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1

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

PubMed

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

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

2013-08-07

2

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

NASA Astrophysics Data System (ADS)

A simple and reliable method for the determination of arsenic in sediment and in coal without sample digestion, based on hydride generation from slurry samples is proposed. After grinding the samples to a particle size of ?50 ?m, the sample powder was mixed with aqua regia and hydrofluoric acid in an ultrasonic bath for 30 min. After diluting the mixture with hydrochloric acid, the slurry was allowed to stand for 48 h, and an aliquot was used for hydride generation with sodium borohydride. More than 80% of the arsenic was leached to the aqueous phase under these conditions, except for one sediment sample with very high silica content. The generated arsine was collected in a graphite tube, treated with 0.5 mg of iridium as a permanent modifier, and the arsenic determination was carried out by electrothermal atomic absorption spectrometry. The same tube could be used for at least 160 cycles without any re-treatment. The greatest advantage of the method was that only a minimum of reagents and sample handling were required, reducing the risks of contamination and/or analyte loss. However, the addition calibration technique had to be used in order to obtain results within the 95% confidence level for 11 certified reference materials, 5 sediments, 5 coals and one coal fly ash. One certified sediment slurry was spiked with the analyte and the resulting addition calibration curve was used for the analysis of the certified sediments. Similarly, one certified coal was used to obtain the addition calibration curve for the coal and coal fly ash samples. The recoveries of the certified values, except for one sediment, were between 91 and 115%. The limits of detection in the samples were 0.54 and 0.7 ?g g -1 for the coal and sediment samples, respectively, obtained for 1 ml of slurry containing 1 mg of sample.

Vieira, Mariana Antunes; Welz, Bernhard; Curtius, Adilson José

2002-12-01

3

Stability and Dynamic Processes in 16VE Iridium(III) Ethyl Hydride and Rhodium(I) ?-Ethane Complexes: Experimental and Computational Studies.  

PubMed

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

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

2013-10-15

4

Synthesis of an (/eta//sup 3/-allyl(hydrido)iridium complex and its reactions with arenes and alkanes. Sequential intermolecular C-H oxidative addition and hydride-to-alkene migratory insertion reactions  

SciTech Connect

The iridium allyl hydride complex (/eta//sup 5/-C/sub 5/Me/sub 5/)(/eta//sup 3/-C/sub 3/H/sub 5/)(H)Ir (2) has been prepared from ((/eta//sup 5/-C/sub 5/Me/sub 5/)IrCl/sub 2/)/sub 2/, and its reaction with arenes and alkanes has been investigated. The hydride reacts with C-H bonds in benzene and cyclopropane in the presence of phosphines L, leading to the phenyl and cyclopropyl complexes (/eta//sup 5/-C/sub 5/Me/sub 5/)(L)Ir(n-propyl)(R) (3,4, and 5). Irradiation of 2 in the presence of PMe/sub 3/ takes a different course, giving the previously uncharacterized (/eta//sup 5/-C/sub 5/Me/sub 5/)Ir(PMe/sub 3/)/sub 2/ (6). Thermal reaction of 2 in alkane solvents such as n-butane and isobutane, which are capable of ..beta..-elimination, leads to products 8a, 8b, and 9 formed by replacement of the allyl group in 2 by a substituted allyl ligand formed by overall dehydrogenation of the alkane. Thermolysis of 2 in the presence of arenes such as n-propylbenzene and cumene leads to more complicated products resulting from intermolecular C-H activation followed by cyclometalation (e.g., 13, 15) and/or dimerization (20). The structure of cyclometalated dimer 20 has been determined by X-ray diffraction. Mechanistic studies, including kinetics, isotope tracer experiments, and intra-versus intermolecular isotope effect determinations, implicate the coordinatively unsaturated species (/eta//sup 5/-C/sub 5/Me/sub 5/)(/eta//sup 2/-propene)Ir (complex A in Scheme XX) as the initially formed intermediate in the thermal reactions of 1 with alkanes and arenes. Significant differences exist between the behavior of this intermediate (cf. Schemes XIX and XXIII) and that of the closely related phosphine-substituted complex (/eta//sup 5/-C/sub 5/Me/sub 5/)(PMe/sub 3/Ir) studied earlier; possible reasons for these differences are discussed.

McGhee, W.D.; Bergman, R.G.

1988-06-22

5

Hydriding process  

DOEpatents

BS>A method is described for hydriding a body of a Group IV-B metal, preferably zirconium, to produce a crack-free metal-hydride bedy of high hydrogen content by cooling the body at the beta to beta + delta boundary, without further addition of hydrogen, to precipitate a fine-grained delta-phase metal hydride in the beta + delta phase region and then resuming the hydriding, preferably preceded by a reheating step. (Official Gazette)

Raymond, J.W.; Taketani, H.

1973-12-01

6

Iridium in natural waters  

SciTech Connect

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

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

1996-09-13

7

Organometallic ruthenium and iridium transfer-hydrogenation catalysts using coenzyme NADH as a cofactor.  

PubMed

Artificial enzymes: half-sandwich arene ruthenium(II) and cyclopentadienyl iridium(III) complexes containing N,N-chelated ligands can use NADH as a source of hydride for the reduction of ketones. Moreover, cyclopentadienyl phenanthroline iridium(III) derivatives at micromolar concentrations are robust catalysts for the production of H(2) from NADH in water and can raise the NAD(+)/NADH ratio in cancer cells. PMID:22415924

Betanzos-Lara, Soledad; Liu, Zhe; Habtemariam, Abraha; Pizarro, Ana M; Qamar, Bushra; Sadler, Peter J

2012-03-13

8

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

9

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

10

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

2012-10-31

11

Hydride compositions  

DOEpatents

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

Lee, Myung W. (North Augusta, SC)

1995-01-01

12

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

13

Iridium: failures & successes  

NASA Astrophysics Data System (ADS)

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

Christensen, CarissaBryce; Beard, Suzette

2001-03-01

14

Hydride compressor  

DOEpatents

Method of producing high energy pressurized gas working fluid power from a low energy, low temperature heat source, wherein the compression energy is gained by using the low energy heat source to desorb hydrogen gas from a metal hydride bed and the desorbed hydrogen for producing power is recycled to the bed, where it is re-adsorbed, with the recycling being powered by the low energy heat source. In one embodiment, the adsorption-desorption cycle provides a chemical compressor that is powered by the low energy heat source, and the compressor is connected to a regenerative gas turbine having a high energy, high temperature heat source with the recycling being powered by the low energy heat source.

Powell, James R. (Wading River, NY); Salzano, Francis J. (Patchogue, NY)

1978-01-01

15

Silica Embedded Metal Hydrides  

SciTech Connect

A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

Heung, L.K. [Westinghouse Savannah River Company, AIKEN, SC (United States); Wicks, G.G.

1998-08-01

16

Iridium Satellite Signal Exploitation  

NASA Astrophysics Data System (ADS)

The Iridium Satellite constellation is unique to satellite communication networks in that it allows for transmission of data between satellites instead of relying on transmission by the bent pipe methodology. As such, this network is far more secure than other satellite communication networks, and forces interception to occur within the locale of the transmission from modem to satellite or within the locale of the downlink from the satellite other modem. The purpose of this project was to demonstrate the security weaknesses within the Iridium protocol, showing that it was possible to track one of these satellites with a high gain antenna, resulting in the ability to anticipate transmission, to acquire the location of that transmission, and to uncover the content of that transmission. This project was completed as part of the summer student program at the Southwest Research Institute. The presentation will demonstrate the thought process used in chronological order, essentially demonstrating how I achieved the result from my point of view as the summer progressed.

McDonough, Peter

2010-03-01

17

Iridium Complexes of Molecular Nitrogen.  

National Technical Information Service (NTIS)

Reaction of trans-chlorocarbonylbis(triphenylphosphine)iridium with organic azides yields a stable complex of molecular nitrogen, 3, and organic isocyanates. The effects of changing the character of the azide, the central metal, and the ancillary ligands ...

J. P. Collman M. Kubota F. D. Vastine J. Y. Sun J. W. Kang

1968-01-01

18

Iridium® worldwide personal communication system  

NASA Astrophysics Data System (ADS)

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

Helm, Jim

1997-01-01

19

Global PCS - The Iridium vision  

NASA Astrophysics Data System (ADS)

The paper discusses the Iridium concept of a global personal communication system (PCS), consisting of a network of low-earth orbiting communication satellites for providing high-quality, ubiquitous, hand-held telephone service to the globe. Particular consideration is given to the impact of the Iridium on the wireless PCS market. The goal is to provide a single phone number to each individual for affordable quality connectivity to the world.

Swan, Peter A.

1993-10-01

20

Iridium-tin mixed oxide anode coatings  

Microsoft Academic Search

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

E. N. Balko; P. H. Nguyen

1991-01-01

21

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

22

Metal hydride technology  

SciTech Connect

A promising alternative for hydrogen storage is storage as a metal hydride. The properties and applications of those systems which have proven or potential utility as hydrogen storage compounds are summarized. Specific systems discussed are magnesium alloy hydrides, iron-titanium alloys, titanium-chromium alloys, and rare earth alloys. (LK)

Reilly, J.J.

1979-02-01

23

Metal hydride heat pump  

SciTech Connect

A metal hydride heat pump is disclosed comprising a first and a second heat medium receptacle having heat media flowing therein and a plurality of closed vessels each containing a hydrogen gas atmosphere and divided into a first chamber having a first metal hydride filled therein and a second chamber having a second metal hydride filled therein. The first and second chambers of each closed vessel are made to communicate with each other so that hydrogen gas passes from one chamber to the other but the metal hydrides do not, and a group of the first chambers of the closed vessels being located within the first heat medium receptacle and a group of the second chambers of the closed vessels being located within the second heat medium receptacle, whereby heat exchange is carried out between the heat media in the first and second heat medium receptacles and the first and second metal hydrides through the external walls of the closed vessels.

Nishizaki, T.; Miyamoto, K.; Miyamoto, M.; Nakata, Y.; Yamaji, K.; Yoshida, K.

1983-12-27

24

Chemistry of intermetallic hydrides  

SciTech Connect

Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

Reilly, J.J.

1991-01-01

25

State of iridium and its distribution in supported iridium catalysts  

Microsoft Academic Search

The presence of two oxidized forms of Ir, the ratio between which depends on its concentration, has been discovered in the surface layers of iridium catalysts obtained following the decomposition of adsorbed hexachloroiridic acid on AlâOâ. The surface Ir\\/Al ratio is more than two times greater than the corresponding ratio calculated from the data from elemental analysis. The Cl\\/Al ratio

A. V. Bulatov; T. P. Gaidei; S. N. Ustritskii; I. Y. Tyuryaev; M. L. Khidekel; Yu. M. Shulga; N. T. Yaroshenko; N. G. Samoilenko

1988-01-01

26

Boron Hydride Polymer Coated Substrates.  

National Technical Information Service (NTIS)

A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced i...

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

1986-01-01

27

A bright tetranuclear iridium(III) complex.  

PubMed

A cyclic tetranuclear cyclometallated iridium(III) complex using cyanide anions as bridging ligands and displaying a tetrahedrally distorted square geometry has been obtained with high yield; photo- and electrochemical characterizations show that most interesting properties of mononuclear cyclometallated iridium complexes are retained in the tetranuclear assembly. PMID:21286629

Baranoff, Etienne; Orselli, Enrico; Allouche, Lionel; Di Censo, Davide; Scopelliti, Rosario; Grätzel, Michael; Nazeeruddin, Md Khaja

2011-02-02

28

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

29

Hydrated hydride anion clusters.  

PubMed

On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed. PMID:17979342

Lee, Han Myoung; Kim, Dongwook; Singh, N Jiten; Ko?aski, Maciej; Kim, Kwang S

2007-10-28

30

Iridium material for hydrothermal oxidation environments  

SciTech Connect

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

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

1996-06-18

31

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

32

Boron hydride polymer coated substrates  

DOEpatents

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

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

1987-01-01

33

Boron hydride polymer coated substrates  

DOEpatents

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

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

1986-08-27

34

Laser spectroscopy of iridium monohydride and iridium monodeuteride  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectra of iridium monohydride (IrH) and monodeuteride (IrD) have been obtained at medium resolution. Eight red-degraded bands for each isotopologue were observed. The bands are assigned as ?' = 4 - ?? = 4 transitions with the ground state common to all bands in each isotopologue. The data are consistent with the ground state being the lowest component of a 3?i state. A global fit of all the rotationally resolved data yielded a set of rotation and distortion constants for each band. Ground state vibrational frequencies for IrH and IrD were determined to be 2216 and 1610 cm-1.

Adam, A. G.; Granger, A. D.; Linton, C.; Tokaryk, D. W.

2012-05-01

35

State of iridium and its distribution in supported iridium catalysts  

SciTech Connect

The presence of two oxidized forms of Ir, the ratio between which depends on its concentration, has been discovered in the surface layers of iridium catalysts obtained following the decomposition of adsorbed hexachloroiridic acid on Al/sub 2/O/sub 3/. The surface Ir/Al ratio is more than two times greater than the corresponding ratio calculated from the data from elemental analysis. The Cl/Al ratio is constant for all the sampling. The x-ray photoelectron spectra were recorded on a Varian IEE-15 spectrometer.

Bulatov, A.V.; Gaidei, T.P.; Ustritskii, S.N.; Tyuryaev, I.Y.; Khidekel', M.L.; Shul'ga, Yu.M.; Yaroshenko, N.T.; Samoilenko, N.G.

1988-08-01

36

Spectrum of Nickel Hydride  

Microsoft Academic Search

RECENTLY we have observed the spectrum obtained by introducing nickel carbonyl vapour into the flame of a Meker burner. Just above the blue-green cones, in the hottest part of the flame, we find a very wide-spaced band structure which can only be attributed to a hydride.

A. G. Gaydon; R. W. B. Pearse

1934-01-01

37

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

Microsoft Academic Search

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

John E. Baur; Thomas W. Spaine

1998-01-01

38

Iridium catalysis: application of asymmetric reductive hydrogenation.  

PubMed

Iridium, despite being one of the least abundant transition metals, has found several uses. N,P-ligated iridium catalysts are used to perform many highly selective reactions. These methodologies have been developed extensively over the past 15 years. More recently, the application of iridium N,P catalysts in asymmetric hydrogenation has been a focus of research to find novel applications and to expand on their current synthetic utility. The aim of this perspective is to highlight the advances made by the Andersson group. PMID:23942652

Cadu, Alban; Andersson, Pher G

2013-09-24

39

Anodic electrodeposition of iridium oxide films  

Microsoft Academic Search

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

Michel A. Petit; Vincent Plichon

1998-01-01

40

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

41

Hydride Formation in Zirconium Alloys  

NASA Astrophysics Data System (ADS)

The ingress of hydrogen during corrosion in service can degrade the mechanical properties of zirconium alloy nuclear fuel cladding because of the formation of brittle hydrides. The formation of these hydrides is reviewed in light of recent synchrotron radiation experimental results and phase-field modeling computational results that provide new insight on the process.

Motta, Arthur T.; Chen, Long-Qing

2012-12-01

42

Hydrogen storage in metal hydrides  

SciTech Connect

The storage of hydrogen as a metal hydride is discussed. Properties of some representative hydrogen-storage mediums (MgH/sub 2/, Mg/sub 2/NiH/sub 4/, VH/sub 2/, FeTiH/sub 1/ /sub 95/, LaNi/sub 5/H/sub 7/, liquid hydrogen, and gaseous hydrogen) are compared. Magnesium hydride, the more promising of the two binary hydrides, is thought to be only a borderline possibility as a hydrogen-storage medium at present. Of the three ternary hydrides listed the leading contender is iron-titanium hydride. It's main advantage over lanthanum-pentanickel hydride is one of cost. All the metal hydrides listed have a higher hydrogen storage capacity than an equal volume of liquid or gaseous hydrogen has. Energy densities (watt-hours per kilogram) of various automotive power sources either already in existence or proposed are tabulated. Metal hydrides lag far behind gasoline in terms of energy density, but they are competitive with electric batteries in this respect.

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

1980-02-01

43

Dimensionally stable metallic hydride composition  

DOEpatents

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

Heung, Leung K. (Aiken, SC)

1994-01-01

44

Thickness-dependent properties of sprayed iridium oxide thin films  

Microsoft Academic Search

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

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

2003-01-01

45

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

46

Scattering effects on the dosimetry of iridium-192  

Microsoft Academic Search

Dosimetry calculations for iridium-192 sources generally assume that a sufficient medium surrounds both the iridium source(s) and the point of calculation so that full scattering conditions exist. In several clinical applications the iridium sources may be anatomically located so that the full scattering requirement is not satisfied. To assess the magnitude of this problem, relative measurements were made with a

Christopher F. Serago; P. V. Houdek; V. Pisciotta; J. G. Schwade; A. A. Abitbol; A. A. Lewin; D. O. Poole; V. Marcial-Vega

1991-01-01

47

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

48

Hydrogen storage and evolution catalysed by metal hydride complexes.  

PubMed

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

Fukuzumi, Shunichi; Suenobu, Tomoyoshi

2013-01-01

49

Development of metal hydride composites  

SciTech Connect

Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydride granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.

Congdon, J.W.

1992-12-01

50

In vitro study of iridium electrodes for neural stimulation.  

PubMed

Iridium is one of the main electrode materials for applications like neural stimulation. Iridium has a higher charge injection capacity when activated and transformed into AIROF (activated iridium oxide film) using specific electrical signals. Activation is not possible in stimulating devices, if they do not include the necessary circuitry for activation. We introduce a method for iridium electrode activation requiring minimum additional on-chip hardware. In the main part, the lifetime behavior of iridium electrodes is investigated. These results may be interesting for applications not including on-chip activation hardware, and also because activation has drawbacks such as worse mechanical properties and reproducibility of AIROF. PMID:23366018

Aryan, Naser Pour; Brendler, Christian; Rieger, Viola; Schleehauf, Sebastian; Heusel, Gerhard; Rothermel, Albrecht

2012-01-01

51

Iridium emissions from Kilauea Volcano  

NASA Astrophysics Data System (ADS)

During May 1983, gas and particulate samples were collected at the cooling vents of Kilauea volcano in Hawaii. Three vents on the southeast rift zone were sampled using base-treated filter packs to absorb acidic gases and Teflon filters for particles. The samples were analyzed for 40 elements by nondestructive neutron activation analysis. As with other volcanoes, the chalcophilic and volatile elements were enriched by up to seven orders of magnitude relative to the erupted basalt. Unlike the case of other volcanoes, iridium was observed to be highly enriched (105 fold) at the two higher temperature vents, and the degree of enrichment appears to be related to both high temperatures and high fluorine content of the gases. Estimates of the emission rates of Ir during eruptions of Kilauea based on the measurements reported here and those of the Hawaiian Volcano Observatory yield an emission rate of about 3 g Ir per 106 m3 of magma. This rate amounts to only about 0.3% of the Ir present in the magma that is being released by the volcano. This previously unidentified Ir source to the atmosphere and ocean may have a significant influence on the geochemical cycle of Ir on the earth. The uniqueness of Kilauea in its emissions of Ir is probably related to the deep source of magma, which contains significant levels of Ir (0.32 ppb) and high levels of the halogens F and Cl.

Olmez, I.; Finnegan, D. L.; Zoller, W. H.

1986-01-01

52

Proximity effect in iridium-gold bilayers  

NASA Astrophysics Data System (ADS)

We have studied the proximity effect in bilayers of thin films of iridium covered by gold. By varying the thicknesses of the iridium and gold layers, we achieved critical temperatures as low as 33 mK. The critical temperature of the bilayers is lower than predicted by the theory of the Gennes-Werthamer (1964), but adding a free parameter to the theory allows good agreement. The transitions of the bilayers typically had widths of a few mK, with the narrowest reaching 0.2 mK, and were always steeper than those of pure iridium films evaporated simultaneously. Such bilayers can be used as superconducting phase transition thermometers in cryogenic particle detectors.

Nagel, U.; Nowak, A.; Gebauer, H.-J.; Colling, P.; Cooper, S.; Dummer, D.; Ferger, P.; Frank, M.; Igalson, J.; Nucciotti, A.

1994-10-01

53

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

Microsoft Academic Search

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

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

2004-01-01

54

Thermophysical properties of zirconium hydride and uranium–zirconium hydride  

Microsoft Academic Search

Thermal diffusivities of ?-phase Zirconium hydrides (ZrH1.69–2.00) were measured in the temperature range from 300 to 600 K by means of a laser-flash method. The thermal diffusivity of ?-phase Zr hydrides increased with increasing hydrogen concentration and decreased with increasing temperature. The thermal diffusivities of ?-phase ZrHx with x>1.83 were larger than that of ?-phase Zr. The experimental data on

B. Tsuchiya; J. Huang; K. Konashi; M. Teshigawara; M. Yamawaki

2001-01-01

55

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

56

Preparation and Characterization of Small Silica-Supported Iridium Particles from Iridium Trisacetylacetonate Precursor  

Microsoft Academic Search

This study treats the synthesis of silica-supported iridium metal particles by several different methods. Iridium trisacetylacetonate was first deposited on silica either by sublimation or by impregnation from a toluene solution. Infrared study showed no difference between the methods, each of which produced Ir(acac)3 physisorbed at the surface. The physisorbed precursor was transformed by two methods and the reactions were

F. Locatelli; B. Didillon; D. Uzio; G. Niccolai; J. P. Candy; J. M. Basset

2000-01-01

57

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

58

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 powdered 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. 6 figs.

Maienschein, J.L.; Barry, P.E.

1990-01-01

59

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 powdered 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. 6 figs.

Maienschein, J.L.; Barry, P.E.

1990-12-31

60

Hydrolytic reactions in hydrated iridium chloride coatings  

Microsoft Academic Search

A hydrolytic side reaction in hydrated iridium chloride films heat-treated on titanium supports was discovered by simultaneous thermal analysis, emission FTIR and SIMS techniques. In the presence of water vapour the degree of hydrolysis increases significantly in the outermost part of the film leading to the formation of oxidic species at low temperatures. In a wet oxygen atmosphere encapsulated hydrogen

J. Kristóf; J. Mihály; S. Daolio; A. De Battisti; L. Nanni; C. Piccirillo

1997-01-01

61

Luminescent Iridium Complexes and Their Applications  

NASA Astrophysics Data System (ADS)

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

Liu, Zhiwei; Bian, Zuqiang; Huang, Chunhui

62

Note: Electrochemical etching of sharp iridium tips  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

63

Sputtered Iridium Oxide for Stimulation Electrode Coatings  

Microsoft Academic Search

This work deals with the reactive RF-powered sputter deposition of iridium oxide for use as the active stimulation layer in functional medical implants. The oxygen gettered by the growing films is determined by an approach based on generic curves. Films deposited at different stages of oxygen integration show strong differences in electrochemical behaviour, caused by different morphologies. The dependence of

Wilfried Mokwa; Boerge Wessling; Uwe Schnakenberg

2007-01-01

64

New Process for Recycling of Rhodium and Iridium from Old Catalysts.  

National Technical Information Service (NTIS)

Recovery of rhodium and iridium from spent catalyst by selective dissolution is considered. The spent catalyst was reduced, impregnated and chlorinated. After dissolution of rhodium and iridium, rhodium was separated by electrolysis, whereas iridium could...

H. Erhard W. Hoerner F. Kummer

1983-01-01

65

Physics of hydride fueled PWR  

NASA Astrophysics Data System (ADS)

The first part of the work presents the neutronic results of a detailed and comprehensive study of the feasibility of using hydride fuel in pressurized water reactors (PWR). The primary hydride fuel examined is U-ZrH1.6 having 45w/o uranium: two acceptable design approaches were identified: (1) use of erbium as a burnable poison; (2) replacement of a fraction of the ZrH1.6 by thorium hydride along with addition of some IFBA. The replacement of 25 v/o of ZrH 1.6 by ThH2 along with use of IFBA was identified as the preferred design approach as it gives a slight cycle length gain whereas use of erbium burnable poison results in a cycle length penalty. The feasibility of a single recycling plutonium in PWR in the form of U-PuH2-ZrH1.6 has also been assessed. This fuel was found superior to MOX in terms of the TRU fractional transmutation---53% for U-PuH2-ZrH1.6 versus 29% for MOX---and proliferation resistance. A thorough investigation of physics characteristics of hydride fuels has been performed to understand the reasons of the trends in the reactivity coefficients. The second part of this work assessed the feasibility of multi-recycling plutonium in PWR using hydride fuel. It was found that the fertile-free hydride fuel PuH2-ZrH1.6, enables multi-recycling of Pu in PWR an unlimited number of times. This unique feature of hydride fuels is due to the incorporation of a significant fraction of the hydrogen moderator in the fuel, thereby mitigating the effect of spectrum hardening due to coolant voiding accidents. An equivalent oxide fuel PuO2-ZrO2 was investigated as well and found to enable up to 10 recycles. The feasibility of recycling Pu and all the TRU using hydride fuels were investigated as well. It was found that hydride fuels allow recycling of Pu+Np at least 6 times. If it was desired to recycle all the TRU in PWR using hydrides, the number of possible recycles is limited to 3; the limit is imposed by positive large void reactivity feedback.

Ganda, Francesco

66

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides  

PubMed Central

Summary Iridium-catalyzed intramolecular [4 + 2] cycloadditions of diene-tethered alkynyl halides were investigated by using [IrCl(cod)]2 as catalyst, and dppe was found to be the most suitable phosphine ligand for the reaction. No oxidative insertion of the iridium into the carbon–halide bond was observed, and the reactions proceeded to provide the halogenated cycloadducts in good yield (75–94%). These results are the first examples of cycloadditions of alkynyl halides using an iridium catalyst.

Tigchelaar, Andrew

2012-01-01

67

Electrochromism in spray deposited iridium oxide thin films  

Microsoft Academic Search

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

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

2005-01-01

68

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

69

Computational Modeling of Uranium Hydriding and Complexes  

Microsoft Academic Search

Uranium hydriding is one of the most important processes that has received considerable attention over many years. Although many experimental and modeling studies have been carried out concerning thermochemistry, diffusion kinetics and mechanisms of U-hydriding, very little is known about the electronic structure and electronic features that govern the U-hydriding process. Yet it is the electronic feature that controls the

K. Balasubramanian; Wigbert J. Siekhaus; William McLean

2003-01-01

70

Method of producing a chemical hydride  

DOEpatents

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

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

2007-11-13

71

Olefin isomerization by iridium pincer catalysts. Experimental evidence for an ?3-allyl pathway and an unconventional mechanism predicted by DFT calculations.  

PubMed

The isomerization of olefins by complexes of the pincer-ligated iridium species ((tBu)PCP)Ir ((tBu)PCP = ?(3)-C(6)H(3)-2,6-(CH(2)P(t)Bu(2))(2)) and ((tBu)POCOP)Ir ((tBu)POCOP = ?(3)-C(6)H(3)-2,6-(OP(t)Bu(2))(2)) has been investigated by computational and experimental methods. The corresponding dihydrides, (pincer)IrH(2), are known to hydrogenate olefins via initial Ir-H addition across the double bond. Such an addition is also the initial step in the mechanism most widely proposed for olefin isomerization (the "hydride addition pathway"); however, the results of kinetics experiments and DFT calculations (using both M06 and PBE functionals) indicate that this is not the operative pathway for isomerization in this case. Instead, (pincer)Ir(?(2)-olefin) species undergo isomerization via the formation of (pincer)Ir(?(3)-allyl)(H) intermediates; one example of such a species, ((tBu)POCOP)Ir(?(3)-propenyl)(H), was independently generated, spectroscopically characterized, and observed to convert to ((tBu)POCOP)Ir(?(2)-propene). Surprisingly, the DFT calculations indicate that the conversion of the ?(2)-olefin complex to the ?(3)-allyl hydride takes place via initial dissociation of the Ir-olefin ?-bond to give a ?-complex of the allylic C-H bond; this intermediate then undergoes C-H bond oxidative cleavage to give an iridium ?(1)-allyl hydride which "closes" to give the ?(3)-allyl hydride. Subsequently, the ?(3)-allyl group "opens" in the opposite sense to give a new ?(1)-allyl (thus completing what is formally a 1,3 shift of Ir), which undergoes C-H elimination and ?-coordination to give a coordinated olefin that has undergone double-bond migration. PMID:22765770

Biswas, Soumik; Huang, Zheng; Choliy, Yuriy; Wang, David Y; Brookhart, Maurice; Krogh-Jespersen, Karsten; Goldman, Alan S

2012-08-02

72

Deoxidization of Iridium Oxide Thin Film  

Microsoft Academic Search

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

Seon Yong Cha; Hee Chul Lee

1999-01-01

73

IV. Radioactivity of neutron excess iridium isotopes  

Microsoft Academic Search

The half-lives, mass assignments and radiation characteristics of the neutron excess iridium isotopes have been determined as follows: The gamma-ray energies of 19-hour Ir have also been examined.The 7-second Ir isomer is either a 125 kev E3 transition followed by the 5·6 mev gamma-ray or possibly a 5·6mev M6, E6 or E7 transition followed by a 125 kev M1. E2

F. D. S. Butement; A. J. Poë

1954-01-01

74

Advances in iridium alloy processing in 1987  

Microsoft Academic Search

A new process for the production of DOP-26 iridium alloy blanks is being evaluated and optimized. The alloy is prepared by electron-beam (EB) melting of Ir-0.3% W powder compacts followed by doping with aluminum and thorium by arc melting. Drop-cast alloy rod segments are EB welded to produce an electrode that is consumable arc melted to produce an ingot for

R. L. Heestand; E. K. Ohriner; T. K. Roche

1988-01-01

75

Iridium isotope ratio measurements by negative thermal ionization mass spectrometry and atomic weight of iridium  

NASA Astrophysics Data System (ADS)

A technique of negative thermal ionization mass spectrometry (NTI-MS) for the precise iridium isotope ratio determination is presented. IrO-2 and IrO-3 ions are formed in a double-filament (Pt) ion source using (NH4)2IrCl6 as a sample compound. The IrO-2 ion current always exceeds the IrO-3 current by a factor of about 50-300 depending on the filament temperature and the oxygen gas introduced into the ion source. IrO-3 ion currents of more than 10-11 A can be obtained at the detector side from 100 ng iridium samples. The relative standard deviation of the 191Ir/193 ratio determination is 0.06%, which is much better than the data quoted in past literature. From such data the atomic weight of iridium could be calculated to be 192.21661 ± 0.00029. This value is a great improvement when compared with the iridium atomic weight of 192.22 ± 0.03 recommended by IUPAC. Additionally, an NTI-MS technique has been developed which allows the simultaneous measurement of iridium and osmium isotope ratio from osmiridium samples without any chemical separation. The iridium isotope ratios of three osmiridium samples agree well with the ratios determined from the hexachloroiridate compound. The direct 187Os/186OS determination from osmiridium samples opens the possibility of studying the evolution of osmium in the Earth's mantle due to the radioactive decay of 187Re into 187Os.

Walczyk, Thomas; Heumann, Klaus G.

1993-02-01

76

Iridium-Catalyzed Hydrogen Transfer Reactions  

NASA Astrophysics Data System (ADS)

This chapter describes the application of iridium complexes to catalytic hydrogen transfer reactions. Transfer hydrogenation reactions provide an alternative to direct hydrogenation for the reduction of a range of substrates. A hydrogen donor, typically an alcohol or formic acid, can be used as the source of hydrogen for the reduction of carbonyl compounds, imines, and alkenes. Heteroaromatic compounds and even carbon dioxide have also been reduced by transfer hydrogenation reactions. In the reverse process, the oxidation of alcohols to carbonyl compounds can be achieved by iridium-catalyzed hydrogen transfer reactions, where a ketone or alkene is used as a suitable hydrogen acceptor. The reversible nature of many hydrogen transfer processes has been exploited for the racemization of alcohols, where temporary removal of hydrogen generates an achiral ketone intermediate. In addition, there is a growing body of work where temporary removal of hydrogen provides an opportunity for using alcohols as alkylating agents. In this chemistry, an iridium catalyst "borrows" hydrogen from an alcohol to give an aldehyde or ketone intermediate, which can be transformed into either an imine or alkene under the reaction conditions. Return of the hydrogen from the catalyst provides methodology for the formation of amines or C-C bonds where the only by-product is typically water.

Saidi, Ourida; Williams, Jonathan M. J.

77

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

Microsoft Academic Search

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

In-Seop Leea; Chung-Nam Whanga; Young-Hee Leeb; Gun Hwan Leec; Bong-Joo Parkd; Jong-Chul Parkd; Won-Seon Seoe; Fu-Zhai Cuif

78

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

Microsoft Academic Search

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

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

2005-01-01

79

Weldability of general purpose heat source new-process iridium  

SciTech Connect

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

Kanne, W.R.

1987-01-01

80

Micro-machined, polyimide stimulating electrodes with electroplated iridium oxide  

Microsoft Academic Search

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

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

1999-01-01

81

Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents.  

PubMed

An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to enantioenriched chlorohydrins via an oxidation-asymmetric reduction sequence. PMID:20871888

Mutti, Francesco G; Orthaber, Andreas; Schrittwieser, Joerg H; de Vries, Johannes G; Pietschnig, Rudolf; Kroutil, Wolfgang

2010-09-27

82

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

83

Iridium Abundances across the Ordovician-Silurian Stratotype  

NASA Astrophysics Data System (ADS)

Chemostratigraphic analyses in the Ordovician-Silurian boundary stratotype section, bracketing a major extinction event in the graptolitic shale section at Dob's Linn, Scotland, show persistently high iridium concentrations of 0.050 to 0.250 parts per billion. There is no iridium concentration spike in the boundary interval or elsewhere in the 13 graptolite zones examined encompassing about 20 million years. Iridium correlated with chromium, both elements showing a gradual decrease with time into the middle part of the Lower Silurian. The chromium-iridium ratio averages about 106. Paleogeographic and geologic reconstructions coupled with the occurrence of ophiolites and other deep crustal rocks in the source area suggest that the high iridium and chromium concentrations observed in the shales result from terrestrial erosion of exposed upper mantle ultramafic rocks rather than from a cataclysmic extraterrestrial event.

Wilde, Pat; Berry, William B. N.; Quinby-Hunt, Mary S.; Orth, Charles J.; Quintana, Leonard R.; Gilmore, James S.

1986-07-01

84

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

Microsoft Academic Search

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

K. Nishio; Y. Watanabe; T. Tsuchiya

1999-01-01

85

Iridium Metal in Chicxulub Impact Melt: Forensic Chemistry on the K-T Smoking Gun  

Microsoft Academic Search

Iridium concentrations in successively smaller subsplits of melt rock and melt breccia from the Chicxulub impact basin were tracked to isolate and identify iridium carrier phases. Iridium-rich particles were isolated from two samples, and a micrometer-scale, silicate-enclosed aggregate of subhedral iridium metal grains was identified in one, confirming earlier reports of iridium at ground zero of the impact at the

Benjamin C. Schuraytz; David J. Lindstrom; Luis E. Marin; Rene R. Martinez; David W. Mittlefehldt; Virgil L. Sharpton; Susan J. Wentworth

1996-01-01

86

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

PubMed

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

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

2013-09-24

87

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Metal hydride storage systems. 173.311 Section 173...Packaging § 173.311 Metal hydride storage systems. The following packing instruction...applicable to transportable UN Metal hydride storage systems (UN3468) with pressure...

2011-10-01

88

IRIDIUM debris protection and mitigation techiques  

NASA Astrophysics Data System (ADS)

The IRIDIUM Program represents the most exciting prospect in space operations in the world today. It represents one of the best commercial opportunities as well as one of the biggest engineering challenges ever. This paper describes the trend-setting approach Motorola has taken in 'designing in' orbital debris mitigation features while keeping associated costs virtually negligible. It delineates the attributes of a comprehensive program instituted during the design phase, maintained through the development phase, and which will be continued through the operations phase. The challenges are being met head-on and Motorola is aggressively seizing the opportunity to set new standards in debris protection mitigation techniques.

Penny, Robert E.

1996-10-01

89

Iridium: Covering the globe with personal communication  

NASA Astrophysics Data System (ADS)

It has become abundantly clear that available, reliable telecommunications is a critical requirement for effective economic development, and that most of the worlds population lacks effective telecommunications today, even on a local basis, with international capability being particularly deficient. The IRIDIUM system, a satellite based communications system utilizing Low Earth Orbit (LEO) satellites, will bring personal communications to every part of the world. This networked LEO system will provide an efficient means of interconnecting hundreds of thousands of towns and villages more cost effectively than any other known approach. Various aspects of the system are discussed.

Gercenstein, Mark

90

Radon hydrides: structure and bonding.  

PubMed

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

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

2010-11-19

91

Isotope Effect in Dissociation of Uranium Hydride  

Microsoft Academic Search

Isotope effect on dissociation behavior of uranium hydride has been studied. The equilibrium dissociation pressure of uranium protide(UH3), deuteride (UD3), and of equimolar mixture of both hydrides are measured. The dissociation pressure of deuteride is higher than that of the protide by a factor of about 2 at 400°C and mixed hydride of UH3 and UD3 has intermediate dissociation pressures.

Tetsuo TANABE; Satoshi MIURA; Sh?suke IMOTO

1979-01-01

92

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

Microsoft Academic Search

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

Yoshihisa Tahra; Tomohiko IWASKI; Kenji KONASKI

2010-01-01

93

HVEM in situ hydriding of hydrogen storage materials  

Microsoft Academic Search

The microstructural changes induced during hydriding have been investigated by high-voltage electron microscopy and in situ hydriding studies. Hydriding generates high dislocation densities, which has implications for the mechanism involved in the hydride transformation and possible effects of prior hydrogen exposures on subsequent hydriding behavior. In situ hydriding of LaCoâ and LaNiâCoâ has been demonstrated. There appears to be an

E. A. Kenik; J. Mullins; S. Spooner; B. R. Livesay

1979-01-01

94

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.

95

Iridium wire grid polarizer fabricated using atomic layer deposition  

PubMed Central

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

2011-01-01

96

PH sensors based on iridium oxide  

SciTech Connect

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

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

1988-01-01

97

Dose Determination in Breast Tumor in Brachytherapy Using Iridium-192.  

National Technical Information Service (NTIS)

Thermoluminescent dosimetry studies in vivo and in vitro aiming to determing radiation dose in the breast tumor, in brachytherapy using Iridium-192 was done. The correlation between radiation doses in tumor and external surface of the breast was investiga...

S. F. Okuno

1984-01-01

98

Intraoperative interstitial implantation of Iridium 192 in the breast  

SciTech Connect

Intraoperative interstitial implantation of iridium 192 during a lumpectomy for carcinoma of the breast has been well tolerated by the patient. This procedure has decreased the need for anesthesia and repeat hospitalization.

Mansfield, C.M.; Jewell, W.R.

1984-02-01

99

Acute radiodermatitis from occupational exposure to iridium 192  

SciTech Connect

Industrial radiography using the man-made radioisotope iridium 192 is commonplace in the southern states. Despite established procedures and safeguards, accidental exposure may result in typical acute radiodermatitis. We have presented a clinical example of this phenomenon.9 references.

Becker, J.; Rosen, T. (Veterans Administration Medical Center, Houston, TX (USA))

1989-12-01

100

Iridium anomaly approximately synchronous with terminal eocene extinctions  

SciTech Connect

An iridium anomaly has been found in coincidence with the known microtektite level in cores from Deep Sea Drilling Project site 149 in the Caribbean Sea. The iridium was probably not in the microtektites but deposited simultaneously with them; this could occur if the iridium was deposited from a dust cloud resulting from a bolide impact, as suggested for the anomaly associated with the Cretaceous-Tertiary boundary. Other workers have deduced that the microtektites are part of the North American strewn tektite field, which is dated at about 34 million years before present, and that the microtektite horizon in deep-sea cores is synchronous with the extinction of five radiolarian species. Mass extinctions also occur in terrestrial mammals within 4 million years of this time. The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago.

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

1982-05-21

101

Use of Iridium, a Commercial Telecommunications Satellite System, in Wartime.  

National Technical Information Service (NTIS)

This study investigates the capabilities and limitations of the commercial telecommunications satellite system, Iridium. In view of the increasing demands for immediate communications in the modern theaters of war, the study analyzes the utility that Irid...

T. L. Yoder

1996-01-01

102

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

SciTech Connect

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

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

2008-01-15

103

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

104

Hydrogen storage technology for metal hydrides  

SciTech Connect

The advantages of using hydrogen as a secondary energy carrier are stated, and numerous factors pertinent to the technology of hydrogen storage via metal hydrides are briefly described. The technology is centered on iron-titanium hydride, FeTiH/sub x/, as the most practical choice for the safe and compact storage of hydrogen. Uses of hydride hydrogen as a fuel or energy carrier are given. The features of hydride reservoir designs are explained, and some performance data are given for two reservoirs constructed at BNL. Results of tests on the long-term behavior of FeTiH/sub x/ are presented along with information on pressure drop in a hydride bed. Two methods of accommodating hydride expansion are described. Other topics include: container materials selection, safety testing of FeTiH/sub x/, hydride materials development, storage systems work at BNL, the proposed Hydrogen-Halogen Energy Storage System, a proposed technique of storing hydrogen in hollow glass microspheres at very high pressure, and information on the commercial availability of materials and equipment for hydride hydrogen. Current development needs are included in the various sections.

Strickland, G

1978-06-01

105

DUAL SITE CATALYSTS FOR HYDRIDE MANIPULATION  

Microsoft Academic Search

This comment describes our efforts to develop dual site catalysts for hydride manipulation. We began by analyzing the mechanism of alcohol oxidation with the ruthenium-based Shvo catalyst, which utilizes a proton transfer to template a hydride transfer from carbon to ruthenium in a single transition state. In our project we are working to extend this concept of reactivity from the

Brian L. Conley; Travis J. Williams

2011-01-01

106

Inhibited Solid Propellant Composition Containing Beryllium Hydride.  

National Technical Information Service (NTIS)

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-te...

W. W. Thompson

1978-01-01

107

Erbium hydride thermal desorption : controlling kinetics.  

SciTech Connect

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

Ferrizz, Robert Matthew

2007-08-01

108

Preparation and catalytic properties of cerium hydride  

Microsoft Academic Search

Cerium hydride was formed at a moderate temperature (523K) and atmospheric pressure using a pulse-flow technique. Its adsorption and catalytic properties were probed using deuterium, oxygen, carbon monoxide, carbon dioxide, methanol, and propyne. Deuterium exchange with the hydrogen of the hydride was examined and not all of the hydrogen was found to be exchangeable. It is likely that this was

S. David Jackson; Gordon J. Kelly; Elaine M. Vass

2008-01-01

109

Positron Annihilation in Rare-Earth Hydrides  

Microsoft Academic Search

Analysis of the angular correlations of positron-annihilation radiation from erbium, gadolinium, holmium, and ytterbium hydrides indicates that the electronic structure of these materials is basically metallic in nature. As was previously found in the case of cerium hydride, the angular correlations were found to be broader than those from their parent metals by amounts which were consistent with the assumption

M. P. CHOUINARDt; D. R. Gustafson

1971-01-01

110

Kinetics of iridium reduction by hydrogen in hydrochloric acid solution  

Microsoft Academic Search

The effects of stirring speed, initial iridium ion concentration, hydrogen pressure, hydrochloric acid, chloride concentrations,\\u000a seeding, and temperature on the reduction rate of iridium ion by hydrogen have been investigated. The whole process of reduction\\u000a occurs in a complicated heterogeneous stage. The reduced metallic Ir serves itself as a catalyst for the reduction. The rate\\u000a in the earlier stage of

Xiansheng Nie; Jing Chen; Qinglin Tan

1992-01-01

111

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

112

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

113

Hydrogenation using hydrides and acid  

DOEpatents

The present invention relates to a very rapid, non-catalytic process for hydrogenating unsaturated organic compounds that can be carried out at temperatures generally lower than previously utilized. In this process organic compounds which contain at least one reducible functional group are hydrogenated non-catalytically by reacting them with a hydride complex and a strong acid. The reducible functional group may be, for example, C=C, C-OH, C-O-C, or a strained cyclic structure. If the reactants are not mutually soluble, they are dissolved in an appropriate inert solvent. 3 tabs.

Bullock, R.M.

1989-12-13

114

Zirconium hydride containing explosive composition  

DOEpatents

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

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

1981-01-01

115

Electrical Measurements on Iridium Dioxide Nanorods  

NASA Astrophysics Data System (ADS)

Iridium dioxide (IrO2) nanorods have been prepared by metal-organic chemical vapor deposition method. Applying the standard electron-beam lithography technique, a single nanorod with a diameter of 110 nm is contacted by three Cr/Au fingers from above. The resistance measurements on this nanorod have been performed between 10 and 300 K, using different probe configurations. We observe that the resistivity ? of the nanorod has a value <= 120 ?? cm at 300 K. On the other hand, the temperature dependence of the contact resistance R obeys the law logR ~ T-1/2 below 100 K. The conduction process through the contact is ascribed to the transport of electrons via hopping in granular metals accidentally formed at the contact region.

Lin, Y. H.; Lee, T. C.; Lin, J. J.; Chang, H. M.; Huang, Y. S.

2006-09-01

116

Raman scattering study in iridium pyrochlore oxides  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

117

Improvements in manufacture of iridium alloy materials  

SciTech Connect

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

Ohriner, E.K.

1992-01-01

118

Improvements in manufacture of iridium alloy materials  

SciTech Connect

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

Ohriner, E.K.

1992-08-01

119

Activated aluminum hydride hydrogen storage compositions and uses thereof  

SciTech Connect

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

120

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

121

Iridium Oxide pH Microelectrode. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The manufacture, calibration, and signal conditioning during construction of an iridium/iridium oxide pH microsensor is described. The microsensor was designed to be used extracellularly, primarily in biofilm research. The sensing tip diameters were typic...

P. VanHoudt Z. Lewandowski B. Little

1992-01-01

122

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...

123

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

124

A long-term stable iridium oxide pH electrode  

Microsoft Academic Search

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

Min Wang; Sheng Yao; Marc Madou

2002-01-01

125

Global Measurement of Birkeland Currents with Iridium: How it Works and Future Prospects  

Microsoft Academic Search

The constellation of more than 70 Iridium satellites offers an unprecedented opportunity to observe the global Birkeland currents. These currents convey stress between the magnetosphere and ionosphere and reflect the state of the M-I system. Each satellite of the Iridium constellation carries a magnetometer as part of the attitude control system and is digitized to 30 nT resolution. The Iridium

B. J. Anderson; H. Korth; D. L. Green; C. L. Waters

2006-01-01

126

Computational Modeling of Uranium Hydriding and Complexes  

SciTech Connect

Uranium hydriding is one of the most important processes that has received considerable attention over many years. Although many experimental and modeling studies have been carried out concerning thermochemistry, diffusion kinetics and mechanisms of U-hydriding, very little is known about the electronic structure and electronic features that govern the U-hydriding process. Yet it is the electronic feature that controls the activation barrier and thus the rate of hydriding. Moreover the role of impurities and the role of the product UH{sub 3} on hydriding rating are not fully understood. An early study by Condon and Larson concerns with the kinetics of U-hydrogen system and a mathematical model for the U-hydriding process. They proposed that diffusion in the reactant phase by hydrogen before nucleation to form hydride phase and that the reaction is first order for hydriding and zero order for dehydriding. Condon has also calculated and measures the reaction rates of U-hydriding and proposed a diffusion model for the U-hydriding. This model was found to be in excellent agreement with the experimental reaction rates. From the slopes of the Arrhenius plot the activation energy was calculated as 6.35 kcal/mole. In a subsequent study Kirkpatrick formulated a close-form for approximate solution to Condon's equation. Bloch and Mintz have proposed the kinetics and mechanism for the U-H reaction over a wide range of pressures and temperatures. They have discussed their results through two models, one, which considers hydrogen diffusion through a protective UH{sub 3} product layer, and the second where hydride growth occurs at the hydride-metal interface. These authors obtained two-dimensional fits of experimental data to the pressure-temperature reactions. Kirkpatrick and Condon have obtained a linear solution to hydriding of uranium. These authors showed that the calculated reaction rates compared quite well with the experimental data at a hydrogen pressure of 1 atm. Powell et al. have studied U-hydriding in ultrahigh vacuum and obtained the linear rate data over a wide range of temperatures and pressures. They found reversible hydrogen sorption on the UH{sub 3} reaction product from kinetic effects at 21 C. This demonstrates restarting of the hydriding process in the presence of UH{sub 3} reaction product. DeMint and Leckey have shown that Si impurities dramatically accelerate the U-hydriding rates. We report our recent results of relativistic computations that vary from complete active space multi-configuration interaction (CAS-MCSCF) followed by multi-reference configuration interaction (MRSDCI) computations that included up to 50 million configurations for modeling of uranium-hydriding with cluster models will be presented.

Balasubramanian, K; Siekhaus, W J; McLean, W

2003-02-03

127

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

128

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

NASA Astrophysics Data System (ADS)

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

129

Intrinsic activation of iridium electrodes over a wireless link.  

PubMed

Activated Iridium Oxide Film (AIROF) microelectrodes are regarded as advantage for stimulation of neural tissue owing to their superior charge injection capabilities, as compared to other noble-metal based electrodes. Including AIROF electrodes within an implantable neural stimulator can be challenging since the stimulator fabrication steps often involve elevated temperatures at which the AIROF can be damaged. In this work, a wireless neural stimulator application-specific-integrated-circuit (ASIC) was used to intrinsically activate iridium microelectrodes. This intrinsic activation allows for the growth of the AIROF as the final assembly step after the entire device is assembled, thus avoiding stress on the AIROF. Since a typical neural stimulator is essentially a current-controlled driver with voltage compliance limits, its output waveform can be tuned to match the traditional voltage pulsing/ramp activation waveform. Here the feasibility of the current driven activation of iridium electrodes, over a wireless link, is demonstrated. PMID:23366504

Hu, Zhe; Troyk, Philip; DeMichele, Glenn; Kayvani, Kevin; Suh, Sungjae

2012-01-01

130

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

PubMed

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

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

2012-08-22

131

Study of iridium and iridium--tungsten alloys for space radioisotopic heat sources. [Up to 4% W; fabrication; microstructure; tensile; oxidation; compatibility; fractures  

Microsoft Academic Search

The physical and mechanical properties of iridium and iridium-tungsten alloys containing up to 4% tungsten were evaluated as potential cladding materials in space isotopic heat sources. The iridium--tungsten alloys are readily fabricable and are compatible with graphite, low-pressure oxygen, and simulated heat source environments up to at least 1300°C. The solubility of oxygen and carbon in the alloys appears to

C. T. Liu; H. Inouye

1976-01-01

132

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

DOEpatents

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

133

Feasibility study of a personal communications system IRIDIUM-like  

NASA Astrophysics Data System (ADS)

A candidate architecture applicable to personal communications systems, via Low Earth Orbit (LEO) satellites is outlined. The concept of the IRIDIUM Motorola system has been adopted as derived from the available public documentation. The following topics are covered: system architecture (IRIDIUM like concept) and scenario; constellation characteristics, user links, coverage and frequency reuse; Leostar-E spacecraft and payload architecture definition; traffic management (access, routing, networking); and organization aspects and manufacturing strategies. Additional efforts are required in order to assess a convenient cost/technology tradeoff.

Caporicci, L.; Delricco, R.; Digirolamo, S.; Soddu, C.; Rondinelli, G.

1993-01-01

134

Atomic replacement and vacancy formation and annihilation on iridium surfaces  

NASA Astrophysics Data System (ADS)

Field ion microscopy is used here to observe surface atomic processes when the chemical nature of an adatom differs from that of the surface atoms. On the iridium 001-plane surface, an adsorbed rhenium atom will displace an iridium atom from the substrate to form an Re-Ir-vacancy bound complex at about 230 K. On heating the sample to about 300 K, this complex dissociates and the rhenium atom becomes incorporated into the surface. This represents a kind of atomic-scale surface alloying. Alternatively, the Re-Ir cluster can be removed by field evaporation to leave a lattice vacancy, into which another adatom can subsequently diffuse.

Tsong, Tien T.; Chen, Chong-Lin

1992-01-01

135

pH sensors based on iridium oxide  

SciTech Connect

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

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

1990-03-01

136

Thin-film metal hydrides.  

PubMed

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

Remhof, Arndt; Borgschulte, Andreas

2008-12-01

137

Automotive Storage of Hydrogen Using Modified Magnesium Hydrides.  

National Technical Information Service (NTIS)

Metal hydrides can store more hydrogen per unit volume than normal high pressure or cryogenic techniques. Little energy is required to store the hydrogen in the hydride, and high stability at room temperature assures low losses over long storage periods. ...

D. A. Rohy J. F. Nachman T. E. Duffy

1975-01-01

138

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

139

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

SciTech Connect

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

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

1987-09-01

140

Antifungal activity of rhodium, iridium, and ruthenium tripodal phosphine complexes.  

PubMed

Twenty-eight rhodium, iridium or ruthenium complexes were evaluated for their in vitro antifungal activities against Candida albicans and Candida tropicalis. Fourteen compounds showed an antifungal activity against C. albicans and C. tropicalis with a range of the minimum inhibitor concentrations (MICs) between 16 and 250 micrograms/mL. PMID:10946408

Sülü, M; Küçükbay, H; Durmaz, R; Günal, S

2000-01-01

141

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

142

pH Sensors Based on Iridium Oxide.  

National Technical Information Service (NTIS)

Results are presented on the pH-potential response of d.c. magnetron reactively sputtered iridium oxide films. The films exhibit a nearly Nernstian response to pH, no hysteresis effects, and minimal response to ionic interferences. Sensitivity to certain ...

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

1990-01-01

143

Iridium oxide and palladium modified nitric oxide microsensor  

Microsoft Academic Search

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

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

1999-01-01

144

Magnetostratigraphy, Late devonian iridium anomaly, and impact hypotheses  

SciTech Connect

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

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

1990-04-01

145

Charge-injection waveforms for iridium oxide (AIROF) microelectrodes  

Microsoft Academic Search

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

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

2003-01-01

146

Iridium and Titanium Thin Oxide Films: Electrochemical and Biological Applications  

Microsoft Academic Search

Neural growth requires good interface between the neural cells and the material used as substrate. It is necessary that the materials used for neuronal growth applications don't show cytotoxicity and have a low inflammatory response yielding good tolerance in implants. Furthermore, it is known that electroactive materials are better electrodes for electrostimulation than noble metals (1-2). The use of iridium

A. M. Cruz; M. Carballo; V. Padial; J. Collazos Castro; N. Casañ-Pastor

147

Interstitial iridium 192 for cutaneous carcinoma of the external nose  

Microsoft Academic Search

Several implantation techniques useful for nasal skin carcinoma have been developed at the Henri Mondor Hospital in Creteil, France and are described in detail. Iridium 192 wires, 0.3 mm in diameter, are afterloaded into either supple plastic tubes or rigid needles implanted according to the rules of the Paris system. Dosimetry is performed by computer, based on either direct measurements

J. M. Crook; J. J. Mazeron; G. Marinello; M. Raynal; J. Huart; S. Leung; J. P. LeBourgeois; B. Pierquin

1990-01-01

148

Iridium 192 implantation of squamous cell carcinomas of the oropharynx  

Microsoft Academic Search

From 1970 to 1984, 127 patients with T1 or T2 carcinomas of the oropharynx were treated with external irradiation to the primary tumor and neck nodes to a dose of 45 Gy, followed by a further 30 Gy delivered by an iridium 192 implant to the primary tumor. Patients with clinically positive nodes had either further neck irradiation using electrons

Jean-Jacques Mazeron; Juanita Crook; Michel Martin; Roger Peynegre; Bernard Pierquin

1989-01-01

149

Discovery of tantalum, rhenium, osmium, and iridium isotopes  

NASA Astrophysics Data System (ADS)

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.

2012-09-01

150

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

151

Kinetics of hydrogen desorption from the powders of metal hydrides  

Microsoft Academic Search

Desorption of hydrogen from the powders of metal hydrides (MH) is affected by several interplaying processes including hydrogen desorption from and recombination on the metal surface, diffusion within the bulk metal and different hydride phases, and decomposition of the hydride phase. In present work, possible mechanisms of hydrogen release from the MH are proposed and discussed. Analytical models are developed

I. E. Gabis; A. P. Voit; E. A. Evard; Yu. V. Zaika; I. A. Chernov; V. A. Yartys

2005-01-01

152

A RATIONALIZATION OF THE FORMATION OF SALINE AND METALLIC HYDRIDES  

Microsoft Academic Search

These two parts were issued separately, but are cataloged as a unit. ; The previously reported observation that internuclear distances in metallic ; hydrides are approximately the sum of the cation radius and hydride anion radius ; (l.29A) is extended, and additional data presented. If it is assumed that the ; lattice energy of a metallic hydride is similar to

Gibb; T. R. P. Jr

1958-01-01

153

HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS  

Microsoft Academic Search

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

K. McCoy

2000-01-01

154

49 CFR 173.311 - Metal hydride storage systems.  

Code of Federal Regulations, 2012 CFR

...173.311 Metal hydride storage systems. The following...transportable UN Metal hydride storage systems (UN3468) with pressure...150 liters (40 gallons) in water capacity and having a maximum...exceeding 25 MPa. Metal hydride storage systems must be...

2012-10-01

155

A model iridium hydroformylation system with the large bite angle ligand xantphos: reactivity with parahydrogen and implications for hydroformylation catalysis.  

PubMed

Iridium complexes containing the large bite angle bisphosphine ligand xantphos have been synthesized and their reactivity studied. Several of these complexes are the first reported Ir(xantphos) systems to be characterized by X-ray diffraction. Variable-temperature NMR spectroscopic studies of IrI(CO)2(xantphos) (1-I) and Ir(COEt)(CO)2(xantphos) (8) show two separate dynamic processes in which the phosphorus donors and the backbone methyl groups of the xantphos ligand are exchanged. The addition of parahydrogen (p-H2) to 1-I leads to the formation of two dihydride isomers including one in which both hydride ligands are trans to the phosphorus donors, suggestive of an Ir(I) xantphos intermediate with the ligand chelated in a trans-spanning fashion (2b). The bromide and chloride Ir(I) analogues (1-Br and 1-Cl) also form this isomer upon reaction with parahydrogen, with 1-Cl yielding only this dihydride species. The trihydride complex IrH3(CO)(xantphos) (7) has been prepared, and its exchange with free hydrogen at elevated temperature is confirmed by reaction with p-H2. The hydride complexes IrH(CO)2(xantphos) (6) and IrH3(CO)(xantphos) (7), as well as the propionyl complex 8, are modest catalysts for the hydroformylation of 1-hexene and styrene under mild conditions. The addition of p-H2 to 8 permits direct observation of the propionyl dihydride species IrH2(COEt)(CO)(xantphos) (9) under both thermal and photolytic conditions, as well as unusual but weak polarization of the aldehydic proton of the propanal product that forms upon reductive elimination from 9. PMID:16933920

Fox, Daniel J; Duckett, Simon B; Flaschenriem, Christine; Brennessel, William W; Schneider, Jacob; Gunay, Ahmet; Eisenberg, Richard

2006-09-01

156

Hydride Transfer from Rhodium Complexes to Triethylborane  

SciTech Connect

The hydrides HRh(depe)2 and HRh(dmpe)2 (depe = Et2PCH2CH2PEt2, dmpe = Me2PCH2CH2PMe2) have thermodynamic hydride donor abilities comparable to LiHBEt3, as indicated by their ability to transfer a hydride ligand to Et3B. These hydrides can be generated from hydrogen gas in the presence of a strong base such as potassium t-butoxide or lithium diisopropylamide. This reaction proceeds through the oxidative addition of hydrogen to form the [H2Rh(diphosphine)2](CF3SO3) complexes, followed by deprotonation. The oxidative addition of H2 is favored by diphosphine ligands with electron donating substituents and large chelate bites. In the present study, the driving force for oxidative addition of H2 follows the order [Rh(dmpe)2](CF3SO3) > [Rh(depe)2](CF3SO3) > [Rh(dppe)2](CF3SO3) with [Rh(dmpe)2](CF3SO3) binding H2 more strongly than [Rh(dppe)2](CF3SO3) (dppe = Ph2PCH2CH2PPh2) by at least 2.7 kcal/mol. The effect of the chelate bite size is larger. [H2Rh(depx)2](CF3SO3) (depx = 1,2-(Et2PCH2)2C6H4) binds H2 more strongly than [Rh(depe)2](CF3SO3) by 12 kcal/mol. An understanding of both hydrogen activation and hydride donor abilities is important for developing powerful hydride donors from H2. Acknowledgment: This research was supported by the Director’s Discretionary Research and Development Program of the National Renewable Energy Laboratory, and in part, by the Chemical Sciences Program of the Office of Basic Energy Sciences of the Department of Energy. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

DuBois, Daniel L.; Blake, D. M.; Miedaner, Alex; Curtis, Calvin J.; DuBois, Mary R.; Franz, James A.; Linehan, John C.

2006-08-28

157

Electrochemical, Optical and Electronic Properties of Iridium Tin Oxide Thin Film as Counter Electrode of Electrochromic Device  

NASA Astrophysics Data System (ADS)

Iridium tin oxide films (IRTOFs) containing dispersed iridium oxide in a tin oxide matrix were prepared by an ion-plating process. The optical, electrochemical, and electronic properties of the films were measured by varying the iridium concentration in the films. The cyclic voltammogram characteristic of the films showed good reproducibility. The coloration efficiency of the IRTOFs increased with an increase in the concentration of iridium. The change ranges of the conductivity become more than 108 times. The activation energy increased with increasing iridium concentration in the iridium concentration range in which the conductivity decreased. The characteristics of an all-solid-state electrochromic device with an IRTOF counter electrode were measured.

Niwa, Tatsuo; Takai, Osamu

2010-10-01

158

Facile synthesis of rhodium and iridium complexes bearing a [PEP]-type ligand (E = Ge or Sn) via E-C bond cleavage.  

PubMed

Rhodium and iridium complexes bearing a tridentate [PEP] type ligand ([PEP] = {o-(Ph(2)P)C(6)H(4)}(2)E(Me); E = Ge or Sn) were synthesized through the phosphine exchange reaction accompanied by selective E-C bond cleavage. The ligand precursors {o-(Ph(2)P)C(6)H(4)}(2)EMe(2) (E = Ge or Sn) were readily obtained in excellent yields by treating {o-(Ph(2)P)C(6)H(4)}(2)Li with 0.5 equivalents of Me(2)ECl(2). Tris(triphenylphosphine)rhodium(I) carbonyl hydride M(H)(CO)(PPh(3))(3) (M = Rh, Ir) cleaved one of the E-Me bonds of {o-(Ph(2)P)C(6)H(4)}(2)EMe(2) exclusively to afford the trigonal bipyramidal (TBP) complexes, [PEP]M(CO)(PPh(3)). Square-planar rhodium complexes [PEP]Rh(PPh(3)) were also prepared from the reactions of tetrakis(triphenylphosphine)rhodium(I) hydride Rh(H)(PPh(3))(4) with {o-(Ph(2)P)C(6)H(4)}(2)EMe(2). Further, the trans influence of group 14 elements E (E = Si, Ge, Sn) in [PEP]Rh(PPh(3)) is discussed in terms of the (1)J(Rh-P) coupling constants, indicating that E exhibited a stronger trans labilizing effect in the order Sn < Ge < Si. PMID:22885800

Kameo, Hajime; Ishii, Sho; Nakazawa, Hiroshi

2012-08-13

159

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

DOEpatents

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

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

1997-01-01

160

Some electrocatalytic properties of anodic iridium oxide nanoparticles in acidic solution  

Microsoft Academic Search

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

Th. Pauporté; F. Andolfatto; R. Durand

1999-01-01

161

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

Microsoft Academic Search

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

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

1986-01-01

162

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

163

Haloaluminum Hydrides and Deuterides. Ditetrahydrofuran Adducts.  

National Technical Information Service (NTIS)

Tetrahydrofuran adducts of haloaluminum hydrides, A1HyX3-y.z(THF) (X = C1, Br, I), and some deuterated analogs were prepared and characterized. The adducts are crystalline solids which are normally isolated as stoichiometric ditetrahydrofuranates. Cryosco...

D. L. Schmidt E. E. Flagg

1966-01-01

164

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

165

Metal hydrides for hydrogen isotope separation  

SciTech Connect

A new continuous chromatographic technique has been developed to separate hydrogen isotopes using metal hydrides. Separation factors are calculated based on the statistical mechanics. A computer simulation has been developed for the process using the results of the separation factors. 11 refs., 5 figs.

Lee, M.W.

1988-01-01

166

Method for Preparation of Uranium Hydride.  

National Technical Information Service (NTIS)

A method for preparation of uranium hydride starting from hydrogen and uranium is described. In the temperature range of 250 deg up to 350 deg C, and pressures above 10 torr, hydrogen reacts smoothly with uranium turnings forming a fine black or dark gray...

M. S. Gorski M. Goncalves A. Mirage W. Lima

1985-01-01

167

Magnetic Properties of Beta-Uranium Hydride  

Microsoft Academic Search

A thorough magnetic investigation of beta-uranium hydride has been carried out. The curve of reciprocal paramagnetic susceptibility against temperature generally follows the Curie-Weiss law and shows the same curvatures near the Curie point and at high temperatures as do the data for the ferromagnetic elements above their Curie points. A considerable number of magnetization curves have been obtained for a

S. T. Lin; A. R. Kaufmann

1956-01-01

168

ENRICHED-URANIUM HYDRIDE CRITICAL ASSEMBLIES  

Microsoft Academic Search

Assemblies considered consist of approximate spheres of enriched-uranium ; hydride composition (approximating UHâ) in 8-in. thick normal uranium and ; nickel reflectors and in a uranium reflector with nickel liner. Data are of the ; following types- (1) critical sizes, (2) values of Rossi alpha in the ; neighborhood of delayed critical, (3) activation rates of various internal ; neutron

G. A. Linenberger; J. D. Orndoff; H. C. Paxton

1960-01-01

169

Hydrogen storage in sodium aluminum hydride  

Microsoft Academic Search

Sodium aluminum hydride, NaAlHâ, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the

Vidvuds Ozolins; J. L. Herberg; Kevin F. McCarty; Robert S. Maxwell; Roland Rudolph Stumpf; Eric H. Majzoub

2005-01-01

170

Electron Microscopy of Hydride Precipitation in Vanadium  

Microsoft Academic Search

Precipitation of hydride from the solid solution of vanadium-hydrogen containing a small amount of hydrogen was observed at temperatures ranging between 300 K and 77 K using the cold stage of a 500 kV electron microscope. Two types of precipitates were found at low temperatures. One has a cubic superstructure with a unit cell twice as large as that of

Toshinobu Chiba; Shigeo Takano

1971-01-01

171

Metal hydride fuel storage and method thereof  

DOEpatents

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

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

2006-10-17

172

The Effect of Stress on Hydride Precipitation.  

National Technical Information Service (NTIS)

A major difficulty in comprehending the mechanism of stress induced hydride fracture has been brought to the attention of one of the authors (HKB) by the other two. This difficulty has arisen because a clear distinction was not made between uniformly and ...

T. B. Flannagan N. B. Mason H. K. Birnbaum

1980-01-01

173

THE HYDRIDING OF CERIUM-MAGNESIUM ALLOYS  

Microsoft Academic Search

Cerium-magnesium alloys containing from 0 to 75 at% Mg were subjected to ; hydriding at room temperature at a Hâ pressure of 0.5 to l.0 atm. The ; hydrogen content of the hydrogenated alloy was determined by measuring the ; evolved Hâ on adding HCl to the sample. In alloys containing up to 5 at.% ; Mg a small constant

V. I. Mikheeva; Z. K. Sterlyadkina

1961-01-01

174

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

PubMed

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

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

2003-12-01

175

Chapter 12 New Expression of the Chemical Bond in Hydrides Using Atomization Energies  

Microsoft Academic Search

Atomization energy diagram is proposed for analyzing the chemical bond in the hydrides including perovskite-type hydrides, metal hydrides and complex hydrides. The atomization energies of hydrogen and metal atoms in them are evaluated theoretically by the energy density analysis (EDA) of the total energy, and used for the construction of the atomization energy diagram. Every hydride can be located on

Yoshifumi Shinzato; Hiroshi Yukawa; Masahiko Morinaga; Takeshi Baba; Hiromi Nakai

2008-01-01

176

Effect of Iridium substitution in Rh17S15  

NASA Astrophysics Data System (ADS)

We have studied the effect of Iridium doping (IrxRh17-xS15) in the Rhodium sites of the strongly correlated superconductor Rh17S15. Even at low levels of doping (x = 1 and 2) we see a drastic decrease in the upper critical fields as compared to the undoped system. We deduce that there is a reduction in the density of states at Fermi level from reduced susceptibilities and Sommerfeld coefficients in the doped samples. The 'fishtails' which were very prominent in the magnetization data of the undoped crystal are strongly supressed here. The resistivity data of the doped crystals show a remarkably different trend from the undoped crystal in the appearance of a minimum at lower temperatures, the position of which is fairly constant at different fields. Our data supports the notion that Iridium, which is a bigger atom than Rhodium, reduces the strong correlations that existed due to interaction between Rhodium atoms in the undoped system.

Naren, H. R.; Tamizhavel, Arumugam; Ramakrishan, S.

2010-01-01

177

Reflectance and structure changes of iridium oxide films by reduction  

SciTech Connect

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

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

1989-03-01

178

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

179

Olefin hydroaryloxylation catalyzed by pincer-iridium complexes.  

PubMed

Aryl alkyl ethers, which are widely used throughout the chemical industry, are typically produced via the Williamson ether synthesis. Olefin hydroaryloxylation potentially offers a much more atom-economical alternative. Known acidic catalysts for hydroaryloxylation, however, afford very poor selectivity. We report the organometallic-catalyzed intermolecular hydroaryloxylation of unactivated olefins by iridium "pincer" complexes. These catalysts do not operate via the hidden Brønsted acid pathway common to previously developed transition-metal-based catalysts. The reaction is proposed to proceed via olefin insertion into an iridium-alkoxide bond, followed by rate-determining C-H reductive elimination to yield the ether product. The reaction is highly chemo- and regioselective and offers a new approach to the atom-economical synthesis of industrially important ethers and, potentially, a wide range of other oxygenates. PMID:24028199

Haibach, Michael C; Guan, Changjian; Wang, David Y; Li, Bo; Lease, Nicholas; Steffens, Andrew M; Krogh-Jespersen, Karsten; Goldman, Alan S

2013-09-27

180

Superconducting iridium thin films as transition edge sensors  

NASA Astrophysics Data System (ADS)

Transition edge sensors are the detectors of choice for a wide range of applications; from dark matter search, neutrino search, to cosmic radiation detection from near infrared to millimeter wavelengths. We are developing transition edge sensors using superconducting iridium thin films and we are proposing their use for future dark matter and neutrino search experiments. Our Ir films are deposited using an radio frequency (RF) magnetron sputtering and photolithographic techniques and measured using an adiabatic refrigerator capable of reaching temperatures of a few tens of mK. This thesis presents a detailed description of superconducting iridium thin films from the fabrication process to the characterization of the film properties at room temperature and low temperature. Alternative options for the bias circuit used to read out the TES signals will be discussed, we are proposing the use of RLC resonant circuits and transformers instead of SQUIDS.

Bogorin, Daniela F.

181

Iridium-Catalyzed Regioselective and Enantioselective Allylation of Trimethylsiloxyfuran  

PubMed Central

We report the regioselective and enantioselective allylation of an ester enolate, trimethylsiloxyfuran. This enolate reacts in the 3-position with linear aromatic allylic carbonates or aliphatic allylic benzoates to form the branched substitution products in the presence of a metallacyclic iridium catalyst. This process provides access to synthetically important 3-substituted butenolides in enantioenriched form. Stoichiometric reactions of the allyliridium intermediate imply that the trimethylsiloxyfuran is activated by the carboxylate leaving group.

Chen, Wenyong; Hartwig, John F.

2012-01-01

182

Microfabricated iridium oxide reference electrode for continuous glucose monitoring sensor  

Microsoft Academic Search

A novel microfabricated iridium oxide(IrOx) reference electrode is introduced which can be used in any buffer solutions. It is formed on Pt electrode by electrodeposition of IrOx easily and uniformly. Its potential is stable in a phosphate buffered saline (PBS) solution and in serum after initial stabilization, and its potential performance is very reproducible. The behavior of a microfabricated glucose

Haesik Yang; Sun Kil Kang; Dong-Ho Shin; Hyokyum Kim; Youn Tae Kim

2003-01-01

183

Theoretical studies of iridium-mediated tautomerization of substituted pyridines  

Microsoft Academic Search

Room temperature reaction of [Ir(COD)2]BF4 (COD = 1,5-cyclooctadiene) and amide-tethered or simple 2,3?-bipyridyls gave iridium(I) complexes bearing chelating protic pyridylidenes. This protic pyridylidene tautomer is stabilized by both chelation effect and by hydrogen bonding. The mechanistic details of this tautomerization of N-heterocycles to N-heterocyclic carbenes (NHCs) were investigated using the density functional theory (DFT). DFT studies suggested that cyclometalation of 2,3?-bipyridyls took

Yan Su; Guoyong Song; Keli Han; Xingwei Li

2011-01-01

184

Chronic neural stimulation with thin-film, iridium oxide electrodes  

Microsoft Academic Search

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

James D. Weiland; David J. Anderson

2000-01-01

185

Chronic neural stimulation with thin-film, iridium oxide electrodes  

Microsoft Academic Search

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

James D. Weiland; David J. Anderson

2000-01-01

186

Novel amperometric immunosensors based on iridium oxide matrices  

Microsoft Academic Search

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

Michael S. Wilson; R. David Rauh

2004-01-01

187

pH electrode based on ALD deposited iridium oxide  

Microsoft Academic Search

We have made planar pH electrodes that use iridium oxide (IrOx) fabricated by atomic layer deposition (ALD) as the pH sensitive layer. As far as we know, ALD has not been reported earlier as the method of producing IrOx layer on pH electrodes. The structure built on glass substrate consists of 300 nm thick titanium electrodes coated with 110 nm

Tomi Ryynánen; Kirsi Nurminen; Jani Hämäläinen; Markku Leskelä; Jukka Lekkala

2010-01-01

188

Long jumps in diffusion of iridium on W(110)  

Microsoft Academic Search

Diffusion of single iridium atoms has been examined on W(110) using the field ion microscope to measure mean-square displacements as well as the distribution of displacements. The Arrhenius plot of the diffusivity, obtained from the mean-square displacements, against the reciprocal temperature gives a straight line without any indication of special behavior. From the distribution of displacements at temperatures of 331K

Grazyna Antczak; Gert Ehrlich

2005-01-01

189

Iridium-catalyzed alkylation of methylquinolines with alcohols.  

PubMed

Iridium-catalyzed alkylation of methylquinolines at the methyl substituent was achieved using alcohols as alkylating agents. The reaction proceeded through a transfer hydrogenation pathway from the alcohol to the Ir complex, affording an aldehyde and Ir-H species, followed by base-assisted aldol condensation and hydrogenation. This method provides an atom-economical and convenient route to alkylquinolines from easily accessible methylquinolines. PMID:23013149

Obora, Yasushi; Ogawa, Shinji; Yamamoto, Nobuyuki

2012-10-03

190

Treatment of malignant bladder tumors by iridium-192 wiring  

Microsoft Academic Search

Small tumors of the mobile portion of the bladder may be treated by means of interstitial irradiation by iridium-192 wiring. Twenty-six tumors (mostly T1, but also T2 and T3) were treated by this procedure. Good results are attained in 89 per cent of 19 cases followed over three years. This method has the benefit of avoiding irradiation to the surgeon's

Henry Botto; Jean Louis Perrin; J. Auvert; Marcel Salle; Bernard Pierquin

1980-01-01

191

Iridium-Catalyzed 1,3-Dipolar Cycloadditions  

NASA Astrophysics Data System (ADS)

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

Carmona, Daniel; Oro, Luis A.

192

Iridium-silicide nanowires on Si(001) surface  

NASA Astrophysics Data System (ADS)

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

Nicholls, Dylan; Oncel, Nuri

2013-03-01

193

Advances in iridium alloy processing in FY 1988  

Microsoft Academic Search

A new process for the production of DOP-26 iridium alloy blanks is being evaluated and optimized. The alloy is prepared by electron-beam (EB) melting of Ir-0.3% W powder compacts followed by doping with aluminum and thorium by arc melting. Drop-cast alloy rod segments are EB welded together into an electrode that is arc melted to produce an ingot for extrusion

E. K. Ohriner; R. L. Heestand

1989-01-01

194

Characterization of iridium film as a stimulating neural electrode.  

PubMed

Iridium films having near-bulk properties were formed by electron-beam evaporation with simultaneous bombardment of Ar ion beam. The charge-injection capabilities of Ir film were investigated, and the detrusor pressure induced by S2 stimulation with Ir-coated Pt electrode was measured and compared with the uncoated Pt electrode. The charge densities of Ir film were continuously increased with increase in the number of cycles in 0.1 M H2SO4 due to the accumulation of the iridium oxide phase. The iridium oxide formed contained nano-pores, and oxides had different dielectric properties. The Ir film could inject various amounts of charge in physiological solution under the identical stimulating condition depending on the degree of activation in 0.1 M H2SO4. S2 stimulation by Ir-coated Pt electrode caused more efficient bladder contraction of the male dog than the uncoated Pt electrode under the identical stimulus condition. PMID:12013185

Lee, In-Seop; Whang, Chung-Nam; Choi, Kyung; Choo, Myung-Soo; Lee, Young-Hee

2002-06-01

195

Sputtered iridium oxide films (SIROFs) for neural stimulation electrodes  

PubMed Central

Sputtered iridium oxide films (SIROFs) deposited by DC reactive sputtering from an iridium metal target have been characterized in vitro for their potential as neural recording and stimulation electrodes. SIROFs were deposited over gold metallization on flexible multielectrode arrays fabricated on thin (15 µm) polyimide substrates. SIROF thickness and electrode areas of 200–1300 nm and 1960–125600 µm2, respectively, were investigated. The charge-injection capacities of the SIROFs were evaluated in an inorganic interstitial fluid model in response to charge-balanced, cathodal-first current pulses. Charge injection capacities were measured as a function of cathodal pulse width (0.2 – 1 ms) and potential bias in the interpulse period (0.0 to 0.7 V vs. Ag|AgCl). Depending on the pulse parameters and electrode area, charge-injection capacities ranged from 1–9 mC/cm2, comparable with activated iridium oxide films (AIROFs) pulsed under similar conditions. Other parameters relevant to the use of SIROF on nerve electrodes, including the thickness dependence of impedance (0.05–105 Hz) and the current necessary to maintain a bias in the interpulse region were also determined.

Cogan, Stuart F.; Ehrlich, Julia; Plante, Timothy D.; Smirnov, Anton; Shire, Douglas B.; Gingerich, Marcus; Rizzo, Joseph F.

2009-01-01

196

Advances in iridium alloy processing in FY 1988  

SciTech Connect

A new process for the production of DOP-26 iridium alloy blanks is being evaluated and optimized. The alloy is prepared by electron-beam (EB) melting of Ir-0.3% W powder compacts followed by doping with aluminum and thorium by arc melting. Drop-cast alloy rod segments are EB welded together into an electrode that is arc melted to produce an ingot for extrusion and subsequent sheet rolling and blanking. Initial results showed rejections for ultrasonic indications for alloy blanks fabricated by this process to be very low. Subsequently, some ingots have exhibited delaminations in the sheet, leading to blank rejection rates similar to that obtained in the standard process. The occurrence of ultrasonic indications in the blanks are now shown to be associated with the presence of subsurface flaws in the arc-melted ingot that are not healed during extrusion or the subsequent rolling of the sheet. There is substantial evidence indicating that the occurrence of surface and subsurface flaws in the ingots are exacerbated by the relatively small clearances between the electrode and the side wall of the 51-mm-diam mold. These results obtained from experimental melts, with both stainless steel and scrap iridium alloy materials, have led to a recommendation for arc melting in a large 63-mm-diam mold. The fabrication of blanks from this larger diameter ingot is under way. The efficiency of iridium material utilization in the new process is also discussed. 2 refs., 23 figs., 12 tabs.

Ohriner, E.K.; Heestand, R.L.

1989-12-01

197

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

198

In vitro comparison of the charge-injection limits of activated iridium oxide (AIROF) and platinum-iridium microelectrodes  

Microsoft Academic Search

The charge-injection limits of activated iridium oxide electrodes (AIROF) and PtIr microelectrodes with similar geometric area and shape have been compared in vitro using a stimulation waveform that delivers cathodal current pulses with current-limited control of the electrode bias potential in the interpulse period. Charge-injection limits were compared over a bias range of 0.1-0.7 V (versus Ag|AgCl) and pulse frequencies

Stuart F. Cogan; Philip R. Troyk; Julia Ehrlich; Timothy D. Plante

2005-01-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

200

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

201

METHOD OF FABRICATING A URANIUM-ZIRCONIUM HYDRIDE REACTOR CORE  

DOEpatents

A method is described of evenly dispersing uranlum metal in a zirconium hydride moderator to produce a fuel element for nuclear reactors. According to the invention enriched uranium hydride and zirconium hydride powders of 200 mesh particle size are thoroughly admixed to form a mixture containing 0.1 to 3% by weight of U/sup 235/ hydride. The mixed powders are placed in a die and pressed at 100 tons per square inch at room temperature. The resultant compacts are heated in a vacuum to 300 deg C, whereby the uranium hydride deoomposes into uranium metal and hydrogen gas. The escaping hydrogen gas forms a porous matrix of zirconium hydride, with uramum metal evenly dispersed therethrough. The advantage of the invention is that the porosity and uranium distribution of the final fuel element can be more closely determined and controlled than was possible using prior methods of producing such fuel ele- ments.

Weeks, I.F.; Goeddel, W.V.

1960-03-22

202

Testing and Evaluation of Oxide-Coated Iridium/Rhenium Chambers.  

National Technical Information Service (NTIS)

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 o...

B. D. Reed

1993-01-01

203

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

Microsoft Academic Search

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

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

2002-01-01

204

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

205

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

206

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

207

SANS Measurement of Hydrides in Uranium  

SciTech Connect

SANS scattering is shown to be an effective method for detecting the presence of hydrogen precipitates in uranium. High purity polycrystalline samples of depleted uranium were given several hydriding treatments which included extended exposures to hydrogen gas at two different pressures at 630 C as well as a furnace anneal at 850 C followed by slow cooling in the near absence hydrogen gas. All samples exhibited neutron scattering that was in proportion to the expected levels of hydrogen content. While the scattering signal was strong, the shape of the scattering curve indicated that the scattering objects were large sized objects. Only by use of a very high angular resolution SANS technique was it possible to make estimates of the major diameter of the scattering objects. This analysis permits an estimate of the volume fraction and means size of the hydride precipitates in uranium.

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

2001-09-04

208

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

209

Electronic structure of light metal hydrides  

NASA Astrophysics Data System (ADS)

The equilibrium lattice constant, cohesive energy, and electron density of states of light metal hydrides (LiBeH3, LiMgH3, LiCaH3, NaMgH3, and LiBH3) are calculated using the linear combination of muffin-tin orbitals method on a perovskite lattice structure. Large gaps in the density of states appear at the Fermi energy of LiBeH3, LiMgH3, LiCaH3, and NaMgH3 indicating that these classes of hydrides are insulators. LiBH3, on the other hand, is metallic and could have interesting electronic properties.

Khowash, P. K.; Rao, B. K.; McMullen, T.; Jena, P.

1997-01-01

210

Hydrogen-diffusion-rate-limited hydriding and dehydriding kinetics  

Microsoft Academic Search

Hydriding and dehydriding kinetics are derived within the framework of the Johnson-Mehl-Avrami equation. Hydriding is considered to be rate limited by hydrogen diffusion through a growing hydride layer, and dehydriding by hydrogen diffusion through a growing metal layer. Incubation time effects due to surface contamination are taken into account by a delayed nucleation function. The dominant composition-dependent terms in the

P. S. Rudman

1979-01-01

211

A theoretical and experimental study of hydrides in zirconium alloys  

Microsoft Academic Search

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

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

2006-01-01

212

ToF-SIMS characterization of uranium hydride  

Microsoft Academic Search

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

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

2007-01-01

213

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

214

Fabrication and characterization of uranium–thorium–zirconium hydrides  

Microsoft Academic Search

Two uranium–thorium–zirconium hydrides, (UTh4Zr10)H1.9 and (U4Th2Zr9)H1.5, have been fabricated and characterized. Fabrication involved arc melting of the constituent pure metals to form homogenous alloys, followed by hydriding at elevated temperatures in a hydrogen gas environment. The compounds were characterized by X-ray powder diffractometry as well as scanning and transmission electron microscopy. These methods revealed a multi-phase mixture of ?-zirconium hydride

Kurt A. Terrani; G. W. Chinthaka Silva; Charles B. Yeamans; Mehdi Balooch; Donald R. Olander

2009-01-01

215

Triethylborane-induced radical reactions with gallium- and indium hydrides  

Microsoft Academic Search

A gallium hydride reagent, HGaCl2, was found to act as a radical mediator. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radical cyclization of halo acetals was also successful with not only the stoichiometric gallium reagent but also a catalytic amount of gallium

Kazuaki Takami; Satoshi Mikami; Hideki Yorimitsu; Hiroshi Shinokubo; Koichiro Oshima

2003-01-01

216

Radiotracer investigation of hydride trapping efficiency within a graphite furnace  

Microsoft Academic Search

Efficiencies of hydride generation and in situ trapping in the transversely heated graphite furnace by using Pd modifier were studied for selenium hydride, arsine and stibine by means of the radiotracers 75Se, 76As and 122Sb. The influence of four experimental parameters, i.e. Pd modifier mass, trapping temperature, carrier gas flow rate and the distance of the hydride introduction capillary from

B. Do?ekal; J. D?dina; V. Krivan

1997-01-01

217

Electrochromism of Mg-Ni hydride switchable mirrors  

Microsoft Academic Search

Switchable mirrors have so far been made of rare-earth and rare-earth-magnesium based metal-hydrides. In this investigation we study Mg-Ni-hydrides, which have been shown by Richardson et al. to exhibit switchable properties similar to those of the rare-earth hydrides. Cyclic voltammetry on MgzNiHx samples with 0.8 less than z less than 3.7 shows that addition of one Mg atom per Mg2Ni

Jan Isidorsson; I. A. Giebels; M. Di Vece; Ronald Griessen

2001-01-01

218

Dissipative hydride precipitates in superconducting niobium cavities  

SciTech Connect

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

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

2011-10-01

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

Separation of hydrogen isotopes with uranium hydride  

Microsoft Academic Search

The isotope effect on the decomposition behavior of uranium hydride is examined, since the separation of hydrogen isotopes is one of the most important processes in fission and fusion power generating systems. The decomposition equilibrium pressure is measured for UH3, UD3, and UH(1.5)D(1.5) in the temperature range of 500-700 K; the decomposition pressure of UD3 is higher than that of

S. Imoto; T. Tanabe; K. Utsunomiya

1981-01-01

221

PULSE HEATING OF ZIRCONIUM-URANIUM HYDRIDES  

Microsoft Academic Search

Apparatus and techniques for measuring power input, electric ; resistivity, temperature, and amount and rate of hydrogen released from Zr--U ; hydrides, (ZrU\\/sub 0.04\\/H\\/sub 1.8 plus or minus 0.1) during transient conditions ; are described. Data are presented for six samples that were heated to their ; destruction. Initial heating rates were about 7500 deg C\\/sec; however, as H ;

R. E. Taylor; H. G. Weidberg; R. T. Albee

1962-01-01

222

Fatigue Crack Growth In Lithium Hydride  

Microsoft Academic Search

Subcritical fatigue crack growth, from cyclic tensile loading, was demonstrated in warm pressed Polycrystalline lithium hydride. Experiments were performed with cyclic tension-tension crack opening (mode I) loads applied to a pre-cracked compact type specimen in an argon environment at a temperature of 21C (70F). The fatigue crack growth was found to occur between 7.56 Ã 10{sup -ll} M\\/cycle (2.98 Ã

T E Healy

1993-01-01

223

Density Functional Screening of Metal Hydride Reactions  

NASA Astrophysics Data System (ADS)

The on-board storage of hydrogen is one of the most vexing problems associated with the development of viable fuel cell vehicles. Hydrides of period 2 or 3 metals can store hydrogen at high gravimetric and volumetric densities. However, existing hydrides either have unacceptable thermodynamics or kinetics. New materials for hydrogen storage are therefore needed. We demonstrate how first principles density functional theory (DFT) can be used to screen potential candidate materials for hydrogen storage. We have used DFT calculations in conjunction with a free energy analysis to screen over a million reactions involving 212 known compounds. This approach has identified several interesting reaction schemes that have not yet been explored experimentally. We have computed the phonon density of states and used this information to predict the van't Hoff plots for some of the most promising candidate reactions identified though our modeling. We have also examined the thermodynamics of thin films and nanoparticles for selected metal hydrides by accounting for the surface energies of the films or nanoparticles.

Johnson, Karl; Alapati, Sudhakar; Dai, Bing; Kim, Ki-Chul; Sholl, David

2008-03-01

224

METHOD AND APPARATUS FOR MAKING URANIUM-HYDRIDE COMPACTS  

DOEpatents

A method and apparatus are presented for making compacts of pyrophoric hydrides in a continuous operation out of contact with air. It is particularly useful for the preparation of a canned compact of uranium hydride possessing high density and purity. The metallic uranium is enclosed in a container, positioned in a die body evacuated and nvert the uranium to the hydride is admitted and the container sealed. Heat is applied to bring about the formation of the hydride, following which compression is used to form the compact sealed in a container ready for use.

Wellborn, W.; Armstrong, J.R.

1959-03-10

225

Materials compatibility and wall stresses in hydride storage beds  

SciTech Connect

Hydrogen isotope handling and storage will be accomplished using solid-state hydride compounds at the Savannah River Site in the new Replacement Tritium Facility (RTF). The hydride powder is contained in a horizontal cylindrical vessel, and the combination of hydride powder, vessel, and associated heating and cooling facilities are termed in a hydride storage bed. The materials compatibility of the storage powder with the stainless steel vessel has been examined, and the stresses developed in the vessel due to expansion of the powder by absorbing hydrogen have been measured.

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

1991-12-31

226

Mechanistically Driven Development of Iridium Catalysts for Asymmetric Allylic Substitution  

PubMed Central

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

Hartwig, John F.; Stanley, Levi M.

2010-01-01

227

Antibacterial activity of rhodium, iridium, and ruthenium tripodal phosphine complexes.  

PubMed

Twenty-eight rhodium, iridium, or ruthenium complexes were evaluated for their in vitro antibacterial activity against Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922 and Pseudomonaa aeruginosa ATCC 27853. Ten compounds showed an antibacterial activity against Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 29213 with a range of the minimum inhibitory concentrations (MICs) between 16 and 125 micrograms/ml. None of the compounds exhibited antimicrobial activity against the gram-negative strains E. coli ATCC 25922 or Pseudomonas aeruginosa ATCC 29213 with a concentration range between 4 and 500 micrograms/ml. PMID:9553688

Sülü, M; Küçükbay, H; Durmaz, R; Günal, S

1998-03-01

228

Levitation of iridium and liquid mercury by ultrasound.  

PubMed

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

Xie, W J; Cao, C D; Lü, Y J; Wei, B

2002-08-20

229

Determination of iridium in mafic rocks by atomic absorption.  

PubMed

Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Inter-element 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. PMID:18960779

Grimaldi, F S; Schnepfe, M M

1970-07-01

230

Atomic Mass and Nuclear Binding Energy for Ir-221 (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-221 (Iridium, atomic number Z = 77, mass number A = 221).

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

231

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

232

Anisotropy and Magnetostriction of Iridium-Substituted Yttrium Iron Garnet  

Microsoft Academic Search

The anisotropy, magnetostriction, and linewidth of iridium-substituted yttrium iron garnet single crystals of the composition Y3-xAxFe5-y- zIryBzO12- deltaFdelta (A=Ca+2,Pb2+ and B=Fe2+,Si4+,Zn2+) have been investigated by means of ferromagnetic resonance. Chemical-analysis data of Ir, Zn, Ca and of the impurities Pb, Si, and F are given for all crystals. The anisotropy and magnetostriction measurements were carried out at 9.15 GHz in

P. Hansen; J. Schuldt; W. Tolksdorf

1973-01-01

233

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

234

Tributylgermanium hydride as a replacement for tributyltin hydride in radical reactions.  

PubMed

Tributylgermanium hydride (Bu(3)GeH) can be used as an alternative to tributyltin hydride (Bu(3)SnH) as a radical generating reagent with a wide range of radical substrates. Tributylgermanium hydride has several practical advantages over tributyltin hydride, e.g. low toxicity, good stability and much easier work-up of reactions. The reagent can be easily prepared in good yield and stored indefinitely. Suitable substrates include iodides, bromides, activated chlorides, phenyl selenides, tert-nitroalkanes, thiocarbonylimidazolides and Barton esters. Alkyl, vinyl and aryl radicals can be generated in radical reactions including reduction and cyclisation processes. Common radical initiators such as ACCN and triethylborane can be used. The slower rate of hydrogen abstraction by carbon-centred radicals from Bu(3)GeH as compared to Bu(3)SnH facilitates improved cyclisation yields. Polarity reversal catalysis (PRC) with phenylthiol can be used in reactions which generate stable radical intermediates which will not abstract hydrogen from Bu(3)GeH. PMID:14770238

Russell Bowman, W; Krintel, Sussie L; Schilling, Mark B

2004-01-22

235

Hydride reactor apparatus for hydrogen comminution of metal hydride hydrogen storage material  

Microsoft Academic Search

This patent describes an apparatus for size reduction of metal hydride hydrogen storage alloy material. It comprises: a reactor body having a substantially hollow interior volume. The volume divided into at least two regions, a comminuting first region and a collection second region; at least one reaction gas inlet port into the hollow interior volume and one reaction gas outlet

M. A. Fetcenko; T. Kaatz; S. P. Summer; J. LaRocca

1990-01-01

236

METHOD AND APPARATUS FOR MAKING URANIUM-HYDRIDE COMPACTS  

Microsoft Academic Search

A method and apparatus are presented for making compacts of pyrophoric ; hydrides in a continuous operation out of contact with air. It is particularly ; useful for the preparation of a canned compact of uranium hydride possessing high ; density and purity. The metallic uranium is enclosed in a container, positioned ; in a die body evacuated and nvert

W. Wellborn; J. R. Armstrong

1959-01-01

237

A nickel metal hydride battery for electric vehicles  

Microsoft Academic Search

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

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

1993-01-01

238

Out-of-Pile Accelerated Hydriding of Zircaloy Fasteners.  

National Technical Information Service (NTIS)

Mechanical joints between Zircaloy and nickel-bearing alloys, mainly the Zircaloy-4/Inconel-600 combination, were exposed to water at 450 exp 0 F and 520 exp 0 F to study hydriding of Zircaloy in contact with a dissimilar metal. Accelerated hydriding of t...

J. C. Clayton

1979-01-01

239

The incipient kinetics of hydride growth on cerium surfaces  

Microsoft Academic Search

The incipient hydriding stage of cerium is characterized by nucleation and growth of the hydride phase on the surface of the metal. The kinetics of this initial growth process were studied utilizing a hot-stage microscope (HSM) equipped with a video camera. Growth velocities of nuclei were determined as a function of reaction temperature and hydrogen pressure over a grid of

M. Brill; J. Bloch; D. Shmariahu; M. H. Mintz

1995-01-01

240

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

NASA Astrophysics Data System (ADS)

Three new iridium anomaly sites have been discovered in Cretaceous/Tertiary boundary sequences in New Zealand. These are at Needles Point, Chancet Rocks, and Waipara, where integrated iridium deposition values were 165, 211, and 7 ng/cm2, respectively. In contrast to the previously reported Woodside Creek stratigraphic sequence that had an iridium anomaly of 187 ng/cm2, a ferruginous boundary clay is absent in the three new sites, though the base of the Tertiary is marked by limonite staining. The relatively weak anomaly at the Waipara section is probably due to extensive bioturbation coupled with a high sedimentation rate at the time of deposition. The discovery of these additional boundary rock sequences in New Zealand negates suggestions that the Woodside Creek iridium anomaly was a fortuitous occurrence caused by unusual weathering conditions. The integrated iridium deposition values at these three new sites of somewhat different geology support the previously reported high iridium level for Woodside Creek, which until now was the only iridium anomaly on land in the Southern Hemisphere.

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

1986-09-01

241

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

PubMed

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

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

2012-06-22

242

A novel plating process for microencapsulating metal hydrides  

SciTech Connect

One approach to increasing the lifetime of the metal hydride electrode has been the use of conventional electroless plating to produce a coating of copper or nickel on the surface of the metal hydride powders. In this paper, a novel method for microencapsulating the active electrode powders is presented. This new plating technique takes advantage of the reducing power of hydrogen already stored inside the metal hydride to plate a variety of metals onto metal hydride materials. This method greatly simplifies electroless plating for these powders, eliminating the need for stabilizers and additives typically required for conventional electroless plating solutions. Metals that can be electrolessly plated with stored hydrogen have been identified based on thermodynamic considerations. Experimentally, micrometers thick coatings of copper, silver, and nickel have been plated on several metal hydrides.

Law, H.H.; Vyas, B.; Zahurak, S.M.; Kammlott, G.W. [AT and T Bell Labs., Murray Hill, NJ (United States)

1996-08-01

243

Porous metal hydride composite and preparation and uses thereof  

DOEpatents

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

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

1980-03-12

244

Porous metal hydride composite and preparation and uses thereof  

DOEpatents

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

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

1982-01-01

245

Analysis of germanium hydride molecular clusters.  

PubMed

Isotope clusters in library electron ionization mass spectra of germanes often appear a few u lower than theoretically expected from elemental composition; for example, the dominant peak of the Ge(4)H(10)(+) pattern is shifted 8 u down. This phenomenon is due to combinations of three essential components: the molecular ion Ge(n)H(2n+2)(+) and two products of hydrogen elimination, Ge(n)H(+) and Ge (n)(+) . Using these components, isotope clusters can be accurately projected for germanium hydrides from Ge(2)H(6) up to Ge(5)H(12). PMID:21472557

Gor?czko, Andrzej J

2011-01-28

246

Hydrogen isotope effects in titanium alloy hydrides  

SciTech Connect

The tritium exchange method was used to determine the isotope effects on a large number of metal-hydrogen systems. Ti was chosen as a constant constitutent in the systems, and the other metals chosen were V, Cr, Mo, Mn, Co, and Ni. The tritium distribution coefficient was determined at temperatures of -20, 0, +20, or 40/sup 0/C and at nearly constant hydrogen pressure. A plot was made of the distribution coefficient of tritium vs the periodic table sequence for 1:1 Ti alloy hydrides, and the plot indicates greatest separation factor for Ti--CrH/sub 2/ alloy. (BLM)

Tanaka, J.; Wiswall, R.H.; Reilly, J.J.

1978-02-01

247

Using hosted payloads on iridium NEXT to provide global warning of volcanic ash  

NASA Astrophysics Data System (ADS)

The Iridium NEXT satellite constellation has designed space to accommodate hosted payloads that provided not only access to space but also allow the user to leverage Iridium's real time communication capability. This is ideal for small sensor payloads and mission areas that require real-time data. The detection of volcanic ash is one such application, meeting a critical need of warning aircraft on the location of volcanic ash. To this end, we have described a system concept that uses small lightweight sensors the fit within the Iridium NEXT hosted payload allocation and provide critical data needed to predict the location and movement of volcanic ash in the atmosphere.

Erlandson, Robert E.; Kelly, Michael A.; Hibbitts, Charles A.; Kumar, C. K.; Darlington, Hugo; Dyrud, Lars; Gupta, Om P.

2012-05-01

248

Recent advances in iridium-catalyzed asymmetric hydrogenation: new catalysts, substrates and applications in total synthesis.  

PubMed

Iridium-catalyzed asymmetric hydrogenation has emerged as a highly efficient method for the synthesis of enantiomerically pure compounds. This account summarizes our recent efforts in this field. We have developed a new type of P,O-ligand that was successfully applied to the asymmetric hydrogenation of ?,?-unsaturated carbonyl compounds. Furthermore we have demonstrated the potential of known iridium catalysts in the hydrogenation of ?,?-unsaturated boronic esters. And finally we could demonstrate the utility of iridium-catalyzed asymmetric hydrogenation in the formal synthesis of the natural product Platensimycin. PMID:22613146

Gani?, Adnan; Rageot, Denise; Tröndlin, Lars; Pfaltz, Andreas

2012-01-01

249

Iridium-192 implants in the treatment of tonsillar region malignancies  

SciTech Connect

A total of 127 patients with histologically proved diagnosis of carcinoma of the tonsillar region and soft palate were treated over the past ten years utilizing interstitial iridium-192 implants. Eighty patients were treated for primary tumors and 47 patients for either recurrent or persistent tumors after definitive irradiation and/or surgery. All patients with primary tumors were treated by a combination of external megavoltage irradiation and interstitial iridium-192 implants, whereas patients with recurrent tumors were treated by interstitial implants alone. In the primary group, 95% of patients with T1 and T2 lesions and 79% with T3 and T4 lesions achieved complete local tumor control. The three-year absolute disease-free survival rate was 72%. Seventy-five percent local tumor control was obtained in patients with recurrent disease, with two-year absolute disease-free survival of 42%. Treatment-related complications such as soft-tissue necrosis or osteoradionecrosis occurred in 6% of patients in the primary group and 23% in recurrent group. This treatment regimen offers an excellent locoregional control with no significant functional or esthetic impairment. Most patients with primary lesions who fail this regimen can be salvaged by surgery or reirradiation using interstitial implants.

Puthawala, A.A.; Syed, A.M.; Gates, T.C.

1985-12-01

250

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

251

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

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

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

1993-01-15

252

Iridium thin films deposited via pulsed laser deposition  

NASA Astrophysics Data System (ADS)

High purity Ir thin films for future applications as transition-edge sensors were deposited on Si (100) via pulsed laser deposition. The iridium deposition rate was investigated and found to have a high value with the pulsed laser power higher than 4.2×10 9 W/cm 2 . At this laser intensity range, the PLD Ir films were deposited at substrate temperature ranging from 100 to 700°C. Ir thin films' characteristics were investigated at both room temperature and low temperature with the emphasis on study of the effect of the substrate temperature during deposition on the structure and morphology of the films. The PLD films exhibited a (110) preferentially oriented polycrystalline structure. Their average grain size increased from about 30 to 110 nm as the deposition temperature was raised from 100 to 600°C. With a 700°C substrate temperature the grain size jumped to 500 nm. Iridium silicide was found in the film deposited at 700°C substrate temperature. This indicated a critical deposition temperature between 600 and 700°C. A 50 mK platform was built for low temperature measurements. At low temperature, the Residual Resistance Ratio (RRR) of the Ir thin films had a typical value of 1.50. A typical transition curve of the film showed a transition temperature higher and wider than expected.

Chen, Chenglin

253

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

254

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

PubMed Central

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

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

2012-01-01

255

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

PubMed

Iridium tissue distribution and excretion in female Wistar rats following oral exposure to iridium (III) chloride hydrate in drinking water (from 1 to 1000 ng/ml) in a sub-chronic oral study were determined. Samples of urine, feces, blood and organs (kidneys, liver, lung, spleen and brain) were collected at the end of exposure. The most prominent fractions of iridium were retained in kidney and spleen; smaller amounts were found in lungs, liver and brain. Iridium brain levels were lower than those observed in other tissues but this finding can support the hypothesis of iridium capability to cross the blood brain barrier. The iridium kidney levels rose significantly with the administered dose. At the highest dose, important amounts of the metal were found in serum, urine and feces. Iridium was predominantly excreted via feces with a significant linear correlation with the ingested dose, which is likely due to low intestinal absorption of the metal. However, at the higher doses iridium was also eliminated through urine. These findings may be useful to help in the understanding of the adverse health effects, particularly on the immune system, of iridium dispersed in the environment as well as in identifying appropriate biological indices of iridium exposure. PMID:22942873

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

2012-01-16

256

Millimeter-Wave Spectroscopy of Ethylmercury Hydride  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

257

Separation of hydrogen isotopes with uranium hydride  

NASA Astrophysics Data System (ADS)

The isotope effect on the decomposition behavior of uranium hydride is examined, since the separation of hydrogen isotopes is one of the most important processes in fission and fusion power generating systems. The decomposition equilibrium pressure is measured for UH3, UD3, and UH(1.5)D(1.5) in the temperature range of 500-700 K; the decomposition pressure of UD3 is higher than that of UH3, and UH(1.5)D(1.5) shows an intermediate decomposition pressure. The enthalpy and entropy formations are obtained and they are in good agreement with those determined by a calorimetric study. When the reaction reaches the point of equilibrium, deuterium is enriched in the gas phase, and the separation factor is approximately 1.3. Experiments on deuterium enrichment, made with a small cascade, also show a separation factor of about 1.3. A thermodynamic model for the case where the mixed hydride is the regular solution, is used, and it is shown that the separation factor is larger for gas mixtures with a high D/H ratio at higher temperatures and for those with a low D/H ratio at lower temperatures.

Imoto, S.; Tanabe, T.; Utsunomiya, K.

258

Regeneration of Aluminum Hydride Using Trimethylamine  

SciTech Connect

Aluminum hydride is an attractive reducing agent and energy storage compound possessing a low decomposition temperature and a high gravimetric and volumetric hydrogen density. However, it is thermodynamically unstable at room temperature and requires extremely high pressures to form the hydride from aluminum and hydrogen gas. Here, we describe an alternate method of synthesizing AlH{sub 3} using Ti-catalyzed Al powder, H{sub 2}, and trimethylamine (TMA) to form an alane adduct. The formation of trimethylamine alane occurs at modest hydrogen pressures ({approx}100 bar), forming the 2:1 bis complex (2 trimethylamine/AlH{sub 3}). Along with the hydrogenation product, mono (1:1) and bis (2:1) standards of TMA-AlH{sub 3} were prepared and characterized using X-ray diffraction and Raman spectroscopy. X-ray absorption spectroscopy of the reaction products showed that the Ti catalyst remains with the unreacted Al powder after hydrogenation and is not present in the alane adduct. We also demonstrate that TMA can be transaminated with triethylamine to form triethylamine alane, which can easily be separated to recover AlH{sub 3}.

D Lacina; J Reilly; Y Celebi; J Wegrzyn; J Johnson; J Graetz

2011-12-31

259

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

260

Anisotropic behavior and rupture of hydrided Zircaloy-4 sheets  

SciTech Connect

In a French pressurized water reactor (PWR), most of the structural parts of the fuel assembly consist of zirconium alloys (ZIRCALOY-2). The mechanical behavior of ZIRCALOY-4 sheets is investigated at room temperature. The effect of hydride precipitation on the mechanical behavior and on the rupture mechanism is also studied, in the range from 200 to 1,200 wt ppm hydrogen and for different stress triaxialities. It is shown that the material exhibits a strong anisotropy die to its pronounced texture, and that its mechanical properties depend on the strain rate. Hydride precipitation appears to have no effect on the anisotropy or on the strain-rate sensitivity, in the range from 10{sup {minus}4} to 10{sup {minus}2} s{sup {minus}1}. The main effect of hydrogen is the reduction of the ductility and of crack resistance. The ductile rupture mechanism is studied, focusing on the stage of damage nucleation by hydride fracture. Observations during scanning electron microscopy (SEM) in situ tests show that hydrides allow the transmission of slip, which occurs in ZIRCALOY-4 grains. Hydrides can also deform, together with surrounding zirconium matrix. Damage appears after a plastic-strain yield of about 14 to 25 pct. Fracture occurs first on intergranular hydrides. Fracture of transgranular hydrides is observed only prior to failure, for higher plastic strains.

Grange, M.; Besson, J.; Andrieu, E.

2000-03-01

261

Electrosorption of Hydrogen in Platinum, Iridium, Gold and the Influence of Preceeding Anodic Oxidation.  

National Technical Information Service (NTIS)

In this paper kinetic studies are reported of hydrogen electrosorption on smooth platinum, iridium, and gold electrodes applying impedance spectroscopy in the frequency range 10 Hz-100 kHz. In different acid and alkaline solutions the Faraday impedance of...

F. Richter

1980-01-01

262

Reduction of mosaic spread using iridium interlayers: A route to improved oxide heteroepitaxy on silicon  

NASA Astrophysics Data System (ADS)

Using epitaxial SrTiO3 and yttria-stabilized zirconia (YSZ) buffer layers deposited on silicon as a starting point, epitaxial iridium layers were grown by electron-beam evaporation using a two-step growth process with an extremely low initial deposition rate. The iridium layers had in-plane (twist) and out-of-plane (tilt) full widths at half maximum as narrow as 0.08° and 0.15°, respectively, up to an order of magnitude narrower than the underlying SrTiO3 and YSZ layers. SrTiO3 and ZnO films grown on the iridium showed significantly narrower twist and tilt values than without the iridium interlayer, demonstrating a route to improved oxide heteroepitaxy on silicon.

Gsell, S.; Fischer, M.; Brescia, R.; Schreck, M.; Huber, P.; Bayer, F.; Stritzker, B.; Schlom, D. G.

2007-08-01

263

Measurements of Iridium and the Meteoric Impact Hypothesis at Cretaceous End.  

National Technical Information Service (NTIS)

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 pe...

F. Sircilli Neto

1986-01-01

264

Iridium-catalyzed oxidative methyl esterification of primary alcohols and diols with methanol.  

PubMed

Oxidative methyl esterification of primary alcohols and diols with methanol was successfully achieved, using acetone as a hydrogen acceptor, under the influence of an iridium complex combined with 2-(methylamino)ethanol (MAE) as catalyst. PMID:21413815

Yamamoto, Nobuyuki; Obora, Yasushi; Ishii, Yasutaka

2011-03-25

265

Iridium-Catalyzed Hydrosilylative Reduction of Glucose to Hexane(s).  

National Technical Information Service (NTIS)

In light of diminishing petroleum feedstocks, there is significant interest in developing carbohydrate defunctionalization reactions. In this context we have examined the use of iridium pincer catalysts for the hydrosilylative reduction of sugars, and we ...

J. J. Becker L. L. Adduci M. P. McLaughlin M. R. Gagne

2013-01-01

266

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

SciTech Connect

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

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

1986-09-01

267

Asymmetric ring-opening of oxabenzonorbornadiene with amines promoted by a chiral iridium-monophosphine catalyst.  

PubMed

A new iridium-monophosphine catalyst is found to be efficient for asymmetric ring-opening of benzonorbornadiene with amines, providing a series of chiral substituted dihydronaphthalenes in high yields (up to 98%) and excellent enantioselectivities (>99%). PMID:24037423

Luo, Renshi; Liao, Jianhua; Xie, Ling; Tang, Wenjun; Chan, Albert S C

2013-10-01

268

Finite element analysis for steady-state hydride-induced fracture in metals by composite model  

Microsoft Academic Search

Delayed hydride cracking, which is observed in hydride-forming metals, due to the precipitation of hydrides near the crack tip, is investigated under conditions of constant temperature and crack velocity, plane strain and small-scale hydride-precipitation. The coupling of the operating physical processes of hydrogen-diffusion, hydride precipitation and material deformation is taken into account. The material is assumed to be an elastic

J. L. Feng; A. G. Varias; Y. K. Sui

2006-01-01

269

Kinetics and mechanism of sorption of chloro complexes of iridium(III) from dilute solutions on hydrated zirconium dioxide  

SciTech Connect

It was shown earlier that chloro complexes of iridium(II) are sorbed by hydrated dioxide (HZD). The purpose of this work was to study the kinetic relationships and mechanism of sorption of chloro complexes of iridium(III) by HZD. The results indicate that the kinetics of sorption of chloro complexes of iridium(III) by hydrated zirconium dioxide from acid solutions with iridium(III) concentration of 10/sup -4/ M is of the external-diffusion type. Sorption of hexachloroiridate(III) ions from solutions of K/sub 3/(IrCl/sub 6/) in 0.01 M HCl proceeds by an anion-exchange mechanism, followed by ligand-exchange interaction in the sorbent phase. In neutral media sorption of chloro complexes of iridium(III) is determined by ligand interaction of aquated forms of iridium with aqua and hydroxo groups of HZD by formation of hydrogen bonds.

Nikol'skaya, L.V.; Simanova, S.A.; Boichinova, E.S.

1987-09-20

270

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

Microsoft Academic Search

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

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

2002-01-01

271

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

Microsoft Academic Search

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

Cristina Tejel; Miguel Ciriano

272

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

Microsoft Academic Search

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

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

2003-01-01

273

Oxygen reduction behavior of rutile-type iridium oxide in sulfuric acid solution  

Microsoft Academic Search

Two different forms of rutile-type iridium oxide catalysts were prepared: IrO2-coated titanium plate electrocatalysts prepared by a dip-coating method (IrO2\\/Ti) and iridium oxide nanoparticles (IrO2) prepared by a wet method, the Adams fusion method. The catalytic behavior of the oxygen reduction reaction (ORR) was evaluated by cyclic voltammetry in 0.5M H2SO4 at 60°C. Both catalysts were found to exhibit considerable

Norihiro Yoshinaga; Wataru Sugimoto; Yoshio Takasu

2008-01-01

274

Effects of synthesis conditions on the electrochemical activity of titanium anodes with iridium oxide coating  

Microsoft Academic Search

The effects of temperature, heat treatment time, and iridium content in the active layer on the electrocatalytic activity\\u000a of titanium anodes with active coating during oxygen evolution in 0.5 M sulfuric acid have been investigated. The highest\\u000a activity of these electrodes is reached when the temperature of final treatment is 450°C, treatment time is 25 min, and iridium\\u000a content in

I. A. Velikanova; N. P. Ivanova; I. M. Zharskii

2008-01-01

275

Iridium192 Implantation for Node-Negative Carcinoma of the Penis: The Cookridge Hospital Experience  

Microsoft Academic Search

Carcinoma of the penis is a rare tumour of the male urogenital tract, which may be treated by using several modalities. We present a single-centre experience of iridium-192 implantation. From 1980 to 1997, 31 patients with node-negative penile cancer were treated with an iridium-192 implant to the penis. A retrospective analysis of the case notes was made. Survival curves were

A. E. Kiltie; C. Elwell; H. J. Close; D. V. Ash

2000-01-01

276

Preparation of platinum/iridium scanning probe microscopy tips  

NASA Astrophysics Data System (ADS)

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

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

1999-07-01

277

Metal-hydride transformation kinetics in Mg nanoparticles  

NASA Astrophysics Data System (ADS)

The hydrogen sorption kinetics of magnesium nanoparticles prepared by inert gas condensation and coated by a magnesium oxide layer were investigated by a volumetric apparatus. The metal-hydride transformation was studied by transmission electron microscopy of the nanoparticles both in the as-prepared state and after hydrogen cycling. In small nanoparticles (~35 nm) hydride formation proceeds by one-dimensional growth controlled by diffusion through the hydride, while the reverse transformation to metal involves interface-controlled three-dimensional growth of nuclei formed at constant rate. Large nanoparticles (~450 nm) exhibit very low reactivity attributed to reduced probability of hydrogen dissociation/recombination and nucleation at the particle surface.

Pasquini, L.; Callini, E.; Piscopiello, E.; Montone, A.; Antisari, M. Vittori; Bonetti, E.

2009-01-01

278

Identification and characterization of a new zirconium hydride.  

PubMed

Zirconium alloys are currently used in nuclear power plants where they are susceptible to hydrogen pick-up. Hydride precipitation may occur when the hydrogen solubility limit is reached. Various Zr hydride phases, gamma, delta and epsilon have been identified since the 1950s. Combining electron precession microdiffraction, electron energy loss spectroscopy and ab initio electronic calculations, a new Zr hydride named zeta has been identified and characterized. It belongs to the trigonal crystal system with space group P3 m1 and it is fully coherent with the alphaZr matrix. PMID:19094018

Zhao, Z; Morniroli, J-P; Legris, A; Ambard, A; Khin, Y; Legras, L; Blat-Yrieix, M

2008-12-01

279

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

PubMed

Stimulating electrode materials must be capable of supplying high-density electrical charge to effectively activate neural tissue. Platinum is the most commonly used material for neural stimulation. Two other materials have been considered: iridium oxide and titanium nitride. This study directly compared the electrical characteristics of iridium oxide and titanium nitride by fabricating silicon substrate probes that differed only in the material used to form the electrode. Electrochemical measurements indicated that iridium oxide had lower impedance and a higher charge storage capacity than titanium nitride, suggesting better performance as a stimulating electrode. Direct measurement of the electrode potential in response to a biphasic current pulse confirmed that iridium oxide uses less voltage to transfer the same amount of charge, therefore using less power. The charge injection limit for titanium nitride was 0.87 mC/cm2, contradicting other reports estimating that titanium nitride was capable of injecting 22 mC/cm2. Iridium oxide charge storage was 4 mC/cm2, which is comparable to other published values for iridium oxide. Electrode efficiency will lead to an overall more efficient and effective device. PMID:12549739

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

2002-12-01

280

Iridium NEXT partnership for Earth observation: exploiting global satellite constellations for new remote sensing capabilities  

NASA Astrophysics Data System (ADS)

A unique opportunity exists to host up to 66 earth observation sensors on the Iridium NEXT LEO constellation in a manner that can revolutionize earth observation and weather predictions. A constellation approach to sensing, using the real-time communications backbone of Iridium, will enable unprecedented geospatial and temporal sampling for now-casting of weather on a global basis as well as global climate monitoring. The Iridium NEXT constellation, with 66 interconnected satellites in 6 near polar orbiting planes, provides a unique platform for hosting a variety of earth observation missions. The opportunity is proposed as a Public-Private Partnership (PPP) allowing for the sharing of infrastructure by government agencies. This has the potential to augment current and planned climate and weather observation programs in a very cost effective manner not achievable in any other way. Iridium, with the assistance of the Group on Earth Observations (GEO), NASA, NOAA, and ESA, has evaluated a number of sensing missions that would be a good fit to the Iridium NEXT constellation. These include GPS radio occultation sensors, earth radiation budget measurements, radio altimetry, tropospheric and stratospheric winds measurements including polar winds measurements, and atmospheric chemistry. Iridium NEXT launches start in 2013 and constellation operational life will extend beyond 2030. Detailed feasibility studies on specific missions are planned to begin later this year.

Gupta, Om P.

2008-08-01

281

Iridium optical constants from x-ray transmission measurements over 2 to 12 keV  

NASA Astrophysics Data System (ADS)

Precise transmission measurements of free standing iridium foils and of iridium coatings supported on thin polyimide film have been made at the X8 beamline of the National Synchrotron Light Source, at energies from 2 to 12 keV. These measurements were conducted to provide iridium optical constants in support of NASA's Advanced X-ray Astrophysics Facility (AXAF). Transmission data were collected at small energy increments across iridium M and L absorption edges to study detailed edge structures. From these data, the imaginary components of the index of refraction were computed. The data also allows computation of the real parts, using the Kramers-Kronig dispersion integral. Preliminary results indicate a measurement accuracy of better than one percent for transmission. Absorption coefficients deviate by varying amounts from values predicted from Henke data table, which is consistent with the accuracy claimed for those table.s Nonuniform thickness in our iridium foils may be a source of errors in our analysis and improved foils are being sought. Additional measurements will also be needed with foils of different thickness to account and correct for possible effects of sample thickness on the determination of absorption edge fine structure. To our knowledge, transmission measurements of this degree of accuracy and precision have not been previously reported in the literature for iridium in the 2- 12 keV energy range.

Harris, Bernard; Graessle, Dale E.; Fitch, J. J.; Juda, Jiahong Z.; Blake, Richard L.; Schattenburg, Mark L.; Gullikson, Eric M.

1996-07-01

282

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

283

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

284

The Hydriding Kinetics of Organic Hydrogen Getters  

SciTech Connect

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

Powell, G. L.

2002-02-11

285

Iridium 192 implantation of squamous cell carcinomas of the oropharynx  

SciTech Connect

From 1970 to 1984, 127 patients with T1 or T2 carcinomas of the oropharynx were treated with external irradiation to the primary tumor and neck nodes to a dose of 45 Gy, followed by a further 30 Gy delivered by an iridium 192 implant to the primary tumor. Patients with clinically positive nodes had either further neck irradiation using electrons or a neck dissection. Crude 5-year disease-free survival was 66% for tonsillar carcinomas, 43% for soft palate, and 51% for base of tongue. Local control was 98%, 85%, and 76%, respectively. Regional control was 97% for N0 patients and 88% for N1-3. Soft tissue ulceration occurred in 17 patients; all healed spontaneously. The high rate of local control achieved in these patients while preserving function and minimizing xerostomia supports the use of this approach.21 references.

Mazeron, J.J.; Crook, J.; Martin, M.; Peynegre, R.; Pierquin, B. (Hospital Henri Mondor, Creteil (France))

1989-09-01

286

Electron beam welding of iridium heat source capsules  

NASA Astrophysics Data System (ADS)

The development of the welding procedures for the production of DOP-26 iridium alloy cups for heat source encapsulation is described. All the final assembly welds were made using the electron beam welding process. The welding of the 0.13-mm weld shield required the use of a computer controlled X-Y table and a run-off tab. Welding of the frit vent to the cup required that a laser weld be made to hold the frit assembly edges together for the final electron beam weld. Great care is required in tooling design and beam placement to achieve acceptable results. Unsuccessful attempts to use laser beam welding for heat shield butt weld are discussed.

Mustaleski, Thomas M.; Yearwood, J. C.; Burgan, Clyde E.; Green, L. A.

287

Large Deformation Change in Iridium Isotopes from Laser Spectroscopy  

SciTech Connect

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

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

1999-12-31

288

Large deformation change in iridium isotopes from laser spectroscopy  

SciTech Connect

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

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

1999-11-16

289

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

290

Interstitial iridium 192 for cutaneous carcinoma of the external nose  

SciTech Connect

Several implantation techniques useful for nasal skin carcinoma have been developed at the Henri Mondor Hospital in Creteil, France and are described in detail. Iridium 192 wires, 0.3 mm in diameter, are afterloaded into either supple plastic tubes or rigid needles implanted according to the rules of the Paris system. Dosimetry is performed by computer, based on either direct measurements of active lengths and spacing, orthogonal films or a tomogram oriented in the central plane of the implant. According to a recent review by the European Curietherapy Group of 468 implants, the optimal dose is 60 Gy. The overall failure rate was 2.6%. Indications for implantation and choice of technique, based on tumor size, site, and gross morphology are discussed.

Crook, J.M.; Mazeron, J.J.; Marinello, G.; Raynal, M.; Huart, J.; Leung, S.; LeBourgeois, J.P.; Pierquin, B. (Hopital Henri Mondor, Creteil (France))

1990-01-01

291

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

292

Growth and structure of MBE-Deposited iridium silicide  

NASA Astrophysics Data System (ADS)

This report describes accomplishments made during the previous three years on a research program to prepare iridium silicide films by Molecular Beam Epitaxy-MBE, and characterize their physical and chemical structure in detail as a function of preparation conditions using the wide variety of probes available in our laboratory. By use of our MBE growth techniques we were able to form pure IrSi3 films at temperatures as low as 450 C, which is almost 200 C lower than previously reported. We also found a previously-unreported c-axis epitaxial IrSi3 growth mode at approx. 700 C, found that the IrSi3 epitaxy on Si(111) was dominated by a Mode B* orientation which had not previously been reported in the literature, as well as showed that the epitaxial growth of IrSi3 on Si(111) was superior to that on Si(100). Measurements made at Rome Laboratory found that the Schottky barrier height of the IrS3 film on Si(111) was considerably larger than that on Si(100) substrates. We also studied in detail the growth and structure of five different types of iridium silicide films: co-deposited and reacted IrSi, co-deposited Ir3Si4, reacted IrSi3, co-deposited lrSi3, and pure Ir reacted on hot Si substrates. This allowed us to form a previously-unreported silicide, Ir3Si4, and identify six epitaxial growth modes of Ir3Si4 crystallites with the Si(100) surface.

Falco, Charles M.

1995-01-01

293

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

294

Synthesis of a chloro protected iridium nitrido complex.  

PubMed

Intramolecular activation processes of vulnerable ligand C-H bonds frequently limit the thermal stability and accessibility of late transition metal complexes with terminal metal nitrido units. In this study chloro substitution of the 2,6-ketimine N-aryl substituents (2,6-C(6)H(3)R(2), R = Cl) of the pyridine, diimine ligand is probed to increase the stability of square-planar iridium nitrido compounds. The thermal stability of iridium azido precursor and nitrido compounds was studied by a combination of thermoanalytical methods (DTG/MS and DSC) and were compared to the results for the related complexes with 2,6-dialkyl substituted N-aryl groups (R = Me, iPr). The investigations were complemented by DFT calculations, which allowed us to unravel details of the thermal decomposition pathways and provided mechanistic insights of further conversion steps and fluctional processes. The DTG/MS and DSC measurements revealed two different types of thermolysis pathways for the azido compounds. For the complexes with R = Cl and iPr substituents, two well-separated exothermic processes were observed. The first moderately exothermic loss of N(2) is followed by a second, strongly exothermic transformation. This contrasts the experimental results for the compound with 2,6-dimethyl substituents (R = Me), where both steps proceed concurrently in the same temperature range. The separation of the two thermal steps in the 2,6-dichloro substituted derivative allowed us to develop a protocol for the isolation of the highly insoluble nitrido complex, which was characterized by UV/vis, IR-spectroscopy and elemental analysis. Its constitution was further confirmed by reaction with silanes, which gave the corresponding silyl amido complexes. PMID:21845255

Sieh, Daniel; Schöffel, Julia; Burger, Peter

2011-08-15

295

Hydrogen storage in sodium aluminum hydride.  

SciTech Connect

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

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

2005-11-01

296

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

SciTech Connect

Kinetic isotope effects are useful in mechanistic studies, since they can provide insight into the transition state of the reaction being examined. Hydride (H{sup {minus}}) 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 such as pyridinium or acridinium cations. Hydride transfer from transition metal hydrides (MH) to Ph{sub 3}C{sup +}BF{sub 4}{sup {minus}} gives M-FBF{sub 3} and Ph{sub 3}CH. Deuterium kinetic isotope effects were determined for several MH/MD pairs (CH{sub 2}Cl solution, 25 C). For hydride transfer from Cp*(CO){sub 3}MoH (Cp{sup *} = {eta}{sup 5}-C{sub 5}Me{sub 5}) to substituted trityl cations containing zero, one, two, or three p-MeO groups [Ph{sub n}(p-MeOC{sub 6}H{sub 4}){sub 3{minus}n}C{sup +}BF{sub 4}{sup {minus}}; n = 3, 2, 1, 0], the isotope effect remains essentially constant at k{sub MoH}/k{sub MoD} = 1.7--1.9 as the rate constant decreases from k{sub H{sup {minus}}} = 6.5 {times} 10{sup 3} to 1.4 M{sup {minus}1} s{sup {minus}1}. For hydride transfer to Ph{sub 3}C{sup +}BF{sub 4}{sup {minus}} from five metal hydrides [Cp(CO){sub 3}MoH, Cp{sup *}(CO){sub 3}WH, (indenyl)(CO){sub 3} WH, Cp{sup *}(CO){sub 3}MoH, and trans-Cp(CO){sub 2}(PCy{sub 3})MoH; Cp = {eta}{sup 5}-C{sub 5}H{sub 5}] with second-order rate constants k{sub H{sup {minus}}} {ge} 3.8 {times} 10{sup 2} M{sup {minus}1} s{sup {minus}1}, the kinetic isotope effects are also k{sub MH}/k{sub MD} = 1.7--1.8. For a series of five tungsten hydrides with substituted Cp ligands, the kinetic isotope effects decrease from k{sub WH}/k{sub WD} = 1.8 to 0.47 as the rate constant decreases (from k{sub H{sup {minus}}} = 2.0 {times} 10{sup 3} to 0.72 M{sup {minus}1} s{sup {minus}1}). The steadily decreasing values of k{sub MH}/k{sub MD} with decreasing rate constants of hydride transfer are interpreted as indicating progressively stronger force constants of isotopically sensitive modes of the transition state, as the reaction slows down in progressing from more electron-donating Cp ligands to less electron-rich Cp ligands. The inverse isotope effect (k{sub WH}/k{sub WD} = 0.47) found for the slowest tungsten hydride, (C{sub 5}H{sub 4}CO{sub 2}Me)(CO){sub 3}WH, is proposed to be due to a product-like transition state for irreversible hydride transfer.

Cheng, T.Y.; Bullock, R.M. [Brookhaven National Lab., Upton, NY (United States). Chemistry Dept.

1999-04-07

297

Materials science of Mg-Ni-based new hydrides  

NASA Astrophysics Data System (ADS)

One of the advantageous functional properties of Mg alloys (or compounds) is to exhibit the reversible hydriding reaction. In this paper, we present our systematic studies regarding the relationship between nanometer- or atomistic-scale structures and the specific hydriding properties of the Mg-Ni binary system, such as(1) nanostructured (n)-Mg2Ni, (2) a mixture of n-Mg2Ni and amorphous (a)-MgNi,(3) pure a-MgNi, and(4) n-MgNi2. Further studies on(5) an a-MgNi-based system for clarifying the effect of the short-range ordering on the structural and hydriding properties and(6) a MgNi2-based system for synthesizing the new Laves phase structure are also presented. The materials science of Mg-Ni-based new hydrides will provide indispensable knowledge for practically developing the Mg alloys as hydrogen-storage materials.

Orimo, S.; Fujii, H.

2001-04-01

298

Two-Step Hydride Shift to Aryl Carbonium Ions.  

National Technical Information Service (NTIS)

A typical reaction of carbonium ions is the hydride shift from hydrocarbons. Mechanisms have been suggested where the shift is regarded as a one-step process. The authors report that perchlorodiphenylcarbonium hexa-chloroantimonate reacts with cycloheptat...

A. Rodriguez-Siurana J. Castaner J. Riera-Figueras M. Ballester

1971-01-01

299

Galvanic corrosion test measurements zircaloy process tube hydriding problem.  

National Technical Information Service (NTIS)

In September of 1965, a program was launched to investigate the cause and to determine appropriate corrective or preventive action for hydriding of Zircaloy process tubes in K Reactors. One phase of the investigation was specifically directed to the measu...

W. R. Thorson

1967-01-01

300

Nonaqueous actinide hydride dissolution and production of actinide $beta$- diketonates  

DOEpatents

Actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a hydride of the actinide material in a mixture of carbon tetrachloride and methanol. (auth)

Crisler, L.R.

1975-11-11

301

Thermally unstable hydrides of titanium aluminide Ti3Al  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

302

Methods and Apparatus for Synthesis of Metal Hydrides.  

National Technical Information Service (NTIS)

An electrochemical process and apparatus for preparing metal hydride compounds from metal salts under a hydrogen atmosphere are disclosed. The electrochemical process may be integrated with chemical reaction of a boron compound to produce borohydride comp...

M. T. Kelly

2005-01-01

303

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

304

Synthesis and characterization of metal hydride electrodes. Interim report.  

National Technical Information Service (NTIS)

The objective of this project is to elucidate the compositional and structural parameters that affect the thermodynamics, kinetics and stability of alloy hydride electrodes and to use this information in the development of new high capacity long life hydr...

J. McBreen J. J. Reilly

1995-01-01

305

The development of lightweight hydride alloys based on magnesium  

SciTech Connect

The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.

Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C.; Bauer, W. [Sandia National Labs., Livermore, CA (United States)

1996-02-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

307

Pyrophoric behaviour of uranium hydride and uranium powders  

Microsoft Academic Search

Thermal stability and spontaneous ignition conditions of uranium hydride and uranium metal fine powders have been studied and observed in an original and dedicated experimental device placed inside a glove box under flowing pure argon. Pure uranium hydride powder with low amount of oxide (<0.5wt.%) was obtained by heat treatment at low temperature in flowing Ar\\/5%H2. Pure uranium powder was

F. Le Guyadec; X. Génin; J. P. Bayle; O. Dugne; A. Duhart-Barone; C. Ablitzer

2010-01-01

308

Potential energy surfaces for the uranium hydriding reaction  

Microsoft Academic Search

We have computed the potential energy surfaces for the low-lying electronic states of uranium hydrides, UHn (n=1-3), which are important in the uranium hydriding reactions. We have employed a number of computational methods including the complete active space multiconfiguration self-consistent field followed by multireference relativistic configuration interaction computations with spin-orbit coupling that included up to 6 million configurations. We find

K. Balasubramanian; Wigbert J. Siekhaus; William McLean II

2003-01-01

309

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

310

Out-of-pile accelerated hydriding of Zircaloy fasteners  

Microsoft Academic Search

Mechanical joints between Zircaloy and nickel-bearing alloys, mainly the Zircaloy-4\\/Inconel-600 combination, were exposed to water at 450°F and 520°F to study hydriding of Zircaloy in contact with a dissimilar metal. Accelerated hydriding of the Zircaloy occurred at both temperatures. At 450°F the dissolved hydrogen level of the water was over ten times that at 520°F. At 520°F the initially high

1979-01-01

311

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

312

Temperature-Dependent Electronic Transition in Cerium Hydride  

Microsoft Academic Search

Resistivity measurements of single crystals of cerium hydride as a function of temperature revealed resistivity anomalies at about 250°K, which may be associated with a previously reported compositional metal-to-semiconductor transition. Precise x-ray diffractiometry disclosed that the cubic fluorite type structure of cerium hydride becomes slightly tetragonal below 250°K. Neutron-diffraction investigations showed no apparent ordering of excess hydrogen atoms in octahedral

G. G. Libowitz; J. G. Pack; W. P. Binnie

1972-01-01

313

THE CRYSTAL STRUCTURE AND DENSITY OF CERIUM HYDRIDES  

Microsoft Academic Search

The structure and density of cerium hydrides of CeH\\/sub o\\/ CeHâ ; composition were studied. Two phases were present in metallic cerium and its ; dihydrides (Ce--CeHâ. A negligible change in the lattice period from 5.55 ; A to 5.53 A for CeH\\/sub 2.73\\/ was observed for CeHâ- CeHâ. The ; cerium hydride density curve is at its minimum for

M. E. Kost; G. A. Golder

1959-01-01

314

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

315

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

316

Metallographic and fractographic observations of hydrides during delayed hydride cracking in Zr-2.5% Nb alloy  

SciTech Connect

Potential drop measurements, optical microscopy, and scanning electron microscopy were performed to study the mechanism of delayed hydride cracking (DHC), the relation of the fracture to the hydride morphology, and the fractography of the DHC mechanism. The material used in this study was taken from modified extrusions of the material used to manufacture Zr-2.5% Nb pressure tubes. The material was electrolytically hydrided to approximately 60 {micro}g/g before testing. Cracking tests were carried out at 250 C with an applied K{sub 1} of 12 MPa {radical}m. The number of potential jumps was strongly correlated to the number of striations on the fracture surface. The results indicate that the DHC process occurs in these samples in an intermittent fashion. Brittle fracture is the operating fracture mechanism for the hydrides that cover most of the fracture surface, but there are some regions of ductile fracture both within the fracture and at the striations.

Jovanovic, M.T.; Eadie, R.L. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Chemical and Materials Engineering; Shek, G.K.; Seahra, H. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

1998-01-01

317

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

Microsoft Academic Search

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

V. V. Gorodetskii; V. A. Neburchilov

2005-01-01

318

Isolation of a mixed valence diiron hydride: evidence for a spectator hydride in hydrogen evolution catalysis.  

PubMed

The mixed-valence diiron hydrido complex (?-H)Fe2(pdt)(CO)2(dppv)2 ([H1](0), where pdt =1,3-propanedithiolate and dppv = cis-1,2-C2H2(PPh2)2), was generated by reduction of the differous hydride [H1](+) using decamethylcobaltocene. Crystallographic analysis shows that [H1](0) retains the stereochemistry of its precursor, where one dppv ligand spans two basal sites and the other spans apical and basal positions. The Fe---Fe bond elongates to 2.80 from 2.66 Å, but the Fe-P bonds only change subtly. Although the Fe-H distances are indistinguishable in the precursor, they differ by 0.2 Å in [H1](0). The X-band electron paramagnetic resonance (EPR) spectrum reveals the presence of two stereoisomers, the one characterized crystallographically and a contribution of about 10% from a second symmetrical (sym) isomer wherein both dppv ligands occupy apical-basal sites. The unsymmetrical (unsym) arrangement of the dppv ligands is reflected in the values of A((31)P), which range from 31 MHz for the basal phosphines to 284 MHz for the apical phosphine. Density functional theory calculations were employed to rationalize the electronic structure of [H1](0) and to facilitate spectral simulation and assignment of EPR parameters including (1)H and (31)P hyperfine couplings. The EPR spectra of [H1](0) and [D1](0) demonstrate that the singly occupied molecular orbital is primarily localized on the Fe center with the longer bond to H, that is, Fe(II)-H···Fe(I). The coupling to the hydride is A((1)H) = 55 and 74 MHz for unsym- amd sym-[H1](0), respectively. Treatment of [H1](0) with H(+) gives 0.5 equiv of H2 and [H1](+). Reduction of D(+) affords D2, leaving the hydride ligand intact. These experiments demonstrate that the bridging hydride ligand in this complex is a spectator in the hydrogen evolution reaction. PMID:23383865

Wang, Wenguang; Nilges, Mark J; Rauchfuss, Thomas B; Stein, Matthias

2013-02-21

319

Feasibility of Improving BWR Performance Using Hydride Fuel  

SciTech Connect

Neutronic and thermal-hydraulic analyses have been performed for U-ZrH{sub 1.6} hydride fueled BWR cores considering a wide range of core design variables: (1) Fuel rod outer diameter in the range from 0.6 to 1.6 cm; (2) Lattice pitch-to-diameter ratio, P/D: 1.1 to 1.6; (3) Several uranium enrichment levels. The design constraints considered include minimum excess reactivity, negative Doppler coefficient, negative void coefficient, MCPR, peak and average fuel temperatures, peak clad surface temperature, coolant inlet temperature, coolant exit quality, coolant pressure drop, as well as constraints imposed by vibrations and structural considerations. It was found that U-ZrH1.6 fuel can significantly simplify the BWR fuel bundle design by eliminating water rods, partial-length fuel rods and wide water channels and by using a single radial enrichment. A 10 x 10 hydride fuel bundle having the volume of the reference 9 x 9 oxide fuel bundle can be loaded with 35% more fuel rods having a similar diameter and lattice pitch. As a result of this along with flatter pin-by-pin power distribution the hydride fuel bundle can deliver {approx} 40% higher power density than the reference oxide fuel bundle, provided the core coolant pressure drop could be increased by {approx} 50%. Alternatively, the hydride fuelled core can be designed not to exceed the reference BWR core pressure drop and to deliver the reference power while using {approx} 40% shorter fuel bundles. The hydride fuelled core has a more negative fuel temperature coefficient of reactivity and a less negative void coefficient of reactivity. These trends are expected to enhance the safety and improve the stability of hydride fueled BWRs. A thorough evaluation of hydride fuel and its implementation possibilities in BWRs is recommended. (authors)

Fratoni, M.; Ginex, F.; Ganda, F.; Greenspan, E. [University of California, Berkeley, CA 94720 (United States); Ferroni, P.; Handwerk, C.; Todreas, N. [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2006-07-01

320

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

321

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

PubMed

An iridium anomaly at the Cretaceous/Tertiary boundary layer has been attributed to an extraterrestrial body that struck the Earth some 65 million 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 enter the atmosphere via ablating meteoroids remains largely unknown. Here we report a record of iridium and platinum fluxes on a climatic-cycle timescale, back to 128,000 years ago, from a Greenland ice core. We find that unexpectedly constant fallout of extraterrestrial matter to Greenland occurred during the Holocene, whereas a greatly enhanced input of terrestrial iridium and platinum masked the cosmic flux in the dust-laden atmosphere of the last glacial age. We suggest that nanometre-sized meteoric smoke particles, formed from the recondensation of ablated meteoroids in the atmosphere at altitudes >70 kilometres, are transported into the winter polar vortices by the mesospheric meridional circulation and are preferentially deposited in the polar ice caps. This implies an average global fallout of 14 +/- 5 kilotons per year of meteoric smoke during the Holocene. PMID:15616558

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

2004-12-23

322

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

323

Fatigue crack growth in lithium hydride  

SciTech Connect

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

Healy, T.E.

1993-09-01

324

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

325

Hydride formation on titanium surfaces by cathodic polarization  

NASA Astrophysics Data System (ADS)

The formation of external layers of TiH 2 on titanium metal by cathodic polarization was studied in buffers of oxalic, tartaric and of acetic acids. Reliable and reproducible hydride layers were obtained from pH 0.8 to 5.3. Variations in pH in this region had little influence. The thickness of the hydride layers increased with increasing current density in the range investigated from 0.14 to 6 mA cm -2. Air-formed titanium oxide film inhibited hydride formation for a period, which could last some hours at low current density. Thereafter the hydride layer thickness increased nearly proportionally with time, a typical value after 20 h treatment with 1 mA cm -2 being 13 ?m. The roughness of the surface increased and formation of titanium nodules was observed after treatment with high current density. The current efficiency for hydride formation was approximately 1% at the lowest current densities and 0.15% at 6 mA cm -2. Tafel slopes in the range 0.3-0.4 V/decade indicated an exceptional electrochemical kinetics.

Videm, Ketil; Lamolle, Sébastien; Monjo, Marta; Ellingsen, Jan Eirik; Lyngstadaas, S. Petter; Haugen, Håvard J.

2008-12-01

326

Design and analysis of heat exchangers for high pressure metal hydride hydrogen storage  

Microsoft Academic Search

This study explores the development of a hydrogen storage system using high-pressure metal hydride, Ti1.1CrMn. When absorbing hydrogen (filling), the metal hydride releases large amounts of heat causing the hydride temperature to rise. The reaction rate depends on the metal hydride temperature, decreasing significantly if the heat is not removed quickly. To store 5 kg hydrogen needed to drive 300

Milan K Visaria

2011-01-01

327

Hydrogen absorption in CeNiAl: Formation of crystalline and amorphous hydride phases  

Microsoft Academic Search

Hydriding studies on mixed valent intermetallic compound, CeNiAl, have been carried out. Absorption as well as desorption routes have been employed to find the composition range of various hydride phases. Stable hydride composition, CeNiAlHx, with a maximum value of x=3.2, is obtained. No single phase crystalline hydride could be stabilized for x<1.9. Further, it is found that any attempt to

K. Shashikala; A. Sathyamoorthy; P. Raj; W. B. Yelon; S. K. Malik

2007-01-01

328

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

329

Formation, phase analysis and properties of iridium containing perovskite  

SciTech Connect

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

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

2004-12-02

330

High Strain Rate Tensile Testing of DOP-26 Iridium  

SciTech Connect

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

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

2007-11-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

332

Color tuning of red phosphorescence: New iridium complexes containing fluorinated 2,3-diphenylquinoxaline ligands  

Microsoft Academic Search

The new iridium complexes containing a derivative of 2,3-diphenylquinoxaline as an emitting ligand were synthesized, and their photophysical properties were investigated. The complexes prepared in this study were bis(6-F-2,3-di(p-fluorophenyl) quinoxalinato)iridium acetylacetonate (Ir(6-F-2,3-dpqx-F2)2(acac)) and bis(6-F-2,3-di(p-fluorophenyl)quinoxalinato)iridium pyrazolonates (Ir(6-F-2,3-dpqx-F2)2(przl1) and Ir(6-F-2,3-dpqx-F2)2(przl2)). Their photoluminescence maxima appeared at 638, 632 and 630 nm, respectively. The electroluminescence study revealed that the CIE coordinates of the devices containing

So Youn Ahn; Hyun Shin Lee; Ji-hyun Seo; Young Kwan Kim; Yunkyoung Ha

2009-01-01

333

Cleavage of carbon dioxide by an iridium-supported Fischer carbene. A DFT investigation.  

PubMed

The reaction of CO(2), OCS, and PhNCO with an iridium-supported Fischer alkoxycarbene has been investigated with density functional theory. We have confirmed the mechanism for the important CO(2) reaction and successfully rationalized the selective cleavage of the CS and CN bonds in OCS and PhNCO. Armed with this information we have used our model to predict that the same iridium system will preferentially cleave the CS bond in methyl thiocyanate (MeNCS) rather than the CN bond. The formation of the iridium-supported carbene itself has also been investigated and a fascinating autocatalytic mechanism has been discovered which nicely fits the observed experimental behavior. PMID:19338328

Brookes, Nigel J; Ariafard, Alireza; Stranger, Robert; Yates, Brian F

2009-04-29

334

Electrogenerated Chemiluminescence of Iridium-Containing ROMP Block Copolymer and Self-Assembled Micelles.  

PubMed

The electrochemical properties and electrogenerated chemiluminescence (ECL) of an Ir(ppy)2(bpy)(+)-containing ROMP monomer, block copolymer (containing Ir(ppy)2(bpy)(+) complexes, PEG chains, and butyl moieties), and self-assembled micelles were investigated. Following polymerization of the iridium complex, we observed multiple oxidation peaks for the block copolymer in cyclic voltammograms (CV) and differential pulse voltammograms (DPV), suggesting the presence of multiple environments for the iridium complexes along the polymer backbone. The ECL signals from monomer 1 and polymer 2 were reproducible over continuous CV cycles and stable over prolonged potential biases, demonstrating their robustness toward ECL-based detection. Comparison of the ECL signal of the block copolymer, containing multiple iridium complexes attached to the backbone, and the monomeric complex showed enhanced signals for the polymer. In fact, formation and reopening of the self-assembled micelles allowed recovery of the polymer and near complete retention of its original ECL intensity. PMID:24047129

Tefashe, Ushula M; Metera, Kimberly L; Sleiman, Hanadi F; Mauzeroll, Janine

2013-10-03

335

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

Microsoft Academic Search

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

Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

2012-01-01

336

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

Microsoft Academic Search

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

Zhou Long; Chen Chen; Xiandeng Hou; Chengbin Zheng

2012-01-01

337

Heat\\/mass flow enhancement design for a metal hydride assembly. Phase II. Final report  

Microsoft Academic Search

The development and demonstration of a metal hydride\\/chemical heat pump (MHHP) is reported. In the design of the MHHP, heat transfer was considered to be the key technical study area. Therefore, the goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger\\/containment assembly. Phase II consisted of the experimental verification of the hydride

Argabright

1983-01-01

338

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

Microsoft Academic Search

The development and demonstration of a metal hydride\\/chemical heat pump (MHHP) is reported. In the design of the MHHP, heat transfer was considered to be the key technical study area. Therefore, the goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger\\/containment assembly. Phase II consisted of the experimental verification of the hydride

T. A. Argabright

1983-01-01

339

Electron-optical study of $beta$-hydride and hydrogen embrittlement of vanadium  

Microsoft Academic Search

The structure of BETA -hydride precipitated in the bcc matrix of ; hydrogen chsrged vanadium has been studied by electron diffraction in conjunction ; with electronmicroscopy. The BETA -hydride precipitate particles are cohcrent ; with the matrix, being composed of microscopic domains. Each domain is an ; elementary hydride of the monoclinic structure with the axial ratio of about 1.10

S. Takano; T. Suzuki

1974-01-01

340

Measurements of metal hydride hydrogen tank for hybrid electrical chair with photovoltaic and fuel cell  

Microsoft Academic Search

This paper discusses the temperature related hydrogen input and output characteristics of a metal hydride tank to be used for a hybrid electrical wheelchair with photovoltaic cells and fuel cells. The temperature of a metal hydride tank increases when it is filled with hydrogen and decreases as the hydrogen is ejected. A metal hydride tank is unable to eject hydrogen

Yoshihiko Takahashi; Yuuta Kaji

2011-01-01

341

A MODEL FOR THE RATIONALIZATION OF SALINE AND METALLIC HYDRIDE FORMATION  

Microsoft Academic Search

The exothermic, reversible formation of solid hydrides from the elements ; is rationalized on the basis of a model in which the hydride consists of hydrogen ; anions and metal cations, the latter likewise engaging in metal--metal bonding in ; the metallic hydrides. The latti ce energy is evaluated as the sum of the ; Madelung energy and this metal--metal

T Gibb; T. R. P. Jr

1962-01-01

342

The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction.  

PubMed

In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion--organo-hydrides--such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties--hydricities--of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal-organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal-organo-hydride systems as catalysts for organic transformations involving 'hydride-borrowing' and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid. PMID:23507957

McSkimming, Alex; Colbran, Stephen B

2013-06-21

343

Hydrogen storage systems based on hydride materials with enhanced thermal conductivity  

Microsoft Academic Search

The reaction of hydrogen gas with a metal to form a metal hydride is exothermic. If the heat released is not removed from the system, the resulting temperature rise of the hydride will reduce the hydrogen absorption rate. Hence, hydrogen storage systems based on hydride materials must include a way to remove the heat generated during the absorption process. The

Hui Wang; Ajay K. Prasad; Suresh G. Advani

344

Catalytic activity of cerium and neodymium hydrides in the hydrogenation of ethylene  

Microsoft Academic Search

1.The hydrides of Ce and Nd are catalytically active in the hydrogenation of ethylene; the activity of the hydrides depends on the conditions of preliminary thermovacuum treatment and the method of conducting the reaction.2.The catalytic activity of the hydrides of Ce and Nd is evidently associated with the presence of superstoichiometric hydrogen in the lattice of the inactive dihydrides.

Yu. S. Khodakov; S. N. Torbin; Kh. M. Minachev

1972-01-01

345

Hydride behavior in Zircaloy cladding tube during high-temperature transients  

Microsoft Academic Search

In order to study the hydride behavior in high burnup fuel cladding during temperature transients expected in anticipated operational occurrences and accidents, unirradiated hydrided Zircaloy-4 cladding tubes were rapidly heated to temperatures ranging from 673 to 1173K and annealed for holding time ranging from 0 to 3600s. Hydrides were localized in the peripheral region of the cladding tubes prior to

Fumihisa Nagase

2011-01-01

346

Titanium compacts produced by the pulvimetallurgical hydride-dehydride method for biomedical applications  

Microsoft Academic Search

Titanium powder production by the hydride-dehydride method has been developed as a non-expensive process. In this work, commercially pure grade two Ti specimens were hydrogenated. The hydrided material was milled in a planetary mill. The hydrided titanium powder was dehydrided and then sieved to obtain a particle size between 37 and 125 µm in order to compare it with a

M. M. Barreiro; D. R. Grana; G. A. Kokubu; M. I. Luppo; S. Mintzer; G. Vigna

2010-01-01

347

ARTICLES: Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex  

NASA Astrophysics Data System (ADS)

A new cyclometalated iridium(III) complex Ir(DPP)3 (DPP = 2,3-diphenylpyrazine) was prepared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, 1H NMR, and mass spectroscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respectively. The complex also shows strong photoluminescence at 573 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.

Wu, Qiu-hua; Wang, Chuan-hong; Song, Xi-ming; Zhang, Guo-lin

2010-06-01

348

White light-emitting organic electroluminescent device based on a new orange organometallic iridium complexes  

Microsoft Academic Search

We develop the white organic light-emitting diodes (WOLEDs) with a new orange electrophosphorescent emission, and the blue electrofluorescent or electrophosphorescent sensitizer. The new orange phosphorescent sensitizer is the thieno-pyridine framework organo-iridium complexes (PO-01). The blue phosphorsensitized electrofluorescent is 4,4'-Bis(9-ethyl-3-carbazovinylene)-1,1'- biphenyl (DSA) doped into 4,4'-Bis(2,2-diphenyl-ethen-1-yl) diphenyl (DPVBi). Beside, the blue phosphorescent sensitizer is Bis(3,5-difluoro-2-(2-pyridyl)phenyl- (2-carboxypyridyl)iridium (FirPic). The Device Type I of

Tien-shou Shieh; Heh-lung Huang; Pey-ching Liu; Mei-Rurng Tseng; Jia-Ming Liu

2007-01-01

349

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

Microsoft Academic Search

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

Ho Wan Ham; Young Sik Kim

2010-01-01

350

Ambipolar organic light-emitting electrochemical transistor based on a heteroleptic charged iridium(III) complex  

NASA Astrophysics Data System (ADS)

High performance organic light-emitting electrochemical transistor (OLECT) based on a phosphorescent heteroleptic charged iridium(III) complex has been developed with low-cost solution processing technique. The new OLECT showed good ambipolar behavior with balanced hole and electron mobilities of 0.20 cm2 V-1 s-1 and 0.22 cm2 V-1 s-1, respectively. Furthermore, light emission has been observed from the OLECT device and modulated by the gate. All these results suggest that charged iridium(III) complexes could be a promising candidate for single-component multifunctional organic light-emitting field-effect transistor.

Zhou, Ye; Han, Suting; Zhou, Guijiang; Wong, Wai-Yeung; Roy, V. A. L.

2013-02-01

351

Heat-actuated metal hydride hydrogen compressor testing  

SciTech Connect

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

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

1985-09-01

352

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

2012-03-20

353

H2 fuel prototype hydride bed performance tests  

SciTech Connect

H2Fuel is a project to design, build, and demonstrate a hydrogen-electric hybrid city bus for Augusta, GA. The H2Fuel bus uses metal hydride technology for on-board hydrogen fuel storage. This document reports on tests by the Savannah River Technology Center (SRTC) to measure the performance of the H2Fuel prototype hydride bed. Bed diameter measurements were made before and after hydrogen testing. Seven hydrogen absorption-desorption cycles were completed. Significant results include: - maximum hydrogen capacity of approximately 3500 STP liters (0.315 kg) - practical hydrogen capacity of approximately 3000 STP liters (0.270 kg) - absorption tests at four hydrogen supply pressures (75, 100, 140, and 300 psia) - desorption tests at three hydrogen rates (20, 30, and 50 slpm) - no measurable swelling of the hydride bed

Dyer, E.F.

1996-10-01

354

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

355

METHOD OF PREPARING SINTERED ZIRCONIUM METAL FROM ITS HYDRIDES  

DOEpatents

The invention relates to the preparation of metal shapes from zirconium hydride by powder metallurgical techniques. The zirconium hydride powder which is to be used for this purpose can be prepared by rendering massive pieces of crystal bar zirconium friable by heat treatment in purified hydrogen. This any then be ground into powder and powder can be handled in the air without danger of it igniting. It may then be compacted in the normal manner by being piaced in a die. The compact is sintered under vacuum conditions preferably at a temperature ranging from 1200 to 1300 deg C and for periods of one to three hours.

Angier, R.P.

1958-02-11

356

Metal hydride reasearch and development program at Brookhaven National Laboratory  

SciTech Connect

A progress report is presented covering work performed in the hydrogen materials development program at Brookhaven National Laboratory (BNL) for FY78 which encompasses the time period from October 1, 1977 through September 30, 1978. The subjects to be discussed here concern properties of importance in the utilization of metal hydrides as energy storage media. Most of the areas of research were initiated prior to FY78, however all of the results contained in this manuscript were obtained during the aforementioned period of time. The following subjects will be discussed: the properties of ferro-titanium and chrome-titanium alloy hydrides.

Johnson, J.R.; Reilly, J.J.

1978-01-01

357

Electrical Resistivities of Nonstoichiometric Cerium Hydride Single Crystals  

Microsoft Academic Search

Electrical resistivities as a function of temperature (?130° to 25°C) were determined on single crystals of cerium hydride ranging in composition from CeH1.94&sngbnd;CeH2.85. Measurements were performed in an inert-atmosphere dry box using the four-point probe technique. Cerium hydride exhibited metallic behavior in the range CeH1.9&sngbnd;CeH2.7. However, at a composition of about CeH2.85, a positive temperature coefficient of conductivity indicative of

G. G. Libowitz; J. G. Pack

1969-01-01

358

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

SciTech Connect

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

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

2013-01-01

359

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

360

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

361

Comparison of irradiation hardening and microstructure evolution in ion-irradiated delta and epsilon hydrides  

NASA Astrophysics Data System (ADS)

A ?-Zr-hydride was irradiated with 6.4 MeV Fe3+ ions to clarify the relationship between hardening and microstructural changes of bulk Zr-hydrides under neutron irradiation. Irradiation hardening was measured by nanoindentation tests. Transmission electron microscope cross-sectional observations showed that the deformation mechanism of the ?-Zr-hydride was both slip and twinning. Dislocation loops were observed in the irradiated hydride matrix. These irradiation-induced defects make slip deformation difficult and consequently promote the twin deformation of ?-Zr-hydride. This work is a continuation of the previous our work (J. Nucl. Mater. 419 (2011) 366-370) focused upon ?-Zr-hydride and we discuss a comparison between the two Zr-hydrides.

Oono, Naoko; Kasada, Ryuta; Higuchi, Toru; Sakamoto, Kan; Nakatsuka, Masafumi; Hasegawa, Akiko; Kondo, Sosuke; Iwata, Noriyuki Y.; Matsui, Hideki; Kimura, Akihiko

2013-11-01

362

Hydride vapor phase epitaxy of aluminum nitride  

NASA Astrophysics Data System (ADS)

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

Kamber, Derrick Shane

363

An iridium-192 mold for use in treating carcinoma of the soft palate.  

PubMed

A Lucite sandwich mold containing Iridium-192 wire for use in the treatment of soft palate carcinoma is described. This mold is very simple to use, produces a homogeneous (+/- 10%) radiation field across the midplane of the tumor, and requires minimal machinist time. PMID:504673

Keys, D J; Marks, J E; Sharma, S C

1979-12-01

364

Remotely controlled iridium-catalyzed asymmetric hydrogenation of terminal 1,1-diaryl alkenes.  

PubMed

Working together: The presence of a remote directing group on terminal 1,1-diaryl and 1,1-dialkyl alkenes led to high and unprecedented enantioselectivity in iridium-catalyzed asymmetric hydrogenation. This strategy offers efficient synthetic pathways towards valuable enantiomerically enriched 1,1-diaryl and 1,1-dialkyl alkanes. Moreover, the directing group can be further functionalized. PMID:23893950

Besset, Tatiana; Gramage-Doria, Rafael; Reek, Joost N H

2013-07-24

365

Luminescent biscarbene iridium(III) complexes as living cell imaging reagents.  

PubMed

Five iridium(III) complexes with two N-heterocyclic carbene (NHC) ligands and an ancillary ligand have been designed and successfully synthesized. With multicolor photoluminescence and low toxicity, these carbene complexes were tested, for the first time, as living cell imaging reagents and showed promise for application beyond the OLED (organic light emitting diode) area. PMID:23482967

Zhou, Yuyang; Jia, Junli; Li, Wanfei; Fei, Hao; Zhou, Ming

2013-03-13

366

Iridium complex probes for monitoring of cellular oxygen levels and imaging of hypoxic tissues  

NASA Astrophysics Data System (ADS)

We have recently reported that a red-emitting iridium complex (btp)2 Ir (acac) (BTP) serves as a hypoxia-sensing probe for tumor imaging in living mice. BTP exhibits oxygen-sensitive phosphorescence that can be utilized to monitor oxygen levels in living cells and to visualize hypoxic tissues. To improve the tissue penetrance of BTP, we designed and synthesized near-IR emitting iridium complexes by two different approaches: extension of the ?- conjugated system of benzothienyl-pyridinato ligand in BTP and introduction of substituents into suitable positions of ligands. The former approach was successful, and near-IR emitting iridium complexes were obtained without reduction in the emission quantum yield. Cellular uptake of BTP was greatly improved by introducing a hydrophilic group into the acetylacetonato ligand. Using these improved probes, in-vivo lifetime measurements were made to substantiate the hypoxia of tumor tissues in SCC-7 tumor-bearing mice. The second-harmonic (532 nm) of Nd3+:YAG laser was used to excite iridium complexes in tissues, and the phosphorescence lifetime was measured using the time-correlated single photon counting technique. The phosphorescence emitted from the tumor region actually gave longer lifetimes compared to those emitted from the normal tissues, demonstrating the hypoxic nature of tumor tissues.

Yoshihara, Toshitada; Kobayashi, Atsushi; Oda, Shinpei; Hosaka, Masahiro; Takeuchi, Toshiyuki; Tobita, Seiji

2012-02-01

367

Global Measurement of Birkeland Currents with Iridium: How it Works and Future Prospects  

NASA Astrophysics Data System (ADS)

The constellation of more than 70 Iridium satellites offers an unprecedented opportunity to observe the global Birkeland currents. These currents convey stress between the magnetosphere and ionosphere and reflect the state of the M-I system. Each satellite of the Iridium constellation carries a magnetometer as part of the attitude control system and is digitized to 30 nT resolution. The Iridium engineering data stream captures these data for telemetry to the ground once every three minutes from each satellite. Even with this relatively coarse time sampling the data have proven particularly effective in specifying the location and intensity of the large-scale Birkeland currents. The techniques used to inter-calibrate, de-trend, identify noise signals are discussed. The analysis techniques developed to derive Birkeland current distributions without making any assumptions regarding the geometry of the currents or ionospheric conductances are also discussed. Comparisons with numerous independent data sets confirm that the results are accurate to within the Nyquist resolution limits of the input data, in particular that the Iridium-derived magnetic perturbations agree with other low altitude satellites and that the derived upward current regions correspond very well with auroral emissions attributed to electron precipitation. A concept has been developed to increase the volume of magnetic field data returned from the satellites yielding up to 100 times better time resolution. This upgrade would allow determination of the Birkeland current system with a 9 minute cadence and dramatically improved accuracy.

Anderson, B. J.; Korth, H.; Green, D. L.; Waters, C. L.

2006-12-01

368

Pentacoordinate Iridium(I) and Rhodium(I) Complexes Derived from Metal Carbonyl Anions.  

National Technical Information Service (NTIS)

Anionic triphenylphosphine carbonyl complexes of iridium and rhodium have been prepared by reduction of (MCl(CO)(P(C6H5)3)2) (M = Ir, Rh) with sodium amalgam in tetrahydrofuran. Reaction of the resulting metallo anions with post-transition metal halides, ...

J. P. Collman F. D. Vastine W. R. Roper

1967-01-01

369

Unexpected Redox Rectification by an Electrochemically Prepared Iridium Oxide Electrode/Aqueous Acid Interface.  

National Technical Information Service (NTIS)

In highly acidic aqueous solutions, electrochemically prepared iridium oxide films behave as steady-state insulators and transient rectifiers towards the Ru(NH3)6 3+/2+ redox couple. In less acidic solutions the films show only partial transient rectifica...

C. S. Johnson J. T. Hupp

1992-01-01

370

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

PubMed

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

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

2013-06-15

371

Synthesis of Nanoporous Activated Iridium Oxide Films by Anodized Aluminum Oxide Templated Atomic Layer Deposition.  

National Technical Information Service (NTIS)

Iridium oxide (IrOx) has been widely studied due to its applications in electrochromic devices, pH sensing, and neural stimulation. Previous work has demonstrated that both Ir and IrOx films with porous morphologies prepared by sputtering exhibit signific...

D. J. Comstock J. W. Elam M. C. Hersam M. J. Pellin S. T. Christensen

2010-01-01

372

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

SciTech Connect

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

Taylor, D.H.

2001-08-09

373

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

ERIC Educational Resources Information Center

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

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

2009-01-01

374

Theoretical study of structure, stability, and the hydrolysis reactions of small iridium oxide nanoclusters.  

PubMed

The geometric structures and relative stabilities of small iridium oxide nanoclusters, Ir(m)O(n) (m = 1-5 and n = 1-2m), have been systematically investigated using density functional theory (DFT) calculations at the B3LYP level. Our results show that the lowest-energy structures of these clusters can be obtained by the sequential oxidation of small "core" iridium clusters. The iridium-monoxide-like clusters have relatively higher stability because of their relatively high binding energy and second difference in energies. On the basis of the optimized lowest-energy structures of neutral and cationic (IrO(2))(n) (n = 1-5), DFT has been used to study the hydrolysis reaction of these clusters with water molecules. The calculated results show that the addition of water molecules to the cationic species is much easier than the neutral ones. The overall hydrolysis reaction energies are more exothermic for the cationic clusters than for the neutral clusters. Our calculations indicate that H(2)O can be more easily split on the cationic iridium oxide clusters than on the neutral clusters. PMID:22985267

Zhou, Xin; Yang, Jingxiu; Li, Can

2012-09-27

375

Radiation control in the intensive care unit for high intensity iridium-192 brain implants  

Microsoft Academic Search

A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the

W. Sewchand; R. E. Drzymala; P. P. Amin; M. Salcman; O. M. Salazar

1987-01-01

376

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

Microsoft Academic Search

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

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

2007-01-01

377

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

ERIC Educational Resources Information Center

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

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

2009-01-01

378

Iridium-catalyzed reaction of enones with alcohols affording 1,3-diketones.  

PubMed

An iridium-catalyzed coupling reaction of alcohols with enones has been successfully developed providing access to 1,3-diketones with high selectivity in good yields. This reaction provides an atom-economical route to 1,3-diketones from readily available alcohols. PMID:22641102

Obora, Yasushi; Nakamura, Kazuhiro; Hatanaka, Shintaro

2012-05-28

379

Chemisorption of carbon monoxide and ammonia on nickel and iridium surfaces  

Microsoft Academic Search

The process of chemisorption of small molecules on transition metal surfaces was investigated from the point of view of two prototype adsorption systems, carbon monoxide on iridium 100 and 111 and ammonia on nickel 111. Microscopic details such as the nature of interactions between adsorbed species were addressed experimentally. Angle resolved ultraviolet photoelectron spectroscopy (UPS) with synchrotron radiation was used

C. W. Seabury

1980-01-01

380

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

Microsoft Academic Search

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

Cappil D Joseph; Melvin Astrahan; James Lipsett; John Archambeau; B. Forell; Frederick W George III

1981-01-01

381

Dosimetric calculations and measurements of gold plaque ophthalmic irradiators using iridium-192 and iodine-125 seeds  

Microsoft Academic Search

The dosimetry of ophthalmic plaques designed to hold iridium-192 or iodine-125 seeds is investigated experimentally and by means of a computer model. A phantom for thermoluminescent dosimetry (TLD) which permits measurements to within 2 mm of the plaque surface is described. TLD data are compared with model calculations that take into account the active length of the seeds, anisotropy of

Gary Luxton; Melvin A. Astrahan; Peter E. Liggett; David L. Neblett; Dierdre M. Cohen; Zbigniew Petrovich

1988-01-01

382

Transpapillary iridium-192 wire in the treatment of malignant bile duct obstruction  

Microsoft Academic Search

Twenty four patients with malignant bile duct obstruction were treated with intraluminal radiotherapy using iridium-192 wire inserted through an endoscopically placed nasobiliary catheter. Biliary drainage after treatment was maintained by an endoprosthesis. The median dose of intraluminal radiotherapy was 6000 cGy; two patients with cholangiocarcinoma were given a second course because of disease extension; four patients with pancreatic carcinoma received

M D Levitt; B H Laurence; F Cameron; P F Klemp

1988-01-01

383

Radiation therapy for carcinoma of the pinna using iridium 192 wires: a series of 70 patients  

Microsoft Academic Search

From January 1970 to November 1982, 70 patients with carcinoma of the pinna were treated by interstitial irradiation. An afterloading technique with Iridium 192 wires was used. One patient recurred and had a total pinnectomy followed by 60 Gy external radiation. This patient was alive without evidence of disease at 134 months. Three patients who had tumors greater than 4

Jean-Jacques Mazeron; Richard Ghalie; Jacques Zeller; Ginette Marinello; Lorraine Marin; Michel Raynal; Jean-Paul le Bourgeois; Bernard Pierquin

1986-01-01

384

Iridium192 brachytherapy for equine sarcoid, one and two year remission rates. Veterinary Radiology  

Microsoft Academic Search

Of 16 sarcoids in 12 adult horses which were treated with iridium-192 interstitial implants, 14 (87.5%) were in remission for at least 12 months and 13 (81.2%) were in remission for at least 24 months. Generally, normal tissue reactions were acceptable. These results further substantiate the benefits of radioactive brachytherapy for equine sarcoid.

M. Walker; W. Adams; J. Hoskinson; J. P. Held; J. Blackford; Geiser Dennis R. DVM; D. Goble; J. Henton

1991-01-01

385

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

386

Synthesis and luminescence properties of iridium(III) azide- and triazole-bisterpyridine complexes.  

PubMed

We describe here the synthesis of azide-functionalised iridium(III) bisterpyridines using the "chemistry on the complex" strategy. The resulting azide-complexes are then used in the copper(I)-catalysed azide-alkyne Huisgen 1,3-dipolar cycloaddition "click chemistry" reaction to from the corresponding triazole-functionalised iridium(III) bisterpyridines. The photophysical characteristics, including lifetimes, of these compounds were also investigated. Interestingly, oxygen appears to have very little effect on the lifetime of these complexes in aqueous solutions. Unexpectedly, sodium ascorbate acid appears to quench the luminescence of triazole-functionalised iridium(III) bisterpyridines, but this effect can be reversed by the addition of copper(II) sulfate, which is known to oxidize ascorbate under aerobic conditions. The results demonstrate that iridium(III) bisterpyridines can be functionalized for use in "click chemistry" facilitating the use of these photophysically interesting complexes in the modification of polymers or surfaces, to highlight just two possible applications. PMID:23896620

Goldstein, Daniel C; Peterson, Joshua R; Cheng, Yuen Yap; Clady, Raphael G C; Schmidt, Timothy W; Thordarson, Pall

2013-07-26

387

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

Microsoft Academic Search

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

W. Alvarez; A. Montanari; F. Asaro

1990-01-01

388

The Mechanism of the Formation of an Iridium Complex of Molecular Nitrogen Via Organic Azides.  

National Technical Information Service (NTIS)

Herein are described the gross features of the mechanism by which the iridium complex of nitrogen III is formed. The concepts inherent in this mechanism may be extended to the preparation of other nitrogen complexes and indeed to a wide range of pi comple...

J. P. Collman M. Kubota J. Y. Sun F. Vastine

1966-01-01

389

Standardization of Iridium-192 Gamma-Ray Sources in Terms of Exposure.  

National Technical Information Service (NTIS)

Iridium-192, in the form of small platinum- or Stainless-steel-clad seeds, is used for radiation therapy. Standardization of this radionuclide, for the quantity exposure was carried out by measuring groups of seeds in an open-air geometry, using the NBS s...

T. P. Loftus

1979-01-01

390

Remarkable effect of iridium cyclometalation on the nonlinear absorption properties of a quadrupolar imine ligand.  

PubMed

A new type of dinuclear iridium complex, based on a quadrupolar Schiff base ligand, is synthesized and its structure fully characterized. Its linear and nonlinear spectroscopic properties are investigated, evidencing a strong contribution of the metal-to-ligand transitions not only to the linear absorption but also to the two- and three-photon absorption properties. PMID:24020389

Massue, Julien; Olesiak-Banska, Joanna; Jeanneau, Erwann; Aronica, Christophe; Matczyszyn, Katarzyna; Samoc, Marek; Monnereau, Cyrille; Andraud, Chantal

2013-09-10

391

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

392

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

393

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

394

A highly active cyclometallated iridium catalyst for the hydrogenation of imines.  

PubMed

A cyclometallated iridium complex containing an imino ligand has been shown to catalyse the hydrogenation of imines. The catalyst is highly active and selective for imino bonds, with a wide variety of imines being hydrogenated in less than 1 hour at a substrate/catalyst (S/C) ratio of 2000 at 20 bar H2 pressure and 75 °C. PMID:23903630

Villa-Marcos, Barbara; Tang, Weijun; Wu, Xiaofeng; Xiao, Jianliang

2013-09-25

395

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

Microsoft Academic Search

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

B. Wessling; W. Mokwa; U. Schnakenberg

2006-01-01

396

STUDY ON PULSED DC-SPUTTERING OF IRIDIUM OXIDE FOR IMPLANTABLE ELECTRODES  

Microsoft Academic Search

A pulsed-DC reactive sputtering technique was used for iridium oxide thin-film deposition. Frequency, pulse width, oxygen flow and deposition time were changed over several deposition sessions, regarding implantable electrode applications. Surface and electrochemistry analysis were performed for deposition evaluation. The results evidenced that the deposited film sputtered with 2 sccm of oxygen flow and 50 KHz pulse frequency, achieved best

N. S. Dias; A. Ferreira da Silva; A. van Ooyen; P. M. Mendes; J. A. Afonso; J. H. Correia; W. Mokwa; U. Schnakenberg

2007-01-01

397

Catalytic arene hydrogenation using early transition metal hydride compounds  

SciTech Connect

Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d[sup 0]-metal hydride compounds, and stoichiometric reactivity of d[sup 0] metal hydrido, aryloxide compounds. (DLC)

Rothwell, I.P.

1993-03-15

398

Free-Radical Addition of Trimethyltin Hydride to Allenes.  

National Technical Information Service (NTIS)

The azobisisobutyronitrile-catalyzed addition of trimethyltin hydride to allene, 1,2-butadiene, 2,3-pentadiene, 2-methyl-2,3-pentadiene, and 3-methyl-1,2-butadiene was studied. Structures and configurations of all of the adducts were assigned on the basis...

H. G. Kuivila W. Rahman R. H. Fish

1965-01-01

399

Electrochromism of Mg-Ni hydride switchable mirrors  

NASA Astrophysics Data System (ADS)

Switchable mirrors have so far been made of rare-earth and rare-earth-magnesium based metal-hydrides. In this investigation we study Mg-Ni-hydrides, which have been shown by Richardson et al. to exhibit switchable properties similar to those of the rare-earth hydrides. Cyclic voltammetry on MgzNiHx samples with 0.8 less than z less than 3.7 shows that addition of one Mg atom per Mg2Ni gives the best ab/desorption kinetics for hydrogen. X- ray diffraction reveals a structural change as hydrogen is absorbed. The metal-insulator transition is confirmed with simultaneous resistivity measurements. A pressure- composition isotherm of Mg2NiHx is also determined electrochemically. Optical spectrometry during gas loading gives an optical band gap of 1.6 eV for Mg2NiH4. This gap increases with increasing Mg content in a way similar to that of the Mg-doped rare-earth hydrides.

Isidorsson, Jan; Giebels, I. A.; Di Vece, M.; Griessen, Ronald

2001-11-01

400

Electronic-Energy-Band Structure of Uranium Hydride.  

National Technical Information Service (NTIS)

We have calculated the electronic energy bands of alpha and beta UH sub 3 . These systems are unique among hydride formers in that a transformation directly to a trihydride occurs without an intervening dihydride phase and in that two trihydride structure...

A. C. Switendick

1982-01-01

401

Search for proton magnetic resonance in ferromagnetic ?-uranium hydride  

Microsoft Academic Search

Proton magnetic resonance (PMR) in a ferromagnetic?-uranium hydride at 77 K has been searched unsuccessfully between 4 and 420 MHz. The present communication reports this experiment and its objectives, and justifies the swept frequency range on the basis of PMR data obtained in the paramagnetic phase and of a new analysis of the Flotow and Osborne low temperature specific heat

J. C. Fernandes; J. B. De Oliveira e Souza

1985-01-01

402

Experimental studies on the behaviours of hydride heat storage system  

Microsoft Academic Search

Experimental examinations and a lumped system model are used to describe the heat transfer characteristics in the design of a single tube type metal hydride heat storage vessel. The apparatus studied was fed heat by water vaporized by an electric furnance with a 3 kWh x 2 capacity. An annular tube in the middle of the reactor vessel contained the

M. Kawamura; S. Ono; S. Higano

1982-01-01

403

Effect of CO in Reformed Gas on Fluorinated Metal Hydride  

NASA Astrophysics Data System (ADS)

For the purpose of following electricity demand change and improving the efficiency of generation for fuel cells, a new system, which is called metal hydride intermediate buffer method, is developing. The system uses the selective reacting function of hydrogen on metal hydride materials. It is said that metal hydride could be easy to be poisoned by impurities except for hydrogen. Therefore a surface treatment has been adopted with the material to avoid it. We have found that the treatment is effective against H2O and CO2, which exist mainly in the reformed gas. One of general concerns about poisoning by CO included slightly in the reformed gas must be confirmed. In order to verify the treatment effect against CO, hydrogen absorption and desorption experiment were repeated with the simulated reformed gas (SRG) including 100ppm or 1% of CO concentration. In the result, it has been clarified that the metal hydride keeps the absorption property in spite of CO existence. In the CO 100ppm condition, functional deterioration due to CO-poisoning is not recognized at all. The hydrogen absorption rate is significantly reduced in the CO 1% experiment compared with the fuel gas without CO, but the absorption property has not been lost entirely. On the other hand, it has been found that the absorption property is gradually degraded, even if pure hydrogen without any impurities is used.

Sasaki, Ryoichi; Ishida, Masayoshi

404

Investigation of Galvanically Induced Hydriding of Titanium in Saline Solutions.  

National Technical Information Service (NTIS)

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

L. A. Charlot

1970-01-01

405

Composition and Structure of Sputter Deposited Erbium Hydride Thin Films.  

National Technical Information Service (NTIS)

Erbium hydride thin films are grown onto polished, a-axis (alpha) A1 (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) pa...

D. P. Adams J. A. Romero M. A. Rodriguez J. A. Floro J. C. Banks

2000-01-01

406

Towards an Accurate Wave Function for Positronium Hydride  

Microsoft Academic Search

A variational wave function for the ground state of positronium hydride is presented. The wave function is considerably more accurate than any previously reported. The only simplifications used are (a) only kinetic and Coulombic potential energy terms are included in the Hamiltonian, (b) the motion of the proton is ignored, and (c) the nucleus-positron distance is excluded from the wave

C. F. Lebeda; David M. Schrader

1969-01-01

407

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

Microsoft Academic Search

A nominal 1500 STP-L Passively Cooled, Electrically heated hydride (PACE) Bed has been developed and tested. Protium absorption rates were measured at pressures of 253, 413, and 680 kPa (1900, 3100, and 5100 torr, respectively) with forced convection cooling air flow rates ranging from 50 to 150 SLPM air. Desorption rates were measured at pressures ranging from 200 to 933

2001-01-01

408

Electronic Principles of Some Trends in Properties of Metallic Hydrides  

NASA Astrophysics Data System (ADS)

Due to their extensive present, important and versatile potential applications, metal hydrides (MH) are among the most investigated solid-state systems. Theoretical, numerical and experimental studies have provided a considerable knowledge about their structure and properties, but in spite of that, the basic electronic principles of various interactions present in MH have not yet been completely resolved. Even in the simplest MH, i.e. alkali hydrides (Alk-H), some trends in physical properties, and especially their deviations, are not well understood. Similar doubts exist for the alkaline-earth hydride (AlkE-H) series, and are even more pronounced for complex systems, like transition metal-doped AlkE-H, alanates and borohydrides. This work is an attempt of explaining some trends in the physical properties of Alk-H and AlkE-H, employing the Bader analysis of the charge distribution topology evaluated by first-principle all-electron calculations. These results are related to some variables commonly used in the explanation of experimental and calculated results, and are also accompanied by simple tight-binding estimations. Such an approach provides a valuable insight in the characteristics of M-H and H-H interactions in these hydrides, and their possible changes along with external parameters, like temperature, pressure, defect or impurity introduction. The knowledge of these basic interactions and processes taking place in simple MH are essential for the design and optimisation of complex MH-systems interesting for practical hydrogen storage applications.

Ivanovi?, Nenad; Novakovi?, Nikola; Colognesi, Daniele; Radisavljevi?, Ivana; Ostoji?, Stanko

409

Intermetallic hydrides: A review with ab initio aspects  

Microsoft Academic Search

The review aims to provide a coverage of different classes of intermetallic systems, which have the ability of absorbing hydrogen in different amounts, like binary and ternary Laves phases and Haucke-type intermetallics. Such intermetallic hydrides are attractive for applied research as potential candidates for on-board vehicular use (engines, batteries, etc.). Focus is made here on the fundamental features regarding the

Samir F. Matar

2010-01-01

410

Reactions of Calcium, Magnesium and Cerium Hydrides with Aqueous Solutions.  

National Technical Information Service (NTIS)

The report describes studies of reactions of CaH2, MgH2 and CeH2 with D2O solutions. The purpose of these studies was to establish the fate of hydride hydrogen in such reactions and the stoichiometry of reactions in which metal ions compete with D(+) as o...

R. A. Sutula J. B. Hunt

1965-01-01

411

HYDRIDATION OF CERIUM ALLOYS WITH MAGNESIUM AND ALUMINUM  

Microsoft Academic Search

Hydridation of Ce - Mg- Al alloy at room temperature and normal pressure ; was studied with an alloy containing 70 to 90 wt% Ce. Maximum of hydrogen ; absorption was in the region of 5 to 10% Al and 35 to 80% Mg. An increased ; amount of Al in the Ce-- Mg system contributes to increased hydrogen absorption.

V. I. Mikheeva; Z. K. Sterlyadkina; A. A. CHertkov

1963-01-01

412

Sintering of sponge and hydride-dehydride titanium powders  

Microsoft Academic Search

The sintering behavior of compacts produced from sponge and hydride-dehydride (HDH) Ti powders was examined. Compacts were vacuum sintered at 1200 or 1300 deg C for 30, 60, 120, 240, 480 or 960 minutes. The porosity decreased with sintering time and\\/or temperature in compacts produced from the HDH powders. Compacts produced from these powders could be sintered to essentially full

David E. Alman; Stephen J. Gerdemann

2004-01-01

413

Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors.  

PubMed

Upon electrochemical oxidation of the precursor complexes [Cp*Ir(H(2)O)(3)]SO(4) (1) or [(Cp*Ir)(2)(OH)(3)]OH (2) (Cp* = pentamethylcyclopentadienyl), a blue layer of amorphous iridium oxide containing a carbon admixture (BL) is deposited onto the anode. The solid-state, amorphous iridium oxide material that is formed from the molecular precursors is significantly more active for water-oxidation catalysis than crystalline IrO(2) and functions as a remarkably robust catalyst, capable of catalyzing water oxidation without deactivation or significant corrosion for at least 70 h. Elemental analysis reveals that BL contains carbon that is derived from the Cp* ligand (? 3% by mass after prolonged electrolysis). Because the electrodeposition of precursors 1 or 2 gives a highly active catalyst material, and electrochemical oxidation of other iridium complexes seems not to result in immediate conversion to iridium oxide materials, we investigate here the nature of the deposited material. The steps leading to the formation of BL and its structure have been investigated by a combination of spectroscopic and theoretical methods. IR spectroscopy shows that the carbon content of BL, while containing some C-H bonds intact at short times, is composed primarily of components with C?O fragments at longer times. X-ray absorption and X-ray absorption fine structure show that, on average, the six ligands to iridium in BL are likely oxygen atoms, consistent with formation of iridium oxide under the oxidizing conditions. High-energy X-ray scattering (HEXS) and pair distribution function (PDF) analysis (obtained ex situ on powder samples) show that BL is largely free of the molecular precursors and is composed of small, <7 Å, iridium oxide domains. Density functional theory (DFT) modeling of the X-ray data suggests a limited set of final components in BL; ketomalonate has been chosen as a model fragment because it gives a good fit to the HEXS-PDF data and is a potential decomposition product of Cp*. PMID:23383971

Blakemore, James D; Mara, Michael W; Kushner-Lenhoff, Maxwell N; Schley, Nathan D; Konezny, Steven J; Rivalta, Ivan; Negre, Christian F A; Snoeberger, Robert C; Kokhan, Oleksandr; Huang, Jier; Stickrath, Andrew; Tran, Lan Anh; Parr, Maria L; Chen, Lin X; Tiede, David M; Batista, Victor S; Crabtree, Robert H; Brudvig, Gary W

2013-02-05

414

Hydride Compressor Sorption Cooler and Surface Contamination Issues  

NASA Astrophysics Data System (ADS)

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

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

2003-07-01

415

Interstitial hyperthermia and iridium-192 treatment alone vs. interstitial iridium-192 treatment\\/hyperthermia and low dose cisplatinum infusion in the treatment of locally advanced head and neck malignancies  

Microsoft Academic Search

Purpose: To determine whether the addition of low dose platinum infusional chemotherapy adds to the effectiveness of interstitial hyperthermia\\/iridium-192 management of locally advanced head and neck malignancies.Methods and Materials: From 1987 to 1993, 36 patients with locally advanced head and neck malignancies were treated locally with interstitial hyperthermia and iridium-192 as part of all of their management. Twenty-two of the

David P. Schreiber; Thomas K. Overett

1995-01-01

416

Nanoscale properties of planar and faceted iridium(210)  

NASA Astrophysics Data System (ADS)

In the presence of a thin layer of adsorbed oxygen, the Ir(210) surface exhibits morphological instability and, upon annealing, becomes covered with nanometer-sized pyramids with facets of {311} and (110) crystallographic orientation. Electron diffraction and temperature programmed desorption experiments show that complete faceting requires 0.5 monolayers of oxygen coverage and annealing temperature of 600 K. For lower temperatures and coverages, faceted and planar surfaces coexist. Oxygen desorption above 950 K causes irreversible facet destruction. In previous adsorbate-induced faceting studies, it has not been possible to remove the adsorbate while preserving the faceted structure. We have accomplished this for O/Ir(210) via two low-temperature chemical methods: catalytic carbon monoxide oxidation and water formation. The clean faceted surface is an excellent substrate for model catalytic studies; it is stable for temperatures below 600 K and irreversibly reverts to planar above 600 K. Real-time low energy electron microscopy shows uniform facet nucleation and growth on the oxygen-covered Ir(210) surface and facet relaxation of the clean faceted surface. Planar and faceted structures coexist between 850 K and 1150 K in the presence of gaseous oxygen. Atomic-resolution scanning tunneling microscopy shows that {311} facets are atomically smooth. The (110) facets consist of unreconstructed terraces separated by steps and of a complicated superstructure formed on the same facet. The facet atomic structure is consistent with models based bulk iridium properties and with first-principle simulations. Facets grow with annealing temperature increase, their average size ranging from 5 nm to 14 nm. Acetylene and ammonia decomposition exhibit structure sensitivity over the planar and faceted surface. Ammonia decomposition additionally exhibits size effects in experiments on faceted surfaces with different average facet size. Subtle differences in core-level high resolution soft x-ray spectra suggest that surface morphology, rather than electronic structure changes, is responsible for the structure and size effects. This work is the first adsorbate-induced faceting study where the preparation of a clean elemental faceted substrate has been accomplished. It paves the way for revealing the mechanisms of substantial mass transport in surface transformations, and is an excellent substrate for the study of structure sensitivity and size effects in catalytic reactions.

Ermanoski, Ivan

417

Catalytic functionalization of methyl group on silicon: iridium-catalyzed C(sp3)-H borylation of methylchlorosilanes.  

PubMed

A methyl group of methylchlorosilanes undergoes C-H borylation in an iridium-catalyzed reaction with bis(pinacolato)diboron in cyclohexane at 80 °C, giving (borylmethyl)chlorosilanes selectively. PMID:23043232

Ohmura, Toshimichi; Torigoe, Takeru; Suginome, Michinori

2012-10-12

418

Magnesium Anode, Seawater/Acid/Catholyte Electrode Utilizing a Palladium and Iridium Carbon Paper Cathode Electrochemical System.  

National Technical Information Service (NTIS)

The present invention relates to an improved magnesium semi-fuel cell which has a magnesium anode, a seawater/catholyte electrolyte, preferably containing acid to solubilize solid precipitates, and an electrocatalyst composed of palladium and iridium cata...

M. G. Medeiros E. G. Dow R. R. Bessette

2000-01-01

419

Dissociation potential curves of low-lying states in transition metal hydrides. 3. Hydrides of groups 6 and 7.  

PubMed

The dissociation curves of low-lying spin-mixed states in monohydrides of groups 6 and 7 were calculated by using an effective core potential (ECP) approach. This approach is based on the multiconfiguration self-consistent field (MCSCF) method, followed by first-order configuration interaction (FOCI) calculations, in which the method employs an ECP basis set proposed by Stevens and co-workers (SBKJC) augmented by a set of polarization functions. Spin-orbit coupling (SOC) effects are estimated within the one-electron approximation by using effective nuclear charges, since SOC splittings obtained with the full Breit-Pauli Hamitonian are underestimated when ECP basis sets are used. The ground states of group 6 hydrides have Omega = (1)/(2)(X(6)Sigma(+)(1/2)), where Omega is the z component of the total angular momentum quantum number. Although the ground states of group 7 hydrides have Omega = 0(+), their main adiabatic components are different; the ground state in MnH originates from the lowest (7)Sigma(+), while in TcH and ReH the main component of the ground state is the lowest (5)Sigma(+). The present paper reports a comprehensive set of theoretical results including the dissociation energies, equilibrium distances, electronic transition energies, harmonic frequencies, anharmonicities, and rotational constants for several low-lying spin-mixed states in these hydrides. Transition dipole moments were also computed among the spin-mixed states and large peak positions of electronic transitions are suggested theoretically for these hydrides. The periodic trends of physical properties of metal hydrides are discussed, based on the results reported in this and other recent studies. PMID:16480317

Koseki, Shiro; Matsushita, Takeshi; Gordon, Mark S

2006-02-23

420

Evidence of FCC titanium hydride formation in. beta. titanium alloy: An X-ray diffraction study  

SciTech Connect

Three types of titanium hydrides have been reported: delta, epsilon and ..gamma.. hydrides. The delta hydride forms in the composition range from TiH/sub 1.5/ to TiH/sub 1.99/ and has a CaF/sub 2/ structure with metal atoms on an fcc lattice and hydrogen atoms randomly occupying tetrahedral interstitial sites. At higher hydrogen concentrations, TiH/sub 2/, the fct (c/a < 1) epsilon hydride phase is formed below 310 K. The c/a ratio decreases with a decreasing temperature and it reaches and maintains a minimum value of 0.943 below 80 K. The fcc to tetragonal, delta ..-->.. epsilon transformation is apparently diffusionless, similar to that operating in the cubic/tetragonal transformation in zirconium hydride. The metastable fct ..gamma.. hydride having a c/a value of 1.09 or 1.12 forms from solid solutions of hydrogen in the hcp ..cap alpha.. matrix. While the titanium hydride precipitation in ..cap alpha..-Ti and its alloys has attracted extensive investigation, hydride formation in bcc ..beta..-Ti alloys has rarely been studied because they have not been thought to be liable to hydride formation. This paper shows conclusive evidence for the fcc delta hydride phase formation in the ..beta.. phase Ti-30 wt% Mo by x-ray diffraction study.

Shih, D.S.; Birnbaum, H.K.

1986-09-01

421

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

Microsoft Academic Search

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

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

2002-01-01

422

Iridium(III) Complexes with Orthometalated Phenylimidazole Ligands Subtle Turning of Emission to the Saturated Green Colour  

Microsoft Academic Search

A series of novel six iridium complexes (1–6) bearing two substituted phenylimidazole and an additional acetylacetone as the third co-auxilary ligand are reported. The\\u000a lowest absorption band for all iridium complexes consist of a mixture of heavy atom Ir(III) enhanced 3MLCT and 3 ?-?* transitions and the phosphorescent peak wavelength can be fine-tuned to cover the spectral range 455–518 nm with

Jayaraman Jayabharathi; Venugopal Thanikachalam; Kanagarathinam Saravanan; Natesan Srinivasan

2011-01-01

423

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

Microsoft Academic Search

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

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

2007-01-01

424

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

425

Reactivity studies of iridium pyridylidenes [Tp(Me2)Ir(C(6)H(5))(2)(C(CH)(3)C(R)NH] (R=H, Me, Ph).  

PubMed

The reactivity of a series of iridium?pyridylidene complexes with the formula [Tp(Me2) Ir(C6 H5 )2 (C(CH)3 C(R)NH] (1?a-1?c) towards a variety of substrates, from small molecules, such as H2 , O2 , carbon oxides, and formaldehyde, to alkenes and alkynes, is described. Most of the observed reactivity is best explained by invoking 16?e(-) unsaturated [Tp(Me2) Ir(phenyl)(pyridyl)] intermediates, which behave as internal frustrated Lewis pairs (FLPs). H2 is heterolytically split to give hydride?pyridylidene complexes, whilst CO, CO2 , and H2 C?O provide carbonyl, carbonate, and alkoxide species, respectively. Ethylene and propene form five-membered metallacycles with an IrCH2 CH(R)N (R=H, Me) motif, whereas, in contrast, acetylene affords four-membered iridacycles with the IrC(?CH2 )N moiety. C6 H5 (C?O)H and C6 H5 C?CH react with formation of Ir?C6 H5 and Ir?C?CPh bonds and the concomitant elimination of a molecule of pyridine and benzene, respectively. Finally the reactivity of compounds 1?a-1?c against O2 is described. Density functional theory calculations that provide theoretical support for these experimental observations are also reported. PMID:23401098

Cristóbal, Crispín; Hernández, Yohar A; López-Serrano, Joaquín; Paneque, Margarita; Petronilho, Ana; Poveda, Manuel L; Salazar, Verónica; Vattier, Florencia; Álvarez, Eleuterio; Maya, Celia; Carmona, Ernesto

2013-02-11

426

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

SciTech Connect

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

Greenspan, Ehud; Todreas, Neil; Taiwo, Temitope

2009-03-10

427

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

428

Preparation and X-ray diffraction studies of curium hydrides  

NASA Astrophysics Data System (ADS)

Curium hydrides were prepared by reaction of curium-248 metal with hydrogen and characterized by X-ray powder diffraction. Several of the syntheses resulted in a hexagonal compound with average lattice parameters of a0 = 0.3769(8) nm and c0 = 0.6732(12) nm. These products are considered to be CmH3-? by analogy with the behavior of lanthanide-hydrogen and lighter actinide-hydrogen systems. Face-centered cubic products with an average lattice parameter of a0 = 0.5322(4) nm were obtained from other curium hydride preparations. This parameter is slightly smaller than that reported previously for cubic curium dihydride, CmH2+x (B. M. Bansal and D. Damien, Inorg. Nucl. Chem. Lett., 6, 603, 1970). The present results established a continuation of typical heavy trivalent lanthanide-like behavior of the transuranium actinide-hydrogen systems through curium.

Gibson, J. K.; Haire, R. G.

1985-10-01

429

Low temperature study of structural phase transitions in niobium hydrides  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

430

Gas-phase Reactions of Hydride Anion, H-  

NASA Astrophysics Data System (ADS)

Rate constants were measured at 300 K for the reactions of the hydride anion, H-, with neutral molecules C2H2, H2O, CH3CN, CH3OH, (CH3)2CO, CH3CHO, N2O, CO2, O2, CO, CH3Cl, (CH3)3CCl, (CH3CH2)2O, C6H6, and D2 using a flowing-afterglow instrument. Experimental work was supplemented by ab initio calculations to provide insight into the viability of reaction pathways. Our reported rate constants should prove useful to models of astrophysical environments where conditions prevail for the existence of both H- and neutral species. The variety of neutral reactants studied includes representative species from prototypical chemical groups, effectively mapping reactivity trends for the hydride anion.

Martinez, Oscar, Jr.; Yang, Zhibo; Demarais, Nicholas J.; Snow, Theodore P.; Bierbaum, Veronica M.

2010-09-01

431

Composition and function in AB{sub 5} hydride electrodes  

SciTech Connect

Multicomponent AB, hydrides are attractive replacements for the cadmium electrode in nickel - cadmium batteries. This paper is concerned with the differential effects of Ni substitution by cobalt, Mn and Al upon electrode corrosion and capacity, using alloys having the generic composition of Al(NiCoMnAl){sub 5} and similar to those used for the preparation of commercial battery electrodes. The corrosion of metal hydride electrodes is determined by two factors, surface passivation due to the presence of surface oxides or hydroxides and crystal lattice expansion - contraction the charge - discharge process. Thus, in addition to determining the effects of Ni substitution we will also address the question of whether an observed change is due to a change lattice expansion or to a change in surface passivation, e.g. the formation a corrosion resistant oxide layer.

Adzic, G.D.; Johnson, J.R.; Mukerjee, S.; McBreen, J.; Reilly, J.J.

1996-12-31

432

Hydride precipitation and stresses in zircaloy-4 observed by synchrotron X-ray diffraction  

Microsoft Academic Search

The grain stresses within hydrides precipitated in rolled zircaloy-4 plates were determined by synchrotron X-ray diffraction experiments using an 80keV photon beam and a high-speed area detector placed in transmission geometry. Results showed large compressive stresses (360±20MPa) in the hydrides along the plate rolling direction. The origin of these stresses was investigated by performing hydride dissolution\\/precipitation in situ for thermal

J. R. Santisteban; M. A. Vicente-Alvarez; P. Vizcaíno; A. D. Banchik; J. D. Almer

2010-01-01

433

Hydride-induced embrittlement and fracture in metals—effect of stress and temperature distribution  

Microsoft Academic Search

A mathematical model for the hydrogen embrittlement of hydride forming metals has been developed. The model takes into account the coupling of the operating physical processes, namely: (i) hydrogen diffusion, (ii) hydride precipitation, (iii) non-mechanical energy flow and (iv) hydride\\/solid-solution deformation. Material damage and crack growth are also simulated by using de-cohesion model, which takes into account the time variation

A. G. Varias; A. R. Massih

2002-01-01

434

Simulation and experimental validation of a hydrogen storage tank with metal hydrides  

Microsoft Academic Search

This paper presents a hydrogen storage system using metal hydrides for a combined heat and power (CHP) system. Hydride storage technology has been chosen due to project specifications: high volumetric capacity, low pressures (3.5bar) and low temperatures (75?C: fuel cell temperature).During absorption, heat from hydride generation is dissipated by fluid circulation. An integrated plate-fin type heat exchanger has been designed

Maxime Botzung; Serge Chaudourne; Olivier Gillia; Christian Perret; Michel Latroche; Annick Percheron-Guegan; Philippe Marty

2008-01-01

435

Energy density analysis of the chemical bond between atoms in perovskite-type hydrides  

Microsoft Academic Search

Atomization energy diagram is proposed for analyzing the chemical bond in the perovskite-type hydrides such as M1MgH3 (M1=Na, K, Rb), RbCaH3, CaNiH3 and SrPdH3. The atomization energies of hydrogen and metal atoms in the hydrides are evaluated theoretically by the energy density analysis (EDA) of the total energy, and used for the construction of the atomization energy diagram. Every hydride

Yoshifumi Shinzato; Hiroshi Yukawa; Masahiko Morinaga; Takeshi Baba; Hiromi Nakai

2007-01-01

436

Failure of hydrided zircaloy-4 under equal-biaxial and plane-strain tensile deformation  

Microsoft Academic Search

The fracture behavior of unirradiated Zircaloy-4 containing either solid hydride blisters or hydrided rims has been examined for the contrasting conditions of equal-biaxial and plane-strain tensile deformation at three temperatures (25, 300, and 375 C). Cold-worked and stress-relieved Zircaloy-4 sheet containing hydride blisters shows nearly identical failure strains in equal-biaxial and plane-strain tensile deformation for a wide range of blister

A. Glendening; D. A. Koss; A. T. Motta; O. N. Pierron; R. S. Daum

2005-01-01

437

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

PubMed Central

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

Felderhoff, Michael; Bogdanovic, Borislav

2009-01-01

438

Electrochemical selenium hydride generation with in situ trapping in graphite tube atomizers  

Microsoft Academic Search

A manifold coupling continuous electrolytic hydride generation of volatile hydrides with atomization in graphite tube atomizers after in situ collection was used for Se(IV) determination. Laboratory-made thin-layer flow-through cells with lead wire (cell I) and granular lead (cell II) as the cathode material were used as the electrolytic generators of volatile selenium hydride. The automatic sampling equipment of the graphite

Jan Š??ma; Petr Rychlovský

2003-01-01

439

Hydriding of the mixed-valent compound CeRhIn: structural and magnetization studies  

Microsoft Academic Search

Mixed-valent compound, CeRhIn, having the hexagonal Fe2P-type structure and a moderate value of the Kondo temperature (TK?150 K), is found to form two distinct hydride phases. The higher hydride phase in CeRhInHy system with y?1.55 is found to be quite unstable and readily transforms to a lower hydride with y?0.55. From structural and magnetization studies, it is found that in

P. Raj; A. Sathyamoorthy; K. Shashikala; C. R. Venkateswara Rao; D. Kundaliya; S. K. Malik

2002-01-01

440

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

441

Thermal diffusivity measurement of uranium–thorium–zirconium hydride  

Microsoft Academic Search

The uranium–thorium mixed zirconium hydrides of UTh4Zr10Hx (x=20, 24, 27) have been successfully fabricated without large crack by means of a Sieverts apparatus. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses show that UTh4Zr10Hx consist of ?-U, ThZr2Hx, and (?, ?)-ZrHx. The thermal diffusivity measurements of UTh4Zr10Hx have been performed over the temperature ranges to around 773 K

B Tsuchiya; J Huang; K Konashi; W Saiki; T Onoue; M Yamawaki

2000-01-01

442

METHOD OF MAKING DELTA ZIRCONIUM HYDRIDE MONOLITHIC MODERATOR PIECES  

DOEpatents

A method is given for preparing large, sound bodies of delta zirconium hydride. The method includes the steps of heating a zirconium body to a temperature of not less than l000 deg C, providing a hydrogen atmosphere for the zirconium body at a pressure not greater than one atmosphere, reducing the temperature slowly to 800 deg C at such a rate that cracks do not form while maintaining the hydrogen pressure substantially constant, and cooling in an atmosphere of hydrogen. (AEC)

Vetrano, J.B.

1962-01-23

443

On X-ray Emission from Highly Loaded Hydrides  

Microsoft Academic Search

X-ray emission (1-2 keV) has been observed in various experiments using electrolytic or plasma methods for loading of hydride targets such as Pd-D to atom ratios > 0.8. Intensities vary from very low-level emission up to laser-like focused beams, depending on experimental conditions(A.G. Lipson et al, JETP Letters, (submitted)). Bremsstralung during thermalization of energetic alphas\\/protons created by nuclear reactions in

George H. Miley; Heinrich Hora; Nie Luo; Andrei Lipson

2004-01-01

444

Use of mechanoactivation for obtaining hydrides of titanium aluminides  

Microsoft Academic Search

The hydrogen storage capacity of titanium aluminides Ti(Al,Nb) (?0) and Ti3 (Al,Nb) (?2) subjected to mechanoactivation has been investigated. It has been found that the mechanoactivation in a hydrogen atmosphere\\u000a makes it possible to obtain hydrides of titanium aluminides with a hydrogen concentration of up to 1.8 wt % at room temperature\\u000a without enhanced requirements for purity and pressure of

N. V. Kazantseva; N. V. Mushnikov; A. G. Popov; V. A. Sazonova; P. B. Terent’ev

2008-01-01

445

Hydride transfer versus hydrogen radical transfer in thymidylate synthase.  

PubMed

The nature of a H-transfer in the thymidylate synthase catalyzed reaction was investigated by comparison of the wild-type enzyme with the W80M mutant. The nature of the H-transfer was not affected, as indicated by intrinsic isotope effects and their temperature dependence. These findings support a single-step hydride transfer instead of a two-step radical transfer. PMID:16637621

Hong, Baoyu; Haddad, Majd; Maley, Frank; Jensen, Jan H; Kohen, Amnon

2006-05-01

446

Corrosion of AB{sub 5} metal hydride electrodes  

SciTech Connect

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

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

1997-11-01

447

Volume dependent vibrational properties of cerium hydrides from first principles  

Microsoft Academic Search

We have performed an ab initio study of structural, volume-dependent elastic and lattice dynamical properties of rare-earth metal-hydrides CeH2 and CeH3. The calculations have been carried out within the density functional theory and linear response formalism using norm-conserving pseudopotentials and a plane-wave basis. The hydrogen incorporation into the octahedral sites of the cubic CeH2 to obtain CeH3 leads to stiffening

Tanju Gürel; Resul Eryi?it

2009-01-01

448

Angular Correlation of Positron-Annihilation Radiation from Cerium Hydride  

Microsoft Academic Search

The angular correlation of positron-annihilation radiation from cerium hydride was measured for hydrogen concentrations in the range H\\/Ce = 1.8–2.8. The angular correlations were found to be broader than that from cerium metal and to increase in width with increasing hydrogen concentration in a manner consistent with the screened protonic model of the electronic structure. The anionic model does not

M. P. Chouinard; D. R. Gustafson; R. C. Heckman

1969-01-01

449

Gas chromatographic separation of hydrogen isotopes using metal hydrides  

SciTech Connect

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

Aldridge, F.T.

1984-05-09

450

Structural and magnetic ordering in the cerium hydride (abstract)  

Microsoft Academic Search

Depending on the H concentration at the octahedral (O) sites, x(O), various tetragonal phases, due to H ordering, are observed in the Ce hydride at low temperatures. While our single crystal work showed that the tetragonal phase for H\\/Ce≊2.7, corresponding to x(O)≊3\\/4, is only stable in a region of x(O)=±0.05, the other one was believed to be caused by a

R. R. Arons; J. K. Cockcroft; E. Ressouche

1994-01-01

451

The Development of a Compact Refrigeration System using Metal Hydrides  

NASA Astrophysics Data System (ADS)

The MH refrigeration systems are regarded as important and compact ones for solving energy and environmental issues. Our purposes are to develop the compact refrigeration system for the vending machine and the show case using MH, and to attain a refrigeration temperature of 243K by using a heat source of 403?423K. The kinetics of MH hydriding and dehydriding reactions is of importance relative to their practical use as a refrigerator system. The kinetics of the reaction between hydrogen and MHHigh (Ti0.18Zr0.84Cr1.0FeO.7Mn0.3CuO.057)has been followed in this paper. A relatively rapid absorption of hydrogen takes place for values of relative composition to about 0.3?0.4. It is evident that a hydrogen diffusion plays a minor role during this stage, as that part of the metal not covered by hydride is always in contact with hydrogen. The direct chemical reaction between the hydrogen and the exposed metal surface is therefore postulated as the rate-controlling process. The rate of the reaction then decreases, and for values of relative composition above about 0.8, the reaction becomes slow. After the metal particles have been completely covered by a hydride layer, the transport of materials through the layer by diffusion becomes rate controlling process

Bae, Sang-Chul; Ogawa, Masahito; Katsuta, Masafumi

452

Dehydrogenation catalyst for optical organic-hydride detection  

NASA Astrophysics Data System (ADS)

The leak detection of organic hydrides, which are approvable carriers to store and transport hydrogen, has importance for safe usage. The potential use of hydrogen gasochromic materials was investigated with the combination of dehydrogenation catalysts for this purpose. The dehydrogenation activity of catalytic metals which are Pt, Pd, Rh, Ir, Ni, and Cu, was determined with loading alumina pellets with a content of 1 wt.% for 5% cyclohexane as a organic hydride in N 2 gas. The hydrogen generation was observed over 100 °C for Pt and Pd, and over 150 °C for Rh and almost negligible for other metals. The Pt and Pd were selected as dehydrogenation catalysts to be combined with WO 3 of hydrogen gasochromic materials. The WO 3 films covered with Pt and Pd were prepared by a reactive RF-sputtering. The coloration of as prepared film was observed over 150 °C when exposing with cyclohexane in N 2 gases. We found that Pt/WO 3 and Pd/WO 3 films heated to around 200 °C were applicable to optical organic-hydride sensors.

Yoshimura, Kimio; Hakoda, Teruyuki; Yamamoto, Shunya; Yoshikawa, Masahito

2011-02-01

453

Experimental studies on the behaviours of hydride heat storage system  

NASA Astrophysics Data System (ADS)

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

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

454

Hydride Molecules in the Local Universe and Beyond  

NASA Astrophysics Data System (ADS)

The Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory (HSO) is providing invaluable data on hydride molecules in the interstellar medium within the Milky Way and nearby galaxies. I would like to present some of the key results from hydride studies with Herschel/HIFI instrument such as the first observations at high spectral resolution of the fundamental J = 1 - 0 rotational transition of hydrogen fluoride (HF) at 1.232 THz, and the discovery of its ubiquitous nature within the ISM of the Milky Way galaxy, first detection of some Cl-bearing molecules in diffuse medium towards a bright submillimeter continuum and the water abundance enhancement towards the Galactic Center. The data that I will present is from the guaranteed time key programs, Probing Interstellar Molecules with Absorption lines Studies (PRISMAS) and Herschel/HIFI Observations of EXtraOrdinary Sources (HEXOS). Following-up on the Herschel discovery on molecular hydrides within the ISM of the Milky Way galaxy, we are conducting a search for the fundamental rotation lines of HF and H2O towards nearby galaxies with Herschel/HIFI and luminous lensed high-redshiftd galaxies with strong submillimeter continuum with the Caltech Submillimeter Observatory (CSO) and the Plateau de Bure Interferometer (PdBI) toward. Results and interpretation from these observations will be presented at the AAS.

Monje, Raquel

2012-05-01

455

Superconductive sodalite-like clathrate calcium hydride at high pressures.  

PubMed

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 H(2) fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particle-swam optimization structural search, we show that in the stoichiometry CaH(6) 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 H(2) of electrons donated by Ca forming an "H(4)" 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 CaH(6). A superconducting critical temperature (T(c)) 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

2012-04-06

456

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

SciTech Connect

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

Nasise, J.E.

1988-01-01

457

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

NASA Astrophysics Data System (ADS)

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.

2012-11-01

458

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

459

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

SciTech Connect

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

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

1989-12-01

460

An inconvenient influence of iridium(III) isomer on OLED efficiency.  

PubMed

The recently reported heteroleptic cyclometallated iridium(III) complex [Ir(2-phenylpyridine)(2)(2-carboxy-4-dimethylaminopyridine)] N984 and its isomer N984b have been studied more in detail. While photo- and electrochemical properties are very similar, DFT/TDDFT calculations show that the two isomers have different HOMO orbital characteristics. As a consequence, solution processed OLEDs made using a mixture of N984 and isomer N984b similar to vacuum processed devices show that the isomer has a dramatic detrimental effect on the performances of the device. In addition, commonly used thermogravimetric analysis is not suitable for showing the isomerization process. The isomer could impact performances of vacuum processed OLEDs using heteroleptic cyclometallated iridium(III) complexes as dopant. PMID:20714627

Baranoff, Etienne; Bolink, Henk J; De Angelis, Filippo; Fantacci, Simona; Di Censo, Davide; Djellab, Karim; Grätzel, Michael; Nazeeruddin, Md Khaja

2010-08-13

461

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

PubMed

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

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

2009-02-28

462

Iridium-catalyzed addition of aroyl chlorides and aliphatic acid chlorides to terminal alkynes.  

PubMed

Iridium complexes show high catalytic activity in intermolecular additions of acid chlorides to terminal alkynes to afford valuable (Z)-?-chloro-?,?-unsaturated ketones. Ligands in the catalytic system play a crucial role in this reaction. An N-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, while dicyclohexyl(2-methylphenyl)phosphine (PCy(2)(o-Tol)) is indispensable for the reaction of aliphatic acid chlorides. The addition reactions proceed regio- and stereoselectively with suppression of decarbonylation and ?-hydrogen elimination, which have been two major intrinsic problems in transition-metal-catalyzed reactions. Stoichiometric reactions of active iridium catalysts with aroyl chlorides and aliphatic acid chlorides are carried out to gain insights into the reaction mechanisms. PMID:22148675

Iwai, Tomohiro; Fujihara, Tetsuaki; Terao, Jun; Tsuji, Yasushi

2011-12-28

463

Sorption of the chloride complexes of iridium(IV) by hydrated zirconium dioxide  

SciTech Connect

Studies have previously been made of the sorption of the chloride complexes of platinum(IV), platinum(II), palladium(II), rhodium(III), and iridium(III) by hydrated zirconium dioxide (HZD). The objective of the present work is the study of the sorption of the chloride complexes of iridium(IV) by HZD in similar circumstances. It has been ascertained that the kinetics of the sorption of the chloride complexes of Ir(IV) on HZD and the capacity of the sorbent are functions of the concentration of the complex, the pH of the solution and its hydrochloric-acid concentration, and the nature and concentration of the base electrolyte. The sorption of the Ir(IV) chlorocomplexes from acid solutions takes place via an ion-exchange mechanism; sorption from neutral solutions is linked to a ligand reaction between the aquated forms of Ir(IV) and the aquo and hydroxo groups of the sorbent.

Nikol'skaya, L.V.; Boichinova, E.S.; Simanova, S.A.

1986-10-20

464

Strongly Phosphorescent Iridium(III)-Porphyrins - New Oxygen Indicators with Tuneable Photophysical Properties and Functionalities  

PubMed Central

Synthesis and characterization of four iridium(III)–octaethylporphyrins and a ?-extended iridium(III)–benzoporphyrin are presented. Strong room-temperature phosphorescence was observed for all of the complexes with quantum yields of up to 30 %. Axial ligands were introduced to tune the photophysical properties and the solubility. Complexes bearing lipophilic ligands such as pyridine or N-(n-butyl)imidazole were incorporated into polystyrene to obtain optical oxygen sensors. Covalent coupling of the dye is possible by introduction of ligands with binding domains (1-imidazoleacetic acid). This enabled preparation of a water-soluble oxygen probe (by staining bovine serum albumin) and a trace oxygen sensor (by coupling to amino-modified silica gel).

Koren, Klaus; Borisov, Sergey M; Saf, Robert; Klimant, Ingo

2011-01-01

465

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

NASA Astrophysics Data System (ADS)

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

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

1994-01-01

466

Iridium anomaly in the Upper Devonian of the Canning Basin, Western Australia  

NASA Astrophysics Data System (ADS)

A moderate iridium anomaly, about 20 times the local background, has been found in Upper Devonian rocks in the Canning Basin. It occurs at or near the Frasnian-Famennian boundary, which is known to be associated with a major mass-extinction event of global extent. The anomaly occurs in an extremely condensed limestone sequence laid down under quiet deepwater conditions. Its occurrence suggests a causal link with some form of meteoroid impact. Moreover, carbon isotope data indicate that a large reduction in biomass could have occurred at this level. However, the anomaly coincides with a stromatolite bed containing the fossil cyanobacterium Frutexites; iridium, platinum, iron, manganese, cobalt, arsenic, antinomy, and cerium are preferentially concentrated in filaments of this organism, with concentations ranging from two to five times that of the matrix. It is possible that Frutexites extracted these elements directly from seawater, without the need for their derivation from an extraterrestrial source.

Playford, P. E.; McLaren, D. J.; Orth, C. J.; Gilmore, J. S.; Goodfellow, W. D.

1984-10-01

467

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

468

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

469

Electrical properties of boron-doped diamond films synthesized by MPCVD on an iridium substrate  

Microsoft Academic Search

Boron-doped diamond films were synthesized on an iridium substrate by microwave plasma-assisted chemical vapor deposition, using trimethylboron as the dopant source. The Ir substrate was bias-treated by the constant-current mode to permit the formation of oriented diamond nuclei. In order to isolate the B-doped diamond layer electrically from the Ir substrate, the non-doped diamond particles that were formed were grown

Katsuki Kusakabe; Akira Sobana; Ken-Ichiro Sotowa; Toshihiko Imato; Toshiki Tsubota

2003-01-01

470

Catalytic wet air oxidation of butyric acid solutions using carbon-supported iridium catalysts  

Microsoft Academic Search

Aqueous solutions of butyric acid were treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor. Under the operating conditions of 6.9bar of oxygen partial pressure and 200°C of temperature, conversions up to 52.9% after 2h were obtained depending on the type of catalyst used. The effects of butyric acid initial concentration, loading of catalyst, oxygen

H. T Gomes; J. L Figueiredo; J. L Faria

2002-01-01

471

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

Microsoft Academic Search

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

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

2004-01-01

472

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

Microsoft Academic Search

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

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

2008-01-01

473

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

Microsoft Academic Search

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

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

2003-01-01

474

Stability of Iridium Oxide-Tantalum Oxide Coated Titanium Electrodes for Oxygen Evolution in Alkaline Solutions  

Microsoft Academic Search

A continuous anodic electrolysis of an iridium oxide-tantalum oxide (70:30 mol%) coated titanium electrode in a 4 mol dm 3 NaOH solution were carried out to assess the electrode's durability. The electrode's potential during the electrolysis indicated that the potential was almost constant except at the end of electrolysis, which could be easily known with a drastic increase in potential.

M. Morimitsu; C. Murakami; K. Kawaguchi; R. Otogawa; M. Matsunaga

475

SOLID STATE IRIDIUM OXIDE–TITANIUM BASED SENSOR FOR FLOW INJECTION pH MEASUREMENTS  

Microsoft Academic Search

Iridium oxide-coated titanium wire is prepared by controlled electrodeposition (current density 5 mA\\/cm for 10 min) and used as a solid state pH sensor. The sensor is sensitive for pH variations over the range 2–10 with calibration slopes of ˜ 65.5 and 59.1 mV\\/pH unit under static and hydrodynamic modes of operation, respectively. The general performance characteristics of the sensor are similar to

Saad S. M. Hassan; S. A. M. Marzouk; N. M. Badawy

2002-01-01

476

Biosensor for chlorogenic acid based on an ionic liquid containing iridium nanoparticles and polyphenol oxidase  

Microsoft Academic Search

A biosensor based on the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF6) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple (Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the

Suellen C. Fernandes; Sally K. Moccelini; Carla W. Scheeren; Pedro Migowski; Jairton Dupont; Melina Heller; Gustavo A. Micke; Iolanda C. Vieira

2009-01-01

477

The Blue Phosphorescent Iridium Complexes Containing New Triazole Ligands for OLEDs  

Microsoft Academic Search

For the application to organic light-emitting diodes (OLEDs), the blue light emitting iridium complexes containing a new triazole (trzl) ancillary ligand were prepared and their photophysical properties was studied with respect to substituent effect at the 5-position of the triazole in the complexes. As substituents, electron donating groups, CMe3 and CH2OMe were introduced to the triazole ligand of the complex

So Youn Ahn; Yunkyoung Ha

2009-01-01

478

Comparison of Iridium Observations of Birkeland Currents Associated With Two Magnetic Cloud Events With MHD Simulations  

NASA Astrophysics Data System (ADS)

We present global observations of Birkeland currents associated with two magnetic clouds passing by the Earth's magnetosphere. During the first event on 19--21 March 2001, the interplanetary magnetic field (IMF) is initially oriented southward with a negative B {y} component. After a sign reversal of B {y}, the IMF turns increasingly northward over the course of 36 hours. For the second event on 17--19 August 2003, the IMF is initially directed due northward and subsequently turns strongly southward while sustaining a negative IMF B {y} component. Following a brief interval of positive B {y}, the B {y} component turns negative once again, and the IMF transitions beyond its initial northward direction toward positive B {y} within a 24-hour period. The events were specifically chosen because of the slow transitions in the IMF orientation and because of the differences in the IMF rotation between the two events. The transitions are slow enough to derive global maps of Birkeland currents from the 70 satellites of the Iridium constellation. The Birkeland current distributions observed by Iridium show characteristic variations in response to changes in IMF orientation, and the most equatorward latitude of the Birkeland currents expands from 60o for northward IMF to 40o during southward IMF orientation. MHD simulations, driven by solar wind conditions observed during the magnetic cloud events, exhibit variations similar to the ones observed by Iridium. We compare the Iridium Birkeland current distributions obtained during the two events with the MHD simulation results and examine the temporal development of the Birkeland currents between observations and simulations.

Korth, H.; Anderson, B. J.; Lyon, J. G.; Wiltberger, M. J.

2004-12-01

479

Emissive metallomesogens based on 2-phenylpyridine complexes of iridium(III).  

PubMed

Preparation of Ir(III) complexes using anisotropic 2,5-di(4-alkoxyphenyl)pyridine ligands leads to emissive, liquid-crystalline complexes containing bound Cl and dimethyl sulfoxide. Using analogous poly(alkoxy) ligands allows the preparation of bis(2-phenylpyridine)iridium(III) acac complexes, which are also mesomorphic. The observation of liquid crystallinity in octahedral complexes of this type is without precedent. PMID:21413706

Santoro, Amedeo; Prokhorov, Anton M; Kozhevnikov, Valery N; Whitwood, Adrian C; Donnio, Bertrand; Williams, J A Gareth; Bruce, Duncan W

2011-03-17

480

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

Microsoft Academic Search

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

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

1995-01-01

481

Effect of support on the conversion of methane to synthesis gas over supported iridium catalysts  

Microsoft Academic Search

A partial oxidation of methane was carried out using iridium catalysts supported on several metal oxides. The productivity\\u000a of the synthesis gas from methane was strongly affected by the choice of support oxides for the catalysts. The synthesis gas\\u000a production proceeded basically via a two-step reaction consisting of methane combustion to give H2O and CO2, followed by the reforming of

Kiyoharu Nakagawa; Kengo Anzai; Naoko Matsui; Naoki Ikenaga; Toshimitsu Suzuki; Yonghong Teng; Tetsuhiko Kobayashi; Masatake Haruta

1998-01-01