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1

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

PubMed

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

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

2013-08-22

2

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

PubMed

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

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

2013-10-23

3

Highly sensitive and interference-free determination of bismuth in environmental samples by electrothermal vaporization atomic fluorescence spectrometry after hydride trapping on iridium-coated tungsten coil  

NASA Astrophysics Data System (ADS)

Bismuthine was on-line trapped on tungsten coil and subsequently electrothermally vaporized for the determination by atomic fluorescence spectrometry (AFS). Several noble metals, including Pd, Rh, Pt, and Ir, were explored as permanent chemical modifier for tungsten coil on-line trapping. Investigation showed that Ir gave the best performance, in which bismuthine was on-line trapped on Ir-coated tungsten coil at 560 °C, and then released at 1550 °C for subsequent transfer to AFS by a mixture of Ar and H 2. Under optimum instrumental conditions, the trapping efficiency was found to be 73 ± 3%. With 120 s (12 mL sample volume) trapping time, a limit of detection (LOD) of 4 ng L - 1 was obtained, compared to conventional hydride generation AFS (0.09 ?g L - 1 ); the LOD can be lowered down to 1 ng L - 1 by increasing the trapping time to 480 s. The LOD was found to be better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental methods such as ICP-MS and GF-AAS. A comprehensive interference study involving conventional hydride-forming elements and some transition metals was carried out, and the result showed that the gas phase interference from other hydride-forming elements was largely reduced, thanks to the use of on-line tungsten coil trapping. Finally, the proposed method was applied to the determination of bismuth in several biological and environmental standard reference materials, and a t-test shows that the analytical results by the proposed method have no significant difference from the certified values at the confidence level of 95%.

Liu, Rui; Wu, Peng; Xu, Kailai; Lv, Yi; Hou, Xiandeng

2008-06-01

4

Sealed aerospace metal-hydride batteries  

Microsoft Academic Search

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

Dwaine Coates

1992-01-01

5

Authentic-blue phosphorescent iridium(III) complexes bearing both hydride and benzyl diphenylphosphine; control of the emission efficiency by ligand coordination geometry.  

PubMed

Sequential treatment of IrCl(3) x nH(2)O with 2 equiv of benzyl diphenylphosphine (bdpH) and then 1 equiv of 3-trifluoromethyl-5-(2-pyridyl) pyrazole (fppzH) in 2-methoxyethanol gave formation to three isomeric complexes with formula [Ir(bdp)(fppz)(bdpH)H] (1-3). Their molecular structures were established by single crystal X-ray diffraction studies, showing existence of one monodentate phosphine bdpH, one terminal hydride, a cyclometalated bdp chelate, and a fppz chelate. Variation of the metal-ligand bond distances showed good agreement with those predicted by the trans effect. Raman spectroscopic analyses and the corresponding photophysical data are also recorded and compared. Among all isomers complex 1 showed the worst emission efficiency, while complexes 2 and 3 exhibited the greatest luminescent efficiency in solid state and in degassed CH(2)Cl(2) solution at room temperature, respectively. This structural relationship could be due to the simultaneously weakened hydride and the monodentate bdpH bonding that are destabilized by the trans-pyrazolate anion and cyclometalated benzyl group, respectively. PMID:19670882

Chiu, Yuan-Chieh; Lin, Chen-Huey; Hung, Jui-Yi; Chi, Yun; Cheng, Yi-Ming; Wang, Kang-Wei; Chung, Min-Wen; Lee, Gene-Hsiang; Chou, Pi-Tai

2009-09-01

6

Iridium alloy  

US Patent & Trademark Office Database

An iridium alloy consists essentially of iridium and at least one of W and Zr, and optionally Rh. When present, W comprises between 0.01 and 5 wt % of the alloy; when present in combination with W, Zr comprises between 0.01 and 0.5 wt % of the alloy; when present alone or in combination with Rh only, Zr comprises between 0.01 and 0.09 wt % of the alloy; and when present, Rh comprises between 0.1 and 5 wt % of the alloy. The alloys may be modified by the addition of platinum and other platinum group metals and base metals. The alloys demonstrate enhanced physical and chemical properties and are suitable for use as electrode materials in spark plugs and other high temperature applications.

2009-01-27

7

Sealed aerospace metal-hydride batteries  

NASA Technical Reports Server (NTRS)

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.

Coates, Dwaine

1992-01-01

8

Sealed aerospace metal-hydride batteries  

NASA Astrophysics Data System (ADS)

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.

Coates, Dwaine

1992-02-01

9

Iridium: failures & successes  

NASA Astrophysics Data System (ADS)

This paper will provide an overview of the Iridium business venture in terms of the challenges faced, the successes achieved, and the causes of the ultimate failure of the venture — bankruptcy and system de-orbit. The paper will address technical, business, and policy issues. The intent of the paper is to provide a balanced and accurate overview of the Iridium experience, to aid future decision-making by policy makers, the business community, and technical experts. Key topics will include the history of the program, the objectives and decision-making of Motorola, the market research and analysis conducted, partnering strategies and their impact, consumer equipment availability, and technical issues — target performance, performance achieved, technical accomplishments, and expected and unexpected technical challenges. The paper will use as sources trade media and business articles on the Iridium program, technical papers and conference presentations, Wall Street analyst's reports, and, where possible, interviews with participants and close observers.

Christensen, CarissaBryce; Beard, Suzette

2001-03-01

10

Hydride compositions  

DOEpatents

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.

Lee, Myung, W.

1994-01-01

11

Method for refining contaminated iridium  

DOEpatents

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.

Heshmatpour, B.; Heestand, R.L.

1982-08-31

12

Method for refining contaminated iridium  

DOEpatents

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.

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

1983-01-01

13

Hydridomethyl iridium complex  

DOEpatents

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.

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

14

Stable Hydride Meisenheimer Adducts.  

National Technical Information Service (NTIS)

The addition of hydride from octahydrotriborate ion to 1-substituted-2,4,6-trinitrobenzenes affords a stable C3-hydride Meisenheimer adduct. Concurrent with this addition reaction, is hydride displacement of the C1-substituent to form 1,3,5-trinitrobenzen...

L. A. Kaplan A. R. Siedle

1970-01-01

15

Iridium-Catalyzed Allylic Substitution  

Microsoft Academic Search

Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced

John F. Hartwig; Mark J. Pouy

2011-01-01

16

Iridium-Catalyzed Allylic Substitution  

NASA Astrophysics Data System (ADS)

Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced cyclometalation at the methyl group of this substituent to generate an iridium metalacycle bound by the COD ligand of the [Ir(COD)Cl]2 precursor and one additional labile dative ligand. Such complexes catalyze the reactions of linear allylic esters with alkylamines, arylamines, phenols, alcohols, imides, carbamates, ammonia, enolates and enolate equivalents, as well as typical stabilized carbon nucleophiles generated from malonates and cyanoesters. Iridium catalysts for enantioselective allylic substitution have also been generated from phosphorus ligands with substituents bound by heteroatoms, and an account of the studies of such systems, along with a description of the development of iridium catalysts is included.

Hartwig, John F.; Pouy, Mark J.

17

Electrochemical utilization of metal hydrides  

SciTech Connect

The electrochemical utilization of metal hydrides is reviewed. Metal hydrides were investigated for hydrogen storage in nickel hydrogen batteries. The use of hydrides lowered the operating pressures in nickel hydrogen cells, which leads to improved energy density. Metal hydrides used as reversible hydrogen electrodes are discussed. Thermodynamic and kinetic investigations of a variety of hydriding materials are reviewed.

Bittner, H.F.; Badcock, C.C.

1982-04-01

18

IRIDIUM LINER FOR NASA 5 LBF CLASS MATERIAL TEST CHAMBER IRIDIUM LINER FOR ATLANTIC RESEARCH CORPORA  

NASA Technical Reports Server (NTRS)

IRIDIUM LINER FOR NASA 5 LBF CLASS MATERIAL TEST CHAMBER IRIDIUM LINER FOR ATLANTIC RESEARCH CORPORATION 5 LBF CLASS ROCKET CHAMBER 25 LBF CLASS 75 HFC 25 TAC CERAMIC COMPOSITE ROCKET CHAMBER FROM REFRACTURY COMPOSITES INC. PURCHASE ORDER C-551941-

1995-01-01

19

High-pressure synthesis and characterization of iridium trihydride.  

PubMed

We have performed in situ synchrotron x-ray diffraction studies of the iridium-hydrogen system up to 125 GPa. At 55 GPa, a phase transition in the metal lattice from the fcc to a distorted simple cubic phase is observed. The new phase is characterized by a drastically increased volume per metal atom, indicating the formation of a metal hydride, and substantially decreased bulk modulus of 190 GPa (383 GPa for pure Ir). Ab initio calculations show that the hydrogen atoms occupy the face-centered positions in the metal matrix, making this the first known noninterstitial noble metal hydride and, with a stoichiometry of IrH(3), the one with the highest volumetric hydrogen content. Computations also reveal that several energetically competing phases exist, which can all be seen as having distorted simple cubic lattices. Slow kinetics during decomposition at pressures as low as 6 GPa suggest that this material is metastable at ambient pressure and low temperatures. PMID:24313503

Scheler, Thomas; Marqués, Miriam; Konôpková, Zuzana; Guillaume, Christophe L; Howie, Ross T; Gregoryanz, Eugene

2013-11-22

20

Iridium-Catalyzed Allylic Substitution  

Microsoft Academic Search

\\u000a \\u000a Abstract  Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles\\u000a at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand\\u000a possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is\\u000a generated by a base-induced

John F. Hartwig; Mark J. Pouy

21

Hysteresis in Metal Hydrides.  

ERIC Educational Resources Information Center

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)

Flanagan, Ted B., And Others

1987-01-01

22

Ammonia fuel cell with iridium catalyst  

Microsoft Academic Search

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.

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

1973-01-01

23

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

Code of Federal Regulations, 2011 CFR

...platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and...platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium, and...

2011-01-01

24

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

Code of Federal Regulations, 2012 CFR

...platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and...platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...Metals (PGM) are Platinum, Iridium, Palladium, Ruthenium, Rhodium, and...

2012-01-01

25

Enantioselective, Iridium-Catalyzed Monoallylation of Ammonia  

PubMed Central

Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations.

Pouy, Mark J.; Stanley, Levi M.; Hartwig, John F.

2009-01-01

26

Improvements in manufacture of iridium alloy materials.  

National Technical Information Service (NTIS)

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricat...

E. K. Ohriner

1992-01-01

27

MEASURING LATENCY IN IRIDIUM SATELLITE CONSTELLATION DATA SERVICES  

Microsoft Academic Search

Abstract The use of Satellite Communications (SATCOM) has become,essential to operations in both Afghanistan and Iraq. In particular, the Iridium satellite constellation has demonstrated its usefulness and flexibility. It has had significant impact on how operations are conducted. ,Iridium provides users both voice and data services. There are two approaches to sending data over the Iridium network: a circuit-switcheddata service

Margaret M. McMahon; Robert Rathburn

28

Hydride reorientation in Zircaloy4 cladding  

Microsoft Academic Search

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 600wtppm 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

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

2008-01-01

29

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

PubMed

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

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

2013-05-01

30

Iridium-catalyzed arylative cyclization of alkynones by 1,4-iridium migration.  

PubMed

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

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

2014-06-16

31

Method for preparing porous metal hydride compacts  

DOEpatents

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.

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

1981-01-01

32

Hydrogen Outgassing from Lithium Hydride  

SciTech Connect

Lithium hydride is a nuclear material with a great affinity for moisture. As a result of exposure to water vapor during machining, transportation, storage and assembly, a corrosion layer (oxide and/or hydroxide) always forms on the surface of lithium hydride resulting in the release of hydrogen gas. Thermodynamically, lithium hydride, lithium oxide and lithium hydroxide are all stable. However, lithium hydroxides formed near the lithium hydride substrate (interface hydroxide) and near the sample/vacuum interface (surface hydroxide) are much less thermally stable than their bulk counterpart. In a dry environment, the interface/surface hydroxides slowly degenerate over many years/decades at room temperature into lithium oxide, releasing water vapor and ultimately hydrogen gas through reaction of the water vapor with the lithium hydride substrate. This outgassing can potentially cause metal hydriding and/or compatibility issues elsewhere in the device. In this chapter, the morphology and the chemistry of the corrosion layer grown on lithium hydride (and in some cases, its isotopic cousin, lithium deuteride) as a result of exposure to moisture are investigated. The hydrogen outgassing processes associated with the formation and subsequent degeneration of this corrosion layer are described. Experimental techniques to measure the hydrogen outgassing kinetics from lithium hydride and methods employing the measured kinetics to predict hydrogen outgassing as a function of time and temperature are presented. Finally, practical procedures to mitigate the problem of hydrogen outgassing from lithium hydride are discussed.

Dinh, L N; Schildbach, M A; Smith, R A; Balazs1, B; McLean II, W

2006-04-20

33

Insight into the mechanism of carbonyl hydrosilylation catalyzed by Brookhart's cationic iridium(III) pincer complex.  

PubMed

New experimental findings suggest partial revision of the currently accepted mechanism of the carbonyl hydrosilylation catalyzed by the iridium(III) pincer complex introduced by Brookhart. Employing silicon-stereogenic silanes as a stereochemical probe results in racemization rather than inversion of the configuration at the silicon atom. The degree of the racemization is, however, affected by the silane/carbonyl compound ratio, and inversion is seen with excess silane. Independently preparing the silylcarboxonium ion intermediate and testing its reactivity then helped to rationalize that effect. The stereochemical analysis together with these control experiments, rigorous multinuclear NMR analysis, and quantum-chemical calculations clearly prove that another silane molecule participates in the hydride transfer. The activating role of the silane is unexpected but, in fact, vital for the catalytic cycle to close. PMID:24784900

Metsänen, Toni T; Hrobárik, Peter; Klare, Hendrik F T; Kaupp, Martin; Oestreich, Martin

2014-05-14

34

Note: electrochemical etching of sharp iridium tips.  

PubMed

We describe an etching procedure for the production of sharp iridium tips with apex radii of 15-70 nm, as determined by scanning electron microscopy, field ion microscopy, and field emission measurements. A coarse electrochemical etch followed by zone electropolishing is performed in a relatively harmless calcium chloride solution with high success rate. PMID:22129021

Lalanne, Jean-Benoît; Paul, William; Oliver, David; Grütter, Peter H

2011-11-01

35

Osmium-191/iridium-191m radionuclide  

DOEpatents

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.

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

1987-01-01

36

Determining the Altitude of Iridium Flares  

NSDL National Science Digital Library

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.

37

Osmium-191/iridium-191m radionuclide  

DOEpatents

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. 4 figs. 3 tabs.

Knapp, F.F. Jr.; Butler, T.A.; Brihaye, C.

1985-08-26

38

Luminescent Iridium Complexes and Their Applications  

NASA Astrophysics Data System (ADS)

Considerable studies have been made on iridium complexes during the past 10 years, due to their high quantum efficiency, color tenability, and potential applications in various areas. In this chapter, we review the synthesis, structure, and photophysical properties of luminescent Ir complexes, as well as their applications in organic light-emitting diodes (OLEDs), biological labeling, sensitizers of luminescence, and chemosensors.

Liu, Zhiwei; Bian, Zuqiang; Huang, Chunhui

39

Enantioselective iridium-catalyzed allylic arylation.  

PubMed

We describe herein the development of the first iridium-catalyzed allylic substitution using arylzinc nucleophiles. High enantioselectivities were obtained from the reactions, which used commercially available Grignard reagents as the starting materials. This methodology was also shown to be compatible with halogen/metal exchange reactions. Its synthetic potential is demonstrated by its application towards the formal synthesis of (+)-sertraline. PMID:19072966

Polet, Damien; Rathgeb, Xavier; Falciola, Caroline A; Langlois, Jean-Baptiste; El Hajjaji, Samir; Alexakis, Alexandre

2009-01-01

40

Iridium-192 Production for Cancer Treatment  

SciTech Connect

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.

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

2004-10-05

41

A heteroleptic cyclometalated iridium(III) fluorophenylpyridine complex from partial defluorohydrogenation reaction: synthesis, photophysical properties and mechanistic insights.  

PubMed

In this paper, a C-F bond activation reaction of a chloro-bridged iridium(III) dimer (dfppy)(2)Ir(?-Cl)(2)Ir(dfppy)(2) (1) (dfppy denotes 2-(4,6-difluorophenyl)pyridyl) in the presence of sodium methoxide has been reported, leading to the formation of a heteroleptic cyclometalated iridium(III) fluorophenylpyridine complex 2. HPLC-mass analysis confirmed the release of formaldehyde in the product mixture. When sodium benzyloxide was used as the base, complex 2 was also generated with the release of a benzaldehyde derivative. Complex 2 has been fully characterized by (1)H-NMR, (19)F-NMR and X-ray crystallographic methods, confirming the partial loss of one of the fluorine atoms on one of the cyclometalated phenylpyridyl ligands. Photophysical studies of complex 2 show that it has a similar absorption spectrum to that of Ir(III)(dfppy)(3). However, the emission spectrum shows a red shift maximum emission band at 478 nm due to the loss of a single fluorine atom, highlighting the critical effect of fluorine on the photoluminescence of these Ir(III) complexes. Finally, intensive mechanistic studies including HPLC-mass analysis, (1)H-NMR, and (19)F-NMR studies demonstrate that the formation of complex 2 should involve a critical ?-hydride elimination of Ir(III)-alkoxide intermediate and the participation of Ir-hydride and/or Ir-fluoride intermediates. PMID:23348919

Li, Liang; Wu, Feng; Zhang, Songlin; Wang, Dawei; Ding, Yuqiang; Zhu, Zhenzhong

2013-04-01

42

PRODUCTION OF LITHIUM HYDRIDE POWDER  

Microsoft Academic Search

A method for the production of lithium hydride powder is described. ; Lithium carbonate was converted into the chloride. From a saturated solution of ; the chloride lithium amalgam was produced by electrolysis. The lithium amalgam ; was then converted into the hydride by heating the amalgam in a hydrogen ; atmosphere. The apparatus used for the reaction of the

J. Novotny; M. Novotna

1959-01-01

43

Hydrogenation using hydrides and acid  

DOEpatents

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.

Bullock, R. Morris (Wading River, NY)

1990-10-30

44

Dimensionally stable metallic hydride composition  

DOEpatents

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.

Heung, Leung K. (Aiken, SC)

1994-01-01

45

Bonding of xenon hydrides.  

PubMed

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability. PMID:19658392

Pérez-Peralta, Nancy; Juárez, Rosalba; Cerpa, Erick; Bickelhaupt, F Matthias; Merino, Gabriel

2009-09-01

46

Bonding of Xenon Hydrides  

NASA Astrophysics Data System (ADS)

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability.

Pérez-Peralta, Nancy; Juárez, Rosalba; Cerpa, Erick; Bickelhaupt, F. Matthias; Merino, Gabriel

2009-08-01

47

Application of the Iridium Satellite System to Aeronautical Communications  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

48

The Cretaceous/ Tertiary Boundary At Iridium Hill, Garfield County, Montana  

NSDL National Science Digital Library

The goal of this virtual field trip to Iridium Hill, Montana is to investigate the disappearance of dinosaur fossils above the Cretaceous/ Tertiary boundary. The site provides rock outcrop photos of Cretaceous and Tertiary strata (Hell Creek and Fort Union Formations), stratigraphic sections and supporting text for this classic iridium-bearing locality. Topics include the K/T boundary, iridium concentrations, stratigraphy, sedimentology and, fluvial and lacustrine depositional environments.

Limited, Athro

49

Metal hydride heat pump  

NASA Astrophysics Data System (ADS)

The materials, design features, and projected performance of a metal hydride heat pump are explored. Two alloys with hydrogen absorption/desorption (endothermic) properties are included, with the hydrogen being driven back and forth between the two and not consumed. Heat rejected by absorption is rejected by the cold side to the air. When the cold side is full, the pressure differential is reversed and the hydrogen returns to the warm section. Heat in a coolant is used at the cold side to initiate dissociation from the hydride. A test unit providing 3.5.7 kWt of cooling capacity with a source temperature of 200 F and a refrigerated cycle of 40-50 F was built using LaNi5 for the warm side and MMNi4.5FeO.85 on the cold side. Full power was reached in 3-6 min and performance coefficients near .5 were attained. Waste heat, solar and fossil fuel heat sources were identified as viable power supply candidates for refrigeration units requiring 0.5-10.0 tons of capacity.

Rohy, D. A.; Argabright, T. A.; Wade, G. W.

50

A molecular dynamics study on iridium  

NASA Astrophysics Data System (ADS)

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.

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

2007-06-01

51

Iridium silicide nanowires on Si(001) surfaces  

NASA Astrophysics Data System (ADS)

An iridium (Ir) modified silicon (001) (Si(001)) surface is studied using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The surface exhibits p(2 × 2) domains in LEED intensity images. The STM images show that the basis of the crystal lattice consists of an Ir atom and a Si dimer and, like Si(001) dimer rows, they are aligned parallel to the orthogonal [110] directions.

Oncel, Nuri; Nicholls, Dylan

2013-01-01

52

Improvements in manufacture of iridium alloy materials  

Microsoft Academic Search

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecrafts. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of

Evan K. Ohriner

1993-01-01

53

Improvements in manufacture of iridium alloy materials  

Microsoft Academic Search

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTG's). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30 percent

E. K. Ohriner

1992-01-01

54

Improvements in manufacture of iridium alloy materials  

Microsoft Academic Search

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecrafts. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of

Evan K. Ohriner

1993-01-01

55

Iridium-Catalyzed Hydrogenation Using Phosphorus Ligands  

NASA Astrophysics Data System (ADS)

Due to the requirement of obtaining enantiomerically pure products through environmentally friendly technologies, the development of new methods in asymmetric catalysis is becoming an important approach to asymmetric synthesis. Asymmetric hydrogenation is one of the most applied catalytic reactions for the preparation of enantiomerically pure products. Iridium complexes containing phosphorus ligands have been less applied as catalysts in hydrogenation reaction than their corresponding rhodium complexes. On the other hand, most of the iridium complexes used as catalyst in hydrogenation reaction contain phosphorus-nitrogen ligands. However, iridium complexes containing a great variety of mono- and bidentate phosphorus ligands (phosphines, phosphinites, phosphites, phosphoramidites, and the combination of these functionalities) have been applied in hydrogenation reaction with different grades of success. In the early days, diphosphines were the most widely used phosphorus ligands. However, they are generally difficult to synthesize and prone to oxidation. In recent years, chiral phosphites, phosphinites, phosphonites, and phosphoroamidites have emerged as new types of ligands, which present several advantages and high catalytic activity and selectivity. Homogeneous and heterogeneous systems have been studied, allowing the recycling of catalysts. Slight modifications in the electronic and steric properties of the ligands influence the catalytic results, which indicates the potentiality of modular ligands. Imines, including unfunctionalized N-H imines and cyclic imines as quinolines and other substrates, have been transformed in the corresponding chiral amines with ee higher than 95% in many cases. Binol-derived phosphoroamidite constitute one of the most successful ligands in these asymmetric reaction achieving, in some cases, practically total enantioselectivity.

Diéguez, Montserrat; Pàmies, Oscar; Claver, Carmen

56

Hydrogen storage in metal hydrides  

NASA Astrophysics Data System (ADS)

The use of metal hydrides as a hydrogen-storage medium for hydrogen-powered vehicles is discussed. Various metal hydrides are compared by their hydrogen content and energy density, and their suitability as a storage medium is evaluated against a set of criteria, such as ease of formation and decomposition, availability, cost, and safety. Compounds based on iron-titanium hydride are shown to be practical for use in motor vehicles as well as in other applications, including energy storage for peak leveling in electric power systems, compressors, pumps, and air-conditioners.

Reilly, J. J.; Sandrock, G. D.

1980-02-01

57

Erbium hydride decomposition kinetics.  

SciTech Connect

Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

Ferrizz, Robert Matthew

2006-11-01

58

Complex Hydrides for Hydrogen Storage  

SciTech Connect

This report describes research into the use of complex hydrides for hydrogen storage. The synthesis of a number of alanates, (AIH4) compounds, was investigated. Both wet chemical and mechano-chemical methods were studied.

Slattery, Darlene; Hampton, Michael

2003-03-10

59

Variation of iridium in a differentiated tholeiitic dolerite  

USGS Publications Warehouse

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.

Greenland, L. P.

1971-01-01

60

Iridium oxide nanomonitors: Clinical diagnostic devices for health monitoring systems  

Microsoft Academic Search

The objective of this research is to demonstrate the potential of iridium oxide (IrOx) nanowires based device towards detection of proteins that are disease biomarkers. This device is based on electrical detection of protein biomarkers wherein an immunoassay is built onto the iridium oxide nanowires that in turn undergoes specific electrical parameter perturbations during each binding event associated with the

Vinu L. Venkatraman; Ravikiran K. Reddy; Fengyang Zhang; David Evans; Bruce Ulrich; Shalini Prasad

2009-01-01

61

Low density metal hydride foams  

DOEpatents

Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.

Maienschein, Jon L. (Oakland, CA); Barry, Patrick E. (Pleasant Hill, CA)

1991-01-01

62

Iridium enrichment in airborne particles from kilauea volcano: january 1983.  

PubMed

Airborne particulate matter from the January 1983 eruption of Kilauea volcano was inadvertently collected on air filters at Mauna Loa Observatory at a sampling station used to observe particles in global circulation. Analyses of affected samples revealed unusually large concentrations of selenium, arsenic, indium, gold, and sulfur, as expected for volcanic emissions. Strikingly large concentrations of iridium were also observed, the ratio of iridium to aluminum being 17,000 times its value in Hawaiian basalt. Since iridium enrichments have not previously been observed in volcanic emissions, the results for Kilauea suggest that it is part of an unusual volcanic system which may be fed by magma from the mantle. The iridium enrichment appears to be linked with the high fluorine content of the volcanic gases, which suggests that the iridium is released as a volatile IrF(6). PMID:17747384

Zoller, W H; Parrington, J R; Kotra, J M

1983-12-01

63

Fundamental experiments on hydride reorientation in zircaloy  

NASA Astrophysics Data System (ADS)

In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and remain constant in the tensile direction during the second precipitation regime. This could be due to the fact that the face of reoriented hydride platelet is in compression once these platelets have grown to a sufficient size. The second goal of this study was to perform a spatially resolved study of the effect of a stress concentration such as a notch or a crack on hydride reorientation. Using SEM and image analysis, it was found that a sharp crack induces a different hydride microstructure than a blunt notch. In the case of sharp crack, hydrides are more localized and align more with the defect than for blunt notches. The hydride connectivity also increases close to a stress concentration which will assist in crack propagation during DHC. Using TEM, the microstructure of hydrides grown near crack tips were observed to be similar to that of circumferential hydrides grown in the bulk. The orientation relationship studied with SEM and micro-X-ray diffraction was found to be in most cases ?(111)// ?(0002) for hydrides grown both near and far from stress concentrations. Using the same micro-X-ray diffraction technique local hydride and matrix elastic strains were measured and observed to vary significantly from grain to grain. It was however observed that hydrides grown close to the stress concentration are in tension in the face of the platelet, similar to reoriented hydrides, while those grown far from the stress concentration are in tension, similar to circumferential hydrides. The orders of magnitude of the measured strains in the hydrides and the zirconium matrix compared well to those predicted by finite element models. This study shows that it is possible to study hydride dissolution and precipitation in-situ using time-dependent techniques. It was found that the precipitation temperature is lowered by hydride reorientation. The evolution of hydride strains during precipitation was found to be different for unstressed, stressed and reoriented hydrides. The reoriented hydride fraction and connectivity increase with number of cycles which could lead to mor

Colas, Kimberly B.

64

Iridium Interfacial Stack - IrIS  

NASA Technical Reports Server (NTRS)

Iridium Interfacial Stack (IrIS) is the sputter deposition of high-purity tantalum silicide (TaSi2-400 nm)/platinum (Pt-200 nm)/iridium (Ir-200 nm)/platinum (Pt-200 nm) in an ultra-high vacuum system followed by a 600 C anneal in nitrogen for 30 minutes. IrIS simultaneously acts as both a bond metal and a diffusion barrier. This bondable metallization that also acts as a diffusion barrier can prevent oxygen from air and gold from the wire-bond from infiltrating silicon carbide (SiC) monolithically integrated circuits (ICs) operating above 500 C in air for over 1,000 hours. This TaSi2/Pt/Ir/Pt metallization is easily bonded for electrical connection to off-chip circuitry and does not require extra anneals or masking steps. There are two ways that IrIS can be used in SiC ICs for applications above 500 C: it can be put directly on a SiC ohmic contact metal, such as Ti, or be used as a bond metal residing on top of an interconnect metal. For simplicity, only the use as a bond metal is discussed. The layer thickness ratio of TaSi2 to the first Pt layer deposited thereon should be 2:1. This will allow Si from the TaSi2 to react with the Pt to form Pt2Si during the 600 C anneal carried out after all layers have been deposited. The Ir layer does not readily form a silicide at 600 C, and thereby prevents the Si from migrating into the top-most Pt layer during future anneals and high-temperature IC operation. The second (i.e., top-most) deposited Pt layer needs to be about 200 nm to enable easy wire bonding. The thickness of 200 nm for Ir was chosen for initial experiments; further optimization of the Ir layer thickness may be possible via further experimentation. Ir itself is not easily wire-bonded because of its hardness and much higher melting point than Pt. Below the iridium layer, the TaSi2 and Pt react and form desired Pt2Si during the post-deposition anneal while above the iridium layer remains pure Pt as desired to facilitate easy and strong wire-bonding to the SiC chip circuitry.

Spry, David

2012-01-01

65

Proton-induced fission of iridium  

SciTech Connect

The isotopic distribution of rubidium produced in the proton induced fission of iridium has been measured at 68, 85, and 100 MeV incident beam energies using an on-line mass spectrometer with a surface ionization ion source. The deduced neutron multiplicities are substantially higher and show a steeper energy dependence compared to similar measurements done with heavy ion beam in this mass region and in the same range of excitation energies. This might confirm an effect of the angular momentum of the fissioning nucleus on the fragment deexcitation mechanism.

Pathak, B.P.; Lessard, L.; Nikkinen, L.; Lee, J.K.P.

1982-05-01

66

Heat Transfer Enhancement in Metal Hydride Systems.  

National Technical Information Service (NTIS)

The Brookhaven National Laboratory, Department of Energy and Environment has been engaged in finding solutions to the engineering problems associated with the storage of hydrogen as metal hydrides - principally iron-titanium hydride. The thermal conductiv...

M. J. Rosso G. Strickland

1979-01-01

67

Hydride reorientation in Zircaloy-4 cladding  

NASA Astrophysics Data System (ADS)

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.

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

2008-02-01

68

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

PubMed

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

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

2013-10-01

69

Vanadium hydride deuterium-tritium generator  

DOEpatents

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.

Christensen, Leslie D. (Livermore, CA)

1982-01-01

70

Method of producing a chemical hydride  

DOEpatents

A method of producing a chemical hydride is described and which includes selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of a hydrocarbon; and reacting the composition with the source of the hydrocarbon to generate a chemical hydride.

Klingler, Kerry M. (Idaho Falls, ID); Zollinger, William T. (Idaho Falls, ID); Wilding, Bruce M. (Idaho Falls, ID); Bingham, Dennis N. (Idaho Falls, ID); Wendt, Kraig M. (Idaho Falls, ID)

2007-11-13

71

Microcalorimetric studies of the iridium catalyst for hydrazine decomposition reaction  

Microsoft Academic Search

Microcalorimetric studies of H2, NH3 and O2 adsorption, as well as the NH3 decomposition activities evaluation were used to characterize the iridium catalysts for hydrazine decomposition with different supports (Al2O3, SiO2) and iridium contents (1.8, 10.8 and 22.1%). The higher H2 chemisorption amounts on Ir\\/Al2O3 catalysts than those on the corresponding Ir\\/SiO2 counterparts revealed that the strong interaction of iridium

Lin Li; Xiaodong Wang; Xuqun Zhao; Mingyuan Zheng; Ruihua Cheng; Lixing Zhou; Tao Zhang

2005-01-01

72

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

NASA Astrophysics Data System (ADS)

The atomic layer deposition of iridium (Ir) and iridium oxide (IrO2) films was investigated using an alternating supply of (ethylcyclopentadienyl)(1,5-cyclooctadiene) iridium and oxygen gas at temperatures between 230 and 290 °C. The phase transition between Ir and IrO2 occurred at the critical oxygen partial pressure during the oxygen injection pulse. The oxygen partial pressure was controlled by the O2/(Ar+O2) ratio or deposition pressures. The resistivity of the deposited Ir and IrO2 films was about 9 and 120 ?? cm, respectively. In addition, the critical oxygen partial pressure for the phase transition between Ir and IrO2 was increased with increasing the deposition temperature. Thus, the phase of the deposited film, either Ir or IrO2, was controlled by the oxygen partial pressure and the deposition temperature. However, the formation of a thin Ir layer was detected between the IrO2 and SiO2 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 IrO2 films.

Kim, Sung-Wook; Kwon, Se-Hun; Kwak, Dong-Kee; Kang, Sang-Won

2008-01-01

73

Iridium anomaly approximately synchronous with terminal eocene extinctions  

SciTech Connect

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 anomaly associated with the Cretaceous-Tertiary boundary. Other workers have deduced that the microtektites are part of the North American strewn tektite field, which is dated at about 34 million years before present, and that the microtektite horizon in deep-sea cores is synchronous with the extinction of five radiolarian species. Mass extinctions also occur in terrestrial mammals within 4 million years of this time. The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago.

Alvarez, W. (Univ. of California, Berkeley); Asaro, F.; Michel, H.V.; Alvarez, L.W.

1982-05-21

74

Warm Hydroforming of Iridium + 0.3 Wt % Tungsten Hemishells.  

National Technical Information Service (NTIS)

A technique for the production of iridium alloy hemispherical shells to be used for the primary encapsulation of plutonium-238 oxide spheres is described. The encapsulated spheres, 24 per heat source, provide the thermal heat used to drive thermoelectric ...

W. C. Wyder

1976-01-01

75

Scattering effects on the dosimetry of iridium-192  

SciTech Connect

Dosimetry calculations for iridium-192 sources generally assume that a sufficient medium surrounds both the iridium source(s) and the point of calculation so that full scattering conditions exist. In several clinical applications the iridium sources may be anatomically located so that the full scattering requirement is not satisfied. To assess the magnitude of this problem, relative measurements were made with a small ionization chamber in phantoms near air and lung-equivalent interfaces. Dose reduction caused by decreasing the volume of scattering material near these interfaces was then evaluated for a few clinical applications. The results show that reductions on the order of 8% may be expected at the interface with minimal dose reduction within the volume of the implant itself. In addition, the results indicate the verification of source strength of iridium sources in phantom require phantom dimensions determined by the source-chamber separation distance.

Serago, C.F. (Cancer Treatment Center, Baptist Hospital of Miami, Miami, Florida (USA) Department of Radiation Oncology, University of Miami, Miami, Florida (USA)); Houdek, P.V. (Department of Radiation Oncology, University of Miami, Miami, Florida (USA)); Pisciotta, V. (Department of Radiation Oncology, University of Miami, Miami, Florida (USA)); Schwade, J.G. (Department of Radiation Oncology, University of Miami, Miami, Florida (USA)); Abitbol, A.A.; Lewin, A.A. (Cancer Treatment Center, Baptist Hospital of Miami, Miami, Florida (USA) Department of Radiation Oncology, University of Miami, Miami, Florida (USA)); Poole, D.O. (Department of Radiation Oncology, VA Hospital, Miami, Florida (USA)); Marcial-Vega, V. (Cancer Treatment Center, Baptist Hospital of Miami, Miami, Florida (USA))

1991-11-01

76

Performance Analysis of the IRIDIUM Low Earth Orbit Satellite System.  

National Technical Information Service (NTIS)

This thesis provides a performance evaluation of the IRIDIUM Low Earth Orbit Satellite system. It examine's the system's ability to meet real time communications constraints with a degraded satellite constellation. The analysis is conducted via computer s...

C. E. Fossa

1998-01-01

77

GPS/GNSS Interference from Iridium Data Transmitters  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

78

CCMR: New Iridium Complexes for the Dehydrogenation of Alkanes  

NSDL National Science Digital Library

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.

Wang, David

2004-08-17

79

Iridium{reg_sign} worldwide personal communication system  

SciTech Connect

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.}

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

1997-01-01

80

Synthesis and characterization of nitrides of iridium and palladiums  

SciTech Connect

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.

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

2008-08-14

81

Processing and properties of iridium alloys for space power applications  

Microsoft Academic Search

Iridium alloys are used as fuel cladding in radioisotope thermoelectric generators due to their high-melting point, high- temperature strength, and oxidation and corrosion resistance. Although iridium has a face-centered cubic crystal structure, it undergoes a distinct ductile-to-brittle transition characteristic of many body-centered cubic metals. Improved ductility in the alloys is achieved through material purification and controlled alloy additions at the

Ohriner

1994-01-01

82

Iridium alloy clad vent set manufacturing qualification studies  

Microsoft Academic Search

Qualification studies have been successfully conducted to demonstrate iridium alloy Clad Vent Set (CVS) manufacturing readiness for the General Purpose Heat Source (GPHS) program at the Oak Ridge Y-12 Plant. These studies were joint comparison evaluations of both the Y-12 Plant and EG&G Mound G-MAT) products. Note: EG&G-MAT formerly manufactured the iridium alloy CVS. The comparison evaluations involved work in

George B. Ulrich

1991-01-01

83

Microindentation hardness evaluation of iridium alloy clad vent set cups  

Microsoft Academic Search

An iridium alloy, DOP-26, is used as cladding for 238PuO2 fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought\\/ground\\/stress relieved blanks are warm formed into CVS cups. These

George B. Ulrich; Larry F. Deroos; Samuel E. Stinnette

1993-01-01

84

Microindentation hardness evaluation of iridium alloy clad vent set cups  

Microsoft Academic Search

An iridium alloy, DOP-26, is used as cladding for 238PuO2 fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration’s Cassini mission to Saturn. Wrought\\/ground\\/stress relieved blanks are warm formed into CVS cups. These

George B. Ulrich; Larry F. DeRoos; Samuel E. Stinnette

1993-01-01

85

Microindentation hardness evaluation of iridium alloy clad vent set cups  

Microsoft Academic Search

An iridium alloy, DOP-26, is used as cladding for ²³⁸PuO² fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought\\/ground\\/stress relieved blanks are warm formed into CVS cups. These

G. B. Ulrich; L. F. DeRoos; S. E. Stinnette

1992-01-01

86

Microindentation hardness evaluation of iridium alloy clad vent set cups  

Microsoft Academic Search

An iridium alloy, DOP-26, is used as cladding for ²³⁸PuO² fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration`s Cassini mission to Saturn. Wrought\\/ground\\/stress relieved blanks are warm formed into CVS cups. These

G. B. Ulrich; L. F. DeRoos; S. E. Stinnette

1992-01-01

87

Improvements in manufacture of iridium alloy materials  

NASA Astrophysics Data System (ADS)

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecrafts. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

Ohriner, Evan K.

1993-01-01

88

Improvements in manufacture of iridium alloy materials  

SciTech Connect

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecrafts. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

Ohriner, E.K. (Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6083 (United States))

1993-01-15

89

Improvements in manufacture of iridium alloy materials  

NASA Astrophysics Data System (ADS)

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTG's). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30 percent of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10 percent.

Ohriner, E. K.

1992-10-01

90

Proton-induced fission of iridium  

NASA Astrophysics Data System (ADS)

The isotopic distribution of rubidium produced in the proton induced fission of iridium has been measured at 68, 85, and 100 MeV incident beam energies using an on-line mass spectrometer with a surface ionization ion source. The deduced neutron multiplicities are substantially higher and show a steeper energy dependence compared to similar measurements done with a heavy ion beam in this mass region and in the same range of excitation energies. This might confirm an effect of the angular momentum of the fissioning nucleus on the fragment deexcitation mechanism. NUCLEAR REACTIONS, FISSION 191,193Ir(p,f), Ep=68, 85, 100 MeV; measured independent relative yields of Rb. Deduced total number of neutrons emitted in symmetric fission.

Pathak, B. P.; Lessard, L.; Nikkinen, L.; Lee, J. K. P.

1982-05-01

91

Improvements in manufacture of iridium alloy materials  

SciTech Connect

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

Ohriner, E.K.

1992-01-01

92

Improvements in manufacture of iridium alloy materials  

SciTech Connect

Iridium alloys are used as fuel-cladding material in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyager 1 and 2, Galileo, and Ulysses spacecraft. This hardware was fabricated from small, 500-g drop-cast ingots. Porosity in these ingots and the resulting defects in the rolled sheets caused rejection of about 30% of the product. An improved manufacturing process was developed with the goal of substantially reducing the level of defects in the rolled sheets. The ingot size is increased to 10 kg and is produced by vacuum arc remelting. In addition, the ingot is hot extruded prior to rolling. Since implementation of the process in 1989, the average rate of rejection of the product has been reduced to below 10%.

Ohriner, E.K.

1992-08-01

93

Synthesis of a novel anionic hydride organosiloxane presenting biochemical properties  

Microsoft Academic Search

Synthesis of an anionic hydride from monomeric silsesquioxanes is described. The novel compound, dubbed “silica hydride” is the first of several newly synthesized compounds from an interstitially embedded hydride family. It is a hydride-based compound with H? ions interstitially embedded in a matrix of caged silica. This compound exhibits profoundly different characteristics than other known compounds in hydride family. Unlike

Cory J Stephanson; G. Patrick Flanagan

2003-01-01

94

?-Oxido-bis-[hydridotris(tri-methyl-phosphane-?P)iridium(III)](Ir--Ir) bis-(tetra-fluorido-borate) dihydrate  

PubMed Central

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.

Merola, Joseph; Husebo, Trang Le

2014-01-01

95

Rechargeable metal hydrides for spacecraft application  

NASA Technical Reports Server (NTRS)

Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

Perry, J. L.

1988-01-01

96

Radon hydrides: structure and bonding.  

PubMed

Quantum chemical calculations, using gradient-correct density functional at the BP86 level in conjunction with TZ2P basis sets, have been carried out for the radon hydrides HRnY (with Y = F, Cl, Br, I, CCH, CN, and NC). The bonding in HRnY is studied using different bond ruptures, establishing the role of those stabilizing (and destabilizing) factors that prevent these species to be dissociated. Although all HRnY systems studied here are bound equilibrium structures, they are metastable species with respect to the HRnY ? Rn + HY decomposition channel. However, the HRnY ? H + Rn + Y reaction is endothermic. So, these results indicate the possibility to identify the radon hydrides in noble-gas matrices. PMID:21088784

Juarez, Rosalba; Zavala-Oseguera, Claudia; Jimenez-Halla, J Oscar C; Bickelhaupt, F Matthias; Merino, Gabriel

2011-02-14

97

THERMOPHYSICAL PROPERTIES OF ZIRCONIUM HYDRIDE  

Microsoft Academic Search

Thermal conductivity values were determined for three Zr--H alloys ; containing 60.0, 56.6, and 45,3 at.% H, A definite negative coefficiert of ; conductivity was observed for the delta hydride (60.0 at.% H) over the test range ; (300 to 720 deg C). The observed conductivities at the lower hydrogen levels are ; discussed in terms of the phases present,

Beck

1962-01-01

98

Ten degree Kelvin hydride refrigerator  

NASA Technical Reports Server (NTRS)

A compact hydride absorption refrigeration system with few moving parts for 10 Kelvin operation is disclosed and comprises liquid hydrogen producing means in combination with means for solidifying and subliming the liquid hydrogen produced. The liquid hydrogen is sublimed at about 10 Kelvin. By using a symmetrical all hydrogen redundant loop system, a 10 Kelvin refrigeration system can be operated for many years with only a fraction of the power required for prior art systems.

Jones, Jack A. (inventor)

1987-01-01

99

Vanadium hydride deuterium-tritium generator  

DOEpatents

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.

Christensen, L.D.

1980-03-13

100

Inhibited solid propellant composition containing beryllium hydride  

NASA Technical Reports Server (NTRS)

An object of this invention is to provide a composition of beryllium hydride and carboxy-terminated polybutadiene which is stable. Another object of this invention is to provide a method for inhibiting the reactivity of beryllium hydride toward carboxy-terminated polybutadiene. It was found that a small amount of lecithin inhibits the reaction of beryllium hydride with the acid groups in carboxy terminated polybutadiene.

Thompson, W. W. (inventor)

1978-01-01

101

Lightweight hydrides for automotive storage of hydrogen  

NASA Astrophysics Data System (ADS)

The primary objectives of the considered investigations are related to the reduction of the dissociation temperature of lightweight materials, and the development of new lightweight hydrides containing little, if any, critical material. Attention is given to the characteristics of metal hydrides, the characteristics of a magnesium-base alloy which is to be employed in hydrogen storage systems for automobiles, aspects of alloy development, and the evaluation of magnesium hydride alloys with the aid of a hydride cycling rig. New information concerning the effect of cycling on magnesium alloys is discussed.

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

102

Synthesis and reactivity of rhodium and iridium alkene, alkyl and silyl complexes supported by a phenyl-substituted PNP pincer ligand.  

PubMed

New rhodium and iridium complexes supported by the phenyl-substituted PNP pincer ligand PNPPhH (HN(2-PPh2-4-Me-C6H3)2) (1) were synthesized. The reaction of 2 equiv. of 1 with [(COD)IrCl]2 afforded the coordination complex [(PNPPhH)Ir(COD)]Cl (2) featuring hydrogen bonding between the N–H group and the chloride anion, as characterized by NMR spectroscopy and X-ray crystallography. Reaction of 1 with [(COE)2IrCl]2 or [(COE)2RhCl]2 in benzene provided a mixture of complexes including (PNPPhH)MHCl2 (M = Ir (4), M = Rh (7)) and (PNP)M(COE) (M = Ir (5), M = Rh (8)). Alkene complexes of the type (PNPPh)M(L) (M = Ir, L = COD (3) and COE (5); M = Rh, L = COE (8) and L = ethylene (9)) were synthesized by reaction of (PNPPh)Li with the appropriate alkene chloride complexes. Reactions of silanes with 5, 8 or 9 produced silyl hydride complexes (PNPPh)MH(SiR3) (M = Ir, R = Ph (16) and R = Et (17); M = Rh, R = Ph (18), Et (19) and Ph2Cl (20)) via Si–H oxidative addition. The JSiH coupling constants for rhodium complexes 18, 19 and 20 were determined to be ca. 35 Hz, while iridium complexes 16 and 17 exhibited coupling constants less than 10 Hz. X-Ray crystal structures of 16 and 18 reveal isostructural complexes featuring a trigonal bipyramidal geometry about iridium with a mer binding of the PNPPh ligand. A hydride ligand, located from the Fourier map for 18, has a short contact of 1.83(3) Å with the silicon atom. Oxidative addition of iodomethane to 5 and 8 afforded (PNPPh)M(Me)(I)(THF) (M = Rh (14), M = Ir (12)), respectively. Arene C–H activation upon thermolysis of 12 in benzene produced (PNPPh)M(Ph)(I)(THF). Iridium silyl iodide complexes (PNPPh)IrI(SiR3) (SiR3 = SiPh3 (21), SiH2Mes (22) and SiH2Xyl (23)) resulted from addition of organosilanes to 12, via elimination of CH4. PMID:20401366

Calimano, Elisa; Tilley, T Don

2010-10-21

103

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

Ferrizz, Robert Matthew

2007-08-01

104

Activated aluminum hydride hydrogen storage compositions and uses thereof  

DOEpatents

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.

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

2010-11-23

105

mer-Hydridotris(tri-methyl-phosphane-?P)(d-valinato-?(2) N,O)iridium hexa-fluorido-phosphate di-chloro-methane 0.675-solvate.  

PubMed

The title compound, [Ir(C5H10NO2)H(C3H9P)3]PF6·0.675CH2Cl2, an iridium compound with a meridional arrangement of PMe3 groups, O,N-bidentate coordination of d-valine and with a hydride ligand trans to the N atom is compared with the l-valine complex reported previously. As expected, the complexes from the corresponding l and d isomers of valine crystallize in enanti-omorphic space groups (P43 and P41, respectively). In the crystal, N-H?O and N-H?F hydrogen bonding is observed, the N-H to carbonyl oxygen hydrogen bond producing a helical motif that proceeds along the 41 screw of the c axis. PMID:24764947

Merola, Joseph S; Slebodnick, Carla; Berg, Michael; Ritchie, Melissa K

2014-03-01

106

Hydrogen-storing hydride complexes  

DOEpatents

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.

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

2012-04-10

107

Interstellar Hydride Spectroscopy with Herschel  

NASA Astrophysics Data System (ADS)

The Herschel satellite is now giving access with unprecedented sensitivity to the THz spectral range. In particular ground state lines of simple neutral and ionized hydrides have been detected in a wide range of interstellar environments, leading to a renewed understanding of the formation processes of interstellar molecules in the diffuse interstellar medium. In this talk, I will present recent results obtained with the Herschel HIFI and PACS instruments on the carbon, oxygen and nitrogen hydrides. I will discuss how CH and HF can be used as tracers of molecular hydrogen in the diffuse interstellar matter, the new diagnostic capabilities of the cosmic ray ionization rate opened by the OH^+ and H_2O^+ molecular ions, and the role of the dissipation of turbulence in the production of the CH^+ and SH^+ reactive ions. Figure 1: Example of Herschel/HIFI spectra towards the massive star forming region G10.6--0.4. The diffuse interstellar matter along the line of sight towards this massive object is producing multiple absortion features from ˜ 6 to˜ 50 km/s while the emission or absortion signals between -20 to 5 km/s are caused by the massive source itself.

Gerin, Maryvonne

2011-06-01

108

The Iridium (tm) system: Personal communications anytime, anyplace  

NASA Technical Reports Server (NTRS)

The Iridium system is designed to provide handheld personal communications between diverse locations around the world at any time and without prior knowledge of the location of the personal units. This paper provides an overview of the system, the services it provides, its operation, and an overview of the commercial practices and relatively high volume satellite production techniques which will make the system cost effective. A constellation of 66 satellites will provide an orbiting, spherical-shell, infrastructure for this global calling capability. The satellites act as tall cellular towers and allow convenient operation for portable handheld telephones. The system will provide a full range of services including voice, paging, data, geolocation, and fax capabilities. Motorola is a world leader in the production of high volume, high quality, reliable telecommunications hardware. One of Iridium's goals is to apply these production techniques to high reliability space hardware. Concurrent engineering, high performance work teams, advanced manufacturing technologies, and improved assembly and test methods are some of the techniques that will keep the Iridium system cost effective. Mobile, global, flexible personal communications are coming that will allow anyone to call or receive a call from/to anyplace at anytime. The Iridium system will provide communications where none exist today. This connectivity will allow increased information transfer, open new markets for various business endeavors, and in general increase productivity and development.

Hatlelid, John E.; Casey, Larry

1993-01-01

109

pH Sensors Based on Iridium Oxide.  

National Technical Information Service (NTIS)

Results are presented on the pH-potential response of d.c. 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 ...

M. J. Tarlov K. G. Kreider S. Semancik P. Huang

1990-01-01

110

Atropisomerism in a thermally switchable, cyclometallated iridium complex.  

PubMed

Two stable diastereomeric atropisomers of a cyclometallated iridium complex containing a pyrene functionalized pyridine imine ligand have been isolated. These are the first fully characterized examples of metal containing atropisomers in which the rotational axis is not between two chelating atoms. The atropisomers can be converted thermally via a rocking motion of the pyrene moiety. PMID:22801383

Howarth, Ashlee J; Davies, David L; Lelj, Francesco; Wolf, Michael O; Patrick, Brian O

2012-09-14

111

Rockot Launch Vehicle Commercial Operations for Grace and Iridium Program  

Microsoft Academic Search

The GRACE mission and the IRIDIUM mission on ROCKOT launch vehicle are presented. Two identical GRACE satellites to measure in tandem the gravitational field of the earth with previously unattainable accuracy - it's called the Gravity Research and Climate Experiment, or and is a joint project of the U.S. space agency, NASA and the German Centre for Aeronautics and Space

Y. Viertel; M. Kinnersley; I. Schumacher

2002-01-01

112

Iridium alloy clad vent set manufacturing qualification studies  

SciTech Connect

In 1987 the Department of Energy-Office of Special Applications (DOE-OSA) decided to transfer the iridium alloy Clad Vent Set (CVS) manufacturing for the General Purpose Heat Source (GPHS) program from EG G Mound Applied Technologies, Inc. (EG G-MAT) to the Oak Ridge Y-12 Plant operated by Martin Marietta Energy Systems, Inc. (Energy Systems). The reason for this transfer was to consolidate the GPHS program iridium hardware manufacturing. The CVS starting stock of iridium powder, foil, and blanks were already being manufactured at another Energy Systems facility - the Oak Ridge National Laboratory (ORNL). Since 1987 CVS manufacturing technology transfer efforts have taken place between EG G-MAT and Energy Systems. EG G-MAT retained all of their tooling, but they supplied all the necessary product drawings, specifications, and procedures, as well as their tooling drawings. Most of the tooling designs and processing steps were duplicated at the Y-12 Plant. Minor changes were required in both tooling design and processing steps, to accommodate particular health, safety, environmental, and manufacturing requirements at the Y-12 Plant. In order to evaluate the effects of the key Y-12 Plant processing modifications, four joint Y-12 Plant/EG G-MAT iridium CVS manufacturing qualification studies were organized. The successful completion of these studies allowed the Y-12 Plant to commence pilot production of CVS components for the CRAF and CASSINI missions. The CVS cup metallurgical qualification work will be presented here.

Ulrich, G.B.

1990-06-15

113

Iridium alloy Clad Vent Set manufacturing qualification studies  

Microsoft Academic Search

Metallurgical qualification studies to demonstrate the manufacturing readiness of the iridium alloy Clad Vent Set (CVS) for the General Purpose Heat Source program at the Oak Ridge Y-12 Plant are described. Microstructural data for various materials\\/test conditions are presented.

George B. Ulrich

1991-01-01

114

Utilization of Low Bandwidth Iridium Modems for Polar Seismology  

NASA Astrophysics Data System (ADS)

Transmission of realtime seismic data is a desirable goal when a rapid response is needed. However, for many science applications sample waveform data, system state of health, and the ability to command and control the seismic station are operationally adequate. Determining the optimal telemetry requirements for a remote polar seismic experiment requires balancing science objective against the expensive, over-subscribed support available in the polar environments? For example there is a significant difference in the resources needed for a permanent "monitoring" effort versus a short-term experiment. We will describe IRIS/PASSCAL's successful approach to utilizing Iridium telemetry for short-term seismic experiments and suggest viable use of an Iridium RUDICs system for higher data-rate, permanent seismic stations such as a monitoring scenario. Most seismic stations are configured to record at a rate that exceeds twice the data rate of a single Iridium Internet modem. The power requirement to run continuous Iridium telemetry better than doubles that of a standalone seismic station. Doubling station power roughly doubles station logistics by requiring an increased number of support flights for installation and service. The tradeoffs between desirable and adequate telemetry requirements and the ramifications these requirements have on support services must be considered for a successful seismic station. We describe two Iridium telemetry systems, developed by the IRIS/PASSCAL Polar Program, for use with seismic stations in Antarctica and the Arctic. The first system uses an inexpensive Iridium 9602 modem based device and short burst data (SBD) transmission to monitor station performance, provide some command and control, and return a small amount of representative seismic data. Power requirements for this SBD system are approximately 10Ah per year for a daily message. The second system uses an Iridium 9522b modem based device the DOD RUDICs system for a 2400 Baud Internet connection. Returning 1 megabyte of data per day requires approximately 1Ah and can return all of the low sample rate (1sps) seismic data and the SOH data each day.

Parker, T.

2012-12-01

115

Liquid suspensions of reversible metal hydrides  

DOEpatents

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.

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

1983-12-08

116

Hydride heat pump with heat regenerator  

NASA Technical Reports Server (NTRS)

A regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided. Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

Jones, Jack A. (Inventor)

1991-01-01

117

Study of Titanium Hydride Destabilized Lithium Aluminum Hydride as a Promising Hydrogen Storage System  

NASA Astrophysics Data System (ADS)

Destabilized hydrides are a class of hydrogen storage systems whereby the theoretical hydrogen desorption temperature is reduced owing to the formation of a stable product phase which is typically comprised of cations from the destabilizer and the hydride phase. This work examines the hydrogen desorption temperatures for a mixture of titanium hydride (TiH2) (as a destabilizer) and lithium aluminum hydride (LiAlH4). X-ray diffraction (XRD) and temperature programmed desorption (TPD) were used to confirm the onset of desorption at temperatures as low as 75 deg C. The thermodynamic phase diagram corresponding to the mixed system will be presented and a reaction mechanism is suggested.

Smith, Troy; Dobbins, Tabbetha

2013-03-01

118

Thermocompressor or Heat Pump Using Metal Hydrides.  

National Technical Information Service (NTIS)

Metallic hydrides present interesting prospects for use in hydrogen storage and in thermodynamic sorption-desorption cycle machines. First the state of art of work at national and international level are exposed. The technical study leads to the choice of...

M. Blondeau M. Bonneton M. Jannot

1981-01-01

119

Method of forming metal hydride films  

NASA Technical Reports Server (NTRS)

The substrate to be coated (which may be of metal, glass or the like) is cleaned, both chemically and by off-sputtering in a vacuum chamber. In an ultra-high vacuum system, vapor deposition by a sublimator or vaporizer coats a cooled shroud disposed around the substrate with a thin film of hydride forming metal which getters any contaminant gas molecules. A shutter is then opened to allow hydride forming metal to be deposited as a film or coating on the substrate. After the hydride forming metal coating is formed, deuterium or other hydrogen isotopes are bled into the vacuum system and diffused into the metal film or coating to form a hydride of metal film. Higher substrate temperatures and pressures may be used if various parameters are appropriately adjusted.

Steinberg, R.; Alger, D. L.; Cooper, D. W. (inventors)

1977-01-01

120

Vinylmercury Hydrides: Synthesis and Spectroscopic Characterization.  

PubMed

The first vinylmercury hydrides, and among them the parent compound, have been prepared by a chemoselective reduction of the corresponding vinylmercury chlorides with tributylstannane in the presence of a radical inhibitor. These hydrides have been characterized on the basis of their spectral data ((1)H, (13)C, and (199)Hg NMR spectroscopy and mass spectrometry). The photoelectron spectra of the ethenylmercury hydride displays bands at 9.79, 10.13, 11.41, and 13.20 eV. On the basis of photoelectron spectra and ab initio quantum chemical calculations some (d-p)pi interaction between the vinyl pi-system and the mercury d-orbitals could be concluded. Vinylmercury hydrides have been condensed and then revaporized in vacuum at low temperature, but they exhibit a very low stability at room temperature even diluted in toluene (tau(1/2) approximately 1 min); elemental mercury and the corresponding divinylmercury were formed under these conditions. PMID:11666808

Guillemin, Jean-Claude; Bellec, Nathalie; Szétsi, Sándor Kis; Nyulászi, László; Veszprémi, Tamás

1996-10-23

121

Characterization and Evaluation of Light Metal Hydrides.  

National Technical Information Service (NTIS)

Evaluation of a light metal hydride in CMDB propellants was continued. Distinct improvements in processibility were observed with recent batch production lots. By contrast, the laboratory scale continuous process to-date has produced a material that is mo...

W. E. Baumgartner G. E. Myers W. S. Baker Y. A. Tajima

1967-01-01

122

Modular hydride beds for mobile applications.  

National Technical Information Service (NTIS)

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 inten...

M. E. Malinowski K. D. Stewart

1997-01-01

123

In?Situ Observation of Surface Species on Iridium Oxide Nanoparticles during the Oxygen Evolution Reaction.  

PubMed

An iridium oxide nanoparticle electrocatalyst under oxygen evolution reaction conditions was probed in?situ by ambient-pressure X-ray photoelectron spectroscopy. Under OER conditions, iridium undergoes a change in oxidation state from Ir(IV) to Ir(V) that takes place predominantly at the surface of the catalyst. The chemical change in iridium is coupled to a decrease in surface hydroxide, providing experimental evidence which strongly suggests that the oxygen evolution reaction on iridium oxide occurs through an OOH-mediated deprotonation mechanism. PMID:24889896

Sanchez Casalongue, Hernan G; Ng, May Ling; Kaya, Sarp; Friebel, Daniel; Ogasawara, Hirohito; Nilsson, Anders

2014-07-01

124

Water-soluble iridium phosphorescent complexes for OLED applications  

NASA Astrophysics Data System (ADS)

Newly prepared water-soluble iridium phosphorescent complexes, trans-[Ir(ppy)(PAr3)2(H)L]0,+ (ppy = bidentate 2-phenylpyridinato anionic ligand; L= Cl (1), CO (2), CN- (3); H being trans to the nitrogen of ppy ligand; PAr3 (TPPTS) = P(m-C6H4SO3Na)3), have been synthesized and characterized. Those complexes containing water-soluble phosphine ligands can emit any color region as altering cyclometalated ligands in aqueous media with high quantum efficiencies. Even though these water-soluble phosphorescent iridium complexes can be the sensing probe for toxic CO gas and CN anion, they will be capable of promising materials in the solution processible OLED applications.

Eum, Min-Sik; Yoon, Heekoo; Kim, Tae Hyung

2012-09-01

125

Processing and properties of iridium alloys for space power applications  

SciTech Connect

Iridium alloys are used as fuel cladding in radioisotope thermoelectric generators due to their high-melting point, high- temperature strength, and oxidation and corrosion resistance. Although iridium has a face-centered cubic crystal structure, it undergoes a distinct ductile-to-brittle transition characteristic of many body-centered cubic metals. Improved ductility in the alloys is achieved through material purification and controlled alloy additions at the parts per million (ppm) level. A vacuum arc remelt operation produces a nearly defect-free casting, which is further processed to sheet products. A change in processing from drop castings of small arc-melted buttons to large arc-remelted ingots has substantially improved product yields. The effects of processing changes on alloy microstructure, sheet textures, oxidation effects, high-strain-rate ductility, and fabricability are discussed.

Ohriner, E.K.

1994-12-31

126

Network flexibility of the IRIDIUM (R) Global Mobile Satellite System  

NASA Technical Reports Server (NTRS)

The IRIDIUM system is a global personal communications system supported by a constellation of 66 low earth orbit (LEO) satellites and a collection of earth-based 'gateway' switching installations. Like traditional wireless cellular systems, coverage is achieved by a grid of cells in which bandwidth is reused for spectral efficiency. Unlike any cellular system ever built, the moving cells can be shared by multiple switching facilities. Noteworthy features of the IRIDIUM system include inter-satellite links, a GSM-based telephony architecture, and a geographically controlled system access process. These features, working in concert, permit flexible and reliable administration of the worldwide service area by gateway operators. This paper will explore this unique concept.

Hutcheson, Jonathan; Laurin, Mala

1995-01-01

127

Iridium alloy clad vent set manufacturing qualification studies  

SciTech Connect

Qualification studies have been successfully conducted to demonstrate iridium alloy Clad Vent Set (CVS) manufacturing readiness for the General Purpose Heat Source (GPHS) program at the Oak Ridge Y-12 Plant. These studies were joint comparison evaluations of both the Y-12 Plant and EG G Mound Applied Technologies, Inc. (EG G-MAT) products. Note: EG G-MAT formerly manufactured the iridium alloy CVS. The comparison evaluations involved work in a number of areas; however, only the CVS cup metallurgical evalution will be presented here. The initial metallurgical comparisons in conjunction with follow-up metallurgical work showed the Y-12 Plant CVS product to be comparable to the fully qualified (for Galileo and Ulysses missions) EG G-MAT product. This allowed the Y-12 Plant to commence pilot production of CVS components for potential use in the CRAF and CASSINI missions.

Ulrich, G.B. (Oak Ridge Y-12 Plant, P.O. Box 2009, Oak Ridge, Tennessee (USA))

1991-01-10

128

Sputtered platinum-iridium as catalyst for hydrogen fuel cells  

Microsoft Academic Search

Co-sputtered platinum-iridium films were deposited and tested as catalysts for an application in hydrogen fuel cells. The morphological and electrochemical investigation of samples with different ratios of both metals revealed that by systematic varying of the components content it is possible to obtain PtIr alloy with optimal composition ensuring high catalytic activity at reduced noble metal loading. Among the tested

G. Ganske; G. Topalov; E. Slavcheva; W. Mokwa; U. Schnakenberg

2009-01-01

129

Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

130

Chronic neural stimulation with thin-film, iridium oxide electrodes  

Microsoft Academic Search

Experiments were conducted to assess the effect of chronic stimulation on the electrical properties of the electrode-tissue system, as measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Silicon, micromachined probes with multiple iridium oxide stimulating electrodes (400-1600 ?m2) were implanted in guinea pig cortex. A 10-17 day post-operative recovery period was followed by five days of monopolar stimulation,

James D. Weiland; David J. Anderson

2000-01-01

131

Iridium-silicide nanowires on Si(001) surface  

NASA Astrophysics Data System (ADS)

Iridium (Ir) modified Silicon (Si) (001) surface is studied with low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The surface exhibits p(2x2) domains on LEED intensity images. The STM images show that the basis of the crystal lattice is consists of an Ir atom and a Si dimer and similar to Si(001) dimer rows, they are aligned parallel to the [110] orthogonal directions.

Nicholls, Dylan; Oncel, Nuri

2013-03-01

132

Analysis of Abrasive Blasting of DOP26 Iridium Alloy  

Microsoft Academic Search

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

Evan Keith Ohriner; Wei Zhang; George B Ulrich

2012-01-01

133

Iridium Oxide Nanomonitors for Real-time Health Monitoring Systems  

Microsoft Academic Search

An innovative lab-on-a-chip device based on iridium oxide (IrOx) nanowires was designed, fabricated, and developed for real-time “point-of-care” diagnostics. The turnaround time in detection and the need for expensive equipment for analysis have considverably limited rapid and “point-of-care” diagnosis. This research demonstrates the potential of IrOx nanowires toward early disease diagnosis by detecting proteins that are disease markers. The device

Vinu L. Venkatraman; Fengyan Zhang; David Evans; Bruce Ulrich; Shalini Prasad

2009-01-01

134

Iridium oxide nanomonitors: clinical diagnostic devices for health monitoring systems.  

PubMed

The objective of this research is to demonstrate the potential of iridium oxide (IrOx) nanowires based device towards detection of proteins that are disease biomarkers. This device is based on electrical detection of protein biomarkers wherein an immunoassay is built onto the iridium oxide nanowires that in turn undergoes specific electrical parameter perturbations during each binding event associated with the immunoassay. Detection of two inflammatory proteins C-reactive protein (CRP) and Myeloperoxidase (MPO) that are biomarkers of cardiovascular diseases is demonstrated. The performance metrics of the device in response to the two biomarkers in pure form and in serum samples were evaluated and compared to standard ELISA assays. The methodology that has been adopted is based on measuring impedance and calibrating its change in magnitude with concentration of proteins. We demonstrate the following performance metrics: limits of detection up to 1 ng/ml for CRP and 500 pg/ml for MPO in pure and serum samples; linear dynamic range of detection from 10 ng/ml to 100 microg/ml for CRP and 1 ng/ml to 1 microg/ml for MPO and cross-reactivity contained at less than 10% of selective binding for both the inflammatory proteins. Iridium oxide has an ability to detect very small changes to the surface charge and this capability is utilized for achieving the performance metrics and forms the basis of the key innovations of this technology, which are, improving the selectivity and sensitivity of detection. PMID:19403299

Venkatraman, Vinu L; Reddy, Ravikiran K; Zhang, Fengyang; Evans, David; Ulrich, Bruce; Prasad, Shalini

2009-06-15

135

Hydride fuel behavior in LWRs  

NASA Astrophysics Data System (ADS)

The U-Zr hydride U 0.31ZrH 1.6 offers a number of advantages over oxide fuel for light-water reactors. Fission-gas release appears to be very small (release fraction ˜10 -4) up to 600 °C, which is close to the maximum fuel temperature. Initial irradiation-induced swelling can be as large as 5% for temperatures exceeding 650 °C. Hydrogen redistributes due to the non-uniform temperature in the fuel from the as-fabricated H/Zr of 1.6 to one that is higher at the pellet periphery than at the centerline. Radial redistribution produces 'hydrogen' stresses in the pellet which add to the usual thermal stresses. In a helium-bonded fuel rod, the total stresses are less than the fracture stress; in a liquid-metal-bonded fuel rod, the fracture stress is exceeded in the central portion of the pellet, but the surface remains in compression. Axial redistribution moves substantial quantities of hydrogen from the middle portion of the fuel stack to the ends. The neutronic effect of this displacement of the moderator is unknown.

Olander, Donald R.; Ng, Marowen

2005-11-01

136

Rockot Launch Vehicle Commercial Operations for Grace and Iridium Program  

NASA Astrophysics Data System (ADS)

The GRACE mission and the IRIDIUM mission on ROCKOT launch vehicle are presented. Two identical GRACE satellites to measure in tandem the gravitational field of the earth with previously unattainable accuracy - it's called the Gravity Research and Climate Experiment, or and is a joint project of the U.S. space agency, NASA and the German Centre for Aeronautics and Space Flight, DLR. In order to send the GRACE twins into a 500x500 km , 89deg. orbit, the Rockot launch vehicle was selected. A dual launch of two Iridium satellites was scheduled for June 2002 using the ROCKOT launch vehicle from Plesetsk Cosmodrome in Northern Russia. This launch will inject two replacement satellites into a low earth orbit (LEO) to support the maintenance of the Iridium constellation. In September 2001, Eurockot successfully carried out a "Pathfinder Campaign" to simulate the entire Iridium mission cycle at Plesetsk. The campaign comprised the transport of simulators and related equipment to the Russian port-of-entry and launch site and also included the integration and encapsulation of the simulators with the actual Rockot launch vehicle at Eurockot's dedicated launch facilities at Plesetsk Cosmodrome. The pathfinder campaign lasted four weeks and was carried out by a joint team that also included Khrunichev, Russian Space Forces and Eurockot personnel on the contractors' side. The pathfinder mission confirmed the capability of Eurockot Launch Services to perform the Iridium launch on cost and on schedule at Plesetsk following Eurockot's major investment in international standard preparation, integration and launch facilities including customer facilities and a new hotel. In 2003, Eurockot will also launch the Japanese SERVI'S-1 satellite for USEF. The ROCKOT launch vehicle is a 3 stage liquid fuel rocket whose first 2 stages have been adapted from the Russian SS-19. A third stage, called "Breeze", can be repeatedly ignited and is extraordinarily capable of manoeuvre. Rockot can place payloads of up to 1900 kilograms in near- earth orbit. The rocket is 29 meters long with a diameter of 2.5 meters. The launch weight is about 107 tons. Satellite launches with Rockot are a service offered and carried out by Eurockot Launch Service GmbH. It is a European Russian joint venture which is 51% controlled by Astrium and 49 % by Khrunichev, Russia's leading launch vehicle firm. The Rockot vehicles can be launched from Plesetsk in northern Russia and Baikonur in Kazakhstan. EUROCKOT provides a wide choice of flight-proven adapters and multi-satellite platforms to the customer to allow such payloads to be accommodated. These range from the Russian Single Pyro Point Attachment System (SPPA)

Viertel, Y.; Kinnersley, M.; Schumacher, I.

2002-01-01

137

Hydriding of Titanium Cones for a Sputter-Ion Source.  

National Technical Information Service (NTIS)

A technique for producing negative ions of hydrogen, deuterium, tritium from a sputter-ion source by sputtering hydrided titanium in the source. The hydridation of the titanium is described. (ERA citation 03:038387)

J. C. Gursky B. A. Sherwood

1978-01-01

138

The IEA\\/DOE\\/SNL on-line hydride databases  

Microsoft Academic Search

.   A series of comprehensive hydride databases have been constructed and made freely available on the Internet (URL http:\\/\\/hydpark.ca.sandia.gov).\\u000a They include extensive listings of alloys reported to hydride, detailed engineering properties on selected hydrogen-storage\\u000a elements and alloys and a hydride-applications database. These databases and an associated reference database are described,\\u000a along with other hydride information available on the web site.

G. Sandrock; G. Thomas

2001-01-01

139

Hydride formation in an Al-Li-Cu alloy  

SciTech Connect

A hydride phase, LiAlH4, is identified in Al-2.0Li-2.2Cu alloy electrochemically charged with hydrogen. The orientation relationship of the hydride and the matrix has been determined and rationalized with the O-lattice theory. The thermodynamic stability of the hydride is discussed and possible formation mechanisms explained. The hydride forms from the grain-boundary phase AlLi. 41 refs.

Balasubramaniam, R.; Duquette, D.J.; Rajan, K. (Rensselaer Polytechnic Institute, Troy, NY (USA))

1991-11-01

140

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

PubMed Central

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.

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

141

Investigation of metal hydride nanoparticles templated in metal organic frameworks  

Microsoft Academic Search

Hydrogen is proposed as an ideal carrier for storage, transport, and conversion of energy. However, its storage is a key problem in the development of hydrogen economy. Metal hydrides hold promise in effectively storing hydrogen. For this reason, metal hydrides have been the focus of intensive research. The chemical bonds in light metal hydrides are predominantly covalent, polar covalent or

Benjamin W. Jacobs; Julie L. Herberg; Aaron M. Highley; Jeffrey Grossman; Lucas Wagner; Raghu Bhakta; D. Peaslee; Mark D. Allendorf; X. Liu; Behrens Richard Jr; Eric H. Majzoub

2010-01-01

142

Mechanistically Driven Development of Iridium Catalysts for Asymmetric Allylic Substitution  

PubMed Central

Conspectus Enantioselective allylic substitution reactions comprise some of the most versatile methods for preparing enantiomerically enriched materials. These reactions form products that contain multiple functionalities by creating carbon–nitrogen, carbon–oxygen, carbon–carbon, and carbon–sulfur bonds. For many years, the development of catalysts for allylic substitution focused on palladium complexes. However, studies of complexes of other metals have revealed selectivities that often complement those of palladium systems. Most striking is the observation that reactions with unsymmetrical allylic electrophiles that typically occur with palladium catalysts at the less hindered site of an allylic electrophile occur at the more hindered site with catalysts based on other metals. In this Account, we describe an iridium precursor and a phosphoramidite ligand that catalyze reactions with a particularly broad scope of nucleophiles. The active form of this iridium catalyst is not generated by the simple binding of the phosphoramidite ligand to the metal precursor. Instead, the initial phosphoramidite and iridium precursor react in the presence of base to form a metallacyclic species that is the active catalyst. This species is generated either in situ or separately in isolated form by reactions with added base. The identification of the structure of the active catalyst led to the development of simplified catalysts as well as the most active form of the catalyst now available, which is stabilized by a loosely bound ethylene. Most recently, this structure was used to prepare intermediates containing allyl ligands, the structures of which provide a model for the enantioselectivities discussed here. Initial studies from our laboratory on the scope of iridium-catalyzed allylic substitution showed that reactions of primary and secondary amines, including alkylamines, benzylamines, and allylamines, and reactions of phenoxides and alkoxides occurred in high yields, with high branched-to-linear ratios and high enantioselectivities. Parallel mechanistic studies had revealed the metallacyclic structure of the active catalyst, and subsequent experiments with the purposefully formed metallacycle increased the reaction scope dramatically. Aromatic amines, azoles, ammonia, and amides and carbamates as ammonia equivalents all reacted with high selectivities and yields. Moreover, weakly basic enolates (such as silyl enol ethers) and enolate equivalents (such as enamines) also reacted, and other research groups have used this catalyst to conduct reactions of stabilized carbon nucleophiles in the absence of additional base. One hallmark of the reactions catalyzed by this iridium system is the invariably high enantioselectivity, which reflects a high stereoselectivity for formation of the allyl intermediate. Enantioselectivity typically exceeds 95%, regioselectivity for formation of branched over linear products is usually near 20:1, and yields generally exceed 75% and are often greater than 90%. Thus, the development of iridium catalysts for enantioselective allylic substitution shows how studies of reaction mechanism can lead to a particularly active and a remarkably general system for an enantioselective process. In this case, a readily accessible catalyst effects allylic substitution, with high enantioselectivity and regioselectivity complementary to that of the venerable palladium systems.

Hartwig, John F.; Stanley, Levi M.

2010-01-01

143

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

144

Measurements of the hard-x-ray reflectivity of iridium  

SciTech Connect

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.

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

2007-01-10

145

The solubility of hydrogen in rhodium, ruthenium, iridium and nickel.  

NASA Technical Reports Server (NTRS)

The temperature variation of the solubility of hydrogen in rhodium, ruthenium, iridium, and nickel in equilibrium with H2 gas at 1 atm pressure has been measured by a technique involving saturating the solvent metal with hydrogen, quenching, and analyzing in resultant solid solutions. The solubilities determined are small (atom fraction of H is in the range from 0.0005 to 0.00001, and the results are consistent with the simple quasi-regular model for dilute interstitial solid solutions. The relative partial enthalpy and excess entropy of the dissolved hydrogen atoms have been calculated from the solubility data and compared with well-known correlations between these quantities.

Mclellan, R. B.; Oates, W. A.

1973-01-01

146

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

PubMed

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. PMID:17268563

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

2007-01-10

147

Hydride Reorientation and Delayed Hydride Cracking of Spent Fuel Rods in Dry Storage  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the effect of thermal creep during vacuum drying of spent fuel rods on hydride reorientation and their delayed hydride cracking (DHC) susceptibility. To these ends, we analyzed Tsai’s thermal creep results of irradiated Zircaloy-4 cladding segments from two pressurized water reactors and Simpson and Ells’ observation where zirconium alloy cladding tube failed during long-term storage at room temperature. On cooling under 190 MPa, the spent fuel rods crept to 3.5 pct strain during vacuum drying showed large radial hydrides, while the ones crept to 0.35 pct strain had very fine radial hydrides. Thus, it is suggested that prior creep deformation promotes hydride reorientation in spent fuel rods on cooling after vacuum drying. Evidence for this suggestion is provided by a model experiment. Considering Kim’s DHC model and experimental facts showing precipitation of hydrides even at room temperature at stress raisers, we suggest that spent fuel rods would fail by DHC in dry storage if stress raisers are present inside the cladding on cooling to below 180 °C, and then axial splits of the failed spent fuel rods would occur by DHC due to fuel expansion by UO2 oxidation.

Kim, Young S.

2009-12-01

148

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

SciTech Connect

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.

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

1994-09-21

149

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

NASA Astrophysics Data System (ADS)

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.

Kubo, T.; Kobayashi, Y.

2013-08-01

150

Metal hydride fuel storage and method thereof  

DOEpatents

Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

Morse, Jeffrey D [Martinez, CA; Jankowski, Alan F [Livermore, CA; Yu, Conrad [Antioch, CA

2009-05-05

151

Anharmonicity in aluminum hydride at high pressures  

Microsoft Academic Search

Aluminum hydride has been predicted to be a superconductor with a transition temperature of 24 K at 110 GPa, in disagreement with the experimental observation. In this work, it is shown that the bulk of the electron–phonon coupling can be associated with modes that are highly anharmonic according to frozen phonon calculations. This large anharmonicity could partially explain the origin of the

Bruno Rousseau; Aitor Bergara

2011-01-01

152

Metal hydride fuel storage and method thereof  

DOEpatents

Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

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

2006-10-17

153

Hydride fuel for LWRs—Project overview  

Microsoft Academic Search

This special issue of Nuclear Engineering and Design consists of a dozen papers that summarize the research accomplished in the DOE NERI Program sponsored project NERI 02-189 entitled “Use of Solid Hydride Fuel for Improved Long-Life LWR Core Designs”. The primary objective of this project was to assess the feasibility of improving the performance of pressurised water reactor (PWR) and

E. Greenspan; M. Fratoni; F. Ganda; F. Ginex; D. Olander; N. Todreas; P. Diller; P. Ferroni; J. Malen; A. Romano; C. Shuffler; J. Trant; B. Petrovic; H. Garkisch

2009-01-01

154

Linear solution for hydriding of uranium.  

National Technical Information Service (NTIS)

A set of equations describing the hydriding of solid pieces of uranium is presented, together with an approximate solution of the equations. The solution predicts a constant velocity of the spall front in the solid piece, which leads to a constant value o...

J. R. Kirkpatrick J. B. Condon

1990-01-01

155

Characterization and Evaluation of Light Metal Hydrides.  

National Technical Information Service (NTIS)

Four samples of a light metal hydride produced by bench-scale continuous process could not be processed in LPC-1032B formulations. A higher density material form was found to be more difficult to passivate and subject to attrition with loss of passivation...

W. E. Baumgartner Y. A. Tajima W. S. Baker

1967-01-01

156

SANS Measurement of Hydrides in Uranium  

Microsoft Academic Search

SANS scattering is shown to be an effective method for detecting the presence of hydrogen precipitates in uranium. High purity polycrystalline samples of depleted uranium were given several hydriding treatments which included extended exposures to hydrogen gas at two different pressures at 630 C as well as a furnace anneal at 850 C followed by slow cooling in the near

S. Spooner; G. M. Ludtka; J. S. Bullock; R. L. Bridges; G. L. Powell

2001-01-01

157

Hydride embrittlement in ZIRCALOY-4 plate; Part 2: Interaction between the tensile stress and the hydride morphology  

SciTech Connect

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 the results and the existing studies were explained by the major self-accommodation 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.

Bai, J.B.; Prioul, C.; Francois, D. (Ecole Centrale Paris, Chatenay-Malabry (France)); Ji, N. (ENSAM, Paris (France)); Gilbon, D. (C.E.N. Saclay, Gif-sur-Yvette (France))

1994-06-01

158

Ductility Evaluation of As-Hydrided and Hydride Reoriented Zircaloy-4 Cladding under Simulated Dry-Storage Condition  

SciTech Connect

Pre-storage drying-transfer operations and early stage storage expose cladding to higher temperatures and much higher pressure-induced tensile hoop stresses relative to normal operation in-reactor and pool storage under these conditions. Radial hydrides could precipitate during slow cooling and provide an additional embrittlement mechanism as the cladding temperature decreases below the ductile-to-brittle transition temperature. As a means of simulating this behavior, unirradiated hydrided Zircaloy-4 samples were fabricated by a gas charging method to levels that encompass the range of hydrogen concentrations observed in current used fuel. Mechanical testing was carried out by the ring compression test (RCT) method at various temperatures to evaluate the sample s ductility for both as-hydrided and post-hydride reorientation treated specimens. As-hydrided samples with higher hydrogen concentration (>800 ppm) resulted in lower strain before fracture and reduced maximum load. Increasing RCT temperatures resulted in increased ductility of the as-hydrided cladding. A systematic radial hydride treatment was conducted at various pressures and temperatures for the hydrided samples with H content around 200 ppm. Following the radial hydride treatment, RCTs on the hydride reoriented samples were conducted and exhibited lower ductility compared to as-hydrided samples.

Yan, Yong [ORNL] [ORNL; Plummer, Lee K [ORNL] [ORNL; Ray, Holly B [ORNL] [ORNL; Cook, Tyler S [ORNL] [ORNL; Bilheux, Hassina Z [ORNL] [ORNL

2014-01-01

159

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for {sup 238}PuO{sup 2} fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration`s Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1992-05-15

160

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for {sup 238}PuO{sup 2} fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1992-05-15

161

Iridium and tantalum foils for spaceflight neutron dosimetry.  

NASA Technical Reports Server (NTRS)

Description of a two-foil system of iridium and tantalum which can measure thermal and intermediate energy neutrons at flux densities of 1 neutron/sq cm-sec over a ten-day lunar mission (1,000,000 neutrons/sq cm). The foils are chemically inert and nontoxic, weigh less than 1 g each, and require only routine gamma pulse height analysis for activation measurement. Detection of fluences below 1,000,000 neutrons/sq cm are achieved for counts of foil activity made as late as two months following neutron exposure. Tantalum foils flown in Apollo 11 indicated a mean dose equivalent to the astronauts of less than 16 mrem from thermal plus intermediate energy neutrons, while nuclear emulsion track analysis indicated approximately 17 mrem from neutrons of energy greater than 0.6 MeV. Iridium foils flown on Apollo 12 indicated dose equivalents of 1.8 to 2.8 mrem from thermal neutrons, excluding tissue thermalized SNAP-27 neutrons.

English, R. A.; Liles, E. D.

1972-01-01

162

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for [sup 238]PuO[sub 2] fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E. (Oak Ridge Y-12 Plant, P.O. Box 2009, Oak Ridge, Tennessee 37831-8096 (United States))

1993-01-15

163

Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors.  

PubMed

Electrodeposition of iridium oxide layers from soluble precursors provides a route to active thin-layer electrocatalysts for use on water-oxidizing anodes. Certain organometallic half-sandwich aqua complexes of iridium form stable and highly active oxide films upon electrochemical oxidation in aqueous solution. The catalyst films appear as blue layers on the anode when sufficiently thick, and most closely resemble hydrous iridium(III,IV) oxide by voltammetry. The deposition rate and cyclic voltammetric response of the electrodeposited material depend on whether the precursor complex contains a pentamethylcyclopentadieneyl (Cp*) or cyclopentadienyl ligand (Cp), and do not match, in either case, iridium oxide anodes prepared from non-organometallic precursors. Here, we survey our organometallic precursors, iridium hydroxide, and pre-formed iridium oxide nanoparticles. From electrochemical quartz crystal nanobalance (EQCN) studies, we find differences in the rate of electrodeposition of catalyst layers from the two half-sandwich precursors; however, the resulting layers operate as water-oxidizing anodes with indistinguishable overpotentials and H/D isotope effects. Furthermore, using the mass data collected by EQCN and not otherwise available, we show that the electrodeposited materials are excellent catalysts for the water-oxidation reaction, showing maximum turnover frequencies greater than 0.5 mol O(2) (mol iridium)(-1) s(-1) and quantitative conversion of current to product dioxygen. Importantly, these anodes maintain their high activity and robustness at very low iridium loadings. Our organometallic precursors contrast with pre-formed iridium oxide nanoparticles, which form an unstable electrodeposited material that is not stably adherent to the anode surface at even moderately oxidizing potentials. PMID:22725667

Blakemore, James D; Schley, Nathan D; Kushner-Lenhoff, Maxwell N; Winter, Andrew M; D'Souza, Francis; Crabtree, Robert H; Brudvig, Gary W

2012-07-16

164

White organic light-emitting devices employing phosphorescent iridium complex as RGB dopants  

Microsoft Academic Search

Efficient phosphorescent white organic light-emitting diodes (WOLEDs) were realized by using a bright blue-emitting layer, iridium (III) bis-[(4,6- di-fluoropheny)-pyridinato-N, C2'] picolinate doped 4.4'-bis-(9-carbazolyl)-2, 2'-dimethyl-biphenyl doped, together with tris-(2-phenylpyridine) iridium and bis-(1-phenyl-isoquinoline) acetylacetonate iridium (III) are codoped into a 4,4'-N,N'-dicarbazole- biphenyl layer to provide blue, green and red emission for colour mixing. The device emission colour is controlled by varying dopant

Ruili Song; Yu Duan; Shufen Chen; Yi Zhao; Jingying Hou; Shiyong Liu

2007-01-01

165

Addition of Iridium to the Biopolymer Mediated Synthesis of YBa2Cu3O7 ?  

NASA Astrophysics Data System (ADS)

This work represents the first study into the addition of iridium into the solgel synthesis of the high temperature superconductor YBa2Cu3O7? (Y123). Through a biopolymermediated synthetic approach, the homogeneous nature of the precursor sol and the preferred nucleation and growth of Y123 phases allow for a high yield of superconducting nanoparticles with no suppression of the superconducting critical temperature, even at high levels (40 wt%) of iridium addition. We attribute this to iridium not substituting into the Y123 crystal lattice, instead forming an associate phase.

Wimbush, Stuart C.; Marx, Werner; Barth, Andreas; Hall, Simon R.

166

A preliminary study of factors affecting the calibration stability of the iridium versus iridium-40 percent rhodium thermocouple  

NASA Technical Reports Server (NTRS)

An iridium versus iridium-40% rhodium thermocouple was studied. Problems associated with the use of this thermocouple for high temperature applications (up to 2000 C) were investigated. The metallurgical studies included X-ray, macroscopic, resistance, and metallographic studies. The thermocouples in the as-received condition from the manufacturer revealed large amounts of internal stress caused by cold working during manufacturing. The thermocouples also contained a large amount of inhomogeneities and segregations. No phase transformations were observed in the alloy up to 1100 C. It was found that annealing the thermocouple at 1800 C for two hours, and then at 1400 C for 2 to 3 hours yielded a fine grain structure, relieving some of the strains, and making the wire more ductile. It was also found that the above annealing procedure stabilized the thermal emf behavior of the thermocouple for application below 1800 C (an improvement from + or - 1% to + or - 0.02% within the range of the test parameters used).

Ahmed, Shaffiq; Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.

1987-01-01

167

Sub-Chronic Oral Exposure to Iridium (III) Chloride Hydrate in Female Wistar Rats: Distribution and Excretion of the Metal  

PubMed Central

Iridium tissue distribution and excretion in female Wistar rats following oral exposure to iridium (III) chloride hydrate in drinking water (from 1 to 1000 ng/ml) in a sub-chronic oral study were determined. Samples of urine, feces, blood and organs (kidneys, liver, lung, spleen and brain) were collected at the end of exposure. The most prominent fractions of iridium were retained in kidney and spleen; smaller amounts were found in lungs, liver and brain. Iridium brain levels were lower than those observed in other tissues but this finding can support the hypothesis of iridium capability to cross the blood brain barrier. The iridium kidney levels rose significantly with the administered dose. At the highest dose, important amounts of the metal were found in serum, urine and feces. Iridium was predominantly excreted via feces with a significant linear correlation with the ingested dose, which is likely due to low intestinal absorption of the metal. However, at the higher doses iridium was also eliminated through urine. These findings may be useful to help in the understanding of the adverse health effects, particularly on the immune system, of iridium dispersed in the environment as well as in identifying appropriate biological indices of iridium exposure.

Iavicoli, Ivo; Fontana, Luca; Bergamaschi, Antonio; Conti, Marcelo Enrique; Pino, Anna; Mattei, Daniela; Bocca, Beatrice; Alimonti, Alessandro

2012-01-01

168

A note on the isotopic assignment of slow neutron resonances in Samarium, Iridium and Gadolinium  

Microsoft Academic Search

Some further isotopic assignments of slow neutron resonances have been ; made with the elements samarium, iridium, and gadoliniuma using tbe Harwell 15 ; Mev linear accelerator and capture gamma ray scintillation detectors.;

E. M. Bowey; J. R. Bird

1958-01-01

169

Dissipative hydride precipitates in superconducting niobium cavities  

SciTech Connect

We report the first direct observation of the microstructural features exhibiting RF losses at high surface magnetic fields of above 100 mT in field emission free superconducting niobium cavities. The lossy areas were identified by advanced thermometry. Surface investigations using different techniques were carried out on cutout samples from lossy areas and showed the presence of dendritic niobium hydrides. This finding has possible implications to the mechanisms of RF losses in superconducting niobium at all field levels.

Romanenko, A.; Cooley, L.D.; /Fermilab; Ciovati, G.; / /Jefferson Lab; Wu, G.; /Argonne

2011-10-01

170

Nickel metal hydride LEO cycle testing  

NASA Technical Reports Server (NTRS)

The George C. Marshall Space Flight Center is working to characterize aerospace AB5 Nickel Metal Hydride (NiMH) cells. The cells are being evaluated in terms of storage, low earth orbit (LEO) cycling, and response to parametric testing (high rate charge and discharge, charge retention, pulse current ability, etc.). Cells manufactured by Eagle Picher are the subjects of the evaluation. There is speculation that NiMH cells may become direct replacements for current Nickel Cadmium cells in the near future.

Lowery, Eric

1995-01-01

171

Metal hydrides for lithium-ion batteries  

Microsoft Academic Search

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

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

2008-01-01

172

Preparation of hydride-forming intermetallic films  

Microsoft Academic Search

Amorphous and polycrystalline films of hydride-forming intermetallic compounds (IMCs) have been prepared by vacuum deposition methods. Structure and composition have been investigated by XRD, XPS and by fluorescent X-ray spectroscopy. La-Ni, Pr-Ni and Ni-Zr films have been obtained on water-cooled Cu substrates by magnetron sputtering of intermetallic targets under an Ar atmosphere. Amorphous films with compositions corresponding to PrNi5 and

O. K Alexeeva; A Chistov; V Sumarokov

1995-01-01

173

ToF-SIMS characterization of uranium hydride  

Microsoft Academic Search

Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) has been employed for the first time to investigate uranium hydride. The deuterated form of uranium hydride (UD3) was formed on a polycrystalline uranium sample by exposure to high-purity D2 gas at room temperature. The characteristic positive and negative secondary-ion fragments observed from uranium hydride are reported and assigned. Our investigations show that negative-ion fragments

P. Morrall; D. W. Price; A. J. Nelson; W. J. Siekhaus; E. Nelson; K. J. Wu; M. Stratman; W. McLean II

2007-01-01

174

Mechanochemical synthesis of nanostructured chemical hydrides in hydrogen alloying mills  

Microsoft Academic Search

Mechanical alloying of magnesium metal powders with hydrogen in specialized hydrogen ball mills can be used as a direct route for mechanochemical synthesis of emerging chemical hydrides and hydride mixtures for advanced solid-state hydrogen storage. In the 2Mg–Fe system, we have successfully synthesized the ternary complex hydride Mg2FeH6 in a mixture with nanometric Fe particles. The mixture of complex magnesium-iron

Z. Wronski; R. A. Varin; C. Chiu; T. Czujko; A. Calka

2007-01-01

175

Thermal Conductivity of Hydride Powders Layers Interacted With Hydrogen  

Microsoft Academic Search

The results of experiments on measurements of reacting with hydrogen hydride beds thermal conductivity coefficient are presented\\u000a in the article. Installation, designs of measuring cell, and experimental technique for measurements of thermal conductivity\\u000a of various hydride layers (including various metal fillers as well) are briefly described. Experiments were carried out with\\u000a use of different hydrides, including LaNi5. Powders with particle

A. I. Solovey; Y. U. I. SHANIN

176

Comparison of Superconducting Transition Characteristics of Two Iridium\\/Gold Bilayer Transition Edge Sensor Devices  

Microsoft Academic Search

We are developing a high-energy-resolution X-ray microcalorimeter for X-ray fluorescent spectrometry using a superconducting transition edge sensor (TES) that consists of a bilayer of iridium and gold (Ir\\/Au). In this paper, we have studied the superconducting transition characteristics of two different bilayer structures. Type 1 is a simple stacked bilayer where a square-pattern film of iridium is covered with an

Yuichi Kunieda; Daiji Fukuda; Masashi Ohno; Hiroyuki Takahashi; Masaharu Nakazawa; Tadashi Inou; Manabu Ataka

2004-01-01

177

A room temperature HSGFET ammonia sensor based on iridium oxide thin film  

Microsoft Academic Search

Gas-sensing properties of hybrid suspended gate FET (HSGFET) sensor containing iridium oxide as sensitive layer are reported in this paper. The sensor response to NH3 and H2 was measured. We obtained a non-amplified signal of 70mV for 50ppm of ammonia and no signal to hydrogen even for 10,000ppm. Further, the gas-sensing properties of thin film of iridium oxide has been

A. Karthigeyan; R. P. Gupta; K. Scharnagl; M. Burgmair; S. K. Sharma; I. Eisele

2002-01-01

178

Development of a platinized platinum\\/iridium electrode for use in vitro  

Microsoft Academic Search

Silver\\/silver chloride (Ag\\/AgCl) electrodes possess excellent electrical properties for measuring the electrical activity\\u000a of gastrointestinal smooth muscle but exert toxic effects on this tissue in vitro. We thus developed a platinum electrode\\u000a for use in vitro, the construction of these electrodes relying upon the formation of a glass-platinum\\/iridium seal. The platinum\\/iridium\\u000a (Pt\\/Ir) electrodes were platinized using a current density of

Kenneth R. Cote; Richard C. Gill

1987-01-01

179

METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW  

SciTech Connect

Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine the metal hydride material itself should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal-hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimized to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation. The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal-hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications.

Bowman Jr, Robert C [ORNL] [ORNL; Yartys, Dr. Volodymyr A. [Institute for Energy Technology (IFE)] [Institute for Energy Technology (IFE); Lototskyy, Dr. Michael V [University of the Western Cape, South Africa] [University of the Western Cape, South Africa; Pollet, Dr. B.G. [University of the Western Cape, South Africa

2014-01-01

180

Iridium-alloy processing experience in FY 1990  

SciTech Connect

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 melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1990 included the consumable-electrode arc melting of four ingots and the extruding and rolling to sheet of four billets. Significant improvements made in the extruding and arc-melting processes during FY 1989 have been demonstrated to dramatically increase the rate of blank acceptance in nondestructive evaluations. Efforts to improve the rolling practice and to better characterize intermetallic particle distributions in the sheet are also described.

Ohriner, E.K.

1991-11-01

181

Particle formation during oxidation catalysis with Cp* iridium complexes.  

PubMed

Real-time monitoring of light scattering and UV-vis profiles of four different Cp*Ir(III) precursors under various conditions give insight into nanoparticle formation during oxidation catalysis with NaIO(4) as primary oxidant. Complexes bearing chelate ligands such as 2,2'-bipyridine, 2-phenylpyridine, or 2-(2'-pyridyl)-2-propanolate were found to be highly resistant toward particle formation, and oxidation catalysis with these compounds is thus believed to be molecular in nature under our conditions. Even with the less stable hydroxo/aqua complex [Cp*(2)Ir(2)(?-OH)(3)]OH, nanoparticle formation strongly depended on the exact conditions and elapsed time. Test experiments on the isolated particles and comparison of UV-vis data with light scattering profiles revealed that the formation of a deep purple-blue color (~580 nm) is not indicative of particle formation during oxidation catalysis with molecular iridium precursors as suggested previously. PMID:22594951

Hintermair, Ulrich; Hashmi, Sara M; Elimelech, Menachem; Crabtree, Robert H

2012-06-13

182

Iridium satellites help map electrical currents in space  

NASA Astrophysics Data System (ADS)

The satellite constellation of Iridium LLC, which filed for Chapter 11 bankruptcy in 1999 after it failed to win enough business for its commercial satellite communications services, is still orbiting at an altitude of about 780 kilometers. Now, however, the satellites are helping to write a new chapter in understanding space weather.Magnetometers onboard each of the system's 66 polar-orbiting satellites are working in conjunction with the high-frequency, multinational Super Dual Auroral Radar Network, or SuperDARN, to provide the first continuous measurements of electrical currents between Earth's upper atmosphere and space. These tools also are generating the first global maps of electrical power flowing into the polar upper atmosphere.

Showstack, Randy

183

Iridium-alloy processing experience in FY 1989  

SciTech Connect

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.

Ohriner, E.K.

1990-11-01

184

Storing hydrogen in the form of light alloy hydrides  

NASA Technical Reports Server (NTRS)

Different hydrides are investigated to find a system with a sufficiently high storage density (at least 3%). The formation of hydrides with light alloys is examined. Reaction kinetics for hydride formation were defined and applied to the systems Mg-Al-H, Mg-Al-Cu-H, Ti-Al-H, Ti-Al-Cu-H, and Ti-Al-Ni-H. Results indicate that the addition of Al destabilizes MgH2 and TiH2 hydrides while having only a limited effect on the storage density.

Freund, E.; Gillerm, C.

1981-01-01

185

Materials compatibility of hydride storage materials with austenitic stainless steels  

SciTech Connect

This task evaluated the materials compatibility of LaNi[sub 5-x]Al[sub x] (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

Clark, E.A.

1992-09-21

186

Materials compatibility of hydride storage materials with austenitic stainless steels  

SciTech Connect

This task evaluated the materials compatibility of LaNi{sub 5-x}Al{sub x} (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

Clark, E.A.

1992-09-21

187

Solution softning and strengthening of iridium in arc-melted tungsten  

NASA Astrophysics Data System (ADS)

A comprehensive investigation has been performed on the hardness, tensile properties, microstructure, and fracture behavior of arc-melted W and W-Ir alloys at room temperature and from 1600 K to 2600 K. The objectives of the present study were to examine solution softening effect of Ir in W at room-temperature, and to characterize the strength properties of dilute W-Ir alloys as the functions of iridium content at high temperatures. Tensile tests were conducted in a vacuum better than 1.3×10-5 Pa (10-7 torr) with a strain rate of 10-3/sec. It was found that iridium was more effective insoften and ductilize tungsten than rhenium at room temperature, and the minimum hardness and maximum elongation occurred at iridium content about 0.4 wt.%. In dilute W-Ir alloys, the high-temperature strength increment was proportional to the atomic content of iridium. And the addition of iridium in arc-melted tungsten substantially increased both the strain-hardening exponent and the activation energy of plastic deformation above 1600 K. Besides, transgranular fracture was found to be the dominant fracture mode for arc-melted W-Ir alloys, but the tendency of fracturing intergranularly became stronger with increasing iridium content and temperature.

Luo, Anhua; Shin, Kwang S.; Jacobson, Dean L.

1991-01-01

188

New yellow-emitting phosphorescent cyclometalated iridium(III) complex  

NASA Astrophysics Data System (ADS)

We have synthesized a new yellow iridium complex Iridium(III) bis[2-phenylbenzothiazolato-N,C2']-(1-phenylicosane-1,3-dionate) (bt)2Ir(bsm), based on the benzothiazole derivative. The synthesized molecule was identified by 1H NMR and elemental analysis. The UV-Visible absorption and photoluminescence (PL) spectra of (bt)Ir2(bsm) in CH2Cl2 solution were found at 273 nm and 559 nm, respectively. The complex was used as a dopant into a hole-transporting layer (HTL) in a multilayered organic light emitting device (OLED) structure: ITO/doped-HTL/EL/ETL/M. ITO was a transparent anode of In2O3:SnO2, M- a metallic Al cathode, HTL- 4,4'-bis(9H-carbazol-9-yl)biphenyl (CBP) incorporated in poly(N-vinylcarbazole) (PVK) matrix, EL- electroluminescent layer of bis(8-hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum (BAlq) and ETL- electron-transporting layer of tris(8-hydroxyquinolinato)aluminum (Alq3). The electroluminescent (EL) spectra of OLEDs were basically the sum of the emissions of BAlq at 496 nm and the emission of (bt)2Ir(bsm) at 559 nm. With increasing (bt)2Ir(bsm) concentration, the relative electroluminescent intensity of greenish-blue emission (at 496 nm) decreased, while the yellow (at 559 nm) - increased and CIE coordinates of the device shifted from (0.21, 0.33) at 0 wt % to (0.40, 0.48) at 8 wt % of the dopant. It was found that OLED with 0.5 wt % (bt)2Ir(bsm) had the best performance and stable color chromaticity at various voltages.

Ivanov, P.; Tomova, R.; Petrova, P.; Stanimirov, S.; Petkov, I.

2012-12-01

189

The Electric Dipole Moment of Iridium Monosilicide, IrSi  

NASA Astrophysics Data System (ADS)

The optical spectrum of iridium monosilicide (IrSi) was recently observed using REMPI spectroscopy in the range 17200 to 23850 cm^{-1}. The observation was supported by an ab initio calculation which predicted a X^{2}?_{5/2} state. Here, we report on the analysis of the optical Stark effect for the X^{2}?_{5/2} and [16.0]1.5 (v=6) states. The (6,0)[16.0]1.5 - X^{2}?_{5/2} and the (7,0)[16.0]3.5- X^{2}?_{5/2} bands of IrSi have been recorded using high-resolution laser-induced fluorescence spectroscopy. The observed optical Stark shifts for the ^{193}IrSi and ^{191}IrSi isotopologues were analyzed to produce the electric dipole moments of -0.4139(64)D and 0.7821(63)D for the X^{2}?_{5/2} and [16.0]1.5 (v=6) states, respectively. The negative sign of electric dipole moment of the X^{2}?_{5/2} state is supported by high-level quantum-chemical calculations employing all-electron scalar-relativistic CCSD(T) method augmented with spin-orbit corrections as well as corrections due to full triple excitations. In particular, electron-correlation effects have been shown to be essential in the prediction of the negative sign of the dipole moment. A comparison with other iridium containing molecules will be made. Maria A. Garcia, Carolin Vietz, Fernando Ruipérez, Michael D. Morse, and Ivan Infante, Kimika Fakultatea, Euskal Herriko. J. Chem. Phys., (submitted)

Le, Anh; Steimle, Timothy C.; Cheng, Lan; Stanton, John F.

2013-06-01

190

A Study of Magnesium Hydride Thin Film Phase Transition Kinetics Using In-Situ Hydriding\\/Dehydriding  

Microsoft Academic Search

Magnesium is an attractive material for hydrogen storage because it stores an appreciable amount of hydrogen (7.6 wt.%) as magnesium hydride (MgH2), is abundant in the earth's crust and is relatively inexpensive. Understanding of the structural changes and associated kinetics for the magnesium\\/magnesium hydride phase transition is crucial to engineering practical metal hydride hydrogen storage materials involving magnesium. A thin

Stephen Kelly; Raj Kelekar; Hermione Giffard; Bruce Clemens

2007-01-01

191

The mechanism of silicon-hydrogen and carbon-hydrogen bond activation by iridium(III): Production of a silylene complex and the first direct observation of Ir(III)/Ir(V) C-H bond oxidative addition and reductive elimination  

SciTech Connect

The complexes Cp*(PMe{sub 3})Ir(Me)OTf (Me = CH{sub 3}, OTf = OSO{sub 2}CF{sub 3}) (1) and Cp*(PMe{sub 3})Ir(Me)(CH{sub 2}Cl{sub 2})[BAr{sub f}] (BAr{sub f}{sup {minus}} = [(3,5-(CF{sub 3}){sub 2}C{sub 6}H{sub 3}){sub 4}B]{sup {minus}}) (2), which contain iridium in oxidation state +3, were recently shown to undergo C-H activation reactions with alkanes under mild thermal conditions. The authors report a series of observations, including the first conversion of Ir(III) precursors to an isolable, structurally characterized Ir(V) aryl-hydride and a spectroscopically observable Ir(V) alkyl-hydride, that lends convincing experimental support to the Ir(III) {r{underscore}arrow} Ir(V) {r{underscore}arrow} Ir(III) mechanism. The complex Cp*(PMe{sub 3})Ir(Me)OTf (1) reacts rapidly with alkanes (H-CR{sub 3}) to produce 1 equiv of methane (CH{sub 4}) and rearranged products derived from Cp*(PMe{sub 3})Ir(CR{sub 3})OTf, which form as a consequence of the {beta}-hydride elimination pathway. When 1 is added to silanes (H-SiR{sub 3}, R = Me, Ph), products of a structural rearrangement type unobserved in C-H activation reactions are isolated along with 1 equiv of methane. These products, Cp*(PMe{sub 3})Ir(SiR{sub 2}OTf)(R), are presumably derived from a 1,2-migration in Cp*(PMe{sub 3})Ir(SiR{sub 3})OTf, wherein one of the groups initially bound to silicon migrates to iridium (eq 1).

Klei, S.R.; Tilley, T.D.; Bergman, R.G.

2000-03-01

192

Characteristics of White Organic Light-Emitting Diodes Using Heteroleptic Iridium Complexes for Green and Red Phosphorescence  

Microsoft Academic Search

We have demonstrated red-green-blue emissive white organic light-emitting diodes (RGB-WOLEDs) by using two emissive materials as dopant, 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (BCzVBi) and heteroleptic tris-cyclometalated iridium(III) complexes. It was found that the heteroleptic iridium complexes, bis(2-phenylquinoline)(2-p-tolylpyridine) iridium(III) [Ir(pq)2(tpy)] and bis(2-p-tolylpyridine)(2-phenylquinoline) iridium(III) [Ir(tpy)2(pq)], used in this study showed double emissive colors, where the pq and tpy ligands emitted red and green colors, respectively. The

Ji Hyun Seo; In Jun Kim; Young Kwan Kim; Young Sik Kim

2008-01-01

193

Metal Hydride Thermal Storage: Reversible Metal Hydride Thermal Storage for High-Temperature Power Generation Systems  

SciTech Connect

HEATS Project: PNNL is developing a thermal energy storage system based on a Reversible Metal Hydride Thermochemical (RMHT) system, which uses metal hydride as a heat storage material. Heat storage materials are critical to the energy storage process. In solar thermal storage systems, heat can be stored in these materials during the day and released at night—when the sun is not out—to drive a turbine and produce electricity. In nuclear storage systems, heat can be stored in these materials at night and released to produce electricity during daytime peak-demand hours. PNNL’s metal hydride material can reversibly store heat as hydrogen cycles in and out of the material. In a RHMT system, metal hydrides remain stable in high temperatures (600- 800°C). A high-temperature tank in PNNL’s storage system releases heat as hydrogen is absorbed, and a low-temperature tank stores the heat until it is needed. The low-cost material and simplicity of PNNL’s thermal energy storage system is expected to keep costs down. The system has the potential to significantly increase energy density.

None

2011-12-05

194

Hydrogen storage in the form of metal hydrides  

NASA Technical Reports Server (NTRS)

Reversible reactions between hydrogen and such materials as iron/titanium and magnesium/ nickel alloy may provide a means for storing hydrogen fuel. A demonstration model of an iron/titanium hydride storage bed is described. Hydrogen from the hydride storage bed powers a converted gasoline electric generator.

Zwanziger, M. G.; Santana, C. C.; Santos, S. C.

1984-01-01

195

A nickel metal hydride battery for electric vehicles  

Microsoft Academic Search

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

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

1993-01-01

196

Modular hydride beds for mobile applications  

SciTech Connect

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.

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

1997-08-01

197

Recent advances in metal hydrides for clean energy applications  

SciTech Connect

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.

Ronnebro, Ewa; Majzoub, Eric H.

2013-06-01

198

Development of nickel-metal hydride cell  

NASA Technical Reports Server (NTRS)

National Space Development Agency of Japan (NASDA) has conducted the research and development (R&D) of battery cells for space use. A new R&D program about a Nickel-Metal Hydride (Ni-MH) cell for space use from this year, based on good results in evaluations of commercial Ni-MH cells in Tsukuba Space Center (TKSC), was started. The results of those commercial Ni-MH cell's evaluations and recent status about the development of Ni-MH cells for space use are described.

Kuwajima, Saburo; Kamimori, Nolimits; Nakatani, Kensuke; Yano, Yoshiaki

1993-01-01

199

Autodissociating Rydberg states of positronium hydride  

NASA Technical Reports Server (NTRS)

Consequences of the nonrelativistic Coulomb Hamiltonian with a fixed proton are considered for positronium hydride (PsH). An optical-potential method and certain simplifying assumptions are used to compute the lowest s-wave resonance parameters on the basis of the /e(+)H(-)/ configuration. Resonance parameters corresponding to a Ps scattering energy of 4.0190 eV and a width of 0.0303 eV are obtained. These results are shown to be in very close agreement with those of previous studies.

Drachman, R. J.

1979-01-01

200

Highly Concentrated Palladium Hydrides/Deuterides; Theory  

SciTech Connect

Accomplishments are reported in these areas: tight-binding molecular dynamics study of palladium; First-principles calculations and tight-binding molecular dynamics simulations of the palladium-hydrogen system; tight-binding studies of bulk properties and hydrogen vacancies in KBH{sub 4}; tight-binding study of boron structures; development of angular dependent potentials for Pd-H; and density functional and tight-binding calculations for the light-hydrides NaAlH4 and NaBH4

Papaconstantopoulos, Dimitrios

2013-11-26

201

Metal hydride fuel storage and method thereof  

DOEpatents

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.

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

2010-08-10

202

Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding  

NASA Astrophysics Data System (ADS)

It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young's modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young's modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found.

Rico, A.; Martin-Rengel, M. A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F. J.

2014-09-01

203

A novel heteroleptic iridium complex with multifunctional ligands used for polymeric light-emitting diodes  

NASA Astrophysics Data System (ADS)

A novel iridium complex using 3-(5-(4-(pyridin-2-yl)phenyl)-1,3,4-oxadiazol-2-yl)-9-hexyl-9H-carbazole containing both hole-transporting group and electron-transporting group as main ligand and 2-(5-p-tolyl-2H-1,2,4-triazol-3-yl)pyridine as ancillary ligand was synthesized and investigated in this paper. The iridium complex possesses high solubility, high thermal stability with 5% weight-reduction temperature (? T5%) of 390 °C and glass-transition temperature ( Tg) of 218 °C. Polymeric light-emitting diodes (PLEDs) based on structure of ITO/PEDOT: PSS/PVK: PBD: iridium complex/TPBI/CsF/Al fabricated by solution-processed technology were measured. The PLED using the iridium complex as phosphorescent dopant at 4 wt.% doping concentration is optimal which shows the maximum luminance of 7746 cd·cm -2, maximum current efficiency of 14.0 cd A -1 and maximum external quantum efficiency of 5.8% with CIE coordinates of (0.48, 0.50). The EL emission originates from both monomers and exciplexes formed from the iridium complex and PVK.

Tang, Huaijun; Li, Yanhu; Chen, Bing; Wu, Hongbin; Yang, Wei; Cao, Yong

2011-06-01

204

Electrodeposition of platinum-iridium alloy nanowires for hermetic packaging of microelectronics.  

PubMed

An electrodeposition technique was applied for fabrication of dense platinum-iridium alloy nanowires as interconnect structures in hermetic microelectronic packaging to be used in implantable devices. Vertically aligned arrays of platinum-iridium alloy nanowires with controllable length and a diameter of about 200 nm were fabricated using a cyclic potential technique from a novel electrodeposition bath in nanoporous aluminum oxide templates. Ti/Au thin films were sputter deposited on one side of the alumina membranes to form a base material for electrodeposition. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to characterize the morphology and the chemical composition of the nanowires, respectively. SEM micrographs revealed that the electrodeposited nanowires have dense and compact structures. EDS analysis showed a 60:40% platinum-iridium nanowire composition. Deposition rates were estimated by determining nanowire length as a function of deposition time. High Resolution Transmission Electron Microscopy (HRTEM) images revealed that the nanowires have a nanocrystalline structure with grain sizes ranging from 3 nm to 5 nm. Helium leak tests performed using a helium leak detector showed leak rates as low as 1 × 10(-11) mbar L s(-1) indicating that dense nanowires were electrodeposited inside the nanoporous membranes. Comparison of electrical measurements on platinum and platinum-iridium nanowires revealed that platinum-iridium nanowires have improved electrical conductivity. PMID:23365995

Petrossians, Artin; Whalen, John J; Weiland, James D; Mansfeld, Florian

2012-01-01

205

Application of AirCell Cellular AMPS Network and Iridium Satellite System Dual Mode Service to Air Traffic Management.  

National Technical Information Service (NTIS)

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 s...

M. A. Shamma

2004-01-01

206

Metal hydrides for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

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.

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

2008-11-01

207

Millimeter-Wave Spectroscopy of Ethylmercury Hydride  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

208

Phosphorescent sensor for phosphorylated peptides based on an iridium complex.  

PubMed

A bis[(4,6-difluorophenyl)pyridinato-N,C(2')]iridium(III) picolinate (FIrpic) derivative coupled with bis(Zn(2+)-dipicolylamine) (ZnDPA) was developed as a sensor (1) for phosphorylated peptides, which are related to many cellular mechanisms. As a control, a fluorescent sensor (2) based on anthracene coupled to ZnDPA was also prepared. When the total negative charge on the phosphorylated peptides was changed to -2, -4, and -6, the emission intensity of sensor 1 gradually increased by factors of up to 7, 11, and 16, respectively. In contrast, there was little change in the emission intensity of sensor 1 upon the addition of a neutral phosphorylated peptide, non-phosphorylated peptides, or various anions such as CO3(2-), NO3(-), SO4(2-), phosphate, azide, and pyrophosphate. Furthermore, sensor 1 could be used to visually discriminate between phosphorylated peptides and adenosine triphosphate in aqueous solution under a UV-vis lamp, unlike fluorescent sensor 2. This enhanced luminance of phosphorescent sensor 1 upon binding to a phosphorylated peptide is attributed to a reduction in the repulsion between the Zn(2+) ions due to the phenoxy anion, its strong metal-to-ligand charge transfer character, and a reduction in self-quenching. PMID:24919563

Kang, Jung Hyun; Kim, Hee Jin; Kwon, Tae-Hyuk; Hong, Jong-In

2014-07-01

209

High-temperature oxidation behavior of iridium-rhenium alloys  

NASA Technical Reports Server (NTRS)

The life-limiting mechanism for radiation-cooled rockets made from iridium-coated rhenium (Ir/Re) is the diffusion of Re into the Ir layer and the subsequent oxidation of the resulting Ir-Re alloy from the inner surface. In a previous study, a life model for Ir/Re rockets was developed. It incorporated Ir-Re diffusion and oxidation data to predict chamber lifetimes as a function of temperature and oxygen partial pressure. Oxidation testing at 1540 deg C suggested that a 20-wt percent Re concentration at the inner wall surface should be established as the failure criterion. The present study was performed to better define Ir-oxidation behavior as a function of Re concentration and to supplement the data base for the life model. Samples ranging from pure Ir to Ir-40 wt percent Re (Ir-40Re) were tested at 1500 deg C, in two different oxygen environments. There were indications that the oxidation rate of the Ir-Re alloy increased significantly when it went from a single-phase solid solution to a two-phase mixture, as was suggested in previous work. However, because of testing anomalies in this study, there were not enough dependable oxidation data to definitively raise the Ir/Re rocket failure criterion from 20-wt percent Re to a Re concentration corresponding to entry into the two-phase region.

Reed, Brian D.

1995-01-01

210

Earth's Radiation Imbalance from a Constellation of 66 Iridium Satellites  

NASA Astrophysics Data System (ADS)

The Earth Radiation Imbalance (ERI) at the top of the atmosphere is the primary driving force for climate change. If ERI is not zero, then Earth's temperature, both oceanic and atmospheric, will change gradually over time, tending toward a new steady state. The best estimates of current ERI from climate models range from 0.4 to 0.9 W/m2 (the imbalance being caused mainly by increasing CO2), but current satellite systems do not have the accuracy to measure ERI to even one significant digit. In this paper, we will describe a proposed constellation of 66 Earth radiation budget instruments, to be hosted on Iridium satellites. This system represents a quantum leap over current systems in several ways, in particular in providing ERI to at least one significant digit, thus enabling a crucial test of climate models. Because of its 24/7 coverage, the system will also provide ERI at three-hourly time scales without requiring extrapolations from narrowband geostationary instruments. This would allow studies of ERI's response to fast-evolving phenomena like dust storms and hurricanes. This offers a new, synoptic view of Earth radiation budget that will transform it from a monthly average into a dynamical variable alongside standard meteorological variables like temperature and pressure.

Chiu, J. C.; Wiscombe, W. J.

2012-04-01

211

Efficient water oxidation with organometallic iridium complexes as precatalysts.  

PubMed

Catalytic water oxidation has been investigated using five iridium complexes as precatalysts and NaIO4 as an oxidant at various pH conditions. An increase in the activity of all complexes was observed with increasing pH. A detailed analysis of spectroscopic data together with O2-evolution experiments using Cp*Ir(6,6?-dihydroxy-2,2?-bipyridine)(OH2)(2+) as a precatalyst indicate that the high catalytic activity is closely connected with transient species (A) that exhibits an absorption band at ?max 590 nm. The formation of this active form is strongly dependent on reaction conditions, and the species was distinctly observed using a small excess of periodate. However, another species absorbing at 600 nm (B), which seems to be a less active catalyst, was also observed and was more prominent at high oxidant concentration. Dynamic light scattering analysis and transmission electron microscopy have identified species B as 120 nm nanoparticles. The ultrafiltration method has revealed that species A can be attributed to particles with size in the range of 0.5–2 nm, possibly small IrOx clusters similar to those described previously by Harriman and co-workers (J. Phys. Chem., 1991, 95, 616–621). PMID:24549266

Lewandowska-Andralojc, Anna; Polyansky, Dmitry E; Wang, Chiu-Hui; Wang, Wan-Hui; Himeda, Yuichiro; Fujita, Etsuko

2014-06-28

212

High Strain Rate Tensile Testing of DOP-26 Iridium  

SciTech Connect

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.

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

2007-11-01

213

Enhancing and inhibiting effects of benzenediols on chemiluminescence of a novel cyclometallated iridium(III) complex.  

PubMed

A novel chemiluminescence (CL) system, including the cyclometallated iridium(III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium}, potassium permanganate and oxalic acid, is proposed for the determination of benzenediols. This method is based on the fact that hydroquinone and catechol exhibited an inhibiting effect, while resorcinol exhibited an enhancing effect on CL intensity. The optimum conditions for CL emission were investigated. Under optimal conditions, the detection limits of hydroquinone, catechol and resorcinol were 6.4?×?10(-8), 2.7?×?10(-9) and 8.1?×?10(-7) ?mol/L, respectively. The method has been successfully applied to the determination of benzenediols in different types of water sample. The luminophors of the CL systems were all identified as the metal-ligand charge-transfer (MLCT) excited state of the iridium complex. PMID:21842518

Dong, Yong Ping; Huang, Li; Tong, Bi Hai; Shi, Ming Juan; Zhang, Wang Bing; Zhang, Qian Feng

2012-01-01

214

Filiform-mode hydride corrosion of uranium surfaces  

NASA Astrophysics Data System (ADS)

Hydride nucleation and growth has previously been studied in uranium with an air-formed oxide. Preferred directional growth of uranium hydride has not been observed, presumably due to the constraint of the oxide layer and/or the presence of a surface layer distorted by mechanical grinding and polishing. Instead, hydrides typically first form as subsurface blisters that do not exhibit preferred growth directionality. By eliminating the strained surface layer through electropolishing, removing the natural oxide through ion sputtering, avoiding exposure of the uranium to air, and then exposing uranium to high purity hydrogen in an environmental cell, hydride growth patterns emerge that correspond to defect structures within the microstructure. These hydride growth patterns are similar to filiform corrosion, a type of corrosion that frequently forms under thin protective films. This work describes the first reported observation of filiform-like corrosion in uranium. The uranium hydride initiates at defects, but grows into filaments up to 20 ?m wide, and tends to form in straight lines, largely propagating along twin boundaries. Propagation is driven by hydrogen reaction at the filament head, promoted by more efficient delivery of reactant. However, this phenomenon does not involve an electrochemical process associated with conventional filiform corrosion and is therefore described as filiform-like. Hydride growth was observed using optical microscopy for a period of nearly three years. Sample characterization included automated electron backscatter diffraction (EBSD) measurements to determine growth directions. Observation of this anomalous hydride growth provides clues as to the mechanisms operating in uranium hydriding for more conventionally prepared sample surfaces.

Hill, M. A.; Schulze, R. K.; Bingert, J. F.; Field, R. D.; McCabe, R. J.; Papin, P. A.

2013-11-01

215

Investigating the recycling of nickel hydride battery scrap  

NASA Astrophysics Data System (ADS)

New nickel hydride alloys have been developed to replace the cadmium-containing negative electrodes of nickel-cadmium batteries. The new, cadmium free alloys promise enhanced electrochemical properties as well as reduced environmental toxicity. Rechargeable batteries using nickel hydride electrodes are strong candidates for electric vehicle applications. The U.S. Bureau of Mines is investigating hydrometallurgical technology that separates and recovers purified metallic components present in nickel hydride battery scrap. A preliminary investigation of acid dissolution and metal recovery techniques using whole batteries and electrode rolls has shown potential options that will allow the successful recycling of much of the battery fabrication scrap.

Lyman, Jane W.; Palmer, Glenn R.

1993-05-01

216

Technical and economic aspects of hydrogen storage in metal hydrides  

NASA Technical Reports Server (NTRS)

The recovery of hydrogen from such metal hydrides as LiH, MgH2, TiH2, CaH2 and FeTiH compounds is studied, with the aim of evaluating the viability of the technique for the storage of hydrogen fuel. The pressure-temperature dependence of the reactions, enthalpies of formation, the kinetics of the hydrogen absorption and desorption, and the mechanical and chemical stability of the metal hydrides are taken into account in the evaluation. Economic aspects are considered. Development of portable metal hydride hydrogen storage reservoirs is also mentioned.

Schmitt, R.

1981-01-01

217

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

NASA Astrophysics Data System (ADS)

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.

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

2001-06-01

218

The Hydriding Kinetics of Organic Hydrogen Getters  

SciTech Connect

The aging of hermetically sealed systems is often accompanied by the gradual production of hydrogen gas that is a result of the decay of environmental gases and the degradation of organic materials. In particular, the oxygen, water, hydrogen ''equilibrium'' is affected by the removal of oxygen due the oxidation of metals and organic materials. This shift of the above ''equilibrium'' towards the formation of hydrogen gas, particularly in crevices, may eventually reach an explosive level of hydrogen gas or degrade metals by hydriding them. The latter process is generally delayed until the oxidizing species are significantly reduced. Organic hydrogen getters introduced by Allied Signal Aerospace Company, Kansas City Division have proven to be a very effective means of preventing hydrogen gas accumulation in sealed containers. These getters are relatively unaffected by air and environmental gases. They can be packaged in a variety of ways to fit particular needs such as porous pellets, fine or coarse [gravel] powder, or loaded into silicone rubber. The hydrogen gettering reactions are extremely irreversible since the hydrogen gas is converted into an organic hydrocarbon. These getters are based on the palladium-catalyzed hydrogenation of triple bonds to double and then single bonds in aromatic aryl compounds. DEB (1,4 bis (phenyl ethynyl) benzene) typically mixed with 25% by weight carbon with palladium (1% by weight of carbon) is one of the newest and best of these organic hydrogen getters. The reaction mechanisms are complex involving solid state reaction with a heterogeneous catalyst leading to the many intermediates, including mixed alkyl and aryl hydrocarbons with the possibilities of many isomers. The reaction kinetics mechanisms are also strongly influenced by the form in which they are packaged. For example, the hydriding rates for pellets and gravel have a strong dependence on reaction extent (i.e., DEB reduction) and a kinetic order in pressure of 0.76. Silicone rubber based DEB getters hydride at a much lower rate, have little dependence on reaction extent, have a higher kinetic order in pressure (0.87), and have a lower activation energy. The kinetics of the reaction as a function of hydrogen pressure, stoichiometry, and temperature for hydrogen and deuterium near ambient temperature (0 to 75 C) for pressures near or below 100 Pa over a wide range (in some cases, the complete) hydrogenation range are presented along with multi-dimensional rate models.

Powell, G. L.

2002-02-11

219

ENVIRONMENTAL REACTIVITY OF SOLID STATE HYDRIDE MATERIALS  

SciTech Connect

In searching for high gravimetric and volumetric density hydrogen storage systems, it is inevitable that higher energy density materials will be used. In order to make safe and commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate mitigation strategies to handle potential material exposure events. A crucial aspect of the development of risk identification and mitigation strategies is the development of rigorous environmental reactivity testing standards and procedures. This will allow for the identification of potential risks and implementation of risk mitigation strategies. Modified testing procedures for shipping air and/or water sensitive materials, as codified by the United Nations, have been used to evaluate two potential hydrogen storage materials, 2LiBH{sub 4} {center_dot} MgH{sub 2} and NH{sub 3}BH{sub 3}. The modified U.N. procedures include identification of self-reactive substances, pyrophoric substances, and gas-emitting substances with water contact. The results of these tests for air and water contact sensitivity will be compared to the pure material components where appropriate (e.g. LiBH{sub 4} and MgH{sub 2}). The water contact tests are divided into two scenarios dependent on the hydride to water mole ratio and heat transport characteristics. Air contact tests were run to determine whether a substance will spontaneously react with air in a packed or dispersed form. In the case of the 2LiBH{sub 4} {center_dot} MgH{sub 2} material, the results from the hydride mixture compared to the pure materials results showed the MgH{sub 2} to be the least reactive component and LiBH{sub 4} the more reactive. The combined 2LiBH{sub 4} {center_dot} MgH{sub 2} resulted in a material having environmental reactivity between these two materials. Relative to 2LiBH{sub 4} {center_dot} MgH{sub 2}, the chemical hydride NH{sub 3}BH{sub 3} was observed to be less environmentally reactive.

Gray, J; Donald Anton, D

2009-04-23

220

Chemical Hydride Slurry for Hydrogen Production and Storage  

SciTech Connect

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

McClaine, Andrew W.

2008-09-30

221

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C-H functionalization  

PubMed Central

Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize poly-functionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe), and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3-and 2,5-di-substituted thiophenes. Electrophilic aromatic C–H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C–B bond, and one-pot C–H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2- and 3-borylated thiophenes.

Chotana, Ghayoor A.; Kallepalli, Venkata A.; Maleczka, Robert E.; Smith, Milton R.

2013-01-01

222

Thermocouples of molybdenum and iridium alloys for more stable vacuum-high temperature performance  

NASA Technical Reports Server (NTRS)

Thermocouples providing stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor are described. Each metal of the sensor is selected from a group of metals comprising molybdenum and iridium and alloys containing only those two metals. The molybdenum, iridium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibility and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys result in improved emf, temperature properties and thermocouple hot junction performance.

Morris, J. F. (inventor)

1978-01-01

223

Boron hydride analogues of the fullerenes  

SciTech Connect

The BH moiety is isoelectronic with C. We have studied the stability of the (BH)[sub 60] analogue of the C[sub 60] fullerene as well as the dual-structure (BH)[sub 32] icosahedron, both of them being putative structures, by performing local-density-functional electronic calculations. To aid in our analysis, we have also studied other homologues of these systems. We find that the latter, i.e., the dual structure, is the more stable although the former is as stable as one of the latter's lower homologues. Boron hydrides, it seems, naturally form the dual structures used in algorithmic optimization of complex fullerene systems. Fully relaxed geometries are reported as well as electron affinities and effective Hubbard [ital U] parameters. These systems form very stable anions and we conclude that a search for BH analogues of the C[sub 60] alkali-metal supeconductors might prove very fruitful.

Quong, A.A. (Sandia Livermore National Laboratory, Livermore, California 94551-0969 (United States)); Pederson, M.R.; Broughton, J.Q. (Naval Research Laboratory, Washington, D.C. 20375 (United States))

1994-08-15

224

Hydrogen storage in sodium aluminum hydride.  

SciTech Connect

Sodium aluminum hydride, NaAlH{sub 4}, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the NaAlH{sub 4} and Na{sub 3}AlH{sub 6} structures are complex-ionic hydrides with Na{sup +} cations and AlH{sub 4}{sup -} and AlH{sub 6}{sup 3-} anions, respectively. Compound formation studies indicate the primary Ti-compound formed when doping the material at 33 at. % is TiAl{sub 3} , and likely Ti-Al compounds at lower doping rates. A general study of sorption kinetics of NaAlH{sub 4}, when doped with a variety of Ti-halide compounds, indicates a uniform response with the kinetics similar for all dopants. NMR multiple quantum studies of solution-doped samples indicate solvent interaction with the doped alanate. Raman spectroscopy was used to study the lattice dynamics of NaAlH{sub 4}, and illustrated the molecular ionic nature of the lattice as a separation of vibrational modes between the AlH{sub 4}{sup -} anion-modes and lattice-modes. In-situ Raman measurements indicate a stable AlH{sub 4}{sup -} anion that is stable at the melting temperature of NaAlH{sub 4}, indicating that Ti-dopants must affect the Al-H bond strength.

Ozolins, Vidvuds; Herberg, J.L. (Lawrence Livermore National Laboratories, Livermore, CA); McCarty, Kevin F.; Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA); Stumpf, Roland Rudolph; Majzoub, Eric H.

2005-11-01

225

RBS characterization of the iridium diffusion in silicon  

NASA Astrophysics Data System (ADS)

In this work, the Ir diffusion in Si has been studied in the high concentration regime. Si (1 0 0) samples were preamorphized by Si implantation and implanted with Ir with a peak concentration of 8×10 21 cm -3, below the minimum necessary to the formation of a continuous layer of iridium silicide. The amorphized region of the substrate was regrown by solid phase epitaxy at 550°C. This procedure eliminates the effect of the end of range region of the Ir implant on the diffusion process. After regrowth, the samples were annealed at temperatures in the 800-1000°C range for different times. The Ir concentration profiles and the crystal quality were determined from random and aligned RBS spectra. Annealing at high temperatures causes a snow plow effect of Ir toward the surface of the sample, with a segregation coefficient close to 1. An Ir diffusion mechanism through the defect-free region of the Si substrate is also clearly identified, and a constant value of the diffusion coefficient D is derived for each temperature. The values of D follow an Arrhenius behavior with an activation energy E a=3.3±0.2 eV . This value agrees with the typical ones found in vacancy assisted diffusion mechanisms reported for other species. Comparison of these results with the previously reported activation energy E a=1.3 eV for Ir diffusion from the vapour phase at low concentrations shows that the diffusion mechanism is dependent on the concentration level. The values of D at high concentrations are 6 to 7 orders of magnitude lower than the ones reported for low concentrations.

Rodríguez, A.; González, C.; Rodríguez, T.; Kling, A.; da Silva, M. F.; Soares, J. C.

2000-03-01

226

Self-Consistent-Field Calculation on Lithium Hydride for Undergraduates.  

ERIC Educational Resources Information Center

Describes a self-consistent-field-linear combination of atomic orbitals-molecular orbital calculation on the valence electrons of lithium hydride using the method of Roothaan. This description is intended for undergraduate physics students.

Rioux, Frank; Harriss, Donald K.

1980-01-01

227

Thermally unstable hydrides of titanium aluminide Ti3Al  

NASA Astrophysics Data System (ADS)

The hydrogen capacity of (Ti, Nb)3Al titanium aluminides subjected to mechanical activation in a hydrogen atmosphere has been studied. It has been shown that the application of this procedure allows one to prepare thermally unstable titanium aluminide (Ti3Al) hydrides with a high hydrogen content (to 2.6 wt %) at room temperature and normal pressure; in this case, no special requirements for the hydrogen purity are placed. The thermally unstable nanostructured Ti3Al hydrides were found to exhibit a higher hydrogen mobility as compared to that of the microcrystalline hydrides. Low niobium additions (to 2.1 at %) have been found to decrease the hydrogen capacity. Experiments on the preparation of bulk samples from the hydride powders obtained were performed.

Kazantseva, N. V.; Popov, A. G.; Mushnikov, N. V.; Skripov, A. V.; Soloninin, A. V.; Aleksashin, B. A.; Novozhenov, V. I.; Sazonova, V. A.; Kharisova, A. G.

2011-04-01

228

Direct observation of hydrides formation in cavity-grade niobium  

NASA Astrophysics Data System (ADS)

Niobium is an important technological superconductor used to make radio frequency cavities for particle accelerators. Using laser confocal microscopy we have directly investigated hydride precipitates formation in cavity-grade niobium at 77 and 140 K. We have found that large hydrides were usually formed after chemical or mechanical treatments, which are known to lead to a strong degradation of the quality factor known as Q disease. From our experiments we can conclude that hydrides causing Q disease are islands with a characteristic thickness of ?100nm and in-plane dimensions 1-10?m. Our results show that mechanical polishing uploads a lot of hydrogen into bulk niobium while electropolishing leads to a mild contamination. Vacuum treatments at 600-800°C are demonstrated to preclude large hydride formation in line with the absence of Q disease in similarly treated cavities.

Barkov, F.; Romanenko, A.; Grassellino, A.

2012-12-01

229

Metal Hydride Preheater for the M2 Diesel Burner.  

National Technical Information Service (NTIS)

This report describes the results of a Phase I Small Business Innovative Research (SBIR) project to demonstrate the feasibility of preheating the catalytic generator of the M2 diesel burner using a metal hydride preheater. Preliminary testing of an electr...

J. Gerstmann M. Golben

1999-01-01

230

Bipolar Nickel-Metal Hydride Battery Being Developed  

NASA Technical Reports Server (NTRS)

The NASA Lewis Research Center has contracted with Electro Energy, Inc., to develop a bipolar nickel-metal hydride battery design for energy storage on low-Earth-orbit satellites. The objective of the bipolar nickel-metal hydride battery development program is to approach advanced battery development from a systems level while incorporating technology advances from the lightweight nickel electrode field, hydride development, and design developments from nickel-hydrogen systems. This will result in a low-volume, simplified, less-expensive battery system that is ideal for small spacecraft applications. The goals of the program are to develop a 1-kilowatt, 28-volt (V), bipolar nickel-metal hydride battery with a specific energy of 100 watt-hours per kilogram (W-hr/kg), an energy density of 250 W-hr/liter and a 5-year life in low Earth orbit at 40-percent depth-of-discharge.

Manzo, Michelle A.

1998-01-01

231

Life test results of hydride compressors for cryogenic refrigerators  

NASA Technical Reports Server (NTRS)

A development status assessment is made, from the viewpoint of system durability, for the hydride compressors used in such cryogenic refrigerators as that of the JPL, which has operated at 29 K for 500 hours and at lower temperatures for over 1000. Attention is given to a novel hydride compressor unit which has operated through 35,000 cycles and exhibits negligible degradation of check valves, hydride particle size, and expansion valves. The power requirement for liquid hydrogen cooling can be halved through the use of recuperative hot water heating methods, making this system comparable in power use to liquid hydrogen refrigeration systems operating on electricity. Due to the lack of moving parts in hydride refrigerator designs, potential service lifetimes of many years, and perhaps decades, are being projected.

Jones, J. A.; Golben, P. M.

1984-01-01

232

Materials science of Mg-Ni-based new hydrides  

NASA Astrophysics Data System (ADS)

One of the advantageous functional properties of Mg alloys (or compounds) is to exhibit the reversible hydriding reaction. In this paper, we present our systematic studies regarding the relationship between nanometer- or atomistic-scale structures 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) n-MgNi2. Further studies on(5) an a-MgNi-based system for clarifying the effect of the short-range ordering on the structural and hydriding properties and(6) a MgNi2-based system for synthesizing the new Laves phase structure are also presented. The materials science of Mg-Ni-based new hydrides will provide indispensable knowledge for practically developing the Mg alloys as hydrogen-storage materials.

Orimo, S.; Fujii, H.

2001-04-01

233

Neutron diffraction studies of transition metal hydrides and chemistry of metal hydride clusters  

NASA Astrophysics Data System (ADS)

In this dissertation we start by presenting a survey of single-crystal neutron diffraction results on molecular transition metal hydrides. Powder neutron diffraction results from stoichiometric ternary (solid state) hydrides which contain transition metal coordination complexes in their structures are also reviewed. Tabulations of all known neutron diffraction transition metal-hydrogen distances from both the molecular compounds and the ternary hydrides are summarized in the first chapter. In the second chapter, we describe the main achievement of our doctoral research, the discovery of five-coordinate hydrogen via the single-crystal neutron diffract on analysis of the cluster complex (NMesb4rbracksb3(Rhsb{13}Hsb2(CO)sb{24}rbrack*(Me)CO(Et). This work definitively shows that both hydrides in the (Rhsb{13}Hsb2(CO)sb{24}rbracksp{3-} anion are located in square pyrmaidal cavities. The shortest Rh-H bonds are those involving the central Rh atom, 1.827(2)A and 1.861(2)A, while the surface Rh-H bond length average is 1.975(2)A. A large number of crystallizations of the related trihydride cluster (Rhsb{13}Hsb3(CO)sb{24}rbracksp{2-} anion were also set up, of which two yielded crystals suitable for data collection. The x-ray analysis of the ((Phsb3PCHsb2)sb2Csb6Hsb4rbracksp{2+} salt shows the same Rhsb{13} cage and pattern of bridging CO ligands as all previous (Rhsb{13}Hsbn(CO)sb{24}rbracksp(5-n)- (n = 1,2,3) structures. Ligand exchange reactions with phosphines were tried with the (Rhsb{13}Hsb{3}(CO)sb{24}rbracksp{2-} cluster; (Phsb2PCHsb2)sb2, P(cyclohexyl)Phsb2, and P(Csb6Fsb5)sb3 appeared to add successfully. Syntheses of both (Rhsb{13}Hsb1(CO)sb{24}rbracksp{4-} and (Rhsb{13}Hsb4(CO)sb{24}rbracksp- were attempted but did not yield acceptable products. The (Nisb9Ptsb3H(CO)sb{24}rbracksp{3-} anion was synthesized, but crystallization attempts yielded only powders. Attempts to dissolve and crystallize some ternary hydrides are also briefly mentioned. In the final chapter, the neutron diffraction analysis of (K(18-crown-6)) ((PPhsb3)sb2ReHsb6Cr(CO)sb3rbrack is described. The results of this structure determination revealed three hydrides bridging the Re-Cr bond and three terminal hydrides bound to Re. This compound can be described as a donor-acceptor complex, in which the bridging Re-H bonds of ((PPhsb3)sb2ReHsb6rbracksp- act as donors to the Cr(CO)sb3 fragment. Based on a comparison of the Re-musb2H and Cr-musb2H distances with those previously measured, as well as comparisons to the other known M-H donor-acceptor complexes, ((PPhsb3)sb2ReHsb6Cr(CO)sb3rbracksp- is found to be a weak donor-acceptor complex. The Re-Cr separation in ((PPhsb3)sb2ReHsb6Cr(CO)sb3rbracksp- is shorter than previously-determined values for Re-Cr bonds, suggesting that the Re-Cr interaction is strong.

Drabnis, Mary Helen

234

Electronic Structures of Zirconium Hydride and Hydrogen Solid Solution  

Microsoft Academic Search

Electronic structures of zirconium hydride and hydrogen solid solution have been evaluated by the X?ray photoelec- tron spectroscopy andrst-principles molecular orbital calculation. From the valence band spectra of the solid zirconium hydride, the occurrence of the valence electron transfer from Zr 4d band to Zr?H bonding state was found to induce the reduction of Zr?Zr metallic bonds with increasing the

Takanori NISHIZAKI; Shinsuke YAMANAKA

235

Solid-state gadolinium{endash}magnesium hydride optical switch  

SciTech Connect

The optical switching properties of gadolinium{endash}magnesium hydride have been demonstrated in a solid-state electrochromic device. With positive polarization of the hydride electrode, the visible reflectance approaches 35{percent} with virtually zero transmission, while with negative polarization, the visible transmission exceeds 25{percent} at 650 nm. The switching is reversible, with intermediate optical properties between the transparent and reflecting states. {copyright} {ital 1999 American Institute of Physics.}

Armitage, R. [Lawrence Berkeley National Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720 (United States); Rubin, M.; Richardson, T. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); OBrien, N. [Optical Coating Laboratory, Inc., 2789 Northpoint Parkway, Santa Rosa, California 95407 (United States)] [Optical Coating Laboratory, Inc., 2789 Northpoint Parkway, Santa Rosa, California 95407 (United States); Chen, Y. [Hewlett-Packard Laboratories, 3500 Deer Creek Road, Palo Alto, California 94304 (United States)] [Hewlett-Packard Laboratories, 3500 Deer Creek Road, Palo Alto, California 94304 (United States)

1999-09-01

236

Sonochemical synthesis of copper hydride (CuH).  

PubMed

We report the sonochemical synthesis of copper(I) hydride (CuH) by the ultrasonic irradiation of a copper(II) aqueous solution. A reaction mechanism based on the reduction of copper(II) by the ultrasound-generated hydrogen atoms is discussed. To the best of our knowledge, this is the first time that a metal hydride has been synthesized through sonochemistry. PMID:22179137

Hasin, Panitat; Wu, Yiying

2012-01-30

237

ZIRCONIUM IRON DISPROPORTIONATION DURING HYDRIDING REACTIONS IN NUCLEAR GETTERING OPERATIONS  

Microsoft Academic Search

We have investigated the hydriding properties of Zr2Fe and Zr3Fe alloys, including SAES Getters St-198. It was found from examining the X-ray diffraction patterns of alloys hydrided at temperatures ranging from 303 K to 773 K that disproportionation occurs in the Zr2Fe alloys at temperatures above 673 K. In Zr3Fe the temperature at which disproportionation takes place is much lower

Michael Coleman; Dhanesh Chandra; Joseph Wermer; Terrence J. Udovic

238

C?H Bond Functionalization through Intramolecular Hydride Transfer.  

PubMed

Known for over a century, reactions that involve intramolecular hydride-transfer events have experienced a recent resurgence. Undoubtedly responsible for the increased interest in this research area is the realization that hydride shifts represent an attractive avenue for C?H bond functionalization. The redox-neutral nature of these complexity-enhancing transformations makes them ideal for sustainable reaction development. This Review summarizes recent progress in this field while highlighting key historical contributions. PMID:24706531

Haibach, Michael C; Seidel, Daniel

2014-05-12

239

AIR PASSIVATION OF METAL HYDRIDE BEDS FOR WASTE DISPOSAL  

SciTech Connect

Metal hydride beds offer compact, safe storage of tritium. After metal hydride beds have reached the end of their useful life, the beds will replaced with new beds and the old beds prepared for disposal. One acceptance criteria for hydride bed waste disposal is that the material inside the bed not be pyrophoric. To determine the pyrophoric nature of spent metal hydride beds, controlled air ingress tests were performed. A simple gas handling manifold fitted with pressure transducers and a calibrated volume were used to introduce controlled quantities of air into a metal hydride bed and the bed temperature rise monitored for reactivity with the air. A desorbed, 4.4 kg titanium prototype hydride storage vessel (HSV) produced a 4.4 C internal temperature rise upon the first air exposure cycle and a 0.1 C temperature rise upon a second air exposure. A total of 346 scc air was consumed by the bed (0.08 scc per gram Ti). A desorbed, 9.66 kg LaNi{sub 4.25}Al{sub 0.75} prototype storage bed experienced larger temperature rises over successive cycles of air ingress and evacuation. The cycles were performed over a period of days with the bed effectively passivated after the 12th cycle. Nine to ten STP-L of air reacted with the bed producing both oxidized metal and water.

Klein, J; R. H. Hsu, R

2007-07-02

240

Effect of niobium additions on initial hydriding kinetics of uranium  

NASA Astrophysics Data System (ADS)

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.

Li, Ruiwen; Wang, Xiaolin

2014-06-01

241

Electronic structure, bonding and chemisorption in metallic hydrides  

SciTech Connect

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.

Ward, J.W.

1980-01-01

242

Hydride absorption refrigerator system for ten Kelvin and below  

NASA Astrophysics Data System (ADS)

A very long-life, lightweight and efficient hydride absorption refrigerator system was built to operate at ten Kelvin and below. The system consists of four basic stages of refrigeration. The first stage is accomplished by an active refrigeration system. The second stage is operated by a hydride absorption system, wherein a heated hydride powder drives off high pressure hydrogen through a Joule-Thomson/heat exchanger expansion loop such that the hydrogen is partially liquefied. In the third stage, the vapor pressure over the collected liquid hydrogen is lowered by absorbing the hydrogen vapor onto a different low pressure, worn hydride. With a 1.7 torr partial pressure of hydrogen gas in the hydride, liquid hydrogen is solidified and sublimes at 10 K. Long-life adiabatic demagnetization refrigerators, helium desorption, or helium diaphragm compressors are used to cool to 4 K or below. It is shown that the hydride concepts provide an extremely efficient means of refrigeration to 10 K, and that an entire sorption refrigeration process can be accomplished solely by using low grade heat energy at about 150 C.

Jones, J. A.

1985-05-01

243

Report of Iridium/{sup 238}PuO{sub 2} Compatibility Test  

SciTech Connect

This study indicates that the chemical purity of the fuel used presently to fabricate fueled clad vent sets will not present any special problems to the performance of the fueled clad vent sets as intended. However, cation impurities in the fuel can have a deleterious effect on the iridium cladding and vents and should be minimized as much as practical.

Taylor, D.H.

2001-08-09

244

Highly efficient transformation of levulinic acid into pyrrolidinones by iridium catalysed transfer hydrogenation.  

PubMed

Levulinic acid (LA) is transformed into pyrrolidinones via iridium-catalysed reductive amination using formic acid as the hydrogen source under aqueous conditions. The catalytic system is the most active and performs under the mildest conditions ever reported for the reductive amination of LA. PMID:23661188

Wei, Yawen; Wang, Chao; Jiang, Xue; Xue, Dong; Li, Jia; Xiao, Jianliang

2013-06-14

245

Sputtered iridium oxide films as electrocatalysts for water splitting via PEM electrolysis  

Microsoft Academic Search

Thin films of iridium oxide deposited by reactive magnetron sputtering have been investigated as catalysts for electrochemical water splitting in a polymer electrolyte membrane (PEM) cell. The sputtered films possess excellent mechanical stability and corrosion resistance at the high anodic potentials where oxygen evolution takes place. Their catalytic activity has been assessed using the conventional electrochemical methods of cyclovoltammetry and

E. Slavcheva; I. Radev; S. Bliznakov; G. Topalov; P. Andreev; E. Budevski

2007-01-01

246

A performance analysis of the IRIDIUM® low earth orbit satellite system with a degraded satellite constellation  

Microsoft Academic Search

There are currently several commercial Low Earth Orbit (LEO) satellite systems under development that will provide worldwide voice, data, facsimile, and paging services. This article presents a performance analysis of the IRIDIUM® LEO satellite system, as several satellites become non-operational. The analysis is conducted using a computer simulation of the system. First, it examines the system's capability to meet real-time

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

1998-01-01

247

Iridium-bearing sublimates at a hot-spot volcano (Piton de la Fournaise, Indian Ocean)  

Microsoft Academic Search

Sublimates and incrustations derived upon the cooling of volcanic gases have been collected on various sites. They have been analyzed for Ir and other volatile elements by means of instrumental neutron activation analysis and proton induced X-ray emission. Among the investigated volcanoes, only Piton de la Fournaise is found to release detectable amounts of iridium. Ir in Piton de la

Jean-Paul Toutain; Georges Meyer

1989-01-01

248

Development of iridium TES by pulsed laser deposition with a Nd:YAG laser  

Microsoft Academic Search

The use of cryogenics micro calorimeters with Transition Edge Sensors for high-resolution spectroscopy for space applications puts several constraints on the detector's performances. Among several requirements, the long term stability of TES from a chemical and physical point of view is one of the most important. Iridium is a very interesting material for TES fabrication due to its excellent chemical

D. Pergolesi; F. Gatti; L. Gastaldo; M. R Gomes; S. Dussoni; R. Valle; P. Repetto; D. Marré; E. Bellingeri

2004-01-01

249

Potential contributions to space geodesy from the IridiumNEXT constellation  

NASA Astrophysics Data System (ADS)

The IridiumNEXT constellation will soon replace the existing Iridium satellite telecommunication network, with initial launches set to start in 2015. In addition to the primary task of providing global telecommunication services, each IridiumNEXT satellite will also carry a hosted payload that will provide both private and public institutions the opportunity to place an instrument suite on one or all of constellation's satellites. This creates the possibility to gather continuous, global observations of Earth over the entire 15 year projected mission lifetime. Access to such a platform creates the potential to investigate many of Earth's highly dynamic processes at a spatiotemporal resolution that is simply not possible from single-satellite missions. Space geodesy is one the numerous fields that would benefit from such a mission. Precise orbits of the IridiumNEXT satellites derived through an on-board GNSS receiver (plus accelerometers and star cameras) have the potential to observe the large-scale, high-frequency variations in Earth's gravity field at time scales as short as one day. Additional positioning data from ground-based laser ranging stations would help improve the orbit determination, in addition to providing the necessary link to improve estimates of geocenter motion and reference frames. In this presentation, we will analyze the expected geodetic science returns from such a mission and will discuss the instrumental requirements needed to achieve these objectives.

Gunter, B. C.; Encarnação, J.; Ditmar, P.; Klees, R.

2012-12-01

250

Room temperature and solvent-free iridium-catalyzed selective alkylation of anilines with alcohols.  

PubMed

A bidentate iridium NHC-phosphine complex has been developed and applied to the N-monoalkylation of aromatic amines with a wide range of primary alcohols and to the N-heterocyclization of amino alcohols. This reaction resulted in high isolated product yields, even at room temperature and under solvent-free conditions. PMID:23732630

Li, Jia-Qi; Andersson, Pher G

2013-07-14

251

Strong enhancement of luminescence from an iridium polypyridyl complex via encapsulation in cucurbituril.  

PubMed

An exceptional, temperature-dependent enhancement of luminescence is reported upon encapsulation of an iridium(III) polypyridyl complex in cucurbit[10]uril (Q[10]). This is the first demonstrated example of a luminescent transition metal complex occupying the Q[10] cavity with this type of differential response. PMID:24129915

Alrawashdeh, Lubna R; Day, Anthony I; Wallace, Lynne

2013-12-21

252

The Allyl Intermediate in Regioselective and Enantioselective Iridium-Catalyzed Asymmetric Allylic Substitution Reactions  

PubMed Central

The isolation and structural characterization of metallacyclic allyl (2a) and crotyl (2b) iridium complexes are reported. Complexes 2a and 2b are rare examples of iriduim allyl complexes that undergo nucleophilic attack at terminal position, rather than the central position, of the allyl unit. Structures of 2a and 2b were obtained by X-ray diffraction. Nucleophilic attack was observed at the carbon that is bound to iridium trans to phosphorus through a longer Ir-C bond. However, the effect of the trans phosphine ligand on the Ir-C bond lengths was smaller than the effect of the substituent on the allyl group in 2b. The competence of complexes 2a and 2b to be intermediates in the catalytic asymmetric allylic substitutions was evaluated by studying their reactivity towards stabilized carbon and heteroatom nucleophiles and comparing the rates and selectivities to those of the catalytic reactions. The stereoselectivity and regioselectivity of stoichiometric reactions of 2b were similar to those of reactions catalyzed by the previously reported iridium catalysts, supporting their intermediacy in the catalytic reactions. Based on the structural data, a model is proposed for the origin of stereoselectivity in iridium-catalyzed asymmetric allylic substitution reactions.

Madrahimov, Sherzod T.; Markovic, Dean; Hartwig., John F.

2010-01-01

253

Iridium-catalyzed enantioselective c?h alkylation of ferrocenes with alkenes using chiral diene ligands.  

PubMed

The first catalytic and enantioselective C?H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C?H bond activation. PMID:24729461

Shibata, Takanori; Shizuno, Tsubasa

2014-05-19

254

Direct asymmetric dearomatization of pyridines and pyrazines by iridium-catalyzed allylic amination reactions.  

PubMed

The first iridium-catalyzed intramolecular asymmetric allylic dearomatization reaction of pyridines and pyrazines has been realized. 2,3-Dihydroindolizine and 6,7-dihydropyrrolo[1,2-a]pyrazine derivatives were obtained with excellent yields and enantioselectivity. This methodology features dearomatization by direct N-allylic alkylation of pyridines or pyrazines under mild reaction conditions. PMID:24861469

Yang, Ze-Peng; Wu, Qing-Feng; You, Shu-Li

2014-07-01

255

Osmium, ruthenium, iridium, and uranium in silicates and chromite from the eastern Bushveld Complex, South Africa  

Microsoft Academic Search

Osmium, ruthenium, iridium, and uranium contents were determined in ; eight orthopyroxene, seven plagioclase, and three chromite mineral separates from ; the eastern Bushveld Complex. Neutron activation analysis was used to measure ; the platinum metals, and uranium was determined by a fission track technique. ; The platinum metals were found to be present within each mineral in the ;

R. H. Gijbels; H. T. Jr. Millard; G. A. Desborough; A. J. Bartel

1974-01-01

256

Plastic Straining of Iridium Alloy DOP26 During Cup Sizing Operations  

Microsoft Academic Search

DOP-26 iridium alloy cups are used for fuel cladding for radioisotope power systems. The cups are deep drawn and recrystallized prior to final fabrication operations. This study characterizes the plastic deformation of cups during a sizing operation following the recrystallization heat treatment. The purpose of the sizing operation is to achieve the specified roundness, diameter, and radius dimensions of the

Evan Keith Ohriner; George B Ulrich; Adrian S Sabau

2007-01-01

257

Phosphorescence color tuning of oxadiazole-based iridium(III) complexes for organic light emitting diode.  

PubMed

The new heteroleptic iridium complexes bearing 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenolate (ODZ), were synthesized and characterized for application to organic light-emitting diodes (OLEDs). As main ligands (C^N), the anions of 2-phenylpyridine (ppy), 2-phenylquinoline (pq) and 2-(2,4-difluorophenyl)pyridine (F2-ppy) were chelated to the iridium center and 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenolate (ODZ) was introduced as an ancillary ligand for luminescence modulation of their iridium complexes. We expected that the relative energy levels of the main and ancillary ligands in the complexes could lead to emission color tuning and luminous efficiency improvement by possible inter-ligand energy transfer (ILET). The photoabsorption, photoluminescence and electroluminescence of the complexes were studied. Ir(F2-ppy)2(ODZ), Ir(ppy)2(ODZ) and Ir(pq)2(ODZ) exhibited the photoluminescence maxima between 505-610 nm at room temperature in CH2Cl2, depending on both main and ancillary ligands. The longer pi conjugation in the cyclometallating pq ligands leads to the bathochromic shift in luminescence of their iridium complexes. The electroluminescent properties of the complexes were influenced by ILET. PMID:22966620

Park, Hye Rim; Kim, Bo Young; Kim, Young Kwan; Ha, Yunkyoung

2012-07-01

258

Synthesis and luminescence properties of iridium complexes chelated with coumarin ligands.  

PubMed

According to a recent report, the organic light-emitting diodes (OLEDs) using the iridium complexes of coumarin derivatives as emissive dopants are highly efficient and stable. Unlike the other Ir(III) phopsphorescent dopants, these coumarin-based Ir(III) complexes can effectively trap and transport electrons in the emissive layer. We have prepared a series of phosphorescent cyclometalated Ir(III) complexes containing 3-(2-pyridinyl)coumarin (pc) as an ancillary ligand. The new heteroleptic iridium complexes, Ir(C--N)2(pc) (CAN = 2-(2,4-difluorophenyl)pyridine (F2-ppy), 2-phenylpyridine (ppy) and 2-phenylquinoline (pq)) were characterized by 1H NMR and mass spectrometer. As main ligands, F2-ppy, ppy and pq were employed, which should have the drastically different ligand molecular orbital energy levels. The iridium complexes showed various emission ranges from 560 to 610 nm, depending upon the relative energy levels of their main and ancillary ligands. The photoabsorption, photoluminescence and electroluminescence of the complexes were studied. We also investigated the electrochemical properties of the iridium complexes to compare the HOMO and LUMO energy levels of these phosphorescent materials. PMID:23858875

Park, Hye Rim; Kim, Bo Young; Kim, Young Kwan; Ha, Yunkyoung

2013-05-01

259

Trialkylborane-Assisted CO2 Reduction by Late Transition Metal Hydrides  

PubMed Central

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.

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

2011-01-01

260

Iridium and Spherules in Late Eocene Impact Deposits  

NASA Technical Reports Server (NTRS)

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.

Kyte, F. T.; Liu, S.

2002-01-01

261

Iridium(III, 0, and -I) Complexes Stabilized by 1,1'-Bis(diphenylphosphino)ferrocene (dppf): Synthesis and Characterization. Crystal Structures of [Na(THF)(5)][Ir(dppf)(2)].THF and [Ir(dppf)(2)].  

PubMed

The iridium(I) complex stabilized by the organometallic ligand 1,1'-bis(diphenylphosphino)ferrocene (dppf), [Ir(dppf)(2)](+), 1, undergoes a cyclometalation reaction in solution to give the iridium(III) hydride [IrH(dppf(-H))(dppf)](+), 2, which has been isolated and characterized by spectroscopic methods. The compound is the final product of the intramolecular oxidative addition of the ortho C-H bond of a phenyl substituent of the diphosphine and is formed through an intermediate hydride, which has also been spectroscopically characterized. 1 can be electrochemically reduced to the Ir(0) and Ir(-I) species, [Ir(dppf)(2]), 3, and [Ir(dppf)(2)](-), 4, respectively, in two reversible single-electron processes. These low-valent metal complexes have been obtained by chemical reduction of 1 with sodium naphthalenide in tetrahydrofuran solution and their crystal and molecular structures determined by single-crystal X-ray analyses. 3 crystallizes in the triclinic system, space group P&onemacr;, with a = 13.019(4) Å, b = 13.765(6) Å, c = 15.549(5) Å, alpha = 93.74(3) degrees, beta = 90.35(3) degrees, gamma = 92.07(3) degrees, V = 2779(2) Å(3), and Z = 2. Anionic complex 4 crystallizes as sodium-solvated salt [Na(THF)(5)][Ir(dppf)(2)].THF, 4b, in which the sodium cation is surrounded by five molecules of THF in a slightly distorted trigonal-bipyramidal environment. 4b crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.325(3) Å, b = 23.976(5) Å, c = 26.774(7) Å, beta = 98.77(2) degrees, V = 8454(4) Å(3), and Z = 4. The coordination geometry around the metal in neutral d(9) complex 3 is intermediate between the highly distorted square-planar geometry, found earlier in cationic d(8) species 1, and the almost regular tetrahedral arrangement of the two diphosphines in the anionic d(10) complex 4. Reduction of Ir(I) to Ir(0) and Ir(-I) causes a stepwise decrease of the Ir-P bond length of 0.04 Å (average) and 0.05 Å, respectively, with a concomitant increase of the bite angle of the diphosphine which ranges from 94.3 degrees (average) in [Ir(dppf)(2)](+) to 102.3 degrees in [Ir(dppf)(2)](-). PMID:11671026

Longato, Bruno; Riello, Lorenzo; Bandoli, Giuliano; Pilloni, Giuseppe

1999-06-14

262

Cleavage of ether, ester, and tosylate C(sp3)-O bonds by an iridium complex, initiated by oxidative addition of C-H bonds. Experimental and computational studies.  

PubMed

A pincer-ligated iridium complex, (PCP)Ir (PCP = ?(3)-C6H3-2,6-[CH2P(t-Bu)2]2), is found to undergo oxidative addition of C(sp(3))-O bonds of methyl esters (CH3-O2CR'), methyl tosylate (CH3-OTs), and certain electron-poor methyl aryl ethers (CH3-OAr). DFT calculations and mechanistic studies indicate that the reactions proceed via oxidative addition of C-H bonds followed by oxygenate migration, rather than by direct C-O addition. Thus, methyl aryl ethers react via addition of the methoxy C-H bond, followed by ?-aryloxide migration to give cis-(PCP)Ir(H)(CH2)(OAr), followed by iridium-to-methylidene hydride migration to give (PCP)Ir(CH3)(OAr). Methyl acetate undergoes C-H bond addition at the carbomethoxy group to give (PCP)Ir(H)[?(2)-CH2OC(O)Me] which then affords (PCP-CH2)Ir(H)(?(2)-O2CMe) (6-Me) in which the methoxy C-O bond has been cleaved, and the methylene derived from the methoxy group has migrated into the PCP Cipso-Ir bond. Thermolysis of 6-Me ultimately gives (PCP)Ir(CH3)(?(2)-O2CR), the net product of methoxy group C-O oxidative addition. Reaction of (PCP)Ir with species of the type ROAr, RO2CMe or ROTs, where R possesses ?-C-H bonds (e.g., R = ethyl or isopropyl), results in formation of (PCP)Ir(H)(OAr), (PCP)Ir(H)(O2CMe), or (PCP)Ir(H)(OTs), respectively, along with the corresponding olefin or (PCP)Ir(olefin) complex. Like the C-O bond oxidative additions, these reactions also proceed via initial activation of a C-H bond; in this case, C-H addition at the ?-position is followed by ?-migration of the aryloxide, carboxylate, or tosylate group. Calculations indicate that the ?-migration of the carboxylate group proceeds via an unusual six-membered cyclic transition state in which the alkoxy C-O bond is cleaved with no direct participation by the iridium center. PMID:23469859

Kundu, Sabuj; Choi, Jongwook; Wang, David Y; Choliy, Yuriy; Emge, Thomas J; Krogh-Jespersen, Karsten; Goldman, Alan S

2013-04-01

263

Fatigue crack growth in lithium hydride  

SciTech Connect

Subcritical fatigue crack growth, from cyclic tensile loading, was demonstrated in warm pressed Polycrystalline lithium hydride. Experiments were performed with cyclic tension-tension crack opening (mode I) loads applied to a pre-cracked compact type specimen in an argon environment at a temperature of 21C (70F). The fatigue crack growth was found to occur between 7.56 {times} 10{sup {minus}ll} M/cycle (2.98 {times} l0{sup {minus}9} in/cycle) and 2.35 {times} l0{sup {minus}8} m/cycle (9.24{times}10{sup {minus}7} in/cycle) for a range of stress intensity factors between 1.04 MPa{center_dot}{radical}m (0.95 ksi{center_dot}{radical}in) and 1.49 MPa{center_dot}{radical}m (1.36 ksi{center_dot}{radical}in). The rate of fatigue crack growth from cyclic tensile loading was found to be in excess of crack growth from sustained loading at an equivalent stress intensity factor. Furthermore, a fatigue threshold was not evident from the acquired data.

Healy, T.E.

1993-09-01

264

Hydrides of DyCo/sub 3/  

SciTech Connect

Hydrogen desorption isotherms have been measured in the system DyCo/sub 3/H/sub x/ for 0 less than or equal to x less than or equal to 4.25 at temperatures of 0/sup 0/, 20/sup 0/, 40/sup 0/, 60/sup 0/, and 80/sup 0/C. Pressure plateaus on the isotherms indicate the existence of two hydride phases in addition to the terminal hydrogen-saturated metal ..cap alpha.. phase. Both exhibit a wide range of solid solutions. The ..beta.. phase runs from x = 1 to x = 1.83, while the ..gamma.. phase runs from 3.1 to at least 4.25. The ..cap alpha.. phase is very narrow. At 20/sup 0/C the plateau pressures are 3 torr and 54 torr, and the heats of absorption are -11.43 and -9.75 kcal/mole(H/sub 2/) respectively. From the temperature dependence of the isotherms, the partial molar heats and entropies of absorption and the heats and entropies of formation have been calculated as a function of x.

Kierstead, H.A.

1980-01-01

265

Investigation of Cracked Lithium Hydride Reactor Vessels  

SciTech Connect

Visual examination of lithium hydride reactor vessels revealed cracks that were adjacent to welds, most of which were circumferentially located in the bottom portion of the vessels. Sections were cut from the vessels containing these cracks and examined by use of the metallograph, scanning electron microscope, and microprobe to determine the cause of cracking. Most of the cracks originated on the outer surface just outside the weld fusion line in the base material and propagated along grain boundaries. Crack depths of those examined sections ranged from {approximately}300 to 500 {micro}m. Other cracks were reported to have reached a maximum depth of 1/8 in. The primary cause of cracking was the creation of high tensile stresses associated with the differences in the coefficients of thermal expansion between the filler metal and the base metal during operation of the vessel in a thermally cyclic environment. This failure mechanism could be described as creep-type fatigue, whereby crack propagation may have been aided by the presence of brittle chromium carbides along the grain boundaries, which indicates a slightly sensitized microstructure.

bird, e.l.; mustaleski, t.m.

1999-06-01

266

Catalytic [3 + 2] annulation of ketimines with alkynes via C-H activation by a cationic iridium(cod) complex.  

PubMed

[3 + 2] Annulation of ketimines with internal and terminal alkynes proceeded via C-H activation to give aminoindene derivatives in high yields, which is catalyzed by a cationic iridium complex coordinated with 1,5-cyclooctadiene (cod). PMID:24797408

Nagamoto, Midori; Nishimura, Takahiro

2014-06-14

267

Study of the electrochemical behavior in tungsten and caustic solutions and platinum/iridium in chloride solutions, informal report.  

National Technical Information Service (NTIS)

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...

C. M. Vitus H. S. Isaacs V. Schroeder

1994-01-01

268

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

NASA Astrophysics Data System (ADS)

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-.

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

2014-02-01

269

Evaluated Iridium, Yttrium, and Thulium Cross Sections and Integral Validation Against Critical Assembly and Bethe Sphere Measurements  

Microsoft Academic Search

We describe new dosimetry (radiochemical) ENDF evaluations for yttrium, iridium, and thulium. These LANL2006 evaluations were based upon measured data and on nuclear model cross section calculations. In the case of iridium and yttrium, new measurements using the GEANIE gamma-ray detector at LANSCE were used to infer (n,xn) cross sections, the measurements being augmented by nuclear model calculations using the

M. B. Chadwick; S. Frankle; H. Trellue; P. Talou; T. Kawano; P. G. Young; R. E. MacFarlane; C. W. Wilkerson

2007-01-01

270

Chinese puzzle molecule: a 15?hydride, 28?copper atom nanoball.  

PubMed

The syntheses of the first rhombicuboctahedral copper polyhydride complexes [Cu28 (H)15 (S2 CNR)12 ]PF6 (NR=N(n) Pr2 or aza-15-crown-5) are reported. These complexes were analyzed by single-crystal X-ray and one by neutron diffraction. The core of each copper hydride nanoparticle comprises one central interstitial hydride and eight outer-triangular-face-capping hydrides. A further six face-truncating hydrides form an unprecedented bridge between the inner and outer copper atom arrays. The irregular inner Cu4 tetrahedron is encapsulated within the Cu24 rhombicuboctahedral cage, which is further enclosed by an array of twelve dithiocarbamate ligands that subtends the truncated octahedron of 24?sulfur atoms, which is concentric with the Cu24 rhombicuboctahedron and Cu4 tetrahedron about the innermost hydride. For these compounds, an intriguing, albeit limited, H2 evolution was observed at room temperature, which is accompanied by formation of the known ion [Cu8 (H)(S2 CNR)6 ](+) upon exposure of solutions to sunlight, under mild thermolytic conditions, and on reaction with weak (or strong) acids. PMID:24803070

Edwards, Alison J; Dhayal, Rajendra S; Liao, Ping-Kuei; Liao, Jian-Hong; Chiang, Ming-Hsi; Piltz, Ross O; Kahlal, Samia; Saillard, Jean-Yves; Liu, C W

2014-07-01

271

Synthesis and Characterization of Carbazolide-Based Iridium PNP Pincer Complexes. Mechanistic and Computational Investigation of Alkene Hydrogenation: Evidence for an Ir(III)/Ir(V)/Ir(III) Catalytic Cycle.  

PubMed

New carbazolide-based iridium pincer complexes ((carb)PNP)Ir(C2H4), 3a, and ((carb)PNP)Ir(H)2, 3b, have been prepared and characterized. The dihydride, 3b, reacts with ethylene to yield the cis-dihydride ethylene complex cis-((carb)PNP)Ir(C2H4)(H)2. Under ethylene this complex reacts slowly at 70 °C to yield ethane and the ethylene complex, 3a. Kinetic analysis establishes that the reaction rate is dependent on ethylene concentration and labeling studies show reversible migratory insertion to form an ethyl hydride complex prior to formation of 3a. Exposure of cis-((carb)PNP)Ir(C2H4)(H)2 to hydrogen results in very rapid formation of ethane and dihydride, 3b. DFT analysis suggests that ethane elimination from the ethyl hydride complex is assisted by ethylene through formation of ((carb)PNP)Ir(H)(Et)(C2H4) and by H2 through formation of ((carb)PNP)Ir(H)(Et)(H2). Elimination of ethane from Ir(III) complex ((carb)PNP)Ir(H)(Et)(H2) is calculated to proceed through an Ir(V) complex ((carb)PNP)Ir(H)3(Et) which reductively eliminates ethane with a very low barrier to return to the Ir(III) dihydride, 3b. Under catalytic hydrogenation conditions (C2H4/H2), cis-((carb)PNP)Ir(C2H4)(H)2 is the catalyst resting state, and the catalysis proceeds via an Ir(III)/Ir(V)/Ir(III) cycle. This is in sharp contrast to isoelectronic (PCP)Ir systems in which hydrogenation proceeds through an Ir(III)/Ir(I)/Ir(III) cycle. The basis for this remarkable difference is discussed. PMID:24746026

Cheng, Chen; Kim, Bong Gon; Guironnet, Damien; Brookhart, Maurice; Guan, Changjian; Wang, David Y; Krogh-Jespersen, Karsten; Goldman, Alan S

2014-05-01

272

An in-situ Raman study of the effect of the support for adsorbed iridium-chelates in catalysing oxygen reduction  

Microsoft Academic Search

In-situ Raman spectroscopy was used to obtain some insight into the mechanism of oxygen reduction at adsorbed layers of iridium-octaethylporphyrin (IrOEP), iridium-tetraphenylporphyrin (IrTPP) and iridium-phthalocyanine (IrPc). The selectivity of adsorbed layers of both porphyrins appears to be very sensitive to the support: on gold only hydrogen peroxide is formed whereas on carbon four-electron reduction is observed. On both supports a

A. L. Bouwkamp-Wijnoltz; B. J. Palys; WHM Visscher; J. A. R. van Veen

1996-01-01

273

Investigation of metal hydride materials as hydrogen reservoirs for metal-hydrogen batteries  

NASA Technical Reports Server (NTRS)

The performance and suitability of various metal hydride materials were examined for use as possible hydrogen storage reservoirs for secondary metal-hydrogen batteries. Lanthanum pentanickel hydride appears as a probable candidate in terms of stable hydrogen supply under feasible thermal conditions. A kinetic model describing the decomposition rate data of the hydride has been developed.

ONISCHAK

1976-01-01

274

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

Microsoft Academic Search

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.

Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

2012-01-01

275

Corrosion of Hydrides of Nickel and Cu30Ni Alloy in Oxygen Containing Solutions  

Microsoft Academic Search

Corrosion behavior of nickel hydride is studied in alkaline, neutral, and weakly acidic oxygen-containing solutions by compensating oxygen consumed in corrosion and spectrophotometric analysis of solution for nickel. It is shown that in the course of nickel hydride corrosion in alkaline solutions, oxygen is consumed solely in its interaction with hydrogen formed at hydride decomposition, while nickel remains at the

G. N. Markos’yan; D. S. Sirota; A. P. Pchel’nikov

2005-01-01

276

System for deposition and hydriding of thin metallic films without air exposure  

Microsoft Academic Search

A non-air exposed hydriding\\/deposition system provides advanced processing capability for hydriding erbium thin films. The system is designed with precise controls for cold crucible electron beam deposition of erbium, film deposition monitoring, and temperature bakeout. Using a mechanical transfer device, a complete hydriding process for erbium deposited films can be completed without air exposure. The system offers many processing improvements

C. C. Eichman; J. L. Comeau; K. R. Rinehuls

1974-01-01

277

Excimer laser deinsulation of Parylene-C on iridium for use in an activated iridium oxide film-coated Utah electrode array  

PubMed Central

Implantable microelectrodes provide a measure to electrically stimulate neurons in the brain and spinal cord and record their electrophysiological activity. A material with a high charge capacity such as activated or sputter-deposited iridium oxide film (AIROF or SIROF) is used as an interface. The Utah electrode array (UEA) uses SIROF for its interface material with neural tissue and oxygen plasma etching (OPE) with an aluminium foil mask to expose the active area, where the interface between the electrode and neural tissue is formed. However, deinsulation of Parylene-C using OPE has limitations, including the lack of uniformity in the exposed area and reproducibility. While the deinsulation of Parylene-C using an excimer laser is proven to be an alternative for overcoming the limitations, the iridium oxide (IrOx) suffers from fracture when high laser fluence (>1000 mJ/cm2) is used. Iridium (Ir), which has a much higher fracture resistance than IrOx, can be deposited before excimer laser deinsulation and then the exposed Ir film area can be activated by electrochemical treatment to acquire the AIROF. Characterisation of the laser-ablated Ir film and AIROF by surface analysis (X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscope) and electrochemical analysis (electrochemical impedance spectroscopy, and cyclic voltammetry) shows that the damage on the Ir film induced by laser irradiation is significantly less than that on SIROF, and the AIROF has a high charge storage capacity. The results show the potential of the laser deinsulation technique for use in high performance AIROF-coated UEA fabrication.

Yoo, Je-Min; Negi, Sandeep; Tathireddy, Prashant; Solzbacher, Florian; Song, Jong-In; Rieth, Loren W.

2013-01-01

278

Heat-actuated metal hydride hydrogen compressor testing  

SciTech Connect

Electric utilities use hydrogen for cooling turbine generators. The majority of the utilities purchase the gas from industrial gas markets. On-site electrolytic hydrogen production may prove advantageous both logistically and economically. In order to demonstrate this concept, Public Service Electric and Gas Co. (PSE and G) and EPRI installed an electrolyzer at the Sewaren (NJ) station. To compress the gas, PSE and G purchased a heat-activated metal hydride compressor from Ergenics, Inc. This report describes closed- and open-cycle tests conducted on this metal hydride hydrogen compressor. Test systems, plans, methodologies, and results are presented. A brief discussion evaluates these performance results, addresses some of the practical problems involved with electrolyzer-compressor interface, and compares the costs and benefits of metal hydride versus mechanical hydrogen compression for utility generator cooling.

Piraino, M.; Metz, P.D.; Nienke, J.L.; Freitelberg, A.S.; Rahaman, R.S.

1985-09-01

279

Interstellar sulfur hydride: a search for the 111-megahertz lines.  

PubMed

Similarities in the energy-level structure of the sulfur hydride radical and the hydroxyl radical suggest that sulfur hydride in the interstellar medium might be detectable because of a population inversion or anti-inversion similar to that of the hydroxyl radical. We have searched for the 111.54-megahertz transition [F (total angular momentum quantum number) = 2 --> 2] and for the 111.22-megahertz transition (F = 1 --> 1) in the galactic radio source W49, one of the brightest hydroxyl emission sources. No sulfur hydride emission lines with half-power widths of 130 hertz or greater were detected with the 1000-foot Arecibo antenna. The upper limits established with 100-hertz filters were 50 and 60 flux units (1 flux unit= 10(26) watt meter(-2) hertz(-1)), respectively, for the two lines. PMID:17738363

Meeks, M L; Gordon, M A; Litvak, M M

1969-01-10

280

Investigation of metal hydride nanoparticles templated in metal organic frameworks.  

SciTech Connect

Hydrogen is proposed as an ideal carrier for storage, transport, and conversion of energy. However, its storage is a key problem in the development of hydrogen economy. Metal hydrides hold promise in effectively storing hydrogen. For this reason, metal hydrides have been the focus of intensive research. The chemical bonds in light metal hydrides are predominantly covalent, polar covalent or ionic. These bonds are often strong, resulting in high thermodynamic stability and low equilibrium hydrogen pressures. In addition, the directionality of the covalent/ionic bonds in these systems leads to large activation barriers for atomic motion, resulting in slow hydrogen sorption kinetics and limited reversibility. One method for enhancing reaction kinetics is to reduce the size of the metal hydrides to nano scale. This method exploits the short diffusion distances and constrained environment that exist in nanoscale hydride materials. In order to reduce the particle size of metal hydrides, mechanical ball milling is widely used. However, microscopic mechanisms responsible for the changes in kinetics resulting from ball milling are still being investigated. The objective of this work is to use metal organic frameworks (MOFs) as templates for the synthesis of nano-scale NaAlH4 particles, to measure the H2 desorption kinetics and thermodynamics, and to determine quantitative differences from corresponding bulk properties. Metal-organic frameworks (MOFs) offer an attractive alternative to traditional scaffolds because their ordered crystalline lattice provides a highly controlled and understandable environment. The present work demonstrates that MOFs are stable hosts for metal hydrides and their reactive precursors and that they can be used as templates to form metal hydride nanoclusters on the scale of their pores (1-2 nm). We find that using the MOF HKUST-1 as template, NaAlH4 nanoclusters as small as 8 formula units can be synthesized inside the pores. A detailed picture of the hydrogen desorption is investigated using a simultaneous thermogravimetric modulated-beam mass spectrometry instrument. The hydrogen desorption behavior of NaAlH4 nano-clusters is found to be very different from bulk NaAlH4. The bulk NaAlH4 desorbs about 70 wt% hydrogen {approx}250 C. In contrast, confinement of NaAlH4 within the MOF pores dramatically increases the rate of H2 desorption at lower temperatures. About {approx}80% of the total H2 desorbed from MOF-confined NaAlH4 is observed between 70 to 155 C. In addition to HKUST-1, we find that other MOFs (e.g. MIL-68 and MOF-5) can be infiltrated with hydrides (LiAlH4, LiBH4) or hydride precursors (Mg(C4H9)2 and LiC2H5) without degradation. By varying pore dimensions, metal centers, and the linkers of MOFs, it will be possible to determine whether the destabilization of metal hydrides is dictated only by the size of the metal hydride clusters, their local environment in a confined space, or by catalytic effects of the framework.

Jacobs, Benjamin W.; Herberg, Julie L. (Lawrence Livermore National Laboratory, Livermore, CA); Highley, Aaron M.; Grossman, Jeffrey (MIT, Cambridge, MA); Wagner, Lucas (MIT, Cambridge, MA); Bhakta, Raghu; Peaslee, D. (University of Missouri, St. Louis, MO); Allendorf, Mark D.; Liu, X. (University of Missouri, St. Louis, MO); Behrens, Richard, Jr.; Majzoub, Eric H. (University of Missouri, St. Louis, MO)

2010-11-01

281

Decomposition of the hexagonal copper hydride at high pressure  

NASA Astrophysics Data System (ADS)

The process of decomposition of hexagonal copper hydride has been observed in situ in a diamond anvil cell (DAC) using the energy dispersive X-ray diffraction (EDXRD) method. The presence and intensity of diffraction lines of the hexagonal CuH 0.8 phase have been taken as a probe for the decomposition process. The intensity of diffraction lines decreases abruptly in the vicinity of 8.4 GPa, indicating complete decomposition of the hydride. The determined value of decomposition pressure is equal to 8.4±0.6 GPa. The standard Gibbs energy of formation of 54.0±1.3 kJ mol -1 (H 2) calculated for copper hydride has been compared with the result obtained from calorimetric studies. The large discrepancy between the two values suggests that the decomposition pressure does not describe 'true' equilibrium conditions in this system.

Tkacz, M.; Burtovyy, R.

2004-10-01

282

The Reactivity Patterns of Low-Coordinate Iron Hydride Complexes  

PubMed Central

We report a survey of the reactivity of the first isolable iron-hydride complexes with a coordination number less than five. The high-spin iron(II) complexes [(?-diketiminate)Fe(?-H)]2 react rapidly with representative cyanide, isocyanide, alkyne, N2, alkene, diazene, azide, CO2, carbodiimide and Brønsted acid containing substrates. The reaction outcomes fall into three categories: (1) addition of Fe-H across a multiple bond of the substrate, (2) reductive elimination of H2 to form iron(I) products, and (3) protonation of the hydride to form iron(II) products. The products include imide, isocyanide, vinyl, alkyl, azide, triazenido, benzo[c]cinnoline, amidinate, formate, and hydroxo complexes. These results expand the range of known bond transformations at iron complexes. Additionally, they give insight into the elementary transformations that may be possible at the iron-molybdenum cofactor of nitrogenases, which may have hydride ligands on high-spin, low coordinate metal atoms.

Yu, Ying; Sadique, Azwana R.; Smith, Jeremy M.; Dugan, Thomas R.; Cowley, Ryan E.; Brennessel, William W.; Flaschenriem, Christine J.; Bill, Eckhard; Cundari, Thomas R.; Holland, Patrick L.

2008-01-01

283

Hydrogen storage in fullerenes and in an organic hydride  

SciTech Connect

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).

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

284

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.  

SciTech Connect

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

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

2012-02-01

285

High-Spin Cobalt Hydrides for Catalysis  

SciTech Connect

Organometallic chemists have traditionally used catalysts with strong-field ligands that give low-spin complexes. However, complexes with a weak ligand field have weaker bonds and lower barriers to geometric changes, suggesting that they may lead to more rapid catalytic reactions. Developing our understanding of high-spin complexes requires the use of a broader range of spectroscopic techniques, but has the promise of changing the mechanism and/or selectivity of known catalytic reactions. These changes may enable the more efficient utilization of chemical resources. A special advantage of cobalt and iron catalysts is that the metals are more abundant and cheaper than those currently used for major industrial processes that convert unsaturated organic molecules and biofeedstocks into useful chemicals. This project specifically evaluated the potential of high-spin cobalt complexes for small-molecule reactions for bond rearrangement and cleavage reactions relevant to hydrocarbon transformations. We have learned that many of these reactions proceed through crossing to different spin states: for example, high-spin complexes can flip one electron spin to access a lower-energy reaction pathway for beta-hydride elimination. This reaction enables new, selective olefin isomerization catalysis. The high-spin cobalt complexes also cleave the C-O bond of CO2 and the C-F bonds of fluoroarenes. In each case, the detailed mechanism of the reaction has been determined. Importantly, we have discovered that the cobalt catalysts described here give distinctive selectivities that are better than known catalysts. These selectivities come from a synergy between supporting ligand design and electronic control of the spin-state crossing in the reactions.

Holland, Patrick L. [Yale University] [Yale University

2013-08-29

286

Photoelectron spectroscopy of boron aluminum hydride cluster anions.  

PubMed

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, BxAlyHz (-), 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. PMID:24784280

Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H; Li, Xiang; Kiran, Boggavarapu; Kandalam, Anil K

2014-04-28

287

Ab-initio study of transition metal hydrides  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

288

Materials science of Mg-Ni-based new hydrides  

Microsoft Academic Search

.   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)

S. Orimo; H. Fujii

2001-01-01

289

Surface studies of iridium-alloy grain boundaries associated with weld cracking  

SciTech Connect

Plutonium-238 oxide fuel pellets for the General Purpose Heat Source (GPHS) Radioisotopic Thermoelectric Generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in iridium alloy at the Savannah River Plant (SRP). Underbead cracks occasionally occur in the girth weld on the iridium-alloy-clad vent sets in the region where the gas tungsten arc is quenched. Grain-boundary structures and compositions were characterized by scanning electron microscopy/x-ray energy spectroscopy, electron microprobe analysis and scanning Auger microprobe analysis to determine the cause of weld quench area cracking. Results suggest that weld quench area cracking may be caused by gas porosity or liquation in the grain boundaries.

Mosley, W.C.

1982-01-01

290

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials  

PubMed Central

Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers.

Kappaun, Stefan; Slugovc, Christian; List, Emil J. W.

2008-01-01

291

Synthesis and phosphorescent properties of the copolymers of N-vinylcarbazole, methyl methacrylate and iridium complex  

NASA Astrophysics Data System (ADS)

The copolymers containing carbazole unit and iridium complexes, such as (Ir(bpy)2Cl, Ir(mbpy)2Cl and Ir(Brbpy)2Cl, were synthesized via radical copolymerization of N-vinylcarbazole, methyl methacrylate and iridium complex. The synthesized copolymers were characterized by FT-IR, UV-Vis absorption spectroscopy and photoluminescence (PL) spectroscopy, respectively. According to the results, the copolymers (Ir(Brbpy)2Cl/PVK and Ir(mbpy)2Cl/PVK) exhibit yellow phosphorescence with an emission peak at around 553 nm under UV-visible light in the solid state. The results also reveal almost complete energy transfer from the host carbazole segments to the guest Ir complex in the copolymer film when the Ir content reaches 1.0 wt.%. The synthesized copolymers are good candidates as blue or yellow phosphorescent materials for PLED applications.

Wang, Wen; Zhou, Minglu; Liang, Luying; Lin, Meijuan; Ling, Qidan

2014-03-01

292

Iridium-bearing sublimates at a hot-spot volcano (Piton de la Fournaise, Indian Ocean)  

SciTech Connect

Sublimates and incrustations derived upon the cooling of volcanic gases have been collected on various sites (Piton de la Fournaise, Poas, Momotombo, Etna, Ardoukoba and Erta-Ale). They have been analyzed for Ir and other volatile elements (Se, As, Cu, Au, Ag, Pb, Tl) by means of instrumental neutron activation analysis (INAA) and proton induced X-Ray emission (PIXE). Among the investigated volcanoes, only Piton de la Fournaise is found to release detectable amounts of iridium. Ir in Piton de la Fournaise sublimates is associated with F-minerals. This confirms its gaseous transport as a volatile fluoride compound. Iridium seems to be preferentialy released by hot-spot type volcanoes, and its detection in Piton de la Fournaise sublimates provides a positive argument in favor of a volcanic hypothesis to explain the KTB events.

Toutain, J.P. (Observatorio Vesuviano, Napoli (Italy)); Meyer, G.

1989-12-01

293

The treatment of malignant diseases in Romania using stainless steel encapsulated iridium-192 sources  

NASA Astrophysics Data System (ADS)

Iridium-192 sources supplied by the Institute for Nuclear Physics and Engineering have been used in Romanian radiotherapy clinics since 1980. The source assembly is sealed in a protective stainless steel sheath which satisfies the requirements of international standards. Since this sheath acts as a filter to change the characteristic spectrum it has been necessary to determine experimentally an accurate value of the specific gamma-ray constant. Some clinical aspects of the complex treatment of carcinomas with iridium-192 are reviewed. Results of the calculation of the dose distribution around single and multiple sources are given for different applications in the treatment of carcinomas of the vaginal and uterine cervix, oral cavity, rectum and vagina.

Stanef, I.; Matache, G.; Cioc?ltei, V.; Gheorghiev, G.

1994-01-01

294

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

SciTech Connect

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.

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

1998-12-31

295

Electrochemical hydride generation for the simultaneous determination of hydride forming elements by inductively coupled plasma-atomic emission spectrometry  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of As, Sb, Se, Sn and Ge were performed by inductively coupled plasma atomic emission spectrometry following their electrochemical hydride generation. An electrochemical hydride generator based on a concentric arrangement with a porous cathode, working in a continuous flow mode was used. The effects of sample flow rate, applied current and electrolytic solution concentration on response were studied and their influence on the mechanisms of hydride generation discussed. Four materials, particulate lead, reticulated vitreous carbon (RVC), silver and amalgamated silver were tested as cathode materials. The best results were achieved with particulate lead and RVC cathodes, wherein generation efficiencies higher than 80% were estimated for most of the analytes. In general, limits of detection between 0.1 and 3.6 ng ml -1 and a precision better than 5% were achieved using a lead cathode. The analysis of a marine sediment reference material (PACS-2, NRC) showed good agreement with the certified values for As and Se.

Bolea, E.; Laborda, F.; Castillo, J. R.; Sturgeon, R. E.

2004-04-01

296

Surface characterization of copper electroless deposition on atomic layer deposited palladium on iridium and tungsten  

Microsoft Academic Search

Iridium and tungsten refractory metals possess high melting points, hardness, and good electrical resistivity. Palladium has been recently deposited on W and Ir via atomic layer deposition and it is also an appropriate catalyst for the electroless deposition of copper. Palladium was deposited at 80±5 °C with a PdII(hfac)2 sublimation temperature of 46.0±0.5 °C using 13 sccm Ar as a

Young-Soon Kim; Jiho Shin; Joong-Hee Cho; Gregory A. Ten Eyck; De-Li Liu; Samuk Pimanpang; Toh-Ming Lu; Jay J. Senkevich; Hyung-Shik Shin

2006-01-01

297

Impurity effects on high-temperature tensile ductility of iridium alloys at high strain rate  

Microsoft Academic Search

The current study was undertaken to determine what effects, if any, larger amounts of certain impurities (Al,Cr,Fe,Ni, and Si) might have on the physical metallurgy and mechanical properties of the DOP-26 iridium alloy. This report summarizes the effects of these impurities on grain growth behavior and high-temperature high-strain-rate tensile ductility. Comparisons are made to the grain growth behavior and high-strain-rate

C. G. McKamey; E. P. George; E. H. Lee; E. K. Ohriner; L. Heatherly; J. W. Cohron

1999-01-01

298

Iridium thin films deposited via pulsed laser deposition for future applications as transition-edge sensors  

Microsoft Academic Search

The University of Miami has recently started developing and studying high-resolution microcalorimeters operating near 100mK for X-ray and particle physics and astrophysics. These detectors will be based on Transition Edge Sensors technology fabricated using iridium thin films deposited via the Pulsed Laser Deposition technique. We report here the preliminary result of the room temperature characterization of the Ir thin films,

M. Galeazzi; C. Chen; J. L. Cohn; J. O. Gundersen

2004-01-01

299

Neutron-Capture Gamma-Rays of Bromine, Copper, Iridium, Nickel and Tungsten  

Microsoft Academic Search

Investigations were undertaken to obtain information about the formation ; and decay of nuclei occurring as the products in neutron-capture reactions. ; Samples of natural bromine, copper, iridium, nickel, and tungsten, and separated ; isotope, samples of Br⁷⁹, Br⁸¹, Ni⁵⁸, Ni⁶° , Ni\\/sup ; 62\\/, W¹⁸², W¹⁸⁴, and W¹⁸⁶, were placed in a neutron beam and ; their neutron-capture gamma-ray

Paul Albert Treado

1962-01-01

300

Sputtered platinum–iridium layers as electrode material for functional electrostimulation  

Microsoft Academic Search

In this study co-sputtered layers of platinum–iridium (PtIr) are investigated as stimulation electrode material. The effects of different sputter parameters on the morphology and the electrochemical behavior are examined. It is shown that films sputtered at the lowest incident energy possess the highest charge storage capacity (CSC). At a Pt:Ir atomic-ratio of 55:45 the obtained CSC of 22mC\\/cm2 is enhanced

G. Ganske; E. Slavcheva; A. van Ooyen; W. Mokwa; U. Schnakenberg

2011-01-01

301

X-ray characteristics of iridium and platinum blacks of various dispersity  

Microsoft Academic Search

X-ray and structural characteristics of iridium and platinum blacks of various dispersity in the coherent scattering region from 40 to 700 Å have been studied. High dispersity blacks are shown to contain crystalline and X-ray amorphous particles with a disordered structure and decreased coordination number. For such blacks a 0.003 Å increase in the unit cell parameter is observed.

E. M. Moroz; S. V. Bogdanov; V. A. Ushakov

1978-01-01

302

Saturation of global field aligned currents observed during storms by the Iridium satellite constellation  

Microsoft Academic Search

We use Iridium constellation magnetometer data to characterize the global-scale storm-time Birkeland currents. For 11–12 August 2000 we find a strong storm main phase dawn–dusk asymmetry in the latitudes of the region 1–2 current systems and that the total current is not linearly related to the interplanetary electric field, Ey. Examination of 23 storms occurring for 1999–2003 shows clear evidence

B. J. Anderson; H. Korth

2007-01-01

303

Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles  

PubMed Central

Summary Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with various aliphatic and aromatic secondary amines are reported for the first time. The reaction gave the corresponding trans-1,2-dihydronaphthalenol derivatives in good yields with moderate enantioselectivities in the presence of 2.5 mol % [Ir(COD)Cl]2 and 5 mol % bisphosphine ligand (S)-p-Tol-BINAP. The trans-configuration of 3f was confirmed by X-ray crystallography.

Hu, Ping; Long, Yuhua; Wu, Yujuan; Zeng, Heping; Wang, Hui; Zuo, Xiongjun

2009-01-01

304

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

PubMed

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

Brayton, Daniel F; Jensen, Craig M

2014-06-01

305

Electrochemical removal of MTBE from water using the iridium dioxide coated electrode  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) is always the most likely found compound at the front of a gasoline plume due to its chemical characteristics. In this study, an iridium dioxide (IrO2) coated electrode was utilized to perform electrochemical removal of MTBE in a lab-scale bath electrolyzer. Depending on the constant-potential controls, electrochemical removal of MTBE can be conducted either through direct

Ting-Nien Wu

2011-01-01

306

Interstitial iridium-192 implantation combined with external radiotherapy in anal cancer: Ten years experience  

Microsoft Academic Search

Purpose: To report our experience in the use of interstitial iridium-192 implantation combined with external radiotherapy in anal cancer.Methods and Matarials: From 1984 to 1994, 79 patients with anal cancer were treated with radical intent using radiotherapy (plus chemotherapy) at Beatson Oncology Centere, Glasgow, Scotland. The mean and median age at presetantion were 68 and 70 years, respectively (range 34–85)

Ajay P. S. Sandhu; R. Paul Symonds; Andrew G. Robertson; Nick S. Reed; Stuart G. McNee; Jim Paul

1998-01-01

307

Interstitial hyperthermia and interstitial Iridium 192 implantation: a technique and preliminary results  

SciTech Connect

A simple technique using interstitial hyperthermia in combination with interstitial Iridium 192 implantation is described in detail. This technique was initially tested on swine and later successfully tested on seven patients. The preliminary results of the City of Hope Interstitial Hyperthermia Pilot protocol are stated. The authors feel that this simple technique could be used by any radiation oncologist while performing interstitial implants in selected sites.

Joseph, C.D. (City of Hope National Medical Center, Duarte, CA); Astrahan, M.; Lipsett, J.; Archambeau, J.; Forell, B.; George, F.W. III

1981-06-01

308

Mechanism of the dehydrogenation of formic acid by iridium and rhodium complexes  

Microsoft Academic Search

The homogeneous catalytic process HCOOH?H2+CO2 has been studied in the presence of carbonyl-free phosphine complexes of iridium (I) and (III), and rhodium (I). The rupture of the C?H bond has been found to be the rate-determining step. The halide ion and phosphine are first substituted by formate ion in the cordination sphere of the metal. The reaction mechanism and its

E. N. Yurtchenko; N. P. Anikeenko

1975-01-01

309

Iridium-Catalyzed Asymmetric Hydrogenation of Pyrrolo[1,2-a]pyrazinium Salts.  

PubMed

Highly enantioselective iridium-catalyzed hydrogenation of pyrrolo[1,2-a]pyrazinium salts has been achieved, providing a direct access to chiral 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine derivatives with up to 95% ee. The key feature of the reaction is the addition of cesium carbonate, which increases the conversion and prohibits the racemization pathway of products. PMID:24911796

Huang, Wen-Xue; Yu, Chang-Bin; Shi, Lei; Zhou, Yong-Gui

2014-06-20

310

DEFORMATION MODELING OF IRIDIUM DOP26 ALLOY TO DETERMINE POTENTIAL FOR SECONDARY RECRYSTALLIZATION  

Microsoft Academic Search

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

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

2008-01-01

311

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

NASA Astrophysics Data System (ADS)

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.

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

1997-10-01

312

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

SciTech Connect

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.

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

1986-06-01

313

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

USGS Publications Warehouse

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??.

Millard, Jr. , H. T.

1987-01-01

314

Synthesis and electrophosphorescence of iridium complexes containing benzothiazole-based ligands.  

PubMed

Four heteroleptic bis-cyclometalated iridium(III) complexes containing 2-aryl-benzothiazole ligands, in which the aryl is dibenzofuran-2-yl [Ir(O-bt)2(acac)], dibenzothiophene-2-yl [Ir(S-bt)2(acac)], dibenzothiophene-S,S-dioxide-2-yl [Ir(SO2-bt)2(acac)] and 4-(diphenylphosphoryl)phenyl [Ir(PO-bt)2(acac)], have been synthesized and characterized for use in organic light-emitting diodes (OLEDs). These complexes emit bright yellow (551 nm) to orange-red (598 nm) phosphorescence at room temperature, the peak wavelengths of which can be finely tuned depending upon the electronic properties of the aryl group in the 2-position of benzothiazole. The strong electron-withdrawing aryls such as dibenzothiophene-S,S-dioxide2-yl and 4-(diphenylphosphoryl)phenyl caused bathochromatic shift of the iridium complex phosphorescence. These iridium complexes were used as doped emitters to fabricate yellow to orange-red OLEDs and good performance was obtained. In particular, a maximum luminance efficiency of 58.4 cd A(-1) (corresponding to 30.6 lm W(-1) and 19%) with CIE coordinates of (0.45, 0.52) was achieved for Ir(O-bt)2(acac)-based yellow device. Furthermore, the yellow emitting Ir(S-bt)2(acac) was used to fabricate two-element white OLED that exhibited a high efficiency of 32.4 cd A(-1) with CIE coordinates of (0.28, 0.44). PMID:23688112

Liu, Di; Ren, Huicai; Deng, Lijun; Zhang, Ting

2013-06-12

315

A Novel Efficient Red Emitting Iridium Complex for Polymer Light Emitting Diodes  

NASA Astrophysics Data System (ADS)

Photo-physical properties of iridium complexes bis(1-(2',4'-difluorobiphenyl -4-yl)isoquinoline)iridium(III)(5-(4-(bis(4-methoxyphenyl)amino)phenyl)picolinic acid) used as phosphorescent dopant in polymer light-emitting devices with a blend ofpoly(9,9-dioctylfluorene) and 2-tert-butyl-phenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix are investigated. The iridium complex exhibits distinct UV-vis absorption bands around 300-450 nm and intense red photoluminescent emissions peaked at around 618 nm in dichloromethane. The devices display a maximum external quantum efficiency of 4.8% and luminous efficiency of 3.1 cd·A-1 at current density of 3.2 mA·cm-2 with a dominant red emission peak around 620 nm and a shoulder around 660 nm. At 100 mA·cm-2, the devices still display a maximum external quantum efficiency as high as 3.9%.

Hu, Zheng-Yong; Yang, Jian-Kui; Luo, Jing; Liang, Min; Wang, Jing

2012-12-01

316

Construction, assessment, and application of a bond-order potential for iridium  

NASA Astrophysics Data System (ADS)

A tight-binding based bond-order potential (BOP) has been constructed for the fcc transition metal iridium that includes explicitly only d orbitals in the evaluation of the total energy. We show that hybridization between the nearly free electron sp band and the unsaturated covalently bonded d orbitals is important in determining the relative stabilities of the close-packed structures and that this effect can be accurately captured through the use of a central force term. The BOP is found to provide an excellent description of the equilibrium properties of iridium, including its negative Cauchy pressure that is fitted using a many-body repulsive term. The transferability of the BOP is assessed by calculating energy differences between different crystal structures, the energetics of the tetragonal and trigonal deformation paths, the phonon spectra, stacking fault, and vacancy formation energies. Comparison of the results of these studies with either experiments or first principles calculations is found to be good. We also describe briefly the application of the constructed BOP to the atomistic simulation of the core structure of the screw dislocation that led to an explanation of the anomalous deformation and fracture behavior exhibited of iridium.

Cawkwell, M. J.; Nguyen-Manh, D.; Pettifor, D. G.; Vitek, V.

2006-02-01

317

Synthesis, characterisation and application of iridium(III) photosensitisers for catalytic water reduction.  

PubMed

The synthesis of novel, monocationic iridium(III) photosensitisers (Ir-PSs) with the general formula [Ir(III)(C^N)(2)(N^N)](+) (C^N: cyclometallating phenylpyridine ligand, N^N: neutral bidentate ligand) is described. The structures obtained were examined by cyclic voltammetry, UV/Vis and photoluminescence spectroscopy and X-ray analysis. All iridium complexes were tested for their ability as photosensitisers to promote homogeneously catalysed hydrogen generation from water. In the presence of [HNEt(3)][HFe(3)(CO)(11)] as a water-reduction catalyst (WRC) and triethylamine as a sacrificial reductant (SR), seven of the new iridium complexes showed activity. [Ir(6-iPr-bpy)(ppy)(2)]PF(6) (bpy: 2,2'-bipyridine, ppy: 2-phenylpyridine) turned out to be the most efficient photosensitiser. This complex was also tested in combination with other WRCs based on rhodium, platinum, cobalt and manganese. In all cases, significant hydrogen evolution took place. Maximum turnover numbers of 4550 for this Ir-PS and 2770 for the Fe WRC generated in situ from [HNEt(3)][HFe(3)(CO)(11)] and tris[3,5-bis(trifluoromethyl)phenyl]phosphine was obtained. These are the highest overall efficiencies for any Ir/Fe water-reduction system reported to date. The incident photon to hydrogen yield reaches 16.4% with the best system. PMID:21557356

Gärtner, Felix; Cozzula, Daniela; Losse, Sebastian; Boddien, Albert; Anilkumar, Gopinatan; Junge, Henrik; Schulz, Thomas; Marquet, Nicolas; Spannenberg, Anke; Gladiali, Serafino; Beller, Matthias

2011-06-14

318

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

SciTech Connect

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.

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

319

Hydride vapor phase epitaxy of aluminum nitride  

NASA Astrophysics Data System (ADS)

AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the masks resulted in films with both smooth surface morphologies and low TD densities.

Kamber, Derrick Shane

320

Uranium Hydride Nucleation Kinetics: Effects of Oxide Thickness and Vacuum Outgassing  

SciTech Connect

Many factors such as impurities in the oxide and metal, microstructure, gas impurities, and oxide thickness may influence the rate and location of the nucleation of hydride on uranium. This work has concentrated on isolating one of these variables, the oxide thickness, and measuring the effect of the oxide thickness on uranium hydride nucleation. Uranium samples, all from the same lot, were prepared with different oxide thicknesses. The oxide thickness was measured using Rutherford Backscattering Spectroscopy. Oxidized uranium samples were then exposed to ultra-high purity hydrogen gas under constant volume conditions. Decreases in pressure indicated hydrogen uptake by the sample. The time for hydride nucleation--as well as the maximum hydriding rate--was then calculated from the measured decreases in pressure. The time to nucleate a hydride was found to increase whereas the maximum hydriding rate was found to decrease with increasing oxide thickness. The density of hydride pits also decreased with increasing oxide thickness. The observed results support the argument that the nucleation of hydride is controlled somewhat by diffusion of hydrogen through the oxide layer. Vacuum outgassing of samples, thereby removing the oxide impurities and keeping the oxide thickness constant, dramatically decreased the nucleation time and increased the maximum hydriding rate. Again, this is consistent with hydrogen diffusion through the oxide controlling the nucleation of hydride. Impurities in the oxide layer can decrease the diffusivity of hydrogen and therefore delay the nucleation of uranium hydride.

David F. Teter; Robert J. Hanrahan; Christopher J. Wetteland

2001-03-01

321

Fabrication of lotus-type porous copper through thermal decomposition of titanium hydride  

NASA Astrophysics Data System (ADS)

Lotus-type porous copper was fabricated by unidirectional solidification through thermal decomposition of titanium hydride. Effects of additive method and additive amount of titanium hydride on pore formation were investigated. The porosity of lotus copper depends on additive method and additive amount of titanium hydride. The pore formation effectively occurs in the method that titanium hydride decomposes in molten copper. For all the additive methods of titanium hydride, the porosity increases and pore diameter does not change with increasing additive amount of titanium hydride. While, for adding large amount of titanium hydride, the porosity became constant. This is because hydrogen solubility in liquid phase does not change owing to bubbling of hydrogen gas.

Ide, T.; Nakajima, H.

2009-05-01

322

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

NASA Astrophysics Data System (ADS)

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.

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

2007-05-01

323

Safety Evaluation of Magnesium Hydride in Energy Storage.  

National Technical Information Service (NTIS)

Investigations of the magnesium/magnesium hydride system and its potential in energy storage have been carried out at Risoe National Laboratory for some years. The results of this research indicate that the system is technically feasible, at least in some...

B. Vigeholm

1986-01-01

324

Aluminium hydride: a reversible material for hydrogen storage.  

PubMed

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

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

2009-07-01

325

Investigation of Galvanically Induced Hydriding of Titanium in Saline Solutions.  

National Technical Information Service (NTIS)

Galvanically induced hydriding of commercially pure titanium and titanium-2 nickel alloy was determined in 3.4 wt percent NaCl air-sparged and argon-sparged solutions at 140, 265, and 390F. Hydrogen charging of the titanium via couple assemblies of titani...

L. A. Charlot

1970-01-01

326

Hydride generation from the Exide load-leveling cells  

NASA Astrophysics Data System (ADS)

Stibine and arsine evolution from lead-acid cells in a 36-kWh Exide load-leveling module was measured as this module approached 1900 cycles of operation. A gas-collection apparatus enabled us to determine the maximum and average rates for evolution of both toxic hydrides. Hydride generation began once the cell voltage exceeded 2.4 V. The maximum rate for arsine occurred just above 2.5 V and consistently preceded the peak rate for stibine for each sampled cell. The average rates of hydride generation were found to be 175 g/min for stibine and 12.6 g/min for arsine. The former rate proved to be the critical value in determining safe ventilation requirements for cell off-gases. The minimum airflow requirement was calculated to be 340 L/min per cell. Projections for a hypothetical 1-MWh Exide battery without an abatement system indicated that the normal ventilation capacity in the Battery Energy Storage Test facility provides nearly five times the airflow needed for safe hydride removal.

Marr, J. J.; Smaga, J. A.

1987-05-01

327

Rhodium Carbonyl Hydride Species. A Theoretical and Experimental Investigation.  

National Technical Information Service (NTIS)

A theoretical investigation (ab initio) and experimental data have been combined in an attempt to characterize the rhodium carbonyl hydride species which has been shown previously in these laboratories and in those of Solymosi to be a long-lived surface s...

M. L. McKee C. H. Dai S. D. Worley

1987-01-01

328

Subcritical crack growth behavior for hydrided Zircaloy4 plate  

Microsoft Academic Search

To study the subcritical crack growth (SCG) behavior for hydrided Zircaloy-4 plate, sustained load tests were performed on fatigue precracked specimens in Ar atmosphere at 200, 250, and 300 °C with hydrogen contents up to 290 ppm. Log crack velocity versus stress intensity curves showed typical three-stage crack growth behavior. The values of threshold stress intensity (Kth) were not sensitive

J.-H. Huang; C.-S. Ho

1997-01-01

329

Paramagnetic Resonance of Irradiated Lithium Hydride Luminescent Crystals.  

National Technical Information Service (NTIS)

The dependence of the intensity and width of the absorption line of the EPR on temperature was investigated in irradiated lithium hydride luminescent crystals. The irradiation was done at room temperature with the unfiltered light of an SVD-120 mercury la...

B. V. Shulgin F. F. Gavrilov B. I. Dvinyaninov V. I. Koryakov A. K. Chirkov

1968-01-01

330

Stable silver(I) hydride complexes supported by diselenophosphate ligands.  

PubMed

The first stable structure of silver(I) cluster cations [Ag(8)(mu(4)-H){Se(2)P(OR)(2)}(6)](+) [R = (i)Pr, 1; Et, 2] containing Ag(I)-hydride bridges (Ag-mu-H-Ag) in T symmetry was reported. The clusters having an interstitial hydride were composed of an octanuclear silver core in tetracapped tetrahedral geometry, which was inscribed within a Se(12) icosahedron represented by six dialkyl diselenophosphate ligands in a tetrametallic-tetraconnective (mu(2), mu(2)) bonding mode. The presence of hydride was unequivocally corroborated by both (1)H and (109)Ag NMR spectroscopies of which a nonet in the (1)H NMR spectrum for the hydride resonance coupled with a doublet peak observed in the (109)Ag NMR spectrum clearly suggests that eight silver nuclei are equivalent in the NMR time scale and a fast exchange of the positions between the vertex and capping silver atoms in solution must occur. The hypothesis was also supported by a density functional theory (DFT) investigation on a simplified model [Ag(8)(H)(Se(2)PH(2))(6)](+), which confirmed that the Ag(8)H cubic core of T(h) symmetry may not be formed as it is energetically highly unfavorable (0.67 eV less stable than the T structure). PMID:20025253

Liu, C W; Chang, Hao-Wei; Sarkar, Bijay; Saillard, Jean-Yves; Kahlal, Samia; Wu, Ying-Yann

2010-01-18

331

Electron and Nuclear Magnetic Resonances in Compounds and Metallic Hydrides.  

National Technical Information Service (NTIS)

Proton pulsed Nuclear Magnetic Resonance measurements were performed on the metallic hydrides ZrCr2 H/sub x/ (x = 2, 3, 4) and ZrV2 H/sub y/ (y = 2, 3, 4, 5) as a function of temperature between 180 and 400K. The ultimate aim was the investigation of the ...

N. Brasil Filho

1985-01-01

332

Process of forming a sol-gel/metal hydride composite  

DOEpatents

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.

Congdon, James W. (Aiken, SC)

2009-03-17

333

Hydriding of titanium. Annual report number 2 for 1997  

SciTech Connect

The reason for undertaking this work is that the US Navy would like to use titanium in a number of critical applications, where it would come in contact with sea water at elevated temperatures. Although the general reputation of titanium is that it is corrosion resistant in these environments, there is the possibility that it could pick up sufficient hydrogen from this environment to form a hydride and thus lose its mechanical integrity. Therefore, one must evaluate all conditions that could lead to hydriding and determine the effects of hydrides on mechanical properties. During the second year of work, the goals have been the following: to determine the effect of solution activity and temperature, material composition and heat treatment on the electrochemical properties of titanium; to determine the effect of these same variables on the corrosion potential of titanium galvanically coupled with other metals; to determine the critical potential of hydride formation as a function of solution activity and temperature, applied strain, and surface conditions; to measure the rate of hydrogen diffusion in titanium; to propose a model to describe crack propagation in titanium in these environments. All of the above work has been completed and the results are contained in this document. The results that the authors have obtained show that grade 2 titanium is generally resistant to hydrogen embrittlement. However, grade 3, with its higher interstitial content and lower hydrogen solubility is quite susceptible to hydrogen embrittlement. The mechanism by which this embrittlement occurs is one in which microcracks, which are centered on hydrides, form ahead of the main crack tip. With increased deformation these microcracks link up to the main crack and cause propagation.

Briant, C.L.; Kumar, K.S.; Wang, Z.

1998-03-01

334

5-year review of Metal Hydride Center of Excellence.  

SciTech Connect

The purpose of the DOE Metal Hydride Center of Excellence (MHCoE) is to develop hydrogen storage materials with engineering properties that allow the use of these materials in a way that satisfies the DOE/FreedomCAR Program system requirements for automotive hydrogen storage. The Center is a multidisciplinary and collaborative effort with technical interactions divided into two broad areas: (1) mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials) and (2) materials development (in which new materials are synthesized and characterized). Driving all of this work are the hydrogen storage system specifications outlined by the FreedomCAR Program for 2010 and 2015. The organization of the MHCoE during the past year is show in Figure 1. During the past year, the technical work was divided into four project areas. The purpose of the project areas is to organize the MHCoE technical work along appropriate and flexible technical lines. The four areas summarized are: (1) Project A - Destabilized Hydrides, The objective of this project is to controllably modify the thermodynamics of hydrogen sorption reactions in light metal hydrides using hydride destabilization strategies; (2) Project B - Complex Anionic Materials, The objective is to predict and synthesize highly promising new anionic hydride materials; (3) Project C - Amides/Imides Storage Materials, The objective of Project C is to assess the viability of amides and imides (inorganic materials containing NH{sub 2} and NH moieties, respectively) for onboard hydrogen storage; and (4) Project D - Alane, AlH{sub 3}, The objective of Project D is to understand the sorption and regeneration properties of AlH{sub 3} for hydrogen storage.

Keller, Jay O.; Klebanoff, Leonard E.

2010-05-01

335

Hydride Compressor Sorption Cooler and Surface Contamination Issues  

NASA Astrophysics Data System (ADS)

A continuous-duty hydrogen sorption cryocooler is being developed for the Planck spacecraft, a mission to map the cosmic microwave background beginning in 2007. This cryocooler uses six individual compressor elements (CEs) filled with the hydriding alloy LaNi4.78Sn0.22 to provide high-pressure (50 bar) hydrogen to a Joule-Thomson (J-T) expander and to absorb low-pressure (~0.3 bar) gas from liquid hydrogen reservoirs cooled to ~18K. Quadrupole Mass Spectrometry (QMS) showed methane in these hydride beds after cycling during initial operation of laboratory tests of the Planck engineering breadboard (EBB) cooler. These contaminants have caused problems involving plugged J-T expanders. The contaminants probably come from reactions with residual hydrocarbon species on surfaces inside the hydride bed. The hydride bed in each CE is contained in an annular volume called a ``gas-gap heat switch,'' which serves as a reversible, intermittent thermal path to the spacecraft radiator. The gas-gap is either ``off'' (i.e., its pressure <1.3 Pa), or ``on'' (i.e., hydrogen gas at ~4 kPa). The hydrogen pressure is varied with an independent hydride actuator containing ZrNiHx. Early EBB cooler tests showed increasing parasitic heat losses from the inner beds, suggesting residual pressures in the gas gap during its ``off'' state. The pressure was shown to be due to hydrogen from outgassing from metallic surfaces in the gas gap and hydrogen permeation through the inner sorbent bed wall. This gas accumulation has serious end-of-life implications, as the ZrNi actuator has limited storage capacity and any excess hydrogen would necessarily affect its operation. This paper summarizes experiments on the behavior of hydrogen in the gas gap switch and formation of methane in the CE sorbent beds.

Bowman, R. C.; Reiter, J. W.; Prina, M.; Kulleck, J. G.; Lanford, W. A.

2003-07-01

336

Exploring metal hydrides using autoclave and multi-anvil hydrogenations  

NASA Astrophysics Data System (ADS)

Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature superconductivity. On the other side of the spectrum are hydrides with small amounts of hydrogen (0.1 - 1 at.%) that are investigated as viable magnetic, thermoelectric or semiconducting materials. Research of metal hydride materials is generally important to gain fundamental understanding of metal-hydrogen interactions in materials. Hydrogenation of Zintl phases, which are defined as compounds between an active metal (alkali, alkaline earth, rare earth) and a p-block metal/semimetal, were attempted by a hot sintering method utilizing an autoclave loaded with gaseous hydrogen (< 9 MPa). Hydride formation competes with oxidative decomposition of a Zintl phase. The oxidative decomposition, which leads to a mixture of binary active metal hydride and p-block element, was observed for investigated aluminum (Al) and gallium (Ga) containing Zintl phases. However, a new phase Li2Al was discovered when Zintl phase precursors were synthesized. Using the single crystal x-ray diffraction (SCXRD), the Li2Al was found to crystallize in an orthorhombic unit cell (Cmcm) with the lattice parameters a = 4.6404(8) Å, b = 9.719(2) Å, and c = 4.4764(8) Å. Increased demand for materials with improved properties necessitates the exploration of alternative synthesis methods. Conventional metal hydride synthesis methods, like ball-milling and autoclave technique, are not responding to the demands of finding new materials. A viable alternative synthesis method is the application of high pressure for the preparation of hydrogen-dominant materials. Extreme pressures in the gigapascal ranges can open access to new metal hydrides with novel structures and properties, because of the drastically increased chemical potential of hydrogen. Pressures up to 10 GPa can be easily achieved using the multi-anvil (MA) hydrogenations while maintaining sufficient sample volume for structure and property characterization. Gigapascal MA hydrogenations using ammonia borane (BH3

Puhakainen, Kati

337

Ir/PuO/sub 2/ compatibility: transfer of impurities from plutonium dioxide to iridium metal during high temperature aging  

SciTech Connect

Plutonium oxide fuel pellets for powering radioisotopic thermoelectric generators for NASA space vehicles are encapsulated in iridium which has been grain-boundary-stabilized with thorium and aluminum. After aging for 6 months at 1310/sup 0/C under vacuum, enhanced grain growth is observed in the near-surface grains of the iridium next to the PuO/sub 2/. Examination of the grain boundaries by AES and SIMS shows a depletion of thorium and aluminum. Iron, chromium, and nickel from the fuel were found to diffuse into the iridium along the grain boundaries. Enhanced grain growth appears to result from thorium depletion in the grain boundaries of the near-surface grains next to the fuel. However, in one instance grain growth was slowed by the formation of thorium oxide by oxygen diffusing up the grain boundaries.

Taylor, D.H.; Christie, W.H.; Pavone, D.

1984-01-01

338

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

NASA Technical Reports Server (NTRS)

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.

Murray, Jennifer; Birr, Richard

2010-01-01

339

A Colorimetric and Luminescent Dual-Modal Assay for Cu(II) Ion Detection Using an Iridium(III) Complex  

PubMed Central

A novel iridium(III) complex-based chemosensor bearing the 5,6-bis(salicylideneimino)-1,10-phenanthroline ligand receptor was developed, which exhibited a highly sensitive and selective color change from colorless to yellow and a visible turn-off luminescence response upon the addition of Cu(II) ions. The interactions of this iridium(III) complex with Cu2+ ions and thirteen other cations have been investigated by UV-Vis absorption titration, emission titration, and 1H NMR titration.

Ma, Dik-Lung; He, Hong-Zhang; Chan, Daniel Shiu-Hin; Wong, Chun-Yuen; Leung, Chung-Hang

2014-01-01

340

Tricyclometalated iridium complexes as highly stable photosensitizers for light-induced hydrogen evolution.  

PubMed

The development of an efficient and stable artificial photosensitizer for visible-light-driven hydrogen production is highly desirable. Herein, a new series of charge-neutral, heteroleptic tricyclometalated iridium(III) complexes, [Ir(thpy)2(bt)] (1-4; thpy = 2,2'-thienylpyridine, bt = 2-phenylbenzothiazole and its derivatives), were systematically synthesized and their structural, photophysical, and electrochemical properties were established. Three solid-state structures were studied by X-ray crystallographic analysis. This design offers the unique opportunity to drive the metal-to-ligand charge-transfer (MLCT) band to longer wavelengths for these iridium complexes. We describe new molecular platforms that are based on these neutral iridium complexes for the production of hydrogen through visible-light-induced photocatalysis over an extended period of time in the presence of [Co(bpy)3](2+) and triethanolamine (TEOA). The maximum amount of hydrogen was obtained under constant irradiation over 72?h and the system could regenerate its activity upon the addition of cobalt-based catalysts when hydrogen evolution ceased. Our results demonstrated that the dissociation of the [Co(bpy)3](2+) catalyst contributed to the loss of catalytic activity and limited the long-term catalytic performance of the systems. The properties of the neutral complexes are compared in detail to those of two known non-neutral bpy-type complexes, [Ir(thpy)2(dtb-bpy)](+) (5) and [Ir(ppy)2(dtb-bpy)](+) (6; ppy = 2-phenylpyridine, dtb-bpy = 4,4'-di-tert-butyl-2,2'-dipyridyl). This work is expected to contribute toward the development of long-lasting solar hydrogen-production systems. PMID:23520149

Yuan, Yong-Jun; Yu, Zhen-Tao; Gao, Hong-Lin; Zou, Zhi-Gang; Zheng, Chao; Huang, Wei

2013-05-10

341

Effect of thermo-mechanical cycling on zirconium hydride reorientation studied in situ with synchrotron X-ray diffraction  

NASA Astrophysics Data System (ADS)

The circumferential hydrides normally present in nuclear reactor fuel cladding after reactor exposure may dissolve during drying for dry storage and re-precipitate when cooled under load into a more radial orientation, which could embrittle the fuel cladding. It is necessary to study the rates and conditions under which hydride reorientation may happen in order to assess fuel integrity in dry storage. The objective of this work is to study the effect of applied stress and thermal cycling on the hydride morphology in cold-worked stress-relieved Zircaloy-4 by combining conventional metallography and in situ X-ray diffraction techniques. Metallography is used to study the evolution of hydride morphology after several thermo-mechanical cycles. In situ X-ray diffraction performed at the Advanced Photon Source synchrotron provides real-time information on the process of hydride dissolution and precipitation under stress during several thermal cycles. The detailed study of diffracted intensity, peak position and full-width at half-maximum provides information on precipitation kinetics, elastic strains and other characteristics of the hydride precipitation process. The results show that thermo-mechanical cycling significantly increases the radial hydride fraction as well as the hydride length and connectivity. The radial hydrides are observed to precipitate at a lower temperature than circumferential hydrides. Variations in the magnitude and range of hydride strains due to reorientation and cycling have also been observed. These results are discussed in light of existing models and experiments on hydride reorientation. The study of hydride elastic strains during precipitation shows marked differences between circumferential and radial hydrides, which can be used to investigate the reorientation process. Cycling under stress above the threshold stress for reorientation drastically increases both the reoriented hydride fraction and the hydride size. The reoriented hydride fraction decreases with increasing hydrogen content although the radial hydride content remains constant (for levels above 200 wt.ppm). The precipitation of reoriented hydrides under stress above the threshold stress for reorientation occurs at a lower temperature than the precipitation of in-plane (circumferential) hydrides in unstressed samples. The effects of cycling on the precipitation temperature when precipitating reoriented hydrides are small. When radial hydrides precipitate under stress, during the first precipitation stage at high temperature the hydride strains become tensile in the direction perpendicular to the hydride platelet face. During the second precipitation regime, these strains remain constant in tension. This indicates a different hydride strain state for reoriented hydrides than for circumferential hydrides. The magnitude of the tensile hydride strain in the transverse direction as measured by the change in d-spacing in the reoriented hydride face increases with cycling, potentially because of the increasing reoriented hydride fraction. The analysis of the FWHM confirms the observed 'signature' of hydride reorientation in a mixed population of hydrides as previously observed in the literature. Once the hydride population is fully reoriented, the FWHM decreases due to the fact that a single population of reoriented hydrides is now present. The strain distribution in this single population is smaller than for a mixed population of circumferential and reoriented hydrides.

Colas, Kimberly B.; Motta, Arthur T.; Daymond, Mark R.; Almer, Jonathan D.

2013-09-01

342

Regeneration of Aluminum Hydride studied with Raman Microscopy.  

NASA Astrophysics Data System (ADS)

We are interested in developing new methods to form aluminum hydride directly from aluminum powder and hydrogen. Due to the low free energy of formation, aluminum and hydrogen require extremely high pressures to react and form the hydride. It is possible to form alane directly at low pressure when it is catalyzed with a small amount of titanium (2 mol %) and stabilized as an adduct. We have studied the formation of amine-alanes by direct hydrogenation of aluminum and have attempted to understand the mechanisms behind these reversible reactions and the role of the catalyst. We will present the results from our recent survey of possible reactions between aluminum, hydrogen and various amines. We will also present the results of a Raman spectroscopy study of the alane polymorphs at ambient and high pressure and alane amines.

Lacina, David; Graetz, Jason; Reilly, J. J.

2009-03-01

343

ALUMINUM HYDRIDE: A REVERSIBLE STORAGE MATERIAL FOR HYDROGEN STORAGE  

SciTech Connect

One of the challenges of implementing the hydrogen economy is finding a suitable solid H{sub 2} storage material. Aluminium (alane, AlH{sub 3}) hydride has been examined as a potential hydrogen storage material because of its high weight capacity, low discharge temperature, and volumetric density. Recycling the dehydride material has however precluded AlH{sub 3} from being implemented due to the large pressures required (>10{sup 5} bar H{sub 2} at 25 C) and the thermodynamic expense of chemical synthesis. A reversible cycle to form alane electrochemically using NaAlH{sub 4} in THF been successfully demonstrated. Alane is isolated as the triethylamine (TEA) adduct and converted to unsolvated alane by heating under vacuum. To complete the cycle, the starting alanate can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride (NaH) This novel reversible cycle opens the door for alane to fuel the hydrogen economy.

Zidan, R; Christopher Fewox, C; Brenda Garcia-Diaz, B; Joshua Gray, J

2009-01-09

344

Low temperature study of structural phase transitions in niobium hydrides  

NASA Astrophysics Data System (ADS)

Niobium (Nb) and its hydrides have been the focus of many studies due to applications as a hydrogen storage material, as a dielectric coating in semiconductor devices and in superconducting radio-frequency cavities. In this paper, we will present the atomic-scale characterization of Nb hydrides using scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) at room and liquid nitrogen temperatures. Although such cavities are formed from ultrahigh purity Nb, using electron beam diffraction, we found that at LN2 temperature, the grains near the surface of cold-worked Nb sheets contain regions exhibiting three different superlattice features, which are identified as ?, ?, and ?-NbHx phases. Z-contrast imaging and EELS at LN2 temperature are utilized to qualify their atomic and electronic structures.

Tao, R.; Romanenko, A.; Cooley, L. D.; Klie, R. F.

2013-07-01

345

Impurity effects on high-temperature tensile ductility of iridium alloys at high strain rate  

SciTech Connect

The current study was undertaken to determine what effects, if any, larger amounts of certain impurities (Al,Cr,Fe,Ni, and Si) might have on the physical metallurgy and mechanical properties of the DOP-26 iridium alloy. This report summarizes the effects of these impurities on grain growth behavior and high-temperature high-strain-rate tensile ductility. Comparisons are made to the grain growth behavior and high-strain-rate tensile properties of the DOP-26 alloy without intentional impurity additions.

McKamey, C.G.; George, E.P.; Lee, E.H.; Ohriner, E.K.; Heatherly, L.; Cohron, J.W.

1999-12-17

346

Relationship between mass extinction and iridium across the Cretaceous-Paleogene boundary in New Jersey  

USGS Publications Warehouse

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.

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

347

Enzymatic determination of diglyceride using an iridium nano-particle based single use, disposable biosensor.  

PubMed

A single use, disposable iridium-nano particle contained biosensor had been developed for the determination of diglyceride (DG). In this study hydrogen peroxide, formed through the enzymatic breakdown of DG via lipase, glycerol kinase and glycerol 3-phosphate oxidase, was electrochemically oxidized at an applied potential of +0.5 V versus the Ag/AgCl reference electrode. The oxidation current was then used to quantify the diglyceride concentration. Optimum enzyme concentrations and the surfactant loading used were established for successful sensor response. Good linear performance was observed over a DG concentration range of 0 to 25 ?M in phosphate buffer and bovine serum media. PMID:22219685

Hsu, Shu-Yi; Bartling, Brandon; Wang, Christina; Shieu, Fuh-Sheng; Liu, Chung-Chiun

2010-01-01

348

Rhodium(I) and iridium(I) complexes of pyrazolyl-N-heterocyclic carbene ligands.  

PubMed

Several Rh(I) and Ir(I) complexes containing an N-heterocyclic carbene-pyrazolyl chelate ligand have been synthesised. Determination of the single-crystal X-ray structure of the Ir(I) complex showed a novel binding mode with the iridium centre coordinated to two ligands via two carbene donors in preference to one ligand forming the entropically favoured chelate. The hydrogenation activity of several of these complexes was investigated along with that of previously synthesised Rh(I) and Ir(I) complexes containing an analogous phosphine-pyrazolyl chelate. PMID:16896454

Messerle, Barbara A; Page, Michael J; Turner, Peter

2006-08-28

349

Hydrogen transfer reduction of polyketones catalyzed by iridium complexes: a novel route towards more biocompatible materials.  

PubMed

Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catalyzed by [Ir(diene)(N-N)X] (N-N = nitrogen chelating ligand; X = halogen) in the presence of a basic cocatalyst. The reactions were performed using dioxane as cosolvent, in order to overcome problems due to low polyketone solubility. The polyalcohols were obtained in yields up to 95%, the conversions being markedly dependent on the nature of the ligands coordinated to iridium as well as on the experimental conditions. PMID:19024366

Milani, Barbara; Crottib, Corrado; Farnetti, Erica

2008-09-14

350

Stereodivergent ?-allylation of linear aldehydes with dual iridium and amine catalysis.  

PubMed

We describe the fully stereodivergent, dual catalytic ?-allylation of linear aldehydes. The reaction proceeds via direct iridium-catalyzed substitution of racemic allylic alcohols with enamines generated in situ. The use of an Ir(P,olefin) complex and a diarylsilyl prolinol ether as catalysts in the presence of dimethylhydrogen phosphate as the promoter proved to be crucial for achieving high enantio- and diastereoselectivity (>99% ee, up to >20:1 dr). The utility of the method is demonstrated in a concise enantioselective synthesis of the antidepressant (-)-paroxetine. PMID:24506196

Krautwald, Simon; Schafroth, Michael A; Sarlah, David; Carreira, Erick M

2014-02-26

351

Practically convenient and industrially-aligned methods for iridium-catalysed hydrogen isotope exchange processes.  

PubMed

The use of alternative solvents in the iridium-catalysed hydrogen isotope exchange reaction with developing phosphine/NHC Ir(i) complexes has identified reaction media which are more widely applicable and industrially acceptable than the commonly employed chlorinated solvent, dichloromethane. Deuterium incorporation into a variety of substrates has proceeded to deliver high levels of labelling (and regioselectivity) in the presence of low catalyst loadings and over short reaction times. The preparative outputs have been complemented by DFT studies to explore ligand orientation, as well as solvent and substrate binding energies within the catalyst system. PMID:24756541

Cochrane, A R; Idziak, C; Kerr, W J; Mondal, B; Paterson, L C; Tuttle, T; Andersson, S; Nilsson, G N

2014-06-14

352

SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS..  

EPA Science Inventory

Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride ...

353

SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS...  

EPA Science Inventory

Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride s...

354

Gas chromatographic separation of hydrogen isotopes using metal hydrides  

SciTech Connect

A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

Aldridge, F.T.

1984-05-09

355

Ground-state energy and relativistic corrections for positronium hydride  

SciTech Connect

Variational calculations of the ground state of positronium hydride (HPs) are reported, including various expectation values, electron-positron annihilation rates, and leading relativistic corrections to the total and dissociation energies. The calculations have been performed using a basis set of 4000 thoroughly optimized explicitly correlated Gaussian basis functions. The relative accuracy of the variational energy upper bound is estimated to be of the order of 2x10{sup -10}, which is a significant improvement over previous nonrelativistic results.

Bubin, Sergiy; Varga, Kalman [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)

2011-07-15

356

Hydriding kinetics of an organic hydrogen getter-DPB  

Microsoft Academic Search

The hydriding rate of DPB (diphenyl butadiyne\\/25% C (1% Pd)) organic hydrogen getter has been measured at 17°C over the range of 10?6 to 10?11molH (gDPB)?1s?1, H2 pressure 100–0.1Pa, reaction extent 0–29mmolH (gDPB)?1 and described by an algebraic model.

G. L. Powell

2007-01-01

357

Optical properties of metal-hydride switchable films  

Microsoft Academic Search

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,

Ronald Griessen

2001-01-01

358

A study of the oxidation of titanium hydride powder by measurements of its electrical resistance  

NASA Astrophysics Data System (ADS)

The oxidation of titanium hydride powder by air oxygen and the influence of oxidation conditions on the degree of oxidation of hydride particles, specific gas content in the powder, and kinetics of its thermal decomposition were studied. The resistometry method was used to determine the effective activation energy of oxidation of titanium hydride by air oxygen. The content of the surface nonconducting phase formed by titanium oxide and oxohydride films under various oxidation conditions was estimated.

Tsarev, M. V.; Mokrushin, V. V.; Sten'gach, A. V.; Tarasova, A. I.; Berezhko, P. G.; Kremzukov, I. K.; Zabavin, E. V.

2010-04-01

359

High Temperature Metal Hydrides as Heat Storage Materials for Solar and Related Applications  

PubMed Central

For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 °C is essential. High temperature metal hydrides offer high heat storage capacities around this temperature. Based on Mg-compounds, these hydrides are in principle low-cost materials with excellent cycling stability. Relevant properties of these hydrides and their possible applications as heat storage materials are described.

Felderhoff, Michael; Bogdanovic, Borislav

2009-01-01

360

Complications from Dual Roles of Sodium Hydride as a Base and as a Reducing Agent  

PubMed Central

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.

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

2012-01-01

361

Non-toxic hydride energy source for biochemical and industrial venues: ORP and NAD + reduction analyses  

Microsoft Academic Search

A recently described novel compound, silica hydride, was used to investigate potential alternative hydrogen energy sources for use in industry, pharmacology and biochemistry. Acting as an anionic hydride, the silica hydride does not react violently with water and produces stable oxidation-reduction potential readings of greater than ?860mV for extended periods providing capacity as an alternative for current transfer, hydrogen production

Cory J. Stephanson; G. Patrick Flanagan

2004-01-01

362

On the role of the indenyl effect in controlling intramolecular hydride transfer in iron carbonyl complexes  

Microsoft Academic Search

Density functional theory reveals multiple pathways for intramolecular hydride transfer in the cyclopentadienyl and indenyl species (?5-C5H5)Fe(CO)3H and (?5-C9H7)Fe(CO)3H. The ability of the indenyl ligand to undergo facile ?5- to ?3-‘ring slippage’ stabilises the isomer where the hydride is bonded directly to the metal, which opens up a low-energy pathway for hydride transfer from CO to metal.

Hakim Ahmed; John E. McGrady

2008-01-01

363

Investigation of long term stability in metal hydrides  

NASA Technical Reports Server (NTRS)

It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation.

Marmaro, Roger W.; Lynch, Franklin E.; Chandra, Dhanesh; Lambert, Steve; Sharma, Archana

1991-01-01

364

Air passivation of metal hydride beds for waste disposal  

SciTech Connect

One waste acceptance criteria for hydride bed waste disposal is that the bed be non-pyrophoric. Batch-wise air ingress tests were performed which determined the amount of air consumed by a metal hydride bed. A desorbed, 4.4 kg titanium prototype hydride storage vessel (HSV) produced a 4.4 deg.C internal temperature rise upon the first air exposure cycle and a 0.1 deg.C temperature rise upon a second air exposure. A total of 346 sec air was consumed by the bed (0.08 sec per gram Ti). A desorbed, 9.66 kg LaNi{sub 4.25}Al{sub 0.75} prototype storage bed experienced larger temperature rises over successive cycles of air ingress and evacuation. The cycles were performed over a period of days with the bed effectively passivated after the 12. cycle. Nine to ten STP-L of air reacted with the bed producing both oxidized metal and water. (authors)

Klein, J. E.; Hsu, R. H. [Savannah River National Laboratory, Aiken, SC 29808 (United States)

2008-07-15

365

Metal hydride/chemical heat pump development project  

NASA Astrophysics Data System (ADS)

A mental hydride heat pump (MHHP) is a chemical heat pump containing two different hydrides and using hydrogen as a working fluid for the storage and/or recovery of thermal energy. It utilizes the heat of reaction of hydrogen with specific metal alloys. The MHHP design can be tailored to provide heating and cooling or temperature upgrading over a wide range of input and ambient temperatures. This system can be used with a variety of heat sources including industrial waste heat, solar energy or a fossil fuel. Temperature as low as 130 F can drive the MHHP when a suitable sink is provided. A project is currently underway to develop this unique heat pump for a specific application. The goals of the project include the development of cost effective hydride containers with high heat transfer and low mass; design and fabrication of a laboratory evaluation model; and design and fabrication of a demonstration unit. Extensive component and system test will provide the data for the design processes.

Madariaga, H. A.; Rohy, D. A.

1982-02-01

366

Delayed hydride cracking of spent fuel rods in dry storage  

NASA Astrophysics Data System (ADS)

Failures of zirconium alloy cladding tubes during a long-term storage at room temperature were first reported by Simpson and Ells in 1974, which remains unresolved by the old delayed hydride cracking (DHC) models. Using our new DHC model, we examined failures of cladding tubes after their storage at room temperature. Stress-induced hydride phase transformation from ? to ? at a crack tip creates a difference in hydrogen concentration between the bulk region and the crack tip due to a higher hydrogen solubility of the ?-hydride, which is a driving force for DHC at low temperatures. Accounting for our new DHC model and the failures of zirconium alloy cladding tubes during long-term storage at room temperature, we suggest that the spent fuel rods to be stored either in an isothermal condition or in a slow cooling condition would fail by DHC during their dry storage upon cooling to below 180 °C. Further works are recommended to establish DHC failure criterion for the spent fuel rods that are being stored in dry storage.

Kim, Young Suk

2008-08-01

367

Diffusional exchange of isotopes in a metal hydride sphere.  

SciTech Connect

This report describes the Spherical Particle Exchange Model (SPEM), which simulates exchange of one hydrogen isotope by another hydrogen isotope in a spherical metal hydride particle. This is one of the fundamental physical processes during isotope exchange in a bed of spherical metal particles and is thus one of the key components in any comprehensive physics-based model of exchange. There are two important physical processes in the model. One is the entropy of mixing between the two isotopes; the entropy of mixing is increased by having both isotopes randomly placed at interstitial sites on the lattice and thus impedes the exchange process. The other physical process is the elastic interaction between isotope atoms on the lattice. The elastic interaction is the cause for {beta}-phase formation and is independent of the isotope species. In this report the coupled diffusion equations for two isotopes in the {beta}-phase hydride are solved. A key concept is that the diffusion of one isotope depends not only on its concentration gradient, but also on the concentration gradient of the other isotope. Diffusion rate constants and the chemical potentials for deuterium and hydrogen in the {beta}-phase hydride are reviewed because these quantities are essential for an accurate model of the diffusion process. Finally, a summary of some of the predictions from the SPEM model are provided.

Wolfer, Wilhelm G.; Hamilton, John C.; James, Scott Carlton

2011-04-01

368

Structural Stabilities and Electronic Properties of Cobalt Hydrides  

NASA Astrophysics Data System (ADS)

Cobalt forms ferromagnetic hydrides CoHx at high pressures of hydrogen [1]. As the hydrogen pressure increases at temperatures 250-350^oC, the concentration of hydrogen in the hcp phase monotonically increases, and reaches x˜0.6 at 7 GPa. At higher pressures, an fcc-based hydride with x˜1.0 is formed. At ambient pressure and 120 K, hydrogen atoms in the solution with x<=0.26 are randomly distributed over octahedral interstitial sites [2]. In the solution with x=0.34 (x>=0.38), hydrogen atoms occupy every third (second) layer. The magnetic moments of the hcp-based hydrides are oriented to the c-axis, and are decreased with increasing hydrogen concentration at a rate of about 0.36 ?B per hydrogen atom. In this study, we optimize the structural parameters for several structures, and investigate the structural stabilities and related electronic properties by using first-principles calculations. The full-potential linearized augmented plane wave method with the generalized gradient approximation is adopted.[4pt] [1] V. E. Antonov, J. Alloys Compd. 330-332, 110 (2002).[0pt] [2] V. K. Fedotov, V. E. Antonov, T. E. Antonova, E. L. Bokhenkov, B. Dorner, G. Grosse, and F. E. Wagner, J. Alloys Compd. 291, 1 (1999).

Matsuura, Yasuyuki; Shishidou, Tatsuya; Oguchi, Tamio

2011-03-01

369

Experimental studies on the behaviours of hydride heat storage system  

NASA Astrophysics Data System (ADS)

Experimental examinations and a lumped system model are used to describe the heat transfer characteristics in the design of a single tube type metal hydride heat storage vessel. The apparatus studied was fed heat by water vaporized by an electric furnance with a 3 kWh x 2 capacity. An annular tube in the middle of the reactor vessel contained the metal hydride (Mg2Ni), which was washed with hydrogen gas. Measurements were taken of the heat transfer medium temperature, H2 flow rate, and temperature responses at sites in the hydride bed. The numerical model was constructed assuming that no pressure gradient was present in the heat storage medium bed, the temperature was uniform throughout the bed, and material characteristics were independent of pressure and temperature encountered. The bed temperature was found to be uniform in the generation and absorption phases, although the latter took longer to stabilize. The lumped parameter model developed is shown to acceptably model the performance of a single tube type heat storage vessel in terms of heat transfer efficiency.

Kawamura, M.; Ono, S.; Higano, S.

370

Moessbauer investigation of intermetallic hydrides. Final report, 1 November 1982-31 October 1985  

SciTech Connect

This research was a study of hydrogen absorption in intermetallic hydrides. Mossbauer and x-ray-diffraction measurements were used to aid in a determination of the hydrogen-absorbing mechanism occurring in hydriding. Information was sought that would provide insight into the nature of bonding and interaction between the absorbed hydrogen and the various sites in the intermetallics. There was also interest in observing what happened to Sn in intermetallic compounds when hydrided. Studies were made of the changes in isomer shift and linewidth upon hydriding.

Oliver, F.W.

1985-12-21

371

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

SciTech Connect

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.

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

2012-10-23

372

Hydride affinities of cumulated, isolated, and conjugated dienes in acetonitrile.  

PubMed

The hydride affinities (defined as the enthalpy changes in this work) of 15 polarized dienes [five phenyl sulfone substituted allenes (1a), the corresponding five isolated dienes (1b), and the corresponding five conjugated dienes (1c)] in acetonitrile solution were determined by titration calorimetry for the first time. The results display that the hydride affinity scales of the 15 dienes in acetonitrile range from -71.6 to -73.9 kcal/mol for 1a, from -46.2 to -49.7 kcal/mol for 1b, and from -45.0 to -46.5 kcal/mol for 1c, which indicates that the hydride-obtaining abilities of the cumulated dienes (1a) are not only much larger than those of the corresponding conjugated dienes (1c) but also much larger than those of the corresponding isolated dienes (1b). The hydrogen affinities of the 15 dienes as well as the hydrogen affinities and the proton affinities of the radical anions of the dienes (1(-*)) in acetonitrile were also evaluated by using relative thermodynamic cycles according to Hess's law. The results show that (i) the hydrogen affinities of the neutral dienes 1 cover a range from -44.5 to -45.6 kcal/mol for 1a, from -20.4 to -21.4 kcal/mol for 1b, and from -17.3 to -18.5 kcal/mol for 1c; (ii) the hydrogen affinities of the radical anions of the dienes (1(-*)) in acetonitrile cover a range from -40.6 to -47.2 kcal/mol for 1a(-*), from -21.6 to -29.6 kcal/mol for 1b(-*), and from -10.0 to -15.4 kcal/mol for 1c(-*); (iii) the proton affinities of the 15 1a(-*) in acetonitrile cover a range from -97.0 to -100.6 kcal/mol for 1a(-*), from -77.8 to -83.4 kcal/mol for 1b(-*), and from -66.2 to -68.9 kcal/mol for 1c(-*). The main reasons for the great difference between the cumulated dienes and the corresponding isolated and conjugated dienes in the hydride affinity, hydrogen affinity, and proton affinity have been examined. It is evident that these experimental results should be quite valuable to facilitate the elucidation of the origins of the especially high chemical potencies of the allenes, the choice of suitable hydride reducing agents to reduce the dienes, and the analyses on the reduction mechanisms. PMID:18821805

Zhu, Xiao-Qing; Liang, Hao; Zhu, Yan; Cheng, Jin-Pei

2008-11-01

373

Dual-mode chemical vapor generation for simultaneous determination of hydride-forming and non-hydride-forming elements by atomic fluorescence spectrometry.  

PubMed

A dual-mode chemical vapor generation integrating hydride generation and photochemical vapor generation was developed for simultaneous multi-element analysis of hydride-forming and non-hydride-forming elements by atomic fluorescence spectrometry. Four elements were selected as model elements of hydride-forming (As, Cd) and non-hydride-forming (Ni, Fe) elements to validate this proposed method. Standard or sample solutions were separately pumped to mix with tetrahydroborate, and concentrated formic acid and ammonia, and then directed to a hydride generator and a photochemical reactor to realize simultaneous hydride generation and photochemical vapor generation, respectively. Optimum conditions for dual-mode chemical vapor generation were carefully investigated. Under the optimized conditions, limits of detection of 0.05, 0.008, 0.8 and 0.1 ?g L(-1) were obtained for As, Cd, Fe and Ni, respectively. The precisions were 5.0, 5.5, 4.3 and 4.5% (n = 6, RSDs) for 2 ?g L(-1) of As, 1 ?g L(-1) of Cd, 50 ?g L(-1) of Fe and 10 ?g L(-1) of Ni, respectively. This method was validated for accuracy with three certified reference water samples and applied to the simultaneous determination of these elements in a tap water sample with spike recoveries in the range of 95-99%. PMID:24691520

Wang, Yu; Xu, Kailai; Jiang, Xiaoming; Hou, Xiandeng; Zheng, Chengbin

2014-04-15

374

Earth Radiation Imbalance from a Constellation of 66 Iridium Satellites: Technological Aspects  

NASA Technical Reports Server (NTRS)

Iridium Communications Inc. is launching a new generation of polar orbiting communication satellites in 2015-2017. Iridium will provide a hosted payload bay on each of the 66 satellites (plus 6 in-space spares). This offers the potential for a paradigm shift in the way we measure Earth radiation imbalance from space, as well as massive cost savings. Because the constellation provides 24/7 global coverage, there is no need to account for diurnal cycle via extrapolations from uncalibrated narrowband geostationary imagers. And the spares can be rolled over to view the Sun and deep space, then transfer their calibration to the other members of the constellation during the frequent cross-overs. In part using simulations of the constellation viewing realistic Earth scenes, this presentation will address the technological aspects of such a constellation: (1) the calibration strategy; (2) the highly-accurate and stable radiometers for measuring outgoing flux; and (3) the GRACE-inspired algorithms for representing the outgoing flux field in spherical harmonics and thus achieving rv500-km spatial resolution and two-hour temporal resolution.

Wiscombe, W.; Chiu, C. J-Y.

2012-01-01

375

Theoretical studies of blue phosphorescent iridium(III) complexes with phenylpyrazole and phosphines.  

PubMed

New blue emitting mixed ligand iridium(III) complexes comprising one cyclometalating, two phosphines trans to each other such as Ir(dppz)(PPhMe2)2(H)(C1) and Ir(dppz)(PPhMe2)2(H)(CN), [dppz = 3,5-Diphenylpyrazole] were studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To achieve deep blue emission and increase the emission efficiency, the following must occur: (1) substitution of phenyl group on the 3-position of the pyrazole ring that lower the triplet energy enough that the quenching channel is not thermally accessible, (2) changing ancillary ligands coordinated to iridium atom to phosphine and cyano groups known as very strong field ligands. Using the density functional theory (DFT) and time-dependent DFT method calculations on the ground and excited states of the complexes, we have studied how the ancillary ligand influences the emission peak as well as MLCT transition efficiency. It is showed that the strong-field ancillary ligand such as CN, PPhMe2 alters the energy gap mainly by changing the highest occupied molecular orbitals (HOMO) energy level. Their inclusion in the coordination sphere can increase the energy gap to achieve the hypsochromic shift in emission color and also lower the triplet energy level to avoid the thermal quenching. PMID:22852392

Park, Se Won; Chang, Dong Min; Kim, Young Sik

2012-05-01

376

Picosecond laser micromachining of nitinol and platinum-iridium alloy for coronary stent applications  

NASA Astrophysics Data System (ADS)

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.

Muhammad, N.; Whitehead, D.; Boor, A.; Oppenlander, W.; Liu, Z.; Li, L.

2012-03-01

377

Development of a platinized platinum/iridium electrode for use in vitro.  

PubMed

Silver/silver chloride (Ag/AgCl) electrodes possess excellent electrical properties for measuring the electrical activity of gastrointestinal smooth muscle but exert toxic effects on this tissue in vitro. We thus developed a platinum electrode for use in vitro, the construction of these electrodes relying upon the formation of a glass-platinum/iridium seal. The platinum/iridium (Pt/Ir) electrodes were platinized using a current density of 0.45 mA mm-2. The electrode impedance at 0.01 Hz showed a minimum with platinization current-time products greater than 500 mA s mm-2. However, deposits in excess of 600 mA s mm-2 were readily removed by mechanical abrasion and proved unsatisfactory. Optimal platinization was obtained with a deposit of platinum-black corresponding to a current-time product of 550 mA s mm-2. Optimally-platinized electrodes (geometric surface area 0.11 mm2) had a stable and reproducible potential with a drift of less than 1 microV min-1 and a lower impedance than optimally chlorided silver electrodes (geometric surface area 0.46 mm2) at frequencies higher than 0.25 Hz. The platinized Pt/Ir electrodes were used to record the electrical activity of gastrointestinal smooth muscle in vitro. PMID:3688577

Cote, K R; Gill, R C

1987-01-01

378

Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications  

SciTech Connect

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.

Huxford, T.J.; Ohriner, E.K.

1992-12-31

379

Electron-beam processing of kilogram quantities of iridium for radioisotope thermoelectric generator applications  

SciTech Connect

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.

Huxford, T.J.; Ohriner, E.K.

1992-01-01

380

Synthesis gas transformations with heterogeneous iridium and homogeneous rhodium metal complexes  

SciTech Connect

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.

Getty, C.S.

1988-01-01

381

Color tuning by changing the substituent of highly luminescent iridium (III) complexes  

NASA Astrophysics Data System (ADS)

Our investigations refer to highly efficient emitting materials used in organic light-emitting diodes (OLED). We are especially interested in the possibility of shifting the emission wavelength in phosphorescent iridium(III) complexes. Depending on the mesomeric and inductive behavior of different substituents, the emission spectrum can be varied by introducing those substituents at various positions of the chromophoric ligand. Therefore, we synthesized Ir(ppy)3- analogue complexes with nitrile, trifluoromethyl and methoxy groups at different positions of the ligand's phenyl ring to determine the influence of the position and of each substituent on the emission spectrum. To further study the adjustability we prepared several heteroleptic complexes and changed the ancillary ligand therein. In addition, we developed a new and as yet unknown ligand system based on hetero five membered rings, cyclometalated to iridium to generate homo- and heteroleptic complexes. Devices obtained with these emitting materials have shown high luminescence efficiencies of up to 30 lm/W @ 500 cd/m2.

Weinaug, U. J.; Ammermann, S.; Gargouri, H.; Hoping, M.; Erk, P.; Kahle, K.; Lennartz, Ch.; Molt, O.; Münster, I.; Tamm, M.; Kowalsky, W.; Johannes, H.-H.

2008-08-01

382

Phase diagram and electrical behavior of silicon-rich iridium silicide compounds  

NASA Technical Reports Server (NTRS)

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.

Allevato, C. E.; Vining, Cronin B.

1992-01-01

383

Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction  

SciTech Connect

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.

Karan, Hiroko I.; Sasaki, Kotaro; Kuttiyiel, Kurian; Farberow, Carrie A.; Mavrikakis, Manos; Adzic, Radoslav R.

2012-05-04

384

Deposition of sputtered iridium oxide—Influence of oxygen flow in the reactor on the film properties  

Microsoft Academic Search

Thin films of iridium oxide have been deposited by reactive magnetron sputtering. The influence of oxygen partial pressure in the sputtering plasma on the composition, surface structure and morphology of the films has been studied by XRD, SEM and AFM analysis. An optimal combination of sputtering parameters yields stable microporous amorphous films with highly extended fractal surface. The electrochemical properties

E. Slavcheva; U. Schnakenberg; W. Mokwa

2006-01-01

385

Luminescence color tuning of the iridium complexes by interligand energy transfer (ILET) with ancillary ligands for organic light emitting diode.  

PubMed

The series of new iridium complexes, Ir(C--N)2(LX), (main ligand, C--N = the anion of 2-phenylpyridine (ppy), 4-difluoro-2-phenylpyridine (F2-ppy) and 4-methyl-2,3-diphenylquinoline (4-Me-2,3-dpq); ancillary ligand, LX = 2-(2-hydroxyphenyl)benzoxazolate (BOX) and 2-(2-hydroxyphenyl)benzothiazolate (BTZ)) were prepared and their luminescence properties were investigated. We expected that the relative energy levels of the main ligands and ancillary ligands in the complexes could determine the possibility of interligand energy transfer (ILET) in the complexes and thereby luminescence properties. As the main ligands, F2-ppy, ppy and 4-Me-2,3-dpq, which have drastically different energy gap between the HOMO and LUMO energy levels, were chosen and their complexes were synthesized. BOX and BTZ were chosen as the ancillary ligands which can form a stable 6-membered metallacycle with the iridium center. The iridium complexes showed various emission ranges from 510 to 643 nm, depending upon the relative energy levels of their main and ancillary ligands. The studies of photoabsorption, electrochemistry, photoluminescence and electroluminescence revealed that ILET might contribute to absorption and luminescence process of the iridium complexes containing the ppy-based ligands and BOX. PMID:24758022

Park, Hye Rim; Lee, Seok Jae; Kim, Young Kwan; Ha, Yunkyoung

2014-07-01

386

Metallurgical Evaluation of Grit Blasted Versus Non-Grit Blasted Iridium Alloy Clad Vent Set Cup Surfaces  

Microsoft Academic Search

Metallurgical evaluations were conducted to determine what, if any, grain size differences exist between grit blasted and non-grit blasted DOP-26 iridium alloy cup surfaces and if grit blasting imparts sufficient compressive cold work to induce abnormal grain growth during subsequent temperature exposures. Metallographic measurements indicated that grit blasting cold worked the outside cup surface to a depth of approximately 19

George B Ulrich; Hu Foster Longmire

2010-01-01

387

Capillary Zone Electrophoresis of Iridium(III) and Ruthenium(II) Polypyridyl Complexes in Non?aqueous Solvents  

Microsoft Academic Search

A method of non?aqueous capillary zone electrophoresis has been optimized for the characterization of five functionalized mixed?ligand iridium(III) polypyridyl complexes and four functionalized ruthenium(II) bis?terpyridine complexes. Their mobilities, the relation to their molar mass, and the capillary lifetime (measured in number of injections) have been determined.

Brian R. Pauw; Elisabeth Holder; Veronica Marin; Bas G. G. Lohmeijer; Ulrich S. Schubert

2007-01-01

388

Capillary Zone Electrophoresis of Iridium(III) and Ruthenium(II) Polypyridyl Complexes in Non?Aqueous Solvents  

Microsoft Academic Search

A method of non?aqueous capillary zone electrophoresis has been optimised for the characterisation of five functionalised mixed?ligand iridium(III) polypyridyl complexes and four functionalised ruthenium(II) bis?terpyridine complexes. Their mobilities, the relation to their molar mass and the capillary lifetime (measured in number of injections) have been determined.

Brian R. Pauw; Bas G. G. Lohmeijer; Elisabeth Holder; Veronica Marin; Ulrich S. Schubert

2007-01-01

389

Determination of Arsenic in Food Samples by Hydride Generation – Atomic Absorption Spectrometry  

Microsoft Academic Search

A method for the determination of trace amounts of arsenic in food samples using flow injection analysis and atomic absorption spectrometry with hydride generation (FI-HG AAS) was developed. The parameters of the flow injection system and the hydride generation were optimized with respect to reagent concentrations, atomization temperature, injection volume, reaction coil length and carrier flow rate. The limits of

Aloísia Laura Moretto; Solange Cadore

2004-01-01

390

Hydrogen storage material and process using graphite additive with metal-doped complex hydrides  

Microsoft Academic Search

A hydrogen storage material having improved hydrogen absorbtion and desorption kinetics is provided by adding graphite to a complex hydride such as a metal-doped alanate, i.e., NaAlH.sub.4. The incorporation of graphite into the complex hydride significantly enhances the rate of hydrogen absorbtion and desorption and lowers the desorption temperature needed to release stored hydrogen.

Ragaiy Zidan; James A. Ritter; Armin D. Ebner; Jun Wang; Charles E. Holland

2008-01-01

391

Elementquerstörungen bei der spurenanalytischen Selen-Bestimmung nach dem Hydrid-AAS-Verfahren  

Microsoft Academic Search

The sodium boro hydride-reduction method for the liberation of selenium from acid sample solutions in connection with its determination by AAS using a heatable optical cell made of quartz (hydride system MHS-1, Bodenseewerk Perkin-Elmer, Überlingen, F.R.G.) is interfered with by numerous concomitant elements occurring even in the trace range in the sample solution.

A. Meyer; Ch. Hofer; G. Tölg; S. Raptis; G. Knapp

1979-01-01

392

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

Microsoft Academic Search

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

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

2007-01-01

393

Heat/mass flow enhancement design for a metal hydride assembly, phase 2  

NASA Astrophysics Data System (ADS)

The development and demonstration of a metal hydride/chemical heat pump (MHHP) is reported. In the design of the MHHP, heat transfer was considered to be the key technical study area. Therefore, the goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger/containment assembly. Phase II consisted of the experimental verification of the hydride alloy design data, fabrication of the hydride heat exchanger module components, heat transfer testing of a single heat exchanger element and preliminary performance testing of the entire module. In Phase II, two hydride heat exchanger modules were constructed. Each module consistes of 14 finned copper tubes in a staggered tube bundle arrangement enclosed in a cylindrical pressure vessel. The hydride powder is stored in the annular spacing between the fins. The heat transfer media, water, flows through the finned tubes. Insulation thermally isolates the tubes and hydride materials from the high mass pressure vessel. A single metallic filter in each vessel prevents hydride migrating from one vessel to another

Argabright, T. A.

1983-09-01

394

Silicon nanowires as a rechargeable template for hydride transfer in redox biocatalysis  

NASA Astrophysics Data System (ADS)

We report a new possible application of hydrogen-terminated silicon nanowires (H-SiNWs) as a rechargeable template for hydride transfer in redox biocatalysis. H-SiNWs transfer hydride efficiently to regenerate NADH by oxidizing Si-Hx bonds. The oxidized H-SiNWs were readily recharged for the continuous regeneration of NADH and enzymatic reactions.

Lee, Hwa Young; Kim, Jae Hong; Son, Eun Jin; Park, Chan Beum

2012-11-01

395

Hydride-related degradation of spent-fuel cladding under repository conditions  

SciTech Connect

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.

Chung, H. M.

2000-04-03

396

Blood and Tissue Selenium Determination by Hydride Generation Atomic Absorption Spectrophotometry  

Microsoft Academic Search

Pechová A., L. Pavlata, J. Illek: Blood and Tissue Selenium Determination by Hydride Generation Atomic Absorption Spectrophotometry. Acta Vet. Brno 2005, 74: 483-490. The aim of the study was to optimize the method of blood and tissue selenium determination in ruminants, and to implement it in research and diagnostic practice. A method was developed for selenium determination by hydride generation

A. PECHOVÁ; L. PAVLATA; J. ILLEK

397

Insertion and reduction chemistry of isocyanide with a cyclometalated ditantalum hydride complex.  

PubMed

Reaction of a ditantalum hydride complex with isocyanide is reported. The hydride complex underwent single and double isocyanide insertion into Ta-H bonds, giving iminoformyl and imine-iminoacyl complexes. The transformation of the iminoformyl complex into the amido-carbyne complex was also observed. PMID:21344109

Watanabe, Takahito; Kurogi, Takashi; Ishida, Yutaka; Kawaguchi, Hiroyuki

2011-08-14

398

Hydrogen desorption kinetics from zirconium hydride and zirconium metal in vacuum  

NASA Astrophysics Data System (ADS)

The kinetics of hydrogen desorption from zirconium hydride is important in many nuclear design and safety applications. In this paper, a coordinated experimental and modeling study has been used to explicitly demonstrate the applicability of existing kinetic theories for hydrogen desorption from zirconium hydride and ?-zirconium. A static synthesis method was used to produce ?-zirconium hydride, and the crystallographic phases of the zirconium hydride were confirmed by X-ray diffraction (XRD). Three obvious stages, involving ?-zirconium hydride, a two-phase region, and ?-zirconium, were observed in the hydrogen desorption spectra of two zirconium hydride specimens with H/Zr ratios of 1.62 and 1.64, respectively, which were obtained using thermal desorption spectroscopy (TDS). A continuous, one-dimensional, two-phase moving boundary model, coupled with the zero- and second-order kinetics of hydrogen desorption from ?-zirconium hydride and ?-zirconium, respectively, has been developed to reproduce the TDS experimental results. A comparison of the modeling predictions with the experimental results indicates that a zero-order kinetic model is valid for description of hydrogen flux away from the ?-hydride phase, and that a second-order kinetic model works well for hydrogen desorption from ?-Zr if the activation energy of desorption is optimized to be 70% of the value reported in the literature.

Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.

2014-05-01

399

Recent Advance of Hydride Generation-Analytical Atomic Spectrometry: Part I-Technique Development  

Microsoft Academic Search

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

Zhou Long; Yamin Luo; Chengbin Zheng; Pengchi Deng; Xiandeng Hou

2012-01-01

400

Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part I—Technique Development  

Microsoft Academic Search

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

Zhou Long; Yamin Luo; Chengbin Zheng; Pengchi Deng; Xiandeng Hou

2012-01-01

401

Storage of Hydrogen in the Form of Metal Hydrides: An Application to Thermal Engines.  

National Technical Information Service (NTIS)

The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage systems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure ...

C. Gales P. Perroud

1981-01-01

402

ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE  

SciTech Connect

Hydrogen storage is one of the greatest challenges for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods; the direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum.

Fewox, C; Ragaiy Zidan, R; Brenda Garcia-Diaz, B

2008-12-31

403

ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE  

SciTech Connect

Hydrogen storage is one of the challenges to be overcome for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods. The direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali metal alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum.

Zidan, R; Christopher Fewox, C; Brenda Garcia-Diaz, B; Joshua Gray, J

2009-01-09

404

Structure and properties of metal hydrides prepared by mechanical alloying  

SciTech Connect

Our research examines the structure and reversible hydrogen storage capacity of alloys based on the LaNi{sub 5} intermetallic. The alloys are prepared by mechanical alloying (MA), a technique particularly useful when alloying LaNi{sub 5} with low melting point elements such as tin and calcium. In LaNi{sub 5-y}Sn{sub y}, x-ray diffraction and Rietveld analysis show that tin preferentially occupies the Ni(3g) sites in the LaNi{sub 5} structure, and the unit cell volume increases linearly with tin content to a maximum tin solubility of 7.33 atomic percent (LaNi{sub 4.56}Sn{sub 0.44}). The addition of tin to LaNi{sub 5} causes (a) a logarithmic decrease in the plateau pressures for hydrogen absorption and desorption, which is consistent with the corresponding increase in the volume of the LaNi{sub 5} unit cell; (b) a decrease in the hysteresis between the pressures for hydride formation and decomposition, which is in agreement with a recent theoretical model for the effect; and (c) a linear decrease in the hydrogen storage capacity. Effect (c) is explained by a rigid-band model whereby electrons donated by the tin atoms occupy holes in the 3d band of LaNi{sub 5}, which could otherwise be occupied by electrons donated by the hydrogen atoms. Thermodynamic van`t Hoff analysis for these alloys show an increase in hydride formation enthalpy and no change in entropy with increasing tin concentration. LaNi{sub 5} with calcium additions shows enhanced kinetics of hydrogen absorption/desorption. The powder particles prepared by MA have a larger surface area than particles of the same overall size prepared by arc casting. All LaNi{sub 5}-based alloys prepared by MA in an inert environment require no activation for hydrogen absorption and suffer less comminution upon hydriding/dehydriding.

Wasz, M.L.; Schwarz, R.B.

1995-09-01

405

Hydride-phase formation and its influence on fatigue crack propagationbehavior in a Zircaloy-4 alloy  

SciTech Connect

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.

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

406

Hydrogen concentration depth profiles and superconductivity in the palladium copper hydride system  

SciTech Connect

A sample configuration has been devised to study palladium copper hydride alloys with respect to hydrogen concentration depth profiles; and superconducting parameters. Superconducting palladium copper hydride samples, which displayed transition temperatures in agreement with data measured by Stritzker, were obtained. Thin palladium copper alloy films, which were formed on top of palladium substrate foils by ion beam and solid state techniques, were hydrogenized using electrolysis, hydrogen gas pressure charging and hydrogen ion implantation. The thin palladium copper surface films proved permeable to hydrogen, which was present in higher near surface concentrations as expected by literature. Correlation of critical superconducting transition temperature data to hydrogen concentration depth profiles was obtained. In situ measurements displayed a transition of a palladium copper hydride sample from the normal metallic to the superconducting state upon annealing treatment. Alloy structure, a parameter so far neglected by literature was determined to be significant for the formation of superconducting palladium hydride as well as palladium copper hydride.

Leiberich, A.

1983-01-01

407

A mechanical-force-driven physical vapour deposition approach to fabricating complex hydride nanostructures  

NASA Astrophysics Data System (ADS)

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.

Pang, Yuepeng; Liu, Yongfeng; Gao, Mingxia; Ouyang, Liuzhang; Liu, Jiangwen; Wang, Hui; Zhu, Min; Pan, Hongge

2014-03-01

408

CEOS: A Small, Low Cost Spectrometer for Use on the Iridium NEXT Constellation  

NASA Astrophysics Data System (ADS)

As part of the proposed GEOScan sensor payload to be placed onboard the Iridium NEXT constellation; a small, low cost spectrometer will be included. The Compact Earth Observing Spectrometer (CEOS) is an ultraviolet-visible and near infrared (UV/VIS/NIR) optical spectrometer ideally suited for detailed earth observations. CEOS is derived from a spectrometer originally designed for NASA's O/OREOS mission, a CubeSat launched in November 2010 that is still performing extended science operations. It is also slated to be the key science payload component of VIOLET, a CubeSat mission designed to characterize the spectral characteristics of the upper atmosphere. The CEOS has several unique design elements that allow for high performance over a broad range of environmental conditions. The CEOS design allows for a range of customizations to tune the instrument performance for a wide range of science applications. The baseline instrument provides 200-1000 nm spectral coverage with 1 nm FWHM optical resolution, which is ideal for wide variety of science objectives. However by simply exchanging gratings in the instrument, it can be customized for narrower spectral range with significantly higher resolution. The CEOS instrument will also add a significant feature to allow for more detailed earth science observations. The optical portion of the spectrometer will be augmented with a second optical path designed to measure spectra from 1000 - 2000 nm. This will make the finished instrument capable of detailed spectral measurements from 200 - 2000 nm, covering the ultraviolet through near-infrared. The instrument will be designed to allow the independent operation of both the UV/VIS and NIR portions of the instrument to provide flexibility in science data product volumes. We will describe the design of this spectrometer as well as discuss the details of its design heritage. In addition to Iridium NEXT, we will describe other platforms that this spectrometer may be suited for. We will outline the potential science returns that can be implemented with this low cost, simple spectrometer in the context of emplacement of a single spectrometer on each of the Iridium NEXT satellites in the constellation, including the potential synergies with the other proposed GEOScan sensor payloads.

Murphy, S. D.; Slagowski, S.; Greenbaum, A.; Landis, D.; Mustard, J. F.; Chance, K.

2012-12-01

409

Terminal and bridging parent amido 1,5-cyclooctadiene complexes of rhodium and iridium.  

PubMed

The ready availability of rare parent amido d(8) complexes of the type [{M(?-NH2)(cod)}2] (M=Rh (1), Ir (2); cod=1,5-cyclooctadiene) through the direct use of gaseous ammonia has allowed the study of their reactivity. Both complexes 1 and 2 exchanged the di-olefines by carbon monoxide to give the dinuclear tetracarbonyl derivatives [{M(?-NH2)(CO)2}2 ] (M=Rh or Ir). The diiridium(I) complex 2 reacted with chloroalkanes such as CH2Cl2 or CHCl3, giving the diiridium(II) products [(Cl)(cod)Ir(?-NH2)2Ir(cod)(R)] (R=CH2Cl or CHCl2) as a result of a two-center oxidative addition and concomitant metal-metal bond formation. However, reaction with ClCH2CH2Cl afforded the symmetrical adduct [{Ir(?-NH2)(Cl)(cod)}2] upon release of ethylene. We found that the rhodium complex 1 exchanged the di-olefines stepwise upon addition of selected phosphanes (PPh3, PMePh2, PMe2Ph) without splitting of the amido bridges, allowing the detection of mixed COD/phosphane dinuclear complexes [(cod)Rh(?-NH2)2Rh(PR3)2], and finally the isolation of the respective tetraphosphanes [{Rh(?-NH2)(PR3)2}2]. On the other hand, the iridium complex 2 reacted with PMe2 Ph by splitting the amido bridges and leading to the very rare terminal amido complex [Ir(cod)(NH2)(PMePh2)2]. This compound was found to be very reactive towards traces of water, giving the more stable terminal hydroxo complex [Ir(cod)(OH)(PMePh2)2]. The heterocyclic carbene IPr (IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) also split the amido bridges in complexes 1 and 2, allowing in the case of iridium to characterize in situ the terminal amido complex [Ir(cod)(IPr)(NH2)]. However, when rhodium was involved, the known hydroxo complex [Rh(cod)(IPr)(OH)] was isolated as final product. On the other hand, we tested complexes 1 and 2 as catalysts in the transfer hydrogenation of acetophenone with iPrOH without the use of any base or in the presence of Cs2CO3, finding that the iridium complex 2 is more active than the rhodium analogue 1. PMID:23504929

Mena, Inmaculada; Jaseer, E A; Casado, Miguel A; García-Orduña, Pilar; Lahoz, Fernando J; Oro, Luis A

2013-04-26

410

Chemical Hydrides for Hydrogen Storage in Fuel Cell Applications  

SciTech Connect

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.

Devarakonda, Maruthi N.; Brooks, Kriston P.; Ronnebro, Ewa; Rassat, Scot D.; Holladay, Jamelyn D.

2012-04-16

411

Electrochemical process and production of novel complex hydrides  

DOEpatents

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.

Zidan, Ragaiy

2013-06-25

412

Synthesis and characterization of solution-processable highly branched iridium (III) complex cored dendrimer based on tetraphenylsilane dendron for host-free green phosphorescent organic light emitting diodes  

Microsoft Academic Search

Solution processable highly branched iridium(III) complex fac-tris(2-phenylpyridyl)iridium-cored dendrimer based on tetraphenylsilane dendron and 2-ethylhexyloxy surface groups was prepared. The structure of dendrimer was confirmed by nuclear magnetic resonance, mass and infrared studies. Thermogravimetric analysis and differential scanning calorimetry studies show the thermal stability (?T5%) of 625 K with high glass transition temperature of 423 K. Photoluminescence studies of dendrimer showed the core

Seul-Ong Kim; Qinghua Zhao; K. Thangaraju; Jang Joo Kim; Yun-Hi Kim; Soon-Ki Kwon

2011-01-01

413

Iridium-catalyzed dehydrogenation of substituted amine boranes: kinetics, thermodynamics, and implications for hydrogen storage.  

PubMed

Dehydrogenation of amine boranes is catalyzed efficiently by the iridium pincer complex (kappa (3)-1,3-(OP ( t )Bu 2) 2C 6H 3)Ir(H) 2 ( 1). With CH 3NH 2BH 3 (MeAB) and with AB/MeAB mixtures (AB = NH 3BH 3), the rapid release of 1 equiv of H 2 is observed to yield soluble oligomeric products at rates similar to those previously reported for the dehydrogenation of AB catalyzed by 1. Delta H for the dehydrogenation of AB, MeAB, and AB/MeAB mixtures has been determined by calorimetry. The experimental heats of reaction are compared to results from computational studies. PMID:18785732

Dietrich, Brandon L; Goldberg, Karen I; Heinekey, D Michael; Autrey, Tom; Linehan, John C

2008-10-01

414

Radiation therapy of early carcinoma of the breast without mastectomy. [Linear acceleraor and iridium implants  

SciTech Connect

The results of the treatment of 176 patients with early breast cancer, using radiation therapy without mastectomy are reported. The likelihood of local recurrence was 5% for Stage I patients and 7% for Stage II patients. Local control was significantly greater in those patients receiving an iridium implant. The cumulative survival probability at five years is 96% for Stage I and 68% for Stage II. Gross tumor resection with careful reapproximation of the breast tissue and well-placed incisions facilitates the radiation therapy. Homogeneous external beam radiation to the breast and draining lymph nodes (4500 to 5000 rads) and supplemental local radiation to the sites of the primary lesion (in this series using interstitial implantation) are recommended. The frequency of normal tissue complications was low.

Hellman, S.; Harris, J.R.; Levene, M.B.

1980-08-15

415

Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes  

NASA Astrophysics Data System (ADS)

Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products—that is, secondary alkyl arenes—with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts—specifically ‘pincer’-ligated iridium complexes—and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.

Ahuja, Ritu; Punji, Benudhar; Findlater, Michael; Supplee, Carolyn; Schinski, William; Brookhart, Maurice; Goldman, Alan S.

2011-02-01

416

Iridium-catalyzed asymmetric hydrogenation of unfunctionalized, trialkyl-substituted olefins.  

PubMed

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

Wang, Aie; Fraga, Rui P A; Hörmann, Esther; Pfaltz, Andreas

2011-02-01

417

Chlorido(?-1,5-cyclo-octa-diene)[(penta-fluoro-eth-yl)diphenyl-phosphane]iridium(I).  

PubMed

The title structure,[IrCl(C(8)H(12))(C(14)H(10)F(5)P)], reveals that (C(2)F(5))PPh(2) (penta-fluoro-ethyl-diphenyl-phosphane or pfepp) disrupts the iridium dimer [(cod)IrCl](2) (cod = cyclo-octa-1,5-diene) by rupturing the bridging chloride ligands and binding in the open coordination site to form (cod)Ir(pfepp)Cl with the Ir(I) atom in a distorted square-planar coordination environment. The structure deviates very little from the Ir(I)-triphenyl-phosphine analog, although a significantly (?20?) shorter Ir-P bond is noted for the title compound. PMID:21522590

Choate, Michelle M; Peters, R Gregory; Baughman, Russell G

2010-01-01

418

Formation of C-C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation  

PubMed Central

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.

Bower, John F.; Krische, Michael J.

2011-01-01

419

Observing iridium oxide (IrO(x)) single nanoparticle collisions at ultramicroelectrodes.  

PubMed

We describe the electrochemical detection of single iridium oxide nanoparticle (IrO(x) NP) collisions on a NaBH(4)-treated Pt ultramicroelectrode (UME). We observe single NP events through the enhanced current by electrocatalytic water oxidation, when IrO(x) contacts the electrode and transiently sticks to it. The overall current transient consists of repeated current spikes that return to the background level, superimposed on a current decay, rather than the staircase response seen where an NP sticks on the UME. Here each event produces a unique current spike (or "blip"). The frequency of the spikes was directly proportional to the particle concentration, and the peak current increased with the applied potential. The observed current is very sensitive to the material and surface state of the measuring electrode; a NaBH(4)-treated Pt UME was important in obtaining reproducible results. PMID:20809574

Kwon, Seong Jung; Fan, Fu-Ren F; Bard, Allen J

2010-09-29

420

An STM and STS study on Iridium modified Si(111) Surface  

NASA Astrophysics Data System (ADS)

The structure of Si(111) ?7 x?7 ,,9.1^0-Ir reconstructed surface have been investigated with the help of scanning tunneling microscopy/spectroscopy and low energy electron diffraction. We propose a model based on the experimental data. The model defines a unit cell containing one surface substitutional iridium atom centered under six silicon ad-atoms. Once the sample is annealed at 1200 ^oC, a low density lattice gas of these ring clusters forms on top of an impurity stabilized '1x1' domains. These ring clusters and '1x1' domains co-exist with 7x7 domains of clean Si(111) surface. The local density of states graphs measured on Si(111) ?7 x?7 ,,9.1^0-Ir reconstructed surface contains an asymmetric peak at the edge of the valence band suggesting that there is a surface state exhibiting a Rashba type spin-orbit coupling.

Oncel, Nuri; Nicholls, Dylan

2013-03-01

421

Iridium 192 implantation of T1 and T2 carcinomas of the mobile tongue  

SciTech Connect

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.

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

422

Deep-blue phosphorescence from perfluoro carbonyl-substituted iridium complexes.  

PubMed

The new deep-blue iridium(III) complexes, (TF)2Ir(pic), (TF)2Ir(fptz), (HF)2Ir(pic), and (HF)2Ir(fptz), consisting of 2',4?-difluororphenyl-3-methylpyridine with trifluoromethyl carbonyl or heptafluoropropyl carbonyl at the 3' position as the main ligand and a picolinate or a trifluoromethylated-triazole as the ancillary ligand, were synthesized and characterized for applications in organic light-emitting diodes (OLEDs). Density function theory (DFT) calculations showed that these iridium complexes had a wide band gap, owing to the introduction of the strong electron withdrawing perfluoro carbonyl group. Time-dependent DFT (TD-DFT) calculations suggested that their lowest triplet excited state was dominated by a HOMO ? LUMO transition and that the contribution of the metal-to-ligand charge transfer (MLCT) was higher than 34% for all four complexes, indicating that strong spin-orbit coupling exists in the complexes. The 10 wt % (TF)2Ir(pic) doped 9-(3-(9H-carbazole-9-yl)phenyl)-3-(dibromophenylphosphoryl)-9H-carbazole (mCPPO1) film exhibited the highest photoluminescence quantum yield of 74 ± 3% among the films based on the four complexes. Phosphorescent OLEDs based on (TF)2Ir(pic) and (TF)2Ir(fptz) exhibited maximum external quantum efficiencies of 17.1% and 8.4% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.141, 0.158) and (0.147, 0.116), respectively. These CIE coordinates represent some of the deepest blue emissions ever achieved from phosphorescent OLEDs with considerably high EQEs. PMID:23998654

Lee, Sunghun; Kim, Seul-Ong; Shin, Hyun; Yun, Hui-Jun; Yang, Kiyull; Kwon, Soon-Ki; Kim, Jang-Joo; Kim, Yun-Hi

2013-09-25

423

Osmium, ruthenium, iridium and uranium in silicates and chromite from the eastern Bushveld Complex, South Africa  

USGS Publications Warehouse

Osmium, ruthenium, iridium and uranium contents were determined in eight ortho pyroxene, seven plagioclase, and three chromite mineral separates from the eastern Bushveld Complex. Neutron activation analysis was used to measure the platinum metals, and uranium was determined by a fission track technique. The platinum metals were found to be present within each mine??ral in the proportions Os:Ru:Ir = 1:7:1, while the concentrations of these metals in the minerals are in the ratios orthopyroxene:plagioclase:chromite = 1:16:700. The concentration of uranium was found to range from 11 to 66 ppb (parts per billion) and not to vary significantly from mineral to mineral. The data for the platinum metals are consistent with a model in which the eastern Bushveld Complex was formed by the fractional crystallization of two separately injected magmas. A computer fit of this model to these data indicates that the initial concentrations of Os, Ru and Ir in the first magma were 0.24, 2.0 and 0.21 ppb and in the second magma were 0.16, 1.1 and 0.18 ppb, respectively. The fit also yields the distribution coefficients for the partitioning between the liquid and cumulus orthopyroxene, cumulus plagioclase and cumulus chromite. These coefficients (mineral/liquid) for osmium are 4.5, 66 and 2700; for ruthenium, they are 5, 65 and 2700; and for iridium, they are 4, 60 and 1600. To make this fit, it was necessary to hypothesize the existence of two types of chromite: one type with a large distribution coefficient, presumably formed as a cumulus phase at high temperature, and another, more prevalent type with a smaller distribution coefficient, which may have been formed by postcumulus growth at a lower temperature. This hypothesis is supported by data for coexisting chromite-silicate pairs, which indicate that the chromite grains expelled these platinum metals as they cooled. ?? 1974.

Gijbels, R. h.; Millard, Jr. , H. T.; Desborough, G. A.; Bartel, A. J.

1974-01-01

424

Mobility of iridium in terrestrial environments: Implications for the interpretation of impact-related mass-extinctions  

NASA Astrophysics Data System (ADS)

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.

Martín-Peinado, F. J.; Rodríguez-Tovar, F. J.

2010-08-01

425

First-principles modelling of magnesium titanium hydrides  

NASA Astrophysics Data System (ADS)

Mixing Mg with Ti leads to a hydride MgxTi(1 - x)H2 with markedly improved (de)hydrogenation properties for x\\lesssim 0.8 , as compared to MgH2. Optically thin films of MgxTi(1 - x)H2 have a black appearance, which is remarkable for a hydride material. In this paper we study the structure and stability of MgxTi(1 - x)H2, x = 0-1 by first-principles calculations at the level of density functional theory. We give evidence for a fluorite to rutile phase transition at a critical composition xc = 0.8-0.9, which correlates with the experimentally observed sharp decrease in (de)hydrogenation rates at this composition. The densities of states of MgxTi(1 - x)H2 have a peak at the Fermi level, composed of Ti d states. Disorder in the positions of the Ti atoms easily destroys the metallic plasma, however, which suppresses the optical reflection. Interband transitions result in a featureless optical absorption over a large energy range, causing the black appearance of MgxTi(1 - x)H2.

Er, Süleyman; van Setten, Michiel J.; de Wijs, Gilles A.; Brocks, Geert

2010-02-01

426

Hydriding of TiZrNiFe nanocompounds  

NASA Astrophysics Data System (ADS)

Ti-based quasicrystals belong to the second largest group of the stable quasicrystals, showing attractive properties as hydrogen storage materials. The Ti 45Zr 38Ni 17 intermetallic compound forms an icosahedral ( i-phase) structure, in which Ti and Zr atoms possess very good chemical affinity for hydrogen absorption. We modified the Ti 45Zr 38Ni 17 compounds by substituting 3d metals (iron) for Ni to obtain amorphous phase. The samples were produced by mechanical alloying. The 3d metal atoms are located in the same positions as nickel. The structural characterization was made by means of XRD measurements. Thermodynamic properties were studied by differential scanning calorimetry (DSC) and thermal desorption spectroscopy (TDS). The obtained amorphous phases Ti 45Zr 38Ni (9,13)Fe (8,4) transform to the i-phase at the similar temperature range as Ti 45Zr 38Ni 17. The final concentration of absorbed hydrogen depends on the amount of Fe. When increasing the amount of iron, the hydrogen release temperature becomes lower. After hydriding, the samples decompose into simple metal hydrides.

?ywczak, A.; Shinya, Daigo; Gondek, ?.; Takasaki, Akito; Figiel, H.

2010-01-01

427

GAS-PHASE REACTIONS OF HYDRIDE ANION, H{sup -}  

SciTech Connect

Rate constants were measured at 300 K for the reactions of the hydride anion, H{sup -}, with neutral molecules C{sub 2}H{sub 2}, H{sub 2}O, CH{sub 3}CN, CH{sub 3}OH, (CH{sub 3}){sub 2}CO, CH{sub 3}CHO, N{sub 2}O, CO{sub 2}, O{sub 2}, CO, CH{sub 3}Cl, (CH{sub 3}){sub 3}CCl, (CH{sub 3}CH{sub 2}){sub 2}O, C{sub 6}H{sub 6}, and D{sub 2} using a flowing-afterglow instrument. Experimental work was supplemented by ab initio calculations to provide insight into the viability of reaction pathways. Our reported rate constants should prove useful to models of astrophysical environments where conditions prevail for the existence of both H{sup -} and neutral species. The variety of neutral reactants studied includes representative species from prototypical chemical groups, effectively mapping reactivity trends for the hydride anion.

Martinez, Oscar; Yang Zhibo; Demarais, Nicholas J.; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, 215 UCB, University of Colorado, Boulder, CO 80309-0215 (United States); Snow, Theodore P., E-mail: Oscar.Martinez@colorado.ed, E-mail: Zhibo.Yang@colorado.ed, E-mail: Nicholas.Demarais@colorado.ed, E-mail: Veronica.Bierbaum@colorado.ed, E-mail: Theodore.Snow@colorado.ed [Department of Astrophysical and Planetary Sciences, 391 UCB, University of Colorado, Boulder, CO 80309-0391 (United States)

2010-09-01

428

Physics of Hydrogen Storage in Metal-Hydrides  

NASA Astrophysics Data System (ADS)

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.

Abdelfattah-Zidan, Ragaiy

429

ACCEPTABILITY ENVELOPE FOR METAL HYDRIDE-BASED HYDROGEN STORAGE SYSTEMS  

SciTech Connect

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.

Hardy, B.; Corgnale, C.; Tamburello, D.; Garrison, S.; Anton, D.

2011-07-18

430

Interferences in electrochemical hydride generation of hydrogen selenide  

NASA Astrophysics Data System (ADS)

Interferences from Cu(II), Zn(II), Pt(IV), As(III) and nitrate on electrochemical hydride generation of hydrogen selenide were studied using a tubular flow-through generator, flow injection sample introduction and quartz tube atomic absorption spectrometry. Comparison with conventional chemical generation using tetrahydroborate was also performed. Lead and reticulated vitreous carbon (RVC), both in particulate form, were used as cathode materials. Signal supressions up to 60-75%, depending on the cathode material, were obtained in the presence of up to 200 mg l-1 of nitrate due to the competitive reduction of the anion. Interference from As(III) was similar in electrochemical and chemical generation, being related to the quartz tube atomization process. Zinc did not interfere up to Se/Zn ratios 1:100, whereas copper and platinum showed suppression levels up to 50% for Se/interferent ratios 1:100. Total signal suppression was observed in presence of Se/Cu ratios 1:100 when RVC cathodes were used. No memory effects were observed in any case. Scanning electron microscopy and squared wave voltametry studies supported the interference mechanism based on the decomposition of the hydride on the dispersed particles of the reduced metal.

Bolea, E.; Laborda, F.; Belarra, M. A.; Castillo, J. R.

2001-12-01

431

Relativistic DMRG calculations on the curve crossing of cesium hydride.  

PubMed

Over the past few years, it has been shown in various studies on small molecules with only a few electrons that the density-matrix renormalization group (DMRG) method converges to results close to the full configuration-interaction limit for the total electronic energy. In order to test the capabilities of the method for molecules with complex electronic structures, we performed a study on the potential-energy curves of the ground state and the first excited state of 1sigma+ symmetry of the cesium hydride molecule. For cesium relativistic effects cannot be neglected, therefore we have used the generalized arbitrary-order Douglas-Kroll-Hess protocol up to tenth order, which allows for a complete decoupling of the Dirac Hamiltonian. Scalar-relativistic effects are thus fully incorporated in the calculations. The potential curves of the cesium hydride molecule feature an avoided crossing between the ground state and the first excited state, which is shown to be very well described by the DMRG method. Compared to multireference configuration-interaction results, the potential curves hardly differ in shape, for both the ground state and the excited state, but the total energies from the DMRG calculations are in general consistently lower. However, the DMRG energies are as accurate as corresponding coupled cluster energies at the equilibrium distance, but convergence to the full configuration-interaction limit is not achieved. PMID:16292897

Moritz, Gerrit; Wolf, Alexander; Reiher, Markus

2005-11-01

432

[Investigation of enhancing effect for hydride generation-atomic fluorescence of transition metal elements].  

PubMed

A mechanism of hydride generation based on disassembly reaction of hydrogen-transferred interim state [M(BH4)m]* was developed by investigating the effect of reaction medium acidity on hydride generation. The effects of Co2+ and Ni2+, phenanthroline and 8-hydroxyquinoline on hydride generation-atomic fluorescence signals of Zn, Cd, Cu and Ni were studied, respectively, and their enhancing mechnism was discussed. The enhancing effect Co2+ and Ni2+ on the fluorescence signals of Zn and Cd was due to the increase in transmission efficiency of hydride of Zn and Cd. There was a synergic enhancing effect between phenanthroline or 8-hydroxyquinoline and Co2+ on the fluorescence signals of Zn and Cd, however no synergic enhancing effect between phenanthroline and 8-hydroxyquinoline on the fluorescence signals of Zn and Cd. The simulative action of cationic surfactant, anion surfactant and non-ionic surfactant surfactant to hydride generation was investigated. It is shown that both cationic surfactant and non-ionic surfactant have obvious enhancing effect on the fluorescence signals of analytes because of the decrease in surface tension of reaction solution. The release characteristics of hydride from the absorption solution containing surfactant was ulteriorly examined by using graphite furnace atomic absorption spectrometry, and the mechanism of enhancing effect of surfactant on hydride generation and transmission was proposed. PMID:19271518

Sun, Han-Wen; Suo, Ran

2008-11-01

433

A deformation and thermodynamic model for hydride precipitation kinetics in spent fuel cladding  

SciTech Connect

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.

Stout, R.B.

1989-10-01

434

Improved Blue-Green Electrophosphorescence from a Tuning Iridium Complex with Benzyl Group in Polymer Light-Emitting Devices  

NASA Astrophysics Data System (ADS)

Electroluminescence performances from a tuning biscyclometlated iridium complex with benzyl group are demonstrated in double-layered polymer light-emitting devices (PLEDs) using a blend of poly(9,9-dioctylfluorene) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix. Blue-green electrophosphorescent emission with a peak at 521 nm and a shoulder at 492 nm was observed. The highest luminance efficiency of 4.8 cd/A at current density of 0.56mA/cm2 and a maximum luminance of 1944cd/m2 at 217.6 mA/cm2 were achieved in the devices at the dopant concentration of 8%. The luminous performance of the devices becomes better with increasing dopant concentrations from 1% to 8%. This implies that the concentration quenching of this iridium complex with benzyl group can be efficiently inhibited in the devices.

Ma, Xiao-Yun; Zhu, Ke-Ming; Wang, Lei; Xiao, Fang-Liang; Wen, Zhong-Lin; Zhu, Mei-Xiang; Zhu, Wei-Guo

2008-02-01

435

The storage of hydrogen in the form of metal hydrides: An application to thermal engines  

NASA Technical Reports Server (NTRS)

The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage sytems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure magnesium hydrides. Several test engines employing hydrogen fuel have been developed: a single cylinder motor originally designed for use with air gasoline mixture; a four-cylinder engine modified to run on an air hydrogen mixture; and a gas turbine.

Gales, C.; Perroud, P.

1981-01-01

436

Nanoscale hydride formation at dislocations in palladium: Ab initio theory and inelastic neutron scattering measurements  

NASA Astrophysics Data System (ADS)

Hydrogen arranges at dislocations in palladium to form nanoscale hydrides, changing the vibrational spectra. An ab initio hydrogen potential energy model versus Pd neighbor distances allows us to predict the vibrational excitations for H from absolute zero up to room temperature adjacent to a partial dislocation and with strain. Using the equilibrium distribution of hydrogen with temperature, we predict excitation spectra to explain new incoherent inelastic neutron-scattering measurements. At 0 K, dislocation cores trap H to form nanometer-sized hydrides, while increased temperature dissolves the hydrides and disperses H throughout bulk Pd.

Trinkle, Dallas R.; Ju, Hyunsu; Heuser, Brent J.; Udovic, Terrence J.

2011-05-01

437

The role of chemical free energy and elastic strain in the nucleation of zirconium hydride  

NASA Astrophysics Data System (ADS)

In this work a combination of synchrotron X-ray diffraction and thermodynamic modelling has been used to study the dissolution and precipitation of zirconium hydride in ?-Zr establishing the role of elastic misfit strain and chemical free energy in the ? ? ? + ? phase transformation. The nucleation of zirconium hydride is dominated by the chemical free energy where the chemical driving force for hydride precipitation is proportional to the terminal-solid solubility for precipitation and can be predicted by a function that is analogous to the universal nucleation parameter for the bainite transformation in ferrous alloys. The terminal-solid solubility for precipitation was found to be kinetically limited ?287 °C at a cooling rate of 5 °C min-1 or greater. The terminal solubilities were established using an offset method applied to the lattice strain data where a resolution of ˜10 wppm H can be achieved in the -direction. This is aided by the introduction of intra-granular strains in the -direction during cooling as a result of the thermal expansion anisotropy which increases the anisotropy associated with the misfitting H atoms within the ?-Zr lattice. The partial molar volume of H in ?-Zr has been shown to be consistent with other metals with BCC, FCC and HCP crystal structures and independent of H concentration. The application of an offset method to lattice strain data has successfully been used to measure the TSSd temperature during heating and the TSSp temperature during cooling based on the tetragonal misfit of H in ?-Zr. The TSSp temperature was measured to a resolution of ˜10 wppm H independently of bulk texture which is an improvement over other techniques. The ? ? ? + ? transformation has been shown to be kinetically limited when the TSSp temperature is >287 °C at a cooling rate of 5°C min-1 or greater. The chemical driving force for ?-hydride nucleation is proportional to the TSSp temperature and can be predicted as a function of temperature by ?GN. This is consistent with the dislocation-based models for hydride nucleation and gives an activation energy that is inversely proportional to the chemical driving force for hydride nucleation. It was not possible to detect the preferential nucleation of ?-hydride and its evolution to ?-hydride using synchrotron radiation due to the detection limit for {1 1 1}?/? (>20 wppm H) reflection and the expected rapid transformation kinetics. With a reduction in the TSSp temperature, the chemical driving force for hydride precipitation increases, promoting the nucleation of a high density of smaller hydrides. Establishing the TSSp temperature where ?-hydrides form on slow cooling will define the minimum chemical driving force needed to transition from ?- to ?-hydride.

Barrow, A. T. W.; Toffolon-Masclet, C.; Almer, J.; Daymond, M. R.

2013-10-01

438

Development of a Gamma-Ray Detector With Iridium Transition Edge Sensor Coupled to a Pb Absorber  

Microsoft Academic Search

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) thermometer and a bulk Pb absorber, which is directly coupled to a TES with Stycast 2850FT epoxy. This paper describes our TES based gamma-ray detector and the first experimental results for

Rathnayaka Mudiyanselage Thushara Damayanthi; Steven W. Leman; Hiroyuki Takahashi; Masashi Ohno; Yasuhiro Minamikawa; Kentaro Nishimura; Naoko Iyomoto

2009-01-01

439

Formation of neutron-deficient isotopes of francium and radon in bombardment of iridium by neon ions  

Microsoft Academic Search

The electromagnetic mass separator EMSONHIB has been used to determine the yields of neutron-deficient isotopes of francium and radon in bombardment of a thick iridium target by ²°Ne ions accelerated to 200 MeV. The experimental results are compared with calculations according to the statistical model of evaporation of neutrons and protons from the excited compound nucleus. Data are obtained on

A. P. Kabachenko; I. V. Kuznetsov; L. G. Soo; N. I. Tarantin

1977-01-01

440

A comparison of the behaviors of tungsten trioxide and anodic iridium oxide film electrochromics in a nonaqueous acidic medium  

Microsoft Academic Search

The performance of anodic iridium oxide film (AIROF) and WO3 electrochromic electrodes was tested in a water-free perchloric acid\\/dimethylsulfoxide solution. WO3 could be colored and bleached electrochemically to nearly the same extent as in water solutions, albeit much more slowly. By contrast, no electrochromic effect could be produced with AIROF electrodes. This proves that the electrochromic processes for these two

C. E. Rice

1979-01-01

441

Detection of lipoprotein-associated phospholipase A 2 using a nano-iridium particle catalyst-based biosensor  

Microsoft Academic Search

The detection and quantification of lipoprotein-associated phospholipase A2 (Lp-PLA2) using an iridium-modified carbon-based biosensor was successfully accomplished in this study. The detection procedure was based on the hydrolysis of short-chain carboxylic esters; which produced as products, organic acids and alcohol. The alcohol was then oxidized by alcohol oxidase producing hydrogen peroxide, which was detected electrochemically. A methyl ester (methyl butyrate)

Wei-Yin Liao; Chung-Chiun Liu; Christina Wang

2008-01-01

442

Mobility of iridium in terrestrial environments: Implications for the interpretation of impact-related mass-extinctions  

Microsoft Academic Search

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 10years after deposition. This has enabled comparisons with the values of past Ir-bearing

F. J. Martín-Peinado; F. J. Rodríguez-Tovar

2010-01-01

443

Enantioselective domino reaction of CO2, amines and allyl chlorides under iridium catalysis: formation of allyl carbamates.  

PubMed

The enantioselective domino reaction between CO2 (1 atm), amines and linear allyl chlorides in the presence of an iridium complex, DABCO and toluene at 15 °C was realized, which gave branched allyl carbamates in acceptable to high yields with up to excellent regioselectivity (99/1) and 94% ee. This is the first example of the synthesis of chiral allyl carbamates through catalytic domino reactions using CO2. PMID:24652315

Zhang, Min; Zhao, Xiaoming; Zheng, Shengcai

2014-05-01

444

Iridio: Una opción para medir el potencial redox Iridium: An option for measurement of the redox potential  

Microsoft Academic Search

Some relevant results are presented of research leading to an alternative redox electrode to platinum. Several different electrodes were subjected to experiments under controlled conditions, mainly in artificial seawater. Among those tested were platinum, graphite, glassy carbon, gold and iridium. Our results, when combined with those estimated by using a model based on the MINEQL+ program, suggest that the O2\\/H2O2

Lorena M. Ríos-Mendoza; J. Vinicio Macías-Zamora; Alberto R. Zirino-Weiss; Naval Command

2003-01-01

445

Highly efficient electrophosphorescence devices based on iridium complexes with high efficiency over a wide range of current densities  

NASA Astrophysics Data System (ADS)

Three new luminescent cyclometalated iridium (II I) complexes are successfully synthesized. The cyclometalated ligand used here is 2-(2-fluorophenyl)-benzothiazole (F-BT). The auxiliary ligands are acetylacetone (acac), 1,1,1-trifluoroacetylaceton (3F-acac), 1,1,1,5,5,5-hexafluoroacetylacetone (6F-acac), respectively. All complexes exhibit bright photoluminescence at room temperature. Organic light-emitting diodes are fabricated by doping the iridium (III) complexes in 4, 4' -N, N'-dicarbazole-biphenyl (CBP), and the device characteristics are investigated. Among these devices, the performances of the optimized devices based on 1 at high current density are among the best reported for devices with iridium (III) complexes as emitters. EL efficiencies show weak dependence on doping concentration and current density. The optimized device exhibits a peak current efficiency of 28.5 cd A-1 and a power efficiency of 11.2 lm W-1, respectively, at 20 mA cm-2, an efficiency of 22.7 cd A-1 at 100 mA cm-2, 80% of the maximum, can be achieved. Short triplet decay time of 1 measured in solid films is supposed to be responsible for the minor loss in EL efficiency, which suggests depressed triplet-triplet annihilation and site saturation of the phosphor. Efficient exciton formation on the molecules of 1 by direct charge trapping and confinement within the emissive layer also make for outstanding electrophosphorescent performances.

Zhang, Liying; Chen, Ping; Li, Bin; Hong, Ziruo; Liu, Shiyong

2008-12-01

446

Four emission bands from a mixed-ligand iridium complex IrQ(ppy)2 at room temperature  

NASA Astrophysics Data System (ADS)

Four photoluminescence bands are observed from iridium complex in UV, violet, green, and red spectral regions at room temperature. Such a multiple emission is found from a mixed-ligand iridium(III) complex, (8-quinolinolato) bis(2-phenylpyridyl) iridium IrQ(ppy)2, which consists of IrQ and Ir(ppy)2 components (Q: 8-quinolinolato, ppy: phenylpyridyl). Of the four emission bands, the UV emission band with maximum at about 330 nm and the red emission band are attributed to the ligand-centered (1LC) 1n?* and metal-to-ligand charge transfer (3MLCT) 3(??*) states from IrQ, respectively, while the violet emission band with maximum at about 400 nm and the green emission band at about 513 nm are attributed to the 1LC 1(n?*) and 3MLCT 3??* states from Ir(ppy). It is suggested that (1) IrQ and Ir(ppy) generate their own emissions by the inefficient Förster energy transfer between IrQ and Ir(ppy) due to the orientation factor of nearly zero, and (2) each of IrQ and Ir(ppy) gives rise to two emissions from the singlet and triplet states by the inefficient intersystem crossing.

Tsuboi, Taiju; Huang, Duo-Fong; Chow, Tahsin J.; Huang, Wei

2014-08-01

447

Hydride-induced embrittlement of Zircaloy-4 cladding under plane-strain tension  

NASA Astrophysics Data System (ADS)

The mechanical response of high-burnup Zircaloy-4 fuel cladding subjected to a postulated reactivity initiated accident (referred to as a rod ejection accident (REA) in a pressurized water reactor) can be affected by hydrogen embrittlement. This study addresses the hydrogen embrittlement of non-irradiated, stress-relieved Zircaloy-4 cladding under conditions (state of stress and temperature) relevant to those of a reactivity initiated accident. Specifically, the study has investigated the effects of a concentrated density of hydride particles (in the form of a rim at the outer surface of the cladding tube introduced by gas-charging) on the cladding ductility when tested under a near-plane-strain tension at 25, 300, and 375°C. The influence of the hydride-rim thickness and local hydrogen contents on cladding ductility is studied as a function of temperature and correlated with the hydride microstructure. Using synchrotron x-ray diffraction, this study has found that the delta-hydride phase (i.e., ZrHx, where x ? 1.66) is the predominant hydride phase to precipitate in stress-relieved Zircaloy-4 cladding for hydrogen contents up to 1250 wt ppm. At hydrogen contents above 2700 wt ppm, although delta-hydride is still the majority phase, both gamma- and epsilon-hydride phases are also observed. The volume fraction of hydrides was estimated as a function of hydrogen content, using the diffracted x-ray intensities. These estimated values agree well with calculated values assuming hydride precipitates are delta-hydride. Under near-plane-strain hoop tension, the ductility and fracture of the cladding is highly dependent on both the hydride-rim thickness and the testing temperature. At room temperature, due to a high density of hydride particles within the rim, a Mode I crack is injected shortly after yielding. This limits cladding ductility, such that it decreases with increasing thickness of the hydride rim. Cladding containing hydride rims with a thickness of ?100 mum was thus macroscopically brittle (the macroscopic failure strain was small) as the result of the initiation and propagation of a Mode I (i.e., tensile) crack through the thickness of the cladding. Crack growth occurred due to void initiation at fractured hydride particles and subsequent strain-induced coalescence. Mode I cracks were also observed at 300°C within the hydride rim, but the substrate failed by a mixed Mode I/II crack with no signs of void nucleation, as the hydride particles in the substrate resisted fracture. Macroscopically brittle behavior occurred for cladding with hydride rims thicker than ?170-mum. In contrast, at 375°C, materials with rim thicknesses up to 260 mum were ductile and failed due to localized necking. As a result, the effect of hydrogen on ductility at this temperature is small. Also, at this highest temperature, small Mode I cracks were occasionally observed within the hydride rim; these cracks were associated with high local hydrogen contents (>4000 wt ppm) and the presence of the tetragonal epsilon-hydride phase near the outer surface, suggesting that this hydride phase is highly brittle at all temperatures of this study. This study also tested specimens with a uniform distribution of hydrides (containing ?2200-wt-ppm hydrogen) in order to compare their behavior to that of hydride-rim specimens. Uniformly-hydrided specimens containing ?2200-wt-ppm hydrogen tested at 300°C showed the initiation of Mode I cracks and macroscopically brittle behavior, similar to that of the hydride-rim cladding. However, when tested at 375°C, cladding with ?2200-wt-ppm hydrogen showed comparable macroscopic ductility (>4% uniform hoop strain) and fracture (i.e., plastic instability) to that of non-hydrided cladding, suggesting that this cladding is macroscopically ductile. The difference between material behavior at 300 and 375°C indicates that the survivability of cladding during a reactivity initiated accident may depend critically on the exact cladding temperature at maximum load.

Daum, Robert S.

448

Hydride transport vessel vibration and shock test report  

SciTech Connect

Sandia National Laboratories performed vibration and shock testing on a Savannah River Hydride Transport Vessel (HTV) which is used for bulk shipments of tritium. This testing is required to qualify the HTV for transport in the H1616 shipping container. The main requirement for shipment in the H1616 is that the contents (in this case the HTV) have a tritium leak rate of less than 1x10{sup {minus}7} cc/sec after being subjected to shock and vibration normally incident to transport. Helium leak tests performed before and after the vibration and shock testing showed that the HTV remained leaktight under the specified conditions. This report documents the tests performed and the test results.

Tipton, D.G.

1998-06-01

449

Ovonic nickel metal hydride batteries for space applications  

NASA Technical Reports Server (NTRS)

Ovonic nickel-metal hydride (NiMH) rechargeable batteries are easily adaptable to a variety of applications. Small consumer NiMH cells were developed and are now being manufactured by licensees throughout the world. This technology was successfully scaled up in larger prismatic cells aimed at electric vehicle applications. Sealed cells aimed at satellite power applications were also built and cycle tested by OBC and other outside agencies. Prototype batteries with high specific energy (over 80 Wh/kg), high energy density (245 Wh/L), and excellent power capability (400 W/kg) were produced. Ovonic NiMH batteries demonstrated an excellent cycle life of over 10,000 cycles at 30 percent DOD. Presently, Ovonic Battery Company is working on an advanced version of this battery for space applications as part of an SBIR contract from NASA.

Venkatesan, S.; Corrigan, D. A.; Fetcenko, M. A.; Gifford, P. R.; Dhar, S. K.; Ovshinsky, S. R.

1993-01-01

450

Final report for the DOE Metal Hydride Center of Excellence.  

SciTech Connect

This report summarizes the R&D activities within the U.S. Department of Energy Metal Hydride Center of Excellence (MHCoE) from March 2005 to June 2010. The purpose of the MHCoE has been to conduct highly collaborative and multi-disciplinary applied R&D to develop new reversible hydrogen storage materials that meet or exceed DOE 2010 and 2015 system goals for hydrogen storage materials. The MHCoE combines three broad areas: mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials), materials development (in which new materials are synthesized and characterized) and system design and engineering (which allow these new materials to be realized as practical automotive hydrogen storage systems). This Final Report summarizes the organization and execution of the 5-year research program to develop practical hydrogen storage materials for light duty vehicles. Major results from the MHCoE are summarized, along with suggestions for future research areas.

Keller, Jay O.; Klebanoff, Leonard E.

2012-01-01

451

Wall pressure exerted by hydrogenation of sodium aluminum hydride.  

SciTech Connect

Wall pressure exerted by the bulk expansion of a sodium aluminum hydride bed was measured as a function of hydrogen content. A custom apparatus was designed and loaded with sodium alanates at densities of 1.0, 1.1, and 1.16 g/cc. Four complete cycles were performed to identify variations in measured pressure. Results