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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

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

PubMed

The hydrogen sorption properties of oxide-supported Ir-Pd nanoalloys have been determined for the first time, and correlated with their catalytic behavior. The addition of Ir to Pd suppresses hydride formation and leads to improved catalytic performances with respect to pure metals in the preferential oxidation of CO in H2 excess (PROX). PMID:25059734

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

2014-09-01

3

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

4

Cation-modulated reactivity of iridium hydride pincer-crown ether complexes.  

PubMed

Complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The pincer-crown ether ligand exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through lithium and sodium cation-macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation (with lithium-containing reactions proceeding about 10 times faster than sodium-containing reactions) or on the basis of the concentration of the cation. Up to 250-fold rate enhancements in H/D exchange rates are observed when catalytic amounts of Li(+) are added. PMID:25275727

Kita, Matthew R; Miller, Alexander J M

2014-10-15

5

Iridium(III) hydride complexes for the catalytic enantioselective hydrogenation of imines  

SciTech Connect

Considerable research during the past 20 years has produced remarkable catalysts based on Rh and Ru for enantioselective homogeneous hydrogenation of olefins and ketones where in many cases optical yields > 95% have been observed. On the other hand, few publications have appeared that deal with asymmetric hydrogenation of the C{double bond}N bond of imines to form chiral amines, the greatest success having been obtained by using in situ mixtures of M/chiral diphosphine/X (M = Rh{sup I} or Ir{sup I}, X = NEt{sub 3} or halide) but the nature and the mechanism of action of the catalyst is not well-defined. The authors report herein the discovery of a new class of iridium(III)-diphosphine-monohydrido complexes that are effective for asymmetric reduction of prochiral imines to the corresponding amine with high turnover numbers and moderate to good enantioselectivity.

Ng Cheong Chan, Y.; Osborn, J.A. (Univ. Louis Pasteur, Strasbourg (France))

1990-12-05

6

Silica-grafted 16-electron hydride pincer complexes of iridium(III) and their soluble analogues: synthesis and reactivity with CO.  

PubMed

The dihydride complexes [IrH2(POCOP)] (1a) and [IrH2(PCP)] (1b) (POCOP = 1,3-bis((di-tert-butylphosphino)oxy)benzene; PCP = 1,3-bis((di-tert-butylphosphino)methyl)benzene) react with the surface silanols of mesoporous amorphous silica (SBA-15) to give H2 and the silica-grafted, 16-electron iridium(III) monohydride species [IrH(O-SBA-15)(pincer)] (2a and 2b). These materials contain a single iridium(III) species, that is a highly dispersed, coordinatively unsaturated siloxo hydride complex, as indicated by solid-state spectroscopic data. The siloxo complexes [IrH((i)Bu-POSS)(POCOP)] (3a) and [IrH((i)Bu-POSS)(PCP)] (3b) ((i)Bu-POSS = OSi8O12(i)Bu7) were prepared as soluble analogues of 2a and 2b to support their spectroscopic characterization. The coordinatively unsaturated, 16-electron species 2a and 2b react with CO to give the six-coordinate iridium(III) adducts [IrH(O-SBA-15)(CO)(POCOP)] (7a) and [IrH(O-SBA-15)(CO)(PCP)] (7b). Due to dissimilar electronic properties of the pincer ligands, 7a undergoes reductive elimination of the silanol forming the Ir(I) complex [Ir(CO)(POCOP)] (8a), whereas 7b is stable in oxidation state of III. The homogeneous siloxo carbonyl complexes [IrH((i)Bu-POSS)(CO)(POCOP)] (9a), [IrH((i)Bu-POSS)(CO)(PCP)] (9b), and [IrH(OSiMe3)(CO)(POCOP)] (11a) were prepared to substantiate the reactivity and the characterization of the silica grafted species. PMID:25345601

Rimoldi, Martino; Mezzetti, Antonio

2014-11-17

7

Determination of arsenic in sediments, coal and fly ash slurries after ultrasonic treatment by hydride generation atomic absorption spectrometry and trapping in an iridium-treated graphite tube  

Microsoft Academic Search

A simple and reliable method for the determination of arsenic in sediment and in coal without sample digestion, based on hydride generation from slurry samples is proposed. After grinding the samples to a particle size of ?50 ?m, the sample powder was mixed with aqua regia and hydrofluoric acid in an ultrasonic bath for 30 min. After diluting the mixture

Mariana Antunes Vieira; Bernhard Welz; Adilson José Curtius

2002-01-01

8

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

PubMed

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

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

2013-04-15

9

Iridium in natural waters  

SciTech Connect

Iridium, commonly used as a tracer of extraterrestrial material, was measured in rivers, oceans, and an estuarine environment. The concentration of iridium in the oceans ranges from 3.0 ({+-}1.3) x 10{sup 8} to 5.7 ({+-}0.8) x 10{sup 8} atoms per kilogram. Rivers contain from 17.4 ({+-}0.9) x 10{sup 8} to 92.9 ({+-}2.2) x 10{sup 8} atoms per kilogram and supply more dissolved iridium to the oceans than do extraterrestrial sources. In the Baltic Sea, {approximately}75% of riverine iridium is removed from solution. Iron-manganese oxyhydroxides scavenge iridium under oxidizing conditions, but anoxic environments are not a major sink for iridium. The ocean residence time of iridium is between 2 x 10{sup 3} and 2 x 10{sup 4} years. 32 refs., 3 figs., 1 tab.

Anbar, A.D.; Wasserburg, G.J.; Papanastassiou, D.A. [California Institute of Technology, Pasadena, CA (United States)] [and others

1996-09-13

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

Hydride compositions  

DOEpatents

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 hydrogen 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 hydrogen and then heating at a temperature below the softening temperature of any of the. constituents so that their chemical and structural integrity is preserved. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P.sub.H.sbsb.2 and determining H/M from the isothermic function of the composition.

Lee, Myung W. (North Augusta, SC)

1995-01-01

12

C?C coupling of ketones with methanol catalyzed by a N-heterocyclic carbene-phosphine iridium complex.  

PubMed

An N-heterocyclic carbene-phosphine iridium complex system was found to be a very efficient catalyst for the methylation of ketone via a hydrogen transfer reaction. Mild conditions together with low catalyst loading (1?mol?%) were used for a tandem process which involves the dehydrogenation of methanol, C?C bond formation with a ketone, and hydrogenation of the new generated double bond by iridium hydride to give the alkylated product. Using this iridium catalyst system, a number of branched ketones were synthesized with good to excellent conversions and yields. PMID:25589169

Quan, Xu; Kerdphon, Sutthichat; Andersson, Pher G

2015-02-23

13

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

14

Mononuclear iridium dinitrogen complexes bonded to zeolite HY.  

PubMed

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

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

2015-01-01

15

Iridium at Kilauea  

Microsoft Academic Search

Trace-element anomalies observed in rocks located stratigraphically at the Cretaceous-Tertiary boundary are considered significant evidence that the boundary is a record of a large meteorite impact (Science, 208, 1095-1108, 1980). In particular, trace metals, including iridium and other members of the platinum metals group, are thought to be enriched in rocks alien to the earth's surface. These elements are indeed

Peter M. Bell

1984-01-01

16

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

17

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

18

Hydrides of intermetallic compounds  

Microsoft Academic Search

s  Aspects of the progress over the recent years on hydrides of intermetallic compounds are reviewed with emphasis on structure,\\u000a stability, solid-state properties, catalysis, and kinetics. Some new routes to an understanding of hydride phenomenology are\\u000a indicated. Generally speaking hydrides represent but one special aspect of intermetallic compounds. They are, however, unique\\u000a as model systems for questions concerning the stability of

H. Oesterreicher

1981-01-01

19

Iridium-tin mixed oxide anode coatings  

Microsoft Academic Search

Mixed oxide coatings of tin and iridium oxide on titanium substrates have been studied over the composition range of 5 to 100 mol % iridium oxide. While stannic oxide behaves as a simple diluent for the electrocatalytically active precious metal oxide, substantial replacement of iridium by tin may be made with little degradation of coating performance in oxygen evolution.

E. N. Balko; P. H. Nguyen

1991-01-01

20

IRIDIUM(R) aeronautical satellite communications  

Microsoft Academic Search

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

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

1998-01-01

21

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

22

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.

23

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

24

Boron hydride polymer coated substrates  

DOEpatents

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

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

1986-08-27

25

Iridium(R) aeronautical satellite communications  

Microsoft Academic Search

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

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

1999-01-01

26

Iridium material for hydrothermal oxidation environments  

SciTech Connect

A process is described for hydrothermal oxidation of combustible materials in which, during at least a part of the oxidation, corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises iridium, iridium oxide, an iridium alloy, or a base metal overlaid with an iridium coating. Iridium has been found to be highly resistant to environments encountered in the process of hydrothermal oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 800 C. 1 fig.

Hong, G.T.; Zilberstein, V.A.

1996-06-18

27

Iridium material for hydrothermal oxidation environments  

DOEpatents

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

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

1996-01-01

28

TCP Performance Enhancement Over Iridium  

NASA Technical Reports Server (NTRS)

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

Torgerson, Leigh; Hutcherson, Joseph; McKelvey, James

2007-01-01

29

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

1981-01-01

30

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

1980-01-21

31

Binuclear platinum-iridium complexes: synthesis, reactivity and luminescence.  

PubMed

The chemistry of the heterobinuclear platinum-iridium complex [PtIr(CO)3(?-dppm)2][PF6], , dppm = Ph2PCH2PPh2, is described. The reaction of a hydride with gave [HPtIr(CO)2(?-dppm)2], by displacement of the carbonyl ligand from platinum, while reaction of with dihydrogen, hydrogen chloride or Ph2MeSiH gave the fluxional complex [PtIrH4(CO)(?-dppm)2][PF6], [PtIrH2Cl2(CO)(?-dppm)2][PF6], or [PtIrH(SiMePh2)(CO)2(?-dppm)2][PF6], respectively, by oxidative addition at iridium. Complex reacted, often regioselectively, with several alkynes to give the ?-?(1),?(1) bridging alkyne complexes [PtIr(?-RCCR')(CO)2(?-dppm)2][PF6], R = H, R' = Ph, 4-C6H4Me, CO2Me; R = Ph, R' = CO2Me; R = R' = CO2Me. The complex [PtIr(?-HCC-4-C6H4Me)(CO)2(?-dppm)2][PF6] reacted reversibly with CO to give [PtIr(?-HCC-4-C6H4Me)(CO)3(?-dppm)2][PF6] and [PtIr(CO)3(?-dppm)2][PF6], . With HCl, [PtIr(?-HCC-4-C6H4Me)(CO)2(?-dppm)2][PF6] reacted to give [PtIrHCl(?-HCC-4-C6H4Me)(CO)2(?-dppm)2][PF6], by oxidative addition at iridium, and then the alkenylplatinum derivative [PtIrCl{HC[double bond, length as m-dash]CH(4-C6H4Me)}(CO)2(?-dppm)2][PF6]. [PtIr(?-HCC-4-C6H4Me)(CO)2(?-dppm)2][PF6] reacted slowly with dihydrogen to give 4-MeC6H4CH[double bond, length as m-dash]CH2 and [PtIrH4(CO)(?-dppm)2][PF6]. The complex [PtIr(?-HCCPh)(CO)2(?-dppm)2][PF6] is intensely luminescent in solution at room temperature, with features characteristic of a d(8)-d(8) face-to-face complex. PMID:25697241

Sterenberg, Brian T; Wrigley, Christian T; Puddephatt, Richard J

2015-03-10

32

Electrochemical deposition of iridium (IV) oxide from alkaline solutions of iridium(III) oxide  

Microsoft Academic Search

Cyclic voltammetry is used to deposit films of hydrous iridium oxide onto glassy carbon electrodes from a basic solution of saturated iridium(III) oxide. An acidic solution of Ir(OH2)2Cl4? is first prepared from either IrCl63 or IrCl62?. When this solution is made basic, iridium (IV) oxide is deposited by oxygen generated from oxidation of hydroxide. A strongly adherent, bright blue deposit

John E. Baur; Thomas W. Spaine

1998-01-01

33

Determining the Altitude of Iridium Flares  

NASA Technical Reports Server (NTRS)

Iridium flares have nothing to do with the element iridium. Iridium is also the name of a telecommunications company that has been launching satellites into low orbits around the Earth. These satellites are being used for a new type of wireless phone and paging service. Flares have been observed coming from these satellites. These flares have the potential, especially when the full fleet of satellites is in orbit, to disrupt astronomical observations. The paper reviews using simple trigonometry how to calculate the altitude of one of these satellites.

Foster, James; Owe, Manfred

1999-01-01

34

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

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

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

35

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

36

Lattice dynamics of metal hydrides  

NASA Astrophysics Data System (ADS)

A simple nonstoichiometric model of metal hydrides is proposed and applied to the study of the phonon dispersion curves and composition-dependent Young's moduli of PdHx (Dx) system. The model can readily take into account the temperature and composition dependence of the metal hydride properties including phase changes.

Rafizadeh, Hamid A.

1981-02-01

37

Lattice dynamics of metal hydrides  

Microsoft Academic Search

A simple nonstoichiometric model of metal hydrides is proposed and applied to the study of the phonon dispersion curves and composition-dependent Young's moduli of PdHx (Dx) system. The model can readily take into account the temperature and composition dependence of the metal hydride properties including phase changes.

Hamid A. Rafizadeh

1981-01-01

38

C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes.  

PubMed

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species. PMID:17535000

Baratta, Walter; Ballico, Maurizio; Del Zotto, Alessandro; Zangrando, Ennio; Rigo, Pierluigi

2007-01-01

39

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

40

Anodic electrodeposition of iridium oxide films  

Microsoft Academic Search

IrOx films have been deposited on conducting transparent SnO2-coated glass substrates with sheet resistance of about 10 ?\\/? by electrochemical oxidation of soluble iridium species in a basic aqueous medium. Before being efficient for deposition, the iridium-containing solutions have to be aged for a minimum time which is determined by UV-visible spectrophotometry. The IrOx films prepared following the procedure described

Michel A. Petit; Vincent Plichon

1998-01-01

41

IRIDIUM (R): A Lockheed transition to commercial space  

NASA Technical Reports Server (NTRS)

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

Tadano, Thomas N.

1995-01-01

42

Electrodeposited iridium oxide for neural stimulation and recording electrodes  

Microsoft Academic Search

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

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

2001-01-01

43

Thickness-dependent properties of sprayed iridium oxide thin films  

Microsoft Academic Search

Iridium oxide thin films with variable thickness were deposited by spray pyrolysis technique (SPT), onto the amorphous glass substrates kept at 350°C. The volume of iridium chloride solution was varied to obtain iridium oxide thin films with thickness ranging from 700 to 2250Å. The effect of film thickness on structural and electrical properties was studied. The X-ray diffraction (XRD) studies

P. S Patil; P. S Chigare; S. B Sadale; T Seth; D. P Amalnerkar; R. K Kawar

2003-01-01

44

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

45

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

46

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

47

Hydrogen recovery with metal hydrides  

SciTech Connect

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

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

1982-03-01

48

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.

49

Annealing Increases Stability Of Iridium Thermocouples  

NASA Technical Reports Server (NTRS)

Metallurgical studies carried out on samples of iridium versus iridium/40-percent rhodium thermocouples in condition received from manufacturer. Metallurgical studies included x-ray, macroscopic, resistance, and metallographic studies. Revealed large amount of internal stress caused by cold-working during manufacturing, and large number of segregations and inhomogeneities. Samples annealed in furnace at temperatures from 1,000 to 2,000 degree C for intervals up to 1 h to study effects of heat treatment. Wire annealed by this procedure found to be ductile.

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

1989-01-01

50

Bulk Hydrides and Delayed Hydride Cracking in Zirconium Alloys  

NASA Astrophysics Data System (ADS)

Zirconium alloys are susceptible to engineering problems associated with the uptake of hydrogen throughout their design lifetime in nuclear reactors. Understanding of hydrogen embrittlement associated with the precipitation of brittle hydride phases and a sub-critical crack growth mechanism known as Delayed Hydride Cracking (DHC) is required to provide the engineering justifications for safe reactor operation. The nature of bulk zirconium hydrides at low concentrations (< 100 wt. ppm) is subject to several contradictory descriptions in the literature associated with the stability and metastability of gamma-phase zirconium hydride. Due to the differing volume expansions (12-17%) and crystallography between gamma and delta hydride phases, it is suggested that the matrix yield strength may have an effect on the phase stability. The present work indicated that although yield strength can shift the phase stability, other factors such as microstructure and phase distribution can be as or more important. This suggests that small material differences are the reason for the literature discrepancies. DHC is characterised by the repeated precipitation, growth, fracture of brittle hydride phases and subsequent crack arrest in the ductile metal. DHC growth is associated primarily the ability of hydrogen to diffuse under a stress induced chemical potential towards a stress raiser. Knowledge of the factors controlling DHC are paramount in being able to appropriately describe DHC for engineering purposes. Most studies characterise DHC upon cooling to the test temperature. DHC upon heating has not been extensively studied and the mechanism by which it occurs is somewhat controversial in the literature. This work shows that previous thermo-mechanical processing of hydrided zirconium can have a significant effect on the dissolution behaviour of the bulk hydride upon heating. DHC tests with gamma-quenched, furnace cooled-delta and reoriented bulk hydrides upon heating and DHC upon cooling suggest that the amount of hydrogen in solution is the primary factor controlling the occurrence of DHC and consistent with the postulation that the stress induced chemical potential is the driving force for DHC.

Tulk, Eric F.

51

Experimental and theoretical mechanistic investigation of the iridium-catalyzed dehydrogenative decarbonylation of primary alcohols.  

PubMed

The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving dehydrogenation of the alcohol and decarbonylation of the resulting aldehyde. The square planar complex IrCl(CO)(rac-BINAP) was isolated from the reaction between [Ir(cod)Cl]2, rac-BINAP, and benzyl alcohol. The complex was catalytically active and applied in the study of the individual steps in the catalytic cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction, and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH2Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment, IrHCl2(CO)(rac-BINAP) was detected from the release of HCl in the dehydrogenation and subsequent reaction with IrCl(CO)(rac-BINAP). This indicated a substitution of chloride with the alcohol to form a square planar iridium alkoxo complex that could undergo a ?-hydride elimination. A KIE of 1.0 was determined for the decarbonylation and 1.42 for the overall reaction. Electron rich benzyl alcohols were converted faster than electron poor alcohols, but no electronic effect was found when comparing aldehydes of different electronic character. The lack of electronic and kinetic isotope effects implies a rate-determining phosphine dissociation for the decarbonylation of aldehydes. PMID:25545272

Olsen, Esben P K; Singh, Thishana; Harris, Pernille; Andersson, Pher G; Madsen, Robert

2015-01-21

52

Sputtered iridium oxide films (SIROFs) for low-impedance neural stimulation and recording electrodes  

Microsoft Academic Search

Iridium oxide films formed by electrochemical activation of iridium metal (AIROF) or by electrochemical deposition (EIROF) are being evaluated as low-impedance charge-injection coatings for neural stimulation and recording. Iridium oxide may also be deposited by reactive sputtering from iridium metal in an oxidizing plasma. The characterization of sputtered iridium oxide films (SIROFs) as coatings for nerve electrodes is reported. SIROFs

S. F. Cogan; T. D. Plante; J. Ehrlich

2004-01-01

53

Iridium emissions from Hawaiian volcanoes  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

54

A new route to metal hydrides  

Microsoft Academic Search

Aqueous borohydride is shown to be an effective reagent for hydriding metals and intermetallics. It is the hydriding equivalent of 20-30 atm of H[sub 2]. The reaction is a convenient way to screen materials for hydride formation and possible utility in applications such as nickel-metal hydride batteries. The reaction is also a convenient alternative to decrepitation for the production of

D. W. Murphy; S. M. Zahurak; B. Vyas; M. Thomas; M. E. Badding; W. C. Fang

1993-01-01

55

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.

2012-08-03

56

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

57

Iridium-Coated Rhenium Combustion Chamber  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

58

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

59

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

60

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

61

Hydrogen, lithium, and lithium hydride production  

DOEpatents

A method of producing high purity lithium metal is provided, where gaseous-phase lithium metal is extracted from lithium hydride and condensed to form solid high purity lithium metal. The high purity lithium metal may be hydrided to provide high purity lithium hydride.

Brown, Sam W; Spencer, Larry S; Phillips, Michael R; Powell, G. Louis; Campbell, Peggy J

2014-03-25

62

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

63

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

Code of Federal Regulations, 2010 CFR

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

2010-01-01

64

76 FR 46313 - Notice of Issuance of Final Determination Concerning Iridium Satellite Telephones  

Federal Register 2010, 2011, 2012, 2013, 2014

...Issuance of Final Determination Concerning Iridium Satellite Telephones AGENCY: U.S...Government Procurement; Country of Origin of Iridium 9555 Satellite Telephones; Substantial...requesting a final determination on behalf of Iridium Satellite, LLC...

2011-08-02

65

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

66

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.

Athro Limited

67

Electrochromism in spray deposited iridium oxide thin films  

Microsoft Academic Search

Electrochromic iridium oxide thin films were deposited onto fluorine doped tin oxide coated glass substrates from an aqueous iridium chloride solution by pneumatic spray pyrolysis technique. The as-deposited samples were X-ray amorphous. The electrochromic properties of thin films were studied in an aqueous electrolyte (0.5N H2SO4) using cyclic voltammetry (CV), chronoamperometry (CA) and spectrophotometry. Iridium oxide films show pronounced anodic

P. S. Patil; R. K. Kawar; S. B. Sadale

2005-01-01

68

Weldability of general purpose heat source iridium capsules  

SciTech Connect

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

Kanne, W.R. Jr.

1988-01-01

69

Iridium-coated rhenium thrusters by CVD  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

70

Handling System for Iridium-192 Seeds  

NASA Technical Reports Server (NTRS)

A complete system is proposed for safe handling of iridium-192 seeds used to internally irradiate malignant growths. A vibratory hopper feeds the seeds onto a transport system for deposit in a magazine or storage area. A circular magazine consisting of segmented plastic tubing with holes in the walls to accommodate the seeds seems feasible. The magazine is indexed to stop and release a seed for calibration and deposition.

Carpenter, W.; Wodicka, D.

1973-01-01

71

Mechanical and Electronic Properties of Iridium Nitride  

NASA Astrophysics Data System (ADS)

Based on the structures of known transition metal compounds, the phase stabilities and mechanical properties of iridium nitride (IrN) in nine structures are explored by using ab initio calculations. The calculation results show that MnP-structured IrN (MnP—IrN) is not only the most energetically stable, but also mechanically and dynamically stable at the ground state. The hardness is estimated to be 12 GPa.

Liu, Qiang; Peng, Wei-Min; Peng, Feng

2014-08-01

72

Deoxidization of Iridium Oxide Thin Film  

Microsoft Academic Search

Deoxidization phenomenon of iridium oxide (IrO2) film, which has been used as a diffusion barrier for ferroelectric capacitors, is investigated changing the temperature and oxygen pressure during the post process.The deoxidization is well understood by explaining the relationship between the temperature and dissociation pressure according to the thermodynamics.A simple thermodynamic calculation for the deoxidization of IrO2 givesa guideline for successive

Seon Yong Cha; Hee Chul Lee

1999-01-01

73

Microstructure of surface cerium hydride growth sites  

SciTech Connect

Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the ?-Ce to ?-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

Brierley, Martin, E-mail: martin.brierley@awe.co.uk [Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR, United Kingdom and The School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Knowles, John; Montgomery, Neil [Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR (United Kingdom); Preuss, Michael [The School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom)

2014-05-15

74

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

75

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

76

Weldability of general purpose heat source new-process iridium  

SciTech Connect

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

Kanne, W.R.

1987-01-01

77

Cyclometallated Iridium and Platinum Complexes with Noninnocent Bhavna Hirani,  

E-print Network

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

Goddard III, William A.

78

Micro-machined, polyimide stimulating electrodes with electroplated iridium oxide  

Microsoft Academic Search

Iridium oxide neural stimulating electrodes were formed by electroplating iridium oxide onto thin-film gold electrodes on a polyimide substrate. 18 million current pulses were applied to 4 electrodes over 7 days. 1 electrode delaminated on day 1. The remaining three electrodes showed characteristics altered by current pulsing. However, the electrodes maintained the ability to deliver large amounts of charge

James D. Weiland; Stuart Cogan; Mark S. Humayun

1999-01-01

79

Ground state of positronium hydride  

SciTech Connect

The ground bound state in the positronium hydride molecule (HPs) is determined from extensive variational four-body calculations with the James-Coolidge four-body variational expansion in the relative coordinates r{sub 12},r{sub 13},r{sub 23},r{sub 14},r{sub 24}, and r{sub 34}. For the positronium hydride with the infinitely heavy nucleus ({sup {infinity}}HPs) the total energy found, E={minus}0.7891369 a.u., is one of the lowest variational values published to date. A number of bound-state properties have been calculated also, including the {delta}-function expectation values, two-body cusps, and the two-photon annihilation rate. {copyright} {ital 1997} {ital The American Physical Society}

Frolov, A.M.; Smith, V.H. , Jr. [Department of Chemistry, Queens University, Kingston, Ontario, K7L3N6 (CANADA)] [Department of Chemistry, Queens University, Kingston, Ontario, K7L3N6 (CANADA)

1997-09-01

80

Catalytic metal hydride space heater  

SciTech Connect

This patent describes an apparatus for heating which consists of: a fuel storage means and wall means forming a combustion area wherein the improvement comprises: (a) the fuel storage means comprising a metal hydride fuel; (b) the wall means forming the combustion area containing a catalyst thereon; (c) the wall means forming the combustion area being in direct proximity to the metal hydride fuel storage means; (d) means for controllable supplying air to the combustion area; (e) the fuel storage means including a semipermeable membrane through which hydrogen may pass; (f) means for conveying hydrogen from the semipermeable membrane to the combustion area; and (g) means for discharging products from the combustion area to an area to be heated.

Kesten, A.S.

1986-09-30

81

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

82

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

83

Use of reversible hydrides for hydrogen storage  

NASA Technical Reports Server (NTRS)

The addition of metals or alloys whose hydrides have a high dissociation pressure allows a considerable increase in the hydrogenation rate of magnesium. The influence of temperature and hydrogen pressure on the reaction rate were studied. Results concerning the hydriding of magnesium rich alloys such as Mg2Ca, La2Mg17 and CeMg12 are presented. The hydriding mechanism of La2Mg17 and CeMg12 alloys is given.

Darriet, B.; Pezat, M.; Hagenmuller, P.

1980-01-01

84

A possible new meteor shower - ? Hydrids  

NASA Astrophysics Data System (ADS)

The radiant analysis that included orbits from the Croatian Meteor Network Catalogues of Orbits 2007 to 2010 plus the orbits from the SonotaCo catalogues for 2007 to 2011 revealed a possible new Hydrid stream with radiant running parallel to, but distinct from, the sigma Hydrids. The stream got a temporary IAU designation 529 EHY and the name ? Hydrids. We present here the results of our analysis of the new stream.

Šegon, Damir; Andrei?, Željko; Korlevi?, Korado; Novoselnik, Filip; Vida, Denis; Skoki?, Ivica

2013-10-01

85

Complex hydrides for hydrogen storage  

DOEpatents

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

Zidan, Ragaiy

2006-08-22

86

Formation of nano iridium oxide: material properties and neural cell culture  

Microsoft Academic Search

Iridium film with the thickness of 30 and 60 nm were formed on both Si wafer and commercially pure (CP) Ti by electron beam evaporation. The thin iridium film showed the identical charge injection capability with the bulk Ir. However, the charge injection value of iridium film was decreased with continuous potential cycling when the deposited iridium became depleted due

In-Seop Lee; Chung-Nam Whang; Young-Hee Lee; Gun Hwan Lee; Bong-Joo Park; Jong-Chul Park; Won-Seon Seo; Fu-Zhai Cui

2005-01-01

87

Iridium enrichment in airborne particles from Kilauea volcano - January 1983  

NASA Astrophysics Data System (ADS)

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 IrF6.

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

1983-12-01

88

Preparation and properties of electrochromic iridium oxide thin film by sol-gel process  

Microsoft Academic Search

We established a method for preparation of iridium oxide thin film by the sol-gel dip-coating process where iridium chloride was used as a starting material. The coating solution was prepared by reacting iridium chloride, ethanol and acetic acid. Iridium oxide coating was formed at 2.0 cm\\/min withdrawing rate. The coating films heat treated at 300°C did not contain impurities. Iridium

K. Nishio; Y. Watanabe; T. Tsuchiya

1999-01-01

89

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

90

Iridium Film For Charge-Coupled Device  

NASA Technical Reports Server (NTRS)

Usability extended to different environments. Application of thin film of iridium to back surface of back-surface-illuminated charge-coupled device expected to increase and stabilize quantum efficiency at wavelengths less than 4,500 Angstrom. Enhances quantum efficiency according to principle discussed in "Metal Film Increases CCD Output" (NPO-16815). Does not react with hydrogen, so device need not be kept in oxygen: Advantage where high absorption of ultraviolet light by oxygen undesirable; for example, when device used to make astronomical observations from high altitudes.

Hecht, Michael H.

1990-01-01

91

Laser Induced Fluorescence Spectrum of Iridium Monophosphide  

NASA Astrophysics Data System (ADS)

Laser induced fluorescence spectrum of IrP in the spectral region between 380-600 nm has been studied. Reacting laser ablated iridium atoms with 1% PH_3 seeded in argon produced the IrP molecule. A few vibronic transitions have been recorded. Preliminary analysis of the rotational structure indicated that these vibronic bands are with ?^' = 0 and ?^'' = 0 and is likely to be ^{1}? - X ^{1}? transition. Vibrational separation of the excited state is estimated to be about 442 cm^{-1}. The ground state bond length is determined to be 1.766 Å. This work represents the first experimental investigation of the spectra of IrP.

Pang, H. F.; Liu, Anwen; Cheung, A. S.-C.

2009-06-01

92

Direct synthesis of catalyzed hydride compounds  

DOEpatents

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

Gross, Karl J.; Majzoub, Eric

2004-09-21

93

PH sensors based on iridium oxide  

SciTech Connect

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

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

1988-01-01

94

Diminiode thermionic conversion with 111-iridium electrodes  

NASA Technical Reports Server (NTRS)

Preliminary data indicating thermionic-conversion potentialities for a 111-iridium emitter and collector spaced 0.2 mm apart are presented. These results comprise output densities of current and of power as functions of voltage for three sets of emitter, collector, and reservoir temperatures: 1553, 944, 561 K; 1605, 898, 533 K; and 1656, 1028, 586 K. For the 1605 K evaluation, estimates produced work-function values of 2.22 eV for the emitter and 1.63 eV for the collector with a 2.0-eV barrier index (collector work function plus interelectrode voltage drop) corresponding to the maximum output of 5.5 W/sq cm at 0.24 volt. The current, voltage curve for the 1656 K 111-iridium diminiode yields a 6.2 W/sq cm maximum at 0.25 volt and is comparable with the 1700 K envelope for a diode with an etched-rhenium emitter and a 0.025-mm electrode gap made by TECO and evaluated by NASA.

Koeger, E. W.; Bair, V. L.; Morris, J. F.

1976-01-01

95

Zirconium hydride containing explosive composition  

DOEpatents

An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising a non-explosive compound or mixture of non-explosive compounds which when subjected to an energy fluence of 1000 calories/cm.sup.2 or less is capable of releasing free radicals each having a molecular weight between 1 and 120. Exemplary donor additives are dibasic acids, polyamines and metal hydrides.

Walker, Franklin E. (18 Shadow Oak Rd., Danville, CA 94526); Wasley, Richard J. (4290 Colgate Way, Livermore, CA 94550)

1981-01-01

96

Oxidation of a thin samarium film on iridium  

NASA Astrophysics Data System (ADS)

Thermal desorption spectroscopy has been used to study the interaction of oxygen with a thin (<1 nm) samarium film deposited onto a textured iridium ribbon. Desorption of Sm atoms from Ir surface takes place from various states (chemisorbed, condensed, from compound with iridium, and oxide). The formation of samarium oxide is observed already at room temperature. As the temperature increases to T = 1100 K, a compound of samarium with iridium is formed at the first stage and then oxygen interacts with Sm atoms from this compound and "slow" (compared to the first process) growth of samarium oxide takes place.

Afanas'eva, E. Yu.

2014-06-01

97

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Rhodium 12,400 8,630 12,000 13,200 14,000 Ruthenium 8,170 9,890 15,900 18,800 24,000 Iridium 3,110 2,100 2.00 Rhodium 1,600.00 838.88 530.28 983.24 2,000.00 Ruthenium 130.67 66.33 35.43 64.22 70.00 Iridium 415.25 294

98

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

99

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

PubMed

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 cyclo-octa-1,5-diene). The asymmetric unit consists of one Ir(III) 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 Ir(III) atoms is disordered across an inversion center with each O atom having a 50% site occupancy. Each Ir(III) 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 mol-ecules hydrogen bond to two BF4 (-) anions in the unit cell. PMID:24826089

Merola, Joseph; Husebo, Trang Le

2014-04-01

100

?-Oxido-bis­[hydridotris(tri­methyl­phosphane-?P)iridium(III)](Ir—Ir) bis­(tetra­fluorido­borate) 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. PMID:24826089

Merola, Joseph; Husebo, Trang Le

2014-01-01

101

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

102

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

SciTech Connect

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

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

2008-01-15

103

The effect of iridium precursor on oxide-supported iridium catalysts prepared by atomic layer deposition  

NASA Astrophysics Data System (ADS)

Alumina, silica and beta zeolite supported iridium catalysts were prepared by atomic layer deposition (ALD) from two different metal precursors, Ir(acac)3 and Ir(thd)(COD). The use of Ir(thd)(COD) in ALD is reported for the first time. The aim was to investigate the effect of the precursor on catalyst surface species, chemical state and characteristics. Controllable ALD reaction was successful with both iridium precursors on alumina and with Ir(acac)3 on ? zeolite. On these catalysts, iridium particle sizes were very small (1-3 nm). Instead, some thermal decomposition of both precursors was observed during deposition on silica. At conditions, where no or very little decomposition of the precursors took place, the differences in the chemical state and characteristics of the as-prepared Ir/support samples were negligible, In ALD, Ir(acac)3 is slightly more stable at high deposition temperatures (>200 °C) while Ir(thd)(COD) enables the utilization of larger temperature range since it vaporizes at lower temperature compared to Ir(acac)3. The results thus indicate that Ir(thd)(COD) is a suitable new precursor for ALD.

Vuori, H.; Pasanen, A.; Lindblad, M.; Valden, M.; Niemelä, M. Veringa; Krause, A. O. I.

2011-02-01

104

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

105

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

106

Iridium anomaly approximately synchronous with terminal eocene extinctions.  

PubMed

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. PMID:17819180

Alvarez, W; Asaro, F; Michel, H V; Alvarez, L W

1982-05-21

107

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

108

pH sensor properties of electrochemically grown iridium oxide  

Microsoft Academic Search

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

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

1990-01-01

109

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

110

Encapsulated Metal Hydride for Hydrogen Separation  

E-print Network

hydrogen separation from gas mixtures containing methane and carbon monoxide. But absorption kinetics;Accomplishments/Progress (1) · Milestones: 1. Begin hydrogen absorption test from mixtures containing nitrogenEncapsulated Metal Hydride for Hydrogen Separation (Formerly Separation Membrane Development) DOE

111

Disposal of tritium-exposed metal hydrides  

SciTech Connect

A plan has been established for disposal of tritium-exposed metal hydrides used in Savannah River Site (SRS) tritium production or Materials Test Facility (MTF) R D operations. The recommended plan assumes that the first tritium-exposed metal hydrides will be disposed of after startup of the Solid Waste Disposal Facility (SWDF) Expansion Project in 1992, and thus the plan is consistent with the new disposal requiremkents that will be in effect for the SWDF Expansion Project. Process beds containing tritium-exposed metal hydride powder will be disposed of without removal of the powder from the bed; however, disposal of tritium-exposed metal hydride powder that has been removed from its process vessel is also addressed.

Nobile, A.; Motyka, T.

1991-01-01

112

Disposal of tritium-exposed metal hydrides  

SciTech Connect

A plan has been established for disposal of tritium-exposed metal hydrides used in Savannah River Site (SRS) tritium production or Materials Test Facility (MTF) R&D operations. The recommended plan assumes that the first tritium-exposed metal hydrides will be disposed of after startup of the Solid Waste Disposal Facility (SWDF) Expansion Project in 1992, and thus the plan is consistent with the new disposal requiremkents that will be in effect for the SWDF Expansion Project. Process beds containing tritium-exposed metal hydride powder will be disposed of without removal of the powder from the bed; however, disposal of tritium-exposed metal hydride powder that has been removed from its process vessel is also addressed.

Nobile, A.; Motyka, T.

1991-12-31

113

A classical but new kinetic equation for hydride transfer reactions.  

PubMed

A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions. PMID:23917398

Zhu, Xiao-Qing; Deng, Fei-Huang; Yang, Jin-Dong; Li, Xiu-Tao; Chen, Qiang; Lei, Nan-Ping; Meng, Fan-Kun; Zhao, Xiao-Peng; Han, Su-Hui; Hao, Er-Jun; Mu, Yuan-Yuan

2013-09-28

114

Iridium NEXT: A Global access for your sensor needs  

NASA Astrophysics Data System (ADS)

The operational Iridium constellation is comprised of 66 satellites, used to primarily provide worldwide voice and data coverage to satellite phones, pagers and integrated transceivers. The satellites are in low Earth orbit at 781 km and inclination of 86.4 deg, resulting in unprecedented 24/7 coverage and real-time visibility of the entire globe. Recently, through funding from the National Science Foundation (NSF), Iridium has been utilized by the Johns Hopkins University Applied Physics Laboratory (APL), with help from The Boeing Company, as an infrastructure for a comprehensive network for space environment measurements. Known as the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), the Iridium-based system provides real-time magnetic field measurements using the satellites as part of a new observation network to forecast weather in space. In February 2007, Iridium announced Iridium NEXT, a novel design for a second-generation satellite constellation. Anticipated to begin launching in 2015, Iridium NEXT will maintain the existing Iridium constellation architecture of 66 cross-linked satellite LEO covering 100 percent of the globe. In the spirit of AMPERE, for commercial, government, and scientific organizations Iridium NEXT also plans to offer new earth and space observation opportunities through hosted hosted payloads on the 66 Iridium NEXT satellite network. To provide seamless support and access to this latest innovation in payload transportation, Iridium NEXT has teamed with Space Dynamics Laboratory - Utah State University which has delivered thousands of successful sensors and subsystems for over 400 space borne and aircraf based payloads. One such innovation called SensorPOD will offer unique benefits such as unprecedented spatial and temporal coverage, real-time relay of data to and from up to 5 Kg payloads in space, and access to space at a fraction of the cost of a dedicated missions such as 3U or larger Cubesats. In this paper we will present the specifications, and various options that have been developed to meet the varying needs of the geosciences and space weather community.

Gupta, O. P.; Fish, C. S.

2010-12-01

115

Heat transfer enhancement in metal hydride systems  

NASA Astrophysics Data System (ADS)

An attempt has been made to enhance the heat transfer of hydrogen storage metal hydride systems by the addition of small fraction of high conductivity materials in various configurations. Results indicate that the form of the enhancement material rather than its composition is the more critical factor. The addition of over 6% aluminum foam enhances the effective thermal conductivity of a hydride bed by a factor of 2.6.

Rosso, M. J., Jr.; Strickland, G.

116

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

EPA Science Inventory

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

117

Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions  

SciTech Connect

In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(?4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(?4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(?4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(?4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(?-Cl)(?2-C8H14)2]2 (M = Rh, Ir) provide {?4-PhB(OxMe2)2ImMes?CH2}Rh(?-H)(?-Cl)Rh(?2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(?3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {?4-PhB(OxMe2)2ImMes?CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis-[Ir](H)(Ph) complex. Alternatively, the rhodium carbonyl 5 or iridium isocyanide {PhB(OxMe2)2ImMes}Ir(CO)CNtBu (15) reacts with PhSiH3 in the dark to form the silyl compound {PhB(OxMe2)2ImMes}RhH(SiH2Ph)CO (14) or {PhB(OxMe2)2ImMes}IrH(SiH2Ph)CNtBu (17). These examples demonstrate the enhanced thermal reactivity of {PhB(OxMe2)2ImMes}-supported iridium and rhodium carbonyl compounds in comparison to tris(oxazolinyl)borate, tris(pyrazolyl)borate, and cyclopentadienyl-supported compounds.

Xu, Songchen [Ames Laboratory; Manna, Kuntal [Ames Laboratory; Ellern, Arkady [Ames Laboratory; Sadow, Aaron D [Ames Laboratory

2014-12-08

118

A long-term stable iridium oxide pH electrode  

Microsoft Academic Search

In this work, a long-term stable pH electrode based on iridium oxide film is reported. A new method, i.e., a ‘carbonate melt oxidation’ method, has been developed to fabricate iridium oxide pH electrode. In this method, a uniform iridium oxide film is coated on the surface of an iridium metal wire through oxidation of the wire in a carbonate melt.

Min Wang; Sheng Yao; Marc Madou

2002-01-01

119

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

E-print Network

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

Boyer, Edmond

120

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

E-print Network

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

Wang, Deli

121

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

E-print Network

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

Steiner, Ullrich

122

Thermal hydraulic analysis of hydride fuels in BWR's  

E-print Network

This thesis contributes to the hydride nuclear fuel project being completed by UC Berkeley and MIT to assess the possible benefits of using hydride fuel in light water nuclear reactors (LWR's). More specifically, this ...

Creighton, John Everett

2005-01-01

123

Optimization of hydride fueled pressurized water reactor cores  

E-print Network

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

Shuffler, Carter Alexander

2004-01-01

124

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

125

Additive effects of amines on asymmetric hydrogenation of quinoxalines catalyzed by chiral iridium complexes.  

PubMed

The additive effects of amines were realized in the asymmetric hydrogenation of 2-phenylquinoxaline, and its derivatives, catalyzed by chiral cationic dinuclear triply halide-bridged iridium complexes [{Ir(H)[diphosphine]}(2)(?-X)(3)]X (diphosphine = (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP], (S)-5,5'-bis(diphenylphosphino)-4,4'-bi-1,3-benzodioxole [(S)-SEGPHOS], (S)-5,5'-bis(diphenylphosphino)-2,2,2',2'-tetrafluoro-4,4'-bi-1,3-benzodioxole [(S)-DIFLUORPHOS]; X = Cl, Br, I) to produce the corresponding 2-aryl-1,2,3,4-tetrahydroquinoxalines. The additive effects of amines were investigated by solution dynamics studies of iridium complexes in the presence of N-methyl-p-anisidine (MPA), which was determined to be the best amine additive for achievement of a high enantioselectivity of (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline, and by labeling experiments, which revealed a plausible mechanism comprised of two cycles. One catalytic cycle was less active and less enantioselective; it involved the substrate-coordinated mononuclear complex [IrHCl(2)(2-phenylquinoxaline){(S)-BINAP}], which afforded half-reduced product 3-phenyl-1,2-dihydroquinoxaline. A poorly enantioselective disproportionation of this half-reduced product afforded (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline. The other cycle involved a more active hydride-amide catalyst, derived from amine-coordinated mononuclear complex [IrCl(2)H(MPA){(S)-BINAP}], which functioned to reduce 2-phenylquinoxaline to (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline with high enantioselectivity. Based on the proposed mechanism, an Ir(I)-JOSIPHOS (JOSIPHOS = (R)-1-[(S(p))-2-(dicyclohexylphosphino)ferrocenylethyl]diphenylphosphine) catalyst in the presence of amine additive resulted in the highest enantioselectivity for the asymmetric hydrogenation of 2-phenylquinoxaline. Interestingly, the reaction rate and enantioselectivity were gradually increased during the reaction by a positive-feedback effect from the product amines. PMID:22915378

Nagano, Takuto; Iimuro, Atsuhiro; Schwenk, Rino; Ohshima, Takashi; Kita, Yusuke; Togni, Antonio; Mashima, Kazushi

2012-09-10

126

High H? ionic conductivity in barium hydride  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

127

High H? ionic conductivity in barium hydride.  

PubMed

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

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

2015-01-01

128

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

129

Iridium oxide-polymer nanocomposite electrode materials for water oxidation.  

PubMed

Nanocomposite anode materials for water oxidation have been readily synthesized by electrodeposition of iridium oxide nanoparticles into poly(pyrrole-alkylammonium) films, previously deposited onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The nanocomposite films were characterized by electrochemistry, transmission electron microscopy, and atomic force microscopy. They showed an efficient electrocatalytic activity toward the oxygen evolution reaction. Data from Tafel plots have demonstrated that the catalytic activity of the iridium oxide nanoparticles is maintained following their inclusion in the polymer matrix. Bulk electrolysis of water at carbon foam modified electrodes have shown that the iridium oxide-polymer composite presents a higher catalytic activity and a better operational stability than regular oxide films. PMID:25045786

Lattach, Youssef; Rivera, Juan Francisco; Bamine, Tahya; Deronzier, Alain; Moutet, Jean-Claude

2014-08-13

130

Can hydridic-to-protonic hydrogen bonds catalyze hydride transfers in biological systems?  

PubMed

Catalysis of hydride transfer by hydridic-to-protonic hydrogen (HHH) bonding in ?-hydroxy carbonyl isomerization reactions was examined computationally in the lithium salts of 7-substituted endo-3-hydroxybicyclo[2.2.1]hept-5-en-2-ones. The barrier for intramolecular hydride transfer in the parent system was calculated to be 17.2 kcal/mol. Traditional proton donors, such as OH and NH(3)(+), stabilized the metal cation-bridged transition state by 1.4 and 3.3 kcal/mol, respectively. Moreover, among the conformers of the OH systems, the one in which the proton donor is able to interact with the migrating hydride (H(m)) has an activation barrier lower by 1.3 and 1.7 kcal/mol than the other possible OH conformers. By contrast, the presence of an electronegative group such as F, which disfavors the migration electronically by opposing development of hydridic charge, destabilizes the hydride migration by 1.5 kcal/mol relative to the epimeric exo system. In both ground and transition states the H(m)···H distance decreased with increasing acidity of the proton donor, reaching a minimum of 1.58 Å at the transition state for NH(3)(+). Both Mulliken and NPA charges show enhancement of negative character of the migrating hydride in the cases in which HHH bonding is possible. PMID:21141894

Marincean, Simona; Jackson, James E

2010-12-30

131

Gold Hydride Complexes DOI: 10.1002/anie.200803842  

E-print Network

Gold Hydride Complexes DOI: 10.1002/anie.200803842 Reactions of a Stable Monomeric Gold(I) Hydride Complex** Emily Y. Tsui,* Peter Müller, and Joseph P. Sadighi Gold hydride complexes have been postulated as intermediates in a number of homogeneous gold- catalyzed reactions,[1] but relatively little is known about

Müller, Peter

132

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2012 CFR

...173.311 Metal hydride storage systems. The following...transportable UN Metal hydride storage systems (UN3468) with...exceeding 25 MPa. Metal hydride storage systems must be designed...H” mark must be used for hydrogen bearing gases or other...

2012-10-01

133

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2013 CFR

...173.311 Metal hydride storage systems. The following...transportable UN Metal hydride storage systems (UN3468) with...exceeding 25 MPa. Metal hydride storage systems must be designed...H” mark must be used for hydrogen bearing gases or other...

2013-10-01

134

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2011 CFR

...173.311 Metal hydride storage systems. The following...transportable UN Metal hydride storage systems (UN3468) with...exceeding 25 MPa. Metal hydride storage systems must be designed...H” mark must be used for hydrogen bearing gases or other...

2011-10-01

135

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2014 CFR

...173.311 Metal hydride storage systems. The following...transportable UN Metal hydride storage systems (UN3468) with...exceeding 25 MPa. Metal hydride storage systems must be designed...H” mark must be used for hydrogen bearing gases or other...

2014-10-01

136

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Rhodium 12,000 13,200 13,600 15,900 18,000 Ruthenium 15,900 18,800 23,200 36,000 37,000 Iridium 2,200 3.00 232.93 203.54 322.93 360.00 Rhodium 530.28 983.24 2,059.73 4,561.06 6,060.00 Ruthenium 35.43 64.22 74

137

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

E-print Network

124 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Rhodium 10,300 18,200 12,400 9,890 8,630 Ruthenium 11,400 20,900 8,170 10,800 9,940 Iridium 2,270 2,700 3,598.67 838.88 750.25 Ruthenium 40.70 129.76 130.67 66.33 55.60 Employment, mine, number 954 1,290 1,320 1

138

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

E-print Network

120 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,900 16,600 12,600 10,200 Ruthenium 23,200 36,000 48,700 49,800 21,600 Iridium 3,010 2,800 3,410 2,550 1.34 355.12 254.00 Rhodium 2,059.73 4,561.06 6,203.09 6,533.57 1,468.00 Ruthenium 74.41 193.09 573.74 324

139

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

E-print Network

122 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Rhodium 8,630 12,000 13,200 13,600 17,000 Ruthenium 9,890 15,900 18,800 23,200 30,000 Iridium 2,100 2.00 232.93 203.54 330.00 Rhodium 838.88 530.28 983.24 2,059.73 4,300.00 Ruthenium 66.33 35.43 64.22 74

140

pH sensors based on iridium oxide  

SciTech Connect

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

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

1990-03-01

141

High resolution spectroscopy of iridium in a hollow cathode discharge  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility of performing high resolution laser spectroscopy of iridium atoms produced by sputtering in a hollow cathode discharge. By resolving the hyperfine structure of ultraviolet transitions from the ground state, we measure the magnetic dipole and electric quadrupole constants of the 5 d 7 6 s 6 p 6 G 11/2 and 5 d 7 6 s 6 p 6 F 7/2 excited levels and we obtain accurate values for the isotope shifts. Iridium is also discussed as possibly providing reference spectra in the 243 nm region, close to the wavelength of the 1 s 2 s two-photon transition of hydrogen.

Gianfrani, L.; Tino, G. M.

1993-06-01

142

Corrosion-resistant iridium-platinum anode material for high polarization application in corrosive acids  

SciTech Connect

The present invention relates to highly corrosion resistant components for use in an electrochemical cell. Specifically, these components are resistant to corrosion under very extreme conditions such as exposure to aqua regia in the presence of a constant current density of 100mA/m{sup 2}. The components are comprised of an iridium-platinum alloy that comprises less than 30% iridium. In a preferred embodiment of the present invention, the iridium-platinum alloy comprises 15-20% iridium. In another preferred embodiment of the present invention, the iridium-platinum alloy is deposited on the surface of an electrochemical cell component by magnetron sputtering. The present invention also relates to a method for conducting an electrochemical reaction in the presence of highly corrosive acids under a high degree of polarization wherein the electrochemical cell comprises a component, preferably the anode, containing an iridium-platinum alloy that comprises less than 30% iridium.

Farmer, J.; Summers, L.; Lewis, P.

1993-09-08

143

Synthesis of new heteroscorpionate iridium(i) and iridium(iii) complexes.  

PubMed

The reactivity of different heteroscorpionate ligands based on bis(pyrazol-1-yl)methane, with different iridium-(i) and -(iii) precursors is reported. The reaction of the heteroscorpionate lithium salts "Li(bdmpza)", [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], "Li(bdmpzdta)" [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] and "Li(S)-mbpam" [(S)-mbpam = (S)-(-)-N-?-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] with 1 equivalent of [IrCl3(THF)3] in THF for 18 h affords high yields of neutral and anionic heteroscorpionate chloride iridium complexes [IrCl2(bdmpza)(THF)] (), [Li(THF)4][IrCl3(bdmpzdta)] () and [IrCl2{(S)-mbpam})(THF)] (). Solution of complex in acetonitrile at room temperature leads to complex [IrCl2{(S)-mbpam})(NCCH3)] (). Complexes and were isolated as enantiopure compounds. The reaction of the lithium salt "Li(bdmpza)" with [IrCl(?(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)]2 in THF for 18 h gave the Ir(i) complex [Ir(bdmpza)(?(4)-CH2[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]CH2)] (). The reaction of complex with CO (2 atm) at room temperature leads to a new complex of Ir(iii), [Ir(bdmpza)(k(2)-CH2C(Me)[double bond, length as m-dash]C(Me)CH2)(CO)] (). Treatment of heteroscorpionate ligand precursors "Li(bdmpza)" and "Li(bdmpzdta)" with [IrCp*Cl2]2 in THF yielded the iridium(iii) complexes [Ir2Cp*2Cl2(bdmpzx)] (x = a , x = dta ). These complexes have helical chirality due to the demands of the fixed pyrazole rings. The stereoisomerism and the self-assembly processes of these helicates have been studied in some detail in solution by NMR spectroscopy and in the solid state by X-ray diffraction. Mixtures of M- and P-handed enantiomers were obtained. Complex undergoes a decarboxylation process initiated by the HCl generated in the previous step leading to the known ionic complex [IrClCp*(bdmpm)][IrCl3Cp*] [bdmpm = bis(3,5-dimethylpyrazol-1-yl)methane] (). The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures of , , and were also established. PMID:25780987

Roa, A E; Campos, J; Paneque, M; Salazar, V; Otero, A; Lara-Sánchez, A; Rodríguez, A M; López-Solera, I; Gómez, M V

2015-04-01

144

Homogeneous and heterogenized iridium water oxidation catalysts  

NASA Astrophysics Data System (ADS)

The development of an efficient catalyst for the oxidative splitting of water into molecular oxygen, protons and electrons is of key importance for producing solar fuels through artificial photosynthesis. We are facing the problem by means of a rational approach aimed at understanding how catalytic performance may be optimized by the knowledge of the reaction mechanism of water oxidation and the fate of the catalytic site under the inevitably harsh oxidative conditions. For the purposes of our study we selected iridium water oxidation catalysts, exhibiting remarkable performance (TOF > 5 s-1 and TON > 20000). In particular, we recently focused our attention on [Cp*Ir(N,O)X] (N,O = 2-pyridincarboxylate; X = Cl or NO3) and [IrCl(Hedta)]Na water oxidation catalysts. The former exhibited a remarkable TOF whereas the latter showed a very high TON. Furthermore, [IrCl(Hedta)]Na was heterogenized onto TiO2 taking advantage of the presence of a dandling -COOH functionality. The heterogenized catalyst maintained approximately the same catalytic activity of the homogeneous analogous with the advantage that could be reused many times. Mechanistic studies were performed in order to shed some light on the rate-determining step and the transformation of catalysts when exposed to "oxidative stress". It was found that the last oxidative step, preceding oxygen liberation, is the rate-determining step when a small excess of sacrificial oxidant is used. In addition, several intermediates of the oxidative transformation of the catalyst were intercepted and characterized by NMR, X-Ray diffractometry and ESI-MS.

Macchioni, Alceo

2014-10-01

145

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

146

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

SciTech Connect

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

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

1987-09-01

147

Effect of yttrium on nucleation and growth of zirconium hydrides  

NASA Astrophysics Data System (ADS)

Addition of yttrium in zirconium causes precipitates of yttrium, which form two types of particles and are oxidized upon heat treatment. One type of particles with sub-micrometer scale sizes has a low population, whereas the other with nano scale sizes has a high population and cluster distribution. Owing to strong affinity of yttrium to hydrogen, the nanoparticles, mostly within the grains of the Zr-Y alloy, attract nucleation of hydrides at the clusters of the nanoparticles and cause preferential distribution of intragranular hydrides. In comparison with that of Zr, additional nanoparticles in the Zr-Y alloy impede further growth of hydride precipitates during hydriding. It is deduced that the impediment of growing hydride precipitates by the nanoparticles is developed during an auto-catalytic nucleation process, which leads to formation of thin and intragranular hydrides, favorable to mitigation of hydride embrittlement.

Li, Changji; Xiong, Liangyin; Wu, Erdong; Liu, Shi

2015-02-01

148

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

DOEpatents

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

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

1997-01-01

149

Iridium-catalyzed enantioselective allyl-allylsilane cross-coupling.  

PubMed

An enantioselective allyl-allylsilane cross-coupling involving racemic branched allylic alcohols and allylsilanes is reported. An iridium-(P,olefin) phosphoramidite complex enables the transformation with high regio- and stereoselectivity under operationally simple conditions. The utility of the coupling is demonstrated in a concise catalytic, enantioselective synthesis of a pyrethroid insecticide protrifenbute. PMID:25111443

Hamilton, James Y; Hauser, Nicole; Sarlah, David; Carreira, Erick M

2014-09-26

150

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

151

Iridium Aluminide Coats For Protection Against Ox idation  

NASA Technical Reports Server (NTRS)

Iridium aluminide coats investigated for use in protecting some metallic substrates against oxidation at high temperatures. Investigation prompted by need for cost-effective anti-oxidation coats for walls of combustion chambers in rocket engines. Also useful in special terrestrial applications like laboratory combustion chambers and some chemical-processing chambers.

Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Jang, Qin

1996-01-01

152

Internationalization of commercial space - The Iridium case study  

Microsoft Academic Search

The paper discusses a concept of a personal telecommunication system, Iridium, designed to bring to reality the 'global village' concept. The concept involves a number of cellular towers placed in LEO above the earth, which will pass the subscriber at about 18,000 miles\\/hr; each satellite will cast fixed beam overlapping cell patterns onto the surface of the earth, to provide

Robert W. Kinzie; Peter A. Swan

1992-01-01

153

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Palladium 78,900 92,500 124,000 146,000 95,000 Rhodium 7,210 7,820 9,600 9,650 7,000 Ruthenium 4,490 9,880 7

154

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

E-print Network

128 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Palladium 92,500 124,000 146,000 148,000 151,000 Rhodium 7,820 9,600 9,650 14,400 8,600 Ruthenium 9,880 7

155

Charge-injection waveforms for iridium oxide (AIROF) microelectrodes  

Microsoft Academic Search

The charge-injection limits of activated iridium oxide (AIROF) microelectrodes subjected to charge-balanced biphasic current pulsing are investigated as a function of anodic bias and asymmetry in the cathodic and anodic pulse widths. The use of asymmetric waveforms, in which the charge balancing anodic phase is delivered at a lower current density and longer pulse width, permits the use of anodic

S. F. Cogan; P. R. Troyk; J. Ehrlich; T. D. Plante; D. B. McCreery; L. Bullara

2003-01-01

156

Magnetostratigraphy, Late devonian iridium anomaly, and impact hypotheses  

SciTech Connect

Paleomagnetism, sedimentology, and fine-scale stratigraphy have been integrated to explain the origin of an iridium anomaly in the Late Devonian of Western Australia. Thermal demagnetization experiments were carried out on 93 specimens of marginal-slope limestone form the northern Canning Basin. Samples are from a condensed sequence of deep-water (> 100 m) Frutexites microstromatolites. Frutexites is a shrublike cyanobacterial organism that probably precipitated hematite, or a metastable precursor, from sea water. When plotted within the microstratigraphic framework for the study area, the observed characteristic directions from the sampled interval (14.5 cm thick) are in five discrete, layer-parallel, normal- and reversed-polarity zones. The measured northeast-southwest declinations and shallow inclinations probably record Late Devonian magnetostratigraphy on a centimetre scale. The Frutexites bed studied there occurs close to the Frasnian/Famennian (Late Devonian) boundary, a time of mass extinction of a wide variety of marine organisms throughout the world. Anomalously high iridium concentrations observed in the Frutexites bed have suggested to some authors that the mass extinction was caused by meteorite impact. This study concludes that iridium, which is present over the span of five layer-parallel magnetic reversals, was concentrated over a long period of time by biologic processes. Thus, the Canning Basin iridium anomaly may be unrelated to meteorite impact.

Hurley, N.F.; Van der Voo, R. (Univ. of Michigan, Ann Arbor (USA))

1990-04-01

157

Iridium oxide and palladium modified nitric oxide microsensor  

Microsoft Academic Search

An electrochemical microsensor, constructed by chemical modification of Nafion, poly(vinyl pyridine) (PVP), palladium and iridium oxide onto a platinum microelectrode, has been developed for the determination of nitric oxide (NO). This microsensor exhibits excellent catalytic activity toward NO oxidation, which is confirmed by differential pulse voltammetry. Cyclic voltammetry and differential pulse amperometry are also performed to measure NO. The catalytic

Yuezhong Xian; Wenliang Sun; Jian Xue; Min Luo; Litong Jin

1999-01-01

158

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

159

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

160

High-Suction Hydride Sorption Pump  

NASA Technical Reports Server (NTRS)

Improved design provides high pumping speed at low pressure. Hydride-forming powder retained in thin layer in contact with inner surface of stainless-steel tube. Configuration provides large surface area and short path for efficient transfer of heat and small resistance to flow.

Bard, Steven; Jones, Jack A.; Bowman, Robert C., Jr.; Dowling, Robert S.

1993-01-01

161

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

162

Bismuth determination in environmental samples by hydride generation-electrothermal atomic absorption spectrometry.  

PubMed

A hydride generation procedure, via flow injection, coupled to electrothermal atomic absorption spectrometry was optimised for Bi determination in sea water and hot-spring water and acid extracts from coal, coal fly ash and slag samples. The effects of several variables such as hydrochloric acid and sodium tetrahydroborate concentrations, hydrochloric acid and sodium tetrahydroborate flow rates, reaction coil length, trapping and atomisation temperatures, trapping time and the Ar flow rate have been investigated by using a 2(9)*3/128 Plackett-Burman design. From these studies, certain variables (sodium tetrahydroborate concentration and trapping time) showed up as significant, and they were optimised by a 2(2)+star central composite design. In addition, a study of the bismuthine trapping and atomisation efficiency from graphite tubes (GTs) permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide and tantalum carbide were investigated. The results obtained were compared with those achieved by iridium and zirconium-treated GTs. The best analytical performances, with characteristic mass of 35 pg and detection limit of 70 ng l(-1), were achieved by using U-treated GTs. Accuracy were checked using several reference materials: 1643d (Trace Elements in Water), TM-24 (Reference Water), GBW-07401 (Soil) and 1632c (Trace Elements in Coal). PMID:18969227

Moscoso-Pérez, Carmen; Moreda-Piñeiro, Jorge; Lopez-Mah?a, Purificacion; Muniategui-Lorenzo, Soledad; Fernández-Fernández, Esther; Prada-Rodr?guez, Dar?o

2003-12-01

163

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

NASA Astrophysics Data System (ADS)

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

Purwaningsih, Anik

2014-09-01

164

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

SciTech Connect

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

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

2014-09-30

165

Interatomic bonding and plastic deformation in iridium and molybdenum disilicide  

NASA Astrophysics Data System (ADS)

Interatomic bonding in the refractory transition metal iridium and transition metal-based intermetallic compound MoSi2 is of mixed metallic and covalent character. Such interatomic bonding is associated with the strong angular dependencies of covalent bonds and these affect significantly the structures and properties of the extended defects, such as dislocations and grain boundaries, that control plastic deformation and fracture in these materials. Bond-order potentials (BOPs) have been developed for iridium and the molybdenum silicides that capture accurately the angular character of bonding. A many-body repulsive term in the expression for the total energy allowed the negative Cauchy pressures of both iridium and MoSi2 to be fitted. The environmental dependencies of bond integrals in the open C11b crystal structure of MoSi2 were introduced explicitly via analytic screening functions derived using non-orthogonal tight-binding theory. The BOPs were constructed by fitting to a small set of experimental and ab initio calculated data. Rigorous testing of the BOPS showed that they are very accurate and transferable to environments substantially different from those used in their construction. Hence, they are eminently suitable for the atomistic simulation of extended defects. Atomistic simulation of the screw dislocation in iridium found a metastable, non-planar configuration for the core in addition to a glissile planar core that corresponds to dissociation into Shockley partials. Stress applications showed that transformations between these two core structures are driven primarily by applied stress and give rise to a mechanism for cross-slip that does not require thermal activation. Such athermal cross-slip then leads to an unusually high rate of dislocation multiplication and extensive plasticity owing to the unusually high frequency of the formation of Frank-Read sources. It is proposed that this process accounts for the high dislocation densities accumulated homogeneously in plastically deformed iridium and the associated strong work hardening found experimentally. This strong work hardening is linked intimately with the tendency of iridium to undergo brittle transgranular cleavage since the mean free path of dislocations can become so small that the material cannot relax stress concentrations around cracks by dislocation mediated plasticity.

Cawkwell, Marc Jon

166

Some electrocatalytic properties of anodic iridium oxide nanoparticles in acidic solution  

Microsoft Academic Search

The electrocatalytic activities of two kinds of iridium oxide electrodes are studied for their ability to evolve hydrogen and oxygen in 1 M H2SO4 at room temperature. The first kind of electrode is made of anodic iridium oxide nanoparticules (AIRONP) prepared by cycling well-defined iridium metal nanoparticles supported on carbon between O2 and H2 evolution potentials. The oxidation process can

Th. Pauporté; F. Andolfatto; R. Durand

1999-01-01

167

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

E-print Network

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

Arizpe, Luis (Luis Alfredo)

2011-01-01

168

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

169

HYDRIDE-INDUCED EMBRITTLEMENT IN METALS - STRESS AND TEMPERATURE EFFECTS  

Microsoft Academic Search

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

A. G. Varias; A. R. Massih

170

Method of binding a metal hydride to a surface  

SciTech Connect

A system for storing hydrogen in the form of a metal hydride is described comprising a hydride-forming metal which is bound to a surface with a silicone rubber. The system defines a flow path for hydrogen, the hydrogen being directed along the flow path to and from the hydride-forming metal. The system incudes a water sorbent disposed to contact the hydrogen before the hydrogen contacts the silicone rubber, the water sorbent being disposed within the flow path.

Retallick, W.B.; Predecki, P.K.

1989-01-24

171

HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS  

SciTech Connect

The purpose and scope of this analysis/model report is to analyze the degradation of commercial spent nuclear fuel (CSNF) cladding under repository conditions by the hydride-related metallurgical processes, such as delayed hydride cracking (DHC), hydride reorientation and hydrogen embrittlement, thereby providing a better understanding of the degradation process and clarifying which aspects of the process are known and which need further evaluation and investigation. The intended use is as an input to a more general analysis of cladding degradation.

K. McCoy

2000-12-12

172

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

173

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

174

Reflectance and structure changes of iridium oxide films by reduction  

SciTech Connect

The reflectance and structure changes of iridium oxide films by reduction were investigated in an attempt to apply the films to optical data storage media. The films were prepared by the thermal oxidation of iridium-carbon composite films. The films were easily reduced by heating them in 5% H/sub 2/ in Ar at temperatures in the range 100/sup 0/-300/sup 0/C. When the films were reduced, the particles size of Ir metal and the reflectance of the films increased with an increase in the reducing temperature. The reduced films were stable against oxidation at temperatures of 250/sup 0/C or higher. Optical writing on the films was carried out with an argon laser at 0.84W power. The writing mechanism was based on changes in the film's optical properties caused by laser-induced reduction.

Sato, Y.; Yanagida, M.; Yamanaka, H.; Tanigawa, H.

1989-03-01

175

The electrochemical impedance of metal hydride electrodes  

Microsoft Academic Search

Electrochemical impedance spectroscopy (EIS) and other characterization methods combined with modelling are very useful tools to gain an understanding of the processes governing the charge and discharge reactions in metal hydride electrodes. Impedance measurements were performed in the range from 10 kHz to 0.1 mHz. The proposed model simulated the experimental data better than previously presented models by a smooth

L. O. Valøen; R. Tunold

2002-01-01

176

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

177

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

178

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

179

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

180

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

181

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data: Platinum 71,500 75,800 77,300 97,200 75,300 Palladium 124,000 146,000 148,000 176,000 195,000 Rhodium 9 26,000 26,700 43,800 36,700 38,900 Rhodium 741 187 282 811 100 Price,2 dollars per troy ounce

182

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

E-print Network

122 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 176,000 189,000 147,000 Rhodium 9,650 14,400 13,500 10,500 19,900 Ruthenium 15,600 11,500 8,880 11,300 19,400 32,572 Palladium 26,700 43,800 36,700 44,000 54,900 Rhodium 187 282 811 114 764 Price,2

183

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

184

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

James D. Weiland; David J. Anderson

2000-01-01

185

Novel amperometric immunosensors based on iridium oxide matrices  

Microsoft Academic Search

Novel immunosensors based on antibodies immobilized in electrochemically grown iridium oxide (IrOx) thin film matrices have been developed. Antibody loading in the oxide was evaluated using a non-competitive electrochemical immunoassay for IgG. Anti-IgG loading in the oxide was found to be dependent on the concentration of anti-IgG present in the oxide growth step, with 400?g\\/ml anti-IgG producing maximum amperometric responses.To

Michael S. Wilson; R. David Rauh

2004-01-01

186

Iridium alloy clad vent set manufacturing qualification studies  

Microsoft Academic Search

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

1990-01-01

187

Iridium-Catalyzed 1,3-Dipolar Cycloadditions  

NASA Astrophysics Data System (ADS)

1,3-Dipolar cycloaddition reactions (DCR) are atom-economic processes that permit the construction of heterocycles. Their enantioselective versions allow for the creation of up to four adjacent chiral centers in a concerted fashion. In particular, well-defined half-sandwich iridium (III) catalysts have been applied to the DCR between enals or methacrylonitrile with nitrones. Excellent yield and stereoselectivities have been achieved. Support for mechanistic proposals stems from the isolation and characterization of the true catalysts.

Carmona, Daniel; Oro, Luis A.

188

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

189

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

190

Plasmonic hydrogen sensing with nanostructured metal hydrides.  

PubMed

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

Wadell, Carl; Syrenova, Svetlana; Langhammer, Christoph

2014-12-23

191

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

E-print Network

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

Cui, Yi

192

Mono- and bis-tolylterpyridine iridium(III) complexes  

SciTech Connect

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

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

2012-01-20

193

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

194

Reactivity of a mononuclear iridium(I) species bearing a terminal phosphido fragment embedded in a triphosphorus ligand.  

PubMed

The first example of an iridium(I) species bearing a terminal phosphido (PR(2)(-)) ligand is reported. This stable compound shows well-behaved reactivity toward various electrophiles, owing to its exposed phosphorus lone pair, allowing reversible protonation, selective alkylation, isolation of a phosphidoborane of iridium, and generation of a phosphido-bridged iridium(I)-gold(I) dinuclear species. PMID:23360393

Gloaguen, Yann; Jacobs, Wesley; de Bruin, Bas; Lutz, Martin; van der Vlugt, Jarl Ivar

2013-02-18

195

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

E-print Network

Catalytic Arene H/D Exchange with Novel Rhodium and Iridium Complexes Jennifer L. Rhinehart of rhodium28,29 with an O-donor ligand and a tetradentate diamine-bis- (phenolate). Both complexes showed an acetate is intricately involved in the C-H activation.30,31 Herein we report new rhodium and iridium

Jones, William D.

196

Flexible Nerve Stimulation Electrode With Iridium Oxide Sputtered on Liquid Crystal Polymer  

Microsoft Academic Search

Current electrode designs require flexible substrates that absorb little moisture and provide large charge injection capability. Sputtered iridium oxide films have superior charge injection capabilities versus noble metals and can adhere to various substrates. Liquid crystal polymers (LCPs) have very little water absorption compared to other flexible substrates. Therefore, the combination of sputtered iridium oxide film on LCP substrate was

Kevin Wang; Chung-Chiun Liu; Dominique M. Durand

2009-01-01

197

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis  

NASA Technical Reports Server (NTRS)

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600 C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

198

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis  

NASA Technical Reports Server (NTRS)

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

199

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. PMID:23457478

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

200

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

Microsoft Academic Search

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

Kazusuke Yamanaka

1989-01-01

201

Discovery and High-Throughput Screening of Heteroleptic Iridium Complexes for Photoinduced Hydrogen Production  

E-print Network

Discovery and High-Throughput Screening of Heteroleptic Iridium Complexes for Photoinduced Hydrogen facilitated the synthesis of a 32 member library of heteroleptic iridium complexes that was screened, using the reduction of water to hydrogen takes place without the concurrent oxidation to form oxygen. Despite its

Bernhard, Stefan

202

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

E-print Network

Improved Turn-on Times of Iridium Electroluminescent Devices by Use of Ionic Liquids Sara T. Parker devices based on the iridium complex [Ir(ppy)2(dtb-bpy)]+(PF6 - ), where ppy is 2-phenylpyridine and dtb(ethylene oxide) (PEO) to films of a tris- (4,7-diphenyl-1,10-phenanthroline disulfonate)ruthenium(II) complex

Bernhard, Stefan

203

In vitro electrical properties for iridium oxide versus titanium nitride stimulating electrodes  

Microsoft Academic Search

Stimulating electrode materials must be capable of supplying high-density electrical charge to effectively activate neural tissue. Platinum is the most commonly used material for neural stimulation. Two other materials have been considered: iridium oxide and titanium nitride. This study directly compared the electrical characteristics of iridium oxide and titanium nitride by fabricating silicon substrate probes that differed only in the

James D. Weiland; David J. Anderson; Mark S. Humayun

2002-01-01

204

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

E-print Network

OF IRIDIUM MOSSBAUER ISOMER SHIFTS ON OXIDATION STATE : AN INVERSION FOR LOW VALENT CARBONYL COMPLEXES (*) RAbstract. -- The 193 Ir IVtossbauer isomer shifts of a set of closely related iridium carbonyl chloride complexes with oxidation states + 1, + 1.1, + 1.4 and + 2 have been found to decrease

Paris-Sud XI, Université de

205

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

E-print Network

Deposition and Stripping Properties of Mercury on Iridium Electrodes S. P. Kounaves*'1 and J ABSTRACT The reduction of mercury on a fresh iridium surface is reversible with a half-wave potential > + 1000 mV returns the reduction wave to its original posi- tion. The peak for the oxidation of bulk Hg

Kounaves, Samuel P.

206

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

PubMed

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

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

2015-01-01

207

Method of making crack-free zirconium hydride  

DOEpatents

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

Sullivan, Richard W. (Denver, CO)

1980-01-01

208

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

209

Initial stages of the interaction with oxygen of samarium thin films grown on the iridium surface  

NASA Astrophysics Data System (ADS)

The interaction of thin (<1 nm) samarium films deposited on a textured iridium ribbon has been investigated by thermal desorption spectrometry. Samarium atoms deposited at T = 300 K desorb in three phases associated with the formation of a submonolayer samarium coverage on iridium, a compound of samarium with iridium, and a multilayer samarium film. The interaction with oxygen leads to the appearance of a new desorption phase, which is associated with the formation of samarium oxide. Oxidation of samarium is observed during exposure in oxygen already at room temperature. An increase in temperature of the iridium ribbon, at which exposure in oxygen occurs, to T = 1100 K leads to the formation of the compound of samarium with iridium. Further, the film of the compound decomposes in the course of interaction with oxygen, and samarium oxide grows on the Ir surface.

Afanas'eva, E. Yu.

2014-08-01

210

Porous metal hydride composite and preparation and uses thereof  

DOEpatents

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

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

1982-01-01

211

On the High-Pressure Behavior of Titanium Hydride  

NASA Astrophysics Data System (ADS)

Hydrogen storage research has recently invested a great deal of efforts into investigations of metal hydrides. Although titanium hydride is not the ideal candidate for storing hydrogen, Ti hydrides can act as active species to catalyze the reversible dehydrogenation of other hydrides and carbon nanotubes. In addition the basic science interest of this project lies in investigating the structure and especially the high-pressure behavior of TiH2. In the present study, we show the first in situ, high-pressure angle-dispersive and energy dispersive synchrotron x-ray diffraction studies of titanium hydride. We investigate the effects of hydrostatic and non-hydrostatic conditions. We also show the results of structural refinements as well as the bulk modulus of TiH2. To the best of our knowledge, this work is the first attempt to measure the equation of state of TiH2 using synchrotron x-ray diffraction and diamond anvil cells.

Kalita, Patricia E.; Sinogeikin, Stanislas; Lipinska-Kalita, Kristina E.; Hartmann, Thomas; Cornelius, Andrew

2007-03-01

212

Porous metal hydride composite and preparation and uses thereof  

DOEpatents

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

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

1980-03-12

213

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

214

Heat and mass transfer considerations in the use of electrically heated thermocouples of iridium versus an iridium\\/rhodium alloy in atmospheric pressure flames. [Up to 2400 K  

Microsoft Academic Search

Some thin (diameters 51, 25, and 13 ..mu..m) thermocouples of iridium and an alloy of 60% iridium\\/40% rhodium have been used with and without electrical heating to measure temperatures in flat laboratory flames of Hâ, Oâ and Nâ up to 2400°K. It was found that they suffered from a decrease in diameter with use, which limited their lifetime. Otherwise, it

A. N. Hayhurst; D. B. Kittelson

1977-01-01

215

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

216

Results of NDE Technique Evaluation of Clad Hydrides  

SciTech Connect

This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing parameters. These contributing factors need to be recognized and a means to control them or separate their contributions will be required to obtain the desired information.

Dennis C. Kunerth

2014-09-01

217

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

218

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); Jankowski, Alan F. (Livermore, CA); Yu, Conrad (Antioch, CA)

2010-08-10

219

An evaluation of the use of metal hydrides for solar thermal energy storage  

Microsoft Academic Search

The basic properties of metal hydrides relevant to their application for storing solar thermal energy are reviewed. Several schemes are discussed and evaluated in which the enthalpy of formation of a primary hydride is used to provide heat and a secondary hydride or compressed gas is utilized for hydrogen storage. The results show that, with present technology, a metal hydride-based

G. G. Libowitz; Z. Blank

1976-01-01

220

Iridium: Global OTH data communications for high altitude scientific ballooning  

NASA Astrophysics Data System (ADS)

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

Denney, A.

221

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

222

Luminescent cyclometallated iridium(III) complexes having acetylide ligands  

DOEpatents

The present invention relates to phosphorescent (triplet-emitting) organometallic materials. The phosphorescent materials of the present invention comprise Ir(III)cyclometallated alkynyl complexes for use as triplet light-emitting materials. The Ir(III)cyclometallated alkynyl complexes comprise at least one cyclometallating ligand and at least one alkynyl ligand bonded to the iridium. Also provided is an organic light emitting device comprising an anode, a cathode and an emissive layer between the anode and the cathode, wherein the emissive layer comprises a Ir(III)cyclometallated alkynyl complex as a triplet emitting material.

Thompson, Mark E.; Bossi, Alberto; Djurovich, Peter Ivan

2014-09-02

223

Determination of iridium in mafic rocks by atomic absorption  

USGS Publications Warehouse

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

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

1970-01-01

224

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

225

Levitation of iridium and liquid mercury by ultrasound.  

PubMed

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

Xie, W J; Cao, C D; Lü, Y J; Wei, B

2002-09-01

226

New horizons in boron hydride chemistry  

SciTech Connect

Pentaborane and diborane undergo hydrogen isotope exchange with deuterated aromatic hydrocarbons. Lewis acid catalyzed hydrogen isotope exchange between benzene-d/sub 6/ and pentaborane forms exclusively 1-DB/sub 5/H/sub 8/ at ambient temperature. In uncatalyzed exchanges, pentaborane reacts with benzene-d/sub 6/ to produce 1,2,3,4,5-D/sub 5/B/sub 5/H/sub 4/ at +45/sup 0/C, and B/sub 5/D/sub 9/ at + 120/sup 0/C. This thermally induced hydrogen isotope exchange apparently occurs via a reversible hydroboration of the aromatic ring. Halopentaboranes are converted to the parent pentaborane using tributyltin hydride as the halogen reducing agent under mild conditions and in high yields. Tributyltin hydride also reacts with other haloboranes and halometalloboranes. Deuterated pentaboranes are produced from halopentaboranes and tributyltin deuteride. Mechanistic features of this hydrogen-halogen exchange system are discussed. A new aminoborane, bis(dimethylamino)tetraborane, has been synthesized. On the basis of physical and spectroscopic data, a structure having the classical tetraborane framework is proposed, with two bridge hydrogen atoms replaced by dimethylamino groups. Solvent and temperature effects on the /sup 11/B and /sup 1/H NMR spectra of decaborane have been observed. Solvent polarizability is the major factor affecting chemical shifts. /sup 11/B-/sup 1/H/sub bridge/ and /sup 11/B-/sup 11/B coupling in decaborane can be measured at the B position.

Kunz, J.C.

1985-01-01

227

A study of hydriding kinetics of metal hydrides using a physically based model  

NASA Astrophysics Data System (ADS)

The reaction of hydrogen with metals to form metal hydrides has numerous potential energy storage and management applications. The metal hydrogen system has a high volumetric energy density and is often reversible with a high cycle life. The stored hydrogen can be used to produce energy through combustion, reaction in a fuel cell, or electrochemically in metal hydride batteries. The high enthalpy of the metal-hydrogen reaction can also be used for rapid heat removal or delivery. However, improving the often poor gravimetric performance of such systems through the use of lightweight metals usually comes at the cost of reduced reaction rates or the requirement of pressure and temperature conditions far from the desired operating conditions. In this work, a 700 bar Sievert system was developed at the Purdue Hydrogen Systems Laboratory to study the kinetic and thermodynamic behavior of high pressure hydrogen absorption under near-ambient temperatures. This system was used to determine the kinetic and thermodynamic properties of TiCrMn, an intermetallic metal hydride of interest due to its ambient temperature performance for vehicular applications. A commonly studied intermetallic hydride, LaNi5, was also characterized as a base case for the phase field model. The analysis of the data obtained from such a system necessitate the use of specialized techniques to decouple the measured reaction rates from experimental conditions. These techniques were also developed as a part of this work. Finally, a phase field model of metal hydride formation in mass-transport limited interstitial solute reactions based on the regular solution model was developed and compared with measured kinetics of LaNi5 and TiCrMn. This model aided in the identification of key reaction features and was used to verify the proposed technique for the analysis of gas-solid reaction rates determined volumetrically. Additionally, the phase field model provided detailed quantitative predictions of the effects of multidimensional phase growth and transitions between rate-limiting processes on the experimentally determined reaction rates. Unlike conventional solid state reaction analysis methods, this model relies fully on rate parameters based on the physical mechanisms occurring in the hydride reaction and can be extended to reactions in any dimension.

Voskuilen, Tyler G.

228

Hot temperatures line lists for metal hydrides  

NASA Astrophysics Data System (ADS)

The ExoMol project is an ERC funded project set up with the purpose of calculating high quality theoretical molecular line list data to facilitate the emerging field of exoplanet and cool star atmospheric haracterisation [1]. Metal hydrides are important building blocks of interstellar physical chemistry. For molecular identification and characterisation in astrophysical sources, one requires accurate and complete spectroscopic data including transitional frequencies and intensities in the form of a line list. The ab initio methods offer the best opportunity for detailed theoretical studies of free diatomic metal hydrides and other simple hydride molecules. In this contribution we present progress on theoretical line lists for AlH, CrH, MgH, NiH, NaH and TiH obtained from first principles, applicable for a large range of temperatures up to 3500 K. Among the hydrides, AlH is of special interest because of a relatively high cosmic abundance of aluminium. The presence of AlH has been detected in the spectra of M-type and S-type stars as well as in sunspots (See [2] and references therein). CrH is a molecule of astrophysical interest; under the classification scheme developed by Kirkpatrick et al [3], CrH is of importance in distinguishing L type brown dwarfs. It has been proposed that theoretical line-lists of CrH and CrD could be used to facilitate a 'Deuterium test' for use in distinguishing planets, brown dwarfs and stars [5] and also it has been speculated that CrH exists in sunspots [4] but a higherquality hot-temperature line-list is needed to confirm this finding. The presence of MgH in stellar spectra is well documented through observation of the A2 ! X 2+ and B0 2+ ! X 2+ transitions. Different spectral features of MgH have been used as an indicator for the magnesium isotope abundances in the atmospheres of different stars from giants to dwarfs including the Sun, to measure the temperature of stars, surface gravity, stars' metal abundance, gravitational, as well as for a deuterium test (see [6] and references therein). MgH is an important part of stellar atmospheric models. NiH is predicted to be the most common nickelbearing molecule [7] and was indentified in sunspot spectra around 15 000 cm-1 (646 cm) over 40 years ago [8]. Knowledge of 58NiH/60NiH isotopologue ratio in stellar spectra is used to test models of supernovae and star formation [9]. The spectra of metal hydrides such can be very complicated due to the large-number of interacting electronic states, to the importance of electron correlation, relativistic and spin-orbit effects and of the various couplings between angular momenta. Via the use of the Born-Oppenheimer approximation, the Schrödinger equation describing the state of a molecule can be factorised into an 'electronic' component and a nuclear (i.e., rotational-vibrational) component. The former is solved using the ab initio quantum chemistry package MOLPRO, yielding potential energy, dipole and transition moment, and spin-orbit curves. The resulting coupled-surface ro-vibronic problem was then solved using the in-house computer program DUO, which is based on expansion in Hund's case (a) wave functions. Potential curves and couplings were then refined semi-empirically using the available experimental spectroscopic data.

Gorman, M.; Lodi, L.; Leyland, P. pC; Hill, C.; Yurchenko, S. N.; Tennyson, J.

2013-09-01

229

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

PubMed

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

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

2015-02-01

230

Fracture Resistance of a Zirconium Alloy with Reoriented Hydrides  

NASA Astrophysics Data System (ADS)

Zirconium alloy cladding materials typically contain circumferential hydrides that may be reoriented to align along the radial direction when the cladding tubes are heated above and then cooled below the solvus temperature. The objectives of this study were to investigate the critical stress levels required to cause hydride reorientation (HRT) and to characterize the fracture resistance of Zircaloy-2 after hydride reorientation. HRT heat-treatment was performed on hydrogen-charged Zircaloy-2 specimens at 593 K (320 °C) or 623 K (350 °C) for 1 to 2 hours, followed by cooling to 473 K (200 °C). Fracture testing was conducted on hydride-reoriented three-point bend specimens at 473 K (200 °C) using an in situ loading stage inside a scanning electron microscope. Direct observations indicated that the reoriented hydrides, which ranged from ?1 to 22 ?m in lengths, were more prone to fracture at larger sizes (>10 ?m) compared to smaller sizes (<0.5 ?m). The reoriented hydrides reduced fracture resistance through a void nucleation, growth, and coalescence process at the crack tip. The resulting crack-resistance curves for Zircaloy-2 with reoriented hydrides decrease from 38 to 21 MPa(m)1/2 with increasing hydrogen contents from 51 to 1265 wt ppm hydrogen.

Chan, Kwai S.; He, Xihua; Pan, Yi-Ming

2015-01-01

231

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

232

Group IV a metal hydride catalysts and preparation thereof  

SciTech Connect

Benzene, or an alkylbenzene, is hydrogenated by reaction with hydrogen in the presence of a Group IVa or Va metal hydride catalyst. The catalyst may be a simple hydride such as ZrH/sub 2/ or a hydride of an alloy such as Cu/sub 3/Zr or may be a complex material. One complex material is the reaction product of a Group IVa or Va metal halide, such as ZrCl/sub 4/ with an alkyllithium or aryllithium, such as n-butyllithium, in a hydrocarbon solvent.

Pez, G. P.

1985-04-30

233

Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision  

NASA Astrophysics Data System (ADS)

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

Anz-Meador, Phillip; Liou, Jer-Chyi

234

Carboranes tuning the phosphorescence of iridium tetrazolate complexes.  

PubMed

New iridium tetrazolate complexes containing o-, m-, or p-carboranyl substitution in different positions of a phenylpyridine ligand have been prepared. The carborane isomers and the effect of their substitution position in the tuning of optical properties have been examined. The neutral complexes with the carboranyl substituent on the phenyl ring in meta position relative to the metal exhibit redshifted emission bands in contrast to blueshifts for those with carboranyl in para position. All cationic complexes display evidently blueshifted dual-peak emission compared with the carborane-free complex (c-TZ) with a broad single-peak emission. Introduction of carborane leads to a blueshift over 70?nm relative to c-TZ. Carboranes also significantly improve phosphorescence efficiency (?P ) and lifetime (?), that is, ?P =0.64 versus 0.21 (c-TZ) and ?=880?ns versus 241?ns (c-TZ). The unique hydrophilic nido-carborane-based Ir(III) complex nido-o-1 shows the largest phosphorescence efficiency (abs ?P =0.57) among known water-soluble iridium complexes, long emission lifetime (?=4.38??s), as well as varying emission efficiency and lifetime with O2 content in aqueous solution. Therefore, nido-o-1 has been used as an excellent oxygen-sensitive phosphor for intracellular O2 sensing and hypoxia imaging. PMID:25352530

Shi, Chao; Tu, Deshuang; Yu, Qi; Liang, Hua; Liu, Yahong; Li, Zhihong; Yan, Hong; Zhao, Qiang; Huang, Wei

2014-12-01

235

Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

236

Precursor transformation during molecular oxidation catalysis with organometallic iridium complexes.  

PubMed

We present evidence for Cp* being a sacrificial placeholder ligand in the [Cp*Ir(III)(chelate)X] series of homogeneous oxidation catalysts. UV-vis and (1)H NMR profiles as well as MALDI-MS data show a rapid and irreversible loss of the Cp* ligand under reaction conditions, which likely proceeds through an intramolecular inner-sphere oxidation pathway reminiscent of the reductive in situ elimination of diolefin placeholder ligands in hydrogenation catalysis by [(diene)M(I)(L,L')](+) (M = Rh and Ir) precursors. When oxidatively stable chelate ligands are bound to the iridium in addition to the Cp*, the oxidized precursors yield homogeneous solutions with a characteristic blue color that remain active in both water- and CH-oxidation catalysis without further induction period. Electrophoresis suggests the presence of well-defined Ir-cations, and TEM-EDX, XPS, (17)O NMR, and resonance-Raman spectroscopy data are most consistent with the molecular identity of the blue species to be a bis-?-oxo di-iridium(IV) coordination compound with two waters and one chelate ligand bound to each metal. DFT calculations give insight into the electronic structure of this catalyst resting state, and time-dependent simulations agree with the assignments of the experimental spectroscopic data. [(cod)Ir(I)(chelate)] precursors bearing the same chelate ligands are shown to be equally effective precatalysts for both water- and CH-oxidations using NaIO4 as chemical oxidant. PMID:23822646

Hintermair, Ulrich; Sheehan, Stafford W; Parent, Alexander R; Ess, Daniel H; Richens, David T; Vaccaro, Patrick H; Brudvig, Gary W; Crabtree, Robert H

2013-07-24

237

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

238

Hydride affinity scale of various substituted arylcarbeniums in acetonitrile.  

PubMed

Combined with the integral equation formalism polarized continuum model (IEFPCM), the hydride affinities of 96 various acylcarbenium ions in the gas phase and CH(3)CN were estimated by using the B3LYP/6-31+G(d)//B3LYP/6-31+G(d), B3LYP/6-311++G(2df,2p)//B3LYP/6-31+G(d), and BLYP/6-311++G(2df,2p)//B3LYP/6-31+G(d) methods for the first time. The results show that the combination of the BLYP/6-311++G(2df,2p)//B3LYP/6-31+G(d) method and IEFPCM could successfully predict the hydride affinities of arylcarbeniums in MeCN with a precision of about 3 kcal/mol. On the basis of the calculated results from the BLYP method, it can be found that the hydride affinity scale of the 96 arylcarbeniums in MeCN ranges from -130.76 kcal/mol for NO(2)-PhCH(+)-CN to -63.02 kcal/mol for p-(Me)(2)N-PhCH(+)-N(Me)(2), suggesting most of the arylcarbeniums are good hydride acceptors. Examination of the effect of the number of phenyl rings attached to the carbeniums on the hydride affinities shows that the increase of the hydride affinities takes place linearly with increasing number of benzene rings in the arylcarbeniums. Analyzing the effect of the substituents on the hydride affinities of arylcarbeniums indicates that electron-donating groups decrease the hydride affinities and electron-withdrawing groups show the opposite effect. The hydride affinities of arylcarbeniums are linearly dependent on the sum of the Hammett substituent parameters ?(p)(+). Inspection of the correlation of the solution-phase hydride affinities with gas-phase hydride affinities and aqueous-phase pK(R)(+) values reveals a remarkably good correspondence of ?G(H(-)A)(R(+)) with both the gas-phase relative hydride affinities only if the ? substituents X have no large electron-donating or -withdrawing properties and the pK(R)(+) values even though the media are dramatically different. The solution-phase hydride affinities also have a linear relationship with the electrophilicity parameter E, and this dependence can certainly serve as one of the most effective ways to estimate the new E values from ?G(H(-)A)(R(+)) or vice versa. Combining the hydride affinities and the reduction potentials of the arylcarbeniums, we obtained the bond homolytic dissociation Gibbs free energy changes of the C-H bonds in the corresponding hydride adducts in acetonitrile, ?G(HD)(RH), and found that the effects of the substituent on ?G(HD)(RH) are very small. Simple thermodynamic analytic platforms for the three C-H cleavage modes were constructed. It is evident that the present work would be helpful in understanding the nature of the stabilities of the carbeniums and mechanisms of the hydride transfers between carbeniums and other hydride donors. PMID:21117661

Zhu, Xiao-Qing; Wang, Chun-Hua

2010-12-23

239

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

240

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

241

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

242

Process for production of a metal hydride  

DOEpatents

A process for production of a metal hydride compound MH.sub.x, wherein x is one or two and M is an alkali metal, Be or Mg. The process comprises combining a compound of formula (R.sup.1O).sub.xM with aluminum, hydrogen and at least one metal selected from among titanium, zirconium, hafnium, niobium, vanadium, tantalum and iron to produce a compound of formula MH.sub.x. R.sup.1 is phenyl or phenyl substituted by at least one alkyl or alkoxy group. A mole ratio of aluminum to (R.sup.1O).sub.xM is from 0.1:1 to 1:1. The catalyst is present at a level of at least 200 ppm based on weight of aluminum.

Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Millar, Dean Michael; Molzahn, David Craig

2014-08-12

243

Zirconium Hydride Space Power Reactor design.  

NASA Technical Reports Server (NTRS)

The Zirconium Hydride Space Power Reactor being designed and fabricated at Atomics International is intended for a wide range of potential applications. Throughout the program a series of reactor designs have been evaluated to establish the unique requirements imposed by coupling with various power conversion systems and for specific applications. Current design and development emphasis is upon a 100 kilowatt thermal reactor for application in a 5 kwe thermoelectric space power generating system, which is scheduled to be fabricated and ground tested in the mid 70s. The reactor design considerations reviewed in this paper will be discussed in the context of this 100 kwt reactor and a 300 kwt reactor previously designed for larger power demand applications.

Asquith, J. G.; Mason, D. G.; Stamp, S.

1972-01-01

244

Novel Hydride Transfer Catalysis for Carbohydrate Conversions  

SciTech Connect

5-Hydroxymethylfurfural (HMF), an important versatile sugar derivative has been synthesized from glucose using catalytic amounts of CrCl2 in 1-ethyl-3-methylimidizolium chloride. Glycerol and glyceraldehyde were tested as sugar model compounds. Glycerol is unreactive and does not interfere with glucose conversion. Glyceraldehyde is reactive and does interfere with glucose conversion in competitive experiments. MnCl2 or FeCl2 catalyze dehydration of glyceraldehyde dimer to form compound I, a cyclic hemiacetal with an exocyclic double bond. Upon aqueous work-up I forms pyruvaldehyde. CrCl2 or VCl3 further catalyze a hydride transfer of I to form lactide. Upon aqueous work-up lactide is converted to lactic acid.

Holladay, John E.; Brown, Heather M.; Appel, Aaron M.; Zhang, Z. Conrad

2008-04-03

245

Ni/metal hydride secondary element  

SciTech Connect

A Ni/metal hydride secondary element having a positive nickel hydroxide electrode, a negative electrode having a hydrogen storage alloy, and an alkaline electrolyte, the positive electrode, provided with a three-dimensional metallic conductive structure, also contains an aluminum compound which is soluble in the electrolyte, in addition to nickel hydroxide and cobalt oxide. The aluminum compound is aluminum hydroxide and/or aluminum oxide, and the mass of the aluminum compound which is present in the positive bulk material mixture is 0.1 to 2% by weight relative to the mass of the nickel hydroxide which is present. In combination with aluminum hydroxide or aluminum oxide, the positive electrode further contains lanthanoid oxidic compounds Y.sub.2 O.sub.3, La.sub.2 O.sub.3 and Ca(OH).sub.2, as well as mixtures of these compounds.

Bauerlein, Peter

2005-04-19

246

Long-term pressure and thermal cycling studies on lithium imide-lithium amide complex hydrides and vanadium-carbon hydrides, and electrochemical hydrogen permeation studies  

Microsoft Academic Search

Solid-state hydrogen storage is becoming increasingly important for future development of non-polluting vehicular fuels and nuclear technology. Understanding the nature of classical and complex hydrides is of great importance in developing new high gravimetric or volumetric capacity hydrides. Towards the nuclear technology, we have studied vanadium hydrides with lattice impurities for high volumetric capacities and very low pressures. For the

Joshua H. Lamb

2008-01-01

247

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

248

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

249

Life test results of hydride compressors for cryogenic refrigerators  

NASA Astrophysics Data System (ADS)

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

250

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

251

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4  

NASA Astrophysics Data System (ADS)

Hydride precipitation and distribution in hot-rolled and annealed Zircaloy-4 plate samples artificially induced by gaseous hydrogen charging were studied primarily by neutron tomography, scanning electron microscopy (SEM), and SEM-based electron backscattered diffraction techniques. The precipitated hydride platelet ( ?-ZrH1.66) at a hydrogen pressure of 20 atm was found following the {111} ?-ZrH1.66//(0001) ?-Zr with the surrounding ?-Zr matrix. The microstructural characterization indicated that hydrides with a relatively uniform distribution were precipitated on the rolling-transverse section of the plate, whereas, on the normal-transverse section, a hydride concentration gradient was present with a dense hydride layer near the surface. Further, the neutron tomography investigations clearly identified the nonuniform spatial distribution of hydrides. Thin hydride layers preferentially formed on the sample surface, and the concentrated hydrides precipitating at the edges/corner of the sample were observed. The causes for the localized hydride accumulation were also discussed.

Wang, Zhiyang; Garbe, Ulf; Li, Huijun; Harrison, Robert P.; Kaestner, Anders; Lehmann, Eberhard

2014-04-01

252

Method of selective reduction of polyhalosilanes with alkyltin hydrides  

DOEpatents

The invention relates to the selective and stepwise reduction of polyhalosilanes by reacting at room temperature or below with alkyltin hydrides without the use of free radical intermediates. Alkyltin hydrides selectively and stepwise reduce the Si--Br, Si--Cl, or Si--I bonds while leaving intact any Si--F bonds. When two or more different halogens are present on the polyhalosilane, the halogen with the highest atomic weight is preferentially reduced.

Sharp, Kenneth G. (Midland, MI); D'Errico, John J. (Fenton, MI)

1989-01-01

253

Development of the Low-Pressure Hydride/Dehydride Process  

SciTech Connect

The low-pressure hydride/dehydride process was developed from the need to recover thin-film coatings of plutonium metal from the inner walls of an isotope separation chamber located at Los Alamos and to improve the safety operation of a hydride recovery process using hydrogen at a pressure of 0.7 atm at Rocky Flats. This process is now the heart of the Advanced Recovery and Integrated Extraction System (ARIES) project.

Rueben L. Gutierrez

2001-04-01

254

Theoretical study of iridium complexes with phenylpyridine based ligands and phosphines.  

PubMed

Recently, iridium complexes with phenylpyridine based ligands and phosphines, Ir(C(see text for symbol)N)2 (PPh3)(CN), [(C(see text for symbol)N) = dfppy, dfMeppy] are reported as blue phosphorescent OLED materials. These iridium complexes have novel blue color and emit light at 441 nm to 439 nm. However, these complexes have low external quantum efficiency because they exhibit less MLCT than iridium complexes with phenylpyridine, and some other ancillary ligands. To improve quantum efficiency of iridium complexes with phenylpyridine based ligands and phosphines, a time dependent density functional theory (TDDFT) study of these phosphors was performed. Using these results, this paper discusses how the ancillary ligand influences the emission peak, as well as the metal to ligand charge transfer (MLCT) transition efficiency. PMID:21780496

Lee, Seung-Chan; Ham, Ho Wan; Kim, Young Sik

2011-05-01

255

Iridium-catalyst-based autonomous bubble-propelled graphene micromotors with ultralow catalyst loading.  

PubMed

A novel concept of an iridium-based bubble-propelled Janus-particle-type graphene micromotor with very high surface area and with very low catalyst loading is described. The low loading of Ir catalyst (0.54?at?%) allows for fast motion of graphene microparticles with high surface area of 316.2?m(2) ?g(-1). The micromotor was prepared with a simple and scalable method by thermal exfoliation of iridium-doped graphite oxide precursor composite in hydrogen atmosphere. Oxygen bubbles generated from the decomposition of hydrogen peroxide at the iridium catalytic sites provide robust propulsion thrust for the graphene micromotor. The high surface area and low iridium catalyst loading of the bubble-propelled graphene motors offer great possibilities for dramatically enhanced cargo delivery. PMID:25293511

Wang, Hong; Sofer, Zden?k; Eng, Alex Yong Sheng; Pumera, Martin

2014-11-10

256

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

Code of Federal Regulations, 2012 CFR

...for each of the PGM may be used for quality marks on articles: “Plat.” or “Pt.” for Platinum; “Irid.” or “Ir.” for Iridium; “Pall.” or “Pd.” for Palladium; “Ruth.” or “Ru.” for Ruthenium; “Rhod.” or “Rh.” for...

2012-01-01

257

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

Code of Federal Regulations, 2013 CFR

...for each of the PGM may be used for quality marks on articles: “Plat.” or “Pt.” for Platinum; “Irid.” or “Ir.” for Iridium; “Pall.” or “Pd.” for Palladium; “Ruth.” or “Ru.” for Ruthenium; “Rhod.” or “Rh.” for...

2013-01-01

258

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

Code of Federal Regulations, 2014 CFR

...for each of the PGM may be used for quality marks on articles: “Plat.” or “Pt.” for Platinum; “Irid.” or “Ir.” for Iridium; “Pall.” or “Pd.” for Palladium; “Ruth.” or “Ru.” for Ruthenium; “Rhod.” or “Rh.” for...

2014-01-01

259

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

Code of Federal Regulations, 2011 CFR

...for each of the PGM may be used for quality marks on articles: “Plat.” or “Pt.” for Platinum; “Irid.” or “Ir.” for Iridium; “Pall.” or “Pd.” for Palladium; “Ruth.” or “Ru.” for Ruthenium; “Rhod.” or “Rh.” for...

2011-01-01

260

Analysis and Implications of the Iridium 33-Cosmos 2251 Collision  

NASA Astrophysics Data System (ADS)

On 2009 February 10, Iridium 33--an operational US communications satellite in low-Earth orbit--was struck and destroyed by Cosmos 2251--a long-defunct Russian communications satellite. This is the first time since the dawn of the Space Age that two satellites have collided in orbit. To better understand the circumstances of this event and the ramifications for avoiding similar events in the future, this paper provides a detailed analysis of the predictions leading up to the collision, using various data sources, and looks in detail at the collision, the evolution of the debris clouds, and the long-term implications for satellite operations. The only publicly available system available to satellite operators for screening for close approaches, SOCRATES, did predict this close approach, but it certainly wasn't the closest approach predicted for the week of February 10. In fact, at the time of the collision, SOCRATES ranked this close approach 152 of the 11,428 within 5 km of any payload. A detailed breakdown is provided to help understand the limitations of screening for close approaches using the two-line orbital element sets. Information is also provided specifically for the Iridium constellation to provide an understanding of how these limitations affect decision making for satellite operators. Post-event analysis using high-accuracy orbital data sources will be presented to show how that information might have been used to prevent this collision, had it been available and used. Analysis of the collision event, along with the distribution of the debris relative to the original orbits, will be presented to help develop an understanding of the geometry of the collision and the near-term evolution of the resulting debris clouds. Additional analysis will be presented to show the long-term evolution of the debris clouds, including orbital lifetimes, and estimate the increased risk for operations conducted by Iridium and other satellite operators in the low-Earth orbit environment. The final portion of the paper will look at how collaborative efforts, such as the current Data Center operations supporting SOCRATES-GEO, might be used to reduce the overall risk of similar events in the future.

Kelso, T. S.

261

Preparation of platinum/iridium scanning probe microscopy tips  

NASA Astrophysics Data System (ADS)

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

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

1999-07-01

262

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

263

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

264

Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding  

SciTech Connect

The purpose of this work is to build on the results reported in the M2 milestone M2FT 13PN0805051, document number FCRD-USED-2013-000151 (Hanson, 2013). In that work, it was demonstrated that unirradiated samples of zircaloy-4 cladding could be pre-hydrided at temperatures below 400°C in pure hydrogen gas and that the growth of hydrides on the surface could be controlled by changing the surface condition of the samples and form a desired hydride rim on the outside diameter of the cladding. The work performed at Pacific Northwest National Laboratory since the issuing of the M2 milestone has focused its efforts to optimize the formation of a hydride rim on available zircaloy-4 cladding samples by controlling temperature variation and gas flow control during pre-hydriding treatments. Surface conditioning of the outside surface was also examined as a variable. The results of test indicate that much of the variability in the hydride thickness is due to temperature variation occurring in the furnaces as well as how hydrogen gas flows across the sample surface. Efforts to examine other alloys, gas concentrations, and different surface conditioning plan to be pursed in the next FY as more cladding samples become available

Shimskey, Rick W.; Hanson, Brady D.; MacFarlan, Paul J.

2013-09-30

265

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

266

Terminal Hydride in [FeFe]-Hydrogenase Model Has Lower Potential for H2 Production Than the Isomeric Bridging Hydride  

PubMed Central

Protonation of the symmetrical tetraphosphine complexes Fe2(S2CnH2n)(CO)2(dppv)2 afforded the corresponding terminal hydrides, establishing that even symmetrical diiron(I) dithiolates undergo protonation at terminal sites. The terminal hydride [HFe2(S2C3H6)(CO)2(dppv)2]+ was found to catalyze proton reduction at potentials 200 mV milder than the isomeric bridging hydride, thereby establishing a thermodynamic advantage for catalysis operating via terminal hydride. The azadithiolate protonates to afford, [Fe2[(SCH2)2NH2](CO)2(dppv)2]+, [HFe2[(SCH2)2NH](CO)2?(dppv)2]+, and [HFe2[(SCH2)2NH2](CO)2(dppv)2]2+, depending on conditions. PMID:18333613

Barton, Bryan E.; Rauchfuss, Thomas B.

2008-01-01

267

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

Microsoft Academic Search

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

Francisco Sircillineto

1986-01-01

268

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

269

Electrodeposition of hydrous iridium oxide on conductive diamond electrodes for catalytic sensor applications  

Microsoft Academic Search

Boron-doped diamond (BDD) electrodes have been modified by hydrous iridium oxide (IrOx) electrodeposition, and depending on the deposition conditions, either highly dispersed iridium oxide nanoparticles or continuous oxide films were obtained. The electrochemical characteristics of IrOx on BDD compare well with those obtained on other substrate materials. The proposed method allows excellent control of the deposited amount, and high reproducibility

Chiaki Terashima; Tata N Rao; Bulusu V Sarada; Nicolae Spataru; Akira Fujishima

2003-01-01

270

NAMBE 2010 Ashish Baraskar, UCSB 1 In-situ Iridium Refractory  

E-print Network

NAMBE 2010 Ashish Baraskar, UCSB 1 In-situ Iridium Refractory Ohmic Contacts to p-InGaAs Ashish - For efficient removal of oxides/impurities #12;NAMBE 2010 Ashish Baraskar, UCSB 7 · Scaled device thin base (For (p-type) 20 nm in-situ Ir Semi-insulating InP Substrate In-situ Ir contacts In-situ iridium (Ir

Rodwell, Mark J. W.

271

Catalysis and Organometallic Chemistry of Rhodium and Iridium in the Oxidation of Organic Substrates  

Microsoft Academic Search

The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis\\u000a of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last\\u000a 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants.\\u000a Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes\\/ketones\\u000a as

Cristina Tejel; Miguel Ciriano

272

The distribution and geochemistry of iridium in river suspended material and marine sediments  

E-print Network

in ferromanganese nodules and deep-sea sediments is less significant than previously thought. The similar enrichment factors of Ni, Co and Ir in ferromanganese nodules supports the sediment data and suggest a related enrichment mechanism for all these elements... Sapropels and Mid-Cretaceous Marine Black Shales Sources of Iridium The Argument for Iridium Enhancement in the Deep-Sea by Geochemical Processes: Ferromanganese Nodules SUMMARF AND CONCLUSIONS REFERENCES APPENDIX A APPENDIX B APPENDIX C APPENDIX...

Fenner, Frederick Donald

1983-01-01

273

EMISSION CHARACTERISTICS OF TANTALUM, TUNGSTEN, RHENIUM, AND IRIDIUM IN PLASMA DIODES  

Microsoft Academic Search

Experimental determinations of the ionic and electronic emission ;\\u000a characteristics of tantalum, tungsten, rhenium, and iridium cathodes in vapor ;\\u000a thermionic converters are compared. It is shown that tantalum provides superior ;\\u000a thermal ionization qualities at high pressure compared with tungsten, rhenium, ;\\u000a and iridium. High electronic current densities may be obtained from cesium on ;\\u000a rhenium and cesium on

Gust

1962-01-01

274

Properties of mixed molybdenum oxide iridium oxide thin films synthesized by spray pyrolysis  

Microsoft Academic Search

Molybdenum-doped iridium oxide thin films have been deposited onto corning glass- and fluorine-doped tin oxide coated corning glass substrates at 350 °C by using a pneumatic spray pyrolysis technique. An aqueous solution of 0.01 M ammonium molybdate was mixed with 0.01 M iridium trichloride solution in different volume proportions and the resultant solution was used as a precursor solution for

P. S. Patil; R. K. Kawar; S. B. Sadale; A. I. Inamdar; H. P. Deshmukh

2006-01-01

275

Properties of mixed molybdenum oxide–iridium oxide thin films synthesized by spray pyrolysis  

Microsoft Academic Search

Molybdenum-doped iridium oxide thin films have been deposited onto corning glass- and fluorine-doped tin oxide coated corning glass substrates at 350°C by using a pneumatic spray pyrolysis technique. An aqueous solution of 0.01M ammonium molybdate was mixed with 0.01M iridium trichloride solution in different volume proportions and the resultant solution was used as a precursor solution for spraying. The as-deposited

P. S. Patil; R. K. Kawar; S. B. Sadale; A. I. Inamdar; H. P. Deshmukh

2006-01-01

276

Generation of selenium hydride from alkaline solutions: a new concept of the hydride generation-atomic absorption technique  

PubMed Central

The use of hydride generation is often useful in environmental analysis. The normal acid sodium tetrahydroborate reaction provides exceptional sensitivity with continuous flow hydride generators. In some situations there are interferences which will mask the sensitivity. An alternative chemistry system is described here and is shown to offer similar sensitivity to that normally used. A commercial continuous flow analyser is used in this work. PMID:18925246

Bye, Ragnar

1989-01-01

277

Evaluating zirconium-zirconium hydride interfacial strains by nano-beam electron diffraction  

NASA Astrophysics Data System (ADS)

Nano-beam electron diffraction has been used to quantify the elastic strain field associated with ?-hydride needles embedded in an ?-Zr matrix. It has been found that the volume misfit associated with precipitation results in elastic strains that are ˜4× greater in the matrix than the hydride. Electron energy loss spectroscopy was used to detect hydrogen enrichment at the matrix-hydride interface by a shift in the zirconium plasmon peak. This work highlights that ?-hydride is metastable and acts as a precursor to equilibrium ?-hydride and that compositional variations within the hydride can be detected using electron energy loss spectroscopy.

Barrow, A. T. W.; Korinek, A.; Daymond, M. R.

2013-01-01

278

Comparative modelling of chemical ordering in palladium-iridium nanoalloys  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

279

Iridium abundance maxima in the Upper Cenomanian extinction interval  

NASA Technical Reports Server (NTRS)

Two iridium abundance peaks, both 0.11 ppb (whole-rock basis) over a local background of 0.017 ppb, have been found in Middle Cretaceous marine rocks near Pueblo, Colorado. They occur just below the 92-million-year-old Cenomanian-Turonian (C-T) stage boundary. No other peaks were found in 45 meters of strata (about 2.5 million years of deposition) above and below the boundary interval. The broad lower peak straddles the first in a series of extinctions of benthic and nektonic macrobiota which comprise the C-T extinction event. The sharp upper peak occurs stratigraphically about 1.2 meters above the lower peak. The excess Ir might be from meteoroid impacts.

Orth, C. J.; Attrep, M., Jr.; Mao, X. Y.; Kauffman, E. G.; Diner, R.

1988-01-01

280

A Porphyrin-Stabilized Iridium Oxide Water Oxidation Catalyst  

SciTech Connect

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

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

2011-01-01

281

Sputtered iridium coatings for grazing incidence x-ray reflectance  

NASA Astrophysics Data System (ADS)

The Advanced X-ray Astrophysics Facility--Imaging is one of two complementary space-based x-ray observatories being developed by NASA. Utilizing grazing incidence mirror elements in a Wolter Type I configuration, it will image x-ray sources over an energy range of 0.1 to 10 KeV. This paper describes the deposition of iridium/chromium coatings on Zerodur substrates using DC magnetron sputtering for use in grazing incidence configuration. Included are a description of the configuration and parameters of the deposition process, the results of x-ray performance measurements, and the implications of the results for scaling the deposition process to the full scale AXAF-I mirror elements.

Bessey, John S.; Roth, James A.

1994-02-01

282

Cytotoxic activity and protein binding through an unusual oxidative mechanism by an iridium(i)-NHC complex.  

PubMed

A new NHC iridium(i) complex () showing significant antiproliferative properties in vitro is described here. Its crystal structure, solution behaviour and interactions with the model proteins cytochrome c (cyt c) and lysozyme were investigated. High resolution ESI-MS measurements suggest that this iridium(i) complex acts as a prodrug and binds cyt c tightly through an unusual "oxidative" mechanism. Eventually, an iridium(iii)-NHC fragment is found associated to the protein. PMID:25605442

Gothe, Y; Marzo, T; Messori, L; Metzler-Nolte, N

2015-02-01

283

Influence of uranium hydride oxidation on uranium metal behaviour  

SciTech Connect

This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

Patel, N.; Hambley, D. [National Nuclear Laboratory (United Kingdom); Clarke, S.A. [Sellafield Ltd (United Kingdom); Simpson, K.

2013-07-01

284

Synthesis and small molecule chemistry of the niobaziridine-hydride functional group  

E-print Network

Chapter 1. Synthesis and Divergent Reactivity of the Niobaziridine-Hydride Functional Group The synthesis, characterization and reactivity of the niobaziridine-hydride complex Nb(H)([eta]²-t- ]Bu(H)C=NAr)(N[Np]Ar)? (la-H; ...

Figueroa, Joshua S

2005-01-01

285

PREPRINT submitted to Journal of Physics B Electronic structure of the Magnesium hydride  

E-print Network

PREPRINT submitted to Journal of Physics B Electronic structure of the Magnesium hydride molecular: 31.15.AR,31.15.Ct,31.50.Be,31.50.Df #12; Electronic structure of the Magnesium hydride molecular ion

Recanati, Catherine

286

Hydrogen storage as a hydride. Citations from the International Aerospace Abstracts data base  

NASA Technical Reports Server (NTRS)

These citations from the international literature concern the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron titanium, lanthanium nickel, magnesium copper and magnesium nickel among others.

Zollars, G. F.

1980-01-01

287

CRYSTALLOGRAPHIC PROPERTIES AND MECHANICAL BEHAVIOR OF TITANIUM HYDRIDE LAYERS GROWN ON TITANIUM IMPLANTS  

E-print Network

CRYSTALLOGRAPHIC PROPERTIES AND MECHANICAL BEHAVIOR OF TITANIUM HYDRIDE LAYERS GROWN ON TITANIUM, Switzerland Keywords: SLA treated titanium - bone-anchored dental implants - transmission and scanning electron microscopy - titanium hydride sub-surface layer - epitaxy Abstract Commercially pure titanium

Paris-Sud XI, Université de

288

Permeation rates for RTF metal hydride vessels  

SciTech Connect

Contamination rates have been estimated for the RTF nitrogen heating and cooling system (NH and CS) due to tritium permeation through the walls of metal hydride vessels. Tritium contamination of the NH and CS will be seen shortly after start-up of the RTF with the majority of it coming from the TCAP units. Contamination rates of the NH and CS are estimated to exceed 400 Ci/year after three years of operation and will elevate tritium concentrations in the NH and CS above 6 {times} 10{sup {minus}3} {mu}Ci/cc. To reduce tritium activity in the NH and CS, a stripper or ``getter`` bed may need to be installed in the NH and CS. Increasing the purge rate of nitrogen from the NH and CS is shown to be an impractical method for reducing tritium activity due to the high purge rates required. Stripping of the NH and CS nitrogen in the glove box stripper system will give a temporary lowering of tritium activity in the NH and CS, but tritium activity will return to its previous level in approximately two weeks.

Klein, J.E.

1992-05-21

289

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

290

Author's personal copy Unusual lithium coordinated platinum and rhodium hydride dimers  

E-print Network

Author's personal copy Unusual lithium coordinated platinum and rhodium hydride dimers Brett D complexes Rhodium complexes Hydride complexes X-ray crystal structures a b s t r a c t Two unusual lithium coordinated binuclear platinum- and rhodium-hydride complexes [M(dip- pe)(H)]2ÁLiHBEt3 were synthesized

Jones, William D.

291

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

Microsoft Academic Search

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

Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

2012-01-01

292

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

293

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

294

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

295

Opening of a Post Doctoral Position Complex hydrides for hydrogen storage applications  

E-print Network

Opening of a Post Doctoral Position Complex hydrides for hydrogen storage applications on complex hydrides for hydrogen storage applications in connection with the « Fast, reliable and cost effective boron hydride based high capacity solid state hydrogen storage materials» project co

296

Evaluation of oxide-coated iridium-rhenium chambers  

NASA Technical Reports Server (NTRS)

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

Reed, Brian D.

1994-01-01

297

AC-impedance studies on metal hydride electrodes  

SciTech Connect

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

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

1994-12-31

298

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

E-print Network

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

Kyle C. Smith; Timothy S. Fisher

2012-05-04

299

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

300

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

301

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

302

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

303

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

NASA Astrophysics Data System (ADS)

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

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

2015-04-01

304

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

305

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

E-print Network

= An experimental study of the solubility and partitioning of iridium, osmium and gold between­melt partitioning experiments to understand the behaviour of iridium, osmium and gold during crust+ oxidation state. This, together with our previous measurements of olivine­melt partitioning for Pt, Pd, Ru

Mcdonough, William F.

306

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

E-print Network

Effects of Electrodeposition Conditions and Protocol on the Properties of Iridium Oxide pH Sensor of California, Berkeley, Berkeley, California 94720-1460, USA The properties of iridium oxide pH sensors of the calibration curves was shown to increase from ca. 49 to 76 mV/pH unit with the fractional coverage of gold

Majda, Marcin

307

Photoelectron spectroscopy of boron aluminum hydride cluster anions  

SciTech Connect

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

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

2014-04-28

308

Ab-initio study of transition metal hydrides  

SciTech Connect

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 [Dept. of Physics, Feroze Gandhi Insititute of Engineering and Technology, Raebareli-229001 (India); Shukla, Seema, E-mail: sharma.yamini62@gmail.com; Dwivedi, Shalini, E-mail: sharma.yamini62@gmail.com; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com [Theoretical Condensed Matter Physics Laboratory, Dept. of Physics Feroze Gandhi College, Raebareli-229001 (India)

2014-04-24

309

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

310

Photoelectron spectroscopy of boron aluminum hydride cluster anions  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

311

OBSERVATION AND MECHANISM OF HYDRIDE IN ZIRCALOY-4 AND LOCAL HYDRIDE RE-ORIENTATION INDUCED BY HIGH PRESSURE AT HIGH TEMPERATURES  

SciTech Connect

Hydrided Zircaloy-4 samples were produced by a gas charging method to desired amounts of hydrogen. For low hydrogen content samples, the hydrided platelets appear elongated and needle-like, orientated in the circumferential direction. Mechanical testing was carried out by the ring compression method at various temperatures. Samples with higher hydrogen concentration resulted in lower strain before fracture and reduced maximum load. The trend between temperature and ductility was also very clear: increasing temperatures resulted in increased ductility of the hydrided cladding. A single through-wall crack was observed for a hydrided sample having very high hydrogen concentration under ring compression testing. For samples having lower hydrogen concentrations, the fracture surfaces traversed both circumferential and radial directions, and for which voids were observed near the hydrides. Mechanical tests to study hydride reorientation in these samples are under way, and the results will be reported in the near future.

Yan, Yong [ORNL] [ORNL; Blackwell, Andrew S [ORNL] [ORNL; Plummer, Lee K [ORNL] [ORNL; Radhakrishnan, Balasubramaniam [ORNL] [ORNL; Gorti, Sarma B [ORNL] [ORNL; Clarno, Kevin T [ORNL] [ORNL

2013-01-01

312

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

313

Homoleptic tetranuclear rhodium carbonyls: comparison with their iridium analogues.  

PubMed

Density functional theory confirms the experimentally known triply bridged Rh4(CO)9(?-CO)3 structure to be the lowest-energy structure. The lowest-energy structures of the unsaturated systems Rh4(CO)n (n = 11, 10, 9, 8) are also triply bridged structures with central Rh4 tetrahedra that can be derived from this Rh4(CO)9(?-CO)3 structure by removal of terminal CO groups in various ways. The M-M distances in these central M4 tetrahedra change very little as CO groups are lost, suggesting reluctance to form metal-metal multiple bonds in these unsaturated systems. The natural bond orbital (NBO) Wiberg bond indices provide depth to this analysis. All of these unsaturated systems are predicted to be highly fluxional, as two to three isomeric structures lie within ?4 kcal/mol of the global minima. The Rh4(CO)8(?-CO)2(?4-CO) structure analogous to the lowest-energy Co4(CO)11 structure with all four atoms of a central Co4 butterfly bridged by a ?-CO group is predicted to lie ?6 kcal/mol in energy above the lowest-energy Rh4(CO)11 structure. Comparisons of the relative energies of analogous Rh4(CO)n and Ir4(CO)n structures indicate that more highly bridged M4(CO)n structures are energetically much more favorable for rhodium than for iridium. Dissociation energies (for loss of CO) and disproportionation energies are reported. PMID:25594490

Gong, Shida; Luo, Qiong; Dou, Na; Chi, Qingkui; Peng, Bin; Xie, Yaoming; King, R Bruce; Schaefer, Henry F

2015-02-19

314

Formation, phase analysis and properties of iridium containing perovskite  

SciTech Connect

Perovskite-type oxide Sr{sub 1.3}La{sub 0.7}MnIrO{sub 6} has been synthesized by solid-state reaction in air at various temperatures and structurally characterized by Rietveld refinement of powder X-ray diffraction data. The structure synthesized at 1473K shows orthorhombic symmetry (S.G. Pnma), whereas that synthesized at 1623K shows cubic symmetry (S.G. Pm3-bar m). For the orthorhombic Sr{sub 1.3}La{sub 0.7}MnIrO{sub 6}, the structural phase transition from orthorhombic to cubic was observed near 773K by the high temperature X-ray diffractometry. The electrical conductivity measurement shows semiconducting property above room temperature for both the phases. Breaking of slope in the temperature dependence of the conductivity brings evidence in support of the phase transition for orthorhombic Sr{sub 1.3}La{sub 0.7}MnIrO{sub 6}. At low temperature, the compounds show ferromagnetic behavior. Magnetic susceptibility data show that both the compounds obey Curie-Weiss law in the high temperature region with the effective magnetic moment consistent with an oxidation state of +3 for manganese and +4 for iridium.

Haque, Md. Tahidul [Department of Materials Science, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441-8580 (Japan); Satoh, Hirohisa [Department of Materials Science, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441-8580 (Japan); Kamegashira, Naoki [Department of Materials Science, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441-8580 (Japan)]. E-mail: nkamegas@tutms.tut.ac.jp

2004-12-02

315

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

316

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

SciTech Connect

We study both the rare gas hydride anions, RG–H{sup ?} (RG = He–Rn) and Group 2 (Group IIa) metal hydride anions, M{sub IIa}H{sup ?} (M{sub IIa} = 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{sup ?} and Be–He species are weakly bound, we show that, as with the previously studied BeH{sup ?} and MgH{sup ?} species, the other M{sub IIa}H{sup ?} species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns{sup 2}) and H{sup ?}(1s{sup 2}). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the M{sub IIa}H{sup ?} species than for RG–H{sup ?}. Our analyses lead us to conclude that the stronger interaction in the case of the M{sub IIa}H{sup ?} species arises from sp and spd hybridization, which allows electron density on the M{sub IIa} atom to move away from the incoming H{sup ?}.

Harris, Joe P.; Manship, Daniel R.; Wright, Timothy G., E-mail: Tim.Wright@nottingham.ac.uk [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Breckenridge, W. H. [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 (United States)] [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 (United States)

2014-02-28

317

Comparison of hydrogen elimination from molecular zinc and magnesium hydride clusters.  

PubMed

In analogy to the previously reported tetranuclear magnesium hydride cluster with a bridged dianionic bis-?-diketiminate ligand, a related zinc hydride cluster has been prepared. The crystal structures of these magnesium and zinc hydride complexes are similar: the metal atoms are situated at the corners of a tetrahedron in which the vertices are bridged either by dianionic bis-?-diketiminate ligands or hydride ions. Both structures are retained in solution and show examples of H(-)???H(-) NMR coupling (Mg: 8.5?Hz; Zn: 16.0?Hz). The zinc hydride cluster [NN-(ZnH)2]2 thermally decomposes at 90?°C and releases 1.8?equivalents of H2 . In contrast to magnesium hydride clusters, there is no apparent relationship between cluster size and thermal decomposition temperature for the zinc hydrides. DFT calculations reproduced the structure of the zinc hydride cluster reasonably well and charge density analysis showed no bond paths between the hydride ions. This contrasts with calculations on the analogous magnesium hydride cluster in which a counter-intuitive H(-)???H(-) bond path was observed. Forcing a reduced H(-)???H(-) distance in the zinc hydride cluster, however, gave rise to a H(-)???H(-) bond path. Such weak interactions could play a role in H2 desorption. The presumed molecular product after H2 release, a Zn(I) cluster, could not be characterized experimentally but DFT calculations predicted a cluster with two localized Zn-Zn bonds. PMID:25066656

Intemann, Julia; Sirsch, Peter; Harder, Sjoerd

2014-08-25

318

The influence of hydride on fracture toughness of recrystallized Zircaloy-4 cladding  

NASA Astrophysics Data System (ADS)

In this work, RXA cladding tubes were hydrogen-charged to target hydrogen content levels between 150 and 800 wppm (part per million by weight). The strings of zirconium hydrides observed in the cross sections are mostly oriented in the circumferential direction. The fracture toughness of hydrided RXA Zircaloy-4 cladding was measured to evaluate its hydride embrittlement susceptibility. With increasing hydrogen content, the fracture toughness of hydrided RXA cladding decreases at both 25 °C and 300 °C. Moreover, highly localized hydrides (forming a hydride rim) aggravate the degradation of the fracture properties of RXA Zircaloy-4 cladding at both 25 °C and 300 °C. Brittle features in the form of quasi-cleavages and secondary cracks were observed on the fracture surface of the hydride rim, even for RXA cladding tested at 300 °C.

Hsu, Hsiao-Hung; Chiang, Ming-Feng; Chen, Yen-Chen

2014-04-01

319

Oxygen atom transfer to a half-sandwich iridium complex: clean oxidation yielding a molecular product.  

PubMed

The oxidation of [Ir(Cp*)(phpy)(NCAr(F))][B(Ar(F))4] (1; Cp* = ?(5)-pentamethylcyclopentadienyl, phpy = 2-phenylene-?C(1')-pyridine-?N, NCAr(F) = 3,5-bis(trifluoromethyl)benzonitrile, B(Ar(F))4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) with the oxygen atom transfer (OAT) reagent 2-tert-butylsulfonyliodosobenzene (sPhIO) yielded a single, molecular product at -40 °C. New Ir(Cp*) complexes with bidentate ligands derived by oxidation of phpy were synthesized to model possible products resulting from oxygen atom insertion into the iridium-carbon and/or iridium-nitrogen bonds of phpy. These new ligands were either cleaved from iridium by water or formed unreactive, phenoxide-bridged iridium dimers. The reactivity of these molecules suggested possible decomposition pathways of Ir(Cp*)-based water oxidation catalysts with bidentate ligands that are susceptible to oxidation. Monitoring the [Ir(Cp*)(phpy)(NCAr(F))](+) oxidation reaction by low-temperature NMR techniques revealed that the reaction involved two separate OAT events. An intermediate was detected, synthesized independently with trapping ligands, and characterized. The first oxidation step involves direct attack of the sPhIO oxidant on the carbon of the coordinated nitrile ligand. Oxygen atom transfer to carbon, followed by insertion into the iridium-carbon bond of phpy, formed a coordinated organic amide. A second oxygen atom transfer generated an unidentified iridium species (the "oxidized complex"). In the presence of triphenylphosphine, the "oxidized complex" proved capable of transferring one oxygen atom to phosphine, generating phosphine oxide and forming an Ir-PPh3 adduct in 92% yield. The final Ir-PPh3 product was fully characterized. PMID:24571611

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

2014-03-12

320

Novel iridium complex and its copolymer with N-vinyl carbazole for electroluminescent devices  

Microsoft Academic Search

A novel iridium complex having the polymerizable functional group as one of the ligands, bis(2-phenylene pyridine) acrylate iridium lr(ppy)2Ac was synthesized as a phosphorescent dopant for electroluminescent (EL) devices. It has a photoluminescence spectrum peak at about 530 nm. EL devices were fabricated by doping lr(ppy)2Ac into host materials, such as BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and poly(N-vinyl carbazole) (PVCz). Bright blue-green luminescence

Xiaodong Wang; Kenji Ogino; Kuniaki Tanaka; Hiroaki Usui

2004-01-01

321

Strong Ligand Field Effects of Blue Phosphorescent Iridium(III) Complexes  

Microsoft Academic Search

In this study, new deep blue emitting mixed ligand iridium(III) complexes such as Ir(dFppy)(PPhMe2)2(H)(Cl), [Ir(dFppy)(PPhMe2)2(H)(NCMe)] and Ir(dFppy)(PPhMe2)2(H)(CN), [dFppy = 2-(2?,4?-difluoro-phenyl)pyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. These iridium complexes comprise one cyclometalating, two phosphines trans to each other and two cis-ancillary ligands. We investigate the electron-withdrawing capabilities of

Ho Wan Ham; Young Sik Kim

2010-01-01

322

Highly efficient electrochemiluminescence from iridium(III) complexes with 2-phenylquinoline ligand.  

PubMed

A series of cyclometalated iridium(III) complexes with 2-phenylquinoline ligand (1-4) were designed and synthesized, which were thoroughly investigated by the photophysics, electrochemistry, theoretical calculations and electrochemiluminescence (ECL). By incorporating methyl groups into the 2-phenylquinoline, the corresponding complexes 2 and 3 displayed lower oxidative potential and higher HOMO energy levels. Most importantly, compared with tris(2,2'-bipyridyl)ruthenium(II) ([Ru(bipy)3](2+)), these iridium(III) complexes demonstrated more intense ECL in acetonitrile solutions. PMID:25482203

Zhou, Yuyang; Li, Wanfei; Yu, Linpo; Liu, Yang; Wang, Xiaomei; Zhou, Ming

2015-01-28

323

Intracavitary irradiation of renal pyelocalyceal transitional cell carcinoma with iridium-192  

SciTech Connect

A case of multicentric urothelial transitional cell carcinoma is presented, in which the patient underwent a left ureteronephrectomy and in the remaining right kidney recurrent transitional cell carcinoma was found in the inferior calyx. Because this area was accessible via a cutaneous nephrostomy, it is treated with a combination of external beam radiation and intracavitary implantation with iridium-192. The iridium was placed in the vicinity of the tumor using an angiographic procedure. The technique successfully preserved remaining renal parenchyma. The case illustrates how angiography skills and procedures can be applied in a novel brachytherapy application.

Kadish, S.P.; Danford, R.; Felton, L.M.; Ascoli, F.A.

1981-11-01

324

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

325

Structure Properties of Ternary Hydrides Ni3AlHx  

NASA Astrophysics Data System (ADS)

The structure properties of the ternary hydrides Ni3AlHx are studied by use of the interatomic pair potentials obtained from the first principles electronic structure calculation and Chen-Mobius 3-dimensional lattice inversion method. The heat of formation and volume expansion of the hydrogenized systems are investigated.

Pan, Yi-wei; Zhang, Wen-qing; Chen, Nan-xian

1996-09-01

326

Generation of hydrogen isotopes with an electricpulse hydride injector  

Microsoft Academic Search

An Electric Pulse Hydride Injector (EPHI) designed for safe interim tritium storagehas been developed for the dosed supply of hydrogen isotopes in a time interval ranging fromseveral milliseconds up to hundreds of seconds. The release of gas occurs via current pulsesthrough the active elements of the EPHI, each of which is made of a thin molybdenum foil coatedon both sides

I. s Glushkov; Yu. A Kareev; Yu. V Petrov; A. n Savotkin; V. V Frunze; E Hutter; G Müller; R.-D Penzhorn; U Tamm

1999-01-01

327

Sites and Diffusion of Muons in Fcc Metal Hydride Systems.  

NASA Astrophysics Data System (ADS)

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

Kempton, James Russell

1987-09-01

328

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

329

Mechanistic insights into iridium-catalyzed asymmetric hydrogenation of dienes.  

PubMed

Hydrogenation of 2,3-diphenylbutadiene (1) with the chiral carbene-oxazoline-iridium complex C has been studied by means of a combined experimental and computational approach. A detailed kinetic profile of the reaction was obtained with respect to consumption of the substrate and formation of the intermediate half-reduction products, 2,3-diphenylbut-1-ene (2) and the final product, 2,3-diphenylbutane (3). The data generated from these analyses, and from NMR experiments, revealed several facets of the reaction. After a brief induction period (presumably involving reduction of the cyclooctadiene ligand on C), the diene concentration declines in a zero-order process primarily to give monoene intermediates. When all the diene is consumed, the reaction accelerates and compound 3 begins to accumulate. Interestingly, the prevalent enantiomer of the monoene intermediate 2 is converted mostly to meso-3 so the enantioselectivity of the reaction appears to reverse. The reaction seems to be first-order with respect to the catalyst when the catalyst concentration is less than 0.0075 M; diffusion of hydrogen across the gas-liquid interface complicates the analysis at higher catalyst concentrations. Similarly, these diffusion effects complicated measurements of reaction rate versus applied pressure of dihydrogen; other factors like stir speed and flask geometry come into play under some, but not all, the conditions examined. Density functional theory (DFT) calculations, using the PBE method, were used to probe the reaction. These studies indicate a transoid-eta(4)-diene-dihydride complex forms in the first stages of the catalytic cycle. Further reaction requires dissociation of one alkene ligand to give a eta(2)-diene-dihydride-dihydrogen intermediate. A catalytic cycle that features Ir(3+)/Ir(5+) seems to be involved thereafter. PMID:16163756

Cui, Xiuhua; Fan, Yubo; Hall, Michael B; Burgess, Kevin

2005-11-18

330

Hyperfine structure and Stark effect in the [18.0] 4 - X3?4 transition of iridium hydride, IrH and [18.2] 4 - X3?4 transition of iridium deuteride, IrD  

NASA Astrophysics Data System (ADS)

High resolution spectra of IrH and IrD, with full width at half maximum (FWHM) of ?0.001 cm-1, have shown well resolved hyperfine structure due to the nuclear spin, I = 3/2, of 193Ir and 191Ir. Analysis of the hyperfine structure in the [18.2] 4 - X3?4 transition of 193IrD and 191IrD yielded well defined magnetic and quadrupole Ir hyperfine parameters which showed that the ground X3?4 state originates predominantly from the two open-shell Ir(5d?35d?3) configuration with a significant contribution from the four open-shell Ir(5d?5d?35d?36s?) configuration. Examination of the Stark effect in the [18.0] 4 - X3?4 transition of 193IrH yielded electric dipole moments of 1.23(1) D and 0.76(1) D for the ground and excited states, respectively. The hyperfine constants and the dipole moment of the ground state are seen to follow the trend shown by the isovalent molecules, CoF, CoH and IrF.

Linton, C.; Granger, A. D.; Adam, A. G.; Steimle, T. C.

2014-10-01

331

``White lines'' in the chlorine K x-ray absorption spectra of osmium(IV), iridium(III), iridium(IV), and platinum(IV) hexachlorides  

NASA Astrophysics Data System (ADS)

The chlorine K absorption spectra from K2OsCl6, K2IrCl6, K2PtCl6, (NH4)2OsCl6, (NH4)3IrCl6, (NH4)2IrCl6, and (NH4)2PtCl6 have been measured and explained in terms of molecular-orbital (MO) theory. Two conspicuous ``white lines'' have been observed at the absorption threshold of the spectra of the iridium(IV) and osmium(IV) hexachlorides in contrast to one intense white line in the spectra of the platinum(IV) and iridium(III) hexachlorides. The latter white line is ascribed to the electronic transition from the Cl 1s core level to the lowest unoccupied antibonding MO eg(?*) for the octahedral complex ions [PtCl6]2- and [IrCl6]3- and the former white lines are attributed to the transitions to the unoccupied MO's eg(?*) and t2g(?*) for the octahedral complex ion [IrCl6]2- or [OsCl6]2-. The energy differences between the eg(?*) and t2g(?*) orbitals for the complex ions [OsCl6]2- and [IrCl6]2- are estimated to be 1.8 and 1.9 eV, respectively. These white lines show the chemical shifts toward higher energies in the order of the platinum(IV) <iridium(IV) < iridium(III) < osmium(IV) hexachlorides. The other absorption structures are broad and are quite alike throughout seven hexachlorides. The chlorine K absorption spectra of the hexachlorides are little influenced by the exchange of the counterions K+ and NH4+.

Sugiura, Chikara

1983-11-01

332

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

333

Efficient catalysis by MgCl2 in hydrogen generation via hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis.  

PubMed

Magnesium chloride efficiently catalyzed the hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis. Hydrogen yield of 1635 mL g(-1) was obtained (MgH(2)), i.e. with 96% conversion in 30 min at 303 K. PMID:22538836

Zhao, Zelun; Zhu, Yunfeng; Li, Liquan

2012-06-01

334

Comparative assessment of iridium oxide and platinum alloy wires using an in vitro glial scar assay.  

PubMed

The long-term effect of chronically implanted electrodes is the formation of a glial scar. Therefore, it is imperative to assess the biocompatibility of materials before employing them in neural electrode fabrication. Platinum alloy and iridium oxide have been identified as good candidates as neural electrode biomaterials due to their mechanical and electrical properties, however, effect of glial scar formation for these two materials is lacking. In this study, we applied a glial scarring assay to observe the cellular reactivity to platinum alloy and iridium oxide wires in order to assess the biocompatibility based on previously defined characteristics. Through real-time PCR, immunostaining and imaging techniques, we will advance the understanding of the biocompatibility of these materials. Results of this study demonstrate iridium oxide wires exhibited a more significant reactive response as compared to platinum alloy wires. Cells cultured with platinum alloy wires had less GFAP gene expression, lower average GFAP intensity, and smaller glial scar thickness. Collectively, these results indicated that platinum alloy wires were more biocompatible than the iridium oxide wires. PMID:23764951

Ereifej, Evon S; Khan, Saida; Newaz, Golam; Zhang, Jinsheng; Auner, Gregory W; VandeVord, Pamela J

2013-12-01

335

Electrolysis of Molten Iron Oxide with an Iridium Anode: The Role of Electrolyte Basicity  

E-print Network

Electrolysis of Molten Iron Oxide with an Iridium Anode: The Role of Electrolyte Basicity Hojong electrolysis (MOE) is a carbon-free, electrochemical technique to decompose a metal oxide directly into liquid. Electrolysis is being investigated by the steel industry as a carbon-lean route that copes with the potential

Sadoway, Donald Robert

336

Optimization and electrochemical characterization of RF-sputtered iridium oxide microelectrodes for electrical stimulation  

NASA Astrophysics Data System (ADS)

A reactively sputtered iridium oxide (IrOx) thin film has been developed as electrochemical modification material for microelectrodes to obtain high stability and charge storage capacity (CSC) in functional electrical stimulation. The effect of the oxygen flow and oxygen to argon ratio during sputtering process on the microstructure and electrochemical properties of the IrOx film is characterized. After optimization, the activated IrOx microelectrode shows the highest CSC of 36.15 mC cm-2 at oxygen flow of 25 sccm and oxygen to argon ratio of (2.5:1). Because the deposition process of the reactively sputtered iridium oxide is an exothermic reaction, it is difficult to form film patterning by the lift-off process. The lift-off process was focused on the partially carbonized photoresist (PR) and normal PR. The higher of the carbonization degree of PR reaches, the longer the immersion duration. However, the patterning process of the iridium oxide film becomes feasible when the sputtering pressure is increasing. The experimental results show that the iridium oxide films forms the pattern with the lowest duration of ultrasonic agitation when the deposition pressure is 4.2 Pa and pressure ratio between O2 and Ar pressure is 3:4.

Kang, Xiaoyang; Liu, Jingquan; Tian, Hongchang; Yang, Bin; NuLi, Yanna; Yang, Chunsheng

2014-02-01

337

A monolith immobilised iridium Cp* catalyst for hydrogen transfer reactions under flow conditions.  

PubMed

An immobilised iridium hydrogen transfer catalyst has been developed for use in flow based processing by incorporation of a ligand into a porous polymeric monolithic flow reactor. The monolithic construct has been used for several redox reductions demonstrating excellent recyclability, good turnover numbers and high chemical stability giving negligible metal leaching over extended periods of use. PMID:25500632

Rojo, Maria Victoria; Guetzoyan, Lucie; Baxendale, Ian R

2015-01-27

338

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

ERIC Educational Resources Information Center

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

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

2009-01-01

339

Activation of Sulfur-and Nitrogen-Containing Heterocycles by a Dinuclear Iridium Complex  

E-print Network

Activation of Sulfur- and Nitrogen-Containing Heterocycles by a Dinuclear Iridium Complex David A-0216 Received September 24, 1998 [Cp*IrH3]2 was found to activate both nitrogen- and sulfur pressures of hydrogen (150-2250 psi) over a hot heterogeneous catalyst (320-440 °C) to remove sulfur

Jones, William D.

340

Iridium-Catalyzed Allylic Amination Route to ?-Aminoboronates: Illustration of the Decisive Role of Boron Substituents  

PubMed Central

The development of a new route to ?-aminoboronates using an iridium-catalyzed allylic amination on boronated substrates is described. Unlike the boronate group, the trifluoroborato substituent was found to govern the regioselectivity exclusively in favor of branched products. The transformation of an allylic substitution product into an ?-aminoboronic ester in an efficient way validated the implementation of this approach. PMID:22350584

Touchet, Sabrina; Molander, Gary A.; Carboni, Bertrand; Bouillon, Alexandre

2012-01-01

341

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

E-print Network

Synthesis and characterization of a series of rhodium, iridium, and ruthenium isocyanide complexes Ruthenium Isocyanide a b s t r a c t Several new electrophilic metal isocyanide complexes have been fully the correspond- ing complexes with the general formula LM(CNAr)I2. For the analogous ruthenium complexes better

Jones, William D.

342

Modes of Activation of Organometallic Iridium Complexes for Catalytic Water and C-H Oxidation  

E-print Network

Modes of Activation of Organometallic Iridium Complexes for Catalytic Water and C-H Oxidation - ) or (cod)IrI (cod = cyclooctadiene) complexes, which are water and C-H oxidation catalyst precursors. Extensive oxidation of the Cp* ligand is observed, likely beginning with electrophilic C-H hydroxylation

Zare, Richard N.

343

RF-sputtering of iridium oxide to be used as stimulation material in functional medical implants  

Microsoft Academic Search

This paper describes the reactive RF-powered sputter deposition of iridium oxide (IrOx) to be used as the active stimulation layer in functional medical implants. Using an approach based on generic curves, the amount of oxygen gettered by the film is determined for various carrier gas flows and pumping speeds. It is shown that under certain conditions the getter effect peaks

B. Wessling; W. Mokwa; U. Schnakenberg

2006-01-01

344

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

345

Electrochemical and In Situ Optical Studies of Supported Iridium Oxide Films in Aqueous Solutions  

E-print Network

Electrochemical and In Situ Optical Studies of Supported Iridium Oxide Films in Aqueous Solutions oxide IrOx films supported on Au microelec- trodes during charge and discharge have been investigated in its various states of oxidation were sought from in situ transmission measurements for IrOx films

Taylor, Philip L.

346

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

347

Anion effects to deliver enhanced iridium catalysts for hydrogen isotope exchange processes.  

PubMed

Synthesis of a series of iridium(I) complexes of the type [(COD)Ir(IMes)(PPh3)]X (X = BF4, OTf, and BArF) has been established. Application of these species in mild hydrogen isotope exchange processes revealed more efficient catalysis and, further, a wider solvent scope when employing larger, more weakly coordinating counterions. PMID:25208265

Kennedy, Alan R; Kerr, William J; Moir, Rory; Reid, Marc

2014-10-28

348

Carbon-Sulfur Bond Cleavage of Methyl-Substituted Thiophenes with Iridium(III)  

E-print Network

Articles Carbon-Sulfur Bond Cleavage of Methyl-Substituted Thiophenes with Iridium(III) Matthew R carbon-sulfur bond(s). In both cases the thiophenes are ring-opened and hydrogenated, resulting-methylthiophene and 2,5-dimethylthiophene at 120 °C in the presence of H2 results in the cleavage of the thiophene

Jones, William D.

349

Neutron-activation determination of iridium in sedimentary rocks after sorption preconcentration  

SciTech Connect

A sorption-neutron-activation technique has been developed for iridium determination in sedimentary rocks with a detection limit of 4 x 10/sup -10/% and a relative standard deviation of 0.35. A polymeric tertiary amine was used as sorbent.

Barsukova, L.D.; Kolesov, G.M.; Malofeeva, G.I.; Nazarov, M.A.; Marcheva, E.V.

1986-11-10

350

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

351

Iridium profile for 10 million years across the Cretaceous-Tertiary boundary at Gubbio (Italy)  

Microsoft Academic Search

The iridium anomaly at the Cretaceous-Tertiary (KT) boundary was discovered in the pelagic limestone sequence at Gubbio on the basis of 12 samples analyzed by neutron activation analysis (NAA) and was interpreted as indicating impact of a large extraterrestrial object at exactly the time of the KT mass extinction. Continuing controversy over the shape of the Ir profile at the

W. Alvarez; A. Montanari; F. Asaro

1990-01-01

352

Testing and evaluation of oxide-coated iridium/rhenium chambers  

NASA Technical Reports Server (NTRS)

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

Reed, Brian D.

1993-01-01

353

Identification of an iridium-containing compound with a formal oxidation state of IX  

NASA Astrophysics Data System (ADS)

One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2, 3, 4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d1, with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4]+), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4]+ species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4]+ and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d0 electron configuration, is the most stable of all possible [IrO4]+ isomers.

Wang, Guanjun; Zhou, Mingfei; Goettel, James T.; Schrobilgen, Gary J.; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

2014-10-01

354

Water reduction systems associated with homoleptic cyclometalated iridium complexes of various 2-phenylpyridines.  

PubMed

The photoreduction of water to hydrogen represents a promising method for generating sustainable clean fuel. The molecular processes of this photoreduction require an effective light absorber, such as the ruthenium polybipyridine complex, to collect and convert the solar energy into a usable chemical form. In the search for a highly active and stable photosensitizer (PS), iridium complexes are attractive because of their desirable photophysical characteristics. Herein, a series of homoleptic tris-cyclometalated iridium complexes, based on different 2-phenylpyridine ligands, were utilized as PSs in photocatalytic systems for hydrogen production with [Rh(dtb-bpy)3 ](PF6 )3 (dtb-bpy=4,4'-di-tert-butyl-2,2'-dipyridyl) serving as the water reduction catalyst (WRC) and triethanolamine (TEOA) as the electron donor. The photophysical and electrochemical properties of these complexes were systematically investigated. The excited state of neutral iridium complexes (PS*) could not be quenched by using TEOA as an electron donor, but they could be quenched by using [Rh(dtb-bpy)3 ](PF6 )3 as an electron acceptor, indicating that the PS* quenching pathway in catalytic reactions was most likely an oxidative quenching process. A set of long-lived and highly active systems for hydrogen evolution were obtained in Ir(III) -Rh(III) -TEOA systems. These systems maintained their activity for more than 72 h with visible-light irradiation, and the total turnover number was up to 3040. Comparative studies indicated that the photocatalytic performance of these homoleptic tris-cyclometalated iridium compounds was superior to that of the cationic iridium complex [Ir(ppy)2 (bpy)](PF6 ) (ppy=2-phenylpyridine, bpy=2,2'-dipyridyl) (4), which was used as a reference. The significant increase in the photocatalytic efficiencies was in part attributed to the higher photostability of the neutral Ir(III) complexes. This assumption was supported by their different coordination modes, photophysical, and electrochemical properties. PMID:23843363

Yuan, Yong-Jun; Yu, Zhen-Tao; Cai, Jian-Guang; Zheng, Chao; Huang, Wei; Zou, Zhi-Gang

2013-08-01

355

Identification of an iridium-containing compound with a formal oxidation state of IX.  

PubMed

One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states. The preparation and characterization of compounds containing elements with unusual oxidation states is of great interest to chemists. The highest experimentally known formal oxidation state of any chemical element is at present VIII, although higher oxidation states have been postulated. Compounds with oxidation state VIII include several xenon compounds (for example XeO4 and XeO3F2) and the well-characterized species RuO4 and OsO4 (refs 2-4). Iridium, which has nine valence electrons, is predicted to have the greatest chance of being oxidized beyond the VIII oxidation state. In recent matrix-isolation experiments, the IrO4 molecule was characterized as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO4 is 5d(1), with a formal oxidation state of VIII. Removal of the remaining d electron from IrO4 would lead to the iridium tetroxide cation ([IrO4](+)), which was recently predicted to be stable and in which iridium is in a formal oxidation state of IX. There has been some speculation about the formation of [IrO4](+) species, but these experimental observations have not been structurally confirmed. Here we report the formation of [IrO4](+) and its identification by infrared photodissociation spectroscopy. Quantum-chemical calculations were carried out at the highest level of theory that is available today, and predict that the iridium tetroxide cation, with a Td-symmetrical structure and a d(0) electron configuration, is the most stable of all possible [IrO4](+) isomers. PMID:25341786

Wang, Guanjun; Zhou, Mingfei; Goettel, James T; Schrobilgen, Gary J; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian

2014-10-23

356

An automated hydride generation-cryogenic trapping-ICP-MS system for measuring inorganic and methylated Ge, Sb and As species  

E-print Network

hydride generation, cryogenic trapping and inductively coupled plasma mass spectrometry (ICP-MS) can and raise the hydride trap into and out of a liquid nitrogen dewar and to control the heating of the hydride

Canberra, University of

357

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...

358

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 ...

359

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

360

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

SciTech Connect

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

Greenspan, Ehud; Todreas, Neil; Taiwo, Temitope

2009-03-10

361

The free-energy barrier to hydride transfer across a dipalladium complex.  

PubMed

We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique. PMID:25652724

Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

2015-01-01

362

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

363

Testing of electroformed deposited iridium/powder metallurgy rhenium rockets  

NASA Technical Reports Server (NTRS)

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

Reed, Brian D.; Dickerson, Robert

1996-01-01

364

Preparation of hydride complexes of ruthenium with bidentate phosphite ligands  

Microsoft Academic Search

Hydride complex RuH2(PFFP)2 (1) [PFFP=(CF3CH2O)2PN(CH3)N(CH3)P(OCH2CF3)2] was prepared by allowing the compound RuCl4(bpy)·H2O (bpy=1,2-bipyridine) to react first with the phosphite PFFP and then with NaBH4. Chloro-complex RuCl2(PFFP)2 (2) was also prepared, either by reacting RuCl4(bpy)·H2O with PFFP and zinc dust or by substituting triphenylphosphine with PFFP in the precursor complex RuCl2(PPh3)3. Hydride derivative RuH2(POOP)2 (3) (POOP=Ph2POCH2CH2OPPh2) was prepared by reacting compound

Jorge Bravo; Jesús Castro; Soledad García-Fontán; Ma Carmen Rodríguez-Martínez; Gabriele Albertin; Stefano Antoniutti; Alessandro Manera

2007-01-01

365

Metal Hydride/Chemical Heat Pump Development Project  

NASA Astrophysics Data System (ADS)

The metal hydride heat pump (MMHP) is a chemical heat pump containing two hydrides for the storage and/or recovery of thermal energy. It utilizes the heat of reaction of hydrogen with specific metal alloys. The MMHP design can be tailored to provide heating and/or cooling over a wide range of input and ambient temperatures. This system can thus be used with a variety of heat sources including industrial waste heat, solar energy or even a fossil fuel. Applications and market sectors, conceptual development, thermal and mechanical design, laboratory verification of design and material performance, cost analysis and the design, fabrication and testing of an Engineering Development Test Unit (EDTU) are included within the scope of the program.

Cunningham, S. J.

1982-03-01

366

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

367

Gas-phase Reactions of Hydride Anion, H-  

NASA Astrophysics Data System (ADS)

Rate constants were measured at 300 K for the reactions of the hydride anion, H-, with neutral molecules C2H2, H2O, CH3CN, CH3OH, (CH3)2CO, CH3CHO, N2O, CO2, O2, CO, CH3Cl, (CH3)3CCl, (CH3CH2)2O, C6H6, and D2 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- 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, Jr.; Yang, Zhibo; Demarais, Nicholas J.; Snow, Theodore P.; Bierbaum, Veronica M.

2010-09-01

368

Reversible metal-hydride phase transformation in epitaxial films.  

PubMed

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

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

2015-03-11

369

Reversible metal–hydride phase transformation in epitaxial films  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

370

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

371

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

PubMed

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

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

2009-03-20

372

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. PMID:19333448

Felderhoff, Michael; Bogdanovi?, Borislav

2009-01-01

373

Determination of trace bismuth by flow injection-hydride generation collection-atomic absorption spectrometry  

Microsoft Academic Search

Bismuth hydride gas was collected on-line and determined via a new flow injection-hydride generation collection-flame atomic absorption spectrometry system. The performance of the gas-liquid separator, hydride gas collection time, acidity of the sample solution, NaBH4 concentration, and the effects of concomitant interferents were investigated to optimize the conditions of this new method. Interferences from concomitant elements were investigated, and recoveries

Shu Yu Chen; Zhi Feng Zhang; Hua Ming Yu

2002-01-01

374

Neutral binuclear rare-earth metal complexes with four ?2-bridging hydrides.  

PubMed

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

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

2015-03-10

375

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

376

[The gaseous phase enrichment techniques in hydride generation (review)].  

PubMed

The gaseous phase of hydride enrichment techniques have been systematically described in this paper. These enrichment techniques including liquid nitrogen trap, balloon collection, in situ pre-concentration in pre-heated graphite furnace, trapped in absorbing solutions, and in some absorbing solid substances. The principle and the application of these techniques have been discussed detail too. The near future trends of the techniques have reviewed also. PMID:12945368

Guo, X; Guo, X; Huang, B

2000-08-01

377

Mechanisms of hydrogen induced delayed cracking in hydride forming materials  

Microsoft Academic Search

Mechanisms which have been formulated to describe delayed hydrogen cracking in hydride-forming metals are reviewed and discussed.\\u000a Particular emphasis is placed on the commercial alloy Zr-2.5 pct Nb (Cb) which is extensively used in nuclear reactor core\\u000a components. A quantitative model for hydrogen cracking in this material is presented and compared with available experimental\\u000a data. The kinetics of crack propagation

R. Dutton; K. Nuttall; M. P. Puls; L. A. Simpson

1977-01-01

378

Fiber optic hydrogen detectors containing Mg-based metal hydrides  

Microsoft Academic Search

We report on the implementation of Pd-capped chemo-chromic metal hydrides as a sensing layer in fiber optic hydrogen detectors. Due to the change in optical properties of Mg-based alloys on hydrogen absorption, a drop in reflectance by a factor of 10 is demonstrated at hydrogen levels down to 15% of the lower explosion limit. The switching takes place in only

M. J. Slaman; B. Dam; M. Pasturel; D. M. Borsa; H. Schreuders; J. H. Rector; R. P. Griessen

2007-01-01

379

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

380

Corrosion of AB{sub 5} metal hydride electrodes  

SciTech Connect

Metal hydride electrodes are an attractive substitute for the cadmium electrode in Cd/Ni batteries because of their relatively benign environmental impact and higher energy density. However, even though MH{sub x}/Ni batteries are currently competitive in certain applications, their full potential as cheap, reliable, energy storage devices is not yet realized: a severe penalty has been incurred in storage capacity and materials costs in order to inhibit corrosion and attain acceptable electrode cycle life. Currently there are two types of alloys which are useful as metal hydride electrodes, the AB{sub 5} and the AB{sub 2} classes of intermetallic compounds. Commercial AB{sub 5} electrodes use mischmetal, a low cost combination of rare earth elements. The B{sub 5} component remains primarily Ni but is substituted in part with Co, Mn, Al etc. The partial substitution of Ni increases thermodynamic stability of the hydride phase and corrosion resistance. Such an alloy is commonly written as MmB{sub 5} where Mm represents the mischmetal component; the B{sub 5} composition in commercial batteries is variable but electrodes consisting of MmNi{sub 3.55}Co{sub .75}Mn{sub .4}Al{sub .3} have good storage capacity and cycle life and most AB{sub 5} battery electrodes have a similar composition. The authors have been concerned with the function that individual components play in such an alloy with respect to lattice expansion, hydride stability, and surface passivation. Thus they have focused on the properties of a similar alloy, A(NiCoMnAl){sub 5} where A is La or La{sub 1{minus}x}Ce{sub x}. Some of their results noted here have previously appeared in separate publications; the purpose of this paper is to combine them with new data to give a more coherent and complete whole.

Adzic, G.D.; Johnson, J.R.; Mukerjee, S.; McBreen, J.; Reilly, J.J. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science

1997-11-01

381

Hydride Compressor Sorption Cooler and Surface Contamination Issues  

Microsoft Academic Search

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

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

2003-01-01

382

Hydride Compressor Sorption Cooler and Surface Contamination Issues  

Microsoft Academic Search

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

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

2003-01-01

383

Hydride Compressor Sorption Cooler and Surface Contamination Issues  

Microsoft Academic Search

A continuous-duty hydrogen sorption cryocooler is being developed for the Planck spacecraft, a mission to map the cosmic microwave background beginning in 2007. Thii cryocooler uses six individual compressor elements (CEs) filled with the hydriding alloy LaNi4.,8Sno.~ to provide high- pressure (50 bar) hydrogen to a Joule-Thomson (J-T) expander and to absorb low-pressure (43 bar) gas fiom liquid hydrogen reservoirs

R. C. Bowman; J. W. Reitert; M. Prina; J. G. Kdleck; W. A. WordT

384

Electrolytic hydriding of TiFe 50\\/50 alloy  

Microsoft Academic Search

The electrolytic insertion of hydrogen into different samples of the intermetallic compound (IMC) TiFe 50\\/50 was investigated by voltammetry and galvanostatic charging–discharging cycles in order to devise conditions which would lead to extensive hydriding. The voltammetric pattern achieved in aqueous KOH shows both reduction and oxidation peaks well positive to the hydrogen evolution reaction. Such a pattern can hardly be

M. Bernardini; N. Comisso; G. Davolio; G. Mengoli

2000-01-01

385

Thermomechanics of hydrogen storage in metallic hydrides: modeling and analysis  

E-print Network

A thermodynamically consistent mathematical model for hydrogen adsorption in metal hydrides is proposed. Beside hydrogen diffusion, the model accounts for phase transformation accompanied by hysteresis, swelling, temperature and heat transfer, strain, and stress. We prove existence of solutions of the ensuing system of partial differential equations by a carefully-designed, semi-implicit approximation scheme. A generalization for a drift-diffusion of multi-component ionized "gas" is outlined, too.

Tomas Roubicek; Giuseppe Tomassetti

2013-09-12

386

Scanning electron microscope techniques for studying Zircaloy corrosion and hydriding  

SciTech Connect

A procedure has been developed for preparing scanning electron microscope (SEM) samples of irradiated or unirradiated Zircaloy, suitable for oxide layer imaging, hydride concentration and morphology determination, and X-ray microanalysis (EPMA). The area fraction of the hydride phase is determined by image analysis of backscattered electron images (BEI). Measurements performed on unirradiated laboratory-hydrided samples, as well as cladding samples from pressurized water reactor (PWR) fuel irradiated to a burnup of about 40 MWd/kg U, gave good agreement with hot extraction hydrogen analysis over a wide range of hydrogen concentrations, based on the assumption that all the hydrogen i present as the {delta}-phase hydride. The local hydrogen concentration can be determined quantitatively with a spatial resolution of less than 100{mu}m. This capability was used to determine the radial hydrogen concentration profiles across the cladding wall for PWR samples with different total hydrogen contents, surface oxide thicknesses, and local heat rating. The results indicated that the hydrogen concentration profile was essentially flat (uniform) across the wall thickness for the samples with a low total hydrogen content ({approx}200 ppm) or a negligible radial heat flux (plenum), while the samples from fueled sections with >200 ppm or a negligible radial heat flux (plenum), while the samples from fueled sections with >200 ppm H had a steep increase in the hydrogen concentration close to the outer surface. Analysis of a longitudinal section showed peak hydrogen concentrations opposite pellet interfaces a factor of two higher than in the mid-pellet region.

Schrire, D.I. [ABB Atom AB, Vaesteraas (Sweden); Pearce, J.H. [AEA Technology, Windscale (United Kingdom)

1994-12-31

387

Nickel metal hydride batteries for high power applications  

Microsoft Academic Search

Nickel metal hydride (Ni\\/MH) is presently the most promising battery system for electric and hybrid vehicle propulsion in the short and mid-term. This paper presents the results obtained in the development of prismatic Ni\\/MH batteries for high power, mainly hybrid vehicle, applications.Valve regulated Ni\\/MH cells rated at 25 and 60Ah have been designed and assembled using improved positive and negative

M. Luisa Soria; Joaqu??n Chacón; J. Carlos Hernández; Daniel Moreno; Araceli Ojeda

2001-01-01

388

12OC-2001-02 New Cu-diffusion Barrier Materials Based on Ruthenium, Iridium and its Oxides  

E-print Network

12OC-2001-02 New Cu-diffusion Barrier Materials Based on Ruthenium, Iridium and its Oxides Advanced-seeding layer is needed to assure good Cu electrofill. Our invention utilizes a new conductive ruthenium/ruthenium

Mohanty, Saraju P.

389

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

390

Uranium metal reactions with hydrogen and water vapour and the reactivity of the uranium hydride produced  

SciTech Connect

Within the nuclear industry, metallic uranium has been used as a fuel. If this metal is stored in a hydrogen rich environment then the uranium metal can react with the hydrogen to form uranium hydride which can be pyrophoric when exposed to air. The UK National Nuclear Laboratory has been carrying out a programme of research for Sellafield Limited to investigate the conditions required for the formation and persistence of uranium hydride and the reactivity of the material formed. The experimental results presented here have described new results characterising uranium hydride formed from bulk uranium at 50 and 160 C. degrees and measurements of the hydrolysis kinetics of these materials in liquid water. It has been shown that there is an increase in the proportion of alpha-uranium hydride in material formed at lower temperatures and that there is an increase in the rate of reaction with water of uranium hydride formed at lower temperatures. This may at least in part be attributable to a difference in the reaction rate between alpha and beta-uranium hydride. A striking observation is the strong dependence of the hydrolysis reaction rate on the temperature of preparation of the uranium hydride. For example, the reaction rate of uranium hydride prepared at 50 C. degrees was over ten times higher than that prepared at 160 C. degrees at 20% extent of reaction. The decrease in reaction rate with the extent of reaction also depended on the temperature of uranium hydride preparation.

Godfrey, H. [National Nuclear Laboratory, Workington Laboratory, Havelock Road, Derwent Howe, Cumbria, CA14 3YQ (United Kingdom); Broan, C.; Goddard, D.; Hodge, N.; Woodhouse, G. [National Nuclear Laboratory, Preston Laboratory, Springfields, Salwick, Preston, Lancashire, PR4 0XJ (United Kingdom); Diggle, A. [Sellafield Limited, Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom); Orr, R. [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom)

2013-07-01

391

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

SciTech Connect

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

Nasise, J.E.

1988-01-01

392

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

393

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

394

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. PMID:18444648

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

395

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

396

Superconductive sodalite-like clathrate calcium hydride at high pressures  

PubMed Central

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

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

2012-01-01

397

Structure and properties of complex hydride perovskite materials.  

PubMed

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

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

2014-01-01

398

Structure and properties of complex hydride perovskite materials  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

399

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

SciTech Connect

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

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

2011-08-03

400

Electrochemical and structural characterizations of electrodeposited iridium oxide thin-film electrodes applied to neurostimulating electrical signal  

Microsoft Academic Search

Thin-film technology takes more and more importance in the development of biomedical devices dedicated to functional neurostimulation. Our research about the design of implantable neurostimulating electrode is oriented toward thin-film cuff electrodes based on PTFE substrate covered by a gold\\/iridium oxide film. A gold-sputtered film serves as adhesion layer and current collector whereas iridium oxide acts as an electrochemical actuator.

S. C Mailley; M Hyland; P Mailley; J. M McLaughlin; E. T McAdams

2002-01-01

401

Kinetic method for the determination of iridium in copper and copper-nickel alloys and in industrial solutions  

Microsoft Academic Search

This article discusses the kinetic determination of iridium in copper and copper-nickel alloys, in ores and ore processing products containing down to 10⁻⁸%, and in waste solutions down to 0.01 mg\\/liter. The procedure for the kinetic determination of iridium based on the oxidation of mercury(I) and cerium(IV) is described. The applications of the schemes presented allows one to widen significantly

F. I. Danilova; I. A. Fedotova; N. V. Ustinova

1986-01-01

402

Highly efficient organic light-emitting diodes based on the red phosphorescent emitter sensitized by the green emitting iridium complex  

Microsoft Academic Search

We demonstrated the red phosphorescent organic light-emitting diodes with sensitizer, iridium(III) tris(2-phenylpyridine) [Ir(ppy)3]. The devices with sensitizer showed a significant improvement in a luminance and efficiency compared to those without sensitizer. Moreover, the electroluminescent (EL) spectra of devices with sensitizer show a similar emission peak with photoluminescent (PL) spectra of iridium(III) bis(2-phenylquinoline)(acetylaceton) [Ir(pq)2(acac)] under the optimized doping ratio of Ir(pq)2(acac)

Ji Hyun Seo; Eun Young Choi; Jun Ho Kim; Seul Ong Kim; Kum Hee Lee; Seung Soo Yoon; Young Kwan Kim

2010-01-01

403

A new re-entrant ionization chamber for the calibration of iridium-192 high dose rate sources.  

PubMed

A re-entrant (well-type) ionization chamber has been designed and fabricated at the University of Wisconsin for use with iridium-192 high dose-rate (HDR) remote after-loading brachytherapy devices. The chamber was designed to provide an ionization current of about 10(-8) ampere with a nominal 10 curie iridium-192 source. A narrow opening is provided into the sensitive volume of the chamber to insert a Nucletron MicroSelectron catheter, or catheters with similar diameters from other HDR manufacturers. The chamber exhibits a flat response (+/- 0.1%) for any source position within +/-4 mm of the chamber center. A 300 volt chamber bias yields a 99.96% ion collection efficiency. The chamber is capable of being calibrated directly with an iridium-192 source which has in turn been calibrated with thimble-type ion chambers. Reproducibility for readings in the current mode for 10 consecutive insertions of the MicroSelectron iridium-192 HDR source is within 0.02% or less. Two thimble chambers calibrated by the U.S. National Institute of Standards and Technology provide calibration traceability of iridium-192 HDR sources and re-entrant chambers to a primary national standards laboratory. Results of activity measurements of 6 commercial iridium-192 HDR sources are reported. PMID:1512153

Goetsch, S J; Attix, F H; DeWerd, L A; Thomadsen, B R

1992-01-01

404

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

405

Synthesis of Highly Active Mg-BASED Hydrides Using Hydriding Combustion Synthesis and NbF5 Additives  

NASA Astrophysics Data System (ADS)

Superiority of the hydriding combustion (HC) technique over conventional metallurgical approach to the synthesis of cost-effective Mg based hydrides, which show promise as hydrogen storage materials, is well known. In the present research, we report further improvements in HC prepared Mg-based materials, achieved by optimizing the preparative parameters of HC and by catalytic addition. Mg90-Ni60-C40 composites prepared using optimized processing parameters were ball-milled with NbF5 (10 h) and characterized for their micro-structural and hydriding properties. The ball-milled/catalyzed powder showed decreased crystallinity with CNTs on its surfaces. Surface area of the ball-milled powder decreased to almost half of the as-HC powder, while TG analysis revealed a four-fold decrease in the desorption temperature of the milled powder compared to that of the as-HC prepared powder. Activated samples achieved the maximum absorption/desorption limits (5.3 wt.%) at as low as 100°C, underlining the possibility of the use of these materials in portable hydrogen storage devices.

Chourashiya, M. G.; Park, C. N.; Park, C. J.

2012-09-01

406

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

PubMed

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. PMID:23458659

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

2013-04-30

407

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. PMID:23458659

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

2013-01-01

408

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

DOEpatents

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

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

2014-11-18

409

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

410

Near-IR phosphorescent ruthenium(II) and iridium(III) perylene bisimide metal complexes.  

PubMed

The phosphorescence emission of perylene bisimide derivatives has been rarely reported. Two novel ruthenium(II) and iridium(III) complexes of an azabenz-annulated perylene bisimide (ab-PBI), [Ru(bpy)2 (ab-PBI)][PF6 ]2 1 and [Cp*Ir(ab-PBI)Cl]PF6 2 are now presented that both show NIR phosphorescence between 750-1000?nm in solution at room temperature. For an NIR emitter, the ruthenium complex 1 displays an unusually high quantum yield (?p ) of 11?% with a lifetime (?p ) of 4.2??s, while iridium complex 2 exhibits ?p <1?% and ?p =33??s. 1 and 2 are the first PBI-metal complexes in which the spin-orbit coupling is strong enough to facilitate not only the Sn ?Tn intersystem crossing of the PBI dye, but also the radiative T1 ?S0 transition, that is, phosphorescence. PMID:25504675

Schulze, Marcus; Steffen, Andreas; Würthner, Frank

2015-01-26

411

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

412

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

413

Highly active iridium catalysts for the hydrogenation of ketones and aldehydes.  

PubMed

The pressure hydrogenation capabilities of the iridium pincer complexes IrH2Cl[((i)Pr2PC2H4)2NH] (1) and IrH3[((i)Pr2PC2H4)2NH] (2) are described and compared to related results obtained previously in transfer hydrogenation. Complex 1 was shown to act as a convenient air-stable entry point to the active catalyst 2, in the presence of base and hydrogen gas. The catalysts are active in a range of solvents, including CH2Cl2 and CHCl3, in contrast to related ruthenium systems. This class of iridium complexes is very effective for the direct hydrogenation of a wide range of carbonyl compounds including ketones, diketones, alpha,beta-unsaturated ketones and aldehydes. A catalytic cycle is proposed for this system which involves an ionic heterolytic bifunctional hydrogenation mechanism. PMID:19462662

Chen, Xuanhua; Jia, Wenli; Guo, Rongwei; Graham, Todd W; Gullons, Meredith A; Abdur-Rashid, Kamaluddin

2009-02-28

414

First Applications of DoD Iridium RUDICS in the NSF Polar Programs  

NASA Astrophysics Data System (ADS)

We will present the first deployment and application of the new Iridium RUDICS service to remote instrumentation projects within the National Science Foundation's polar programs. The rise of automated observing networks has increased the demand for real-time connectivity to remote instruments, not only for immediate access to data, but to also interrogate health and status. Communicating with field sites in the polar regions is complicated by the remoteness from existing infrastructure, low temperatures and limited connection options. Sites located above 78° latitude are not able to see geostationary satellites, leaving the Iridium constellation as the only one that provide a direct connection. Some others, such as Orbcomm, only provide a store-and-forward service. Iridium is often used as a dial up modem to establish a PPP connection to the Internet with data files transferred via FTP. On low-bandwidth, high-latency networks like Iridium (2400bps with ping times of seconds), this approach is time consuming and inefficient. The dial up time alone takes upwards of a minute, and standard TCP/IP and FTP protocols are hampered by the long latencies. Minimizing transmission time is important for reducing battery usage and connection costs. The new Iridium RUDICS service can be used for more efficient transfers. RUDICS is an acronym for "Router-based Unstructured Digital Inter-working Connectivity Solution" and provides a direct connection between an instrument in the field and a server on the Internet. After dialing into the Iridium gateway, a socket connection is opened to a registered port on a user's server. Bytes sent to or from the modem appear at the server's socket. The connection time is reduced to about 10 seconds because the modem training and PPP negotiation stages are eliminated. The remote device does not need to have a full TCP/IP stack, allowing smaller instruments such as data loggers to directly handle the data transmission. Alternative protocols can be deployed that better exploit the characteristics of the Iridium channel. In addition, the setup naturally scales to handle hundreds of remote devices, an important aspect for larger sensor networks. As part of the NSF's Arctic Research Support and Logistics Services, we have deployed RUDICS systems with three different research projects. These are the first NSF RUDICS deployments for projects using the Department of Defense Iridium gateway, which allows for unlimited connection time at a flat monthly rate for US government users. The first project is O-Buoy, an IPY-OASIS project for self-contained, autonomous observations of atmospheric chemical species in the polar marine boundary layer. The second project is collection of low-power instrument towers on Alaska's North Slope at Imnavait Creek, part of the Arctic Observation Network (AON). Lastly, the autonomous instrument platform at Ivotuk, Alaska, uses RUDICS to provide telemetry about the renewable energy systems. A set of real-time web displays allow researchers for each project to monitor their remote sites and access real-time data.

Valentic, T.; Stehle, R.

2008-12-01

415

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. PMID:19325819

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

2008-01-01

416

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

NASA Astrophysics Data System (ADS)

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

Xu, Lingzhe; Yang, Shihai

2010-07-01

417

In-situ study of hydride precipitation kinetics and re-orientation in Zircaloy using synchrotron radiation  

E-print Network

, mechanical resistance, especially in degradation processes such as delayed hydride cracking. The hydride in previously hydrided Zircaloy samples. The hydrogen solubility limit observed in situ was 1 #12;found in light water reactors (LWR) causes hydrogen pickup into the zirconium alloy cladding of the reactor fuel

Motta, Arthur T.

418

Performance improvement analysis of boiling water reactors by incorporation of hydride fuel  

Microsoft Academic Search

The feasibility of improving the neutronic characteristics of boiling water reactors (BWR) by using U–Zr hydride fuel is studied. Several modified BWR fuel assembly designs are considered. These include designs in which hydride fuel rods replace water rods only, replace water rods and a fraction of the oxide fuel rods, replace oxide fuel in the upper half of all the

Wang Kan; Greenspan Ehud

2004-01-01

419

Complex Hydrides for Hydrogen Storage Darlene K. Slattery and Michael D. Hampton  

E-print Network

Complex Hydrides for Hydrogen Storage Darlene K. Slattery and Michael D. Hampton Florida Solar Energy Center 1679 Clearlake Road Cocoa, FL 32922 Abstract Complex hydrides, containing a minimum of 7.5 wt% hydrogen, are being investigated as hydrogen storage compounds for automotive use. As a new

420

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

421

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

422

Fermi levels of FCC and FCT hydrides of Ti and Zr  

NASA Astrophysics Data System (ADS)

Measurements of the work functions of films of TiH x and ZrH x during the FCC/FCT transition have given the change of Fermi level between these two phases of the hydrides. The results agree with modern calculations of the band structures of these hydrides.

Kandasamy, K.; Surplice, N. A.

1984-03-01

423

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

DOEpatents

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.

Zidan, Ragaiy (Aiken, SC); Ritter, James A. (Lexington, SC); Ebner, Armin D. (Lexington, SC); Wang, Jun (Columbia, SC); Holland, Charles E. (Cayce, SC)

2008-06-10

424

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

425

Theory of the chemical bond. V. Bond polarities of post-transition hydrides  

Microsoft Academic Search

A classical derivation of a dipole moment model derived earlier by a quantum mechanical implicit perturbation technique is given. This model is used to determine the bond polarities of the post transition (Groups IIIA–VIIA) hydrides. The polarity measures the extent of charge transfer in a bond. Polarities of alkali halides and posttransition hydrides are used to illustrate the gradual change

Robert L. Matcha; Stephen C. King; B. M. Pettitt

1980-01-01

426

Theory of the chemical bond. V. Bond polarities of post-transition hydrides  

Microsoft Academic Search

A classical derivation of a dipole moment model derived earlier by a quantum mechanical implicit perturbation technique is given. This model is used to determine the bond polarities of the post transition (Groups IIIA-VIIA) hydrides. The polarity measures the extent of charge transfer in a bond. Polarities of alkali halides and posttransition hydrides are used to illustrate the gradual change

Robert L. Matcha; Stephen C. King; B. M. Pettitt

1980-01-01

427

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

428

Iridium abundance anomaly at the palynological Cretaceous-tertiary boundary in northern New Mexico  

SciTech Connect

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

Orth, C.J. (Los Alamos National Lab., NM); Gilmore, J.S.; Knight, J.D.; Pillmore, C.L.; Tschudy, R.H.; Fassett, J.E.

1981-12-18

429

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

USGS Publications Warehouse

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

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

1981-01-01

430

Iridium(III)-Catalyzed C-7 Selective C-H Alkynylation of Indolines at Room Temperature.  

PubMed

An iridium-catalyzed direct C-7 selective C-H alkynylation of indolines at room temperature, for the first time, has been developed via C-H bond activation. Furthermore, the first example of direct C-H alkynylation of carbazoles at the C1 position is also achieved. More importantly, the resulting product can be readily transformed into C7-alkynylated indoles, further widening the C-7 derivatization of indoles and highlighting the synthetic utility of this methodology. PMID:25587810

Wu, Yunxiang; Yang, Yaxi; Zhou, Bing; Li, Yuanchao

2015-02-01

431

Surface Diffusion on Iridium Surfaces: the Discovery of a New Surface Diffusion Mechanism  

Microsoft Academic Search

Self- and hetero-surface diffusion on iridium surfaces have been studied with field ion microscope. For self-diffusion, an Ir adatom on Ir(111) surface diffuses along the smoothest closely packed channel direction by the ordinary atomic hopping mechanism; on Ir(001) surface an Ir adatom is surprisingly found to jump along the directions instead of the smoother closely packed atomic-channel directions by the

Chonglin Chen

1994-01-01

432

Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation  

Microsoft Academic Search

Microelectrodes using activated iridium oxide (AIROF) charge-injection coatings have been pulsed in cat cortex at levels from near-threshold for neural excitation to the reported in vitro electrochemical charge-injection limits of AIROF. The microelectrodes were subjected to continuous biphasic current pulsing, using an 0.4V (versus Ag|AgCl) anodic bias with equal cathodal and anodal pulse widths, for periods up to 7h at

Stuart F Cogan; Andrew A Guzelian; William F Agnew; Ted G. H Yuen; Douglas B McCreery

2004-01-01

433

Activated iridium oxide films fabricated by asymmetric pulses for electrical neural microstimulation and recording  

Microsoft Academic Search

An efficient and reliable electrochemical method for preparation of activated iridium oxide films (AIROFs) microelectrodes by applying an asymmetric pulse train in Na2HPO4 solution was reported. The AIROFs microelectrodes exhibited a very high safe charge injection (Qinj) limit (?4.1mC\\/cm2), as well as excellent mechanical and electrochemical stability. Electrode impedance at 1kHz has been significantly reduced by ?92%. All of these

Yi Lu; Zhengxu Cai; Yuliang Cao; Hanxi Yang; Yanwen Y. Duan

2008-01-01

434

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

Microsoft Academic Search

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

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

1995-01-01

435

Substrate temperature dependent structural, optical and electrical properties of spray deposited iridium oxide thin films  

Microsoft Academic Search

Iridium oxide thin films were deposited onto the glass substrates by spray pyrolysis technique (SPT) using aqueous solution of IrCl3·3H2O at various substrate (deposition) temperatures ranging from 250 to 400°C. Emission of both physisorbed and chemisorbed water takes place during thermal decomposition process and Ir2O3 forms below 600°C, above which dehydrated IrO2 formation takes place. The as-deposited samples at all

R. K Kawar; P. S Chigare; P. S Patil

2003-01-01

436

A Cascade Isomerization/Prins Strategy through Iridium(III)/Brønsted Acid Cooperative Catalysis**  

PubMed Central

A mild and efficient isomerization/protonation sequence involving an appropriately functionalized indole precursor to generate a wide variety of pyran-fused indoles utilizing cooperative catalysis between cationic iridium (III) and bismuth triflate has been developed. Three distinct cyclization manifolds lead to bioactive scaffolds that can be obtained in good yields. In addition, N-substituted indoles can be synthesized enantioselectively via an oxocarbenium• chiral phosphate counterion strategy. PMID:24218144

Lombardo, Vince M.; Thomas, Christopher D.; Scheidt, Karl A.

2014-01-01

437

Study of the Electronic Structure and Physical Properties of the Iridium Based Intermetallic Compounds Under Pressure  

Microsoft Academic Search

The electronic structure of the Iridium based L12 intermetallic compounds (A3B) such as Ir3Ti, Ir3Zr, Ir3Hf, Ir3V, Ir3Nb and Ir3Ta, which have wide applications as high temperature structural materials are studied by means of Self-Consistent Tight Binding Linear Muffin Tin Orbital (TB-LMTO) method. These compounds are found to crystallize in the Cu3Au type structure. The total energies are calculated as

M. Sundareswari; M. Rajagopalan

2005-01-01

438

Applications of Osmium and Iridium as Biogeochemical Tracers in the Environment  

Microsoft Academic Search

\\u000a Osmium (Os) and Iridium (Ir) and are among the rarest elements on the surface of the earth and ones whose applications in\\u000a modern industry are quite limited. However, their environmental burden has been increasing as they occur in nature with other\\u000a platinum group elements, which have a wide variety of industrial, chemical, electrical and pharmaceutical applications. This\\u000a review traces the

Mukul Sharma

439

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

Microsoft Academic Search

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

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

2002-01-01

440

Iridium-Catalyzed Selective Hydrogenation of 3-Hydroxypyridinium Salts: A Facile Synthesis of Piperidin-3-ones.  

PubMed

The selective hydrogenation of 3-hydroxypyridinium salts has been achieved using a homogeneous iridium catalyst, providing a direct access to 2- and 4-substituted piperidin-3-one derivatives with high yields, which are important organic synthetic intermediates and the prevalent structural motifs in pharmaceutical agents. Mild reaction conditions, high chemoselectivity, and easy scalability make this reaction highly practical for the synthesis of piperidin-3-ones. PMID:25803488

Huang, Wen-Xue; Wu, Bo; Gao, Xiang; Chen, Mu-Wang; Wang, Baomin; Zhou, Yong-Gui

2015-04-01

441

Anal. Chem. 1993, 65, 375-379 Analytical Utility of the Iridium-Based Mercury  

E-print Network

Anal. Chem. 1993, 65, 375-379 Analytical Utility of the Iridium-Based Mercury,134,1191- 1193. (3) Pendley, P. D.; Abruiia, H. D. Anal. Chem. 1990, 62,782-784. (4) Singleton, S. T.;O'Dea, J. J.;Osteryoung,J.Anal.Chen.1989,61, (5) Penner, R. M.; Heben, M. J.; Lewis,N. S. Anal. Chem. 1989, 61, (6) Wightman, R. M. Science

Kounaves, Samuel P.

442

Transformation of a Cp*-iridium(III) precatalyst for water oxidation when exposed to oxidative stress.  

PubMed

The reaction of [Cp*Ir(bzpy)NO3 ] (1; bzpy=2-benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water-oxidation catalyst, with several oxidants (H2 O2 , NaIO4 , cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI-MS techniques provided evidence for the formation of many species that all had the intact Ir-bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen-Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a ?(3) interaction with iridium (2?a). Formal addition of H2 O to 2?a or H2 O2 to 1 leads to 2?b, in which a double MeCOH functionalization of Cp* is present with one MeCOH engaged in an interaction with iridium. The structure of 2?b was unambiguously determined in the solid state and in solution by X-ray single-crystal diffractometry and advanced NMR spectroscopic techniques, respectively. Further oxidation led to the opening of Cp* and transformation of the diol into a diketone with one carbonyl coordinated at the metal (2?c). A ?(3) interaction between the three non-oxygenated carbons of "ex-Cp*" and iridium is also present in both 2?b and 2?c. Isolated 2?b and mixtures of 2?a-c species were tested in water-oxidation catalysis by using CAN as sacrificial oxidant. They showed substantially the same activity than 1 (turnover frequency values ranged from 9 to 14?min(-1) ). PMID:24523138

Zuccaccia, Cristiano; Bellachioma, Gianfranco; Bortolini, Olga; Bucci, Alberto; Savini, Arianna; Macchioni, Alceo

2014-03-17

443

Photocatalytic water oxidation by Nafion-stabilized iridium oxide colloids Michikazu Hara and Thomas E. Mallouk*  

E-print Network

Photocatalytic water oxidation by Nafion-stabilized iridium oxide colloids Michikazu Hara IrO2·xH2O stabilized by soluble Nafion, tris(2,2A-bipyridyl)ruthenium(II), and persulfate efficiently conventional catalysts. In this paper, we report O2 evolution from a [Ru(bpy)3]2+­Nafion- stabilized IrO2·xH2O

444

Highly efficient deep-blue phosphorescence from heptafluoropropyl-substituted iridium complexes.  

PubMed

New deep-blue iridium complexes, consisting of a heptafluoropropyl (HFP) substituent at the 3' position of 2',4''-difluorophenyl, have a deep HOMO level and decreased shoulder electronic transition and inhibit self-quenching due to the sterically hindered group without conjugation. An OLED using (HFP)2Ir(mpic) exhibited a maximum EQE of 21.4% with a CIE of (0.146, 0.165). PMID:25407660

Kim, Jung-Bum; Han, Seung-Hoon; Yang, Kiyull; Kwon, Soon-Ki; Kim, Jang-Joo; Kim, Yun-Hi

2015-01-01

445

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

446

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

447

Theoretical study of new blue iridium complexes comprising a bipyridine derivative and various ancillary ligands.  

PubMed

New blue emitting ligand Iridium(III) complexes with two phosphines trans to each other and two ancillary ligands, such as Ir(dfpypy)(PPh3)2(H)(CI) and Ir(dfpypy)(PPh3)2(H)(CN), [dfpypy = 2,6-difluoro-3-(pyridin-2-yl)pyridine] were designed and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To gain insight into the factors responsible for the emission color change and the different luminescence efficiency, we performed the DFT and TD-DFT calculations on the ground and excited states of these phosphors. (1) The fluorine-substituted dfpypy ligand lower the HOMO energy levels because a N of the pyridyl ligand is more electronegative than a C of the nonsubstituted phenyl ligand and also (2) mono-cyclometalated Iridium(III) complexes using two phosphines trans to each other increased HOMO-LUMO gap by strong field effects of ancillary ligands. From these results, we discuss how the dfpypy ligand and the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. As the maximum emission spectra of FIrpic known as blue phosphorescence material is about 475 nm. The resulting Iridium(III) complexes, Ir(dfpypy)(PPh3)2(H)(CN), would appear pure blue region about 415 nm with more intensified efficiency. PMID:24758024

Park, Se Won; Kim, Young Sik

2014-07-01

448

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, H.T., Jr.

1987-01-01

449

The new iridium complexes involving pyridylpyridine derivatives for the saturated blue emission.  

PubMed

To obtain a saturated blue phosphorescent material with a good color purity, we have synthesized the new blue emitting iridium complexes with 2, 6-difluoro-3-(4-methylpyridin-2-yl)pyridine (4-Me-dfpypy) as a main ligand. We expected that the LUMO energy levels of the complex might increase upon introduction of an electron donating group such as a methyl group to the pyridyl moieties of the ligand, leading to a wide energy gap of the complex to give the saturated blue emission. We have also introduced a variety of the ancillary ligands to the iridium center to compare the effect of the ancillary ligards on the emission of their complexes. The resulting iridium complexes, Ir(4-Me-dfpypy)3, Ir(4-Me-dfpypy)2(acac), Ir(4-Me-dfpypy)2(pic) and Ir(4-Me-dfpypy)2(trzl-CH3) where acac, pic, and trzl-CH3 represent acetylacetonate, picolinate, and 2-(5-methyl-2H-1,2,4-triazol-3-yl) pyridinate, respectively exhibited the blue emission at 451, 447, 440 and 425 nm in CH2Cl2 solution. The organic light emitting device (OLED) employing homoleptic Ir(4-Me-dfpypy), as the blue dopant was prepared and their electroluminescence was investigated. Ir(4-Me-dfpypy)3 exhibited the blue emission of CIE coordinates (0.22, 0.32). PMID:22524037

Park, Hye Rim; Lim, Dong Hwan; Kim, Young Kwan; Ha, Yunkyoung

2012-01-01

450

Electrochemical activation of Cp* iridium complexes for electrode-driven water-oxidation catalysis.  

PubMed

Organometallic iridium complexes bearing oxidatively stable chelate ligands are precursors for efficient homogeneous water-oxidation catalysts (WOCs), but their activity in oxygen evolution has so far been studied almost exclusively with sacrificial chemical oxidants. In this report, we study the electrochemical activation of Cp*Ir complexes and demonstrate true electrode-driven water oxidation catalyzed by a homogeneous iridium species in solution. Whereas the Cp* precursors exhibit no measurable O2-evolution activity, the molecular species formed after their oxidative activation are highly active homogeneous WOCs, capable of electrode-driven O2 evolution with high Faradaic efficiency. We have ruled out the formation of heterogeneous iridium oxides, either as colloids in solution or as deposits on the surface of the electrode, and found indication that the conversion of the precursor to the active molecular species occurs by a similar process whether carried out by chemical or electrochemical methods. This work makes these WOCs more practical for application in photoelectrochemical dyads for light-driven water splitting. PMID:25188635

Thomsen, Julianne M; Sheehan, Stafford W; Hashmi, Sara M; Campos, Jesús; Hintermair, Ulrich; Crabtree, Robert H; Brudvig, Gary W

2014-10-01

451

Direct Observation of Reversible Electronic Energy Transfer Involving an Iridium Center  

PubMed Central

A cyclometalated iridium complex is reported where the core complex comprises naphthylpyridine as the main ligand and the ancillary 2,2?-bipyridine ligand is attached to a pyrene unit by a short alkyl bridge. To obtain the complex with satisfactory purity, it was necessary to modify the standard synthesis (direct reaction of the ancillary ligand with the chloro-bridged iridium dimer) to a method harnessing an intermediate tetramethylheptanolate-based complex, which was subjected to acid-promoted removal of the ancillary ligand and subsequent complexation. The photophysical behavior of the bichromophoric complex and a model complex without the pendant pyrene were studied using steady-state and time-resolved spectroscopies. Reversible electronic energy transfer (REET) is demonstrated, uniquely with an emissive cyclometalated iridium center and an adjacent organic chromophore. After excited-state equilibration is established (5 ns) as a result of REET, extremely long luminescence lifetimes of up to 225 ?s result, compared to 8.3 ?s for the model complex, without diminishing the emission quantum yield. As a result, remarkably high oxygen sensitivity is observed in both solution and polymeric matrices. PMID:24555716

2014-01-01

452

Half-sandwich iridium complexes for homogeneous water-oxidation catalysis.  

PubMed

Iridium half-sandwich complexes of the types Cp*Ir(N-C)X, [Cp*Ir(N-N)X]X, and [CpIr(N-N)X]X are catalyst precursors for the homogeneous oxidation of water to dioxygen. Kinetic studies with cerium(IV) ammonium nitrate as primary oxidant show that oxygen evolution is rapid and continues over many hours. In addition, [Cp*Ir(H(2)O)(3)]SO(4) and [(Cp*Ir)(2)(?-OH)(3)]OH can show even higher turnover frequencies (up to 20 min(-1) at pH 0.89). Aqueous electrochemical studies on the cationic complexes having chelate ligands show catalytic oxidation at pH > 7; conversely, at low pH, there are no oxidation waves up to 1.5 V vs NHE for the complexes. H(2)(18)O isotope incorporation studies demonstrate that water is the source of oxygen atoms during cerium(IV)-driven catalysis. DFT calculations and kinetic experiments, including kinetic-isotope-effect studies, suggest a mechanism for homogeneous iridium-catalyzed water oxidation and contribute to the determination of the rate-determining step. The kinetic experiments also help distinguish the active homogeneous catalyst from heterogeneous nanoparticulate iridium dioxide. PMID:20964386

Blakemore, James D; Schley, Nathan D; Balcells, David; Hull, Jonathan F; Olack, Gerard W; Incarvito, Christopher D; Eisenstein, Odile; Brudvig, Gary W; Crabtree, Robert H

2010-11-17

453

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

PubMed

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

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

2012-09-01

454

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

455

Getting metal-hydrides to do what you want them to  

SciTech Connect

With the discovery of AB/sub 5/ compounds, intermetallic hydrides with unusual properties began to be developed (H dissociation pressures of one to several atmospheres, extremely rapid and reversible adsorption/desorption very large amounts of H adsorbed). This paper reviews the factors that must be controlled in order to modify these hydrides to make them useful. The system LaNi/sub 5/ + H/sub 2/ is used as example. Use of AB/sub 5/ hydrides to construct a chemical heat pumps is discussed. Results of a systematic study substituting Al for Ni are reported; the HYCSOS pump is described briefly. Use of hydrides as hydrogen getters (substituted ZrV/sub 2/) is also discussed. Finally, possible developments in intermetallic hydride research in the 1980's and the hydrogen economy are discussed. 10 figures. (DLC)

Gruen, D.M.

1981-01-01

456

Mathematical modeling of the nickel/metal hydride battery system  

SciTech Connect

A group of compounds referred to as metal hydrides, when used as electrode materials, is a less toxic alternative to the cadmium hydroxide electrode found in nickel/cadmium secondary battery systems. For this and other reasons, the nickel/metal hydride battery system is becoming a popular rechargeable battery for electric vehicle and consumer electronics applications. A model of this battery system is presented. Specifically the metal hydride material, LaNi{sub 5}H{sub 6}, is chosen for investigation due to the wealth of information available in the literature on this compound. The model results are compared to experiments found in the literature. Fundamental analyses as well as engineering optimizations are performed from the results of the battery model. In order to examine diffusion limitations in the nickel oxide electrode, a ``pseudo 2-D model`` is developed. This model allows for the theoretical examination of the effects of a diffusion coefficient that is a function of the state of charge of the active material. It is found using present data from the literature that diffusion in the solid phase is usually not an important limitation in the nickel oxide electrode. This finding is contrary to the conclusions reached by other authors. Although diffusion in the nickel oxide active material is treated rigorously with the pseudo 2-D model, a general methodology is presented for determining the best constant diffusion coefficient to use in a standard one-dimensional battery model. The diffusion coefficients determined by this method are shown to be able to partially capture the behavior that results from a diffusion coefficient that varies with the state of charge of the active material.

Paxton, B K [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

1995-09-01

457

Improvement in thallium hydride generation using iodide and Rhodamine B.  

PubMed

A continuous flow hydride generation atomic absorption spectrometry (CF-HG-AAS) system was used to study the enhancement effect of different substances for conventional chemical HG of thallium. At room temperature, the acidified sample solution containing the respective enhancement reagent merged with the aqueous NaBH4 solution. The generated thallium hydride was stripped from the eluent solution by the addition of a nitrogen flow and thereafter the bulk phases were separated in a gas-liquid separator. The main factors under study were concentration and type of enhancement reagent (Te, iodide added as KI, Rhodamine B, malachite green and crystal violet) and acid (HCl, H2SO4 or HNO3). Other parameters affecting the thallium hydride generation, such as: NaBH4 concentration, carrier gas flow rate, length of reaction-mixing coil and reagents flow rates, were studied and optimized. Among the enhancement reagents tested, the combination of Rhodamine B and iodide produced the best results. A linear response was obtained between the detection limit (LOD (3?)) of 1.5?gL(-1) and 1000?gL(-1). The RSD% (n=10) for a solution containing 15?gL(-1) of Tl was 2.9%. The recoveries of thallium in environmental water samples by spiking the samples with 10 and 20µgL(-1) of Tl were in the 97.0-102.5% range. The accuracy for Tl determination was further confirmed by the analysis of a water standard reference material (1643e form NIST, USA). Finally, it was demonstrated that malachite green and crystal violet showed similar enhancement effect like Rhodamine B for thallium HG. PMID:25702995

Picón, David; Carrero, Pablo; Valero, Maribel; de Peña, Yaneira Petit; Gutiérrez, Luís

2015-05-01

458

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

459

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

460

Stress analysis of hydride bed vessels used for tritium storage  

SciTech Connect

A prototype hydride storage bed, using LaNi{sub 4.25}Al{sub 0.75} as the storage material, was fitted with strain gages to measure strains occurring in the stainless steel bed vessel caused by expansion of the storage powder upon uptake of hydrogen. The strain remained low in the bed as hydrogen was added, up to a bed loading of about 0.5 hydrogen to metal atom ratio (H/M). The strain then increased with increasing hydrogen loading ({approximately} 0.8 H/M). Different locations exhibited greatly different levels of maximum strain. In no case was the design stress of the vessel exceeded.

McKillip, S.T.; Bannister, C.E.; Clark, E.A.

1991-12-31

461

Stress analysis of hydride bed vessels used for tritium storage  

SciTech Connect

A prototype hydride storage bed, using LaNi{sub 4.25}Al{sub 0.75} as the storage material, was fitted with strain gages to measure strains occurring in the stainless steel bed vessel caused by expansion of the storage powder upon uptake of hydrogen. The strain remained low in the bed as hydrogen was added, up to a bed loading of about 0.5 hydrogen to metal atom ratio (H/M). The strain then increased with increasing hydrogen loading ({approximately} 0.8 H/M). Different locations exhibited greatly different levels of maximum strain. In no case was the design stress of the vessel exceeded.

McKillip, S.T.; Bannister, C.E.; Clark, E.A.

1991-01-01

462

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

463

Bipolar Nickel-Metal Hydride Battery Development Project  

NASA Technical Reports Server (NTRS)

This paper reviews the development of the Electro Energy, Inc.'s bipolar nickel metal hydride battery. The advantages of the design are that each cell is individually sealed, and that there are no external cell terminals, no electrode current collectors, it is compatible with plastic bonded electrodes, adaptable to heat transfer fins, scalable to large area, capacity and high voltage. The design will allow for automated flexible manufacturing, improved energy and power density and lower cost. The development and testing of the battery's component are described. Graphic presentation of the results of many of the tests are included.

Cole, John H.

1999-01-01

464

The calculated rovibronic spectrum of scandium hydride, ScH  

E-print Network

The electronic structure of six low-lying electronic states of scandium hydride, $X\\,{}^{1}\\Sigma^+$, $a\\,{}^{3}\\Delta$, $b\\,{}^{3}\\Pi$, $A\\,{}^{1}\\Delta$ $c\\,{}^{3}\\Sigma^+$, and $B\\,{}^{1}\\Pi$, is studied using multi-reference configuration interaction as a function of bond length. Diagonal and off-diagonal dipole moment, spin-orbit coupling and electronic angular momentum curves are also computed. The results are benchmarked against experimental measurements and calculations on atomic scandium. The resulting curves are used to compute a line list of molecular ro-vibronic transitions for $^{45}$ScH.

Lodi, Lorenzo; Tennyson\\, Jonathan

2015-01-01

465

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

466

Statistical theory of forming structural vacancies in palladium hydride  

NASA Astrophysics Data System (ADS)

Based on molecular-kinetic representations, the theory of forming structural vacancies and vacant-ordered superstructure of Cu3Au type in palladium hydride is developed. Free energies of PdH and Pd3VH4 phases are calculated. The constitution diagram is constructed that determines ranges of temperature and concentration in which phases with A1 and L12 structures are formed and regions of two A1 + L12 phases are realized. Results of theoretical calculations are in agreement with the available experimental data.

Zaginaichenko, S. Yu.; Matysina, Z. A.; Shchur, D. V.

2011-07-01

467

Geoneutrinos and Hydridic Earth (or primordially hydrogen-rich planet)  

NASA Astrophysics Data System (ADS)

Geoneutrino is a new channel of information about geochemical composition of the Earth. We analyzed here the following problem. What statistics do we need to distinguish between predictions of Bulk Silicate Earth model and Hydridic Earth model for Th/U signal ratio? We obtained the simple formula for estimation of error of Th/U signal ratio. Our calculations show that we need more than 22 kt · year exposition for Gran-Sasso underground laboratory and Sudbury Neutrino Observatory. We need more than 27 kt · year exposition for Kamioka site in the case of stopping of all Japanese nuclear power plants.

Bezrukov, L.; Sinev, V.

2015-03-01

468

Metal hydride based isotope separation: Large-scale operations  

SciTech Connect

A program to develop a metal hydride based hydrogen isotope separation process began at the Savannah River Laboratory in 1980. This semi-continuous gas chromatographic separation process will be used in new tritium facilities at the Savannah River Site. A tritium production unit is scheduled to start operation in 1993. An experimental, large-scale unit is currently being tested using protium and deuterium. Operation of the large-scale unit has demonstrated separation of mixed hydrogen isotopes (55% protium and 45% deuterium), resulting in protium and deuterium product streams with purities better than 99.5%. 3 refs., 4 figs.

Horen, A.S.; Lee, Myung W.

1991-12-31

469

Metal hydride based isotope separation: Large-scale operations  

SciTech Connect

A program to develop a metal hydride based hydrogen isotope separation process began at the Savannah River Laboratory in 1980. This semi-continuous gas chromatographic separation process will be used in new tritium facilities at the Savannah River Site. A tritium production unit is scheduled to start operation in 1993. An experimental, large-scale unit is currently being tested using protium and deuterium. Operation of the large-scale unit has demonstrated separation of mixed hydrogen isotopes (55% protium and 45% deuterium), resulting in protium and deuterium product streams with purities better than 99.5%. 3 refs., 4 figs.

Horen, A.S.; Lee, Myung W.

1991-01-01

470

Kinetics of Electron Transfer and Oxygen Evolution in the Reaction of [Ru(bpy)3]3+ with Colloidal Iridium Oxide  

E-print Network

Iridium Oxide Natalie D. Morris, Masahiro Suzuki, and Thomas E. Mallouk* Department of Chemistry the colloidal iridium oxide catalysts originally investigated by Harriman and co-workers23-25 for the water to oxidation of Ir(III) to Ir(IV). Further oxidation of surface Ir atoms occurs concomitantly with oxygen

471

Regio- and enantioselective allylic substitution with less active N- or O-nucleophiles catalyzed by iridium-complex of bis(oxazolinyl)pyridine.  

PubMed

The utility of hydroxylamines as nitrogen nucleophiles was investigated in the iridium-catalyzed regio- and enantioselective allylic substitution. Allylic substitution with hydroxylamines proceeded with good enantioselectivities by using the iridium-complex of bis(oxazolinyl)pyridine ligand. The good regio- and enantioselectivities were also achieved in the reaction with alkylamines, p-anisidine, and 4-methoxyphenol. PMID:21628906

Miyabe, Hideto; Moriyama, Katsuhiko; Takemoto, Yoshiji

2011-01-01

472

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

E-print Network

Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl and emission, and a shorter luminescence lifetime. Cyclometallated iridium(III) complexes are well known in optoelectronic devices2 and as new luminescent sensors for analytes,3 including protons,4 ions5 and biomolecules

Boyer, Edmond

473

Reactions of ruthenium hydrides with ethyl-vinyl sulfide.  

PubMed

The Ru-hydride precursors (Im(OMe)2)(PPh3)2RuHCl () and (Me2Im(OMe)2)(PPh3)2RuHCl () reacted with ethyl-vinyl-sulfide to give ((MeOCH2CH2)C3H2N2(CH2CH(OMe))RuCl(PPh3)2 () and ((MeOCH2CH2)C3Me2N2(CH2CH(OMe))RuCl(PPh3)2 (), respectively. Dissolution of () in C6D6 prompts formation of ((MeOCH2CH2)C5H6N2(CHCH)RuCl(PPh3)2 (). The analogous reactions of the bis-carbene Ru-hydride precursors (Im(OMe)2)(IMes)(PPh3)RuHCl (), (Im(OMe)2)(SIMes)(PPh3)RuHCl () and (Im(OMe)2)(IMes-Cl2)(PPh3)RuHCl () gave ((MeOCH2CH2)C3H2N2(CHCH)RuCl(PPh3)(NHC) (NHC = IMes (), SIMes (), IMes-Cl2 (), respectively. The formation of compounds () and () is thought to go through an initial insertion of the vinyl-fragment into the Ru-H prompting subsequent C-H activation and loss of diethyl sulfide. This yields () and (), while subsequent loss of methanol yields () and (-). PMID:24441082

Dahcheh, Fatme; Stephan, Douglas W

2014-03-01

474

Multi-scale characterization of nanostructured sodium aluminum hydride  

NASA Astrophysics Data System (ADS)

Complex metal hydrides are the most promising candidate materials for onboard hydrogen storage. The practicality of this class of materials is counter-poised on three critical attributes: reversible hydrogen storage capacity, high hydrogen uptake/release kinetics, and favorable hydrogen uptake/release thermodynamics. While a majority of modern metallic hydrides that are being considered are those that meet the criteria of high theoretical storage capacity, the challenges lie in addressing poor kinetics, thermodynamics, and reversibility. One emerging strategy to resolve these issues is via nanostructuring or nano-confinement of complex hydrides. By down-sizing and scaffolding them to retain their nano-dimensions, these materials are expected to improve in performance and reversibility. This area of research has garnered immense interest lately and there is active research being pursued to address various aspects of nanostructured complex hydrides. The research effort documented here is focused on a detailed investigation of the effects of nano-confinement on aspects such as the long range atomic hydrogen diffusivities, localized hydrogen dynamics, microstructure, and dehydrogenation mechanism of sodium alanate. A wide variety of microporous and mesoporous materials (metal organic frameworks, porous silica and alumina) were investigated as scaffolds and the synthesis routes to achieve maximum pore-loading are discussed. Wet solution infiltration technique was adopted using tetrahydrofuran as the medium and the precursor concentrations were found to have a major role in achieving maximum pore loading. These concentrations were optimized for each scaffold with varying pore sizes and confinement was quantitatively characterized by measuring the loss in specific surface area. This work is also aimed at utilizing neutron and synchrotron x-ray characterization techniques to study and correlate multi-scale material properties and phenomena. Some of the most advanced instruments were utilized for this work and their data collection and analysis are reported. Quasielastic neutron scattering experiments were conducted at NIST Center for Neutron Research to characterize atomic hydrogen diffusion in bulk and nano-confined NaAlH4. It was observed that upon confinement of NaAlH4, a significantly higher fraction of hydrogen atoms were involved in diffusive motion on the pico-second to nano-second timescales. However, the confinement had no impact on the lattice diffusivities (jump/hopping rates) of atomic hydrogen, indicating that the improved hydrogen release rates were not due to any kinetic destabilization effects. Instead, the investigation strongly suggested thermodynamic destabilization as the major effect of nano-confinement. The local interaction of the metal sites in metal organic frameworks with the infiltrated hydride was studied using extended x-ray absorption spectroscopy technique. The experiments were conducted at Center for Advanced Microstructures and Devices at Louisiana State University. The metal sites were found to be chemically un-altered, hence ruling out any catalytic role in the dehydrogenation at room temperatures. The fractal morphology of NaAlH4 was characterized by ultra-small angle x-ray scattering experiments performed at Argonne National Lab. The studies quantitatively estimated the extent of densification in the course of one desorption cycle. The particle sizes were found to increase two-fold during heat treatment. Also, the nano-confinement procedure was shown to produce dense mass fractals as opposed to pristine NaAlH4, exhibiting a surface fractal morphology. Based on this finding, a new method to identify confined material from un-confined material in nano-composites was developed and is presented. Preliminary results of modeling and correlating multi-scale phenomena using a phase-field approach are also presented as the foundation for future work.

NaraseGowda, Shathabish

475

Studies of hydride formation and superconductivity in hydrides of alloys Th-M /M = La, Y, Ce, Zr and Bi/  

NASA Technical Reports Server (NTRS)

In order to gain a better insight into both the unusual composition of ThH15 and its superconductivity, an experimental study was conducted to assess the influence of partial replacement of Th in Th4H15 by elements which allow for a systematic alteration of spatial and electronic effects. For this purpose, substituent elements with the same number of valence electrons (4) but of smaller size (Zr) as well as elements with a smaller number of valence electrons (3) and either larger (La) or smaller size (Y) were selected. A few data with Ce and Bi as substituent atoms are also included. The matrix alloys for hydriding were obtained by induction melting under Ar in water-cooled Cu boats. Superconducting transition temperatures are found to decrease on substitution for Th in Th4H15. Hydrides derived from LaH3 by substitution for La by Th do not become superconducting. It is suggested that superconductivity in Th4H15 is connected with a deviation from the exact stoichiometry of Th4H15. A model of unsatisfied valencies may be of more general validity in predicting superconductivity.

Oesterreicher, H.; Clinton, J.; Misroch, M.

1977-01-01

476

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

477

Electrochemical and spectroelectrochemical characterization of an iridium-based molecular catalyst for water splitting: turnover frequencies, stability, and electrolyte effects.  

PubMed

We present a systematic electrochemical and spectroelectrochemical study of the catalytic activity for water oxidation of an iridium-N-dimethylimidazolin-2-ylidene (Ir-NHC-Me2) complex adsorbed on a polycrystalline gold electrode. The work aims to understand the effect of the electrolyte properties (anions and acidity) on the activity of the molecular catalyst and check its stability toward decomposition. Our results show that the iridium complex displays a very strong dependence on the electrolyte properties such that large enhancements in catalytic activity may be obtained by adequately choosing pH and anions in the electrolyte. The stability of the adsorbed compound was investigated i