These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Photoswitchable hydride transfer from iridium to 1-methylnicotinamide rationalized by thermochemical cycles.  

PubMed

Visible light-triggered hydride transfer from [Cp*Ir(bpy)(H)](+) (1) to organic acids and 1-methylnicotinamide (MNA(+)) is reported (Cp* = pentamethylcyclopentadienyl; bpy = 2,2'-bipyridine). A new thermochemical cycle for determining excited-state hydride donor ability (hydricity) predicted that 1 would be an incredibly potent photohydride in acetonitrile. Phototriggered H2 release was indeed observed from 1 in the presence of various organic acids, providing experimental evidence for an increase in hydricity of at least 18 kcal/mol in the excited state. The rate and product selectivity of hydride transfer to MNA(+) are photoswitchable: 1,4-dihydro-1-methylnicotinamide forms slowly in the dark but rapidly under illumination, and photolysis can also produce doubly reduced 1,4,5,6-tetrahydro-1-methylnicotinamide. PMID:25299959

Barrett, Seth M; Pitman, Catherine L; Walden, Andrew G; Miller, Alexander J M

2014-10-22

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

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

5

Processing of Iridium and Iridium Alloys  

SciTech Connect

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

Ohriner, Evan Keith [ORNL

2008-01-01

6

Iridium(III) azuliporphyrins.  

PubMed

Azuliporphyrins were reacted with [Ir(COD)Cl](2) in refluxing o- or p-xylene to give novel iridium(III) derivatives that regioselectively incorporated an oxidized solvent molecule. The iridium(III) is inserted within the porphyrinoid macrocycle and possesses an additional apical acyl unit. PMID:23111425

Lash, Timothy D; Pokharel, Komal; Zeller, Matthias; Ferrence, Gregory M

2012-12-14

7

The IRIDIUM communications system  

Microsoft Academic Search

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

R. J. Leopold; A. Miller

1993-01-01

8

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

9

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

10

Hydridomethyl iridium complex  

SciTech Connect

This patent describes a hydridomethyl complex of the formula: CpIr(P(R{sub 1}){sub 3})HMe. Cp represents a cyclopentadienyl or alkyl cyclopentadienyl radical; Ir represents an iridium atom; P represents a phosphorus atom; R{sub 1} represents an alkyl group; and Me represents a methyl group.

Bergman, R.G; Buchanan, J.M.; Stryker, J.M.; Wax, M.J.

1989-07-18

11

Mechanistic studies on iridium catalyzed allylic substitution.  

E-print Network

??Mechanistic studies on iridium catalyzed allylic substitution reactions catalyzed by iridium phosphoramidite complexes revealed that the active catalyst is generated through a base assisted cyclometalation… (more)

Madrahimov, Sherzod

2012-01-01

12

Method for refining contaminated iridium  

DOEpatents

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

Heshmatpour, B.; Heestand, R.L.

1982-08-31

13

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

14

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

15

Modelling of hydride cracking  

SciTech Connect

Zirconium alloys may be susceptible to hydride formation under certain service conditions, due to hydrogen diffusion and precipitation in the presence of stress concentrations and temperature gradients. The inhomogeneous brittle hydride platelets that form are modeled as plane defects of zero thickness, with fracture toughness less than that of the matrix. A fracture criterion based on sufficient energy and stress is proposed for either delayed hydride cracking (DHC) under constant loading conditions, or hydride cracking at rising loads, such as in a fracture toughness test. The fracture criterion is validated against available experimental data concerning initiation of hydride fracture in smooth specimens, and DHC in cracked specimens under various loading and temperature conditions.

Zheng, X.J.; Metzger, D.R. [Ontario Hydro Technology, Toronto, Ontario (Canada); Glinka, G.; Dubey, R.N. [Univ. of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering

1996-12-01

16

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

E-print Network

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

Ashley, Michael C. B.

17

Analytical Characterization of Microlithographically Fabricated Iridium-Based Ultramicroelectrode Arrays  

E-print Network

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

Kounaves, Samuel P.

18

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

19

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

20

Multistage metal hydride compressor  

SciTech Connect

Metal hydride compressors can compress hydrogen to high pressures without using mechanical moving parts. They are particularly suited for tritium applications because they require minimal maintenance. A three-stage metal hydride compressor which can compress hydrogen from 14.7 to 20,000 psia has been demonstrated. The design principle and experimental results are presented.

Heung, L.K.

1986-01-01

21

Hysteresis in Metal Hydrides.  

ERIC Educational Resources Information Center

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

Flanagan, Ted B., And Others

1987-01-01

22

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

23

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

24

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

25

Link strategy for the mobile satellite system Iridium  

Microsoft Academic Search

This paper develops crosslink routing strategies for the mobile satellite system Iridium. Motorola's Iridium satellite constellation, based on the orbit design of Adams and Rider [1987] is to provide a mobile satellite service for hand-held personal telephones. The Iridium system will have 66 satellites in 6 orbital planes at an altitude of h=780 km and a minimum elevation angle of

Harald Keller; Horst Salzwedel

1996-01-01

26

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

27

"Globalstar, Iridium and other Satellite-Based Mobile Phone  

E-print Network

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

28

Iridium Model 9500 and 9505 AT Command Compliance  

E-print Network

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

Ashley, Michael C. B.

29

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data uses include platinum-iridium alloys in prosthetic and biomedical devices. Salient Statistics,520 15,600 14,000 Iridium 896 926 1,450 1,810 1,500 Osmium 130 55 73 329 100 Exports, refined: Platinum

30

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

E-print Network

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

31

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

E-print Network

124 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data uses include platinum-iridium alloys in prosthetic and biomedical devices. Salient Statistics,500 8,880 11,400 20,900 5,500 Iridium 1,860 1,950 2,270 2,700 3,500 Osmium 54 71 23 133 70 Exports

32

Compact Helical Ring Antenna for Iridium Communication C. Morlaas1  

E-print Network

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

Paris-Sud XI, Université de

33

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

34

Iridium Anomaly Approximately Synchronous with Terminal Eocene Extinctions  

Microsoft Academic Search

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

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

1982-01-01

35

Mechanically alloyed metal hydride systems  

NASA Astrophysics Data System (ADS)

Mechanosynthesis of metal hydrides is a new field in which important progress has been reported. In this paper, we present recent developments in mechanosynthesis of magnesium-based hydrides for storage applications. The effect of intense milling on magnesium and magnesium hydrides is presented. The influence of various additives on hydrogen-sorption properties is discussed with special emphasis on nanocomposite MgH2+5 at.%V, where hydrogen-storage characteristics, cycling properties and the mechanism of hydrogen desorption are presented. The production of novel nanocrystalline porous structures by mechanical alloying followed by a leaching technique is discussed. Hot ball-milling, as a new method for rapid synthesis of alloys, is also presented. Finally, two other methods of production of metal hydrides are discussed. One is reactive milling where metal hydrides are synthesized by mechanical alloying under hydrogen pressure, while the other is milling elemental hydrides to produce complex hydrides.

Huot, J.; Liang, G.; Schulz, R.

2001-04-01

36

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

37

Iridium satellites light up the sky  

NASA Astrophysics Data System (ADS)

Motorola's Iridium satellite system is the largest and most ambitious of a set of competing satellite-based mobile phone systems. Motorola's objective is to allow handheld mobiles to be used from anywhere on the planet, with the call being routed directly from handset to handset via one or several of the satellites. After a bad start when the first Delta launch failed, Iridium spacecraft have been launched up to five at a time and the system is due to go operational late this year.

James, N. D.

1998-08-01

38

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

39

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

40

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

41

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

42

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

43

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

44

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

45

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

Code of Federal Regulations, 2013 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,...

2013-01-01

46

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

Code of Federal Regulations, 2011 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,...

2011-01-01

47

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

Code of Federal Regulations, 2012 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,...

2012-01-01

48

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

49

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

50

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

E-print Network

Efficient Yellow Electroluminescence from a Single Layer of a Cyclometalated Iridium Complex Jason been tried in single-layer electroluminescent devices. Complexes of iridium have been used extensively

Bernhard, Stefan

51

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

NSDL National Science Digital Library

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

Limited, Athro

52

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

E-print Network

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

53

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 for disposal FY 20034 FY 2003 Platinum 650 -- 650 1,560 -- Palladium 1,823 -- 1,823 10,900 5,213 Iridium 631

54

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

E-print Network

124 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,000 Iridium 2,700 3,110 2,100 2,200 3,900 Osmium 133 77 36 53 70 Exports: Platinum 25,000 31,300 27,800 22 6,220 1,070 Iridium 501 21 501 187 108 Prepared by Henry E. Hilliard [(703) 648-4970, hhilliar

55

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

E-print Network

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

56

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

E-print Network

126 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,800 Rhodium 13,500 10,300 18,200 12,400 7,560 Ruthenium 8,880 11,400 20,900 8,170 10,800 Iridium 1,950 2,270 2 Platinum 649 -- 649 4,354 4,055 Palladium 7,027 241 16,714 18,662 9,687 Iridium 784 -- 784 187 -- Prepared

57

Preliminary study of iridium coating on carbon\\/carbon composites  

Microsoft Academic Search

Iridium coating was deposited on as-received, polished and chemical vapour deposited (CVD) pyro carbon-coated carbon\\/carbon composite by d.c. sputtering. The as-received surface of the carbon\\/carbon composite was not fully covered by an iridium coating up to 12 µm thick, whereas better deposition and surface coverage with the iridium coating were obtained on the polished surface and CVD pyro carbon-coated carbon\\/carbon

K. Mumtaz; J. Echigoya; M. Taya

1993-01-01

58

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

59

Studies of size selected palladium and iridium model catalysts.  

E-print Network

??This dissertation describes size-dependent investigations of supported palladium and iridium clusters, used as model catalysts for carbon monoxide oxidation and hydrazine decomposition reactions. Chapter 1… (more)

Kaden, William E

2010-01-01

60

Square-planar iridium(II) and iridium(III) amido complexes stabilized by a PNP pincer ligand.  

PubMed

Squaring the circle: the novel dienamido pincer ligand N(CHCHPtBu(2))(2)(-) affords the isolation of the unusual square-planar iridium(II) and iridium(III) amido complexes [IrCl{N(CHCHPtBu(2))(2)}](n) (n=0 (1), +1 (2)). In contrast, the corresponding iridium(I) complex of the redox series (n=-1) is surprisingly unstable. The diamagnetism of 2 is attributed to strong N?Ir ? donation. PMID:21744449

Meiners, Jenni; Scheibel, Markus G; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Boeddinghaus, M Bele; Fässler, Thomas F; Herdtweck, Eberhardt; Khusniyarov, Marat M; Schneider, Sven

2011-08-22

61

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

62

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 melting temperature of iridium, 2400 C (4350 F).

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

1989-01-01

63

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

64

Engineering Issues of Iridium Coated Rhenium Rockets  

Microsoft Academic Search

The key to the performance and lifetime of radiation-cooled rockets is the chamber temperature capability. Temperature limitations (1370°C) of current state-of-art chamber materials force the use of film cooling, which degrades rocket performance and imposes plume contamination from unburned fuel. A material system composed of a rhenium (Re) substrate and an iridium (Ir) coating has demonstrated operation, for long lifetimes

Brian D. Reed; James A. Biaglow; Steven J. Schneider

1998-01-01

65

Iridium oxide nanomonitors: Clinical diagnostic devices for health monitoring systems  

Microsoft Academic Search

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

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

2009-01-01

66

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

67

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 evolution is a critical enabling component for the technol- ogy. To this end, iridium has been evaluated to have a dramatic effect on the stability of the iridium anode. The rate of iridium loss in an acidic

Sadoway, Donald Robert

68

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

69

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

70

Metal hydride-air battery  

Microsoft Academic Search

Portable metal-hydride fueled fuel cell systems, producing regulated 28VDC output at 30 watts and 60 watts, have been built. The systems are easily refuelable with pellets of solid sodium aluminum hydride and water to generate hydrogen. Ambient air, supplied by natural convection, is the oxidant. The energy density approaches 960 watt-hours per pound of fuel. A power conditioning unit provides

M. Onischak; B. S. Baker

1975-01-01

71

Decomposition kinetics of plutonium hydride  

Microsoft Academic Search

Kinetic data for decomposition of PuH⁠ââ provides insight into a possible mechanism for the hydriding and dehydriding reactions of plutonium. The fact that the rate of the hydriding reaction, K\\/sub H\\/, is proportional to P¹² and the rate of the dehydriding process, K\\/sub D\\/, is inversely proportional to P¹² suggests that the forward and reverse reactions proceed by opposite

J. M. Haschke; J. L. Stakebake

1979-01-01

72

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

73

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

74

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

75

Iridium/Rhenium Parts For Rocket Engines  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

76

Rhodium and iridium complexes with a new scorpionate phosphane ligand.  

PubMed

A straightforward synthesis of a new hybrid scorpionate ligand [(allyl)2B(CH2PPh2)(Pz)](-) ([A2BPN](-)) is reported. Coordination to rhodium resulted in square-planar complexes [Rh(?(2)-A2BPN)(L)(L')] [L = L' = (1)/2cod (1,5-cyclooctadiene), CN(t)Bu, CO (6); L = CO, L' = NH3, pyridine, PPh3, PMe3] for which spectroscopic data and the molecular structure of [Rh(?(2)-A2BPN)(CO)PPh3] (11) indicate the ligand to be ?N,?P-bound to rhodium with two dangling free allyl groups. Studies in solution point out that the six-membered Rh-N-N-B-C- P metallacycle undergoes a fast inversion in all of them. The bis(carbonyl) complex 6 easily loses a CO group to give [{Rh(A2BPN)(CO)}2], a dinuclear compound in which two mononuclear subunits are brought together by two bridging allyl groups. Coordination to iridium is dominated by a tripodal ?N,?P,?(2)-C?C binding mode in the TBPY-5 complexes [Ir(?(3)-A2BPN)(L)(L')] [L = L' = (1)/2cod (3), CN(t)Bu (5), CO (7); L = CO, L' = PPh3 (13), PMe3 (14), H2C?CH2, (17), MeO2CC?CCO2Me (dmad, 18)], as confirmed by the single-crystal structure determination of complexes 3 and 18. A fast exchange between the two allyl arms is observed for complexes having L = L' (3, 5, and 7), while those having CO and L ligands (14, 17, and 18) were found to be nonfluxional species. An exception is complex 13, which establishes an equilibrium with the SP-4 configuration. Protonation reactions on complexes 13 and 14 with HCl yielded the hydride complex [Ir(?(2)-A2BPN)(CO)(Cl)(H)PPh3] (15) and the C-alkyl compound [ Ir{?(3)-(allyl)B(CH2 CHCH3)(CH2PPh2)(Pz)}(Cl)(CO)PMe3] (16), respectively. The bis(isocyanide) complex 5 reacts with dmad to form [Ir(?(2)-A2BPN)(CN(t)Bu)2(dmad)]. On the whole, the electronic density provided to the metal by the [A2BPN](-) ligand is very sensitive to the coordination mode. The basicity of the new ligand is similar to that of the Tp(Me2) ligand in the ?N,?P mode but comparable to Tp if coordinated in the ?N,?P,?(2)-C?C mode. PMID:23763522

Serrano, Angel L; Casado, Miguel A; López, José A; Tejel, Cristina

2013-07-01

77

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.

78

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

79

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 2.41 150.00 Iridium 294.62 93.02 185.33 169.51 350.00 Employment, mine, number1 1,580 1,540 1,580 1,620 1

80

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 3.41 193.09 610.00 Iridium 93.02 185.33 169.51 349.45 440.00 Employment, mine, number1 1,540 1,580 1,620 1

81

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

E-print Network

120 PLATINUM-GROUP METALS (Platinum, palladium, rhodium, ruthenium, iridium, osmium) (Data,600 12,600 11,200 12,800 12,000 Ruthenium 48,700 49,800 21,200 14,100 15,000 Iridium 3,410 2,550 1,520 3.60 97.28 198.45 170.00 Iridium 444.43 448.34 420.40 642.15 1,030.00 Employment, mine, number 1 1,630 1

82

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

83

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

84

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/ruthenium oxide and iridium/iridium oxide barrier material to eliminate the costly additional Cu-seeding layer

Mohanty, Saraju P.

85

Solar energy storage by metal hydride  

Microsoft Academic Search

Metal hydride systems for long-term solar thermal energy storage are examined. Various materials for solar heat storage for architectural applications are reviewed, including water, pebble beds, insulators such as rock wool, glass wool and synthetic resins, molten salts and reaction heat storage systems, of which the metal hydride system is considered the most effective. The thermodynamics of metal hydride systems

S. Ono; M. Yamaguchi; T. Ohta

1979-01-01

86

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

87

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

88

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

89

Highly efficient D2 generation by dehydrogenation of formic acid in D2O through H+/D+ exchange on an iridium catalyst: application to the synthesis of deuterated compounds by transfer deuterogenation.  

PubMed

Deuterated compounds have received increasing attention in both academia and industrial fields. However, preparations of these compounds are limited for both economic and practical reasons. Herein, convenient generation of deuterium gas (D(2)) and the preparation of deuterated compounds on a laboratory scale are demonstrated by using a half-sandwich iridium complex with 4,4'-dihydroxy-2,2'-bipyridine. The "umpolung" (i.e., reversal of polarity) of a hydrogen atom of water was achieved in consecutive reactions, that is, a cationic H(+)/D(+) exchange reaction and anionic hydride or deuteride transfer, under mild conditions. Selective D(2) evolution (purity up to 89?%) was achieved by using HCO(2)H as an electron source and D(2)O as a deuterium source; a rhodium analogue provided HD gas (98?%) under similar conditions. Furthermore, pressurized D(2) (98?%) without CO gas was generated by using DCO(2)D in D(2)O in a glass autoclave. Transfer deuterogenation of ketones gave ?-deuterated alcohols with almost quantitative yields and high deuterium content by using HCO(2)H in D(2)O. Mechanistic studies show that the H(+)/D(+) exchange reaction in the iridium hydride complex was much faster than ?-elimination and hydride (deuteride) transfer. PMID:22718518

Wang, Wan-Hui; Hull, Jonathan F; Muckerman, James T; Fujita, Etsuko; Hirose, Takuji; Himeda, Yuichiro

2012-07-23

90

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

91

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

92

Synthesis and characterization of nitrides of iridium and palladiums  

SciTech Connect

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

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

2008-08-14

93

CO adsorption on neutral iridium clusters  

E-print Network

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

Kerpal, Christian; Meijer, Gerard; Fielicke, André

2010-01-01

94

PURIFICATION OF IRIDIUM BY ELECTRON BEAM MELTING  

SciTech Connect

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

Ohriner, Evan Keith [ORNL

2008-01-01

95

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

PubMed Central

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

Merola, Joseph; Husebo, Trang Le

2014-01-01

96

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

E-print Network

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

Burgess, Kevin

97

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 Of relevance to the present work, the dinuclear iridium complex [Cp*IrH3]2 (1) was previously found to react

Jones, William D.

98

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

Bernhard, Stefan

99

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

E-print Network

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

Jones, William D.

100

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...

101

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

E-print Network

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

Kounaves, Samuel P.

102

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

103

Synthesis, Separation, and Circularly Polarized Luminescence Studies of Enantiomers of Iridium(III) Luminophores  

E-print Network

Synthesis, Separation, and Circularly Polarized Luminescence Studies of Enantiomers of Iridium spectra for each of the enantio-enriched iridium complexes were obtained. The experimentally measured. Introduction Organic light-emitting diodes (OLEDs)1 incorporating cyclometalated iridium(III) complexes have

Bernhard, Stefan

104

Chiral Proline-Based Ligands for Iridium-Catalyzed Asymmetric Hydrogenation  

E-print Network

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

Amrhein, Valentin

105

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

E-print Network

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

Goddard III, William A.

106

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

E-print Network

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

Petersen, Brent

107

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 to improve the efficiency of the system. Periana has reported using iridium26,27 with a wide variety an acetate is intricately involved in the C-H activation.30,31 Herein we report new rhodium and iridium

Jones, William D.

108

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

109

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

E-print Network

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

Kounaves, Samuel P.

110

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 documented in the literature, the same cannot be said for iridium. During the past 30 years, only a few

Kounaves, Samuel P.

111

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

E-print Network

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

Chiao, Jung-Chih

112

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

E-print Network

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

Paris-Sud XI, Université de

113

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

E-print Network

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

Lewis, Brian Murray

114

DOI: 10.1002/adfm.200500523 Amorphous Diphenylaminofluorene-Functionalized Iridium  

E-print Network

DOI: 10.1002/adfm.200500523 Amorphous Diphenylaminofluorene-Functionalized Iridium Complexes and efficient emissive cores in the syn- thesis of useful iridium complexes.[9] One advantage of fluo- rene). Two new phosphorescent iridium(III) cyclometalated complexes, [Ir(DPA-Flpy)3] (1) and [Ir(DPA-Flpy)2

115

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

E-print Network

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

Grütter, Peter

116

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

E-print Network

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

Smith, Ryan N.

117

Rechargeable metal hydrides for spacecraft application  

NASA Astrophysics Data System (ADS)

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.

1988-09-01

118

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

119

Hydrogen /Hydride/-air secondary battery  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

120

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

121

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

122

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

123

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

E-print Network

Ab initio treatment of electron correlations in polymers: Lithium hydride chain and berylliumH and beryllium hydride Be2H4 . First, employing a Wannier-function-based approach, the systems are studiedH and the beryllium hydride polymer Be2H4 . As a simple, but due to its ionic character, non- trivial model polymer

Birkenheuer, Uwe

124

Lightweight hydrides for automotive storage of hydrogen  

NASA Astrophysics Data System (ADS)

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

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

125

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

126

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

127

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

SciTech Connect

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

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

2009-07-15

128

Rechargeable metal hydrides for spacecraft application  

Microsoft Academic Search

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

J. L. Perry

1988-01-01

129

Magnesium hydride-promoted dearomatisation of pyridine.  

PubMed

Reaction of pyridine with well defined magnesium hydride species results in heterocycle dearomatisation by a hydride transfer which occurs with the formation of magnesium compounds containing 1,2- and 1,4-dihydropyridide anions as the respective kinetic and thermodynamic products. PMID:20959940

Hill, Michael S; MacDougall, Dugald J; Mahon, Mary F

2010-12-14

130

Vibrational spectrum of magnesium hydride  

NASA Astrophysics Data System (ADS)

The vibrational spectrum of hydrogen atoms in magnesium hydride has been studied by means of inelastic-neutron and Raman-scattering experiments between 12 and 295 K. After careful evaluation of multiple scattering and multiphonon contributions, we provide a vibrational frequency spectrum up to 180 meV and the mean-square displacement of hydrogen atoms. The inelastic light scattering spectra of MgH2 powders show three Raman allowed modes (A1g, B1g, and Eg) and some smaller features that can be related with second-order and disorder-induced processes.

Santisteban, J. R.; Cuello, G. J.; Dawidowski, J.; Fainstein, A.; Peretti, H. A.; Ivanov, A.; Bermejo, F. J.

2000-07-01

131

Discovery of tantalum, rhenium, osmium, and iridium isotopes  

SciTech Connect

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

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

2012-09-15

132

Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes  

E-print Network

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

R. Robinson; M. Thoennessen

2011-09-02

133

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

134

Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes  

E-print Network

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

Robinson, R

2011-01-01

135

A comparison of the IRIDIUM and AMPS systems  

Microsoft Academic Search

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

Yvette C. Hubbel

1997-01-01

136

Iridium alloy clad vent set manufacturing qualification studies  

SciTech Connect

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

Ulrich, G.B.

1990-06-15

137

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

138

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

139

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

140

Interstellar Hydride Spectroscopy with Herschel  

NASA Astrophysics Data System (ADS)

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

Gerin, Maryvonne

2011-06-01

141

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

142

Hydride heat pump with heat regenerator  

NASA Technical Reports Server (NTRS)

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

Jones, Jack A. (Inventor)

1991-01-01

143

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

144

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

E-print Network

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

Paris-Sud XI, Université de

145

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

Microsoft Academic Search

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

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

2004-01-01

146

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

147

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

148

Isotope effects on hydride transfer reactions from transition metal hydrides to trityl cation. An inverse isotope effect for a hydride transfer  

Microsoft Academic Search

Kinetic isotope effects are useful in mechanistic studies, since they can provide insight into the transition state of the reaction being examined. Hydride (H⁻) transfer reactions between carbons are pertinent to the chemistry of nicotinamide adenine dinucleotide (NAD{sup +}) analogues. Kinetic and mechanistic studies have established details of hydride transfers from 1,4-dihydropyridines and related hydride donors to carbon-based hydride acceptors

Tan-Yun Cheng; R. Morris Bullock

1999-01-01

149

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.

150

Thermal conductivity of metal hydride beds  

Microsoft Academic Search

Experimental results on the thermal conductivity and hydrogen absorption and desorption behavior of the TiMn1.5 hydride are correlated by means of a kinetic theory of gas and equilibrium behaviors. The effective thermal conductivity of the hydride is defined as the sum of two independent terms related to pressure and composition, and an empirical equation based on the experimental data is

S. Suda; N. Kobayashi; K. Yoshida

1981-01-01

151

A Metal Hydride Mobile Air Conditioning System  

Microsoft Academic Search

This paper describes the development of an electrical compressor-driven air conditioning system for automotive applications. The system uses the thermal properties of reversible metal hydride alloys, which are retained within advanced-design hydride heat exchangers. Calculations on system performance predict high energy efficiency in a package of competitive size and cost. A proof-of-principle prototype has been constructed and bench tested. Measurements

Daniela Magnetto; Stefano Mola; Centro Ricerche Fiat; David H. DaCosta; Mark Golben; Matthew Rosso

152

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

153

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

154

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

155

Asymmetric hydrogenation of pyridinium salts with an iridium phosphole catalyst.  

PubMed

Iridium-catalyzed asymmetric hydrogenation of N-alkyl-2-alkylpyridinium salts provided 2-aryl-substituted piperidines with high levels of enantioselectivity. Simple benzyl and other alkyl groups successfully activated the challenging pyridine substrates toward hydrogenation. The use of the unusual chiral-phosphole-based MP(2) -SEGPHOS was the key to the success of this approach which provides a versatile and practical procedure for the synthesis of chiral piperidines. PMID:25297378

Chang, Mingxin; Huang, Yuhua; Liu, Shaodong; Chen, Yonggang; Krska, Shane W; Davies, Ian W; Zhang, Xumu

2014-11-17

156

Iridium in marine organisms from the Gulf of Mexico  

E-print Network

the scientific and popular literature of possible causes of the Iridium (Ir) enrichment in Cretaceous-Tertiary (K-T) boundary sediments and the concomitant biological extinctions (65 m. y. BP). No published data exist for Ir in marine biota, therefore... and also caused the very large biological extinctions (Alvarez et al. , 1984; Brooks et al. , 1984; Kasmer et al. , 1984). The meteorite impact theory has generated much discussion in both the scientific and popular literature. Since 1980 many articles...

Wells, Mona Cara

2012-06-07

157

Warm hydroforming of iridium + 0.3 wt % tungsten hemishells  

Microsoft Academic Search

A technique for the production of iridium alloy hemispherical shells to ;\\u000a be used for the primary encapsulation of plutonium-238 oxide spheres is described. ;\\u000a The encapsulated spheres, 24 per heat source, provide the thermal heat used to ;\\u000a drive thermoelectric converters which supply power for the Department of ;\\u000a Defense's LES 8\\/9 satellites. The technique used a standard production

Wyder

1976-01-01

158

Analysis and Implications of the Iridium 33Cosmos 2251 Collision  

Microsoft Academic Search

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,

T. S. Kelso

2009-01-01

159

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

160

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

161

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

162

Enhanced luminescent iridium(III) complexes bearing aryltriazole cyclometallated ligands.  

PubMed

Herein we report the synthesis of 4-aryl-1-benzyl-1H-1,2,3-triazoles (atl), made via "Click chemistry" and their incorporation as cyclometallating ligands into new heteroleptic iridium(III) complexes containing diimine (N(^)N) ancillary ligands 2,2'-bipyridine (bpy) and 4,4'-di-tert-butyl-2,2'-bipyridine (dtBubpy). Depending on decoration, these complexes emit from the yellow to sky blue in acetonitrile (ACN) solution at room temperature (RT). Their emission energies are slightly blue-shifted and their photoluminescent quantum efficiencies are markedly higher (between 25 and 80%) than analogous (C(^)N)(2)Ir(N(^)N)(+) type complexes, where C(^)N is a decorated 2-phenylpyridinato ligand. This increased brilliance is in part due to the presence of the benzyl groups, which act to sterically shield the iridium metal center. X-ray crystallographic analyses of two of the atl complexes corroborate this assertion. Their electrochemistry is reversible, thus making these complexes amenable for inclusion in light-emitting electrochemical cells (LEECs). A parallel computational investigation supports the experimental findings and demonstrates that for all complexes included in this study, the highest occupied molecular orbital (HOMO) is located on both the aryl fragment of the atl ligands and the iridium metal while the lowest unoccupied molecular orbital (LUMO) is located essentially exclusively on the ancillary ligand. PMID:21961698

Ladouceur, Sébastien; Fortin, Daniel; Zysman-Colman, Eli

2011-11-21

163

Substituent effects of iridium complexes for highly efficient red OLEDs.  

PubMed

This study reports substituent effects of iridium complexes with 1-phenylisoquinoline ligands. The emission spectra and phosphorescence quantum yields of the complexes differ from that of tris(1-phenylisoquinolinato-C2,N)iridium(iii)(Irpiq) depending on the substituents. The maximum emission peak, quantum yield and lifetime of those complexes ranged from 598-635 nm, 0.17-0.32 and 1.07-2.34 micros, respectively. This indicates the nature of the substituents has a significant influence on the kinetics of the excited-state decay. The substituents attached to phenyl ring have an influence on a stability of the HOMO. Furthermore, those substituents have effect on the contribution to a mixing between 3pi-pi* and (3)MLCT for the lowest excited states. Some of the complexes display the larger quantum yield than Irpiq, which has the quantum yield of 0.22. The organic light emitting diode (OLED) device based on tris [1-(4-fluoro-5-methylphenyl)isoquinolinato-C2,N]iridium(iii)(Ir4F5Mpiq) yielded high external quantum efficiency of 15.5% and a power efficiency of 12.4 lm W(-1) at a luminance of 218 cd m(-2). An emission color of the device was close to an NTSC specification with CIE chromaticity characteristics of (0.66, 0.34). PMID:15852106

Okada, Shinjiro; Okinaka, Keiji; Iwawaki, Hironobu; Furugori, Manabu; Hashimoto, Masashi; Mukaide, Taihei; Kamatani, Jun; Igawa, Satoshi; Tsuboyama, Akira; Takiguchi, Takao; Ueno, Kazunori

2005-05-01

164

Luminescence of carbazolyl-containing polymers doped with iridium chelates  

NASA Astrophysics Data System (ADS)

White light emission is shown to be obtainable at room temperature through the mixing of poly-N-vinylcarbazole (PVC) host fluorescence with fac-tris(2-phenylpyridyl)Ir(III) [Ir(ppy)3] and bis[2-(2'-benzothienyl)pyridinato-N,C3'](acetylacetonate)iridium (III) [Btp2Ir(acac)] dopant phosphorescence whereas at very low temperature through the superposition of poly-N-epoxypropyl-3,6-dibromocarbazole (3,6-DBrPEPC) host and Btp2Ir(acac) dopant phosphorescence emissions. The balance between basic colors is adjusted by the variation of triplet-emitter dopant concentrations. Spin-allowed singlet-singlet energy transfer from the host to iridium chelate dopants by the Forster mechanism is the dominant process in PVC. Spin-forbidden triplet-singlet transfer by the Forster mechanism from the host to the dopant occurs at low temperatures in 3,6-DBrPEPC due to strong spin-orbit coupling induced by the heavy bromine atoms. Spin-allowed transfer from the same host’s triplet excited state to the iridium chelate occurs via electron exchange at high temperatures.

Skryshevskii, Yu. A.

2008-05-01

165

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

166

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 substrates with iridium oxide. Increasing the film thickness beyond the full coverage did not further

Majda, Marcin

167

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 between�melt partitioning experiments to understand the behaviour of iridium, osmium and gold during crust; osmium; iridium; gold; partitioning; olivine 1. Introduction Owing to their refractory nature, and unique

Mcdonough, William F.

168

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

E-print Network

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

Vitek, Vaclav

169

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

E-print Network

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

Petersen, Brent

170

N-H activation of hydrazines by iridium(I). Double N-H activation to form iridium aminonitrene complexes.  

PubMed

Iridium(I) complexes of aromatic (PCP) and aliphatic (D(t)BPP) pincer ligands undergo single cleavage of the N-H bonds of hydrazine derivatives to form hydrazido complexes and geminal double cleavage to form unusual late transition metal aminonitrene complexes. In some cases, the cleavage of the N-N bond in the hydrazine is also observed. Oxidative additions of the N-H bonds of benzophenone hydrazone and 1-aminopiperidine to iridium(I) complexes give the corresponding hydridoiridium(III) hydrazido complexes within minutes. The complex containing an aromatic pincer ligand, (PCP)Ir(H)(NHNC(5)H(10)), slowly undergoes a second N-H bond cleavage at the alpha-N-H bond and elimination of hydrogen to generate an aminonitrene complex and dihydrogen in high yield. The reactions of the (PCP)Ir(I) fragment containing an aromatic pincer ligand with methyl-substituted hydrazines form a mixture of aminonitrene complexes, isocyanide iridium(III) dihydride complexes, and ammonia. The latter two products are likely formed by initial oxidative addition of the methyl C-H bond and the subsequent N-N bond cleavage. Reactions of the aminonitrene complex with CO or reagents that undergo oxidative addition (MeI and PhOH) lead to release of the "isodiazine" fragment to give tetrazene and tetrazine derivatives. PMID:20672808

Huang, Zheng; Zhou, Jianrong Steve; Hartwig, John F

2010-08-25

171

Adsorption and desorption of samarium atoms on the surface of pure iridium and iridium covered with a graphite monolayer  

NASA Astrophysics Data System (ADS)

Methods of thermionic emission and thermodesorption spectroscopy (TDS) have been used to study the adsorption and condensation of samarium on the surface of pure iridium and iridium covered with a graphite monolayer (valence-saturated neutral substrate) Ir(111)-C. It is shown that at temperatures of 700 < T a < 1200 K the work function ? decreases monotonically from 5.8 to 2.7 eV and during the subsequent deposition of samarium grows slowly to 2.9 eV. It has been found that in all TDS peaks there were observed several phases of samarium. The deposition of samarium onto an Ir-C surface at 700 < T < 1700 K led to a very weak change in the thermionic current in comparison with pure iridium. At temperatures above ˜700 K, samarium is not condensed on the surface of Ir-C, but it is condensed at lower temperatures. By the method of temperature modulation, the heat of samarium desorption was determined to be E ˜ 1.9 eV upon the desorption from an Ir-C surface (at a small coverage) and ˜6 eV upon the desorption from pure Ir.

Orudzhov, A. K.; Dashdemirov, A. O.

2009-01-01

172

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

173

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

174

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

Microsoft Academic Search

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

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

1996-01-01

175

Real-Time Characterization of Formation and Breakup of Iridium Clusters in Highly Dealuminated Zeolite Y  

SciTech Connect

The chemistry of formation of iridium clusters from mononuclear iridium diethylene complexes anchored in dealuminated Y zeolite, and their subsequent breakup -- all including changes in the metal-metal, metal-support, and metal-ligand interactions -- is demonstrated by time-resolved EXAFS, XANES, and IR spectroscopy.

Uzun, Alper; Gates, Bruce C. (UCD)

2009-01-15

176

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

Microsoft Academic Search

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

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

1998-01-01

177

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

178

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

Microsoft Academic Search

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

Sidney P. Kadish; Richard Danford; Lester M. Felton; Frank A. Ascoli

1981-01-01

179

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

180

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

181

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

182

Reactivity of yttrium carboxylates toward alkylaluminum hydrides.  

PubMed

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

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

2013-11-25

183

Hydride-containing molten salts and their technology implications  

Microsoft Academic Search

Hydride-conducting molten salts such as LiH in eutectic LiCl-KCl are attractive electrolyte systems for intermediate-temperature applications. The chemically reducing characteristics of these hydride melts provide a unique method to clean metal surfaces. The high conductivity of these hydride melts makes them the best electrolytes for hydrogen-based energy applications at intermediate temperatures. We will review some earlier work on hydride-conducting molten

Bor Y. Liaw

1993-01-01

184

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

185

Scattering law of a magnesium hydride moderator  

NASA Astrophysics Data System (ADS)

Metal hydrides have long been considered possible moderator and pre-moderator materials for neutron sources. These materials have hydrogen density comparable to liquid hydrogen or light water. They usually do not undergo phase transitions in the desired operating range of 0-300 K, and display reasonable resistance to radiation damage. Magnesium hydride is such a simple, robust hydride system. To assess its neutronic usefulness as a moderator material, we determined experimentally the total scattering cross-section of the material. We compared our theoretical results to the experimental total neutron cross-section and to the data from quasi-elastic neutron scattering experiments, and produced a scattering kernel suitable for neutron transport calculations.

Muhrer, G.; Hartl, M.; Daemen, L.; Tovesson, F.; Schnegg, A.; Russina, M.; Schachinger, E.

2011-02-01

186

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.

187

Atomic Mass and Nuclear Binding Energy for Ir-171 (Iridium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Ir-171 (Iridium, atomic number Z = 77, mass number A = 171).

Sukhoruchkin, S. I.; Soroko, Z. N.

188

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

189

Atomic Mass and Nuclear Binding Energy for Ir-227 (Iridium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Ir-227 (Iridium, atomic number Z = 77, mass number A = 227).

Sukhoruchkin, S. I.; Soroko, Z. N.

190

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

191

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

192

A hydride-rich magnesium cluster.  

PubMed

High-de-hydride! A straightforward reaction between a magnesium silylamido/N-heterocyclic carbene adduct and phenylsilane provides a {Mg(4)H(6)} cluster molecule that may be regarded as a combination of two magnesium dihydride and two magnesium monohydride moieties. PMID:19405069

Arrowsmith, Merle; Hill, Michael S; MacDougall, Dugald J; Mahon, Mary F

2009-01-01

193

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

194

Cation insertion reactions of electrochromic tungsten and iridium oxide films  

NASA Astrophysics Data System (ADS)

Electrochemical coloration mechanisms of electrochromic (EC), amorphous tungsten and iridium oxide films have been investigated by direct elemental analysis of their compositions in oxidized and reduced states. Combined Rutherford backscattering and nuclear-reaction-analysis techniques were employed to determine the identities and concentrations of ions injected as charge compensators from the contacting electrolyte during EC redox reactions. In aqueous electrolytes, the cathodic coloration of an anodically formed, hydrous tungsten oxide film (composition ~WO3.H2O), is accompanied by injection of protons, in accordance with mechanisms determined for anhydrous WO3. The anodic coloration and coloration bleaching of an anodically formed, hydrous iridium oxide (IROX) film, which has a varying degree of hydration throughout its thickness, is accompanied by ejection and injection of H+ and H3O+ ions. In nonaqueous aprotic electrolytes, the slow but reversible insertion of Li+ (r=0.60 Å) and Na+ (r=0.95 Å) ions into IROX films has been successfully demonstrated for the first time. Li+ ions were found to exchange with H+ ions in these hydrous films. No evidence could be found for insertion of K+ (r=1.33 Å), F- (r=1.36 Å), or OH- (r=1.55 Å) ions as charge compensators. These results provide a measure of the size and concentration of vacancies and defects in amorphous IROX films.

McIntyre, J. D. E.; Basu, S.; Peck, W. F., Jr.; Brown, W. L.; Augustyniak, W. M.

1982-06-01

195

Iridium and tantalum foils for spaceflight neutron dosimetry.  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

196

Analysis of Abrasive Blasting of DOP-26 Iridium Alloy  

SciTech Connect

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

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

2012-01-01

197

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

198

Light-emitting iridium complexes with tridentate ligands.  

PubMed

Once the Cinderella amongst the Platinum Group Metals at the Photochemistry Ball, iridium has become of intense interest since the beginning of the decade. Complexes of iridium(III) can be prepared that are highly luminescent, with emission wavelengths tuneable over the whole of the visible region. Whilst most studies have focused on tris-bidentate complexes, a rich and varied chemistry is also possible using tridentate ligands. In this review, we discuss the synthesis and excited-state properties of such complexes, exploring in particular how the number of cyclometallating carbon atoms in the coordination sphere of the metal ion influences the luminescence. Moving from [IrN6]3+ to [IrN3X3] coordination via [IrN5X]2+ and cis/trans-[IrN4X2]+ complexes, where N is a heterocyclic nitrogen and X is an anionic ligand or cyclometallated carbon, a whole range of luminescence efficiencies are encountered, ranging from the barely detectable to room temperature quantum yields approaching unity. We consider the extent to which these profound differences, arising as a result of subtle changes in molecular structure, can be rationalised in terms of the nature of the frontier orbitals. PMID:18398532

Williams, J A Gareth; Wilkinson, Andrew J; Whittle, Victoria L

2008-04-28

199

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

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

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

1992-05-15

200

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

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

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

1992-05-15

201

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

202

DEVELOPMENT OF A FABRICATION PROCESS FOR SOL-GEL\\/METAL HYDRIDE COMPOSITE GRANULES  

Microsoft Academic Search

An external gelation process was developed to produce spherical granules that contain metal hydride particles in a sol-gel matrix. Dimensionally stable granules containing metal hydrides are needed for applications such as hydrogen separation and hydrogen purification that require columns containing metal hydrides. Gases must readily flow through the metal hydride beds in the columns. Metal hydrides reversibly absorb and desorb

E Hansen; E Eric Frickey; L Leung Heung

2004-01-01

203

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

204

Luminescent cyclometalated iridium (III) polypyridine complexes as biomolecular and cellular probes.  

E-print Network

???A series of luminescent cyclometalated iridium(III) dipyridoquinoxaline complexes [Ir(N^C)2(N^N)](PF6) (HN^C = Hppz, Hbzq, Hpq; N^N = dpq and dpqa) has been synthesized and characterized. The… (more)

Zhang, Yin (??)

2010-01-01

205

Utilisation of luminescent cyclomentallated iridium (III) polypyridine complexes as biological labelling reagents and probes.  

E-print Network

??A family of thirty luminescent cyclometallated iridium(llI) diimine complexes with different functionalised diimine ligands [Ir(N-C)2(N-N)](PF6) has been synthesised and characterised. The X-ray crystal structures of… (more)

Chung, Chi Keung (???)

2005-01-01

206

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

207

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.

208

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

E-print Network

THE DISTRIBUTION AND GEOCHEMISTRY OF IRIDIUM IN RIVER SUSPENDED MATERIAL AND MARINE SEDIMENTS A Thesis by FREDERICK DONALD FENNER Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1983 Ma j or Sub j ect: Oceanography THE DISTRIBUTION AND GEOCHEMISTRY OF IRIDIUM IN RIVER SUSPENDED MATERIAL AND MARINE SEDIMENTS A Thesis by FREDERICK DONALD FENNER Approved as to style and content by: (Chai man...

Fenner, Frederick Donald

2012-06-07

209

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

210

Iridium satellites help map electrical currents in space  

NASA Astrophysics Data System (ADS)

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

Showstack, Randy

211

Iridium-alloy processing experience in FY 1989  

SciTech Connect

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

Ohriner, E.K.

1990-11-01

212

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

213

Iridium-alloy processing experience in FY 1990  

SciTech Connect

Iridium-alloy blanks and foil are produced at the Oak Ridge National Laboratory for use as fuel cladding material in radioisotope thermoelectric generators for space power sources. Until 1984, the material was produced from small, 500-g drop castings. A new process has been developed in which consumable electrodes of about 10 kg are melted, extruded, and then rolled to produce the sheet products. The work performed during FY 1990 included the consumable-electrode arc melting of four ingots and the extruding and rolling to sheet of four billets. Significant improvements made in the extruding and arc-melting processes during FY 1989 have been demonstrated to dramatically increase the rate of blank acceptance in nondestructive evaluations. Efforts to improve the rolling practice and to better characterize intermetallic particle distributions in the sheet are also described.

Ohriner, E.K.

1991-11-01

214

Numerical study of a magnesium hydride tank  

NASA Astrophysics Data System (ADS)

Hydrogen storage in metal hydride tanks (MHT) is a very promising solution. Several experimental tanks, studied by different teams, have already proved the feasibility and the interesting performances of this solution. However, in much cases, an optimization of tank geometry is still needed in order to perform fast hydrogen loading. The development of efficient numerical tools is a key issue for MHT design and optimization. We propose a simple model representing a metal hydride tank exchanging its heat of reaction with a thermal fluid flow. In this model, the radial and axial discretisations have been decoupled by using Matlab® one-dimensional tools. Calculations are compared to experimental results obtained in a previous study. A good agreement is found for the loading case. The discharging case shows some discrepancies, which are discussed in this paper.

Delhomme, Baptiste; de Rango, Patricia; Marty, Philippe

2012-11-01

215

The Electric Dipole Moment of Iridium Monosilicide, IrSi  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

216

New yellow-emitting phosphorescent cyclometalated iridium(III) complex  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

217

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

218

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

SciTech Connect

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

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

2000-03-01

219

Uranium–zirconium hydride fuel properties  

Microsoft Academic Search

Properties of the two-phase hydride U0.3ZrH1.6 pertinent to performance as a nuclear fuel for LWRs are reviewed. Much of the available data come from the Space Nuclear Auxiliary Power (SNAP) program of 4 decades ago and from the more restricted data base prepared for the TRIGA research reactors some 3 decades back. Transport, mechanical, thermal and chemical properties are summarized.

D. Olander; Ehud Greenspan; Hans D. Garkisch; Bojan Petrovic

2009-01-01

220

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

221

Hydrogen and deuterium diffusion in lithium hydride  

NASA Astrophysics Data System (ADS)

Hydrogen is considered a promising candidate to achieve an alternative source to overcome future energy supply problems. Very recently, an ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides appeared by Ramzan and Ahuja [J. Appl. Phys. 106, 016104 (2009)]. Here, we alternatively report the calculation of the temperature dependence of the diffusion coefficients of hydrogen and deuterium in LiH in terms of a thermodynamical model. The resulting values agree fairly well with experimental data.

Dologlou, Elisabeth

2010-04-01

222

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

223

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

224

Precipitation of hydrides in high purity niobium after different treatments  

NASA Astrophysics Data System (ADS)

Precipitation of lossy non-superconducting niobium hydrides represents a known problem for high purity niobium in superconducting applications. Using cryogenic optical and laser confocal scanning microscopy, we have directly observed surface precipitation and evolution of niobium hydrides in samples after different treatments used for superconducting RF cavities for particle acceleration. Precipitation is shown to occur throughout the sample volume, and the growth of hydrides is well described by the fast diffusion-controlled process in which almost all hydrogen is precipitated at T = 140 K within ˜30 min. 120 °C baking and mechanical deformation are found to affect hydride precipitation through their influence on the number of nucleation and trapping centers.

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

2013-10-01

225

Neue 1,4-Chelatkomplexe von Rhenium, Ruthenium, Rhodium, Iridium, Palladium und Platin mit aromatischen N,N'- und N,P-Liganden.  

E-print Network

??In der vorliegenden Arbeit werden stabile Übergangsmetall-Komplexe der d6-konfigurierten Metalle Rhenium(1), Ruthenium(2), Rhodium(3) und Iridium(3), sowie von Rhodium(1), Iridium(1), Palladium(2) und Platin(2) mit d8-Konfiguration hergestellt.… (more)

Neumann, Bernd

2006-01-01

226

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

SciTech Connect

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

None

2011-12-05

227

Electrochemical investigation of hydrogen storage in metal hydrides  

Microsoft Academic Search

One of the problems regarding the use of hydrogen as an energy carrier is related to storage. One approach for a solution is related to the use of solid metal hydrides. Many studies regarding the formation of metal hydrides have included the conduction of absorption experiments in which hydrogen from the gas phase reacts with solid alloys. However, electrochemical methods

C. M. Luedecke; G. Deublein; R. A. Huggins

1985-01-01

228

Hydride-Containing Molten Salts and their Technology Implications.  

National Technical Information Service (NTIS)

Hydride-conducting molten salts such as LiH in eutectic LiCl-KCl are attractive electrolyte systems for intermediate-temperature applications. The chemically reducing characteristics of these hydride melts provide a unique method to clean metal surfaces. ...

B. Y. Liaw

1993-01-01

229

DISPROPORTIONATION RESISTANT ALLOY DEVELOPMENT FOR HYDRIDE HYDROGEN COMPRESSION  

E-print Network

DISPROPORTIONATION RESISTANT ALLOY DEVELOPMENT FOR HYDRIDE HYDROGEN COMPRESSION Mark Golben David H compressor is an absorption-based system that uses the properties of reversible metal hydride alloys to silently and cleanly compress hydrogen; hydrogen is absorbed into an alloy bed at ambient temperature and

230

Incorporation of Hydride Nuclear Fuels in Commercial Light Water Reactors  

E-print Network

water reactor (PWR) core designs utilizes uranium-thorium-thorium-zirconium hydride matrix, which is one of the critical parameters affecting fabrication and in-reactorthorium-zirconium hydrides, (UThZr 4 )H 1.7 and (UTh 2 Zr 6 )H 1.3 , were irradiated at the Japan Materials Testing Reactor (

Terrani, Kurt Amir

2010-01-01

231

Solid-state gadolinium-magnesium hydride optical switch  

NASA Astrophysics Data System (ADS)

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

Armitage, R.; Rubin, M.; Richardson, T.; O'Brien, N.; Chen, Yong

1999-09-01

232

Lithium hydride anode for use in alkaline batteries  

SciTech Connect

This patent describes a battery comprising an aqueous alkaline electrolyte, an anode comprising a lithium hydride layer in contact with a current collector, the aqueous electrolyte being sufficiently concentrated so as to minimize the decomposition of the lithium hydride layer to hydrogen.

Juda, W.

1987-04-28

233

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

234

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

Boyer, Edmond

235

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

E-print Network

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

Chiao, Jung-Chih

236

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

E-print Network

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

Chiao, Jung-Chih

237

Evaluation of oxide-coated iridium-rhenium chambers  

NASA Astrophysics Data System (ADS)

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.

1994-03-01

238

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

239

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

240

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

241

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

242

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

PubMed

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

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

2012-01-01

243

The high-temperature work function of sintered dilute solution tungsten-iridium alloys  

SciTech Connect

The effect of transition element additives molybdenum, rhenium, iridium, and osmium on the effective work function of tungsten has been the focus of thermionics research for several years. In this study, iridium-added tungsten powder mixtures were cold compacted and sintered to produce a range of tungsten-iridium electrodes. An electron emission study was subsequently carried out to evaluate the work function behavior of the consolidated alloys. The work function was obtained from measurements of the current emitted from the electrode surface under ultrahigh vacuum conditions in the temperature range of 1,800 to 2,500 K using a vacuum emission vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature. Microstructural evaluation of the alloys indicated that the tested surfaces displayed accentuated thermal etching of the grain boundaries together with the fact that the final grain sizes in the sintered alloys were three to five times smaller than those found in equivalent arc-melted alloys that were studied in earlier work. Scanning electron microscopy (SEM) micrographs of the tested surfaces of the sintered alloys containing the highest iridium levels ([approximately]2 wt%) show a high level of structural distortion, particularly in the vicinity of grain boundaries and corners. The extent of these distortions was found to vary with the iridium content, i.e., the W-IR3M and W-IR2M. The samples with compositions lower than 0.5 wt% Ir were virtually devoid of distortions.

D'Cruz, L.A.; Bosch, D.R.; Jacobsen, D.L. (Arizona State Univ., Tempe (United States))

1993-02-01

244

Nanostructured Magnesium Hydride for Reversible Hydrogen Storage  

NASA Astrophysics Data System (ADS)

The aim of this work was to develop suitable materials to store hydrogen in a solid state. A systematic investigation of the co-milling process of magnesium hydride with a transition metal was undertaken in order to produce nanostructured and highly reactive powders. The initiating role of the transition metal was evidenced by in situ neutron diffraction experiments. High performances in terms of thermal and mechanical behavior were achieved introducing expanded graphite and compacting the mixture to form composite materials. Absorption and desorption kinetics have been measured versus temperature and H2 pressure.

de Rango, P.; Chaise, A.; Fruchart, D.; Miraglia, S.; Marty, Ph.

2013-05-01

245

Synthesis and structure of iridium complex with thiocarbamide  

SciTech Connect

A single crystal of the [Ir(Thio){sub 2}Cl{sub 4}][Ir(Thio){sub 4}Cl{sub 2}] compound synthesized by the reaction of K{sub 3}[IrCl{sub 6}] with thiocarbamide (Thio, SC(NH{sub 2}){sub 2}) in a microwave field is investigated using X-ray diffraction. The compound crystallizes in the monoclinic crystal system with space group Cc(C{sub s}{sup 4}). The unit cell parameters are as follows: a = 13.554(1) A, b = 8.251(1) A, c = 24.992(2) A, {beta} = 92.58(1){sup o}, V = 2791.87(10) A{sup 3}, and Z = 4. The compound has an island structure with two crystallographically independent iridium atoms. Thiocarbamide is coordinated to the central atom through the sulfur atom. The coordination sphere of the Ir(1) atom involves two Cl atoms and four S atoms, whereas the coordination sphere of the Ir(2) atom consists of four Cl atoms and two S atoms. The assignment of the bands in the IR absorption spectrum of the synthesized compound is presented. The thermal behavior of the compound in air is investigated.

Buslaeva, T. M., E-mail: buslaevatm@mail.ru; Kravchenko, V. V.; Kopylova, E. V.; Kashiricheva, I. I. [Lomonosov Moscow State Academy of Fine Chemical Technology (Russian Federation); Alekseeva, O. A.; Kazantsev, S. S. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2008-09-15

246

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

247

Efficient water oxidation with organometallic iridium complexes as precatalysts.  

PubMed

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

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

2014-06-28

248

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

NASA Astrophysics Data System (ADS)

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 spraying. The as-deposited samples were annealed at 600 °C in air medium for 1 h. The structural, electrical and optical properties of as-deposited and annealed Mo-doped iridium oxide were studied and values of room temperature electrical resistivity, and thermoelectric power were estimated. The as-deposited samples with 2% Mo doping exhibit more pronounced electrochromism than other samples, including pristine Ir oxide.

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

2006-09-01

249

Surface passivation of metal hydrides for applications  

SciTech Connect

Properties and characteristics of hydriding alloys are strongly dependent on surface compositions and morphologies. For instance, oxides such as La{sub 2}O{sub 3} on AB{sub 5} alloys and ZrO{sub 2} on AB{sub 2}, AB, and body-centered-cubic (BCC) alloys act as the barriers for the conversion of molecular and ionic hydrogen to atomic hydrogen at the surface, thus reducing the kinetics in both the gas-solid and electrochemical reactions. Alloy surfaces chemically treated by an aqueous F-ion containing solution have been developed to solve such problems. F-treated surfaces exhibit significantly improved characteristics in regard to the hydrogen uptakes and the protection against impurities and electrolyte solution. In addition, highly conductive metallic Ni layers can be formed on the surface of the alloy particles by the fluorination. The authors report the properties and characteristics of fluorinated hydriding alloys, mainly of a typical AB{sub 2} Laves phase material which represents the difficult activation characteristics and poor long-term durability during electrochemical charge/discharge cycles.

Suda, S.; Li, Z.P.; Sun, Y.M.; Liu, B.H.; Gao, X.P. [Kogakuin Univ., Hachioji, Tokyo (Japan). Dept. of Environmental and Chemical Engineering

1998-12-31

250

Formation and reactivity of ketene ligands on an iridium fragment  

SciTech Connect

Metal-ketene complexes have been invoked as intermediates in a number of organometallic transformations. In a search for new routes to metal-ketene complexes, the interaction of the fragment [Ir] = ClIr[P(iPr){sub 3}]{sub 2} with 1 has been examined. Depending on R{sup 1} and R{sup 2}, either (C,O) or (C,C)-bound ketene complexes are obtained, allowing a unique opportunity to study both coordination modes on a single metal fragment. In 1 + [Ir] {yields} 2-4, spectral evidence for an intermediate has been obtained. The coordinative unsaturation of ketene complexes 2 and 3 leads to unusual rearrangements. Unprecedented {alpha}-metallation of P(i-Pr){sub 3} in 3 leads to 5, for which a crystal structure will be presented. Photochemical rearrangement of 2 is reversed thermally, whereas heating 2 results in a 1,3 hydride shift.

Grotjahn, D.B.; Lo, H.C. [Arizona State Univ., Tempe, AZ (United States)

1995-12-31

251

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.

252

Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds  

SciTech Connect

Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H{sub 2} gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe){sub 2}, dmpe = 1,2-bis(dimethylphosphinoethane) was capable of reducing a variety of BX{sub 3} compounds having hydride affinity (HA) greater than or equal to HA of BEt{sub 3}. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, (HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +}), to form B-H bonds. The hydride donor abilities ({Delta}G{sub H{sup -}}{sup o}) of HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +} were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX{sub 3} compounds. The collective data guided our selection of BX{sub 3} compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe){sub 2} was observed to transfer H{sup -} to BX{sub 3} compounds with X = H, OC{sub 6}F{sub 5} and SPh. The reaction with B(SPh){sub 3} is accompanied by formation of (BH{sub 3}){sub 2}-dmpe and (BH{sub 2}SPh){sub 2}-dmpe products that follow from reduction of multiple BSPh bonds and loss of a dmpe ligand from Co. Reactions between HCo(dmpe){sub 2} and B(SPh){sub 3} in the presence of triethylamine result in formation of Et{sub 3}N-BH{sub 2}SPh and Et{sub 3}N-BH{sub 3} with no loss of dmpe ligand. Reactions of the cationic complex [HNi(dmpe){sub 2}]{sup +} with B(SPh){sub 3} under analogous conditions give Et{sub 3}N-BH{sub 2}SPh as the final product along with the nickel-thiolate complex [Ni(dmpe){sub 2}(SPh)]{sup +}. The synthesis and characterization of HCo(dedpe){sub 2} (dedpe = diethyldiphenyl(phosphino)ethane) from H{sub 2} and a base is also discussed; including the formation of an uncommon trans dihydride species, trans-[(H{sub 2})Co(dedpe){sub 2}][BF{sub 4}].

Mock, Michael T.; Potter, Robert G.; O'Hagan, Molly J.; Camaioni, Donald M.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.

2011-12-05

253

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

254

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

255

Frontispiece: iridium-catalyst-based autonomous bubble-propelled graphene micromotors with ultralow catalyst loading.  

PubMed

Self-Propelled Motors Research on self-propelled micro-/nanoscale motors provides various potential applications ranging from the biomedical field to addressing environmental issues. In their Communication on page 14946?ff., M. Pumera et?al. describe the new concept of self-propelled micromotors with high surface areas and a very low loading of catalyst. The iridium-based graphene micromotor (exemplified here by a graphene fish with an iridium eye over a coral reef in Lombok, Indonesia) can display autonomous bubble propulsion in the presence of hydrogen peroxide, even at a very low concentration of catalyst (0.54 at%). PMID:25359209

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

2014-11-10

256

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

257

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

258

Air–metal hydride secondary battery with long cycle life  

Microsoft Academic Search

We report the evaluation of a novel air–metal hydride rechargeable battery. A copper plated MmNi3.5Co0.7Al0.7Mn0.1 alloy was used as the active material in the metal hydride electrode. The metal hydride electrode was charged and discharged via a gas diffusion electrode based on a La0.6Ca0.4CoO3 perovskite (supported on carbon) as the catalyst for both oxygen reduction (discharge) and oxygen evolution (charge).

D Chartouni; N Kuriyama; T Kiyobayashi; J Chen

2002-01-01

259

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

260

Finite difference program for calculating hydride bed wall temperature profiles  

SciTech Connect

A QuickBASIC finite difference program was written for calculating one dimensional temperature profiles in up to two media with flat, cylindrical, or spherical geometries. The development of the program was motivated by the need to calculate maximum temperature differences across the walls of the Tritium metal hydrides beds for thermal fatigue analysis. The purpose of this report is to document the equations and the computer program used to calculate transient wall temperatures in stainless steel hydride vessels. The development of the computer code was motivated by the need to calculate maximum temperature differences across the walls of the hydrides beds in the Tritium Facility for thermal fatigue analysis.

Klein, J.E.

1992-10-29

261

Technical and economic aspects of hydrogen storage in metal hydrides  

NASA Technical Reports Server (NTRS)

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

Schmitt, R.

1981-01-01

262

Influence of expansion of metal hydride during hydriding–dehydriding cycles  

Microsoft Academic Search

The mechanical behavior of metal hydride reactor and the mechanism of the advent of strain caused by Ti0.71Zr0.29Mn0.8CrCu0.2 alloy expansion have been studied using pressure vessel controlled to be no pressure difference between the inner and outer wall of the reactor tube occurred. Strain gauges were set on the various locations in the reactor. The change of strain was continuously

T Saito; K Suwa; T Kawamura

1997-01-01

263

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

264

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

265

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

266

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

267

Transient analysis of hydride fueled pressurized water reactor cores  

E-print Network

This thesis contributes to the hydride nuclear fuel project led by U. C. Berkeley for which MIT is to perform the thermal hydraulic and economic analyses. A parametric study has been performed to determine the optimum ...

Trant, Jarrod Michael

2004-01-01

268

Metal Hydride Chemical Heat Pumps for Industrial Use  

E-print Network

Hydriding alloys are intermetallic absorbent compounds which have the remarkable quality of absorbing very large quantities of hydrogen gas per unit volume of metallic powder. The absorption and desorption of hydrogen are exothermic and endothermic...

Ally, M. R.; Rebello, W. J.; Rosso, M. J., Jr.

1984-01-01

269

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

270

High-pressure synthesis of noble metal hydrides.  

PubMed

The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures. PMID:23574244

Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

2013-04-01

271

Structure and bonding of second-row hydrides  

E-print Network

The atomic orbitals, hybridization and chemical bonding of the most common hydrides of boron, carbon, nitrogen and oxygen are described. This can be very instructive for beginning students in chemistry and chemical physics.

Blinder, S M

2014-01-01

272

Pi-systems as simultaneous hydride and hydrogen bond acceptors.  

PubMed

A theoretical study of the hydride bond complexes with tetrafluoro- and tetracyanoethylene, C2F4 and C2(CN)4, has been carried out by means of density functional theory (DFT) and ab initio methods, up to the MP2/aug-cc-pVTZ computational level. In addition, the ternary complexes formed by an additional standard hydrogen bond donor, such as hydrogen fluoride, have been explored. The results show that the hydride bond complexes are stable and an electron transfer took place from the hydride to the C2F4 and C2(CN)4 molecules. While these molecules are not able to form stable complexes between the pi-electrons and hydrogen bond donors, the presence of the hydrides in the opposite face of the pi-system of C2F4 stabilizes the ternary complexes showing cooperativity effects. PMID:18593106

Alkorta, Ibon; Blanco, Fernando; Elguero, Jose

2008-07-24

273

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

274

Ab-Initio Study of the Group 2 Hydride Anions  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

275

Comparison of Iridium Determined Field-Aligned Current Patterns with MHD Simulations  

Microsoft Academic Search

The engineering magnetometers aboard the 70+ Iridium satellites arranged in six equally spaced polar orbital planes provide a unique database for determination of global field-aligned currents [Waters et al., 2001]. In this study we compare these field-aligned currents with MHD simulation results to quantitatively evaluate the MHD results in a global way. We report analysis for three events of steady

H. Korth; B. J. Anderson; C. C. Goodrich; C. L. Waters; V. G. Merkine

2002-01-01

276

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

Microsoft Academic Search

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

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

1987-01-01

277

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

Microsoft Academic Search

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

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

1999-01-01

278

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

279

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

Microsoft Academic Search

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

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

1986-01-01

280

Iridium-catalyzed regio- and enantioselective allylic substitution of silyl dienolates derived from dioxinones.  

PubMed

Reported herein is the iridium-catalyzed regio- and enantioselective allylic substitution reactions of unstabilized silyl dienolates derived from dioxinones. Asymmetric allylic substitution of a variety of allylic trichloroethyl carbonates with these silyl dienolates gave ?-allylated products selectively in 60-84?% yield and 90-98?%?ee. PMID:25223593

Chen, Ming; Hartwig, John F

2014-11-01

281

The effects of iridium on the renal function of female Wistar rats  

Microsoft Academic Search

Despite the widespread use of iridium (Ir) in catalytic converters for improved capacity for reducing carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) emissions, there is a lack of studies that have assessed possible toxicological hazards of exposure to Ir. The present investigation indicates that female Wistar rats exposed to Ir in the drinking water for 90 days displayed

Ivo Iavicoli; Luca Fontana; Alessandro Marinaccio; Alessandro Alimonti; Anna Pino; Antonio Bergamaschi; Edward J. Calabrese

2011-01-01

282

Sulfur-resistant carbon-supported iridium catalysts: Cyclohexane dehydrogenation and benzene hydrogenation  

SciTech Connect

Carbon-supported iridium catalysts, with different metal loadings, were prepared by impregnation of a high-purity activated carbon. The dispersion of the metallic phase was studied by hydrogen and carbon monoxide chemisorption and transmission electron microscopy (TEM). The hydrogen chemisorption on the iridium crystallites supported on activated carbon was quite different from the chemisorption on an Ir/alumina catalyst. TEM observations of the catalysts show metal particles as spheres in the former case and as rafts in the latter. The cyclohexane dehydrogenation and the benzene hydrogenation were studied for both catalyst types. Both reactions are insensitive to the iridium dispersion and to the support. The thiotolerance level of the cyclohexane dehydrogenation, the thiotolerance level is affected neither by the support (activated carbon versus alumina) not by the metallic dispersion of the Ir/carbon catalysts. However, in the benzene hydrogenation the carbon-supported iridium catalysts are more resistant toward the poisoning than the Ir/alumina counterpart. This behavior is interpreted as due to the different metallic microstructures produced on the two supports.

Rodriguez-Ramos, I. (Campus Univ. Autonoma, Madrid (Spain)); Guerrero-Ruiz, A. (UNED, Madrid (Spain))

1992-06-01

283

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

PubMed

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

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

2013-05-01

284

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

285

Asymmetric hydrogenations of aryl alkenes using imidazol-2-ylidene iridium complexes  

E-print Network

Catalysts.......................32 1.4 Lanthanide-based Chiral Catalysts....................................................36 1.5 Rhodium- and Ruthenium-based Systems ........................................38 1.6 Conclusions... iodides 60.......................................................................................................47 2.2 X-ray crystal structures of three iridium complexes and one rhodium complex...

Cui, Xiuhua

2005-08-29

286

Potential contributions to space geodesy from the IridiumNEXT constellation  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

287

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 over several days use. The applicationof SWASV theory for mercury film electrodes is shown The mercury electrode in ita many forms has been the overwhelmingsubstrate-of-choicefor electrochemistrysince

Kounaves, Samuel P.

288

Mitochondria-targeting phosphorescent iridium(iii) complexes for living cell imaging.  

PubMed

Two phosphorescent iridium(iii) complexes conjugated to a lipophilic triphenylphosphonium cation moiety, IrMitoOlivine and IrMitoNIR, were synthesized. The complexes show high mitochondria-specificity and relatively lower cytotoxicity. Time-lapse confocal imaging indicates that both complexes exhibit an excellent anti-photobleaching capability under continuous laser irradiation. PMID:25287363

Zhang, Qingqing; Cao, Rui; Fei, Hao; Zhou, Ming

2014-10-22

289

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

290

Hydride-containing molten salts and their technology implications  

NASA Astrophysics Data System (ADS)

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

Liaw, Bor Y.

1993-03-01

291

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

292

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

293

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

294

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

295

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

296

Electrochemical behaviour of intermetallic-based metal hydrides used in Ni\\/metal hydride (MH) batteries: a review  

Microsoft Academic Search

Hydrogen storage alloys are a group of new functional intermetallics which can be used in heat pumps, catalysts, hydrogen sensors and Ni\\/MH batteries. The development of Ni\\/MH (Metal Hydride) batteries based on MH negative electrodes has seen considerable activity in recent years. Batteries based on such hydride materials have some major advantages over the more conventional lead–acid and nickel–cadmium systems.

F Feng; M Geng; D. O Northwood

2001-01-01

297

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

298

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

299

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

E-print Network

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

Leman, Steven W.

300

Addition of C-C and C-H bonds by pincer-iridium complexes: a combined experimental and computational study.  

PubMed

We report that pincer-ligated iridium complexes undergo oxidative addition of the strained C-C bond of biphenylene. The sterically crowded species ((tBu)PCP)Ir ((R)PCP = ?(3)-1,3-C6H3(CH2PR2)2) initially reacts with biphenylene to selectively add the C(1)-H bond, to give a relatively stable aryl hydride complex. Upon heating at 125 °C for 24 h, full conversion to the C-C addition product, ((tBu)PCP)Ir(2,2'-biphenyl), is observed. The much less crowded ((iPr)PCP)Ir undergoes relatively rapid C-C addition at room temperature. The large difference in the apparent barriers to C-C addition is notable in view of the fact that the addition products are not particularly crowded, since the planar biphenyl unit adopts an orientation perpendicular to the plane of the (R)PCP ligands. Based on DFT calculations the large difference in the barriers to C-C addition can be explained in terms of a "tilted" transition state. In the transition state the biphenylene cyclobutadiene core is calculated to be strongly tilted (ca. 50°-60°) relative to its orientation in the product in the plane perpendicular to that of the PCP ligand; this tilt results in very short, unfavorable, non-bonding contacts with the t-butyl groups in the case of the (tBu)PCP ligand. The conclusions of the biphenylene studies are applied to interpret computational results for cleavage of the unstrained C-C bond of biphenyl by ((R)PCP)Ir. PMID:25250874

Laviska, David A; Guan, Changjian; Emge, Thomas J; Wilklow-Marnell, Miles; Brennessel, William W; Jones, William D; Krogh-Jespersen, Karsten; Goldman, Alan S

2014-10-14

301

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

302

Highly active iridium/iridium-tin/tin oxide heterogeneous nanoparticles as alternative electrocatalysts for the ethanol oxidation reaction.  

PubMed

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(71)Sn(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(71)Sn(29)/C particles as Ir/Ir-Sn/SnO(2), which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO(2) present on the surface. The Ir(71)Sn(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(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. PMID:21812458

Du, Wenxin; Wang, Qi; Saxner, David; Deskins, N Aaron; Su, Dong; Krzanowski, James E; Frenkel, Anatoly I; Teng, Xiaowei

2011-09-28

303

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

304

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

305

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

306

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

307

Neutral and Ionized Hydrides in Star-Forming Regions. Observations with Herschel/HIFI  

E-print Network

, an ion, or another hydride. Hydrides are the most basic molecules through which astrochemistry develops further. They are of fundamental importance for astrochemistry (reviews, e.g., in refs 2 and 3

308

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

309

Hydrides of DyCo/sub 3/  

SciTech Connect

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

Kierstead, H.A.

1980-01-01

310

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

E-print Network

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

Paris-Sud XI, Université de

311

Metal hydride electrode for high energy density sealed nickel-metal hydride battery  

NASA Astrophysics Data System (ADS)

By choosing an appropriate hydrogen storage alloy for a negative electrode with a higher density than a cadmium electrode, there is a possibility of greatly increasing the energy density of a nickel-metal hydride Ni-H(MH) battery system over that of nickel-cadmium (Ni-Cd) battery system of approximately the same cell voltage. Thus with an MmNi5 (Mm: abbreviation for mish metal) alloy system having a CaCu5 type of crystal structure as the object of study, the alloy composition and its homogenization, electrode structure etc. were studied and the high capacity metal hydride electrodes were used in the Ni-H(MH). Although a sealed Ni-H(MH) cylindrical cell was built and achieved a high initial capacity, this decreased with repeated charge-discharge cycles. To investigate the cause of this deterioration, the composition of the alloy and the effect of etching treatment of the powder surface were analyzed by SEM photos and X-ray diffraction patterns. The results made it clear that an Ni-H(MH) cell of AA (R6) size with a discharge capacity of 1.05 to 1.1 Ah, that is, with an energy density approximately 40 percent higher than an Ni-Cd cell, and with a long life exceeding 500 complete charge-discharge cycles could be achieved.

Ogawa, Hiromichi; Ikoma, Munehisa; Kawano, Hiroshi; Matsumoto, Isao

312

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

313

Solid-State Gadolinium-Magnesium Hydride Optical Switch R. Armitage  

E-print Network

Solid-State Gadolinium-Magnesium Hydride Optical Switch R. Armitage Lawrence Berkeley National The optical switching properties of gadolinium-magnesium hydride have been demonstrated in a solid and reflecting states. Keywords: gadolinium-magnesium; electrochromic hydride; optical switching device. 2 #12;A

314

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

315

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

316

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

SciTech Connect

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

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

2008-01-01

317

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

318

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

PubMed

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

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

2014-09-01

319

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

320

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

321

CO2 hydrogenation on a metal hydride surface.  

PubMed

The catalytic hydrogenation of CO(2) at the surface of a metal hydride and the corresponding surface segregation were investigated. The surface processes on Mg(2)NiH(4) were analyzed by in situ X-ray photoelectron spectroscopy (XPS) combined with thermal desorption spectroscopy (TDS) and mass spectrometry (MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). CO(2) hydrogenation on the hydride surface during hydrogen desorption was analyzed by catalytic activity measurement with a flow reactor, a gas chromatograph (GC) and MS. We conclude that for the CO(2) methanation reaction, the dissociation of H(2) molecules at the surface is not the rate controlling step but the dissociative adsorption of CO(2) molecules on the hydride surface. PMID:22433948

Kato, Shunsuke; Borgschulte, Andreas; Ferri, Davide; Bielmann, Michael; Crivello, Jean-Claude; Wiedenmann, Daniel; Parlinska-Wojtan, Magdalena; Rossbach, Peggy; Lu, Ye; Remhof, Arndt; Züttel, Andreas

2012-04-28

322

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

323

Intercomparison of ionospheric electrodynamics from the Iridium constellation with global MHD simulations  

Microsoft Academic Search

Global magnetospheric simulation results of the field-aligned current (FAC) density at low altitudes are compared with global two-dimensional distributions of Birkeland currents at the topside ionosphere derived from magnetic field data of the Iridium satellite constellation. We present two events with opposite direction of the interplanetary magnetic field By, 23 November 1999 1400–1700 UT, By > 0, and 31 March

H. Korth; B. J. Anderson; M. J. Wiltberger; J. G. Lyon; P. C. Anderson

2004-01-01

324

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

Microsoft Academic Search

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

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

2000-01-01

325

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

SciTech Connect

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

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

2007-01-01

326

Ionization cross section measurements for autoionizing states of iridium and rhenium  

NASA Astrophysics Data System (ADS)

New autoionizing states for neutral iridium and rhenium atoms were observed in the continuum structure near the first ionization limit by using a two-colour two-step laser resonance ionization technique. The saturation curves for the autoionizing states were measured, and the ionization cross sections were experimentally determined by solving the rate equations for the ground, intermediate, and autoionizing state populations. Efficient ionization schemes are expected to be useful for applications such as laser ion sources of unstable nuclei.

Hirayama, Yoshikazu; Mukai, Momo; Watanabe, Yutaka; Imai, Nobuaki; Ishiyama, Hironobu; Jeong, Sun-Chan; Miyatake, Hiroari; Oyaizu, Michihiro; Matsuo, Yukari; Sonoda, Tetsu; Wada, Michiharu

2014-04-01

327

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

Microsoft Academic Search

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

John L. Barker Jr.; Edward Anders

1968-01-01

328

Enantio-, Diastereo- and Regioselective Iridium-Catalyzed Asymmetric Allylic Alkylation of Acyclic ?-Ketoesters  

PubMed Central

The first regio-, diastereo- and enantioselective allylic alkylation of acyclic ?-ketoesters to form vicinal tertiary and all-carbon quaternary stereocenters is reported. Critical to the successful development of this method was the employment of iridium catalysis in concert with N-aryl-phosphoramidite ligands. Broad functional group tolerance is observed at the keto-, ester-, and ?-positions of the nucleophile. Various transformations demonstrating the utility of this method for rapidly accessing complex enantioenriched compounds are reported. PMID:24160327

Liu, Wen-Bo; Reeves, Corey M.; Stoltz, Brian M.

2013-01-01

329

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

Microsoft Academic Search

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

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

1993-01-01

330

Biocompatibility and durability of Teflon-coated platinum-iridium wires implanted in the vitreous cavity.  

PubMed

Teflon-coated platinum-iridium wires are placed in the vitreous as electrodes in artificial vision systems. The purpose of this study was to determine whether these wires have toxicity in the vitreous cavity, and to examine the durability of their coating when grasped by forceps. Rabbits were implanted with platinum-iridium wires that were 50 ?m in diameter and coated with Teflon to a total diameter of 68 or 100 ?m. To examine the biocompatibility, electroretinograms (ERGs) and fluorescein angiography (FA) were performed before and 1 week, 1, 3, and 6 months after the implantation of the electrode. After 6 months, the eyes were histologically examined with light microscopy. To check the durability, the surface of a coated wire was examined with scanning electron microscopy after grasping with different types of forceps. At all times after the implantation the amplitudes and implicit times of the ERGs recorded were not significantly different from those recorded before the implantation (P > 0.05). FA showed no notable change during the follow-up periods. Histological studies showed that the retinas were intact after 6 months of implantation. There was no damage to the Teflon-coated wire after grasping the wire with forceps with silicon-coated tips, while surface damage of the Teflon that did not extend to the platinum-iridium wire was found when grasped by vitreoretinal forceps. We conclude that Teflon-coated platinum-iridium wire is highly biocompatible in the vitreous for at least 6 months. Wires should be handled with vitreoretinal forceps with silicone-coated tips in order to avoid causing damage during wire manipulation. PMID:21769688

Nishida, Kentaro; Sakaguchi, Hirokazu; Xie, Ping; Terasawa, Yasuo; Ozawa, Motoki; Kamei, Motohiro; Nishida, Kohji

2011-12-01

331

Iridium-N,P-ligand-catalyzed enantioselective hydrogenation of diphenylvinylphosphine oxides and vinylphosphonates.  

PubMed

Diphenylvinylphosphine oxides and di- and trisubstituted vinylphosphonates have been employed as substrates in iridium-catalyzed asymmetric hydrogenations. Complete conversions and excellent enantioselectivities (up to and above 99% ee) were observed for a range of substrates with both aromatic and aliphatic groups at the prochiral carbon. We have also hydrogenated electron-deficient carboxyethylvinylphosphonates with excellent stereoselectivity (up to and above 99% ee). The hydrogenated products of both classes of substrates are synthetically useful intermediates. PMID:19462955

Cheruku, Pradeep; Paptchikhine, Alexander; Church, Tamara L; Andersson, Pher G

2009-06-17

332

Shape-selective formation and characterization of catalytically active iridium nanoparticles  

Microsoft Academic Search

Iridium (Ir) nanoparticles (NPs) of variable shapes have been synthesized via the reduction of Ir(III) ions in CTAB micellar media containing alkaline 2,7-DHN under 4h of UV-irradiation. The one-step process generates different shapes, such as nano-spheres, nano-chains, nano-flakes, and nano-needles. The synthesized Ir NPs are stable for more than a month in ambient conditions. The particles’ morphology can be tuned

Subrata Kundu; Hong Liang

2011-01-01

333

Measurements of iridium and the meteoric impact hypothesis at cretaceous end  

Microsoft Academic Search

Both instrumental and radiochemical neutron activation analysis methods were developed for trace-element determination, such as iridium and gold, for application in cosmochemistry. The magnitude of the determined concentrations is in the range of parts per billion. In the instrumental method 1.5 grams of sample were submitted to irradiation by 10 to the 13th power thermal neutrons\\/sq cm\\/s during 32 hours.

F. Sircillineto

1986-01-01

334

Direct core functionalisation of naphthalenediimides by iridium catalysed C-H borylation.  

PubMed

We report the first boron-substituted naphthalenediimides (NDIs), prepared by iridium catalysed C-H activation. When the NDI substrates bear N-benzyl substituents, the naphthyl NDI core is borylated in preference, suggestive of a directed borylation mechanism. Borylated NDIs are substrates for Suzuki-Miyaura couplings and borylation of an NDI bearing two inequivalent N-substituents has also been demonstrated. PMID:25259375

Lyall, Catherine L; Shotton, Camilla C; Pérez-Salvia, Monserrat; Dan Panto?, G; Lewis, Simon E

2014-10-14

335

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

336

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

337

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

338

Supported Molecular Iridium Catalysts: Resolving Effects of Metal Nuclearity and Supports as Ligands  

SciTech Connect

The performance of a supported catalyst is influenced by the size and structure of the metal species, the ligands bonded to the metal, and the support. Resolution of these effects has been lacking because of the lack of investigations of catalysts with uniform and systematically varied catalytic sites. We now demonstrate that the performance for ethene hydrogenation of isostructural iridium species on supports with contrasting properties as ligands (electron-donating MgO and electron-withdrawing HY zeolite) can be elucidated on the basis of molecular concepts. Spectra of the working catalysts show that the catalytic reaction rate is determined by the dissociation of H{sub 2} when the iridium, either as mono- or tetra-nuclear species, is supported on MgO and is not when the support is the zeolite. The neighboring iridium sites in clusters are crucial for activation of both H{sub 2} and C{sub 2}H{sub 4} when the support is MgO but not when it is the zeolite, because the electron-withdrawing properties of the zeolite support enable even single site-isolated Ir atoms to bond to both C{sub 2}H{sub 4} and H{sub 2} and facilitate the catalysis.

Lu, Jing; Serna, Pedro; Aydin, Cerem; Browning, Nigel D.; Gates, Bruce C. (UCD)

2012-02-07

339

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

340

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

341

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

342

Cycle performance of a silver-metal hydride cell  

SciTech Connect

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

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

1996-11-01

343

Method for preparing hydride configurations and reactive metal surfaces  

DOEpatents

A method for preparing reactive metal surfaces, particularly uranium surfaces is disclosed, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure. The metal surfaces are first pretreated by exposure to an acid which forms an adherent hydride-bearing composition on the metal surface. Subsequent heating of the pretreated metal at a temperature sufficient to decompose the hydride coating in vacuum or inert gas renders the metal surface instantaneously reactive to hydrogen gas at room temperature and low pressure.

Silver, G.L.

1984-05-18

344

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

345

A stable 16-electron iridium(III) hydride complex grafted on SBA-15: a single-site catalyst for alkene hydrogenation.  

PubMed

The dihydride pincer complex [IrH2(POCOP)] reacts with surface silanols of mesoporous silica (SBA-15) to give the coordinatively unsaturated, yet stable hydridesiloxo Ir(III) species [IrH(O-SBA-15)(POCOP)]. The silica-grafted complex catalyses the hydrogenation of ethene and propene at low temperature and pressure without prior activation. PMID:24158159

Rimoldi, Martino; Fodor, Daniel; van Bokhoven, Jeroen A; Mezzetti, Antonio

2013-12-14

346

An Electrolytic Method to Form Zirconium Hydride Phases in Zirconium Alloys with Morphologies Similar to Hydrides Formed in Used Nuclear Fuel  

E-print Network

AN ELECTROLYTIC METHOD TO FORM ZIRCONIUM HYDRIDE PHASES IN ZIRCONIUM ALLOYS WITH MORPHOLOGIES SIMILAR TO HYDRIDES FORMED IN USED NUCLEAR FUEL A Thesis by SAMUEL HOUSTON KUHR Submitted to the Office of Graduate Studies of Texas A...&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2012 Major Subject: Nuclear Engineering ii An Electrolytic Method to Form Zirconium Hydride Phases...

Kuhr, Samuel Houston

2012-10-19

347

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

SciTech Connect

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

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

2001-03-01

348

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

349

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

350

Heat-mass flow enhancement system for a metal hydride assembly  

NASA Astrophysics Data System (ADS)

Southern California Gas Company and Solar Turbines Incorporated are cooperating in the development and demonstration of a metal hydride/chemical heat pump (MHHP). In the design of the MHHP, heat transfer was considered to be the key technical study area. The goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger/containment assembly. Phase 1 resulted in the detailed design of an advanced hydride heat exchanger. Phase 2 consisted of the experimental verification of the hydride alloy design data, fabrication of the hydride heat exchanger module components, heat transfer testing of the single heat exchanger element and preliminary performance testing of the entire module. Phase 3 was devoted to the complete characterization of the hydride heat exchanger modules through further operation and testing. A review of other possible hydride heat transfer concepts was also conducted in Phase 2.

Argabright, T. A.

1985-02-01

351

Synthesis, photophysical and electroluminescent properties of novel iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives  

NASA Astrophysics Data System (ADS)

A new series of phosphorescent iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives as main ligands, i.e. bis(5-methyl-2- phenylbenzo[d]oxazole-N,C2?)iridium(acetylacetonate) [(mpbo)2Ir(acac)], bis(2-(4-fluorophenyl)-5-methylbenzo[d]oxazole-N,C2?)iridium(acetylacetonate) [(fmbo)2Ir(acac)] and bis(5-methyl-2-p-tolylbenzo[d]oxazole-N,C2?) iridium(acetylacetonate) [(mtbo)2Ir(acac)], were synthesized for organic light-emitting diodes (OLEDs), and their photophysical, electroluminescent properties were investigated. All complexes have high thermal stability and emit intense phosphorescence from green to yellow at room temperature with high quantum efficiencies and relatively short lifetimes. The OLED based on (fmbo)2Ir(acac) as dopant emitter showed very high luminance of 26,004 cd m-2 and luminance efficiency of 18.5 cd A-1. The evidences indicated that this series of iridium (III) complexes were potential candidates for applications in organic electroluminescent devices.

Li, Xiao; Chi, Hai-Jun; Dong, Yan; Xiao, Guo-Yong; Lei, Peng; Zhang, Dong-Yu; Cui, Zheng

2013-12-01

352

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

E-print Network

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

Paris-Sud XI, Université de

353

Atomic hydrogen desorption from thin palladium hydride films  

NASA Astrophysics Data System (ADS)

It has been proved that hydrogen atoms desorb from the surface of a decomposing thin palladium hydride film. A thin gold film deposited and sintered in situ was used as a selective adsorbent for atomic hydrogen. The TDMS (thermal desorption mass spectrometry) technique was applied to detect the adsorption of hydrogen on gold and to determine the amount adsorbed.

Lisowski, W.; Nowicka, E.; Wolfram, Z.; Du?, R.

1988-01-01

354

Oriented xenon hydride molecules in the gas phase  

Microsoft Academic Search

The production of the xenon hydride molecules HXeX with X = I and Cl in the gas phase is reviewed. These molecules are generated by the photolysis of the hydrogen halide HI and HCl molecules on the surface of large xenon Xen clusters. Molecular dynamics simulations show that the flexible H atoms react with the heavy XeX moiety and form

Udo Buck; Michal Fárník

2006-01-01

355

Photoelectron spectroscopy of phosphorus hydride anions Kent M. Ervina  

E-print Network

, University of Colorado and National Institute of Standards and Technology, and Department of Chemistry February 2005; published online 13 May 2005 Negative-ion photoelectron spectroscopy is applied to the PH apply negative-ion photoelectron spec- troscopy to a series of phosphorus hydride anions, PH- , PH2

Lineberger, W. Carl

356

Structural and Electronic Properties of Magnesium Hydride Surfaces.  

NASA Astrophysics Data System (ADS)

The Mg--MgH2 system is of considerable interest in hydrogen technology, though the hydride forms very slowly. The microscopic mechanisms of hydriding/dehydriding Mg are not yet fully understood. In particular, transmission electron microscopy experimentsootnotetextB. Bokhonov et al., Mat. Lett. 5, 218 (1987); A. Altmann and T. Schober, Scripta Met. 25, 723 (1991). have shown differences in the relative orientation between the MgH2 lattice and the (hexagonal) Mg substrate during the formation process [ ,100)hydride; | ; (0001)Mg,, and the decomposition one [ ,110)hydride; | ; (0001)Mg,. In order to contribute to the understanding of the above orientation differences, and in general of the reactions occurring at the MgH2 surface, we have performed a comparative study of the unrelaxed and relaxed (100) and (110) surfaces. The electronic structure has been calculated using the LAPW method, and the chemical bonding has been obtained from the corresponding Wannier functions. Bonding at the surface differs from that of the bulk, and strongly depends on surface orientation and relaxation.

Posternak, Michel A.

2005-03-01

357

The importance of vibrations in modelling complex metal hydrides  

Microsoft Academic Search

Crystalline materials have zero point energy (ZPE) associated with phonon vibrations. This ZPE not only significantly alters the energetics of reactions involving complex metal hydrides, but also alters the equilibrium structure of these materials as determined by first principles calculations. This paper focuses on the structural effect of ZPE in the potential hydrogen storage material LiBH4.

Terry J. Frankcombe

2007-01-01

358

Process of forming a sol-gel/metal hydride composite  

DOEpatents

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

Congdon, James W. (Aiken, SC)

2009-03-17

359

5-year review of Metal Hydride Center of Excellence.  

SciTech Connect

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

Keller, Jay O.; Klebanoff, Leonard E.

2010-05-01

360

Hydride transfer catalyzed by xylose isomerase: mechanism and quantum effects.  

PubMed

We have applied molecular dynamics umbrella-sampling simulation and ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT) to calculate the reaction rate of xylose-to- xylulose isomerization catalyzed by xylose isomerase in the presence of two Mg2+ ions. The calculations include determination of the free energy of activation profile and ensemble averaging in the transmission coefficient. The potential energy function is approximated by a combined QM/MM/SVB method involving PM3 for the quantum mechanical (QM) subsystem, CHARMM22 and TIP3P for the molecular mechanical (MM) environment, and a simple valence bond (SVB) local function of two bond distances for the hydride transfer reaction. The simulation confirms the essential features of a mechanism postulated on the basis of kinetics and X-ray data by Whitlow et al. (Whitlow, M.; Howard, A. J.; Finzel, B. C.; Poulos, T. L.; Winborne, E.; Gilliland, G. L. Proteins 1991, 9, 153) and Ringe, Petsko, and coworkers (Labie, A.; Allen, K.-N.; Petsko, G. A.; Ringe, D. Biochemistry 1994, 33, 5469). This mechanism involves a rate-determining 1,2-hydride shift with prior and post proton transfers. Inclusion of quantum mechanical vibrational energy is important for computing the free energy of activation, and quantum mechanical tunneling effects are essential for computing kinetic isotope effects (KIEs). It is found that 85% of the reaction proceeds by tunneling and 15% by overbarrier events. The computed KIE for the ratio of hydride to deuteride transfer is in good agreement with the experimental results. The molecular dynamics simulations reveal that proton and hydride transfer reactions are assisted by breathing motions of the mobile Mg2+ ion in the active site, providing evidence for concerted motion of Mg2+ during the hydride transfer step. PMID:12497598

Garcia-Viloca, Mireia; Alhambra, Cristóbal; Truhlar, Donald G; Gao, Jiali

2003-01-30

361

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

E-print Network

the potential energy surface. Classical free energy curves in both acetonitrile and water are calculatedDevelopment of a Potential Surface for Simulation of Proton and Hydride Transfer Reactions; In Final Form: March 26, 1997X This paper presents a new augmented molecular mechanical potential

Hammes-Schiffer, Sharon

362

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

363

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

364

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

365

Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan  

USGS Publications Warehouse

The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

Nichols, D.J.; Jarzen, D.M.; Orth, C.J.; Oliver, P.Q.

1986-01-01

366

A colorimetric chemosensor for Cu(2+) ion detection based on an iridium(III) complex.  

PubMed

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu(2+) ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu(2+) ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu(2+) ions in tap water or natural river water samples was demonstrated. PMID:25348724

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W J; Leung, Chung-Hang; Ma, Dik-Lung

2014-01-01

367

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

SciTech Connect

Highly dealuminated Y zeolite-supported mononuclear iridium complexes with reactive ethylene ligands were synthesized by chemisorption of Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}). The resultant structure and its treatment in He, CO, ethylene, and H2 were investigated with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The IR spectra show that Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) reacted readily with surface OH groups of the zeolite, leading to the removal of C{sub 5}H{sub 7}O{sub 2} ligands and the formation of supported mononuclear iridium complexes, confirmed by the lack of Ir-Ir contributions in the EXAFS spectra. The EXAFS data show that each Ir atom was bonded to four carbon atoms at an average distance of 2.10 {angstrom}, consistent with the presence of two ethylene ligands per Ir atom and in agreement with the IR spectra indicating {pi}-bonded ethylene ligands. The EXAFS data also indicate that each Ir atom was bonded to two oxygen atoms of the zeolite at a distance of 2.15 {angstrom}. The supported iridium-ethylene complex reacted with H{sub 2} to give ethane, and it also catalyzed ethylene hydrogenation at atmospheric pressure and 294 K. Treatment of the sample in CO led to the formation of Ir(CO){sub 2} complexes bonded to the zeolite. The sharpness of the V{sub CO} bands indicates a high degree of uniformity of these complexes on the support. The iridium-ethylene complex on the crystalline zeolite support is inferred to be one of the most nearly uniform supported metal complex catalysts. The results indicate that it is isostructural with a previously reported rhodium complex on the same zeolite; thus, the results are a start to a family of analogous, structurally well-defined supported metal complex catalysts.

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

2009-06-04

368

Evolution of odd A transitional iridium nuclei at the strong deformation limit levels of $\\^{185}$Ir  

E-print Network

A level scheme is proposed for neutron deficient /sup 185/Ir obtained by the decay of /sup 185/Pt produced with the ISOLDE on-line separator (CERN). This level scheme is compared to those of heavier mass iridium nuclei where the negative parity levels had been interpreted in the asymmetric-rotor-plus-particle model. In /sup 185/Ir similar systems of levels appear with a stronger prolate deformation of the nucleus. They seem correctly described by coupling an odd-particle (or a hole) to a symmetric rotor.

Sébille-Schück, C; Genevey-Rivier, J; Höglund, A; Huck, A; Knipper, A; Richard-Serre, Claude; Walter, G

1976-01-01

369

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

Microsoft Academic Search

Between 1970 and 1986, 166 patients with T1 or T2 epidermoid carcinomas of the mobile tongue were treated by iridium 192 implantation (70 T1N0, 83 T2N0, 13 T1-2 N1-3). Five-year actuarial survival was 52% for T1N0, 44% for T2aN0, and 8% for or T1-2 N1-3. Cause specific survivals were 90%, 71%, and 46%, respectively. Local control was 87% for both

J. J. Mazeron; J. M. Crook; V. Benck; G. Marinello; M. Martin; M. Raynal; E. Haddad; R. Peynegre; J. P. Le Bourgeois; W. Walop

1990-01-01

370

A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex  

NASA Astrophysics Data System (ADS)

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated.

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

2014-10-01

371

Epitaxial (100) iridium on A-plane sapphire: A system for wafer-scale diamond heteroepitaxy  

Microsoft Academic Search

Large-scale heteroepitaxial growth of diamond depends critically on the development of a suitable lattice-matched buffer layer and substrate system. Epitaxial (100) iridium films have been grown on terraced, vicinal a-plane (1120) alpha-Al2O3 (sapphire) by electron-beam evaporation. The epitaxial relationship, Ir(100)\\/\\/Al2O3(1120) with Ir[011]\\/\\/Al2O3[1100], was determined by x-ray diffraction and electron backscattering diffraction analysis. For a 300-nm thickness of Ir, a (200)

Z. Dai; C. Bednarski-Meinke; R. Loloee; B. Golding

2003-01-01

372

Measurement of dosimetric parameters for the Alpha-Omega high-dose-rate Iridium-192 source  

SciTech Connect

Thermoluminescent (TLD) measurements of dose-rate constant, anisotropy function, and radial dose function are reported for the Alpha-Omega high dose rate (HDR) Iridium-192 ({sup 192}Ir) source, which has been available since 1998 for use in the MicroSelectron HDR afterloader manufactured by the Nucletron Corporation. Measurement results are compared with published or available Monte Carlo calculations for both sources. They are found in good agreement, and, within experimental accuracy, no difference is seen in the dosimetric parameters of both sources.

Muller-Runkel, R. [Department of Radiation Oncology, Saint Margaret Mercy Healthcare Centers, Hammond, IN (United States)]. E-mail: renate.muller@ssfhs.org

2005-09-30

373

A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex  

PubMed Central

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1?3 bearing a rhodamine-linked NˆN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated. PMID:25348724

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

2014-01-01

374

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

PubMed

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

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

2014-02-26

375

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

USGS Publications Warehouse

We directly link iridium (Ir) anomalies in New Jersey to the mass extinction of marine plankton marking the Cretaceous-Paleogene (K-Pg) boundary. We confirm previous reports of an Ir anomaly 20 cm below the extinction of Cretaceous macrofauna (the "Pinna" bed) with new results from a muddy sand section from Tighe Park, Freehold, New Jersey (United States), but we also show that Ir anomalies correlate with marine mass extinctions at three other clay-rich New Jersey sections. Thus, we attribute the anomaly at Freehold to the downward movement of Ir and reaffirm the link between impact and mass extinction. ?? 2010 Geological Society of America.

Miller, K.G.; Sherrell, R.M.; Browning, J.V.; Field, M.P.; Gallagher, W.; Olsson, R.K.; Sugarman, P.J.; Tuorto, S.; Wahyudi, H.

2010-01-01

376

Sublimation not an innocent technique: a case of bis-cyclometalated iridium emitter for OLED.  

PubMed

Isomerization of a neutral bis-cyclometalated iridium(III) complex has been observed for the first time during the preparation of vacuum-processed organic light-emitting devices (OLEDs) and reproduced in solution. Isolation of the isomer revealed a cis organization of the two pyridine rings of the cyclometalating ligands. Photophysical studies show very similar emission properties of the two isomers. However, due to in situ isomerization, it is only possible to prepare vacuum-processed OLED devices having a mixture of isomers. PMID:18590328

Baranoff, Etienne; Suàrez, Stéphane; Bugnon, Philippe; Barolo, Claudia; Buscaino, Roberto; Scopelliti, Rosario; Zuppiroli, Libero; Graetzel, Michael; Nazeeruddin, Md K

2008-08-01

377

The Collision of Iridium 33 and Cosmos 2251: The Shape of Things to Come  

NASA Technical Reports Server (NTRS)

The collision of Iridium 33 and Cosmos 2251 was the most severe accidental fragmentation on record. More than 1800 debris approx. 10 cm and larger were produced. If solar activity returns to normal, half of the tracked debris will reenter within five years. Less than 60 cataloged debris had reentered by 1 October 2009. Some debris from both satellites will remain in orbit through the end of the century. The collision rate of one every five years will increase without future removal of large derelict spacecraft and launch vehicle orbital stages.

Nicholas, Johnson

2009-01-01

378

Effect of hydride orientation on fracture toughness of Zircaloy-4 cladding  

NASA Astrophysics Data System (ADS)

Hydrogen embrittlement is one of the major degradation mechanisms for high burnup fuel cladding during reactor service and spent fuel dry storage, which is related to the hydrogen concentration, morphology and orientation of zirconium hydrides. In this work, the J-integral values for X-specimens with different hydride orientations are measured to evaluate the fracture toughness of Zircaloy-4 (Zry-4) cladding. The toughness values for Zry-4 cladding with various percentages of radial hydrides are much smaller than those with circumferential hydrides only in the same hydrogen content level at 25 °C. The fractograghic features reveal that the crack path is influenced by the orientation of zirconium hydride. Moreover, the fracture toughness measurements for X-specimens at 300 °C are not sensitive to a variation in hydride orientation but to hydrogen concentration.

Hsu, Hsiao-Hung; Tsay, Leu-Wen

2011-01-01

379

Composition and structure of sputter deposited erbium hydride thin films  

SciTech Connect

Erbium hydride thin films are grown onto polished, a-axis {alpha} Al{sub 2}O{sub 3} (sapphire) substrates by reactive ion beam sputtering and analyzed to determine composition, phase and microstructure. Erbium is sputtered while maintaining a H{sub 2} partial pressure of 1.4 x 10{sup {minus}4} Torr. Growth is conducted at several substrate temperatures between 30 and 500 C. Rutherford backscattering spectrometry (RBS) and elastic recoil detection analyses after deposition show that the H/Er areal density ratio is approximately 3:1 for growth temperatures of 30, 150 and 275 C, while for growth above {approximately}430 C, the ratio of hydrogen to metal is closer to 2:1. However, x-ray diffraction shows that all films have a cubic metal sublattice structure corresponding to that of ErH{sub 2}. RBS and Auger electron that sputtered erbium hydride thin films are relatively free of impurities.

ADAMS,DAVID P.; ROMERO,JUAN A.; RODRIGUEZ,MARK A.; FLORO,JERROLD A.; BANKS,JAMES C.

2000-05-10

380

Quantum molecular dynamics simulation of hydrogen diffusion in zirconium hydride  

NASA Astrophysics Data System (ADS)

The behavior of hydrogen in zirconium hydride in the high-temperature range has been investigated using the quantum molecular dynamics method. The ? phases of compositions ZrH1.75 and ZrH2 and the liquid phase are considered. The self-diffusion coefficients of hydrogen are calculated as a function of the temperature in the range from 1000 to 6000 K. For the ZrH1.75 and ZrH2 hydrides, the obtained values are close to each other. At temperatures of 1000-2000 K, the hydrogen diffusion is determined not only by the mobility of hydrogen atoms but also by the transition from the energetically favorable tetrahedral positions into the excited state. The obtained values of the diffusion coefficients in the temperature range of 1000-1200 K are in good agreement with the experimental data.

Yanilkin, A. V.

2014-09-01

381

Compton scattering study of the electronic structure of magnesium hydride  

NASA Astrophysics Data System (ADS)

Compton scattering measurements have been made on magnesium hydride (MgH2) using the 59.54-keV gamma rays from a 300-mCi 241Am source at a scattering angle of 150°. Two different theoretical approaches have been used for comparison with the experimental data. In the first approach, the Compton profile of the valence electrons in MgH2 was calculated by the pseudopotential orthogonalized-plane-wave (OPW) method, including core orthogonalization. In the second approach, the Compton profile of MgH2 was calculated using the tight-binding linear combination of atomic orbitals (LCAO) method, including large overlaps. Both calculations yielded profiles which are in fairly good agreement with the experimental isotropic profile. The results indicate that the ionic picture of MgH2 is not simple since its outer electrons are extended. Possible implications of the production process of the hydride are briefly discussed.

Felsteiner, J.; Heilper, M.; Gertner, I.; Tanner, A. C.; Opher, R.; Berggren, K.-F.

1981-05-01

382

Nb clusters formation in Nb-doped magnesium hydride  

NASA Astrophysics Data System (ADS)

Extended x-ray absorption fine structure spectroscopy, x-ray diffraction and transmission electron microscopy were used to analyze the Nb coordination and clustering in Nb-doped (5 at. %) h-Mg film samples deposited by rf magnetron sputtering. Results show that the catalytic effect of the Nb doping in the H2 absorption and desorption kinetics is connected with the formation of Nb nanoclusters dispersed in the host matrix. The H2 desorption from ?-MgH2 is favored by local elastic stresses produced by ?-NbH0.89 clusters on the MgH2 matrix that reduces the stability of the hydride phase and by preferential paths in the nanocomposite hydride.

Checchetto, R.; Bazzanella, N.; Miotello, A.; Maurizio, C.; D'Acapito, F.; Mengucci, P.; Barucca, G.; Majni, G.

2005-08-01

383

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

384

X-ray diffraction analysis of titanium hydrides in commercial titanium alloys  

Microsoft Academic Search

1.Commercial a titanium alloys with 0.01–0.03% H have a complex phase composition and contain precipitates of saturated and unsaturated cubic hydrides, and also regions of the matrix supersaturated with hydrogen.2.Under ordinary conditions, no hydrides are precipitated in a+ß alloys with the same hydrogen concentration. Titanium hydrides may be precipitated during welding and with application of stresses in zones with an

N. V. Ageev; A. A. Babaréko; E. B. Rubina; S. Ya. Betsofen; L. A. Bunin

1976-01-01

385

High temperature metal hydrides as heat storage materials for solar and related applications.  

PubMed

For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 degrees 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

386

Ag enhances optical and switching properties of gadolinium hydride films  

Microsoft Academic Search

An improvement of the optical properties of switchable mirrors is obtained by incorporating of silver (Ag) into the palladium (Pd) cap layer of nanocrystalline gadolinium hydride system Gd\\/GdH3. Two methods for modification of Pd layer with Ag are employed. The first method is the forming of an AgPd binary alloy. The second method is the forming of Ag\\/Pd bilayer. In

E. Shalaan; A. A. Al-Ghamdi

2010-01-01

387

Oxidation kinetics of hydride-bearing uranium metal corrosion products  

Microsoft Academic Search

The oxidation behavior of hydride-bearing uranium metal corrosion products from Zero Power Physics Reactor (ZPPR) fuel plates was studied using thermo-gravimetric analysis (TGA) in environments of Ar–4%O2, Ar–9%O2, and Ar–20%O2. Ignition of corrosion product samples from two moderately corroded plates was observed between 125°C and 150°C in all environments. The rate of oxidation above the ignition temperature was found to

Terry C Totemeier; Robert G Pahl; Steven M Frank

1999-01-01

388

Isotope Effect in the Spectrum of Cadmium Hydride  

Microsoft Academic Search

IN an earlier paper1, I dealt with the structure of different band systems in the spectrum of cadmium hydride. In several respects, however, my analysis suffered from incomplete resolution of the spectrum, especially regarding the isotope splitting of the band lines. Recently I repeated the investigation, using a large concave grating in the third order (0.6 A.\\/mm.). Much work was

Erik Svensson

1933-01-01

389

Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications  

NASA Astrophysics Data System (ADS)

Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

Thanawala, Sachin

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

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

392

Hydrogen pressures and dissociation enthalpies of americium and curium hydrides determined by Knudsen effusion mass spectrometry  

SciTech Connect

A Knudsen effusion mass spectrometric technique has been developed for the study of milligram-sized samples of metal hydrides. This new technique is necessary for the determination of the dissociation pressures and thermal stabilities of hydrides of the scarce and highly radioactive transplutonium elements. The sensitivity of this technique was such that experiments could be carried out with as little as {approximately} 50 {mu} mol of metal. Dissociation pressures were determined for americium and curium hydrides; studies were also made with selected lanthanide hydrides, for comparison. The decomposition thermodynamics of these materials are discussed.

Gibson, J.K.; Haire, R.G. (Oak Ridge National Lab., TN (USA))

1990-01-25

393

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

394

Electronic structure of ternary rhodium hydrides with lithium and magnesium.  

PubMed

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

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

2014-01-21

395

Materials for Hydrogen Storage: From Nanostructures to Complex Hydrides  

NASA Astrophysics Data System (ADS)

The limited supply of fossil fuels, its adverse effect on the environment, and growing worldwide demand for energy has necessitated the search for new and clean sources of energy. The possibility of using hydrogen to meet this growing energy need has rekindled interest in the study of safe, efficient, and economical storage of hydrogen. This talk will discuss the issues and challenges in storing hydrogen in light complex hydrides and discuss the role of nanostructuring and catalysts that can improve the thermodynamics and kinetics of hydrogen. In particular, we will discuss how studies of clusters can help elucidate the fundamental mechanisms for hydrogen storage and how these can be applied in Boron Nitride and Carbon nanocages and how metallization of these nanostructures is necessary to store hydrogen with large gravimetric density. We will also discuss the properties of complex light metal hydrides such as alanates and magnesium hydrides that can store up to 18 wt % hydrogen, although the temperature where hydrogen desorbs is rather high. Using first principles calculations, we will provide a fundamental understanding of the electronic structure and stability of these systems and how it is affected due to catalysts. It is hoped that the understanding gained here can be useful in designing better catalysts as well as hosts for hydrogen storage.

Jena, Puru

2006-03-01

396

Dyads containing iridium(III) bis-terpyridine as photoactive center: synthesis and electron transfer study.  

PubMed

A series of Ir(III)-D dyads based on an iridium(III) bis-terpyridine complex as a photoactive center and tertiary amines as donor groups, as well as their individual components, have been designed to generate photoinduced charge separation. Depending on the donor group, a modular approach or a "chemistry-on-the-complex" approach has been used to prepare three different Ir(III)-D dyads. A detailed photophysical study has been performed on one Ir(III)-D dyad in which a triarylamine is linked to the iridium bis-terpyridine complex with an amido-phenyl group used as a spacer. In acetonitrile at room temperature, steady-state and time-resolved methods gave evidence of a photoinduced charge-separated state Ir(-)-D(+) with a lifetime of 70 ps. This relatively short lifetime could be due to the close proximity between the negative charge, likely localized in the bridging terpyridine, and the oxidized donor group. PMID:15132611

Baranoff, Etienne; Dixon, Isabelle M; Collin, Jean-Paul; Sauvage, Jean-Pierre; Ventura, Barbara; Flamigni, Lucia

2004-05-17

397

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

SciTech Connect

Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

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

1992-01-01

398

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

SciTech Connect

Iridium alloys are used as fuel-cladding materials in radioisotope thermoelectric generators (RTGs). Hardware produced at the Oak Ridge National Laboratory (ORNL) has been used in Voyagers I and 2, Galilee, and Ulysses spacecraft. An integral part of the production of iridium-sheet metal involves electron-beam (EB) processing. These processes include the degassing of powder-pressed compacts followed by multiple meltings in order to purify 500-g buttons of Ir-0.3% W alloy. Starting in 1972 and continuing into 1992, our laboratory EB processing was Performed (ca. 1970) in a 60-kW (20 kV at 3 A), two-gun system. In 1991, a new 150-kW EB gun facility was installed to complement the older unit. This paper describes how the newly installed system was qualified for production of RTG developmental work is discussed that will potentially improve the existing process by utilizing the capabilities of the new EB system.

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

1992-12-31

399

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

SciTech Connect

A new type of electrocatalyst with a core?shell structure that consists of a platinum monolayer shell placed on an iridium? rhenium nanoparticle core or platinum and palladium bilayer shell deposited on that core has been prepared and tested for electrocatalytic activity for the oxygen reduction reaction. Carbon-supported iridium? rhenium alloy nanoparticles with several different molar ratios of Ir to Re were prepared by reducing metal chlorides dispersed on Vulcan carbon with hydrogen gas at 400 °C for 1 h. These catalysts showed specific electrocatalytic activity for oxygen reduction reaction comparable to that of platinum. The activities of PtML/PdML/Ir2Re1, PtML/Pd2layers/Ir2Re1, and PtML/Pd2layers/Ir7Re3 catalysts were, in fact, better than that of conventional platinum electrocatalysts, and their mass activities exceeded the 2015 DOE target. Our density functional theory calculations revealed that the molar ratio of Ir to Re affects the binding strength of adsorbed OH and, thereby, the O2 reduction activity of the catalysts. The maximum specific activity was found for an intermediate OH binding energy with the corresponding catalyst on the top of the volcano plot. The monolayer concept facilitates the use of much less platinum than in other approaches. The results with the PtML/PdML/Ir2Re electrocatalyst indicate that it is a promising alternative to conventional Pt electrocatalysts in low-temperature fuel cells.

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

2012-05-04

400

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

401

Tuning the Emission Lifetime in Bis-cyclometalated Iridium(III) Complexes Bearing Iminopyrene Ligands.  

PubMed

Bis-cyclometalated Ir(III) complexes with the general formula Ir(ppz)2(X^NPyrene), where ppz = 1-phenylpyrazole and X^NPyrene is a bidentate chelate with X = N or O, are reported. Modifications on the ancillary ligand containing pyrene drastically affect the emission lifetimes observed (0.329 to 104 ?s). Extended emission lifetimes in these complexes compared to model complexes result from reversible electronic energy transfer or the observation of dual emission containing along-lived pyrene ligand-centered triplet ((3)LC) component. A combination of steady-state and time-resolved spectroscopic techniques are used to observe reversible electronic energy transfer in solution between the iridium core and pyrene moiety in the complex [Ir(ppz)2(NMe^NCH2Pyr)][PF6] (2), where NMe^NCH2Pyr = N-(pyren-1-ylmethyl)-1-(pyridin-2-yl)ethaneimine. Studies on [Ir(ppz)2(NMe^NCH2Pyr)][PF6] in a poly(methyl methacrylate) (PMMA) film reveal that reversible energy transfer is no longer effective, and instead, dual emission with a long-lived (3)LC component from pyrene is observed. Dual emission is observed in additional cyclometalated iridium complexes bearing pyrene-containing ancillary ligands N^NPyrene and O^NPyrene when the complexes are dispersed in a PMMA film. PMID:25347609

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

2014-11-17

402

Treatment of bladder cancer with interstitial iridium-192 implantation and external beam irradiation  

SciTech Connect

Although interstitial implantation of invasive carcinoma of the bladder has been shown to be an effective treatment in Europe, there has been little experience with this method in the U.S. During the past 6 years, 14 patients at the Hospital of the University of Pennsylvania with single bladder tumors less than 5 cm and no evidence of carcinoma in situ on random bladder biopsies have been treated by a combination of external beam radiation and iridium wire implant. The iridium wire is inserted by an afterloading technique following tumor exposure via suprapubic cystotomy. Following delivery of the prescribed dose, the sources are removed percutaneously. Three patients with recurrent or high grade T1 lesions and 11 patients with T2-T3A lesions have been treated. With a median follow-up of 22 months (range 17 to 65 months), 9 patients are currently NED, 4 patients have died of disease, and 1 patient has died of intercurrent disease. There have been two isolated bladder recurrences, both non-invasive, one having been treated with cystectomy and one being treated locally. In addition, one patient developed regional failure, two developed distant metastases only, and one developed local recurrence following distant failure. The 2-year actuarial local control rate is 84%, with an overall 2-year actuarial survival of 66%. Complications have been minimal. Bladder implantation by this method is technically simple and produces excellent local control with acceptable morbidity.

Straus, K.L.; Littman, P.; Wein, A.J.; Whittington, R.; Tomaszewski, J.E.

1988-02-01

403

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

404

[Brachytherapy in France: Current situation and economic outlook due to the unavailability of iridium wires].  

PubMed

In 2013, about 6000 patients were treated with brachytherapy, the number diminishing by 2.6% per year since 2008. Prostate, breast and gynecological cancers are the most common types of cancers. Since 2008, the number of brachytherapy facilities has decreased by 18%. In medicoeconomic terms, brachytherapy faces many problems: the coding system is outdated; brachytherapy treatments cost as much as internal radiation; fees do not cover costs; since iridium wire has disappeared from the market, the technique will be transferred to more expensive high-speed or pulse dose rates. The French financing grid based on the national study of costs lags behind changes in such treatments and in the best of cases, hospitals resorting to alternatives such as in-hospital brachytherapy are funded at 46% of their additional costs. Brachytherapy is a reference technique. With intense pressure on hospital pricing, financing brachytherapy facilities will become even more problematic as a consequence of the disappearance of iridium 192 wires. The case of brachytherapy illustrates the limits of the French financing system and raises serious doubts as to its responsiveness. PMID:25195115

Le Vu, B; Boucher, S

2014-10-01

405

Site-isolated Iridium Complexes on MgO Powder: Individual Ir Atoms Imaged by Scanning Transmission Electron Microscopy  

SciTech Connect

Iridium complexes were synthesized on MgO powder by adsorption of Ir(C{sub 2}H{sub 4}){sub 2}(acac) [acac = acetonylacetonate]; images determined by aberration-corrected scanning transmission electron microscopy show individual Ir atoms, demonstrating that the supported complexes were site-isolated.

Uzun, A.; Ortalan, V; D. Browning, N; C. Gates , B

2009-01-01

406

Development of novel rhodium and iridium complexes with a fac-chelating ligand for electrophilic C-H activation.  

E-print Network

??Several new bis-3,5(dimethylpyrazol-1-yl)acetate rhodium and iridium complexes were synthesized from MCl3•H2O. [Rh(bdmpza)Cl3]- was isolated with three different cations, lithium, sodium and tetraethylamonium, to obtain a… (more)

Rhinehart, Jennifer Lee (1984 - )

2012-01-01

407

Prognostic factors of local outcome for T1, T2 carcinomas of oral tongue treated by iridium 192 implantation  

Microsoft Academic Search

The results of Iridium 192 implantation for 121 node negative T1 or T2 squamous carcinomas of mobile tongue were reviewed to look for predictors of local control and necrosis. Age, sex, total dose, dose rate, linear activity, and intersource spacing were examined. Minimum follow-up was 2 years but no patient with local recurrence or necrosis was excluded. There were 57

J. J. Mazeron; J. M. Crook; G. Marinello; W. Walop; B. Pierquin

1990-01-01

408

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

NASA Technical Reports Server (NTRS)

The AirCell/Iridium dual mode service is evaluated for potential applications to Air Traffic Management (ATM) communication needs. The AirCell system which is largely based on the Advanced Mobile Phone System (AMPS) technology, and the Iridium FDMA/TDMA system largely based on the Global System for Mobile Communications(GSM) technology, can both provide communication relief for existing or future aeronautical communication links. Both have a potential to serve as experimental platforms for future technologies via a cost effective approach. The two systems are well established in the entire CONUS and globally hence making it feasible to utilize in all regions, for all altitudes, and all classes of aircraft. Both systems have been certified for air usage. The paper summarizes the specifications of the AirCell/Iridium system, as well as the ATM current and future links, and application specifications. the paper highlights the scenarios, applications, and conditions under which the AirCell/Iridium technology can be suited for ATM Communication.

Shamma, Mohammed A.

2004-01-01

409

Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes  

PubMed Central

Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and purines have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431

Stanley, Levi M.

2010-01-01

410

High-Efficiency White Organic Light-Emitting Devices Based on a Highly Amorphous Iridium(III) Orange Phosphor  

E-print Network

High-Efficiency White Organic Light-Emitting Devices Based on a Highly Amorphous Iridium ReceiVed August 14, 2006 An efficient multilayer white organic light-emitting diode (WOLED) based cd/m2 at 10 V and 30 mA/cm2 . The color of the white light corresponds to the Commission

411

Results of an Iridium-Based Data Communication System Providing Internet Access to Polar Expeditions  

NASA Astrophysics Data System (ADS)

The Polar Radar for Ice Sheet Measurements (PRISM) Project at the University of Kansas has developed and field-tested a versatile communications system for use by researchers in high-latitude Polar Regions. The PRISM project is developing advanced intelligent remote sensing technology that involves radar systems, an autonomous rover, and communications systems to measure detailed ice sheet characteristics, and to determine bed conditions (frozen or wet) below active ice sheets in both Greenland and Antarctica. We also have a very strong public outreach and educational program aimed at K-12 educators and students that requires data, voice and video feeds from Polar field locations in near real time. Hence, PRISM requires a robust communications system for use in the field between a base camp and the mobile remote sensing system, and from the field back to the University of Kansas and onto the Internet. The communication system that has been developed is truly mobile and is relatively inexpensive. We initially considered various satellite services during the design phase of this project. The two feasible options for high-latitude locations were Iridium, with its low-bit-rate service (2.4 Kb/s), and Inmarsat/Intelsat with broadband service. We selected the Iridium option for testing and development because it provided coverage in both Antarctica and Greenland. To achieve higher capacity communications, the multilink point-to-point protocol (MLPPP) implemented in Linux was tuned to operate efficiently over the Iridium satellite system. This mechanism combines multiple channels to obtain a seamless data connection with a capacity equal to the sum of the individual link rates. We used four Iridium modems to obtain an aggregate capacity of about 9.6 Kb/s. Standard Internet protocols (TCP/IP) were then used to provide end-to-end connectivity. The communications system field experiments were conducted at the NorthGRIP ice core drilling camp in Greenland (75° 06' N, 42° 20' W) from June 23-July 17, 2003. We measured the reliability, throughput and general performance of this system over periods of up to 24 hours. This included delay, loss, throughput, call drops/up-time, relative signal strengths, connection time and number of connection retries. The system was also successfully tested while moving across the ice sheet at speeds of up to 30 km/h. We were successful in uploading and downloading large files (.2MB to 7.2MB) to the Internet. In combination with a modified Wi-Fi deployment, wireless Internet access was also provided to the entire NorthGRIP camp for a few days. The field experiments have shown that standard Internet protocols combined with MLPPP and Iridium modems can provide Internet access for polar expeditions at useful data rates. The 4-modem configuration we tested was observed to be >90 % efficient, e.g., a 2.5 MB video file was transferred in 35 min. at 9.524 Kb/s. The system had an average up-time of over 90 % and thus is stable and suitable for autonomous operation. Mobile performance results were very similar to that of stationary systems. While the end-to-end network architecture developed to provide Internet access worked well, the system round trip time is significant ( ˜ 1.8 seconds), which can impair real time interactions.

Mohammad, A.; Frost, V.; Braaten, D.

2003-12-01

412

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

NASA Astrophysics Data System (ADS)

Magnesium is an attractive material for hydrogen storage because it stores an appreciable amount of hydrogen (7.6 wt.%) as magnesium hydride (MgH2), is abundant in the earth's crust and is relatively inexpensive. Understanding of the structural changes and associated kinetics for the magnesium/magnesium hydride phase transition is crucial to engineering practical metal hydride hydrogen storage materials involving magnesium. A thin film architecture allows us to deposit and analyze precisely controlled structures in order to gain insight into the kinetic mechanisms present in the phase change. Using UHV sputter deposition onto a variety of substrates we have grown Mg thin films with varying degrees of structural texture and orientation. Using x-ray diffraction with in-situ sample heating we see evidence for a solid phase epitaxial (SPE) regrowth mechanism for the Mg regrowing from the MgH2 in epitaxial Mg thin films and observe kinetic differences for the discharging of films with different Mg orientations (Mg c-axis in/out of the sample plane). We also determined the crystallographic orientation correlation for the Mg to MgH2 transition in our epitaxial thin films. Here we also present our recent work examining and analyzing the kinetics for sample charging utilizing a variety of methods.

Kelly, Stephen; Kelekar, Raj; Giffard, Hermione; Clemens, Bruce

2007-03-01

413

The effect of surface depletion on the work function of arc-melted dilute solution tungsten-iridium alloys  

SciTech Connect

The requirements of thermionic electrode materials have emphasized the need for substantial improvements in microstructural stability, strength, and creep resistance at service temperature in excess of 2,500K. The present work extends an earlier study of the effective work function trends of a series of dilute solution tungsten, iridium alloys with iridium contents of 1, 3, and 5 wt%. Since the lifetime of candidate electrode materials is an important consideration, the present work attempts to evaluate the repeatability of the work function trends in these alloys. The effective work function was obtained from measurements of the current emitted from the electrode surface under UHV conditions in the temperature range of 1,800-2,500K using a Vacuum Emission Vehicle (VEV). The data generated in this work have been compared with data obtained in earlier studies performed on these alloys. It was found that the magnitude of the effective work function of these alloys was affected by changes in the subsurface iridium concentration. Furthermore, these alloys exhibited a dependence of the work function on temperature, after prolonged exposure to elevated temperatures. Such a temperature dependence can be explained by diffusion-controlled changes in the coverage of an iridium monolayer on the surface. It is proposed that the significant difference in effective work function trends obtained after prolonged exposure to elevated temperatures is a direct consequence of changes in the coverage of an iridium-rich monolayer on the electrode surface. The constitution of such a surface layer, however, would be governed by composition changes in the subsurface regions of the electrode caused thermally-activated transport processes.

D'Cruz, L.A.; Bosch, D.R.; Jacobson, D.L. (Arizona State Univ., Tempe, AZ (United States). Dept. of Chemical, Bio and Materials Engineering)

1991-08-01

414

Vinyl and ring-opening metathesis polymerization of norbornene with novel half-sandwich iridium(III) complexes bearing hydroxyindanimine ligands.  

PubMed

Half-sandwich iridium complexes bearing hydroxyindanimine ligands were synthesized and employed as catalysts for the ROMP and vinyl-type polymerization of norbornene in the presence of methylaluminoxane (MAO). PMID:18594734

Meng, Xia; Tang, Guang-Rong; Jin, Guo-Xin

2008-07-21

415

Selenium hydride atomization, fate of free atoms and spectroscopic temperature in miniature diffusion flame atomizer studied by atomic absorption spectrometry  

Microsoft Academic Search

The mechanism of hydride atomization and the fate of free atoms was investigated in the miniature diffusion flame. Selenium hydride was used as a model for the other hydrides. Mercury vapor was employed as an analyte to study physical processes, such as macroscopic movements and free atom diffusion, controlling the distribution of free analyte atoms in the observation volume, separately

J. Dedina; A. D'Ulivo; L. Lampugnani; T. Matoušek; R. Zamboni

1998-01-01

416

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

417

Photoelectron Spectra and Valence Shell Orbital Structures of Groups V and VI Hydrides  

Microsoft Academic Search

Photoelectron spectra are reported for the hydrides of group V and VI elements. Vibrational structure has been observed in bands associated with all but the inner-most valence orbitals. It has been used to obtain changes in bond angles or bond distances which result from the ionization of successive molecular orbitals. Ionization from the inner (1a1) orbitals of the hydrides has

A. W. Potts; W. C. Price

1972-01-01

418

Bulk and surface energetics of crystalline lithium hydride: Benchmarks from quantum Monte Carlo and quantum chemistry  

E-print Network

-structure technique that al- low one to go beyond DFT and achieve better accuracy: quantum Monte Carlo QMCBulk and surface energetics of crystalline lithium hydride: Benchmarks from quantum Monte Carlo hydride can be computed by the complementary techniques of quantum Monte Carlo QMC and wave

Alfè, Dario

419

Phase-field simulation of hydride precipitation in bi-crystalline zirconium  

E-print Network

the precipitation process, different variants are arranged in such a way that the free energy is minimized. The aPhase-field simulation of hydride precipitation in bi-crystalline zirconium X.Q. Ma a , S.Q. Shi a Abstract The morphological evolution of c-hydride precipitation and growth in a zirconium bi

Chen, Long-Qing

420

Overview of nickel metal hydride battery technology for aerospace applications. Technical report  

Microsoft Academic Search

For thirty years, the scientific community has investigated using intermetallic metal hydrides as hydrogen reservoirs and electrodes for secondary batteries. They are now replacing nickel-cadmium batteries in small electronics and may become attractive for aerospace applications. Metal hydride batteries do not require high-pressure containers, and prismatic cell designs are possible. With alloying, a wide range of operational temperatures can be

Wasz

1996-01-01

421

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, Nanotechnology and Microsystems of the National Center for Scientific Research "Demokritos", is seeking on complex hydrides for hydrogen storage applications in connection with the « Fast, reliable and cost

422

Surface Modification to Improve Hydrogen Entry Efficiency and Storage Capabilities of Metal Hydride Alloys  

E-print Network

Engineering, University of South Carolina Objectives: To develop anode materials for Ni-MH cells with high) Recognize the importance of particle pulverization and corrosion processes in developing high cycle life Metal Hydride Test Station (top) and alloy oxidation in bare metal hydrides (bottom) #12;Ni-MH Battery

Popov, Branko N.

423

Develop improved metal hydride technology for the storage of hydrogen. Final technical report  

Microsoft Academic Search

The overall objective was to develop commercially viable metal hydrides capable of reversibly storing at least 3 wt.% hydrogen for use with PEM fuel cells and hydrogen fueled internal combustion engine (HICE) applications. Such alloys are expected to result in system capacities of greater than 2 wt.%, making metal hydride storage systems (MHSS`s) a practical means of supplying hydrogen for

Sapru

1998-01-01

424

Enhancement of heat and mass transfer in metal hydride beds with the addition of Al plates  

E-print Network

parameters, such as the thickness of hydride bed and the inlet pressure. List of symbols C hydrogen] y vertical coordinate [m] Greek symbols b plateau hysteresis factor porosity of powder d thickness The applications of metal hydride span a wide variety of technologies, e.g., energy conversion, chemical compres

Guo, Zhixiong "James"

425

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

426

Nd2K2IrO7 and Sm2K2IrO7: Iridium(VI) Oxides Prepared under Ambient Pressure  

SciTech Connect

The most-oxidized iridium oxides known to date are prepared in a hydroxide flux under normal pressure. They contain iridium centers exclusively in the +VI oxidation state and are characterized crystallographically. The picture shows the structure of the Ln2K2IrO7 (Ln=Nd, Sm) and its structural components: IrO6 octahedra (black), KO10 polyhedra (beige), LnO10 polyhedra (blue).

Mugavero, III, S.; Smith, M; Yoon, W; zur Loye, H

2009-01-01

427

Analytical and numerical models of uranium ignition assisted by hydride formation  

SciTech Connect

Analytical and numerical models of uranium ignition assisted by the oxidation of uranium hydride are described. The models were developed to demonstrate that ignition of large uranium ingots could not occur as a result of possible hydride formation during storage. The thermodynamics-based analytical model predicted an overall 17 C temperature rise of the ingot due to hydride oxidation upon opening of the storage can in air. The numerical model predicted locally higher temperature increases at the surface; the transient temperature increase quickly dissipated. The numerical model was further used to determine conditions for which hydride oxidation does lead to ignition of uranium metal. Room temperature ignition only occurs for high hydride fractions in the nominally oxide reaction product and high specific surface areas of the uranium metal.

Totemeier, T.C.; Hayes, S.L. [Argonne National Lab., Idaho Falls, ID (United States). Engineering Div.

1996-05-01

428

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

429

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

PubMed

Nanoscale hydrides desorb and absorb hydrogen at faster rates and lower temperatures than bulk hydrides because of their high surface areas, abundant grain boundaries and short diffusion distances. No current methods exist for the direct fabrication of nanoscale complex hydrides (for example, alanates, borohydrides) with unique morphologies because of their extremely high reducibility, relatively low thermodynamic stability and complicated elemental composition. Here, we demonstrate a mechanical-force-driven physical vapour deposition procedure for preparing nanoscale complex hydrides without scaffolds or supports. Magnesium alanate nanorods measuring 20-40?nm in diameter and lithium borohydride nanobelts measuring 10-40?nm in width are successfully synthesised on the basis of the one-dimensional structure of the corresponding organic coordination polymers. The dehydrogenation kinetics of the magnesium alanate nanorods are improved, and the nanorod morphology persists through the dehydrogenation-hydrogenation process. Our findings may facilitate the fabrication of such hydrides with improved hydrogen storage properties for practical applications. PMID:24663074

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

2014-01-01

430

Materials for Hydrogen Storage: From Complex Hydrides to Functionalized Nanostructures  

NASA Astrophysics Data System (ADS)

The world wide effort for a transition to renewable and clean (i.e. carbon-free) form of energy has resulted in an upsurge of interest in harnessing and utilizing Hydrogen. Apart from being the most abundant element in the universe, hydrogen offers many advantages over other fuels: it is non-toxic, clean to use, and packs more energy per mass than any other fuel. Hydrogen energy production, storage and distribution constitute a multi-disciplinary area of research. Coming to the material issues for solid state storage of hydrogen, the most desirable criteria are high storage capacity, satisfactory kinetics, and optimal thermodynamics. Complex hydrides involving light metals, such as Alanates, Imides, Borates, Amidoboranes etc. show impressive gravimetric efficiencies, although the hydrogen desorption temperatures turn out to be rather high. Apart from complex hydrides, there are other kinds of novel materials that have been investigated, e.g. carbon based materials activated with nano-catalysts, clathrate hydrates, metal-organic complexes, and more recently nanostructured cages viz. fullerenes and nanotubes decorated with simple or transition metals that serve to attract hydrogen in molecular form. In this talk, after giving a broad overview on hydrogen economy, I shall focus on first-principles design of materials for hydrogen storage, from complex hydrides to various kinds of functinalized nanostructures, and discuss the recent results obtained in our laboratory [1-6]. Some outstanding issues and challenges, like how to circumvent the problem of metal clustering on surface, or how to bring down the hydrogen desorption temperature etc. will be discussed.

Das, G. P.

2011-07-01

431

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]|[Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.

1995-09-01

432

Magnesium hydrides and the dearomatisation of pyridine and quinoline derivatives.  

PubMed

Reactions of the ?-diketiminato n-butyl magnesium complex, [HC{(Me)CN(2,6-(i)Pr(2)C(6)H(3))}(2)Mg(n)Bu], with a range of substituted pyridines and fused-ring quinolines in the presence of PhSiH(3) has been found to result in dearomatisation of the N-heterocyclic compounds. This reaction is proposed to occur through the formation of an unobserved N-heterocycle-coordinated magnesium hydride and subsequent hydride transfer via the C2-position of the heterocycle prior to hydride transfer to the C4-position and formation of thermodynamically-favoured magnesium 1,4-dihydropyridides. This reaction is kinetically suppressed for 2,6-dimethylpyridine while the kinetic product, the 1,2-dihydropyridide derivative, was isolated through reaction with 4-methylpyridine (4-methylpyridine), in which case the formation of the 1,4-dihyropyridide is prevented by the presence of the 4-methyl substituent. X-ray structures of the products of these reactions with 4-methylpyridine, 3,5-dimethylpyridine and iso-quinoline comprise a pseudo-tetrahedral magnesium centre while the regiochemistry of the particular dearomatisation reaction is determined by the substitution pattern of the N-heterocycle under observation. The compounds are all air-sensitive and exposure of the magnesium derivatives of dearomatised pyridine and 4-dimethylaminopyridine (DMAP) to air resulted in ligand rearomatisation and the formation of dimeric ?(2)-?(2)-?(2)-peroxomagnesium compounds which have also been subject to analysis by single crystal X-ray diffraction analysis. An unsuccessful extension of this chemistry to N-heterocycle hydrosilylation is suggested to be a consequence of the low basicity of the silane reagent in comparison to the pyridine substrates which effectively impedes any further interaction with the magnesium centres. PMID:21986998

Hill, Michael S; Kociok-Köhn, Gabriele; MacDougall, Dugald J; Mahon, Mary F; Weetman, Catherine

2011-12-14

433

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

434

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

435

N-Heterocyclic carbene boranes are good hydride donors.  

PubMed

The nucleophilicity parameters (N) of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene borane and 1,3-dimethylimidazol-2-ylidene borane are 9.55 and 11.88. This places N-heterocyclic carbene boranes (NHC-boranes) among the most nucleophilic classes of neutral hydride donors. Reductions of highly electron-poor C?N and C?C bonds provide hydrogenation products along with new, stable borylated products. The results suggest that NHC-boranes have considerable untapped potential as neutral organic reductants. PMID:22149270

Horn, Markus; Mayr, Herbert; Lacôte, Emmanuel; Merling, Everett; Deaner, Jordan; Wells, Sarah; McFadden, Timothy; Curran, Dennis P

2012-01-01

436

Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.  

SciTech Connect

Dehydrogenation of ammonia borane (AB) and methylamine-borane (MeAB) is catalyzed efficiently by the iridium pincer complex (?3-1,3-(OPtBu2)2C6H3)Ir(H)2 (1). With MeAB and with MeAB/AB mixtures, rapid release of one equivalent of H2 is observed to yield soluble oligomeric products at rates similar to those previously reported for the dehydrogenation of AB catalyzed by 1. The rapid dehydrogenation reaction has allowed the experimental determination of the reaction enthalpy (?H) for the dehydrogenation of AB, MeAB, and AB/MeAB mixtures by calorimetry. The reactions are significantly more exothermic than suggested by some computational studies. This work was supported by the U.S. Department of Energy (DOE) as part of the Center of Excellence for Chemical Hydrogen Storage. PNNL is operated by Battelle for DOE.

Dietrich, Brandon L.; Goldberg, Karen I.; Heinekey, D. M.; Autrey, Thomas; Linehan, John C.

2008-10-06

437

Chemoselective hydrogenation of functionalized nitroarenes and imines by using carbon nanofiber-supported iridium nanoparticles.  

PubMed

The reaction of three types of carbon nanofibers (CNFs; platelet: CNF-P, tubular: CNF-T, herringbone: CNF-H) with Ir4(CO)12 in mesitylene at 165 °C provided the corresponding CNF-supported iridium nanoparticles, Ir/CNFs (Ir content=2.3-2.6 wt.%). Transmission electron microscopy (TEM) studies of these Ir/CNF samples revealed that size-controlled Ir nanoparticles (average particle size of 1.1-1.5 nm) existed on the CNFs. Among the three Ir/CNF samples, Ir/CNF-T showed an excellent catalytic activity and chemoselectivity towards hydrogenation of functionalized nitroarenes and imines; the corresponding aniline derivatives were obtained with high turnover numbers at ambient temperature under 10 tm of H2 , and the catalyst is reusable. Ir/CNF-T was also effective for the reductive N-alkylation of anilines with carbonyl compounds. PMID:24347068

Motoyama, Yukihiro; Taguchi, Masahiro; Desmira, Nelfa; Yoon, Seong-Ho; Mochida, Isao; Nagashima, Hideo

2014-01-01

438

Functional ruthenium(II)- and iridium(III)-containing polymers for potential electro-optical applications.  

PubMed

The need for novel materials with luminescent properties and advanced processing features requires reliable and reproducible synthetic routes for the design of suitable materials, such as e.g. polypyridyl ruthenium(II) and iridium(III)-containing polymers. The most popular ligand for those purposes is the 4,4'-functionalized bipyridine unit. Therefore, several synthetic strategies for the derivatization of the 4,4'-dimethyl-2,2'-bipyridine are highlighted, and in particular functionalities, which enable further covalent linkage to polymeric structures, are discussed in this critical review. Subsequently, the different synthetic strategies for the preparation of polymeric metal-complexes are described, either starting from small functionalized complexes (later covalently attached to the polymer), or from macroligands (subsequently coordinated to the metal ions). The designed materials reveal good processing properties using spin coating and inkjet printing, as well as beneficial electro-optical properties for potential thin functional film applications, such as light-emitting electrochemical cells. PMID:17387410

Marin, Veronica; Holder, Elisabeth; Hoogenboom, Richard; Schubert, Ulrich S

2007-04-01

439

Role of electronic localization in the phosphorescence of iridium sensitizing dyes  

E-print Network

In this work we present a systematic study of three representative iridium dyes, namely, Ir(ppy)3, FIrpic and PQIr, which are commonly used as sensitizers in organic optoelectronic devices. We show that electronic correlations play a crucial role in determining the excited-state energies in these systems, due to localization of electrons on Ir d orbitals. Electronic localization is captured by employing hybrid functionals within time-dependent density-functional theory (TDDFT) and with Hubbard-model corrections within the delta-SCF approach. The performance of both methods are studied comparatively and shown to be in good agreement with experiment. The Hubbard-corrected functionals provide further insight into the localization of electrons and on the charge-transfer character of excited-states. The gained insight allows us to comment on envisioned functionalization strategies to improve the performance of these systems. Complementary discussions on the delta-SCF method are also presented in order to fill some...

Himmetoglu, Burak; Dabo, Ismaila; Cococcioni, Matteo

2012-01-01

440

A non-catastrophist explanation for the iridium anomaly at the Cretaceous/Tertiary boundary  

NASA Technical Reports Server (NTRS)

The iridium (Ir) anomaly at the Cretaceous/Tertiary (C/T) boundary can be explained by dissolution of normal pelagic limestones producing an insoluble clay residue containing Ir-rich meteoritic material. Further concentration of Ir and other trace metals in the clay can be explained by deposition under reducing conditions. Clay-mineral analyses indicate that the boundary clay is similar to locally derived clays in the limestones above and below the boundary, and contains no detectable exotic components. This supports a terrestrial origin for the boundary clay. The genesis of the boundary clay is attributed to changes in ocean chemistry (pH and oxygenation), leading to an interval of widespread dissolution of carbonate sequences in the oceans, and culminating in the development of submarine pyritic hardgrounds and a disconformity of global extent.

Rampino, M. R.

1982-01-01

441

Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium  

E-print Network

We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.

Elke Neu; David Steinmetz; Janine Riedrich-Moeller; Stefan Gsell; Martin Fischer; Matthias Schreck; Christoph Becher

2010-08-27

442

Vacuum deposition of iridium on large astronomical mirrors for use in the far UV  

NASA Technical Reports Server (NTRS)

An iridium coating has been deposited by electron-beam evaporation on a 0.91-m mirror which serves as the telescope primary of a sounding rocket instrument for far-UV spectrometry. The evaporation was carried out by applying 8 kV at 400 mA to the electron gun. Zone refined Ir of 99.99% purity was used, and the electron beam was electromagnetically swept over the surface of the evaporant. Under these conditions, deposition rates of 0.55 A/sec were achieved. The reflectance distribution achieved at a wavelength of 584 A was extremely uniform; the mean reflectance was 21.2% with a standard deviation of only 0.3%. This represents a substantial improvement over Al + MgF2 and Al + LiF coatings for applications involving multiple reflections and weak signals, as might be expected in a high-resolution spectrograph studying distant celestial objects.

Herzig, H.; Spencer, R. S.

1982-01-01

443

Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium  

E-print Network

We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.

Neu, Elke; Riedrich-Moeller, Janine; Gsell, Stefan; Fischer, Martin; Schreck, Matthias; Becher, Christoph

2010-01-01

444

Conodont survival and low iridium abundances across the Permian-Triassic boundary in south China  

NASA Technical Reports Server (NTRS)

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion + or - 20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.

Clark, D. L.; Wang, C.-Y.; Orth, C. J.; Gilmore, J. S.

1986-01-01

445

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

PubMed Central

The formation of C–C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C–C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and ?-unsaturated reactants generates electrophile–nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C–H bonds. PMID:21822399

Bower, John F.; Krische, Michael J.

2011-01-01

446

Green and blue electrochemically generated chemiluminescence from click chemistry--customizable iridium complexes.  

PubMed

Cationic cyclometalated iridium complexes containing two anionic phenylpyridine (ppy) ligands and the neutral bidentate triazole-pyridine ligand, 2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine (pytl), were investigated. The complexes display a rich and reversible electrochemical behavior, upon investigations by cyclic voltammetry in strictly aprotic conditions, that couples with excellent emission quantum yields and long lifetimes of the excited states. Therefore, in organic media, all complexes have generated intense green electrochemiluminescence (ECL) through the so-called annihilation procedure and, importantly, a modulation of the emission energy (to blue) has been easily obtained by simple fluorination of the ppy ligand. Finally, taking advantage of their remarkable solubility in water, intense ECL was also obtained from aqueous buffer solutions using the co-reactant method, thus making all the investigated complexes highly promising for their effective use as ECL labels in bioanalytical applications. PMID:21433123

Zanarini, Simone; Felici, Marco; Valenti, Giovanni; Marcaccio, Massimo; Prodi, Luca; Bonacchi, Sara; Contreras-Carballada, Pablo; Williams, Rene M; Feiters, Martin C; Nolte, Roeland J M; De Cola, Luisa; Paolucci, Francesco

2011-04-11

447

Iridium abundance maxima at the latest Ordovician mass extinction horizon, Yangtze Basin, China: Terrestrial or extraterrestrial  

SciTech Connect

Neutron activation analyses of the Chinese Ordovician/Silurian (O/S) boundary sections at two distant localities in the Yangtze Basin, spanning the horizon of a major latest Ordovician global extinction event, show the maxima of iridium abundances to be coincident with the extinction horizon at the base of the graptolite Glyptograptus persculputs zone. The 0.23 ppb Ir maximum in the Yichang type section is almost as large as the late Eocene impact Ir anomaly. However, the authors have observed that the Ir abundances in the Chinese sections are closely correlated with the sedimentation rates, and therefore have concluded that Ir maxima do not indicate a cataclysmic extraterrestrial impact at this extinction level.

Kun Wang; Chatterton, B.D.E. (Univ. of Alberta, Edmonton (Canada)); Attrep, M. Jr; Orth, C.J. (Los Alamos National Lab., NM (United States))

1992-01-01

448

Hot rocket plume experiment - Survey and conceptual design. [of rhenium-iridium bipropellants  

NASA Technical Reports Server (NTRS)

Attention is given to a space-borne engine plume experiment study to fly an experiment which will both verify and quantify the reduced contamination from advanced rhenium-iridium earth-storable bipropellant rockets (hot rockets) and provide a correlation between high-fidelity, in-space measurements and theoretical plume and surface contamination models. The experiment conceptual design is based on survey results from plume and contamination technologists throughout the U.S. With respect to shuttle use, cursory investigations validate Hitchhiker availability and adaptability, adequate remote manipulator system (RMS) articulation and dynamic capability, acceptable RMS attachment capability, adequate power and telemetry capability, and adequate flight altitude and attitude/orbital capability.

Millard, Jerry M.; Luan, Taylor W.; Dowdy, Mack W.

1992-01-01

449

Synthesis, structure and electroluminescent properties of cyclometalated iridium complexes possessing sterically hindered ligands.  

PubMed

New CN donor ligands incorporating pyridine or benzoimidazole N donors and a sterically hindered cyclometalating aromatic core featuring a polyphenylenephenyl, fluoranthene, or triphenylene segment are prepared and successfully converted into heteroleptic iridium(III) cyclometalated complexes with acetylacetone auxiliary ligands. The X-ray structure of the complex, derived from a ligand containing a fluoranthene fragment, has been solved to unveil the corresponding structure. The results clearly demonstrate that the nature of the sigma-coordinating ligand segment plays a key role in dictating the emission profile and peak position, such that the emission hue has been successfully tuned ranging from green to red. Supplementary support of this viewpoint is also rendered by computational (DFT) approaches. Electroluminescent devices fabricated using a complex as dopant in the PVK matrix were found to exhibit bright greenish yellow emission with promising device characteristics (maximum brightness 26450 cd m(-2) at 30 V and a maximum current efficiency of 40 cd A(-1)). PMID:17622420

Velusamy, Marappan; Thomas, K R Justin; Chen, Chih-Hsin; Lin, Jiann T; Wen, Yuh S; Hsieh, Wan-Ting; Lai, Chin-Hung; Chou, Pi-Tai

2007-07-28

450

Catalytic iridium-based Janus micromotors powered by ultralow levels of chemical fuels.  

PubMed

We describe catalytic micromotors powered by remarkably low concentrations of chemical fuel, down to the 0.0000001% level. These Janus micromotors rely on an iridium hemispheric layer for the catalytic decomposition of hydrazine in connection to SiO2 spherical particles. The micromotors are self-propelled at a very high speed (of ~20 body lengths s(-1)) in a 0.001% hydrazine solution due to osmotic effects. Such a low fuel concentration represents a 10,000-fold decrease in the level required for common catalytic nanomotors. The attractive propulsion performance, efficient catalytic energy-harvesting, environmentally triggered swarming behavior, and magnetic control of the new Janus micromotors hold considerable promise for diverse practical applications. PMID:24475997

Gao, Wei; Pei, Allen; Dong, Renfeng; Wang, Joseph

2014-02-12

451

Iridium Oxide Nanotube Electrodes for Highly Sensitive and Prolonged Intracellular Measurement of Action Potentials  

PubMed Central

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

2014-01-01

452

Epitaxially stabilized iridium spinel oxide without cations in the tetrahedral site  

NASA Astrophysics Data System (ADS)

Single-crystalline thin film of an iridium dioxide polymorph Ir2O4 has been fabricated by the pulsed laser deposition of LixIr2O4 precursor and the subsequent Li-deintercalation using soft chemistry. Ir2O4 crystallizes in a spinel (AB2O4) without A cations in the tetrahedral site, which is isostructural to ?-MnO2. Ir ions form a pyrochlore sublattice, which is known to give rise to a strong geometrical frustration. This Ir spinel was found to be a narrow gap insulator, in remarkable contrast to the metallic ground state of rutile-type IrO2. We argue that an interplay of a strong spin-orbit coupling and a Coulomb repulsion gives rise to an insulating ground state as in a layered perovskite Sr2IrO4.

Kuriyama, Hiromichi; Matsuno, Jobu; Niitaka, Seiji; Uchida, Masaya; Hashizume, Daisuke; Nakao, Aiko; Sugimoto, Kunihisa; Ohsumi, Hiroyuki; Takata, Masaki; Takagi, Hidenori

2010-05-01

453

Introduction of the benzoquinoline ancillary ligand to the iridium complexes for organic light-emitting diodes.  

PubMed

The new iridium complexes, Ir(C^N)2(bq), (C^N = ppy, F2-ppy, 2,3-dpqx-F2 or 4-Me-2,3-dpq) were prepared and their luminescence properties were investigated, where ppy, F2-ppy, 2,3-dpqx-F2, 4-Me-2,3-dpq and bq represent 2-phenylpyridine, 2-(4',6'-difluorophenyl)-pyridine, 2,3-bis (4'-fluorophenyl)quinoxaline, 4-methyl-2,3-diphenylquinoline and 10-hydroxybenzoquinoline ligands, respectively. We expected that the relative energy levels of the main ligands (C^N) and ancillary ligand, bq, in the complexes could determine the possibility of interligand energy transfer (ILET) in the complexes and thereby luminescence properties. The main ligands, F2-ppy and 2,3-dpqx-F2, which have drastically different energy gaps between the HOMO and LUMO energy levels were chosen and their complexes were synthesized. The photoabsorption, photoluminescence and electroluminescence of the complexes were studied. Ir(ppy)2(bq), Ir(F2-ppy)2(bq) Ir(2,3-dpqx-F2)2(bq) and Ir(4-Me-2,3-dpq)2(bq) exhibited the luminescence maxima between 600-694 nm and their efficiencies were affected by the main ligands. While Ir(ppy)2(bq) and Ir(F2-ppy)2(bq) showed relatively high luminous efficiencies (> 10 cd/A), Ir(2,3-dpqx-F2)(bq) had poor luminous efficiency (0.30 cd/A). The electrochemical properties were studied to support ILET in the ppy-based iridium complexes. Their luminescence performances were compared with those of the complexes containing acetylacetonate (acac) ancillary ligand which are not allowed to have ILET. PMID:22629958

Park, Hye-Rim; Ha, Yunkyoung

2012-02-01

454

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

USGS Publications Warehouse

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

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

1974-01-01

455

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

PubMed

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

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

2013-09-25

456

REACTOR MATERILAS STUDY. RESEARCH AND DEVELOPMENT OF METAL HYDRIDES. Quarterly Report No. 2 for January 1, 1959 to March 31, 1959  

Microsoft Academic Search

The ease of preparation of relatively large crack-free hydrided ; specimens was found to be largely dependent on the phsse state of the hydride at ; the hydriding temperature. Cracking apparently resulted from hydrogen ; concentration gradients (with resulting phase concentration gradients) within a ; two phase region. The control of grinding cracks in the preparation of hydrided ; tensile

R. L. Beck; W. M. Mueller

1959-01-01

457

ACCEPTABILITY ENVELOPE FOR METAL HYDRIDE-BASED HYDROGEN STORAGE SYSTEMS  

SciTech Connect

The design and evaluation of media based hydrogen storage systems requires the use of detailed numerical models and experimental studies, with significant amount of time and monetary investment. Thus a scoping tool, referred to as the Acceptability Envelope, was developed to screen preliminary candidate media and storage vessel designs, identifying the range of chemical, physical and geometrical parameters for the coupled media and storage vessel system that allow it to meet performance targets. The model which underpins the analysis allows simplifying the storage system, thus resulting in one input-one output scheme, by grouping of selected quantities. Two cases have been analyzed and results are presented here. In the first application the DOE technical targets (Year 2010, Year 2015 and Ultimate) are used to determine the range of parameters required for the metal hydride media and storage vessel. In the second case the most promising metal hydrides available are compared, highlighting the potential of storage systems, utilizing them, to achieve 40% of the 2010 DOE technical target. Results show that systems based on Li-Mg media have the best potential to attain these performance targets.

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

2011-07-18

458

First-principles modelling of magnesium titanium hydrides.  

PubMed

Mixing Mg with Ti leads to a hydride Mg(x)Ti((1 - x))H(2) with markedly improved (de)hydrogenation properties for x ? 0.8, as compared to MgH(2). Optically thin films of Mg(x)Ti((1 - x))H(2) have a black appearance, which is remarkable for a hydride material. In this paper we study the structure and stability of Mg(x)Ti((1 - x))H(2), x = 0-1 by first-principles calculations at the level of density functional theory. We give evidence for a fluorite to rutile phase transition at a critical composition x(c) = 0.8-0.9, which correlates with the experimentally observed sharp decrease in (de)hydrogenation rates at this composition. The densities of states of Mg(x)Ti((1 - x))H(2) have a peak at the Fermi level, composed of Ti d states. Disorder in the positions of the Ti atoms easily destroys the metallic plasma, however, which suppresses the optical reflection. Interband transitions result in a featureless optical absorption over a large energy range, causing the black appearance of Mg(x)Ti((1 - x))H(2). PMID:21386386

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

2010-02-24

459

Physics of Hydrogen Storage in Metal-Hydrides  

NASA Astrophysics Data System (ADS)

Physical aspects of the hydrogenation-dehydrogenation mechanisms of metal-metal hydride systems were examined. Experimental investigation was conducted for magnesium hydride as a case study. Theoretical analysis and computational study were carried out. The kinetics of hydrogenation-dehydrogenation of traditionally prepared Mg-MgH_2 and chemically synthesized Mg-MgH_2 were experimentally investigated. A detailed investigation was carried out to determine the reasons for the improved performance of a chemically synthesized Mg-MgH _2 previously reported by Bogdanovic and co-workers. A scanning electron microscope was used to examine the surface morphology of the samples. The surface of chemically prepared samples appeared to be covered with micro-spheroidal beads ranging in radius between 0.5 ?m and 0.05 ?m formed in a fractal-like configuration. Theoretical analysis indicated that the unusual surface structure of the chemically prepared samples could be responsible for the rapid uptake and release of hydrogen. The uptake and release enhancement is believed to be partially due to the substantial increase in the surface area and partially due fast diffusion into the smaller particles. The effect of the addition of nickel to the surface was also investigated. Theoretical analysis was carried out. Models for the process at the surface as well as in the bulk were developed. Diffusion equation was examined taking into account the diffusion coefficient being function of concentration. A non-linear differential equation resulted for this case. The differential equation was numerically solved.

Abdelfattah-Zidan, Ragaiy

460

Method of generating 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; Niemann, Michael U; Goswami, D. Yogi; Stefanakos, Elias K

2013-05-14

461

Gas phase contributions to topochemical hydride reduction reactions  

SciTech Connect

Alkali and alkali earth hydrides have been used as solid state reductants recently to yield many interesting new oxygen-deficient transition metal oxides. These reactions have tacitly been assumed to be a solid phase reaction between the reductant and parent oxide. We have conducted a number of experiments with physical separation between the reductant and oxides, and find that in some cases reduction proceeds even when the reagents are physically separated, implying reactions with in-situ generated H{sub 2} and, to a lesser extent, getter mechanisms. Our findings change our understanding of these topochemical reactions, and should enhance the synthesis of additional new oxides and nanostructures. - Graphical abstract: Topochemical reductions with hydrides: Solid state or gas phase reaction? Display Omitted - Highlights: • SrFeO{sub 2} and LaNiO{sub 2} were prepared by topochemical reduction of oxides. • Separating the reducing agent (CaH{sub 2}, Mg metal) from the oxide still results in reduction. • Such topochemical reactions can occur in the gas phase.

Kobayashi, Yoji [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012 (Japan); Li, Zhaofei [Institute for Integrated Cell-Material Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirai, Kei [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Tassel, Cédric [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); The Hakubi Center for Advanced Research, Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto 606-8302 (Japan); Loyer, François [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Institut des Sciences Chimiques de Rennes, UMR 6226 Université de Rennes 1-CNRS, équipe CSM, Bât. 10B, Campus de Beaulieu, 263, Avenue du Général Leclerc, 35042 Rennes Cedex (France); Ichikawa, Noriya [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012 (Japan); Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Abe, Naoyuki [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Yamamoto, Takafumi [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Shimakawa, Yuichi [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012 (Japan); Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); and others

2013-11-15

462

The potential of the F127-water soft system towards selective solubilisation of iridium(III) octahedral complexes.  

PubMed

In order to obtain new functional soft systems for use as templating agents for the construction of functional mesostructured materials, the dynamic ordered soft systems formed by a hydrophilic ionic iridium(III) complex (IrPa) embedded into two different concentration F127-water mixtures have been investigated. To this aim, combined spectral and time-resolved photophysical techniques and rheological methods have been employed. The position of the chromophore inside the micellar, cubic and hexagonal phases of the F127 polymeric neutral surfactant in water was effectively determined. The hydrophilic character of the iridium(III) complex chosen allowed preferential functionalization of the F127 corona in the micellar and cubic phases. PMID:25074753

Talarico, Anna Maria; Szerb, Elisabeta Ildyko; Ghedini, Mauro; Rossi, Cesare Oliviero

2014-09-21

463

Supramolecular sky-blue phosphorescent polymer iridium complexes for single-emissive-layer organic light-emitting diodes.  

PubMed

Novel supramolecular phosphorescent polymers (SPPs) are synthesized as a new class of solution-processable electroluminescent emitters. The formation of these SPPs takes advantage of the efficient non-bonding assembly between bis(dibenzo-24-crown-8)-functionalized iridium complex monomer and bis(dibenzylammonium)-tethered co-monomer, which is monitored by (1) H NMR spectroscopy and viscosity measurements. These SPPs show good film morphology and an intrinsic glass transition with a Tg of 94-116 °C. Noticeably, they are highly photoluminescent in solid state with quantum efficiency up to ca. 78%. The photophysical and electroluminescent properties are strongly dependent on the molecular structures of the iridium complex monomers. PMID:23873657

Liang, Ai-Hui; Dong, Sheng; Zhang, Kai; Xiao, Xiao; Huang, Fei; Zhu, Xu-Hui; Cao, Yong

2013-08-01

464

Diastereo- and enantioselective iridium-catalyzed allylation of cyclic ketone enolates: synergetic effect of ligands and barium enolates.  

PubMed

We report asymmetric allylic alkylation of barium enolates of cyclic ketones catalyzed by a metallacyclic iridium complex containing a phosphoramidite ligand derived from (R)-1-(2-naphthyl)ethylamine. The reaction products contain adjacent quaternary and tertiary stereocenters. This process demonstrates that unstabilized cyclic ketone enolates can undergo diastereo- and enantioselective Ir-catalyzed allylic substitution reactions with the proper choice of enolate countercation. The products of these reactions can be conveniently transformed to various useful polycarbocyclic structures. PMID:25337972

Chen, Wenyong; Chen, Ming; Hartwig, John F

2014-11-12

465

Interstitial radiation therapy for carcinoma of the penis using iridium 192 wires: the Henri Mondor experience (1970-1979)  

Microsoft Academic Search

From 1970 to 1979, a group of 50 patients was treated for squamous cell carcinoma of the penis by interstitial irradiation using an afterloading technique and iridium 192 wires. The group included 9 patients with T1 tumors, 27 with T2 tumors, and 14 with T3 tumors. Forty-five patients presented with no metastatic inguinal nodes (NO), 3 patients with N1 nodes,

Jean J. Mazeron; Denis Langlois; Philip A. Lobo; Judith A. Huart; Elie Calitchi; Antoine Lusinchi; Michel Raynal; Jean P. Le Bourgeois; Clément C. Abbou; Bernard Pierquin

1984-01-01

466

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

Microsoft Academic Search

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

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

2003-01-01

467

Iridium-catalyzed intermolecular amidation of sp³ C-H bonds: late-stage functionalization of an unactivated methyl group.  

PubMed

Reported herein is the iridium-catalyzed direct amidation of unactivated sp(3) C-H bonds. With sulfonyl and acyl azides as the amino source, the amidation occurs efficiently under mild conditions over a wide range of unactivated methyl groups with high functional group tolerance. This procedure can be successfully applied for the direct introduction of an amino group into complex compounds and thus can serve as a powerful synthetic tool for late-stage C-H functionalization. PMID:24580093

Kang, Taek; Kim, Youngchan; Lee, Donggun; Wang, Zhen; Chang, Sukbok

2014-03-19

468

Reply to comment on 'aggregation-induced phosphorescent emission (AIPE) of iridium(III) complexes': origin of the enhanced phosphorescence.  

PubMed

An obvious enhanced phosphorescence emission in the solid state (EPESS) was observed for two iridium(III) complexes with restricted (even fixed) intramolecular rotational motion, which is contrary to the opinion ("restricted intramolecular rotational motion as the origin of EPESS") of Park et al., and our observation confirmed that the pi-pi stacking of adjacent pyridyl rings of ppy ligands played a key role in EPESS. PMID:19240887

Huang, Kewei; Wu, Huazhou; Shi, Mei; Li, Fuyou; Yi, Tao; Huang, Chunhui

2009-03-14

469

Structural characterization and comparison of iridium, platinum and gold/palladium ultra-thin film coatings for STM of biomolecules  

SciTech Connect

Scanning tunneling microscopy (STM) is capable of atomic resolution and is ideally suited for imaging surfaces with uniform work function. A biological sample on a conducting substrate in air does not meet this criteria and requires a conductive coating for stable and reproducible STM imaging. In this paper, the authors describe the STM and transmission electron microscopy (TEM) characterization of ultra-thin ion-beam sputtered films of iridium and cathode sputtered gold/palladium and platinum films on highly ordered pyrolytic graphite (HOPG) which were developed for use as biomolecule coatings. The goals were the development of metal coatings sufficiently thin and fine grained that 15--20 {angstrom} features of biological molecules could be resolved using STM, and the development of a substrate/coating system which would allow complementary TEM information to be obtained for films and biological molecules. The authors demonstrate in this paper that ion-beam sputtered iridium on highly ordered pyrolytic graphite (HOPG) has met both these goals. The ion-beam sputtered iridium produced a very fine grained (< 10 {angstrom}) continuous film at 5--6 {angstrom} thickness suitable for stable air STM imaging. In comparison, cathode sputtered platinum produced 16 {angstrom} grains with the thinnest continuous film at 15 {angstrom} thickness, and the sputtered gold/palladium produced 25 {angstrom} grains with the thinnest continuous film at 18 {angstrom} thickness.

Sebring, R.; Arendt, P.; Imai, B.; Bradbury, E.M.; Gatewood, J. [Los Alamos National Lab., NM (United States); Panitz, J. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Physics and Astronomy; Yau, P. [Univ. of California, Davis, CA (United States)

1997-10-30

470

Iridium-coated micropore x-ray optics using dry etching of a silicon wafer and atomic layer deposition.  

PubMed

To enhance x-ray reflectivity of silicon micropore optics using dry etching of silicon (111) wafers, iridium coating is tested by use of atomic layer deposition. An iridium layer is successfully formed on sidewalls of tiny micropores with a pore width of 20 ?m and depth of 300 ?m. The film thickness is ?20??nm. An enhanced x-ray reflectivity compared to that of silicon is confirmed at Ti K? 4.51 keV, for what we believe to be the first time, with this type of optics. Some discrepancies from a theoretical reflectivity curve of iridium-coated silicon are noticed at small incident angles <1.3°. When a geometrical shadowing effect due to occultation by a ridge existing on the sidewalls is taken into account, the observed reflectivity becomes well represented by the modified theoretical curve. An estimated surface micro roughness of ?1??nm rms is consistent with atomic force microscope measurements of the sidewalls. PMID:24084996

Ogawa, Tomohiro; Ezoe, Yuichiro; Moriyama, Teppei; Mitsuishi, Ikuyuki; Kakiuchi, Takuya; Ohashi, Takaya; Mitsuda, Kazuhisa; Putkonen, Matti

2013-08-20

471

A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy  

SciTech Connect

Supported mononuclear iridium complexes with ethene ligands were prepared by the reaction of Ir(C{sub 2}H{sub 4}){sub 2}(acac) (acac is CH{sub 3}COCHCOCH{sub 3}) with highly dehydroxylated MgO. Characterization of the supported species by extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopies showed that the resultant supported organometallic species were Ir(C{sub 2}H{sub 4}){sub 2}, formed by the dissociation of the acac ligand from Ir(C{sub 2}H{sub 4}){sub 2}(acac) and bonding of the Ir(C{sub 2}H{sub 4}){sub 2} species to the MgO surface. Direct evidence of the site-isolation of these mononuclear complexes was obtained by aberration-corrected scanning transmission electron microscopy (STEM); the images demonstrate the presence of the iridium complexes in the absence of any clusters. When the iridium complexes were probed with CO, the resulting IR spectra demonstrated the formation of Ir(CO){sub 2} complexes on the MgO surface. The breadth of the {nu}{sub CO} bands demonstrates a substantial variation in the metal-support bonding, consistent with the heterogeneity of the MgO surface; the STEM images are not sufficient to characterize this heterogeneity. The supported iridium complexes catalyzed ethene hydrogenation at room temperature and atmospheric pressure in a flow reactor, and EXAFS spectra indicated that the mononuclear iridium species remained intact. STEM images of the used catalyst confirmed that almost all of the iridium complexes remained intact, but this method was sensitive enough to detect a small degree of aggregation of the iridium on the support.

Uzun, A.; Ortalan, V; Browning, N; Gates , B

2010-01-01

472

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

NASA Technical Reports Server (NTRS)

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

Gales, C.; Perroud, P.

1981-01-01

473

Deep acceptor states of platinum and iridium in 4H-silicon carbide  

SciTech Connect

Band gap states of platinum and iridium in the hexagonal polytype 4H of silicon carbide are investigated by means of deep level transient spectroscopy (DLTS) in n- as well as p-type epitaxial layers. To establish a definite chemical assignment of band gap states to Pt and Ir the radioactive isotope {sup 188}Pt was incorporated into 4H-SiC samples by recoil implantation. During the nuclear decay of {sup 188}Pt via the unstable {sup 188}Ir to the stable {sup 188}Os, the concentration of band gap states is traced by DLTS whereby characteristic concentration changes lead to an unambiguous assignment of two band gap states to {sup 188}Pt. The two levels are interpreted as one Pt-related defect structure with two different charge states in the band gap of 4H-SiC: a double-negative acceptor at 0.81 eV and a single-negative acceptor at 1.47 eV below the conduction band edge E{sub C}.