of micro-hardness distribution near the cut zones.

  5. Synthesis gas transformations with heterogeneous iridium and homogeneous rhodium metal complexes

    SciTech Connect

    Getty, C.S.

    1988-01-01

    The emphasis of this work has been on the development of homogeneous and heterogeneous catalytic systems capable of the indirect transformation of H{sub 2} and CO into chemicals under mild reaction conditions. Supported iridium carbonyl and aluminum chloride were investigated in an attempt to heterogenize an analogous homogeneous catalyst. The presence of aluminum chloride was found to lead to cluster interactions resulting in a system capable of selective reduction of carbon monoxide under mild reaction conditions. When a gaseous mixture of H{sub 2}, CO, and HCl was passed over the supported cluster at 125 C, methyl chloride, methane, carbon dioxide and water were observed as major products. Unlike the homogeneous analog, only trace C{sub 2} products were detected. Infrared spectroscopy was used to investigate the preparation of the deposited clusters as well as the iridium species formed on the support during reaction. The second study involved the investigation of a rhodium carboxylate triphenylphosphine complex which was found to be an active, homogeneous hydroformylation catalyst. The system selectively produced more of the linear aldehyde than the branched. The product selectivity was found to depend upon the amount of phosphine present. Spectroscopic studies supported that a bis(triphenylphosphine)rhodium(I) trifluoroacetate carbonyl species was the active catalyst. Comparative studies with other rhodium carboxylate complexes and hydroformylation catalysts showed that the perfluorocarboxylate complexes exhibited greater activity.

  6. Radiation therapy for carcinoma of the pinna using iridium 192 wires: a series of 70 patients

    SciTech Connect

    Mazeron, J.J.; Ghalie, R.; Zeller, J.; Marinello, G.; Marin, L.; Raynal, M.; Bourgeois, J.P.; Pierquin, B.

    1986-10-01

    From January 1970 to November 1982, 70 patients with carcinoma of the pinna were treated by interstitial irradiation. An afterloading technique with Iridium 192 wires was used. One patient recurred and had a total pinnectomy followed by 60 Gy external radiation. This patient was alive without evidence of disease at 134 months. Three patients who had tumors greater than 4 cm in size at presentation developed late necrosis which required subsequent total pinnectomy. Cosmetic results were assessed in 55 patients and were good with few late sequelae (in 78% of cases (36/46) when the tumor measured less than 4 cm, but only in 1/9 when the tumor measured more than 4 cm). We advocate interstitial Iridium 192 irradiation for treatment of pinna tumors smaller than 4 cm. None of 39 patients with squamous cell carcinoma had biopsy proven cervical lymph node metastasis at the time of diagnosis. Four patients with squamous cell carcinoma (4/39: 10%) later developed a regional nodal metastasis after treatment of the pinna. All four relapsed in the parotid region and were managed by partial parotidectomy and neck dissection followed by external irradiation. One of these four patients died from uncontrolled cervical node disease. In our opinion, when regular follow-up is dependable, it is reasonable to save treatment of the cervical nodes for those patients who relapse with involved metastatic cervical nodes.

  7. Possible world-wide middle miocene iridium anomaly and its relationship to periodicity of impacts and extinctions

    Microsoft Academic Search

    F. Asaro; W. Alvarez; H. V. Michel; L. W. Alvarez; Mark H. Anders; A. Montanari; James P. Kennett

    1988-01-01

    In a study of one million years of Middle Miocene sediment deposition in ODP Hole 689B in the Weddell Sea near Antarctica, a single iridium (Ir) anomaly of 44 (+ or - 10) x 10 to the 12th gram Ir per gram rock (ppt) was observed in core 6H, section 3, 50 to 60 cm, after background contributions associated with

  8. Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes

    PubMed Central

    Stanley, Levi M.

    2010-01-01

    Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and purines have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431

  9. Green electroluminescence from an ionic iridium complex Jason D. Slinker, Cheong Y. Koh, and George G. Malliarasa

    E-print Network

    Bernhard, Stefan

    Green electroluminescence from an ionic iridium complex Jason D. Slinker, Cheong Y. Koh, and George. As a result, electroluminescence was observed at 531 nm CIE coordinates: 0.3230 and 0.5886 , the lowest of Physics. DOI: 10.1063/1.1919387 A recent concept in solid-state electroluminescent de- vices involves

  10. A study of the electrochemical behavior in tungsten and caustic solutions and platinum\\/iridium in chloride solutions, informal report

    Microsoft Academic Search

    C. M. Vitus; H. S. Isaacs; V. Schroeder

    1994-01-01

    Platinum\\/iridium and tungsten wires were electronically etched in chloride and caustic solution, respectively, to produce tips with high aspect ratio. A direct relationship between the meniscus and the aspect ratio of etched tips was established. Scanning electron micrographs indicated that higher aspect ratios were obtained by changing the geometry of the meniscus during the etch either by an increase in

  11. Facile synthesis of Nafion-stabilized iridium nanoparticles and their direct use for fuel cells and water electrolyzers.

    PubMed

    Zhang, Yining; Zhang, Huamin; Zhang, Yu; Ma, Yuanwei; Zhong, Hexiang; Ma, Haipeng

    2009-11-21

    Using a quite small but suitable amount of Nafion as stabilizer, iridium colloids with well controlled particle size were synthesized and directly used for fuel cells or water electrolyzers without further removal or addition of Nafion, meanwhile, a strategy for fabrication of supported catalyst with high utilization was also proposed. PMID:19865659

  12. Site-isolated Iridium Complexes on MgO Powder: Individual Ir Atoms Imaged by Scanning Transmission Electron Microscopy

    SciTech Connect

    Uzun, A.; Ortalan, V; D. Browning, N; C. Gates , B

    2009-01-01

    Iridium complexes were synthesized on MgO powder by adsorption of Ir(C{sub 2}H{sub 4}){sub 2}(acac) [acac = acetonylacetonate]; images determined by aberration-corrected scanning transmission electron microscopy show individual Ir atoms, demonstrating that the supported complexes were site-isolated.

  13. Prognostic factors of local outcome for T1, T2 carcinomas of oral tongue treated by iridium 192 implantation

    Microsoft Academic Search

    J. J. Mazeron; J. M. Crook; G. Marinello; W. Walop; B. Pierquin

    1990-01-01

    The results of Iridium 192 implantation for 121 node negative T1 or T2 squamous carcinomas of mobile tongue were reviewed to look for predictors of local control and necrosis. Age, sex, total dose, dose rate, linear activity, and intersource spacing were examined. Minimum follow-up was 2 years but no patient with local recurrence or necrosis was excluded. There were 57

  14. Application of AirCell Cellular AMPS Network and Iridium Satellite System Dual Mode Service to Air Traffic Management

    NASA Technical Reports Server (NTRS)

    Shamma, Mohammed A.

    2004-01-01

    The AirCell/Iridium dual mode service is evaluated for potential applications to Air Traffic Management (ATM) communication needs. The AirCell system which is largely based on the Advanced Mobile Phone System (AMPS) technology, and the Iridium FDMA/TDMA system largely based on the Global System for Mobile Communications(GSM) technology, can both provide communication relief for existing or future aeronautical communication links. Both have a potential to serve as experimental platforms for future technologies via a cost effective approach. The two systems are well established in the entire CONUS and globally hence making it feasible to utilize in all regions, for all altitudes, and all classes of aircraft. Both systems have been certified for air usage. The paper summarizes the specifications of the AirCell/Iridium system, as well as the ATM current and future links, and application specifications. the paper highlights the scenarios, applications, and conditions under which the AirCell/Iridium technology can be suited for ATM Communication.

  15. Determination of iridium in industrial concentrates by controlled-potential coulometry with a glassy-carbon electrode

    Microsoft Academic Search

    T. G. Strilchenko; O. L. Kabanova; F. I. Danilova

    1987-01-01

    The authors present a coulometric method for determining iridium without separating nonferrous and noble metals using a glassy-carbon (GC) crucible instead of the expensive platinum electrode. The crucible also serves as the electrochemical cell for the coulometric determination and as a vessel in which an aliquot weight of the analyzed solution is taken. The KP-3 concentrate contains several metals that

  16. Comparison of pressurized sulfur hydride with conventional superconductors

    NASA Astrophysics Data System (ADS)

    Nicol, E. J.; Carbotte, J. P.

    2015-06-01

    A recent report that sulfur hydride under pressure is an electron-phonon superconductor with a Tc of 190 K has been met with much excitement although it is yet to be confirmed. Based on several electron-phonon spectral density functions already available from density functional theory, we find that the electron-phonon spectrum is near optimum for Tc with a particularly large value of its characteristic phonon energy ?ln which is due to the small hydrogen mass. We find that the thermodynamic universal BCS ratios are near those for Pb and Nb3Sn . We suggest that optical measurements could be a useful tool to establish the existence and nature of the superconductivity in this system. Conventional superconductors are in the impurity-dominated dirty limit. By contrast sulfur hydride will be in the clean limit because of its large energy gap scale. The ac optical conductivity will display distinct and separate signatures of the superconducting gap in the low-energy impurity-dominated range of the optical spectrum and additional phonon structures at higher energies where the clean limit applies.

  17. ACCEPTABILITY ENVELOPE FOR METAL HYDRIDE-BASED HYDROGEN STORAGE SYSTEMS

    SciTech Connect

    Hardy, B.; Corgnale, C.; Tamburello, D.; Garrison, S.; Anton, D.

    2011-07-18

    The design and evaluation of media based hydrogen storage systems requires the use of detailed numerical models and experimental studies, with significant amount of time and monetary investment. Thus a scoping tool, referred to as the Acceptability Envelope, was developed to screen preliminary candidate media and storage vessel designs, identifying the range of chemical, physical and geometrical parameters for the coupled media and storage vessel system that allow it to meet performance targets. The model which underpins the analysis allows simplifying the storage system, thus resulting in one input-one output scheme, by grouping of selected quantities. Two cases have been analyzed and results are presented here. In the first application the DOE technical targets (Year 2010, Year 2015 and Ultimate) are used to determine the range of parameters required for the metal hydride media and storage vessel. In the second case the most promising metal hydrides available are compared, highlighting the potential of storage systems, utilizing them, to achieve 40% of the 2010 DOE technical target. Results show that systems based on Li-Mg media have the best potential to attain these performance targets.

  18. Kinetic deuterium isotope effects on ligand migrations in metal hydrides

    SciTech Connect

    Bracker-Novak, J.; Hajela, S.; Lord, M.; Zhang, Minsheng; Rosenberg, E. (California State Univ., Northridge (USA)); Gobetto, R.; Milone, L.; Osella, D. (Universita di Torino (Italy))

    1990-05-01

    Variable-temperature (VT) {sup 1}H and {sup 13}C NMR studies of the complexes ({mu}-X){sub 2}Os{sub 3}(CO){sub 9}({mu}{sub 3}-{eta}{sup 2}-(CH{sub 3}CH{sub 2}){sub 2}C{sub 2}) (X = H or D) reveal that alkyne migration over the face of the cluster is directly linked to hydride migrations on the metal core as evidenced by a temperature-independent isotope effect (k{sub HH}/k{sub DD} = 1.7). In a related study of the VT {sup 13}C NMR of ({mu}-X){sub 2}M{sub 3}(CO){sub 9}({mu}{sub 3}-S) (X = H or D; M = Ru, Os) the observation of a k{sub HH}/k{sub DD} = 1.6 for both the osmium and ruthenium complexes demonstrates that the first stage of carbonyl averaging is brought about by hydride migration and not axial-radial exchange of carbonyl groups, a process that occurs only at higher temperatures. The mechanistic implications of these results are discussed in the context of the reactivity of metal clusters and the dynamic properties of the metal-hydrogen bond.

  19. Hydride formation in Ce(La)–Ni–Si ternary compounds

    Microsoft Academic Search

    S. A Lushnikov; S. N Klyamkin; A. V Morozkin; V. N Verbetsky

    1999-01-01

    Hydrogen interaction with R2Ni0.8Si1.2, R2NiSi, R2Ni1.2Si0.8 and R6Ni2Si3 (R=La, Ce) compounds were studied. The new hydride phases, namely, La2Ni0.8Si1.2H3.75, La2NiSiH3.9, La2Ni1.2Si0.8H4.4, Ce2Ni0.8Si1.2H3.7, Ce2NiSiH4.4, Ce2Ni1.2Si0.8H4.9, La6Ni2Si3H12 and Ce6Ni2Si3H10.9 have been synthesised and characterised by X-ray diffraction and thermodesorption methods. All hydrides retained the structure type of the starting compounds with pronounced anisotropic distortion of crystal lattice: the increase of the «a»

  20. Method of generating hydrogen-storing hydride complexes

    DOEpatents

    Srinivasan, Sesha S; Niemann, Michael U; Goswami, D. Yogi; Stefanakos, Elias K

    2013-05-14

    A ternary hydrogen storage system having a constant stoichiometric molar ratio of LiNH.sub.2:MgH.sub.2:LiBH.sub.4 of 2:1:1. It was found that the incorporation of MgH.sub.2 particles of approximately 10 nm to 20 nm exhibit a lower initial hydrogen release temperature of 150.degree. C. Furthermore, it is observed that the particle size of LiBNH quaternary hydride has a significant effect on the hydrogen sorption concentration with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160.degree. C. and the other around 300.degree. C., with the main hydrogen release temperature reduced from 310.degree. C. to 270.degree. C., while hydrogen is first reversibly released at temperatures as low as 150.degree. C. with a total hydrogen capacity of 6 wt. % to 8 wt. %. Detailed thermal, capacity, structural and microstructural properties have been demonstrated and correlated with the activation energies of these materials.

  1. Physics of Hydrogen Storage in Metal-Hydrides

    NASA Astrophysics Data System (ADS)

    Abdelfattah-Zidan, Ragaiy

    Physical aspects of the hydrogenation-dehydrogenation mechanisms of metal-metal hydride systems were examined. Experimental investigation was conducted for magnesium hydride as a case study. Theoretical analysis and computational study were carried out. The kinetics of hydrogenation-dehydrogenation of traditionally prepared Mg-MgH_2 and chemically synthesized Mg-MgH_2 were experimentally investigated. A detailed investigation was carried out to determine the reasons for the improved performance of a chemically synthesized Mg-MgH _2 previously reported by Bogdanovic and co-workers. A scanning electron microscope was used to examine the surface morphology of the samples. The surface of chemically prepared samples appeared to be covered with micro-spheroidal beads ranging in radius between 0.5 ?m and 0.05 ?m formed in a fractal-like configuration. Theoretical analysis indicated that the unusual surface structure of the chemically prepared samples could be responsible for the rapid uptake and release of hydrogen. The uptake and release enhancement is believed to be partially due to the substantial increase in the surface area and partially due fast diffusion into the smaller particles. The effect of the addition of nickel to the surface was also investigated. Theoretical analysis was carried out. Models for the process at the surface as well as in the bulk were developed. Diffusion equation was examined taking into account the diffusion coefficient being function of concentration. A non-linear differential equation resulted for this case. The differential equation was numerically solved.

  2. A deformation and thermodynamic model for hydride precipitation kinetics in spent fuel cladding

    SciTech Connect

    Stout, R.B.

    1989-10-01

    Hydrogen is contained in the Zircaloy cladding of spent fuel rods from nuclear reactors. All the spent fuel rods placed in a nuclear waste repository will have a temperature history that decreases toward ambient; and as a result, most all of the hydrogen in the Zircaloy will eventually precipitate as zirconium hydride platelets. A model for the density of hydride platelets is a necessary sub-part for predicting Zircaloy cladding failure rate in a nuclear waste repository. A model is developed to describe statistically the hydride platelet density, and the density function includes the orientation as a physical attribute. The model applies concepts from statistical mechanics to derive probable deformation and thermodynamic functionals for cladding material response that depend explicitly on the hydride platelet density function. From this model, hydride precipitation kinetics depend on a thermodynamic potential for hydride density change and on the inner product of a stress tensor and a tensor measure for the incremental volume change due to hydride platelets. The development of a failure response model for Zircaloy cladding exposed to the expected conditions in a nuclear waste repository is supported by the US DOE Yucca Mountain Project. 19 refs., 3 figs.

  3. Magnetic properties of the intermetallic compounds RNi (R=Gd, Tb, Dy, Sm) and their hydrides

    Microsoft Academic Search

    Yu. L. Yaropolov; V. N. Verbetsky; A. S. Andreenko; K. O. Berdyshev; S. A. Nikitin

    2010-01-01

    Hydrogen interaction with RNi intermetallic compounds and the influence of hydrogen on magnetic properties of these compounds\\u000a were investigated. Ternary hydrides GdNiH3.2, TbNiH3.4, DyNiH3.4 and SmNiH3.7 were prepared by hydrogenation of the initial alloys at room temperature and hydrogen pressure up to 0.1 MPa. Hydrides possess\\u000a orthorhombic CrB-type structure (S.G. Cmcm). The formation of hydrides results in substantial expansion of

  4. Nd2K2IrO7 and Sm2K2IrO7: Iridium(VI) Oxides Prepared under Ambient Pressure

    SciTech Connect

    Mugavero, III, S.; Smith, M; Yoon, W; zur Loye, H

    2009-01-01

    The most-oxidized iridium oxides known to date are prepared in a hydroxide flux under normal pressure. They contain iridium centers exclusively in the +VI oxidation state and are characterized crystallographically. The picture shows the structure of the Ln2K2IrO7 (Ln=Nd, Sm) and its structural components: IrO6 octahedra (black), KO10 polyhedra (beige), LnO10 polyhedra (blue).

  5. Photoelectron spectra and molecular orbital calculations of dicarbonyl- and dinitrosyl-bridged cobalt, rhodium and iridium cyclopentadienyl dimers and of disulfido- and diselenido-nonacarbonyltriosmium

    E-print Network

    Griewe, Greg Lewis

    1987-01-01

    PHOTOELECTRON SPECTRA AND MOLECULAR ORBITAL CALCULATIONS OF DICARBONYL- AND DINITROSYL-BRIDGED COBALT, RHODIUM AND IRIDIUM CYCLOPENTADIENYL DIMERS AND OF DISULFIDO- AND DISELENIDO-NONACARBONYLTRIOSMIUM. A Thesis by GREG LEWIS GRIEWE Submitted...-BRIDGED COBALT, RHODIUM AND IRIDIUM CYCLOPENTADIENYL DIMERS AND OF DISULFIDO- AND DISELENIDO-NONACARBONYLTRIOSMIUM. A Thesis by GREG LEWIS GRIEWE Approved as to style and content by: Michael B. Hall (Chairman) M rcetta arensbo rg (Member) James R. Wild...

  6. Crystal structure of di-?-chlorido-bis-[di-chlorido-bis-(methanol-?O)iridium(III)] dihydrate: a surprisingly simple chlorido-iridium(III) dinuclear complex with methanol ligands.

    PubMed

    Merola, Joseph S; Slebodnick, Carla; Houser, Christopher

    2015-05-01

    The reaction between IrCl3·xH2O in methanol led to the formation of small amounts of the title compound, [Ir2Cl6(CH3OH)4]·2H2O, which consists of two IrCl4O2 octa-hedra sharing an edge via chloride bridges. The mol-ecule lies across an inversion center. Each octa-hedron can be envisioned as being comprised of four chloride ligands in the equatorial plane with methanol ligands in the axial positions. A lattice water mol-ecule is strongly hydrogen-bonded to the coordinating methanol ligands and weak inter-actions with coordinating chloride ligands lead to the formation of a three-dimensional network. This is a surprising structure given that, while many reactions of iridium chloride hydrate are carried out in alcoholic solvents, especially methanol and ethanol, this is the first structure of a chloridoiridium compound with only methanol ligands. PMID:25995872

  7. Short-Lived Proton Entanglement in Yttrium Hydrides

    NASA Astrophysics Data System (ADS)

    Karlsson, E. B.; Abdul-Redah, T.; Udovic, T. J.; Hjörvarsson, B.; Chatzidimitriou-Dreismann, C. A.

    2002-10-01

    Previous experiments on NbH0.8 and PdH0.6 have shown large anomalies in the cross sections for protons, when studied by neutron Compton scattering. Here, these investigations are extended to the metallic hydrides YH2, YH3, YD2, YD3, and Y(HxD1-x)3. Considerably reduced cross sections for hydrogen are observed both in YH2 and YH3, but only minor ones for YD2 and YD3. The scattering time depends on the neutron scattering angle, which allows a time-differential analysis where the time window lies around one femtosecond. The anomalies persist longer in YH2 and YH3 than in NbH0.8 and PdHo.6 The reduced cross sections are interpreted as a result of quantum entanglement between protons, surviving for a few fs in the solids.

  8. Optical transmission spectroscopy of switchable yttrium hydride films

    NASA Astrophysics Data System (ADS)

    Kremers, M.; Koeman, N. J.; Griessen, R.; Notten, P. H. L.; Tolboom, R.; Kelly, P. J.; Duine, P. A.

    1998-02-01

    The optical transmission of the recently discovered switchable yttrium hydride films is determined spectroscopically as a function of hydrogen content. This is done during electrochemical loading of Pd-capped Y film electrodes, thereby continuously changing the hydrogen concentration. The effect of the Pd cap layer on the film transmission is determined from measurements on a series of films with varying Pd layer thickness. The results are in good agreement with transmission measurements of in situ gas phase loaded, uncapped Y films. Both data sets can be consistently described with simple optical decay lengths such as 277.8 nm for YH3-? and 15.1 nm for Pd at ??=1.96 eV. The hydrogen concentration dependence of the optical transmission is discussed and compared with previous optical measurements on bulk samples and band-structure calculations.

  9. Short-lived proton entanglement in yttrium hydrides

    NASA Astrophysics Data System (ADS)

    Karlsson, E. B.; Abdul-Redah, T.; Udovic, T. J.; Hjörvarsson, B.; Chatzidimitriou-Dreismann, C. A.

    Earlier experiments on NbH0.8 and PdH0.6 have shown large anomalies in the cross sections for protons, when studied by neutron Compton scattering. Here, these investigations are extended to the metallic hydrides YH2, YH3, YD2, YD3, and Y(HxD1-x)3. Strongly reduced cross sections for hydrogen are observed both in YH2 and YH3, but only minor ones for YD2 and YD3. The scattering time depends on the neutron-scattering angle, which allows a time-differential analysis where the time window lies at around one femtosecond. The anomalies persist longer in YH2 and YH3 than in NbH0.8 and PdH0.6. The reduced cross sections are interpreted as a result of quantum entanglement between protons, surviving for a few femtoseconds in the solids.

  10. UV inverse photoemission from cerium and its hydrides

    NASA Astrophysics Data System (ADS)

    Osterwalder, J.; Schlapbach, L.

    1984-11-01

    Isochromate spectra of polycrystalline Ce, CeH 2.1 and CeH 2.9 were measured at a photon energy of 9.7 eV. The intensity at E F is 4 to 5 times lower on CeH 2.1 than it is on the metal, and it vanishes on CeH 2.9. This is in accordance with XPS, UPS and conductivity data. In both hydrides broad features ( ˜2 eV FWHM) appear, centered between 4 and 5 eV. From cross section arguments and from comparison with a CeRu 2 spectrum taken at the same photon energy, we conclude that we do not see any 4f contribution in our spectra. A signal at 7 eV on the CeH 2.9 spectrum is assigned to the 2? +u shape resonance of the H 2- ion, formed by desorbed H 2 molecules.

  11. Comparison of delayed hydride cracking behavior of two zirconium alloys

    NASA Astrophysics Data System (ADS)

    Ponzoni, L. M. E.; Mieza, J. I.; De Las Heras, E.; Domizzi, G.

    2013-08-01

    Delayed hydride cracking (DHC) is an important failure mechanism that may occur in Zr alloys during service in water-cooled reactors. Two conditions must be attained to initiate DHC from a crack: the stress intensity factor must be higher than a threshold value called KIH and, hydrogen concentration must exceed a critical value. Currently the pressure tubes for CANDU reactor are fabricated from Zr-2.5Nb. In this paper the critical hydrogen concentration for DHC and the crack velocity of a developmental pressure tube, Excel, was evaluated and compared with that of Zr-2.5Nb. The DHC velocity values measured in Excel were higher than usually reported in Zr-2.5Nb. Due to the higher hydrogen solubility limits in Excel, its critical hydrogen concentration for DHC initiation is 10-50 wppm over that of Zr-2.5Nb in the range of 150-300 °C.

  12. Modelling zirconium hydrides using the special quasirandom structure approach.

    PubMed

    Wang, H; Chroneos, A; Jiang, C; Schwingenschlögl, U

    2013-05-28

    The study of the structure and properties of zirconium hydrides is important for understanding the embrittlement of zirconium alloys used as cladding in light water nuclear reactors. Simulation of the defect processes is complicated due to the random distribution of the hydrogen atoms. We propose the use of the special quasirandom structure approach as a computationally efficient way to describe this random distribution. We have generated six special quasirandom structure cells based on face centered cubic and face centered tetragonal unit cells to describe ZrH(2-x) (x = 0.25-0.5). Using density functional theory calculations we investigate the mechanical properties, stability, and electronic structure of the alloys. PMID:23588997

  13. A resonant state and the ground state of positronium hydride

    NASA Technical Reports Server (NTRS)

    Ho, Y. K.

    1978-01-01

    The lowest-lying resonance occurring in S-wave positronium-hydrogen scattering is reinvestigated, using the complex-rotation method. By employing a generalized Hylleraas-type wave function that includes all six interparticle coordinates, a very accurate value of the resonance position is obtained, along with a good value of the width. The present result for the resonance position (-1.205 plus or minus 0.001 Ry) is lower than the previous result of Drachman and Houston, who omitted the interelectronic coordinate in their trial function. In addition, the lowest ground-state energy of positronium hydride is obtained by using 210 terms in the trial wave function. The effect of the interelectronic coordinate and others on both the resonant energy and the binding energy of PsH is discussed.

  14. LaNi5 hydride cryogenic refrigerator test results

    NASA Technical Reports Server (NTRS)

    Jones, J. A.

    1983-01-01

    A complete LaNi5 hydrogen absorption cryogenic refrigerator system was developed. The system uses low temperature waste heat of approximately 100 C as a power source, and has no moving parts other than self operating valves. The cycle continues automatically by an electronic sequencing timing mechanism for the three compressors which are phased such that a constant supply of high pressure hydrogen gas is provided. It is indicated that with a fully clean hydrogen system, hundreds of thousand cycles should be attainable, even though some degradation may eventually occur. Simple vacuum reactivation of the hydride of moving parts, other than self operating, long life valves, the refrigerators predicted life is extremely long.

  15. Hydrogen generation from magnesium hydride by using organic acid

    NASA Astrophysics Data System (ADS)

    Ho, Yen-Hsi

    In this paper, the hydrolysis of solid magnesium hydride has been studied with the high concentration of catalyst at the varying temperature. An organic acid (acetic acid, CH3COOH) has been chosen as the catalyst. The study has three objectives: first, using three different weights of MgH 2 react with aqueous solution of acid for the hydrogen generation experiments. Secondly, utilizing acetic acid as the catalyst accelerates hydrogen generation. Third, emphasizing the combination of the three operating conditions (the weight of MgH2, the concentration of acetic acid, and the varying temperature) influence the amount of hydrogen generation. The experiments results show acetic acid truly can increase the rate of hydrogen generation and the weight of MgH2 can affect the amount of hydrogen generation more than the varying temperature.

  16. Bipolar nickel-metal hydride battery for hybrid vehicles

    NASA Astrophysics Data System (ADS)

    Reisner, David E.; Klein, Martin

    1994-05-01

    Hybrid electric vehicles are receiving increased interest as an approach to decrease vehicle pollution, dependence, and consumption of liquid petroleum and meet forthcoming government vehicle emission standards. A number of schemes are under consideration (heat engine battery, fuel cell battery, peaking battery, inner-city battery, etc.). The success of any of the approaches will be dependent on battery capabilities, i.e., power, density, life, and cost. The nickel-metal hydride system appears to be the most promising of the candidate battery chemistries. Preliminary designs and analysis have been prepared and are presented for various configurations. Initial performance characterization tests are presented. It is concluded that a bipolar package arrangement for the Ni-MH chemistry appears most suited for the hybrid vehicle application considered.

  17. Electronic structure and stability of complex hydrides Mg2 MH x ( M = Fe, Co)

    NASA Astrophysics Data System (ADS)

    Shelyapina, M. G.; Pinyugzhanin, V. M.; Skryabina, N. E.; Hauback, B. C.

    2013-01-01

    This paper reports on the results of theoretical investigations carried out for the hydrides Mg2FeH6 and Mg2CoH5 and the mixed hydride Mg2(FeH6)0.5(CoH5)0.5 in terms of the full-potential linearized augmented plane wave (FLAPW) method. It has been shown that the partial substitution of the Co atoms for the Fe atoms leads to a slight increase in the stability of the hydride, but, at the same time, makes it impossible to increase the stability of the alloy. The high stability of the hydrides under investigation has been explained by the strong bonding between atoms of the transition metal and hydrogen.

  18. Formation and Characterization of Hydride Blisters in Zircaloy-4 Cladding Tubes

    E-print Network

    Paris-Sud XI, Université de

    in a CANDU Zircaloy-2 pressure tube along an array of hydride blisters on the external surface is the material that replaced Zircaloy-2 alloy for pressure tubes in the CANDU reactors. In all these studies

  19. Concerted proton-coupled electron transfer from a metal-hydride complex.

    PubMed

    Bourrez, Marc; Steinmetz, Romain; Ott, Sascha; Gloaguen, Frederic; Hammarström, Leif

    2014-02-01

    Metal hydrides are key intermediates in the catalytic reduction of protons and CO2 as well as in the oxidation of H2. In these reactions, electrons and protons are transferred to or from separate acceptors or donors in bidirectional protoncoupled electron transfer (PCET) steps. The mechanistic interpretation of PCET reactions of metal hydrides has focused on the stepwise transfer of electrons and protons. A concerted transfer may, however, occur with a lower reaction barrier and therefore proceed at higher catalytic rates. Here we investigate the feasibility of such a reaction by studying the oxidation–deprotonation reactions of a tungsten hydride complex. The rate dependence on the driving force for both electron transfer and proton transfer—employing different combinations of oxidants and bases—was used to establish experimentally the concerted, bidirectional PCET of a metal-hydride species. Consideration of the findings presented here in future catalyst designs may lead to more-efficient catalysts. PMID:25615667

  20. Hydrogen Internal Combustion Engine Two Wheeler with on-board Metal Hydride Storage

    E-print Network

    Hydrogen Internal Combustion Engine Two Wheeler with on-board Metal Hydride Storage K. Sapru*, S, as a transition, the hydrogen internal combustion engine can lead the way to a hydrogen economy, allowing

  1. Green and blue electrochemically generated chemiluminescence from click chemistry--customizable iridium complexes.

    PubMed

    Zanarini, Simone; Felici, Marco; Valenti, Giovanni; Marcaccio, Massimo; Prodi, Luca; Bonacchi, Sara; Contreras-Carballada, Pablo; Williams, Rene M; Feiters, Martin C; Nolte, Roeland J M; De Cola, Luisa; Paolucci, Francesco

    2011-04-11

    Cationic cyclometalated iridium complexes containing two anionic phenylpyridine (ppy) ligands and the neutral bidentate triazole-pyridine ligand, 2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine (pytl), were investigated. The complexes display a rich and reversible electrochemical behavior, upon investigations by cyclic voltammetry in strictly aprotic conditions, that couples with excellent emission quantum yields and long lifetimes of the excited states. Therefore, in organic media, all complexes have generated intense green electrochemiluminescence (ECL) through the so-called annihilation procedure and, importantly, a modulation of the emission energy (to blue) has been easily obtained by simple fluorination of the ppy ligand. Finally, taking advantage of their remarkable solubility in water, intense ECL was also obtained from aqueous buffer solutions using the co-reactant method, thus making all the investigated complexes highly promising for their effective use as ECL labels in bioanalytical applications. PMID:21433123

  2. Epitaxially stabilized iridium spinel oxide without cations in the tetrahedral site

    NASA Astrophysics Data System (ADS)

    Kuriyama, Hiromichi; Matsuno, Jobu; Niitaka, Seiji; Uchida, Masaya; Hashizume, Daisuke; Nakao, Aiko; Sugimoto, Kunihisa; Ohsumi, Hiroyuki; Takata, Masaki; Takagi, Hidenori

    2010-05-01

    Single-crystalline thin film of an iridium dioxide polymorph Ir2O4 has been fabricated by the pulsed laser deposition of LixIr2O4 precursor and the subsequent Li-deintercalation using soft chemistry. Ir2O4 crystallizes in a spinel (AB2O4) without A cations in the tetrahedral site, which is isostructural to ?-MnO2. Ir ions form a pyrochlore sublattice, which is known to give rise to a strong geometrical frustration. This Ir spinel was found to be a narrow gap insulator, in remarkable contrast to the metallic ground state of rutile-type IrO2. We argue that an interplay of a strong spin-orbit coupling and a Coulomb repulsion gives rise to an insulating ground state as in a layered perovskite Sr2IrO4.

  3. Conodont survival and low iridium abundances across the Permian-Triassic boundary in south China

    NASA Technical Reports Server (NTRS)

    Clark, D. L.; Wang, C.-Y.; Orth, C. J.; Gilmore, J. S.

    1986-01-01

    The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion + or - 20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.

  4. Growth of N-doped heteroepitaxial diamond thin films on iridium for cold cathode

    NASA Astrophysics Data System (ADS)

    Mine, T.; Yamada, T.; Sawabe, A.; Okamura, H.; Koizumi, S.; Yamaguchi, H.; Okano, K.

    2003-09-01

    Heavily nitrogen (N)-doped polycrystalline diamond is reported to have excellent electron emission properties although its emission sites are limited. This report describes the fabrication processes, characterisation and electron emission properties of N-doped heteroepitaxial diamond which posses high potential as broad area emitter devices. We have obtained epitaxial diamond films on iridium (Ir) substrates by hot filament CVD using urea [(NH2)2CO] as a dopant for N. The Ir substrates are bias treated via direct current plasma CVD (d.c. plasma CVD) method prior to the growth. Surface of the deposited films is smooth and continuous in scanning electron microscopy (SEM) observation. The epitaxial diamond growth is confirmed from reflective high energy electron diffraction (RHEED) pattern. It is found that the electron emission from heteroepitaxial diamond film is dominated by standard Fowler-Nordheim type emission due to the existence of strong electric field in the vacuum with the value of 26 V/m. (

  5. Epitaxial (100) iridium on A-plane sapphire: A system for wafer-scale diamond heteroepitaxy

    NASA Astrophysics Data System (ADS)

    Dai, Z.; Bednarski-Meinke, C.; Loloee, R.; Golding, B.

    2003-06-01

    Large-scale heteroepitaxial growth of diamond depends critically on the development of a suitable lattice-matched buffer layer and substrate system. Epitaxial (100) iridium films have been grown on terraced, vicinal a-plane (112¯0) ?-Al2O3 (sapphire) by electron-beam evaporation. The epitaxial relationship, Ir(100)//Al2O3(112¯0) with Ir[011]//Al2O3[11¯00], was determined by x-ray diffraction and electron backscattering diffraction analysis. For a 300-nm thickness of Ir, a (200) rocking curve yielded a linewidth of 0.21°, and the film exhibited a macrostepped surface with low pinhole density. This Ir/sapphire system provides a basis for large-area growth of (100) heteroepitaxial diamond.

  6. Iridium-catalyzed asymmetric hydrogenation of unfunctionalized, trialkyl-substituted olefins.

    PubMed

    Wang, Aie; Fraga, Rui P A; Hörmann, Esther; Pfaltz, Andreas

    2011-02-01

    Chiral iridium complexes with bicyclic pyridine-based N,P ligands have emerged as efficient catalysts for the enantioselective hydrogenation of unfunctionalized trialkyl-substituted olefins. Optimization of the reaction conditions by variation of the solvent, pressure, and temperature led to enantiomeric excesses of up to 99%. Three pure alkenes, (E)-2-cyclohexyl-2-butene and (E)- and (Z)-3,4-dimethyl-2-pentene were converted into the corresponding chiral alkanes with 97%, 94%, and 93% ee, respectively. Hydrogenation of the three C=C bonds of both ?- and ?-tocotrienyl acetate led to ?- and ?-tocopheryl acetate with very high diastereoselectivity. The same catalysts were successfully applied in the hydrogenation of trisubstituted alkenes with a carboxylic ester or a keto group in the ? position. This reaction was used as a key step in a highly enantioselective synthesis of the pheromone of the caddisfly Hesperophylax occidentalis. The hydrogenation of a structurally analogous allylic alcohol also gave high enantioselectivities. PMID:20967822

  7. Formation of C–C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

    PubMed Central

    Bower, John F.; Krische, Michael J.

    2011-01-01

    The formation of C–C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C–C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and ?-unsaturated reactants generates electrophile–nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C–H bonds. PMID:21822399

  8. A non-catastrophist explanation for the iridium anomaly at the Cretaceous/Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.

    1982-01-01

    The iridium (Ir) anomaly at the Cretaceous/Tertiary (C/T) boundary can be explained by dissolution of normal pelagic limestones producing an insoluble clay residue containing Ir-rich meteoritic material. Further concentration of Ir and other trace metals in the clay can be explained by deposition under reducing conditions. Clay-mineral analyses indicate that the boundary clay is similar to locally derived clays in the limestones above and below the boundary, and contains no detectable exotic components. This supports a terrestrial origin for the boundary clay. The genesis of the boundary clay is attributed to changes in ocean chemistry (pH and oxygenation), leading to an interval of widespread dissolution of carbonate sequences in the oceans, and culminating in the development of submarine pyritic hardgrounds and a disconformity of global extent.

  9. Hot rocket plume experiment - Survey and conceptual design. [of rhenium-iridium bipropellants

    NASA Technical Reports Server (NTRS)

    Millard, Jerry M.; Luan, Taylor W.; Dowdy, Mack W.

    1992-01-01

    Attention is given to a space-borne engine plume experiment study to fly an experiment which will both verify and quantify the reduced contamination from advanced rhenium-iridium earth-storable bipropellant rockets (hot rockets) and provide a correlation between high-fidelity, in-space measurements and theoretical plume and surface contamination models. The experiment conceptual design is based on survey results from plume and contamination technologists throughout the U.S. With respect to shuttle use, cursory investigations validate Hitchhiker availability and adaptability, adequate remote manipulator system (RMS) articulation and dynamic capability, acceptable RMS attachment capability, adequate power and telemetry capability, and adequate flight altitude and attitude/orbital capability.

  10. Anodic Deposition of a Robust Iridium-Based Water-Oxidation Catalyst from Organometallic Precursors

    SciTech Connect

    Blakemore, James D; Schley, Nathan D; Olack, G.; Incarvito, Christopher D; Brudvig, Gary W; Crabtree, Robert H

    2011-01-01

    Artificial photosynthesis, modeled on natural light-driven oxidation of water in Photosystem II, holds promise as a sustainable source of reducing equivalents for producing fuels. Few robust water-oxidation catalysts capable of mediating this difficult four-electron, four-proton reaction have yet been described. We report a new method for generating an amorphous electrodeposited material, principally consisting of iridium and oxygen, which is a robust and long-lived catalyst for water oxidation, when driven electrochemically. The catalyst material is generated by a simple anodic deposition from Cp*Ir aqua or hydroxo complexes in aqueous solution. This work suggests that organometallic precursors may be useful in electrodeposition of inorganic heterogeneous catalysts.

  11. Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium

    E-print Network

    Elke Neu; David Steinmetz; Janine Riedrich-Moeller; Stefan Gsell; Martin Fischer; Matthias Schreck; Christoph Becher

    2010-11-26

    We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.

  12. Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium

    E-print Network

    Neu, Elke; Riedrich-Moeller, Janine; Gsell, Stefan; Fischer, Martin; Schreck, Matthias; Becher, Christoph

    2010-01-01

    We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.

  13. Iridium-catalyzed reductive carbon-carbon bond cleavage reaction on a curved pyridylcorannulene skeleton.

    PubMed

    Tashiro, Shohei; Yamada, Mihoko; Shionoya, Mitsuhiko

    2015-04-27

    The cleavage of C?C bonds in ?-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic C?C bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amount of IrCl3 ?n?H2 O in ethylene glycol at 250?°C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ghi]fluoranthene skeleton through a site-selective C?C cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on C?C bond cleavage reactions. PMID:25756834

  14. Catalyst-controlled regiodivergent c?h borylation of multifunctionalized heteroarenes by using iridium complexes.

    PubMed

    Sasaki, Ikuo; Taguchi, Jumpei; Hiraki, Shotaro; Ito, Hajime; Ishiyama, Tatsuo

    2015-06-15

    The regiodivergent C?H borylation of 2,5-disubstituted heteroarenes with bis(pinacolato)diboron was achieved by using iridium catalysts formed in situ from [Ir(OMe)(cod)]2 /dtbpy (cod=1,5-cyclooctadiene, dtbpy: 4,4'-di-tert-butyl-2,2'-bipyridine) or [Ir(OMe)(cod)]2 /2?AsPh3 . When [Ir(OMe)(cod)]2 /dtbpy was used as the catalyst, borylation at the 4-position proceeded selectively to afford 4-borylated products in high yields (dtbpy system?A). The regioselectivity changed when the [Ir(OMe)(cod)]2 /2?AsPh3 catalyst was used; 3-borylated products were obtained in high yields with high regioselectivity (AsPh3 system?B). The regioselectivity of borylation was easily controlled by changing the ligands. This reaction was used in the syntheses of two different bioactive compound analogues by using the same starting material. PMID:25966001

  15. Formation of C-C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

    NASA Astrophysics Data System (ADS)

    Bower, John F.; Krische, Michael J.

    The formation of C-C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C-C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and ?-unsaturated reactants generates electrophile-nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C-H bonds.

  16. Topological phases in Iridium oxide superlattices: quantized anomalous charge or valley Hall insulators

    NASA Astrophysics Data System (ADS)

    Kee, Hae-Young; Chen, Yige

    2015-03-01

    Designing materials is one of intense topics in modern condensed matter physics. Recently, how to achieve a topological insulator in transition metal oxides with strong spin-orbit coupling became an interesting subject. We have investigated possible topological phases in orthorhombic perovskite Iridium (Ir) oxide superlattices grown along the [001] crystallographic axis. We found that bilayer Ir oxide superlattices exhibit quantized anomalous Hall effects in magnetic topological insulating phases. We also found, depending on the stacking of two layers, a valley Hall insulator with nontrivial valley dependent surface modes and a topological crystalline insulator with the crystal symmetry protected edge states can be realized. Experimental tools to detect such topological phases are also discussed.

  17. Physicochemical studies of green phosphorescent light-emitting materials from cyclometalated heteroleptic iridium(III) complexes

    NASA Astrophysics Data System (ADS)

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Perumal, Marimuthu Venkatesh

    2011-07-01

    A series of novel imidazole ligands were synthesized and characterized. Phosphorescence studies of series of heteroleptic cyclometalated iridium(III) complexes reveal that these complexes possess dominantly 3MLCT and 3?-?* excited states and the solvent shifts of these complexes are interpreted by Richardt-Dimroth and Marcus solvent functions. The results consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition ( kr), increases with increasing ?em and linear correlation exists between ln( knr) and energy gap. Electronic transition theory is applied to study the effect of Eg and ? Qe on non-radiative transition ( knr). With a larger ? Qe, favouring vibrational overlap and leading to a larger value for knr.

  18. Physicochemical studies of green phosphorescent light-emitting materials from cyclometalated heteroleptic iridium(III) complexes.

    PubMed

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Srinivasan, Natesan; Perumal, Marimuthu Venkatesh

    2011-07-01

    A series of novel imidazole ligands were synthesized and characterized. Phosphorescence studies of series of heteroleptic cyclometalated iridium(III) complexes reveal that these complexes possess dominantly (3)MLCT and (3)?-?* excited states and the solvent shifts of these complexes are interpreted by Richardt-Dimroth and Marcus solvent functions. The results consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition (k(r)), increases with increasing ?(em) and linear correlation exists between ln(k(nr)) and energy gap. Electronic transition theory is applied to study the effect of E(g) and ?Q(e) on non-radiative transition (k(nr)). With a larger ?Q(e), favouring vibrational overlap and leading to a larger value for k(nr). PMID:21470904

  19. New iridium complexes with cyclometalated 2-arylimidazole ligands as highly efficient saturated green emitters.

    PubMed

    Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Saravanan, Kanagarathinam; Venkatesh Perumal, Marimuthu

    2012-06-01

    Phosphorescence studies of a series of heteroleptic cyclometalated iridium(III) complexes have been carried out. From the photoluminescent properties, it was found that these complexes possess dominantly (3)MLCT and (3)?-?* excited states. The solvent shifts are interpreted in terms of Reichardt-Dimroth solvent E(T) parameters and Marcus theory. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies reveal that k(r) increases with increasing ?(em) and linear correlation between ln(k(nr)) and energy gap. The effect of E(g) and ?Q(e) on k(nr) is discussed in detail. PMID:22381786

  20. Efficient red-emitting cyclometalated Iridium(III) complexes containing lepidine-based ligands.

    PubMed

    Thomas, K R Justin; Velusamy, Marappan; Lin, Jiann T; Chien, Chin-Hsiung; Tao, Yu-Tai; Wen, Yuh S; Hu, Ya-Hui; Chou, Pi-Tai

    2005-08-01

    Heteroleptic cyclometalated iridium(III) complexes featuring lepidine-based ligands and acetyl acetone auxiliary ligand are synthesized. Multiple lowest energy absorption bands are observed for these complexes indicating substantial mixing of the singlet and triplet levels. All the complexes emit orange or red color in dichloromethane solutions with lifetimes in the range 1.6-3.7 micros. The emission in the complexes probably originates from the (3)MLCT state. The complexes are applied as emitting guests in LED devices of the structure ITO/HTL(BPAPF or NPB)/6% Ir in CBP/BCP/Alq(3)/LiF/Al. They exhibit excellent device characteristics with an orange to red EL profile. PMID:16060618

  1. Synthesis, structure and electroluminescent properties of cyclometalated iridium complexes possessing sterically hindered ligands.

    PubMed

    Velusamy, Marappan; Thomas, K R Justin; Chen, Chih-Hsin; Lin, Jiann T; Wen, Yuh S; Hsieh, Wan-Ting; Lai, Chin-Hung; Chou, Pi-Tai

    2007-07-28

    New CN donor ligands incorporating pyridine or benzoimidazole N donors and a sterically hindered cyclometalating aromatic core featuring a polyphenylenephenyl, fluoranthene, or triphenylene segment are prepared and successfully converted into heteroleptic iridium(III) cyclometalated complexes with acetylacetone auxiliary ligands. The X-ray structure of the complex, derived from a ligand containing a fluoranthene fragment, has been solved to unveil the corresponding structure. The results clearly demonstrate that the nature of the sigma-coordinating ligand segment plays a key role in dictating the emission profile and peak position, such that the emission hue has been successfully tuned ranging from green to red. Supplementary support of this viewpoint is also rendered by computational (DFT) approaches. Electroluminescent devices fabricated using a complex as dopant in the PVK matrix were found to exhibit bright greenish yellow emission with promising device characteristics (maximum brightness 26450 cd m(-2) at 30 V and a maximum current efficiency of 40 cd A(-1)). PMID:17622420

  2. Iridium Oxide Nanotube Electrodes for Highly Sensitive and Prolonged Intracellular Measurement of Action Potentials

    PubMed Central

    Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

    2014-01-01

    Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

  3. Mobility of iridium in terrestrial environments: Implications for the interpretation of impact-related mass-extinctions

    NASA Astrophysics Data System (ADS)

    Martín-Peinado, F. J.; Rodríguez-Tovar, F. J.

    2010-08-01

    Traditionally, iridium has been considered an element of low mobility, but its behavior is still debated. Ir concentration in a soil affected by a catastrophic mining spill in 1998 that covered the soil with a layer of tailings offers the opportunity to analyse an exceptional Ir-bearing horizon 10 years after deposition. This has enabled comparisons with the values of past Ir-bearing horizons associated to impact-related mass-extinction events. Iridium concentration in the tailings (0.349 ppm) was 5-fold higher than the anomaly in the K-Pg at The Moody Creek Mine section (the highest values obtained from terrestrial sections). The oxidative weathering of the tailings caused the release of Ir and infiltration into the soil. Iridium distribution in depth indicates redistribution throughout the profile in relation to the change in the physico-chemical properties of the soil. With regard to the background concentration in the soil (0.056 ppm), anomalous values of Ir (0.129 ppm) can be detected to 11 cm below the layer of tailings. The correlation analysis between the Ir concentration and the main properties and constituents of the soils indicated a significant correlation with sulfur, iron, clay content, and pH. Selective extractions were made to study the forms in which Ir can be mobilized in the soil. The residual/insoluble fraction was >90% of the total Ir concentration in soil. Soluble-in-water concentration of Ir (1.5% of total) was detected in the uppermost 2-3 cm of the soil, which were directly affected by the leaching of acidic waters coming from the oxidation of the pyrite tailings. Iridium retention in the affected part of the soil reached 9% of the total Ir concentration; this retention could be related to the amorphous iron forms dissolved by the oxalic-oxalate extraction. However, according to our research, original Ir abundance could be secondarily modified, and then a direct analysis of the iridium values recorded in sediments could induce misinterpretations. The comparison between the actual example and the fossil record belonging to terrestrial settings, can be considered as a valuable approach, especially when Iridium data were used by researchers to interpret the impact-related mass-extinction events in the past.

  4. Solvation dynamics and energetics of intramolecular hydride transfer reactions in biomass conversion.

    PubMed

    Mushrif, Samir H; Varghese, Jithin J; Krishnamurthy, Chethana B

    2015-02-21

    Hydride transfer changes the charge structure of the reactant and thus, may induce reorientation/reorganization of solvent molecules. This solvent reorganization may in turn alter the energetics of the reaction. In the present work, we investigate the intramolecular hydride transfer by taking Lewis acid catalyzed glucose to fructose isomerization as an example. The C2-C1 hydride transfer is the rate limiting step in this reaction. Water and methanol are used as solvents and hydride transfer is simulated in the presence of explicit solvent molecules, treated quantum mechanically and at a finite temperature, using Car-Parrinello molecular dynamics (CPMD) and metadynamics. Activation free energy barrier for hydride transfer in methanol is found to be 50 kJ mol(-1) higher than that in water. In contrast, in density functional theory calculations, using an implicit solvent environment, the barriers are almost identical. Analysis of solvent dynamics and electronic polarization along the molecular dynamics trajectory and the results of CPMD-metadynamics simulation of the hydride transfer process in the absence of any solvent suggest that higher barrier in methanol is a result of non-equilibrium solvation. Methanol undergoes electronic polarization during the hydride transfer step. However, its molecular orientational relaxation is a much slower process that takes place after the hydride transfer, over an extended timescale. This results in non-equilibrium solvation. Water, on the other hand, does not undergo significant electronic polarization and thus, has to undergo minimal molecular reorientation to provide near equilibrium solvation to the transition state and an improved equilibrium solvation to the post hydride shift product state. Hence, the hydride transfer step is also observed to be exergonic in water and endergonic in methanol. The aforementioned explanation is juxtaposed to enzyme catalyzed charge transfer reactions, where the enhanced solvation of the transition and product states by enzymes, due to electrostatic interactions, reduces the activation free energy barrier and the free energy change of the reaction. Similarly, we suggest that, in the intramolecular hydride shift, improved solvation of the transition state and of the product state by water is achieved due to minimal polarization and reorientation, and (near) equilibrium solvation. PMID:25591500

  5. Deep acceptor states of platinum and iridium in 4H -silicon carbide

    NASA Astrophysics Data System (ADS)

    Grillenberger, J.; Grossner, U.; Svensson, B. G.; Albrecht, F.; Witthuhn, W.; Sielemann, R.

    2004-11-01

    Band gap states of platinum and iridium in the hexagonal polytype 4H of silicon carbide are investigated by means of deep level transient spectroscopy (DLTS) in n - as well as p -type epitaxial layers. To establish a definite chemical assignment of band gap states to Pt and Ir the radioactive isotope P188t was incorporated into 4H-SiC samples by recoil implantation. During the nuclear decay of P188t via the unstable I188r to the stable O188s , the concentration of band gap states is traced by DLTS whereby characteristic concentration changes lead to an unambiguous assignment of two band gap states to P188t . The two levels are interpreted as one Pt -related defect structure with two different charge states in the band gap of 4H-SiC : a double-negative acceptor at 0.81eV and a single-negative acceptor at 1.47eV below the conduction band edge EC . Iridium was found to generate one acceptorlike state (EC-0.82eV) in the band gap of 4H-SiC . Further, acceptor states at EC-0.31eV , EC-0.41eV , EC-0.50eV and donor states at EV+0.60eV , EV+0.90eV , EV+1.09eV ( EV is the valence band edge) are preliminarily assigned to defects involving osmium. It was found that recoil processes taking place during the nuclear decay may generate different complex structures related to Os . Therefore, the assignment to specific Os structures is not definite. The deep acceptor state of platinum is considered an interesting candidate for a compensating center close to the midgap position in 4H-SiC in order to produce semi-insulating SiC layers and control carrier lifetimes.

  6. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; Manuel, P.; Chapon, L. C.; Cao, G.; Qi, T. F.

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm?cm?, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) ?B. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  7. Manipulating the Excited States of Cyclometalated Iridium Complexes with ?-Ketoiminate and ?-Diketiminate Ligands.

    PubMed

    Radwan, Yousf K; Maity, Ayan; Teets, Thomas S

    2015-07-20

    A series of cyclometalated iridium complexes with ?-ketoiminate and ?-diketiminate ligands are described. Two different cyclometalating (C^N) ligands-2-phenylpridine (ppy) and 2-phenylbenzothiazole (bt)-are used in concert with three different ancillary (LX) ligands-a phenyl-substituted ?-ketoiminate (acNac(Me)), a phenyl-substituted ?-diketiminate (NacNac(Me)), and a fluorinated version of the ?-diketiminate (NacNac(CF3))-to furnish a suite of six complexes. The complexes are prepared by metathesis reactions of chloro-bridged dimers [Ir(C^N)2(?-Cl)]2 with potassium or lithium salts of the ancillary LX ligand. Four of the complexes are characterized by X-ray crystallography, and all six were subjected to in-depth optical and electrochemical interrogation. Cyclic voltammetry shows both reduction and oxidation waves, with the latter strongly dependent on the identity of the LX ligand. The complexes are all luminescent, with the nature of the emissive excited state and the quantum yield (?) dependent on the identity of both the C^N and LX ligands. Whereas the complexes Ir(ppy)2(NacNac(Me)) and Ir(ppy)2(acNac(Me)) are weakly luminescent (? ? 0.01), the complexes Ir(bt)2(NacNac(Me)) and Ir(bt)2(acNac(Me)) are strongly luminescent, with the latter's quantum efficiency (? = 0.82) among the highest ever observed for cyclometalated iridium complexes. Fluorination of the NacNac ligand gives rise to completely disparate emission behavior suggestive of a NacNac-centered emissive state. The results described here, in comparison with previous groups' studies on acetylacetonate (acac) analogues, suggest that the weaker-field NacNac and acNac ligands raise the energy of the metal-centered HOMO, with energy of the HOMO increasing in the order NacNac(CF3) < acNac(Me) < NacNac(Me). PMID:26158354

  8. Iridium 192 implantation of T1 and T2 carcinomas of the mobile tongue

    SciTech Connect

    Mazeron, J.J.; Crook, J.M.; Benck, V.; Marinello, G.; Martin, M.; Raynal, M.; Haddad, E.; Peynegre, R.; Le Bourgeois, J.P.; Walop, W. (Hopital Henri Mondor, Creteil (France))

    1990-12-01

    Between 1970 and 1986, 166 patients with T1 or T2 epidermoid carcinomas of the mobile tongue were treated by iridium 192 implantation (70 T1N0, 83 T2N0, 13 T1-2 N1-3). Five-year actuarial survival was 52% for T1N0, 44% for T2aN0, and 8% for or T1-2 N1-3. Cause specific survivals were 90%, 71%, and 46%, respectively. Local control was 87% for both T1N0 and T2N0, and 69% for T1-2 N1-3. Seven of 23 failures were salvaged by surgery, increasing local control to 96% for T1 and 90% for T2. Thirty-six patients developed a minor or moderate necrosis (16% T1, 28% T2). Half of these involved bone but only five required surgical intervention. Both local control (LC) and necrosis (nec) increased with increasing dose but improvement beyond 65 Gy is minimal (less than or equal to 60 Gy: LC = 78% nec = 13%; 65 Gy: LC = 90% nec = 29%; greater than or equal to 70 Gy: LC = 94% nec = 23%). For N0 patients, neck management consisted of surveillance (n = 78), elective neck dissection followed with external irradiation for pathologically positive nodes (n = 72), or irradiation (n = 3). Clinically positive nodes (13 patients) were managed by either neck dissection followed by external irradiation if pathologically positive (n = 10) or irradiation alone (n = 3). Regional control was 79% for N0 patients, improving to 88% after surgical salvage, and was 9/13 for N1-3 patients. We recommend that T1 and T2 carcinomas of the mobile tongue be treated by iridium 192 implantation to deliver 65 Gy. Mandibular necrosis should be reduced by using an intra-oral lead-lined dental mold.

  9. Cationic iridium(III) complexes with two carbene-based cyclometalating ligands: cis versus trans isomers.

    PubMed

    Monti, Filippo; La Placa, Maria Grazia I; Armaroli, Nicola; Scopelliti, Rosario; Grätzel, Michael; Nazeeruddin, Mohammad Khaja; Kessler, Florian

    2015-03-16

    A series of cationic iridium(III) complexes with two carbene-based cyclometalating ligands and five different N^N bipyridine and 1,10-phenanthroline ancillary ligands is presented. For the first time--in the frame of a rarely studied class of bis(heteroleptic) iridium complexes with two carbene-based cyclometalating ligands--a pair of cis and trans isomers has been isolated. All complexes (trans-1-5 and cis-3) were characterized by (1)H NMR, (13)C NMR, (31)P NMR, and HRMS (ESI-TOF); in addition, crystal structures of cis-3 and trans-4 are reported and discussed. Cyclic voltammetric studies show that the whole series exhibits highly reversible oxidation and reduction processes, suggesting promising potential for optoelectronic applications. Ground-state DFT and TD-DFT calculations nicely predict the blue shift experimentally observed in the room-temperature absorption and emission spectra of cis-3, compared to the trans complexes. In CH3CN, cis-3 displays a 4-fold increase in photoluminescence quantum yield (PLQY) with respect to trans-3, as a consequence of drastically slower nonradiative rate constant. By contrast, at 77 K, the emission properties of all the compounds, including the cis isomer, are much more similar, with a pronounced hypsochromic shift for the trans complexes. A similar behavior is found in solid state (1% w/w poly(methyl methacrylate) matrix), with all complexes displaying PLQY of ?70-80%, comparable emission lifetimes (? ? 1.3 ?s), and a remarkable rigidochromic shift. To rationalize the more pronounced nonradiative deactivation (and smaller PLQY) observed for photoexcited trans complexes, comparative temperature-dependent emission studies in the range of 77-450 K for cis-3 and trans-3 were made in propylene glycol, showing that solvation effects are primarily responsible for the observed behavior. PMID:25741900

  10. Corrosion and hydriding of three zirconium alloys in N-Reactor process tube 0553

    Microsoft Academic Search

    Johnson; A. B. Jr

    1985-01-01

    Coupons of three zirconium alloys - Zircaloy-2 (two lots and three metallurgical conditions); Zircaloy-4; and Zr-2.5Nb - were exposed in N-Reactor pressure tube 0553 for 155 days at 1.2 x 10²° n\\/cm², >1 MeV. Although the exposure was relatively mild, significant differences in hydriding trends were observed for the three alloys. Hydriding rates differed for the three alloys: the rates

  11. Large relativistic effects in molecular properties of the hydride of superheavy element 111

    Microsoft Academic Search

    Michael Seth; Peter Schwerdtfeger; Michael Dolg; Knut Faegri; Bernd A. Hess; Uzi Kaldor

    1996-01-01

    Relativistic and electron correlation contributions in the hydride of the recently discovered superheavy element 111 were studied using ab-initio methods within different relativistic approaches. Relativistic effects decrease the (111)H bond distance by 0.42 Å. As a result of this large bond contraction, the bond distance of (111)H (1.51 Å) is comparable to that of the hydride of its lighter congener

  12. Scaling up effects of Mg hydride in a temperature and pressure-controlled hydrogen storage device

    Microsoft Academic Search

    M. Verga; F. Armanasco; C. Guardamagna; C. Valli; A. Bianchin; F. Agresti; S. Lo Russo; A. Maddalena; G. Principi

    2009-01-01

    A research program addressed to evaluate the magnesium hydride storage scaling up effects is being developed by CESI RICERCA, Milano, and the Hydrogen Group of Padova University. A storage device containing 500g of magnesium hydride powder (manufactured by Venezia Tecnologie S.p.A. using high-energy ball milling) has been designed and tested in different operating conditions. A number of absorption and desorption

  13. Enhancement of heat and mass transfer in metal hydride beds with the addition of Al plates

    Microsoft Academic Search

    Z. Guo

    1999-01-01

    A numerical study is made of transient heat and mass transfer in metal hydride beds in the hydriding process with the addition\\u000a of internal aluminum plates. The two-dimensional equations governing the hydration kinetics, hydrogen flow and heat transfer\\u000a are solved by using the iterative method based on the finite-volume technique. It is found that the heat transfer is enhanced\\u000a by

  14. New binding materials for metal hydride electrodes which permit good recyclability

    Microsoft Academic Search

    T. Hara; N. Yasuda; Y. Takeuchi; T. Sakai; A. Uchiyama; H. Miyamura; N. Kuriyama; H. Ishikawa

    1993-01-01

    Thermoplastic elastomers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-ethylene\\/butylene-styrene block copolymer (SEBS) were used successfully as binding materials for metal hydride (MH) electrodes of a nickel-metal hydride battery. These binding materials have a rubber-like nature and are soluble in organic solvents. It was easy to remove the alloy powder from a used electrode for recycling. The battery performance depended

  15. Electrolyser-metal hydride-fuel cell system for seasonal energy storage

    Microsoft Academic Search

    J. P. Vanhanen; P. D. Lund; J. S. Tolonen

    1998-01-01

    A small-scale seasonal energy storage system, comprising an electrolyser, metal hydride hydrogen store and fuel cell, has been studied. According to the feasibility study, solid polymer electrolysers and fuel cells are the best options for the electrolyser-metal hydride-fuel cell energy storage systems. A round-trip efficiency of 30% has already been demonstrated, and the next target is to reach a round-trip

  16. A variety of electrostatic interactions and adducts can activate NAD(P) cofactors for hydride transfer

    Microsoft Academic Search

    Rob Meijers; Eila Cedergren-Zeppezauer

    2009-01-01

    In NAD(P)-dependent enzymes the coenzyme gives or takes a hydride ion, but how the nicotinamide ring is activated to form the transition state for hydride transfer is not clear. On the basis of ultra-high resolution X-ray crystal structures of liver alcohol dehydrogenase (LADH) in complex with NADH and a number of substrate analogues we proposed that the activation of NADH

  17. A process steam generator based on the high temperature magnesium hydride\\/magnesium heat storage system

    Microsoft Academic Search

    B. Bogdanovi?; A. Ritter; B. Spliethoff; K. Stra?burger

    1995-01-01

    As a first pilot project application of the reversible thermochemical high temperature heat storage system magnesium hydride\\/magnesium a process steam generator has been built and tested. It draws the heat for the generation of superheated steam from a magnesium hydride\\/magnesium (MgH2Mg) heat store and is primarily meant for the storage of high grade industrial waste heat which can be made

  18. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    SciTech Connect

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  19. Hydride Formation Process for the Powder Metallurgical Recycle of Zircaloy from Used Nuclear Fuel

    NASA Astrophysics Data System (ADS)

    Parkison, Adam J.; McDeavitt, Sean M.

    2011-01-01

    A Zircaloy recycle process is being investigated based on the underlying principle that Zr reacts with H2 to form ZrH2, which is the same reaction that produces performance limiting ZrH2 formations in reactor cladding. However, in the proposed application, hydride formation is an enabling phenomenon that will embrittle and crumble Zircaloy as a precursor for milling and dehydration to form Zircaloy metal powder. Hydride formation experiments were performed to quantify the primary process variables of time and temperature. These experiments were performed by hydriding nuclear grade Zircaloy-4 tubes under flowing gas (Ar-5 pct H2) for various times and temperatures. The results were used to create a correlation for the formation of zirconium hydride as a function of time and temperature. Further, it was observed that it was much more effective to hydride the Zircaloy-4 tubes at temperatures below the ?- ?- ? eutectoid temperature of 818 K (545 °C), presumably related to the high hydrogen solubility of ?-Zr. Samples treated below this temperature readily crumbled during the hydride formation reaction and were subsequently easily ground to powder, making this the ideal temperature range for the proposed recycle method. Hydrogen pickup was faster above 818 K (545 °C), but the samples were generally tougher.

  20. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.